KR20220125990A - Quantitative measuring method for point defect area of silicon wafer - Google Patents

Abstract

An embodiment provides a quantitative measuring method of a spot defect region of a silicon wafer which comprises the following steps of: (a) stabilizing the existing oxygen precipitation nucleus without generating an additional nucleus in a vacancy region by heat-treating a silicon wafer; (b) expanding the pre-stabilized oxygen precipitation nucleus to an observable size; (c) measuring density of an oxygen precipitate; and (d) defining a spot defect region of the silicon wafer according to the density of the oxygen precipitate.

Description

Quantitative measurement method of point defect area of silicon wafer

The embodiment relates to a method for measuring a point defect area of a silicon wafer, and more particularly, to a method for quantitatively evaluating a point defect area of a silicon wafer.

A typical silicon wafer includes a single crystal growth process for making an ingot by the Czochralski method (hereinafter referred to as the 'CZ method'), etc., and a thin disk-shaped wafer by slicing the single crystal. A cutting process, a grinding process for removing damage due to mechanical processing remaining on the wafer due to the cutting, a polishing process for mirror-finishing the wafer, and mirror-finishing the polished wafer It is manufactured through a cleaning process that removes abrasives or foreign substances attached to the surface.

In a silicon wafer manufactured by the CZ method, various defects are generated depending on the growth conditions of the silicon single crystal ingot.

Oxygen precipitates (bulk microdefects; BMD) generated during thermal processing in silicon wafers manufactured by the CZ method are defects caused by residual vacancy and interstitial oxygen (Oi). The generation of , removes metal contamination in the wafer through gettering, has an effect of preventing leakage fail of the device.

However, when oxygen precipitates are excessively generated, a denuded zone (DZ) of the wafer is reduced to deteriorate the quality of the wafer, and the strength of the wafer is deteriorated, which may cause mechanical failure. In addition, when a vacancy-rich wafer is subjected to a high temperature process of 1100° C. or higher, oxygen precipitates may cause additional defects such as oxidation-induced stacking fault (OISF). Here, OISF is a stacking defect created from oxygen precipitation nuclei when self-interstitial is implanted due to rapid surface oxidation such as wet oxidation when oxygen precipitates exist in a silicon wafer of a certain size or more.

Therefore, when manufacturing a wafer, it is necessary to accurately check the distribution of oxygen precipitates and residual vacancies, that is, information on point defect regions in the crystal growth step.

After oxygen is precipitated in the heat treatment process, the most basic analysis method is to measure the density distribution of oxygen precipitates in the surface of the wafer. Although this method has the advantage of indirectly quantifying the distribution of point defect regions, it is difficult to perform high-dimensional analysis other than the line profile as long-term heat treatment is required and cross-sectional analysis of the wafer is forced.

In addition, as a method for directly measuring the residual vacancy, there is an analysis method in which platinum is diffused over the entire wafer to electrically activate the vacancy, and then an electrical characteristic analysis is applied using a deep level transient spectroscope (DLTS). However, this method has the disadvantages of a long analysis time and inappropriateness to know the distribution of point defect regions within the wafer.

Therefore, there is a need for an analysis method that can clearly reveal the point defect area while being fast and simple in terms of quality control of the wafer.

The embodiment is intended to solve the above-mentioned problems, and it is intended to provide a measurement method capable of quickly, simply and clearly revealing a point defect region of a silicon wafer in terms of quality control.

The embodiment includes the steps of: (a) stabilizing the existing oxygen precipitation nuclei without additional nucleation in the vacancy region by heat-treating the silicon wafer; (b) expanding the pre-stabilized oxygen precipitation nuclei to an observable size; (c) measuring the density of the oxygen precipitate; and (d) defining a point defect area of the silicon wafer according to the density of the oxygen precipitates.

Step (a) may be performed at a temperature of 950 ° C. to 1100 ° C. for 1 hour to 5 hours.

In step (a), dry oxidation of the silicon wafer may be performed.

In step (b), the stabilized oxygen precipitation nuclei can be expanded to a size of 20 nanometers or more.

Step (b) may be performed at a temperature of 1100°C to 1200°C for 1 hour to 3 hours.

