TW201738980A - Wafer metal contamination evaluation method - Google Patents

Abstract

The present invention relates to a wafer metal contamination evaluation method. The method comprises the steps of: performing multiple chemical treatments for the wafer, sequentially performing surface inspection, SEM-X ray scans, and defect classification. Compared with current method, multiple chemical treatments can detect the deeper defects and metal concentration to increase the reliability of the metal contamination evaluation. Besides, the method of the present invention performs two surface inspections, SEM-X ray scans, and defect classifications that will also help to obtain more accurate metal contamination evaluation data to further assist better metal contamination evaluation results.

Description

Method for evaluating wafer metal contamination

The invention relates to the field of semiconductor defect analysis, and in particular to a method for evaluating metal contamination of a wafer.

In the semiconductor process, metal ions are called mobile ion pollution sources, which have strong mobility in semiconductor materials, which will cause oxide-polysilicon gate structure defects, increased leakage current of PN junction, and reduced lifetime of minority carriers. The change in threshold voltage is a serious hazard to component yield and reliability. The TXRF elemental analyzer (Total X-ray Fluorescence) can only achieve an accuracy of 1E10atoms/cm ² , but a smaller amount of metal ions is difficult to detect. The TXRF elemental analyzer shows that there is no metal ion exceeding the standard, but there is still metal contamination. possibility.

Japanese Patent (JP2009-139148) and Japanese Patent (JP2005-063984) describe a method for evaluating metal contamination, for example, scanning electron microscopy-X-ray spectroscopy (SEM-EDX) for surface scanning; LS and SP- 3 Surface inspection, in particular, LS can distinguish between crystal primary pits (COP) and particles; chemical analysis for metal contamination assessment.

In order to evaluate metal contaminants, the Japanese patent (JP2015-220296) documents the following steps:

Wafer cleaning is first performed; then the wafer is chemically treated; then the wafer is subjected to high sensibility surface inspection; then the wafer is subjected to Scanning electron microscopy-X-ray energy spectrum analysis (SEM-EDX); then performing defect classification on the defects detected in the wafer; and then performing a transmission electron microscope observation (TEM) on the wafer; Finally, according to the above test results, the wafer is subjected to defect volume calculation, metal density calculation, surface metal concentration calculation and wafer metal concentration analysis, and finally the metal contaminant evaluation result is obtained.

However, all of the above methods can only detect metal contaminants on the surface of the wafer and at shallow locations inside the wafer. When metal contaminants are deep inside the wafer, it is difficult to detect. Therefore, how to detect most of the metal contaminants inside the wafer as much as possible is a technical problem to be solved by those skilled in the art.

It is an object of the present invention to provide a method for evaluating metal contamination of a wafer, which solves the problem of only detecting metal contaminants on the surface of the wafer and at shallow locations inside the wafer in the prior art.

The technical solution of the present invention is a method for evaluating metal contamination of a wafer, comprising the following steps: Step S01: performing multiple chemical treatments on the wafer; Step S02: sequentially performing surface inspection on the wafer, scanning electron microscope-X-ray Energy spectrum analysis and defect classification.

Further, in the method for evaluating the metal contamination of the wafer, in step S01, the wafer is subjected to two chemical treatments.

Further, in the method for evaluating the metal contamination of the wafer, after each chemical treatment, the step S02 needs to be completed, and then the next chemical treatment is performed.

Further, in the method for evaluating the metal contamination of the wafer, after the step S01 and the step S02 are repeated, the method further includes the step S03: sequentially performing projection electron microscope observation, defect volume calculation, metal density calculation, and Surface metal concentration calculation and wafer metal concentration analysis.

Further, in the method for evaluating the metal contamination of the wafer, the first surface inspection data is combined with the second surface inspection data, and the combination method is: the first surface inspection and the first The coincident defects in the secondary surface inspection are regarded as one defect, and the non-coincident defects are regarded as additional defects.

Further, in the method for evaluating the metal contamination of the wafer, the total defects of the wafer include coincident defects and non-coincident defects.

Further, in the method for evaluating the metal contamination of the wafer, the method for classifying the defect is: treating a defect in which the species overlap in the surface inspection in the surface inspection as a defect, and the different types of the defects are different Defects serve as two defects in surface inspection.

Further, in the method for evaluating the contamination of the wafer metal, the volume of the defect is calculated based on the data of the two defect classifications and the depth of the defect observed by the projection electron microscope.

