JP2011129830A - Method of cleaning silicon wafer, and cleaning liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of cleaning a silicon wafer having a hydrophobic surface, and a cleaning liquid. <P>SOLUTION: A cleaning liquid containing 0.01-0.05 wt.% of HF and ozone is used for this cleaning liquid. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for cleaning a silicon wafer, particularly a silicon wafer having a hydrophobic surface, and a cleaning liquid therefor.

  In the production of electronic materials such as semiconductor devices, semiconductor wafers, and liquid crystal glass, the cleaning process is performed before and after various processes. The main purpose of cleaning is to remove various contaminants adhering and adsorbing on the surface and in the vicinity of the surface in the previous process. Specifically, organic substances such as oil, organic or inorganic adhered fine particles, various types of metals (fine particles, ions, salts, etc.), nonmetallic ions, and the like are applicable. For cleaning, a semiconductor wafer or the like to be cleaned is usually immersed in a cleaning solution in a cleaning tank, and the cleaning solution is mechanically stirred or irradiated with ultrasonic waves to ensure cleaning efficiency. Until now, for example, various acidic cleaning liquids have been developed and used depending on the types and amounts of contaminants to be removed as cleaning liquids.

Among them, hydrofluoric acid containing ozone (hereinafter sometimes referred to as “HF / O ₃ ”) cleaning liquid has been found to be able to achieve a significant reduction in wafer surface impurities (metal, adhered fine particles, organic matter, etc.). It has been widely used (Patent Documents 1 and 2).

JP-A-8-45886 JP-A-10-98018

  The present invention provides a method for cleaning a silicon wafer having a hydrophobic surface, and a cleaning liquid.

When applying the above-described hydrofluoric acid cleaning liquid containing ozone to a silicon wafer immediately after epitaxial deposition or a silicon wafer immediately after argon annealing, the cleaning effect is achieved by the present inventors. However, it has been found that the haze deterioration (so-called surface roughness) of the surface after cleaning tends to occur. This phenomenon of haze deterioration was not found in the case where the silicon wafer immediately after epitaxial deposition or argon annealing was first made hydrophilic with an oxidizing chemical such as hydrogen peroxide or ozone and then washed with HF / O _3. It occurred in the range.

The present inventor has earnestly studied to find a HF / O ₃ cleaning method that exhibits a sufficient cleaning effect without causing haze deterioration even on a silicon wafer immediately after epitaxial deposition or a hydrophobic surface immediately after argon annealing. As a result, the inventors have found that it is possible to use a cleaning liquid that regulates HF and ozone within a specific concentration range, and completed the present invention.

  That is, the present invention is a method for cleaning a silicon wafer having a hydrophobic surface, characterized in that a cleaning liquid containing 0.01 to 0.05% by weight of HF and ozone is used as a cleaning liquid. The present invention relates to a cleaning method.

  The present invention also relates to a cleaning method, wherein the silicon wafer having a hydrophobic surface is a silicon wafer immediately after epitaxial deposition.

  The present invention also relates to a cleaning method, wherein the silicon wafer having a hydrophobic surface is a silicon wafer immediately after argon annealing.

  The present invention also relates to a cleaning method characterized by containing at least 5 ppm of the ozone.

  Furthermore, the present invention relates to a silicon wafer cleaning solution having a hydrophobic surface and containing 0.01 to 0.05% by weight of HF and at least 5 ppm of ozone.

Furthermore, the present invention provides 0.01 to 0.05% by weight of HF,
The present invention relates to a silicon wafer cleaning solution containing ozone concentration (ppm)> 625 × HF concentration (wt%) − 15.625 and 5 ppm or more.

  In the method for cleaning a silicon wafer having a hydrophobic surface according to the present invention, the use of a cleaning liquid containing HF of 0.01 to 0.05% by weight and ozone as a cleaning liquid deteriorates the haze of the surface. In addition, the cleaning surface has an extremely excellent impurity removal effect.

FIG. 1 shows the results of an embodiment of the present invention. ○ indicates no surface roughness, and ◆ indicates surface roughness. A broken line indicates a boundary line indicating whether or not surface roughness occurs. FIG. 2 is a diagram showing the results of the example of the present invention (a map showing the presence or absence of surface roughness is shown in black and white binarization). FIG. 3 is a diagram showing the results of the embodiment of the present invention (a map showing the presence or absence of surface roughness is shown in black and white binarization).

(Silicon wafer with hydrophobic surface)
There is no particular limitation on the shape, thickness, and size of the silicon wafer as the object to be cleaned to which the cleaning method of the present invention can be applied, and all or a part of the surface may be hydrophobic. Specific examples of the shape include a circular shape or a substantially circular plate shape. The thickness and size (diameter) are not particularly limited and can be applied.

  In general, there is no clear definition for clearly discussing the physical properties of hydrophilicity and hydrophobicity. Here, the surface of a silicon wafer is hydrophobic, for example, immediately after epitaxial deposition, immediately after argon annealing, or immediately after polishing such as CMP. Immediately after the oxide film is removed with a hydrofluoric acid aqueous solution or an alkaline cleaning solution, the surface is not sufficiently covered with an oxide film, such as the surface immediately after the vapor phase decomposition removal of the oxide film with vapor containing hydrofluoric acid. Means an active surface condition. Such a surface state is known to have a strong tendency to adhere and adsorb various contaminants.

