JP5129456B2 - Method of manufacturing structure having beam portion and MEMS device - Google Patents

Description

  The present invention relates to a method for manufacturing a structure including a beam portion and a micro electro mechanical system (MEMS) device.

  Conventionally, a manufacturing method for manufacturing a structure (for example, a MEMS device) having a beam portion using a micromachining technique has been researched and developed in various places (for example, see Patent Documents 1 and 2).

  For example, an acceleration sensor or a gyro sensor is widely known as a MEMS device having a movable part. However, Patent Document 1 describes a manufacturing method of a microheater which is a kind of a MEMS device having no movable part. ing. Hereinafter, the manufacturing method of this micro heater will be described with reference to FIG.

First, an insulating film 101 made of a TiO ₂ film is formed on one surface of the silicon substrate 100, and subsequently, a metal made of a Pt film that forms the basis of the heating element 103 (see FIG. 7C) on the insulating film 101. By forming the film 102, the structure shown in FIG. 7A is obtained. In Patent Document 1, TiO ₂ is used as the material of the insulating film 101 in order to reduce the difference in linear expansion coefficient between the material of the metal film 102 and the material of the insulating film 101.

  Next, the structure shown in FIG. 7B is obtained by forming a first resist layer 104 patterned according to the shape of the heating element on the metal film 102 using photolithography technology.

  Thereafter, unnecessary portions of the metal film 102 are removed by etching using the first resist layer 104 as a mask to form a heating element 103 made of a part of the metal film 102, thereby obtaining the structure shown in FIG. 7C. .

  Further, after removing the first resist layer 104, the beam portion 111 (see FIG. 7 (f)) on the one surface side of the silicon substrate 100 and the shape of the support portion 110 that supports the beam portion 111 are used. By forming the patterned second resist layer 105, the structure shown in FIG. 7D is obtained.

  Subsequently, by using the second resist layer 105 as a mask, unnecessary portions of the insulating film 101 are removed by etching to form apertures 106, thereby obtaining the structure shown in FIG.

  After that, the silicon substrate 100 is separated from the silicon substrate 100 by forming the cavity 107 by anisotropically etching the silicon substrate 100 from the one surface side through the opening 106 with an alkaline solution (for example, TMAH solution, KOH solution, etc.). By forming the beam portion 111 and removing the second resist layer 105, a microheater having a structure shown in FIG. 7F is obtained.

  In short, in Patent Document 1, the beam portion 111 is separated from the silicon substrate 100 by forming the cavity portion 107 by anisotropic etching utilizing the crystal orientation dependence of the etching rate.

Conventionally, after thin films made of different materials are laminated on one surface side of a silicon substrate, the thin film on the outermost surface side is patterned into a desired shape, and then the thin film on the silicon substrate side is selectively etched as a sacrificial layer. A technique for manufacturing a structure by forming a cavity is known as a surface micromachining technique. However, in Patent Document 2 described above, a silicon layer (active layer) on one surface side of an SOI substrate is patterned. Then, by selectively etching a part of the SiO ₂ film of the SOI substrate as a sacrificial layer to form a cavity, the movable part including the beam part made of a part of the silicon layer is separated from the support substrate of the SOI substrate. Technology is disclosed.
JP-A-8-69858 JP 2004-136396 A

  By the way, in the method for manufacturing a structure including a beam portion disclosed in Patent Document 1, the shape of the cavity 107 is restricted by the surface orientation of the one surface of the silicon substrate 100. There were restrictions on the shape. Although it is conceivable to perform isotropic etching instead of anisotropic etching in the separation step for forming the cavity 107, it is more difficult to control the shape of the cavity 107 in the isotropic etching.

  In general surface micromachining technology, aluminum, polyimide, or the like is used as the material of the above-described sacrificial layer. However, when a structure having a beam portion is manufactured using general surface micromachining technology. Since the gap length between the beam portion and the one surface of the silicon substrate is limited by the thickness of the sacrificial layer, sticking of the separated beam portion to the one surface of the silicon substrate is likely to occur, resulting in a decrease in yield. There was a case.

