MEMS devices and fabrication methods thereof

1. A method comprising:

providing a micro-electro-mechanical system (MEMS) substrate having:

a sacrificial layer on a first side, wherein the sacrificial layer comprises a plurality of sealed trenches and the sealed trenches are embedded in the sacrificial layer, and wherein:

top surfaces of the sealed trenches are covered by the sacrificial layer;

sidewalls of the seal trenches are surrounded by the sacrificial layer; and

bottom surfaces of the sealed trenches are on the sacrificial layer;

providing a carrier including a plurality of cavities;

bonding the first side of the MEMS substrate on the carrier;

forming a first bonding material layer on a second side of the MEMS substrate;

applying a sacrificial layer removal process to the MEMS substrate;

providing a semiconductor substrate including a second bonding material layer; and

bonding the semiconductor substrate on the second side of the MEMS substrate.

2. The method of claim 1 , further comprising:

depositing a first dielectric layer on the first side of the MEMS substrate;

depositing a vapor HF stop layer on the first dielectric layer;

depositing a second dielectric layer on the vapor HF stop layer; and

forming a bonding layer on the second dielectric layer.

3. The method of claim 1 , further comprising:

depositing a third dielectric layer on the carrier;

forming a plurality of openings in the carrier through an etching process;

forming a dielectric protection layer on sidewalls of the openings; and

enlarging the openings through an isotropic etching process.

4. The method of claim 1 , further comprising:

forming a plurality of MEMS openings in the MEMS substrate from the second side of the MEMS substrate;

depositing a third dielectric layer to fill the MEMS openings;

forming a thin conductive layer on the third dielectric layer;

forming the first bonding material layer on the thin conductive layer; and

patterning the thin conductive layer to form a plurality of conductive elements and movable elements.

5. The method of claim 1 , further comprising:

sealing a first side of a cavity of the carrier with a first sealing layer;

applying a thinning process to a second side of carrier until a second side of the cavity is exposed, wherein the second side of the carrier is a nonbonding side of the carrier; and

sealing the second side of the cavity with a second sealing layer.

6. The method of claim 5 , further comprising:

forming an electrical readout structure over the second side of the carrier.

7. A method comprising:

providing a micro-electro-mechanical system (MEMS) device including:

forming a first sacrificial dielectric layer having a plurality of sealed trenches on a first side of the MEMS substrate;

forming a plurality of electrodes and mechanical bumps on the first sacrificial dielectric layer;

depositing a vapor HF stop layer on the first sacrificial dielectric layer;

depositing a second sacrificial dielectric layer on the vapor HF stop layer; and

forming a bonding layer on the second sacrificial dielectric layer;

providing a carrier including a plurality of cavities;

bonding the first side of the MEMS substrate on the carrier;

forming a first bonding material layer on a second side of the MEMS substrate;

applying a sacrificial layer removal process to the MEMS substrate;

providing a semiconductor substrate including a second bonding material layer; and

bonding the semiconductor substrate on the second side of the MEMS substrate.

8. The method of claim 7 , further comprising:

depositing an oxide material on the first side of the MEMS substrate;

patterning the oxide material to form a plurality of trenches; and

depositing the oxide material on the trenches to form the sealed trenches.

9. The method of claim 7 , further comprising:

forming a plurality of MEMS openings in the MEMS substrate from the second side of the MEMS substrate;

depositing a third dielectric layer to fill the MEMS openings;

forming a thin conductive layer on the third dielectric layer;

forming the first bonding material layer on the thin conductive layer; and

patterning the thin conductive layer to form a plurality of conductive bumps and mechanical structures.

10. A method comprising:

providing a first substrate comprising a first sacrificial layer on a first side, wherein the first sacrificial layer comprises a plurality of sealed trenches and the sealed trenches are embedded in and fully enclosed by the first sacrificial layer;

providing a carrier comprising a plurality of cavities;

bonding the first side of the first substrate on the carrier;

depositing a bonding layer on a second side of the first substrate;

applying a sacrificial layer removal process to the first substrate; and

bonding a second substrate on the second side of the first substrate.

11. The method of claim 10 , further comprising:

depositing a dielectric layer over the first substrate;

patterning the dielectric layer to form a plurality of openings; and

applying an oxide deposition process to the dielectric layer to form the first sacrificial layer.

12. The method of claim 10 , further comprising:

applying the oxide deposition process to the dielectric layer in a non-conformable manner.

13. The method of claim 12 , further comprising:

after the step of applying the oxide deposition process to the dielectric layer in the non-conformable manner, forming at least one overhang to seal off an upper terminal of a corresponding opening.

14. The method of claim 13 , further comprising:

forming a plurality of electrodes and mechanical bumps on the first sacrificial layer; and

depositing a vapor HF stop layer on the first sacrificial dielectric layer.

15. The method of claim 14 , further comprising:

depositing a second sacrificial layer on the vapor HF stop layer; and

forming a bonding layer on the second sacrificial layer.

16. The method of claim 10 , further comprising:

applying a first etching process to the carrier to form a plurality of deep openings;

depositing an oxide layer over the carrier; and

applying a second etching process to the deep openings to form a plurality of cavities.

17. The method of claim 10 , wherein:

bonding the first side of the first substrate on the carrier through a fusion bonding process.

18. The method of claim 10 , wherein:

bonding the second substrate on the second side of the first substrate through a eutectic bonding process.

19. The method of claim 10 , wherein:

the first substrate is a micro-electro-mechanical system (MEMS) substrate.

20. The method of claim 10 , wherein:

the second substrate is a semiconductor substrate.