There are two kinds of defects in vacuum system of semiconductor equipment: one is the defect of vacuum pump unit and measuring system, the other is the disclosure of vacuum system. As for the first kind of defect, it can be confirmed by testing the limit vacuum degree of vacuum pump or changing a good vacuum gauge. For the second type of defects, leakage detection is required.
Two methods are often used in leak detection of semiconductor equipment: static pressure leak detection and he mass spectrometry leak detection. Static pressure leak detection method is to use the valve to separate the vacuum chamber and the vacuum pump group, and measure the change of its internal pressure. Leak detection by mass spectrometry is more complicated.
Mass spectrometer leak detector is usually required to be taken to the site. There is a molecular pump in the leak detector, so it should be handled with care. The high sensitivity of leak detector is often selected to detect leakage, which is beneficial to maintain the molecular pump.
The leak detector has limited ability to extract air, so it often needs the equipment to vacuum itself. Vacuum to 0.5 ~ 10Pa. Wait until the leakage rate appears to be stable or from stable to reduced, then start leak detection. In the process of leak detection, if it is necessary to stop the operation of valve, coarse suction valve and vent valve, it is necessary to stop the leak detection of the leak detector and select the leak detection port without venting, so as to avoid damaging the detector due to the sudden entrance of a large amount of gas into the vacuum chamber.
After the vacuum is pumped, the valve and the rough suction valve should be opened to avoid the diversion, and the measured value of vacuum leakage rate is less than the theoretical value. It is better to stop the molecular pump and mechanical pump on the equipment, so as to avoid their interference; if the equipment with cold pump wants to detect the leakage thoroughly, it should stop the cold pump. When the vacuum method is used to detect the leakage rate of double sealed structure products, the phenomenon of “slow increase” of leakage rate often occurs.
Therefore, it is necessary to pay attention to this point in the process of leak detection. In addition, it is necessary to ensure that there is no air leakage in the he bag, and the flow rate of he ejected from ordinary request is small, which is helpful to confirm the location of the leakage point.
However, there are special cases where it is necessary to spray more he in the center where he is not easy to reach, so as to avoid missing inspection. The bellows installed during leak detection cannot be detected. The second confirmation shall be suspended after the leakage point is found, and the leakage detection confirmation shall be stopped after the leakage point is repaired.
There are many parts in the vacuum part of semiconductor equipment. If one part has a large leakage rate, it is easy to lead to high vacuum pumping. Most of the defects of semiconductor equipment in vacuum are that high vacuum cannot be pumped due to micro leakage. Pay attention to the details of the leak detection, the part of the difficulty is to be patient. In addition, the choice of domestic high vacuum timing should leave room, otherwise it will not be able to show the desired high vacuum.