JP2001093950A - Method and device for inspecting semiconductor pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspecting device for semiconductor pattern where, when a semiconductor circuit pattern region of a sample is inspected, a clear contrast between a defective part and a base material is obtained, various patterns of defects, voids and foreign matters of various materials are detected, and the defects are classified using the result of detection of the inspected defects, and a method for inspecting semiconductor pattern. SOLUTION: Inspection conditions decided by at least the eyelectronic optical conditions in a charged particle source and an irradiating optical means are a plurality of different inspection conditions, and a defect classification means that classifies the defects of a sample using a plurality of defect information obtained by irradiating the sample under a plurality of inspection conditions is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pattern inspection apparatus and a semiconductor pattern inspection method for inspecting a circuit pattern formed on a semiconductor wafer for defects such as voids and foreign matter.

[0002]

2. Description of the Related Art Along with miniaturization of a circuit pattern of a semiconductor wafer, a circuit pattern inspection apparatus using an electron beam instead of conventional light has been put to practical use.

For example, Japanese Patent Publication No. 59-192943, Japanese Patent Publication No. 5-258703, and Sandl.
and, et al. , “An electron-beam inspect
ion system for x-ray maskproduction ”, J. Vac. Sc
i. Tech. B, Vol. 9, No. 6, pp. 3005-3009
(1991), reference Meisburger, et al., “Requirements
and performance of anelectron-beam column designed
for x-ray mask inspection ”, J. Vac. Sci. Tech. B,
Vol. 9, No. 6, pp. 3010-3014 (1991),
Reference Meisburger, et al., “Low-voltage electron-optic.
al system for the high-speed inspection of integra
ted circuits ”, J. Vac. Sci. Tech. B, Vol. 10, N
o.6, pp. 2804-2808 (1992), Reference Hendr
icks, et al., “Characterization of a New
Automated Electron-Beam Wafer Inspection System ”,
SPIE Vol. 2439, pp. 174-183 (20-22)
February, 1995) is known.

In order to carry out high-throughput and high-precision inspection following the increase in the diameter of a wafer and the miniaturization of a semiconductor circuit pattern, it is necessary to obtain an image with a high SN ratio at a very high speed. Therefore, a normal scanning electron microscope (Sca
100 times or more (for example, 1
(0 nA or more), the number of electrons irradiated by using a large current beam is secured, and a high SN ratio is maintained. Furthermore, high-speed and high-efficiency detection of secondary electrons and reflected electrons generated from the substrate is essential.

In addition, a semiconductor substrate having an insulating film such as a resist is irradiated with a low-acceleration electron beam of 2 KeV or less so as not to be affected by charging. This technology is described in “The Electron and Ion Beam Handbook (2nd Edition)” edited by the 132nd Committee of the Japan Society for the Promotion of Science (Nikkan Kogyo Shimbun, 1986).
It is described on pages 22 to 623. However, with a large current,
In addition, low-acceleration electron beams cause aberrations due to the space charge effect, making observation with high resolution difficult.

As a method for solving this problem, there is known a method of decelerating a high acceleration electron beam immediately before a sample and irradiating the sample with a substantially low acceleration electron beam. For example, Japanese Patent Application Laid-open No. Hei 2-14045, Japanese Patent Application Laid-open No. Hei 6-139895
There is a technique described in Japanese Unexamined Patent Application Publication No. HEI 9-86.

[0007]

In the above-mentioned prior art, an image is obtained by irradiating an arbitrary region of the substrate to be inspected with an electron beam under only a single electron optical condition. Detection of defects using this image is based on the difference in shape and brightness from the comparison target.
It is important whether there is a contrast between a defective portion such as a white defect on a black base and a black defect on a white base, and the base. But,
In the conventional defect detection based on an image obtained by irradiating an electron beam only under a single electron optical condition, a clear contrast is not always obtained between a defective portion and a base, and defects of a wide variety of patterns and foreign materials of various materials are removed. There was a problem that it could not be detected. Therefore, if the defects are classified as the same type of defects even though the defects have different causes, it becomes difficult to determine the correct cause. Further, there is a problem that even if there is a defect, the defect is not captured in the image and the defect is overlooked.

[0008] As described above, in any given inspection area,
Since defects of various materials and their bases can be present at the same time, in order to detect these defects with high contrast, it is effective to repeatedly detect them under a plurality of irradiation conditions of the electro-optical device. As a result, it is possible to detect more types of defects than before. Defects include defects in patterns of various materials, defects such as thickening and thinning, voids and other voids, residues due to poor etching, and adhesion of foreign matter from the outside. Characteristic cannot be obtained.

