In order to ensure the normal operation of CVD equipment for a long time, in addition to requiring the operator to operate and use the equipment correctly, taking some effective methods to maintain the equipment is the key to protect the normal operation of CVD equipment. Therefore, the following measures can be taken:
(l) Keep the vacuum system of CVD equipment in vacuum state as much as possible. According to the deposition process requirements, the process gas used in CVD equipment and by-products generated from the reaction are generally highly corrosive. If
If the reaction residual gas is not pumped out in time after Si3N4 film deposition, the gas circuit interface, bellows, vacuum gauge, vacuum pump, etc. are likely to be corroded. Therefore, after Si3N4 film deposition is completed, the pumping time of the vacuum pump shall be extended as far as possible to pump out the residual gas as much as possible. When not in use for several days, open the vacuum pump once to improve the serviceability of the equipment.
(2) Fill nitrogen in time. After the process is completed, the quartz boat in the furnace tube is equipped with deposited silicon wafers, which must be stored in an environment full of nitrogen to prevent oxidation and corrosion, so that they can be better preserved.
(3) Replace the vacuum pump oil regularly. Although the vacuum system used is equipped with a vacuum pump oil filter, it can keep the pump oil clean for a long time. However, for reaction systems such as SiH2C12+NH3, NH4CI white powder, a by-product, is generated at the furnace tail and at both ends of the furnace mouth during the reaction. NH4CI deposits on the corrugated pipe and the wall of the vacuum pipe at the rear of the reaction pipe is quite serious. It and HCI and other harmful impurities may be pumped to the vacuum pump at any time. These particles continuously enter the vacuum pump in small amount to thicken the pump oil, block the pump oil filtering system and affect the normal operation of the equipment. Therefore, the vacuum pump oil must be replaced regularly.
(4) Maintain the solenoid valve regularly. In order to prevent the vacuum pump oil from returning to the vacuum pipeline, a solenoid valve is installed on the vacuum pump. The common fault of the solenoid valve is that there is a small amount of NH4CI powder in the solenoid valve, which reduces the sealing performance of the O-ring in the solenoid valve, leading to slow leakage in the vacuum system. The vacuum system of the entire equipment cannot maintain the vacuum state after shutdown, and the solenoid valve must be repaired regularly, After cleaning, replace the O-ring in the solenoid valve to keep the vacuum system of CVD equipment in vacuum state after the film deposition is completed.
(5) Clean the quartz tube regularly. In the process of deposition, a layer of film will be deposited on the quartz tube and the quartz boat. After each process, the quartz boat should be properly moved in situ to avoid adhesion between the quartz boat and the quartz tube. With the increase of process production, the films deposited on quartz tubes and quartz boats become thicker and thicker. After reaching a certain degree, the quartz tube appears silicon crack, which also increases the load of the whole quartz tube, exceeding its maximum load, and one quartz tube sinks to a certain extent (the original two quartz tubes are on the same horizontal plane). As a result, the silicon chips on the quartz boat also sink together, deviating from the center of the furnace tube, resulting in uneven film deposition. Therefore, regular cleaning can ensure the stability and repeatability of the process, thus ensuring product quality