KR20090017273A - Method for detecting defect of soi wafer - Google Patents

Abstract

A method for detecting detect of SOI wafer to detect original morphology is provided to reduce defect and failure detection time by omitting the process of forming the oxide film on the wafer surface. The wafer is provided to detect defect(S11). The oxide film is formed in the surface of the wafer. The surface of the SOI wafer is processed by using the hydrofluoric acid(HF) solution(S12). The copper decoration is performed on the SOI wafer(S13). The SOI wafer is dipped in the electrolyte. The cathode is connected to the SOI wafer. The anode is connected to the copper plate and the voltage is applied. The SOI wafer is cleaned and dried and then the defect of the SOI wafer is detected by the naked eye.

Description

SOI wafer defect detection method

The present invention relates to a method for detecting defects in an SOI wafer using a copper decoration method.

Today, a silicon wafer, which is widely used as a material for manufacturing a semiconductor device, refers to a crystalline silicon thin film made of polycrystalline silicon as a raw material.

As the degree of integration of semiconductor devices increases, the quality of a wafer serving as a substrate for manufacturing semiconductor devices has a great influence on the yield and reliability of semiconductor devices. The quality of the wafer depends on crystal growth and defects that occur during the process of manufacturing the wafer. The defects are largely divided into crystal defects occurring during the wafer manufacturing process and defects caused by external contaminants.

Here, the crystal defects are generally classified into point defects and agglomerates (three-dimensional defects). There are two general forms of point defects: vacancy point defects and interstitial point defects. The vacancy point defect is one silicon atom deviated from one of the normal positions in the silicon crystal lattice, and the interstitial point defect is found at the non-lattice point (interstitial position) of the valence silicon crystal.

These point defects are usually formed at the boundary between the silicon melt and the solid ingot. As the ingot is continuously pulled up, the boundary portion is cooled, and the bacony defects and the interstitial defects are diffused to merge with each other to form bacony aggregates or interstitial aggregates. Such agglomerates are called three-dimensional structures called COPs (crystal originated particles) or D-defects.

Defects caused by the external contaminant can be easily removed by an etching or cleaning process, but the crystal defects are difficult to remove. In addition, the crystal defects cause defects in the subsequent manufacturing steps of the semiconductor device, and cause a decrease in yield and reliability of the semiconductor device. Therefore, in order to prevent defects in the semiconductor device manufacturing process described above, it is important to accurately and quickly analyze crystal defects occurring on the wafer.

Conventionally, as a method for detecting the crystal defects, there is a method using a particle measuring device, an etching equipment, a laser scattering particle counter or an oxide film dielectric breakdown by manufacturing a MOS device.

However, the above methods have some problems as follows. The particle measuring method can detect only crystal defects present in a small size of 0.12 mu m or less. In addition, the etching apparatus and the method of using the laser scattering particle counter can detect crystal defects existing in the wafer, but there is a problem in that the prototype of the crystal defects is destroyed in the process of detecting the crystal defects. In addition, in the method of using the oxide dielectric breakdown by fabricating the MOS device, the effect of the crystal defect on the oxide film can be analyzed, but the morphology of the crystal defect cannot be detected.

Another method for detecting crystal defects of the wafer is to use hydrofluoric acid (HF).

In the hydrofluoric acid defect detection method, the crystal defect is etched by the hydrofluoric acid by immersing the wafer in a 50% hydrofluoric acid solution for a predetermined time, and the crystal defect of the wafer can be detected by observing under a microscope.

However, in the hydrofluoric acid defect detection method, it is difficult to detect defects with the naked eye, and since defects are detected using an optical microscope, there is a problem that it is difficult to detect fine defects of 30 μm or less. In addition, since defects are detected locally, it is difficult to accurately grasp the distribution and density of the crystal defects for the entire wafer. In addition, it takes a long time to detect the crystal defects, there is a problem that grasping the number of the crystal defects is largely dependent on the operator, the accuracy and reliability of the defect detection results are lowered.

