JPS5936257B2 - How to remove resist material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for peeling off a strong resist material formed on a substrate. More specifically, the present invention relates to a method for removing strong resist material formed on a substrate. An object of the present invention is to provide a new method that can completely remove a strong coating of resist material without damaging the substrate.

The ultrafine processing method for manufacturing semiconductor integrated circuits, etc. involves forming a thin oxide film layer (SiO2) on the surface of a single-crystal silicon substrate, and then applying a photosensitive resin solution compatible with the energy beam used later. After coating and drying, ultraviolet rays, electron beams, X-rays, and other curing or decomposition energy rays are irradiated through a mask with the desired circuit pattern, and processing such as development, rinsing, and post-baking is performed to create various desired products. Form a resist pattern.

Thereafter, an etching process is performed by applying an etching solution such as hydrofluoric acid to the exposed portion of the oxide film. Next, the used resist material, that is, the resist material remaining on the substrate, is immersed in a stripping solution such as a mixture of hot hydrogen peroxide and sulfuric acid, hot sulfuric acid, hot nitric acid, etc., to strip the resist material. There is.
In this way, an oxide film (convex portions) and exposed silicon portions (concave portions) are formed on the surface of the substrate. Next, phosphorus, boron, antimony,
The required amount of arsenic and the like is diffused at a high temperature of about 1,000° C., using a silicon oxide film as a mask. Furthermore, junctions are created by repeatedly diffusing the target impurity into the necessary areas using the method described above, and finally aluminum is vapor deposited on each necessary area, and wiring, electrode extraction, etc. are performed using the same method as described above. That is, it is produced by a photo application method. In the above-mentioned photoablation method, the step of stripping off the resist material is very important. In this stripping step, only the resist material is dissolved or decomposed and removed, and other parts, e.g. Ideally, the resist material should be completely removed without damaging the aluminum, silicon, or other components.

Conventionally, the removal of resist materials formed on aluminum and other metals involves the use of a removal solution with a special composition such as inorganic acids, various surfactants, and halogenated hydrocarbon solvents.
This has been done by applying oxygen plasma under reduced pressure to ash and peel off the resist material. However, in the former method, the resist material is incompletely removed, while in the latter method, the device may be damaged.While this problem can sometimes be solved by annealing at high temperature, this method is not applicable. There are many cases. Furthermore, due to advances in diffusion technology in recent years, there is a strong tendency for ion implantation methods to be used more frequently than thermal diffusion methods, and this tendency is particularly strong for new devices. This ion implantation method ionizes the target diffusion agent under reduced pressure, and then directly implants impurity ions into the silicon part according to the desired pattern using the resist material or other material as a mask. Since the resist material is exposed to ions, it becomes even stronger, and it is extremely difficult to peel and remove the resist material to a satisfactory extent by the conventionally known methods as described above. Therefore, if an oxygen plasma method is used, it is possible to completely remove the film, but the above-mentioned disadvantages cannot be avoided. On the other hand, as the patterns of circuits and the like become finer, as typified by ultra-LSI, etching becomes extremely uneven in so-called wet etching using solutions, and bubbles on the surface generated during etching cannot be ignored. Because fine and precise etching is required, plasma etching using plasma gas or ion etching performed by implanting ions is performed, but these methods expose the resist material to ions under reduced pressure. In either method, the resist material becomes even stronger, and the resulting incomplete peeling of the resist material is a major cause of a decrease in product yield, and as with the above, this is a problem that urgently needs to be resolved. be.

In addition, so-called dry processes such as the oxygen plasma method do not use solvents or chemicals, so they do not contaminate the working environment, are low in danger, and are easy to take measures against pollution, so they are used by semiconductor integrated circuit manufacturers and others. As a result, there is a strong need in the art for the development of a method for completely stripping resist materials that is more robust for the reasons mentioned above. The present inventors have solved the above-mentioned drawbacks of the conventional technology and, as a result of intensive research to meet the demands of the industry, have developed various resist materials that have been made even stronger by ion irradiation.
When the coating is irradiated with high-energy ultraviolet rays under reduced pressure or in an inert gas atmosphere, the irradiated coating decomposes into low molecular weight substances, which can then be completely removed by using a conventionally known stripping solution. The inventors have discovered that various problems can be solved all at once, and have completed the present invention.

That is, the present invention is a method for stripping a resist material formed on a substrate, which comprises irradiating the resist material with high-energy ultraviolet rays under reduced pressure or in an inert gas atmosphere, and then treating the resist material with an organic solvent.

To explain the present invention in detail, typical examples of the substrate referred to in the present invention include single crystal silicon substrates used in the manufacture of semiconductor integrated circuits, materials belonging to group 3 of the periodic table such as germanium, gallium, arsenic, and phosphorous; Although the substrate is made of a Group 4 or Group 5 element compound semiconductor, these are representative examples of preferred ones, and the present invention is not limited to these examples.