In addition, as described above, even when the beam portion is configured by a part of the silicon layer using the SiO ₂ film of the SOI substrate as a sacrificial layer, sticking that the separated beam portion sticks to the support substrate easily occurs, and the yield decreases. There was a case. Further, when the beam portion is formed by a part of the silicon layer of the SOI substrate, there is an advantage that a transistor, an IC, or the like can be formed in the silicon layer, but the SOI substrate is expensive, The desired performance of the MEMS device may not be obtained due to the residual stress of the beam portion.

  On the other hand, in the method for manufacturing a structure including a beam portion disclosed in Patent Document 1, the gap length between the inner bottom surface of the cavity portion 107 and the beam portion 111 can be sufficiently increased. However, the etching is performed before the separation step of forming the beam portion 111 separated from the silicon substrate 100 by forming the cavity portion 107 by anisotropic etching utilizing the crystal orientation dependence of the etching rate. It is necessary to protect the parts other than the part in advance, and the etching time in the separation process is long (the etching time of 6 to 7 hours may be required depending on the width dimension of the beam portion 111), which increases the manufacturing cost. End up. A technique for manufacturing a structure having a beam portion by a bulk micromachining technique using an inductively coupled plasma (ICP) type dry etching apparatus is also known, but an ICP type dry etching apparatus is expensive, Manufacturing costs including capital investment will increase.

  The present invention has been made in view of the above-mentioned reasons, and its purpose is that there are few restrictions on the shape of the structure provided with the beam portion, and the structure provided with the beam portion that can reduce the manufacturing cost. A manufacturing method and a MEMS device are provided.

The invention according to claim 1, a structure manufacturing method of having the in the beam portion so as to form the beam portion by processing the thin film and the semiconductor substrate is formed on one surface side of the semiconductor substrate, p-type or an anode forming step of forming the n-type pre-Symbol semiconductor substrate an anode and pattern design in accordance with the shape of the porous portion to form a removal site on the one surface side to another surface side of the semiconductor substrate, the anode and the electrolyte Forming the porous portion having an in-plane distribution of thickness larger than that of the anode on the one surface side of the semiconductor substrate by energizing between the cathode disposed on the one surface side of the semiconductor substrate in the liquid An anodizing step, a thin film forming step for forming the thin film on the one surface side of the semiconductor substrate after the anodizing step, and an unnecessary area around the portion to be the beam portion in the thin film after the thin film forming step. Etching away the part Separating from the semiconductor substrate by forming a cavity by selectively removing the porous part through an opening formed in the opening part forming step and an opening part forming step for forming a hole part And a separation step of forming a beam portion.

  According to the present invention, since the in-plane distribution of the current density of the current flowing through the semiconductor substrate in the anodizing process is determined by the anode pattern formed in the anode forming process, the thickness of the porous part formed in the anodizing process is determined. The in-plane distribution can be controlled, and the beam portion separated from the semiconductor substrate is formed by selectively etching away the porous portion in the separation step to form the cavity portion. In addition, there are few restrictions on the shape of the structure with, and the etching time can be shortened compared to the case where the cavity is formed by anisotropic etching utilizing the crystal orientation dependence of the etching rate, and the manufacturing cost is reduced. Is possible.

  According to a second aspect of the present invention, in the first aspect of the invention, in the thin film forming step, an insulating film is formed as the thin film.

According to the present invention, it is possible to increase the reliability of the beam portion by using a general insulating material in a semiconductor manufacturing process such as SiO ₂ , SiN, or SiON as the material of the thin film.

  According to a third aspect of the present invention, in the first aspect of the invention, in the thin film forming step, a multilayer film is formed as the thin film.

  According to this invention, the residual stress and film thickness of the thin film can be easily controlled, and the degree of freedom of the shape of the beam portion is increased.

  According to a fourth aspect of the invention, in the first aspect of the invention, the semiconductor substrate is a single crystal silicon substrate, and in the thin film formation step, at least a single crystal silicon film is formed as the thin film.

  According to this invention, it is possible to form an electronic circuit portion or the like in the thin film, and it is also possible to form an electronic circuit portion or the like in a portion of the thin film that becomes the beam portion.

  The invention according to claim 5 is characterized in that it has a structure including a beam portion manufactured by the manufacturing method according to any one of claims 1 to 4.

  According to the present invention, the manufacturing cost of the MEMS device can be reduced.

