A PVD apparatus and process method integrating evaporation and sputtering functions

Abstract

The application discloses a PVD device and process method integrating evaporation and sputtering functions. The device creatively adopts a "vacuum sealed tunnel" architecture, linearly connecting multiple chambers such as etching, sputtering and evaporation, to ensure that the substrate is not exposed to the atmosphere throughout the process. The core includes a liftable dynamic sealing evaporation source module, which effectively solves the pollution problem of evaporation process on integrated equipment through the coordinated timing action of bellows connection, lifting mechanism and shielding plate. The device is equipped with a full-automatic control system, realizing one-key completion of complex processes. The application creates a process condition for replacing high-stress sputtering with low-stress evaporation through integration, which is particularly suitable for preparing high-performance solar cell back electrodes, and has the outstanding advantages of eliminating pollution, optimizing stress, improving yield and efficiency.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device manufacturing and thin film deposition technology, specifically relating to a composite physical vapor deposition (PVD) equipment and process method for preparing back electrodes of devices such as high-efficiency solar cells. Background Technology

[0002] The back electrode of high-efficiency solar cells (such as gallium arsenide cells) typically requires the fabrication of multilayer metal thin films (e.g., NiMo / Ag / NiMo / Cu structures) to achieve good ohmic contact, high conductivity, strong adhesion, and low stress. Currently, the industry mainly uses two PVD technologies: sputtering and evaporation.

[0003] Sputtering produces films with good adhesion and high density, but it typically exhibits significant intrinsic stress, especially for thicker Cu layers. This high stress can easily lead to warping or detachment from the substrate, affecting the yield of subsequent processes and device reliability. Vapor evaporation produces films with significantly lower stress than sputtered films, but its adhesion is relatively poor. Furthermore, the evaporated material (especially Cu) is prone to volatilization at high temperatures, contaminating the entire vacuum chamber and resulting in frequent equipment maintenance, increased particulate contamination, and impacting the cleanliness of other process steps (such as sputtering).

[0004] In existing technologies, sputtering and evaporation equipment are mostly independent, stand-alone devices. When sputtering and evaporation need to be performed sequentially on the same substrate, the substrate must be transferred between different devices. This transfer process inevitably exposes the substrate to the atmosphere, leading to: Oxidation at the interface of deposited films (especially the bottom layer) severely affects interlayer adhesion and electrical properties; Defects are introduced when the substrate surface is contaminated by particles and moisture in the air.

[0005] In addition, stand-alone equipment occupies a large area, has complex operating procedures, and incurs high overall investment and operating costs.

[0006] Therefore, there is an urgent need in this field for a device that can integrate sputtering and evaporation functions and continuously complete the deposition of multiple thin films in the same vacuum environment, so as to fundamentally solve problems such as interface contamination, film stress control, process stability and cost. Summary of the Invention

[0007] The primary objective of this invention is to overcome the deficiencies of the prior art and provide a highly integrated PVD device that can continuously and automatically complete composite thin film preparation processes, including etching and cleaning, sputtering deposition, and evaporation deposition, within a single vacuum system, completely eliminating atmospheric exposure between processes.

[0008] A further objective of this invention is to provide a process platform that can flexibly control film stress (especially by using low-stress evaporated Cu layers to replace high-stress sputtered Cu layers) through equipment integration and process optimization.

[0009] Another objective of this invention is to provide a composite PVD equipment and process method that is stable in operation, highly repeatable, and highly automated, so as to improve product yield and reduce production costs.

[0010] To achieve the above objectives, this invention proposes a systematic integrated solution. Its core innovation lies not in simple improvements to individual components, but in addressing the two major contradictions of "complex process contamination control" and "stable integration of multi-process automation," by proposing a complete set of innovative equipment architecture, subsystem design, and collaborative control methods. Specifically, this is reflected in the following four aspects: 1. Overall Equipment Architecture – “Vacuum-Sealed Tunnel” System This invention abandons the approach of simply piecing together independent devices, and creatively designs a linearly connected "vacuum-sealed tunnel" architecture. This architecture connects different functional process chambers (loading, etching, sputtering, evaporation, cooling, etc.) into a continuous whole through high-vacuum valves. The substrate travels through this "tunnel," moving from one process zone to the next, completely isolated from the atmosphere. This fundamental architectural innovation provides the physical basis for solving the problems of interface oxidation and cross-contamination.

