JP2001345305A - Method for etching semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To etch a semiconductor substrate and form it into a designed shape. SOLUTION: Before forming a concave 27 on the surface of a semiconductor substrate (active layer of an SOI board) 21, a resist 35 for protecting corners is formed on a substrate surface area as an opening end edge of the concave 27. Then, a mask pattern 36 for forming a concave is formed and the semiconductor substrate 21 is etched with the resist 35 and mask pattern 36 to form a concave 27. The mask pattern 36 is removed and a mask pattern 37 is formed on the surface of the substrate 21 so that a substrate processing area including the concave 27 may be formed into a prescribed shape. Furthermore, the substrate 21 is etched with the resist 35 and mask pattern 37 to form the substrate 21 into the prescribed shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for etching a semiconductor substrate for forming an angular velocity sensor, an acceleration sensor and the like by processing the semiconductor substrate.

[0002]

2. Description of the Related Art FIG. 2A is a perspective view schematically showing an example of an angular velocity sensor, and FIG.
Is a cross-sectional view taken along the line AA shown in FIG. These figures 2
The angular velocity sensor 1 shown in (a) and (b) is, for example,
A semiconductor substrate such as single crystal silicon is bonded to a fixed substrate 2 made of glass, and the semiconductor substrate is formed into a predetermined shape by dry etching or the like.

That is, as shown in FIGS. 2A and 2B, a cavity (recess) 4 is formed in the upper surface 2a of the fixed substrate 2. A plane vibrator 5 is provided so as to float on the bottom surface 4 a of the cavity 4.

The planar vibrating body 5 shown in FIG. 2 is a combined body in which a rectangular vibrating plate 7 is connected to a quadrangular frame 6 by four connecting beams (detection beams) 8. Each of the connecting beams 8 is formed in an L-shape, and the four corners of the diaphragm 7 are connected to the leading ends of the L-shaped short sides 9 of the connecting beam 8 respectively. The L-shaped long side portion 10 of each connecting beam 8 is formed to extend from the short side portion 9 side along the side of the frame body 6 with an interval from the frame body 6, and the long side portion 10 of each connecting beam 8 is formed. Are connected to the corners of the frame body 6 in communication with each other.

The thickness D of the frame 6 and the diaphragm 7 is, for example, about 43 μm, while the thickness d of each connecting beam 8 is
The thickness d of each connecting beam 8 is very thin, for example, 10 μm, and the connecting beam 8 is configured to be easily bent and displaced in the thickness direction (that is, the Z direction shown in FIG. 2). Each of these connecting beams 8 is shown in FIG.
As shown in (b), the frame 6 and the diaphragm 7 are disposed so as to face substantially the center in the thickness direction.

Since the connecting beams 8 are formed thin as described above, the diaphragm 7 can be displaced in the Z direction with respect to the frame 6 with the joint between the frame 6 and the connecting beams 8 as a fulcrum. ing.

The four corners of the frame 6 of the plane vibrating body 5 are respectively fixed to the fixing portion 1 via claw-shaped support beams (driving beams) 12.
3 is fixedly supported. The fixed part 13 is a fixed substrate 2
It is fixed to. The support beam 12 has an extremely high aspect ratio (that is, the ratio of the length in the thickness direction (Z direction) to the length in the width direction (X direction)).
Further, as described above, since the support beam 12 is bent and formed in a claw shape, the support beam 12 is supported by the fixing portion 13 as a fulcrum in FIG.
, And is hardly displaced in the Z direction. The support beam 12 allows the plane vibrator 5 to be used.
The whole can be displaced in the X direction shown in FIG.

The movable comb electrodes 14 (14a, 14a) on the left and right sides in FIG.
b), and the movable comb electrode 14
The fixed comb electrode 15 (1
5a, 15b) are provided. The fixed portion 1 is sandwiched between the left and right sides in FIG.
6 are provided, and the fixed side comb-teeth electrode 15 is formed to extend from each of the fixed portions 16.

