Vertical semiconductor device with thinned substrate
A vertical semiconductor device (e.g. a vertical power device, an IGBT device, a vertical bipolar transistor, a UMOS device or a GTO thyristor) is formed with an active semiconductor region, within which a plurality of semiconductor structures have been fabricated to form an active device, and below which at least a portion of a substrate material has been removed to isolate the active device, to expose at least one of the semiconductor structures for bottom side electrical connection and to enhance thermal dissipation. At least one of the semiconductor structures is preferably contacted by an electrode at the bottom side of the active semiconductor region.
1. An integrated circuit chip comprising:
an active semiconductor region having a plurality of fabricated semiconductor structures comprising a source, drain and channel that form a vertical semiconductor device, the active semiconductor region being exposed on a bottom side by the absence of substrate material such that the drain and channel of the semiconductor structures are exposed semiconductor structures that provide the vertical semiconductor device with an electrical contact; and
a bottom side electrode connected to the drain or the channel;
wherein:
the channel isolates the source from the drain;
the channel has a bottom boundary and a side boundary extending downward from a top surface of the active semiconductor region to the bottom boundary; and
the drain and channel are in contact along the side boundary and are not in contact along the bottom boundary.
2. The integrated circuit chip of claim 1 , further comprising:
a handle wafer layer bonded above the active semiconductor region to enable thinning of the substrate material.
3. The integrated circuit chip of claim 1 , wherein:
the plurality of semiconductor structures form a plurality of vertical semiconductor devices; and
each of the plurality of vertical semiconductor devices is connected to a separate bottom side electrode.
4. The integrated circuit chip of claim 1 , further comprising:
a trench region extending along a vertical side of the active semiconductor region and horizontally surrounding the active semiconductor region;
wherein the trench region electrically isolates the vertical semiconductor device from a second active semiconductor region on the integrated circuit chip.
5. The integrated circuit chip of claim 4 , wherein:
the vertical semiconductor device is contained within a first region of the integrated circuit chip;
the first region of the integrated circuit chip has a first thickness;
a second region of the integrated circuit chip has a second thickness that is smaller than the first thickness, and the second region contains at least one non-vertical semiconductor device; and
the trench region electrically isolates the first region from the second region.
6. The integrated circuit chip of claim 1 , wherein a vertical or horizontal dimension of at least one of the semiconductor structures has been minimized to reduce parasitic capacitance in the vertical semiconductor device.
7. The integrated circuit chip of claim 1 , wherein the active semiconductor region is formed in a semiconductor on insulator (SOI) wafer.
8. The integrated circuit chip of claim 1 , wherein:
the bottom side electrode is connected to the drain; and
a second bottom side electrode is coupled to a gate located over the active semiconductor region.
9. A device comprising:
a gate region;
an active region having source, drain, and channel regions arranged as a veritcal power device, at least a portion of a substrate material below the active region having been removed to isolate the active region and to expose the drain and channel regions; and
at least one bottom side electrode connected to at least one of the exposed drain and channel regions;
and wherein:
the drain region is located below the gate region;
the channel region isolates the drain region from the source region;
the channel region has a bottom boundary and a side boundary;
the side boundary extends downward from below the gate region to the bottom boundary; and
the drain and channel regions are in contact along the side boundary and are not in contact along the bottom boundary.
10. The device of claim 9 , further comprising:
a trench region extending along an entire vertical side of the active region and horizontally surrounding the active region to electrically isolate the active region within an integrated circuit chip.
11. The device of claim 10 , wherein:
the vertical power device is contained within a first region of the integrated circuit chip;
the first region of the integrated circuit chip has a first thickness;
a second region of the integrated circuit chip has a second thickness smaller than the first thickness and contains at least one non-vertical semiconductor device; and
the trench region electrically isolates the first and second regions from each other.
12. The device of claim 10 , wherein the portion of the substrate material below the active region has been removed up to both the active region and the trench region to further electrically isolate the active region.
13. The device of claim 9 , wherein the portion of the substrate material below the active region has been removed to expose the drain and channel regions for bottom side electrical connection and to enhance thermal dissipation.
14. The device of claim 9 , further comprising:
a first bottom side electrode connected to the drain region; and
a second bottom side electrode coupled to the gate region.