Structures with through vias passing through a substrate comprising a planar insulating layer between semiconductor layers
View Patent ↗A through via contains a conductor ( 244, 262 ) passing through a substrate ( 140 ). The substrate can be SOI or some other substrate containing two semiconductor layers ( 140.1, 140.2 ) on opposite sides of an insulating layer ( 140 B). The through via includes two constituent vias ( 144.1, 144.2 ) formed from respective different sides of the substrate by processes stopping on the insulating layer ( 140 B). Due to the insulating layer acting as a stop layer, high control over the constituent vias' depths is achieved. Each constituent via is shorter than the through via, so via formation is facilitated. The conductor is formed by separate depositions of conductive material into the constituent vias from each side of the substrate. From each side, the conductor is deposited to a shallower depth than the through-via depth, so the deposition is facilitated. Other embodiments are also provided.
1. A structure comprising:
a planar insulating layer;
a first semiconductor layer overlying the planar insulating layer, the first semiconductor layer having a planar bottom surface contacting a top surface of the planar insulating layer;
a second semiconductor layer underlying the planar insulating layer, the second semiconductor layer having a planar top surface contacting a bottom surface of the planar insulating layer;
one or more through vias each of which passes through the planar insulating layer and the first and second semiconductor layers;
wherein each through via comprises:
a respective first via portion passing through the first semiconductor layer and having a first sidewall portion adjacent to the planar insulating layer and provided by the first semiconductor layer;
a respective second via portion passing through the second semiconductor layer; and
a respective third via portion passing through the planar insulating layer;
wherein in at least one through via, at least adjacent to the planar insulating layer, the first via portion is wider than the third via portion.
2. The structure of claim 1 wherein in at least one trough via, the first via portion is wider than the third via portion.
3. The structure of claim 1 wherein each of the one or more through vias comprises a conductor which provides a conductive path between the first and second semiconductor layers.
4. The structure of claim 3 wherein at least one of the one or more through vias is filled with the respective conductor or with a combination of the respective conductor and an insulator provided between the conductor and the first semiconductor layer and/or between the conductor and the second semiconductor layer.
5. The structure of claim 1 wherein the first and second semiconductor layers have the same thickness at each through via.
6. The structure of claim 1 wherein for each through via,
1 /k *Th2≦Th1 ≦k *Th2
wherein Th1 is the thickness of the first semiconductor layer at the through via, Th2 is the thickness of the second semiconductor layer at the through via, and k is a value greater than 1 but less than or equal to 10.
7. The structure of claim 6 wherein k is less than or equal to 5.
8. The structure of claim 6 wherein k is less than or equal to 3.