TWI777474B - Testing method and apparatus for metal pollution of a silicon slice - Google Patents

Abstract

The present invention disclose a testing method and an apparatus for metal pollution of a silicon slice. After a heat treatment for the silicon slice, SPV testing may be performed to obtain SPV testing data in relation to content of metal pollution in the silicon slice. Through analyzing the SPV testing data, a comparison between the SPV testing data and a threshold may be obtained to determine quality of the silicon slice. The present invention may digitalize the metal pollution of the silicon slice and perform automatic testing to promote sensibility, accuracy and efficiency of testing. Further, no chromic acid is required so as to lower pollution and risk factor and avoid cleaning process. Then, the testing for metal pollution of the silicon slice may be performed in a convenient, fast, high-sensitive, high-accurate, manpower-saving and resource-saving way.

Description

Silicon wafer metal contamination test method and device

The invention belongs to the technical field of semiconductors, and relates to a silicon wafer metal pollution testing method and device.

With the development of the semiconductor industry, higher and higher requirements are placed on the quality of silicon materials, among which the minority carrier (minority carrier) diffusion length and minority carrier lifetime are an important physical parameter to characterize the performance of materials. Since metal impurities can diffuse from the surface of the silicon wafer into the interior through the thermal process, they become interstitial metals, which are very effective recombination centers, which will greatly promote the recombination of carriers, thereby reducing the minority carrier lifetime of the silicon wafer, thereby affecting the performance and performance of the device. reliability, and therefore metal contamination is one of the main factors affecting minority carrier diffusion length and minority carrier lifetime.

However, in the semiconductor manufacturing process, the equipment and fixtures that come into contact with the product can easily cause metal contamination to the product, and the silicon wafers contaminated with metal will seriously affect the reliability and yield of the components when making components.

In the prior art, most of the silicon wafers are tested for metal contamination by chromic acid treatment and the Graff test is performed, that is, the silicon wafers are first heat treated to drive the metal contamination components into the silicon wafers, and then the silicon wafers are immersed in chromic acid. , to perform chromic acid treatment on the silicon wafer, and then perform a cleaning process on the silicon wafer, Finally, under the irradiation of strong light, a manual visual inspection is performed to observe whether the silicon wafer has fog marks, so as to judge whether the silicon wafer has passed the test. However, this test method requires human judgment, so the accuracy of the test results is low; and chromic acid needs to be used for acid treatment, and because chromic acid is harmful to the human body and the environment, its application has been limited, such as Shanghai in 2019. The city has controlled the use of chromic acid; and after the chromic acid treatment, the silicon wafers need to be cleaned, so the testing steps are cumbersome, time-consuming, and waste manpower and material resources.

Therefore, it is necessary to provide a method for testing metal contamination of silicon wafers.

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method and device for measuring metal contamination of silicon wafers, which are used to solve the problems of complicated steps, time-consuming and waste of resources in the prior art method for measuring metal contamination of silicon wafers.

In order to achieve the above object and other related objects, the present invention provides a method for testing metal contamination of silicon wafers, comprising the following steps: heat treatment of silicon wafers; SPV test data about metal contamination content in the silicon wafer; and performing SPC data analysis on the SPV test data to obtain a comparison result between the SPV test data and a threshold, so as to judge the quality of the silicon wafer.

Optionally, the metal contamination content includes one or a combination of the number of Ni metal atoms and the number of Cu metal atoms per unit volume.

Optionally, the heating temperature of the heat treatment ranges from 700°C to 900°C.

Optionally, the threshold value ranges from 5E10/cm ³ to 7E10/cm ³ . When the metal contamination content is not less than the threshold value, the silicon wafer is determined to be a defective product. When less than the threshold value, the silicon wafer is judged as a qualified product.

The present invention also provides a silicon wafer metal contamination testing device, the silicon wafer metal contamination testing device includes: silicon wafer heat treatment equipment, the silicon wafer heat treatment equipment performs heat treatment on the silicon wafer; SPV testing equipment, the SPV testing equipment performing an SPV test on the silicon wafer to obtain SPV test data on the metal contamination content in the silicon wafer; and an SPC data analysis device, which performs SPC data analysis on the SPV test data to obtain the SPV test The comparison result of the data and the threshold value is used to judge the quality of the silicon wafer.

Optionally, the silicon wafers are automatically transmitted sequentially from the silicon wafer heat treatment equipment, the SPV testing equipment and the SPC data analysis equipment.