Conventionally, a defect inspection is performed under only one inspection condition. Therefore, there is a defect that cannot be detected and is overlooked, and even if it can be detected, what kind of the defect is. What was the real cause was wrong. As a result, a semiconductor chip is extracted as a defect only at the time of an electrical characteristic test of a semiconductor chip after the completion of the manufacturing process, and then the type of the defect and the cause thereof are investigated.

An object of the present invention is to provide a method for inspecting a semiconductor circuit pattern region of a sample, in which a clear contrast is obtained between a defective portion and a base, and a wide variety of pattern defects, voids,
It is an object of the present invention to provide a semiconductor pattern inspection apparatus and a semiconductor pattern inspection method capable of detecting foreign substances of various materials and classifying defects using the detected defect detection results.

[0011]

According to the present invention, there is provided a charged particle source for generating a primary charged particle beam.
Irradiation optical means for converging the primary charged particle beam and scanning a sample having a semiconductor pattern, a detector for detecting charged particles generated from the sample, and a defect for obtaining defect information of the sample from a detection signal of the detector In the semiconductor pattern inspection apparatus having information means, the inspection conditions determined by at least the charged particle source and the electron optical conditions in the irradiation optical means are a plurality of different inspection conditions, and the sample is subjected to the plurality of inspection conditions. A defect classification unit is provided for classifying defects of the sample using a plurality of pieces of defect information obtained by irradiation.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment) FIG. 1 is a longitudinal sectional view showing the structure of a semiconductor pattern inspection apparatus 1 according to a first embodiment of the present invention. The semiconductor pattern inspection apparatus 1 includes an inspection room 2 in which the inside of the room is evacuated, and a spare room (not shown in this embodiment) for transporting the sample substrate 9 into the inspection room 2. Are configured to be evacuated independently of the inspection room 2. The semiconductor pattern inspection apparatus 1 includes a control unit 6 and an image processing unit 5 in addition to the inspection room 2 and the spare room. The inside of the inspection room 2 is roughly composed of an electron optical device 3, a secondary electron detection unit 7, a sample room 8, and an optical microscope unit 4. The electron optical device 3 includes an electron gun 10, an electron beam extraction electrode 11, a condenser lens 12, a deflector 13, a diaphragm 14, a scanning deflector 15, an objective lens 16, a reflector 17, and an E × B deflector 18. ing.

As the sample substrate 9, a substrate having a fine circuit pattern such as a semiconductor wafer, a chip or a liquid crystal or a mask is used and inspected.

A secondary electron detector 20 of the secondary electron detector 7 is disposed above the objective lens 16 in the inspection room 2. The output signal of the secondary electron detector 20 is amplified by a preamplifier 21 installed outside the inspection room 2 and is output by the AD converter 2
2 becomes digital data. The sample chamber 8 contains the sample stage 3
0, X stage 31, Y stage 32, rotary stage 3
3, a position monitor length measuring device 34 and a sample substrate height measuring device 35.

The optical microscope unit 4 is installed near the electron optical device 3 in the inspection room 2 and at a position away from the electron optical device 3 so as not to affect each other.
The distance between and the optical microscope unit 4 is known. And X
The stage 31 or the Y stage 32 reciprocates a known distance between the electron optical device 3 and the optical microscope unit 4. The optical microscope unit 4 includes a white light source 40, an optical lens 41, and a CCD camera 42.

The image processing unit 5 includes a first storage unit 46, a second storage unit 47, a calculation unit 48, a defect determination unit 49, a monitor 50,
It comprises a defect classification unit 53, an inspection condition input unit 54, and an inspection condition storage unit 55. The captured electron beam image or optical image is displayed on the monitor 50.

Operation commands and operation conditions of each section of the apparatus are input and output from the control section 6. The inspection conditions input from the inspection condition input unit 54 are stored in the inspection condition storage unit 55 and sent to the control unit 6. In the control unit 6, conditions such as an acceleration voltage at the time of generation of an electron beam, an electron beam deflection width, a deflection speed, a signal capture timing of a secondary electron detection device, and a sample stage moving speed are arbitrarily or selected according to the purpose. It has been entered so that it can be set. The control unit 6 monitors the position and height deviations from the signals from the position monitor length measuring device 34 and the sample substrate height measuring device 35 by using the correction control circuit 43, generates a correction signal from the result, and generates an electronic signal. A correction signal is sent to the objective lens power supply 45 and the scanning signal generator 44 so that the line is always irradiated to the correct position. In order to acquire an image of the sample substrate 9, the sample substrate 9 is irradiated with a finely squeezed electron beam 19 to generate secondary electrons 51, and these are irradiated with the electron beam 19.
, And an image of the surface of the sample substrate 9 is obtained by detecting in synchronization with the movement of the X stage 31 and the Y stage 32.

