JPH07335534A - Formation of fine resist pattern - Google Patents

Abstract

PURPOSE:To eliminate the occurrence of a residue resulting from the development of a negative type resist layer at the time of forming a fine resist pattern of a two-layer resist composed of the negative type resist layer and a positive type resist layer. CONSTITUTION:When a negative type resist layer 30 is dipped in a developing solution 50 after exposing the resist layer 30 to an electron beam 40 in a prescribed pattern, the exposed surface of the resist layer 30 is brought to the down side in the direction of gravity in the solution 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithographic technique used in a semiconductor integrated circuit or a superconducting integrated circuit, and more particularly to a method for forming a fine resist pattern of submicron or less with high precision.

[0002]

2. Description of the Related Art In the process of manufacturing semiconductor layer integrated circuits and superconducting integrated circuits, in order to pursue high-speed performance of various functional devices such as transistors and Josephson junctions to be manufactured and to further increase the integration density, Various attempts have been made to reduce the size of individual devices, that is, to reduce the area occupied by unit devices on an integrated circuit board, and to reduce the line width of wiring and the wiring interval. However, in the first place, in order to construct such various fine structures such as minute elements and minute width wirings, it is necessary to form a resist pattern serving as an etching mask for cutting them with high precision.

Generally, such a resist pattern is obtained by exposing a resist material layer, which is applied in a series on the surface of an underlayer to be etched, in a predetermined pattern and then developing the resist material layer. An electron beam exposure method has been attracting attention as an exposure method capable of drawing a fine pattern reaching a wide range. In fact, as the performance of the electron beam exposure apparatus itself, it has been reported that it is possible to draw up to a dimension of 10 nm.

On the other hand, much research has been conducted on resist materials and the resist structure itself, and as a resist structure capable of simultaneously achieving high resolution and high aspect ratio,
Techniques using a multilayer resist such as a two-layer resist and a three-layer resist have been proposed. Above all, PCM proposed by BJ Lin, a member of IBM Corporation in the United States.
(Portable Comformal Mask) method, that is, the pattern of the upper patterned resist layer is exposed to deep UV light (wavelength 2
As an example of concrete implementation of the conceptual method of transferring to the lower resist layer by total irradiation of 00-300 nm short-wavelength ultraviolet light), Proceedings of the 45th Annual Meeting of the Society of Applied Physics, 1984 (12p) -T-11), p.247, CMS (chloromethylated polystyrene) which is a negative resist material in the upper layer,
A method using PMMA (polymethylmethacrylate) which is a positive resist material for the lower layer is disclosed.

Certainly, the two-layer resist method using such a combination of CMS and PMMA is suitable as a resist or the like used in an etching step for forming a fine junction in the production step of a Josephson junction element, for example. This is because the lift-off process in the organic solvent can be applied, and thus the interlayer insulating film formation and the like can be easily performed by the self-alignment method after the etching process.

[0006]

However, CMS as a negative type resist material (crosslinking type resist material) formed on PMMA which is a positive type resist material has a special problem, and even a few microns after development. Residues of a large size tend to remain. In fact, this was a disaster, and even small scale integrated circuits could only yield around 50%. If CMS is passed through a fine filter to make the particle diameter uniform and fine before application, the generation of resist residue can be suppressed to some extent, but it was not perfect.

As the negative resist material or the cross-linked resist material, in addition to the above CMS, αM-CMS
(Chloromethylated poly alpha methyl styrene) or C
There are PMS (chlorinated polymethylstyrene) and the like, which are good materials themselves, but as a common drawback, residues due to development tend to remain.

In view of the above points, the present invention is a method for forming a fine resist pattern in which a negative resist layer formed on a positive resist layer is exposed and developed so that no material residue of the negative resist material remains. Is intended to be provided.

[0009]

In order to achieve the above object, the present invention applies a positive / negative two-layer resist method, and when the negative resist layer subjected to electron beam exposure according to a predetermined pattern is immersed in a developing solution. , Proposing that the exposed surface of the negative resist layer is oriented downward along the direction of gravity so that the unexposed portion of the negative resist layer that has not been subjected to electron beam exposure dissolves in the developer in the direction of gravity drop. To do.

