Wafer arrangement method and system for improving wavelength uniformity of MOCVD epitaxial wafer

Abstract

This invention provides a wafer arrangement method and system for improving the wavelength uniformity of MOCVD epitaxial wafers. The wafer arrangement method for improving the wavelength uniformity of MOCVD epitaxial wafers includes: measuring and calibrating the wavelength offset of each groove on the carrier; calculating the predicted wavelength offset of the wafer to be processed using a pre-built wavelength test model; sorting the wafers to be processed in the current batch according to their predicted wavelength offsets; sorting the grooves on the carrier in the opposite manner to their predicted wavelength offsets; then matching the sorted wafers with the sorted grooves in sequence; mapping the matching results back to the original physical number of the groove to generate a visual placement guide, which is then used by an operator or robot to perform the corresponding placement under the guidance of the visual placement guide.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a wafer arrangement method and system for improving the wavelength uniformity of MOCVD epitaxial wafers. Background Technology

[0002] In the epitaxial growth of semiconductors such as blue-green LEDs, graphite substrates are typically used to carry multiple patterned sapphire substrates (PSS) into the MOCVD reaction chamber for epitaxial growth.

[0003] Due to limitations in machining precision, dimensional tolerances (such as depth and levelness) inevitably exist between different pockets on the graphite carrier, resulting in differences in the actual heating temperature of each pocket within the reaction chamber: pockets with higher temperatures inhibit the incorporation of indium (In), causing the emission wavelength of the multiple quantum well (MQW) grown at that location to be shorter; conversely, pockets with lower temperatures have longer wavelengths. This wafer-to-wafer wavelength variation caused by hardware errors significantly reduces product yield.

[0004] In the existing technology, the existing solutions mainly attempt to eliminate temperature difference by improving the design of graphite disks (such as adding heat insulation / thermal conduction structures) or upgrading the heating system (such as multi-zone temperature control compensation). However, these solutions are costly, time-consuming, and cannot completely eliminate inherent processing errors. At the same time, the physical parameters of the substrate itself (such as warpage and bevel angle) will also systematically affect the output wavelength. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a wafer arrangement method and system for improving the wavelength uniformity of MOCVD epitaxial wafers, which can effectively solve the shortcomings of the prior art.

[0006] A wafer arrangement method for improving wavelength uniformity of MOCVD epitaxial wafers includes the following steps: S1, Vehicle Calibration; Measure and calibrate the wavelength offset of each groove on the vehicle. The This reflects the actual contribution of the temperature characteristics of each groove to the wavelength shift of the produced wafer; S2, Wafer Prediction; The predicted wavelength offset of the wafer to be processed is calculated using a pre-built wavelength testing model. The This reflects the expected shift in wavelength of the produced wafer caused by the characteristics of its substrate. S3, Matching operation; The wafers to be processed in the current batch are offset according to their predicted wavelength. Sort the grooves on the vehicle according to their wavelength offset. offset from predicted wavelength The wafers are sorted in the opposite way, and then the sorted wafers are matched one-to-one with the sorted grooves in sequence. S4. Perform the operation; Based on the matching result of step S3, the original physical number of the groove is mapped back to generate a visual placement guide, which is then used by the operator or robot to perform the corresponding placement.

[0007] Compared with the prior art, the beneficial effect of the present invention is that it shifts the predicted wavelength of the wafer by... Wavelength offset from the groove By performing systematic matching and sorting, active compensation is achieved between the wafer's own substrate characteristics and the carrier temperature characteristics. Compared with the traditional random placement or simple centrosymmetric placement method, this method can cancel out the differences between the wafer substrate and the carrier thermal field, significantly reducing the wavelength range and standard deviation between different wafers in the same carrier, thereby improving the wavelength uniformity between epitaxial wafers. At the same time, this method does not change the hardware structure of the MOCVD equipment, and uniformity can be improved only through layout strategy optimization, which has the characteristics of low cost and easy implementation.

[0008] Furthermore, step S1 specifically includes: Growth was performed using standard wafers under a fixed process, and the actual wavelength of the wafers produced from each notch on the carrier was measured and recorded. According to the formula Calculate its average wavelength relative to a standard wafer. wavelength offset .

[0009] Furthermore, step S2 specifically includes: The physical parameters of the substrate and the wavelength offset of the processed wafer are collected. A wavelength test model is pre-built using regression analysis to obtain the physical parameters of the substrate of the wafer to be processed. The obtained physical parameters of the substrate to be processed are then input into the pre-built wavelength prediction model to calculate the predicted wavelength offset of the wafer to be processed. .

[0010] Furthermore, the physical parameters of the substrate of the wafer to be processed include warpage. and bevel angle .

