JPH10178014A - Method for manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a reduction in throughput in manufacturing a semiconductor device by chemical dry etching, and also remove substantially all residues of a metal film while taking care of excessively digging the metal film of an electrode connection hole. SOLUTION: A tungsten film 14 in a region other than an electrode connection hole 11 is removed by chemical dry etching. This step for chemical dry etching comprises a first etching in which an etching speed is relatively high; and a second etching in which an etching speed after this first etching is relatively low. The first etching uses a first reactive gas of a mixture of a gas containing fluoric atoms, a gas containing chlorine atoms and an oxygen gas, and the second etching uses a second reactive gas of a mixture of a gas containing fluoric atoms and an oxygen gas and is carried out at lower power than the first dry etching. In this second reactive gas, a ratio of a gas containing fluoric atoms to an oxygen gas is 1:(1.5 to 1.0).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device in which a metal film such as tungsten is buried in a connection hole for an electrode formed in an interlayer insulating film of a semiconductor substrate. .

[0002]

2. Description of the Related Art In semiconductor devices, circuit line widths have become increasingly finer as the degree of integration increases. For this reason, the diameter of the electrode contact hole, that is, the electrode connection hole is also reduced, and tungsten is buried in the electrode connection hole in order to obtain sufficient coverage of the wiring layer. The burying of tungsten is generally performed as follows. That is, an electrode connection hole is formed in an interlayer insulating film of a semiconductor substrate by dry etching, then a titanium film and a titanium compound film are formed as a barrier metal film by sputtering, and a tungsten film is formed on the entire surface of the semiconductor substrate by a CVD method. Is formed and a tungsten film is buried in the electrode connection hole, and thereafter, the tungsten film in a region other than the electrode connection hole is removed by etching.

[0003] Such removal of tungsten on the barrier metal film needs to be performed so that no tungsten residue remains on the barrier metal film, and for this reason, over-etching is performed.

[0004]

However, the above-described conventional method for manufacturing a semiconductor device has a problem that the tungsten film in the electrode connection hole is often excessively dug when attempting to remove all the tungsten residue by over-etching. . More specifically, in general, the etching of the tungsten film is performed at as high a speed as possible in order to increase the throughput of semiconductor device production. If overetching is performed so as to remove all of the tungsten residue by this high-speed etching, the tungsten film in the electrode connection hole will be dug too much.

[0005] Japanese Patent Application Laid-Open No. 7-221178 discloses that
In the reactive ion etching process, first, a tungsten film is first etched using a mixed gas of a fluorine-based gas and an oxygen gas, and thereafter, a mixed gas of a fluorine-based gas and a nitrogen gas is used. A method of manufacturing a semiconductor device that performs over-etching for removing a tungsten residue is disclosed. In this way, the etching process
By performing the steps separately, all the tungsten residues are removed while preventing the tungsten film in the electrode connection holes from being dug too much.

However, the above-mentioned Japanese Patent Application Laid-Open No. 7-221
No. 178 discloses a method of manufacturing a semiconductor device capable of removing a tungsten residue by a reactive ion etching process, but does not disclose a method of removing a tungsten residue by a chemical dry etching process. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a chemical dry etching method that avoids a decrease in the throughput of the manufacture of a semiconductor device and removes substantially all residues of a metal film while preventing the metal film in an electrode connection hole from being dug. To provide a method for manufacturing a semiconductor device.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a process for forming a connection hole for an electrode in an interlayer insulating film of a semiconductor substrate, and a method for forming the connection hole for an electrode. Forming a metal film on the connection hole for the electrode and the barrier metal film so as to fill the connection hole for the electrode, and forming the metal film on the barrier metal film. Removing the metal film in a region other than the connection hole for the electrode by etching, wherein the chemical dry etching step comprises the steps of: A first dry etching using a first reactive gas mixed with a gas, and a first dry etching using the first reactive gas mixed with a gas containing a fluorine atom and an oxygen gas. A second dry etching using a second reactive gas, wherein the second dry etching is performed at a lower power than the first dry etching, and the second reactive gas is The ratio between the gas containing atoms and the oxygen gas is 1: (1.5 to 10).

