Method for forming semiconductor structure
Method for forming a semiconductor structure includes: providing a first substrate including a first surface and second surface opposite to each other, where the first substrate includes first ions with a first concentration; forming a first epitaxial layer on the first surface of the first substrate, where the first epitaxial layer includes second ions with a second concentration smaller than the first concentration; forming a second epitaxial layer on the first epitaxial layer and a third epitaxial layer located on the second epitaxial layer, where the second epitaxial layer includes third ions with a third concentration and the third epitaxial layer includes fourth ions with a fourth concentration smaller than the third concentration; and thinning the first substrate from the second surface of the first substrate until the surface of the second epitaxial layer is exposed.
1 . A method for forming a semiconductor structure, comprising:
providing a first substrate, the first substrate including a first surface and second surface opposite to each other, wherein the first substrate includes first ions and the first ions have a first concentration;
forming a first epitaxial layer on the first surface of the first substrate, wherein the first epitaxial layer includes second ions and the second ions have a second concentration and the second concentration is smaller than the first concentration;
forming a second epitaxial layer on the first epitaxial layer and a third epitaxial layer located on the second epitaxial layer, wherein: the second epitaxial layer includes third ions, the third ions have a third concentration, the third epitaxial layer includes fourth ions, the fourth ions have a fourth concentration, and the fourth concentration is smaller than the third concentration; and
thinning the first substrate from the second surface of the first substrate until a surface of the second epitaxial layer is exposed.
2 . The method according to claim 1 , wherein thinning the first substrate includes:
etching the first substrate from the second surface of the first substrate until a surface of the first epitaxial layer is exposed; and performing planarization treatment on the first epitaxial layer until the surface of the second epitaxial layer is exposed.
3 . The method according to claim 2 , wherein:
the etching is a wet etching process, and processing parameters of the wet etching include an etching solution including an HNA solution, wherein the HNA solution is a mixed solution of HF, HNO 3 , and acetic acid.
4 . The method according to claim 2 , wherein:
the planarization treatment is a chemical mechanical polishing; and processing parameters of the chemical mechanical polishing include: a polishing liquid including SiO 2 , and a polishing time of about 50 to 100 seconds.
5 . The method according to claim 1 , wherein:
the first ions have a conductive type opposite to a conductive type of the second ions.
6 . The method according to claim 5 , wherein:
the first ions are P-type ions, and the P-type ions include one or more types of boron ions, indium ions, or gallium ions.
7 . The method according to claim 5 , wherein:
the second ions are N-type ions, and the N-type ions include one or more types of phosphorus ions, arsenic ions, or antimony ions.
8 . The method according to claim 1 , wherein:
the third ions have a conductive type same as a conductive type of the fourth ions.
9 . The method according to claim 8 , wherein:
the third ions are P-type ions, and the P-type ions include one or more types of boron ions, indium ions, or gallium ions.
10 . The method according to claim 1 , wherein:
the first concentration is in a range of about 2E18˜5E18 atoms/cm 3 .
11 . The method according to claim 1 , wherein:
the second concentration is in a range of about 5E12˜1E15 atoms/cm 3 .
12 . The method according to claim 1 , wherein:
the third concentration is in a range of about 6E17˜5E18 atoms/cm 3 .
13 . The method according to claim 1 , wherein:
the fourth concentration is in a range of about 1E13˜2E14 atoms/cm 3 .
14 . The method according to claim 1 , wherein:
a thickness of the first epitaxial layer is about 1 μm to about 3 μm.
15 . The method according to claim 1 , wherein:
a thickness of the second epitaxial layer is about 1 μm to about 5 μm.
16 . The method according to claim 1 , wherein:
a thickness of the third epitaxial layer is about 4 μm to about 10 μm.
17 . The method according to claim 1 , wherein:
the third epitaxial layer includes a third surface, and the third surface faces away from the second epitaxial layer; and
before thinning the first substrate, the method further includes: forming a plurality of photoelectric doped regions in the third epitaxial layer; forming a first dielectric layer covering the third surface of the third epitaxial layer and the plurality of photoelectric doped regions; and forming an electrical interconnection structure in the first dielectric layer.
18 . The method according to claim 17 , after forming the electrical interconnection structure in the first dielectric layer, further comprising: providing a second substrate, and bonding the first surface of the first substrate to the second substrate.
19 . The method according to claim 18 , wherein:
the second epitaxial layer includes a fourth surface, wherein the fourth surface is in contact with the first epitaxial layer; and
after thinning the first substrate, the method further includes: forming a second dielectric layer on the fourth surface of the second epitaxial layer; forming a through hole in the second dielectric layer, the second epitaxial layer and the third epitaxial layer, wherein the through hole exposes the first dielectric layer; forming a contact hole at a bottom of the through hole and in the first dielectric layer, exposing the electrical interconnection structure; and forming a conductive layer in the through hole and the contact hole.
20 . The method according to claim 19 , further comprising:
forming a plurality of optical filters on the second dielectric layer and lenses on the plurality of optical filters.