Process stabilization method and process stabilization system compatible with single and dual chamber etch modes

Abstract

This invention provides a process stabilization method and system compatible with both single-cavity and dual-cavity etching modes. In dual-cavity etching mode, the etching rate of the first cavity spray head on the wafer is obtained as a reference etching rate. After removing the wafer from the second cavity, the dependence of the etching rate of the first cavity spray head on the wafer and the applied RF power to the second cavity spray head is obtained. Then, a stable RF power is obtained based on the reference etching rate and the dependence. In single-cavity etching mode, the RF power applied in dual-cavity etching mode is applied to the first cavity spray head, and the stable RF power is applied to the second cavity spray head. This can greatly reduce the difference in wafer etching between single-cavity and dual-cavity etching modes, improving product quality and yield.

Description

Technical Field

[0001] This invention relates to the field of semiconductor etching technology, and in particular to a process stabilization method and system compatible with single and dual-cavity etching modes. Background Technology

[0002] In semiconductor manufacturing, etching is a crucial step, determining the precision of circuit cluster formation on the chip. To improve production efficiency, dual-head etching equipment is widely used. Dual-head etching equipment can drive two etching units simultaneously, significantly increasing wafer etching efficiency. However, in practical applications, when a dual-head etching equipment uses only a single RF electrode to etch one wafer (single-head etching mode), the etching rate differs significantly from the etching rate when using two RF electrodes to etch two wafers simultaneously (dual-head etching mode). Furthermore, the etching uniformity on the wafer surface also deteriorates.

[0003] Therefore, it is necessary to provide a novel process stabilization method and system compatible with single and dual-cavity etching modes to solve the above-mentioned problems in the prior art. Summary of the Invention

[0004] The purpose of this invention is to provide a process stabilization method and system compatible with single and dual-cavity etching modes, which improves etching efficiency and optimizes etching uniformity without excessively increasing costs.

[0005] To achieve the above objectives, the process stabilization method compatible with single and dual-cavity etching modes of the present invention includes: In the dual-cavity etching mode, the etching rate of the first cavity spray head on the wafer is obtained as the reference etching rate. After removing the wafer from the second cavity, the dependence of the etching rate of the first cavity spray head on the wafer and the RF power applied to the second cavity spray head is obtained. Then, a stable RF power is obtained based on the reference etching rate and the dependence. In single-cavity etching mode, the radio frequency power applied in dual-cavity etching mode is applied to the first cavity spray head, and the stable radio frequency power is applied to the second cavity spray head, so that the difference between the etching rate of the first cavity spray head on the wafer and the preset etching rate is less than or equal to 1%, and / or, the difference between the etching uniformity of the first cavity spray head on the wafer and the preset etching uniformity is less than or equal to 1%.

[0006] Optionally, the process stabilization method compatible with single and dual-cavity etching modes further includes: setting the process recipe that meets the preset process requirements for wafer etching under dual-cavity etching mode as a standard process recipe, wherein the standard process recipe includes standard radio frequency power.

[0007] Optionally, in the dual-cavity etching mode, standard radio frequency power is applied to both the first cavity spray head and the second cavity spray head, and then the etching rate of the wafer by the first cavity spray head is obtained as the reference etching rate.

[0008] Optionally, the wafer of the second cavity is removed in the dual-cavity etching mode, and then the radio frequency power applied to the second cavity spray head is adjusted at least twice. The etching rate of the first cavity spray head on the wafer is obtained before adjusting the radio frequency power applied to the second cavity spray head and after adjusting the applied power of the second cavity spray head. Based on the etching rate of the wafer by several first-cavity spray heads and several radio frequency powers applied to the second-cavity spray heads, the dependence of the etching rate of the wafer by the first-cavity spray heads on the radio frequency power applied to the second-cavity spray heads is obtained.

[0009] Optionally, when adjusting the radio frequency power applied to the second cavity spray head, the radio frequency power applied to the second cavity spray head is adjusted each time to x% of the standard radio frequency power, where x is a natural number greater than or equal to 0 and less than 100.

[0010] Optionally, the radio frequency power applied to the second chamber spray head is different each time the adjustment is made.