  The invention of claim 6 is characterized in that, in the invention of claim 5, a sensor element and an electronic circuit part cooperating with the sensor element are formed on the beam part.

  According to the present invention, the distance between the sensor element and the electronic circuit unit can be shortened, and the sensor performance can be improved.

  In the invention of claim 1, there are few restrictions on the shape of the structure provided with the beam portion, and the manufacturing cost can be reduced.

  In the invention of claim 5, there is an effect that the manufacturing cost of the MEMS device can be reduced.

(Embodiment 1)
Hereinafter, referring to FIGS. 1A to 1E, a thin film formed on one surface side of a semiconductor substrate and a manufacturing method of a structure including a beam portion formed by processing the semiconductor substrate to form a beam portion will be described. While explaining.

  First, a porous portion 3 made of a porous silicon portion formed as a removal site on one surface side (upper surface side of FIG. 1A) of a semiconductor substrate 1 made of a single crystal silicon substrate (see FIG. 1B). A structure shown in FIG. 1A is obtained by performing an anode forming process in which the anode 2 having a pattern designed according to the shape of the semiconductor substrate 1 is formed on the other surface side of the semiconductor substrate 1 (the lower surface side of FIG. 1A). Here, in the anode forming step, a conductive layer made of an aluminum film serving as the basis of the anode 2 is formed on the one surface side of the semiconductor substrate 1 by, for example, sputtering or vapor deposition, and then photolithography technology and etching technology are used. The anode 2 made of a part of the conductive layer is formed by patterning the conductive layer.

  After the anode forming step, current is passed between the anode 2 and the cathode disposed on the one surface side of the semiconductor substrate 1 in the electrolytic solution for anodic oxidation, and the above-mentioned porosity is formed on the one surface side of the semiconductor substrate 1. The structure shown in FIG. 1B is obtained by performing the anodic oxidation process for forming the mass portion 3. In the present embodiment, since the semiconductor substrate 1 having a p-type conductivity is used, it is not necessary to irradiate light on the one surface side of the semiconductor substrate 1 in the anodizing process. When using an n-type conductivity type, it is necessary to irradiate light. Moreover, as the above-mentioned electrolytic solution, a mixed solution in which a 55 wt% hydrogen fluoride aqueous solution and ethanol are mixed at a ratio of 1: 1 is used. However, the concentration of the hydrogen fluoride aqueous solution or the mixture of the hydrogen fluoride aqueous solution and ethanol is used. The ratio is not particularly limited.

By the way, in this embodiment, since the silicon substrate is used as the semiconductor substrate 1 as described above, when a part of the semiconductor substrate 1 is made porous in the anodic oxidation process, the holes are h ⁺ and the electrons are e ^If this is the case, the following reaction is considered to have occurred.
Si + 2HF + (2-n) h ⁺ → SiF ₂ + 2H ⁺ + ne ⁻
SiF ₂ + 2HF → SiF ₄ + H ₂
SiF ₄ + 2HF → SiH ₂ F ₆
That is, in the anodic oxidation of the semiconductor substrate 1 made of a silicon substrate, it is known that porosity or electropolishing occurs due to the balance between the supply amount of F ions and the supply amount of holes h ⁺ , and the supply amount of F ions. When the number of holes is larger than the supply amount of holes, porosification occurs, and when the supply amount of holes h ⁺ is larger than the supply amount of F ions, electrolytic polishing occurs. Accordingly, when a semiconductor substrate 1 having a p-type conductivity is used as in the present embodiment, the rate of pore formation by anodic oxidation is determined by the supply amount of holes h ^+. The speed of the porous formation is determined by the current density of the current flowing through and the thickness of the porous portion 3 is determined. Here, for example, when the planar shape of the anode 2 is circular, the current density has an in-plane distribution in which the current density gradually decreases as the distance from the center line along the thickness direction of the anode 2 decreases. Thus, the porous portion 3 formed on the one surface side of the semiconductor substrate 1 is gradually thinned away from the center line of the anode 2. The shape of the porous portion 3 is not only the shape of the anode 2, but also the resistivity and thickness of the semiconductor substrate 1, the electric resistance value of the electrolytic solution, the distance between the semiconductor substrate 1 and the cathode, and the planar shape of the cathode. It can also be controlled by, for example.