[0011] Furthermore, the wavelength prediction model is a linear regression model: ; In the formula, 'a' represents the degree of warpage. The regression coefficient, where b is the tangent angle. The regression coefficients, Warp The process target value, bevel angle The process target value.

[0012] Furthermore, it also includes an exception handling step, which specifically includes: If the wavelength shift of a certain groove If the groove exceeds ±3 times the standard deviation, it is marked as an abnormal groove before performing step S3. The abnormal groove does not participate in the sorting in step S3 and is left empty in the carrier. The matching operation is only performed on the remaining normal grooves and an equal number of wafers.

[0013] On the other hand, the present invention also provides a wafer arrangement system for improving the wavelength uniformity of MOCVD epitaxial wafers, comprising: The vehicle calibration module is used to measure and store the wavelength offset of each groove on the vehicle. ; The wafer prediction module has a built-in pre-built wavelength test model, which is used to calculate the predicted wavelength offset based on the substrate physical parameters of the wafer to be processed. ; The matching decision module is used to offset the wafers to be processed in the current batch according to their predicted wavelength. Sort the grooves on the vehicle according to their wavelength offset. offset from predicted wavelength The sorting is done in the opposite way to generate a one-to-one matching scheme between wafers and grooves; The execution guidance module is used to map the matching scheme back to the original physical number of the groove and generate a visual placement guide output to the display terminal or the robot control system. Attached Figure Description

[0014] Figure 1 This is a schematic flowchart of the wafer arrangement method for improving the wavelength uniformity of MOCVD epitaxial wafers in Embodiment 1 of the present invention; The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0015] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0016] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0018] Example 1 Please see Figure 1 Embodiment 1 of this invention provides a wafer arrangement method to improve the wavelength uniformity of MOCVD epitaxial wafers. Specifically, the MOCVD equipment used in this embodiment is an AIXTRON CCS 6×2-inch system, and the carrier is a graphite disk containing a total of 6 recesses (numbered P1-P6). Each recess is used to place a 2-inch sapphire substrate wafer. The average wavelength of the standard wafer is... It is 455nm; S1, Vehicle Calibration; Measure and calibrate the wavelength offset of each groove on the vehicle. The This reflects the actual contribution of the temperature characteristics of each groove to the wavelength shift of the produced wafer; Furthermore, step S1 specifically includes: Growth was performed using standard wafers under a fixed process, and the actual wavelength of the wafers produced from each notch on the carrier was measured and recorded. According to the formula Calculate its average wavelength relative to a standard wafer. wavelength offset ; Specifically, in this embodiment, three sapphire substrate wafers with known stable substrate characteristics and minimal fluctuations in historical production data are selected as standard wafers. The warpage of these three wafers... All are controlled within the range of -30μm to -20μm, with an average of -25μm, and the chamfer angle is... All were controlled within the range of 0.20°-0.25°, with an average of 0.22°, and the warpage within each batch was also controlled. The standard deviation is less than 2μm, and the intra-batch bevel angle is... The standard deviation is less than 0.02°; MOCVD growth was carried out under fixed process conditions, with the following process parameters: growth temperature: 1050℃; reaction chamber pressure: 200mbar; trimethylgallium (TMGa) flow rate: 50sccm; ammonia (NH3) flow rate: 10000sccm; growth time: 60 minutes. After growth was completed, the center wavelength of each wafer was measured using a photoluminescence (PL) meter. The measurement was repeated three times for each groove using three standard wafers, and the average value was taken. The results are as follows: Groove P1: =454.2nm, ; Groove P2: =455.6nm, ; Groove P3: =455.1nm, ; Groove P4: =453.8nm, ; Groove P5: =456.2nm, ; Groove P6: =454.8nm, ; Furthermore, it also includes an exception handling step, which specifically includes: If the wavelength shift of a certain groove If the groove exceeds ±3 times the standard deviation, it is marked as an abnormal groove before performing step S3. The abnormal groove does not participate in the sorting in step S3 and is left empty in the carrier. The matching operation is only performed on the remaining normal grooves and an equal number of wafers. Calculate the wavelength offset of the grooves in this batch. Standard deviation ; All grooves The mean of the sum ; ≈0.88, 3* =2.64nm, wavelength offset of all grooves All samples were within ±3 standard deviations, with no abnormal grooves, and were all used for subsequent matching. Among them, groove P5 (Slightly longer), P4 groove (Shorter than average) indicates that the vehicle has obvious thermal inhomogeneity, with moderate temperature in the central region (P3, P6) and significant temperature difference in the edge region; S2, Wafer Prediction; The predicted wavelength offset of the wafer to be processed is calculated using a pre-built wavelength testing model. The This reflects the expected shift in wavelength of the produced wafer caused by the characteristics of its substrate. Furthermore, step S2 specifically includes: The physical parameters of the substrate and the wavelength offset of the processed wafer are collected. A wavelength test model is pre-built using regression analysis to obtain the physical parameters of the substrate of the wafer to be processed. The obtained physical parameters of the substrate to be processed are then input into the pre-built wavelength prediction model to calculate the predicted wavelength offset of the wafer to be processed. ; Specifically, in this embodiment, the physical parameters of the substrate of the processed wafer include the warpage of the processed wafer and the bevel angle of the processed wafer; Specifically, in this embodiment, a wavelength test model is pre-built by collecting data on the warpage, bevel angle, and actual wavelength offset of more than 10,000 processed wafers produced in the past three months, and through regression analysis. ; In the formula, This represents the actual wavelength offset of the processed wafer. The warpage of the processed wafer. The beveled angle of the processed wafer. Warp the median of bevel angle the median; Specifically, in this embodiment, the least squares method was used to perform linear regression on 10,000 samples, resulting in a regression coefficient a = +0.032 nm / μm, indicating that for every 1 μm increase in warp, the wavelength increases by 0.032 nm; the regression coefficient b = -2.15 nm / °, indicating that for every 1° increase in the chamfer angle, the wavelength decreases by 2.15 nm; and the model fit R² = 0.87, indicating that the model explains 87% of the wavelength variation. Furthermore, the physical parameters of the substrate of the wafer to be processed include warpage. and bevel angle ; Furthermore, the wavelength prediction model is a linear regression model: ; In the formula, 'a' represents the degree of warpage. The regression coefficient, where b is the tangent angle. The regression coefficients, Warp The mean, bevel angle The mean; Take the median of warpage from historical data. -25μm; Take the median of the bevel angles from the historical data. It is 0.22°; Using regression models : Wafer W1 to be processed: =-35μm, , ; Wafer W2 to be processed: =-28μm, , ; Wafer W3 to be processed: =-22μm, , ; Wafer W4 to be processed: =-40μm, , ; Wafer W5 to be processed: =-18μm, , ; Wafer W6 awaiting processing: =-25μm, , ; S3, Matching operation; The wafers to be processed in the current batch are offset according to their predicted wavelength. Sort the grooves on the vehicle according to their wavelength offset. offset from predicted wavelength The wafers are sorted in the opposite way, and then the sorted wafers are matched one-to-one with the sorted grooves in sequence. Specifically, in this embodiment, the wafers to be processed in the current batch are offset according to their predicted wavelength. Sort by size from smallest to largest: < < < < < ; The grooves on the vehicle are offset according to their wavelength. offset from predicted wavelength Sort in reverse order from largest to smallest: ; The expected wavelength deviation after compensation for P5 is 0.634nm for W4, 0.237nm for W1, -0.0175nm for W2, -0.2nm for W6, -0.6825nm for W3, and -0.9115nm for W5. After compensation, the expected wavelength range is 1.5455nm, which is less than the process allowable range of 2.0nm, thus meeting the uniformity requirements.

