JP2720814B2 - Aperture for electron beam lithography apparatus and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aperture for an electron beam drawing apparatus for drawing a pattern on a semiconductor substrate by an electron beam, and a method of manufacturing the same.

[0002]

2. Description of the Related Art This type of aperture for an electron beam lithography system requires an aperture pattern formed by passing an electron beam to be fine and formed in a narrow area, which is difficult with a normal machining method. . Therefore, many of them have been manufactured using semiconductor manufacturing technology.

FIGS. 4 (a) to 4 (e) are cross-sectional views showing an example of a method of manufacturing a conventional aperture for an electron beam lithography apparatus in the order of manufacture. First, as shown in FIG. 4A, a method of manufacturing the aperture for the electron beam writing apparatus is as follows. As shown in FIG. 4A, a thin Si substrate 7a and a thick Si substrate 7b with a SiO ₂ film 6 of about 1 μm interposed therebetween. To prepare a bonded substrate 8. Then, the Si substrate 7a on the front side (about 2
A resist is coated, exposed, developed and etched in the same manner as in the LSI lithography process to form a plurality of resist surface mask patterns 9.

Next, etching is performed on the resist on the substrate 8 using the plurality of surface mask patterns 9 as masks.
An opening pattern group opening 9a having a plurality of opening patterns is formed as shown in FIG. Next, as shown in FIG. 4C, a Si ₃ N ₄ film 10 is formed on the entire surface of the substrate 8, and a SiO ₂ film is formed on the surface of the Si substrate 7b on the side where the electron beam is emitted.
A film 11 is formed, a resist is applied, and a back mask pattern 13 made of the resist 12 left by the lithography process is formed.
To form

Next, as shown in FIG. 4D, back etching is performed from the back surface (thickness of about several hundred μm) to the SiO ₂ film 6 serving as an etching stopper by using the back mask pattern 13 as a mask to form a large opening. Escape part 13a with
To form Thereafter, as shown in FIG. 4E, the mask and the stopper are removed, and then the conductive film 14 is divided into individual opening patterns, or the conductive film 1 is formed.
4, the aperture pattern is divided into individual aperture patterns to form aperture patterns, and then divided into individual apertures to simultaneously manufacture a plurality of apertures for an electron beam writing apparatus.

Here, as a method of back etching a surface of a silicon semiconductor substrate largely, Japanese Patent Laid-Open Publication No.
As disclosed in Japanese Unexamined Patent Publication (Kokai) No. 63-328 or JP-A-63-2328, an etching solution containing KOH, ethanolamine, ethylenediamine, pyrocatechol, water, pepyridine, hydrogen peroxide, and the like is used. Also, JP-A-63
Japanese Patent Application Laid-Open No. 2328 discloses that an etchant for back etching is optimized to improve the etching property.

[0007] As disclosed in Japanese Patent Application Laid-Open Nos. 4-94125 and 63-2328, Si etching using an alkaline solution proceeds while generating hydrogen gas bubbles from the etched surface. Are all (11
When the material becomes the 1) plane or becomes only the material chemically stable with the (111) plane, generation of hydrogen gas bubbles disappears, and the etching ends. For the detection of the end point, conventionally, the presence or absence of bubbles generated from the Si etching surface has been confirmed from outside the etching tank.

[0008]

In the above-mentioned conventional method of manufacturing an aperture for an electron beam writing apparatus, the end point of Si etching is detected visually for the presence or absence of air bubbles.
et al. Proc. SPIE Vol. 1924
(1993), as disclosed in p183-192, an opening pattern group forming region in which a plurality of opening patterns as the apertures are formed is about 500 μm × 500 μm.
When it is narrow, it is extremely difficult to visually check for the occurrence of bubbles.

In order to keep the etching rate constant, a constant temperature bath for etching liquid and its equipment are usually required. Furthermore, in order to keep the temperature of the etching solution constant and to increase the etching rate, etching may be performed at the boiling point of the etching solution. For example, when KOH is used as an etching solution, the boiling point (about 114.5) is used.
When the etching is performed at (.degree. C.), some bubbles are generated by boiling, and it is more difficult to visually detect the etching end point.

If the detection of the etching end point is uncertain, for example, the detection is delayed, the opening pattern formed on the front surface side is over-etched, and the pattern dimension exceeds an allowable value. This causes a problem of dimensional defects.