Optionally, the SPV testing equipment and the SPC data analysis equipment are integrated in the same equipment.

Optionally, the silicon wafer metal contamination testing device further includes a warning device, and the warning device includes one or a combination of an audible warning device and a light warning device, or the warning device is an acousto-optic warning device.

Optionally, the silicon wafer metal contamination testing device is suitable for testing one or a combination of Ni metal and Cu metal in the silicon wafer.

Optionally, the threshold value set in the SPC data analysis device ranges from 5E10/cm ³ to 7E10/cm ³ .

As mentioned above, in the method and device for testing metal contamination of silicon wafers of the present invention, after heat treatment of the silicon wafers, the SPV test on the silicon wafers can be used to obtain information about the metal contamination content in the silicon wafers. SPV test data; By analyzing the SPV test data by SPC data, the comparison result between the SPV test data and the threshold value can be obtained to judge the quality of the silicon wafer. The present invention can realize digital and automatic testing of metal contamination of silicon wafers, so as to improve test sensitivity, test accuracy and test efficiency; it does not need to use chromic acid, thus can reduce pollution and risk factor, and does not need to carry out cleaning procedures; thus, the present invention can It is convenient, fast, high-sensitivity, high-accuracy, and effective to save manpower and material resources for testing silicon wafer metal pollution.

100: first threshold

200: Second threshold

FIG. 1 is a schematic diagram showing a process flow of a method for testing metal contamination of a silicon wafer according to an embodiment of the present invention.

FIG. 2 is a structural block diagram of a silicon wafer metal contamination testing device according to an embodiment of the present invention.

FIG. 3 is a schematic diagram showing the comparison result between the SPV test data and the threshold in the embodiment of the present invention.

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

When describing the embodiments of the present invention in detail, for the convenience of description, the cross-sectional views showing the structure of the components are not partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the protection scope of the present invention. In addition, the three-dimensional spatial dimensions of length, width and depth should be included in the actual production.

For convenience of description, spatially relative terms such as "below," "below," "below," "below," "above," "on," etc. may be used herein to describe an element shown in the figures or The relationship of a feature to other components or features. It will be understood that these spatially relative terms are intended to encompass other directions of elements in use or operation than those depicted in the figures. In addition, when a layer is referred to as being 'between' two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. As used herein, "between" means including both endpoints.

In the context of this application, descriptions of structures where a first feature is "on" a second feature can include embodiments in which the first and second features are formed in direct contact, and can also include further features formed over the first and second features. Embodiments between the second features such that the first and second features may not be in direct contact.

It should be noted that the diagrams provided in this embodiment are only to illustrate the basic concept of the present invention in a schematic way, so the diagrams only show the components related to the present invention rather than the number, shape and the number of components in the actual implementation. For dimension drawing, the type, quantity and proportion of each component can be arbitrarily changed in actual implementation, and the component layout may also be more complicated.

As described in the background art, since there are many problems in the metal contamination test of silicon wafers in the prior art, there is an urgent need to find an alternative technical solution.

Surface Photo-Voltage (SPV) test is an advanced method for non-destructive whole-chip scanning measurement of minority carrier lifetime, diffusion length and metal impurity content of silicon wafers. Its test principle is to obtain the minority carrier diffusion length by measuring the surface voltage generated by the light on the surface of the semiconductor material. It calculates the metal content through the change of the carrier diffusion length before and after illumination. The calculation formula is as follows: N _metal (atoms/cm ³ )=1.05×10 ¹⁶ (1/L ² _after -1/L ² _before ).

Therefore, based on the principle of the SPV test, the inventors conducted the following verification tests. The specific operations are as follows: using the ICPMS standard solution to prepare copper solution and nickel solution with concentrations of 3ppb and 0.03ppb respectively, and provide the first silicon wafer and the second silicon wafer A copper solution with a concentration of 3ppb and a nickel solution with a concentration of 3ppb were dropped on different areas on the first silicon wafer; and a copper solution with a concentration of 0.03ppb was dropped on different regions on the second silicon wafer. and nickel solution with a concentration of 0.03ppb; put the first silicon wafer and the second silicon wafer into a fume hood and dry at room temperature for 12 hours; grow a 2 μm-thick epitaxial silicon layer on the surface of the first silicon wafer and the second silicon wafer respectively , so that the metal is completely between the epitaxial silicon layer and the silicon wafer to form the first composite silicon wafer and the second composite silicon wafer; use a 5% HF solution to clean the first silicon wafer and the second silicon wafer for 10min to avoid The metal composition on the surface of the composite silicon wafer interferes with the measurement results; the first composite silicon wafer and the second composite silicon wafer are tested by SPV measuring equipment.