[0019] S4. Perform the operation; Based on the matching result of step S3, the original physical number of the groove is mapped back to generate a visual placement guide, which is then used by the operator or robot to perform the corresponding placement. Understandably, this is achieved by shifting the predicted wavelength of the wafer. Wavelength offset from the groove By performing systematic matching and sorting, active compensation is achieved between the wafer's own substrate characteristics and the carrier temperature characteristics. Compared with the traditional random placement or simple centrosymmetric placement method, this method can cancel out the differences between the wafer substrate and the carrier thermal field, significantly reducing the wavelength range and standard deviation between different wafers in the same carrier, thereby improving the wavelength uniformity between epitaxial wafers. At the same time, this method does not change the hardware structure of the MOCVD equipment, and uniformity can be improved only through layout strategy optimization, which has the characteristics of low cost and easy implementation.

[0020] Example 2 On the other hand, the present invention also provides a wafer arrangement system for improving the wavelength uniformity of MOCVD epitaxial wafers, comprising: The vehicle calibration module is used to measure and store the wavelength offset of each groove on the vehicle. ; The wafer prediction module has a built-in pre-built wavelength test model, which is used to calculate the predicted wavelength offset based on the substrate physical parameters of the wafer to be processed. ; The matching decision module is used to offset the wafers to be processed in the current batch according to their predicted wavelength. Sort the grooves on the vehicle according to their wavelength offset. offset from predicted wavelength The sorting is done in the opposite way to generate a one-to-one matching scheme between wafers and grooves; The execution guidance module is used to map the matching scheme back to the original physical number of the groove and generate a visual placement guide output to the display terminal or the robot control system.

