Ultra-high vacuum leak detection technology with the lower limit of 10 −16 Pam 3 /s for nano devices

At present, many vacuum devices based on nanotechnology are widely used. The life time of the device depends mainly on the outgassing rate and the seal leak rate of the device. The leak rate is required to be less than 10 −14 Pam 3 /s in some application fields of long-life and high reliability devices. To solve this problem, the ultra-high vacuum leak detection apparatus with the lower limit of 10 −16 Pam 3 /s was developed with accumulation and comparison method. Compared with the conventional method of dynamic leak detection method, the accumulation method has the advantage of extending the lower limit to 10 −16 Pam 3 /s. The apparatus consists of an accumulation comparison system and a standard gas flowmeter with the constant conductance method. The constant conductance element is an important part of the flowmeter, of which the conductance can achieve a constant value of 10 −10 m 3 /s by using the laser drilling and multi-coating technology. The inlet pressure of the element can be as low as 10 −6 Pa with the static expansion method. During the accumulation, a quadruple mass spectrometer (QMS) was used to measure the ion current increment caused by the leak gas, with a non-evaporable getter (NEG) pump working in the accumulation chamber. Experimental results show that the leak detection range of the apparatus is from 10 −10 Pam 3 /s to 10 −16 Pam 3 /s with the relative standard uncertainty of 2%∼10%. This technology can be used for leak detection of nano devices, and it has broad application prospects in all kinds of small leakage detection field.