After the above-described anodic oxidation step, a structure shown in FIG. 1C is obtained by performing a thin film forming step of forming the thin film 4 made of an insulating film on the one surface side of the semiconductor substrate 1. Here, as the insulating film constituting the thin film 4, for example, a low-stress SiN film, a stress-adjusted SiON film, a laminated film of a SiO ₂ film and a SiN film, or the like may be formed. Here, in order to form a low-stress SiN film, for example, the LPCVD method may be adopted as a film-forming method, and the SiN film may be deposited under Si-rich conditions. The stress of the SiN film having a strong tensile stress can be reduced. In addition, in order to form a stress-adjusted SiON film, for example, a PECVD method is adopted as a film formation method, and a gas flow rate ratio of SiH ₄ gas, N ₂ O gas, and N ₂ gas (or NH ₃ gas) is set. The stress can be adjusted by appropriately setting and adjusting the composition ratio of O and N in the SiON film. In other words, the residual stress of the SiO film becomes compressive stress, but by using the SiON film, the compressive stress can be reduced, or the residual stress can be changed to tensile stress instead of compressive stress. In the case where the thin film 4 is composed of a laminated film of SiO ₂ film and SiN film, for example, a SiN film deposition process by LPCVD method, a SiO ₂ film deposition process by PECVD method, a SiN film deposition by PECVD method, and the like. The steps may be performed sequentially, and the stress can be adjusted by laminating a SiN film in which tensile stress is generated and a SiO ₂ film in which compressive stress is generated.

  After the above-described thin film forming step, an opening portion is formed in which an unnecessary portion around a portion that becomes the beam portion 7 (see FIG. 1E) in the thin film 4 is removed by etching to form an opening portion (through hole) 5. By performing the process, the structure shown in FIG. In addition, by performing this opening part formation process, the thin film 4 remains in the site | part corresponding to the beam part 7, and the site | part corresponding to the support part 8 (refer FIG.1 (e)) which supports the beam part 7. FIG.

  The separation step of forming the beam portion 7 separated from the semiconductor substrate 1 is performed by selectively removing the porous portion 3 by etching through the opening portion 5 formed in the opening portion forming step to form the cavity portion 6. Thus, a structure including the beam portion 7 having the structure shown in FIG. 1E can be obtained, and a dicing process may be performed thereafter. Here, as an etchant for selectively removing the porous portion 3 by etching, an alkaline solution such as a KOH solution or a TMAH solution may be used. Unlike a bulk silicon substrate, the porous portion 3 is etched even at room temperature. Therefore, the etching selectivity can be increased. Here, the etching rate of the porous part 3 composed of the porous silicon part is higher than that of the bulk silicon substrate and depends on the porosity, but the etching rate at room temperature is 80 ° C. to 100 ° C. A value of about 20 to 30 times the etching rate can be obtained, and the etching time required for forming the cavity 6 can be greatly shortened. Further, by using an alkaline solution as an etchant in the separation step, the anode 2 made of an aluminum film can be removed by etching in the separation step, so there is no need to provide a separate step for removing the anode 2. There are also advantages. Note that the number of the opening portions 5 formed in the above-described opening portion forming step may be one. However, the formation of a plurality of openings is a solution of an etching solution when the porous portion 3 is selectively removed by etching in the separation step. It becomes easy to pull out.

According to the manufacturing method of the structure including the beam portion 7 of the present embodiment described above, the current density of the current flowing in the semiconductor substrate 1 in the anodic oxidation process is determined by the pattern of the anode 2 formed in the anode forming process. Since the distribution is determined, it is possible to control the in-plane distribution of the thickness of the porous portion 3 formed in the anodic oxidation process, and the porous portion 3 is selectively removed by etching in the separation step. Since the beam portion 7 separated from the semiconductor substrate 1 is formed by forming the structure, there are few restrictions on the shape of the structure including the beam portion 7, and the etching rate depends on the crystal orientation as in Patent Document 1 above. Compared with the case where the cavity 107 (see FIG. 7) is formed by anisotropic etching utilizing the property, the etching time can be shortened, and the manufacturing cost can be reduced. Further, as described above, the reliability of the beam portion 7 can be improved by using a general insulating material in the semiconductor manufacturing process such as SiO ₂ , SiN, or SiON as the material of the thin film 4.

