JPH0298928A - Cleaning of semiconductor substrate - Google Patents

Abstract

PURPOSE:To prevent the surface of a substrate from being contaminated and to realize a safe operation by a method wherein an extraction tank as a high- pressure container for substrate cleaning use and a heater used to heat the inside of the extraction tank are installed and a gas at a critical temperature or higher and at a critical pressure or higher is used. CONSTITUTION:A substrate 2 is arranged inside an extraction tank 1; a temperature of the extraction tank 1 is raised to 400 deg.C; carbon dioxide at 60 deg.C is introduced into the extraction tank 1 at a pressure of 400 atm. In this case, a critical temperature of the carbon dioxide is 31.06 deg.C and its critical pressure is 73.8 atm; the inside of the extraction tank 1 contains a supercritical gas. During this process, an outer wall of a separation tank 11 is cooled by using cooling water at 10 deg.C. Accordingly, an extracted organic substance is separated in the separation tank 11. When, e.g., a photoresist film coated on the substrate 2 in a photoetching process is stripped off, a silicon oxide film at 1000Angstrom is formed on a silicon substrate, an aluminum electrode thin film with a thickness of 1mum is evaporated on it and a test pattern where lines and spaces are repeated alternately is formed. After that, the resist is stripped off. Thereby, it is possible to prevent the surface of the substrate from being contaminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for cleaning a four-piece substrate, and more particularly to a method for removing contamination on the surface of a semiconductor substrate using a fluid. .

(Conventional technology) Semiconductors in the semiconductor industry! Cleaning of J and N (sea urchins/%) is extremely important regardless of whether it is in the production of semiconductor substrate materials, the production process of semiconductor elements, the assembly process of elements, etc. Objects to be subjected to the cleaning process include fine particles, metal deposits, acid/alkali residual contamination, and 9-organic contamination. To remove these, physical or chemical cleaning methods are used depending on each object.

The above-mentioned q mechanical contamination that is a problem for cleaning in the semiconductor process is: Futoko etching] Futoshi resist coating film used in the second step, substrate material manufacturing process, and element assembly! Wax or paraffin materials used in 2 (e.g. pasting the substrate during substrate lapping), or oil mist, floating 'ifi'b- to fuse the wafer throughout the process.
An example of this is organic pollution from the outside world caused by machinery.

Traditionally, organic solvents such as methyl alcohol, acetone, trichloroethylene, methylene chloride, isopropyl alcohol, and butyl acetate are most commonly used to remove these organic contaminants. Furthermore, a mixture of sulfuric acid and hydrogen peroxide solution is conventionally used for photoresist coatings.

The bottlenecks in removing organic contamination caused by these chemicals are: (1) organic contamination cannot be removed safely and the process lacks stability; For example, a mixture of sulfuric acid and hydrogen peroxide is used to remove photoresist coatings in the photoetching process, but resist residue is scattered on the wafer surface, which can cause sub-layers of highly integrated semiconductor devices. Process defects such as pattern defects often occur in micron processes. (2) Organic solvents are flammable, combustible, and harmful; sulfuric acid is strongly acidic and corrosive;
This is inherently undesirable from the standpoint of making semiconductor processes harmless and work safety. In particular, the use of chlorinated solvents poses many problems in terms of safety management and pollution prevention.

(Problems to be Solved by the Invention) As described above, the method of removing contamination on the surface of a semiconductor substrate using chemicals lacks process stability, often causes process defects such as pattern defects, and is flammable. This was developed to solve the problem that combustibility is harmful and inherently undesirable from the viewpoint of making semiconductor processes harmless and work safety. It is an object of the present invention to provide a method for cleaning a semiconductor substrate, which enables uniform removal, improves process yield, renders the semiconductor process harmless, and makes work safer.

[Structure J of the Invention (Means for Solving the Problems) The method for cleaning a semiconductor substrate of the present invention is characterized in that contamination on the surface of the semiconductor substrate is removed using a gas at a temperature higher than a critical temperature and a pressure higher than the critical pressure. .

(Function) Gases such as carbon dioxide, water vapor, or nitrogen have the property of exhibiting particularly high dissolving power against organic contamination under conditions of a critical temperature or above and a critical pressure. , it is possible to uniformly remove contamination on the surface of a semiconductor substrate, making semiconductor processes harmless and work safer.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of a cleaning apparatus used in a semiconductor substrate cleaning method. That is, 1 is an extraction tank which is a high pressure container for cleaning substrates, 2 is a semiconductor substrate which is an object to be cleaned, and 9
, is held in the extraction tank 1 by a carrier.

3 is a heater for heating the inside of the extraction tank 1; 4 is a pressure gauge that indicates the pressure inside the extraction tank 1; A valve 5, a heat exchanger 6, a filter 7, a compressor 8, a heat exchanger 9, and a valve 10 are arranged in this order on a path for introducing cleaning gas into the extraction tank 1. Furthermore, a minute MFf411 is disposed in a path for discharging the organic matter extracted in the extraction tank 1. 12 is a cooler for cooling the temperature of the outer wall of the separation tank 11 with cooling water.

Next, a method for removing contamination on the surface of a semiconductor substrate using the cleaning apparatus of the above embodiment will be described.

(First Example) The substrate 2 is placed in a carrier and placed in an extraction tank, the temperature of the extraction tank 1 is raised to 400°C, and carbon dioxide at 60'C is added to the
It is introduced into the extraction tank 1 at a pressure of 0a Lm.

