Method for Forming Passivation Layer

Abstract

A method for forming a passivation layer is disclosed. In the method, a substrate containing a top surface and a bottom surface opposite to the top surface is first provided, wherein a plurality of conductive pads are disposed on the top surface thereof. Thereafter, a first passivation layer is formed on the top surface of the substrate, wherein the first passivation layer has a characteristic of photoresist. A first exposure/develop step is then performed to form a plurality of first openings in the first passivation layer, wherein the conductive pads are exposed through the first openings. Then, a second passivation layer is formed on the first passivation layer, wherein the second passivation layer has a characteristic of photoresist. A second exposure/develop step is then performed to form a plurality of second openings in the second passivation layer, wherein the conductive pads are exposed through the second openings.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of this invention are more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic cross-sectional view showing the structure of a conventional solder bump prepared by a film electro-deposition process;

FIG. 2A to FIG. 2D are schematic cross-sectional views showing the process for making the passivation layer shown in FIG. 1; and

FIG. 3A to FIG. 3F are schematic cross-sectional views showing the process for making a passivation layer according to a preferred embodiment of the present invention.

Claims

1. A method for forming a passivation layer, comprising: providing a substrate having a top surface and a bottom surface opposite to the top surface, the top surface having a plurality of conductive pads;forming a first passivation layer on the top surface;performing a first exposure/develop step to form a plurality of first openings in the first passivation layer, wherein the conductive pads are exposed through the first openings;forming a second passivation layer on the first passivation layer; andperforming a second exposure/develop step to form a plurality of second openings in the second passivation layer, wherein the conductive pads are exposed through the second openings.

2. The method of claim 1, further comprising: performing a baking step for curing the first passivation layer and the second passivation layer.

3. The method of claim 1, wherein the first passivation layer is a negative photoresist.

4. The method of claim 1, wherein the first passivation layer is a positive photoresist.

5. The method of claim 1, wherein the second passivation layer is a negative photoresist.

6. The method of claim 1, wherein the second passivation layer is a positive photoresist.

7. The method of claim 1, wherein the ratio of the thickness of the first passivation layer and the thickness of the second passivation layer is substantially at least two.

8. The method of claim 1, wherein the substrate is a wafer.

9. The method of claim 1, wherein the first passivation layer is made of polyimide.

10. The method of claim 1, wherein the second passivation layer is made of polyimide.

11. The method of claim 1, wherein the thickness of the first passivation layer is 8 μm.

12. The method of claim 1, wherein the thickness of the second passivation layer is 2 μm.

13. The method of claim 1, wherein the first passivation layer is formed by spin coating.

14. The method of claim 1, wherein the second passivation layer is formed by spin coating.

15. The method of claim 2, wherein the ratio of the thickness of the first passivation layer and the thickness of the second passivation layer is substantially at least two.

16. The method of claim 1, wherein at least one void is formed in a portion of the first passivation layer to expose the substrate in the first exposure/develop step.

17. The method of claim 16, wherein the at least one void is filled up with the second passivation layer after forming the second passivation layer.