Protective coating for silicon substrate

Patent metadata

Field	Value
Publication number	US-9514925-B1
Application number	US-201514850658-A
Country	US
Kind code	B1
Filing date	Sep 10, 2015
Priority date	Sep 10, 2015
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

Various approaches discussed herein enable techniques for protecting die units made of silicon substrate. A substrate, or wafer, is provided that has multiple die units built onto it, as well as saw streets between the die units. The substrate is cut into along the saw streets at a first width, after which a coating is applied to a side of the wafer so that the side of the wafer is covered with the coating as well as the channels created by the cutting being substantially filled with the coating. After curing the coating, a second cut is made along the saw streets and through the cured coating, so that the individual die units, once separated, have a protective layer of the coating attached to one side and the periphery of the die unit.

First claim

What is claimed is:

1. A method for fabricating a silicon wafer, the method comprising:
providing a silicon wafer comprising a plurality of die units, each die unit of the plurality of die units having an active side and a passive side, the active side having circuitry disposed thereon, and a saw street between each of the die units, the silicon wafer having a top side and a bottom side opposing the top side, the top side having circuitry disposed thereon and the bottom side having a first UV curable dicing tape disposed thereon;
mounting the silicon wafer onto a dicing plate such that the bottom side is in contact with the dicing plate;
forming, in the top side of the silicon wafer along the saw street, a first plurality of channels using a first blade, the first blade having a first width;
turning the die units over so that the active side of each of the die units is in contact with the dicing plate and second UV curable dicing tape;
irradiating the first UV curable dicing tape with ultraviolet light;
applying a layer of an epoxy adhesive to the passive side of each of the die units, the layer of the epoxy adhesive substantially covering the passive side of each of the die units and substantially filling the first plurality of channels;
curing the epoxy adhesive;
cutting with a second blade to completely separate the die units from each other, the second blade having a second width smaller than the first width;
irradiating the second UV curable dicing tape with ultraviolet light; and
extracting the die units,
wherein each of the die units has a portion of the layer of the epoxy adhesive on a back side and a periphery of the die unit.

2. The method of claim 1 , wherein the cutting using the second blade is into the bottom side of the silicon wafer along the saw street, the method further comprising:
creating markings along a periphery of the silicon wafer, the markings being aligned with the saw streets between the die units.

3. The method of claim 1 , wherein turning the die units over further comprises:
singulating the die units;
attaching the second UV curable dicing tape to a carrier plate; and
placing the die units in an arrangement onto the second UV curable dicing tape attached to the carrier plate, such that the active side of each of the die units is in contact with the second UV curable dicing tape attached to the carrier plate.

4. The method of claim 3 , wherein the layer of adhesive is applied to the die units on the carrier plate, the method further comprising:
irradiating the second UV curable dicing tape attached to the carrier plate to separate the die units from the carrier plate.

5. A method, comprising:
providing a substrate comprising a plurality of die units, the substrate having a first side and a second side opposing the first side;
attaching first UV curable dicing tape to the second side of the substrate;
forming, into the first side of the substrate, first channels through the substrate, the first channels having a first width, and being along a saw street between the die units;
irradiating the first UV curable dicing tape with ultraviolet light;
attaching second UV curable dicing tape to the first side of the substrate;
applying a coating to the second side of the substrate, the coating substantially filling the channels;
cutting second channels through the coating, so that the die units are separated from each other and each die unit has a layer of the coating on a back side and a periphery of the die unit, the second channels having a second width narrower than the first width and being along the saw street; and
irradiating the second UV curable dicing tape with ultraviolet light.

6. The method of claim 5 , wherein the first UV curable dicing tape is attached to the second side of the substrate prior to forming the first channels, and wherein the second UV curable dicing tape is attached to the first side of the substrate prior to cutting the second channels.

7. The method of claim 5 , the method further comprising:
mounting the second side of the substrate to a dicing plate; and
after forming the channels having the first width, turning the substrate over so that the first side of the substrate is contacting the dicing plate.

8. The method of claim 5 , further comprising:
mounting a camera module unit onto one of the die units.

9. The method of claim 5 , further comprising:
prior to applying the coating to the second side of the substrate,
singulating the die units, each die unit having an active side and a passive side, the active side having circuitry disposed thereon and the passive side comprising a portion of substrate;
attaching the second UV curable dicing tape to a carrier plate; and
placing the active side of each of the die units onto the second UV curable dicing tape attached to the carrier plate,
wherein the die units are placed in an arrangement on the second UV curable dicing tape to generate an arrangement of die units having saw streets in the coating between the die units in the arrangement.

10. The method of claim 9 , wherein the coating is applied to the die units on the carrier plate, and further comprising:
trimming, after applying the coating, the carrier plate such that non-essential portions of the carrier plate are removed; and
placing, after the trimming, the carrier plate having the arrangement of die units onto a dicing plate such that the active side of the die units is facing up.

11. The method of claim 9 , further comprising:
irradiating the second UV curable dicing tape such that the active side of each of the die units is separated from the carrier plate, the active side of each of the die units free of the coating.

12. The method of claim 5 , further comprising:
curing the coating prior to cutting through the coating,
wherein the coating is applied using one of spin coating, stencil printing, or transfer molding.

13. The method of claim 5 , further comprising:
forming rounded corners on the periphery of the die units, wherein the rounded corners are substantially covered with the coating,
wherein at least one of the cutting through the coating or the forming rounded corners is performed by a laser.

14. The method of claim 5 , wherein a depth of the channels is less than a thickness of the substrate.

15. A system for singulating a substrate comprising a plurality of die units, comprising:
a dicing frame onto which the substrate is mounted;
a first cutting implement configured to cut channels having a first width into the substrate;
a second cutting implement configured to cut channels having a second width into the substrate, the second width being narrower than the first width;
a coating application device configured to dispense a layer of coating material onto the substrate; and
a controller configured to:
cause the first cutting implement to cut along a saw street between the die units on the substrate, the substrate having a first side and a second side, wherein the first side is opposite the second side;
cause first UV curable dicing tape to be applied to the second side of the substrate;
cause the first UV curable dicing tape to be irradiated with ultraviolet light;
cause second UV curable dicing tape to be applied to the first side of the substrate;
cause the coating application device to dispense the coating material on the second side of the substrate, such that the coating material substantially covers the second side of the substrate and substantially fills the saw street between the die units;
cause the second cutting implement to cut along the saw street, such tha

Assignees

• Amazon Tech Inc

Inventors

• Tam Samuel Waising
• Pang Tak Shing

Classifications

• H10W46/301

  for alignment · CPC title

• H10W46/501

  for use before dicing · CPC title

• H10P72/7422

  used to protect an active side of a device or wafer · CPC title

• H10P72/7416

  used during dicing or grinding · CPC title

• H10P72/744

  Details of chemical or physical process used for separating the auxiliary support from a device or a wafer · CPC title