An exciter that excites and vibrates the plane vibrator 5 in the X direction shown in FIG. 2 is constituted by the set of the movable comb electrode 14 and the fixed comb electrode 15. That is, each of the fixed side comb-teeth electrodes 15a and 15b is
The conductive pattern is conductively connected through, for example,
The fixed comb electrodes 15a, 15
By applying AC voltages having phases different from each other by 180 ° to b, between the movable comb electrode 14a and the fixed comb electrode 15a and between the movable comb electrode 14b and the fixed comb electrode 15b, respectively. The opposite electrostatic forces are generated. The entire surface of the planar vibrator 5 can be excited and vibrated in the X direction by this electrostatic force.

[0010] As shown in FIG.
A fixed detection electrode 17 is disposed on the bottom surface 4a of the cavity 4 so as to face the diaphragm 7 with an interval therebetween. Also,
As shown in FIG. 2A, a bottom surface 4a of the cavity 4 is formed.
An electrode pad 18 is formed in a region outside the facing region of the planar vibrator 5, and a conductive pattern 19 for electrically connecting the electrode pad 18 and the fixed detection electrode 17 is formed.

In the angular velocity sensor 1, the diaphragm 7 is made of, for example, single crystal silicon or the like, and the diaphragm 7 itself functions as a moving-side detection electrode. According to the set, an electric signal corresponding to the capacitance between the diaphragm 7 and the fixed detection electrode 17 is output from the electrode pad 18 to the signal processing unit (not shown) via the conductive pattern 19.

In the angular velocity sensor 1 shown in FIGS. 2A and 2B, the plane vibrator 5 (the frame 6, the diaphragm 7, the connecting beam 8), the supporting beam 12, the fixing portion 13, The movable comb electrode 14, the fixed comb electrode 15, and the fixed portion 16 are formed by etching a semiconductor substrate.

In the angular velocity sensor 1 shown in FIG. 2, when the entire plane vibrator 5 is excited and vibrated in the X direction by the application of an AC voltage to the fixed comb electrodes 15a and 15b, the angular velocity When the sensor 1 rotates with the Y direction as the rotation center axis, a Z direction Coriolis force is generated.
Due to this Coriolis force, the diaphragm 7 of the plane vibrator 5 detects and vibrates in the Z direction. Due to the detection vibration of the diaphragm 7 in the Z direction, the distance between the diaphragm 7 and the fixed detection electrode 17 changes, and the capacitance between the diaphragm 7 and the fixed detection electrode 17 changes.
The magnitude of the angular velocity around the Y axis is detected based on the electric signal corresponding to the capacitance.

An example of a method of manufacturing the angular velocity sensor 1 will be described below with reference to FIGS. 4, 5, and 6 show portions corresponding to the AA portion shown in FIG.

For example, first, an SOI (Silicon On Insulator) substrate 2 which is a semiconductor substrate as shown in FIG.
Prepare 0. The SOI substrate 20 is a substrate in which an active layer 21 of single crystal silicon or the like, an oxide layer 22 of SiO ₂ or the like, and a support layer 23 of single crystal silicon or the like are laminated and integrated.

On the surface of the active layer 21 of the SOI substrate 20, a connecting beam forming mask pattern 2 as shown in FIG.
4 is formed. The connection beam forming mask pattern 24 is made of a resist material and has a shape covering the surface region of the active layer 21 excluding the region serving as the connection beam 8.

The connecting beam forming mask pattern 24 is formed as follows. For example, first, as shown in FIG. 3A, a resist material 31 is dropped on the center of the surface of the active layer 21, and then, as shown in FIG. The part is rotated by a spin coater around the center of rotation. Due to the centrifugal force caused by this rotation, the resist material 31 diffuses almost uniformly from the center of the active layer 21 toward the edge thereof, and
The resist material 31 is applied to the entire surface of the substrate 1.

In the case where the resist material 31 is of a negative type, after the resist material 31 is applied to the entire surface of the active layer 21 as described above, an electron is applied to the resist material portion excluding the region that becomes the connection beam 8. A beam is irradiated to cure the resist, and the resist material formed in the region serving as the connection beam 8 is removed. Thus, the connecting beam forming mask pattern 24 is formed.