The results of the above verification tests are based on SPV measurement equipment, which can clearly reflect the corresponding positions of copper metal and nickel metal in the first composite silicon wafer and the second composite silicon wafer and the metal contamination content. Therefore, the SPV measurement equipment can be applied to the data collection of the metal in the silicon wafer.

SPC (Statistical Process Control) data analysis is a process control tool with the help of mathematical statistics. It can analyze and evaluate the production process, find the signs of systemic factors in time according to the feedback information, and take measures to eliminate its influence, so as to achieve the purpose of quality control.

Therefore, based on SPV test and SPC data analysis, the inventor proposes a silicon wafer metal contamination test method and a silicon wafer metal contamination test device to solve the problem of cumbersome steps, time-consuming, and waste of resources in the prior art silicon wafer metal contamination test method. The problem.

As shown in FIG. 1 , this embodiment provides a method for testing metal contamination of silicon wafers. The method for testing metal contamination of silicon wafers includes the following steps: heat treatment of silicon wafers; SPV testing of silicon wafers to obtain the silicon wafers SPV test data on metal contamination content in ; According to the SPC data analysis, the comparison result between the SPV test data and the threshold is obtained to judge the quality of the silicon wafer.

In the method for testing metal contamination of silicon wafers in this embodiment, after the silicon wafers are heat-treated, the SPV test is performed on the silicon wafers to obtain all information about the metal contamination content in the silicon wafers. The SPV test data; by performing the SPC data analysis on the SPV test data, the comparison result between the SPV test data and the threshold can be obtained to judge the quality of the silicon wafer.

This embodiment can realize digital and automated testing of the metal contamination of the silicon wafer, thereby improving the test sensitivity, test accuracy and test efficiency; without using chromic acid, thereby reducing the pollution and risk factor, and without the need for cleaning procedures; Thus, a test method is provided which is convenient, fast, high in sensitivity and high in accuracy, and can effectively save manpower and material resources. Specifically, it includes: first, providing silicon wafers, and placing the silicon wafers in a heating furnace to perform heat treatment on the silicon wafers.

Specifically, a robotic arm can be used to send the silicon wafer into the heating furnace for the heat treatment, so that metal impurities can diffuse into the silicon wafer from the surface of the silicon wafer through a thermal process through the heat treatment. The inside of the silicon wafer becomes interstitial metal atoms, so that the metal impurities can form a metal complex with the silicon wafer, so that the SPV test equipment can be used to perform the SPV test on the silicon wafer subsequently. The size of the silicon wafer and the type of heat treatment equipment are not limited here.

As an example, the heating temperature of the heat treatment is 700°C to 900°C.

Specifically, because the heat treatment can make the metal impurities diffuse into the inside of the silicon wafer, so that the metal impurities can form a metal complex with the silicon wafer, so as to improve the accuracy of the test, this implementation In an example, the heating temperature of the heat treatment is preferably 700°C to 900°C, such as 700°C, 750°C, 800°C, and 900°C, but not limited to this, so as to ensure the complete diffusion of the metal impurities. into the interior of the silicon wafer. Specifically, the heating temperature of the heat treatment can be set as required, which is not excessively limited here.

Next, the SPV test is performed on the silicon wafer to obtain SPV test data on the metal contamination content in the silicon wafer.

Specifically, the structure and test operation of the SPV test equipment are not excessively limited here, and the existing SPV test equipment can be directly used for the test. New SPV test equipment is formed as needed, without undue limitation.

As an example, the metal contamination content includes one or a combination of the number of Ni metal atoms and the number of Cu metal atoms per unit volume.

Specifically, in the semiconductor manufacturing process, the equipment and jigs used for manufacturing can easily cause metal contamination to the silicon wafer, wherein metal impurities mainly include Cu metal and Ni metal, and the silicon wafer after being contaminated by metal When manufacturing subsequent semiconductor elements, the reliability and yield of semiconductor elements will be seriously affected, so it is necessary to measure and control the metal contamination content in the silicon wafers to prepare high-quality silicon wafers for subsequent production. process is used to manufacture high-quality semiconductor components.