The film formed on the substrate is a film formed by crosslinking and reticulating a resin that is cured mainly by various energy rays by irradiation with these energy rays, and hardening the film, and is a film formed by resins that are cured by various energy rays. It is a resin that is cured by various well-known energy rays. Typical examples include polyvinyl cinnamate, polymethyl methacrylate, cyclized rubber with various photocrosslinking agents added, gelatin, hard tin, and polyvinyl alcohol. , dextrin, etc. A resin that cures with these energy rays is applied onto a substrate, dried, and irradiated with various energy rays, preferably light, through a desired pattern to form a latent image of a cured film, which is developed to form a latent image of the cured film on the exposed parts of the substrate and harden. This is the part where the coating remains. As mentioned above, this cured film is exposed to ions and becomes very strong due to recent advances in technology. The main objective of the present invention is to completely and accurately peel off this hardened remaining coating without causing any damage to the substrate. The method of the present invention can fully achieve the object of the present invention by irradiating the strengthened coating, that is, the resist material with high-energy ultraviolet rays under reduced pressure or in an inert gas atmosphere. What is the high-energy ultraviolet light used in this invention? Ultraviolet rays having energy capable of cleaving the carbon-carbon bonds forming the resist material or gradually decomposing and disintegrating the resist material with oxidation in the presence of a small amount of oxygen;
2,600 UV (deep ultraviolet) rays are particularly effective, and this wavelength has about 3 to 5 times higher energy than UV rays around 4,000 V or the ultraviolet rays in sunlight.

When irradiating the resist material with ultraviolet rays, which is preferable for the method of the present invention, the atmosphere is under reduced pressure (vacuum), or an inert gas atmosphere such as nitrogen, helium, argon, xenon, krypton, etc. It is more effective to carry out in these atmospheres containing a small amount of oxygen. Further, when irradiating such ultraviolet rays, the effects of the present invention are further enhanced by heating the resist material, which is the object to be irradiated, to a temperature of approximately 50 to 200°C.
The ultraviolet light used in the method of the present invention can be obtained by various conventionally known ultraviolet generators, but the most suitable generators are ultra-low pressure mercury lamps, deuterium lamps, krypton lamps, etc. Gas plasma generation light generated by applying a voltage is preferable. In this case, suitable gases include argon and krypton. Although the irradiation time cannot be determined unconditionally depending on various other conditions,
Usually, sufficient effects are exerted within a short period of about 1 to 10 minutes. The resist material that has been irradiated with ultraviolet rays as described above has its structure in various forms, and some parts of the resist material are decomposed into low molecular weight substances with the generation of gas, and then completely removed by using an ordinary stripping solution. The object of the present invention is achieved without causing any damage to the substrate.

Therefore, according to the method of the present invention, a strong resist material film can be easily and accurately formed in a very short time without using oxygen plasma or highly corrosive chemicals that can damage the substrate. Since it can be peeled off, it is very useful in this technical field and provides a high degree of technical value.

The present invention will now be described in more detail with reference to the accompanying drawings that illustrate apparatus used in embodiments of the present invention, but the present invention is not limited to these embodiments.

Example 1 Referring to FIG. 1 of the attached drawings, 1 is a chamber, 2 is a chamber cover (reflector, light shielding plate), and 3 is a chamber.
, 3 is front and rear lid, 4 is ultra-low pressure mercury lamp, 5 is connecting pipe to vacuum pump, 6 is support plate (with heating device and temperature control device)
, 7 is a wafer, 8 is a gas flow meter, and 9 is a heating device electric wire.

The above-mentioned chamber is not limited to a semi-cylindrical shape, but can also be cylindrical, bowl-shaped, or other shapes, and is made of quartz, calcium fluoride, or corrosion-resistant metal materials that are stable against high-energy ultraviolet rays, and is made of ultra-low pressure. Mercury lamp output 3
At 00W, it emits a strong emission line with a wavelength of 2537 people. A wafer with the photoresist side facing upward is placed on a support plate in a chamber configured as described above.

Of course, a plurality of wafers can be processed simultaneously depending on the capacity of this apparatus. Although a heater for heating the wafer is embedded in this support plate, heating is not limited to this method, and any other heating method can be used. To explain the operation of the method of the present invention, for example, 15
0°C (this temperature can be changed arbitrarily if necessary).

