JP6610443B2 - Surface defect inspection method for semiconductor silicon wafer - Google Patents

Description

  The present invention relates to a surface defect inspection method for a semiconductor silicon wafer.

  In general, a semiconductor silicon wafer manufacturing method includes a single crystal manufacturing process for growing a single crystal ingot by a method such as a Czochralski method (CZ method) or a floating zone method (FZ method), and slicing the manufactured single crystal. There is a processing process in which the wafer is lapped, etched, ground, polished, etc., the surface of the wafer is mirror-finished, and the surface is cleaned.

  In addition, there is a process in which the mirror-polished wafer is further epitaxially grown. Wafers manufactured by these processes are further processed by a device manufacturing process to manufacture memories, ICs, and the like.

  Low quality is required as a quality of the silicon wafer before forming this device, and it is desired that there are few defects especially on the wafer surface.

  As one method for inspecting the surface defects of semiconductor silicon wafers, the surface of a semiconductor silicon wafer for inspection is etched with an inspection solution prepared by mixing ammonia water, hydrogen peroxide water, and pure water. Defects formed on the surface of the wafer are measured with a laser scattering type wafer surface defect inspection system, and a method for determining whether a semiconductor silicon wafer is good or defective based on the measured number of defects and in-plane distribution is performed. (Patent Document 1).

JP-A-4-212433

  As described above, since the conventional surface defect inspection method uses a mixed solution of ammonia water, hydrogen peroxide solution, and pure water, surface roughness is caused by surface etching of the semiconductor silicon wafer using the mixed solution. As a result, there has been a phenomenon in which minute size defect measurement that has been performed before surface etching by the laser scattering type surface defect inspection apparatus cannot be performed after surface etching due to surface roughness.

  The present invention has been made in view of the above problems, and an object thereof is to provide a highly sensitive inspection method for surface defects of a semiconductor silicon wafer.

  In order to achieve the above object, the present invention is a method for inspecting a surface defect of a semiconductor silicon wafer, wherein a natural oxide film is formed on the surface of the semiconductor silicon wafer and the natural oxide film is peeled off by hydrofluoric acid cleaning. By alternately and repeatedly exposing the defects present on the surface of the semiconductor silicon wafer, and measuring the revealed defects on the surface of the semiconductor wafer using a laser scattering type wafer surface defect inspection apparatus. A surface defect inspection method for a semiconductor silicon wafer is provided.

  Such a method for inspecting surface defects of a semiconductor silicon wafer reveals defects present on the surface of the semiconductor silicon wafer without causing surface roughness such as etching by a mixed solution of ammonia water, hydrogen peroxide water and pure water. It becomes possible to make it. Therefore, it is possible to measure a defect from a size smaller than that of the conventional method, and to inspect a surface defect of the semiconductor silicon wafer with high sensitivity.

  Further, at this time, in the surface defect inspection method for the semiconductor silicon wafer, the formation of the natural oxide film and the peeling of the natural oxide film by the hydrofluoric acid cleaning are alternately repeated 10 times or more on the surface of the semiconductor silicon wafer. It is preferable to carry out.

  In this way, it is possible to measure the surface defects of the semiconductor silicon wafer with higher sensitivity by alternately repeating the formation of the natural oxide film and the peeling of the natural oxide film by hydrofluoric acid cleaning 10 times or more. Become.

  In addition, the formation of the natural oxide film on the surface of the semiconductor silicon wafer may be performed using any one of ozone water, hydrogen peroxide solution, and a mixed solution of hydrochloric acid, hydrogen peroxide solution, and pure water. preferable.

  In this way, by forming a natural oxide film using any one of ozone water, hydrogen peroxide water, and a mixed solution of hydrochloric acid, hydrogen peroxide water, and pure water, semiconductor silicon can be formed with higher sensitivity. It becomes possible to measure the surface defects of the wafer.

  With the surface defect inspection method for a semiconductor silicon wafer according to the present invention, it is possible to measure the surface defects of the semiconductor silicon wafer, particularly minute defects, with higher sensitivity than the conventional method. Therefore, by this inspection method, it is possible to obtain a high-quality semiconductor silicon wafer in which even minute defects that cannot be measured by the conventional method are inspected.

