JPH11214707A - Manufacture of semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sensitivity and yield of a semiconductor element by cutting down the strain in a thin-film silicon substrate, for increasing the accuracy of photolithography. SOLUTION: In the manufacture of a semiconductor element, a recession 1a having at least one protrusion 1c is formed on a supporting substrate 1 for supporting a silicon substrate by the protrusion 1c to joint a silicon substrate with a surface 1b containing the recession 1a of the supporting substrate 1. Next, the silicon substrate is polished to be processed into a thin-film silicon substrate 2h which is supported by the protrusion 1c and then the thin-film silicon substrate 2h is photoetched by the use of a photomask 16 to form a movable part separated from the protrusion part 1c in the region of the recession 1a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device such as an angular velocity sensor or an acceleration sensor using a photo-etching technique, a semiconductor fine processing technique, or the like.

[0002]

2. Description of the Related Art Conventionally, ultra-small semiconductor elements such as angular velocity sensors, acceleration sensors, pressure sensors, and the like have been manufactured using photoetching technology and semiconductor fine processing technology. A method of manufacturing the angular velocity sensor 20 will be described as a conventional method of manufacturing a semiconductor device with reference to FIGS.

In FIG. 17, reference numeral 11 denotes a maximum thickness of 500
A support substrate made of a Pyrex glass substrate having a thickness of μm. As shown in FIG. 25, a free vibration space of a movable portion of the angular velocity sensor 20 shown in FIG.
For example, a concave portion 11a having a size of 1 mm square and a depth of 50 μm
Is formed. Reference numeral 11b denotes a surface of the support substrate 11 including the concave portion 11a. A silicon substrate 12 has a thickness of 300 μm and has the same size as the support substrate 11.

[0004] In FIG.
The surface 11b containing a and the silicon substrate 12 are anodically bonded in a 400 ° C. atmosphere. The internal pressure of the concave portion 11a sealed by the anodic bonding becomes a low pressure of less than 1 atm depending on the temperature conditions at the time of the anodic bonding.

In FIG. 19, a silicon substrate 12 is formed to a predetermined thickness, for example, 20 μm by mechanical polishing and chemical polishing.
After polishing to a thickness of m, a thin film silicon substrate 12a is obtained.
Since the internal pressure of the concave portion 11a is lower than the atmospheric pressure, the thin film silicon substrate 12a is distorted inward under the atmospheric pressure. The amount of this distortion depends on the thin film silicon substrate 12a.
And the size of the recess 11a. In the thin-film silicon substrate 12a having a thickness of 20 μm and the concave portion 11a having a size of 1 mm square, distortion of about 5 μm at maximum, that is, inward bending occurs.

In FIG. 20, a positive photoresist 13 is applied on a thin-film silicon substrate 12a. The coating surface of the photoresist 13 is similarly distorted in response to the distortion of the thin film silicon substrate 12a. The photoresist 13 is exposed and developed using the positive type photomask 14 having the planar shape of the angular velocity sensor 20 shown in FIG. 26 to form a resist mask 13a shown in FIG.

In FIG. 22, a thin film silicon substrate 12a is dry-etched by RIE (reactive ion etching) using a resist mask 13a and sulfur hexafluoride (SF ₆ ) gas in the same atmosphere as atmospheric pressure. I do. FIG. 22 shows a state in the middle of dry etching, and the thin film silicon substrate 12a is in a curved state for the above-described reason. However, as shown in FIG. 23, when the etching of the thin film silicon substrate 12a progresses and the etching hole leads to the closed recess 11a, the internal pressure of the recess 11a becomes the same pressure as the atmospheric pressure, and 12a (such as the vibrating section 21 shown in FIG. 26) has no distortion and is in a uniform plane state. Then, as shown in FIG. 24 and FIG. 26, the angular velocity sensor 20 is completed by removing the resist mask 13a.

Next, the structure of the angular velocity sensor 20 will be described with reference to FIG. 21 is an angular velocity sensor 20
A plurality of movable electrodes 2b, 2c, 2d, and 2e are respectively formed on the end faces of four sides of the rectangular vibrating portion serving as a load mass.

