JPH1124286A - Pattern forming method for photosensitive resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily obtain a reversed tapered pattern shape by exposing the whole surface of a first positive photosensitive resin having high heat resistance applied on a substrate, then applying a second photosensitive resin, and exposing the resin through a photomask. SOLUTION: A positive photosensitive resin (novolac resin) is dropped and uniformly applied by spin coating on a silicon substrate to form a layer of a first photosensitive resin 12. Then the whole surface of the positive photosensitive resin is exposed by using a specified stepper. Then a positive photosensitive resin 13 as a second layer is uniformly applied on the first photosensitive resin. As applied, the whole substrate is heat treated on a hot plate under specified conditions. Then the substrate is exposed through a specified photomask 14. The surface of the second photosensitive resin 13 is changed into hardly soluble and is naturally dried under specified conditions so as to prevent the edge part of the surface from dulling during development. Then, finally, the layer is developed with a developer comprising a specified alkali soln.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a photosensitive resin pattern, and more particularly, to a method for forming a semiconductor integrated circuit, a thermopile, a piezoelectric element, and the like.

[0002]

2. Description of the Related Art In order to achieve high integration of a semiconductor integrated circuit or downsizing of a thermoelectric stack as an infrared sensor and downsizing of a piezoelectric element as a pressure sensor, an acceleration sensor and the like, pattern dimensions, particularly, It is necessary to make the photosensitive resin finer, but when the photosensitive resin is made finer, it becomes difficult to obtain a fine pattern forming ability (resolution) and a profile having a good cross-sectional shape.

[0003] At present, reduction projection exposure apparatuses are mainly used for forming fine patterns. In order to form a fine pattern with the reduction projection exposure apparatus, it is necessary to improve three items described by the Rayleigh equation. That is, the resolution is
This is a value obtained by dividing the value obtained by multiplying the process constant by the exposure wavelength by the numerical aperture of the projection lens.

Therefore, in order to improve the resolution, that is, to form a fine pattern of photosensitive resin, it is necessary to reduce the process constant, shorten the exposure wavelength, or increase the numerical aperture of the projection lens. Any one of the above may be performed. The exposure wavelength ranges from a 436 nm wavelength g line to a 36 wavelength wavelength line.
The wavelength has been reduced to a 5 nm i-line and a KrF excimer laser having a wavelength of 248 nm, and has been put to practical use. The numerical aperture of the projection lens is also increasing.

On the other hand, as a method for reducing the process constant, for example, a pattern forming method described in JP-A-63-133626 is applied. After that, exposure and development are performed.

[0006]

Even if a pattern having a steep cross-sectional profile is formed of a positive photosensitive resin by a conventional method, a metal film or the like is formed on the positive photosensitive resin of the pattern. When the film is formed, the positive photosensitive resin is peeled off by a peeling liquid by a lift-off method, and when the metal film or the like is patterned, the metal film or the like formed on the substrate is necessarily formed of the positive photosensitive resin. In contact with the wall,
In many cases, the stripping solution cannot easily dissolve the positive photosensitive resin.

Further, when the cross-sectional profile of the positive photosensitive resin is a forward taper, the metal film or the like formed on the substrate is continuously formed on the forward taper of the positive photosensitive resin. Therefore, the substrate is connected to the surface of the positive photosensitive resin on the forward taper of the positive photosensitive resin from the substrate. Therefore, the positive photosensitive resin is not sufficiently eroded by the stripping solution and cannot be stripped, or even if it can be stripped, it is connected to the metal film and the like remaining on the substrate and stripped. Result.

Therefore, when a film is removed by a lift-off method, a negative photosensitive resin capable of easily forming a reverse taper is often used. The main component of the resin is a rubber-based resin, and its heat-resistant temperature is lower than that of a novolak-based positive photosensitive resin. That is, it is disadvantageous when the substrate is to be heated in order to improve the adhesion between the metal film or the like and the substrate.

An object of the present invention is to solve the above-mentioned problems. That is, using a positive heat-sensitive resin having higher heat resistance, a metal film or the like formed on a substrate is not in contact with a wall of the positive-type photosensitive resin, in other words, lift-off can be easily performed. The purpose of the present invention is to provide a reverse tapered pattern formation.

