Coatings for use in remote plasma source applications and methods of making same - Patents.com

Abstract

A method of coating a plasma channel of a plasma source includes providing at least one electrolyte having one or more chelating agents therein, treating at least one surface to produce a treated surface, smoothing the surface of the treated surface with at least one post-treatment technique to produce at least one smoothed treated surface, and cleaning the smoothed surface.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 331,735, filed April 15, 2022, entitled “Coatings for Use in Remote Plasma Source Applications and Methods for Making the Same.”

[0002] FIELD OF THEINVENTION This application relates to coatings for use in remote plasma source applications and methods for the manufacture of such coatings. [Background technology]

[0003] Background technology Remote plasma sources are commonly used in semiconductor manufacturing. Historically, remote plasma sources, remote plasma applicators, and products (hereafter RPS) have been manufactured from a variety of materials. Typically, the plasma-facing surfaces in the RPS are modified or coated to meet insulation requirements, extend chamber life, and aid in chamber cleanliness between process cycles. The choice of plasma-facing material for the aluminum-based plasma applicator in an RPS product is strongly related to plasma conditions, application requirements, manufacturability, cost, and many other considerations. Many factors preclude the use of many commercially available materials and available coating techniques in remote plasma source applications. For example, the geometry and complexity of the applicator design (partially enclosed inner surfaces, narrow plasma channels, and constraints on overall dimensions) and the extreme operating conditions (high plasma density, high temperatures, chemical erosion, and ion bombardment) greatly reduce the number of commercially available materials and available coating techniques useful in RPS applications.

[0004] Hard anodization (HA) has been used for over 20 years to treat aluminum in RPS applicators. HA oxide coatings offer the advantages of good chemical resistance, suitable manufacturing processes for complex geometries, and good cost-effectiveness. In the past, HA coatings for RPS applications have focused on chamber cleaning purposes. Although HA coatings have proven useful, a number of shortcomings have been identified, especially in relation to NF3 plasma. For example, anodized coatings have relatively good plasma resistance in NF3 environments after exposure to fluorine chemicals, but amorphous aluminum oxide and hydroxide react with fluorine to form a flaky layer of aluminum fluoride on top of the anodized layer, which can become a contamination in RPS. Furthermore, the anodized layer deteriorates over time, shortening the service life of blocks used in RPS. In addition, the porous nature and cracks in the HA coating due to thermal mismatch in the anodization also adversely affect its dielectric strength. Arcing problems occur, especially on worn surfaces. These deleterious effects on the top surface of the anodized layer are illustrated in Figures 1a-c: More specifically, Figure 1a shows a plan view of the porous surface of the anodized surface, Figure 1b shows a cross-sectional view of the cracked and defective anodized coating after plasma exposure, and Figure 1c shows arcing marks on the curved anodized surface after plasma exposure.

[0005] In light of the above, a number of alternative processing techniques and materials have been developed. For example, plasma electrolytic oxidation (PEO) coatings have been used in some RPS applications for some time. Unlike anodization, the partially crystallized aluminum oxide in the PEO coating provides more robust corrosion resistance (at least 2 to 3 times longer life than HA) in NF3 plasma and other chemicals. In addition, the denser, less porous structure formed by the PEO process results in a coating with approximately 1.5 to 2 times higher dielectric strength than the HA process. Unfortunately, there are also drawbacks to the PEO process. For example, the high voltage / energy required during the film growth process breaks through the oxide layer and creates open channels in the base alloy. In addition, trace metals in the base alloy may migrate to the surface over time during the process. As the PEO coating process continues until the desired thickness is reached, these trace metals may oxidize and solidify after cooling down. As a result, it has been found that a number of factors, including the mobility of the trace metals, result in a very non-uniform distribution of some metals (such as copper, iron, and manganese) in the PEO coating. This high metal concentration characteristic on the PEO surface may lead to potential metal contamination downstream of the RPS after exposure to plasma.

