JPH0653115A - Pattern formation - Google Patents

Abstract

PURPOSE:To form a pattern with excellent inner plane controllability and sure phase shift effects by forming the pattern, which has a thickness that allows the phase shift effect, on first resist by developing second resist after exposure. CONSTITUTION:Second resist is formed on first resist. Patterning exposure is performed by KrF excimer laser stepper. Then, the pattern is developed by xylene and a structure which has the resist pattern 2b for the second resist is provided. Flood exposure is performed using an (i) line demagnification projection aligner, PEB is performed at 11 deg.C for 90 seconds for one-minute paddle development. As a result, a 0.21mum isolated line pattern is formed by the resist pattern for the first resist. Thus, the pattern is formed with excellent inner plane controllability and sure phase shift effects.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method. The pattern forming method of the present invention can be used for forming various patterns when forming an electronic material (semiconductor device or the like), for example.

[0002]

2. Description of the Related Art In the field of electronic materials and the like, for example, in the field of semiconductor devices, miniaturization and high integration are progressing increasingly,
The minimum feature size of semiconductor integrated circuits is now in the sub-half micron range. Along with this, the phase shift method, which can obtain high resolution, has been attracting attention. However, the mask (reticle) used for the phase shift method is difficult to put into practical use because it is difficult to manufacture, find and correct defects.

In this connection, a phase shift method called POST, which is placed directly on the substrate, has been proposed (IEDM).
91 (1991, IEEE) 91-63 to 91-6
6, Tabuchi et. al. "Novel 0.
2um i-Line Lithography by
Phase-Shifting on the Su
bstrate (POST) ”).

According to this technique, as shown in FIGS. 15 to 18, the resist 1A is thinly exposed to light E ₃ by a mask M in advance (FIG. 15) and developed to develop a step (this step t is A resist pattern 1B provided with a phase difference of 180 ° is formed (FIG. 16), and by utilizing this, a flood (floo
d) After exposure E ₂ (FIG. 17), the pattern 1C is left at the edge portion (FIG. 18) so as to give an effect just like a so-called chromeless shifter. 1 in the figure
0 indicates a substrate. According to this method, a phase shift reticle having a complicated structure is unnecessary. Therefore, this method can be said to be simple and excellent.

[0005]

However, in the above technique, a step is formed by the thin exposure E ₃ (see FIG. 1).
5) It is difficult to perform uniform treatment so that the in-plane is well controlled and the phase shift effect is sufficiently produced. This problem is the biggest bottleneck in putting the above technology into practical use.

An object of the present invention is to solve the above problems and to provide a pattern forming method capable of forming a pattern with good in-plane controllability and with a sufficient phase shift effect. .

[0007]

The invention according to claim 1 of the present application comprises a step of applying a first resist on a substrate, and a step of applying a second resist on the first resist. And a step of forming a pattern having a thickness that provides a phase shift effect on the first resist by developing the second resist after exposure, and irradiating the first resist on the entire surface through the second resist pattern. And a step of removing the second resist pattern and developing the first resist pattern, thereby achieving the above object. .

According to a second aspect of the present invention, a step of applying a first resist to a substrate, a step of forming a buffer layer on the first resist, and a step of forming a second resist on the buffer layer. A step of applying, a step of exposing and developing the second resist to form a pattern having a thickness that provides a phase shift effect on the first resist, and a step of applying the first resist through the second resist pattern. A pattern forming method, which comprises at least a step of irradiating a whole surface of a resist and a step of removing the second resist pattern and developing the first resist pattern, thereby achieving the above object. To do.

The invention of claim 3 of the present application is the method for forming a pattern according to claim 2, wherein the buffer layer is an aqueous buffer layer, and thereby achieves the above object. .

According to the invention of claim 4 of the present application, the thickness t which brings about the phase shift effect of the second resist is t = λ / 2.
It is (n-1), The pattern formation method of Claim 1 or 2 characterized by this, The said objective is achieved by this. Where λ is the exposure wavelength and n is the first
Is the refractive index of the resist.

