Stress and overlay management for semiconductor processing
Provided are methods of reducing the stress of a semiconductor wafer. A wafer map of a free-standing wafer is created using metrology tools. The wafer map is then converted into a power spectral density (PSD) using a spatial frequency scale. The fundamental component of bow is then compensated with a uniform film, e.g., silicon nitride (SiN), deposited on the back side of the wafer.
1. A method of reducing wafer distortion, the method comprising:
creating a wafer map of a wafer having at least one field formed on a front side, the at least one field comprising a film, and using a spatial frequency scale to convert the wafer map into a power spectral density (PSD);
depositing a blanket film on a back side of the wafer to reduce wafer distortion to a first distortion; and
using the PSD to perform a field-level film modification of the blanket film on the back side of the wafer to reduce the wafer distortion to a second distortion less than the first distortion.
2. The method of claim 1 , wherein the blanket film has a thickness in a range of from 10 nm to 200 nm.
3. The method of claim 1 , wherein depositing the blanket film comprises physical vapor deposition of a material.
4. The method of claim 3 , wherein the material comprises silicon nitride (SiN).
5. The method of claim 1 , wherein the first distortion is paraboloid in shape.
6. The method of claim 1 , wherein the blanket film is under compressive stress.
7. The method of claim 1 , wherein the blanket film is under tensile stress.
8. The method of claim 1 , wherein the blanket film is deposited at a temperature in a range of from 100° C. to 500° C.
9. The method of claim 1 , wherein performing the field-level film modification comprises exposing the back side of the wafer to ions in a predetermined pattern, the predetermined pattern determined by filtering the power spectral density (PSD) with a strain transfer characteristic of the blanket film to provide a residual PSD.
10. The method of claim 1 , wherein performing the field-level film modification comprises exposing the back side of the wafer to photons in a predetermined pattern, the predetermined pattern determined by filtering the power spectral density (PSD) with a strain transfer characteristic of the blanket film to provide a residual PSD.
11. The method of claim 1 , wherein there are in the range of 100 to 400 fields on the front side of the wafer.
12. The method of claim 11 , wherein each of the fields is in the range of 10 mm to 30 mm wide.
13. The method of claim 11 , wherein each of the fields is in the range of 20 mm to 50 mm long.