In step (b), wet oxidation of the silicon wafer may be performed.

In step (c), the density of the oxygen precipitates may be measured using a laser scattering method, or the density of the oxygen precipitates may be measured using a microscope after selective etching.

In step (d), the region where the density of oxygen precipitates is 1.6Х10 ⁸ cm ^-3 or more is defined as the OISF region, and the region where the density of oxygen precipitates is less than 1.6Х10 ⁸ cm ^-3 is defined as the VDP region, and oxygen precipitates are generated An area that is not used can be defined as an IDP area.

In the method of measuring the point defect area of a silicon wafer according to the embodiment, it is possible to distinguish at a time using the density of oxygen precipitates after heat treatment, and it is also possible to quantitatively compare and analyze the difference in the depth of the defect area even within the same area, Since the occurrence of OISF can be predicted using the density of oxygen precipitates, the occurrence width and density of OISF can be easily predicted without directly counting OISF through additional etching or microscopic analysis.

1 is a flowchart of a method for measuring a point defect area of a silicon wafer according to an embodiment;
2 is a view comparing the results according to the measuring method according to the conventional method and the measuring method of the point defect area of the silicon wafer according to the embodiment,
3 is a diagram illustrating OISF density and void density of a wafer including various crystal defect regions.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings to help the understanding of the present invention, examples will be described in detail.

However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided in order to more completely explain the present invention to those of ordinary skill in the art.

Also, as used hereinafter, relational terms such as "first" and "second," "upper" and "lower", etc., shall not necessarily require or imply any physical or logical relationship or order between such entities or elements. In other words, it may be used only to distinguish one entity or element from another entity or element.

1 is a flowchart of a method for measuring a point defect area of a silicon wafer according to an embodiment. As shown in FIG. 1 , in the method for measuring a point defect region of a silicon wafer according to the present embodiment, the silicon wafer is heat treated to stabilize the existing oxygen precipitation nuclei without additional nucleation in the vacancy region (a). (S110), (b) step (S120) of expanding the stabilized oxygen precipitate nuclei to an observable size, (c) step (S130) of measuring the density of oxygen precipitates, and a silicon wafer according to the density of oxygen precipitates (d) defining a point defect region of ( S140 ) may be included. Here, the oxygen precipitate nuclei in steps (a) and (b) may be grown to become oxygen precipitates in steps (c) and (d).

In detail, it is as follows.

First, a silicon single crystal ingot is grown by the CZ method, and a silicon wafer is prepared through processing. In this case, the silicon wafer may have a resistivity greater than 0.1 (Ω·cm) and an initial Oi greater than 8 ppma.

In addition, by heat-treating the silicon wafer, it is possible to stabilize the existing oxygen precipitation nuclei without additional nucleation in the vacancy region. This step may be a step of imparting selectivity to a self-interstitial region having no oxygen precipitation nuclei.

In this case, the heat treatment may be performed at a temperature of 950 ° C to 1100 ° C. When the heat treatment temperature is 950° C. or less, additional nucleation may occur in the VDP region. Here, the VDP region is a region in which OISF precipitation nuclei do not exist because the grown-in vacancy concentration is relatively low, but oxygen precipitation nuclei can easily occur due to vacancy. And, when the heat treatment temperature is 1100° C. or higher, the oxygen precipitation nuclei may be dissolved due to the high temperature.

And, the heat treatment may be performed for 1 hour to 5 hours. If the heat treatment time is shorter than 1 hour, the oxygen precipitation nuclei may not be sufficiently stabilized and may be dissolved in a subsequent process. In addition, when the heat treatment time exceeds 5 hours, the VDP region is excessively formed, and the effect of region division may be reduced.

In addition, by dry oxidation of the silicon wafer after this process, the OISF generation region can be distinguished.

Then, the stabilized oxygen precipitation nuclei can be expanded to an observable size. In detail, the oxygen precipitation nuclei may be expanded and expanded into stabilized oxygen precipitation nuclei having a size of 20 nanometers or more.