In a fifth aspect of the present invention, the second resist is arbitrarily selected from soluble polysiloxane, cyclized rubber negative resist, naphthoquinone diazide positive resist, and polymethylmethacrylate. The pattern forming method according to any one of claims 1 to 4, wherein the above object is achieved.

Basically, the present invention is as shown in FIG.
Step I of applying a first resist, step of forming a buffer layer IA on the first resist if necessary, and step of applying a second resist on the buffer layer or the first resist II, a step III of forming a pattern having a thickness that provides a phase shift effect on the first resist by developing the second resist after exposure, and the first resist through the second resist pattern. Process IV of whole surface irradiation
And a step V of removing the second resist pattern and developing the first resist pattern.

The invention of the present application has the following aspects.
It can be carried out preferably. That is, the surface of the first resist is a light-sensitive material having a sensitivity 10 times or more higher than that of the resist at the same wavelength, or a light-sensitive material having sensitivity at different wavelengths or different energy beams, and A step of applying a material having a transparency equivalent to that of the first resist at the flood exposure wavelength as a second resist, and applying the second resist with a solvent that does not damage the underlying first resist; Exposure with an energy beam such as EB (electron beam) or X-ray light (post-exposure bake P
EB is performed), and the film thickness t of the remaining second resist material after development with a developer that does not cover the first resist is
and a step of forming a pattern on the first resist so that λ / 2 (n-1) (λ: exposure wavelength, n: refractive index of this second resist material). Then, it can be preferably carried out as a method for forming a pattern by flood exposure (PEB as required) and development.

It is also preferable to carry out the following method. That is, it can be coated on the surface of the first resist as a buffer layer with, for example, xylene, decalin, water, or a fluorine-based solvent that is transparent at the flood exposure wavelength and does not dissolve the first resist, and is formed as an upper layer. A layer of a material that does not dissolve in the coating solvent of the second resist (photosensitive material) is provided, and a layer of the second resist (photosensitive material) is further provided thereon to expose the pattern, and PEB if necessary, then develop, flood expose using this pattern, PEB if necessary, peel off the intermediate buffer layer (in general, when the buffer layer is water-soluble or alkali-soluble, development Since it is possible to remove them at the same time, it is possible to preferably use a mode in which the entire development is performed after this peeling step is unnecessary).

In this embodiment, the buffer layer is PVA
(Polyvinyl alcohol), PVP (polyvinylpyrrolidone), xylene-soluble polysiloxane, CYTOP,
It may be selected from TEFLON · AF, pullulan, cellulose, sputtered SiO, sputtered SiO ₂ .

In the embodiment using this buffer layer, the second resist (photosensitive material) and the underlying first resist can be the same.

According to the present invention described above, it is possible to eliminate the above-mentioned problems of the prior art and provide a substrate direct phase shift technology with excellent controllability and uniformity. That is, the first
After the light sensitive material (second resist) for the shifter is placed directly on the resist of above, or through the buffer layer, the upper layer is patterned with a certain margin, and then flood exposure is performed. Can be done.

Here, the film thickness t of the second resist, which is the upper photosensitive layer, after patterning is λ / 2.
(N-1) (λ is the flood exposure wavelength of the underlying first resist, and n is the refractive index of the photosensitive material that is the second resist at that wavelength). , Most preferred. For example, when photosensitive polysiloxane is used as the upper second resist material, the refractive index is about 1.41 when flood exposure is performed with i-line,
A film thickness of 450 nm is preferred. This gives you exactly 180
° Phase shift exposure with phase inversion can be performed.

What is next desired is that the second resist (the buffer layer when the buffer layer is necessary), which is the upper photosensitive material, is transparent in the flood exposure wavelength region. The photosensitive material that can be preferably used as the second resist is selected from materials such as photosensitive polysiloxane, negative resist (cyclized rubber type), positive type resist (naphthoquinone diazide type), PMMA and the like. You can As the buffer layer, non-photosensitive polysiloxane, PVA, PVP, CYTOP, Tef
It is preferably selected from fluororesins such as lonAF, glycosides such as pullulan, and cellulose.

