JP2002319684A - Method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device manufacturing method which is capable of reducing man-hours required for forming the recessed part of a diaphragm or the like, eliminating complicated treatments applied to a wafer, when etching is carried out for the formation of the recessed part, and preventing the inner wall of the recessed part from becoming too large in curvature. SOLUTION: Pressure is applied to the predetermined region of a silicon substrate 1, where a diaphragm is to be formed by the use of a body whose tip is formed into the shape of a triangular pyramid. Thereafter, etching is carried out for the formation of the diaphragm. As a result of this, a rounded recess 3 is formed as the center on a part, where a pressure has been applied. The recess 3 is used as a diaphragm.

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 having a concave portion such as a diaphragm, and is particularly suitable for a method for manufacturing a pressure sensor or an acceleration sensor.

[0002]

2. Description of the Related Art In processing a semiconductor sensor (for example, a pressure sensor or an acceleration sensor) manufactured using silicon as a material, silicon is processed to a thickness of several microns in order to form a detection portion (for example, a diaphragm). There is a need to. For this purpose, for example, an etching method using an alkaline solution is used.

It is known that the etching rate of silicon with an alkaline solution varies depending on the plane orientation of silicon.
Therefore, by using an etching technique utilizing this anisotropy, it is possible to form a diaphragm (recess) on a flat surface.

However, anisotropic etching with alkali is very sensitive to the plane orientation of silicon,
In many cases, the cross-sectional shape is as shown in FIG.
Is formed sharply. Therefore, when the pressure sensor is formed in such a shape, when a high pressure is applied to the diaphragm 11, the diaphragm 11 is easily broken.

Therefore, when a pressure sensor or the like to be used under a high pressure is prepared, the etching is first performed halfway with an alkaline solution, and the etching is performed using an acidic solution in which the etching proceeds isotropically in finishing. As shown in FIG. 4, the diaphragm 11 and the side wall surface 12 are formed.
The device is designed to form a roundness at an angle between them.

[0006]

However, in the above method, the number of steps for forming the diaphragm is increased,
There is a problem that the wafer must be treated to cope with both alkali and acid.

In recent years, a circular diaphragm shape has been required. On the other hand, it is conceivable to form the diaphragm by a method using only an acid which isotropically etches. However, according to such a method, as shown in FIG. 5, the curvature of the inner wall surface of the diaphragm 11 is large. It becomes too difficult to use as a diaphragm.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and can simplify the man-hours for forming a concave portion such as a diaphragm, and can eliminate complicated processing of a wafer for etching for forming a concave portion. The purpose is to prevent the curvature of the inner wall surface from becoming too large.

[0009]

In order to achieve the above object, according to the present invention, there is provided a method of manufacturing a semiconductor device in which a concave portion (3) is formed in a main surface of a semiconductor material (1). Applying pressure by pressing an object (4) against an arbitrary portion of a main surface of a semiconductor material;
Thereafter, by etching the main surface, a concave portion is formed in a portion of the main surface to which pressure is applied.

As described above, pressure is applied to a region of the semiconductor material in which a concave portion is to be formed by pressing an object in advance, and thereafter, the semiconductor material is etched to apply the pressure. In this case, a rounded concave portion can be formed. For this reason, the number of steps for forming a rounded concave portion can be simplified, and complicated processing of the wafer for etching for forming the concave portion can be eliminated.

According to the third aspect of the present invention, a mask layer (2) serving as a mask material at the time of etching is formed on the main surface of the semiconductor material, and a desired region of the mask layer is opened, and then the opening is performed. The etching is performed in the region. By providing the mask layer in this manner, the shape of the region where the concave portion is formed can be controlled by the shape of the region opened in the mask layer.

According to a fourth aspect of the present invention, the surface of the semiconductor material is etched without forming a mask layer. When the etching is performed in such a state where the mask layer is not provided, the semiconductor material can be reduced in thickness as a whole, so that an element suitable for detecting minute physical quantities can be formed.

For example, silicon as described in claim 5 can be used as the semiconductor material. In particular, in the case of silicon, when the crystal orientation of the main surface is set to the <100> orientation, the concave portion can be effectively formed.

As an etching material, for example,
An alkaline chemical solution as described in claim 7 can be used. Examples of the alkaline chemical include an aqueous solution comprising an alkali metal hydroxide as described in claim 8, an aqueous ammonia solution as described in claim 9, a solution obtained by dissolving an organic alkali hydroxide in water, and an organic alkali solution. Either a solution in which a hydroxide is dissolved in an organic solvent or a solution in which a hydroxide of an organic alkali is dissolved in water or an organic solvent can be used.