It is the process flow figure showing an example of the surface defect inspection method of the semiconductor silicon wafer of the present invention. It is a process flow diagram of the surface defect inspection method of the semiconductor silicon wafer of Example 1 and Example 2. It is a process flow figure of the surface defect inspection method of the semiconductor silicon wafer of a comparative example.

  As described above, in the conventional method for inspecting surface defects of a semiconductor silicon wafer, the surface of the silicon wafer is roughened by surface etching with a mixed solution of ammonia water, hydrogen peroxide water and pure water before the defect is measured by the defect inspection apparatus. For this reason, there is a problem in that it is impossible to measure a minute size defect after surface etching. And if the present inventors can measure the defect of the minute size which had been able to be measured after the surface treatment (surface etching) and before the surface treatment (surface etching), the surface defects of the semiconductor silicon wafer with higher sensitivity can be obtained. It was found that the inspection can be performed.

  And as a result of repeated earnest studies to achieve the above object, the present inventors, as a pretreatment before defect measurement by the defect inspection apparatus, formed a natural oxide film and stripped the natural oxide film by hydrofluoric acid cleaning. By alternately repeating the above, it was found that defects existing on the surface of the semiconductor silicon wafer can be revealed without causing surface roughness of the semiconductor silicon wafer, and the present invention has been achieved.

  That is, the present invention is a method for inspecting a surface defect of a semiconductor silicon wafer, wherein a natural oxide film is formed on the surface of the semiconductor silicon wafer and the natural oxide film is peeled off alternately by hydrofluoric acid cleaning. A semiconductor silicon wafer characterized by revealing defects present on the surface of the semiconductor silicon wafer and measuring the revealed defects on the surface of the semiconductor wafer with a laser scattering type wafer surface defect inspection apparatus This is a surface defect inspection method.

  Hereinafter, the surface defect inspection method for a semiconductor silicon wafer according to the present invention will be described with reference to the process flow diagram shown in FIG.

  First, an inspected semiconductor silicon wafer to be inspected is prepared (FIG. 1A). The semiconductor silicon wafer to be prepared is not particularly limited, and examples thereof include a semiconductor silicon wafer after mirror polishing and an epitaxial wafer.

  Next, a natural oxide film is formed on the surface of the semiconductor silicon wafer (FIG. 1B). Note that the semiconductor silicon wafer may be cleaned in advance with hydrofluoric acid before the natural oxide film is formed.

  The “natural oxide film” formed in the present invention is not a thermal oxide film (thickness: about several hundred nm to 1 μm) formed by heat treatment in an oxidizing atmosphere, for example, an oxide film formed by cleaning or the like. Means. In the present invention, the thickness of the natural oxide film formed every time is not particularly limited, but may be, for example, 0.9 nm to 1.1 nm.

  The natural oxide film is preferably formed using any one of ozone water, hydrogen peroxide water, and a mixed solution of hydrochloric acid, hydrogen peroxide water, and pure water. As the ozone water, for example, if the ozone concentration is higher than 5 ppm, it is preferable because surface defects can be measured with higher sensitivity. The hydrogen peroxide solution preferably has a concentration of 0.1 to 30 wt%. Moreover, as a mixed liquid of hydrochloric acid, hydrogen peroxide solution, and pure water, for example, a volume ratio (hydrochloric acid: hydrogen peroxide solution: pure water) of 1: 1: 10 to 1: 1: 5 is preferable. The temperature of the hydrogen peroxide solution and the mixed solution of hydrochloric acid, hydrogen peroxide solution, and pure water is preferably 60 ° C. or higher, and more preferably adjusted to 80 ° C.

  Next, the natural oxide film thus formed is peeled off by hydrofluoric acid cleaning (FIG. 1C). The HF concentration of hydrofluoric acid is not particularly limited, but can be, for example, 0.5 to 5.0 wt%. It should be noted that the higher the HF concentration, the shorter the stripping time of the natural oxide film on the semiconductor silicon wafer surface. In this hydrofluoric acid cleaning, the natural oxide film formed in FIG. 1B is removed, but the semiconductor silicon wafer is not etched.

  In the present invention, the formation of the natural oxide film (FIG. 1B) and the peeling of the natural oxide film by hydrofluoric acid cleaning (FIG. 1C) are repeated alternately.

