A target ingot base for use in a coating apparatus and a method of manufacturing the same

Abstract

This invention discloses a target substrate for use in coating equipment and its preparation method. The target substrate includes a base and a cylinder made of pure copper material, and the outer surface of the target substrate is provided with a tungsten layer or a molybdenum layer. This invention targets the placement of N-type or P-type oxide targets, forming a continuous and dense tungsten or molybdenum coating on the outer surface of the pure copper target substrate. While maintaining the high thermal and electrical conductivity of the target substrate, it significantly improves its surface resistance to ablation and sputtering contamination, solving the engineering pain points of existing pure copper substrates such as short lifespan, high particulate contamination, and frequent maintenance, and has significant promotional value.

Description

Technical Field

[0001] This invention relates to the field of vacuum coating and plasma deposition equipment technology, specifically to a target substrate for RPD (reactive plasma deposition) coating equipment and its preparation method. Background Technology

[0002] Reactive plasma deposition (RPD) processes typically involve introducing working and reactive gases into a vacuum chamber, relying on plasma discharge to sputter the target material, generate a reaction, and deposit a thin film onto the substrate. In actual production, to achieve high film deposition rates and film density, frequent ignition, shutdown, power modulation, and process switching are required. The target feeding system is one of the core components of the RPD equipment. The target feeding system includes the target base, lifting motor, and rotating table. The target base is usually made of pure copper or a high-conductivity copper alloy because copper has excellent thermal and electrical conductivity, facilitating rapid heat dissipation from the target area and the formation of a stable current loop. However, with increased process power and more complex reaction systems, pure copper bases exhibit a series of typical failures and quality problems. For example, the degree of base ablation is affected by process parameters, equipment status, and the matching degree between the target material and the target (base). Mild ablation results in surface oxidation, pitting, and micro-cracking defects, while severe ablation leads to localized melting, coating peeling, and even substrate damage. When the target surface is contaminated, has nodules, or poor flatness, or when the vacuum level or gas flow rate of the equipment fluctuates, the arc spot will drift from the target surface to the edge or surface of the target holder, forming an abnormal arc discharge. The target holder is instantly subjected to the high energy of the arc, directly causing surface erosion and burning pits. At the same time, the trace amounts of oxygen and water vapor remaining in the vacuum chamber will react with the high-temperature copper surface of the target holder to form an oxide layer, accompanied by slight ablation of the surface material. The peeling off of the oxide layer will further aggravate the subsequent abnormal arc initiation. After the target surface is ablated, a rough surface, nodules, or oxide layers will form. These defects will become new abnormal arc initiation points, forming a vicious cycle of "ablation → abnormal arc initiation → more severe ablation". At the same time, the debris generated by the ablation of the target holder will enter the vacuum chamber, contaminating the substrate and thin film, causing pinholes and particle defects in the deposited TCO film, which seriously affects the uniformity and photoelectric performance of the film. In other words, the "debris" generated by the continuous ablation of the substrate will seriously damage the uniformity and photoelectric performance of the film deposition.

[0003] During the RPD process, the atoms and nanoclusters generated by the high-energy plasma bombardment sputtering of the target, as well as the compounds generated by the gas phase reaction of these particles with the reactive gases (O2, Ar, etc.) in the vacuum chamber, will frequently collide with the process gas molecules in the chamber as they are directed to the substrate. Some particles change their trajectory due to the collisions or even undergo backscattering, forming backsplash. A large number of backsplashed particles will continue to be deposited on the upper surface of the target substrate, the bonding edge between the target and the substrate, and the exposed sidewalls.

