Flexible substrate a-Si:H TFTs for space applications

We have fabricated hydrogenated amorphous silicon (a-Si:H) TFTs on Kapton^(R) polyimide flexible substrates and characterized their response to deployment-like mechanical stresses and to radiation exposure. To maintain substrate flatness and provide improved thermal transfer during fabrication, we used a pressure-sensitive silicone gel adhesive layer to mount Kapton^(R) substrates onto glass carriers. The test results, presented in this paper, are encouraging for space use of a-Si:H TFTs on polymeric substrates. Device function was retained even after 1 Mrad fast electron irradiation, and irradiation-induced device changes were removed by low-temperature thermal annealing. Although some TFTs were destroyed by substrate stressing, the majority survived with only small changes, suggesting that care in device design and placement may reduce or eliminate this problem.