On the other hand, as disclosed in Japanese Unexamined Patent Publication No. 4-94125, a light source and its detector are arranged vertically, an object to be etched is put between them, and etching is performed by a device which detects transmitted light from a portion where etching has been completed. In the method of detecting the end point, it is difficult to arrange the detector in a narrow area of about 500 μm × 500 μm of the aperture in the wet etching tank. In addition, providing such a detection mechanism at a position corresponding to each escape portion has a problem that equipment parts for the etching solution in a constant temperature bath are complicated, which increases not only the equipment cost but also the operating cost.

In addition, a nitride film or the like serving as a mask is formed on the surface of this aperture to protect the surface pattern from an etching solution. Since these films do not easily transmit light, it is not a feasible method to use this method for the method of manufacturing the aperture for the electron beam writing apparatus.

On the other hand, the method disclosed in Japanese Patent Application Laid-Open No. 63-240029 is a method in which an end point is detected by a device that collects a minute sound of bubbles generated during etching. Is difficult to arrange in a narrow area, and even if it is arranged, the sound of bubbles generated by boiling is also collected, and it is difficult to distinguish it from the minute sound of bubbles generated during etching. In addition, in this case, the object to be etched is a metal film, and it is difficult to apply the method to a method of manufacturing an aperture for an electron beam lithography apparatus on a silicon plate as a semiconductor substrate.

Accordingly, an object of the present invention is to provide an aperture for an electron beam lithography apparatus which can obtain a desired opening pattern accurately and inexpensively without specially providing an etching end point detecting means, and a method of manufacturing the same.

[0015]

According to the present invention, electron beam writing is performed.
The aperture for the device allows the electron beam to pass through the surface of the semiconductor substrate.
To form a cross section of the electron beam into various shape patterns.
A plurality of opening patterns to be formed, and a back surface area of the semiconductor substrate.
Facing the opening pattern via a silicon oxide film
And the semiconductor so as not to hinder the passage of the electron beam.
The first of which the back surface of the substrate is removed by wet etching
Aperture for electron beam lithography with pits formed
And the semiconductor substrate is provided on a back surface region of the semiconductor substrate.
Is removed by the wet etching, and
A second recess not facing the opening pattern,
The first recess and the second recess are provided on the side surfaces of the semiconductor substrate.
But at the opening where the silicon oxide film is exposed at the bottom
The second depression is larger than the opening of the first depression
Air bubbles generated in the second dent with a large opening
It is used for detecting the end point of the wet etching.
It is characterized by the following.

Further, a peripheral portion of a region where the first recess is formed.
The second recess is formed in the second recess.
The shape is a long groove in one direction or the first
It is desirable that the second dent is formed in the dent formation region .

Still another feature of the present invention is that an aperture pattern is provided.
The opening pattern is formed on the back surface of the semiconductor substrate on which the surface is formed.
First opening opposite to the first opening and the same as the opening of the first depression
Part and the opening pattern do not face each other and
Applying a mask having a second opening larger than the first opening;
And, thereafter the semiconductor substrate immersed in an etching solution, before
Bubbles generated when etched from the second opening
Said first recess by detecting that eliminates
This is a method for fabricating an aperture for an electron beam lithography apparatus that completes the formation of a pattern.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIGS. 1 (a) and 1 (b) are cross-sectional views showing a substrate in the course of production for explaining an embodiment of an aperture for an electron beam lithography apparatus and a method for producing the same according to the present invention, and are immersed in an etching bath. FIG. As shown in FIG. 1A, the aperture for the electron beam lithography apparatus corresponds to a region where the opening pattern group opening 3 is formed.
Depressions 1 a and 1 b which are eroded by etching at openings larger than any of the escape portions 2 under the iO ₂ film 6 are provided on the back surface of the substrate 8.

