Semiconductor device having trench structures and method
View Patent ↗In one embodiment, a pair of sidewall passivated trench contacts is formed in a substrate to provide electrical contact to a sub-surface feature. A doped region is diffused between the pair of sidewall passivated trenches to provide low resistance contacts.
1. A method of forming a semiconductor device comprising the steps of:
providing a substrate having a major surface and a sub-surface feature to be contacted;
forming a first trench in the substrate and extending from the major surface;
forming a second trench in the substrate and extending from the major surface;
forming a blocking layer overlying exposed surfaces of the first and second trenches;
forming a first conductive layer overlying the blocking layer in the first trench, wherein the first conductive layer is coupled to the sub-surface feature through a first opening in the blocking layer; and
forming a second conductive layer overlying the blocking layer in the second trench, wherein the second conductive layer is coupled to the substrate through a second opening in the blocking layer.
2. The method of claim 1 further comprising the steps of:
forming a third trench in the substrate and extending from the major surface;
forming the blocking layer overlying exposed surfaces of the third trench; and
forming the first conductive layer overlying the blocking layer in the third trench.
3. The method of claim 2 further comprising the step of forming an isolation region overlying the third trench.
4. The method of claim 2 , wherein the step of forming the third trench includes forming the third trench in proximity to the first trench, the method further comprising the step of forming a doped region between the first and third trenches, wherein the first and third trenches form a diffusion shield to minimize lateral diffusion of the doped region.
5. The method of claim 4 wherein the step of forming the doped region includes forming the doped region to extend to the sub-surface feature.
6. The method of claim 1 , wherein the step of forming the first conductive layer includes forming a doped polycrystalline semiconductor layer of a first conductivity type.
7. The method of claim 6 , wherein the step of forming the second conductive layer comprises forming a doped polycrystalline semiconductor layer of a second conductivity type.
8. A method for forming a semiconductor device including the steps of:
providing a semiconductor substrate having a major surface and a sub-surface feature;
forming a first trench in the semiconductor substrate in proximity to the sub-surface feature;
forming a second trench in the semiconductor substrate in proximity to the first trench;
forming a first blocking layer overlying surfaces of the first trench;
forming a second blocking layer overlying surfaces of the second trench;
forming openings in the first and second blocking layers;
forming a first conductive layer overlying the first and second blocking layers, wherein the first conductive layer is coupled to the sub-surface feature through the openings; and
forming a doped region between the first and second trenches, wherein the first and second trenches form a diffusion shield to control lateral diffusion of the doped region.
9. The method of claim 8 , wherein the step of forming the first conductive layer comprises forming a doped polycrystalline layer.
10. The method of claim 8 , further comprising the steps of:
forming a third trench in the semiconductor substrate;
forming a third blocking layer overlying surfaces of the third trench;
forming an opening in the third blocking layer; and
forming a second conductive layer overlying the third blocking layer, wherein the second conductive layer is coupled to the semiconductor substrate through the opening.
11. The method of claim 10 wherein the step of forming the second conductive layer comprises a forming a doped polycrystalline semiconductor layer.
12. The method of claim 11 further comprising the step of diffusing dopant from the doped polycrystalline semiconductor layer into the semiconductor substrate.
13. The method of claim 8 further comprising the steps of:
forming a third trench in the semiconductor substrate;
forming a third blocking layer over surfaces of the third trench;
forming the first conductive layer overlying the third blocking layer; and
forming an isolation region over the third trench.
14. A process for forming a semiconductor device having a plurality of trenches including the steps or:
providing a semiconductor substrate having a major surface and a sub-surface feature;
forming the plurality of trenches including first and second trenches in the semiconductor substrate and extending from the major surface, wherein the first trench overlies the sub-surface feature and extends thereto, and wherein the second trench overlies another portion of the semiconductor substrate;
forming a blocking layer overlying sidewall surfaces of the first and second trenches, wherein at least portions of lower surfaces of the first and second trenches are devoid of the blocking layer;
forming a first polycrystalline semiconductor layer at least within the first and second trenches; and
forming a second polycrystalline semiconductor layer within the second trench but not the first trench, wherein the second polycrystalline semiconductor layer is coupled to the semiconductor substrate within the second trench.
15. The process of claim 14 further comprising the step of removing the first polycrystalline semiconductor layer from the second trench before the step of forming the second polycrystalline semiconductor layer.
16. The process of claim 14 , wherein the step of forming tue first polycrystalline semiconductor layer includes forming an undoped polycrystalline semiconductor layer, and wherein the step of forming the second polycrystalline semiconductor layer includes forming the second polycrystalline semiconductor layer wherein the second polycrystalline semiconductor layer and the semiconductor substrate are of the same conductivty type.
17. The process of claim 16 further comprising the step of selectively doping the first polycrystalline semiconductor layer in the first trench with a dopant having a conductivity type opposite to the conductivity type of the second polycrystalline semiconductor layer.
18. The process of claim 14 , wherein the step of forming the second trench includes forming the second trench wider than the first trench.
19. The process of claim 14 , wherein the step of providing the semiconductor substrate includes providing a semiconductor substrate of a first conductivity type, a semiconductor layer of a second conductivity type opposite to the first overlying the major surface of the semiconductor substrate, and the sub-surface feature of the second conductivity type.
20. The process of claim 14 , wherein the step of forming the plurality of trenches includes forming a third trench adjacent the first trench and extending to the sub-surface feature, and wherein the step of forming the blocking layer includes forming the blocking layer at least on sidewall surfaces of the third trench, and wherein the step of forming the first polycrystalline semiconductor layer includes forming the first polycrystalline semiconductor layer within the third trench, and wherein the step of forming the second polycrystalline semiconductor layer includes forming the second polycrystalline semiconductor layer in the second trench but not in the third trench, and wherein the process further includes the step of forming a doped region between the first and third trenches, wherein the blocking layer is configured to reduce lateral diffusion of the first doped region between the first and third trenches.