[0010]

FIG. 1 shows an embodiment of a fine resist pattern forming method according to the present invention for each of the elementary steps (A) to (G). Hereinafter, this example will be described together with a specific resist material, except that the final step shown in FIG.
As shown in, since the specific structure of the lower layer structure portion that is finally etched by using the fine resist pattern 90 formed by the present invention as an etching mask is not directly related to the present invention, It is shown simply as the underlayer 10 to be etched.

First, in the first step, as shown in FIG. 1 (A), on the underlayer 10 which is the etching target layer,
PMMA selected as a positive type resist material is applied to a thickness of 0.5 μm by a spinner to form a first applied layer 21. The first coating layer 21 is baked in the temperature range of 120 ° C. to 150 ° C. in air or dry nitrogen for 30 to 60 minutes. The temperature at this time is not limited to the above range and is preferably higher, but the fine resist pattern 90 shown in FIG. 1 (G) manufactured by the present invention is lifted off after etching the underlayer 10. If it is too high, it becomes difficult to dissolve in the organic solvent used at this time, so that it is suitable to be within the above temperature range, particularly 120 ° C. which is the lower limit of the temperature range. However, the temperature range, the time range, and various parameters such as the coating thickness, including those in the following description, allow slight errors.

On the first coating layer 21, as shown in FIG. 1B, PMMA, which is the same positive resist material, is used.
Is again coated with a spinner to an appropriate thickness, for example 0.5 μm, to form a second coating layer 22, and this second coating layer 22 is preferably in air or dry nitrogen in a temperature range of about 135 ° C to 155 ° C. Bake for 30 to 60 minutes. It is desirable that the baking temperature of the second coating layer 22 is also high, but if the underlayer 10 may be adversely affected by heat, for example, a lower temperature, for example, around 135 ° C. is desirable.

In any case, when the formation of the positive resist layer 20 composed of the first and second coating layers 21 and 22 is completed in this manner, then, as shown in FIG. 1 (C). As described above, as the negative resist material, αM-CMS is selected from the above-mentioned material group, and this is applied on the positive resist layer 20 with a spinner to a thickness of 0.5 μm, and also at an appropriate temperature. For example, the negative resist layer 30 is formed by baking at 135 ° C. for 20 to 30 minutes in air or dry nitrogen.

The main surface of the negative resist layer 30 thus formed is exposed by the electron beam 40 in a pattern corresponding to the fine resist pattern 90 to be finally obtained, as shown in FIG. 1 (D). To do.

Next, as shown in FIG. 1 (E), both the underlayer 10 and the exposed negative type resist layer 30 are turned upside down so that the exposed surface faces downward in the direction of gravity. To immerse in developer 50. As the developing tank, other mechanical devices required for development, a substrate holder that mechanically holds the sample having the underlayer 10, and the like, known existing ones can be used. For example, in general, the substrate holder holds the sample by holding the side edge or the peripheral edge of the sample (wafer).
When using such a holder,
All you have to do is flip the sample over and hold it.

As the developing solution 50, α selected in this embodiment is used.
For M-CMS, a mixed solution of isoamyl acetate, isoamyl nitrate (iAA) / di-n-butyl ether, and dinormal butyl ether (DnBE) can be used. Preferably, in order to achieve uniform development in such a developing solution, according to a known method, the underlayer in the developing solution 50.
10 Together, the negative resist layer 30 is rotated or swung in a plane parallel to the main surface.

In the present invention, however, since the exposed surface of the negative resist layer 30 is directed downward in the direction of gravity as described above in the present invention, the negative resist layer 30 which has not undergone electron beam exposure is not exposed. The exposed part melts in the developing solution 50 in the direction of falling by its own weight, and even if there is a part that melts out as a minute solid at this time, they float in the developing solution 50 and eventually settle down below due to their own weight. Because I'm going to
It does not adhere as a residue on the exposed surface of the positive resist layer 20.