As the non-photosensitive polysiloxane, a polysiloxane polymer can be used, and in this case, polyladder siloxane can be preferably used as the polysiloxane polymer.

CYTOP (Cytop. Trade name.
Asahi Glass Co., Ltd. and perfluorotributylamine

[Chemical 1]

Is a fluoropolymer having the following structure, which can be used as a specific solvent.

[0023]

[Chemical 2]

Taflon AF (trade name DuPont) is a so-called amorphous fluororesin which is soluble only in a specific fluorocarbon solvent.

As in the present invention, the above-mentioned two layers (first and second resists) or three layers (first and second resists,
Also, in order to construct a buffer layer structure for both, it is preferable that the organic films do not intermix (mix with each other). When a novolac-based photoresist is used as the lower first resist, the material coated on it is xylene, decalin, hexane, chlorobenzene,
A solvent that can be dissolved in a solvent such as a fluorine-based solvent (such as Fluorinert) or water is preferable.

According to the present invention, it is possible to surely realize the phase shift method of placing the surface directly on the surface. The technology of the present invention is 64M
The present invention can be applied to a 0.35 μm rule device represented by DRAM and 16 MSRAM, to a 0.25 μm rule device thereafter, or to a later device.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. However, it goes without saying that the present invention is not limited to the embodiments.

Example 1 In this example, the following operation was performed. A 5-inch silicon wafer dehydrated and baked at 200 ° C. was treated with HMDS (hexamethyldisilazane) vapor at 25 ° C. for 1 minute, and this was used as a substrate 10 on which PFi-20 (manufactured by Sumitomo Chemical i. (Line resist) was spin-coated at a thickness of 1.2 μm, and then baked at 90 ° C. for 90 seconds. As a result, as shown in FIG.
A first resist 1 was formed on the (silicon wafer).
(Note that the drawing is a schematic view, and the resist 1 is partially formed on the substrate 10, but in reality, the entire surface is coated).

On top of this, Ph ₂ I ⁺ O was added as a photoacid generator.
5wt of Tf (diphenyliodonium triflate)
% Xylene-soluble polysiloxane was used as a second resist, spin-coated and baked at 90 ° C. for 90 seconds. Thus, as shown in FIG. 3, the second resist 2 was formed on the first resist 1.

Patterning exposure is performed with Kr of NA 0.42.
F excimer laser stepper (NSR1505EX, manufactured by Nikon) was used. In FIG. 4, the exposure of the second resist is indicated by E ₁ , and the exposed portion 2a is indicated by a dot. The exposure amount was 10 mJ / cm ² .

Thereafter, PEB was applied at 90 ° C. for 90 seconds, and development with xylene was performed to remove unnecessary polysiloxane. Thus, as shown in FIG. 5, a structure having a resist pattern 2b of the second resist was obtained. The film thickness t of the formed resist pattern 2b of the second resist in the upper layer was set to 450 nm, which is optimum for i-line.

Thereafter, the i-line reduction projection exposure apparatus RA-10 is used.
1VL2 (Hitachi, NA 0.42, 10: 1 stepper)
Flood exposure E ₂ with an exposure dose of 200 mJ / c
m ² (FIG. 6). After that, PEB at 9 ° C for 9
After 0 seconds, paddle development was performed for 1 minute with NMD-W (used in Tokyo Oka, alkaline developer 2.38%). As a result, as shown in FIG. 7, a 0.21 μm isolated line pattern could be formed by the resist pattern 1b of the first resist.

Example 2 Reference is made to FIGS. 8 to 14. In this example, first, in the same manner as in Example 1, a layer of PFi-20 was formed as the first resist 1 (FIG. 8).

After that, PVA (polyvinyl alcohol) was applied as a buffer layer to a film thickness of 0.15 μm (FIG. 9).

