Systems, methods and metrics for wafer high order shape characterization and wafer classification using wafer dimensional geometry tool
Systems and methods for improving results of wafer higher order shape (HOS) characterization and wafer classification are disclosed. The systems and methods in accordance with the present disclosure are based on localized shapes. A wafer map is partitioned into a plurality of measurement sites to improve the completeness of wafer shape representation. Various site based HOS metric values may be calculated for wafer characterization and/or classification purposes, and may also be utilized as control input for a downstream application. In addition, polar grid partitioning schemes are provided. Such polar grid partitioning schemes may be utilized to partition a wafer surface into measurement sites having uniform site areas while providing good wafer edge region coverage.
1. A polar grid partitioning method for partitioning a wafer surface, the method comprising:
specifying a number of sectors and a number of zones required for the polar grid partitioning;
calculating, with one or more processors, a sector angular span based on the number of sectors specified;
calculating, with one or more processors, a radial span for each of the number of zones, wherein the radial span for a first zone having a first radial distance to the center of the wafer is different from the radial span for a second zone having a second radial distance to the center of the wafer;
partitioning, with one or more processors, the wafer surface into a plurality of sites based on the sector angular span and the radial span for each zone to improve accuracy of wafer shape analysis performed on the wafer, wherein the plurality of sites have uniform site areas;
calculating, with one or more processors, one or more measurement metrics based on the partitioning of the wafer surface into the plurality of sites based on the sector angular span and the radial span for each zone; and
providing, with one or more processors, the one or more measurement metrics to control a process of one or more process tools.
2. The polar grid partitioning method of claim 1 , wherein the radial span for the first zone is greater than the radial span for the second zone when the first radial distance is smaller than the second radial distance.
3. The polar grid partitioning method of claim 1 , wherein the radial span for the i th radial zone is defined as the span between boundaries:
r i =√ i L and r i-1 =√ i− 1 L, i= 1,2,3, . . . K
wherein
L
=
R
K
,
and R is the radius of the wafer and K is the number of zones.
4. The method of claim 1 , wherein the one or more measurement metrics includes at least one of:
a plurality of surface shape metrics; and
a plurality of deviation metrics.
5. The method of claim 1 , wherein the one or more measurement metrics are calculated based on surface coefficients obtained utilizing at least one of: a polynomial fitting process or a pixel-based shape-slope computation process.
6. The method of claim 1 , wherein the one or more measurement metrics are utilized for controlling at least one of: a Chemical Mechanical Planarization or Polishing (CMP) process, a wafer specification development process, an unpatterned wafer geometry control process, or a wafer uniformity control process.
7. The method of claim 4 , wherein the surface shape metrics includes at least one of:
an average slope of a measurement site in x-direction;
an average slope of a measurement site in y-direction;
a magnitude of a measurement site slope;
a magnitude of a second order surface component for a measurement site;
a radial slope of a measurement site; or
a tangential slope of a measurement site.
8. A polar grid partitioning method for partitioning a wafer surface, the method comprising:
specifying a number of zones K required for the polar grid partitioning and a number of angular segments M in a center region of the wafer;
calculating, with one or more processors, a radial zone length L based on the number of zones specified;
calculating, with one or more processors, an angular span θ i for the i th radial zone, wherein i=1, 2, 3, . . . K;
partitioning, with one or more processors, the wafer surface into a plurality of sites based on the radial zone length L and the angular span for each radial zone to improve accuracy of wafer shape analysis performed on the wafer, wherein the plurality of sites have uniform site areas;
calculating, with one or more processors, one or more measurement metrics based on the partitioning of the wafer surface into the plurality of sites based on the radial zone length L and the angular span for each radial zone; and
providing, with one or more processors, the one or more measurement metrics to control a process of one or more process tools.
9. The polar grid partitioning method of claim 8 , wherein the angular span θ i is less than the angular span θ i-1 for i>1.
10. The polar grid partitioning method of claim 9 , wherein the angular span θ i for the i th radial zone is calculated according to equation:
θ
i
=
1
2
i
-
1
2
π
M
,
i
=
1
,
2
,
3
,
…
K
.
11. The method of claim 8 , wherein the one or more measurement metrics includes at least one of:
a plurality of surface shape metrics; and
a plurality of deviation metrics.
12. The method of claim 8 , wherein the one or more measurement metrics are calculated based on surface coefficients obtained utilizing at least one of: a polynomial fitting process or a pixel-based shape-slope computation process.
13. The method of claim 8 , wherein the one or more measurement metrics are utilized for controlling at least one of: a Chemical Mechanical Planarization or Polishing (CMP) process, a wafer specification development process, an unpatterned wafer geometry control process, or a wafer uniformity control process.
14. The method of claim 11 , wherein the surface shape metrics includes at least one of:
an average slope of a measurement site in x-direction;
an average slope of a measurement site in y-direction;
a magnitude of a measurement site slope;
a magnitude of a second order surface component for a measurement site;
a radial slope of a measurement site; or
a tangential slope of a measurement site.