The core component of sputtering pressure sensor is its sensitive core (also known as sensitive chip), Nano film pressure sensor Mass production is the first solution to the large-scale production of sensitive chips. A typical sensitive chip is a thin film with four or five layers deposited on a metal elastomer. Among them, the key is the dielectric insulation film which is isolated from the elastomer metal and the functional material film which acts as strain on the insulating film.
The main technical requirements for dielectric insulating film: its thermal expansion coefficient is basically the same as that of metal elastomer. In addition, the insulation constant of dielectric film should be high, so the thinner film will have higher insulation resistance value. The results show that when the dielectric film thickness is less than 100 μ m, the film should have the maximum elastic strength in the range of 1.06 μ m to 1.5 μ m in the range of 100 μ m to 500 μ m, and the film should have the highest elastic strength in the range of 1.08 μ m to 100 μ M above.
The strain film is generally composed of more than two elements, the stoichiometric ratio between the elements is basically the same as that of the bulk material; its thermal expansion coefficient is basically consistent with that of the dielectric insulation film; the thickness of the film should be on the premise of ensuring a stable average thickness of continuous thin film, the thinner the better, so as to achieve high resistance, low power consumption and reduce the resistance caused by self heating When the sensor stability is 0.1% FS, the change of resistance should be less than 0.05%.
As we all know, the preparation of high-quality thin films with high density, strong adhesion, no pinhole defects, small internal stress, no impurity pollution, with certain elasticity and stoichiometric ratio, involves many factors in the film process, including the particle size of the deposition material, the energy carried by the particles, the space environment before the particles reach the substrate, the surface condition of the substrate, the substrate temperature, and the particle absorption The growth process of nucleation, the rate of film formation and so on. According to the theoretical model of thin film deposition, the key is the quality of the first layer or the first few layers. If the particle size is large, the energy carried by the film is small, and the precipitation rate is fast. If the deposited film is affected by the bad environment, for example, the gas adsorbed by the film will form a cavity after being released, and the impurity pollution will affect the stoichiometric ratio of the elements, which will reduce the mechanical, electrical and temperature characteristics of the film.
NASA "thin film pressure sensor research report" pointed out that in high frequency sputtering, the sputtered material with molecular size particles with certain energy continuously passes through the plasma to deposit thin films on the substrate. In this way, the film quality is denser and the adhesion is better than that of thermal evaporation deposition film. However, when the sputtered particles pass through the plasma area, the gas in the plasma will be adsorbed, and the deposited film will be affected by the impurity pollution in the plasma and the thermal dynamic effect of high temperature instability, which will cause more defects in the film, reduce the strength of the insulation film and low yield. These are the main limitations of high frequency sputtering equipment technology for mass production of sputtered thin film pressure sensors.
Japanese vacuum film expert Professor Takaki Junyi has proved through experiments that in 10-7 Torr high vacuum, in tens of seconds, the residual gas atoms can form a molecular layer and attach to the surface of the workpiece to pollute the workpiece, thus affecting the quality of the film. It can be seen that the higher the vacuum degree, the better the film quality.
In addition, there are several factors worth considering: the high temperature in plasma can soften or even carbonize the photoresist of resist mask pattern. High frequency sputtering target is not only a part of the working parameters for producing plasma, but also a part of the process parameters for producing sputtered particles. Therefore, the working parameters and process parameters of the equipment restrict each other and cannot be adjusted separately. It is difficult to master the process and the production and operation process are complex.
For the ion beam sputtering technology and equipment, the ion beam is from the ion source plasma, through the ion optical system to form ions. The target and substrate are placed in the high vacuum environment far away from the plasma. The ion beam bombards the target, and the target atoms sputter out, and the film is deposited on the substrate. This process is completely overcome without the adverse environmental impact of plasma The defects of thin films prepared by high frequency sputtering technology. It is worth noting that ion beam sputtering is generally considered to be one or several atoms. As we all know, the atomic size is much smaller than the molecular size, the particles are smaller when forming the film, and the gap between the particles is small, which can effectively reduce the holes and pinhole defects in the film, improve the adhesion of the film and enhance the elasticity of the film.
In addition, the ion beam deposition device which is not conducive to the in-situ deposition of the film by using the ion beam sputtering device is not conducive to the in-situ deposition of the film When the growing film is bombarded with oxygen or nitrogen ions, it is more effective to form a specific stoichiometric oxide or nitride than gas molecules. Secondly, the working parameters of plasma forming and film processing can be adjusted independently, which can not only obtain the optimal adjustment of equipment working state and the quality control of the best process, but also simplify the operation of the equipment and grasp the process easily.
These advantages of ion beam sputtering technology and equipment have become the leading technology and equipment for the production of sputtered thin film pressure sensors at home and abroad. The ion beam co sputtering film equipment can be used not only to manufacture various kinds of films for high performance thin film pressure sensors, but also for preparing high temperature alloy conductor films and precious metal films in integrated circuits, magnetic thin films such as magnetic devices, magneto-optical waveguides, magnetic memory, etc., and for preparing high-quality optical films, especially for laser high damage threshold window films, etc It is used to prepare nano and micro films for magnetic, force, temperature, temperature and humidity sensors; it is used for preparing films used in optoelectronic devices, metal heterojunction devices, solar cells, surface acoustic wave devices, high temperature superconductors, etc.; it is used for preparing various thin films in thin film integrated circuits and MEMS systems It can be used to prepare other high quality nano films or micro films. This article originates from Zetian sensing Please keep the source.