Method for improving surface roughness of plasma concentration ring and application
The surface of the plasma concentrated ring is processed by dry etching and the use of carbon tetrafluoride etching gas is solved, which is a problem of etching defects caused by the rough surface of the plasma concentrated ring, extends the service life and saves costs.
Patent Information
- Application Number
- CN202411426860.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-14
- Publication Date
- 2025-02-14
AI Technical Summary
During the etching process, the surface of the plasma concentrated ring is rough due to the damage of the oxide layer and chemical reaction, which leads to etching defects, limiting its service life and increasing production costs.
The rough surface of the plasma concentrated ring is treated by dry etching, using carbon tetrafluoride as the etching gas, controlling the gas flow rate and radio frequency parameters, and repeating the etching and cleaning steps until the surface roughness decreases below 0.4.
Effectively restore the flatness of the surface of the plasma concentration ring, extend its service life, reduce production costs, and reduce the occurrence of etching defects.
Smart Images
Figure CN119446878A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of semiconductor manufacturing, and in particular to a method for improving the surface roughness of a plasma concentration ring and its application. Background Art
[0002] The edge ring is an important component of the capacitive coupled plasma (CCP) etching chamber, which functions as a focused plasma. The chamber can be used for single and double Damascus etching processes, and its component material is single crystal silicon. During the etching process, the oxide layer of the edge ring will be gradually destroyed, which can easily lead to the accumulation of etching products on its surface. After that, the etching products react chemically with the surface of the edge ring, causing the surface of the edge ring to gradually become rough and cause damage. Figure 1 As shown, during the etching process, carbon fluoride (CFx) ions and carbon fluoride (CFx) atoms accumulate on the surface of the concentrating ring to form a carbon fluoride (CF) film, in which oxygen (O) ions react with the carbon fluoride (CF) film to generate carbon monoxide (CO) or carbon dioxide (CO2), and the remaining fluorine (F) ions gradually corrode the silicon surface of the concentrating ring, making the silicon surface rough.
[0003] If the plasma concentrating ring is still used after being damaged, some particles on its rough surface will be brought to the wafer surface after being bombarded by plasma during the etching process, causing etching defects. Figure 2 and Figure 3 As shown, Figure 2 In the figure, the concentrating ring is not damaged and the surface is flat. Figure 3 In the process, the surface of the concentrating ring is rough. During the etching process, the rough surface particles are easily brought to the wafer, causing etching defects.
[0004] Therefore, the service life of the plasma concentrating ring is greatly limited, and directly replacing the plasma concentrating ring with a new one will undoubtedly increase the production cost. Summary of the invention
[0005] In order to solve the above technical problems, the present invention provides a method for improving the surface roughness of a plasma concentrating ring, by dry etching the rough surface of the plasma concentrating ring to restore it to a flat surface, thereby extending the service life of the plasma concentrating ring and saving production costs.
[0006] A technical solution adopted by the present invention is to provide a method for improving the surface roughness of a plasma concentration ring, comprising:
[0007] Step 1: introducing a first etching gas to etch the rough surface of a rough plasma concentration ring, wherein the plasma concentration ring is made of single crystal silicon, the first etching gas is carbon tetrafluoride, and the flow rate of the first etching gas is 200-400 sccm;
[0008] Step 2: removing the surface products of the plasma concentration ring;
[0009] Repeat step 1 to step 2. Repeat step 1 to step 2 until the surface roughness of the plasma concentration ring drops below 0.4, at which time the surface of the plasma concentration ring is flat and can be used normally.
[0010] The method also includes introducing a second etching gas to pre-treat the cavity where the plasma concentration ring is located before performing step 1, wherein the second etching gas is a mixed gas containing oxygen and carbon tetrafluoride, and repeating the pre-treating step to step 2 until the surface roughness of the plasma concentration ring is less than 0.4. The pre-treating step is mainly to clean the suspended carbon particles in the cavity.
[0011] In step 1, the flow rate of the first etching gas is 200-400 sccm. When the flow rate of carbon tetrafluoride is lower than 200 sccm, the reaction rate is too slow, which prolongs the etching time. When the flow rate of carbon tetrafluoride is higher than 400 sccm, the fluorine content is too high, fluorine ions react excessively with silicon, and the generated silicon fluoride easily forms a topological structure, which is deposited on the surface of the plasma concentration ring and is not easy to be removed.
[0012] During the pretreatment process, a high-frequency power of 1200-1500W and a low-frequency power of 1500-2000W are provided; during the etching process of step one, a high-frequency power of 1200-1800W and a low-frequency power of 800-1200W are provided.
[0013] The pretreatment process includes two pretreatment stages, the first pretreatment stage is carried out at a high chamber pressure of 200-300mT, and the second pretreatment stage is carried out at a low chamber pressure of 30-40mT. The pretreatment step is mainly to clean the suspended carbon particles in the cavity. First, under a high chamber pressure environment, the first etching gas forms a relatively dispersed plasma to remove the suspended particles in the upper part of the cavity, and then under a low chamber pressure environment, the suspended particles remaining in the lower part of the cavity are removed.
[0014] In the first pretreatment stage, the flow rate of oxygen is 300-600sccm, the flow rate of carbon tetrafluoride is 150-300sccm, and the RF time is 20-60 seconds; in the second pretreatment stage, the flow rate of oxygen is 800-1200sccm, the flow rate of carbon tetrafluoride is 150-300sccm, and the RF time is 20-60 seconds.
[0015] The step 1 is performed under a chamber pressure of 80-100 mT, and the radio frequency time is 200-300 seconds.
[0016] The cleaning process of step 2 includes two cleaning stages. In the first cleaning stage, argon gas with a flow rate of 1200-1500sccm is introduced at a high chamber pressure of 400-600mT. In the second cleaning stage, argon gas with a flow rate of 200-300sccm is introduced at a low chamber pressure of 10-20mT.
[0017] The total duration of the radio frequency is greater than 60 minutes. When the total duration of the radio frequency is greater than 60 minutes, the surface roughness Ra of the plasma concentration ring can be reduced to less than 0.4, the surface is flat, and can be used normally.
[0018] During the etching process from the pretreatment step to step 2, a high frequency radio frequency of 60 MHz or 40 MHz and a low frequency radio frequency of 13 MHz or 2 MHz are provided.
[0019] Another object of the present invention is to process the plasma concentrating ring of a capacitively coupled plasma Damascus etching chamber by using a method for improving the surface roughness of a plasma concentrating ring as described in any of the above technical solutions.
[0020] The beneficial effects of the present invention are:
[0021] A method for improving the surface roughness of a plasma concentrating ring is provided. The rough surface of the plasma concentrating ring is treated by dry etching using carbon tetrafluoride etching gas to restore the rough surface of the plasma concentrating ring to a flat surface, thereby extending the service life of the plasma concentrating ring and saving costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0023] Figure 1 This is a schematic diagram of the principle of roughening the surface of the plasma concentration ring;
[0024] Figure 2 This is a schematic diagram of the etching process of the plasma concentration ring under normal use;
[0025] Figure 3 This is a schematic diagram of the etching process after the plasma concentration ring is damaged;
[0026] Figure 4 is a flow chart of a method for improving the surface roughness of a plasma concentration ring provided in Example 1 of the present invention;
[0027] Figure 51 is a comparison diagram of the surface roughness of the plasma concentration ring before and after the treatment of Example 1 of the invention, wherein (a) is before the treatment and (b) is after the treatment;
[0028] Figure 6 This is a flow chart of a method for improving the surface roughness of a plasma concentration ring provided in Example 2 of the present invention.
[0029] 1. Plasma concentrating ring; 2. Lower electrode (ESC). DETAILED DESCRIPTION
[0030] In order to make the purpose, technical scheme and advantages of the present invention clearer, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the present invention shown in the accompanying drawings and described according to the accompanying drawings are merely exemplary, and the present invention is not limited to these embodiments.
[0031] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.
[0032] Example 1
[0033] like Figure 4 As shown, a method for improving the surface roughness of a plasma concentration ring provided in this embodiment includes the following steps:
[0034] Step 1: Introduce a first etching gas to etch the rough surface of a rough plasma concentration ring, wherein the plasma concentration ring is made of single crystal silicon, the first etching gas is carbon tetrafluoride, and the flow rate of the first etching gas is 200-400 sccm.
[0035] Before etching begins, a wafer is placed on the lower electrode (ESC) to protect the ESC from damage during etching. The surface roughness Ra of the rough surface plasma concentration ring is 0.8-0.9.
[0036] Specifically, a high-frequency radio frequency of 60MHz or 40MHz and a low-frequency radio frequency of 13MHz or 2MHz are provided in the process. The step 1 is carried out at a chamber pressure of 80-100mT, the applicable high-frequency power is 1200-1800W, the applicable low-frequency power is 800-1200W, and the radio frequency time is 200-300 seconds. The flow rate of the etching gas is related to the density of the plasma and directly affects the final etching effect. In this step, the flow rate of the CF4 is 200-400sccm. If the flow rate of the CF4 is lower than 200sccm, the reaction rate is too slow, resulting in an extended etching time; if the flow rate of the CF4 is higher than 400sccm, the fluorine content is too high, and the fluorine ions react excessively with silicon. The generated silicon fluoride is easy to form a topological structure and is deposited on the surface of the plasma concentration ring and is not easy to be removed. After the completion of this step, some particles remain on the surface of the plasma concentration ring, and the surface products of the plasma concentration ring need to be removed.
[0037] Step 2: removing the surface products of the plasma concentration ring.
[0038] The cleaning process in step 2 includes two cleaning stages. In the first cleaning stage, argon (Ar) with a flow rate of 1200-1500 sccm is introduced at a high chamber pressure of 400-600 mT, and in the second cleaning stage, Ar with a flow rate of 200-300 sccm is introduced at a low chamber pressure of 10-20 mT. By introducing Ar, residual particles on the surface of the plasma concentration ring are taken away to keep its surface clean.
[0039] In this example, repeat steps 1 to 2, and the total RF duration is greater than 60 minutes. When the total RF duration is greater than 60 minutes, the surface roughness Ra of the plasma concentration ring can be reduced from 0.8 to 0.9 to below 0.4, and the surface is flat and can be used normally. Figure 5 As shown, (a) is a photo of a damaged plasma concentration ring, whose surface is rough, and (b) is a photo of a plasma concentration ring after being processed by the technical solution of the present invention, whose surface is smooth and can be used normally.
[0040] The types of etching gases used in conventional dry etching processes are relatively complex. In addition to CF4 gas, they generally include hydrogen-containing carbon fluorine gases such as CH3F, CHF3, and CH2F2. The chemical activity is low, and the proportion of CF4 is relatively small. It is easy to generate more and more complex carbon fluorine aggregates, which are more likely to be deposited on the surface of the plasma concentration ring, causing damage to the plasma concentration ring. In the present invention, only CF4, a carbon fluorine gas, is used. Since CF4 has high oxidizing properties and CF plasma has strong chemical reaction activity, after treating the rough surface of the plasma concentration ring, the reaction product is easy to volatilize and is extracted from the reaction chamber through the vacuum system. Compared with conventional dry etching processes, the problem of product deposition is not easy to occur, thereby reducing the damage phenomenon of the plasma concentration ring and extending the service life of the plasma concentration ring.
[0041] At the same time, during the research and development process, attempts were made to replace CF4 with other carbon-fluorine gases such as C4F8, C5F8, and C4F6 to treat the rough surface of the plasma concentrating ring. It was found that none of them could solve the technical problem of damage to the plasma concentrating ring. Only CF4 gas can reduce the deposition of products on the surface of the plasma concentrating ring and reduce the risk of damage to the plasma concentrating ring.
[0042] Example 2
[0043] This embodiment is improved on the basis of the scheme of embodiment 1. The processing process of step 1 and step 2 is the same as that of embodiment 1. The difference is that this embodiment adds a pretreatment step of the cavity where the plasma concentration ring with a rough surface is located before step 1, which is used to clean the suspended carbon particles in the cavity, provide a cleaner cavity environment for step 1, and ensure the etching effect of step 1. Figure 6 , Figure 6 A schematic flow chart of a method for improving the surface roughness of a plasma concentrating ring provided in this embodiment.
[0044] In this pretreatment stage, a second etching gas is introduced to pretreat the cavity where the rough surface plasma concentration ring is located. The second etching gas is a mixed gas of oxygen (O2) and carbon tetrafluoride (CF4). Provide a high-frequency radio frequency of 60MHz or 40MHz and a low-frequency radio frequency of 13MHz or 2MHz. The high-frequency power applicable to this step is 1200~1500W, and the applicable low-frequency power is 1500~2000W. A mixed gas of O2 and CF4 is introduced as the second etching gas to pretreat the reactor cavity.