In this embodiment, the metal contamination content may include one or a combination of the number of Cu metal atoms and the number of Ni metal atoms per unit volume, but the types of the metal impurities are not limited to this, and the metal contamination content The characterization is not limited to this.

Next, SPC data analysis is performed on the SPV test data, and a comparison result between the SPV test data and the threshold is obtained, so as to judge the quality of the silicon wafer.

Specifically, after the SPV test data is imported into the SPC data analysis device provided with the threshold, the SPV test data can be automatically compared through SPC data analysis. Yes, by comparing the obtained SPV test data with the threshold, the quality of the silicon wafer can be automatically judged, and test results with high sensitivity and high accuracy can be obtained in a timely and effective manner, thereby improving efficiency, Save manpower and material resources. The type of the SPC data analysis device is not limited here, and the operation of the SPC data analysis can be adaptively transformed according to the type of the applied device, which is not limited here.

As an example, the threshold value ranges from 5E10/cm ³ to 7E10/cm ³ . When the metal contamination content is not less than the threshold, the silicon wafer is determined to be a defective product, and when the metal contamination content is less than When the threshold value is reached, the silicon wafer is judged as a qualified product.

Specifically, referring to FIG. 3 , after the SPV test data is acquired, the SPV test data can be compared with the threshold to digitally and automatically determine the quality of the silicon wafer. Wherein, the setting of the threshold may be 5E10/cm ³ , 5.5E10/cm ³ , 6E10/cm ³ , 6.5E10/cm ³ , 7E10/cm ³ , etc., but not limited to this, and can be specifically set as required. Of course, as required, the threshold is not limited to a single threshold, and two or more thresholds can be set at the same time to further control the quality of the silicon wafers at multiple levels, thereby improving the operation efficiency. FIG. 3 shows the comparison result between the SPV test data and the threshold obtained after setting the first threshold 100 and the second threshold 200 simultaneously in the SPC data analysis device. Wherein, when the metal contamination content is greater than or equal to the first threshold of 100, the silicon wafer is determined to be a defective product, and when the metal contamination content is less than the first threshold of 100, the silicon wafer is determined to be a qualified product , and when the metal contamination content is greater than or equal to the first threshold value of 200, the silicon wafer is determined to be scrapped, etc. Of course, more thresholds can be set as needed to divide the silicon wafer into Higher grades to suit different application requirements without repeated testing and comparison.

Referring to FIG. 2 , the present embodiment also provides a silicon wafer metal contamination testing device. The silicon wafer metal contamination testing device includes: silicon wafer heat treatment equipment, SPV testing equipment, and SPC data analysis equipment, wherein the silicon wafer heat treatment equipment The silicon wafer is subjected to heat treatment; the SPV testing device performs SPV testing on the silicon wafer to obtain SPV test data on the metal contamination content in the silicon wafer; the SPC data analysis device performs SPC data analysis on the SPV test data , to obtain the comparison result between the SPV test data and the threshold to judge the quality of the silicon wafer. It can be understood that the silicon wafer metal pollution testing device also includes a controller and other equipment to realize intelligent management and control, which is not excessively limited here.

As an example, the silicon wafers are sequentially automatically transferred from the silicon wafer heat treatment equipment, the SPV testing equipment and the SPC data analysis equipment.

Specifically, the silicon wafer heat treatment equipment, the SPV testing equipment and the SPC data analysis equipment can be set independently, but not limited to this, the silicon wafer heat treatment equipment, the SPV testing equipment and the SPC data analysis equipment can also be integrated in the same In order to reduce the equipment occupied area and shorten the transmission path, etc. Among them, 3 sets of equipment can be equipped with silicon wafer transfer parts at the entrance and exit to realize the purpose of automatic transfer of the silicon wafers, so as to reduce the pollution and damage to the silicon wafers during the test process. etc., but not limited to this. The connection method and layout of the silicon wafer heat treatment equipment, SPV testing equipment and SPC data analysis equipment, etc., are not excessively limited here.

As an example, the SPV test equipment and the SPC data analysis equipment are integrated in the same equipment.

Specifically, when the SPV testing equipment and the SPC data analysis equipment are integrated into the same equipment, the quality results of the silicon wafers can be obtained in a timely and effective manner, thereby further improving the testing efficiency, but not limited to this , the SPV test equipment and the SPC data analysis equipment can also be set independently.

As an example, the silicon wafer metal contamination testing device may further include a warning device, and the warning device may include one or a combination of an audible warning device and a light warning device, or the warning device is an acousto-optic warning device.