After the formation of the connecting beam forming mask pattern 24, the active layer 21 is etched based on the connecting beam forming mask pattern 24 to form the connecting beam 8 as shown in FIG. A recess 25 is formed in the region.
Thereafter, the connecting beam forming mask pattern 24 is removed.

On the other hand, a glass substrate as the fixed substrate 2 is prepared, and a cavity 4 is formed in the glass substrate (fixed substrate) 2 as shown in FIG.
As shown in (b), the fixed detection electrode 17, the electrode pad 18, and the conductive pattern 19 are formed on the bottom surface 4a of the cavity 4 by using a film formation technique such as sputtering.

Then, as shown in FIG.
The surface of the active layer 21 of the OI substrate 20 where the concave portion 25 is formed and the surface of the fixed substrate 2 where the cavity 4 is formed face each other, and the SOI substrate 20 and the fixed substrate 2 are anodically bonded. Next, as shown in FIG.
The oxide layer 22 and the support layer 23 of the OI substrate 20 are removed.

Thereafter, as shown in FIG. 6C, a connecting beam forming mask pattern 26 is formed on the surface of the active layer 21 with a resist. Similar to the connection beam forming mask pattern 24, the connection beam forming mask pattern 26 has a shape covering the surface region of the active layer 21 excluding the region serving as the connection beam 8. The mask pattern 24 is formed by the same forming method.

Next, the connecting beam forming mask pattern 2
6, the surface side of the active layer 21 is etched to form a concave portion 27 in a region serving as the connection beam 8 as shown in FIG. Then, after the formation of the recess 27, the connection beam forming mask pattern 26 is
Removed from the surface.

Thereafter, as shown in FIG. 6E, a molding mask pattern 28 is formed on the surface of the active layer 21 by using a resist. This molding mask pattern 28 is shown in FIG.
(A) is for forming a pattern shape as shown in FIG. 1, and includes a plane vibrator 5 (inner frame 6, diaphragm 7, connecting beam 8), a supporting beam 12, a fixed portion 13, and a movable comb electrode 14. ,
The shape is such that a resist material is formed on the surface region of the active layer 21 that becomes the fixed comb electrode 15 and the fixed portion 16. This forming mask pattern 28 is formed by the same forming method as the connecting beam forming mask patterns 24 and 26.

After the formation of the molding mask pattern 28, the active layer 2 is formed based on the molding mask pattern 28.
6 is etched to form a through hole from the front side to the back side in the active layer 21 region where the molding mask pattern 28 is not formed, as shown in FIG.
As a result, the active layer 21 is formed into a set pattern shape as shown in FIG. Thereafter, the molding mask pattern 28 is removed.

As described above, the angular velocity sensor 1 shown in FIG. 2 can be manufactured.

[0027]

By the way, in the manufacturing process of the angular velocity sensor 1, as shown in FIG. 6D, after the concave portion 27 is formed on the surface of the active layer 21, the active portion in which the concave portion 27 is formed is formed. When forming the molding mask pattern 28 on the surface of the layer 21, the following problems occur.
The problem is that, as described above, the anode material of the fixed substrate 2 and the active layer 21 is rotated using a spin coater, and the resist material dropped on the center of the surface of the active layer 21 is coated on the entire surface of the active layer 21. 7, the resist material 31 is not applied to the opening edge X of the concave portion 27, or even if the resist material 31 is formed, the thickness of the resist material 31 is extremely large. It is that it becomes thin.

As described above, if the resist material 31 is not applied to the opening edge X of the concave portion 27, or if the resist material 31 at the opening edge X of the concave portion 27 becomes very thin, the resist When the active layer 21 is etched using the molding mask pattern 28 made of the material 31, the opening edge X of the concave portion 27 that should not be etched away is etched away.
Thereby, for example, as shown in FIG. 2, there is a serious problem that the connecting beam 8, which should have been connected to the frame 6, is separated from the frame 6 and cannot function as an angular velocity sensor. A problem had arisen, which reduced yield.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to prevent a problem caused by etching and removing an edge of an opening of a concave portion and to set a semiconductor substrate by etching. The present invention relates to a method for etching a semiconductor substrate which can be formed into a shape with high processing accuracy.

