Fabrication Study And Integration Design Of The Infrared-array Based On Polysilicon

Infrared imaging system was wide applied to national economy, and infrared focal plane array is the core of infrared imaging system. Beginning with the fabrication of micro-bolometer array in this thesis, thermally sensitive polysilicon was studied. The array structure with free-standing stencil cantilever was designed and successfully fabricated with the technique of bulk micromachining and surface micromachining. The integration project of array structure with a CMOS circuit was brought forward according to characteristics of the array structure and the process is not compatible with CMOS. Primary work and result in this thesis are displayed as follows:1. Polysilicon film was deposited with SiH₂Cl2 and was studied with scan-electronic-mirror(SEM), following with X radial diffraction (XRD) and film stress measurement. The film thickness was measured by interferometer. Low-stress polysilicon film has been obtained by the chemical vapor deposition (CVD) using SiH2Cl2 at temperature 950°C.2. The resistivity of the polysilicon films could be controlled under different dopant (boron) concentration and different anneal temperature. The changes of resistance with the temperature were measured. The temperature coefficient of resistance (TCR) value was about 1‰ when the boron concentration was 5X 10 /cm and the anneal temperature was 900℃. Influence of the doping concentration and the anneal temperature to TCR were analyzed, in which TCR was increased with the decrease of dope concentration and the increase of anneal temperature.3. The array structure with free-standing stencil cantilever was designed. The thermal isolation effect of array structure was theoretically analyzed, with the total thermal conductance of each pixel 1.73* 10'6 ( W/K ) . The double-protection technology was designed, by which 16 pixels line-array and 16x16 pixels plane-array were successfully fabricated.4. Integration project of array with CMOS signal circuit was brought forward according to the fabrication process of plane-array sensor and its structure characters.