In this case, the critical temperature of carbon dioxide is 31.06° C., the critical pressure is 73.8 atm, and the inside of the extraction tank 1 is filled with supercritical gas. At this time, minutes! The outer wall of M11 is cooled with cooling water at 10°C. This results in
The nine extracted substances are separated into zero by a separation tank 11.

The processing time during this period is 20 minutes.

Here, for example, when peeling off a photoresist film applied to a substrate in a photoetching process, we will discuss the evaluation results of the substrate cleaning effect according to Example 1 and the conventional method using a mixture of sulfuric acid and hydrogen peroxide solution. FIG. 2 shows the evaluation results of the substrate cleaning effect. In this case, the substrate 2 is a silicon oxide film formed on a silicon substrate with a thickness of 1 μm.
After a thick aluminum electrode thin film was vaporized and a test pattern of alternating lines and spaces was formed using a photo-etching process, the resist was separated by Jl. The cleaning effect was evaluated based on pattern defect rate.

As can be seen from FIG. 2, while the conventional method has a defective rate of 2%, in the above embodiment, the defective rate is 0.596 because the uniformity of the resist 21M is improved. ,
It has been reduced to about 1/4 compared to the conventional method, making it possible to improve the process yield.

Further, FIGS. 3(a) and 3(b) show the test pattern failure rate when the pressure or temperature of carbon dioxide was absorbed by the same method as in the above embodiment. Figure 3(a)
shows the pressure dependence when the temperature is 60° C. (above the critical temperature), and FIG. 3(b) shows the temperature dependence when the pressure is 400 atm (above the critical pressure). In either case, the test pattern failure rate tends to decrease as the pressure or temperature increases.

As mentioned above, carbon dioxide under conditions above the critical temperature and critical pressure has the property of exhibiting high dissolving power, especially for organic contamination, and by utilizing this property, it is possible to Contamination can be removed uniformly,
It becomes possible to improve the process yield.

(Second Example) The substrate 2 is placed in a carrier and placed in the extraction tank 1. The temperature of the extraction tank 1 is raised to 400°C, and 90% carbon dioxide at 150°C is added.
, 150° C. steam is introduced into the extraction tank 1 at a rate of 10% at a pressure of 300 atm.

As a result, the inside of the extraction tank 1 is filled with supercritical gas. At this time, the outer wall of the minute M tank 11 is cooled with cooling water at 10°C. Thereby, the extracted organic matter is separated by the separation tank 11.

In the second embodiment, the same effects as in the first embodiment were obtained. In addition, the temperature of the carbon dioxide and water vapor is set to 1
Even when the temperature was 00 to 200°C and the pressure was 200 to 400 atm, the same effects as in the first embodiment were obtained.

(Third Example) A substrate with paraffin material attached to it used in the semiconductor device assembly process was subjected to a treatment similar to the first example for 40 minutes.
It was confirmed by Auger spectroscopy that the paraffin material could be removed uniformly by performing the process under the conditions of 300 atm and 300 °C.

From the results of the above examples, the gas used is 40 to 400
A temperature range of .degree. C. and a pressure range of 100 to 600 atm are practical for semiconductor processing. Also, 40 to 40
Contamination on the surface of the semiconductor substrate can also be removed using water vapor or nitrogen under conditions of 0° C. and 100 to 600 atm, as in the above embodiments.

[Effects of the Invention] As described above, according to the semiconductor substrate cleaning method of the present invention, contamination on the surface of the semiconductor substrate can be uniformly removed compared to the case where conventional solvents or strong acid-based chemicals are used. It was possible to reduce defects such as pattern defects caused by resist residue during photoresist peeling in the photoetching process, and improve process yield.

Further, since there is almost no resist residue on the substrate cleaned by the above method, the withstand voltage of the gate oxide film of a MOS capacitor formed on this substrate by a normal MOS forming process is improved.

In addition, conventionally, trichlorethylene was used to remove wax or paraffin materials used in the manufacturing process of substrate materials and in device assembly frames, which was harmful, but the semiconductor substrate of the present invention The cleaning method has made it possible to make semiconductor processes harmless and work safer.

Further, according to the semiconductor substrate cleaning method of the present invention, if the used gas is recycled and used, it is also possible to reduce manufacturing costs.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram showing an example of a semiconductor substrate cleaning apparatus used in an embodiment of the semiconductor substrate cleaning method of the present invention, and FIG. FIGS. 3(a) and 3(b) are diagrams showing the evaluation results of the cleaning effect, and are diagrams showing the pressure dependence and temperature dependence in the cleaning method of the present invention. 1... Extraction tank for substrate cleaning, 2... Semiconductor substrate to be cleaned, 3... Heater, 4... Pressure gauge, 5
．． 10... Valve, 6.9... Heat exchanger, 7...
Filter, 8... Compressor, 11... Minute M tank, 12.
··Cooler. Applicant's agent Patent attorney Takehiko Suzue μka (atm) (a) Kodo (@C) (b) Figure 3

Claims (3)

[Claims] (1) A method for cleaning a semiconductor substrate, characterized in that contamination on the surface of the semiconductor substrate is removed using a gas at a temperature or pressure higher than a critical temperature. (2) Temperature of 40-400℃ and 100-600at
1. A method for cleaning a semiconductor substrate, the method comprising removing contamination on the surface of the semiconductor substrate using carbon dioxide, water vapor, or nitrogen under a pressure of m. (3) Temperature of 100-200℃ and 200-400a
Under conditions of pressure of tm, carbon dioxide and water vapor are mixed at 9:
1. A method of cleaning a semiconductor substrate, comprising removing contamination on the surface of the semiconductor substrate using a gas having a ratio of 1:1.