JPH0582496A - Method of removing resist and device thereof - Google Patents

Abstract

PURPOSE:To remove bubbles, which are generated in a fine pattern, to remove completely a resist residue, which has intruded into the pattern, by a method wherein the resist residue is removed under a reduced atmosphere. CONSTITUTION:Substrates 4 set in a wafer cassette 3 are inserted in a cleaning liquid 7 poured in a liquid tank 1 through an introducing port 6, gas is evacuated through an exhaust vent 9 to decompress the interior of the tank 1 and the substrates 4 are cleaned under a reduced pressure. After that, gas is introduced through a gas introducing port 8 to return the interior of the tank 1 to normal pressures and the substrates 4 are taken out together with the cassette 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of transferring a circuit pattern to a resist coated on a silicon substrate, etching the resist using the resist as a mask, and removing the resist residue remaining after removing most of the resist. And a device used therefor.

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor device in which a processing dimension is miniaturized due to its high integration, improvement of etching technology is an important issue.

As a method of forming a fine pattern on an insulating film or a conductive film deposited on a silicon substrate, a resist applied on the deposited film is exposed and developed to transfer the pattern to form a resist pattern on the deposited film. After forming, the resist pattern is used as a mask for RF plasma, μ
Generally, a method of forming a fine circuit pattern on the deposited film by performing RIE (Reactive Ion Etching) using a wave plasma or the like. In such a method, the resist must be removed after the circuit pattern is formed.

The pattern to be etched is also miniaturized as the device is highly integrated. For example, in the case of 16M DRAM, the pattern is 0.5 μm.
For m and 64M DRAM, 0.4 μm fine pattern forming technology is required. In order to form such a fine pattern, as well as a technique for forming a fine pattern of a resist, an improvement in etching processing accuracy, and a technique for removing a damage generated during etching, a method for completely removing a resist after etching is established. Is an important issue.

Conventionally, after removing most of the resist adhering to the substrate surface by an ashing device using ozone or μ wave, a mixed solution of sulfuric acid / hydrogen peroxide solution and ammonium hydroxide / hydrogen peroxide solution is removed. Generally, a method of removing the residue of the resist after etching and the etching side wall protective film formed for anisotropic etching by immersing in a mixed solution of and washing with water, and drying the substrate after removing the residue of the resist is generally used. Is becoming

[0006]

However, with the miniaturization of the etching pattern, it is considered that the resist residue and the incompleteness of the removal of the etching sidewall protection film, which have not been a problem in the past, cause instability in the subsequent steps. Is becoming

In particular, it has become difficult to remove a resist residue after forming a contact hole of 0.6 μm or less and a side wall protective film formed to secure anisotropy, and a high contact resistance is caused during the subsequent metal wiring formation. This causes resistance and poor contact.

FIG. 1 is a graph showing the relationship between the contact hole diameter and the contact resistance of a sample having an oxide film thickness of 1.5 μm obtained by a conventional resist removing method. As can be seen from the figure, a contact hole with a diameter of 0.6 μm or more has a stable resistance value and a stable contact is formed. There is a large variation at μm or less.

The cause of such a variation in the resistance value is largely related to the instability of the fine contact hole forming process due to the microloading effect and the like caused by the dependence of the etching rate on the etching area. There is also a cause for imperfect removal of the residue and the etching sidewall protection film.

However, when the resist residue and the side wall protective film are removed in a mixed solution of sulfuric acid / hydrogen peroxide solution and an ammonium hydroxide / hydrogen peroxide solution after forming the contact hole of 0.6 μm or less, the contact hole is removed. Since the debris is fine, degassing becomes insufficient, and the mixed solution does not flow into the pattern because it is obstructed by the bubbles formed inside the contact hole, and it cannot be sufficiently contacted with the resist residue and the etching sidewall protection film, so these are removed. Becomes incomplete.