  In this manner, the process of alternately repeating the formation of the natural oxide film (FIG. 1 (B)) and the peeling of the natural oxide film by the hydrofluoric acid cleaning (FIG. 1 (C)) allows the aqueous ammonia and hydrogen peroxide to be removed. Without causing surface roughness such as etching with a mixed solution of hydrogen oxide water and pure water, it is possible to perform a process of revealing defects present on the surface of the semiconductor silicon wafer. As a result, even after processing to form a natural oxide film on the surface of the semiconductor silicon wafer and remove the natural oxide film by fluoric acid cleaning, the surface of the semiconductor silicon wafer is not roughened, and the defects are as small as before the processing. Measurement is possible.

  The number of repetitions of the formation of the natural oxide film and the peeling of the natural oxide film by the hydrofluoric acid cleaning is not particularly limited, but it is possible to perform a more sensitive defect inspection by alternately repeating 10 times or more and 50 times or less. This is preferable because it is possible.

  In addition, the formation of a natural oxide film on the surface of a semiconductor silicon wafer (FIG. 1B) and the removal of the natural oxide film by cleaning with hydrofluoric acid (FIG. 1C) include a batch method in which a semiconductor silicon wafer is immersed in a treatment tank. Any one of the single wafer spin methods in which a chemical solution is alternately applied while rotating and holding a semiconductor silicon wafer can be used.

  Next, the wafer surface defects are measured with a laser scattering type wafer surface defect inspection apparatus (FIG. 1D). Examples of the laser scattering type wafer surface defect inspection apparatus include a wafer surface defect inspection apparatus Surfscan SP3 manufactured by KLA-Tencor.

  According to the surface defect inspection method of the present invention, measurement from a small defect size of, for example, 30 nm or less, which cannot be measured by the method of performing surface treatment with a mixed solution of ammonia water, hydrogen peroxide solution, and pure water, becomes possible. . Therefore, by this inspection method, it is possible to obtain a high-quality semiconductor silicon wafer in which even minute defects that cannot be measured by the conventional method are inspected.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these Examples.

Example 1
According to the flow shown in FIG. 2, the semiconductor silicon wafer was subjected to surface treatment by a batch surface treatment method, and surface defects were inspected.

  First, a silicon single crystal semiconductor silicon wafer (PW1 (low defect product), PW2 (low defect product), PW3 (defective product)), and epitaxial wafer (EPW1), both surfaces of which are 300 mm in diameter and finished with mirror surfaces, are prepared. (FIG. 2 (1)). Next, in order to measure the number of defects before defect inspection of this semiconductor silicon wafer, a defect measurement of ≧ 32 nm was performed by a wafer surface defect inspection apparatus (Surfscan SP3 manufactured by KLA-Tencor) (FIG. 2 (2)). . As a result of the measurement, the number of defects before the inspection was all 50 or less, and there were no characteristic patterns.

  Next, the surface treatment by the batch type surface treatment method was performed as follows. Each semiconductor silicon wafer after the defect measurement is cleaned with hydrofluoric acid (FIG. 2 (3)), rinsed with pure water (FIG. 2 (4)), and treated with ozone water (FIG. 2 (5)). The hydrofluoric acid cleaning (FIG. 2 (3)) to the ozone water treatment (FIG. 2 (5)) were repeated. Table 1 shows the processing contents (the number of oxide film separations) for each semiconductor silicon wafer. Further, the immersion time of the chemical solution was set to 1 minute for each treatment tank.

  As chemical treatment conditions, the HF concentration of hydrofluoric acid was 1.0 wt% and the ozone concentration of ozone water was 10 ppm. The higher the HF concentration, the shorter the time required for stripping the natural oxide film on the semiconductor silicon wafer surface. If the ozone water concentration is higher than 5 ppm, surface defects can be measured with higher sensitivity. However, in the case of ozone water, the effect is not obtained as the concentration increases, so in Example 1, it was performed at 10 ppm.

  In silicon wafer surface treatment by repetitive hydrofluoric acid and ozone water, only the natural oxide film formed on the wafer surface with ozone water is removed with hydrofluoric acid, so 1.0 nm surface etching is performed with one chemical treatment. Will do. In other words, the surface of the silicon wafer was etched by 10 nm by performing 10 times of oxide film peeling. Similarly, 20 nm after 20 times of oxide film peeling, 30 nm after 30 times of oxide film peeling, and 50 times of oxide film. 50 nm is etched by peeling.