[0004] Due to the combined effects of continuous plasma bombardment and low-energy deposition of backsplashed particles, the surface of a pure copper substrate is highly susceptible to forming a target redeposition layer (poor layer) with low density and weak adhesion. Under the repeated thermal cycling of the RPD process, long-term accumulation of interfacial stress, and high-energy impacts from localized abnormal micro-arc discharges, this porosity layer is prone to microcracks that gradually propagate, eventually leading to peeling and flaking, producing particles that fall into the film deposition area. These particles become heterogeneous nuclei for film growth, causing pinholes, breakdowns, and surface defects, particularly affecting optical films, rigid functional films, and precision device films. In other words, the backsplashing of the target material forms a porosity layer on the substrate surface, and the particles generated from the fragmentation of this porosity layer severely impact the quality of the deposited film.

[0005] The RPD target base uses a pure copper substrate with a high coefficient of thermal expansion of 16.5 × 10⁻⁻⁻⁶. 6 / ℃, which differs from the material of other structural components in the cavity (e.g., stainless steel 18×10⁻). 6 / ℃). During the cyclical thermal cycling process, the base heats up rapidly with the arc discharge of the target material, and cools down quickly through heat conduction. Repeated temperature changes cause continuous thermal stress accumulation inside the base. After long-term cycling, the plastic deformation characteristics of pure copper prevent the stress from being completely released, gradually leading to stress relaxation and micro-deformation of the base as a whole. This manifests as increased flatness deviation, misalignment of assembly holes, and slight warping of edges, disrupting the tight fit between the target material and the base.

[0006] Meanwhile, pure copper has a Brinell hardness of only 35-45 HB, making it relatively soft. During target assembly and disassembly, bolt tightening pressure, minor bumps during handling, or contact friction with the target and positioning components can easily create geometric defects such as indentations and scratches with a depth of 0.02-0.1 mm on the surface of the base. These micro-deformations and surface damage alter the electric field distribution in the base area, leading to localized electric field concentration and becoming weak points for charge accumulation. This can trigger abnormal discharges and localized micro-arcs, not only exacerbating ablation and composite layer peeling on the base surface but also affecting plasma stability and performance degradation. In other words, thermal cycling causes deformation and surface damage to the base, leading to ablation and composite layer peeling, which in turn affects plasma stability and performance degradation.

[0007] While existing pure copper target bases offer advantages in thermal and electrical conductivity, the aforementioned problems of ablation, contamination, and spalling shorten their service life and lead to frequent disassembly, cleaning, polishing, or replacement, resulting in downtime losses and increased spare parts costs. Therefore, there is an urgent need for an improved solution that balances thermal conductivity with surface resistance to ablation, arcing, and sputtering contamination. Summary of the Invention

[0008] This invention addresses the problems in RPD coating processes, where existing pure copper target substrates are prone to ablation, contamination, and peeling, shortening their service life and leading to frequent disassembly, cleaning, polishing, or replacement, resulting in downtime losses and increased spare parts costs. The invention provides a copper target substrate with a tungsten or molybdenum coating for use in RPD coating equipment, along with its preparation method. Specifically, for N-type or P-type oxide targets, a continuous and dense functional layer, such as a tungsten or molybdenum coating, is formed on the surface of the pure copper target substrate. This allows the target substrate to simultaneously possess the high thermal and electrical conductivity of copper and the high melting point, high hardness, arc erosion resistance, and sputtering resistance of tungsten or molybdenum.

[0009] To address the aforementioned problem, the present invention provides a target ingot base, comprising a base and a cylinder made of pure copper material, characterized in that the outer surface of the target ingot base is provided with a tungsten layer or a molybdenum layer.

[0010] Preferably, a diffusion barrier layer is provided between the target substrate surface and the tungsten layer to reduce copper migration to the surface and copper re-sputtering into the thin film by plasma.

[0011] Preferably, the outer surface of the molybdenum layer of the target ingot base is provided with an inert top layer to reduce electric field distortion and micro-arc triggering.

[0012] The present invention also provides a method for preparing a target ingot base, comprising the following steps: Step 1: Perform surface pretreatment on the pure copper target ingot base that meets the requirements; Step 2: Vacuum deposit a tungsten or molybdenum layer on the outer surface of the target substrate. The tungsten or molybdenum layer is a continuous dense layer with a thickness of 5 μm to 100 μm; Step 3: Perform low-temperature stress relief heat treatment on the target substrate after deposition in a vacuum atmosphere with a vacuum degree ≤1×10⁻³Pa. Step 4: After inspection, the product is put into storage.

