JPS5925228A - Method for lift-off process - Google Patents

Abstract

PURPOSE:To easily remove the resist residual layer remaining on the aperture part of a substrate surface by a method wherein the substrate surface, whereon a resist stencil has been formed, is exposed on the ultraviolet-ray source which is lit in the clean air or in an oxygen atmosphere. CONSTITUTION:The ultraviolet-ray source 1, such as a low-pressure mercury-arc lamp or a high-pressure mercury-arc lamp or the like, of the wavelength of 195nm or less is lit in the clean air or in an oxygen atmosphere. Then, the surface of a substrate 5, whereon the stencil for lift-off consisting of a resist film, is exposed on ultraviolet rays. The resist residual layer located on the surface of the substrate is removed by the ozone gas generated by the photochemical reaction of oxygen gas. If a desired metal film or an insulating film is vapor- deposited after the resist residual layer has been removed as above-mentioned, the deterioration of the adhesive property of a vapor-deposited film due to a resist residual film and the adverse effect on the electric connections between an under layer metal film and a vapor-deposited layer can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a batten forming technique using a lift-off processing method, and is particularly suitable for application to forming battens made of a metal film or an insulating film for semiconductor integrated circuit devices, Josephnon integrated circuit devices, etc. This paper relates to a lift-off processing method.

The current state of this technology is outlined below.

In the batten forming method using the lift-off processing method, in order to obtain a desired batten made of a metal film or an insulating film on a substrate, first a lift-off pad made of a positive resist film is formed on the substrate, and then vacuum After depositing the desired metal film or insulating film in the tank, the film is immersed in a good solvent for removing the resist film, such as acetone.
At the same time, by mechanically removing unnecessary metal films or insulating films on the resist film, a desired film or insulating film is obtained.

- During the step of forming a lift-off stencil made of a positive type film, the stencil is formed using 1-1 light exposure -) Following the IC or electron beam exposure, the stencil is also formed. A resist baton is formed by developing with a specified positive photoresist developer. In this case, the resist film is dissolved and removed to expose the substrate surface, that is, the area where the desired metal film or insulating film is to be covered in the subsequent process is The presence of a resist residue layer of λ to several tens of layers is recognized. (For example, published publications 1.
11゜Kaplan and 13. To, Bcrg
in °” 11.csicJuesfrom W
et1'roccssingof Po5itive
R,esists”, J, Elcctro
-cl+c+nic old SOC, V (11, i27,
No. 7, February 1980, l), 386-I
), 396) When a deposited film is coated on a substrate on which such a resist residue layer exists, the adhesion of the deposited film deteriorates and the electrical connection between the underlying metal film and the deposited metal film is significantly reduced. interfere with

In the past, as a method for removing the above-mentioned ink/stamp residue layer, the conventional method was to create an oxygen gas atmosphere in the vacuum chamber and apply I'CF power to generate 02 gas plasma immediately before coating the vapor deposited film. Generally, a method is adopted in which the residual layer stuck to the substrate surface is removed by plasma etching.

Conventional methods such as this require strict control of oxygen plasma cleaning conditions. In other words, if the cleaning is insufficient, the removal of the residual layer is incomplete, and if it is excessive, an unnecessary oxide layer will be formed on the surface of the metal film and the electrical connection between the metals will be damaged. In addition, in order to apply RF power to the substrate in the vacuum chamber, it is necessary to electrically insulate the holder from which the substrate can be accessed from other parts of the vacuum chamber. Unfortunately, in order to make the density of the 02 force spisma generated by applying RF power uniform, there are large constraints on the structure of the substrate holder and the structure of the vacuum chamber. Due to its shortcomings, the Ocasplus Mac Cleaning method is not a very versatile technique.

The object of the present invention is to solve the above-mentioned drawbacks of the prior art, namely, to provide a novel lift-off process that removes the silica/stack residue layer remaining on the surface of the aperture substrate after the formation of the stencil with an extremely simple process. It is there to provide a method.

