Study On The Fabrication And Properties Of Capillary Standard Leak Made Of Silicon And Pyrex Glass

The commonly used standard leak cannot accurately reflect the real flow regime of leakage gases,and it is difficult to make feature dimension controllable.Recently,the investigation of the fabrication and applications of standard leaks is of great interest.It has become a new research hotspot to develop the leak assembly possessing controllable size and exhibiting molecular flow over a wide pressure range in the field of vacuum technology.In this paper,a new capillary leak has been designed based on fluidic nanochannels.It possesses a feature dimension of about 280 nm,which can be controlled by adjusting process parameters during the fabrication procedure.The channels are formed on silicon wafers and enclosed with Pyrex glass using laser interference lithography,reactive ion etching and anodic bonding.The flow rate and conductance are measured by a homemade experiment apparatus based on the difference method,whereupon helium,nitrogen,oxygen,and argon are individually used as test gases.The measured results illustrate that the conductance remains roughly constant at pressures pup=10–60 kPa for nitrogen,oxygen,and argon,and the leak can therefore operate in the molecular flow regime.For helium,the scale extends up to atmospheric pressure.The conductance of the leaks with same length is approximately proportional to the inverse square root of the molecular mass.For a particular gas,the conductance is approximately inversely proportional to the length of the leaks.The same leaks are tested using a helium mass spectrometric leak detector,whose results are about 11.64% less than the values obtained by the difference method.The uncertainty of the conductance measurement is estimated and the combined uncertainty is less than 7.40%.We propose a new leak that allows simple calibration and possesses controllable feature dimension,constant conductance and a wide leak rate range.It is capable of predicting the conductance for other non-condensable gases when we just know the conductance for helium.