When the developing process is completed in this way, the negative resist layer 30 becomes a patterned negative resist layer 30 'cut into a predetermined pattern. After that, the negative resist layer 30 is taken out from the developing solution 50 and then exposed. The positive type resist layer 20 thus formed, together with the remaining patterned negative type resist layer 30 ′, for example, 110 ° C.
After baking for 20 to 30 minutes in air or dry nitrogen in the temperature range of 120 to 120 ° C (the baking in this step is referred to as the first baking for convenience in the following description), As shown in 1 (F), the entire surface of the positive type resist layer 20 including the surface of the remaining patterned negative type resist layer 30 'is exposed to deep UV light 60,
Expose. In other words, this step is a selective exposure treatment of the positive resist layer 20 using the patterned negative resist layer 30 'as a mask. The term deep UV light is not confirmed as a scientific term, but as is well known, it is well-established in the lithography field and refers to short wavelength ultraviolet light having a wavelength of 200 to 300 nm.

After this, preferably again from 110 ° C. to 120 ° C.
20 minutes to 30 minutes in air or dry nitrogen in the temperature range of ° C
After baking for a minute (this is referred to as a second baking for convenience), a known developer suitable for PMMA used as the material of the positive resist layer 20 in this embodiment, for example, MIBK (methyl isobutyl ketone) is used. ), The exposed positive type resist layer 20 is subjected to a development treatment, and then, as shown in FIG.
As shown in Fig. 5, a patterned positive resist layer 20 'is formed, and this gives a fine resist pattern to be finally obtained.
See the completion of 90.

Deep UV of the positive type resist layer 20
At the time of exposure with light or at the time of subsequent development, it is not particularly necessary to turn it over (although it may be left inside out), and known exposure methods and development methods may be used. Positive resist layer 20
The positive type resist material for forming is not only PMMA used in the above-mentioned examples but also PGMA (polyglycidyl methacrylate), PMGI (polydimethylglutarimide), PM.
There are IPK (polymethyl isopropenyl ketone) etc.,
Any of them can be used in place of the PMMA of the above-mentioned embodiment, and the residue generated by the development treatment of these positive resist material layers hardly causes a problem. In particular, there is no need to consider in forming the high precision fine resist pattern 90 which is the object of the present invention.

On the other hand, as the negative type resist layer 30 serving as a patterning mask for the positive type resist layer 20, the above-mentioned CMS, CPMS or the like can be used instead of the αM-CMS used in the above embodiment. However, the negative resist layer made of these materials has a problem of its development residue. Therefore, although the type of the developing solution may differ depending on the negative resist material used (a suitable developing solution for each material is known), both are in accordance with the present invention during the development process.
It should be developed with the exposed surface facing downward in the direction of gravity.

In fact, in an experiment for verifying the above-mentioned embodiment according to the present invention, it was confirmed that there was no negative resist layer residue in all the test samples, and a fine resist pattern 90 up to 0.3 μm width was obtained. I got it successfully. In other words, none of the devices failed due to the resist residue. Furthermore, when this fine resist pattern 90 was used to cut out a Josephson junction, a fine Josephson junction of up to 0.5 μm square was obtained.

In the above description, for the sake of convenience, there is no particular problem in the quality of the obtained fine resist pattern 90 even if either of the two baking steps, first and second, is omitted. . However, before the whole surface of the negative type resist layer 20 is exposed with the deep UV light 60, it takes some preparation time, so if the first baking is performed during that time, the manufacturing time can be saved.

Further, in the above-mentioned embodiment, as shown in FIGS. 1A and 1B, the positive type resist layer 20 is formed by two coating steps. It may be formed only by one application process. Other parameters such as the thickness of each layer 20, 30 and the baking temperature and the baking time may be in accordance with the values actually required at the manufacturing site and are not directly specified in the present invention.

[0025]

Although the negative and positive two-layer resist method is essentially suitable for forming a fine resist pattern, the conventional method has a problem in that residues are generated due to the development of the negative resist layer located on the upper side. On the other hand, according to the present invention, since the exposed surface of the negative resist layer is turned over and development is performed, even if there is a negative resist material in the developing solution that melts out as a solid, it is not allowed to move downward due to its own weight. It does not have a chance to deposit as a residue on the exposed positive type resist layer. Therefore, it is possible to obtain a fine resist pattern in which the occurrence of defects due to the resist residue is sufficiently suppressed, and thus, the manufacturing yield of an integrated circuit in which a large number of extremely fine semiconductors or superconducting elements are integrated is significantly improved. be able to.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of each elementary process in an embodiment of a method for forming a fine resist pattern according to the present invention.