From the four corners of the vibrating part 21, L
The four beams 2f bent in a letter shape extend and are connected to the fixed portion 2g. The fixing portion 2 g is provided in the concave portion 11 of the support substrate 11.
It is formed on the surface containing a. And the vibrating part 21
Are supported by the fixed portion 2g via these four beams 2f, and can freely vibrate in the XY directions by bending of the beams 2f.

Further, the movable electrodes 2b, 2c, 2d, 2e
Face the fixed electrodes 3b, 3c, 3d, and 3e via gaps, respectively. Then, the capacitor 4 is formed by the movable electrode 2b and the fixed electrode 3b. The capacitor 5 is formed by the movable electrode 2c and the fixed electrode 3c.
The capacitor 6 is formed by the movable electrode 2d and the fixed electrode 3d. Further, the capacitor 7 is formed by the movable electrode 2e and the fixed electrode 3e. The fixed electrodes 3b, 3
c, 3d, 3e are respectively coupled to rectangular fixing portions 4b, 5c, 6d, 7e insulated from the support substrate 11.

The vibrating section 21, the movable electrodes 2b to 2e,
The beam 2f forms a movable part of the angular velocity sensor 20, and
Fixed part 2g, fixed electrodes 3b to 3e, fixed parts 4b and 5c,
6 d and 7 e constitute a fixed portion of the angular velocity sensor 20.

Next, the operation of the angular velocity sensor 20 shown in FIG. 26 will be described. Since the fixed portion 2g is connected to the ground and operated, the vibrating portion 21 and the movable electrodes 2b, 2b
c, 2d and 2e are also connected to the ground.

A voltage is alternately applied to the capacitors 4 and 5, and the vibrating section 21 is vibrated in the X-axis direction by electrostatic attraction. As described above, when the angular velocity sensor 20 rotates about the Z axis while the vibrating section 21 is vibrating, the vibrating section 21 vibrates also in the Y-axis direction by receiving the Coriolis force generated by the rotational force. Become like The vibration component in the Y-axis direction is detected as a change in capacitance by the capacitors 6 and 7, and the changed capacitance is converted into a voltage and differentially amplified to obtain an angular velocity.

[0014]

However, in the conventional method for manufacturing a semiconductor device, as shown in FIG. 19, when the silicon substrate 12 is polished thinly, the thin film silicon substrate 12a is distorted inward due to atmospheric pressure. Therefore, in the resist coating step, the surface of the resist 13 is also similarly distorted like the thin film silicon substrate 12a.
Further, as shown in FIGS. 20 and 21, when performing photolithography using a contact aligner, the adhesion between the photomask 14 and the resist 13 is deteriorated at the distorted portion, and the patterned resist mask 13a has a defect. And the variation in the pattern size of the resist mask 13a increases. This variation increases by about 0.2 μm as compared with a case where there is no distortion. Therefore, as shown in FIG. 26, the semiconductor element 20 manufactured by the conventional manufacturing method is, for example, a movable electrode 2b.
2e and the miniaturization of the fixed electrodes 3b to 3e were hindered, the sensitivity was reduced, and the yield was poor.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a semiconductor device in which the accuracy of photolithography is improved by reducing the distortion of a thin film silicon substrate, and the sensitivity and yield of the semiconductor device are improved. .

[0016]

According to a first aspect of the present invention, in a method of manufacturing a semiconductor device having a movable portion and a fixed portion, a concave portion having at least one projecting portion is formed on a supporting substrate, and the projecting portion is formed. The silicon substrate is bonded to the surface including the concave portion of the support substrate by supporting the silicon substrate, and the silicon substrate is thinly polished and processed into a thin film silicon substrate supported by the protrusions. The movable portion is formed in a region of the concave portion apart from the projecting portion by photoetching.