The electron gun 10 uses a diffusion-supply type thermal field emission electron source. Since the electron gun 10 can secure a stable electron beam current as compared with a field emission type electron source, an electron beam image with less fluctuation in brightness can be obtained. The electron beam 19 is extracted from the electron gun 10 by applying a voltage between the electron gun 10 and the extraction electrode 11. By applying a high negative voltage to the electron gun 10, the electron beam 19
Is accelerated. As a result, the electron beam 19 travels in the direction of the sample stage 30 with energy corresponding to the potential, is converged by the condenser lens 12, and is further narrowed down by the objective lens 16 to the sample substrate 9 mounted on the sample stage 30. Irradiated.

A scanning signal generator 44 for generating a scanning signal and a blanking signal is connected to the deflector 13, and an objective lens power supply 45 is connected to the objective lens 16.

The sample substrate 9 has a retarding power source 36
Thus, a negative voltage can be applied. By adjusting the voltage of the retarding power supply 36, the primary electron beam 19 can be decelerated, and the electron beam irradiation energy on the sample substrate 9 can be adjusted to an optimum value without changing the potential of the electron gun 10.

The secondary electrons 51 generated by irradiating the sample substrate 9 with the electron beam 19 are accelerated by the negative voltage applied to the sample substrate 9. Above the sample substrate 9,
The E × B deflector 18 is arranged, and the accelerated secondary electrons 51 are deflected in a predetermined direction. ExB deflector 1
The amount of deflection can be adjusted by the voltage applied to 8 and the strength of the magnetic field. Further, the electric field and the magnetic field can be changed in conjunction with a negative voltage applied to the sample. Ex
The secondary electrons 51 deflected by the B deflector 18 collide with the reflector 17 under predetermined conditions.

The reflection plate 17 has a conical shape integrally with the shield pipe of the deflector for the primary electron beam 19 for irradiating the sample substrate 9. When the accelerated secondary electrons 51 collide with the reflector 17, several eV to 50 e
A second secondary electron 52 having V energy is generated.

The secondary electron detector 7 includes a secondary electron detector 20 in the inspection room 2 which has been evacuated, a preamplifier 21 outside the inspection room 2, an AD converter 22, an optical converter 23, and a transmitter 2.
4, electric conversion means 25, high voltage power supply 26, preamplifier drive power supply 27, AD converter drive power supply 28, reverse bias power supply 2
9. As already described, the secondary electron detector 20 of the secondary electron detector 7 is disposed above the objective lens 16 in the inspection room 2. Secondary electron detector 20, preamplifier 21, AD converter 22, light conversion means 2
3, preamplifier drive power supply 27, AD converter drive power supply 28
Are floating at a positive potential by the high voltage power supply 26. Second secondary electrons 5 generated by colliding with reflector 17
2 is guided to the secondary electron detector 20 by this attraction electric field. The secondary electron detector 20 detects that the secondary electrons 51 generated during the irradiation of the sample substrate 9 with the electron beam 19 are then accelerated and collide with the reflector 17 to generate the second secondary electrons 5.
2 is configured to be detected in conjunction with the scanning timing of the electron beam 19. An output signal of the secondary electron detector 20 is amplified by a preamplifier 21 installed outside the inspection room 2 and converted into digital data by an AD converter 22. A
The D converter 22 is configured to convert an analog signal detected by the secondary electron detector 20 into a digital signal immediately after being amplified by the preamplifier 21 and transmit the digital signal to the image processing unit 5. Since the detected analog signal is digitized immediately after detection and then transmitted, a signal having a higher SN ratio and a higher SN ratio than before can be obtained.

A sample substrate 9 is mounted on the X stage 31 and the Y stage 32. When the inspection is performed, the X stage 31 and the Y stage 32 are stopped and the electron beam 19 is two-dimensionally scanned. Sometimes, the X stage 31 and the Y stage 32 are continuously moved in the Y direction at a constant speed, and any one of the methods of scanning the electron beam 19 linearly in the X direction can be selected. When inspecting a specific relatively small area, it is effective to make the former stage stationary while inspecting it, and when inspecting a relatively large area, it is effective to continuously move the stage at a constant speed and inspect it It is. When it is necessary to blank the electron beam 19,
The electron beam 19 is deflected by the deflector 13 and becomes
Can be controlled not to pass through the aperture 14.

In this embodiment, a length measuring device based on laser interference is used as the position monitor measuring device 34. The positions of the X stage 31 and the Y stage 32 can be monitored in real time and transmitted to the control unit 6. Similarly, data such as the number of rotations of the motors of the X stage 31, the Y stage 32, and the rotation stage 33 are also transferred from the respective drivers to the control unit 6, and the control unit 6 performs the operations based on these data. Thus, the region and position where the electron beam 19 is irradiated can be accurately grasped, and the correction control circuit 43 corrects the positional deviation of the irradiation position of the electron beam 19 in real time as needed. ing. Further, an area irradiated with the electron beam 19 can be stored for each sample substrate 9.