According to a tenth aspect of the present invention, in the method of manufacturing a micro concave mirror for forming a micro concave mirror by forming a micro concave portion (22) on the main surface of the semiconductor material (1), An object (2)
The method is characterized in that a pressure is applied by pressing 1) and then the main surface is etched to form a concave portion in the main surface where the pressure is applied. Thus, it is also possible to manufacture a concave mirror using the method described in claim 1.

In this case, a jig (21) having projections formed in an array is used as the object, and the projections of the jig are pressed against the main surface of the semiconductor material. The concave portions can be formed in an array.

On the other hand, after forming a transparent film (23) on the main surface of the semiconductor material in which the concave portion is formed, the semiconductor material is removed, and the fine lens ( 24) can also be manufactured.

Also in this case, a jig (21) having projections formed in an array is used as an object, and the projections of the jig are pressed against the main surface of the semiconductor material. The concave portions are formed in an array, and the microlenses can be formed in an array by each of the concave portions formed in the array.

Note that the reference numerals in parentheses of the above means indicate the correspondence with specific means described in the embodiments described later.

[0020]

(First Embodiment) FIG. 1 shows a manufacturing process of a semiconductor device having a diaphragm to which one embodiment of the present invention is applied. A method for manufacturing a semiconductor device will be described with reference to FIG. FIG. 1 (a)
In each of the drawings (a) to (d), the left side of the paper shows a state when the semiconductor device is viewed from above, and the right side of the paper shows a cross-sectional configuration of the semiconductor device.

First, as shown in FIG.
Is prepared by subjecting the silicon substrate 1 to a normal orientation, such as a silicon nitride film or a silicon oxide film, by subjecting the silicon substrate 1 to a normal semiconductor processing step or the like. The deposited mask layer 2 is deposited. Subsequently, a photolithography process is performed on the mask layer 2 to expose a region of the silicon substrate 1 to be processed by etching. Note that the mask layer 2 in each of the top views is indicated by oblique lines in order to make the exposed portion of the silicon substrate 1 easy to understand. Further, in this figure, a square-shaped exposed portion is formed on the silicon substrate 1, but may be circular or polygonal.

Thereafter, an object having a tip shape of a triangular pyramid, a quadrangular pyramid, a sphere, or the like, that is, an object on which pressure is locally concentrated is prepared. It is pressed against the central part, and pressure is applied to the main surface of the silicon substrate 1. This allows
Some defect which cannot be confirmed visually or with a microscope is formed in the portion of the silicon substrate 1 to which pressure is applied.

Then, the silicon substrate 1 is etched with an alkaline chemical. Specifically, as an alkaline chemical, K was heated to 70 ° C. at about 30 wt%.
Etching is performed for several tens minutes using an OH aqueous solution. As the alkaline chemical used at this time, an aqueous solution comprising a hydroxide of an alkali metal (for example, KOH, NaOH, LiOH, etc.) may be used, but an aqueous ammonia solution or an organic alkali hydroxide dissolved in water may be used. Alternatively, any of a solution obtained by dissolving an organic alkali hydroxide in an organic solvent (for example, alcohol) or a solution obtained by dissolving an organic alkali hydroxide in water and an organic solvent may be used. As the organic alkali, for example, TMAH (Tet
ramethylammoniumhydroxide
e Tetramethylammonium hydroxide) or TEAH (T
ethraethylammoniumhydroxidi
de tetraethylammonium hydroxide) and the like.

Thus, the silicon substrate 1 is anisotropically etched in the above-described exposed region. At this time, first, as shown in FIG. 1B, when the etching is advanced to a depth of several microns, a concave portion 3 having a substantially square upper surface is formed in a portion where pressure is applied. Subsequently, FIG.
As shown in (c), even if etching is continued for a depth of several microns, the shape of the upper surface of the concave portion 3 is increased in the length of each side, but remains substantially square. In addition, the Si (100) surface is exposed on the bottom surface of the concave portion 3, and the side wall of the concave portion 3 is rounded around the position where the pressure is applied. Then, as shown in FIG. 1D, when the etching is further continued, the upper surface shape of the concave portion 3 collapses from a square shape,
It changes to a circular shape. In addition, the inner wall surface of the concave portion 3 is in a rounded state. The curvature of the inner wall surface of the concave portion 3 is sufficiently smaller than the case where the diaphragm is formed only by isotropic etching.

On the other hand, the depth of the concave portion 3 is determined at the beginning of etching, specifically, the depth D when the Si (100) surface is exposed. Hardly change. When this was examined by experiments, it was confirmed that the depth of the concave portion 3 substantially depends on the shape of the object to which pressure is applied and the applied pressure, and is controlled by the manner in which the pressure is applied.

Although such a phenomenon has been confirmed by experiments to occur when the main surface of the silicon substrate 1 has various plane orientations, it is particularly remarkable when the silicon substrate 1 has an orientation of <100>. there were.

