Method and apparatus for ultrasonic detection of ring-open defects in semiconductor silicon rings

Abstract

A method and dedicated device for ultrasonic detection of microcracks in semiconductor silicon rings are disclosed, specifically comprising: selecting a piezoelectric crystal with a size of 6–10 mm and a frequency range of 1 MHz–15 MHz for a water immersion focusing ultrasonic probe; calculating the required incident angle for the ultrasonic waves to refract into transverse waves, surface waves, and creeping waves at the water / silicon interface; adjusting multiple sets of ultrasonic probes to emit ultrasonic waves at different tilt angles according to the incident angle value; the ultrasonic waves are refracted on the surface of the semiconductor silicon ring, resulting in waveform conversion; the refracted waves excited by ultrasonic waves at different incident angles in the semiconductor silicon ring propagate in the silicon wafer along a certain propagation path; when they encounter a defect, ultrasonic scattering occurs, and the reflected waves in the scattering return along the original path and are received by the ultrasonic probe; the ultrasonic probe converts the reflected wave signal into a detection electrical signal and transmits it to the ultrasonic instrument; the ultrasonic instrument uploads the result signal to an industrial control computer; the imaging software in the industrial control computer images the detection results and displays the distribution information of the microcracks in the entire semiconductor silicon wafer.

Description

TECHNICAL FIELD

[0001] The present application relates to the non-destructive testing technology of macroscopic defects of non-metallic ring-shaped components in the field of semiconductors, in particular to a method for detecting various crack defects of components by using multi-waveform ultrasonic scattered waves, and the detection object is non-metallic brittle components in the field of semiconductors. BACKGROUND

[0002] The core materials for integrated circuit (chip) manufacturing include silicon, germanium, and various brittle semiconductor materials such as silicon carbide and gallium nitride. In addition to being used as wafers, these materials are also used to process ring-shaped components of different specifications in core processes such as etching and oxidation to assist in completing the corresponding processing of wafers. Such components are in the same environment as wafers, and the purity, crystal form, dimensional accuracy, thermophysical properties, and macroscopic defects of the raw materials will directly affect the yield of wafers. Among the many issues of bring-in, crack is a very dangerous component defect, because the presence of component cracks can easily cause large-area particle contamination in the cavity, leading to the entire batch of wafers being scrapped. For this problem, component suppliers usually use single or multi-pass manual inspection methods to exclude. This method is only suitable for detecting surface cracks visible to the naked eye, and is time-consuming and labor-intensive, and there is a risk of missed detection, and it is helpless for hidden cracks that may exist.

[0003] Currently, the detection methods for crack defects of brittle materials mainly fall into two categories: one is destructive detection method, and the other is non-destructive detection method.

[0004] The destructive detection method is easy to operate and has mature technology, mainly including etching method, cross-section microscopic method, taper polishing method, etc. However, the destructive detection method has the following problems: 1. Destructive detection belongs to destructive detection, which will cause material loss and increase production cost. 2. The detection efficiency is low, which belongs to sampling detection and is easy to cause missed detection. 3. It is a selective detection method, which can only detect defects at a certain position and cannot characterize the overall defect distribution of silicon rings at one time. 4. The sample preparation process is complex and time-consuming, and toxic corrosive reagents are needed, which poses a risk to the safety of the operators.

[0005] The non-destructive detection method mainly includes optical coherence method, laser scattering method, infrared thermal imaging method, machine vision method, and ultrasonic method. The optical coherence method and the laser scattering method have high requirements for the surface roughness of the workpiece. The infrared thermal imaging method requires uniform heating of the workpiece, which has high requirements for the heating method. The machine vision method has requirements for lighting conditions and CCD camera resolution, and some need to spray fluorescent agents and take pictures in a dark room, and the image recognition algorithm is also relatively complex, with poor reliability. In comparison, the ultrasonic method has the advantages of wide detection area, intuitive defect display, high detection efficiency, and easy automation, and has broad potential application prospects in the detection of defects of semiconductor non-metallic components. SUMMARY

[0006] In order to solve the common problem that the hidden crack defects in the sheet-shaped parts made of brittle materials such as silicon and silicon carbide, like semiconductor etching rings, are difficult to detect, the present application provides a method and a special device for detecting the hidden crack defects of semiconductor silicon rings by using the detection technology of oblique incidence multi-waveform ultrasonic waves to realize automatic and efficient detection.

