Micro-electromechanical device inspection

Details Micro-electromechanical device inspection Micro-electromechanical device inspection

1998-12-23

2001-05-01

Williams, Hezron (Department: 2856)

Measuring and testing

With fluid pressure

Leakage

C073S040700, C073S049300

Reexamination Certificate

active

06223586

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to inspection methods for integrated circuit (IC) and micro-electromechanical (MEM) devices and more particularly to inspection of these devices for hermeticity.
BACKGROUND OF THE INVENTION
For certain IC and MEM devices, the environment in which they will be operating requires that they are hermetically sealed in order to operate properly. As used herein, when referring to the term “devices”, it is meant to refer to MEM devices or IC devices that contain enclosed cavities. For these devices, then, some type of test or inspection is needed to assure that the ones which are not sealed properly are rejected. A common practice in the integrated circuit industry is to test for hermeticity using helium leak detectors, but this does not work for every type of package and substrate. While this method generally works well for ceramic packages, it does not work well with glass substrates since the glass will readily absorb the helium. The result is that the helium leak detector will detect a leak when in fact there may not be one. Consequently, the need arises for a reliable and inexpensive method to test for hermeticity of the devices, particularly for those applications that employ glass substrates.
SUMMARY OF THE INVENTION
In its embodiments, the present invention contemplates a method for inspecting for hermeticity of a device containing a cavity. The method comprises the steps of: submerging the device in a liquid; pressurizing the liquid to greater that one atmosphere for a given time period; removing the pressure from the liquid; and inspecting the device under magnification for indications of the liquid in the cavity.
Accordingly, an object of the present invention is to soak devices in high pressure liquid to force the liquid into the cavities of defective devices and then inspect the devices for hermeticity.
Another object of the present invention is to inspect the devices while in a liquid in order to avoid evaporation of the liquid that may be within the cavities.
An advantage of the present invention is that hermeticity can be assured, thus preventing defective devices from being assembled into finished electronic components.
A further advantage of the present invention is that hermeticity testing can be conducted for those devices employing glass substrates.
Another advantage of the present invention is that multiple devices can be subjected to the inspection process at one time, thus assuring an efficient and cost effective inspection process.
An additional advantage of the present invention is that the inspection for leakage can take place with the devices underwater to assure that the liquid which leaks into any of the cavities will not evaporate prior to inspection.


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