Backside illuminated sensor and manufacturing method thereof
Disclosed is a backside illuminated image sensor including a light receiving element formed in a first substrate, an interlayer insulation layer formed on the first substrate including the light receiving element, a via hole formed through the interlayer insulation layer and the first substrate while being spaced apart from the light receiving element, a spacer formed on an inner sidewall of the via hole, an alignment key to fill the via hole, interconnection layers formed on the interlayer insulation layer in a multilayer structure in which a backside of a lowermost layer of the interconnection layers is connected to the alignment key, a passivation layer covering the interconnection layers, a pad locally formed on a backside of the first substrate and connected to a backside of the alignment key, and a color filter and a microlens formed on the backside of the first substrate corresponding to the light receiving element.
1. An image sensor, comprising:
a first substrate including a light-receiving element configured to receive light from a first side of the first substrate;
a second substrate bonded to a second side of the first substrate, wherein the second substrate comprises peripheral circuitry configured to process signals associated with the light-receiving element;
an interlayer insulation layer positioned between the first substrate and the second substrate;
a via hole formed through the interlayer insulation layer and the first substrate;
a spacer formed on an inner sidewall of the via hole;
an alignment key configured to fill the via hole;
a barrier layer positioned between the spacer and the alignment key along an inner surface of the via hole;
interconnection layers formed between the interlayer insulation layer and the second substrate with at least one layer of the interconnection layer coupled to the alignment key; and
a pad formed on the first side of the first substrate and coupled to the alignment key.
2. The image sensor of claim 1 , further comprising a color filter and a microlens both formed on the first side of the first substrate, wherein the color filter and microlens are configured to direct light toward the light-receiving element.
3. The image sensor of claim 1 , further comprising an adhesive layer formed between the barrier layer and the spacer.
4. The image sensor of claim 1 , wherein the barrier layer comprises a layer selected from the group consisting of Ti, TiN, Ta, TaN, AlSiTiN, NiTi, TiBN, ZrBN, TiAlN, TiB2, Ti/TiN, and Ta/TaN.
5. The image sensor of claim 1 , wherein the spacer comprises a nitride layer having an etching selectivity that is higher than an etching selectivity of the first substrate.
6. The image sensor of claim 2 , further comprising an anti-light scattering layer positioned between the first substrate and the color filter.
7. The image sensor of claim 1 , wherein the alignment key comprises a conductive material.
8. The image sensor of claim 1 , further comprising a plurality of alignment keys configured to extend through the interlayer insulation layer and the first substrate.
9. The image sensor of claim 1 , further comprising a passivation layer positioned between the first substrate and the second substrate.
10. The image sensor of claim 1 , wherein the alignment key extends through a buried oxide layer of the first substrate.
11. An image sensor, comprising:
a first substrate including a front side and a back side;
a light-receiving element formed in the front side of the first substrate;
a microlens formed on the back side of the first substrate and configured to direct light toward the light-receiving element;
a second substrate bonded to the front side of the first substrate, wherein the second substrate includes circuitry configured to process image signals generated by the light-receiving element;
an interlayer insulation layer positioned between the first substrate and the second substrate;
a plurality of via holes formed through the interlayer insulation layer and the first substrate;
a spacer formed on an inner sidewall of each via hole;
a plurality of alignment keys, each alignment key configured to fill a corresponding via hole; and
a barrier layer positioned between the spacer and the alignment key along an inner surface of each via hole.
12. The image sensor of claim 11 , further comprising:
a plurality of interconnection layers formed between the first substrate and the second substrate; and
a pad formed on the back side of the first substrate and coupled to the plurality of interconnection layers via an alignment key from the plurality of alignment keys.