A method for improving etch uniformity

Abstract

The application discloses a method for improving etching uniformity, S1: taking the phase angle in the case of etching eccentricity as a reference phase angle, and obtaining an etching rate distribution diagram of the reference phase angle; S2: setting a plurality of different radio frequency phase angles for etching a wafer in a preset scanning range with a preset step length, and obtaining an etching rate distribution diagram of each radio frequency phase angle; S3: taking the etching rate distribution diagram corresponding to the reference phase angle as a reference, performing difference value operation on the etching rate distribution diagrams of the remaining radio frequency phase angles respectively, and obtaining a difference value rate distribution diagram of each radio frequency phase angle; S4: calculating a range of each difference value rate distribution diagram respectively; S5: selecting a corresponding radio frequency phase angle with a range value greater than a judgment threshold as a candidate radio frequency phase angle; and S6: performing etching test on each candidate radio frequency phase angle, obtaining a corresponding key size distribution diagram, and determining an optimal radio frequency phase angle. The method effectively improves the problem of etching eccentricity, and improves wafer etching uniformity and product yield.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, and particularly relates to a method for improving etching uniformity. Background Technology

[0002] In semiconductor etching processes, etching uniformity is one of the key indicators affecting product yield. As the feature size of integrated circuits continues to shrink, the requirements for etching uniformity are becoming increasingly stringent. Currently, conventional methods for improving etching uniformity mainly involve optimizing traditional process parameters such as gas distribution, temperature distribution, and current distribution, which can improve etching uniformity to a certain extent.

[0003] In actual mass production applications, the etching process is often affected by factors such as the etching rate, resulting in wafer misalignment after etching. Conventional methods such as adjusting gas, temperature, or current distribution often fail to achieve the desired improvement and cannot meet the stringent requirements for wafer uniformity.

[0004] Based on the above problems, there is a need to provide a method to improve etching uniformity, effectively correct etching eccentricity, and improve the etching uniformity of wafers. Summary of the Invention

[0005] The purpose of this invention is to solve all or part of the above-mentioned problems and provide a method to improve etching uniformity. By systematically scanning and analyzing the radio frequency phase angle, the radio frequency phase angle with significant control over eccentricity is screened out, and the key dimension distribution is verified by patterned wafers. This ensures screening efficiency while ensuring the final process effect, specifically compensates for the eccentricity problem that is difficult to solve by conventional methods, effectively improves the uniformity of etching rate, and enhances the stability of etching process and product yield.

[0006] This invention provides a method for improving etching uniformity: S1: Using the phase angle when etching misalignment exists as a reference phase angle, an etching rate distribution map is obtained at the reference phase angle; S2: Multiple different radio frequency (RF) phase angles are etched within a preset scan range with a preset step size to obtain etching rate distribution maps for each RF phase angle; S3: Using the etching rate distribution map corresponding to the reference phase angle as the reference distribution map, the etching rate distribution maps of the remaining RF phase angles are compared with the reference distribution map to obtain a difference rate distribution map for each RF phase angle; S4: The range of each difference rate distribution map is calculated; S5: The corresponding RF phase angle with a range value greater than a judgment threshold is selected as a candidate RF phase angle; S6: For each candidate RF phase angle, an etching test is performed on the wafer to obtain a corresponding critical dimension distribution map, and the optimal RF phase angle is determined. By systematically scanning and analyzing the RF phase angle, we screened out the RF phase angles that have a significant ability to control the eccentricity. We also verified the key dimension distribution through patterned wafers to ensure screening efficiency while ensuring the final process effect, and specifically compensated for the eccentricity problem that is difficult to solve by conventional methods.

[0007] The radio frequency phase angle is the phase difference between the output waveforms of the source radio frequency power supply and the bias radio frequency power supply. By controlling the excitation state of the plasma through the synergistic effect of the source radio frequency and the bias radio frequency, the plasma density distribution and other parameters can be regulated.

[0008] The radio frequency phase angle is adjusted by regulating the bias radio frequency power supply. Phase difference adjustment can be achieved by simply controlling the bias radio frequency power supply, eliminating the need to adjust the operating state of the source radio frequency power supply. This simple and convenient control method reduces process debugging variables, lowers operational complexity and difficulty, and effectively improves wafer etching uniformity and process adaptability.