[0010]

To achieve the above object, the present invention employs the following method.

A step of applying a photosensitive resin on the substrate, a step of exposing the entire surface of the substrate to which the photosensitive resin has been applied, and a step of again applying the photosensitive resin on the substrate to which the photosensitive resin has been applied. Coating, heating the substrate on which the photosensitive resin is coated twice, exposing using a predetermined photomask, and developing with an alkaline aqueous solution. This is a pattern forming method.

According to the present invention, it is possible to form a reverse-tapered pattern with a positive photosensitive resin, form a film of a metal or the like at a high temperature, and easily peel off the film of the metal or the like by a lift-off method. Can be formed.

Next, a step of applying a photosensitive resin on the substrate, a step of performing a first heat treatment on the substrate on which the photosensitive resin has been applied, and exposing the entire surface of the substrate on which the photosensitive resin has been applied A step of again applying a photosensitive resin on the substrate on which the photosensitive resin has been applied, a step of performing a second heat treatment on the substrate on which the photosensitive resin has been applied twice, And a developing process using an alkaline aqueous solution.

According to the present invention, when the first heat treatment is applied to the first applied photosensitive resin, the organic solvent contained in the photosensitive resin is instantaneously evaporated and hardened.
When the photosensitive resin to be a layer is applied, the total thickness of the photosensitive resin in the first layer and the second layer tends to be large. That is,
A thick photosensitive resin layer can be obtained, and a reverse tapered pattern can be formed with this thickness.

A step of applying a photosensitive resin on the substrate; a step of subjecting the substrate to which the photosensitive resin has been applied to a first heat treatment; and a step of exposing the entire surface of the substrate to which the photosensitive resin has been applied. And further, a step of applying the photosensitive resin again on the substrate on which the photosensitive resin has been applied, a step of performing a second heat treatment on the substrate on which the photosensitive resin has been applied twice, and A pattern comprising a step of exposing using a photomask, a step of subjecting the substrate coated with the double photosensitive resin to a third heat treatment, and a step of performing development with an alkaline aqueous solution. It is a forming method.

According to the present invention, when the third heat treatment is performed after the exposure, the portions which were not exposed due to the shadow of the photomask at the time of the exposure are further hardened, and the portions which are exposed and are easily dissolved in the developing solution. There is a clear difference in hardness at the boundary of. Therefore, a pattern having a steeper reverse taper can be formed during development.

Finally, a step of forming a pattern of a first metal or the like on the substrate by any of the methods described above, and stripping the photosensitive resin having the reverse taper formed on the substrate with a stripping liquid. A reverse taper on the substrate is formed in the same manner as in the step and the step of forming a pattern of a second metal or the like such that the first metal pattern and a certain specific portion are in contact with each other by any of the methods described above. Stripping the photosensitive resin with a stripping liquid.
In particular, the present invention is applicable to the case where a thermoelectric bank is formed so as to amplify the electromotive force generated at the hot junction and the cold junction of the first metal and the second metal.

According to the present invention, since the film of metal or the like is formed on the photosensitive resin patterned with a complete reverse taper, the first and second metal films formed on the substrate are formed. Since the edge portion of the pattern such as is completely separated from the metal deposited on the photosensitive resin, the photosensitive resin can be easily peeled off with a peeling liquid. Therefore, the metal or the like formed on the substrate is not pulled when the photosensitive resin is separated, and the pattern of the first and second metals and the like is hindered from the adhesion to the substrate. Without being left on the substrate. There is no burr at the edge of the pattern of the metal or the like on the remaining substrate, and the edge of the pattern becomes a very clean edge.
No (short).

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION A step of applying a photosensitive resin on a substrate, a step of exposing the entire surface of the substrate to which the photosensitive resin has been applied, and a step of re-applying the photosensitive resin on the substrate. A step of applying a photosensitive resin, a step of heating the substrate on which the photosensitive resin is applied twice, a step of exposing with a predetermined photomask, and a step of developing with an alkaline aqueous solution. A method for forming a pattern of a photosensitive resin, comprising:

[0020]

【Example】

(Embodiment 1) A first embodiment of the present invention will be described below with reference to FIG. As shown in FIG. 1A, a positive photosensitive resin, for example, AZ6130 manufactured by Hoechst Co., Ltd. is formed on a silicon substrate 11.
(Novolak type) is dropped and uniformly applied by a spin coating method. This becomes the first layer photosensitive resin 12.