[0006] In some applications, hydrogen may be used to form the plasma. In applications involving hydrogen-related plasmas (such as H2 and NH3), PEO-coated RPSs may have significantly lower power output (~40 to 50% lower) than HA-coated RPSs. In addition to the increased surface recombination rate of the PEO coating, a number of factors may cause the reduced power output of PEO-coated RPSs, including the increased surface area of ​​the PEO coating. As mentioned above, the PEO coating process may continuously bring metals to the top surface of the coating, which may then be oxidized and solidified. When the process is complete, a nodular structure may form on the top surface. The layer thickness of the nodular structure may range from about 0.25 μm to 35 μm, with a total thickness of up to 50 μm. The total surface area is approximately 3 to 4 times larger than HA. Thus, the increased surface area may significantly increase the probability of radical absorption, which leads to a high recombination rate. In addition, the increased metal concentration and relatively lower hydroxide content (which is known to have a lower H recombination rate than oxides) on the PEO surface may also contribute to the higher recombination rate.

[0007] In view of the above, there continues to be a need for a coating for the plasma-facing surface of an RPS that possesses the advantages of both HA and PEO coatings while avoiding their disadvantages. Summary of the Invention

[0008] overview The present application discloses various embodiments and methods for providing solutions to the targeted technical needs set forth above, as will become apparent from the following description.

[0009] In one embodiment, the present application discloses a method of coating a plasma channel of a plasma source, comprising providing at least one electrolyte solution having one or more chelating agents therein, treating at least one surface of the plasma channel to produce a treated surface, smoothing the surface of the treated surface by at least one post-treatment technique to produce at least one smoothed treated surface, and cleaning the smoothed surface. The surface may be a surface facing the plasma of the plasma source. Treating the surface to produce a treated surface comprises treating at least one surface with a plasma electrolytic oxidation process. Alternatively, treating the surface produces a plasma electrolytic oxidation treated surface. The post-treatment technique comprises a dry bead blasting process, the dry bead blasting process utilizing high purity aluminum oxide as a blasting medium. The post-treatment technique may be performed at a pressure of about 10 psi to about 200 psi and a blasting angle of about 15 degrees to about 90 degrees. The post-treatment technique is configured to remove about 0.25 μm to about 35 μm layers of the surface and reduce the surface roughness and surface area by 30 to 50% of its original size. The post-treatment technique includes a vapor blasting process. The vapor blasting uses pressurized water with at least one abrasive media to finish the surface. Cleaning includes applying clean high frequency ultrasonic energy for an extended period of time to remove small size particles and embedded process residues from the surface.

[0010] According to another embodiment, the present application discloses a coating for use in a remote plasma source application. [Brief description of the drawings]

[0011] Brief explanation of the figure The above and other aspects, features, and advantages of the coatings used in remote plasma source applications and methods of making same disclosed herein will become more apparent from the following description thereof, taken in conjunction with the following drawings.

[0012] [Figure 1a-1c] 1a-1c show the deleterious effect of hard anodizing on the surface of an anodized layer.

[0013] [Figure 2a-2b] 2a-b show 3D images of a standard PEO surface in plan view and a post-treated PEO surface in plan view, respectively.

[0014] [Diagram 3] FIG. 3 shows the test results for metal levels collected on downstream wafers.

[0015] [Figure 4] FIG. 4 presents the experimental data.

[0016] [Diagram 5] FIG. 5 shows a flow chart of a method for coating a plasma channel of a plasma source. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Detailed Description In the following, exemplary embodiments of a method for coating a plasma channel of a plasma source and a coating for use in a remote plasma source application are described with reference to the accompanying drawings, in which, unless expressly stated to be so, the sizes, positions, etc. of components, features, elements, etc. as well as distances therebetween are not necessarily to scale and may be disproportionate and / or exaggerated for clarity.

[0018] The terms used herein are for the purpose of describing particular exemplary embodiments only and are not intended to be limiting. As used herein, the singular form is also intended to include the plural form unless the context clearly indicates otherwise. It should be understood that the terms "comprises" and / or "comprising", as used herein, specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Unless otherwise specified, when a range of values ​​is listed, the range includes both the upper and lower limits of the range as well as any subranges therebetween. Unless otherwise indicated, the terms "first", "second", etc. are used only to distinguish each element from one another.

[0019] Unless otherwise indicated, terms such as "about," "approximately," and the like mean that amounts, sizes, compositions, parameters, and other quantities and characteristics are not, and need not be, exact, but may be approximated and / or larger or smaller, as appropriate, to reflect tolerances, conversion factors, rounding, measurement error, and the like, as well as other factors known to those of ordinary skill in the art.