As the sample substrate height measuring device 35, an optical measuring device using a measuring method other than the electron beam, for example, a laser interference measuring device or a reflected light measuring device for measuring a change in the position of reflected light is used. The height of the sample substrate 9 mounted on the X stage 31 and the Y stage 32 is measured in real time. In the present embodiment, the sample substrate 9 is irradiated with the elongated white light passing through the slit through the transparent window, the position of the reflected light is detected by the position detection monitor, and the height change amount is calculated from the position change. The method was used. Based on the measurement data of the sample substrate height measuring device 35, the focal length of the objective lens 16 for narrowing down the electron beam 19 is dynamically corrected, so that the electron beam 19 always focused on the inspection area can be irradiated. It has become. Further, the warp and the height distortion of the sample substrate 9 are measured in advance before the irradiation with the electron beam 19, and the correction condition for each inspection area of the objective lens 16 may be set based on the data. It is possible.

The image processing section 5 comprises a first storage section 46, a second storage section 47, an operation section 48, a defect determination section 49, and a monitor 50. The image signal of the sample substrate 9 detected by the secondary electron detector 20 is amplified by the preamplifier 21 and
After being digitized by the D converter 22, the signal is converted into an optical signal by the optical conversion unit 23, transmitted by the transmission unit 24, and converted again into an electric signal by the electric conversion unit 25, and then the first storage unit 46 or the second storage unit 46. It is stored in the storage unit 47. The arithmetic unit 48 performs alignment of the stored image signal with the image signal of the other storage unit, normalizes the signal level, performs various image processing for removing a noise signal, and compares the two image signals. Calculate. The defect judging unit 49 compares the absolute value of the difference image signal calculated by the operation unit 48 with a predetermined threshold value. If the difference image signal level is larger than the predetermined threshold value, the pixel is determined to be defective. The position is determined as a candidate, and the number of defects and the like are displayed on the monitor 50. Further, the defect determination unit 49
And a defect classifying unit 53 for classifying a plurality of pieces of defect information from the user according to the type and cause thereof, and a function of displaying the result on the monitor 50.

The monitor 50 displays the inspection conditions stored in the inspection condition storage unit 55 in addition to the image of the semiconductor pattern and the defect information.

Next, the operation in the case where the semiconductor pattern inspection apparatus 1 inspects a semiconductor wafer which has been subjected to pattern processing in the manufacturing process as the sample substrate 9 will be described. First, although not shown in FIG. 1, the sample substrate 9 is loaded into the sample exchange chamber by the transfer means. Therefore, the sample substrate 9 is mounted on a sample holder, held and fixed, and evacuated, and when the sample exchange chamber reaches a certain degree of vacuum, the sample substrate 9 is transferred to the inspection room 2 for inspection.

In the inspection room 2, the sample stage 30, the X stage 3
The sample holder is mounted on the Y stage 32 and the rotary stage 33 together with the sample holder, and held and fixed. The set sample substrate 9 is arranged at predetermined first coordinates below the optical microscope unit 4 by moving the X stage 31 and the Y stage 32 in the X and Y directions based on predetermined inspection conditions registered in advance. An optical microscope image of the semiconductor circuit pattern formed on the sample substrate 9 is observed by the monitor 50, and compared with an equivalent circuit pattern image at the same position stored in advance for position rotation correction. A position correction value of the coordinates is calculated.

Next, the lens moves to a second coordinate having a circuit pattern equivalent to the first coordinate which is at a fixed distance from the first coordinate, and an optical microscope image is similarly observed. The stored position is compared with the stored semiconductor circuit pattern image, and the position correction value of the second coordinate and the amount of rotation deviation with respect to the first coordinate are calculated. The rotation stage 33 rotates by the calculated rotation deviation amount, and corrects the rotation amount. In the present embodiment, the amount of rotation deviation is corrected by the rotation of the rotation stage 33. However, a method of correcting the scanning deflection position of the electron beam 19 based on the calculated amount of rotation deviation without providing the rotation stage 33 is also possible. Can be corrected.

In this optical microscope image observation, a semiconductor circuit pattern that can be observed not only with the optical microscope image but also with the electron beam image is selected. In order to correct the position in the future, the first coordinates, the amount of displacement of the first semiconductor circuit pattern by optical microscope image observation, the second coordinates,
The amount of displacement of the second semiconductor circuit pattern by the optical microscope image observation is stored and transferred to the control unit 6.