Further, in the method for evaluating the metal contamination of the wafer, the density of the metal is calculated based on the results of the scanning electron microscope-X-ray energy spectrum analysis twice.

Further, in the method for evaluating the metal contamination of the wafer, the contamination of the nickel telluride is chemically treated with diluted hydrofluoric acid.

Compared with the prior art, the method for evaluating the metal contamination of the wafer provided by the present invention has the following beneficial effects: 1. The present invention can perform subsequent chemical processing on the wafer by performing multiple chemical treatments on the wafer. During processing, defects at deeper positions inside the wafer are detected to increase the accuracy of metal contamination detection and improve the accuracy of evaluation of metal contamination of the wafer; 2. The invention performs two surface inspections, two scanning electron microscopes - X-rays The energy spectrum analysis and the two defect classifications, and the two results are comprehensively analyzed, so that the information of metal pollution can be obtained more accurately, and the metal contamination of the wafer can be accurately evaluated.

10‧‧‧ wafer

11‧‧‧First defect

12‧‧‧second defect

1 is a flow chart of a method for evaluating contamination of a wafer metal according to an embodiment of the present invention.

2a-2c are cross-sectional views of a wafer having defects in an embodiment of the present invention.

In order to make the content of the present invention clearer and easier to understand, the contents of the present invention will be further described below in conjunction with the accompanying drawings. Of course, the invention is not limited to the specific embodiment, and general replacements well known to those skilled in the art are also encompassed within the scope of the invention.

Secondly, the present invention is described in detail using a schematic diagram. When the examples of the present invention are described in detail, for convenience of explanation, the schematic diagram is not partially enlarged in accordance with the general scale, and should not be taken as The definition of the invention.

The core idea of the present invention is that the present invention can detect defects in deeper positions inside the wafer in the subsequent processing of the wafer to increase metal pollution by performing chemical treatment on the wafer multiple times compared with the existing evaluation method. The accuracy of the detection improves the accuracy of the evaluation of the metal contamination of the wafer; the present invention performs two surface inspections, two scanning electron microscopy-X-ray energy spectrum analysis, and two defect classifications, and comprehensively analyzes the two results. This allows for more accurate information on metal contamination and accurate assessment of wafer metal contamination.

1 is a flow chart of a method for evaluating metal contamination of a wafer according to an embodiment of the present invention. As shown in FIG. 1 , the present invention provides a method for evaluating metal contamination of a wafer, which includes the following steps: Step S01: Performing on a wafer A plurality of chemical treatments; Step S02: sequentially performing surface inspection, scanning electron microscope-X-ray energy spectrum analysis, and defect classification on the wafer.

In step S01, by performing chemical treatment on the wafer a plurality of times, defects at deeper positions inside the wafer can be detected, thereby increasing the accuracy of metal contamination detection, and making the evaluation result more accurate. For the contamination of nickel telluride, it is chemically treated with diluted hydrofluoric acid.

It can be understood that the shallower position inside the wafer and the deeper position inside the wafer mentioned in this embodiment are relatively shallow, and the shallower position inside the wafer is deeper than the inside of the wafer, and the distance inside the wafer is The wafer surface is closer, with the interior of the wafer being deeper in position relative to the interior of the wafer and being further inside the wafer from the wafer surface.

According to the present invention, defects in deeper positions inside the wafer can be detected by chemically treating the wafer a plurality of times. Please refer to FIGS. 2a-2c, which is a cross-sectional view of the wafer having defects. As shown in Figure 2a, there are two defects at different depths inside the wafer 10: the first defect The depression 11 and the second defect 12 are located at a deeper position inside the wafer with respect to the second defect 12. The existing method for wafer metal contamination evaluation can only detect the second defect 12 located at a shallow position inside the wafer. As shown in FIG. 2b, the first defect 11 located at a deeper position inside the wafer is limited by the method. Can not be detected, but in fact the defect exists, this test results in inaccurate results of metal pollution assessment. Through the method for evaluating the metal contamination of the wafer provided by the present invention, the wafer is subjected to multiple chemical treatments, and the first defect 11 can be detected in the subsequent processing of the wafer, as shown in FIG. 2c, thereby increasing The accuracy of metal contamination detection improves the accuracy of wafer metal contamination assessment.

In step S02, the chemically treated wafer is sequentially subjected to surface inspection, scanning electron microscopy-X-ray energy spectroscopy (SEM-EDX), and defect classification.

