THIN FILM COATING PLANTS

Transcription

1 P&P Thin Film Advanced Technologies THIN FILM COATING PLANTS Coating plants parts and technologies

2 PVD COATING TECHNOLOGIES SUMMARY INTRODUCTION VACUUM COATING SYSTEM VACUUM SYSTEM DEPOSITION CHAMBER, FRAMES AND ACCESSORIES GAS SUPPLY CONTROL SYSTEM TECNOLOGY CATHODIC ARC TECHNOLOGY SPUTTERING PLASMA BEAM SOURCE - PBS... 14

3 INTRODUCTION PVD acronym stands for Physical Vapor Deposition which indicates a technology used to evaporate solid metal, inside a vacuum chamber, usually in plasma environment. Due to kinetic energy and a potential difference, ions move towards the product s surface where they condense combine with process gas creating the desired coating. PVD coating plant can be divided in 4 areas: Vacuum system Deposition chamber, frames and accessories Gas system Control system Follow a short description of each parts. 1. VACUUM COATING SYSTEM Picture 1: PVD coating plant

4 1.1 VACUUM SYSTEM Vacuum is made by a combination pumps. Typically there are 2 different steps: A) Low-Medium vacuum to achieve 10-2 mbar (mechanical pumps) B) High vacuum to achieve 10-5 mbar (diffusion pumps, turbomolecular pumps, cryogenic pumps) In some case, it is possible to add cryogenic traps. Pumps number depends on chamber volume. LOW-MEDIUM VACUUM 10-2 mbar vacuum is reached with 2 different pumps: ROTATIVE PUMPS (Picture 2): gas enters in the first chamber (a), compressed in the second (b) and, then, expelled through a valve (c). Rotative pumps have oil to guarantee perfect airtight. Picture 2: Rotative pumps. ROOTS PUMS (Picture 3): Inside the chamber synchronous oval lobs rotate with opposite direction. Oval lobs does not have any contact between each other and with the chamber wall (1 mm tolerance). Picture 3: Roots pump.

5 HIGH VACUUM 10-5 mbar vacuum is reached with 2 different pumps: TURBO MOLECULAR PUMPS (Picture 4): Turbo molecular pumps is divided in different disc, in which there are many fins inclined with opposite direction. Thanks to high rotation speed and different inclination, fins move air molecular in below disc until they are eliminated. With this system it is possible to achieve a pressure about mbar. Picture 4: Turbo molecular system DIFFUSION PUMP (Picture 5): Oil, heated in the bottom (1), goes up inside the pump (2). Oil, streaming from the nozzles (3), capture gas molecules in the bottom where they are eliminated. Coiling system (4) is necessary to avoid oil contamination inside the camber. With this system it is possible to achieve a pressure about 10-8 mbar.

6 Picture 5: Diffusion pump system 1.2 DEPOSITION CHAMBER, FRAMES AND ACCESSORIES

7 DEPOSITION CHAMBER Deposition chamber is the metallic structure where samples are coated. There are many configuration depending on different needs. Follow most common deposition chamber: DIRECT LOAD SYSTEM o BATCH-TYPE SYSTEM: the chamber is opened to load /unload samples Picture 6: "Direct" configuration chamber IN-LINE SYSTEM: Different chambers are connected. This configuration is suggested with high productivity level. Picture 7: "In-line" chamber configuration FRAMES Frames are the structures where products are loaded inside the chamber. A right frames configuration in necessary to achieve a uniform coating and optimized productivity. Frames are fix or they move around the chamber. Inside the chamber they are fixed on a turntable located on the bottom or on the chamber top.

8 Frames configuration depend on different applications, soma example: SINGLE PALLET: For sheet deposition (in line system) Picture 8: Single pallet HORIZONTAL o VERTICAL DRUM: samples are loaded on external frame surface and it turns in front of sources. Picture 9: Horizontal o vertical drum HORIZONTAL OR VERTICAL 2-AXIS DRUM: Three-dimensional and uniform coatings. Picture 10: Horizontal or vertical 2-axis drum

9 OTHER ACCESSORIES Coating system is divided in different parts. Two important components are heating system and cooling system. HEATING SYSTEM: At the process beginning, heating is made by resistances (central or on the chamber walls) or in soma case by gas ions bombarding. COOLING SYSTEM: Chamber deposition, sources, pumps and other parts are connected to the cooling system to guarantee right operation. 1.3 GAS SUPPLY Different process phases need gas supply with different aim: 1) During vacuum phase gas supply stabilize pressure inside chamber; 2) For Sputtering technology, gas supply produces ions necessary for target bombarding; 3) During coating phase, gas supply is required for reactive color (a chemical reaction generates a compound) Generally the most common gases are Argon, Acetylene, Methane, Oxygen and Nitrogen. The gas quantity is important to create different coatings. Picture 11: Gas supply system Above picture represents general gas supply system inside a chamber deposition.

