Wafer-level package with silicon gasket

Details Wafer-level package with silicon gasket Wafer-level package with silicon gasket

2001-12-20

2004-09-07

Cuneo, Kamand (Department: 2827)

Active solid-state devices (e.g., transistors, solid-state diode

Housing or package

Insulating material

C174S050510, C174S050510

Reexamination Certificate

active

06787897

ABSTRACT:

FIELD OF THE INVENTION
The present invention is directed towards semiconductor packaging techniques, and more specifically, towards the fabrication of wafer-level packages.
BACKGROUND OF THE INVENTION
Many semiconductor devices are sensitive to contamination, humidity, and other such environmental factors. To protect them from harm, the devices must be put in a hermetically sealed package. In the past, a device had to first be cut or otherwise separated from its wafer before it could be put into a package. In wafer-level packaging, packaging is performed while the device remains on the wafer. In this fashion, hundreds or thousands of packages can be created simultaneously, and then separated by sawing or other means.
FIG. 1
illustrates an exemplary wafer-level package
101
. A first wafer
102
has a gasket
103
bonded to a second wafer
107
, creating a hermetically sealed environment
109
between the two wafers to protect a device
111
. Only a portion of wafer
102
and wafer
107
are shown in the figure, but there can be hundreds or thousands of such wafer-level packages formed simultaneously between the two wafers. The gasket
103
is created by depositing material such as metal or a polyimide onto wafer
102
in the desired gasket shape. The two wafers are then bonded together at the gasket. This method is effective in creating hermetically sealed environment
109
. However, the deposited material is not very rigid, and is prone to deformation when pressure is applied during the bonding process. Since much of the applied pressure is used up by gasket deformation, very little of the applied pressure actually transfers to the bond juncture itself. Therefore, more pressure has to be applied for a longer period of time to create the bond. Furthermore, the process of depositing material creates an irregular gasket bonding surface, which causes problems during bonding. Finally, it is difficult to precisely control the geometry of the gasket, since the deposited material tends to shrink or change shape during the deposition process.
SUMMARY OF THE INVENTION
In accordance with an illustrated preferred embodiment of the present invention, a gasket for a wafer-level package is carved out from the wafer material itself. The wafer is typically made of silicon, although materials such as glass, 3-5 compounds, ceramics, plastics or other materials can be used. Silicon is extremely rigid, and therefore an ideal gasket material. When pressure is applied during bonding, the silicon gasket will not deform, and the applied pressure is concentrated at the bond juncture. As a result, it takes less force and/or time to bond the wafer-level package. Furthermore, the original wafer surface is manufactured to be extremely flat. Since the gasket surface is the original wafer surface, the gasket will also have an extremely flat surface, which facilitates a uniformly tight bond.
The present invention also uses existing silicon etching technology that offers high precision in both etch depth and gasket width when carving out the desired shape. This allows greater control over the dimensions of the hermetically sealed cavity. Also, due to the high strength of silicon, the gaskets can be made narrower than in the past—usually no more than 10 &mgr;m wide. The surface area of the gasket determines the amount of pressure on the bond juncture during bonding for a given bonding force. Since a narrower gasket has less surface area, it is able to concentrate more of the applied bonding force at the bond juncture to create a strong seal.
Further features and advantages of the present invention, as well as the structure and operation of preferred embodiments of the present invention, are described in detail below with reference to the accompanying exemplary drawings. In the drawings, like reference numbers indicate identical or functionally similar elements.


REFERENCES:
patent: 6228675 (2001-05-01), Ruby
patent: 6229404 (2001-05-01), Hatanaka
patent: 6265246 (2001-07-01), Ruby
patent: 6285067 (2001-09-01), Hyoudo et al.
patent: 6359333 (2002-03-01), Wood et al.
patent: 6453749 (2002-09-01), Petrovic et al.
patent: 6470594 (2002-10-01), Boroson et al.
patent: 6489679 (2002-12-01), Tsukiyama et al.

Affiliated with

Also associated with

Rating

Wafer-level package with silicon gasket does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Wafer-level package with silicon gasket, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wafer-level package with silicon gasket will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3244927