Preferably, the wafer is chemically treated twice. Each time a chemical treatment is performed, the wafer is subjected to a surface inspection, scanning electron microscopy-X-ray spectroscopy (SEM-EDX), and defect classification, and then the next chemical treatment.

Combining the data of the first surface inspection with the data of the second surface inspection is performed by combining the defects of the first surface inspection and the second surface inspection as a defect, which is not coincident Defects are added as defects. The total wafer defects include coincident defects and non-coincident defects. The method of classifying the defects is to treat, as the original defects, defects in which the kinds of the overlapped defects in the surface inspection are coincident, and the defects of different types among the overlapped defects are two defects of the surface inspection.

The invention performs two surface inspections, two scanning electron microscope-X-ray energy spectrum analysis and two defect classifications, and comprehensively analyzes the two results, so that the information of metal pollution can be obtained more accurately, and the crystal is accurately aligned. Round metal contamination is assessed.

After the steps S01 and S02 are repeated, the method further includes the step S03: sequentially performing a penetration electron microscope observation (TEM), a defect volume calculation, a metal density calculation, a surface metal concentration calculation, and a wafer metal concentration analysis on the wafer. .

The penetration electron microscope observation can obtain the depth of the defect, and the calculation of the defect volume is calculated based on the data of the two defect classifications and the defect depth observed by the projection electron microscope. The metal density was calculated based on the results of two scanning electron microscope-X-ray energy spectrum analyses. Finally, the calculation of the surface metal concentration is completed according to the defect volume and the metal density, thereby performing concentration analysis on a large amount of metal in the wafer to obtain an evaluation result of the wafer metal contamination.

In summary, the method for evaluating the metal contamination of the wafer provided by the present invention can detect the deeper position inside the wafer in the subsequent processing of the wafer by performing multiple chemical treatments on the wafer compared with the existing evaluation method. Defects to increase the accuracy of metal contamination detection and improve the accuracy of wafer metal contamination assessment; the present invention performs two surface inspections, two scanning electron microscopy-X-ray energy spectrum analysis, and two defect classifications, and The results of the two analyses were comprehensively analyzed to provide more accurate information on metal contamination and accurate assessment of wafer metal contamination.

The above is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any changes in the technical solutions and technical contents disclosed in the present invention may be made by those skilled in the art without departing from the technical scope of the present invention. The content is still within the scope of protection of the present invention.

S01~S03‧‧‧Steps

Claims (10)

A method for evaluating metal contamination of a wafer includes the following steps: Step S01: performing multiple chemical treatments on the wafer; Step S02: sequentially performing surface inspection, scanning electron microscopy-X-ray energy spectrum analysis, and defect classification on the wafer . The method of evaluating a metal contamination of a wafer according to claim 1, wherein in step S01, the wafer is subjected to two chemical treatments. The method for evaluating a metal contamination of a wafer according to claim 2, wherein after each chemical treatment, step S02 is completed, and then the next chemical treatment is performed. The method for evaluating the metal contamination of the wafer according to claim 3, after the step S01 and the step S02 are repeated, further comprising the step S03: sequentially performing projection electron microscope observation, defect volume calculation, metal density calculation, and Surface metal concentration calculation and wafer metal concentration analysis. The method for evaluating metal contamination of a wafer according to claim 4, wherein the data of the first surface inspection is combined with the data of the second surface inspection, and the bonding method is: combining the first surface inspection with The defects that coincide in the second surface inspection are regarded as one defect, and the defects that are not coincident are regarded as additional defects. The method of evaluating a metal contamination of a wafer according to claim 5, wherein the total defect of the wafer comprises coincident defects and non-coincident defects. The method for evaluating a metal contamination of a wafer according to claim 5, wherein the method of classifying the defects is: treating a defect in which the types are coincident among the defects overlapped in the surface inspection as a defect, and the types of the defects are different The defects are two defects of the surface inspection. The method of evaluating a metal contamination of a wafer according to claim 7, wherein the volume of the defect is calculated based on the data of the two defect classifications and the depth of the defect observed by the projection electron microscope. The method of evaluating metal contamination of a wafer according to claim 7, wherein the density of the metal is calculated based on the results of the two scanning electron microscope-X-ray energy spectrum analysis. The method for evaluating metal contamination of a wafer according to any one of claims 1 to 9, wherein the contamination of the nickel telluride is carried out by chemical treatment using diluted hydrofluoric acid.