JPS58118641A - Radiation sensitive positive type resist for forming fine pattern - Google Patents

Abstract

PURPOSE:To obtain the titled positive type resist with superior radiation sensitivity, superior resolution and sufficient dry etching resistance by using a copolymer of methyl methacrylate with alkoxyalkyl methacrylate. CONSTITUTION:A radiation sensitive positive type resist material made of a copolymer of >=50mol% methyl methacrylate with alkoxyalkyl methacrylate represented by the formula (where R is 1-10C alkoxyalkyl) is dissolved in a suitable solvent and applied to a support to form a resist film having 0.1-2mum thickness and the film is cross-linked by heating. The desired part of this resist film is irradiated to draw a pattern, and by selectively removing the irradiated part by development, a resist pattern is formed. Thus, a high density resist pattern with high resolution and sufficient dry etching resistance is obtd. while saving the quantity of radiation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation-sensitive positive resist suitable for forming fine patterns for manufacturing semiconductors, photomasks, etc.

Traditionally, as a pattern forming method for semiconductors and photomasks, a method using a wet etching method using a photoresist sensitive to ultraviolet light has been widely put into practical use.However, in recent years, solid-state devices have become denser and more integrated. From 4N sunny,
Microfabrication techniques are being put into practical use in which patterns are formed by exposure to ionizing radiation such as electron beams and X-rays, and dry etching methods such as reactive ion etching are used.

The resist used for such microfabrication needs to have high sensitivity and high resolution, from the viewpoint of forming a highly accurate resist pattern with good productivity and transferring it to the substrate with good JN quality by dry etching. In addition, it is claimed to have sufficient dry etching resistance.

However, a radiation-sensitive positive resist having high sensitivity and sufficient dry etching resistance has not yet been developed. For example, PH1, which is known as a highly sensitive positive electron beam resist, is easily thermally decomposed and cannot be used in the dry etching process, and PMMA, a typical positive electron beam resist, also has sufficient dry etching resistance. does not have.

On the other hand, Az -2400, Ax -1350 (5hip
It has been reported that photoresists such as those manufactured by Ray Co., Ltd. (111) are used as positive radiation resists for dry etching, but although these positive resists have sufficient dry etching resistance, It has a low sensitivity of 7 and lacks practicality as an electron beam resist.

The present invention is based on the above-mentioned actual situation KI! Therefore, the present invention aims to provide a positive lid resist having high radiation sensitivity, high lubricability, and sufficient dry etching resistance by using a specific polymer.

That is, the radiation-sensitive positive resist material of the present invention is:
It is characterized by being composed of a copolymer of methyl methacrylate and alkoxyalkyl methacrylate represented by the general formula [1].

(tlR represents an alkoxyalkyl group having 1 to 10 carbon atoms.) In general formula [1], the alkoxyalkyl group is l-methoxymethyl group.

1-/'14' diethyl group, 1-methoxypropyl group,
1-ethoxybutyl group, 1-ethoxyethyl group, l-ethoxypropyl group, l-ethoxybutyl group, 2-meth)-
IF diethyl group, 2-methoxypropyl group, 2-methoxybutyl group, 2-ethoxyethyl group, 2-ethquinpropyl group, 2-ethoxybutyl group, 3-methoxypropyl group, 4-methoxybutyl group.

Examples include 1-methoxyneopentyl group.

In the present invention, the radiation-sensitive positive plate resist may be composed of a polymer represented by the general formula (1) and a resist such as PBS or PMMA.

Next, a method of forming a pattern using the ionizing radiation-sensitive positive resist material of the present invention will be explained by showing an example.

First, a positive resist solution is prepared by dissolving the radiation-sensitive positive resist material in a suitable solvent such as methyl cellosolve acetate. Subsequently, this resist solution is uniformly applied onto a semiconductor substrate or a mask substrate by a spray method or the like to form a resist film having a thickness of 0.1 to 2 μm. In addition.