The present invention has been made in order to solve such a problem. When the resist after etching is largely removed, the substrate is washed in a liquid to remove the residue of the resist. An object of the present invention is to provide a method and an apparatus for completely removing the residue of the resist adhered to a fine pattern by performing it under reduced pressure.

[0012]

A method of removing a resist according to the present invention is a method of removing a residue of a resist by cleaning the substrate in a cleaning liquid after etching using a resist patterned on the substrate as a mask, It is characterized in that the step of cleaning the substrate in a cleaning liquid to remove the residue of the resist is performed under reduced pressure.

Further, the resist removing apparatus according to the present invention is
In an apparatus for cleaning a substrate in a cleaning liquid to remove residue of the resist after etching processing using a resist patterned on the substrate as a mask, a liquid tank for storing the cleaning liquid, and a holder for holding the substrate in the cleaning liquid. It is characterized by comprising a decompression means for decompressing the inside of the liquid tank and a means for returning the decompressed inside of the liquid tank to normal pressure.

[0014]

The resist removing method according to the present invention is such that the etched substrate is inserted into the cleaning liquid stored in the liquid tank and held by the holder, the inside of the liquid tank is depressurized to wash the substrate, and then the inside of the liquid tank is cleaned. Return to normal pressure and take out the substrate.

Therefore, the air bubbles generated in the recessed fine pattern such as the contact hole are removed, and the cleaning liquid sufficiently circulates to almost completely remove the resist residue and the etching sidewall protection film.

[0016]

The present invention will be described below with reference to the drawings showing the embodiments thereof. FIG. 2 is a schematic sectional view showing the structure of the resist removing apparatus according to the present invention. In the drawing, 1 is a liquid tank for storing a cleaning liquid 7 for a substrate such as a chemical liquid or pure water. A heater for heating the cleaning liquid 7 from the inner peripheral wall of the liquid tank 1 to the peripheral edge of the bottom is built in, and the center of the bottom is A drain port 5 for draining the cleaning liquid 7 to the outside is provided, and the upper portion is covered with an upper lid 10.

The side wall of the liquid tank 1 is provided with an inlet 6 for the cleaning liquid 7 and a gas inlet 8 for nitrogen gas for returning the inside of the liquid tank 1 to normal pressure. A port 9 is provided, and the exhaust port 9 is connected to an aspirator (not shown).

The wafer cassette 3 is inserted into the cleaning liquid 7 while holding the substrate 4, and the substrate 4 is fixedly held in the cleaning liquid 7.

Next, the resist removing method according to the present invention (hereinafter referred to as the present invention method) using the resist removing apparatus having the above-described structure will be described. In the method of the present invention, an apparatus in which the liquid tank 1 shown in FIG. 2 is provided for each type of cleaning liquid 7 is used.

The oxide film or polycrystalline silicon film deposited on the silicon substrate is etched after resist patterning. After etching, most of the resist remaining on the substrate surface is removed by ozone asher. Ozone ashing chamber temperature 300 ℃, oxygen flow 10 liters / mi
n, ashing time is 60 sec. and 1.2 μm thick resist is removed.

After the resist ashing, the cleaning liquid 7 consisting of a mixed liquid of sulfuric acid / hydrogen peroxide water (140: 1) is poured into the first liquid tank 1a through the inlet 6, and heated by the heater 2 to heat the liquid.
The substrate 4 set in the wafer cassette 3 is inserted into the substrate while keeping the temperature at 140 ° C.

After the substrate 4 is inserted, the upper lid 10 is closed and the aspirator is operated to degas the inside of the liquid tank 1a to about 200 mmHg through the exhaust port 9 to wash the substrate 4 for 12 minutes.

Thereafter, the evacuation is stopped, nitrogen gas is introduced into the first liquid tank 1a from the gas introduction port 8 to return to atmospheric pressure, the substrate 4 is taken out together with the wafer cassette 3, and the substrate 4 is deionized under normal pressure. Rinse in running water for 10 minutes.