Due to the above problems, copper decoration method has been used recently.

The copper decoration is a method of identifying crystal defects by contaminating the surface of the wafer with copper ions (Cu 2+).

Specifically, a silicon oxide film is formed on the upper surface of the wafer, the wafer and the copper plate are immersed in an electrolyte in which copper ions are dissolved, and a voltage is applied. By applying a cathode to the wafer and an anode to the copper plate, copper ions in the electrolyte are deposited on the wafer. In particular, a thinning phenomenon occurs locally on the oxide film around the crystal defect on the wafer, and when voltage is applied to the wafer, copper ions are deposited on the crystal defect region and grown to a size that can be visually observed. Therefore, the morphology and distribution of crystal defects of the wafer can be confirmed.

However, the conventional method of detecting defects using copper decoration has a problem that takes a long time. That is, the oxide film is formed by heat treating the wafer. The heat treatment process for growing the oxide film comprises a process of heating the wafer to a predetermined temperature, a process of maintaining the temperature at a high temperature for a predetermined time and a process of cooling the heated wafer, thereby, the heat treatment process It takes a lot of time.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, to shorten the time required for defect detection, and to provide a method for easily detecting defects of an SOI wafer with the naked eye.

The present invention also provides a defect detection method for an SOI wafer which shortens the time required for defect detection and simplifies the defect detection process.

The present invention also provides a defect detection method of an SOI wafer which can easily grasp the morphology of the defect, the distribution of the defect, the density, and the like, and the cause of the defect through the detected result.

In order to achieve the above object, a defect detection method of an SOI wafer comprises decorating copper in a defect region of a silicon on insulator wafer, and visually observing copper deposited on the surface of the SOI wafer. Defect density, distribution and morphology can be identified.

In an embodiment, the copper decoration step, the copper ions are dissolved in the electrolyte, and the SOI wafer and the copper plate in the electrolyte solution in which the copper ions are dissolved. For example, the electrolyte solution includes methanol. Then, a cathode is connected to the SOI wafer and an anode is connected to the copper plate to apply a voltage. After a predetermined time elapses, the copper ions dissolved in the electrolyte are deposited on the SOI wafer.

In an embodiment, the copper decoration is characterized by depositing copper directly on the SOI wafer without an oxide heat treatment process of the SOI wafer.

On the other hand, in the defect detection method of the SOI wafer according to another embodiment for achieving the above object, after pre-treating the SOI wafer using a hydrofluoric acid solution, the SOI wafer is decorated with copper. By visually observing copper deposited on the surface of the SOI wafer, it is possible to grasp the defect density, distribution, and morphology of the SOI wafer.

In the copper decoration method, copper ions are dissolved in an electrolyte, and the SOI wafer and the copper plate are immersed in an electrolyte in which the copper ions are dissolved. For example, the electrolyte solution includes methanol. Then, a cathode is connected to the SOI wafer and an anode is connected to the copper plate to apply a voltage. After a predetermined time elapses, the copper ions dissolved in the electrolyte are deposited on the SOI wafer.

According to the present invention, first, defects of the SOI wafer can be easily detected with the naked eye.

In addition, the distribution of defects can be detected not only for the morphology of the defects but also for the entire SOI wafer. In addition, defect detection does not depend on the operator, thereby improving the accuracy and reliability of the detection result.

Second, since the SOI wafer includes an oxide film, the step of forming an oxide film on the wafer surface to be a defect detection target can be omitted, and the defect detection time can be shortened.

Third, it is possible to detect the original morphology of the defect without changing the morphology of the crystal defect present in the SOI wafer, and determine the cause of occurrence of the defect based on the morphology of the detected defect and the distribution of the defect. Can be.

As described above, although described with reference to the preferred embodiment of the present invention, those skilled in the art various modifications and variations of the present invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited or limited by the embodiments.

Hereinafter, a defect detection method of an SOI wafer according to an embodiment of the present invention will be described with reference to FIGS. 1 to 7.