The first etching is performed at a relatively high speed by using a first reactive gas obtained by mixing a gas containing a fluorine atom, a gas containing a chlorine atom, and an oxygen gas. The metal film on the barrier metal film is removed by etching. The second etching is performed using a second reactive gas in which a gas containing a fluorine atom and an oxygen gas are mixed, and has lower power than the first etching. The metal film residue remaining during the etching is removed.

Since the first etching is performed at a relatively high speed, it is possible to avoid a decrease in the throughput of manufacturing the semiconductor device.
Since the second etching is performed at a relatively low speed, it is relatively easy to control the end point of the second etching. Therefore, the residue of the metal film is substantially eliminated while the metal film in the electrode connection hole is not excessively dug. All can be removed. According to a second aspect of the present invention, in the method of manufacturing a semiconductor device according to the first aspect, the gas containing fluorine atoms is CF ₄ and C _4.
Is any one selected from ₂ F ₆ and _C 3 _{F 8} and NF ₃ and SF ₆ Prefecture, is characterized in that gas containing the chlorine atom is Cl _2.

As the gas containing a fluorine atom, gases having various compositions can be used, and CF ₄ and C ₂ F ₆ can be used.
And C ₃ F ₈ , NF ₃ and SF ₆ are preferred. According to a third aspect of the present invention, in the method of manufacturing a semiconductor device according to the second aspect, the first and second dry etchings are discharge-separated microwave-excited plasma type dry etching, The microwave power of the first dry etching is not more than about 1/2 of the microwave power of the first dry etching.

The microwave power of the second dry etching is reduced to about 1 of the microwave power of the first dry etching.
By setting the ratio to / 2 or less, the second dry etching can be performed at a sufficiently low speed as compared with the first dry etching. According to a fourth aspect of the present invention, in the method of manufacturing a semiconductor device according to the second aspect, in the chemical dry etching step, the metal film is selectively etched at a selectivity of 100 or more with respect to the barrier metal film. It is characterized by doing.

By using the first reactive gas and the second reactive gas, the metal film can be selectively etched at a selectivity of 100 or more with respect to the barrier metal film.
According to a fifth aspect of the present invention, in the method of manufacturing a semiconductor device according to the fourth aspect, the first and second dry etchings are performed at a temperature of about 40 ° C. or less. . In order to make the above-mentioned selectivity 100 or more, it is desirable to select the temperature to be about 40 ° C. or less.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a semiconductor device according to the present invention will be described below with reference to FIGS.
FIG. 1 shows a discharge separation type microwave-excited dry etching apparatus suitable for carrying out a first embodiment of a method of manufacturing a semiconductor device according to the present invention. In the etching chamber 2 of the vacuum vessel 1, a mounting table 3 on which the workpiece W is mounted is installed. The mounting table 3 has a temperature control mechanism, and can control the heating temperature of the mounted workpiece W. A gas introduction tube 4 communicates with the upper wall of the vacuum vessel 1, and a discharge tube 5 is connected to the gas introduction tube 4. Reactive gas is introduced into the discharge tube 5 from the gas inlet 6. A microwave waveguide 7 is connected to the discharge tube 5. The microwave waveguide 7 applies a microwave to the discharge tube 5 to generate plasma in the discharge tube 5. An exhaust pipe 8 is connected to a lower wall of the vacuum vessel 1.

Next, the structure of the workpiece W mounted on the mounting table 3 will be described. As shown in FIG. 2, the workpiece W includes a silicon substrate 9, an interlayer insulating film 10 made of a silicon oxide film stacked thereon, an electrode connection hole 11 formed in the interlayer insulating film 10, A titanium film 12 and a titanium nitride film 13 functioning as barrier metal films formed in the electrode connection holes 11 and on the surface of the interlayer insulating film 10, and tungsten laminated on the entire surface of the silicon substrate 9 so as to fill the electrode connection holes 11. And a film 14. In addition,
As the tungsten film 14, a tungsten alloy film or another metal film can be used.