Further, the semiconductor circuit pattern formed on the sample substrate 9 is observed by using an image obtained by an optical microscope, and the position of the chip of the semiconductor circuit pattern on the sample substrate 9, the distance between the chips, or The repetition pitch of a repetition pattern such as a memory cell is measured in advance, and the measured value is input to the control unit 6.

The chip to be inspected on the sample substrate 9 and the region to be inspected in the chip are set from the image of the optical microscope and input to the control unit 6 in the same manner as described above.

The image of the optical microscope can be observed at a relatively low magnification, and when the surface of the sample substrate 9 is covered with, for example, a silicon oxide film, the image can be observed by penetrating to the base. Therefore, the arrangement of the chips and the layout of the semiconductor circuit patterns in the chips can be easily observed, and the inspection area can be easily set. When the preparatory work such as the predetermined correction work and the setting of the inspection area by the optical microscope unit 4 is completed as described above, the X stage 3
The sample substrate 9 is moved below the electron optical device 3 by the movement of 1 and the Y stage 32.

When the sample substrate 9 is placed under the electron optical device 3, the same operation as the correction operation and the setting of the inspection area performed by the optical microscope unit 4 is performed by the electron beam image. The acquisition of the electron beam image at this time is performed by the following method. Based on the coordinate values stored and corrected in the alignment by the optical microscope image, the electron beam 19 is two-dimensionally shifted in the X and Y directions by the deflector 13 on the same semiconductor circuit pattern as observed in the optical microscope unit 4. Scanned and illuminated. By the two-dimensional scanning of the electron beam 19, the secondary electrons 51 generated from the observed part are detected by the configuration and operation of each unit for the secondary electron detection, and an electron beam image is obtained. Easy inspection position confirmation, position adjustment, and position adjustment have already been performed using the optical microscope image, and rotation correction has also been performed in advance, so the position resolution and position correction are higher in resolution and higher in magnification than optical images with higher precision. , Rotation correction can be performed.

When the sample substrate 9 is irradiated with the electron beam 19, the irradiated portion is charged. In order to avoid the influence of the electrification at the time of the inspection, the semiconductor circuit pattern irradiated with the electron beam 19 in the pre-inspection preparation work such as the above-described position rotation correction or the setting of the area to be inspected is a semiconductor circuit pattern existing outside the area to be inspected in advance. Or an equivalent semiconductor circuit pattern in a chip other than the chip to be inspected can be automatically selected from the control unit 6. As a result, during the inspection, the electron beam 1 is
9 does not affect the inspection image.

Next, a scanning method of the electron beam 19 for forming an electron beam image for performing the inspection according to the present invention will be described. In a normal SEM (scanning electron microscope), an electron beam is two-dimensionally scanned while a stage is stationary, and an image of a certain region is formed. According to this method, when inspecting a wide area thoroughly, for each image acquisition area, in addition to the time for scanning the electron beam at rest, the acceleration, deceleration,
It takes time to add the position setting. Therefore, a long time is required for the entire inspection time. Therefore, in the present invention, while moving the stage in one direction continuously at a constant speed,
An inspection method was used in which an electron beam was scanned in one direction at a high speed in a direction orthogonal to or crossing the stage movement direction to obtain an image of a region to be inspected. Accordingly, the electron beam acquisition time for one scanning width of the predetermined distance is only the time for the stage to move the predetermined distance.

FIG. 2 is a plan view of a part of the sample substrate showing a method of scanning a primary electron beam. An example of a method in which the electron beam 19 scans while the Y stage 32 continuously moves in the Y direction at a constant speed by the above method is shown. Electron beam 19
Is scanned by the scanning deflector 44, the electron beam 19 is irradiated to the sample substrate 9 in only one direction as shown by the solid line, and the electron beam is applied to the sample substrate 9 during the return of the electron beam 19 shown by the broken line. By blanking so that the electron beam 19 is not irradiated, the electron beam 19 is uniformly and spatially and temporally formed on the sample substrate 9.
Can be irradiated. Blanking is performed by the deflector 13
This is performed by deflecting the electron beam 19 so that the electron beam 19 does not pass through the opening of the diaphragm 14.

Next, irradiation conditions which affect the contrast of an electron beam image will be described. The contrast of the electron beam image is generated by the amount of the secondary electrons 51 generated and detected by the electron beam 19 irradiating the sample substrate 9. For example, the generation of the secondary electrons 51 depends on the material of the sample substrate 9 and the like. The difference in the amount causes a difference in brightness to be displayed on the monitor 50. The amount of the secondary electrons 51 generated is correlated with the degree of charging of the sample substrate 9 and differs depending on the material, shape, and density of the semiconductor circuit pattern on the sample substrate 9. In addition, the stability of the charge amount with respect to the irradiation time also changes depending on the material, shape and density of the semiconductor circuit pattern on the sample substrate 9 and the irradiation conditions of the primary electron beam. As described above, in order to obtain an electron beam image having an optimum contrast for comparative inspection, irradiation of the primary electron beam according to the material, shape and density of the base and the defect of the semiconductor circuit pattern on the sample substrate 9 is performed. It is necessary to change the conditions.

