| abstract |
By providing a silicon nitride substrate having a high thermal conductivity in the thickness direction and a high fracture toughness in the thickness direction, a silicon nitride wiring board having low thermal resistance and high reliability can be provided, and furthermore, a semiconductor module using the silicon nitride wiring board Low heat resistance and high reliability are achieved.n n n The disclosed silicon nitride substrate contains β-type silicon nitride and at least one rare earth element. In addition, the silicon nitride substrate also has an in-plane orientation degree fa of 0.4 to 0.8 indicating an orientation ratio in the plane perpendicular to the thickness direction determined from the ratio of the respective X-ray diffraction ray intensities of the predetermined lattice plane of the β-type silicon nitride. |