Next, as shown in FIG. 1B, the entire surface of the positive photosensitive resin is exposed by a reduction projection exposure apparatus having a photosensitive wavelength of g-line and a projection lens opening of 0.54. The exposure conditions are an exposure intensity of 10 mW / cm ² and an exposure time of 10 seconds. By this overall exposure, the positive photosensitive resin 2 of the first layer is in a state of being very easily dissolved in a developing solution of an alkaline aqueous solution.

In FIG. 1C, AZ6130 as the positive photosensitive resin 13 to be the second layer is uniformly applied on the AZ6130 of the first layer photosensitive resin 2 under the same conditions. In the state of application, the entire substrate 1 is heated at 100 ° C. for 1 minute 30
Heat treatment is performed on a hot plate under the condition of seconds.

Thereafter, as shown in FIG. 1D, mask exposure is performed using a predetermined photomask 14. The exposure conditions are an exposure intensity of 10 mW / cm ² and an exposure time of 6 seconds.

Next, AZ61 of the second layer photosensitive resin 13
For the purpose of rendering the surface of 30 hardly soluble and not dulling the edge of the surface during development, it is immersed in chlorobenzene for 10 minutes at room temperature and air-dried for 5 minutes.

After these steps, development is carried out for 1 minute and 30 seconds with a developing solution of an alkaline aqueous solution containing 2.38% of tetramethylammonium hydroxide, for example, NMD-3 manufactured by Tokyo Ohka. The developer temperature at this time is 20
C. to 30C. Fig. 1 (e) shows the reverse tapered shape after development.
9 is shown. With respect to the open end of the surface of the second layer AZ6130,
The adhesive portion between the AZ6130 of the first layer photosensitive resin 2 and the substrate 11 which hits the bottom is developed in a spread state, and has an optimum cross-sectional shape for lift-off.

Finally, the effect of forming a film of metal or the like and lifting off the film will be described. FIG. 1 (f) shows the reverse tapered A
This shows a state in which aluminum 15 is formed on Z6130 by sputtering. During film formation, the entire substrate is heated to 100 ° C. Hoechst's exclusive stripper remover 200 in which the photosensitive resin AZ6130 is heated to 80 ° C.
After immersion for 20 minutes, the photosensitive resin AZ6130 combined with the first layer and the second layer is completely peeled off, and only the well-patterned aluminum 15 remains on the substrate 1. This is shown in FIG.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 2 (h), a positive photosensitive resin such as AZ6130 manufactured by Hoechst is formed on a silicon substrate 21.
(Novolak type) is dropped and uniformly applied by a spin coating method. This becomes the first layer photosensitive resin 22. further,
First baking is performed on a hot plate under a condition of a first heat treatment, for example, at 100 ° C. for 1 minute and 30 seconds. By this heat treatment, the organic solvent contained in the photosensitive resin of the first layer is completely evaporated, so that the surface of the photosensitive resin of the first layer is cured, and the photosensitive resin corresponding to the second layer is removed. When applied, the film thickness tends to be large. That is, it can be said that this method is suitable for thickening the film.

Next, as shown in FIG. 2 (i), the entire surface of the positive type photosensitive resin is exposed by a reduction projection exposure apparatus having a photosensitive wavelength of g line and a projection lens opening of 0.54. The exposure conditions are an exposure intensity of 10 mW / cm ² and an exposure time of 10 seconds. By this overall exposure, the positive photosensitive resin 22 of the first layer is in a state of being very easily dissolved in a developing solution of an alkaline aqueous solution.

In FIG. 2J, AZ6130 as the positive photosensitive resin 23 to be the second layer is uniformly applied on the AZ6130 of the first layer photosensitive resin 22 under the same conditions. In the coated state, the entire substrate 1 is subjected to a second heat treatment, and prebaking is performed again on a hot plate at 100 ° C. for 1 minute and 30 seconds under the same conditions.

