Method and apparatus for producing epitaxial wafer
After removing deposit on a susceptor in an epitaxial growth furnace by a cleaning recipe (step S 101 ), a first epitaxial wafer is produced by growing an epitaxial layer on a first wafer based on a process recipe A (step S 102 ). Subsequently, a step of producing an epitaxial wafer by growing an epitaxial layer on a wafer based on a process recipe B including second control parameters set such that the epitaxial wafer has approximately the same film thickness profile as the first wafer (step S 103 ) is repeated a plurality of times to successively produce a plurality of epitaxial wafers (step S 104 ). The cleaning recipe, the process recipe A, and the process recipe B repeated a plurality of times are carried out repeatedly (step S 105 ).
1. A method for producing epitaxial wafers using a single wafer processing epitaxial growth furnace, comprising the steps of:
cleaning for removing deposit on a susceptor in the epitaxial growth furnace, wherein the epitaxial growth furnace includes a layer formation chamber which is substantially partitioned into an upper space and a lower space by the susceptor;
after the step of cleaning, performing first wafer processing for obtaining a first epitaxial wafer by mounting a first wafer on the susceptor and growing an epitaxial layer on the first wafer based on first control parameters;
without a step of cleaning for removing deposit on the susceptor in the epitaxial growth furnace after the first wafer processing, performing second wafer processing after transferring the first epitaxial wafer from the susceptor, for obtaining a second epitaxial wafer by mounting a second wafer on the susceptor and growing an epitaxial layer on the second wafer based on second control parameters set such that the second epitaxial wafer has approximately the same film thickness profile as the first epitaxial wafer;
without a step of cleaning for removing deposit on the susceptor in the epitaxial growth furnace after the second wafer processing, performing at least third wafer processing after transferring the second epitaxial wafer from the susceptor, for obtaining a third epitaxial wafer by mounting a third wafer on the susceptor and growing an epitaxial layer on the third wafer based on the second control parameters set such that the third epitaxial wafer has approximately the same film thickness profile as the first and second epitaxial wafers; and
wherein the first control parameters and the second control parameters each include a flow rate of reactive gas supplied to the upper space of the layer formation chamber and a flow rate of inert gas supplied to the lower space of the layer formation chamber, and the flow rate of the inert gas supplied to the lower space in the second control parameters is lower than the flow rate of the inert gas supplied to the lower space in the first control parameters, and
wherein the first and the second control parameters are set such that a difference in epitaxial layer film thickness between the first wafer and the second wafer at a position 2 mm from each respective wafer's edge toward a center of the wafer (ROA2 difference) is 5 nm or less over the peripheries of the first and second wafers.
2. The method for producing epitaxial wafers according to claim 1 , wherein a process sequence of performing the step of cleaning, subsequently performing the step of the first wafer processing, and successively performing the steps of the second wafer processing and the at least third wafer processing after the first wafer processing, is carried out repeatedly.
3. The method for producing epitaxial wafers according to claim 1 , wherein the first control parameters and the second control parameters are different from each other in at least one of process conditions of the flow rate of reactive gas for growing the epitaxial layer, processing time, and a flow rate of dopant gas.
4. The method for producing epitaxial wafers according to claim 1 , wherein the flow rate of the reactive gas, which is included in the second control parameters, is lower than the flow rate of the reactive gas, which is included in the first control parameters.
5. The method for producing epitaxial wafers according to claim 4 , wherein a decrease in the flow rate of the inert gas supplied to the lower space in the second control parameters relative to the flow rate of the inert gas supplied to the lower space in the first control parameters is greater than a decrease in the flow rate of the reactive gas supplied to the upper space in the second control parameters relative to the flow rate of the reactive gas supplied to the upper space in the first control parameters.
6. The method for producing epitaxial wafers according to anyone of claims 1 to 3 and 4 , wherein at least a surface portion of the susceptor made of silicon carbide (SiC) is exposed by the cleaning step.
7. The method for producing epitaxial wafers according to anyone of claims 1 to 3 and 4 , wherein the reactive gas is trichlorosilane (SiHCl 3 ).
8. The method for producing epitaxial wafers according to anyone of claims 1 to 3 and 4 , wherein the inert gas is hydrogen gas (H 2 gas).
9. The method for producing epitaxial wafers according to claim 1 , wherein the epitaxial layer is grown on the second wafer based on second control parameters set such that the second epitaxial wafer has approximately the same film thickness profile at the wafer periphery as the first epitaxial wafer.
10. The method for producing epitaxial wafers according to claim 1 , wherein the second control parameters are set such that that a difference between the thickness of the epitaxial layer at the wafer periphery of the second epitaxial wafer and the thickness of the epitaxial layer at the wafer periphery of the first epitaxial wafer is reduced.
11. The method for producing epitaxial wafers according to claim 1 , wherein in the first and second control parameters, a gas pressure of the inert gas supplied to the lower space is greater than a gas pressure of the gas supplied to the upper space.