[0011] Optionally, the etching rate of the wafer by a number of first-cavity spray heads and a number of radio frequency powers applied to the second-cavity spray heads are fitted to obtain a relationship line between the etching rate of the wafer by the first-cavity spray heads and the radio frequency power applied to the second-cavity spray heads as a dependency.

[0012] Optionally, the process stabilization method compatible with single and dual-cavity etching modes further includes a stable RF power verification step, which includes: In single-cavity etching mode, the etching rate and etching uniformity of the first cavity spray head on the wafer are obtained; The first difference between the etching rate of the first cavity spray head on the wafer and the preset etching rate is obtained, and the second difference between the etching uniformity of the first cavity spray head on the wafer and the preset etching uniformity is obtained. If the first difference is greater than 1% and / or the second difference is greater than 1%, then a stable RF power is reacquired.

[0013] Optionally, the RF power corresponding to the etching rate closest to the reference etching rate is obtained as the stable RF power based on the dependency relationship.

[0014] The present invention also provides a process stabilization system for implementing any of the process stabilization methods compatible with single and dual cavity etching modes.

[0015] The beneficial effects of this invention are as follows: In the dual-cavity etching mode, the etching rate of the first cavity spray head on the wafer is obtained as the reference etching rate. After removing the wafer from the second cavity, the dependence of the etching rate of the first cavity spray head on the wafer and the applied radio frequency power to the second cavity spray head is obtained. Then, a stable radio frequency power is obtained based on the reference etching rate and the dependence. In the single-cavity etching mode, the radio frequency power applied in the dual-cavity etching mode is applied to the first cavity spray head, and the stable radio frequency power is applied to the second cavity spray head. This can greatly reduce the difference in wafer etching between the single-cavity etching mode and the dual-cavity etching mode, and improve the quality and yield of the product. Attached Figure Description

[0016] Figure 1 This is a flowchart of a process stabilization method compatible with single and dual-cavity etching modes in some embodiments of the present invention; Figure 2 This is a schematic diagram of the structure of a dual-RF electrode etching apparatus in some embodiments of the present invention; Figure 3 This is a schematic diagram illustrating the relationship between different radio frequency powers and etching rates and etching uniformity of two radio frequency electrodes in dual-head and single-head modes in some embodiments of the present invention.

[0017] Explanation of reference numerals in the attached figures 101, First radio frequency electrode; 102, First wafer stage; 103, First gas channel; 201, Second radio frequency electrode; 202, Second wafer stage; 203, Second gas channel. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed following the word and its equivalents, but do not exclude other elements or objects.

[0019] To address the problems existing in the prior art, embodiments of the present invention provide a process stabilization method compatible with single and dual-cavity etching modes, referring to... Figure 2The process stabilization method compatible with single and dual-cavity etching modes is applied to a dual-RF electrode etching apparatus. The dual-RF electrode etching apparatus includes a first etching unit and a second etching unit. The first etching unit includes a first cavity, a first cavity spray head, and a first wafer stage 102. The first cavity spray head includes a first RF electrode 101 and a first gas channel 103. The second etching unit includes a second cavity, a second cavity spray head, and a second wafer stage 202. The second cavity spray head includes a second RF electrode 201 and a second gas channel 203. The first cavity and the second cavity are in communication. The first wafer stage 102 is disposed in the first cavity, and the second wafer stage 202 is disposed in the second cavity. The first gas channel 103 is located on the upper side of the first cavity and is in communication with the first cavity. The first RF electrode 101 is disposed on the upper side of the first cavity and surrounds the first gas channel 103. The second gas channel 203 is located on the upper side of the second cavity and is in communication with the second cavity. The second RF electrode 201 is disposed on the upper side of the second cavity and surrounds the second gas channel 203.