Thereafter, as shown in FIG. 2 (k), mask exposure is performed using a predetermined photomask 24. The exposure conditions are an exposure intensity of 10 mW / cm ² and an exposure time of 7 seconds.

Next, AZ613 of the second layer photosensitive resin 3
For the purpose of making the surface of No. 0 hardly soluble and not dulling the edge of the surface during development, it is immersed in chlorobenzene for 10 minutes at room temperature and air-dried for 5 minutes.

After these steps, development is performed for 1 minute and 50 seconds with a developing solution of an alkaline aqueous solution containing 2.38% of tetramethylammonium hydroxide, for example, NMD-3 manufactured by Tokyo Ohka. The developer temperature at this time is 20
C. to 30C. Figure 2 (l) shows the reverse tapered shape after development.
9 is shown. With respect to the open end of the surface of the second layer AZ6130,
The bonding portion between the AZ6130 of the first layer photosensitive resin 2 and the substrate 21, which is at the bottom, is developed in a spread state, and has an optimum cross-sectional shape for lift-off.

Finally, the effect of forming a film of metal or the like and performing lift-off will be described. FIG. 2 (m) shows the reverse tapered A
A state in which aluminum 25 is formed on Z6130 by sputtering is shown. During film formation, the entire substrate is heated to 100 ° C. The photosensitive resin AZ6130 is thickly coated in two layers, but when it is immersed in a Hoechst special stripper remover 200 heated to 80 ° C. for 20 minutes, the photosensitive resin of the first layer and the second layer is combined. AZ61
30 is completely stripped, leaving only the cleanly patterned aluminum on the substrate 21. In this method, since the photosensitive resin can be formed in a thicker pattern, an aluminum pattern can be formed in a thicker film. Figure 2
(N). (Embodiment 3) Next, a third embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 3 (o), a positive photosensitive resin, for example, AZ6130 manufactured by Hoechst, is formed on a silicon substrate 31.
(Novolak type) is dropped and uniformly applied by a spin coating method. This becomes the first layer photosensitive resin 32. further,
First baking is performed on a hot plate under a condition of a first heat treatment, for example, at 100 ° C. for 1 minute and 30 seconds.

Next, as shown in FIG. 3 (p), the entire surface of the positive photosensitive resin is exposed by a reduction projection exposure apparatus having a g-line photosensitive wavelength and a projection lens opening of 0.54. The exposure conditions are an exposure intensity of 10 mW / cm ² and an exposure time of 10 seconds. By this overall exposure, the positive photosensitive resin 32 of the first layer is in a state of being very easily dissolved in a developing solution of an alkaline aqueous solution.

In FIG. 3 (q), AZ6130 as the positive photosensitive resin 33 to be the second layer is uniformly applied on the AZ6130 of the first layer photosensitive resin 32 under the same conditions. In the coated state, the entire substrate 31 is subjected to a pre-bake again on a hot plate at 100 ° C. for 1 minute and 30 seconds as a second heat treatment.

Thereafter, as shown in FIG. 3 (r), mask exposure is performed using a predetermined photomask 34. The exposure conditions are an exposure intensity of 10 mW / cm ² and an exposure time of 7 seconds.

Next, AZ61 of the second layer photosensitive resin 33
For the purpose of rendering the surface of 30 hardly soluble and not dulling the edge of the surface during development, it is immersed in chlorobenzene for 10 minutes at room temperature and air-dried for 5 minutes. Then, as a third heat treatment, a bake after exposure at 120 ° C. for 1 minute and 10 seconds (P
EB) is performed on a hot plate. Due to the third heat treatment, a portion which is not exposed to light behind the photomask at the time of exposure is further hardened, and a clearer difference in hardness is generated at a boundary between the exposed portion and a portion which is easily dissolved in a developing solution. .
Therefore, a pattern having a steeper reverse taper can be formed during development.

After these steps, development is performed for 1 minute and 50 seconds with a developing solution of an alkaline aqueous solution containing 2.38% of tetramethylammonium hydroxide, for example, NMD-3 manufactured by Tokyo Ohka. The developer temperature at this time is 20
C. to 30C. Fig. 3 (s) shows the reverse tapered shape after development.
9 is shown. With respect to the open end of the surface of the second layer AZ6130,
The adhesive portion between the AZ6130 of the first layer photosensitive resin 32 and the substrate 1, which is at the bottom, is developed in a spread state, and has an optimum cross-sectional shape for lift-off. Moreover, the second layer AZ6
The pattern opening end on the surface 130 keeps a steep acute angle, and has a more favorable reverse tapered shape.

