JPH04239727A - Dry cleaning of semiconductor substrate - Google Patents

Abstract

PURPOSE:To offer a method for dry cleaning of a semiconductor substrate contaminated by a heavy metal in a high-concentration degree by means of suppressing etching of the semiconductor substrate. CONSTITUTION:Removal of a heavy metal is performed by making a chlorine radical to contact with a semiconductor substrate contaminated by a heavy metal, and removal of contamination of the semiconductor is so constituted that a temperature and a time where no contamination is generated, are experimentally decided, and with these experimentally decided temperature and time, a chlorine radical is made to contact with a substrate of the same kind with the substrate of aforesaid semiconductor. Further, a spectrum of an element constituting aforesaid semiconductor to be contained in exhaust gas is detected during dry cleaning at the same time by using a spectrum detection device, and when this spectrum detecting device detects the spectrum of an element constituting the semiconductor, dry cleaning is finished.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry cleaning method for semiconductor substrates contaminated with heavy metals at a high concentration.

Currently, the mainstream cleaning technology for semiconductor substrates in semiconductor manufacturing processes is wet cleaning technology, which uses a chemical solution such as nitric acid or a mixture of aqueous ammonia and hydrogen peroxide. However, semiconductor manufacturing processes have become increasingly dry, and dry cleaning techniques using gas have been attracting attention from the viewpoint of compatibility with these dry processes. The advantage of dry cleaning, in addition to its compatibility with other dry processes, is that it provides higher cleaning efficiency than wet cleaning due to the absence of redeposition from solutions.

0003

2. Description of the Related Art As a dry cleaning method for removing heavy metals attached to a semiconductor substrate, a method of bringing chlorine radicals into contact with the semiconductor substrate is effective.

Chlorine radicals react with heavy metal contaminants attached to the surface of the semiconductor substrate to generate heavy metal chlorides.
Heavy metal contaminants are removed by vaporizing this chloride.

In particular, photo-excited dry cleaning technology that uses chlorine excited by irradiation with ultraviolet rays is effective in removing heavy metals such as iron, and is effective in removing iron-contaminated silicon substrates at a level of 1013 particles/cm2. Previous 1010 pieces/c
m2 level can be recovered.

[0006]

[Problem to be Solved by the Invention] However, chlorine radicals also react with semiconductor substrates; for example, in the case of silicon substrates, SiCl4 is generated and vaporized, so that as cleaning progresses, etching of the semiconductor substrate also progresses. It has the disadvantage of being

An object of the present invention is to eliminate this drawback, and to provide a method for dry cleaning a semiconductor substrate highly contaminated with heavy metals while suppressing etching of the semiconductor substrate.

[0008]

[Means for Solving the Problems] The above object is to provide a dry cleaning method for a semiconductor substrate in which chlorine radicals are brought into contact with a semiconductor substrate contaminated with heavy metals, in which the removal of the semiconductor does not substantially occur. This is achieved by a method of dry cleaning a semiconductor substrate, which comprises bringing the semiconductor substrate into contact with the chlorine radicals at a certain temperature and time. Note that the semiconductor substrate is irradiated with light for a short period of time during the period in which the chlorine radicals are brought into contact with the semiconductor substrate.

Specifically, chlorine radicals are brought into contact with a semiconductor substrate contaminated with heavy metals, and the temperature and time at which the heavy metals are removed but the semiconductors are not removed are determined experimentally. Then, at this experimentally determined temperature and time, dry cleaning is performed on a semiconductor substrate of the same type as the aforementioned semiconductor substrate, or
By bringing chlorine radicals into contact with a semiconductor substrate contaminated with heavy metals, a temperature is determined experimentally at which the heavy metals are removed but the semiconductor is not substantially removed. A semiconductor substrate of the same type as the semiconductor substrate is dry-cleaned at the determined temperature, and at the same time, a spectrum detection device is used to detect the spectrum of the elements constituting the semiconductor contained in the exhaust gas. However, when this spectrum detection device detects the spectrum of the elements constituting the semiconductor, the dry cleaning is completed.

0010

[Operation] When etching a highly contaminated semiconductor substrate, such as a silicon substrate, using chlorine gas excited by irradiation with ultraviolet light, if the processing temperature is high as shown in FIG. ℃, etching starts immediately, as shown by the dotted line in the figure, but if the processing temperature is low, for example 140℃, there is a time period during which etching does not proceed, as shown by the solid line in the figure. The inventors of the present invention have discovered that bands exist.

Furthermore, as a result of further research, it has become clear that heavy metal contaminants are removed during this time period when etching does not proceed. In Figure 2, the processing temperature is 17
The dry cleaning of a semiconductor substrate highly contaminated with iron at 0° C. is shown, and it is clear that the surface concentration drops rapidly at the very beginning of etching.

[0012] In the dry cleaning method for a semiconductor substrate according to the present invention, the newly discovered natural law described above is utilized to clean a semiconductor substrate contaminated with heavy metals at a high concentration so that there is a period of time during which etching does not proceed. The temperature is lowered to bring chlorine radicals into contact with the substrate, and during this period when etching is not progressing, dry cleaning is performed using chlorine radicals to remove heavy metals adhering to the substrate surface.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, methods for dry cleaning semiconductor substrates according to three embodiments of the present invention will be described with reference to the drawings.

