Surface pretreatment method for upper electrode of CCP etching equipment

Abstract

The invention provides a surface pretreatment method for an upper electrode of CCP etching equipment, which comprises the following steps: providing etching equipment, arranging the upper electrode in an etching cavity of the etching equipment, and enabling the electrode to be made of a silicon dioxide material; transferring a wafer into the etching cavity; argon is introduced, and bombardment treatment is conducted on the surface of the upper electrode; first process gas is introduced, first etching treatment is carried out on the surface of the upper electrode, and the first process gas comprises fluorine-containing etching gas; second process gas is introduced, second etching treatment is carried out on the surface of the upper electrode, and the second process is mixed gas of argon and oxygen; the wafer is conveyed out; and repeatedly executing the steps for a preset number of times until a preset time length. According to the method, the large fracture surface of the upper electrode is destroyed through physical bombardment of the plasma, the first etching treatment key point is provided subsequently to remove the degraded area, then cleaning and repairing are conducted through the second etching, the steps are executed circularly, pretreatment of the surface of the electrode can be efficiently achieved, and the service life is prolonged.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a surface pretreatment method for the upper electrode of a CCP etching device. Background Technology

[0002] Dry etching is a process that selectively removes unwanted material from the surface of a semiconductor substrate using physical and / or chemical methods. It is a crucial step in the semiconductor device and integrated circuit manufacturing industry. In CCP (capacitively coupled plasma) etching equipment, the upper electrode in the etching chamber is more susceptible to plasma bombardment, leading to surface degradation. This is especially true for upper electrodes made of quartz (SiO2), whose surface is rougher than that of single-crystal silicon upper electrodes. This makes them more prone to etching byproduct adsorption and particle shedding that contaminates the wafer. To ensure product quality, current practice necessitates replacing the upper electrode periodically (usually every 500 hours), which inevitably leads to decreased production efficiency and increased costs.

[0003] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0004] The purpose of this invention is to provide a surface pretreatment method for the upper electrode of a CCP etching device, comprising the following steps: S1. An etching apparatus is provided, wherein an upper electrode is installed in the etching chamber of the etching apparatus, and the surface layer of the upper electrode is made of silicon dioxide. S2. Transfer the wafer into the etching cavity; S3. Argon gas is introduced into the etching cavity to bombard the surface of the upper electrode. S4. Introduce a first process gas into the etching cavity to perform a first etching process on the surface of the upper electrode. The first process gas includes a fluorine-containing etching gas. S5. Introduce a second process gas into the etching cavity to perform a second etching process on the surface of the upper electrode. The second process gas is a mixture of argon and oxygen. S6. The wafer is transferred out of the etching cavity; S7. Repeat steps S2 and S6 a predetermined number of times until the predetermined duration.

[0005] This application first uses plasma to physically bombard and destroy the large fracture surface of the upper electrode, then provides a first etching process to focus on removing the fracture area, and then uses a second etching process for cleaning and repair. This process is repeated cyclically, which can efficiently achieve the pretreatment of the electrode surface and improve its service life.

[0006] The bombardment treatment includes bombarding the surface of the upper electrode with plasma formed by the ionization of argon gas under a first pressure; the first pressure is 200 mT, the high-frequency power is 1500 W, and the low-frequency power is 1000 W. Using a lower low-frequency power can effectively increase the ion bombardment energy and ensure sufficient bombardment effect.

[0007] In the bombardment process, the flow rate of argon gas is 1200 sccm, and the bombardment time is 20 seconds.

[0008] The first process gas is a mixture of carbon tetrafluoride, argon, and oxygen.

[0009] The first etching process includes etching the surface of the upper electrode under a second pressure using plasma generated by the ionization of the first process gas; the second pressure is 100 mT, the high-frequency power is 3000 W, and the low-frequency power is 1500 W. Using higher high-frequency power can effectively increase the dissociation effect, increase the plasma density, and increase the etching rate.

[0010] In the first etching process, the flow rate of carbon tetrafluoride is 600 sccm, the flow rate of argon is 1200 sccm, the flow rate of oxygen is 200 sccm, and the time of the first etching process is 200 seconds.

[0011] The second etching process includes etching the etching chamber under a third pressure using plasma formed by the ionization of argon and oxygen; the third pressure is 50 mT, the high-frequency power is 1500 W, and the low-frequency power is 1000 W. This effectively removes etching byproducts, repairs the electrode surface, and provides a foundation for the next cycle.

[0012] In the second etching process, the flow rate of argon is 800 sccm, the flow rate of oxygen is 100 sccm, and the etching time is 20 seconds.

[0013] In steps S3 to S5, the cavity temperature is 50-100 ℃, the center pressure of the back helium is 30 T, and the edge pressure is 40 T.

[0014] Repeat steps S3 to S5 a predetermined number of times until the total processing time exceeds 30 hours.

[0015] Compared with the prior art, the beneficial effects of the present invention mainly include the following: The present application first uses the physical bombardment of ions to destroy the large fracture surface of the upper electrode, then provides a first etching process to remove the deteriorated area, and then cleans and repairs it through a second etching process. This cycle is repeated to efficiently achieve the pretreatment of the electrode surface and increase the service life of the upper electrode by 2-3 times. Attached Figure Description

[0016] 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.

[0017] Figure 1 The flowchart of the pretreatment process for the upper electrode surface provided by the present invention.

[0018] Figure 2 This is a surface condition diagram of the upper electrode in Comparative Example 1 after 50 hours of use.

[0019] Figure 3 This is a surface state diagram of the upper electrode in Example 1 after 50 hours of use. Detailed Implementation

[0020] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the accompanying drawings. The directional terms mentioned in the following embodiments, such as up, down, left, right, front, or back, are merely for reference to the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the present invention.

[0021] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0022] The steps in the following embodiments do not correspond one-to-one with the contents of the invention.

[0023] Example 1 In existing capacitively coupled dry etching equipment, two parallel disc-shaped electrodes are usually set up at the top and bottom of the etching chamber. The surface of the upper electrode is usually made of silicon dioxide and also serves as the inlet spray head for process gases (gas injection through holes are uniformly arranged in the upper electrode). The lower electrode is generally used to place and fix the wafer.

[0024] The upper electrode is typically grounded, while the lower electrode is usually the main application point for RF power. When the RF power is turned on, a high-frequency alternating electric field is generated between the two parallel plate electrodes (i.e., the upper and lower electrodes). This field dissociates the introduced process gas molecules into electrons, ions, and reactive free radicals. Since electrons have a smaller mass than ions (such as Ar⁺), electrons move much faster than ions. Consequently, in each RF cycle, the number of electrons reaching the electrode surface is far greater than the number of ions. This creates a negative potential on the electrode surface, attracting ions to accelerate towards the electrode surface for physical and chemical etching.

[0025] It is understandable that the above process will also occur on the surface of the upper electrode. When the surface of the upper electrode is relatively rough, it is more likely to be adsorbed by etching byproducts, thereby increasing the risk of particles falling off and forming particle defects.

[0026] Therefore, such as Figure 1 The diagram shown is a flowchart of the surface pretreatment process for the upper electrode provided by the present invention. The present invention provides a surface pretreatment method for the upper electrode of a CCP etching device, comprising the following steps: Step 1: Provide a CCP etching device, and install a new upper electrode in the etching chamber of the CCP device. The surface layer of the upper electrode is made of silicon dioxide. First, a new upper electrode is provided and installed into the etching chamber of the etching machine. In this embodiment, the surface of the provided upper electrode is made of SiO2 material, which has a relatively rough surface (surface roughness Ra is about 6.3), making it easy to adsorb etching byproducts.

[0027] Step 2: Transfer a wafer to the etching cavity.

[0028] In this embodiment, a wafer is first transferred to the etching cavity.

[0029] Step 3: Introduce argon gas into the etching chamber to bombard the surface of the upper electrode; In this embodiment, the surface of the upper electrode is pretreated by a combination of physical bombardment and chemical etching. First, the surface of the upper electrode is bombarded with argon ions, which breaks down the large fracture surfaces on the surface of the upper electrode. This allows for effective removal of the fracture areas during the subsequent etching process, while minimizing the impact on other areas. This improves the overall etching rate, reduces the total time of surface pretreatment, and minimizes the impact on the remaining areas of the upper electrode.

