Supply vacuum vapor deposition furnace
1. Equipment composition and features
True air phase deposition furnace is mainly composed of high temperature vacuum furnace, vacuum system, electronic control system, air supply system, scraper and cleaning device and exhaust gas treatment device. The sedimentary components are placed in the sedimentation furnace, which are crucible, nozzle, mixing chamber, sedimentation chamber and discharge box from bottom to top.
1.1 high temperature vacuum furnace
Vacuum furnace is square, vertical, front and rear door structure, mainly by the furnace shell, front and rear door, heater, heat shield, workpiece support, electrode interface, air interface and thermocouple interface. In this equipment, the vacuum furnace shell is the key equipment in this system. The size is large. The effective size of the furnace body is 2050 mm(length) 2050 mm(width) 4200 mm(height). As the equipment is an internal heating resistance furnace, so the furnace shell is a double-layer water-cooled jacket structure, the inner wall material is stainless steel, the outer wall is carbon steel. For the traditional vacuum vessels, the circular furnace shell is widely used, with good vacuum pumping stability and high pressure bearing. Square to open the door before and after the furnace shell structure, however, in the structure of QianHouMen place is empty, by special vacuum when two side wall pressure, cause a large wall deformation, before and after the flange is not level off, the stability is poor, so you have to optimize the furnace shell welding structure design, the strength calculation, found that many times on the inner wall of the furnace shell stiffened plates directly welding well glyph, in vacuum, furnace shell deformation, and in the middle of the two side wall position of stiffened plate should be high enough, after the completion of welding glyph stiffened plate in well glyph frame welding jacket again, this kind of structure form can guarantee the minimal square in the vacuum furnace shell deformation, high strength, good stability.
Heat insulation screen set up inside the furnace shell, as a result of H2S gas can produce corrosive to metal, so can't in setting metal furnace heat insulation screen, through the experiment found that carbon felt can be used in H2S atmosphere long-term stability, the equipment in the furnace shell with 50 mm thick carbon felt, carbon felt outside set stainless steel support plate, stainless steel support plate fixed on the inner wall of the furnace shell. Heater for squirrel cage type structure, a total of all sides, respectively arranged on the oven door and wall before and after, use the static pressure such as high strength graphite tube heater material, in the height direction will be divided into three regions, middle and upper heater respectively to heating of sedimentary chamber and unloading box, bottom heater to heat of crucible, mixing chamber, due to large size of crucible, in order to guarantee the crucible area temperature uniformity and furnace structure is compact, the bottom of the crucible side alone setting auxiliary heater.
According to process needs in production, need to open the QianHouMen to place crucible, mixing chamber, discharging, deposition, so before and after oven door need to often open, and the device to the top of the oven door reached nearly 5 m from ground, height is higher, rely on people to screw bolts or the handwheel oven door lock, the device adopts the cylinder pressure oven door lock structure, simple operation, and compression strength, sealed performance is good. Oven door and oven shell adopts a hinge structure, a single door weight is 3 t, in order to avoid the oven door hinge after using for a long time opening and closing is not flexible, adopted the way of electric oven door open, equipped with roller at the bottom of the oven door before and after the lateral, to better support oven door, open, close, lock is simple, flexible, safe and reliable. The temperature in the furnace is controlled by three K dividing thermocouples, which are respectively used to control the temperature in three heating temperature zones. One k-type thermocouple is arranged in the lower part, middle part and upper part respectively to detect the temperature overshoot in the temperature zone. In order to meet the customers' requirement of regularly testing the temperature uniformity of the high-temperature furnace, a temperature uniformity measuring port is set on the furnace body, and 9 k-dividing thermocouples are installed for temperature uniformity measurement.
1.2 vacuum system
The equipment is required to have a rapid vacuum pumping system and good vacuum retention performance. The working vacuum degree of the system is 1 Pa. Therefore, an RTO600 roots pump and two gl-70 slide valve pumps are used to vacuum the equipment. The vacuum valve is a pneumatic baffle valve, which will shut down automatically when the power is cut off suddenly to protect the system from damage. There are leak detection interfaces at all levels of pipelines to facilitate leak detection step by step. In order to avoid misoperation, the system is equipped with perfect safety interlock. Since the process of this system is to charge H2S gas into the furnace after vacuum extraction, the pressure of the whole deposition process should be controlled within the range of 5000 ~ 10000 Pa, and the whole deposition process should be carried out continuously for 13 ~ 20 days, so electric diaphragm valve is set in front of the slide valve pump and behind the lotz, so as to realize real-time automatic control of the pressure in the furnace. Vacuum system work process is as follows: vacuum to 1 Pa and then heated to a temperature requirements, to the furnace charge H2S, Ar, at this time to shut down roots pump, close the main valve, by-pass valve, according to the pressure inside the furnace automatic control two plunger pump, when the furnace pressure fall so fast, electronic control system automatically shut down two plunger pump one of them, then electric diaphragm valve began to automatic control of pressure in the furnace.
1.3 electrical control system
The equipment is equipped with industrial computer (upper computer) monitoring and management, programmable controller mainly for the logic and timing control of the equipment, intelligent temperature control meter furnace temperature control automatic control system, mainly composed of process control and temperature control.
The process control part is composed of programmable controller and relevant electrical components, composite vacuum gauge, pressure controller, etc., which can realize all manual or automatic control functions of vacuum system such as pumping and valve opening. The temperature control part of the furnace is composed of a closed loop through k-type armored thermocouple, intelligent temperature controller, voltage regulating power supply, etc., with PID self-tuning, adaptive stepless voltage regulation function, ensuring the stability, uniformity and repeatability of temperature control. Multiple process curves can be set and stored. Temperature can be controlled automatically or manually. The temperature control precision is within plus or minus 0.1 ℃, which can realize heating, heat preservation, cooling process requirement.
The automatic control system can simultaneously collect the process parameters, electrical parameters and operating information of equipment working conditions (vacuum pumping, heating, heat preservation), monitor and store the field data, display the temperature setting curve and thermocouple temperature curve in dynamic form, and display the process curve setting parameters in tabular form. The control program can be programmed according to the requirements of the equipment and process. The operator only needs a simple mouse, keyboard and touch screen to perform system function configuration, issue instructions to each part of the control level, and automatically generate process data reports. High degree of automation, flexible and convenient operation.