[0045] The pretreatment step is divided into two pretreatment stages. The first pretreatment stage is carried out under high chamber pressure, the pressure is 200-300mT, the flow rate of O2 is 300-600sccm, the flow rate of CF4 is 150-300sccm, and the RF time is 20-60 seconds. The second pretreatment stage is carried out under low chamber pressure, the pressure is 30-40mT, the flow rate of O2 is 800-1200sccm, the flow rate of CF4 is 150-300sccm, and the RF time is 20-60 seconds. The pretreatment step is mainly to clean the suspended carbon particles in the cavity. First, under high chamber pressure environment, the second etching gas forms a more dispersed plasma to remove the suspended particles in the upper part of the cavity, and then under low chamber pressure environment, the suspended particles remaining in the lower part of the cavity are removed.
[0046] In this embodiment, the pretreatment step to step 2 is repeated, and the total RF duration is greater than 60 minutes. When the total RF duration is greater than 60 minutes, the surface roughness Ra of the plasma concentration ring can be reduced from 0.8 to 0.9 to below 0.4, and the surface is flat and can be used normally.
[0047] A method for improving the surface roughness of a plasma concentration ring provided by an embodiment of the present invention is used for processing a plasma concentration ring of a capacitively coupled plasma Damascus etching chamber.
[0048] In addition, it should be noted that in this specification, "includes", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.
[0049] It should be understood that although this specification is described according to implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.
Claims
1. A method for improving the surface roughness of a plasma concentration ring, characterized in that: include: Step 1: introducing a first etching gas to etch the rough surface of a rough plasma concentration ring, wherein the plasma concentration ring is made of single crystal silicon, the first etching gas is carbon tetrafluoride, and the flow rate of the first etching gas is 200-400 sccm; Step 2: removing the surface products of the plasma concentration ring; Repeat step 1 to step 2.
2. A method for improving the surface roughness of a plasma concentration ring according to claim 1, characterized in that: The method also includes introducing a second etching gas to pre-treat the cavity where the plasma concentration ring is located before performing step one, wherein the second etching gas is a mixed gas containing oxygen and carbon tetrafluoride, and repeating the pre-treatment steps to step two.
3. A method for improving the surface roughness of a plasma concentration ring according to claim 2, characterized in that: During the pretreatment process, a high-frequency power of 1200-1500W and a low-frequency power of 1500-2000W are provided; during the etching process of step one, a high-frequency power of 1200-1800W and a low-frequency power of 800-1200W are provided.
4. The method for improving the surface roughness of a plasma concentration ring according to claim 2, characterized in that: The pretreatment process includes two pretreatment stages. The first pretreatment stage is performed at a high chamber pressure of 200-300 mT, and the second pretreatment stage is performed at a low chamber pressure of 30-40 mT.
5. The method for improving the surface roughness of a plasma concentration ring according to claim 4, characterized in that: In the first pretreatment stage, the flow rate of oxygen is 300-600sccm, the flow rate of carbon tetrafluoride is 150-300sccm, and the RF time is 20-60 seconds; in the second pretreatment stage, the flow rate of oxygen is 800-1200sccm, the flow rate of carbon tetrafluoride is 150-300sccm, and the RF time is 20-60 seconds.
6. The method for improving the surface roughness of a plasma concentration ring according to claim 1, characterized in that: The step 1 is performed under a chamber pressure of 80-100 mT, and the radio frequency time is 200-300 seconds.
7. The method for improving the surface roughness of a plasma concentration ring according to claim 1, characterized in that: The cleaning process of step 2 includes two cleaning stages. In the first cleaning stage, argon gas with a flow rate of 1200-1500sccm is introduced at a high chamber pressure of 400-600mT. In the second cleaning stage, argon gas with a flow rate of 200-300sccm is introduced at a low chamber pressure of 10-20mT.
8. A method for improving the surface roughness of a plasma concentration ring according to claim 1 or 2, characterized in that: The total RF duration is greater than 60 minutes.
9. The method for improving the surface roughness of a plasma concentration ring according to claim 2, characterized in that: During the etching process from the pretreatment step to step 2, a high frequency radio frequency of 60 MHz or 40 MHz and a low frequency radio frequency of 13 MHz or 2 MHz are provided.
10. A method for improving the surface roughness of a plasma concentrating ring according to any one of claims 1 to 9 is used to treat a plasma concentrating ring of a capacitively coupled plasma Damascus etching chamber.