[0030] Specifically, in this embodiment, the bombardment treatment includes bombarding the surface of the upper electrode with plasma formed by argon ionization under a first pressure; the first pressure is 200 mTorr (i.e., millitor, the same below), the argon flow rate is 1200 sccm (standard cubic centimeters per minute, the same below), the high-frequency power is 1500 W, the low-frequency power is 1000 W, the bombardment treatment time is 20 seconds, the cavity temperature is 50-100 ℃ (corresponding to the temperatures of the bottom, side wall and top of the cavity are 50 / 100 / 100 ℃ respectively), the center pressure of the back helium is 30 mTorr, and the edge pressure is 40 mTorr.

[0031] It is understandable that in CCP dry etching equipment, high-frequency radio frequency (RF) and low-frequency radio frequency (RF) each have their own specific functions. High-frequency RF is primarily used to achieve gas dissociation, mainly affecting plasma density, while low-frequency RF is mainly used to adjust the bombardment energy of the physical impact. In this embodiment, a lower-power low-frequency RF was selected to improve the physical bombardment of argon ions.

[0032] Step 4: Introduce a first process gas into the etching chamber to perform a first etching treatment on the surface of the upper electrode. The first process gas includes a fluorine-containing etching gas. In this embodiment, a first process gas is introduced to chemically etch the surface of the upper electrode, using CF... 2+ Or CF 3+ Ions react chemically with silicon dioxide to generate volatile SiF4 and CO2, which transform the large fracture surface on the upper electrode surface into a small fracture surface, thus improving its surface condition.

[0033] Specifically, in this embodiment, the first process gas is a mixture of carbon tetrafluoride, argon, and oxygen; the etching process includes etching the surface of the upper electrode using plasma formed by the ionization of the first process gas under a second pressure. The second pressure is 100 mT, the flow rate of carbon tetrafluoride is 600 sccm, the flow rate of argon is 1200 sccm, the flow rate of oxygen is 200 sccm, the high-frequency power is 3000 W, the low-frequency power is 1500 W, the etching time is 200 seconds, the cavity temperature is 50-100 ℃, the center pressure of the back helium is 30 mTorr, and the edge pressure is 40 mTorr.

[0034] In this embodiment, a higher power high-frequency radio frequency is used to increase the density of the generated plasma in order to ensure etching efficiency.

[0035] Step 5: Introduce a second process gas into the etching chamber to perform a second etching process on the etching chamber. The second process gas is a mixture of argon and oxygen. To prevent contaminant residues (silicon dioxide particles and their etching byproducts) from the previous bombardment and etching processes, and to repair the surface of the upper electrode, a second etching process was performed. Specifically, this involved etching the surface of the upper electrode using plasma formed by the ionization of argon and oxygen under a third pressure. The third pressure was 50 mT, the argon flow rate was 800 sccm, the oxygen flow rate was 100 sccm, the high-frequency power was 1500 W, the low-frequency power was 1000 W, the processing time was 20 seconds, the chamber temperature was 50-100℃, the center pressure of the back helium was 30 mTorr, and the edge pressure was 40 mTorr.

[0036] Step 6: Transfer the wafer from the etching cavity.

[0037] Step 7: Repeat steps 2 and 6 a predetermined number of times until the predetermined duration is reached.

[0038] Then, steps 2 through 6 above were repeated a certain number of times, that is, each time a new wafer was provided and bombarded, etched and repaired sequentially, until the total processing time exceeded 30 hours. Tests showed that the surface condition of the upper electrode (i.e., the surface roughness Ra decreased from 6.3 to below 1.6) met the expected requirements and could be used in subsequent normal production.

[0039] Comparative Example 1 The new product's upper electrode is used directly in the normal process without the aforementioned surface pretreatment.

[0040] In Comparative Example 1, if the upper electrode of the new product is not pretreated, its single service life is usually around 500 hours. When this time limit is reached, PM needs to be performed and the upper electrode needs to be replaced.

[0041] to this end, Figure 2 and Figure 3 The surface condition of the upper electrode of Comparative Example 1 and Example 1 after 500 hours of use is shown. Figure 2 The image shows the surface condition of the upper electrode in Comparative Example 1 after 500 hours of use. Figure 2 In the diagram, 'a' represents the surface condition of the flat area of ​​the upper electrode after 500 hours of use. Figure 2 In the diagram, 'b' represents the surface condition of the porous region of the upper electrode after 500 hours of use. Similarly, Figure 3 The image shown is a surface state diagram of the upper electrode in Example 1 after 500 hours of use. Figure 3 In the diagram, 'a' represents the surface condition of the flat area of ​​the upper electrode after 500 hours of use. Figure 3 In the diagram, b represents the surface condition of the pore area of ​​the upper electrode after 500 hours of use.