[0020] In some embodiments, reference is made to Figure 1 The process stabilization method compatible with single and dual-cavity etching modes includes the following steps: S1: In the dual-cavity etching mode, the etching rate of the first cavity spray head on the wafer is obtained as the reference etching rate. After removing the wafer from the second cavity, the dependence of the etching rate of the first cavity spray head on the wafer and the RF power applied to the second cavity spray head is obtained. Then, a stable RF power is obtained based on the reference etching rate and the dependence. S2: In single-cavity etching mode, the radio frequency power applied in dual-cavity etching mode is applied to the first cavity spray head, and the stable radio frequency power is applied to the second cavity spray head, so that the difference between the etching rate of the first cavity spray head on the wafer and the preset etching rate is less than or equal to 1%, and / or, the difference between the etching uniformity of the first cavity spray head on the wafer and the preset etching uniformity is less than or equal to 1%.

[0021] In this application, the dual-cavity etching mode means that both the first and second cavities contain wafers, or in other words, both the first and second wafer stages support wafers; the single-cavity etching mode means that only one cavity contains a wafer, or in other words, only one wafer stage supports a wafer. Here, the cavity containing the wafer is the first cavity, and the cavity without the wafer is the second cavity.

[0022] In existing technologies, during dual-cavity etching, process gases are introduced into both the first and second gas channels, and both the first and second radio frequency (RF) electrodes are operational. The plasma in the first and second cavities can complement each other, thus maintaining process stability in both cavities. In single-cavity etching, the gas channels and RF electrodes corresponding to the cavity with the wafer are operational, while those corresponding to the cavity without the wafer are inactive. Plasma in the cavity with the wafer diffuses into the cavity without the wafer, leading to a decrease in plasma concentration in the cavity with the wafer. This ultimately results in a decrease in the wafer etching rate and a deterioration in etching uniformity within that cavity. For example, if there is a wafer on the first wafer stage and no wafer on the second wafer stage, and the first gas channel introduces process gas into the first cavity while the first RF electrode is operational, and the second gas channel stops introducing gas into the second cavity, the second RF electrode stops operating, and the plasma in the first cavity diffuses into the second cavity. This leads to a decrease in plasma concentration in the first cavity, ultimately resulting in a decrease in the wafer etching rate on the first wafer stage and a deterioration in etching uniformity.

[0023] In this application, the etching rate of the first cavity spray head on the wafer is obtained as a reference etching rate in the dual-cavity etching mode. After removing the wafer from the second cavity, the dependence of the etching rate of the first cavity spray head on the wafer on the RF power applied to the second cavity spray head is obtained. Then, a stable RF power is obtained based on the reference etching rate and the dependence. In the single-cavity etching mode, the RF power applied in the dual-cavity etching mode is applied to the first cavity spray head, and the stable RF power is applied to the second cavity spray head. This can prevent excessive diffusion of plasma from the first cavity into the second cavity, greatly reduce the difference in wafer etching between the single-cavity etching mode and the dual-cavity etching mode, and improve product quality and yield.

[0024] In some embodiments, the difference between the etching rate and the preset etching rate refers to the absolute value of the difference between the etching rate and the preset etching rate; the difference between the etching uniformity and the preset etching uniformity refers to the absolute value of the difference between the etching uniformity and the preset etching uniformity.

[0025] In some embodiments, the process recipe that meets the preset process requirements for wafer etching in dual-cavity etching mode is set as the standard process recipe. The standard process recipe includes standard RF power, standard process gas flow rate, etching pressure, type of etching gas, and etching temperature. For example, the etching pressure is 300 mT, the standard RF power is 600 W, the type of etching gas includes tetrafluoromethane (CF4), oxygen (O2), and helium (He), the flow rate of tetrafluoromethane is 300 sccm, the flow rate of oxygen is 200 sccm, the flow rate of helium is 100 sccm, and the etching temperature is 90°C.

[0026] It should be noted that the process formulation is not limited to the etching pressure, standard RF power, type of etching gas, etching gas flow rate, and etching temperature mentioned above, but is determined according to the specific process and is not specifically limited here.

[0027] In some embodiments, in dual-cavity etching mode, standard RF power (e.g., 600W) is applied to both the first and second cavity spray heads. The etching rate of the wafer by the first cavity spray head is then used as the baseline etching rate. The standard process formulation consists of mature process parameters that have been verified and are satisfactory in terms of etching rate, on-wafer uniformity, and morphology under dual-cavity etching mode. At this time, standard RF power is applied to both spray heads, and the plasma coupling, electromagnetic field distribution, gas flow field, and temperature field between the cavities are in a standard equilibrium steady state as designed by the equipment. Using the measured etching rate of the first cavity under this condition as the baseline etching rate essentially sets the successful process result of dual-cavity mass production as the process target to be replicated in subsequent single-cavity mode, ensuring that the final process results of the two working modes are consistent.