Therefore, time control or the like is performed so that the thickness of the diaphragm becomes a desired value and the area of a region used as the diaphragm becomes a desired value based on the depth and the upper surface shape of the concave portion 3 due to the above phenomenon. Then, the etching is completed. Thereby, a state in which the angle between the diaphragm and the side wall is rounded, that is, a diaphragm shape as shown in FIG. 4 described above is obtained.

Thereafter, steps such as removal of the mask layer 2 are performed to complete a semiconductor device having a diaphragm.

As described above, the pressure is applied to the region of the silicon substrate 1 where the diaphragm is to be formed by pressing the object in advance, and then the silicon substrate 1 is subjected to etching so that the pressure is reduced. A rounded concave portion 3 can be formed in the added portion.

Therefore, the number of steps for forming a round diaphragm can be simplified. Further, since etching for forming the diaphragm can be performed using only alkali, it is possible to eliminate complication of processing of the wafer for etching. Further, the curvature of the inner wall surface of the diaphragm can be reduced, and a sufficient diaphragm area can be secured, as compared with the case where the diaphragm is formed only by isotropic etching.

As described above, the silicon substrate 1
1 may be used as a diaphragm in all regions thinned by etching.
The etching may be stopped in the state of (d), and only the concave portion 3 may be used as the diaphragm. In this case, the angle between the thinned portion and the side wall of the silicon substrate 1 becomes sharp, but since the thinned portion is thicker than the diaphragm, it has high durability even under high pressure. Will have.

(Second Embodiment) FIG. 2 shows a manufacturing process of a semiconductor device to which a second embodiment of the present invention is applied. Less than,
The method of manufacturing the semiconductor device according to the present embodiment will be described with reference to FIG. However, since the outline of the manufacturing method of the present embodiment is the same as that of the first embodiment, the same parts are omitted.

First, as shown in FIG. 2A, a silicon substrate 1 having a thickness of, for example, about 100 μm and a main surface oriented to <100> is prepared. Subsequently, FIG.
As shown in (b), pressure is applied to a desired position on the main surface of the silicon substrate 1 by the object 4 whose tip shape is such that pressure is locally concentrated. As a result, dislocations or minute cracks 5 are formed inside the silicon substrate 1. Thereafter, as shown in FIG.
The silicon substrate 1 is etched with the alkaline chemical solution 6 without disposing.

As a result, as shown in FIG. 2D, a portion of the silicon substrate 1 to which pressure is applied is preferentially etched, and a rounded concave portion 3 is formed as in the first embodiment. , A diaphragm is formed. In this manner, a diaphragm having a rounded inner wall surface can also be formed by etching (maskless etching) processing that does not include the mask layer 2.

At this time, since the mask layer 2 is not disposed on the silicon substrate 1, the silicon substrate 1 is entirely etched except for the portion to which pressure is applied, and the thickness is reduced. For this reason, it is possible to obtain a configuration suitable for using a minute physical quantity detecting element.

(Other Embodiments) In the above embodiment, an example is shown in which etching is performed until the upper surface shape of the concave portion 3 serving as the diaphragm becomes circular. However, the etching is stopped while the square shape remains, and the upper surface shape is changed. It may be a square diaphragm. In this case, it is preferable that the etching time be about 程度 of the time (70 minutes) shown in the first embodiment.

In the above embodiment, the silicon substrate 1
Although the area for applying pressure is not specifically described, it is possible to form a diaphragm having a larger area by increasing the area for applying pressure.

In the above embodiment, the semiconductor device using the concave portion 3 for the diaphragm has been described.
However, the present invention is not limited to this, and can be used for a structure such as a micromachine that requires the concave portion 3 such as a circle or a square.

Further, it is possible to form a lens using the concave portion 3 having a round shape as described above. For example, after the process up to the step of FIG. 2D in the second embodiment, for example, a silicon oxide film is deposited so as to fill the recess 3. Thereafter, the silicon oxide film is flattened to leave the silicon oxide film only in the concave portion 3, and the silicon substrate 1 is removed by etching or the like to leave only the silicon oxide film. If you do this,
It is also possible to manufacture a lens using the roundness of the concave portion 3.

It is also possible to form a plurality of such lenses at the same time. This is shown in FIG.
As shown in FIG. 6A, pressure is applied to the silicon wafer 1 by a jig 21 in which projections are arranged in an array or by a device capable of mechanically applying pressure in an array.
Thereafter, as shown in FIG. 6B, etching is performed using a KOH etching solution or the like. Then, as shown in FIG. 6C, the minute concave mirrors 22 are arrayed on the silicon wafer 1 in an array.
Is formed. By dicing this or the like, a micro concave mirror chip or the like can be formed.

