Method for fabricating a polycrystalline silicon carbide carrier substrate

A method of manufacturing a polycrystalline silicon carbide support substrate, comprising the following steps:

• a) growing an initial polycrystalline silicon carbide support substrate on a seed of graphite or silicon carbide;
• on conclusion of step a), the initial substrate having a free front face and a rear face in contact with the seed;
• b) forming a stiffening carbon film on the front face of the initial substrate, the initial substrate having, in a plane of its front face and just before formation of the stiffening carbon film, a first average silicon carbide grain, size;
• c) removing the seed, so as to free the rear face of the initial substrate, the initial substrate having, in a plane of its rear face and just after removal of the seed, a second average silicon carbide grain size, smaller than the first average silicon carbide grain size;
• and
• d) thinning the rear face of the initial substrate to a thickness for which the initial substrate has, in the plane of its thinned rear face, a third average grain size equal to the first average silicon carbide grain size to within ±30%, the thinned initial substrate forming the polycrystalline silicon carbide support substrate.