Method for forming spaced electrically isolated regions in a body of semiconductor material

A method for making a grid arrangement in a body of semiconductor material of a semiconductor device to produce a plurality of regions of semiconductor material of the body electrically isolated from one another, the method comprising

• a. selecting a body of single crystal semiconductor material having a preferred crystallographic structure, two major opposed surfaces being respectively the top and bottom surfaces thereof, a preferred planar orientation of at least the top surface, the planar orientation being one selected from the group consisting of (100) and (111), a first selected type conductivity, a selected level of resistivity and having a vertical axis substantially aligned with a first axis of the crystal structure;
• b. forming a first region of second type conductivity in the body including the bottom surface thereof, a P-N junction being formed by the contiguous surfaces of the material of the body and the region and being substantially parallel to the major surface;
• c. etching selectively the major surface having the preferred planar orientation to form an array of planar trough-like depressions in the surface thereof, the trough-like depressions being oriented substantially aligned with a first preferred wire direction;
• d. disposing at least one dopant material in each of the trough-like depressions in intrinsic contact with the material of the body which when migrated through the body will convert the material of the body to a second type conductivity and a selected resistivity;
• e. heating the body and the metal wires to a preselected elevated temperature to form an array of liquid wires of metal and semiconductor material in the trough-like depressions on the surface;
• f. establishing a temperature gradient of from 50.degree. C/cm to 200.degree. C/cm substantially along the vertical axis aof the body, the surface on which the liquid wires are formed being at the lower temperature;
• g. migrating the liquid wires through the body and the first region from one major opposed surface to the other major opposed surface substantially along the vertical axis of the body and the first axis of the crystal structure to form a plurality of planar regions of recrystallized semiconductor material of the body having solid solubility of at least the dopant material therein which intersect and are integral with the first region;
• h. etching selectively the top surface of the body to form a second array of linear trough-like depressions in the top surrface thereof, each of the trough-like depressions being oriented substantially aligned with a second preferred wire direction and at a first preselected angle to the first wire direction;
• i. disposing at least one dopant material in each of the trough-like depressions in intiamate contact with the material of the body which when migrated through the body and the first region will convert the material of the body to a second type conductivity and a second resistivity;
• j. heating the body and the material in the trough-like depressions to an elevated temperature sufficient to form an array of liquid wires of metal and semiconductor material in the trough-like depressions in the top surface;
• k. establishing a temperature gradient substantially along the vertical axis of the body, the top surface being at the lower temperature;
• and
• l. migrating the liquid wires through the body and the first region from the top to the bottom surface substantially along the vertical axis of the body and the first axis of the crystal structure to form a plurality of second planar regions, which intersect and are integral with the first region and the plurality of first planar regions, the material of the second planar regions comprising recrystallized semiconductor material of the body having solid solubility of the at least one metal therein.