[0007] The technical solution of the present application is as follows:

[0008] A method for detecting the hidden crack defects of semiconductor silicon rings by ultrasonic waves, comprising the following steps:

[0009] 1) The size range of the piezoelectric wafer of the water-immersed focused ultrasonic probe is 6-10mm, and the frequency range is 1MHz-15MHz; the required incidence angle of the refraction of ultrasonic waves into transverse waves, surface waves and creeping waves at the water / silicon interface is calculated;

[0010] 2) According to the numerical values of the specific incidence angles of different waveforms, adjust the multiple ultrasonic probes to emit ultrasonic waves at different inclination angles;

[0011] 3) The ultrasonic waves are scattered on the surface of the semiconductor silicon ring, and the waveform conversion phenomenon occurs, the refraction waves, i.e. transverse waves, surface waves and creeping waves, excited by ultrasonic waves at different incidence angles in the semiconductor silicon ring; the refraction waves propagate in the silicon wafer along a certain propagation path, and when they meet the crack defects, ultrasonic scattering occurs, and the reflected waves in the scattering return along the original path and are received by the ultrasonic probe; the ultrasonic probe converts the reflected wave signals into detection electrical signals, then transmits the detection electrical signals to the ultrasonic instrument, the ultrasonic instrument uploads the result signals to the industrial computer, the imaging software in the industrial computer images the detection results, and displays the hidden defect distribution information of the entire semiconductor silicon wafer in the display.

[0012] In step 1), the calculation method of the required incidence angle of the refraction of ultrasonic waves into transverse waves, surface waves and creeping waves at the water / silicon interface is as follows:

[0013] According to Snell's law formula (1), the required incidence angle α of the refraction of ultrasonic waves into transverse waves, surface waves and creeping waves at the water / silicon interface is calculated.

[0014]

[0015] Wherein α represents the incidence angle of the ultrasonic waves incident from water into the silicon ring, β represents the refraction angle of the ultrasonic waves incident from water into the silicon ring, C1 represents the longitudinal wave velocity of the ultrasonic waves in water, and C2 represents the propagation velocity of different forms of ultrasonic waves in the silicon wafer.

[0016] In step 2), the angle adjuster is used to adjust the multiple ultrasonic probes to emit ultrasonic waves at different inclination angles.

[0017] In step 3), the ultrasonic waves are scattered on the surface of the semiconductor silicon ring to produce wave shape conversion phenomenon, and ultrasonic waves with different incident angles can excite three kinds of refracted waves, i.e., transverse waves, surface waves and creeping waves, in the semiconductor silicon ring workpiece. The transverse waves are used to detect open cracks and penetrating cracks on the upper and lower surfaces of the silicon ring; the surface waves are used to detect cracks with shallow depth on the surface of the silicon ring; and the creeping waves are used to detect hidden cracks on the surface of the silicon ring.

[0018] The refracted waves propagate in the silicon wafer along certain propagation paths, and when meeting the crack defects, the ultrasonic waves are scattered, and the reflected waves in the scattering are returned along the original paths to be received by the ultrasonic probe. The ultrasonic probe converts the reflected wave signals into electric signals, and then transmits the electric signals to the ultrasonic instrument, and the ultrasonic instrument uploads the result data to the industrial computer.

[0019] The industrial computer performs post-processing on the uploaded detection data, and the post-processing process is as follows:

[0020] 1. Mean value filtering is performed to eliminate noise components in the detection data;

[0021] 2. The instrument data acquisition module extracts effective crack signals in the detection data and fills in the amplitude matrix A, while recording the corresponding position parameter i;

[0022] 3. A blank image zero matrix S is created according to formula (2);

[0023] 4. The pixel coordinate values x and y of the ring image are calculated according to formula (3) and formula (4);

[0024] 5. The amplitude matrix A is filled into the S matrix according to the corresponding pixel coordinates to obtain a new S matrix with ring image, and then the S matrix is imaged; the obtained image can display the hidden defect distribution information of the entire semiconductor silicon wafer;

[0025] S = zeros(2R, 2R) (2)

[0026] x = round(R + 50 + (R * cos(i * 360 / 1000 * pi))) (3)

[0027] y = round(R = 50 + (R * sin(i * 360 / 1000 * pi))) (4)

[0028] In the formula, S represents the zero matrix, R represents the actual radius value of the silicon ring, i represents the position parameter, x represents the pixel horizontal coordinate value, and y represents the pixel vertical coordinate value.

