Spatial inhomogeneous distribution of high Si-H$_{\mathrm{2}}$ bond density in a-Si:H films deposited by MHPCVD.

Hydrogenated amorphous silicon (a-Si:H) solar cells are promising as a power sources for IoT devices because of its flexible features and a low production cost. t Si-H$_{\mathrm{2}}$ bond density in the films tends to correlate with light-induced degradation degree; leading to 20{\%} reduction of efficiency. The high Si-H$_{\mathrm{2}}$ bond density regions are located at random in the plane. That is one of the problems for industrial production. To decrease Si-H$_{\mathrm{2}}$ bond density and to make the better film uniformity, we study the spatial distribution of Si-H$_{\mathrm{2}}$ bond density in the plane as a parameter of substrate temperature. A-Si:H films were deposited on Si substrate by using a multi-hollow discharge plasma CVD method with a cluster-eliminating filter. Spectra of Si-H$_{\mathrm{2}}$ bond (2090cm-1) and Si-H (2000cm-1) were measured by FTIR spectrometer and from their peaks the I$_{\mathrm{SiH2}}$/I$_{\mathrm{SiH}}$ values are obtained. The spatial aperture size was 50 um x 50 um, and a total 900 points were measured in 30 rows and 30 columns (1.5mm x 1.5mm). The average value of I$_{\mathrm{SiH2}}$/I$_{\mathrm{SiH}}$ decreases from 0.23 at 170${^\circ}$ to 0.022 at 250${^\circ}$ and its uniformity becomes better as well. I will report the results with some images of distribution of Si-H$_{\mathrm{2}}$ bonds and the frequency distributions of Si-H$_{\mathrm{2}}$ bonds.