In the method of manufacturing the aperture for the electron beam lithography apparatus, first, the thickness of Si on the surface is about 10 to 20 μm.
m and an Si film having a thickness of several hundreds μm using the SiO ₂ film 6 having a thickness of about 1 to ₂ μm. Next, the surface portion of the substrate 8 is patterned as in the semiconductor lithography process. That is, a SiO ₂ film is formed on the surface of the substrate 8 to a thickness of about 1 to ₂ μm, a resist is applied thereon, and the resist is formed into a desired pattern until the back etching for processing the back surface of the substrate 8 is substantially the same as described in the conventional example. After forming, exposing and developing, the SiO ₂ film is dry-etched to form a mask for the opening pattern group opening 3. Next, the SiO
_{Using the two} films as masks, the thin surface side Si film is dry-etched by about 10 to 20 μm down to the SiO ₂ film 6 to form the opening pattern group openings 3. Then, a mask nitride film 4 which is a Si ₃ N ₄ film serving as a back surface mask is formed on the entire substrate 8 by about 100 n.
m.

Next, a resist is applied, exposed, and developed on the back surface of the substrate 8 to selectively remove the nitride film for mask 4 by etching, so that the clearance 2 and the openings of the depressions 1a and 1b have the same shape and the same size. Except for the nitride film indicated by the two-dot chain line, the window 17 for the escape portion 2 and the windows 16a and 16b for the depression are opened to form the back surface mask pattern 4a.

Next, the substrate 8 having the backside mask pattern 4a on the backside is heated to the boiling point and the back etching solution 5
(30 wt% KOH aqueous solution at 114.5 ° C.) to perform back etching. The back etching solution 5 is placed in a back etching bath and heated by a hot plate.

Since the etching rate for the (100) crystal plane of the substrate 8 is about 6 μm / min,
Assuming that the thickness of the Si film on the back surface is 500 μm, about 80 mi
n, when the thickness of the back surface Si is 650 μm, about 110 mi
Etching is completed with n. At this time, the Si portion without the Si ₃ N ₄ film in the back mask pattern 4a is filled with hydrogen bubbles 5
Etching is performed while generating a and 5b. Since the etching is performed at the boiling point, boiling bubbles 5c are also generated in the etching solution 5. As the etching proceeds in such a state, first, the bubbles 5a from the escape portion 2 disappear, and then the bubbles 5b in the depression 1b and the bubbles in the depression 1a disappear in order. At this point, the etching is completed.

That is, the size of the opening pattern 3 region on the mask on which the electron beam directly acts is, for example, 500 μm.
If the thickness is set to × 500 μm, the wet etching of the Si film proceeds isotropically at an angle of about 55 °. For example, if the Si film thickness on the back side is set to 500 μm, the initial size of the opening of the escape portion 2 is 1200 μm. And the back surface Si film thickness is 6
If it is 50 μm, it will be 1410 μm. As the area of Si to be etched becomes smaller than the initial opening size as it approaches the opening pattern 3 at an angle of about 55 degrees as the wet etching is performed, the generated bubbles gradually decrease, and eventually. When reaching the SiO ₂ film 6 serving as a stopper, the end point is reached.

Therefore, in the present invention, the back surface mask pattern 4a corresponding to the depressions 1a, 1b having openings (windows 16a, 16b) larger than the opening (window 17) of any of the escape portions 2 is provided.
Is formed, it can be confirmed whether or not the etching of the escape portion 2 has been completed by checking whether there is a bubble 5b in which the depressions 1a, 1b reaching the etching end point later than the escape portion 2 exist. Also, a depression 1 for detecting the etching end point
The larger the volumes of a and 1b are, the easier it is to detect the end point visually.

FIG. 2 is a plan view showing a first embodiment of the aperture for an electron beam writing apparatus according to the present invention. As shown in FIG. 2, the aperture for the electron beam lithography apparatus is provided on the back surface of the substrate 8 outside the region where the opening 2a of the escape portion corresponding to the opening pattern group opening where the plurality of opening patterns 3 are formed is formed. There are depressions 1c, 1d, 1e. Considering the layout on the substrate 8 so as to increase the number of opening pattern group regions formed from one substrate 8 as much as possible, the depressions 1c and 1 serving as the etching end point detection patterns are thus considered.
d and 1e are preferably formed on the outer peripheral portion of the bonded substrate 8. The depressions 1c, 1d, and 1e can be used for inserting pins for positioning on the stage.