[0011] 2. Design of Key Subsystems – Dynamically Sealed Evaporation Source To address the inherent contamination problem in evaporation processes within integrated equipment, this invention presents a liftable, dynamically sealed evaporation source module. Its inventiveness lies in: Dynamic sealing connection: The evaporation source is connected to the cavity through a bellows, allowing the evaporation source to move significantly in the vertical direction while ensuring a vacuum seal.

[0012] Lifting and Isolation Synergy: The system creatively combines the functions of a "lifting mechanism" and a "baffle plate," and sets a strict "lift-open-plating-close-lower" action sequence. In non-process states, the evaporation source descends and closes the baffle plate, physically separating it from the main process space, greatly reducing contamination of sensitive areas such as the sputtering chamber by the evaporation material.

[0013] Functional expansion: The lifting function is not only used for isolation, but also for online adjustment of the distance between the evaporation source and the substrate, becoming an active control method to optimize film thickness uniformity.

[0014] 3. Process Integration Concept – “Functional Substitution” and Stress Control This invention does not simply combine two processes; rather, it creates a new approach to process optimization through integration. The most typical example is its ability to address the industry challenge of high stress in sputtered Cu layers. This invention directly provides the feasibility of replacing (or partially replacing) high-stress sputtered Cu layers with low-stress vapor-deposited Cu layers under the same vacuum environment. This "functional substitution" approach, a process innovation that can only be conveniently and reliably implemented on this integrated equipment platform, directly solves the key performance bottlenecks in existing technologies.

[0015] 4. System Control Logic – Fully Automatic Cooperative Control To achieve stable and repetitive operation across multiple chambers and processes, this invention employs a centralized automatic control system (PLC + host computer). Its innovation lies in establishing event-driven control logic centered on substrate position and process status. The system precisely coordinates hundreds of actions, including valve opening and closing, drive start / stop, vacuum extraction, and process initiation / closing, ensuring: The correct establishment and maintenance of the vacuum gradient.

[0016] Precise positioning and synchronization of substrate transmission.

[0017] Critical components (such as the evaporation source) must operate strictly according to the safe operating sequence.

[0018] The entire complex process can be fully automated with a single click, minimizing human intervention and operational errors, and ensuring extremely high process repeatability and stability.

[0019] Compared with the prior art, the present invention has the following significant advantages: 1. Completely eliminate interface contamination: Based on the "vacuum-sealed tunnel" architecture, it realizes a truly complete process without atmospheric exposure, ensuring the cleanliness of the membrane interface and excellent electrical properties.

[0020] 2. Effective control of cross-contamination: The unique dynamic sealed evaporation source design limits evaporation contamination to a localized and controllable area, protecting the long-term cleanliness of sputtering and other process areas.

[0021] 3. Proactive optimization of film performance: It provides a direct solution to replace sputtered Cu layers with evaporated low-stress Cu layers, which helps improve device reliability and yield. The evaporation source lifting function provides a new dimension for optimizing film thickness uniformity.

[0022] 4. Achieve efficient and stable production: Highly automated control makes complex multilayer film processes simple and reliable, significantly improving production efficiency and product consistency, and reducing overall manufacturing costs.

[0023] 5. Compact and space-saving design: The integrated design significantly reduces the floor space required compared to using multiple independent devices. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall chamber layout of the PVD equipment that integrates evaporation and sputtering functions according to the present invention.

[0025] Figure 2 This is a top view of the evaporation source module layout inside the evaporation chamber.

[0026] Figure 3 This is a side cross-sectional view of the liftable, dynamically sealed evaporator module.

[0027] Figure 4 This is a schematic diagram of the evaporator chamber baffle mechanism.

[0028] Figure 5 This is a logic block diagram of the automatic control system of the device of the present invention. Detailed Implementation

[0029] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can fully understand and implement the present invention.

