Wafer structure and chip structure having through-hole electrical connection for bonded chips

1. A chip structure, comprising:

a first chip and a second chip that are stacked, wherein:

a front surface of the first chip faces a front surface of the second chip;

a bonding layer is provided between the front surface of the first chip and the front surface of the second chip;

the first chip comprises a photosensitive array region, a peripheral circuit region and a pad region;

a first interconnection layer is formed on the front surface of the first chip at the pad region and the peripheral circuit region;

the second chip comprises a logic device, and a second interconnection layer connected with the logic device;

a first insulating layer, covering a back surface of the first chip at the pad region;

a first electrical-connection through-hole located at the pad region, running from the first insulating layer, via a top wiring layer in the first interconnection layer at the pad region, to a top wiring layer in the second interconnection layer;

a pad located on the first electrical-connection through-hole;

a second insulating layer, covering the back surface of the first chip at the photosensitive array region; and

a reflective grating, located in the second insulating layer at the photosensitive array region, wherein:

the reflective grating is arranged in correspondence to a peripheral region of a photosensitive unit;

a fillable opening is provided among the reflective grating; and

a part of the second insulating layer is located under the fillable opening and the reflective grating.

2. The chip structure according to claim 1 , wherein:

the second insulating layer further covers the back surface of the first chip at the peripheral circuit region, and

the chip structure further comprises:

a shielding layer located in the second insulating layer at the peripheral circuit region, wherein another part of the second insulating layer are located under the shielding layer.

3. The chip structure according to claim 2 , wherein the second insulating layer and the first insulating layer are identical in structure and in composition.

4. The chip structure according to claim 3 , wherein the reflective grating, the shielding layer, and the first electrical-connection through-hole comprise a same metal material.

5. The chip structure according to claim 2 , further comprising:

a third insulating layer located above the first insulating layer and the second insulating layer, wherein:

the third insulating layer covers the shielding layer and the reflective grating, and a part of the pad is located on the third insulating layer at the pad region.

6. The chip structure according to claim 1 , further comprising:

a second electrical-connection through-hole located at the peripheral circuit region, running from the first insulating layer, via a top wiring layer in the first interconnection layer at the peripheral circuit region, to the top wiring layer in the second interconnection layer.

7. A wafer structure, comprising a wafer bonding structure, wherein the wafer bonding structure comprises an array of the chip structures according to claim 1 .

8. A method for manufacturing a wafer structure, comprising:

providing a bonded wafer, wherein:

the bonded wafer comprises a first wafer and a second wafer that are stacked;

a front surface of the first wafer faces a front surface of the second wafer;

a bonding layer is provided between the front surface of the first wafer and the front surface of the second wafer;

the first wafer comprises first chips arranged in an array;

each of the first chips comprises a photosensitive array region, a peripheral circuit region and a pad region;

a first interconnection layer is arranged on the front surface of the first wafer at the pad region and at the peripheral circuit region;

the second wafer comprises second chips arranged in an array; and

each of the second chips comprises a logic device and a second interconnection layer connected with the logic device;

forming a first insulating layer on a back surface of the first wafer at the pad region;

forming a first electrical-connection through-hole at the pad region, wherein the first electrical-connection through-hole runs from the first insulating layer, via a top wiring layer in the first interconnection layer at the pad region, to a top wiring layer in the second interconnection layer; and

forming a pad on the first electrical-connection through-hole;

wherein the first insulating layer is further formed on the back surface of the first wafer at the photosensitive array region; and

wherein the method further comprises:

forming a reflective grating that is located in the first insulating layer at the photosensitive array region, wherein the reflective grating is arranged in correspondence to a peripheral region of a photosensitive unit, a fillable opening is provided among the reflective grating, and a part of the first insulating layer is located under the fillable opening and the reflective grating.

9. The method according to claim 8 ,

wherein forming the first electrical-connection through-hole at the pad region comprises:

forming a first through-hole running from the first insulating layer, via the top wiring layer in the first interconnection layer at the pad region, to the top wiring layer in the second interconnection layer; and

filling the first through-hole to form the first electrical-connection through-hole; and

wherein forming the reflective grating that is located in the first insulating layer at the photosensitive array region comprises:

forming a to-be-filled opening in the first insulating layer at the region out of the pad region, wherein a depth of the to-be-filled opening is smaller than a thickness of the first insulting layer, and the to-be-filled opening comprises a grating opening located at the photosensitive array region;

filling the to-be-filled opening to form a filled opening, wherein the filled opening comprises the reflective grating formed by filling the grating opening; and

forming a third insulating layer above the filled opening.

10. The method according to claim 9 , wherein forming the third insulating layer above the filled opening comprises:

forming the third insulating layer that covers the back surface of the first wafer; and

removing the third insulating layer that is above the first electrical-connection through-hole, before forming the pad on the first electrical-connection through-hole.

11. The method according to claim 9 , further comprising:

forming the fillable opening among the reflective grating, wherein the fillable opening runs from the third insulating layer, and the first insulating layer remains at a bottom and a sidewall of the fillable opening.

12. The method according to claim 8 , further comprising:

cutting the bonding wafer, to obtain an independent chip structure.

13. The method according to claim 9 , wherein the first insulating layer is further formed on the back surface of the first wafer at the peripheral circuit region, and wherein the to-be-filled opening further comprises a shielding opening located at the peripheral circuit region, and the filled opening further comprises a shielding layer formed by filling the shielding opening.