When forming the resist film, a method other than the spin code method such as plasma polymerization may be used. Next, the formed resist film is crosslinked by heat treatment at a temperature sufficient to thermally crosslink it, thereby making it insolubilized or exfoliated in organic solvents and at the same time sufficiently increasing its dry etching resistance. The new value portion of the resist film is irradiated with radiation to form a pattern 7111. The pattern drawing means is a direct pattern drawing method using an electron beam or an ion beam, in which pattern formation can be easily controlled from the outside by scanning the beam, or a mask having a desired pattern is placed between the resist film and the radiation source. An indirect pattern writing method using electron beams, X-rays, etc., which forms a pattern by intervening the pattern, can be adopted. Next, the substrate after the pattern has been drawn is subjected to a wet phenomenon treatment such as a dip or spray method, or a dry development treatment using gas plasma, etc., to selectively remove only the radiation-exposed portions of the resist film, thereby forming the resist pattern. Form.

As described above, since the radiation-sensitive positive lid resist material of the present invention easily undergoes a crosslinking reaction by appropriate heat treatment, a resist film with strong heat resistance, dry etching resistance, and solvent resistance can be obtained by heat treatment. It is also presumed that because the cross-linked portions are efficiently cut by radiation, the dissolution rate ratio of the irradiated area to the non-irradiated area can be high, resulting in high sensitivity. It is sufficient to set the molecular weight of the positive resist material of the present invention to a level that does not affect the coating properties, specifically, from tens of thousands to several millions.

There is no particular need to increase the molecular weight.

Several radiation-sensitive positive resist materials using such a thermal crosslinking process have been proposed, including, for example, a warm polymer of methyl memethacrylate-methacryloyl chloride copolymer and methyl memethacrylate-methacrylic acid copolymer. However, the resolution was generally inferior to that of ordinary positive resists, and it was difficult to control the thermal crosslinking treatment, and the re-familiarity during formation was often poor.

On the other hand, the positive resist material according to the present invention has high resolution and is a copolymer containing methyl methacrylate, which is a polymer unit of resist PMM (polymethyl methacrylate). It is an extremely practical positive resist material that does not require strict temperature control during heat treatment and can obtain the same characteristics with good reproducibility within an appropriate temperature range. As mentioned above, the resist of the present invention is composed of methyl methacrylate, 1-rukoxy methacrylate, and 0 copolymer, but PMMA
In order to obtain the same Xs image properties as above, it is desirable that the copolymerization ratio of alco, 7, 7, methacrylate, and O is 50 molar or less.

Therefore, the radiation-sensitive positive resist material of the present invention is
By using this resist material, which is easy to handle, it is possible to form a high-density resist pattern with high resolution and sufficient dry etching resistance with a lower radiation dose than conventional methods. It is possible.

Next, the present invention will be explained in detail.

Methyl methacrylate-1-methoxyethyl methacrylate copolymer synthesized from Ikkan 110 by normal radical 1 combination (copolymerization composition ratio 70:30, average molecular weight Mv = 62
．． 7.times.10') was dissolved in methyl selonorub acetate, and a 10% resist # solution was poured into the solution.

Subsequently, this resist Se was spin-coated onto the t-silicon wafer to form a resist film with a thickness of 0.5 μm, and a circle was formed.

Subsequently, this resist film was heat-treated at 200° C. for 60 minutes to induce a crosslinking reaction, and a resist film that was resistant to solvents was formed. Apply an accelerating voltage of 20 KV to the desired portion of the resulting resist film.
After irradiating the pattern with an electron beam, a development process was carried out using ethylselonrug as a liquid solution to remove 1 ft. of the electron beam irradiated area, and a resist film (turn) was formed on the 7-recon Ueno.

Ratio WIIR Examples 1 to 3 PMMk(BOI)lfk'l/+)V-)), AZ-2
400 (5hiplay) PBX (polybutene-1-
A resist film was formed on 7 Lico/Ueno to a thickness of 0.5μ in the same manner as in Example 1, and after the usual pre-baking treatment, irradiation with an accelerating voltage of 20 KVOt was carried out. I drew a pattern. Thereafter, a FET development process was performed to form a resist pattern on the silicone resin.