FIG. 3 is a plan view showing a second embodiment of the aperture for an electron beam writing apparatus according to the present invention. As shown in FIG. 3, the aperture for the electron beam writing apparatus has depressions 1f and 1g in a region where an opening pattern group opening is formed. That is, depressions 1g and 1f having large openings 2a are formed in place of the escape portions. This case is applied to the case where the number of opening patterns is relatively small and the interval between the opening patterns is wide. An opening pattern is provided in these depressions 1f and 1g as necessary, and can be used for checking wafer rotation during surface patterning, for XY alignment of the substrate 8, or for TEG for checking process conditions.

Here, one of the opening pattern group openings may be divided as an aperture chip as in the conventional example, but in the case of the present invention, various patterns are formed so that electron beams can be drawn on a resist of a semiconductor substrate. This is a large aperture having a plurality of apertures for an electron beam writing apparatus without being divided. Also, this aperture does not necessarily need to be covered with a conductive film.

[0029]

As described above, the present invention is directed to a back surface etching mask having a window on the back surface of a semiconductor substrate that defines an opening of a relief portion corresponding to an opening pattern group formation region. By additionally providing a window forming a depression having an opening larger than the opening of the above, and etching through this back surface etching mask, the presence or absence of air bubbles from the depression generated for a longer time than the escape portion, the escape portion Can accurately detect the etching end point at which the wafer is completely etched, eliminating over-etching and insufficient etching in the opening pattern, accurately obtaining the opening pattern, and inexpensively eliminating the need for special etching end point detection means in the etching tank. There is an effect that an opening pattern having the following dimensions can be obtained.

[Brief description of the drawings]

FIGS. 1A and 1B are a cross-sectional view showing a substrate in the course of manufacture and a cross-sectional view of a state of being immersed in an etching bath for explaining an embodiment of an aperture for an electron beam lithography apparatus of the present invention and a method of manufacturing the same.

FIG. 2 is a plan view showing a first embodiment of an aperture for an electron beam writing apparatus according to the present invention.

FIG. 3 is a plan view showing an aperture for an electron beam writing apparatus according to a second embodiment of the present invention.

4A to 4C are cross-sectional views illustrating an example of a method of manufacturing a conventional aperture for an electron beam writing apparatus, which is illustrated in a manufacturing order.

[Explanation of symbols]

1a, 1b, 1c, 1d, 1e, 1f, 1g Depression 2 Escape portion 2a Escape portion opening 3,9a Opening pattern group opening 3a Opening pattern 4 Masking nitride film 4a, 13 Backside mask pattern 5a, 5b, 5c Bubbles 6 , 11 SiO ₂ film 7a, 7b Si substrate 8 substrate 9 surface mask pattern 10 Si ₃ N ₄ 1 film 12 resist 14 conductive film 16a, 16b, 17 window

Claims (4)

(57) [Claims] 1. A plurality of opening patterns which passes the electron beam to shape the cross section of the electron beam into a variety of shapes pattern on the surface of the semiconductor substrate, the back surface region of said semiconductor substrate
And the opening pattern is opposed via a silicon oxide film.
Then, the back surface of the semiconductor substrate is removed by wet etching so as not to hinder the passage of the electron beam.
An aperture for an electron beam lithography apparatus having a depression formed therein , wherein the semiconductor substrate is provided on a back surface region of the semiconductor substrate.
Is removed by the wet etching, and
A second recess not facing the opening pattern,
The first recess and the second recess are provided on the side surfaces of the semiconductor substrate.
But at the opening where the silicon oxide film is exposed at the bottom
The second depression is larger than the opening of the first depression
Air bubbles generated in the second dent with a large opening
An aperture for an electron beam writing apparatus, which is used for detecting an end point of a wet etching . 2. A method according to claim, wherein the shape of said second recess with the the periphery second recess is formed in the first recess forming region is long groove shape in one direction 1
An aperture for an electron beam writing apparatus according to the above. 3. The method according to claim 1, wherein the second recess is formed in an area where the first recess is formed.
2. The aperture for an electron beam lithography apparatus according to claim 1, wherein a depression is formed. 4. A first opening which is opposite to the opening pattern on the back surface of the semiconductor substrate having an opening pattern formed on a front surface thereof and which is the same as the opening of the first depression, and which does not face the opening pattern and which one of them A mask having a second opening larger than the first opening is applied, and then the semiconductor substrate is immersed in an etchant to detect that bubbles generated when being etched from the second opening disappear. Forming an aperture for the electron beam lithography apparatus by completing the formation of the first depression.