Specifically, the warning device can be electrically connected to the SPC data analysis device, and when the metal contamination content is not less than (greater than or equal to) the threshold, that is, when the silicon wafer is judged to be defective, it will pass The warning device can emit sound, light, or a combination of sound and light to remind the staff in time, so that the staff can pay attention in time to deal with it in time, reduce the number of abnormal products, and reduce losses.

As an example, the silicon wafer metal contamination testing device may be suitable for testing one or a combination of Ni metal and Cu metal in the silicon wafer, but is not limited thereto.

As an example, the threshold value set in the SPC data analysis device may range from 5E10/cm ³ to 7E10/cm ³ .

Specifically, after the SPC data analysis device acquires the SPV test data, the SPV test data can be compared with the threshold set in the SPC data analysis device, so as to realize the analysis of the silicon wafer. Digital, automated judgment of quality. Wherein, the setting of the threshold may be 5E10/cm ³ , 5.5E10/cm ³ , 6E10/cm ³ , 6.5E10/cm ³ , 7E10/cm ³ , etc., but not limited to this, and can be specifically set as required. Of course, as required, the threshold is not limited to a single threshold, and two or more thresholds can be set at the same time to further control the quality of the silicon wafer at multiple levels, thereby improving the operation efficiency.

To sum up, the method and device for testing metal contamination of silicon wafers of the present invention can obtain SPV test data on metal contamination content in silicon wafers by performing SPV testing on silicon wafers after heat treatment of silicon wafers; SPC data analysis of test data, SPV test data can be obtained and Threshold comparison results to judge the quality of silicon wafers. The present invention can realize digital and automatic testing of metal contamination of silicon wafers, so as to improve test sensitivity, test accuracy and test efficiency; it does not need to use chromic acid, thus can reduce pollution and risk factor, and does not need to carry out cleaning procedures; thus, the present invention can It is convenient, fast, high-sensitivity, high-accuracy, and effective to save manpower and material resources for testing silicon wafer metal pollution.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (10)

A method for testing metal contamination of silicon wafers, comprising the following steps: heat treatment of silicon wafers; performing an SPV test on the silicon wafer to obtain SPV test data on the metal contamination content in the silicon wafer; and SPC data analysis is performed on the SPV test data, and a comparison result between the SPV test data and a threshold is obtained, so as to judge the quality of the silicon wafer. The method for testing metal contamination of silicon wafers according to claim 1, wherein the metal contamination content includes one or a combination of the number of Ni metal atoms and the number of Cu metal atoms per unit volume. The method for testing metal contamination of silicon wafers according to claim 1, wherein the heating temperature of the heat treatment is 700°C to 900°C. The silicon wafer metal contamination test method according to claim 1, wherein the threshold value ranges from 5E10/cm ³ to 7E10/cm ³ , and when the metal contamination content is not less than the threshold value, the silicon wafer is determined to be defective When the metal contamination content is less than the threshold, the silicon wafer is judged as a qualified product. A silicon wafer metal contamination testing device, comprising: a silicon wafer heat treatment equipment, the silicon wafer heat treatment equipment heat treatment of silicon wafers; an SPV testing device that performs SPV testing on the silicon wafer to obtain SPV testing data on the metal contamination content in the silicon wafer; and An SPC data analysis device, the SPC data analysis device performs SPC data analysis on the SPV test data, and obtains a comparison result between the SPV test data and a threshold value, so as to judge the quality of the silicon wafer. The silicon wafer metal contamination testing device according to claim 5, wherein the silicon wafer is automatically transmitted from the silicon wafer heat treatment equipment, the SPV testing equipment and the SPC data analysis equipment in sequence. The silicon wafer metal contamination testing device according to claim 5, wherein the SPV testing equipment and the SPC data analysis equipment are integrated in the same equipment. The silicon wafer metal contamination testing device as claimed in claim 5, wherein the silicon wafer metal contamination testing device further includes a warning device, and the warning device includes one or a combination of an audible warning device and a light warning device, or the warning device is a Sound and light warning equipment. The silicon wafer metal contamination testing device according to claim 5, wherein the silicon wafer metal contamination testing device is suitable for testing one or a combination of Ni metal and Cu metal in the silicon wafer. The silicon wafer metal contamination testing device according to claim 5, wherein the threshold value set in the SPC data analysis equipment ranges from 5E10/cm ³ to 7E10/cm ³ .

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