Therefore, when we investigated the irradiation dose (electron beam sensitivity) required to completely remove the resist portions that were irradiated with electron beams in Example 1 and Comparative Examples 1 to 3, we found that the results are shown in Table 1 below. The result was

Margin below: 1 Table Comparative Example I PMMA 40-10
0 Comparative Example 2 Person Z -240020~80 Comparative Example 3
pBs As is clear from Table 1 above, the positive resist of the present invention has a sensitivity that is more than one order of magnitude higher than that of PMMA and Human Z-2400, and has a sensitivity that is equivalent to or higher than that of the high-sensitivity resist (PB8). It was confirmed that it has.

Examples 2 to 4 311 resist films (turns) were formed on 71 sheets of paper in the same manner as in Example 1, except that the radiation-sensitive resist shown in Table 182 below was used.

Therefore, in Examples 2 to 4, a high irradiation dose was used to completely remove the resist portions that were irradiated with electron beams.
Table 2 The results are also listed in Table 2. As is clear from Table 2 above, it was confirmed that the positive resist of the present invention has a 4-hour sensitivity.

Example 5 Methyl methacrylate-1-methoxyethyl methacrylate was applied onto a Cr mask substrate to a thickness of one cape, and a resist pattern was formed in the same manner as in Example 1. Erasing of Cr was performed using a 11VA DIM-451 dry etching device using the obtained resist pattern as a mask.The etching at that time was B Dopattu 150W.

Etching pressure 0.3 Torr, etch/da gas flow rate C
Cl47Q SCCM% Air 90 Performed in the etching case of SCCM. When the resist was removed using oxygen plasma after etching, the high-density pattern was found to be C.
It was confirmed that the image was transferred onto the r mask at high latitudes.

Comparative Example 4-6 4-6P, AZ-2400, PB8 (03 types O Hoshi II) resists were coated on a Cr mask substrate so as to have an lfimO film thickness, and each resist was coated in the same manner as Comparative Examples 1 to 3. A pattern was formed. Thereafter, dry etching of C was performed in the same manner as in Example 5.

Example 6-8 Methyl methacrylate-1-methoxyethyl methacrylate copolymer (70
:30), Methyl methacrylate-1-methoxymethyl methacrylate copolymer (22 Near 2), Methyl methacrylate-1-methoxypropyl methacrylate copolymer (60:40), Methyl methacrylate-2-methoxyethyl methacrylate Etching of C was carried out in the same manner as in Example 5 except that a copolymer (75:25) was used. Examples 5 to 8 and Comparative Example 4
The etch speed of the resist in steps 6 to 6 was determined as shown in Table 3 below.

Hihonga 4 PMM people
, 36EI2M5 AZ-2400243 As is clear from the above @3 table, all of the positive resists of the present invention have dry resistance that is approximately 1.6 times higher than that of the conventional positive electron beam resist PMMA, and more than 10 times higher than that of PB8. In some cases, it was confirmed that the resist patterns obtained in Examples 1 to 4 had high Ps. It showed the same high resolution as the image resist l'MMA, and was fine and 4 degrees fine, respectively.

As detailed above, according to the present invention, it has extremely high sensitivity and high resolution to the radiation edge, and at the same time has sufficient dry etching resistance and heat resistance, and is extremely practical for forming fine patterns. A radiation-sensitive positive resist can be provided.

Representative Patent Attorney Noriyuki Chika (1 other person)

Claims (2)

[Claims] (1) A radiation positive resist for fine pattern formation characterized by being composed of a copolymer of methyl methacrylate and an alkoxyalkyl methacrylate represented by the general formula (1) (Indicates an alkoxyalkyl group.) (2) B in general formula (1) is a 1-methoxy group, l-methoxyethyl Jti, l-methoxypropyl group, 2-
A radiation positive resist for forming fine patterns according to claim 11, which is a methoxyethyl group.