[0030] Equipment structure implementation: like Figure 1 As shown, the PVD equipment of this invention has a linear layout. The substrate enters from the loading chamber 1 at the far left. The loading chamber 1 has an independent evacuation system for initial vacuuming. Subsequently, the substrate is transported by a transmission system, passing sequentially through the buffer chamber 2, etching chamber 3, sputtering chamber 4, evaporation chamber 5, and finally reaching the cooling chamber 6. Each chamber is separated by a high-vacuum gate valve 7. The buffer chamber 2 is used for process buffering and vacuum transition. The etching chamber 3 is purged with gases such as Ar to generate plasma for cleaning the substrate surface. The sputtering chamber 4 is equipped with targets such as Ni, Mo, and Ag for depositing the bottom layer of the back electrode. The evaporation chamber 5 is one of the key components of this invention, and its internal structure is as follows: Figure 2 , Figure 3 As shown.

[0031] like Figure 3 As shown, the evaporator source module 8 is vacuum-sealed to the bottom plate of the evaporation chamber via a metal bellows. A lifting mechanism driven by a servo motor or cylinder is connected to the evaporator source, enabling the entire evaporator source to move vertically (stroke ±100mm). A baffle plate driven by pneumatic or electric power is located directly above the evaporator source. Figure 4 ). Figure 2 It shows that multiple (e.g., three) independent evaporation sources can be arranged side by side in the evaporation chamber to expand the process capacity or co-evaporate different materials.

[0032] Transmission system implementation: The drive system runs through the bottom of all chambers. It employs a magnetohydrodynamic sealed rotary feed method to introduce power into the vacuum chamber, driving a series of polyimide (PI) insulated drive wheels. These drive wheels are arranged at precise 250mm intervals and fitted with synchronous belts. The carrier plate rests on the synchronous belt, achieving smooth and precise linear transmission through friction. The PI material prevents arcing and is wear-resistant. This design ensures the substrate's positional accuracy and attitude stability as it traverses multiple chambers and valves.

[0033] Control system and process implementation (emphasizing collaboration and automation): like Figure 5 As shown, the PLC is the brain of the entire equipment. The host computer is used to edit and issue "process recipes," which contain the process parameters (such as power, time, and gas flow rate) for each chamber, as well as all the timing logic.

[0034] Taking a typical NiMo / Ag / Cu back electrode fabrication process as an example, the innovative synergistic work of the system is illustrated: Startup: The operator selects the "back electrode deposition" recipe on the host computer and starts the system. The system first automatically executes the pre-vacuuming process, and each pump starts in sequence.

[0035] Loading and Transfer: The substrate is placed into the loading chamber. After the PLC confirms that the vacuum level in the loading chamber is sufficient, it opens the valve between the loading chamber and the buffer chamber, controls the transmission system to send the substrate into the buffer chamber, and then closes the valve. This process is completed under vacuum.

[0036] Etching and Sputtering: The substrate is sequentially transferred to the etching chamber and then the sputtering chamber. Each chamber immediately closes its valves upon substrate entry, creating an independent process environment. The PLC controls gas injection, plasma ignition, and sputtering power output according to the formula to complete cleaning and NiMo / Ag layer deposition. All process gases and byproducts are confined within their respective chambers.

[0037] Evaporation (core feature: collaborative control): The substrate enters the evaporation chamber from the sputtering chamber. Once the PLC detects that the substrate has arrived, it immediately closes the evaporation chamber inlet valve.

[0038] Step 1 (Preparation): The PLC issues a command, the lifting mechanism starts, and smoothly raises the evaporator to the working height set in the recipe (e.g., 80mm). At the same time, the evaporator power supply begins to preheat.

[0039] Step 2 (Deposition): After the PLC confirms that the evaporation source is in place and the temperature meets the standard, it issues a command to open the shield. Then, the evaporation power supply is immediately started to deposit Cu. During this process, the evaporation source is in an elevated state, shortening the material transport distance and improving uniformity.

[0040] Step 3 (Isolation): After the deposition time is reached, the PLC first shuts off the evaporation power supply, then instructs the shielding plate to close, completely covering the still-hot evaporation material. After waiting a few seconds (adjustable) for the surface of the evaporation source to cool down initially, the PLC instructs the lifting mechanism to lower the evaporation source back to its original position. At this point, the evaporation source is "hidden" below the chamber and doubly isolated by the closed shielding plate, greatly reducing the continuous contamination of the chamber by heat radiation and material volatilization.

[0041] Cooling and Removal: The substrate enters the cooling chamber and is cooled naturally or by forced cooling. It is then transferred to the loading chamber or a dedicated removal port, and the entire process is kept under vacuum or protected by inert gas.