[0028] In some specific embodiments, in step S1, two wafers are placed on a first wafer stage and a second wafer stage, respectively. A first gas channel delivers process gas into a first cavity according to a standard process gas flow rate, and a second gas channel delivers process gas into a second cavity according to a standard process gas flow rate. Standard radio frequency power is applied to both the first and second radio frequency electrodes, and then the etching rate of the wafer in the first cavity is obtained as a reference etching rate.

[0029] In some embodiments, the wafer in the second cavity is removed in a dual-cavity etching mode. Then, the RF power applied to the second cavity spray head is adjusted at least twice. The etching rate of the wafer by the first cavity spray head is obtained before and after adjusting the RF power applied to the second cavity spray head. Based on several etching rates of the wafer by the first cavity spray head and several RF powers applied to the second cavity spray head, the dependence of the etching rate of the wafer by the first cavity spray head on the RF power applied to the second cavity spray head is obtained. Specifically, when adjusting the RF power applied to the second cavity spray head, each adjustment is x% of the standard RF power, where x is a natural number greater than or equal to 0 and less than 100. Preferably, the RF power applied to the second cavity spray head is different each time.

[0030] In a dual-RF electrode etching apparatus, the discharge of RF electrodes in the two cavities generates electromagnetic fields and plasma coupling. When the second cavity is empty of wafers, changes in the applied RF power directly alter the plasma distribution within the cavity, thus affecting the etching rate of the wafer by the first cavity's spray head. After removing the wafer from the second cavity, the RF power applied to the second cavity's spray head is adjusted multiple times, with each power set to a different percentage of the standard RF power. Simultaneously, the etching rate of the wafer by the first cavity's spray head under the corresponding operating conditions is collected, yielding multiple sets of one-to-one power-etching rate measured data. Based on fitting multiple sets of valid samples, a quantitative dependence between the two is obtained. This allows for a true and objective characterization of the coupling effect of the second cavity's spray head's RF power on the first cavity's etching process, avoiding fitting distortion caused by a single sample and ensuring an accurate and reliable data foundation for subsequent calculations of stable RF power.

[0031] In some embodiments, the number of times the radio frequency power applied to the second chamber spray head is adjusted includes 2 times, 4 times, 5 times, 20 times, or even 100 times.

[0032] In some embodiments, the etching rate of the wafer by a plurality of first-cavity spray heads and a plurality of radio frequency powers applied to a second-cavity spray head are fitted to obtain a relationship line between the etching rate of the wafer by the first-cavity spray head and the radio frequency power applied to the second-cavity spray head as a dependency. Specifically, the fitting includes linear fitting, nonlinear function fitting, interpolation-type fitting, nonparametric fitting, etc.

[0033] In some embodiments, the process stabilization method compatible with single and dual-cavity etching modes further includes a stable RF power verification step. Since the etching rate of the wafer obtained by the first cavity spray head may have some error, this can lead to a deviation in the final stable RF power. Ultimately, this can cause drastic changes in the wafer etching rate and / or etching uniformity in single-cavity etching mode (i.e., the difference between the wafer etching rate and the preset etching rate is greater than 1%, and / or the difference between the wafer etching uniformity and the preset etching uniformity is greater than 1%). The stable RF power verification step can avoid the adverse consequences caused by this deviation in stable RF power.

[0034] In some embodiments, the stable RF power verification step includes: in single-cavity etching mode, obtaining the etching rate and etching uniformity of the first cavity spray head on the wafer; calculating a first difference between the etching rate of the first cavity spray head on the wafer and a preset etching rate, and a second difference between the etching uniformity of the first cavity spray head on the wafer and a preset etching uniformity; if the first difference is greater than 1% and the second difference is greater than 1%, then re-obtaining the stable RF power.