1 is a flowchart illustrating a defect detection method according to an exemplary embodiment of the present invention, and FIGS. 2 to 4 are cross-sectional views of an SOI wafer for explaining the defect detection method of FIG. 1. 5 to 7 are images of an SOI wafer for explaining the defect detection method of FIG. 1.

Referring to the drawings, a wafer 100 to be detected as a defect is provided (S11).

Here, the target wafer 100 is a wafer having an oxide film formed on a surface thereof. For example, the target wafer 100 is a silicon on insulator wafer.

The SOI wafer 100 includes a buried oxide layer 120 serving as an insulating film on the base silicon layer 110 serving as a supporting portion, and a single crystal serving as a semiconductor substrate on which the semiconductor device is substantially to be fabricated on the buried oxide layer 120. The top silicon layer 130, which is a silicon thin film, is stacked and formed.

The SOI wafer 100 has advantages in that device isolation of semiconductor devices is easy, and electrical properties of semiconductor devices, including high temperature characteristics, low power consumption characteristics, and high speed characteristics, are excellent.

The method for manufacturing the SOI wafer 100 includes a bonding method for joining a wafer on which an oxide film is formed with a normal wafer, and a buried oxide layer (BOX) buried by injecting oxygen ions and heat treatment at a high temperature of 1300 ° C. or more. There is a SIMOX (Separation by Implanted Oxygen) method.

Referring to FIG. 2, the SOI wafer 100 has a structure in which a base silicon layer 110, the buried oxide layer 120, and the top silicon layer 130 are stacked. In addition, a defect (hereinafter, referred to as a first defect region) 131 is present on the top silicon layer 130.

Here, the first defect region 131 is a crystal defect (COP or D-defect) generated in the process of manufacturing the SOI wafer 100.

That is, the first defect region 131 may have a hole shape partially or completely penetrating the top silicon layer 130. For example, as illustrated in FIG. 2, the first defect region 131 may have a hole shape that completely penetrates the top silicon layer 130 and exposes the buried oxide layer 120. However, the first defect region 131 is not limited to the drawings and the above-described embodiment, and the first defect region 131 partially covers the buried oxide layer 120 as well as the top silicon layer 130. It may be in the form of a hole or through it completely. In addition, the first defect region 131 may have a shape of a cavity generated in the buried oxide layer 120.

The surface of the SOI wafer 100 is pretreated with a hydrofluoric acid (HF) solution (S12).

The hydrofluoric acid pre-treatment (S12) process is to increase the accuracy of defect detection, and enables detection of even minute defects existing in the SOI wafer 100.

In detail, the hydrofluoric acid pretreatment (S12) process immerses the SOI wafer 100 in the hydrofluoric acid solution for a predetermined time. For example, the SOI wafer 100 is immersed in 50% hydrofluoric acid solution for 30 minutes.

The hydrofluoric acid solution reacts with the SOI wafer 100 to expand defects in the SOI wafer 100. In particular, the hydrofluoric acid solution reacts with the buried oxide layer 120 to etch the buried oxide layer 120.

Referring to FIG. 3, the hydrofluoric acid solution may penetrate the buried oxide layer 120 through the first defect region 131. Accordingly, the buried oxide layer 120 is etched by the hydrofluoric acid solution to form a second defect region 121. The buried oxide layer 120 is etched until the second defect region 121 is exposed to the base silicon layer 110.

Next, copper decoration is performed on the hydrofluoric acid pretreated SOI wafer 100 (S13).

In the copper decoration (S13) process, first, a process of ionizing copper is performed. In detail, a dummy SOI wafer and a copper plate are immersed in an electrolyte, and a cathode is connected to the copper plate so that copper ions (Cu 2+) are dissolved in the electrolyte.

For example, the electrolyte may include methanol. Methanol is mainly used as an electrolyte for copper decoration because of its excellent solubility in copper ions.

In addition, the copper ionization process is performed for a sufficient time so that the copper ions are sufficiently dissolved. For example, it is ionized for 1 hour while applying a predetermined voltage.