[0029] The semiconductor silicon ring can be an etching ring for supporting a wafer in a chip etching process.

[0030] The application also provides a detection device for the method, characterized in that the device is composed of an angle adjuster 1, a machine base 7, a three-dimensional automatic scanning device, a cable 10, an ultrasonic flaw detector 11, an industrial computer 12, an electrical control device 13, a probe group 15, a positioning fixture 16, and a W-axis rotary motion device 17, wherein:

[0031] The machine base 7 is a hollow box structure without a cover, and is provided with the three-dimensional automatic scanning device and the W-axis rotary motion device 17. The three-dimensional automatic scanning device is composed of an X-axis linear motion device 8, a Y-axis linear motion device 9, and a Z-axis linear motion device 14, and the angle adjuster 1 is installed on the Z-axis linear motion device 14. The W-axis rotary motion device 17 is arranged inside the machine base 7, and the positioning fixture 16 is arranged on the upper portion of the W-axis rotary motion device 17 for placing the detected semiconductor silicon ring 3.

[0032] The probe group 15 is arranged on the angle adjuster 1, and is composed of a surface wave ultrasonic probe 4, a transverse wave ultrasonic probe 5, and a creeping wave ultrasonic probe 6.

[0033] The probe group 15 is connected to the ultrasonic flaw detector 11 on the electrical control device 13 through the cable 10, and the ultrasonic flaw detector 11 is connected to the industrial computer 12.

[0034] The application has the following advantages:

[0035] In terms of detection principle, the application establishes a detection system composed of a specially designed ultrasonic probe group and an X / Y / Z-axis three-dimensional automatic scanning device by utilizing the characteristics of the hidden crack defects of the semiconductor silicon ring and the ultrasonic propagation characteristics, and formulates a unique detection process method, thereby realizing the nondestructive detection of the hidden crack defects in the sheet-shaped parts made of brittle materials such as silicon and silicon carbide.

[0036] In terms of detection device, the device is a high-precision automatic detection equipment. X-Y-Z three-dimensional adjustment can be provided to complete the automatic detection of the silicon ring parts in cooperation with the W-axis rotary motion.

[0037] In terms of instrument function, the device can realize the excitation and reception of ultrasonic waves, and perform full-waveform acquisition and preservation of ultrasonic signals.

[0038] In terms of signal data post-processing, the device has A-scan, B-scan, and C-scan display functions and time-domain-to-frequency-domain conversion analysis functions. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 Detection principle schematic diagram;

[0040] Figure 2 Detection process flowchart;

[0041] Figure 3 Schematic diagram of the detection device;

[0042] Figure 4 A diagram of a semiconductor silicon ring structure with a hidden crack defect;

[0043] Figure 5 The C-scan display of the test results;

[0044] Reference numerals: 1. Angle adjuster; 2. Latent crack; 3. Semiconductor silicon ring; 4. Surface wave ultrasonic probe; 5. Transverse wave ultrasonic probe; 6. Climbing wave ultrasonic probe; 7. Base; 8. X-axis linear motion device; 9. Y-axis linear motion device; 10. Cable; 11. Ultrasonic flaw detector; 12. Industrial computer; 13. Electrical control device; 14. Z-axis linear motion device; 15. Probe group; 16. Positioning clamp; 17. W-axis rotary motion device. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to the embodiments.

[0046] Example 1

[0047] like Figure 3 As shown, the detection device consists of an angle adjuster 1, a base 7, a three-dimensional automatic scanning device, cables 10, an ultrasonic flaw detector 11, an industrial computer 12, an electrical control device 13, a probe assembly 15, a positioning fixture 16, and a W-axis rotary motion device 17, wherein:

[0048] The base 7 is a coverless hollow box structure. The base 7 is equipped with a three-dimensional automatic scanning device and a W-axis rotary motion device 17. The three-dimensional automatic scanning device consists of an X-axis linear motion device 8, a Y-axis linear motion device 9, and a Z-axis linear motion device 14. An angle adjuster 1 is installed on the Z-axis linear motion device 14. The W-axis rotary motion device 17 is located inside the base 7. A positioning fixture 16 is provided on the upper part of the W-axis rotary motion device 17 for placing the semiconductor silicon ring 3 to be inspected.