[0009] In step S2, the adjustment range of the RF phase angle is 0°-360°. This allows for full-cycle screening of the RF waveform phase difference, preventing missed phase points due to limited scanning range and improving the success rate of process optimization and product yield.

[0010] In step S2, the preset step size is 45°. This ensures uniform coverage of the phase interval while reasonably reducing the overall testing workload, balancing testing efficiency and the accuracy of test results.

[0011] In step S3, the difference calculation is as follows: subtract the etching rate value of the corresponding measurement point under the reference phase angle from the etching rate value of each measurement point under each RF phase angle to obtain the etching rate change at each measurement point. This eliminates interference from other factors, and the difference result only reflects the influence of RF phase angle changes on the etching rate distribution, facilitating the selection of RF phase angles.

[0012] In step S4, the range is the difference between the maximum and minimum values ​​in the difference rate distribution diagram of each candidate RF phase angle. The range reflects the influence of the RF phase angle on the etching rate distribution. A larger range indicates that the phase angle has a stronger ability to adjust the plasma distribution and has a better effect on improving eccentricity.

[0013] In step S5, the determination threshold is 70%-90% of the maximum range. This allows for precise locking of the angle range with high correction capability.

[0014] In step S6, the 3σ value of each critical dimension distribution map is calculated, and the optimal radio frequency phase angle is determined based on the 3σ value. The critical dimension distributions corresponding to the selected radio frequency phase angles are comprehensively compared and confirmed, and the critical dimension distributions are evaluated using the 3σ index to determine the optimal radio frequency phase angle within the angular range.

[0015] In step S6, the candidate RF phase angle with the smallest 3σ value is selected as the optimal RF phase angle. This objectively reflects the wafer's process variation level and avoids errors from subjective human judgment.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: by systematically scanning and analyzing the radio frequency phase angle, radio frequency phase angles with significant control over eccentricity are screened out, and the key dimension distribution is verified through patterned wafers, ensuring screening efficiency while ensuring the final process effect. It specifically compensates for the eccentricity problem that is difficult to solve by conventional methods, effectively makes up for the problem that traditional process parameters cannot correct the etching eccentricity distribution, and can improve the etching uniformity of the wafer, the etching process stability and the product yield. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A process flow diagram of the method for improving etching uniformity provided by the present invention.

[0019] Figure 2 The ER map and differential rate distribution diagram corresponding to each radio frequency phase angle are provided for the embodiment.

[0020] Figure 3 The extreme value diagrams corresponding to each radio frequency phase angle are provided for the embodiments.

[0021] Figure 4 The CD map corresponding to each radio frequency phase angle is provided for the embodiment. Detailed Implementation

[0022] The technical solutions in specific embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example This embodiment provides a method to improve etching uniformity by adjusting the radio frequency (RF) phase angle to solve the etching misalignment problem. The RF phase angle (RFPA) is the phase difference between the output waveforms of the source RF power supply (SRF) and the bias RF power supply (BRF). In this embodiment, the RF phase angle is set by adjusting the bias RF power supply, while the output of the source RF power supply remains constant. The adjustment range of the bias RF power supply is 0°-360°. Figure 1 As shown, it includes the following steps: S1: The phase angle when etching misalignment exists is used as the reference phase angle to obtain the etching rate distribution map at the reference phase angle; in this embodiment, the 0° phase angle is used as the reference phase angle, such as... Figure 2 As shown, the etching rate distribution map when RFPA is 0° is obtained, which serves as a unified benchmark for subsequent calculations; S2: The wafer is etched with multiple different radio frequency (RF) phase angles within a preset scan range using a preset step size to obtain an etching rate distribution map for each RF phase angle. In this embodiment, multiple different RF phase angles are set within a preset scan range of 0°-360° using a preset step size of 45°. Figure 3 As shown, etching rate distribution maps (ER maps) corresponding to each radio frequency phase angle of 45°, 90°, 135°, 180°, 225°, 270°, 315°, and 360° are obtained. S3: Using the etching rate distribution map corresponding to 0° phase angle as the reference distribution map, the etching rate distribution maps corresponding to other RF phase angles are compared with the reference distribution map to eliminate interference from other factors and obtain the difference rate distribution map corresponding to each RF phase angle. The difference result only reflects the influence of RFPA change on etching, which is convenient for subsequent RFPA screening. S4: As Figure 3 As shown, based on the difference rate distribution map corresponding to each RF phase angle, the range of each difference rate distribution map is calculated. The range is the difference between the maximum and minimum values ​​in the difference rate distribution map. The range reflects the ability of the RFPA to adjust the etching rate distribution. A large range indicates that the RFPA has a strong ability to adjust the etching. S5: Find the maximum value from the range values ​​of the above RFPA, and use 70%-90% of the maximum value as the judgment threshold; select the RF phase angles corresponding to the range values ​​greater than the judgment threshold as candidate RF phase angles. In this embodiment, 85% of the maximum value is used as the judgment threshold. After calculation, the range values ​​of 135°, 180°, and 225° are greater than 85% of the maximum range value, therefore 135°, 180°, and 225° are selected as candidate RF phase angles; S6: For the above candidate RF phase angles, wafer etching tests are performed to obtain the CD map corresponding to each candidate angle, such as... Figure 4 As shown, the 3σ values ​​of each critical dimension distribution map are calculated, and the RF phase angle with the smallest 3σ value is selected as the final determined RF phase angle. In this embodiment, actual etching tests revealed that the RFPA at 135°, 180°, and 225° all significantly improved etching uniformity, with the 3σ value of the critical dimension distribution map corresponding to 135° being the smallest. Therefore, 135° was determined as the optimal RFPA. By analyzing the actual etching effects of different RFPAs, it was ensured that the finally selected RFPA could effectively improve etching uniformity.

[0024] In this embodiment, the process of screening candidate RF phase angles can be carried out by using a baffle plate for etching testing, which can achieve rapid screening while saving costs. The RFPA is determined by the process of full-range scanning initial selection combined with wafer critical dimension final selection, which can optimize and control the etching uniformity. This can effectively make up for the problem that traditional parameters such as gas, temperature, and current cannot correct etching eccentricity, and improve process consistency and production yield.

[0025] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for improving etching uniformity, characterized in that, To improve wafer etching misalignment, the following steps are included: S1: Using the phase angle when there is etching eccentricity as the reference phase angle, obtain the etching rate distribution map at the reference phase angle; S2: Set multiple different RF phase angles within a preset scanning range with a preset step size to etch the wafer and obtain the etching rate distribution map for each RF phase angle; S3: Using the etching rate distribution map corresponding to the reference phase angle as the reference distribution map, perform difference calculations between the etching rate distribution maps of the other RF phase angles and the reference distribution map to obtain the difference rate distribution map of each RF phase angle. S4: Calculate the range of each of the aforementioned difference rate distribution maps; S5: Select the corresponding radio frequency phase angle whose range value is greater than the judgment threshold as the candidate radio frequency phase angle; S6: For each of the candidate RF phase angles, perform wafer etching tests to obtain the corresponding critical dimension distribution map and determine the optimal RF phase angle.

2. The method for improving etching uniformity according to claim 1, characterized in that, The radio frequency phase angle is the phase difference between the output waveforms of the source radio frequency power supply and the bias radio frequency power supply.

3. The method for improving etching uniformity according to claim 2, characterized in that, The radio frequency phase angle is adjusted by adjusting the bias radio frequency power supply.

4. The method for improving etching uniformity according to claim 1, characterized in that, In step S2, the adjustment range of the radio frequency phase angle is 0°-360°.

5. The method for improving etching uniformity according to claim 1, characterized in that, In step S2, the preset step size is 45°.

6. The method for improving etching uniformity according to claim 1, characterized in that, In step S3, the difference calculation is as follows: subtract the etching rate value of the corresponding measurement point under the reference phase angle from the etching rate value of each measurement point under each radio frequency phase angle to obtain the etching rate change of each measurement point.

7. The method for improving etching uniformity according to claim 1, characterized in that, In step S4, the range is the difference between the maximum and minimum values ​​in the difference rate distribution diagram of each candidate radio frequency phase angle.

8. The method for improving etching uniformity according to claim 1, characterized in that, In step S5, the determination threshold is 70%-90% of the maximum range.

9. The method for improving etching uniformity according to claim 1, characterized in that, In step S6, the 3σ value of each key dimension distribution map is calculated, and the optimal radio frequency phase angle is determined based on the 3σ value.

10. The method for improving etching uniformity according to claim 9, characterized in that, The candidate RF phase angle with the smallest 3σ value is selected as the optimal RF phase angle.

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