Heat spreading isolation structure for semiconductor devices
A structure includes an active device over an area of a substrate, and a heat spreading isolation structure adjacent the active device. The isolation structure includes a dielectric layer above a heat-conducting layer. The heat-conducting layer may include polycrystalline graphite. The heat-conducting layer provides a heat sink, which provides a high thermal conductivity path for heat with low electrical conductivity. The heat-conducting layer may extend into the substrate. The substrate may include an SOI substrate in which case the heat-conducting layer may extend through the buried insulator thereof.
1 . A structure, comprising:
an active device over an area of a substrate, the substrate including a semiconductor-on- insulator (SOI) layer over a buried insulating layer over a base semiconductor substrate; and
a heat spreading isolation structure adjacent the active device, wherein the heat spreading isolation structure includes a dielectric layer above and abutting an upper surface of a polycrystalline graphite, heat-conducting layer, and wherein an upper surface of the polycrystalline graphite, heat-conducting layer is concave and a lowermost surface of the polycrystalline graphite, heat-conducting layer extends into the base semiconductor substrate; and
a heat spreading through semiconductor via (TSV) adjacent to the heat spreading isolation structure and located within the base semiconductor substrate, wherein a bottom surface of the polycrystalline graphite, heat-conducting layer within the base semiconductor substrate contacts an upper surface of the heat spreading TSV within the base semiconductor substrate.
2 . The structure of claim 1 , wherein the heat spreading isolation structure is in-between two portions of the SOI layer.
3 . The structure of claim 1 , wherein the heat-conducting layer is directly above the buried insulating layer.
4 . The structure of claim 1 , wherein the heat spreading isolation structure extends through the buried insulating layer.
5 . The structure of claim 1 , wherein the heat-conducting layer has an electrical resistivity of at least 50 ohm-centimeters.
6 . The structure of claim 1 , wherein the active device is a metal-oxide semiconductor (MOS) transistor.
7 . The structure of claim 1 , wherein the active device is a bipolar transistor.
8 . The structure of claim 1 , wherein the heat spreading isolation structure surrounds the active device.
9 . A heat spreading isolation structure, comprising:
a substrate including a semiconductor-on-insulator (SOI) layer over a buried insulating layer over a base semiconductor substrate;
in a trench in the substrate, the trench adjacent an active device on the substrate and adjacent the SOI layer, a body including:
a dielectric layer; and
a polycrystalline graphite, heat-conducting layer below the dielectric layer an extending into the base semiconductor layer, wherein an upper surface of the polycrystalline graphite, heat-conducting layer is not planar, wherein the body surrounds the active device, and wherein a lower surface of the polycrystalline graphite, heat- conducting layer in the base semiconductor layer is non-planar.
10 . The heat spreading isolation structure of claim 9 , wherein the body extends through the buried insulating layer.
11 . The heat spreading isolation structure of claim 10 , wherein the polycrystalline graphite, heat-conducting layer has an electrical resistivity of at least 50 ohm-centimeters.
12 . The heat spreading isolation structure of claims 9 , further comprising:
an additional active device over a different area of the substrate from the active device; and
an additional body surrounding the additional active device, the additional body including:
a dielectric layer; and
a polycrystalline graphite, heat-conducting layer below the dielectric layer,
wherein an upper surface of the polycrystalline graphite, heat-conducting layer is not planar.
13 . The heat spreading isolation structure of claim 12 , wherein the body and the additional body are physically separated by a distance.
14 . The heat spreading isolation structure of claim 9 , wherein the body is adjacent a first side of an active device over the substrate, and the TSV thermally connects the body to an additional body adjacent a second side of the active device.