(Embodiment 2)
In the present embodiment, there is a structure manufactured by the method for manufacturing a structure including the beam portion 7 described in the first embodiment, and at least one of the element portions 10 is formed on the beam portion 7 as shown in FIG. As an example of the MEMS device having a portion, a micro heater having the configuration shown in FIG. 3 is illustrated.

The MEMS device of the present embodiment uses a structure including the beam portion 7 for a heat insulating structure, and the thin film 4 is configured by a laminated film of a SiO ₂ film and a SiN film. A heating element 11 made of a Pt thin film patterned in a predetermined shape is formed on the beam portion 7 and is electrically connected to the heating element 11 on the surface side of the support portion 8 supporting the beam portion 7 in the thin film 4. Connected pads 12 and 12 are formed. Therefore, the heating element 11 can be caused to generate heat by flowing a current to the heating element 11 through the pair of pads 12 and 12.

In the MEMS device of the present embodiment, the planar shape of the support portion 8 is formed in a rectangular frame shape, the planar shape of the beam portion 7 is formed in a strip shape, and both end portions of the beam portion 7 are support portions. 8 are formed integrally with two corners, and triangular openings 5 are formed on both sides of the beam portion 7 in the width direction. Here, in the MEMS device of this embodiment, the film thicknesses of the lower SiO ₂ film and the upper SiN film constituting the thin film 4 are set to 1 μm and 0.1 μm, and the depth of the cavity 6 is set to 100 μm. Although set, these numerical values are not particularly limited. However, it is desirable that the depth dimension of the cavity 6 is large in order to prevent the heat generated by the heating element 11 from being absorbed by the semiconductor substrate 1.

  Therefore, since the MEMS device according to the present embodiment includes the structure manufactured by the method for manufacturing the structure including the beam portion 7 described in the first embodiment, the cost of the MEMS device can be reduced. In addition to achieving high performance. In the present embodiment, the thin film 4 is composed of a laminated film of a SiO2 film and a SiN film. However, the material of the thin film 4 is not limited to the laminated film, and for example, as a material of an interlayer insulating film by ULSI A low dielectric constant (low-k) insulating material such as the used porous silica may be employed, and the heat insulation can be improved by employing the low-k insulating material.

  In the present embodiment, the micro heater is illustrated as an example of the MEMS device using the structure including the beam portion 7 for the heat insulating structure. However, the MEMS device using this type of heat insulating structure is not limited to the micro heater. For example, an infrared sensor, a pressure wave generator that generates an ultrasonic wave or an impulse pressure wave, and the like are also conceivable.

(Embodiment 3)
In this embodiment, it has a structure manufactured by the manufacturing method of the structure provided with the beam part 7 demonstrated in Embodiment 1, and as shown in the above-mentioned FIG. As an example of the MEMS device having at least a part, a resonance type ultrasonic sensor having the configuration shown in FIG. 4 is illustrated.

  In the MEMS device of the present embodiment, a structure including the beam portion 7 is used for the resonance structure, the beam portion 7 is cantilevered by the support portion 8, and a piezoelectric element is formed as the element portion 10. In the element portion 10 made of a piezoelectric element, a lower electrode 13 having a rectangular planar shape is formed across the beam portion 7 and the support portion 8. A rectangular shape having a smaller planar size than the lower electrode 13 is formed on the lower electrode 13. The piezoelectric thin film 14 is formed, a rectangular upper electrode 15 having a smaller planar size than the piezoelectric thin film 14 is formed on the piezoelectric thin film 14, and the piezoelectric thin film 14 is not laminated on the lower electrode 13. A pad 16 a is formed, and a pad 16 b is formed on the upper electrode 15. Here, each of the pads 16 a and 16 b is formed at a position overlapping the support portion 8 in the thickness direction of the semiconductor substrate 1.

In the MEMS device of the present embodiment, Yes in the same manner as a thin film 4 and Embodiment 2 is constituted by a laminated film of a SiO ₂ film and the SiN film, the lower layer of SiO ₂ film and the upper layer of the SiN film constituting the thin film 4 The respective film thicknesses are set to 1 μm and 0.1 μm, and the depth dimension of the cavity 6 is set to 100 μm, but these numerical values are not particularly limited.

