YIELD Engineering Systems Inc.

In wafer fabrication, photoresist is used to transfer a circuit pattern onto the wafer. Once a pattern is transferred, the remaining photoresist must be removed from the wafer before it can move to the next processing step. The process of removing residues (scum) is known as descumming.
Plasma systems are effective for stripping thick layers of photoresist, descumming, etching, and removing organics. Plasma is an ionized gas capable of conducting electricity and absorbing energy from an electrical supply. (Lightning and the Aurora Borealis are naturally occurring examples of plasma). Manmade plasma is generally created in a low-pressure environment.
When a gas absorbs electrical energy, its temperature increases causing the ions to vibrate faster. In an inert gas, such as Argon, the excited ions can bombard a surface ("sandblast") and remove a small amount of material. In the case of an active gas such as Oxygen, ion bombardment as well as chemical reactions occur. As a result, organic compounds and residues volatilize and are removed.

YES-CV200 systems remove thick layers of photoresist in the shortest amount of production time. Powerful plasma stripping "sandblasts" tough resist in an automated, user-friendly system. Or, for gentler cleaning operations, the "descum" function can be selected at the switch of a button.
Touch screen control and real time pictorial readout of system status and maintenance requirements are standard. Process data is output to a recording computer and compiled into a Microsoft® Excel report.

  YES CV200RF Plasma Photoresist Strip/Descum System

Refinements of Plasma Processing Technical Note 
TF1 Wafer Testing Technical Note 

YIELD ENGINEERING SYSTEMS INC.

We have 2 standard plasma units a CV100PLE-APS for up to 6 inch wafers and a CV108 for 6 to 8 inch wafers. The patented gas swirl process gives better uniformity and allows Polyimide descumm to be more controllable. After significant work with microwave mode control we achieved better than + or - 10% control.  M.F.C. control of the gas mixtures can allow high CF4 concentration during etch with low CF4 concentration at the end of the etch cycle so the wafer silicon would not get severe etching at the end of the Polyimide etch cycle. Software control of the M.F.C setting over the expected etch time of the Polyimide allows this feature. We can also control software allowing variations of the CF4 and Oxygen concentration during etch so the slope of the etched line can be controlled. Software control of the temperature gives the etch rate and slope of the etched line more control. The software allows multiple process parameters to be entered. A full cassette of wafers can be run, with each wafer receiving a separate process so development of a variation of the process can be programmed in and tested and run quickly.

YES CV108 is a single-wafer, downstream plasma stripper/descummer. For removal of photoresist or polyimide coatings from 150 or 200mm wafer the YES CV108 uses microwave energy to ionize Oxygen gas. The resulting Oxygen plasma reacts with the organic coatings and turns them to CO2 and H2O vapors which are drawn out by the vacuum pump and removed through the house exhaust. No hazardous fluids are involved. No hazardous wastes are generated. The high frequency of the microwave assures no ion acceleration to speeds that could cause physical sputter damage to the wafer surfaces. The downstream design of the chamber assures that no electron damage can occur to delicate gates on the wafers. 
Technology is ever evolving and the equipment required to produce it must evolve as well. A demand from IC manufactures for uniformity, faster etch-rate, and versatility was heard. We responded with the CV108. With an improved process chamber design, outstanding components, and flexible software to maximize the process, the demand will be satisfied. Just take a look at the features.

CV-108

An online feature that gives abort recovery options, trouble-shooting tips, and insures proper data input to minimize down-time and make operation simple. The operating system has been designed to allow minimum operator interface for your established process. But, you the Process Engineer have extensive options in fine tuning a process ideal for your product. The microwave power. process gas flows and wafer temperatures are all programmable. You have final control over the setting.

The YES-CV100-PLE-APS Downstream Plasma Stripper offers the latest technology in downstream wafer stripping in a compact, competitively priced, fully automated system. Designed as a full service system, the CV100PLE-APS can be quickly interchanged between stripping and descum modes by simply flipping a control switch on the front panel. Specifically designed for use with 2 to 6 inch wafers, the system includes automatic, robotic, cassette to cassette loading and real time temperature readout. The system provides an aggressive strip rate of up to 15,000 /min, while maintaining a benign environment for even the most sensitive devices (less than 10mV electron shift in 200 Gate Oxide). 
The YES-CV100-PLE-APS is controlled by a touchscreen interfaced PLC controller. The system can be linked via RS232 to a host computer for data acqusition or other purposes. 

CV-100PLE-PTS