The electrode connection hole 11 is formed in the interlayer insulating film 10
After a resist is applied and patterned, dry etching is performed to make holes. The titanium film 12 and the titanium nitride film 13 are formed by sputtering, and the tungsten film 14 is formed by a CVD (chemical vapor deposition) method.

When the workpiece W having the structure shown in FIG. 2 is mounted on the mounting table 3 shown in FIG. 1, a first etching process is performed. In the first etching process, the workpiece W is heated to about 25 ° C. by the temperature control mechanism built in the mounting table 3, the pressure in the etching chamber 2 is set to 30 Pa, and the microwave power is set to 700 W. ing. In this state, the first reactive gas obtained by mixing the CF ₄ gas, the Cl ₂ gas, and the O ₂ gas is introduced into the discharge tube 5 from the gas inlet 6, and the microwave of 700 W power is applied to the microwave waveguide. 7 is applied to the discharge tube 5 to generate plasma. The first reactive gas introduced into the discharge tube 5 is activated by the plasma, flows into the etching chamber 2, etches the tungsten film 14 of the workpiece W mounted on the mounting table 3, and exhausts the gas. It is discharged from the pipe 8.

In the first etching process, the tungsten film 14 of the workpiece W is etched at a relatively high speed. As a result, as shown in FIG. Tungsten residue 15
Are removed except for The workpiece W undergoes the second etching process after the first etching process. In the second etching process, the heating temperature of the workpiece W and the pressure in the etching chamber 2 are selected to be approximately 25 ° C. and 30 Pa, respectively, which are the same as those in the first etching process, and the microwave power is set to the first etching process. It is selected to be 300 W which is less than half of the case of processing. In this state,
A second reactive gas in which a CF ₄ gas and an O ₂ gas are mixed is introduced into the discharge tube 5 from the gas inlet 6 and 300
A microwave of W power is applied from the microwave waveguide 7 to the discharge tube 5 to generate plasma. The second reactive gas introduced into the discharge tube 5 is activated by the plasma, flows into the etching chamber 2, and etches the tungsten film residue 15 of the workpiece W placed on the mounting table 3. Are discharged from the exhaust pipe 8. The ratio of the CF ₄ gas to the O ₂ gas is 1: (1.5 to 1).
0). The main purpose of selecting this range is to keep the etching rate low. This is because the etching rate can be reduced by setting the ratio of the oxygen gas to all the reactive gases to 50% or more.

In the second etching process, since the amount of the tungsten film to be removed, that is, the tungsten residue 15 to be removed is extremely small as compared with the first etching process, the microwave power is sufficiently reduced as compared with the first etching process. And the etching rate can be sufficiently reduced. Therefore, the titanium nitride film 13 is hardly digged in the tungsten film 14 buried in the electrode connection hole 11.
The upper tungsten film 14 can be almost completely removed.

As described above, by the combination of the first etching and the second etching, the digging amount d of the tungsten film 14 buried in the electrode connection hole 11 can be made extremely small without increasing the overall etching time. Can be controlled so that Further, since the heating temperature of the workpiece W is set to 25 ° C., the tungsten film 14 can be etched with a selectivity of 100 or more with respect to the titanium nitride film 13.

FIG. 4 shows the relationship between the etching time and the etching amount (thickness) of the tungsten film in the above-described first and second etching processes. The straight line A indicates the relationship in the case of the first etching process. And a straight line B represents a relationship in the case of the first etching process, and a hatched region represents a range where a tungsten residue is likely to remain. As can be seen by comparing the straight lines A and B, the etching rate of the first etching process is much higher than the etching speed of the second etching process. Therefore, the first etching process is performed with only a slight tungsten residue remaining.
For example, if the process is completed near T in FIG. 4 and then the second etching process is performed, the digging amount d of the tungsten film 14 in FIG. 3 can be extremely reduced while shortening the entire etching time as much as possible. In particular, since the second etching process is performed at a relatively low speed, the end point can be controlled with high accuracy.

