Sharp Kabushiki Kaisha Corporation

Sharp Microelectronics Technology, Inc.

Implanted Material Technology, Inc.

Narayanan Meyyappan

Tatsuo Nakato

The method is a technique for making silicon-on-insulator (SOI) wafers which are suitable for use in the production of CMOS devices, which are designed to operate with low power and low voltage. The method of the invention provides high quality SOI material at relatively low cost by implanting, in one form of the invention, a very low dose of nitrogen or oxygen ions at a very low energy into silicon, and thereafter diffusing oxygen during an annealing process to form a continuous buried layer of silicon-oxy-nitride (Si.sub.x,O.sub.y N.sub.z, or SON) or SiO.sub.2. The process includes using an ion beam to implant ions into the substrate, thereby damaging a region of the crystal. The feed gas for the ion beam may be a variety of nitro-oxide gases, such as NO, N.sub.2 O, NO.sub.2, as well as a simple mixture of nitrogen and oxygen gases. Other elemental ions may be implanted to create the desired crystal defects. The wafer is then annealed in an atmosphere that allows the diffusion of the second species, usually oxygen, through an upper layer of the substrate to the region wherein the crystal has been damaged, wherein the second species reacts with the damaged crystal material to form a thin layer of insulating material which is located a very small distance below the surface of the wafer.

Method of treating silicon to obtain thin, buried insulating layer

The invention provides a method of forming shallow SIMOX (Separation by IMplantation of OXygen) substrates by implantation of molecular oxygen ions (O.sub.2 +), instead of implanting atomic oxygen ions (O+) as is done in prior art SIMOX processes. Use of molecular oxygen ions (O.sub.2 +) doubles the yield of oxygen atoms implanted for each unit of electric charge deposited in the wafer. The resultant structure, after annealing, has a defect density which is not substantially different from SIMOX processing using atomic oxygen ions (O+). An alternative method for implanting molecular nitrogen ions is also disclosed.

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Woburn, MA, United States of America

Narayanan Meyyappan