First Example FIG. 3 shows a configuration diagram of a photo-excited dry cleaning apparatus. In the figure, 1 is a reaction chamber, 2 is a chlorine gas inlet, and 3 is a gas outlet. 4 is a high-pressure mercury lamp that generates ultraviolet light for optical excitation, and 5 is an infrared lamp that heats a semiconductor substrate 6 placed on a substrate support 7 provided in the reaction chamber 1.

A sample is taken from a semiconductor substrate manufactured in a certain semiconductor manufacturing process, and the relationship between ultraviolet irradiation time and etching depth as shown in FIG. 1 is measured using the apparatus shown in FIG. is measured at various gas phase temperatures.

For example, if a sample substrate contaminated with iron at a level of 1013 pieces/cm2 was measured and the time required to start etching at a chlorine gas pressure of 20 Torr and a gas phase temperature of 140° C. is 30 seconds, then
Semiconductor substrates manufactured in the same semiconductor manufacturing process and contaminated with iron at a level of 1013 pieces/cm2 are subjected to photoexcited dry cleaning by irradiating them with ultraviolet light for 30 seconds at a chlorine gas pressure of 20 Torr and a gas phase temperature of 140°C. For example, heavy metal contaminants are removed without substantially etching the semiconductor substrate. Note that "without being substantially etched" as used herein means a distance of at most 50 Å before steady etching of the substrate by chlorine radicals begins.
This includes etching to a certain extent.

Second Example In the second example, the time point at which etching of a semiconductor substrate is started is automatically detected, and dry cleaning is stopped at that point.

FIG. 4 shows a configuration diagram of the optically excited dry cleaning apparatus used in the second example. In the figure, the same components as those shown in FIG. This is a cleaning stop means for stopping dry cleaning.

A mass spectrometer 8 installed at the exhaust port 3 of the reaction chamber 1 is used to monitor the mass spectrum of the exhaust gas, and when a spectrum of elements constituting the semiconductor substrate appears in the exhaust gas, the signal indicates that cleaning is to be stopped. inputted into means 9;
Outputs a cleaning stop signal. In response to this cleaning stop signal, the high-pressure mercury lamp 4 is turned off, the introduction of chlorine gas is stopped, the chamber 1 is forcibly evacuated, and the infrared lamp 5 is turned off, thereby stopping the dry cleaning.

Third Example FIG. 5 shows a configuration diagram of a photo-excited dry cleaning apparatus used in the third example. In the figure, the same parts as those shown in FIG. 3 are indicated by the same symbols, 10 is a transparent window, 11
1 is a spectrometer, and 12 is a cleaning stop means that stops dry cleaning when the spectrometer 11 detects a spectrum of an element constituting the semiconductor substrate.

Absorption analysis of the exhaust gas is performed using the spectrometer 11, and when an absorption spectrum of an element constituting the semiconductor substrate appears, the signal is input to the cleaning stop means 12, which outputs a cleaning stop signal. This cleaning stop signal causes the second
Washing is stopped in the same manner as in the example.

[0022]

[Effects of the Invention] As explained above, in the dry cleaning method for a semiconductor substrate according to the present invention, heavy metals are removed from a semiconductor substrate contaminated with heavy metals, but the temperature and time are such that the removal of semiconductors does not substantially occur. Since dry cleaning is performed by bringing chlorine radicals into contact with the semiconductor substrate, heavy metal contaminants adhering to the semiconductor substrate are removed without etching the semiconductor substrate.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between ultraviolet irradiation time and etching depth.

FIG. 2 is a diagram showing the relationship between etching depth and surface iron concentration.

[Figure 3]

[Figure 4]

FIG. 5 is a configuration diagram of an apparatus used for dry cleaning of a semiconductor substrate according to the present invention.

[Explanation of symbols]

1 Reaction chamber 2 Chlorine gas inlet 3 Gas outlet 4 High pressure mercury lamp 5 Infrared lamp 6 Semiconductor substrate 7 Board support stand 8 Mass spectrometer 9.12 Cleaning stop means 10 Translucent window 11 Spectrometer

Claims (4)

[Claims] 1. A method of dry cleaning a semiconductor substrate by bringing chlorine radicals into contact with a semiconductor substrate contaminated with heavy metals, wherein the semiconductor substrate is cleaned at a temperature and for a period of time such that substantially no removal of the semiconductor occurs. A method for dry cleaning a semiconductor substrate, comprising: bringing the chlorine radicals into contact with the chlorine radicals. 2. The dry cleaning method for a semiconductor substrate according to claim 1, wherein light is irradiated for a short period of time during the period in which the semiconductor substrate is brought into contact with the chlorine radicals. 3. Bringing chlorine radicals into contact with a semiconductor substrate contaminated with heavy metals, and experimentally determining a temperature and time at which the heavy metals are removed but the semiconductors are not substantially removed. 2. The process is performed on a semiconductor substrate of the same type as the semiconductor substrate at a temperature and time determined experimentally.
The method for dry cleaning a semiconductor substrate described above. 4. A semiconductor substrate contaminated with heavy metals is brought into contact with chlorine radicals, and a temperature is determined experimentally at which the heavy metals are removed but the semiconductor is not substantially removed; A semiconductor substrate of the same type as the semiconductor substrate is dry-cleaned at an experimentally determined temperature, and at the same time, a spectrum detection device is used to measure the spectrum of the elements constituting the semiconductor contained in the exhaust gas. 3. The dry cleaning method for a semiconductor substrate according to claim 1, wherein the dry cleaning is completed when the spectrum detection device detects the spectrum of the element constituting the semiconductor.