[0035] In some other embodiments, the stable RF power verification step includes: in single-cavity etching mode, obtaining the etching rate and etching uniformity of the first cavity spray head on the wafer; calculating a first difference between the etching rate of the first cavity spray head on the wafer and a preset etching rate, and a second difference between the etching uniformity of the first cavity spray head on the wafer and a preset etching uniformity; if the first difference is greater than 1% and the second difference is less than or equal to 1%, then re-obtaining the stable RF power.

[0036] In other embodiments, the stable RF power verification step includes: in single-cavity etching mode, obtaining the etching rate and etching uniformity of the first cavity spray head on the wafer; calculating the first difference between the etching rate of the first cavity spray head on the wafer and a preset etching rate, and the second difference between the etching uniformity of the first cavity spray head on the wafer and a preset etching uniformity; if the first difference is less than or equal to 1% and the second difference is greater than 1%, then the stable RF power is obtained again, that is, step S1 is executed again.

[0037] In some embodiments, the radio frequency power corresponding to the etching rate closest to the reference etching rate is obtained as the stable radio frequency power based on the dependency relationship.

[0038] In some embodiments, the etching rate of the wafer is obtained by: measuring the initial thickness of the wafer thin film before etching; measuring the thickness of the wafer thin film after etching; subtracting the thickness of the wafer thin film after etching from the initial thickness of the wafer thin film to obtain the etching thickness; and dividing the etching thickness by the etching time to obtain the etching rate. Specifically, the initial thickness and the thickness of the wafer thin film after etching are measured using an ellipsometry, a profilometer, or similar instruments.

[0039] In some embodiments, the etching uniformity of the wafer is obtained by the following method: obtaining the etching rate at several points on the wafer, and then calculating the etching uniformity of the wafer using a non-uniformity algorithm. For example, if the etching rates at 9 points on the wafer are 98 nm / min, 99 nm / min, 101 nm / min, 97 nm / min, 102 nm / min, 100 nm / min, 99 nm / min, 98 nm / min, and 96 nm / min, with a maximum value of 102 nm / min and a minimum value of 96 nm / min, the average etching rate of the 9 points is approximately 99 nm / min, and the etching uniformity of the wafer is approximately (102-96) / (2×99)×100%≈3.03%.

[0040] Reference Figure 2 and Figure 3A1 represents the RF power applied to the first RF electrode 101, and A2 represents the RF power applied to the second RF electrode 201. Two wafers are placed on the first wafer stage 102 and the second wafer stage 202, respectively. Etching gas is introduced into the first gas channel 103 and the second gas channel 203 according to the process formula. The RF power applied to the first RF electrode 101 and the RF power applied to the second RF electrode 201 (i.e., the standard RF power) according to the process formula are both 600W. Then, the etching rate of the wafer on the first wafer stage 102 is obtained as 111.5 nm / min, and the etching uniformity is 2.5%. The wafer on the second wafer stage 202 is removed. Etching gas is introduced into the first gas channel 103 and the second gas channel 203 according to the process formula. The RF power applied to the first RF electrode 101 and the RF power applied to the second RF electrode 201 are maintained at 600W. The etching rate of the wafer on the first wafer stage is obtained as 116.8 nm / min. At a etching rate of nm / min and an etching uniformity of 3.3%, it can be observed that the etching rate on the wafer on the first stage 102 varies significantly, while the etching uniformity varies relatively little. Maintaining the RF power applied to the first RF electrode 101 at 600W and adjusting the power of the second RF electrode 201 to 0W, the etching rate on the wafer on the first stage 102 is obtained as 107.7 nm / min, with an etching uniformity of 5.1%. It can be observed that the etching rate on the wafer on the first stage 102 varies relatively little, while the etching uniformity varies significantly. Fitting several values ​​of the power of the second RF electrode 201 to several values ​​of the etching rate on the wafer on the first stage 102 yields a relationship curve between the etching rate of the first RF electrode 101 and the RF power applied to the second RF electrode. In this relationship curve, the etching rate calculated when the power of the second RF electrode 201 is 400W is closest to 111.5 nm / min, indicating that the stable RF power obtained is 400W. In single-cavity etching mode, the radio frequency power applied to the second radio frequency electrode 201 is 400W, resulting in an etching rate of 110.4 nm / min and an etching uniformity of 2.6%. At this time, the etching rate and etching uniformity of the wafer on the first wafer stage 102 do not change much, thus optimizing the etching rate and etching uniformity.

