Mechanisms for forming micro-electro mechanical system device

1. A micro-electro mechanical system (MEMS) device, comprising:

a substrate;

a MEMS structure over the substrate, wherein the MEMS structure has a movable element, the movable element is surrounded by a cavity; and

a fuse layer on the movable element.

2. The MEMS device as claimed in claim 1 , wherein a portion of the fuse layer extends outside of the movable element.

3. The MEMS device as claimed in claim 1 , wherein the fuse layer is made of a metal material.

4. The MEMS device as claimed in claim 1 , wherein the fuse layer comprises a curled structure.

5. The MEMS device as claimed in claim 4 , wherein the curled structure curls upwardly and away from the movable element.

6. The MEMS device as claimed in claim 1 , wherein the fuse layer comprises a stack of multiple sub-layers.

7. The MEMS device as claimed in claim 6 , wherein the stack comprises a first metal sub-layer and a second metal sub-layer, the first metal sub-layer is between the second metal sub-layer and the movable element, and a coefficient of thermal expansion (CTE) of the first metal sub-layer is higher than that of the second metal sub-layer.

8. The MEMS device as claimed in claim 1 , wherein the MEMS structure further has an element, a gap is between the element and the movable element, and the element and the movable element are made of the same material.

9. The MEMS device as claimed in claim 8 , further comprising:

a dielectric layer over the MEMS structure;

a cap substrate bonded to the dielectric layer; and

a through substrate via formed in the cap substrate and connected to the fuse layer.

10. The MEMS device as claimed in claim 1 , further comprising:

a dielectric layer over the MEMS structure; and

a cap substrate bonded to the dielectric layer, wherein the cap substrate is made of a material capable of allowing a light to penetrate through the cap substrate.

11. The MEMS device as claimed in claim 1 , wherein the fuse layer is in direct contact with the movable element.

12. A semiconductor device, comprising:

a substrate;

a MEMS structure over the substrate, wherein the MEMS structure comprises a first element and a second element, the first element is surrounded by a cavity, and a gap is between the first element and the second element; and

a fuse layer on the MEMS structure and securing the first element and the second element, wherein the fuse layer extends across the gap.

13. The semiconductor device as claimed in claim 12 , wherein the fuse layer is a single layer.

14. The semiconductor device as claimed in claim 12 , wherein the fuse layer comprises a stack of multiple sub-layers, and at least two of the sub-layers have different coefficients of thermal expansion.

15. The semiconductor device as claimed in claim 12 , further comprising a conductive structure electrically connected to the fuse layer.

16. A method for forming a micro-electro mechanical system (MEMS) device, comprising:

providing a substrate;

forming a support layer over the substrate;

forming a MEMS structure over the substrate, wherein the MEMS structure comprises a first element and a second element;

forming a fuse layer to secure the first element and the second element; and

partially removing the support layer such that the first element is surrounded by a cavity, and gap is formed between the first element and the second element.

17. The method for forming a MEMS device as claimed in claim 16 , wherein the fuse layer extends across the gap.

18. The method for forming a MEMS device as claimed in claim 17 , further comprising forming a conductive structure electrically connected to the fuse layer.

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

forming a dielectric layer over the MEMS structure;

bonding a cap substrate to the dielectric layer; and

forming a through substrate via in the cap substrate to form a portion of the conductive structure.

20. The method for forming a MEMS device as claimed in claim 17 , wherein the fuse layer is made of a material capable of being blown by applying a current to the fuse layer or irradiating the fuse layer with a light.