For example, in a given inspection area, there are defects of various materials, shapes, and densities and bases thereof.
In order to detect these defective portions with high contrast, it is necessary to repeatedly detect the defective portions under a plurality of irradiation conditions of the electron optical device 3.

FIG. 3 is a plan view showing an example of a semiconductor circuit pattern on a sample substrate. This pattern is an example of a gate pattern formed on the element isolation pattern.
FIG. 4 is a longitudinal sectional view showing an AA section of FIG. Oxide film SiO ₂ exists on silicon Si, and Po
Gate lines of ly-Si and WSi are formed.

FIG. 5 is an example of an image obtained by acquiring the pattern shown in FIG. 3 under the electro-optical condition of irradiation energy of 3.0 KeV. FIG. 6 is a diagram showing the pattern shown in FIG. FIG. 4 is a diagram showing an example of an image acquired in FIG. As described below, when the inspection condition is set as a parameter, it is found that there are defects that can be captured in the image and defects that are not.

In FIG. 5, the irradiation energy is 3.0 KeV.
In the case of (1), only the edge of the gate pattern composed of Poly-Si and WSi becomes brightly bright due to the edge effect. In such an image, an image having a high contrast such as a foreign substance of Poly-Si positioned between the gate patterns can be obtained. In FIG. 6, when the irradiation energy is 0.5 KeV, a conductive pattern is strongly observed. In this case, an image with a high contrast such as a non-conductive foreign substance below the gate pattern can be obtained. The irradiation energy of the poly-Si foreign matter located between the gate patterns shown in FIG. 5 is 0.5 KeV.
In this case, since the film is conductive, it shines strongly, and the background also shines, so that contrast cannot be obtained and cannot be detected. Also,
Non-conducting foreign matter below the gate pattern shown in FIG. 6 is dark because of non-conductivity at an irradiation energy of 3.0 KeV. .

As described above, in any given inspection area,
Since defects of various materials and their bases can be present at the same time, in order to detect these defects with high contrast, it is effective to repeatedly detect them under a plurality of irradiation conditions of the electro-optical device. As a result, it is possible to detect more types of defects than before.

Further, by arranging whether or not each electron optical device can be detected under irradiation conditions, it is possible to know and classify the electrical characteristics and the like of the defects detected under certain conditions. The semiconductor pattern inspection apparatus shown in FIG. 1 includes a defect classification unit 53 that automatically performs the sorting and the classification.

FIG. 7 is a view showing an example of an image when the electro-optical conditions of the pattern shown in FIG. 3 are changed. The irradiation energy is of two types, 3.0 KeV and 0.5 KeV.

In the working process, first, the first detection is performed at an irradiation energy of 0.5 KeV, and as shown in the first column of FIG. 7, defects such as foreign substances at three places in the inspection areas P1, P2 and P3 are detected. Suppose you can. A detection ID 101, a detection ID 102, and a detection ID 103 are given as name tags of the respective images. If the position information is given to these detection IDs, it is convenient for specifying a defective portion and comparing images. In this embodiment, the last first digit of the three-digit number is
It corresponds to the number of the inspection area. It is assumed that these images have the same luminance. When the luminance is the same, different defects are different from each other, and defects caused by a common cause can be captured in an image in the same manner.

In the second detection, the irradiation energy was 3.0.
As shown in the fourth column of FIG. 7, images of defects such as foreign substances at the same three points as in the first detection are acquired, and the detection ID 201 and the detection ID 20 are respectively obtained.
2. A detection ID 203 is assigned. These images had the same luminance.

The detection ID 101 of the first detection and the detection ID 201 of the second detection are images at the same position P1, and different irradiation IDs as shown in the second and third columns in FIG. Since the shape of the foreign matter and the supposed thing captured by the energy are almost the same, it can be determined that the foreign matter is a single foreign matter or a defect.

On the other hand, the irradiation energy of the inspection area P2 is set at 0.
The foreign substance and the thing which are possibly captured in the image of the detection ID 102 of the first detection at 5 KeV are not captured in the image of the detection ID 202 of the second detection at the irradiation energy of 3.0 KeV. Further, although not detected in the image of the detection ID 103 of the first detection at the irradiation energy of 0.5 KeV in the inspection area P3, the irradiation energy of 3.0 KV
In the image of the detection ID 303 of the second detection at eV, a foreign substance and a suspected substance are captured.