[0030]

Means for Solving the Problems In order to achieve the above object, the present invention has the following structure to solve the above problems. That is, a first invention is a method of etching a semiconductor substrate for forming a concave portion in a semiconductor substrate by etching, and then etching a substrate processing region including the concave portion into a set shape. Before forming the concave portion, a corner-protecting resist is formed in the semiconductor substrate surface region to be the opening edge of the concave portion, and then the concave-portion forming mask pattern is formed of a resist material different from the above-mentioned corner-protecting resist. Is formed on the surface of the semiconductor substrate, and thereafter, the semiconductor substrate is etched based on the corner protection resist and the mask pattern for forming the concave portion to form the concave portion. Then, the mask pattern for forming the concave portion is formed on the semiconductor substrate. From the semiconductor substrate, and then a molding mask pattern for processing the substrate processing region including the recess into a set shape. Formed on the surface, then, it is characterized in that etching the substrate processing region based on the molding mask pattern and the corners protective resist.

According to a second aspect of the present invention, there is provided the configuration of the first aspect, wherein the forming mask pattern is formed by processing a resist applied to the surface of the semiconductor substrate using a spin coater. .

According to a third aspect of the present invention, there is provided the configuration of the first or second aspect, wherein the corner protection resist is formed of a negative resist.

In the invention having the above structure, before forming the concave portion on the surface of the semiconductor substrate, a corner protection resist is formed in a semiconductor substrate surface region which is an opening edge of the concave portion. Then, a concave portion is formed on the surface of the semiconductor substrate, and the above-mentioned corner portion protecting resist is left on the surface of the semiconductor substrate until the etching of the semiconductor substrate surface based on the molding mask pattern is completed.

By forming such a corner protection resist, it is possible to prevent a problem caused by etching and removing the opening edge of the concave portion. That is, after forming a concave portion on the surface of the semiconductor substrate, when a resist for forming a molding mask pattern is applied to almost the entire surface of the semiconductor substrate by a spin coater, for example, Even if the resist is not formed at the opening edge of the recess, or even if the resist is formed thin, since the corner protection resist is provided at the opening edge of the recess, the resist is formed based on the molding mask pattern. When the semiconductor substrate is etched, the opening edge of the concave portion is protected by the corner protection resist and is not etched away. Thus, it is possible to prevent a problem caused by the etching removal of the opening edge of the concave portion, and it is possible to manufacture the semiconductor substrate into a set shape with high processing accuracy.

[0035]

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

In this embodiment, an example of a method for etching a semiconductor substrate using the angular velocity sensor shown in FIG. 2 will be described. In the description of the embodiment, the same components as those of the conventional example are denoted by the same reference numerals, and the description of the common portions will not be repeated.

In this embodiment, a recess 25 is formed in the SOI substrate 20 in the same manner as in the conventional example, while
The cavity 4 is formed in the fixed substrate 2, and the SOI substrate 20 and the fixed substrate 2 are anodically bonded. And the above S
The oxide layer 22 and the support layer 23 of the OI substrate 20 are removed. The steps up to this point are the same as those in the conventional example.

Thereafter, as shown in FIG. 1A, the most characteristic corner protection resist 3 in this embodiment.
5 is formed on the surface of the active layer 21 which is a semiconductor substrate. This corner protection resist 35 is made of a negative resist that is cured by electron beam irradiation.
As shown in (a), the active layer 21 is formed at least in the surface region of the active layer 21 (semiconductor substrate surface region) which avoids the region Y serving as the opening of the recess 27 and serves as the opening edge of the opening of the recess 27. The resist 35 applied to the surface of the active layer 21 is also processed using a spin coater in the same manner as the connection beam forming mask patterns 24 and 26 as described in the above-mentioned conventional example. It is formed by

After forming the corner protection resist 35, a mask pattern 36 for forming a concave portion is formed as shown in FIG. The concave portion forming mask pattern 36 is made of a different resist material from the corner portion protecting resist 35, and is for forming the concave portion 27 together with the corner portion protecting resist 35.