[0041] The present invention also provides a process stabilization system for implementing the above-mentioned process stabilization method compatible with single and dual cavity etching modes.

[0042] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A process stabilization method compatible with single and dual chamber etch modes, comprising: include: In the dual-cavity etching mode, the etching rate of the first cavity spray head on the wafer is obtained as the reference etching rate. After removing the wafer from the second cavity, the dependence of the etching rate of the first cavity spray head on the wafer and the RF power applied to the second cavity spray head is obtained. Then, a stable RF power is obtained based on the reference etching rate and the dependence. In single-cavity etching mode, the radio frequency power applied in dual-cavity etching mode is applied to the first cavity spray head, and the stable radio frequency power is applied to the second cavity spray head, so that the difference between the etching rate of the first cavity spray head on the wafer and the preset etching rate is less than or equal to 1%, and / or, the difference between the etching uniformity of the first cavity spray head on the wafer and the preset etching uniformity is less than or equal to 1%.

2. The process stabilization method for compatible single and dual chamber etch mode according to claim 1, wherein, Also includes: The process recipe that meets the preset process requirements for wafer etching in dual-cavity etching mode is set as the standard process recipe, and the standard process recipe includes standard RF power.

3. The process stabilization method compatible with single and dual-cavity etching modes according to claim 2, characterized in that, In the dual-cavity etching mode, standard radio frequency power is applied to both the first and second cavity spray heads, and then the etching rate of the wafer by the first cavity spray head is obtained as the reference etching rate.

4. The process stabilization method compatible with single and dual-cavity etching modes according to claim 2, characterized in that, The wafer in the second cavity is removed in the dual-cavity etching mode. Then the RF power applied to the second cavity spray head is adjusted at least twice. The etching rate of the first cavity spray head on the wafer is obtained before adjusting the RF power applied to the second cavity spray head and after adjusting the applied power of the second cavity spray head. Based on the etching rate of the wafer by several first-cavity spray heads and several radio frequency powers applied to the second-cavity spray heads, the dependence of the etching rate of the wafer by the first-cavity spray heads on the radio frequency power applied to the second-cavity spray heads is obtained.

5. The process stabilization method compatible with single and dual-cavity etching modes according to claim 4, characterized in that, When adjusting the radio frequency power applied to the second chamber spray head, the radio frequency power applied to the second chamber spray head is adjusted each time to x% of the standard radio frequency power, where x is a natural number greater than or equal to 0 and less than 100.

6. The process stabilization method compatible with single and dual-cavity etching modes according to claim 5, characterized in that, The radio frequency power applied to the second chamber spray head is different each time it is adjusted.

7. The process stabilization method compatible with single- and dual-cavity etching modes according to any one of claims 4 to 6, characterized in that, The etching rates of the wafer by several first-cavity spray heads and the radio frequency power applied to the second-cavity spray heads are fitted to obtain a relationship line between the etching rates of the wafer by the first-cavity spray heads and the radio frequency power applied to the second-cavity spray heads as a dependency.

8. The process stabilization method compatible with single and dual-cavity etching modes according to claim 1, characterized in that, It also includes a stable radio frequency power verification step, which includes: In single-cavity etching mode, the etching rate and etching uniformity of the first cavity spray head on the wafer are obtained; The first difference between the etching rate of the first cavity spray head on the wafer and the preset etching rate is obtained, and the second difference between the etching uniformity of the first cavity spray head on the wafer and the preset etching uniformity is obtained. If the first difference is greater than 1% and / or the second difference is greater than 1%, then a stable RF power is reacquired.

9. The process stabilization method compatible with single and dual-cavity etching modes according to claim 1, characterized in that, Based on the dependency relationship, the RF power corresponding to the etching rate that is closest to the reference etching rate is obtained as the stable RF power.

10. A process stabilization system for implementing the process stabilization method compatible with single- and dual-cavity etching modes as described in any one of claims 1 to 9.

Images