[Explanation of symbols]

 10 Underlayer to be etched, 20 Positive resist layer (PMMA), 20 'patterned positive resist layer, 21 First coating layer of positive resist layer, 22 Second coating layer of positive resist layer, 30 Negative type Resist layer (αM-CMS), 30 'patterned negative resist layer, 40 electron beam, 50 developer, 60 deep UV light, 90 fine resist pattern.

Front Page Continuation (72) Inventor Masaaki Maesawa 1-4-1 Umezono, Tsukuba-shi, Ibaraki Industrial Technology Research Institute (72) Inventor Susumu Takada 1-4-1 Umezono, Tsukuba-shi, Ibaraki Industrial Technology Inside Institute of Electronics Technology

Claims (14)

[Claims] 1. A positive type resist layer and a negative type resist layer are laminated and formed on an underlayer to be etched, and the negative type resist layer is exposed to an electron beam according to a predetermined pattern and then dipped in a developing solution to form the above predetermined layer. To form a patterned negative resist layer having a shape corresponding to that of the pattern, and then developing the positive resist layer by exposing it to deep UV light to develop the pattern of the negative patterned resist layer. A method for forming a fine resist pattern according to the predetermined pattern by a patterned positive resist layer having a shape corresponding to, and a laminated structure of the positive patterned resist layer and the negative patterned resist layer. When the negative resist layer subjected to electron beam exposure according to the predetermined pattern is immersed in the developing solution, the exposed surface of the negative resist layer is exposed. Forming a fine resist pattern, which is oriented downward along the direction of gravity so that the unexposed portion of the negative resist layer that has not been exposed to the electron beam is dissolved in the developing solution in the direction of falling by its own weight. Method. 2. A positive resist layer forming step of forming a positive resist layer by applying a positive resist material on an underlayer to be etched and then baking the resist material; and a negative resist on the positive resist layer. A negative resist layer forming step of forming a negative resist layer by applying a material and baking; a negative resist layer exposing step of exposing the negative resist layer with an electron beam according to a predetermined pattern; A negative resist layer developing step in which the exposed surface of the already used negative resist layer is oriented downward along the direction of gravity and immersed in a developing solution to develop; and the positive resist layer exposed by the development of the negative resist layer. A positive resist layer baking step of baking the resist; a positive resist layer exposing step of exposing the positive resist layer to deep UV light; Positive resist layer developing step of developing the di-type resist layer; 3. The method according to claim 2, wherein the positive resist layer forming step includes a second applying step of the positive resist material; a second applying step after a first applying step. And a baking step of the positive resist material first coating layer coated in the first coating step. 4. A method according to claim 2 or 3;
A step of baking the positive resist layer between the positive resist layer exposure step and the positive resist layer developing step; 5. A method according to claim 2 or 3;
The positive resist layer baking step is performed before the positive resist layer exposing step, but after the exposing step and before the positive resist layer developing step. how to. 6. The method according to claim 1, 2, 3, 4 or 5, wherein the positive resist material is polymethylmethacrylate. 7. The method according to claim 1, 2, 3, 4 or 5, wherein the positive resist material is polyglycidyl methacrylate. 8. The method according to claim 1, 2, 3, 4 or 5, wherein the positive resist material is polydimethylglutarimide. 9. The method according to claim 1, 2, 3, 4 or 5, wherein the positive resist material is polymethyl isopropenyl ketone. 10. Claims 1, 2, 3, 4, 5, 6, 7,
8. The method according to 8 or 9, wherein the negative resist material is chloromethylated polystyrene. 11. Claims 1, 2, 3, 4, 5, 6, 7,
8. The method according to 8 or 9, wherein the negative resist material is chloromethylated polyalphamethylstyrene. 12. The method according to claim 1, 2, 3, 4, 5, 6, 7,
8. The method according to 8 or 9, wherein the negative resist material is chlorinated polymethylstyrene. 13. The method according to claim 2, 3, 4 or 5, wherein the positive resist material is polymethylmethacrylate, and the negative resist material is chloromethylated polystyrene. And how to. 14. The method according to claim 2, 3, 4 or 5, wherein the positive resist material is polymethylmethacrylate, and the negative resist material is chloromethylated polyalphamethylstyrene. A method characterized by: