JPS5893047A - Positive type far ultraviolet resist - Google Patents

Abstract

PURPOSE:To obtain positive type resist which has high sensitivity, high resolution, and excellent dry etching resistance by adding p-tert-butyl benzoic acid as a sensitizer to a copolymer of methyl methacrylate and oxime methacrylate. CONSTITUTION:A copolymer of 10,000-800,000 number average mol.wt. consisting of 70-99mol% methyl methacrylate and 1-30mol% oxime methacrylate having acyloxyimino groups is used, and said copolymer which is added with p-tert-butyl benzoic acid as a sensitizer at 2-20g based on 100g said copolymer is used, whereby the far ultraviolet resist having dry etching resistance is obtained. The above-mentioned copolymer is obtained by block polymn. of monomers by using a-a'-azobisisobutyronitrile as an initiator.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a deep ultraviolet resist used in forming fine patterns for semiconductor elements, integrated circuits, and the like.

2. Description of the Related Art Mask transfer technology using ultraviolet light has traditionally been used to create circuit patterns in the integrated circuit manufacturing process. The resolution limit when using ultraviolet light is due to the phenomenon of light diffraction, etc. Even if a reduction projection method (10:1) is used,
In practical terms, it is 2 μm.

However, in recent years, the high density of integrated circuits has required even higher resolution, and transfer technology using ultraviolet light has reached its limit. There is a need for a promising far-UV resist. Polymethyl methacrylate (hereinafter referred to as P) is being considered as a positive resist for this purpose.
lviMA).

There are polymethyl improbenyl ketone, a copolymer of glycidyl methacrylate and methyl methacrylate (hereinafter referred to as MMA), and a copolymer of diacetyl monoxime methacrylate containing an acyloxime imino group and MMA. In addition, novolak-diazoquinone resist IAz 135 is used as a conventional UV resist.
0J and AZ2400 (Azoplate-8hiple
(manufactured by company y).

Although PMMA has high resolution, it has low sensitivity and requires several minutes for exposure. It also has poor dry etching resistance. By adding a sensitizer, polymethyl isopropenyl ketone is about 20 times more sensitive than PMMA. However, this is insufficient for the practical sensitivity required in semiconductor manufacturing processes.

Although its resolution is inferior to that of PMMA, its dry etching resistance is superior.

A copolymer of glycidized monomethacrylic acid and MMA is PMM
It has a high resolution close to that of A, and has excellent heat resistance and adhesion, but its sensitivity is about twice that of PMMA, which is low.

Methacrylic acid/diacetyl monooxime (3-oximino-2-butanone methacrylate) and PMMA
A copolymer with PMMA of up to 10
It shows twice the sensitivity. Furthermore, a terpolymer with acrylonitrile added has a maximum sensitivity of 85 times that of PMMA. The resolution of this type of resist is as high as that of PMMA, and the sensitivity is also practical. However, it has poor dry etching resistance, which is required for future VLSI manufacturing processes, and is similar to that of PMMA.

AZ-1asoJ, which is currently used for ultraviolet exposure,
The AZ-2400 uses light of 436 nm, 405 nm, and 366 nm in the emission spectrum of an ultra-high pressure mercury lamp. 'AZ-1360J (D case, extinction coefficient a(1=-αt IO, e HIO@Intensity of incident light, d: intensity of transmission.

Film thickness = 1 μm) is 0.2 (436 nm), respectively.
), α8 (405nm:'1・), 1.1 (36
5 nm), but in the 300 nm region, a=2 or more, and exposure in this region is difficult. On the other hand, AZ-24
00 is.

At 300 nm, transmission is relatively good with a=o and B.

At 280 nm, α=6, which is a large value, and the sensitivity is highly dependent on the film thickness. As a deep ultraviolet resist, at a wavelength of 250 nm.

The extinction coefficient must be 1 or less. This is absorption.

If it is too strong, the light will not reach the bottom of the resist.

This is because a problem arises in that buttering cannot be performed.

From this point of view, AZ-1asoJ and AZ-2400fJ, which have a large extinction coefficient at a wavelength of 250 nm, cannot be used as deep ultraviolet resists.

Furthermore, AZ-13501, AZ-2400 (d,,,
It also has the disadvantage of lower resolution than PMMA.

As mentioned above, there are currently resists that can be exposed to deep ultraviolet light at 250 nm, have a high resolution comparable to that of PMMA, and have excellent practical sensitivity (100 times that of PMMA) and dry etching resistance. It doesn't exist.

The present invention aims to provide a positive type deep ultraviolet resist having high sensitivity and resolution and excellent dry etching resistance.

The positive deep ultraviolet resist of the present invention is a copolymer of methacrylic acid oxime represented by methacrylate\R2 (where R1 is methyl, ethyl, propyl, butylmatahaphenyl, and R2 is phenyl or naphthyl), and P-te
rt-butylbenzoic acid is added as a sensitizer.

The present invention has been made based on the following design concept in order to improve these drawbacks. In other words, when designing polymers for deep ultraviolet resists, in order to improve sensitivity and dry etching resistance while retaining the high resolution of P and MMA, (a) the resolution should be on the methyl ester side of MMA and MMA. Obtained by copolymerization of acrylates whose chains are converted to other ester side chains. (b) To improve sensitivity, oxime methacrylate 'f: containing an acyloxime imino group having photodegradability as described above is used as a copolymerizable monomer with MMA, and a sensitizer is further added. (c)
For dry etching resistance, a resist having aromatic rings is used because aromatic rings have high resistance to ions and plasma. By the way, a resist made of 100% monomers having aromatic rings has a large absorption in the 250 nm region, so
As mentioned above, the light does not reach the bottom of the resist and cannot be patterned. Therefore, by using a material having an aromatic ring as a copolymer with MMA as described in the previous section (a), it is possible to obtain dry-resistant properties as a far-UV resist at an appropriate copolymerization rate (including an appropriate amount of aromatic rings). It is possible to make products with etching properties. By molecularly designing a resist that satisfies the above three items, it is possible to obtain a positive resist for far ultraviolet light that has high resolution, high sensitivity, and dry etching resistance. About the general manufacturing method of monomers C″″′°cH
3 ■ COCl! .

was synthesized. Here R1 is CH3, C2H6, C3H7
゜C4H9 or phenylene, R represents phenyl or subbutyl.

A copolymer with MMA was obtained by bulk polymerization of these monomers using α-α' azobisisobutyronitrile as an initiator. The composition of the copolymer was determined by elemental analysis.If the molecular weight of any of the copolymers exceeds 800,000, film forming properties on St substrates are poor.

Adhesion to the substrate was also poor. Furthermore, if the molecular weight is less than 10,000, the difference in solubility in a developer between the unirradiated area and the irradiated area during development is small, making it impractical. Furthermore, MMA
Regarding the copolymerization composition of oxime methacrylate and oxime methacrylate, when the molar concentration of the oxime monomer was 30% or more, the film formability and adhesion were poor as with high molecular weight products. Further, when the amount was 30% or more, deep ultraviolet rays did not reach the lower part of the resist due to the thickness of the film, making it impossible to pattern. On the other hand, when the molar concentration of the oxime monomer was 1% or less, the sensitivity to C radiation was comparable to that of PMMA.

The present invention will be explained in more detail below using Examples.

Example 1 Pyridine 9y and benzophenone oxime 16y were placed in methine chloride/16o11/, and methacryloyl chloride 7y was added dropwise at room temperature. This mixture was reacted at 40°C for 2 hours. After methylene chloride was distilled off, the residue was recrystallized from cyclohexane to obtain benzophenone oxime methacrylate.

A copolymer of benzophenone oxime methacrylate and methyl methacrylate with MMA was obtained by bulk polymerization using aa'-azoisobutyronitrile as an initiator. The amount of benzophenone oxime methacrylate in the obtained copolymer was 6 mol, and the number average molecular weight was 300,000. The obtained copolymer was dissolved in ethyl cellosolve acetate, and P-ta was added as a sensitizer to 1 ooy of the copolymer.
rt-butylbenzoic acid at 1.9. F, 29.5y, 10
y, 15j'.

Prepare a resist solution containing 209,
It was filtered through a 0.2 μm filter, and the filtrate was placed on a silicon substrate using a spin code method at a rotational speed of 200 Or pm.
, applied for 25 seconds, and the coated silicon substrate was coated for 15 seconds.
The solvent was removed by heat treatment in air at 0°C for 20 minutes.

The film thickness at this time was 1 μm.

After this, 1. Change the irradiation time, lightInd
The exposure amount was measured using ex (LI value), that is, the integral value of the light amount. Thereafter, the exposure amount at which the film thickness became zero was determined from the relationship curve between the exposure amount and the residual film thickness after development, and this value was taken as the sensitivity of the resist. P-tar obtained by such a procedure
Table 1 shows the relationship between the amount of t-butylbenzoic acid added and the sensitivity.

Table 1 From Table 1, it can be seen that when the amount of P-tart-butylbenzoic acid added is 1.9y or less per 10Oy of the copolymer.

It can be seen that the effect of sensitization is not small. On the other hand, the amount added is 2
When the amount exceeds y, excellent sensitivity is shown, but as the amount added increases, the copolymer content in the coated resist film decreases, resulting in poor solvent resistance of the resist film and the possibility of non-irradiation during development. The difference in solubility in the developing solution between the irradiated area and the irradiated area is small, and the practicality is slightly reduced.
When it becomes more than that, P −t er for the object 1oOy
The amount of t-butylbenzoic acid added is preferably in the range of 2.0y to 2oy.

Next, the resistance of the resist film to dry etching was evaluated under the following conditions.

That is, as the discharge condition of the plasma etching device, C
Cl4: 0,1 torr, Bar7-: 1soW
The electrode conditions were two M2o3 plates as targets and an inter-electrode distance of 6α. At this time, when the change in film thickness per unit time was measured, it was 200 to 24 OA/min when the amount of P-tert-butylbenzoic acid added was in the range of 0 to 2 oy.

Table 2 shows the results of actual measurement of the sensitivity to deep ultraviolet rays and dry etching resistance of known PMMA or copolymers of diacetyl monooxime methacrylate and MMA. The actual measurements were carried out as follows. '1 PMMA is a commercially available product (Tokyo Ohka 0EBR-1000'ii
A copolymer of dibucetyl monooxime methacrylate and MMA was polymerized in the same manner as in Example 1. The amount of diacetyl monooxime methacrylate in the obtained copolymer was 6 mol %, and the number average molecular weight was 30,000. Regarding the resist film thus obtained, sensitivity to deep ultraviolet rays and dry etching resistance were measured in the same manner as in Example 1.

Comparing the LI value and etching speed of the conventional resist film shown in Table 2 with the Ll value (Table 1) and etching speed of the resist film in Example 9, the sensitivity of the resist film according to Example 9 is compared with that of the conventional resist film. It can be seen that the dry etching resistance is 6 to 200 times higher than that of the same, and the dry etching resistance is also about 3 to 4 times higher, indicating that it has excellent properties.

Example 2 Table 3 shows the results obtained by repeating the same operations as in Example 1 except for using various oxime instead of benzophenone oxime.

In this case, in any copolymer, the oxime amount was 6 to 8 molti and the number average molecular weight was 270,000 to 400,000.

From Table 3, even when various oximes are used, the sensitivity is 5 to 200% higher than that of the conventional resist film shown in Table 2.
It can be seen that the dry etching resistance is 1.2 to 1.9 times better.

As mentioned above in the margin below, oxime-based methacrylates (copolymers of arsenide and MMA) with aromatic rings.

The deep-UV positive resist of the present invention to which F'-tert-butylbenzoic acid is added has unprecedented characteristics in terms of deep-UV sensitivity and dry etching resistance, and its industrial value is great. There is something.

Name of agent: Patent attorney Toshio Nakao and 1 other person: 1

Claims (1)

[Claims] ＼R2 (However, R1 is CH3, C2H6, C3H7, C4H9
A deep ultraviolet resist characterized by adding P-tert-butylbenzoic acid as a sensitizer to a copolymer with a methacrylic acid oxime compound represented by (R2 is phenyl or naphthyl) . ('4) The far ultraviolet resist according to claim 1, characterized in that the copolymerization rate of the copolymer is in the range of 1 to 30 molar. ('4 The number average molecular weight of the copolymer is 10 ,00
The deep ultraviolet resist according to claim 1 or 2, characterized in that the UV rays have a UV radiation in the range of 0 to 800,000. A deep ultraviolet resist characterized in that 2y to 20y is added to 100 parts of the copolymer according to any one of items 1 to 3.