[0049] An angle adjuster 1 is equipped with a probe group 15, which consists of a surface wave ultrasonic probe 4, a transverse wave ultrasonic probe 5, and a creeping wave ultrasonic probe 6.

[0050] The probe assembly 15 is connected to the ultrasonic flaw detector 11 on the electrical control device 13 via cable 10, and the ultrasonic flaw detector 11 is connected to the industrial computer 12.

[0051] Example 2

[0052] Using the apparatus described in Example 1, ultrasonic testing was performed on a microcrack in an etched ring of φ350mm single-crystal silicon, including the following steps:

[0053] Step 1), the size range of the piezoelectric wafer of the water immersion focused ultrasonic probe is 6-10 mm, and the frequency range is 1 MHz-15 MHz. The required incident angle range of the refraction of ultrasonic waves into creeping waves, transverse waves and surface waves at the water / silicon interface is 9-10°, 10-14° and 14-15° respectively;

[0054] Step 2), connect the surface wave ultrasonic probe 4, the transverse wave ultrasonic probe 5 and the creeping wave ultrasonic probe 6 with the ultrasonic flaw detector 11 through the cable 10, place the semiconductor silicon ring 3 to be detected on the positioning fixture 16 of the detection device workbench, and adjust the probe to the edge of the detection area of the semiconductor silicon ring 3.

[0055] Step 3), according to the numerical range of the incident angle, adjust the multiple ultrasonic probes to emit ultrasonic waves at different inclination angles by using the angle adjuster 1.

[0056] Step 4), automatic scanning: move the probe group 15 to the edge of the semiconductor silicon ring 3 as the starting point of scanning.

[0057] Set the scanning range of the X-direction linear motion device 8 so that the X-W two-dimensional scanning area completely covers the detected area, and set the step value of the X-direction linear motion device 8 to 0.5 mm, see Figure 3 .

[0058] Step 5), instrument parameter setting and ultrasonic wave excitation: start the ultrasonic flaw detector 11 to synchronously excite the probe groups 15 of the three channels to emit ultrasonic waves. The repetition frequency of ultrasonic wave excitation is related to the W-axis scanning speed, the rotation speed of the W-axis is set to 60 r / min, and the repetition frequency of ultrasonic wave excitation is 5 KHz; the instrument gain is 53 dB, and the gate starting position is set to 5.0-10.0 mm after the interface wave.

[0059] Step 6), defect echo signal collection: when the ultrasonic waves emitted by the probe in step 5) meet the water / silicon interface, they will be converted into refraction waves such as transverse waves, surface waves and creeping waves, and when the refraction waves meet the crack defects, they will emit reflected waves. The reflected wave signals are received by the receiving probe and converted into electrical signals which are collected by the ultrasonic instrument 11 and uploaded to the industrial computer 12 for storage.

[0060] Step 7), the result analysis software in the industrial computer 12 performs data post-processing on the stored ultrasonic signals, identifies the defect wave signals, and finally realizes the C-scan display of the results, see Figure 5 .

[0061] The detected workpiece is a semiconductor silicon ring 3 containing natural defects, and the metallographic microscope observation shows that there is an implicit crack 2 at the edge of the semiconductor silicon ring 3, see Figure 4 . Figure 5For the detection result C scan image display, the oblique line at A in the figure is the hidden crack 2 in the semiconductor silicon ring 3. It is measured that the defect indication position in the detection result figure basically coincides with the actual defect position in the semiconductor silicon ring 3, which shows that the method described in the application can effectively detect the hidden crack defect.

[0062] The details of the application are known.

[0063] The above examples are only for illustrating the technical concept and characteristics of the application, and the purpose is to enable the person skilled in the art to understand the content of the application and implement it, and cannot limit the protection scope of the application. Any equivalent changes or modifications made according to the spirit and essence of the application shall be covered within the protection scope of the application.

