Method for forming packaged semiconductor die with micro-cavity

#Surface Acoustic Wave (SAW) components require packaging that leaves the surface of the SAW device thereof uncovered and keeps the surface of the SAW device clean and dry. Otherwise the micro-acoustic wave would be attenuated. Accordingly, SAW components typically include sealed cavities that leave the SAW device(s) internally exposed. Micro Electrical Mechanical Systems (MEMS) and Bulk Acoustic Wave (BAW) components also require an internal sealed cavity for the respective devices thereon.

#Conventional processes for forming packages for SAW, BAW or MEMS components having internal sealed cavities apply a glob-top sealing material to the carrier substrate, with sealing structures on the substrate side such as solder rings (e.g., Au/Sn solder rings), protective foils, buffer layers at the chip edges or metal shielding used to prevent the glob-top sealing material from entering the cavity. One problem with these conventional processes is that the glob-top material can enter into the cavity, damaging the SAW, MEMS or BAW device. Also, conventional processes that use solder rings, protective foils, buffer layers at the chip edges and metal shielding are expensive.

#Accordingly, there is a need for a method and apparatus that will provide for good sealing of a device requiring a sealed cavity at reduced cost.

#The invention will be explained in more detail in the following with reference to examples and to the drawing in which are shown. It is appreciated that the drawings are not drawn to scale.

#FIG. 1 is a block diagram showing a method for forming a packaged electronic die having a micro-cavity in accordance with an example of the invention.

#FIG. 2 is a diagram showing a cross-sectional view of a portion of a device wafer after a metal layer has been deposited and patterned to form bonding pads and a metal region that extends completely around a device, in accordance with an example of the invention.

#Persons of ordinary skill in the art will realize that the following description is illustrative only and not in any way limiting. Other examples will readily suggest themselves to such skilled persons.

#FIG. 1 shows a method 100 for forming a packaged die. A device is formed (101) on a device wafer. Bonding pads are formed (102) on the device wafer. Optionally, a first metal layer is deposited over the device wafer and is patterned (103) to form a first metal region that extends completely around the device. In one example, a first portion of the patterned first metal layer forms a plurality of bonding pads and a second portion of the patterned first metal layer forms the first metal region that extends completely around the device. The patterning of step 103 may include depositing a photoresist, exposing the photoresist in the desired pattern, one or more bake steps, photoresist strip, an etch to remove the portion of the metal layer not overlain by the photoresist and a resist stripping process.

#In the example shown in FIG. 2, a device wafer 1 is shown that has a device 4 formed thereon. Steps 102-103 pattern a metal layer to form bonding pads 3 and first metal region 2 that extends completely around device 4. Bonding pads 3 are electrically coupled to device 4 for providing input and output to device 4. First metal region 2 extends completely around both device 4 and bonding pads 3.