The lift-off processing method of the present invention for the above purpose is characterized by a wavelength of 195 +1 compared to that of a low-pressure quartz-mercury lamp lit in a clean oxygen atmosphere and a high-pressure mercury lamp.
After exposing the surface of the substrate on which the lift-off stainless steel film is formed under an ultraviolet light source that emits ultraviolet light within 111 nm, a desired metal film or metal film is applied to the surface of the substrate in a vacuum chamber. The purpose is to deposit an insulating film.

When using the method of the present invention, it is extremely easy to
Ensures that it remains on the substrate surface/removes the residual layer.
This can produce the effect of depositing a metal film or an insulating film.

FIG. 1 is a side cross-sectional view showing the principle of an example of an ultraviolet irradiation device that can be used to expose the substrate surface to an ultraviolet light source in the lift-off processing method of the present invention.

In FIG. 1, numerals 1.1, . . . are a group of low-pressure mercury lamps, 2 is a wafer transport belt, 6 is a clean air vent or oxygen gas introduction hole, 4 is an exhaust hole, and 5 is a wafer.

Here, the low-pressure mercury lamp group 1.1, .
The tube is made of synthetic quartz glass, which has low absorption of short-wavelength ultraviolet rays. The distance from the center of the tube to the surface of the tube is approximately 15 mm. The intensity of ultraviolet rays on the surface is approximately 50 O/hahe'/C1l+2.254.7111TI with a wavelength of 184.9 nm and approximately 10
/lW/C1112, and the intensity of ultraviolet rays on the longer wavelength side is 1 μW or less. When irradiated with ultraviolet rays with a wavelength of 195 nm or less in air or an oxygen gas atmosphere, a photochemical reaction of oxygen causes
Ozone gas is generated. When the concentration of osmotic acid near the wafer surface of this irradiation device was measured, it was 50 to 70.
1) It was pm.

Hereinafter, an embodiment of the lift-off processing method using the ultraviolet irradiation device described in "-" will be described in detail.

S + 0 with a thin surface, immersed in a mixture of concentrated sulfuric acid and hydrogen peroxide for about 10 minutes, then washed with pure water and dried.
Hexamethyl/
/ Lasan (111vIDS) was applied, followed by spin coating of Bonn type photoresist 1- (trade name of Shiplcy), followed by a brihake treatment for 60 minutes in a convection oven heated to 70°C. Subsequently, a desired pattern was transferred using a normal light exposure method, and the substrate was immersed in Frombensen solution at a temperature of 20°C for 10 minutes and dried. 6 during (temperature 20℃)
After being immersed for a minute and developed, it was washed with pure water and dried to form a resist residue layer, which was used as an example sample.

As a comparative sample, instead of exposing and developing a substrate that had been coated and prebaked with a drying/stripping film, it was immersed in methyl isobutyl ketone (MI 13K)-i or acetone, or sulfuric acid and peroxide. Mixing hydrogen water KI7. (11
A substrate was prepared by washing with 2SO4/lI202) to dissolve and remove the desist film.

After that, the substrate of each of the above samples was irradiated with ultraviolet rays for 0.5 to 5 minutes using the above-mentioned ultraviolet irradiation device, and the thickness of the resist film and the contact angle of the surface of the S02 substrate with pure water were measured. did.

Figure 2 shows the relationship between ultraviolet irradiation time and film thickness of AZ-1470 7-stroke film.The graph shows the initial film thickness of 1.47/silicon.
It can be seen that the resist film size decreases depending on the UV irradiation time, and after 6 minutes of irradiation, film burrs of 1.44μ and 300λ have occurred. From this result, it can be inferred that the components of the resist film are oxidized by ultraviolet irradiation and decomposed and removed into CO2, 1120, and the like. As mentioned above, in order to remove a reliable layer of thickness from several to several tens of amps, it is necessary to
It is clear that an irradiation time of about 2 minutes is sufficient to achieve the objective.