This process may be performed at a temperature of 1100° C. to 1200° C. for 1 hour to 3 hours. When the temperature of this process is lower than 1100 °C or higher than 1200 °C, dissolution of oxygen precipitation nuclei may occur. In addition, when the present process is performed for less than 1 hour, it may be difficult to accurately measure the density of the grown oxygen precipitates due to insufficient growth of oxygen precipitates. And, when the heat treatment time exceeds 3 hours, mechanical deformation such as slip may occur in the silicon wafer.

In addition, by wet oxidation of the silicon wafer in this process, the OSIF generation region can be distinguished.

Then, the density of the oxygen precipitate can be measured. In this case, the density of the oxygen precipitates may be measured using laser-scattering tomography (LST), or the density of the oxygen precipitates may be measured using a microscope after selective etching of the silicon wafer. The laser scattering method is a method of measuring a position and size of a defect through light scattered by a defect existing in the silicon wafer by injecting a laser beam into the silicon wafer.

In addition, the point defect region of the silicon wafer may be defined according to the density of the oxygen precipitates. In this case, the point defect region of the silicon wafer may be quantitatively defined according to the measured density of oxygen precipitates. For example, a region in which the density of oxygen precipitates is 1.6Х10 ⁸ cm ^-3 or more may be defined as the OISF region, and a region in which the density of oxygen precipitates is less than 1.6Х10 ⁸ cm ^-3 may be defined as the VDP region, and oxygen precipitates may be defined as the VDP region. An area where this does not occur can be defined as an IDP area.

At this time, the OISF region is a region in which a precipitate capable of expressing OISF in the ingot growth stage because of a high grown-in vacancy concentration already exists, and may also be referred to as an O-band region. The VDP region may be a region in which OISF precipitation nuclei do not exist because the grown-in vacancy concentration is relatively low, but oxygen precipitation nuclei easily occur due to vacancy. In addition, the IDP region may be a region in which oxygen precipitates are hardly generated because there is no grown-in vacancy due to recombination between point defects and self-interstitial is predominant.

In the method of measuring a point defect region of a silicon wafer, the generation behavior of oxygen precipitates is selective for regions including OISF and vacancy, and does not occur in an interstitial-rich region.

And, the density of the precipitate may reflect the relative level of vacancy in the crystal. That is, in the conventional haze method, etc., the boundary between the O-band and the VDP region, which were separated through a plurality of heat treatments, can be distinguished at once using the density of oxygen precipitates after heat treatment in this embodiment, and also within the same region. The difference in the depth of the defect region can be quantitatively compared and analyzed.

In addition, since the occurrence of OISF and the like can be predicted using the density of oxygen precipitates, the occurrence width and density of OISF can be easily predicted without directly counting the OISF through additional etching or microscopic analysis.

FIG. 2 is a view comparing the results of the measurement method of the point defect area of the silicon wafer according to the embodiment and the measurement method according to the conventional method.

In FIG. 2, the upper part shows the LST (Laser-scattered tomography) measurement result of the wafer according to the method for measuring the point defect region of the silicon wafer according to the present embodiment, and the lower part shows the measurement according to the conventional heat treatment method for precipitates The LST measurement results of the wafer using the method are shown.

For a total of 7 wafer samples, the method according to the present embodiment and the measurement method according to the precipitation heat treatment method according to the conventional copper-haze method were performed. Each wafer may be a wafer having a diameter of about 300 millimeters, and in the case of conventional precipitation heat treatment, LST was measured after heat treatment at 800° C. for 4 hours and at 1000° C. for 16 hours.

It can be seen that the density profile of the precipitates of the wafer according to the measurement method of this embodiment matches the distribution of the point defect regions of the wafer using the conventional copper-haze method, and the relative depth of the VDP region is well reflected in the density of the precipitates. can In particular, since BMD was not detected at all in the region identified as IDP in the wafer according to the copper-haze method, it can be seen that the selectivity to the vacancy region is clear in this embodiment.

3 is a diagram illustrating OISF density and void density of a wafer including various crystal defect regions.

In FIG. 3 , the OISF density is shown on the left side and voids (COP) are shown on the right side for the plurality of wafers in FIG. 3 . On the left, it can be seen that the OISF density on the wafer surface increases sharply when it exceeds a specific density (1.6Х10 ⁸ cm ^-3 ). It is possible to clearly confirm the position, and it can be seen that the measurement method according to the present embodiment reflects the point defect level of the silicon wafer grown by the CZ method.