Thereafter, as shown in FIG. 1B, the corner protecting resist 35 and the concave portion forming mask pattern 3 are formed.
6, the surface of the active layer 21 is etched.
A recess 27 is formed.

Next, as shown in FIG. 1C, the concave portion forming pattern 36 is removed by, for example, a dedicated stripper. Here, a stripping solution that can remove the concave portion forming mask pattern 36 and leave the corner protecting resist 35 (does not adversely affect the corner protecting resist 35) is used. Only the concave portion forming mask pattern 36 of the part protecting resist 35 and the concave portion forming mask pattern 36 is removed as described above.

Thereafter, as shown in FIG. 1D, a molding mask pattern 37 is formed on the surface of the active layer 21 which is the substrate processing region including the concave portion 27. The shaping mask pattern 37 is for etching the active layer 21 together with the corner protection resist 35 into a pattern shape as shown in FIG. The fixed portion 13, the movable comb electrode 14, the fixed comb electrode 15, and the fixed portion 16 are formed in the surface region of the active layer 21. This molding mask pattern 37
As described above, the active layer 21 is formed by using a spin coater.
It is formed by processing the resist applied to the substrate. The resist material constituting the molding mask pattern 37 may be the same resist material as the corner protection resist 35, or may be a different resist material from the corner protection resist 35.

Thereafter, as shown in FIG. 1E, the active layer 21 is etched based on the corner protection resist 35 and the forming mask pattern 37 to form the active layer 21.
Then, a plurality of through holes are formed from the surface side to the bottom side, and the active layer 21 is formed into a shape as shown in FIG.

Thereafter, as shown in FIG. 1F, the corner protection resist 35 and the forming mask pattern 37 are removed by, for example, ashing.

Thus, the angular velocity sensor 1 is manufactured.

According to this embodiment, the corner protection resist 35 is formed before the recess 27 is formed, and the etching of the corner protection resist 35 based on the forming mask pattern 37 is completed. Until the concave portion 27 is formed, when the forming mask pattern 37 is formed on the surface of the active layer 21 where the concave portion 27 is formed, the opening end of the concave portion 27 is formed. Even if the molding mask pattern 37 is not formed on the edge X or the thickness of the molding mask pattern 37 is thin, the corner protecting resist 35 is formed on the opening edge X of the recess 27. Therefore, during the subsequent etching, the opening edge X of the concave portion 27 is protected by the corner protecting resist 35 and is removed by etching. It is possible to prevent.

As a result, it is possible to avoid a decrease in the yield of the angular velocity sensor 1 due to the etching removal of the edge of the opening of the concave portion.

In this embodiment, since the corner protection resist 35 is formed in a negative type, the concave portion forming mask pattern 36 is formed on the surface of the active layer 21 on which the corner protection resist 35 is formed. And molding mask pattern 3
Even when the corner protection resist 35 is irradiated with an electron beam when forming 7, the corner protection resist 35 is not damaged by the electron beam. This allows
Corner protection resist 35 and molding mask pattern 3
When the active layer 21 is etched based on the pattern 7, the recesses 27 are surely formed by the corner protection resist 35.
Can be protected, and the angular velocity sensor 1 can be manufactured in a shape as designed.

Note that the present invention is not limited to the above-described embodiment, but can adopt various embodiments. For example, in the above embodiment, the angular velocity sensor 1 as shown in FIG. 2 has been described as an example, but the present invention is not limited to the manufacture of the angular velocity sensor 1 as shown in FIG. Can be applied to all products manufactured by etching the substrate processing region including the concave portion after the formation.