[0013] Preferably, during the vacuum deposition process, ion beam-assisted deposition of the tungsten or molybdenum layer is employed; Preferably, a diffusion barrier layer is prepared between the target substrate and the tungsten layer using any one of Ta, Nb, TaN, NbN, TaC, or NbC.

[0014] Preferably, an inert top layer is prepared on the outer surface of the molybdenum layer of the target substrate using any one of Ru, Ir, or Pt.

[0015] Preferably, in step 1, high-purity copper or oxygen-free copper is selected as the target ingot base to maintain the geometric continuity of the target ingot base surface and the rounded corner area of ​​the edge, and to avoid sharp corners; the coating surface is subjected to alkaline degreasing, deoxidation, pure water rinsing and vacuum drying; and then micro-roughening treatment is performed.

[0016] Preferably, in step 2, magnetron sputtering deposition is used to control the deposition rate and energy input. During the deposition process, the target substrate is rotated to appropriately shield the rounded corner area of ​​the target substrate's edge, thus avoiding excessively thick edge coating.

[0017] Preferably, in step 3, the outer surface of the target base is lightly ground or polished to bring the surface roughness back to the set range, so as to avoid the appearance of particles or peaks on the outer surface.

[0018] To address the problems of surface ablation, sputtering backsplash contamination, deposit peeling, thermal cycling deformation, and frequent maintenance that commonly occur with target substrates under existing RPD conditions, this invention addresses the use of different N-type or P-type oxide targets. It forms a continuous and dense tungsten (W) or molybdenum (Mo) coating on the outer surface of a pure copper target substrate. This leverages the high thermal and electrical conductivity of copper, along with the high melting point, high hardness, sputter resistance, and chemical stability of tungsten or molybdenum, to reduce particulate contamination, improve discharge stability, and extend substrate life. Furthermore, an inert top layer (such as Ru, Ir, Pt, etc.) can be placed on the surface of the molybdenum coating on the target substrate, or a diffusion barrier layer (such as Ta, Nb; TaN, NbN, TaC, NbC) can be introduced at the Cu-W interface of the target substrate to reduce Cu contamination, suppress backsplash peeling, and improve surface electrical stability under oxidizing plasma conditions. The coating can be prepared by magnetron sputtering, ion beam assisted deposition or chemical vapor deposition. This method can be used for the modification and new fabrication of target substrates for RPD equipment, and has the advantages of process feasibility, cost control and high reliability. Attached Figure Description

[0019] Figure 1 A schematic diagram of the three-dimensional structure of the target ingot base; Figure 2 This is a schematic diagram of the coating on the surface of the target ingot base used for N-type oxide targets; Figure 3 This is a schematic diagram of the coating on the surface of the target ingot base used for P-type oxide targets.

[0020] Reference numerals: 1-base, 2-cylinder, 3-inner circle. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the following specific embodiments are only used to explain the invention and do not constitute a limitation thereof.

[0022] like Figure 1 As shown, this invention provides an embodiment of a target ingot base, comprising a base 1 made of pure copper and a cylinder 2. The outer surface of the target ingot base is coated with a tungsten layer or a molybdenum layer. An N-type oxide or P-type oxide target can be placed within the inner circle of the cylinder 2. When an N-type oxide target is placed in the target ingot base, a target ingot base coated with a tungsten layer is selected; when a P-type oxide target is placed in the target ingot base, a target ingot base coated with a molybdenum layer is selected. Please refer to... Figure 2 In another embodiment of the present invention, when an N-type oxide target is placed on the target substrate, a diffusion barrier layer can be formed between the target substrate surface and the tungsten layer to reduce copper migration to the surface and copper re-sputtering into the thin film by plasma. This diffusion barrier layer can be prepared using any one of Ta, Nb; TaN, NbN, TaC, or NbC. Please refer to [reference needed]. Figure 3 In another embodiment of the present invention, when a P-type oxide target is placed on the target substrate, an inert top layer that reduces electric field distortion and micro-arc triggering can be formed on the outer surface of the molybdenum layer of the target substrate. This inert top layer can be prepared using any one of Ru, Ir, or Pt.