Claims

1. A method for ultrasonic detection of microcracks in semiconductor silicon rings, characterized in that: The following testing steps are included: 1) Select a piezoelectric crystal size range of 6-10 mm and a frequency range of 1 MHz-15 MHz for the water immersion focused ultrasonic probe; calculate the incident angle required for the ultrasonic wave to refract into transverse waves, surface waves, and creeping waves at the water / silicon interface; 2) Adjust multiple sets of ultrasonic probes to emit ultrasonic waves at different tilt angles according to the specific incident angle values ​​of different waveforms; 3) Ultrasonic waves are scattered on the surface of the semiconductor silicon ring, resulting in waveform conversion. The refracted waves excited by ultrasonic waves at different incident angles in the semiconductor silicon ring propagate in the silicon wafer along a certain propagation path. When they encounter crack defects, ultrasonic scattering occurs, and the reflected waves in the scattering return along the original path and are received by the ultrasonic probe. The ultrasonic probe converts the reflected wave signal into a detection electrical signal, and then transmits the detection electrical signal to the ultrasonic instrument. The ultrasonic instrument uploads the result signal to the industrial control computer. The imaging software in the industrial control computer images the detection result and displays the distribution information of the hidden defects of the entire semiconductor silicon wafer on the monitor.

2. The method for ultrasonic detection of microcracks in semiconductor silicon rings according to claim 1, characterized in that: The semiconductor silicon ring is a sheet-like part made of silicon and silicon carbide.

3. The method for ultrasonic detection of microcracks in semiconductor silicon rings according to claim 1, characterized in that: In step 1), the calculation method for the incident angle required for the ultrasonic wave to refract into a transverse wave, surface wave, and creeping wave at the water / silicon interface is as follows: According to Snell's Law (1), the incident angle α required for the ultrasonic wave to refract into transverse wave, surface wave and creeping wave at the water / silicon interface is calculated. Where α represents the incident angle of the ultrasonic wave from the water into the silicon ring, β represents the refraction angle of the ultrasonic wave from the water into the silicon ring, C1 represents the longitudinal wave velocity of the ultrasonic wave in the water, and C2 represents the propagation speed of different forms of ultrasonic waves in the silicon wafer.

4. The method for ultrasonic detection of microcracks in semiconductor silicon according to claim 1, characterized in that, In step 3), the industrial control computer performs post-processing on the uploaded detection data. The post-processing process is as follows: First, perform mean filtering to eliminate noise components in the test data; 2. The instrument data acquisition module extracts the effective crack signals from the detection data and fills them into the amplitude matrix A, while recording the corresponding position parameter i.

3. Create a blank image zero matrix S according to formula (2); IV. Calculate the pixel coordinates x and y of the ring image according to formulas (3) and (4); 5. Fill the amplitude matrix A into the S matrix according to the corresponding pixel coordinates to obtain a new S matrix with a ring image, and then image the S matrix; the obtained image can display the distribution information of hidden defects of the entire semiconductor silicon wafer. S = zeros(2R, 2R) (2) x=round(R+50+(R*cos(i*360 / 1000*pi))) (3) y=round(R=50+(R*sin(i*360 / 1000*pi))) (4) In the formula, S represents the zero matrix, R represents the actual radius of the silicon ring, i represents the position parameter, x represents the pixel horizontal coordinate value, and y represents the pixel vertical coordinate value.

5. A dedicated detection device for the method of claim 1, characterized in that: The device consists of an angle adjuster (1), a base (7), a three-dimensional automatic scanning device, cables (10), an ultrasonic flaw detector (11), an industrial computer (12), an electrical control device (13), a probe group (15), a positioning fixture (16), and a W-axis rotary motion device (17), wherein: The base (7) is a hollow box structure without a cover. The base (7) is equipped with a three-dimensional automatic scanning device and a W-axis rotary motion device (17). The three-dimensional automatic scanning device consists of an X-axis linear motion device (8), a Y-axis linear motion device (9), and a Z-axis linear motion device (14). An angle adjuster (1) is installed on the Z-axis linear motion device (14). The W-axis rotary motion device (17) is located inside the base (7). A positioning fixture (16) is provided on the upper part of the W-axis rotary motion device (17) for placing the semiconductor silicon ring (3) to be tested. An angle adjuster (1) is provided with a probe group (15), which consists of a surface wave ultrasonic probe (4), a transverse wave ultrasonic probe (5), and a climbing wave ultrasonic probe (6). The probe assembly (15) is connected to the ultrasonic flaw detector (11) on the electrical control device (13) via cable (10), and the ultrasonic flaw detector (11) is connected to the industrial computer (12).

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