Further, as shown in FIG. 6D, a transparent film 23, for example, C
A silicon oxide film by VD, an SOG (Spin On Glass) film that can be formed by a spinner, or a film of an organic material is formed. At this time, the thickness is set to several μm to several tens μm so that the transparent film 23 is completely buried in the depression. Next, the surface of the transparent film 23 is
A flattening process is performed by MP or the like, and then the silicon forming the minute concave mirror 22 is removed as shown in FIG. For example, only silicon is etched by wet etching or the like. As a result, only the transparent film 23 remains as shown in FIG. 6F, so that the microlenses 24 can be formed by dicing or the like. At this time,
The individual lenses can be cut more easily by using a dicing device before removing the silicon.

Here, the description has been given of the case where the minute lens is formed by forming the transparent film 23.
If a metal film made of, for example, copper, nickel, aluminum or the like is used instead of the transparent film 23, it is possible to form a Braille block instead of a microlens.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a manufacturing process of a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a view illustrating a manufacturing process of a semiconductor device according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a cross-sectional shape of a conventional diaphragm formed by anisotropic etching.

FIG. 4 is a diagram showing a cross-sectional shape of a diaphragm subjected to a conventional rounding process.

FIG. 5 is a diagram showing a cross-sectional shape when a diaphragm is formed only by isotropic etching.

FIG. 6 is a view showing a process of forming a micro concave mirror chip and a micro lens.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Mask layer, 3 ... Depression, 4 ... Object, 5 ... Dislocation or minute crack, 6 ... Alkaline chemical solution.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuo Sato Nagoya University, Furo-cho, Chigusa-ku, Nagoya-shi, Aichi (72) Inventor Mitsuhiro Shikita Nagoya University, Furo-cho, Chigusa-ku, Nagoya-shi, Aichi (72) Inventor Chida Atsushi 1-1-1 Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (reference) 2F055 AA40 BB16 CC02 DD05 EE40 FF38 GG01 4M112 AA01 AA02 CA03 CA05 DA04 DA06 EA03 EA06 EA07 EA11 EA13 FA20 5F043 AA02 BB01

Claims (13)

[Claims] 1. A recess (3) in a main surface of a semiconductor material (1).
In a method of manufacturing a semiconductor device, a pressure is applied by pressing an object (4) against an arbitrary portion of a main surface of the semiconductor material, and thereafter, the main surface is etched. A method for manufacturing a semiconductor device, comprising: forming the recess in a portion of the main surface to which pressure is applied. 2. When applying pressure to the semiconductor material,
2. The method according to claim 1, wherein the object is configured such that pressure is locally concentrated on a main surface of the semiconductor material. 3. 3. A mask layer (2) serving as a mask material at the time of the etching is formed on the main surface of the semiconductor material, a desired region of the mask layer is opened, and the etching is performed in the opened region. The method according to claim 1, wherein the method is performed. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the etching is performed without forming a mask layer on a surface of the semiconductor material. 5. The method of manufacturing a semiconductor device according to claim 1, wherein silicon is used as the semiconductor material. 6. The silicon according to claim 5, wherein a crystal orientation of said main surface in said silicon is a <100> orientation.
13. The method for manufacturing a semiconductor device according to item 5. 7. The method according to claim 6, wherein the etching is performed with an alkaline chemical solution. 8. The method according to claim 7, wherein an aqueous solution comprising an alkali metal hydroxide is used as the alkaline chemical. 9. The alkaline chemical solution may be an aqueous ammonia solution, a solution obtained by dissolving an organic alkali hydroxide in water, a solution obtained by dissolving an organic alkali hydroxide in an organic solvent, or a solution obtained by dissolving an organic alkali hydroxide in water. 8. The method for manufacturing a semiconductor device according to claim 7, wherein the method comprises any one of a solution dissolved in an organic solvent. 10. A manufacturing method of a micro concave mirror for forming a micro concave mirror by forming a micro concave portion (22) on a main surface of a semiconductor material (1); Object (21)
And applying a pressure by applying pressure, and thereafter, etching the main surface to form the concave portion in a portion of the main surface to which the pressure is applied. 11. The object is a jig (21) having projections formed in an array, and the depressions are formed in an array by pressing the projections of the jig against a main surface of the semiconductor material. A method of manufacturing a micro concave mirror. 12. A pressure is applied to an arbitrary portion of the main surface of the semiconductor material (1) by pressing an object (21), and thereafter, the main surface is etched to thereby apply a pressure to the main surface. Forming a concave portion in a portion to which pressure is applied, forming a transparent film (23) on a main surface of the semiconductor material in which the concave portion is formed, and removing the semiconductor material;
Producing a microlens (24) from the remaining transparent film. 13. The object is a jig (21) having projections formed in an array, and the depressions are formed in an array by pressing the projections of the jig against a main surface of the semiconductor material. And forming the microlenses in an array by each of the concave portions formed in the array.