  Therefore, since the MEMS device according to the present embodiment includes the structure manufactured by the method for manufacturing the structure including the beam portion 7 described in the first embodiment, the cost of the MEMS device can be reduced. In addition to achieving high performance.

  In the present embodiment, an ultrasonic sensor is exemplified as an example of a MEMS device using a structure including the beam portion 7 as a resonance structure. However, as a MEMS device using this type of resonance structure, an ultrasonic sensor is used. For example, a gyro sensor is also conceivable.

(Embodiment 4)
In this embodiment, as a MEMS device manufactured according to the manufacturing method of the structure including the beam portion 7 described in the first embodiment, for example, infrared rays are applied on the beam portion 7 as shown in FIG. The MEMS device in which the element unit 10 including the sensor element to be detected is formed and the electronic circuit unit 30 that cooperates with the element unit 10 is formed in the beam unit 7 is illustrated.

  In the present embodiment, the thin film 4 serving as the foundation of the beam portion 7 is configured by a laminated film of a single crystal silicon film 4a and an insulating film 4b, and on the portion corresponding to the beam portion 7 in the insulating film 4b. The element portion 10 is formed, and the electronic circuit portion 30 is formed on the surface side of the portion corresponding to the beam portion 7 in the single crystal silicon film 4a. The element portion 10 and the electronic circuit portion 30 are connected to the insulating film 4b. Are electrically connected through a plurality of through-hole wirings (not shown) penetrating in the thickness direction of the portion corresponding to the beam portion 7. The electronic circuit unit 30 is composed of an integrated circuit including a resistor, a diode, a transistor, and the like, and is designed to have a function of performing signal processing for amplifying the output signal of the element unit 10 that is a sensor element. .

  Therefore, since the MEMS device according to the present embodiment includes the structure manufactured by the method for manufacturing the structure including the beam portion 7 described in the first embodiment, the cost of the MEMS device can be reduced. In addition to achieving high performance. Further, in the MEMS device of the present embodiment, the distance between the sensor element constituting the element unit 10 and the electronic circuit unit 30 can be shortened, and the element unit 10 and the electronic circuit unit 30 are determined depending on the thickness dimension of the insulating film 4b. Therefore, it is possible to prevent noise from being superimposed on a weak output signal from the element unit 10 and improve the sensor performance.

  Hereinafter, the manufacturing method of the MEMS device according to the present embodiment will be described with reference to FIGS. 5A to 5G. However, the manufacturing method is the same as the manufacturing method of the structure including the beam portion 7 described in the first embodiment. Explanation of the steps is omitted as appropriate.

  First, a porous portion 3 composed of a porous silicon portion formed as a removal site on one surface side (upper surface side in FIG. 5A) of a semiconductor substrate 1 composed of a single crystal silicon substrate (see FIG. 5B). A structure shown in FIG. 5A is obtained by performing an anode forming step in which the anode 2 having a pattern designed according to the shape of the semiconductor substrate 1 is formed on the other surface side of the semiconductor substrate 1 (the lower surface side of FIG. 5A).

  After the anode forming step, current is passed between the anode 2 and the cathode disposed on the one surface side of the semiconductor substrate 1 in the electrolytic solution for anodic oxidation, and the above-mentioned porosity is formed on the one surface side of the semiconductor substrate 1. The structure shown in FIG. 5B is obtained by performing the anodic oxidation process for forming the mass portion 3.

  After the above-described anodic oxidation step, by performing a crystal growth step of forming the single crystal silicon film 4a on the one surface side of the semiconductor substrate 1 by a PVD method such as a PECVD method, an LPCVD method, or a sputtering method, The structure shown in FIG. 5C is obtained.

  Next, the structure shown in FIG. 5D is obtained by performing a circuit forming process for forming the above-described electronic circuit section 30 on the single crystal silicon film 4a using a known IC manufacturing technique or the like.

