YIELD Engineering Systems Inc.

Plasma is an ionized gas capable of conducting electricity and absorbing energy from an electrical supply.  Typically, plasma is created in a low-pressure environment. Plasma cleaning systems are an effective way to remove small amounts of contaminants from a substrate surface.
(For removing thick photoresist layers, see our Plasma Photoresist Strip/Descum Systems).

The use of plasma is an effective way to clean without using hazardous solvents. When a gas absorbs electrical energy, its temperature increases causing the ions to vibrate faster and “scrub” a surface.

  YES Plasma Cleaning Systems

Manufactures of CD/DVD discs have found the Glen Plasma Systems excellent for removing photo-resist residues in their pre-production process.
NOTE: The G1000 with the new temperature control and loop program can ideally be used as a plasma stripper. It takes about 1 hour of continuous plasma to remove 1 micron of resist.

Model YES-G500 Two Powered Shelves Technical Note 
Model YES-G1000 Four Powered Shelves Technical Note 
Model YES-G1000LMC Loaded Magazine Cleaner Technical Note 

GT 110 The use of Plasma for Surface modification Technical Note 
GT 115 Chamber Design & Adhesion Strength Technical Note 
GT 125 Electron-Free Plasma for ESD samples Technical Note 

Plasma & Plasma Cleaning Technical Note 

In semiconductor processing, plasma cleaning is commonly used to prepare a wafer surface prior to wire bonding. Removing contamination (flux) strengthens the bond adhesion, which helps extend device reliability and longevity.
In biomedical applications, plasma cleaning is useful for achieving compatibility between synthetic biomaterials and natural tissues. Surface modification minimizes adverse reactions such as inflammation, infection, and thrombosis formation.

Plasma processing equipment commonly uses RF to generate gas plasma. A variety of parameters can affect the physical characteristics of plasma and subsequently affect the surface chemistry obtained by plasma modification.  In order to achieve uniform, superior results, Yield Engineering Systems recommends low frequency plasma (40-50 kHz) over high frequency plasma (13.56 MHz or 2.54 GHz) for the following reasons:

Higher Ion Density, Low frequency plasma provides more energy per square inch than high frequency cleaning. While this may seem counterintuitive, high frequency plasma cleaning systems actually lose considerable energy through heat loss. Energy loss with a 13.56 MHz system is up to 850 times greater than with a 40 kHz system.
Higher Ion Density, Low frequency plasma provides more energy per square inch than high frequency cleaning. While this may seem counterintuitive, high frequency plasma cleaning systems actually lose considerable energy through heat loss. Energy loss with a 13.56 MHz system is up to 850 times greater than with a 40 kHz system.
Increased Efficiency, The efficiency of a plasma system is the ratio of the energy used in producing the plasma vs. the energy dissipated in losses such as heat. A low frequency plasma system acts like a perfect capacitor with infinite capacitive impedance, or zero current drain when in standby mode. Current applied across the capacitive pair (electrodes) causes the gas to ionize, and the impedance is bridged causing current flow (plasma) between the electrodes.
Better Uniformity, Low frequency systems have no "shadowing," which occurs when samples on upper shelves form a mask that prevents plasma from reaching samples on the lower shelves.

Choosing the appropriate system and frequency for your specific process depends on multiple factors. It's important to note that a higher RF power doesn't necessarily equate to higher plasma density (especially at low pressures). The additional power is often wasted through increased ion bombardment and through the creation of hot electrons, not in promoting ionization. Also, if the average voltage between the plasma and chamber walls (plasma potential) becomes too high, it can cause sputtering and contamination to substrates.

In semiconductor fabrication, after an IC chip is affixed to the ceramic substrate, it’s baked to cure the epoxy. But this process causes small amounts of contamination on top of the bond pads that can inhibit wire bonding. Plasma cleaning the surface to remove contaminants improves the wire bond.
In biomedical applications, plasma cleaning removes small amounts of contaminants as well as sterilizes substrates. Plasma cleaning increases biocompatibility and controls surface tension to achieve either a hydrophobic or hydrophilic surface.
Power density and capability are the same in both machines; capacity is the only difference.

G500

G1000

No. of powered shelves

2

4

Clean Room Compatibility

Class 10

Operation Temperature

145°C Max.

20-100C°

N2 Flow Rate

1.0 SCFM

1.7 SCFM

Process Gas Flow Rate

0.9 x 10-3 SCFM Average

Interior Chamber Dimensions

18"W x 18"D x 8.25" H

18"W x 18"D x 12"H

Chamber Process Area

233 sq. in per shelf or 700 sq. in max.
(mode dependant)

233 sq. in per shelf or 931 sq. in max.
(mode dependant)

Overall System Dimensions

23.5"W x 28.03"D x 40.87"H
(add 10.62" to height for light tower)

23.5"W x 28.03"D x 40.87"H
(add 10.62" to height for light tower)

Chamber Material

6061-T6 ALUMINUM

Process Gas Inputs

3 Standard

3 Standard, 4 Optional

Mass Flow Controllers

Optional, up to 3 for Gas Mixing

SEMI Certifications

S2 Compliance

No. of Recipes

12 with Load/Save/Loop/Link Capability

RF Plasma Power

100-500 Watts, Selectable Power

0-1000 Watts, Selectable Power

RF Leakage Magnetic

0.6mA/m, 4.15 x 10-7 sq. A/sq. m Average

 
Click on picture to enlarge
(Picture from YES-G1000LMC Magazine System)

 
Click on picture to enlarge
(Picture from YES-G1000LMC Magazine System)

 
Click on picture to enlarge
(Picture from YES-G1000LMC Magazine System)

 
Click on picture to enlarge
(Picture from YES-G1000LMC Magazine System)