[0042] contrast Figure 2 and Figure 3 It can be observed that the flat area of ​​Comparative Example 1 has a relatively large fracture surface, and the morphology of its pore area is also significantly changed with large fluctuations; while in Example 1, the fracture surface of the flat area of ​​the upper electrode is significantly smaller, the morphology of its pores is better, and the fluctuations of the surrounding area are smaller.

[0043] Multiple tests have shown that after the surface pretreatment described in Example 1, the service life of the upper electrode is increased by 2-3 times compared to the original upper electrode, and its service life can be increased from 500 hours to nearly 1500 hours.

[0044] The common English terms or letters used in this invention for clarity of description are for illustrative purposes only and are not limiting interpretations or specific uses. They should not be used to limit the scope of protection of this invention based on their possible Chinese translations or specific letters.

[0045] It should also be noted that in this article, relational terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

Claims

1. A surface pretreatment method for the upper electrode of a CCP etching device, characterized in that, Includes the following steps: S1. An etching apparatus is provided, wherein an upper electrode is installed in the etching chamber of the etching apparatus, and the surface layer of the upper electrode is made of silicon dioxide. S2. Transfer the wafer into the etching cavity; S3. Argon gas is introduced into the etching cavity to bombard the surface of the upper electrode. S4. Introduce a first process gas into the etching cavity to perform a first etching process on the surface of the upper electrode. The first process gas includes a fluorine-containing etching gas. S5. Introduce a second process gas into the etching cavity to perform a second etching process on the surface of the upper electrode. The second process gas is a mixture of argon and oxygen. S6. The wafer is transferred out of the etching cavity; S7. Repeat steps S2 and S6 a predetermined number of times until the predetermined duration.

2. The surface pretreatment method for the upper electrode of a CCP etching device according to claim 1, characterized in that, The bombardment treatment includes bombarding the surface of the upper electrode with plasma formed by the ionization of argon gas under a first pressure; the first pressure is 200 mT, the high-frequency power is 1500 W, and the low-frequency power is 1000 W.

3. The surface pretreatment method for the upper electrode of a CCP etching device according to claim 2, characterized in that, In the bombardment process, the flow rate of argon gas is 1200 sccm, and the bombardment time is 20 seconds.

4. The surface pretreatment method for the upper electrode of a CCP etching device according to claim 1, characterized in that, The first process gas is a mixture of carbon tetrafluoride, argon, and oxygen.

5. The surface pretreatment method for the upper electrode of a CCP etching device according to claim 4, characterized in that, The first etching process includes etching the surface of the upper electrode under a second pressure using plasma formed by the ionization of the first process gas; the second pressure is 100 mT, the high-frequency power is 3000 W, and the low-frequency power is 1500 W.

6. The surface pretreatment method for the upper electrode of a CCP etching device according to claim 5, characterized in that, In the first etching process, the flow rate of carbon tetrafluoride is 600 sccm, the flow rate of argon is 1200 sccm, the flow rate of oxygen is 200 sccm, and the time of the first etching process is 200 seconds.

7. The surface pretreatment method for the upper electrode of a CCP etching device according to claim 1, characterized in that, The second etching process includes etching the etching chamber under a third pressure using plasma formed by the ionization of argon and oxygen; the third pressure is 50 mT, the high-frequency power is 1500 W, and the low-frequency power is 1000 W.

8. The surface pretreatment method for the upper electrode of a CCP etching device according to claim 7, characterized in that, In the second etching process, the flow rate of argon is 800 sccm, the flow rate of oxygen is 100 sccm, and the etching time is 20 seconds.

9. The surface pretreatment method for the upper electrode of a CCP etching device according to claim 1, characterized in that, In steps S3 to S5, the cavity temperature is 50-100 ℃, the center pressure of the back helium is 30 T, and the edge pressure is 40 T.

10. A surface pretreatment method for the upper electrode of a CCP etching device according to claim 9, characterized in that, Repeat steps S3 to S5 a predetermined number of times until the total processing time exceeds 30 hours.

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