In the above embodiment, the resist 35 for protecting the corner portions, the mask pattern 36 for forming the concave portions, and the mask pattern 37 for forming are formed by processing the resist applied on the entire surface of the semiconductor substrate using a spin coater. Although each of the above mask patterns may be formed by processing a resist applied to the surface of a semiconductor substrate by a method other than a coating method using a spin coater.

Further, although the corner protection resist 35 is formed of a negative resist, for example, after the corner protection resist 35 is formed, the corner protection resist 35 is irradiated with an electron beam. Is not irradiated, the corner protection resist 35 may be formed of a positive resist.

[0052]

According to the present invention, before forming a concave portion in a semiconductor substrate, a corner portion protecting resist is provided in a semiconductor substrate surface region to be an opening edge of the concave portion, and thereafter, the concave portion is formed. Further, after that, until the etching of the substrate processing region including the concave portion is completed, the corner protection resist remains on the surface of the semiconductor substrate, so that the etching of the substrate processing region including the concave portion is performed. Sometimes, even if the molding mask pattern is not formed on the opening edge of the recess, or is formed very thin,
Since the opening edge of the recess is protected by the corner protection resist, it is possible to prevent the opening edge of the recess from being etched away.
As a result, it is possible to avoid a decrease in yield due to the etching removal of the edge of the opening of the concave portion.

The mask pattern for molding is formed by processing the resist applied to the surface of the semiconductor substrate using a spin coater. When the resist is applied to the surface of the semiconductor substrate using the spin coater, However, a situation in which the resist is not applied to the opening edge of the concave portion is likely to occur, but in the present invention, since the corner protecting resist is formed at the opening edge of the concave portion, during etching, As described above, the opening edge of the recess is protected by the corner protection resist, and the opening edge of the recess can be reliably prevented from being etched away, which is very effective.

In the case where the corner protection resist is formed of a negative type resist, when the semiconductor substrate surface is irradiated with an electron beam after the formation of the corner protection resist, the corner beam is irradiated by the electron beam. Damage to the protective resist can be prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram extracting and showing a characteristic portion in the present embodiment.

FIG. 2 is an explanatory diagram showing an example of an angular velocity sensor that can be manufactured by applying the semiconductor substrate etching method of the embodiment.

FIG. 3 is a diagram for explaining a method of applying a resist to the surface of a semiconductor substrate using a spin coater.

FIG. 4 is an explanatory view showing an example of a processing step of an SOI substrate constituting the angular velocity sensor shown in FIG.

FIG. 5 is an explanatory view showing an example of a processing step of a glass substrate constituting the angular velocity sensor shown in FIG. 2;

6 is an explanatory view showing a conventional example of a manufacturing process of the angular velocity sensor shown in FIG.

FIG. 7 is a diagram for explaining a conventional problem.

[Explanation of symbols]

 Reference Signs List 3 semiconductor substrate 20 SOI substrate 21 active layer 27 recess 35 resist for corner protection 36 mask pattern for forming recess 37 mask pattern for forming

Claims (3)

[Claims] 1. A method of etching a semiconductor substrate for forming a concave portion in a semiconductor substrate by etching and then etching a substrate processing region including the concave portion into a predetermined shape, wherein the concave portion is formed in the semiconductor substrate. Before forming the recess, a corner-protecting resist is formed in the surface region of the semiconductor substrate that is to be the opening edge of the recess, and then the recess-forming mask pattern is formed on the semiconductor substrate using a resist material different from the corner-protecting resist. Formed on the surface, and thereafter, the semiconductor substrate is etched based on the corner protection resist and the concave portion forming mask pattern to form the concave portion, and then the concave portion forming mask pattern is removed from the semiconductor substrate. Thereafter, a molding mask pattern for processing the substrate processing region including the concave portion into a set shape is formed on the surface of the semiconductor substrate. And thereafter etching the substrate processing region based on the molding mask pattern and the corner protection resist. 2. The method for etching a semiconductor substrate according to claim 1, wherein the forming mask pattern is formed by processing a resist applied to the surface of the semiconductor substrate using a spin coater. 3. The corner portion protecting resist is made of a negative type resist.
The method for etching a semiconductor substrate according to the above.