According to the present invention, a concave portion for providing a free vibration space of a movable portion of a semiconductor element is formed in a support substrate. And
The supporting substrate is anodic-bonded or directly bonded to the silicon substrate on the surface including the concave portion. Due to this joining, the internal pressure of the recess sealed decreases to a level lower than the atmospheric pressure due to the temperature conditions of the joining and the like. In order to make movable parts of semiconductor elements,
When the silicon substrate is thinly etched and processed into a thin film silicon substrate, the thin film silicon substrate in the concave region tends to be distorted inward due to atmospheric pressure. However, since at least one protruding portion is provided in the concave portion and supports the thin film silicon substrate from the inside, the thin film silicon substrate can maintain a uniform flat surface without being distorted inward of the concave portion.

As described above, according to the present invention, the thin film silicon substrate can be maintained in a uniform plane against the atmospheric pressure by the protrusion, the resist coating surface can be maintained in a uniform plane, and the thin film silicon substrate is distorted. In this case, the adhesion between the photomask and the photoresist is improved as compared with the case where the resist mask is provided, and a decrease in the accuracy of the resist mask can be prevented. This allows
The movable part and the fixed part of the semiconductor element can be miniaturized, and the sensitivity and the yield can be improved. The protruding portion is formed in an appropriate shape at a position apart from the movable portion of the semiconductor element.

According to a second aspect of the present invention, in the method of manufacturing a semiconductor device having a movable portion and a fixed portion, a concave portion having at least one protrusion is formed in a silicon substrate.
The projection supports the silicon substrate, and a support substrate is bonded to the surface of the silicon substrate including the concave portion. The silicon substrate is thinly polished and processed into a thin film silicon substrate supported by the projection. The movable portion is formed in the region of the concave portion apart from the projecting portion by photoetching a silicon substrate.

According to the present invention, a concave portion providing a free vibration space of a movable portion of a semiconductor element is formed in a silicon substrate, and at least one protrusion is formed in the concave portion. Then, the surface of the silicon substrate including the concave portion and the support substrate are anodic-bonded or directly bonded. At the same time, the tip surface of the protrusion is joined to the support substrate. By this joining, similarly to the first aspect of the present invention, a closed concave portion having a pressure lower than the atmospheric pressure is formed. Other functions are substantially the same as those of the first aspect.

According to a third aspect of the present invention, the concave portion is formed by leaving the protruding portion in a region of the support substrate or the silicon substrate where the concave portion is formed.

According to the present invention, the concave portion is formed by leaving a part of the support substrate or the silicon substrate, that is, the projecting portion in the region where the concave portion is formed. Therefore, the thin-film silicon substrate is supported on a uniform plane by the projection, and no distortion occurs.

According to a fourth aspect of the present invention, after the concave portion is formed in the support substrate or the silicon substrate, a projecting portion is formed in the concave portion.

According to the present invention, after the concave portion is formed in the support substrate or the silicon substrate, a protrusion having a substantially uniform plane with the surface including the concave portion of the support substrate or the silicon substrate is formed in the concave portion. This protruding portion is made by depositing or bonding a material such as silicon, glass, or metal, but any material can be used as long as it does not deform under atmospheric pressure. The projections support the thin-film silicon substrate in a uniform plane, so that no distortion occurs.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS.
As a first embodiment of a method for manufacturing a semiconductor device according to the present invention, a method for manufacturing an angular velocity sensor 10 will be described.

In FIG. 1, 1 indicates a maximum thickness of 500 μm.
As shown in FIG. 8, a center portion on the front side provides a free vibration space for a movable portion of the acceleration sensor 10 as shown in FIG.
A concave portion 1a having an m-square and a depth of 50 μm is formed. In the concave portion 1a, the tip surface has a size of 10 μm at each of the four corners and the center.
The columns 1c each having an m-square and a height of 50 μm are formed. Since these columns 1c have the same height as the height of the side wall of the concave portion 1a, the front end surface of the column 1c is flush with the surface 1b of the support substrate 1. These pillars 1c are used to form the recess 1a by, for example, etching.
The support substrate 1 may be formed partially, or after the concave portion 1a is formed, another structural material such as silicon, glass, metal, or the like may be deposited or bonded.
Reference numeral 2 denotes a silicon substrate having a thickness of 300 μm and the same size as the support substrate 1.