[0020] Many of the embodiments described in the following description share common components, devices, and / or elements. Similarly named components and elements refer consistently to similarly named elements. Thus, identical or similarly named components or features may be described with reference to other drawings even if not mentioned or described in the corresponding drawing. Also, even elements not labeled with a reference number may be described with reference to other drawings.

[0021] Many different forms and embodiments are possible without departing from the spirit and scope of this disclosure, and therefore this disclosure should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will convey the scope of the disclosure to those skilled in the art.

[0022] This application discloses various coatings for use with remote plasma sources, and methods of applying coatings to surfaces of remote plasma sources, and related devices. In one embodiment, the coatings may be applied to plasma-facing surfaces of remote plasma sources and related devices, although one skilled in the art will understand that the coatings may be applied to any surface. Furthermore, one skilled in the art will understand that a variety of materials may be applied using the methods described herein. For example, there are two potential metal sources that may directly contribute to metal concentrations in the coating. More specifically, as discussed above with respect to PEO coatings, contamination may come from trace metals from the Al6061 base alloy, and also from the coating environment (e.g., corroded electrodes). Thus, among other things, this application is directed to finding a solution to prevent metal oxides from forming on surfaces.

[0023] Chelating agents are compounds that bind with metal ions to form stable, water-soluble metal complexes that prevent undesired precipitation, dissolve scale deposits, and optimize the oxidation process. Different areas can use these materials, such as medical, corrosion control, and water treatment. An approach to provide more desirable coatings for plasma-facing surfaces of RPS and related systems involves the use of one or more chelating agents to control and reduce metal levels in the PEO coating. More specifically, a selected chelating agent is added to the electrolyte prior to coating. During the PEO coating process, the chelating agent binds with undesired metal ions (either from the base alloy or the corroded electrode) near the surface area in the electrolyte, preventing the formation of metal oxides in the coating. The metal complexes formed remain in the electrolyte and reduce or prevent the metal from returning to the coating.

[0024] Various types of chelating agents or materials can be used. The selection of the appropriate chelating agent material requires consideration of different factors such as the type of ions to be removed, the strength of the metal complex formed, the pH value of the electrolyte, and the possible effect on the coating regime and quality. Furthermore, the electrical regime may be adjusted to maintain the coating quality.

[0025] In one embodiment, the PEO coated surface is post-treated to enhance the performance of the RPS. Various types of post-treatment processes designed to smooth the rough surface of the PEO coating, such as dry bead blasting process, can be used. For example, high purity aluminum oxide (e.g. high purity AlO (i.e., over 90%)) may be used as the blasting media. The pressure, blast angle, and treatment time may be optimized to obtain the desired surface flatness. Typically, the blasting media contains 400 mesh particulates with particle sizes of ∼20 to 40 μm and large shapes with sharp edges. These transfers are performed by spraying through a nozzle using pressurized air.

[0026] In one embodiment, post-treatment is performed at a pressure and blast angle (about 10 psi to about 200 psi at an angle of about 15 degrees to about 90 degrees), although one skilled in the art will understand that a wide variety of pressures, blast angles, and treatment times can be used to remove any amount of material from the coated surface.

[0027] In one embodiment, the post-treatment pressure, blast angle, and treatment time were optimized to remove a layer of coating from about 0.25 μm to about 35 μm thick and reduce the surface roughness and surface area by 30 to 50% or more from the original. Optimization was done by treating many separate samples with different angles, pressures, treatment times, and media types. Microscopy was then used to measure the resulting surface area and roughness and select the best condition.

[0028] The surface produced by the above-mentioned post-treatment enhances the surface produced by the PEO process, resulting in a surface with a roughness similar to that obtained from a standard PEO-treated surface. Therefore, the advanced bead blasting process described herein can also be directly adapted and applied to the chelating agent-enhanced PEO-treated surface to achieve the same finish on the surface. Figures 2a and 2b show 3D images of a standard PEO surface, with the insets being the top view and the 3D image of a post-treated PEO surface. The insets are the top views, respectively.