10 Gas supply, with a pressure about 2 bar, is guarantees and controls by MASS CONTROL to regulate quantity. FLOW 1.4 CONTROL SYSTEM During coating process there are many parameters. The most important are: 1) TEMPERATURE: It is possible to use a thermocouple or an infrared system. Process temperature depend on different based material and application ( C in decorative applications, C in technical applications). 2) PRESSURE: Vacuum gauges measure low-medium vacuum and high vacuum. 3) GAS SUPPLY: Different gas mass flows control gas quantity. 4) BIAS: It is the potential difference between substrate and chamber deposition. 5) METALS EVAPORATION A user-friendly and completely automatic system controls all parameters. Each coating process is define with different Recipe with defined parameters (temperature, pressure, gas supply, BIAS, etc.). A data base memorizes all process parameters in order to facilitate innovation and quality control. Picture 12: System / operator interface

11 2. TECNOLOGY PVD acronym stands for Physical Vapor Deposition which indicates a technology used to evaporate solid metal, inside a vacuum chamber, usually in plasma environment. Most common technologies are: - CATHODIC ARC: an electric arc, randomly ranging on the metal surface, melts the metal promoting its sublimation - MAGNETRON SPUTTERING: accelerated ions (plasma) impact on the solid metal causing its evaporation by mechanical removal. - PLASMA BEAM SOURCE PBS: Source dedicated PECVD system Depend on different costumer needs it is possible to plan and realized personalized hybrid equipment with all technologies. 2.1 CATHODIC ARC TECHNOLOGY Cathodic arc has different configuration inside deposition chamber: - RANDOM ARC SOURCES: typically random arc sources are circular, located in a positive protection. The erosion is controlled by a magnetic field.

12 Picture 13: Random arc source Above picture shows the Random Arc Source operation. A trigger stars to evaporate Cathodic arc (negative charge). Due to positive charge of target protection, negative ions move to target protection, while positive ions (metals) are attracted on the product surface (negative charge). - STEERED ARC SOURCES: erosion path is defined by a magnetic field inside the target. Generally Steered arc sources are rectangular or circular with an inside trigger.

13 2.2 SPUTTERING Often PVD and Sputtering words are used incorrectly. Some people thinks that PVD and Sputtering are two different coatings. Magnetron Sputtering is a technology used to evaporate solid metals necessary to coat. Thus there is no real difference between PVD coating and Sputtering coating, but only the PVD coating could be made through Sputtering technique. There are many Magnetron Sputtering configuration: - MAGNETRON SPUTTERING - BALANCED MAGNETRON SPUTTERING - DUAL MAGNETRON SPUTTERING - DUAL PULSED MAGNETRON SPUTTERING - UNBALANCED MAGNETRON SPUTTERING - RF SPUTTERING, - HPPMS etc. It is possible to use pure metal sources or alloy sources. MAGNETRON SPUTTERING To increase ions efficiency, it is possible to use a magnetic field. Magnetron Sputtering sources have different configurations: - PLANAR MAGNETRON: It is the most common configuration is Planar. Picture 14: Planar Magnetron - CYLINDRICAL MAGNETRON: For high plasma density, good control. Source erosion is uniform. Picture 15: Cylindrical Magnetron

14 2.3 PLASMA BEAM SOURCE - PBS Plasma Beam Source is used for PECVD coatings. Thanks to this technology it is possible to create a denser and more energetic plasma to obtain high quality coatings. Picture 16: Plasma Beam source PBS source is used in Hybrid PVD-PECVD system. One of the most common coating is the DLC family (Diamon Like Carbon). DLC is an innovative Carbon coating with high sp3 bonds (diamond). It is used in different application where it is required high abrasion resistance, high surface hardness, low wear coefficient, perfect characteristics in aggressive ambient. Picture 17: DLC coating on Robertson diagram REFERENCES: - HANDBOOK OF PHYSICAL VAPOR DEPOSITION (PVD) PROCESSING. Film Formation, Adhesion, Surface Preparation and Contamination Control, 1998, Donald M. Mattox,USA - Material Science and Engineering, R 37 (2002) , Diamond like amorphous carbon, J. Robertson.

15 P&P Via Benaco 88, Bedizzole, Italy Tel info-pholding.com