[0023] The method for preparing the target substrate provided by the present invention is further illustrated below through examples: Example 1: Fabrication of a pure copper target ingot base suitable for N / P type oxide targets by magnetron sputtering Step 1: Perform surface pretreatment on the pure copper target base that meets the requirements. High-purity copper or oxygen-free copper is selected to make the substrate of the target ingot base in order to retain its advantages in thermal conduction and current loop, and to meet the requirements of thermal conductivity and vacuum compatibility. During machining, it is ensured that the flatness and dimensional accuracy of the outer surface of the substrate meet the assembly requirements, and the geometric continuity of the surface and the rounded corner areas is guaranteed to avoid electric field concentration caused by sharp corners.

[0024] Then, the surface to be plated is subjected to alkaline degreasing, deoxidation (weak acid or plasma cleaning), pure water rinsing and vacuum drying; subsequently, micro-roughening (e.g., sandblasting or chemical micro-etching) is performed to improve the adhesion between the coating and the target substrate surface.

[0025] Step 2: Deposit a tungsten or molybdenum layer by magnetron sputtering on the outer surface of the target substrate. Depending on the requirements, a coating can be deposited on the entire outer surface of the target ingot base or on the outer wall of its vertical cylinder to reduce edge electric field concentration and arc initiation risk. This embodiment chooses to deposit the coating on the entire outer surface of the target ingot base. The electrical characteristics and oxidation tendencies of the backsplashed deposited layers differ depending on the conductivity type of the oxide target: under N-type oxide conditions, backsplashed oxide clusters easily form localized high resistance on the metal surface, inducing charge accumulation and electric field concentration. Therefore, a tungsten coating is preferred for target ingot bases used to mount N-type oxide targets; under P-type oxide conditions, a thick, high-resistivity redeposited layer is usually more likely to form, leading to a higher risk of surface state drift and abnormal arc initiation. Therefore, a molybdenum coating is preferred for target ingot bases used to mount P-type oxide targets. The coating is a continuous, dense layer with a thickness of 5 μm to 100 μm, preferably 20 μm to 50 μm, to improve the bonding strength between the copper material and the coating and to mitigate thermal expansion mismatch.

[0026] The tungsten or molybdenum layers are deposited using magnetron sputtering (PVD), with a deposition rate controlled at 0.6-2 nm / s to achieve a dense structure, balancing resistance to arc erosion and thermal conductivity. During deposition, the target substrate can be rotated to improve coating uniformity; simultaneously, the rounded corner areas are appropriately masked / compensated to prevent excessive edge coating thickness, which could lead to stress concentration. Other vacuum deposition methods, such as CVD (chemical vapor deposition), can also be used as needed.

[0027] Step 3: Perform low-temperature stress relief heat treatment on the target substrate after deposition in a vacuum atmosphere with a vacuum degree ≤1×10⁻³Pa. After vacuum deposition, the target substrate undergoes a low-temperature, short-time stress-relieving heat treatment in a vacuum atmosphere (vacuum degree ≤ 1×10⁻³ Pa) to avoid rapid cooling and the generation of new thermal stress. If necessary, the outer surface can be lightly ground or polished to bring the surface roughness back to the set range, preventing the appearance of particles or peaks. This ensures the adhesion, density, and reliability of the coating during thermal cycling.

[0028] Step 4: After inspection, the goods are put into storage. The coating thickness of the target ingot base is measured, cross-sectional microscopic observation is performed, and adhesion is tested (e.g., scratches or pull-off). Thermal cycling and plasma bombardment simulation verification are carried out to confirm that there are no obvious peeling, cracking, or bulging phenomena before it is put into storage.

