The YES-VertaVac series of automated high vacuum ovens is designed for today’s most demanding MEMS and semiconductor process applications. These tools are designed to ensure moisture and hydrogen removal using high vacuum (10-5) and high temperature (up to 450°C). Our patented nitrogen purge precedes process ramp and creates a successful procedure for improved MEMS lifetime and performance.
Nitrogen purge also results in a low oxygen environment which allows for proper copper annealing or aluminum annealing.
The tool incorporates the laminar flow technology of the YES-PB HV Series. It accommodates 200 and 300mm wafers with one or two load ports and a wafer handling robot inside an integrated Class 1 minienvironment. Up to 50 wafers are loaded into a stainless steel cassette-type rack on the oven chamber door and, when loading is complete, lifted up into the vacuum chamber.
Wafer Dehydration – The moisture on the surface of wafers will cause unintended reactions with various deposition steps. These reactions result in unstable surface which degrade over time. Vacuum dehydration provides a clean stable starting surface resulting in superior films.
The process begins with vacuum cycle purges to remove oxygen and water vapor followed by a continuous horizontal laminar flow of up to four process gasses. The laminar flow of gas can be maintained during a recipe-driven temperature profile. Operating temperatures are 150°C to 450°C; laminar flow pressure range is 0.50-500 Torr. The tool is also capable of evacuation down to 1E-5 Torr using a turbo vacuum pump.
The YES-VertaVac gives engineers moisture resistant surface modification and increased time available between process steps.
Getter Activation – Getters are used to scavenge unwanted gases in many applications. In MEMS devices, getters may be used to tie up excess moisture or hydrogen which may interfere with the long term operation of the device. Activating the getter material involves high temperature and high vacuum processing to ensure the material starts as moisture / hydrogen-free as possible. 400°C and high vacuum (10-5) removes moisture/hydrogen gas from both wafers and getters at the same time.
Metal Annealing – Annealing is a heat treatment where the microstructure of a material is altered, causing changes in its properties such as strength and hardness. In the semiconductor industry, silicon wafers are annealed so that dopant atoms (such as boron, phosphorus or arsenic), can be incorporated in substitutional positions into the crystal lattice, which drastically changes the electrical properties of the semiconducting material.
In the case of copper, adding an anneal step:
- Improves properties of the copper layer
- Increases grain size for faster polishing
- Provides better conductivity
- Reduces surface tension
- Minimizes electromigration
- Allows a consistent CMP rate across the wafer
Thermal treatment of Thin Film Resistors – Thin film resistors can change properties rapidly as they age unless they are properly thermally treated. The process stabilizes the crystal grain and ensures long term predictable behavior.