Patent ID: 7939173

Claim:
A polycrystalline silicon rod having a diameter, obtained by deposition of high-purity silicon from a silicon-containing reaction gas which has been thermally decomposed or reduced by hydrogen onto a filament rod, wherein the polycrystalline silicon rod has at least four different regions having different microstructures in a radial cross section of the rod, these regions comprising: a) a polycrystalline filament rod as an innermost region A, at the center of the polycrystalline silicon rod, b) a region B of deposited polycrystalline silicon containing no or only very few needle crystals around the innermost region A, the region B having a diameter, c) an outer region D having a polycrystalline microcrystal-containing matrix, and having a proportion by area of needle crystals of less than 7%, wherein the length of the needle crystals is less than 15 mm and the width of the needle crystals is less than 2 mm and in this outer region D the length of the microcrystals of the matrix does not exceed 0.2 mm, and d) between the regions B and D, a mixed region C, in which the crystal microstructure undergoes transition fluidly from the microstructure in region B to the microstructure in region D.