System and method for correcting non-ideal wafer topography
A scanner includes a light source configured to apply a light to a backside of a wafer. The light is reflected from the backside of the wafer. A first mirror is configured to receive the light from the backside of the wafer and reflect the light. A sensor is configured to receive the light from the first mirror and generate an output signal indicative of a backside topography of the wafer.
1. A scanner comprising:
a light source configured to apply a light to a surface of a wafer at a first incident angle with respect to a first horizontal axis;
a first mirror positioned to receive light reflected from the surface of the wafer, wherein a change in the first incident angle of ΔΘ corresponds to a horizontal movement of the first mirror Δx on a second horizontal axis parallel to the first horizontal axis; and
a sensor positioned to receive light reflected from the first mirror when the light source is applied to the surface of the wafer, wherein the sensor is configured to generate an output signal indicative of a surface topography of the wafer.
2. The scanner of claim 1 , wherein the light source is moveable on the first horizontal axis.
3. The scanner of claim 1 , wherein the first mirror reflects the light at a second incident angle with respect to the first horizontal axis.
4. The scanner of claim 1 , comprising a second mirror positioned to receive the light reflected from the first mirror and reflect the light to the sensor when the light is applied to the surface of the wafer.
5. The scanner of claim 4 , wherein the second mirror is horizontally aligned with the first mirror.
6. The scanner of claim 4 , wherein the second mirror is fixed.
7. The scanner of claim 1 , comprising a processor configured to receive the output signal from the sensor and generate a corrected overlay map.
8. The scanner of claim 7 , wherein the corrected overlay map is configured to correct for at least one non-linear overlay error.
9. The scanner of claim 7 , wherein the corrected overlay map is generated by combining an uncorrected overlay map and a topographical map, wherein the topographical map is generated from the output signal of the sensor.
10. The scanner of claim 1 , wherein the light is reflected from the surface of the wafer at a first angle and reflected from the first mirror at a second angle.
11. A method, comprising:
applying a light from a light source to a first portion of a surface of a wafer at a first incident angle;
reflecting the light applied at the first incident angle from the surface of the wafer to a sensor;
generating, by the sensor, a signal indicative of a surface topography of the wafer;
generating a corrected overlay map based on the signal indicative of the surface topography of the wafer;
adjusting at least one of a horizontal position of a light source or a first mirror;
applying the light to a second portion of the surface of the wafer; and
reflecting the light from the second portion of the surface of the wafer to the sensor, wherein the signal indicative of the surface topography of the wafer includes a backside topography of the first portion and the second portion of a backside of the wafer.
12. The method of claim 11 ,
wherein the light is reflected from the surface of the wafer at a first angle and reflected from the first mirror at a second angle.
13. The method of claim 11 , comprising manufacturing one or more circuits on the wafer using the corrected overlay map.
14. The method of claim 11 , comprising:
reflecting the light from a first mirror to a second mirror; and
reflecting the light from the second mirror to the sensor.
15. The method of claim 14 , wherein the second mirror is horizontally aligned with the first mirror.
16. A system, comprising:
a scanner comprising:
a light source configured to apply a light to a semiconductor wafer at a first incident angle with respect to a first horizontal axis;
a first mirror positioned to receive light reflected from the semiconductor wafer when the light source is applied to the semiconductor wafer and reflect the light, wherein a change in the first incident angle of ΔΘ corresponds to a horizontal movement of the first mirror Δx on a second horizontal axis parallel to the first horizontal axis; and
a sensor configured positioned to receive the light reflected from the first mirror when the light source is applied to the semiconductor wafer and generate an output signal indicative of a topography of the wafer;
a wafer table configured to support the semiconductor wafer thereon;
a processor configured to receive the output signal from the sensor and generate a corrected overlay map based on at least the output signal; and
a semiconductor manufacturing system configured to form at least one layer of a semiconductor device on a semiconductor wafer coupled to the wafer table, wherein the corrected overlay map is configured to compensate for a topography of the semiconductor wafer.
17. The system of claim 16 , wherein the light source is moveable on the first horizontal axis.
18. The system of claim 16 , wherein the wafer table is configured to support the semiconductor wafer with a backside of the semiconductor wafer oriented toward the scanner.
19. The system of claim 18 , comprising a second mirror configured to receive the light from the first mirror and reflect the light to the sensor, wherein the second mirror is horizontally aligned with the first mirror.
20. The system of claim 16 , wherein the corrected overlay map is generated by combining an uncorrected overlay map and a topographical map, wherein the topographical map is generated from the output signal of the sensor.