On top of this, OCD (Polysiloxane, manufactured by Tokyo Ohka Co., Ltd.) was added by spin coating a mixture of 3 wt% of Ph ₃ S ⁺ OTf (triphenylsulfonium triflate) as a photosensitive material (methanol solvent). A resist 2 was formed (FIG. 10).

Thereafter, in the same manner as in Example 1, the second resist exposure E ₁ (FIG. 11), the second resist resist pattern formation (FIG. 12), and the flood exposure E ₂ (FIG. 1).
3) was performed to obtain a resist pattern 1b of the first resist (FIG. 14).

During development, the second upper resist 2 is formed.
Was removed together with the PVA forming the buffer layer 3 (PVA is aqueous, so it is dissolved and removed during development).

According to this example, an isolated line pattern of 0.23 μm could be formed.

In this embodiment, the buffer layer 3 is replaced with CY.
When formed by TOP or Teflon AF and carried out, similar results were obtained. However, in order to remove the buffer layer, it was necessary to perform removal using each specific solvent.

[0040]

According to the present invention, the prior art, eg PO
It has been possible to provide a pattern forming method capable of overcoming the drawbacks of the ST method, having good in-plane controllability, and performing pattern formation while ensuring that a sufficient phase shift effect occurs.

[Brief description of drawings]

FIG. 1 is a process explanatory diagram of a pattern forming method of the present invention.

FIG. 2 is a diagram showing a process of Example 1 (1).

FIG. 3 is a diagram showing a process of Example 1 (2).

FIG. 4 is a diagram showing the process of Example 1 (3).

FIG. 5 is a diagram showing the process of Example 1 (4).

FIG. 6 is a diagram showing the process of Example 1 (5).

FIG. 7 is a diagram showing a process of Example 1 (6).

FIG. 8 is a diagram showing a process of Example 2 (1).

FIG. 9 is a diagram showing a process of Example 2 (2).

FIG. 10 is a diagram showing a process of Example 2 (3).

FIG. 11 is a diagram showing the process of Example 2 (4).

FIG. 12 is a diagram showing the process of Example 2 (5).

FIG. 13 is a diagram showing a process of Example 2 (6).

FIG. 14 is a diagram showing the process of Example 2 (7).

FIG. 15 is a diagram showing a process of a conventional technique (POST method) (1).

FIG. 16 is a diagram showing a process of a conventional technique (POST method) (2).

FIG. 17 is a diagram showing a process of a conventional technique (POST method) (3).

FIG. 18 is a diagram showing a process of a conventional technique (POST method) (4).

[Explanation of symbols]

I First resist coating step IA Buffer layer forming step II Second resist coating step III Second resist resist pattern forming step having phase shift effect IV Whole surface irradiation step V First resist resist pattern forming step 1st 1 resist 1b 1st resist resist pattern 2 2nd resist 2b 2nd resist resist pattern 3 buffer layer

Claims (5)

[Claims] 1. A step of applying a first resist to a substrate,
A step of applying a second resist on the first resist; a step of developing the second resist after exposure to form a pattern having a thickness that provides a phase shift effect on the first resist; A pattern including at least a step of entirely irradiating the first resist through a second resist pattern, and a step of removing the second resist pattern and developing the first resist pattern. Forming method. 2. A step of applying a first resist to a substrate,
Forming a buffer layer on the first resist;
Applying a second resist on the buffer layer,
Developing the second resist after exposure to form a pattern having a thickness that provides a phase shift effect on the first resist; and the first resist pattern through the first resist pattern.
2. A pattern forming method comprising: at least the step of irradiating the entire surface of the resist, and the step of removing the second resist pattern and developing the first resist pattern. 3. The pattern forming method according to claim 2, wherein the buffer layer is an aqueous buffer layer. 4. The pattern forming method according to claim 1, wherein the thickness t of the second resist that causes the phase shift effect is t = λ / 2 (n−1). Where λ is the exposure wavelength and n is the refractive index of the first resist. 5. The second resist is any one selected from soluble polysiloxane, cyclized rubber negative resist, naphthoquinonediazide positive resist, and polymethylmethacrylate. 5. The pattern forming method described in 1 to 4.