Further, while the pure water is poured into the second liquid tank 1b and the temperature is kept at 50 ° C. by the heater 2, the substrate 4 is inserted together with the wafer cassette 3 to evacuate the second liquid tank 1b, and the substrate 4
Wash for 15 minutes.

After the evacuation is stopped and nitrogen gas is introduced into the first liquid tank 1a from the gas inlet 8 to return to atmospheric pressure, the substrate 4 is taken out together with the wafer cassette 3. The substrate 4 is washed with running pure water under atmospheric pressure for 10 minutes.

Next, a mixed solution of ammonium hydroxide, hydrogen peroxide solution, and pure water (1: 1: 5) was placed in the third liquid tank 1c,
The substrate 4 is inserted together with the wafer cassette 3 while the liquid temperature is kept at 70 ° C. by the heater 2. 200m by aspirator
A vacuum is drawn up to mHg, and the substrate 4 is washed under reduced pressure for 5 minutes.

After that, the inside of the third liquid tank 1c is returned to normal pressure by introducing nitrogen from the gas introduction port 8, the substrate 4 is taken out, and washed with running water for 10 minutes in pure water under normal pressure.

Further, after the pure water in the second liquid tank 1b is drained from the drain port 5 to wash the inside of the tank, new pure water is put in the second liquid tank 1b to keep the room temperature, and the substrate 4 Wafer cassette 3
And the substrate 4 is cleaned under reduced pressure for 10 minutes.

After the completion of washing with water under reduced pressure, the inside of the second liquid tank 1b is returned to normal pressure, the substrate 4 is taken out together with the wafer cassette 3 and rinsed with pure water under normal pressure for 15 minutes to wash the washed substrate 4. dry.

FIG. 3 shows that after removing the resist by the method of the present invention,
It is a graph which shows the result of having evaluated contact resistance with respect to the contact diameter of the sample which carried out metal wiring.

Compared with the conventional example shown in FIG. 1, 0.6 μm
Even in the contact holes below, the variation in the resistance value was reduced and the resistance value was stable, showing that the method of the present invention effectively acted to remove the resist residue remaining on the fine pattern sidewall and the sidewall protective film. ing.

In this embodiment, the case where the aspirator is used for cleaning the substrate under reduced pressure has been described, but the pressure reducing device is not limited to the aspirator, and it is more preferable to use a device capable of achieving higher vacuum. It can be applied even when forming a fine pattern.

[0033]

As described above, the method of removing a resist according to the present invention, when the resist residue after removing and removing most of the resist by ashing or the like is removed by cleaning with a cleaning liquid,
By performing under reduced pressure, it is possible to remove the bubbles generated in the fine pattern and sufficiently spread the cleaning liquid to the depressions of the pattern, so that it is possible to remove the resist residue and the etching sidewall protection film almost completely. Play.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a contact resistance and a contact hole diameter according to a conventional resist removing method.

FIG. 2 is a schematic cross-sectional view showing the configuration of a resist removing apparatus according to the present invention.

FIG. 3 is a graph showing the relationship between the contact hole diameter and the contact resistance of the sample obtained by the method of the present invention.

[Explanation of symbols] 1 liquid tank 2 heater 3 wafer cassette 4 substrate 6 inlet 7 cleaning liquid 9 exhaust port

Claims (2)

[Claims] 1. A method of cleaning a substrate in a cleaning liquid to remove resist residues after etching using a resist formed as a pattern on a substrate as a mask, wherein the substrate is cleaned in a cleaning liquid to remove the resist residues. A method of removing a resist, wherein the step of performing is performed under reduced pressure. 2. An apparatus for cleaning a substrate in a cleaning liquid to remove residue of the resist after etching using a resist formed as a pattern on the substrate as a mask, and a liquid tank for storing the cleaning liquid and the substrate in the cleaning liquid. A holding body to hold,
A resist removing apparatus comprising: a decompression unit for decompressing the inside of a liquid tank, and a unit for returning the decompressed liquid tank to normal pressure.