Epitaxial silicon wafer and method for producing the same
AssigneeSumco Corporation
InventorMasayuki Miura
Life of this patent
Estimating the term…
Abstract
An epitaxial silicon wafer comprises a silicon wafer in which the entire surface, excluding an edge region from the outermost edge to 2 mm inward, is a COP region, and an epitaxial silicon layer formed on the surface of the silicon wafer. The average COP size in the peripheral region, located within 5 mm inward from the outermost edge of the silicon wafer, is 75 nm or less.
Claims27
An epitaxial wafer comprising a silicon substrate and an epitaxial layer on top of the silicon substrate, the epitaxial wafer further including crystal-originated particles (COPs) throughout the silicon substrate, wherein an average size of COPs in a region within 5 mm radially of a wafer edge is 75 nm or less.
An epitaxial wafer comprising a silicon substrate and an epitaxial layer on top of the silicon substrate,
- the epitaxial wafer further including crystal-originated particles (COPs) throughout the silicon substrate,
- the silicon substrate forming bulk micro defects (BMDs) in a gettering layer when heated, and
- a BMD variation of densities of the BMDs throughout the silicon substrate is 0.6 or less.
A method of making an epitaxial wafer of 300 mm in diameter comprising:
- providing a silicon melt in a crucible and doping the silicon melt with nitrogen;
- pulling a crystal from the silicon melt at a pulling speed of 60 to 90% of a maximum pulling speed, the silicon melt and the crystal forming an interface;
- applying a cooling system to the crystal to achieve a cooling rate of 2.1 to 2.8° C./min at an outer portion of the crystal when the outer portion reaches a temperature of about 1100° C., the outer portion being about 145 mm from a center axis of the crystal;
- applying a magnetic field of 2000 to 4000 Gauss to the silicon melt;
- providing a gap between the silicon melt and a heat shield of 40 to 80 mm;
- cutting the crystal into a plurality of silicon substrates;
- and
- forming an epitaxial layer on at least one of the silicon substrates;
- wherein the maximum pulling speed means a pulling speed beyond which the crystal begins to deform.
A method of making an epitaxial wafer of 300 mm in diameter comprising:
- providing a silicon melt in a crucible and doping the silicon melt with nitrogen;
- pulling a crystal from the silicon melt at a pulling speed (V) of 60 to 90% of a maximum pulling speed, the silicon melt and the crystal forming an interface;
- applying a cooling system to the crystal to achieve a cooling rate (CR) of 2.105 to 2.839° C./min at an outer portion of the crystal when the outer portion reaches a temperature of about 1100° C., the outer portion being about 145 mm radially from a center axis of the crystal;
- applying a magnetic field of 2000 to 4000 Gauss to the silicon melt;
- providing a gap between the silicon melt and a heat shield of 40 to 80 mm so as to maintain:
- 0.183≤V/G≤(0.1035×CR)−0.0350, where
- 2.105≤CR≤2.839, and where G means the temperature gradient about the outer portion in a direction of growth of the crystal between the temperature at the interface to about 1350° C.;
- cutting the crystal into a plurality of silicon substrates;
- and
- forming an epitaxial layer on top of at least one of the plurality of silicon substrates;
- wherein the maximum pulling speed means a pulling speed beyond which the crystal begins to deform.
A method of making an epitaxial wafer of 300 mm in diameter comprising:
- providing a silicon melt in a crucible and doping the silicon melt with nitrogen;
- pulling a crystal from the silicon melt at a pulling speed (V) of 60 to 90% of a maximum pulling speed, the silicon melt and the crystal forming an interface;
- applying a cooling system to the crystal to achieve a cooling rate (CR) of 1.940 to 2.624° C./min at a center axis of the crystal when the center axis reaches a temperature of about 1100° C.;
- applying a magnetic field of 2000 to 4000 Gauss to the silicon melt;
- providing a gap between the silicon melt and a heat shield of 40 to 80 mm so as to maintain:
- 0.174≤V/G≤(0.1096×CR)−0.0387, where
- 1.940≤CR≤2.624, and where G means the temperature gradient about the center axis in a direction of growth of the crystal between the temperature at the interface to about 1350° C.;
- cutting the crystal into a plurality of silicon substrates;
- and
- forming an epitaxial layer on top of at least one of the plurality of silicon substrates;
- wherein the maximum pulling speed means a pulling speed beyond which the crystal begins to deform.
Dependencies are inferred from the claim text.