  Thereafter, an insulating film forming step for forming the insulating film 4b on the single crystal silicon film 4a is performed, and then the element portion 10 is formed on the insulating film 4b by using a thin film forming technique, a photolithography technique, an etching technique, and the like. The structure shown in FIG. 5E is obtained by performing the element part forming step. Here, as a method for forming the insulating film 4b in the insulating film forming step, a method similar to the method for forming the thin film 4 described in the first embodiment may be employed. In the present embodiment, as described above, the single crystal silicon film 4a and the insulating film 4b constitute the thin film 4 serving as the foundation of the beam portion 7 and the support portion 8, and the above-described crystal growth step and insulating film formation are performed. The process forms a thin film forming process for forming the thin film 4.

  After the above-described thin film forming step, an opening portion is formed in which an unnecessary portion around the portion that becomes the beam portion 7 (see FIG. 5G) in the thin film 4 is removed by etching to form an opening portion (through hole) 5. By performing the steps, the structure shown in FIG. In addition, by performing this opening part formation process, as for the thin film 4, the site | part corresponding to the beam part 7 and the site | part corresponding to the support part 8 (refer FIG.5 (g)) which support the beam part 7 remain.

  The separation step of forming the beam portion 7 separated from the semiconductor substrate 1 is performed by selectively removing the porous portion 3 by etching through the opening portion 5 formed in the opening portion forming step to form the cavity portion 6. Thus, the MEMS device having the structure shown in FIG. 5G can be obtained, and then a dicing process may be performed. In this embodiment, the anode 2 made of the aluminum film can be removed by etching in the separation step by using an alkaline solution as an etchant in the separation step. Therefore, a step for removing the anode 2 is separately performed. There is also an advantage that it is not necessary to provide it.

(Embodiment 5)
In the present embodiment, a capacitive acceleration sensor having the configuration shown in FIG. 6 is illustrated as a MEMS device manufactured according to the method for manufacturing a structure including the beam portion 7 described in the first embodiment. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted suitably.

  In the acceleration sensor of the present embodiment, the thin film 4 is made of a single crystal silicon film, and the rectangular frame-shaped spring portions 23 are formed at both ends of the beam portion 7 in the longitudinal direction (vertical direction in FIG. 6). Thus, the intermediate part inside the both spring parts 23 can be displaced in the longitudinal direction. Here, a plurality of (five in the illustrated example) movable comb electrodes 22 are arranged in the longitudinal direction of the beam portion 7 on both side surfaces in the width direction of the beam portion 7. On the other hand, a plurality of (five in the illustrated example) fixed combs respectively facing the movable comb electrode 22 in the longitudinal direction of the beam portion 7 on the inner surface of the support portion 8 and facing the beam portion 7. The tooth electrode 21 is arranged in a line. Each movable comb electrode 22 and each fixed comb electrode 21 are separated from each other, and the distance between the movable comb electrode 22 and the fixed comb electrode 21 when the beam portion 7 is displaced in the longitudinal direction of the beam portion 7. A change in electrostatic capacitance accompanying the change can be detected.

Each of the support portion 8, the beam portion 7, each spring portion 23, each fixed comb electrode 21, and each movable comb electrode 22 is configured by a part of the thin film 4 made of a single crystal silicon film. The spring portions 23, the fixed comb electrodes 21, and the movable comb electrodes 22 are separated from the semiconductor substrate 1 by forming the cavity 6 in the semiconductor substrate 1. Here, the movable comb electrode 22 provided on one side of the beam portion 7 and the movable comb electrode 22 provided on the other side are from the center line of the comb groove formed between the fixed comb electrodes 21. They are arranged in different directions, and electrostatic force between the movable comb electrode 22 and the fixed comb electrode 21 on both sides in the width direction of the beam portion 7 when acceleration acts in the longitudinal direction of the beam portion 7. Since the change in capacitance value is different, the direction of acceleration can be detected. Further, the movable comb electrode 22 and the fixed comb electrode 21 are not short-circuited by providing an insulating separation portion at an appropriate portion of the thin film 4 by an ion implantation technique or the like.
In the acceleration sensor of this embodiment, the thickness of the beam portion 7 can be controlled by the growth thickness of the single crystal silicon film constituting the thin film 4, and the film quality of the single crystal silicon film is the silicon layer (active layer) of the SOI substrate. Therefore, the same characteristics as those of an acceleration sensor formed using an SOI substrate can be obtained.