Finally, the effect of forming a film of metal or the like and lifting off the film will be described. FIG. 3 (t) shows the reverse tapered A
This shows a state where aluminum 35 is formed on Z6130 by sputtering. During film formation, the entire substrate is heated to 100 ° C. Hoechst's exclusive stripper remover 200 in which the photosensitive resin AZ6130 is heated to 80 ° C.
After immersion for 20 minutes, the photosensitive resin AZ6130 including the first layer and the second layer is completely peeled off, and only the patterned aluminum remains on the substrate 31. This is shown in FIG. (Embodiment 4) Next, a method for forming a thermoelectric deposit using the pattern forming method of the present invention will be described with reference to FIG.

FIG. 4 (v) corresponds to FIG. 3 (s) described in the third embodiment of the present invention, and has a reverse tapered structure after development.
FIG. 3 is a cross-sectional view of a positive photosensitive resin before film formation of metal or the like. The conditions for forming the positive photosensitive resin are all the same as those in Embodiment 3 of the present invention.
This is equivalent to the condition introduced in. For the thermoelectric bank, the composition of antimony and bismuth, which have relatively high electromotive force, was selected from the relationship between the Seebeck coefficient and the specific resistance.

FIG. 4 (w) is a cross-sectional view of the substrate 41 in which antimony is formed on the reverse-tapered positive photosensitive resin by resistance heating evaporation. When depositing antimony, the substrate 41 and the positive photosensitive resin 42
Are heated to 130 ° C. The antimony 43 enters the positive-type photosensitive resin 42 and the gap formed by patterning the positive-type photosensitive resin 42 and adheres to the substrate 41 to form a film.

FIG. 4 (x) shows a cross section after the positive photosensitive resin 42 is peeled off by a peeling liquid. After being lifted off, only the pattern of antimony 45 remains on the substrate 41 cleanly.

Here, the positive photosensitive resin 44 is patterned again on the substrate 41 on which the antimony 43 is formed by the method described in the third embodiment of the invention. FIG. 4 (y) shows a cross section in which an inverted tapered shape is formed. The antimony 4
Since the pattern No. 3 has already been formed, the positive photosensitive resin 44 has a raised shape only on the pattern of the antimony 43. The reverse tapered groove is the antimony 4
3 between the three patterns. This is because the bismuth constituting the thermoelectric bank is patterned between the antimony 43.

FIG. 4 (z) shows a sectional view of the substrate 41 on which the positive photosensitive resin 44 is formed, which is heated to 120 ° C. and bismuth is deposited by resistance heating evaporation. Like antimony, bismuth is formed on the substrate 41 from the patterned gap of the positive photosensitive resin 44.

Finally, FIG. 4A shows a cross-sectional view of the substrate 41 from which the positive photosensitive resin 44 has been peeled off by a peeling liquid. If antimony and bismuth are alternately arranged and patterned so as to overlap at the ends, a serial thermoelectric bank can be formed, and the output can be amplified by the number of thermoelectric banks.

[0048]

As is clear from the above description, according to the inventions described in the embodiments, the first heat-resistant first material coated on the substrate is used.
The entire surface of the photosensitive resin layer is exposed, and the photosensitive resin of the second layer is coated and exposed by a photomask, so that a reverse tapered pattern can be easily obtained. The metal film can be formed after the film is improved, and the pattern of the photosensitive resin is reversely tapered, so that the film of metal and the like attached to the substrate surface and the film of metal and the like on the photosensitive resin are completely separated. As a result, the photosensitive resin can be easily peeled off.

