Gridded susceptor
View Patent ↗Susceptor designs are provided for controlling damage to wafers, particularly during cold wafer drops-off on a hot susceptor. The designs include axisymmetric grid designs, such that thermal gradients are symmetrical in the circumferential (θ) direction and the same traversing any particular radial line. The grids are preferably arcuate and each have the same surface area. In one embodiment an outer zone is asymmetrically designed to induce predictable wafer curling in a saddle shape.
1. A grid patterned susceptor, comprising:
a circular susceptor face with an arcuate grid pattern defined by a pattern of grooves on the face of the susceptor,
said pattern of grooves comprising circumferential grooves concentric about a center of the circular face, and
equiangular radial grooves emanating outwards from the circumferential grooves and pointing inwards to the center of the circular face and cutting the concentric grooves,
wherein each arcuate grid on said circular face is a raised surface bounded on all sides by grooves and has substantially the same surface area as any other arcuate grid on the circular susceptor face.
2. The susceptor of claim 1 , wherein the arcuate grids are continuous annular projections between adjacent circular grooves.
3. The susceptor of claim 1 , wherein the grid patterned susceptor is substantially shaped as a concave bowl.
4. The susceptor of claim 1 , wherein the grid pattern is defined by concentric circular grooves.
5. The susceptor of claim 4 , wherein the susceptor face is further configured with spoke grooves running radially and cutting across the concentric grooves.
6. The susceptor of claim 5 , wherein the spoke grooves are provided as a plurality of sets of radial grooves, each set of radial grooves originating from a different concentric circle.
7. The susceptor of claim 5 , wherein the arcuate grids are progressively narrower in radial direction with increasing radial distance from a center of the susceptor.
8. The susceptor of claim 5 , wherein the grid pattern comprises:
a first area wherein the surface area of the grids is configured to be substantially constant through decreased radial length compensating for increased circumferential length at greater radial distance from a center of the susceptor; and
a second area wherein the surface area of the grids is configured to be substantially constant through increased radial length compensating for decreased circumferential length at greater radial distance from the center of the susceptor.
9. The susceptor of claim 8 , wherein the grid pattern alternates between patterns of the first area and patterns of the second area as a radius of the susceptor is traversed.
10. A grid patterned susceptor, comprising:
a circular susceptor face; and a plurality of arcuate grids defined as raised continuous surfaces surrounded on all sides by circular and straight line grooves on the face of the susceptor, said arcuate grids forming concentric circles about a center of the circular susceptor face, said arcuate grids having top substantially planar surfaces, wherein the top surface of every arcuate grid in any given concentric circle has a surface area that is substantially the same as the top surface of any other arcuate grid in that concentric circle, and wherein the top surface of any arcuate grid in one concentric circle has substantially the same surface area as the top surface of any other arcuate grid in any other concentric circle.