Semiconductor substrates such as circular wafers are processed into semiconductor chips by sequentially exposing each substrate to a number of individual processes such as photomasking, etching, implantation and cleaning. Cleaning typically consists of removing resist and/or etching residue from the surface of the substrate. Generally, there are two methods for cleaning the surface of the substrate, namely, wet and dry processing. The wet process consists of a series of steps of spraying and/or immersing the substrate in chemical solutions or solvents. These conventional solvent-aided processes are currently being re-evaluated due to environmental concerns. Also, recent environmental legislation mandates that many of these organic solvents used in wet processes be banned or their use severely limited. Dry processing, on the other hand, use a series of steps that use gases instead of wet chemical solutions to clean the substrate. However, such processes sometimes leave a residue after drycleaning which is unacceptable because such residues may cause device failures or limit operation efficiency. Cleaning with dense phase fluids is desirable because these fluids retain the properties of a liquid but have the diffusivity and viscosity of a gas. Dense phase fluids also act as a solvent to remove contaminants from the wafer surface and effectively clean the surface of the substrate. Modern dense phase fluid cleaning systems however, operate at high pressures in the order of 4000 psi or more to generate and maintain dense phase fluids for cleaning. These systems are consequently very expensive to design and build and also expensive to maintain in production. The inventions described here provide an inexpensive alternative to current dense phase fluid cleaning systems. The inventions describe a computer controlled process, using ultrasonics and dense phase fluids at low to mid pressures (about 1500 psi).
Two patents are being offered for sale in the area of mid pressure dense phase gas and ultrasonic cleaning of semiconductor substrates. 1) US Patent 7,361,231 describes a cleaning method which operates at low pressure (about 1500 psi) using ultrasonics and dense phase fluids. 2) US Patent 6,857,437 describes a computer controlled system which provides for maintaining the high efficiency of the cleaning process even with multiple surface profiles and variations of the substrate to be cleaned, by continuously analysing the contaminants in the exhaust fluid and making upstream adjustments to the process conditions in the cleaning chamber. more
Development information was not provided for this TechPak.
This technology is supported by 2 US patents. more