Large diameter silicon carbide wafers
Silicon carbide (SiC) wafers and related methods are disclosed that include large diameter SiC wafers with wafer shape characteristics suitable for semiconductor manufacturing. Large diameter SiC wafers are disclosed that have reduced deformation related to stress and strain effects associated with forming such SiC wafers. As described herein, wafer shape and flatness characteristics may be improved by reducing crystallographic stress profiles during growth of SiC crystal boules or ingots. Wafer shape and flatness characteristics may also be improved after individual SiC wafers have been separated from corresponding SiC crystal boules. In this regard, SiC wafers and related methods are disclosed that include large diameter SiC wafers with suitable crystal quality and wafer shape characteristics including low values for wafer bow, warp, and thickness variation.
1 . A silicon carbide (SiC) wafer comprising:
a diameter of at least 195 millimeters (mm);
a thickness in a range from 300 microns (μm) to 1000 μm; and
a total thickness variation (TTV) of less than 7 μm, wherein the TTV is defined as difference between a maximum elevation and a minimum elevation of a front surface of the wafer relative to a back surface of the wafer.
2 . The SiC wafer of claim 1 , wherein the total thickness variation (TTV) is less than 2.6 μm.
3 . The SiC wafer of claim 1 , wherein the total thickness variation (TTV) is less than 2.2 μm.
4 . The SiC wafer of claim 1 , wherein the total thickness variation (TTV) is measured when the wafer is clamped.
5 . The SiC wafer of claim 1 , wherein the total thickness variation (TTV) is measured when the wafer is held in place by a vacuum chuck applied at the back surface of the wafer.
6 . The SiC wafer of claim 1 , wherein the diameter is in a range from 195 mm to 455 mm.
7 . The SiC wafer of claim 1 , wherein the diameter is in a range from 195 mm to 305 mm.
8 . The SiC wafer of claim 1 , wherein the thickness is in a range from 300 to 500 μm.
9 . The SiC wafer of claim 1 , wherein the thickness is in a range from 300 to 800 μm.
10 . The SiC wafer of claim 1 , further comprising a local thickness variation (LTV) of less than 4 μm for a site area of 1 cm2, wherein the LTV is defined as a difference in a local maximum elevation and a local minimum elevation of a front surface relative to a back surface for the site area of the wafer when the wafer is held in a clamped state.
11 . The SiC wafer of claim 1 , further comprising a site front least-squares (SFQR) maximum value of less than 1.5 μm for a site area of 1 cm2, wherein the SFQR for the site area is defined as a sum of the absolute value of a maximum distance from a localized focal plane to a surface of the wafer above the localized focal plane and a maximum distance from the localized focal plane to a surface of the wafer below the localized focal plane, wherein the localized focal plane is defined by a local least squares fit for the site area.
12 . The SiC wafer of claim 1 , wherein the SiC wafer comprises 4-H SiC.
13 . The SiC wafer of claim 1 , wherein the SiC wafer comprises semi-insulating SiC.
14 . The SiC wafer of claim 1 , wherein the SiC wafer comprises n-type SiC.
15 . The SiC wafer of claim 14 , wherein the SiC wafer comprises nitrogen for an n-type dopant.
16 . The SiC wafer of claim 15 , wherein the n-type dopant forms a higher doping region and a lower doping region such that the higher doping region is laterally bounded the lower doping region.
17 . The SiC wafer of claim 16 , wherein the higher doping region is registered with a central region of the SiC wafer.
18 . The SiC wafer of claim 16 , wherein the higher doping region is offset from a central region of the SiC wafer.
19 . The SiC wafer of claim 15 , wherein the SiC wafer further comprises at least one of boron, aluminum, germanium, beryllium, gallium, tin, arsenic, phosphorus, titanium, and vanadium.
20 . A silicon carbide (SiC) wafer comprising:
a diameter of at least 195 millimeters (mm);
a thickness in a range from 300 microns (μm) to 1000 μm; and
a local thickness variation (LTV) of less than 4 μm for a site area of 1 cm2, wherein the LTV is defined as a difference in a local maximum elevation and a local minimum elevation of a front surface relative to a back surface for the site area of the wafer.