New technology has created a demand for more proficient electropolishing. Methods used in the past no longer meet the criteria set by industries that require high purity, such as the manufacturers of semiconductors, vacuum systems, medical devices and food-processing equipment. Electromatic has cooperated with many component manufacturers to achieve results leading to qualification and acceptance of their products for UHP applications.
Large Scale Integration
The development of ultra-clean gas delivery systems is critically important to the advancement of submicron LST fabrication technologies. Electromatic is in the forefront in process research in surface cleaning and chromium enrichment of tubing and other components used in these systems.
Cleanliness: The component must meet three general characteristics: particle-free, outgas-free, and with trace-element cross-contamination below certain levels.
To improve yields on submicron-level chip manufacturing, we place a strong emphasis on eliminating Na+
4 and SO2–
4, chemical species that can cause catastrophic failure if allowed to reach the final etching of a circuit. We have developed methods to deal with such cross-contamination and can reliably process components to meet the criteria set by Intel:
During manufacture, certain operations may contribute to material degradation leading to eventual failure. To avoid such defects, Electromatic works closely with our customers' engineers to provide innovative methods for surface treatment.
To prevent contamination during the electropolishing, Electromatic observes strict quality standards. These include use of hot and cold D.I. water rinses, with water quality monitored at 18 megohms @ 25°C filtered to 0.02 microns. The final rinse is followed by a total dry nitrogen blow-down from a cryogenic source 99.999% pure.
Surface Integrity: Smoothness of the metal surface, usually in the range of 4 – 10 Ra, and absence of defects are important factors. Pitting, haze, gas marks, etching, cracks and scratches are causes for rejection, as these are sites where corrosion originates. By the use of custom-engineered racking systems, and correct electropolishing techniques, such defects can be prevented, with the exception of those caused by material imperfections, or irreparable damage from prior manufacturing processes. At Electromatic, parts are subjected to incoming, in-process, and outgoing inspection, and carefully evaluated as to acceptability.
Chromium Enrichment: Perhaps the most significant requisite is the generation of chromium at the surface of the metal. The causes for the changes in chemical composition are complex, but the results are quantifiable. Measurement of the ratios and depths of the resultant chromium-oxide layer provides a good test of the quality of the electropolishing. The generally accepted UHP values for 316L stainless steel, in accordance with SEMATEC standards, are as follows:
|Cr/Fe Ratio:||1.5 or greater, usually found at ½ oxide thickness|
|CrO/FeO Ratio:||2.0 or greater|
|Depth of Enrichment:||18-23Å|
To reach optimum values on a particular component may take experimentation and require analyses of several replicates. However, once the electropolishing parameters have been established, Electromatic can assure that such values will be reproduced.
Surface Analysis: The recognized methods for the measurement of surfaces include electron spectroscopy for chemical analysis (ESCA), Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). Electromatic has undertaken extensive testing and analyses of the results using all of these methods. Samples taken from production runs are submitted on a regular basis to an independent testing laboratory to assure qualification. Some of these reports are reproduced below and demonstrate how Electromatic meets and even exceeds industry standards.
|Sample ID||Reduced Chromium||Chromium Oxide||Reduced Iron||Iron
Cr / Fe
|Cr Oxide / Fe Oxide|
|Sample ID||Oxide Thickness (Å)||Max Cr / Fe Ratio (depth, Å)||Depth of Enrichment (Å)||Surface Iron Oxide Thickness||Cr Enriched Layer Thickness||Carbon Layer Thickness (Å)|
Other UHP Applications
From the in-depth experience gained in LSI component processing, Electromatic can assist manufacturers in other high-tech industries achieve outstanding results.
Vacuum: In the manufacture of high vacuum chambers used for vacuum deposition, our processes are capable of providing surfaces that have a very low out gassing profile. This enables the final system to pump down to 10-7 Torr three to five times faster than if the surface were not treated.
Medical: Electropolishing is widely used for the equipment and surgical tools used in the medical and dental professions. The Electromatic UHP Process particularly applies to bodily invasive devices such as ear, dental, joint and bone implants, where super-clean, inert, non-pitted surfaces are a necessity.
Pre-Coating: When parts require special coating, the UHP Process provides a means for microsizing to close tolerances, and at the same time producing a surface free of contaminants that inhibit adhesion. Electromatic has used this technique effectively as a pre-treatment for polymer coatings that must guarantee a 25-year life to components in the propulsion and cooling systems of the Freedom Space Station.