Methods for forming a silicon substrate with reduced grown-in nuclei for epitaxial defects and methods for forming an epitaxial wafer
AssigneeGlobalWafers Co., Ltd.
InventorsPietro Valcozzena, Maria Porrini, Januscia Duchini
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Abstract
Methods for preparing single crystal silicon substrates for epitaxial growth are disclosed. The methods may involve control of the (i) a growth velocity, v, and/or (ii) an axial temperature gradient, G, during the growth of an ingot segment such that v/G is less than a critical v/G and/or is less than a value of v/G that depends on the boron concentration of the ingot. Methods for preparing epitaxial wafers are also disclosed.
Claims16
A method for forming a silicon substrate with reduced grown-in nuclei for epitaxial defects, the silicon substrate being boron doped, the method comprising:
- adding an initial charge of polycrystalline silicon to a crucible;
- heating the crucible comprising the initial charge of polycrystalline silicon to cause a silicon melt to form in the crucible;
- adding boron to the crucible to produce a doped silicon melt;
- contacting a silicon seed crystal with the doped silicon melt;
- withdrawing the silicon seed crystal to grow a single crystal silicon ingot, the ingot having a constant diameter portion, wherein a segment of the constant diameter portion of the ingot has a boron concentration from 2.8×1018 atoms/cm3 to 5.4×1018 atoms/cm3;
- controlling (i) a growth velocity, v, and/or (ii) an axial temperature gradient, G, during the growth of the segment such that v/G is less than 0.20 mm2/(min*K) and interstitials are the dominant intrinsic point defect in the segment;
- cooling the segment of the constant diameter portion of the ingot from its solidification temperature to 950° C. or less, wherein the dwell time the segment of the constant diameter portion of the ingot is in the temperature range from 1150° C. to 950° C. is less than 160 minutes;
- and
- slicing the substrate from the single crystal silicon ingot.
A method for forming a silicon substrate with reduced grown-in nuclei for epitaxial defects, the silicon substrate being boron doped, the method comprising:
- adding an initial charge of polycrystalline silicon to a crucible;
- heating the crucible comprising the initial charge of polycrystalline silicon to cause a silicon melt to form in the crucible;
- adding boron to the crucible to produce a doped silicon melt;
- contacting a silicon seed crystal with the doped silicon melt;
- withdrawing the silicon seed crystal to grow a single crystal silicon ingot, the ingot having a constant diameter portion, wherein a segment of the constant diameter portion of the ingot has a boron concentration from 5.4×1018 atoms/cm3 to 8.0×1018 atoms/cm3;
- controlling (i) a growth velocity, v, and/or (ii) an axial temperature gradient, G, during the growth of the segment such that v/G is less than 0.25 mm2/(min*K) and interstitials are the dominant intrinsic point defect in the segment;
- cooling the segment of the constant diameter portion of the ingot from its solidification temperature to 950° C. or less, wherein the dwell time the segment of the constant diameter portion of the ingot is in the temperature range from 1150° C. to 950° C. is less than 160 minutes;
- and
- slicing the substrate from the single crystal silicon ingot.
Dependencies are inferred from the claim text.