Two-dimensional optical deflector including two SOI structures and its manufacturing method

1. A two-dimensional optical deflector comprising:

a first SOI structure consisting of a first monocrystalline silicon support layer, a first monocrystalline silicon active layer and a first intermediate silicon dioxide layer sandwiched by said first monocrystalline silicon support layer and said first monocrystalline silicon active layer;

a second SOI structure consisting of a second monocrystalline silicon support layer, a second monocrystalline silicon active layer and a second intermediate silicon dioxide layer sandwiched by said second monocrystalline silicon support layer and said second monocrystalline silicon active layer, a height of said first monocrystalline silicon active layer being smaller than a height of said second monocrystalline silicon active layer;

a mirror;

an inner frame surrounding said mirror;

an inner piezoelectric actuator coupled between said mirror and said inner frame and adapted to rock said mirror around a first axis;

an outer frame surrounding said inner frame; and

an outer piezoelectric actuator coupled between said inner frame and said outer frame and adapted to rock said mirror around a second axis,

wherein said mirror includes said second monocrystalline silicon active layer without said first monocrystalline silicon active layer,

wherein said inner frame, said inner piezoelectric actuator and said outer frame include said first monocrystalline silicon active layer and said second monocrystalline silicon active layer, and

wherein said outer piezoelectric actuator includes said first monocrystalline silicon active layer without said second monocrystalline silicon active layer.

2. The two-dimensional optical deflector as set forth in claim 1 , wherein said mirror and said inner frame further include said second monocrystalline silicon support layer and said second intermediate silicon dioxide layer,

wherein said outer frame further includes said first monocrystalline silicon support layer and said first intermediate silicon dioxide layer.

3. The two-dimensional optical deflector as set forth in claim 2 , wherein a height of said first monocrystalline silicon support layer is larger than a total height of a height of said second monocrystalline silicon active layer and a height of said second monocrystalline silicon support layer.

4. The two-dimensional optical deflector as set forth in claim 1 , further comprising a torsion bar coupled between said mirror and said inner frame along said first axis,

wherein said torsion bar includes said second monocrystalline silicon active layer without said first monocrystalline silicon active layer.

5. The two-dimensional optical deflector as set forth in claim 4 , wherein a width of said torsion bar is smaller than twice a height of said second monocrystalline silicon active layer.

6. The two-dimensional optical deflector as set forth in claim 1 , wherein said inner piezoelectric actuator is of a meander-type including a plurality of first piezoelectric cantilevers coupled in series and in parallel with said second axis.

7. The two-dimensional optical deflector as set forth in claim 6 , wherein a width of each of said first piezoelectric cantilevers is smaller than twice a height of said second monocrystalline silicon active layer.

8. The two-dimensional optical deflector as set forth in claim 1 , wherein said outer piezoelectric actuator is of a meander-type including a plurality of second piezoelectric cantilevers coupled in series and in parallel with said first axis.

9. The two-dimensional optical deflector as set forth in claim 8 , wherein a width of each of said second piezoelectric cantilevers is larger than eight times a height of said first monocrystalline silicon active layer.

10. A method for manufacturing a two-dimensional optical deflector including: a mirror; an inner frame surrounding said mirror; an inner piezoelectric actuator coupled between said mirror and said inner frame and adapted to rock said mirror around a first axis; an outer frame surrounding said inner frame; and an outer piezoelectric actuator coupled between said inner frame and said outer frame and adapted to rock said mirror around a second axis, said method comprising:

preparing a first SOI structure consisting of a first monocrystalline silicon support layer, a first monocrystalline silicon active layer and a first intermediate silicon dioxide layer sandwiched by said first monocrystalline silicon support layer and said first monocrystalline silicon active layer;

preparing a second SOI structure consisting of a second monocrystalline silicon support layer, a second monocrystalline silicon active layer and a second intermediate silicon dioxide layer sandwiched by said second monocrystalline silicon support layer and said second monocrystalline silicon active layer, a height of said first monocrystalline silicon active layer being smaller than a height of said second monocrystalline silicon active layer;

forming an upper portion of said inner piezoelectric actuator and said outer piezoelectric actuator on said first monocrystalline silicon active layer;

perforating a first opening in said first monocrystalline silicon support layer except for said first monocrystalline silicon support layer of said outer frame, after said upper portion forming;

forming a lower portion of said mirror, said inner frame and said inner piezoelectric actuator in said second SOI structure;

bonding said second SOI structure to said first SOI structure at the first opening of said first monocrystalline silicon support layer;

perforating a second opening in said first monocrystalline silicon active layer for said mirror after said bonding; and

forming a reflective metal layer on said second monocrystalline silicon active layer at said second opening for said mirror.

11. The method as set forth in claim 10 , wherein a height of said first monocrystalline silicon support layer is larger than a total height of a height of said second monocrystalline silicon active layer and a height of said second monocrystalline silicon support layer.

12. The method as set forth in claim 10 , wherein said two-dimensional optical deflector further includes a torsion bar coupled between said mirror and said inner frame along said first axis,

wherein said torsion bar includes said second monocrystalline silicon active layer without said first monocrystalline silicon active layer, and

wherein a width of said torsion bar is smaller than twice a height of said second monocrystalline silicon active layer.

13. The method as set forth in claim 10 , wherein said inner piezoelectric actuator is of a meander-type including a plurality of first piezoelectric cantilevers coupled in series and in parallel with said second axis, and

wherein a width of each of said first piezoelectric cantilevers is smaller than twice a height of said second monocrystalline silicon active layer.

14. The method as set forth in claim 10 , wherein said outer piezoelectric actuator is of a meander-type including a plurality of second piezoelectric cantilevers coupled in series and in parallel with said first axis, and

wherein a width of each of said second piezoelectric cantilevers is larger than eight times a height of said first monocrystalline silicon active layer.