Semiconductor wafer boat for a vertical furnace
View Patent ↗A wafer boat for use in heat treatment of semiconductor wafers in a vertical furnace comprises support rods extending generally vertically when the wafer boat is placed in the vertical furnace. Fingers are supported by and extend along vertical extent of the support rods. Wafer holder platforms are adapted to be supported by groups of fingers lying in generally different common horizontal planes. The fingers are adapted to underlie the wafer holder platforms and support the platforms at the support locations. The fingers and wafer holder platforms each have a respective first overall maximum thickness. The support location of at least one of the fingers and the wafer holder platforms have a second maximum thickness less than the first overall maximum thickness.
1. A wafer boat for use in heat treatment of semiconductor wafers in a vertical furnace, the wafer boat comprising:
support rods disposed in fixed arrangement relative to each other and extending generally vertically when the wafer boat is placed in the vertical furnace;
fingers supported by the support rods and extending from the rods, the fingers being arranged in groups lying generally in different common horizontal planes along the vertical extent of the support rods;
wafer holder platforms each adapted to be supported by respective groups of fingers generally at different ones of said horizontal planes, the fingers being adapted to underlie the wafer holder platforms and support the platforms at support locations, the wafer holder platforms each being sized and shaped for receiving one of the semiconductor wafers thereon;
the fingers and wafer holder platforms each having a respective first overall maximum thickness, each support location of at least one of the fingers and the wafer holder platforms having a second maximum thickness less than the first overall maximum thickness.
2. A wafer boat as set forth in claim 1 wherein each finger and wafer holder platform have a combined maximum thickness at the support location which is less than the first maximum overall thickness of the finger plus the first maximum overall thickness of the wafer holder platform.
3. A wafer boat as set forth in claim 2 wherein the combined maximum thickness of each finger and wafer holder platform at the support location is less than about 4 mm.
4. A wafer boat as set forth in claim 3 wherein the combined maximum thickness of each finger and wafer holder platform at the support location is about 3 mm.
5. A wafer boat as set forth in claim 2 wherein the support location of each finger is at a free end margin of the finger.
6. A wafer boat as set forth in claim 5 wherein each wafer holder platform has a groove therein sized and shaped for receiving the free end margin of one of the fingers, each wafer holder platform having the second maximum thickness in the groove.
7. A wafer boat as set forth in claim 2 wherein each wafer holder platform has a groove therein sized and shaped for receiving one of the fingers, each wafer holder platform having the second maximum thickness in the groove.
8. A wafer boat as set forth in claim 2 wherein the support rods include a central rod and two side rods, the two side rods being located in a vertical plane which is spaced forward of a parallel vertical plane tangent to the wafer boat a distance greater than 50% of a nominal diameter of the semiconductor wafers to be held in the wafer boat and less than about 85% of the nominal diameter of the semiconductor wafers.
9. A wafer boat as set forth in claim 8 wherein the vertical plane including the support rods is spaced from the parallel vertical plane tangent to the wafer boat a distance greater than 50% of a nominal diameter of the semiconductor wafers to be held in the wafer boat and less than about 80% of the nominal diameter of the semiconductor wafers.
10. A wafer boat as set forth in claim 8 wherein the fingers supported by the side rods are angled with respect to the vertical plane including the side rods.
11. A wafer boat as set forth in claim 10 wherein the fingers supported by the side rods are angled with respect to the vertical plane including the side rods in a direction away from the central rod.
12. A wafer boat as set forth in claim 11 wherein the fingers supported by the side rods are angled about 15° with respect to the vertical plane including the side rods.
13. A wafer boat as set forth in claim 8 wherein the side rods have tapered cross sections.
14. A wafer boat for use in heat treatment of semiconductor wafers having a nominal diameter in a vertical furnace, the wafer boat comprising:
support rods disposed in fixed arrangement relative to each other and extending generally vertically when the wafer boat is place in the vertical furnace, the support rods including a pair of forward rods and at least one other rod;
fingers supported by the support rods and extending from the rods, the fingers being arranged in groups lying generally in different common horizontal planes along the vertical extent of the support rods, the forward rods lying generally in a vertical plane, the fingers extending from the forward rods making an angle with the vertical plane of the forward rods;
wafer holder platforms each adapted to be supported by respective groups of fingers generally at different ones of said horizontal planes, the fingers being adapted to underlie the wafer holder platforms and supporting the platforms at support locations, the wafer holder platforms each being sized and shaped for receiving one of the semiconductor wafers thereon;
the two forward rods being located in a vertical plane which is spaced forward of a parallel vertical plane tangent to the wafer boat a distance greater than 50% of a nominal diameter of the semiconductor wafers to be held in the wafer boat and less than about 85% of the nominal diameter of the semiconductor wafers.
15. A wafer boat as set forth in claim 14 wherein the vertical plane including the forward rods is spaced from the parallel vertical plane tangent to the wafer boat a distance greater than 50% of a nominal diameter of the semiconductor wafers to be held in the wafer boat and less than about 80% of the nominal diameter of the semiconductor wafers.
16. A wafer boat as set forth in claim 15 wherein the forward rods have tapered cross sections.
17. A wafer boat as set forth in claim 14 wherein the fingers supported by the forward rods are angled with respect to the vertical plane including the forward rods in a direction away from the other rod.
18. A wafer boat as set forth in claim 17 wherein the fingers supported by the forward rods are angled about 150 with respect to the vertical plane including the forward rods.
19. A wafer boat as set forth in claim 14 wherein the fingers have a first thickness generally adjacent their intersection with the support rods, and a second, lesser thickness at free end portions of the fingers.
20. A wafer boat as set forth in claim 19 wherein the wafer platform support includes grooves adapted to receive the free end portions of the fingers.