From the above, the following has been found.

(1) The defect captured in the image of the detection ID 101 and the detection ID 201 in the inspection area P1 is likely to be a single defect having the same material and the same cause.

(2) Defects captured in the images of the detection ID 101 and the detection ID 201 in the inspection area P1 are the same as those in the inspection area P2.
There is a great possibility that the material and the cause of occurrence are different from the defect captured in the image of the detection ID 102 and the defect captured in the image of the detection ID 203 in the inspection area P3.

(3) The defect captured in the image of the detection ID 102 in the inspection area P2 is the detection ID 203 in the inspection area P3.
There is a high possibility that the material and the cause of occurrence are different from those of the defect captured in the image.

In the conventional inspection method, a defect such as a foreign substance is detected under only one inspection condition. Therefore, a plurality of obtained defects have substantially the same size, similar shape characteristics, and the same luminance. In such a case, it has been determined that there is a high possibility that these defects have the same material and the same cause.

According to the present invention, the same location is inspected under a plurality of inspection conditions, and the image of the detected defect is managed by an ID accompanied with the position information, so that the same position detected under different inspection conditions is obtained. Can be determined to be the same defect. As a result, according to the present invention, a defect having conventionally been similar in size and shape under the single irradiation condition and determined to be in the same classification is also determined to be a different classification as a defect of a different type. The accuracy of defect classification has been significantly improved.

In the above embodiment, the case where the irradiation energy of the primary electron beam irradiating the sample is changed as a parameter of the inspection condition has been described. The number of times the primary electron beam is scanned, the scanning speed, and the like can also be used as parameters.

To change the irradiation energy for irradiating the sample, a zero or negative potential is applied to the sample, the sample table, or the vicinity of the sample, and the applied voltage is adjusted, so that a series of The irradiation energy of the primary electron beam to the substrate can be changed at high speed during the inspection operation.

When changing the number of times of scanning of the primary electron beam,
When the X stage 31 and the Y stage 32 are continuously moved in the Y direction, the average irradiation time for a certain point on the sample can be changed by setting the X stage 31 and the Y stage 32 at a low speed or a high speed. Or X stage 3
The stage movement and the electron beam scanning are performed, for example, by intermittently operating the Y stage 32 and performing n scans while the stage is stopped, and then moving the X stage 31 and the Y stage 32 to the next point. It may be performed alternately.

In addition, when changing the scanning speed of the primary electron beam, it is realized by changing the clock frequency applied to the scanning deflector 15.

When changing the irradiation amount of the primary electron beam per unit time, a plurality of large and small openings are provided in the stop 14 of the electron optical device 3 so that the electron beam 19 passes through a desired opening. The diaphragm 14 is moved in and out using an actuator. Alternatively, it can be realized by selecting a desired opening with the deflector 13 without moving the diaphragm 14. Alternatively, the irradiation amount per unit time can be changed by changing the voltage of the suppressor electrode of the electron source 10 or the voltage of the extraction electrode 11.

In the semiconductor pattern inspection apparatus according to the present invention, the inspection conditions as described above, that is, the material, shape, density, etc. of defects, voids, estimated foreign substances, etc. of a semiconductor circuit pattern in a given inspection area are considered. Are registered in advance in the inspection condition storage unit 55 shown in FIG. 1, and the inspection conditions registered at the time of inspection can be called and automatically set by the inspection condition input unit 54. It is configured. For example, prior to the inspection, the inspection conditions displayed on the monitor 50 are changed by the inspection condition input unit 54, a test inspection is performed to simulate the inspection without actually performing the inspection, and the inspection conditions are determined. Can be registered in the inspection condition storage unit 55. As described above, when an electron beam image is obtained by irradiating an electron beam to perform a comparative inspection, a primary image is obtained so as to obtain an optimal image for the comparative inspection in accordance with the material, shape, and density of the defect or foreign object to be inspected. Although the embodiment in which the conditions for irradiating the sample with the electron beam are changed has been described, the present invention also relates to an inspection method and an inspection apparatus that combine a plurality of features described in the claims without departing from the scope of the present invention. It is feasible.

[0065]

As described above, according to the present invention, since a semiconductor circuit pattern region of a sample is inspected under a plurality of different inspection conditions, a clear contrast can be obtained between a defective portion and a base, and a wide variety of types can be obtained. An excellent effect not found in the conventional inspection apparatus can be obtained, in which defects of patterns, voids, and foreign materials of various materials can be detected, and defects can be classified using the detected defect detection results.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a semiconductor pattern inspection apparatus.