According to the invention described in the second embodiment, after the first layer positive photosensitive resin having high heat resistance is applied on the substrate, the first layer is formed.
Since the photosensitive resin is sufficiently dried and cured, the friction on the surface of the photosensitive resin increases, and when the positive photosensitive resin of the second layer is applied after the entire surface is exposed, the heat treatment is performed in a horizontal direction. Difficult to spread and easy to thicken. At the same time, since an inverted taper pattern shape can be easily obtained, it is very effective when a thick metal film or the like is desired to be formed. Even if the film is thickly attached, the film of metal or the like on the substrate surface and the film of metal or the like on the photosensitive resin can be completely separated, and the photosensitive resin can be easily peeled off (lift-off).

According to the invention described in the third embodiment, claim 1
In addition to having the advantages of claim 2 and the third heat treatment before development, the difference in hardness at the boundary between the exposed and unexposed portions in the photomask exposure of the photosensitive resin of the second layer is obtained. Since the size can be increased, an acute reverse tapered shape of the photosensitive resin can be obtained after development. Since the angle is sharp and the hardness is increased, the inverted tapered shape can be maintained even at a higher temperature, so that a metal film or the like can be formed at a higher temperature of the substrate.

According to the invention described in the fourth embodiment, claim 3
When a photosensitive resin is patterned into a reverse tapered shape by the method described above to form a thermoelectric deposit composed of antimony and bismuth, the thermoelectric deposit has high adhesion to the substrate, and the edge of the pattern has no burrs. Since the edge becomes smooth, there is no short circuit between adjacent patterns. In addition, since antimony and bismuth can be formed thicker,
Since the cross-sectional area of the pattern can be increased and the resistance value can be reduced, a thermopile with high sensitivity can be obtained.

[Brief description of the drawings]

FIG. 1 is an embodiment of a process of forming a reverse tapered pattern of a positive photosensitive resin according to the present invention.

FIG. 2 is an embodiment of a thick-film reverse tapered pattern forming step of the positive photosensitive resin of the present invention.

FIG. 3 is an embodiment of a pattern forming step of a positive photosensitive resin thick film type and a sharply tapered opening end portion of the present invention.

FIG. 4 shows an embodiment of forming an infrared sensing thermoelectric bank composed of antimony and bismuth using the positive photosensitive resin reverse tapered pattern of the present invention. (V) to (aa)
Up to this point, sectional views are shown in the order of steps.

[Explanation of symbols]

41 Substrate 42 Positive photosensitive resin with reverse taper formed 43 Metal antimony 44 Positive photosensitive resin with reverse taper formed after antimony formed 45 Metal bismuth

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI H01L 21/306 H01L 21/306 N

Claims (4)

[Claims] A step of applying a photosensitive resin on a substrate;
Exposing the entire surface of the substrate coated with the photosensitive resin,
Further, on the substrate on which the photosensitive resin has been applied, a step of applying the photosensitive resin again, a step of heating the substrate on which the photosensitive resin has been applied twice, and using a predetermined photomask A method for forming a pattern of a photosensitive resin, comprising: a step of exposing; and a step of performing a developing treatment with an alkaline aqueous solution. 2. A step of applying a photosensitive resin on a substrate;
A step of performing a first heat treatment on the substrate on which the photosensitive resin has been applied, a step of exposing the entire surface of the substrate on which the photosensitive resin has been applied, and Applying a photosensitive resin, performing a second heat treatment on the substrate on which the photosensitive resin is applied twice, exposing the substrate using a predetermined photomask, and performing a developing process using an alkaline aqueous solution. And a method for forming a pattern of a photosensitive resin. 3. A step of applying a photosensitive resin on a substrate;
A step of performing a first heat treatment on the substrate on which the photosensitive resin has been applied, a step of exposing the entire surface of the substrate on which the photosensitive resin has been applied, and Applying a photosensitive resin, performing a second heat treatment on the substrate on which the photosensitive resin has been applied twice, exposing the substrate using a predetermined photomask, 3. A method for forming a pattern of a photosensitive resin, comprising: a step of performing a third heat treatment on a substrate to which is applied, and a step of performing a development treatment with an alkaline aqueous solution. 4. A step of forming a pattern of a first metal or the like on a substrate by the method according to any one of claims 1 to 3, and peeling the photosensitive resin having an inverse taper formed on the substrate. A step of peeling off with a liquid;
Forming a pattern of a second metal or the like so that the first metal pattern contacts a specific portion by any one of the methods described above. Stripping the photosensitive resin with a stripping liquid.