[0029] Example 2: Introduction of Ion Beam Assisted Deposition Based on Example 1, ion beam-assisted deposition was used simultaneously with coating the target substrate. That is, an ion beam was introduced during the deposition process to simultaneously bombard the growth surface of the coating, promoting the migration and densification of molybdenum or tungsten atoms and improving the bonding strength between the coating and the substrate.

[0030] In a high-vacuum environment, tungsten and molybdenum materials are vaporized into atoms via electron beam evaporation and deposited onto a substrate surface. Simultaneously, a low-energy argon ion beam generated by an independent ion source bombards the thin film growing on the substrate. This ion bombardment allows for better control of surface morphology and microstructure, resulting in high-density, low-stress, strong film-substrate adhesion, and a smooth surface—high-quality tungsten or molybdenum thin film layers. High corrosion resistance lifetimes can be achieved even with relatively thin thicknesses. The ion beam energy should be controlled within a range that does not significantly increase temperature or introduce excessive residual stress.

[0031] Example 3: Selective plating on the outer surface of the target substrate to reduce costs. like Figure 1 As shown, when retrofitting existing equipment, only the outer wall of the vertical cylinder 2 of the target ingot base can be plated, while the copper body surface of the base 1 remains intact. This solution strengthens the critical failure area on the original target ingot base, while reducing the plating area, shortening the deposition time, and lowering the overall cost.

[0032] Example 4: A reinforcing layer can also be introduced into the target ingot base for N-type / P-type oxide targets. For N / P type oxide targets, a diffusion barrier layer or an inert top layer can be further introduced based on the “Cu substrate / coating” examples 1-3 to adapt to different target systems and optimize the stability of the RPD process.

[0033] like Figure 2 As shown, a diffusion barrier layer is fabricated between the target substrate and the tungsten layer using any one of the following materials: Ta, Nb, TaN, NbN, TaC, or NbC. This diffusion barrier layer reduces the migration of Cu to the surface and the risk of copper being re-sputtered into the thin film by plasma, thereby improving the electrical and optical consistency of the transparent conductive oxide film.

[0034] like Figure 3 As shown, the target substrate for placing P-type oxides can have an ultrathin noble metal layer further deposited on the outer surface of its molybdenum layer. Specifically, an inert top layer can be prepared on the outer surface of the molybdenum layer of the target substrate using any of Ru, Ir, or Pt, serving as a stabilizing layer. This improves the surface chemical inertness and electrical stability under oxidizing plasma, reducing electric field distortion and micro-arc triggering caused by localized insulating regions. Both the diffusion barrier layer and the inert top layer are deposited using magnetron sputtering. Other deposition methods can also be used as needed, such as CVD-chemical vapor deposition; CVD deposition is also an option. Ion beam-assisted deposition can also be introduced, as described in Example 2.

[0035] For example, this embodiment provides the following material combination:

[0036] The tungsten or molybdenum coating used in this invention has a melting point much higher than that of the copper ingot base, significantly improving the ablation and arc erosion resistance of the ingot base. Even in the event of transient arc initiation, the coating can significantly reduce the amount of material removed from the ingot base by the arc point, suppressing the vicious cycle of "molten pit-bulge-re-arc initiation," reducing the probability of micro-arc discharge and the damage to the ingot base caused by arc energy, and improving discharge stability and process window tolerance. The dense coating has high hardness and strong sputtering resistance, making it less likely to form a source of spalling for loose redeposition layers; at the same time, it can reduce metal spalling caused by direct bombardment of copper, reducing the entry of particles into the deposition area. That is, it reduces the spalling of backsplashed deposits and particle contamination. This makes the surface state of the ingot base more stable. Compared with copper, tungsten / molybdenum has better surface stability in reaction atmospheres and plasma environments, which can reduce process fluctuations caused by copper escape; the hardness and wear resistance of the tungsten / molybdenum layer are significantly better than copper, which can effectively reduce scratches, indentations and wear on the assembly positioning surface. A stable target substrate surface condition extends service life and reduces maintenance costs: by reducing arc shutdowns, cleaning frequency, and polishing wear, spare parts costs and production line downtime losses can be significantly reduced. Under typical RPD conditions with a discharge voltage of 60–70 V, it significantly improves the continuous operation stability of the equipment and the life of the substrate, demonstrating significant engineering economics and making it suitable for retrofitting existing equipment with a low implementation threshold. Maintaining thermal conductivity advantages: This invention adopts a basic composite structure of "copper substrate + tungsten / molybdenum coating," where heat is still mainly rapidly dissipated by the copper substrate, meaning it has little impact on the overall thermal conductivity of the substrate; combined with more stable discharge and fewer hot spot defects, it can improve the consistency of target surface temperature control and enhance the consistency of film thickness and film quality.