[0021] In summary, the wafer arrangement method and system for improving the wavelength uniformity of MOCVD epitaxial wafers in the above embodiments of the present invention improves the wavelength uniformity of MOCVD epitaxial wafers by adjusting the predicted wavelength offset of the wafer. Wavelength offset from the groove By performing systematic matching and sorting, active compensation is achieved between the wafer's own substrate characteristics and the carrier temperature characteristics. Compared with the traditional random placement or simple centrosymmetric placement method, this method can cancel out the differences between the wafer substrate and the carrier thermal field, significantly reducing the wavelength range and standard deviation between different wafers in the same carrier, thereby improving the wavelength uniformity between epitaxial wafers. At the same time, this method does not change the hardware structure of the MOCVD equipment, and uniformity can be improved only through layout strategy optimization, which has the characteristics of low cost and easy implementation.

[0022] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0023] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A wafer arrangement method for improving the wavelength uniformity of MOCVD epitaxial wafers, characterized in that, Includes the following steps: S1, Vehicle Calibration; Measure and calibrate the wavelength offset of each groove on the vehicle. The This reflects the actual contribution of the temperature characteristics of each groove to the wavelength shift of the produced wafer; S2, Wafer Prediction; The predicted wavelength offset of the wafer to be processed is calculated using a pre-built wavelength testing model. The This reflects the expected shift in wavelength of the produced wafer caused by the characteristics of its substrate. S3, Matching operation; The wafers to be processed in the current batch are offset according to their predicted wavelength. Sort the grooves on the vehicle according to their wavelength offset. offset from predicted wavelength The wafers are sorted in the opposite way, and then the sorted wafers are matched one-to-one with the sorted grooves in sequence. S4. Perform the operation; Based on the matching result of step S3, the original physical number of the groove is mapped back to generate a visual placement guide, which is then used by the operator or robot to perform the corresponding placement.

2. The wafer arrangement method for improving wavelength uniformity of MOCVD epitaxial wafers according to claim 1, characterized in that, Step S1 specifically involves: Growth was performed using standard wafers under a fixed process, and the actual wavelength of the wafers produced from each notch on the carrier was measured and recorded. According to the formula Calculate its average wavelength relative to a standard wafer. wavelength offset .

3. The wafer arrangement method for improving wavelength uniformity of MOCVD epitaxial wafers according to claim 1, characterized in that, Step S2 specifically involves: The physical parameters of the substrate and the wavelength offset of the processed wafer are collected. A wavelength test model is pre-built using regression analysis to obtain the physical parameters of the substrate of the wafer to be processed. The obtained physical parameters of the substrate to be processed are then input into the pre-built wavelength prediction model to calculate the predicted wavelength offset of the wafer to be processed. .

4. The wafer arrangement method for improving the wavelength uniformity of MOCVD epitaxial wafers according to claim 3, characterized in that, The physical parameters of the substrate of the wafer to be processed include warpage. and bevel angle .

5. The wafer arrangement method for improving the wavelength uniformity of MOCVD epitaxial wafers according to claim 4, characterized in that, The wavelength prediction model is a linear regression model: ； In the formula, 'a' represents the degree of warpage. The regression coefficient, where b is the tangent angle. The regression coefficients, Warp The process target value, bevel angle The process target value.

6. The wafer arrangement method for improving wavelength uniformity of MOCVD epitaxial wafers according to claim 1, characterized in that, It also includes an exception handling step, which specifically includes: If the wavelength shift of a certain groove If the groove exceeds ±3 times the standard deviation, it is marked as an abnormal groove before performing step S3. The abnormal groove does not participate in the sorting in step S3 and is left empty in the carrier. The matching operation is only performed on the remaining normal grooves and an equal number of wafers.

7. A wafer arrangement system for improving the wavelength uniformity of MOCVD epitaxial wafers, characterized in that, include: The vehicle calibration module is used to measure and store the wavelength offset of each groove on the vehicle. ; The wafer prediction module has a built-in pre-built wavelength test model, which is used to calculate the predicted wavelength offset based on the substrate physical parameters of the wafer to be processed. ; The matching decision module is used to offset the wafers to be processed in the current batch according to their predicted wavelength. Sort the grooves on the vehicle according to their wavelength offset. offset from predicted wavelength The sorting is done in the opposite way to generate a one-to-one matching scheme between wafers and grooves; The execution guidance module is used to map the matching scheme back to the original physical number of the groove and generate a visual placement guide output to the display terminal or the robot control system.

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