Package structure and method for forming the same

1. A method for forming a package structure, comprising:

providing a semiconductor substrate comprising a first surface and a second surface opposite to the first surface;

partially removing the semiconductor substrate from the first surface to form a trench;

forming a first buffer layer over the semiconductor substrate to fill the trench;

attaching the first buffer layer and the second surface of the semiconductor substrate to an adhesive layer;

cutting the first buffer layer and the adhesive layer to form a die comprising the semiconductor substrate, the first buffer layer and the adhesive layer, wherein the first buffer layer covers a sidewall of the semiconductor substrate; and

forming an encapsulation layer surrounding the die, wherein the first buffer layer separates the semiconductor substrate from the encapsulation layer, wherein a top surface of the adhesive layer is in direct contact with the second surface of the semiconductor substrate and the first buffer layer, and a bottom surface of the adhesive layer is level with a bottom surface of the encapsulation layer.

2. The method for forming a package structure as claimed in claim 1 , further comprising:

thinning the semiconductor substrate from the second surface until the first buffer layer filled in the trench is exposed before the cutting of the first buffer layer.

3. The method for forming a package structure as claimed in claim 1 , further comprising:

thinning the semiconductor substrate from the second surface until the trench is exposed, wherein the first buffer layer is formed after the thinning of the semiconductor substrate.

4. The method for forming a package structure as claimed in claim 1 , wherein the semiconductor substrate further comprises a third surface exposed through the trench, and the method further comprises:

oxidizing the third surface exposed through the trench before the formation of the first buffer layer.

5. The method for forming a package structure as claimed in claim 1 , further comprising:

depositing a second buffer layer over the first surface of the semiconductor substrate before the formation of the first buffer layer, wherein the second buffer layer extends into the trench.

6. The method for forming a package structure as claimed in claim 1 , further comprising:

thinning the semiconductor substrate from the second surface until the trench is exposed; and

depositing a second buffer layer extending from the second surface of the semiconductor substrate into the trench before the formation of the first buffer layer.

7. The method for forming a package structure as claimed in claim 1 , further comprising:

forming a connector over the first surface of the semiconductor substrate;

forming a second buffer layer over the first surface of the semiconductor substrate to surround the connector;

partially removing the second buffer layer so that the trench penetrates through the second buffer layer into the semiconductor substrate; and

thinning the second buffer layer until the connector is exposed after the formation of the first buffer layer.

8. The method for forming a package structure as claimed in claim 1 , further comprising:

forming a connector over the first surface of the semiconductor substrate, wherein a top surface of the connector is level with a top surface of the first buffer layer.

9. A method for forming a package structure, comprising:

forming a semiconductor substrate having a trench on a top surface of the semiconductor substrate;

forming a first buffer layer over the semiconductor substrate to fill the trench;

attaching an adhesive layer to a bottom surface of the semiconductor substrate;

cutting the first buffer layer and the adhesive layer along the trench, wherein a portion of the adhesive layer extends outwardly from a sidewall of the semiconductor substrate so that a top surface of the adhesive layer is in direct contact with the semiconductor substrate and the first buffer layer;

forming an encapsulation layer surrounding the first buffer layer and the adhesive layer, wherein the encapsulation layer is in direct contact with a sidewall of the adhesive layer; and

forming a redistribution layer over the first buffer layer and the encapsulation layer.

10. The method for forming a package structure as claimed in claim 9 , wherein the first buffer layer and the encapsulation layer comprise different materials.

11. The method for forming a package structure as claimed in claim 9 , wherein the first buffer layer is between the encapsulation layer and the sidewall of the semiconductor substrate.

12. The method for forming a package structure as claimed in claim 9 , wherein the first buffer layer overlies the portion of the adhesive layer extending outwardly from the sidewall of the semiconductor substrate.

13. The method for forming a package structure as claimed in claim 9 , wherein an interface between the adhesive layer and the encapsulation layer is substantially coplanar with an interface between the first buffer layer and the encapsulation layer.

14. The method for forming a package structure as claimed in claim 9 , further comprising:

forming a second buffer layer covering the sidewall of the semiconductor substrate, wherein the first buffer layer surrounds the second buffer layer.

15. The method for forming a package structure as claimed in claim 14 , wherein the second buffer layer extends from the sidewall of the semiconductor substrate to a bottom surface of the semiconductor substrate.

16. The method for forming a package structure as claimed in claim 9 , further comprising:

forming a connector over the semiconductor substrate, wherein the redistribution layer is electrically connected to the connector; and

forming a second buffer layer over the top surface of the semiconductor substrate, wherein the connector is embedded in the second buffer layer and separated from the first buffer layer by the second buffer layer.

17. A method for forming a package structure, comprising:

forming a semiconductor substrate having a trench on a top surface of the semiconductor substrate;

forming a first buffer layer over the semiconductor substrate, wherein the first buffer layer covers the top surface and a sidewall of the semiconductor substrate;

depositing a second buffer layer extending from a bottom surface of the semiconductor substrate into the trench before the formation of the first buffer layer;

forming an encapsulation layer surrounding the first buffer layer, wherein the encapsulation layer and the sidewall of the semiconductor substrate are separated by the first buffer layer;

forming a passivation layer over the encapsulation layer; and

forming a redistribution layer over the passivation layer, wherein the redistribution layer is electrically connected to the semiconductor substrate.

18. The method for forming a package structure as claimed in claim 17 , wherein forming the first buffer layer comprises:

forming the first buffer layer to fill the trench; and

cutting the first buffer layer.

19. The method for forming a package structure as claimed in claim 18 , further comprising:

thinning a bottom surface of the semiconductor substrate until the first buffer layer filled in the trench is exposed before the cutting of the first buffer layer.

20. The method for forming a package structure as claimed in claim 9 , wherein a bottom surface of the adhesive layer is substantially coplanar with a bottom surface of the encapsulation layer.