Silicon wafer heat treatment method

A method for heat treating a silicon wafer, comprising the step of:

• performing a heat treatment, by heat treatment furnace, under a condition enabling an amount of oxygen precipitation and a density of oxygen precipitates that effectively suppress a slip in a silicon wafer to which oxygen is added,
• wherein the condition is determined by utililizing
• τ=τ1+τ2 =2.2 ×10−13·Co·exp(0.215eV/kT)+μ·b ·(N·D·cos(54.7°))1/2 (K)
• where Co is a solid solution oxygen concentration (atoms/cm3;
• JEITA), k is the Boltzmann constant, T is a temperature in the absolute temperature (K), b is a magnitude of the Burgers vector in the silicon crystal, and μ is a modulus of rigidity of the silicon crystal, N is a density of the oxygen precipitates, and D is a diameter of the oxygen precipitate.

A method for heat treating a silicon wafer to which oxygen is added, comprising the steps of:

• determining in advance a strength T1 to suppress a slip based on solid solution oxygen and a strength T2 to suppress the slip based on precipitated oxygen to determine a rate R of temperature increase/decrease such that a shear stress S caused by a thermal stress and a holding way of the silicon wafer to which the oxygen is added does not exceed a sum of the strength T1 based on the solid solution oxygen and strength T2 based on the precipitated oxygen to suppress the slip, wherein the strength is given by
• τ=τ1+τ2 =2.2×10−13·Co·exp(0.215eV/kT)+μ·b·(N·D·cos(54.7°))1/2 (K)
• where Co is a solid solution oxygen concentration (atoms/cm3;
• JEITA), k is the Boltzmann constant, T is a temperature in the absolute temperature (K), b is a magnitude of the Burgers vector in the silicon crystal, and μ is a modulus of rigidity of the silicon crystal, N is a density of the oxygen precipitates, and D is a diameter of the oxygen precipitate;
• calculating a critical rate of temperature increase/decrease from a relationship of a wafer diameter and an interval distance between wafers in a heat treatment so as to prevent the slip;
• and
• performing the heat treatment, by heat treatment furnace, of the wafer with a rate of temperature increase/decrease not exceeding the calculated rate R so as to prevent the slip in the heat treatment.

A method for determining a condition for heat treating a silicon wafer containing a predetermined amount of solid solution oxygen, comprising the steps of:

• adjusting the condition so as to obtain a strength higher than a shear stress generated in a heat treatment step by utilizing a predetermined theoretical formula capable of calculating the strength against a slip;
• determining a shear stress generated in a heat treatment process from a size, a shape, and a way of holding during treatment of the silicon wafer;
• determining a strength against a slip determined from a residual solid solution oxygen and an amount and a shape of precipitated oxygen, the strength being given by
• τ=τ1+τ2 =2.2×10−13·Co·exp(0.215eV/kT)+μ·b·(N·D·cos(54.7°))1/2 (K)
• where Co is a solid solution oxygen concentration (atoms/cm3;
• JEITA), k is the Boltzmann constant, T is a temperature in the absolute temperature (K), b is a magnitude of the Burgers vector in the silicon crystal, and μ is a modulus of rigidity of the silicon crystal, N is a density of the oxygen precipitates, and D is a diameter of the oxygen precipitate;
• determining a heat treatment condition that effectively suppresses slip by comparing the shear stress with the strength;
• and
• performing the heat treatment, by heat treatment furnace, under the condition.