[0042] In step 4 of this invention, a series of precise and coordinated automated control actions are performed on the evaporation source. This control logic is deeply integrated with the equipment hardware (bellows, lifting mechanism, baffle plate) to form an intelligent closed loop for pollution prevention and process optimization, which cannot be achieved by discrete equipment or simply integrated equipment.

[0043] Through the above methods, this invention provides a complete, efficient and reliable integrated PVD equipment and process solution, which is particularly suitable for the preparation of solar cell back electrodes and other multilayer film devices with stringent requirements for interface quality, film stress and process stability.

Claims

1. A physical vapor deposition apparatus integrating evaporation and sputtering functions, characterized in that, include: A vacuum-sealed tunnel system consisting of multiple process chambers connected in series, wherein the chambers include at least a loading chamber, an etching chamber, a sputtering chamber, an evaporation chamber, and a cooling chamber connected in sequence, and adjacent chambers are connected by a high-vacuum isolation valve; A continuous, high-precision drive system running through all the process chambers is used to transport the substrate carrier within the vacuum-sealed tunnel system; A liftable, dynamically sealed evaporation source module is located inside the evaporation chamber. It is sealed to the bottom of the evaporation chamber via a bellows and is equipped with an openable and closable baffle. A vacuum system that provides and maintains the vacuum environment required for the process of the vacuum-sealed tunnel system; A centralized automatic control system is configured to coordinate and control the opening and closing of each valve of the vacuum-sealed tunnel system, the operation of the continuous high-precision transmission system, the lifting and shielding actions of the liftable dynamic sealing evaporation source module, the operation of the vacuum system, and the process parameters of each chamber, so that the substrate can automatically complete the composite process of etching, sputtering deposition of the first film layer, and evaporation deposition of the second film layer in sequence without breaking the vacuum.

2. The device according to claim 1, characterized in that, The lifting stroke of the liftable dynamic sealed evaporation source module is ±100mm, and the automatic control system is programmed to: before the evaporation process begins, control the evaporation source to rise to the working position and then open the baffle; after the evaporation process ends, first close the baffle and then control the evaporation source to descend to the non-working isolation position.

3. The device according to claim 1, characterized in that, The continuous high-precision transmission system consists of a magnetic fluid sealed drive shaft, an insulated drive wheel made of polyimide, and a synchronous belt sleeved on the drive wheel. The drive wheel is arranged at equal intervals of 250mm along the substrate transmission path.

4. The device according to claim 1, characterized in that, A buffer chamber is also provided between the sputtering chamber and the evaporation chamber for process isolation and vacuum gradient transition.

5. The device according to claim 1, characterized in that, The sputtering chamber is configured for depositing Ni, Mo, or Ag or their alloys, and the evaporation chamber is configured for depositing Cu films.

6. A liftable dynamic sealed evaporation source module for the device of claim 1, characterized in that, include: Evaporation source body; The sealing connection component is a metal bellows, with its upper end sealed to the bottom plate of the evaporation chamber and its lower end sealed to the top of the evaporation source body, forming a retractable vacuum sealing structure. A lifting drive mechanism, connected to the evaporation source body, is used to drive it to move up and down in a direction perpendicular to the substrate; A shielding mechanism is disposed above the evaporation source body and is used to cover the surface of the evaporation material in the non-evaporation state.

7. A method for fabricating a solar cell back electrode using the apparatus according to any one of claims 1 to 5, characterized in that, The method includes the following steps: The substrate is fed into the loading cavity; Under the control of the automatic control system, the substrate is sequentially transferred to the etching chamber for surface cleaning; The cleaned substrate is transferred to the sputtering cavity, where a NiMo / Ag composite layer is sputtered in a vacuum environment. The sputtered substrate is transferred to the evaporation chamber, where a Cu layer is deposited under vacuum. The vapor-deposited substrate is transferred to a cooling chamber to cool down before being removed. Throughout the entire process from the time the substrate enters the etching chamber to the time it is removed from the cooling chamber, the substrate remains in a vacuum or protective atmosphere maintained by the vacuum-sealed tunnel system, and the switching of each process step is automatically completed by the automatic control system.

8. The method according to claim 7, characterized in that, When forming a Cu layer by vapor deposition, the evaporation source is controlled to rise to a specific height from the substrate before vapor deposition is performed to optimize the uniformity of film thickness.

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