(HF / O ₃ cleaning solution)
The cleaning method of the present invention cleans particularly a silicon wafer having such a hydrophobic surface, exhibits a sufficient cleaning effect of the HF / O ₃ cleaning liquid, and also suppresses deterioration of haze on the surface after cleaning. For this purpose, an HF cleaning solution containing ozone is used.

  Although there is no restriction | limiting in particular in content of ozone, What is necessary is just to contain at least 5 ppm in HF aqueous solution. The upper limit can be used by saturating the HF aqueous solution.

  Here, the HF aqueous solution may be a commercially available product as long as it is an HF aqueous solution having a concentration and purity usually used in the art, or may be prepared by a known method. The concentration is preferably in the range of 0.01 to 0.05% by weight. When it is smaller than this range, it is difficult to obtain a sufficient synergistic effect with ozone. On the other hand, if it is larger than this range, a sufficient cleaning effect can be obtained, but haze deterioration often occurs on the surface after cleaning. From the viewpoint of the cleaning effect and haze deterioration, a more preferable concentration range in the present invention is 0.015 to 0.045% by weight, and particularly preferably 0.02 to 0.04% by weight.

  As described above, the cleaning liquid used in the present invention exhibits a sufficient cleaning effect while suppressing deterioration of haze due to the synergistic effect of ozone and HF. Therefore, a more remarkable effect can be obtained by selecting the ozone concentration and the HF concentration within a more preferable range. Specifically, various HF aqueous solutions containing various concentrations of ozone are actually prepared, the wafer is cleaned as a cleaning solution, and the cleaning effect and haze are qualitatively or quantitatively measured and evaluated to be optimal. Can be As a specific method for optimization, plotting the HF concentration on the horizontal axis and the ozone concentration on the vertical axis, and evaluating the cleaning effect and haze deterioration of the silicon wafer after cleaning at each point, the optimal HF and It is possible to set the ozone concentration by empirical expression.

(Cleaning method)
The cleaning method of the present invention is characterized by using the HF / O ₃ cleaning solution described above. Accordingly, there is no particular limitation on the cleaning apparatus used for carrying out the method of the present invention. Commercially available washing tanks, washing solution circulation devices, washing solution stirring devices (mechanical, ultrasonic irradiation, etc.), and temperature control devices can be used as they are or after being appropriately modified. In addition, if necessary, after washing with this cleaning liquid, a rinse process with ultrapure water, an alkaline cleaning process such as ammonia hydrogen peroxide mixed liquid (APM), an acid cleaning process including hydrochloric acid, hydrofluoric acid, nitric acid, etc. are continued. You may carry out.

  Hereinafter, although it demonstrates in more detail based on an Example, this invention is not limited to these Examples.

  A cleaning solution having HF and ozone concentration shown in the following table was prepared, cleaned, and evaluated for surface roughness after cleaning.

Object to be cleaned:
A P-type silicon wafer substrate (resistance value: 10 to 20Ω) having a diameter of 200 mm and a thickness of 0.725 mm was prepared by depositing an epi film having a thickness of 10 to 20 μm and a resistance of 10Ω.

Cleaning conditions:
Hydrofluoric acid concentration: 0 wt% to 0.06 wt%
Ozone concentration: 5-20 ppm
Temperature: Room temperature Cleaning time: 5 minutes With tank agitation by chemical circulation After washing Ultra pure water rinse: 5 minutes

Cleaning effect evaluation:
The presence or absence of surface roughness was determined by a foreign matter map on the wafer surface measured by Surfscan SP1 manufactured by KLA-Tencor. The map shown in FIG. 2 is determined to have no surface roughness, and the map shown in FIG. 3 is determined to have surface roughness. In the map of FIG. 3, several hundreds of foreign objects having a size of 0.11 μm or more are detected, but when the position coordinates of these foreign substances are recorded and observed with an electron microscope, no actual particles are seen. . Therefore, it can be determined that a large amount of foreign matter detected by Surfscan SP1 represents surface roughness.

The above results are shown in FIG. From this figure, it can be seen that the optimum range of HF and ozone can be expressed by the following empirical formula.
Ozone concentration (ppm)> 625 × HF concentration (wt%) − 15.625 and 5 ppm or more.

  The cleaning method according to the present invention can be widely used for cleaning semiconductor wafers having a hydrophobic surface.

Claims (6)

  A method for cleaning a silicon wafer having a hydrophobic surface, wherein a cleaning liquid containing 0.01 to 0.05% by weight of HF and ozone is used as a cleaning liquid.   The cleaning method according to claim 1, wherein the silicon wafer having a hydrophobic surface is a silicon wafer immediately after epitaxial deposition.   The cleaning method according to claim 1, wherein the silicon wafer having a hydrophobic surface is a silicon wafer immediately after argon annealing.   The cleaning method according to claim 1, wherein at least 5 ppm of ozone is contained.   A cleaning solution for silicon wafers having a hydrophobic surface, wherein HF is 0.01 to 0.05% by weight and ozone is contained at least 5 ppm. HF is 0.01 to 0.05% by weight;
Ozone concentration (ppm)> 625 × HF concentration (wt%) − 15.625 and a cleaning solution for silicon wafer containing 5 ppm or more.

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