  Moreover, in Example 1, the cassetteless automatic processing apparatus which immerses only a semiconductor silicon wafer was used without using the cassette which accommodates a semiconductor silicon wafer at the time of chemical | medical solution immersion. An experiment was conducted by setting a chemical silicon wafer chemical immersion program in this cassetteless automatic processing apparatus.

  Each semiconductor silicon wafer after such surface treatment is rinsed with pure water (FIG. 2 (6)) and dried (FIG. 2 (7)), and a wafer surface defect inspection apparatus (Surfscan SP3 manufactured by KLA-Tencor) ) Was used to measure defects of ≧ 32 nm (FIG. 2 (8)). Table 2 shows the defect measurement results when the batch surface treatment method is used.

  From the above results, EPW1 having no wafer surface defects did not increase in the number of defects even when the number of oxide film separations was increased. However, PW1 to PW3 having crystal defects and defects caused by processing depend on the defect level. A difference in the number of defects increased. PW1 and PW2 were found to have increased defects due to processing-induced defects, and PW3 was found to have increased defects due to crystals.

(Example 2)
According to the flow shown in FIG. 2, the semiconductor silicon wafer was subjected to surface treatment by a single wafer spin method surface treatment method, and surface defects were inspected.

  A silicon single crystal semiconductor silicon wafer (PW4 (low defect product), PW5 (low defect product), PW6 (defective product)), and epitaxial wafer (EPW2) having a mirror finished surface with a diameter of 300 mm are prepared (see FIG. 2 (1)). Next, in order to measure the number of defects before defect inspection of this semiconductor silicon wafer, defect measurement of ≧ 32 nm was performed by a wafer surface defect inspection apparatus (Surfscan SP3 manufactured by KLA-Tencor). As a result of the measurement, the number of defects before the inspection was all 50 or less, and there were no characteristic patterns.

  Next, the surface treatment by the single wafer spin method surface treatment method was performed. Each semiconductor silicon wafer after the defect measurement is cleaned with hydrofluoric acid (FIG. 2 (3)), rinsed with pure water (FIG. 2 (4)), and treated with ozone water (FIG. 2 (5)). The hydrofluoric acid cleaning (FIG. 2 (3)) to the ozone water treatment (FIG. 2 (5)) were repeated. Table 3 shows the processing contents (the number of oxide film separations) for each semiconductor silicon wafer. Further, the treatment time with the chemical solution was such that the hydrofluoric acid cleaning time was 1 minute, the pure water rinse time was 10 seconds, and the ozone water treatment time was 1 minute.

  Moreover, as chemical | medical solution processing conditions, HF density | concentration was 1.0 wt% and ozone water density | concentration was 10 ppm. The higher the HF concentration, the shorter the time required for stripping the natural oxide film on the surface of the semiconductor silicon wafer. If the ozone water concentration is higher than 5 ppm, surface defects can be measured with higher sensitivity. However, in the case of ozone water, the effect is not obtained as the concentration increases, so in Example 2, it was performed at 10 ppm. In silicon wafer surface treatment by repetitive hydrofluoric acid and ozone water, only the natural oxide film formed on the wafer surface with ozone water is removed with hydrofluoric acid, so 1.0 nm surface etching is performed with one chemical treatment. Will do. In other words, the surface of the silicon wafer was etched by 10 nm by performing 10 times of oxide film peeling. Similarly, 20 nm after 20 times of oxide film peeling, 30 nm after 30 times of oxide film peeling, and 50 times of oxide film. 50 nm is etched by peeling. In Example 2, an automatic single wafer spin processing apparatus was used, but an experiment was performed by setting a semiconductor silicon wafer processing program in the single wafer spin automatic processing apparatus.

  Each semiconductor silicon wafer after such surface treatment is rinsed with pure water (FIG. 2 (6)) and dried (FIG. 2 (7)), and a wafer surface defect inspection apparatus (Surfscan SP3 manufactured by KLA-Tencor) ) Was used to measure defects of ≧ 32 nm (FIG. 2 (8)). Table 4 shows the defect measurement results when the single wafer spin method surface treatment method is used.

  From the above results, EPW2 having no wafer surface defects did not increase the number of defects even when the number of oxide film peeling was increased, but PW4 to 6 having crystal defects or processing-induced defects depend on the defect level. A difference in the number of defects increased. PW4 and PW5 were found to increase in the number of defects due to processing-induced defects, and PW6 was found to be due to crystal-induced defects.