[0037] This invention targets N-type or P-type oxide targets, forming a continuous and dense tungsten or molybdenum coating on the outer surface of a pure copper target substrate. While maintaining the high thermal and electrical conductivity of the target substrate, it significantly improves the surface's resistance to ablation and sputtering contamination, solving the engineering pain points of existing pure copper substrates such as short lifespan, high particulate contamination, and frequent maintenance. It has significant promotional value.

[0038] The above description is merely a specific embodiment of the present invention. It should be noted that any modifications, equivalent substitutions, and variations made within the spirit and framework of the present invention should be included within the protection scope of the present invention.

Claims

1. A target ingot base, comprising a base and a cylinder made of pure copper, characterized in that, The outer surface of the target base is provided with a tungsten layer or a molybdenum layer.

2. The target ingot base as described in claim 1, characterized in that, A diffusion barrier layer is provided between the surface of the target substrate and the tungsten layer to reduce copper migration to the surface and copper re-sputtering into the thin film by plasma.

3. The target ingot base as described in claim 1, characterized in that, The outer surface of the molybdenum layer of the target ingot base is provided with an inert top layer to reduce electric field distortion and micro-arc triggering.

4. A method for preparing a target substrate as described in any one of claims 1 to 3, comprising the following steps: Step 1: Perform surface pretreatment on the pure copper target ingot base that meets the requirements; Step 2: Vacuum deposit a tungsten layer or a molybdenum layer on the outer surface of the target substrate; Step 3, under vacuum In a vacuum atmosphere, the target substrate after deposition is subjected to low-temperature stress relief heat treatment; Step 4: After inspection, the product is put into storage.

5. The preparation method according to claim 4, characterized in that, During the vacuum deposition process, ion beam-assisted deposition of the tungsten or molybdenum layer is employed.

6. The preparation method according to claim 4 or 5, characterized in that, A diffusion barrier layer is prepared between the target ingot base and the tungsten layer using any one of the following materials: Ta, Nb; TaN, NbN, TaC, or NbC.

7. The preparation method according to claim 4 or 5, characterized in that, An inert top layer is prepared on the outer surface of the molybdenum layer of the target substrate using any one of Ru, Ir, or Pt.

8. The preparation method according to claim 4, characterized in that, In step 1, high-purity copper or oxygen-free copper is selected as the target ingot base to maintain the geometric continuity of the target ingot base surface and the rounded corner area of ​​the edge, and to avoid sharp corners; the coating surface is subjected to alkaline degreasing, deoxidation, pure water rinsing and vacuum drying; and then micro-roughening treatment is performed.

9. The preparation method according to claim 4, characterized in that, In step 2, magnetron sputtering deposition is used to control the deposition rate. During the deposition process, the target substrate is rotated to appropriately shield the rounded corners of the target substrate's edges, thus preventing the edge coating from becoming too thick.

10. The preparation method according to claim 4, characterized in that, In step 3, the outer surface of the target base is lightly ground or polished to bring the surface roughness back to the set range and avoid the appearance of particles or peaks on the outer surface.

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