Method of fabricating a wafer level chip scale package without an encapsulated via
View Patent ↗An improved wafer level chip scale packaging technique is described which does not use an encapsulated via to connect between a redirection layer and a pad within the pad ring on the semiconductor die. In an embodiment, a first dielectric layer is formed such that it terminates on each die within the die's pad ring. Tracks are then formed in a conductive layer which contact one of the pads and run over the edge of an opening onto the surface of the first dielectric layer. These tracks may be used to form an electrical connection between the pad and a solder ball.
1. A method of fabricating a packaged semiconductor device, comprising:
forming a first dielectric layer on an active face of a semiconductor wafer comprising an array of semiconductor die, wherein each semiconductor die comprises a plurality of pads arranged in a pad ring around the periphery of the die on an active face of the die and wherein the first dielectric layer comprises a first region terminated on each die within the pad ring and a further region on each die between the pad ring and an edge of the die, such that an area around the pad ring on each die is clear of the first dielectric layer;
forming a plurality of tracks in a conductive layer on the active face and the first dielectric layer, wherein each track on a die is connected to one of the plurality of pads and comprises a lower portion formed on one of the plurality of pads and an upper portion which is formed on the first dielectric layer and wherein at least one of the plurality of tracks comprises an upper portion which is formed on the further region of the first dielectric layer;
forming a second dielectric layer over each semiconductor die, wherein the second dielectric layer is arranged to encapsulate the active face;
forming a plurality of solder elements, each of the solder elements being electrically connected to an upper portion of a track; and
dicing the semiconductor wafer into a plurality of packaged semiconductor devices.
2. A method according to claim 1 , wherein each track comprises a centre portion which is formed over a termination of the first dielectric layer.
3. A method according to claim 2 , wherein each track comprises a further portion, between the lower portion and the centre portion, the further portion being formed on the active surface of the die.
4. A method according to claim 1 , wherein the lower portion of each track terminates within an area of one of the plurality of pads.
5. A method according to claim 1 , wherein forming a first dielectric layer on an active face of a semiconductor wafer further comprises:
depositing a first dielectric layer on the active face of a semiconductor wafer; and
selectively etching the first dielectric layer to terminate the first dielectric layer on each die within the plurality of pads around the periphery of the active face of the die.
6. A method according to claim 5 , wherein selectively etching the first dielectric layer to terminate the first dielectric layer on each die within the plurality of pads around the periphery of the active face of the die further comprises:
selectively etching the first dielectric layer to terminate the first dielectric layer on each die within the plurality of pads around the periphery of the active face of the die and to form a further region of the first dielectric layer between the plurality of pads and an edge of the die.
7. A method according to claim 1 , wherein forming a first dielectric layer on an active face of a semiconductor wafer further comprises:
depositing a first dielectric layer on the active face of a semiconductor wafer; and
selectively etching the first dielectric layer to create regions around groups of the plurality of pads which are clear of the first dielectric layer.
8. A method according to claim 1 , wherein the device is a wafer level chip scale packaged device.
9. A method according to claim 1 , wherein at least one of the plurality of tracks connects more than one pad together and comprises an upper portion which is formed on the further region of the first dielectric layer.