In FIG. 2, the silicon substrate 2 is anodically bonded to the front surface 1b of the support substrate 2 including the concave portion 1a and the tip surface of the column 1c. In this anodic bonding, the substrate temperature of the support substrate 1 and the silicon substrate 2 is set to 400 ° C., the support substrate 1 is used as a cathode, and the silicon substrate 2 is used as an anode.
This is performed by applying a DC voltage of kV. Then, due to the anodic bonding, the concave portion 1a is hermetically closed and has an internal pressure lower than the atmospheric pressure depending on the temperature conditions of the anodic bonding. Then, the silicon substrate 2 has a structure supported by the columns 1c.

In FIG. 3, the silicon substrate 2 is etched with an aqueous solution of potassium hydroxide (KOH) to have a thickness of 20%.
It is processed into a 2 μm thin film silicon substrate 2h. The thin-film silicon substrate 2h tries to be distorted into the recess 1a due to the atmospheric pressure, but maintains a uniform plane without being distorted by the support 1c.

In FIG. 4, a positive photoresist 15 is applied on the thin film silicon substrate 2h. And FIG.
The photoresist 15 is exposed and developed using a positive photomask 16 having the planar shape of the angular velocity sensor 10 excluding the column 1c shown in FIG. 5 to form a patterned resist mask 15a shown in FIG.

In FIG. 6, RIE using sulfur hexafluoride (SF ₆ ) gas is performed using a resist mask 15a.
Dry etching is performed on the thin-film silicon substrate 2h by (reactive ion etching).

In FIGS. 7 and 9, the unnecessary resist mask 15a is removed by O ₂ ashing,
An angular velocity sensor 10 is formed. The structure and operation of the angular velocity sensor 10 are the same as those of the conventional angular velocity sensor 20 shown in FIG.
Since the structure and operation are substantially the same as those described above, the same portions are denoted by the same reference numerals and the description thereof will be referred to. The structure of the different part will be described below.

The recess 1a of the support substrate 1 has a plurality of columns 1c extending upward from the bottom surface to a substantially extended plane of the surface 1b.
However, these columns 1c are provided at portions that do not come into contact with the movable portions (the vibrating portions 2a, the movable electrodes 2b to 2e, the beams 2f, and the like) of the angular velocity sensor 10 so as not to hinder the vibration. Has become. In particular, an opening 2j larger than the column 1c is provided at the center of the vibrating section 2a, and the tip of the column 1c at the center of the recess 1a is connected to the vibrating section 2a.
To avoid contact with

Next, a method of manufacturing the angular velocity sensor 10a will be described as a second embodiment of the method of manufacturing a semiconductor device according to the present invention with reference to FIGS. In FIG. 10, reference numeral 11 denotes a support substrate made of a Pyrex glass substrate having a thickness of 500 μm. A silicon substrate 17 has a maximum thickness of 300 μm and has the same size as the support substrate 11. On the back side of the silicon substrate 17, a free vibration space of a movable portion of the acceleration sensor 10a shown in FIG.
A recess 17a of 0 μm is formed. Reference numeral 17b denotes a surface of the silicon substrate 17 including the concave portion 17a. Reference numeral 17c denotes a column extending downward from the top surface of the concave portion 17a and having a height of approximately 10 μm square and substantially equal to the depth of the concave portion 17a. A total of five pillars 17c are formed at the center and four corners of the recess 17a. These pillars 17c
Is formed by etching while forming the recess 17a while partially leaving the silicon substrate 17, or by depositing or bonding another material after the formation of the recess 17a.

