Method of making semiconductor devices by single step diffusion

A method of making a semiconductor device by first placing organic volatizable films carrying impurity diffusion material, preferably including aluminum oxide, in contact with the opposed major surfaces of at least one doped semiconductor body; and positioning the assembly in an open-tube diffusion furnace with films contacting the opposed major surfaces of the body alternately carrying N-type and P-type impurity diffusion material. The diffusion furnace is then heated to at least about 1,000 DEG C. and preferably to at least 1,100 DEG C. to volatilize the organic films and simultaneously diffuse the N-type and P-type impurities into the respective opposed major surfaces of the semiconductor body to form at least one PN junction therein. The semiconductor body is then preferably additionally heated to a temperature higher than about 1250 DEG C., preferably in a nitrogen ambient, to drive the impurities into the semiconductor body and also preferably diffuse aluminum from the aluminum oxide into P impurity regions of the semiconductor body. The semiconductor body is thereafter cooled from the diffusion temperature to a temperature between about 550 DEG and 880 DEG C. and preferably between about 575 DEG and 675 DEG C at a rate less than about 3 DEG C. per minute and preferably less than about 2 DEG C. per minute, and thereafter cooled from said temperature to below 300 DEG C. at a rate greater than about 25 DEG C. per minute.