Method to delineate crystal related defects
View Patent ↗This invention generally relates to a process for detecting grown-in-defects in a semiconductor silicon substrate. The process includes contacting a surface of the semiconductor silicon substrate with a gaseous acid in a reducing atmosphere at a temperature and duration sufficient to grow grown-in -defects disposed in the semiconductor silicon substrate to a size capable of being detected by an optical detection device.
1. A method for detecting grown-in-defects in a surface of a semiconductor substrate, said method comprising:
exposing the surface of the semiconductor substrate to a first reducing atmosphere comprising hydrogen at a first temperature between about 900° C. and about 1250° C. for a duration sufficient to remove oxide from the surface of the semiconductor substrate;
exposing the surface of the semiconductor substrate to a second reducing atmosphere comprising hydrogen and a gaseous etchant selected from the group consisting of hydrogen chloride, hydrogen bromide, hydrogen iodide, and combinations thereof at a second temperature between about 800° C. and about 1100° C. for a duration sufficient to etch the surface of the semiconductor substrate and delineate grown-in-defects disposed in the semiconductor substrate, wherein the second temperature is lower than the first temperature; and
scanning the surface of the semiconductor substrate having delineated grown-in-defects thereon with an optical detection device.
2. The method of claim 1 wherein the semiconductor substrate comprises a semiconductor wafer comprising two major, generally parallel surfaces, one of which is a front surface of the substrate and the other of which is a back surface of the substrate, a circumferential edge joining the front and back surfaces, and a central plane between the front and back surfaces.
3. The method of claim 2 wherein the semiconductor wafer comprises a material selected from the group consisting of silicon, silicon carbide, silicon germanium, silicon nitride, silicon dioxide, gallium arsenic, gallium nitride, indium phosphide, indium gallium arsenide, germanium, and combinations thereof.
4. The method of claim 2 wherein the semiconductor wafer comprises a wafer sliced from a single crystal silicon ingot grown by the Czochralski method.
5. The method of claim 1 wherein the grown-in-defects are selected from the group consisting of COPs, oxygen precipitates, A-defects, and DSODs.
6. The method of claim 1 wherein the second reducing atmosphere comprises hydrogen and gaseous hydrogen chloride at a concentration between about 0.05% and about 5%.
7. The method of claim 1 wherein the second reducing atmosphere comprises hydrogen and the gaseous hydrogen chloride at a concentration between about 0.25% and about 1%.
8. The method of claim 1 wherein the second temperature is between about 900° C. to about 1050° C.
9. The method of claim 1 wherein the method further comprises subjecting the semiconductor substrate to a thermal cycle prior to exposing the surface of the semiconductor substrate to the first reducing atmosphere, wherein the thermal cycle comprises heating the semiconductor substrate to a third temperature between about 800° C. and about 1150° C. for at least 2 hours.
10. The method of claim 9 wherein the third temperature is between about 900° C. and about 1000° C., and the duration of the thermal cycle is between 2hours and about 20 hours.
11. A method of sorting a plurality of semiconductor wafers, said method comprising:
exposing the surface of the semiconductor substrate to a first reducing atmosphere comprising hydrogen at a first temperature between about 900° C. and about 1250° C. for a duration sufficient to remove oxide from the surface of the semiconductor substrate;
exposing the plurality of semiconductor wafers to a second reducing atmosphere comprising hydrogen and a gaseous etchant selected from the group consisting of hydrogen chloride, hydrogen bromide, hydrogen iodide, and combinations thereof at a second temperature between about 800° C. and about 1100° C. for a duration sufficient to etch the surface of the plurality of semiconductor substrates and delineate grown-in-defects disposed in the plurality of semiconductor substrates, wherein the second temperature is lower than the first temperature;
scanning the surface of the wafers with an optical detection device for the delineated grown-in-defects; and
sorting the wafers based on the type, concentration, and size of the defects detected.