(Comparative example)
As a comparative example, surface treatment of a semiconductor silicon wafer is performed according to the flow shown in FIG. 3 using a mixed solution of ammonia water, hydrogen peroxide water and pure water described in JP-A-2000-208578. Defect inspection was performed.

  First, a silicon single crystal semiconductor silicon wafer (PW7 (low defect product), PW8 (low defect product), PW9 (defective product)), and epitaxial wafer (EPW3) having a mirror finished surface with a diameter of 300 mm are prepared. (FIG. 3 (1)). Next, in order to measure the number of defects before the defect inspection of this semiconductor silicon wafer, a defect measurement of ≧ 32 nm was performed by a wafer surface defect inspection apparatus (Surfscan SP3 manufactured by KLA-Tencor) (FIG. 3 (2)). . As a result of the measurement, the number of defects before the inspection was all 50 or less, and there were no characteristic patterns.

  Next, a chemical solution is prepared so that the concentrations of ammonia water and hydrogen peroxide water are 3.0 wt% ammonia and 0.6 wt% hydrogen peroxide, respectively, and surface treatment is performed with this chemical solution by a batch surface treatment method. (FIG. 3 (3)) and then a pure water rinse (FIG. 3 (4)) was performed, and this was performed 1 to 5 times. The chemical temperature at this time was 70 ° C., and the treatment time was 6 minutes and 30 seconds. For easy comparison with the examples, the etching amount for one chemical treatment was set to 10 nm, and therefore the time for one chemical treatment was set to 6 minutes 30 seconds. Since the etching rate of the silicon wafer surface under the condition of the ammonia water and hydrogen peroxide solution mixture is 1.5 nm / min, the processing time was set so that the etching amount by one processing becomes 10 nm. Table 5 shows the processing contents for each semiconductor silicon wafer.

  The etching amount of the silicon wafer surface per chemical solution treatment in the comparative example is 10 nm, and similarly, 20 nm is obtained by two chemical treatments, 30 nm is obtained by three chemical treatments, and 50 nm is etched by five chemical treatments. It will be.

  Each semiconductor silicon wafer after such surface treatment is dried (FIG. 3 (5)), and a defect measurement of ≧ 32 nm is performed using a wafer surface defect inspection apparatus (Surfscan SP3 manufactured by KLA-Tencor). (FIG. 3 (6)). Table 6 shows the defect measurement results of the comparative example.

  From the above results, in the results up to the second time, as in the example, EPW3 without wafer surface defects did not increase in the number of defects even when the number of oxide film peeling was increased, but PW7 (low defect Product), PW8 (low defect product), and PW9 (defective product), an increase in defects was observed. However, in the third and subsequent experimental results, the wafer surface defect could not be measured due to surface roughness of the silicon wafer surface caused by etching with ammonia water and hydrogen peroxide solution.

  As described above, in the method for inspecting the surface defect of the semiconductor silicon wafer according to Example 1 and Example 2, it was possible to measure the surface defect of the semiconductor silicon wafer with higher sensitivity than in the comparative example.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

Claims (3)

A method for inspecting a surface defect of a semiconductor silicon wafer,
The surface of the semiconductor silicon wafer by performing alternately repeated a release of the natural oxide film by forming and hydrofluoric acid cleaning of a native oxide film, a process Ru is actualized defects present in the semiconductor silicon wafer surface Done
Following the processing of Ru is manifested the defects, the defects of the semiconductor wafer surface, a surface defect inspection method of a semiconductor silicon wafer, comprising measuring the wafer surface defect inspection apparatus of a laser scattering method. In the surface defect inspection method for the semiconductor silicon wafer, the natural oxide film having a thickness of 0.9 nm to 1.1 nm is formed on the surface of the semiconductor silicon wafer, and the natural oxide film is peeled off by the hydrofluoric acid cleaning. 2. The method for inspecting a surface defect of a semiconductor silicon wafer according to claim 1, wherein the step is alternately repeated 10 times or more. The natural oxide film is formed on the surface of the semiconductor silicon wafer using any one of ozone water, hydrogen peroxide solution, and a mixed solution of hydrochloric acid, hydrogen peroxide solution, and pure water. A method for inspecting a surface defect of a semiconductor silicon wafer according to claim 1 or 2.

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