[0029] Alternatively, in other embodiments, vapor blasting may be used in place of dry bead blasting. Unlike dry bead blasting, vapor blasting uses pressurized water along with at least one abrasive media to finish the surface. Additionally, vapor blasting is a substantially dust-free process, resulting in less residue embedded in the finished surface and a smoother surface than a dry bead blasted surface.

[0030] Optionally, an optimized post-cleaning process may be used to further treat the coated surface after the bead blasting step. More specifically, the additional cleaning process includes applying longer duration, higher frequency ultrasonic energy cleaning to remove small size particles and embedded process residues. Ultrasonic and megasonic cleaning use sound waves passing through the liquid, causing cycles of compression and rarefaction. During rarefaction, cavities form in the liquid, generating vapor-filled bubbles. The bubbles continue to grow and eventually collapse, creating localized heat and energy. The forces generated by these small internal breaks physically remove embedded particles and contaminants. Ultrasonic cleaning advantageously dissolves and displaces particles quickly and completely. Typical frequency ranges for ultrasonic cleaning are between 25 and 270 kHz, while frequencies for megasonic cleaning range from 360 kHz to over 2 MHz. The present invention contemplates the use of frequencies above 100 kHz for precision cleaning. According to an embodiment of the present invention, a frequency of 120 kHz is used. Higher frequency cleaning (such as megasonic cleaning) is particularly useful for removing sub-micron particles from flat surfaces. In this frequency range, the fluid motion provides more stable cavitation without internal collapse, which can cause less damage to the substrate. In one embodiment, the surface may be post-treated using ultrasonic cleaning followed by dry blasting.

[0031] The above described process offers several advantages over prior art methods and coatings. More specifically, the bead blasting and post-treatment bead blasting ultrasonic cleaning of the post-treatment PEO process combined with the chelating agent enhanced PEO process results in: (1) Coating Cleanliness (low metal contamination) - The coating inside the RPS applicator is part of the material that faces the plasma. Some level of erosion and surface reaction is expected after exposure to plasma. Metal concentration in the coating can directly affect the metal contamination level at the RPS exit. Therefore, the (source) must be improved most directly to reduce the metal level in the coating. The test results in Figure 3 show that most of the metal levels collected on the downstream wafer were significantly reduced. In semiconductor manufacturing processes, metal contamination can very seriously damage the wafer. A cleaner coating applicator is needed to increase the chances that the RPS will be applied to the process on the wafer. (2) Lower recombination rate / higher radical output - Previous tests have shown that standard PEO coatings have much lower (less than half) radical output in hydrogen and NH3 plasma than HA coatings. This may be due to the higher radical recombination rate on the PEO surface. The larger surface area with nodular structure was identified as the potential root cause. The implementation of proper post-treatment and cleaning processes significantly improved the surface finish and cleanliness. Experimental data (see Figure 4, where PED refers to the calorimetric output of RPS with PEO, NC-1 and NC-2 refer to the new coatings, and HA refers to the coatings in H2 (top) and NH3 (bottom) plasmas) confirm that these treated coatings perform comparable (or better) to PEO and HA in hydrogen-based plasma. This improvement in radical output further enhances the opportunities of RPS in applications that are particularly demanding for hydrogen-based plasmas, such as etching and deposition processes. (3) Compared with HA and standard PEO coatings, the coatings and methods described herein have the advantages of standard PEO coatings, such as high erosion resistance and dielectric strength, along with further significant improvements in metal levels and reduced surface recombination rates. The RPS process described herein is expected to be applied to more semi-finished processes beyond chamber cleaning with superior performance.

[0032] Additionally, various other processing steps may be added to the methods described herein or may replace one or more of the steps described herein. For example, extrusion honing may be used for the finish and interior surfaces. More specifically, in one embodiment, a chemically inert, non-corrosive media may be flowed over the workpiece. Abrasive particles in the media may be used to wear away undesirable material to reach the desired finish.

[0033] Optionally, atomic layer deposition (ALD) may be used to provide a conformal coating on the surface of the RPS and may be configured to provide a layer of a selected coating for a desired purpose. For example, ALD coatings of aluminum oxide, aluminum nitride, or silicon oxide may be less susceptible to reaction with chlorine or hydrogen radicals.