) A photoresist (0MR-83,
Four silicon wafers coated with photoresist (manufactured by Tokyo Ohka) were arranged horizontally with the photoresist side facing up. With conventional techniques, the photoresist after ion implantation could only be removed by ashing using an oxygen plasma method. A chamber is placed over the support plate of these four silicon wafers, and the pressure is reduced to 1T0rr using a vacuum pump. The support plate is heated to 160° C., and then an ultraviolet lamp is turned on to irradiate the photoresist surface with high-energy ultraviolet light (bright line spectrum around 2537A) for about 6 minutes. Due to this irradiation, the photoresist was decomposed into low molecular weight and gasified, and the function of the photoresist almost disappeared after 6 minutes. Thereafter, the photoresist was completely peeled off without causing any damage to the substrate by cleaning in a conventional manner using trichlorethylene. Example 2 The procedure described in Example 1 was repeated except that the high-energy ultraviolet rays were irradiated for 3 minutes.

Although some photoresist remained, it was immersed in a conventionally known stripping solution (for 0MR) at about 80°C for 1 minute, and then washed with a trichlorethylene-acetone (1 volume: 1 volume) mixture. As in Example 1, the photoresist was completely removed. Furthermore, by increasing the temperature of the support plate to 200° C., the peeling of the photoresist became more noticeable. Example 3 In the operation of Example 1, silicon nitride prepared on a silicon wafer was etched using carbon tetrafluoride (CF4) plasma using the same photoresist as a mask.

Conventionally, this photoresist could only be removed by ashing using oxygen plasma, but it was completely removed by the method described in Example 1. Example 4 Referring to FIG. 2 of the attached drawings, in the figure, 1 is a chamber, 2 is a chamber cover (reflector, light shielding plate),
3 and 3' are the front and rear lids, and 4' is the high frequency (13
, 56MHz) quartz reduced pressure plasma discharge lamp, 5 is a connection tube to the vacuum pump, 10 is a connection tube to the plasma discharge lamp vacuum pump, 11 is a plasma gas introduction tube, 6 is a support plate (
(with heating device and temperature control device), 7 is wafer, 8
indicates a gas flow meter and 12 indicates a high frequency oscillator.

Using the apparatus shown in Figure 2, the inside of the plasma discharge lamp was depressurized to 1T0rr with a vacuum pump, and xenon (X
e) When the gas is passed at a flow rate of 100 m or 4-4 and high frequency is applied, xenon plasma is discharged and emitted, generating high-energy ultraviolet rays having a peak around 1,700 people. Using such an apparatus, a wafer similar to that in Example 1 was exposed to high-energy ultraviolet light from a plasma discharge lamp under the same conditions for about 30 minutes.
exposed for minutes. As a result, the irradiated photoresist was decomposed and volatilized. The wafer was taken out and further washed with trichlorethylene to completely remove the photoresist and obtain a product with no other damage. Example 5 By using argon (Ar) in the plasma discharge lamp instead of xenon in Example 4, continuous spectrum plasma emission of high-energy ultraviolet light having a peak around 1250 was obtained, and the same as in Example 4 was obtained. Good results similar to those of Example 4 were obtained.

Example 6 The procedure of Example 4 was repeated with 230wL1Z cod oxygen being introduced into the chamber through a flow meter with similarly excellent results.

Example 7 Krypton (Kr) was used instead of xenon in Example 4.
By using this in a plasma discharge lamp, continuous spectrum plasma emission of high-energy ultraviolet light having a peak around 1550λ was obtained, and good results were obtained in the same manner as in Example 4.

Example 8 Using the apparatus shown in FIG. 1, nitrogen gas was passed through the flow meter at a flow rate of 2000 ml/Tnlt, and the same procedure as in Example 1 was followed to obtain excellent results.

Example 9 When a polymethyl methacrylate electron beam resist with a film thickness of 0.5 μm was used in place of 0MR-83 in Example 1, even if the irradiation in Example 1 was performed for 30 seconds, the irradiated resist was completely methylated. It was dissolved in isobutyl ketone and the resist was completely removed.

[Brief explanation of drawings]

Figure 1 shows a conceptual diagram of an apparatus used in an embodiment of the present invention, and Figure 2 shows a high-energy ultraviolet ray generator using a gas plasma generator that applies a high-frequency voltage in a pressure reducing tube sealed with xenon. FIG. 3 is a conceptual diagram of an apparatus used in another embodiment of the present invention.

Claims (1)

[Scope of Claims] 1. A method for peeling off a resist material formed on a substrate, which comprises irradiating the resist material with high-energy ultraviolet rays under reduced pressure or in an inert gas atmosphere, and then treating the resist material with an organic solvent. 2. The method according to claim 1, wherein the resist material is heated. 3 High-energy ultraviolet rays have a wavelength of approximately 1,000 Å to approximately 2,000 Å,
600 Å. 4. The method according to claim 1, wherein the resist material is a photoresist.