JPS5840333B2 - Microcircuit manufacturing method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method of manufacturing a microcircuit.

It is an object of the present invention to increase the resist's resistance to etching and to increase the density of the features of the formed device.

Conventionally, electron beam etching and plasma etching are performed, for example, in the Journal of Vacuum Science
eTechnology, Volume 14, No. 1, No. 26
6 (1977) and Electronics, No. 8
This is a well-known technique as described on pages 9 to 98 (May 12, 1977).

However, conventional lithographic resist systems have been found to have marginal etching resistance against dry plasma etching processes in the manufacture of microcircuits.

Heretofore, thick resist layers have had to be used to adequately protect the substrate from unwanted etching in non-patterned areas.

Therefore, the geometrical density of the formed device is limited,
There was also a negative impact on alignment.

The method according to the invention significantly reduces the resist thickness, requiring only 1/10 to 2/3 of the thickness of the prior art.

Cross-linking as such in the method according to the invention is well known, for example as shown in US Pat. No. 4,007,047.

However, the above patent specification does not propose any treatment using metal ions.

In the method according to the invention, a coat of resist is first formed by conventional means such as spin coating, baking, exposure and development.

The resist is then further cross-linked by means appropriate to that particular resist.

The means may be, for example, prior exposure to plasma or treatment with a solution of acid and formaldehyde.

After this cross-linking, the surface of the resist is contacted with a solution containing reactive metal ions, ie, metal ions that chemically react with the resist.

In this contact, metal ions are incorporated into the resist.

As a result, the resist has greater resistance to etching by commonly used plasma etching and reactive ion etching methods.

The surface of a resist system subjected to the method according to the invention can vary the depth of penetration of metal ions, thereby controlling the degree of resistance to etching and concomitantly controlling the etching profile. Means are achieved.

Sodium and potassium are the most preferred metal ions.

Particularly preferred is an aqueous solution of metal hydroxide.

Ota, Mg++, Mn++, Cotan, and A, 7-1-
Other reactive metal ions selected from groups 1, 2, 2, 2, 2, and 2, such as ++, may also be used.

This is achieved by first treating the cross-linked system with, for example, sodium hydroxide or potassium hydroxide, which then causes exchange with polyvalent metal ions.

The method according to the invention can be applied to a wide variety of any resists, especially those containing substitutable female hydrogens, such as carboxylic acid groups, alcohol groups and amine groups.

Chelates, acid anhydrides, and their related systems are also structures that can facilitate the introduction of metal ions.

In particular, this process has achieved very good results with resins consisting of phenol-formaldehyde resins or derivatives thereof and with polymers and copolymers of methacrylic acid and/or methacrylic anhydride.

In particular, terpolymers of methyl methacrylate, methacrylic acid, and methacrylic anhydride achieved significantly better results.

Any of several different methods may be used to remove resist containing metal, such as oxygen ashing followed by water or dilute acid cleaning to remove both resist and metal. Ru.

It is also possible to directly treat with dilute acid to remove metal ions.

Example 1 Three coatings of 2 μm thick m-cresol/formaldehyde resin with photoactive compounds were spin coated onto a wafer with a silicon dioxide surface and heated at 80°C.
heated for 15 minutes at
heated for minutes.

Two of these coatings were cross-linked by reacting in an aqueous solution of hydrochloric acid/formaldehyde at 85° C. for 15 minutes.

One of the cross-linked films is 25 hydroxide)
It was immersed in an aqueous solution of IJum for 1 minute.

All three coatings were then heated at a temperature of 170'C to 180C for 30 minutes.

The three coatings were then etched in an 8% oxygen and 92% carbon tetrafluoride plasma at 0.55 Torr and 200 watts of radio frequency power.

The coating treated with metal ions according to the method according to the invention exhibited an etching rate of 340 people per minute while the other two coatings showed an etching rate of 640 people per minute.

Example 2 Two quartz disks were coated with approximately 2 μm of resist similar to the resist used in Example 1.

The inner plates were heated at 85° C. for 30 minutes, then immersed in standard developer for 2 minutes and rinsed with water for 5 minutes.

One of the discs was cross-coupled as in Example 1 and 25
% sodium hydroxide solution and briefly immersed in water, then dried.

Both discs were heated for 30 minutes at a temperature of 185-190°C and then etched in a bipolar carbon tetrafluoride plasma.

The etching rate ratio of the untreated coating to the treated coating was 1.48 at 100 μHg pressure and 50 watts of RF power, and 1.48 at 100 μHg pressure and 100 watts of RF power 31 and 2.16 at a pressure of 20 μHg and RF power of 50 Watts.

Example 3 A silicon wafer was spin coated with a terpolymer of methacrylic acid, methyl methacrylate, and methacrylic anhydride.

The coated wafer was heated in an oven in air at 180° C. for 30 minutes.

It was then immersed in a 25% V/V solution of diphenyldichlorosilane in toluene for 15 minutes.

It was then washed in toluene and then heated on a hot plate for 10 minutes at a temperature of 80-90°C.

The wafer was then immersed in an aqueous solution of 0.1N hydroxide and then in deionized water.

It was then spin dried and heated at 120°C for 30 minutes.

Plasma etching was carried out at a pressure of 0.55 Torr and 200
Watts radio frequency power in a carbon tetrafluoride/oxygen discharge.

A significant reduction in terpolymer removal was observed in the case of the treated coatings.

Only 4,000 people thick was removed in 30 minutes,
In the case of untreated coatings, a thickness of 2 μm was removed in about 20 minutes.

After about 30 minutes, the etching rate of the treated coating was about 90 per minute.
0, but this rate was higher than the equilibrium etching rate (e
quilibrium etch rate).

Under the above plasma etching conditions, 2 μm of silicon becomes 1
It was removed in less than 0 minutes, and 5 in 2 of 2 μm was removed in about 30 minutes.

This shows that the method according to the invention is useful.

Claims (1)

[Claims] 1. Forming a resist layer capable of forming cross-links on a substrate, performing a lithographic process on the resist to form a resist pattern, and then treating the resist with a plasma treatment or a solution of acid and formaldehyde. cross-linking and then exposing the surface of the resist to an aqueous solution containing sodium hydroxide or potassium hydroxide to increase the resistance of the resist to reactive ion etching or plasma etching, and A method of manufacturing a microcircuit including a plasma etching process.