Micromachined device packaged to reduce stiction

DETAILED DESCRIPTION It is an object of the present invention to provide methods for reducing stiction of surfaces of a packaged die.
It is another object of the present invention to provide apparatus for packaging a die so that stiction is reduced.
The present invention provides methods and systems for reducing stiction of a packaged die.
In one embodiment, a micromachined device having at least one component that moves relative to others is packaged so that a cavity around the device has a level of moisture with a minimum level that is at least about 1000 ppm and preferably at least 2000 ppm.
While moisture at such desired levels can be used as the sole antistiction material, a die treated with an antistiction agent can be sealed with a level of moisture to provide enhanced antistiction effects.
The device is preferably an accelerometer having a beam suspended over a substrate and mounted for lateral movement relative to the substrate, and the package is preferably a hermetically sealed package, such as a ceramic dual in-line package (cerdip), a cerpac, or a header.
In another embodiment of the present invention, a die is positioned in an unsealed package, and a liquid dispenser dispenses a small quantity of an organic liquid into the package.
The package is closed and sealed.
The liquids that are used are preferably silicones but can be another organic material that vaporizes at the temperature of the sealing process or any suitable high temperature process and then, when the device is cooled, coats the movable components of the die.
According to another embodiment of the present invention, a cap is formed with a cavity region and an organic material that is solid at room temperature is deposited into the cap.
The cap is bonded over the die, either hermetically or nonhermetically, and plastic is flowed around the die and the cap.
The organic material that is used should vaporize at temperatures that are used for the plastic encapsulation, e.
g.
, 175.
degree.
C.
, and should condense on the surfaces of the movable parts of the die when cooled