FIG. 2 is a plan view of a part of a sample substrate showing a method of scanning a primary electron beam.

FIG. 3 is a plan view showing an example of a semiconductor circuit pattern on a sample substrate.

FIG. 4 is a longitudinal sectional view of FIG. 3;

FIG. 5 shows a pattern shown in FIG.
FIG. 9 is a diagram illustrating an example of an image acquired under V electro-optical conditions.

FIG. 6 shows a pattern shown in FIG.
FIG. 4 is a diagram illustrating an example of an image acquired under KeV electro-optical conditions.

FIG. 7 is a view showing an example of an image when the electro-optical conditions of the pattern shown in FIG. 3 are changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor pattern inspection apparatus, 2 ... Inspection room, 3 ... Electronic optical device, 5 ... Image processing part, 6 ... Control part, 7 ... Secondary electron detection part, 8 ... Sample chamber, 9 ... Sample substrate, 19 ... Electronics Line, 20
... Secondary electron detector, 30 ... Sample stage, 31 ... X stage,
32 Y stage, 46 first storage unit, 47 second storage unit, 48 arithmetic unit, 49 defect determination unit, 51 secondary electron, 52 second secondary electron, 53 defect classification unit , 54 ...
Inspection condition input unit, 55 ... Inspection condition storage unit.

Continued on the front page (72) Inventor Hiroshi Miyai 882 Ma, Ichihiro, Hitachinaka-shi, Ibaraki F-term (reference) 2F067 AA45 AA54 AA62 BB01 BB04 CC17 EE03 HH06 JJ05 KK04 PP12 QQ02 QQ03 RR12 RR35 SS02 SS13 UU32 2G001 AA03 AA09 BA07 CA03 FA06 FA16 GA01 GA06 GA09 HA13 JA02 JA03 JA08 JA11 JA14 KA03 LA11 MA05 PA07 PA11 PA12 SA02 SA03 2G011 AA01 AC06 AE01 AE03 AF06 2G032 AD08 AE04 AE08 DB39A01 DB11 DJ01 DJ04 DJ27 DJ28

Claims (8)

[Claims] 1. A charged particle source for generating a primary charged particle beam;
Irradiation optical means for converging the primary charged particle beam and scanning a sample having a semiconductor pattern, a detector for detecting charged particles generated from the sample, and a defect for obtaining defect information of the sample from a detection signal of the detector In the semiconductor pattern inspection apparatus having information means, the inspection conditions determined by at least the charged particle source and the electron optical conditions in the irradiation optical means are a plurality of different inspection conditions, and the sample is subjected to the plurality of inspection conditions. A semiconductor pattern inspection apparatus, comprising: a defect classification unit that classifies defects of the sample using a plurality of pieces of defect information obtained by irradiation. 2. The defect classification means according to claim 1, wherein said defect classification means classifies a defect commonly detected under said plurality of different inspection conditions and a defect not detected under any of said inspection conditions. Characteristic semiconductor pattern inspection equipment. 3. The semiconductor pattern according to claim 1, wherein the electron optical condition is an irradiation energy of the primary charged particles on the sample or an irradiation amount of the primary charged particles per unit time. Inspection equipment. 4. The apparatus according to claim 1, wherein at least one of the plurality of different inspection conditions is the number of times of scanning of the primary charged particle beam on the sample or the scanning speed of the primary charged particle beam on the sample. A semiconductor pattern inspection apparatus characterized by the above-mentioned. 5. An accelerating / decelerating means according to claim 1, wherein at least a voltage is applied to said sample to decelerate said primary charged particle beam and accelerate charged particles generated from said sample by irradiation thereof. A semiconductor pattern inspection apparatus, wherein at least one of the electro-optical conditions is the applied voltage value. 6. The semiconductor pattern inspection apparatus according to claim 1, wherein an identification number or symbol accompanied by at least positional information on the sample is added to the defect information of the sample. 7. A sample having a semiconductor pattern is irradiated with a primary charged particle beam under predetermined inspection conditions to detect generated charged particles, and defect information of the sample obtained from the charged particles is obtained. In the semiconductor pattern inspection method for inspecting the sample based on the above, a plurality of the inspection conditions are provided, and the same portion on the sample is inspected by changing the inspection condition. 8. A primary charged particle beam generated by a charged particle source is converged based on electron-optical conditions, a sample having a semiconductor pattern is scanned, and charged particles generated from the sample are detected to obtain defect information of the sample. In the semiconductor pattern inspection method, at least the inspection conditions determined by the charged particle source and the electron-optical conditions are a plurality of different inspection conditions, and a plurality of defect information obtained by irradiating the sample under the plurality of inspection conditions. A method for inspecting a semiconductor pattern, wherein defects of the sample are classified by using the method.