In the first embodiment, as shown in FIG. 8, a concave portion 1a and a column 1c are formed in a support substrate 1 made of a Pyrex glass substrate. In this embodiment, a concave portion 17a having a column 17c in a silicon substrate 17 is formed. Is formed. Therefore, the silicon substrate 17 of this embodiment has a shape obtained by inverting the support substrate 1 of the first embodiment shown in FIG. In FIG. 11, the support substrate 11 and the silicon substrate 17 are anodically bonded. This anodic bonding is performed between the front surface 17b of the silicon substrate 17 including the concave portion 17a and the tip surface of the support 17c and the surface of the support substrate 11. The conditions of the anodic bonding are the same as in the first embodiment.

In FIG. 12, the silicon substrate 17 is etched with an aqueous solution of potassium hydroxide (KOH) to obtain a thin film silicon substrate having a thickness of 70 μm (the thickness of the top surface of the concave portion 17a is 20 μm and the depth of the concave portion 17a is 50 μm). 17d
Process into

The concave portion 17a of the thin film silicon substrate 17d
Since the concave portion 17a has an internal pressure lower than the atmospheric pressure due to the anodic bonding, it tends to be distorted into the concave portion 17a due to the atmospheric pressure.
It maintains a uniform plane without being distorted by being supported by.

In FIG. 13, the thin film silicon substrate 17d
A positive photoresist 15 is applied on the upper surface of the substrate. Then, the angular velocity sensor 10 shown in FIG.
The photoresist 15 is exposed and developed using a positive photomask 16 having the planar shape of FIG.
A patterned resist mask 15a shown in FIG.

Referring to FIG. 15, RIE is performed using a resist mask 15a and sulfur hexafluoride (SF ₆ ) gas.
The thin film silicon substrate 17d is dry-etched by (reactive ion etching).

In FIG. 16, the unnecessary resist mask 15a is removed by O ₂ ashing to form the angular velocity sensor 10a shown in FIG. This angular velocity sensor 1
The structure and operation of Oa is substantially the same as the structure and operation of the angular velocity sensor 10 shown in FIG. However, as compared with the column 1c in the first embodiment, the tip of the column 17c 'is shaved lower by etching.

In the above embodiment, the pillars 1c and 17c are shown as vertical pillars.
Any shape is possible as long as it has a function to support h and 17d and has a structure that does not contact the movable part of the semiconductor element.

Further, in the above embodiment, the Pyrex glass substrate is used as the support substrate and the anodic bonding is performed with the silicon substrate. However, the silicon and the silicon are directly bonded using the silicon substrate as the support substrate. You can also.

[0042]

According to the first or second aspect of the present invention, a projection is provided in a recess formed in a support substrate or a silicon substrate, and the projection supports a thin-film silicon substrate to withstand atmospheric pressure. Since the thin-film silicon substrate is held on a uniform plane without distortion, photolithography can be performed with high accuracy. Thereby, the sensitivity and the yield of the semiconductor element can be improved.

According to the third aspect of the present invention, a projection is formed by leaving a part of the support substrate or the silicon substrate, and the projection is formed together with the recess. This makes it possible to easily and easily form a protrusion having the same plane as the surface of the support substrate or the silicon substrate including the recess. Other effects are the same as the effects of the first or second aspect of the present invention.

According to a fourth aspect of the present invention, after a concave portion is formed in a support substrate or a silicon substrate, a protrusion having substantially the same plane as the surface of the support substrate or the silicon substrate including the concave portion is formed of glass, silicon, or silicon. Since it is formed of a material such as metal, it has the same effect as the effect of the invention described in claim 1 or 2.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a method for manufacturing a semiconductor device of the present invention, in which a concave portion having a support is formed on a support substrate;
On the other hand, a process diagram for preparing a silicon substrate

FIG. 2 is a process diagram of anodically bonding a support substrate and a silicon substrate.

FIG. 3 is a process diagram of polishing a silicon substrate to process it into a thin-film silicon substrate.

FIG. 4 is a process diagram of applying a photoresist on a thin-film silicon substrate and setting a photomask on the photoresist.

FIG. 5 is a process chart for forming a resist mask by exposing and developing a photoresist.

