ClassOne Technology, Kalispell, Montana, has developed the CopperMax plating chamber, a design that is said to extend bath life by a factor greater than 20. In this chamber, a cation-exchange semipermeable membrane divides the copper bath into two sections, an upper and a lower. The upper section contains all of the additives, and it actively plates the wafer. The lower section of the bath contains the anode that supplies elemental copper — which is able to travel through the membrane and into the upper section to ultimately plate the wafer.
However, the membrane prevents additives from traveling down to the anode, where they would break down and form process-damaging waste products. As a result, the CopperMax bath remains much cleaner, and bath life is extended by over 20 times. This increases uptime, enables higher-quality, higher-rate copper plating, and reduces cost of ownership very substantially.
ClassOne cites actual performance data from a CopperMax pilot installation on a Solstice tool at a Fortune 100 customer. Over a six-month period, the customer tracked its actual production operating costs while using the new chamber for copper TSV, Damascene, and high-rate copper plating. For the three processes with CopperMax, engineers reported that operating costs were reduced between 95.8% and 98.4% compared with previously used conventional plating chambers.
ClassOne points out that consumables are the largest cost factor in copper plating. Optimizing copper plating generally requires expensive organic additives — which are consumed very rapidly and need to be replenished frequently.
“We learned, however, that over 97% of those expensive additives were not being consumed by the actual plating process,” says Kevin Witt, President of ClassOne Technology. “Most were being used up simply by contact with the anode throughout the process! So, we designed our new copper chamber specifically to keep additives away from the anode — and the results are pretty dramatic. Significant savings can be realized by high- and medium-volume users with high throughputs as well as by lower-volume and R&D users that have long idle times.”
For example, a customer using a Solstice system with six CopperMax chambers and running TSV and high-rate copper plating will save over $300,000 per year just from additive use reductions.
In addition, the CopperMax also reduces copper anode expenses. The chamber is designed to use inexpensive bulk anode pellets instead of solid machined copper, which cuts anode costs by over 50%. And since the pellets have ten times more surface area, they also increase the allowable plating rates.