In the above-described embodiment, CF ₄ gas was used as the first and second reactive gases as a gas containing fluorine atoms. However, in addition to CF ₄ gas, C ₂ F ₆ and C ₂
Etc. ₃ F ₈ and NF ₃ and SF ₆ can be used.
Further, a gas other than Cl ₂ can also be used as the gas containing a chlorine atom. Further, in order to etch the tungsten film 14 with respect to the titanium nitride film 13 at a selectivity of 100 or more, in the above-described embodiment, the heating temperature of the workpiece W is set to 25 degrees.
C., but the same effect can be obtained if the temperature is about 40 ° C. or less.

Further, in the embodiment, a discharge-separated type microwave-excited plasma type chemical dry etching method is used, but a dry etching method such as ECR or ICP having a small self-bias effect can also be used.

[0024]

As is apparent from the above description, according to the present invention, since the first etching is performed at a relatively high speed, it is possible to avoid a decrease in the throughput of manufacturing a semiconductor device. Since the etching is performed at a relatively low speed, the end point can be controlled relatively easily. Therefore, substantially all of the residue of the metal film is removed while preventing the metal film in the electrode connection hole from being dug. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a discharge-separated microwave-excited plasma type chemical dry etching apparatus used in an embodiment of a method of manufacturing a semiconductor device according to the present invention.

FIG. 2 is a cross-sectional view showing an object to be processed before etching a tungsten film.

FIG. 3 is a cross-sectional view illustrating a processing object in which a residue of a tungsten film remains.

FIG. 4 is a graph showing a relationship between an etching time and an etching amount for first and second etching processes.

[Explanation of symbols]

 Reference Signs List 9 semiconductor substrate 10 interlayer insulating film 11 electrode connection hole 12, 13 barrier metal film 12 titanium film 13 titanium nitride film 14 metal film (tungsten film)

Claims (5)

[Claims] A step of forming a connection hole for an electrode in an interlayer insulating film of a semiconductor substrate; a step of forming a barrier metal film on the connection hole for the electrode and the interlayer insulating film; Forming a metal film on the connection hole for the electrode and the barrier metal film so as to fill the connection hole, and removing the metal film in a region other than the connection hole for the electrode by chemical dry etching. In the method for manufacturing a semiconductor device provided, the chemical dry etching step includes a first dry etching using a first reactive gas obtained by mixing a gas containing a fluorine atom, a gas containing a chlorine atom, and an oxygen gas; A second dry etching using a second reactive gas obtained by mixing a gas containing a fluorine atom and an oxygen gas, which is performed after the first dry etching; The dry etching is performed at a lower power than the first dry etching, and the ratio of the fluorine-containing gas to the oxygen gas in the second reactive gas is 1: (1.5 to 10). A method for manufacturing a semiconductor device, comprising: 2. The gas containing a fluorine atom comprises CF ₄ and C <sub>2
3. The</sub> method according to claim ₂ , wherein the gas containing chlorine atoms is one selected from F ₆ , C ₃ F ₈ , NF _3, and SF _6, and the gas containing chlorine atoms is Cl _{2. 4.} . 3. The first and second dry etchings are discharge-separated microwave-excited plasma type dry etching, and the microwave power of the second dry etching is the microwave power of the first dry etching. 3. The method of manufacturing a semiconductor device according to claim 2, wherein the ratio is about 1/2 or less. 4. The method according to claim 1, wherein the chemical dry etching step is performed such that the selectivity of the metal film to the barrier metal film is 100.
3. The method according to claim 2, wherein the etching is performed selectively. 5. The method according to claim 4, wherein said first and second dry etchings are performed at a temperature of about 40 ° C. or less.
13. The method for manufacturing a semiconductor device according to item 5.