Monocrystalline SiC substrates having an asymmetrical geometry and method of producing same
The present invention provides a monocrystalline SiC substrate with an asymmetric shape for enhancing substrate stiffness against thermal induced deformations, the substrate comprising: a main region, and an asymmetric region located at a peripheral region of the substrate and adjacent to the main region, wherein the asymmetric region is inclined inwards, relative to the main region, to provide an asymmetric shape to the substrate. The present invention also provides a method of producing one or more substrates with an asymmetric shape, comprising: performing a multi-wire sawing process in which one or more substrates are cut with an wire-sawing web from an ingot placed on a stage, and cutting the one or more substrates with the asymmetric shape by controlling a relative movement between the wire-sawing web and the stage, the relative movement causing the wire-sawing web to describe a non-linear sawing path across the ingot to cut the asymmetric shape.
1 . A monocrystalline SiC substrate with an asymmetric shape for enhancing substrate stiffness against thermal induced deformations, the monocrystalline SiC substrate comprising:
a main region with a substantially flat surface; and
an asymmetric region located at a peripheral region of the substrate and adjacent to the main region, wherein the asymmetric region is inclined inwards, relative to a front side of the main region, to provide said asymmetric shape to the monocrystalline SiC substrate,
wherein the asymmetrical region has the shape of a circular segment delimited between the adjacent main region and a rim of the substrate,
wherein the asymmetric shape formed by the main region and the asymmetric region is provided by cutting the monocrystalline SiC substrate with said asymmetric shape from a SiC crystal.
2 . The monocrystalline SiC substrate of claim 1 , wherein
the asymmetric region joins the main region in a continuous manner, the inclination between the asymmetric region and the main region defining a cross-section of the asymmetric shape with either a sharp bend or a rounded bend on a backside of the substrate.
3 . The monocrystalline SiC substrate of claim 1 , wherein
the asymmetric region is so dimensioned and inclined inwards, relative to the main region, such that a maximum height of the substrate rim that delimits the asymmetric region is in the range of 15 μm to 60 μm with respect to a reference place of the main region.
4 . The monocrystalline SiC substrate of claim 3 , wherein
said maximum height corresponds to a maximum height at an intersection of a reference plane of the asymmetric region with the substrate rim that delimits the asymmetric region, with respect to the reference plane of the main region, and/or
said maximum height corresponds to 25 μm.
5 . The monocrystalline SiC substrate of claim 1 , wherein
the asymmetric region is so dimensioned and inclined inwards, relative to the main region, such that a maximum distance between a projection, onto a reference plane of the main region, of the substrate rim that delimits the asymmetric region and the main region is in the range of 5 mm to 30 mm.
6 . The monocrystalline SiC substrate of claim 3 , wherein
the reference plane of the main region corresponds to a median surface of the substrate without the peripheral region of the substrate, and/or
the reference plane of the asymmetric region corresponds to a median surface of the asymmetric region; and/or
said maximum distance corresponds to 15 mm.
7 . The monocrystalline SiC substrate of claim 1 , wherein
the substrate is provided with an orientation flat or an orientation notch, the asymmetric region being located on the substrate peripheral area that is opposed to the orientation flat or the orientation notch, and
the angular displacement of the asymmetric region is between ±90° with respect to the orientation flat or notch or notch.
8 . The monocrystalline SiC substrate of claim 1 , wherein
the asymmetric region is so dimensioned and inclined inwards, relative to the main region, such that a maximum height of the substrate rim that delimits the asymmetric region, with respect to a Si-side of the substrate at the main region, is a positive height.
9 . The monocrystalline SiC substrate of claim 1 , wherein the substrate formed by the main and asymmetric regions is characterized by:
a BOW value in the range of −40 μm to 0 μm, and/or
a WARP value of less than 70 μm.
10 . The monocrystalline SiC substrate of claim 1 , wherein
the thickness of the asymmetric and main regions is in the range of 200 μm to 1000 μm, and/or
the substrate has a partial cylindrical shape, at the main region, with a diameter d larger than 149.5 mm, and/or
the substrate has a total thickness variation smaller than 5 μm, and/or
at the main region, the SiC crystal structure has an a° off-axis orientation of the basal plane (1000) which is between 0.5° and 8° off-axis orientation.
11 . The monocrystalline SiC substrate of claim 1 , wherein
said asymmetrical region has a substantially flat shape or a non-flat shape with a convex or a concave curvature.
12 . The monocrystalline SiC substrate of claim 7 , wherein
the angular displacement of the asymmetric region with respect to the orientation flat or notch corresponds to ±60°.
13 . The monocrystalline SiC substrate of claim 10 , wherein
the BOW value is in the range of −35 μm to 0 μm, and/or
the WARP value corresponds to 45 μm.
14 . The monocrystalline SiC substrate of claim 11 , wherein
said thickness of the asymmetric and main regions is in the range of 250 μm to 500 μm, and/or
said α° off-axis orientation of the basal plane (1000) corresponds to a 4° off-axis orientation.