FIG. 6 is a process diagram of etching a thin-film silicon substrate using a resist mask.

FIG. 7 is a process diagram for removing an unnecessary resist mask.

FIG. 8 is a perspective view of a support substrate having a concave portion having a plurality of columns.

FIG. 9 is a plan view of a semiconductor device manufactured according to the first and second embodiments.

FIG. 10 is a view showing a second embodiment of the method for manufacturing a semiconductor device according to the present invention, in which a concave portion having a pillar is formed in a silicon substrate and a supporting substrate is prepared.

FIG. 11 is a process diagram of anodically bonding a silicon substrate and a support substrate.

FIG. 12 is a process chart for polishing a silicon substrate to process it into a thin-film silicon substrate.

FIG. 13 is a process diagram of applying a photoresist on a thin-film silicon substrate and setting a photomask on the photoresist.

FIG. 14 is a process chart of forming a resist mask by exposing and developing a photoresist.

FIG. 15 is a process diagram of etching a thin-film silicon substrate using a resist mask.

FIG. 16 is a process chart for removing an unnecessary resist mask.

FIG. 17 shows a conventional method for manufacturing a semiconductor device, in which a recess is formed in a support substrate and a silicon substrate is prepared.

FIG. 18 is a process diagram of anodically bonding a support substrate and a silicon substrate.

FIG. 19 is a process chart of polishing a silicon substrate to process it into a thin film silicon substrate.

FIG. 20 is a process diagram of applying a photoresist on a thin-film silicon substrate and setting a photomask on the photoresist.

FIG. 21 is a process chart of forming a resist mask by exposing and developing a photoresist.

FIG. 22 is an intermediate process diagram of etching a thin film silicon substrate using a resist mask.

FIG. 23 is a diagram showing a step of finishing etching of a thin film silicon substrate.

FIG. 24 is a process chart for removing an unnecessary resist mask.

FIG. 25 is a perspective view of a support substrate in a conventional manufacturing method.

FIG. 26 is a plan view of a semiconductor device manufactured by a conventional manufacturing method.

[Explanation of symbols]

Reference numerals 1, 11 Support substrate 1a Depression of support substrate 1b Surface including depression of support substrate 1c, 17c, 17c 'Support 2, 17 Silicon substrate 2a Vibrating parts 2b, 2c, 2d, 2e Movable electrode 2f Beam 2g Fixed part 2h, 17d Thin film silicon substrate 2j Opening 3b, 3c, 3d, 3e Fixed electrode 4, 5, 6, 7 Capacitor 4b, 5c, 6d, 7e Fixed part 10, 10a Angular velocity sensor 15, 15a Photoresist 16 Photomask 17a Concave part 17b of silicon substrate Surface including recesses of silicon substrate

Claims (4)

[Claims] In a method of manufacturing a semiconductor device having a movable portion and a fixed portion, a recess having at least one protrusion is formed on a support substrate, and the recess is formed on the support substrate by supporting the silicon substrate with the protrusion. The silicon substrate is bonded to the surface including the silicon substrate, the silicon substrate is thinly polished and processed into a thin-film silicon substrate supported by the projecting portion, and the thin-film silicon substrate is photo-etched, so that the projecting portion is formed in the recessed region. Forming the movable portion away from the portion. 2. A method of manufacturing a semiconductor device having a movable portion and a fixed portion, wherein a recess having at least one protrusion is formed on a silicon substrate, and the recess is formed on the silicon substrate by supporting the silicon substrate with the protrusion. By joining a support substrate to the surface including, processing the silicon substrate into a thin-film silicon substrate supported by the protrusions by thin polishing, and photo-etching the thin-film silicon substrate,
The method of manufacturing a semiconductor device, wherein the movable portion is formed in a region of the recess away from the protrusion. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the recess is formed while leaving the protrusion in a region of the support substrate or the silicon substrate where the recess is formed. . 4. The method for manufacturing a semiconductor device according to claim 1, wherein a projection is formed in the recess after the recess is formed in the support substrate or the silicon substrate.