On the other hand, in the capacitance type acceleration sensor using the SOI substrate, in order to prevent the beam portion from hitting the support substrate of the SOI substrate when the beam portion is displaced, the support substrate in addition to the SiO ₂ film below the beam portion. It is necessary to etch away a part of the surface from the back side. However, in the acceleration sensor of the present embodiment, it is possible to prevent the beam portion 7 from hitting the semiconductor substrate 1 by forming the cavity portion 6. Moreover, since the cover member only needs to be joined to the support portion 8 when packaging, the manufacturing becomes easy and the entire cost including the package can be reduced. In addition, if the porous portion is selectively etched away at room temperature using an alkaline solution such as a TMAH solution or a KOH solution as an etchant in the separation step described in the first embodiment, at the time of etching in the separation step, It is possible to prevent the portions corresponding to the beam portion 7, each spring portion 23, each fixed comb electrode 21, each movable comb electrode 22, etc. from being eroded, and to prevent deterioration of sensor characteristics. .

  Therefore, since the MEMS device according to the present embodiment includes the structure manufactured by the method for manufacturing the structure including the beam portion 7 described in the first embodiment, the cost of the MEMS device can be reduced. In addition to achieving high performance.

  In this embodiment, an acceleration sensor is illustrated as an example of a MEMS device that uses a structure including the beam portion 7 as a displacement mechanism. However, a MEMS device that uses this type of displacement mechanism is not limited to an acceleration sensor. For example, a pressure sensor, a gyro sensor, etc. are also considered.

  By the way, in each said embodiment, although the silicon substrate is employ | adopted as the semiconductor substrate 1, the semiconductor substrate 1 is not restricted to a silicon substrate, For example, it can be made porous by anodic oxidation processes, such as a Ge substrate and a SiC substrate. Other semiconductor substrates may be used.

6 is an explanatory diagram of a method for manufacturing a structure including a beam portion in Embodiment 1. FIG. 6 is a schematic cross-sectional view showing a basic configuration of a MEMS device in Embodiment 2. FIG. It is a schematic plan view which shows an example of the MEMS device same as the above. 10 is a schematic plan view illustrating an example of a MEMS device according to Embodiment 3. FIG. It is explanatory drawing of the manufacturing method of the MEMS device in Embodiment 4. FIG. 10 is a schematic plan view illustrating an example of a MEMS device according to a fifth embodiment. It is explanatory drawing of the manufacturing method of the microheater which shows a prior art example. It is sectional drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Anode 3 Porous part 4 Thin film 5 Opening part 6 Cavity part 7 Beam part 8 Support part

Claims (6)

A structure manufacturing method of having the in the beam portion so as to form the beam portion by processing the thin film and the semiconductor substrate is formed on one surface side of the semiconductor substrate, p-type or n-type before Symbol semiconductor substrate Forming an anode on the other surface side of the semiconductor substrate with a pattern designed according to the shape of the porous portion formed as a removal site on the one surface side of the semiconductor substrate; An anodic oxidation step of energizing between the cathode disposed on the one surface side and forming the porous portion having an in-plane distribution of thickness larger than the anode on the one surface side of the semiconductor substrate; A thin film forming step for forming the thin film on the one surface side of the semiconductor substrate after the oxidation step, and an unnecessary portion around the portion that becomes the beam portion in the thin film after the thin film forming step is removed by etching. Open to form a hole Part forming step and separation step of forming a beam part separated from the semiconductor substrate by selectively etching away the porous part through the hole part formed in the hole part forming process to form a cavity part A method of manufacturing a structure having a beam portion, characterized by comprising:   2. The method for manufacturing a structure having a beam portion according to claim 1, wherein an insulating film is formed as the thin film in the thin film forming step.   The method for manufacturing a structure having a beam portion according to claim 1, wherein a multilayer film is formed as the thin film in the thin film forming step.   2. The method of manufacturing a structure having a beam portion according to claim 1, wherein the semiconductor substrate is a single crystal silicon substrate, and in the thin film formation step, at least a single crystal silicon film is formed as the thin film.   A MEMS device comprising a structure including a beam portion manufactured by the manufacturing method according to claim 1.   6. The MEMS device according to claim 5, wherein a sensor element and an electronic circuit part that cooperates with the sensor element are formed on the beam part.

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