When the copper ionization process is completed, the dummy SOI wafer is removed, and the SOI wafer 100 to detect defects is immersed in the electrolyte. In addition, a cathode is connected to the SOI wafer 100 and a cathode is connected to the copper plate, and a voltage is applied thereto. Therefore, copper ions dissolved in the electrolyte are deposited on the SOI wafer 100.

When voltage is applied to the SOI wafer 100, break down occurs on the surface of the SOI wafer 100, and the copper ions are deposited on the surface of the SOI wafer 100. In the process of depositing the copper ions, yield occurs first than other regions of the SOI wafer 100 in which the first defect region 131 is normal. Therefore, if the intensity of the voltage applied to the SOI wafer 100 is properly adjusted, copper may be deposited only on the defect region of the SOI wafer 100.

The copper decoration (S13) process is performed for about 30 minutes so that the copper ions can be sufficiently deposited on the SOI wafer 100.

After cleaning and drying the SOI wafer 100 on which copper is deposited, defects of the SOI wafer 100 are detected by visually observing the deposited copper 140 (S14).

After the copper decoration S13 is completed, the copper is deposited on the surface of the SOI wafer 100 at a position corresponding to the first defect region 131.

Referring to FIG. 4, when a cathode is applied to the SOI wafer 100, copper ions in the electrolyte are transferred to the first defect region 131 through the first defect region 131 and the second defect region 121. ) And the second defect area 121. In addition, as time elapses, the deposited copper 140 continues to grow outside the first defect region 131 to become larger than the original size of the first defect region 131. In particular, the deposited copper 240 is grown to a size that can be observed with the naked eye.

In addition, the deposited copper 240 is deposited in a form in which the morphology of the first defect region 131 is enlarged without deforming the morphology of the first defect region 131. Accordingly, the operator can grasp the defect density, defect distribution and morphology of the SOI wafer 100 by observing copper 140 deposited on the SOI wafer 100 with the naked eye.

As shown in FIG. 5, defects present in the SOI wafer 100 are difficult to detect even with an optical microscope in the state where no processing is performed. In order to detect a defect using an optical microscope, it is possible to detect a defect having a size of at least 30 μm or more, but it is impossible to detect a small defect of 30 μm or less. However, as in this embodiment, after the defect of the SOI wafer 100 is magnified through the hydrofluoric acid pretreatment S12 and the copper decoration S13 is performed, as shown in FIG. Observation is also possible.

Here, according to the present embodiment, since the defect of the SOI wafer 100 is expanded through the hydrofluoric acid pretreatment (S12), the microscopic defect having a size of 1 to 30 μm can be easily visually recognized.

In addition, in the case of a defect existing in the buried oxide layer 120, since the top silicon layer 130 existing on the buried oxide layer 120 covers the defect in the buried oxide layer 120, a general defect It is difficult to detect a defect through the detection method. However, according to the embodiment of the present invention, it is possible to easily detect defects existing in the buried oxide film layer 120 with the naked eye.

Meanwhile, in the above-described embodiment, the SOI wafer 100 is pretreated (S12) with a hydrofluoric acid solution prior to the copper decoration (S13), but immediately on the SOI wafer 100 without the hydrofluoric acid pretreatment (S12). Copper decoration (S13) may be performed.

Hereinafter, a defect detection method of the SOI wafer 200 according to another embodiment of the present invention will be described with reference to FIGS. 8 to 11. In the following description, the same components as those in the above-described embodiment will be denoted by the same names, and redundant descriptions thereof will be omitted.

First, an SOI wafer 200 to detect a defect is prepared (S21).

As illustrated in FIG. 9, the SOI wafer 200 has a structure in which a base silicon layer 210, a buried oxide layer 220, and a top silicon layer 230 are stacked.

A defect (hereinafter referred to as a first defect region) 231 is formed in the top silicon layer 230. For example, the first defect region 231 may have a hole shape that exposes the buried oxide layer 220 through the top silicon layer 230. Alternatively, the first defect region 231 may have a hole shape partially or completely penetrating the buried oxide layer 220.

