Sealing Collaboration Pays Dividends in Chamber Cleaning

plasma erosion data

The Challenge

In the very competitive environment of semiconductor chip manufacturing, reduced cost per wafer is a top priority. DuPont successfully collaborated with Spansion Inc. Fab 25 in Austin, Texas to evaluate an O-ring product designed to help increase the uptime of HDPCVD equipment operating under aggressive chamber cleaning plasma conditions.

The dramatic improvement in seal performance enabled Spansion to make a step change in their preventative maintenance (PM) schedule that resulted in increased productivity and reduced cost-of-ownership. Spansion is the largest provider of Flash memory solutions in the world for the integrated electronics market.

The Solution

For Roger Sorum, equipment engineer at Spansion Fab 25, uptime and quality are his primary responsibilities to help maintain a competitive advantage. A problem occurred in the HDPCVD equipment when process gases (SiH4, O2, He) and chamber cleaning plasma (two stage NF3 and O2 plasma) created an aggressive process environment. High particle count and leaks from seal erosion and compression set caused sealing issues in IMD and STI processes. The scheduled PM cycle was 90 days, but premature sealing issues occurred within 30–60 days with the isolation valve poppet seal, slit valve door seal and the MESC port flange insert seal. The incumbent O-ring performance issues were related to physical as well as chemical plasma attack creating seal erosion.

Replacing O-rings can take up to 12 hours to bring the machine back on line and pass wafer qualification. Some seal locations limit individual chamber production, while others limit the entire tool. “The challenge is to increase availability while reducing the total cost-of-ownership” says Sorum.

Spansion turned to DuPont for options to produce longer seal life with reduced particle generation. Within several months, DuPont developed a prototype.

After reviewing test results, parts were produced for trials against other competitive FFKM products. Kalrez® 9100 parts outperformed the competitive FFKM products under all conditions. The DuPont and Spansion team, working together, pushed Kalrez® 9100 parts to extreme parameters faster than anyone expected and contributed to the success of this process.

Key Advantages

Key learnings from the collaboration were the following:

  1. Active feedback during development in real time;
  2. Testing Kalrez® 9100 parts in the harshest possible conditions;
  3. Extending testing well beyond timeframes for planned maintenance to establish a new, far-reaching standard for PM limits, all with Spansion process engineering agreement. Currently, Kalrez® 9100 continues to exceed the normal Spansion PM schedule by up to 6 times longer, extending the 30-day PM out to 180 days, depending upon the seal location. Increased equipment availability has increased the fab production capacity by more than 20%, without the need to purchase and install additional equipment. Spansion has now expanded their adoption of Kalrez® 9100 to other tools in both thin films and dry etch with consistently favorable results.