The haze method analyzes point defects of a wafer through forced contamination of transition metals such as copper (Cu) and diffusion heat treatment. That is, in a region where oxygen precipitates are generated at a high density due to a high residual vacancy in the wafer, the forcibly contaminated transition metal is all gettered in the precipitates and does not diffuse outward to the surface of the wafer, In a region where vacancy is low or self-interstitial is dominant, oxygen precipitates do not occur, so that transition metal gettering does not occur.

Therefore, the transition metal diffused to the surface forms a silicide defect. When the pretreated wafer is etched by selective etching to reflect the difference in the relative gettering capability for each point defect area of the wafer, the silicide on the surface is etched and transformed into a dish-shaped pit (S-pit) to scatter incident light. This can be observed as a haze of bright color.

The haze method described above is suitable for analyzing a large amount of wafers and has an intuitive and convenient advantage because the distribution of the point defect area is visually revealed under a highlight, but quantitative information other than the point defect area boundary is absent.

In addition, there is a milk-haze method that can perform a haze test using background nickel contamination generated in a furnace without forced contamination of the metal, but this method also provides quantitative information. did not provide enough.

In the method of measuring the point defect area of a silicon wafer according to the above-described embodiment, it is possible to distinguish at once using the density of oxygen precipitates after heat treatment, and also to quantitatively compare and analyze the difference in the depth of the defect area even within the same area. Also, the occurrence of OISF can be predicted using the density of oxygen precipitates, so the width and density of OISF can be easily predicted without directly counting OISF through additional etching or microscopic analysis.

As described above, although the embodiment has been described with reference to the limited embodiment and the drawings, the present invention is not limited to the above embodiment, and those skilled in the art to which the present invention pertains various modifications and variations from these descriptions. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the following claims as well as the claims and equivalents.

Claims (13)

(a) stabilizing the existing oxygen precipitation nuclei without additional nucleation in the vacancy region by heat-treating the silicon wafer;
(b) expanding the stabilized oxygen precipitation nuclei to an observable size;
(c) measuring the density of the oxygen precipitate; and
and (d) defining a point defect area of the silicon wafer according to the density of the oxygen precipitates. The method of claim 1,
The step (a) is a quantitative measurement method of the point defect area of the silicon wafer is carried out at a temperature of 950 ℃ to 1100 ℃. The method of claim 1,
The step (a) is a quantitative measurement method of a point defect area of a silicon wafer, which is performed for 1 hour to 5 hours. The method of claim 1,
In the step (a), a quantitative measurement method of a point defect area of a silicon wafer in which the dry oxidation of the silicon wafer is performed. The method of claim 1,
In the step (b), a quantitative measurement method of a point defect area of a silicon wafer by expanding the stabilized oxygen precipitation nuclei to a size of 20 nanometers or more. The method of claim 1,
The step (b) is a quantitative measurement method of the point defect area of the silicon wafer is carried out at a temperature of 1100 ℃ to 1200 ℃. The method of claim 1,
The step (b) is a quantitative measurement method of a point defect area of a silicon wafer, which is performed for 1 to 3 hours. The method of claim 1,
In step (b), a method for quantitatively measuring a point defect area of a silicon wafer in which wet oxidation of the silicon wafer is performed. The method of claim 1,
In the step (c), a quantitative measurement method of a point defect region of a silicon wafer for measuring the density of the oxygen precipitates using a laser scattering method. The method of claim 1,
In the step (c), after selective etching, the density of the oxygen precipitates is measured using a microscope. The method of claim 1,
In the step (d), a quantitative measurement method of a point defect region of a silicon wafer, defining a region in which the density of the oxygen precipitates is 1.6×10 ⁸ cm ⁻³ or more as an OISF region. The method of claim 1,
In the step (d), a quantitative measurement method of a point defect region of a silicon wafer defining a region in which the density of the oxygen precipitates is less than 1.6×10 ⁸ cm ⁻³ as a VDP region. The method of claim 1,
In the step (d), a quantitative measurement method of a point defect region of a silicon wafer, defining the region in which the oxygen precipitate does not occur as an IDP region.

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