Table 1 shows an experimental example in which the contact angle of the substrate surface with pure water before and after the ultraviolet irradiation treatment was measured in order to know whether the resist residual layer was completely removed or not after the ultraviolet irradiation treatment.
1 and a comparative sample. After cleaning with a mixture of sulfuric acid and hydrogen peroxide to remove the surface contamination layer consisting of organic matter, the contact angle of the surface of the Shida S Io 2 substrate with water is as shown in Table 1. Shows hydrophilicity of 2° to 6° regardless of the presence or absence of irradiation. On the other hand, when there is a layer of adsorbed contaminants such as organic substances on the surface, the contact angle shown in Table 1 is generally large, and it is observed that the property changes from hydrophilic to hydrophobic.

As is clear from the experimental results in Table 1, AZ-1470
After coating and pre-baking the Lenst, the Lenst film was removed by ultrasonic cleaning for about 20 minutes in AZ developer diluted to 1:1 or M I 13 K and acetone.
The contact angle of the 102 substrate surface is large, ranging from 20° to 60°, but when each of the above substrates is subjected to UV irradiation treatment for 2 minutes, the contact angle changes from 2° to 0, changing from hydrophobic to hydrophilic. is changing. Therefore, the results shown in Table 1 indicate that the residual layer of oxide/stain deposited on the surface of the substrate could be removed by UV irradiation treatment for 2 minutes.

However, on the resist stain/ru substrate, the film thickness Q,
8/Zln circle)/LIT/Au alloy film and a SiO film with a film thickness of Q671+n were each vacuum-deposited to 41
Previously, ultrasonic waves of 28kllZ and 75W were applied in the liquid to dissolve the resin and at the same time remove the film, and form a batten by lift-off treatment.

At this time, ultraviolet waves were applied to row A:') for a longer time than necessary for the lift-off process, and a visual autopsy was performed to determine whether or not the above-mentioned vapor-deposited film had peeled off from the substrate. As a result, if the ultraviolet irradiation treatment is not performed, 1. 'b / I IT /A, 1
On the other hand, the sample exposed to ultraviolet rays for 2 minutes could withstand the force of peeling of the film for 20 minutes and 40 minutes for the SiO film. However, for the sample exposed to ultraviolet rays for 2 minutes, the force for peeling could be tolerated even after approximately 60 minutes and 60 minutes of treatment, respectively. No peeling was observed, and a clear significant difference was observed between the two.

As explained above, according to the present invention, the resist residue layer existing on the substrate surface can be easily removed using a simple device. As a result of the omission of the plasma cleaning process, the structure of the vapor deposition equipment, the simplification of the lift-off process, and the reduction in the cost of the vapor deposition equipment have become the riJ performance. This can greatly contribute to improving yield and reducing manufacturing costs.

[Brief explanation of drawings]

FIG. 1 is a side cross-sectional explanatory view showing the principle of an example of an ultraviolet irradiation device that can be used in the lift-off processing method of the present invention. FIG. 2 is a graph showing the remaining film thickness of the 8Z147[] resist with respect to the ultraviolet irradiation time. 1...Low-pressure mercury lamp 2...Wafer conveyor belt 6 -Introduction hole 4...Exhaust hole 5...Wafer patent applicant Nippon Telegraph and Telephone Corporation Representative Patent Attorney Junnosuke Nakatoshi 1 Figure '8P2 Figure

Claims (1)

[Claims] The substrate surface on which the lift-off stain made of the resist film is formed is exposed to an ultraviolet light source emitting ultraviolet light within a wavelength of 195 nm, such as a low-pressure quartz mercury lamp or a high-pressure mercury lamp, which is lit in clean air or an oxygen atmosphere. A lift-off processing method characterized by depositing a desired metal film or insulating film on the surface of the substrate in a vacuum chamber after the exposure.