Then, copper is decorated in the defect region 231 of the SOI wafer 200 (S22).

The copper decoration (S22) is carried out in substantially the same manner as in the above-described embodiment, and overlapping description is omitted.

When the SOI wafer 200 is immersed in an electrolyte in which copper ions are dissolved, a cathode is connected to the SOI wafer 200, and a voltage is applied, the copper ions are deposited on the SOI wafer 200. In particular, the copper ions are deposited only on the first defect region 231.

Referring to FIG. 10, the copper ions are deposited on the first defect region 231, and copper is deposited on the surface of the SOI wafer 200 as time passes. In particular, the deposited copper 240 is deposited in an extended form to the peripheral region of the first defect region 231. In addition, the deposited copper 240 on the surface of the SOI wafer 200 is formed to a size that is visible to the naked eye.

When the copper decoration S22 is completed, defects of the SOI wafer 200 are visually detected. In detail, as shown in FIG. 11, the density and distribution of defects of the SOI wafer 200 and the morphology of the defects may be determined through the copper 240 deposited on the surface of the SOI wafer 200. In addition, defects of the SOI wafer 200 may be visually observed through the deposited copper 240.

According to the present exemplary embodiment, since the copper decoration S22 is formed by enlarging a defect, the copper 140 is deposited, and thus it is possible to easily detect minute defects with the naked eye. In addition, since copper is deposited on the surface of the SOI wafer 200, defects existing in the buried oxide layer 220 may be easily detected with the naked eye.

1 is a flowchart illustrating a defect detection method according to an embodiment of the present invention;

2 to 4 are cross-sectional views illustrating a defect detection method according to the flowchart of FIG. 1;

FIG. 5 is an image of an SOI wafer including defects in the defect detection method of FIG. 1; FIG.

FIG. 6 is an image of an SOI wafer after performing a hydrofluoric acid treatment process on the SOI wafer of FIG. 5; FIG.

7 is an image of an SOI wafer subjected to a copper decoration process on the SOI wafer of FIG. 6;

8 is a flowchart illustrating a defect detection method according to another embodiment of the present invention;

9 and 10 are cross-sectional views illustrating a defect detection method according to the flowchart of FIG. 8;

11 is an image of an SOI wafer in which defects are detected according to the defect detection method of FIG. 8.

<Explanation of symbols for the main parts of the drawings>

100: SOI wafer 110: base silicon layer

120: buried oxide layer 121: second defect region

130: top silicon layer 131: first defect region

140: deposited copper

Claims (5)

Providing an SOI wafer; Decorating copper on the SOI wafer surface; And Identifying defects in the SOI wafer through copper deposited on the SOI wafer surface; And a method of detecting defects in an SOI wafer, wherein the process of forming an oxide film on the surface of the SOI wafer is omitted. The method of claim 1, The copper decoration step; Dissolving copper ions in the electrolyte; Immersing the SOI wafer in an electrolyte in which the copper ions are dissolved; And Connecting a cathode to the SOI wafer and connecting a cathode to a copper plate to apply a voltage; Defect detection method of the SOI wafer comprising a. The method of claim 2, The electrolyte solution is a defect detection method of the SOI wafer, characterized in that methanol. Treating the surface of the SOI wafer using a hydrofluoric acid solution; Decorating copper on the SOI wafer; And Identifying defects in the SOI wafer through copper deposited on the SOI wafer; And a method of detecting defects in an SOI wafer, wherein the process of forming an oxide film on the surface of the SOI wafer is omitted. The method of claim 4, wherein The copper decoration method is; Dissolving copper ions in the electrolyte; Immersing the SOI wafer in an electrolyte in which the copper ions are dissolved; And Connecting a cathode to the SOI wafer and connecting a cathode to a copper plate to apply a voltage; Defect detection method of the SOI wafer comprising a.

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