[0034] According to other embodiments, the ALD processing is performed after bead blasting the surface, although one of ordinary skill in the art will understand that an ALD coating may be applied to the RPS at any time.

[0035] According to further embodiments, other deposition methods such as CVD and PVD may be used instead of ALD, either alone or in combination.

[0036] FIG. 5 illustrates a schematic representation of the method of the invention according to one of its embodiments.

[0037] Specifically, Figure 5 illustrates a method 400 for coating a surface of a plasma source. As shown, the method 400 includes a step 402 of providing at least one electrolyte having one or more chelating agents therein, a further step 404 of treating the at least one surface to produce a treated surface, a further step 406 of smoothing a face of the treated surface with at least one post-treatment technique to produce at least one smoothed treated surface, and a further step 408 of cleaning the smoothed surface.

[0038] The surface may be a surface facing the plasma of a plasma source. Treating the surface to produce a treated surface step 404 includes treating the at least one surface with a plasma electrolytic oxidation process. Treating the at least one surface produces a plasma electrolytic oxidation treated surface. The post-treatment technique includes a dry bead blasting process, which uses high purity aluminum oxide as a blasting medium.

[0039] The post-treatment technique may be performed at a pressure of about 10 psi to about 200 psi, and a blasting angle of about 15 degrees to about 90 degrees. In one embodiment, the post-treatment technique is configured to remove about a 0.25 μm to about 35 μm layer of the surface, reducing the surface roughness and surface area by 30 to 50% of its original size.

[0040] Optionally, the post-treatment technique may include a vapor blasting process, which uses pressurized water with at least one abrasive media to finish the surface. The cleaning step 408 includes applying clean high frequency ultrasonic energy for an extended period of time to remove small size particles and embedded process residues from the surface.

[0041] The embodiments disclosed herein are illustrative of the principles of the invention. Other modifications may be made within the scope of the invention. Thus, the devices disclosed in this application are not limited to the exact ones shown and described herein.

Claims

1. 1. A method for coating a plasma channel of a plasma source, comprising: providing at least one electrolyte solution having one or more chelating agents therein; treating at least one surface of the plasma channel to produce a treated surface; smoothing the surface of the treated surface with at least one post-treatment technique to produce at least one smoothed treated surface; Cleaning the smoothed surface A method comprising:

2. The method of claim 1 , wherein the surface is a plasma-facing surface of a plasma source.

3. The method of claim 1 , wherein treating at least one surface of the plasma channel to produce a treated surface comprises treating the at least one surface with a plasma electrolytic oxidation process.

4. The method of claim 1 , wherein the treatment produces a plasma electrolytic oxidation treated surface.

5. The method of claim 1 , wherein the at least one post-processing technique comprises a dry bead blasting process.

6. 6. The method of claim 5, wherein the dry bead blasting process utilizes high purity aluminum oxide as a blasting media.

7. 10. The method of claim 1, wherein the at least one post-treatment procedure is performed at a pressure of about 10 psi to about 200 psi and a blasting angle of about 15 degrees to about 90 degrees.

8. 10. The method of claim 1, wherein the at least one post-processing technique is configured to remove a layer of about 0.25 μm to about 35 μm of the surface, reducing the surface roughness and surface area by 30 to 50% of its original size.

9. The method of claim 1 , wherein the at least one post-treatment technique comprises a vapor blasting process.

10. 10. The method of claim 9, wherein the vapor blasting process uses pressurized water with at least one abrasive media to finish the surface.

11. 10. The method of claim 1, wherein said cleaning comprises applying clean high frequency ultrasonic energy for an extended period of time to remove small size particles and embedded process residues from said surface.

12. 1. A coating for use in a remote plasma source application, comprising: a surface, the surface comprising: providing at least one electrolyte solution having one or more chelating agents therein; treating at least one surface to produce a treated surface; smoothing the surface of the treated surface with at least one post-treatment technique to produce at least one smoothed treated surface; Cleaning the smoothed surface This is obtained by coating.

13. The coating of claim 12 , wherein the surface is a surface facing the plasma of a plasma source.

14. 13. The coating of claim 12, wherein the surface comprises a plasma electrolytic oxidation treated surface.

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