Method of forming a field-effect transistor (FET) or other semiconductor device with front-side source and drain contacts
View Patent ↗A method is provided for forming an integrated circuit (IC) structure including trench-based semiconductor devices, e.g., trench FETs, having front-side drain contacts. The method may include forming an epitaxy region, forming a poly gate trench in the epitaxy region, forming a drain contact trench through the poly gate trench and extending below the poly gate trench, forming a poly gate in the poly gate trench, forming a front-side drain contact in the drain contact trench, and forming a source region in the epitaxy region adjacent the poly gate. The device may define a drift region from the poly gate/source intersection to the front-side drain contact. The drift region may be located within the epitaxy layer, without extending into an underlying substrate or transition layer. The front-side drain contact depth may be selected to influence the device breakdown voltage. The front-side drain contacts may allow flip-chip mounting of the IC structure.
1. A method of forming a semiconductor device, the method comprising:
forming an epitaxy region;
forming a poly gate trench in the epitaxy region;
forming a drain contact trench through the poly gate trench and extending downwardly to a further vertical depth in the epitaxy region than the poly gate trench;
forming a poly gate in the poly gate trench after forming the drain contact trench;
forming a gate contact contiguous with the poly gate and extending laterally over the epitaxy region in a direction away from the poly gate trench;
forming a front-side drain contact in the drain contact trench, wherein the front-side drain contact extends downwardly to a further vertical depth than the poly gate, but only partially through a vertical depth of the epitaxy region, such that a bottom of the front-side drain contact is located above and spaced-apart from a bottom surface of the epitaxy region; and
forming a source region in the epitaxy region adjacent the poly gate;
wherein a drift region extending from an intersection of the poly gate and source region to the bottom of front-side drain contact is fully contained within the epitaxy region.
2. The method of claim 1 , wherein the front-side drain contact in the drain contact trench is isolated from each of the at least one poly gate by a respective insulating spacer.
3. The method of claim 1 , comprising:
forming a bulk substrate; and
forming the epitaxy region over the bulk substrate;
wherein the drift region does not extend into the bulk substrate.
4. The method of claim 3 , comprising forming the epitaxy region direct on the bulk substrate such that the epitaxy region is directly coupled to the bulk substrate.
5. The method of claim 1 , comprising:
forming a bulk substrate; and
forming or defining a transition region between the epitaxy region and the bulk substrate;
wherein the drift region does not extend into the transition region.
6. The method of claim 1 , comprising:
forming a pair of poly gates in the poly gate trench;
forming the front-side drain contact in the drain contact trench such that the front-side drain contact extends between the pair of poly gates in the poly gate trench.
7. The method of claim 6 , comprising forming a respective insulating spacer between the front-side drain contact and each of the pair of poly gates.
8. The method of claim 1 , wherein the semiconductor device comprises a trench field-effect transistor (FET).
9. A method of forming a semiconductor device, the method comprising:
forming an epitaxy region;
forming a poly gate trench in the epitaxy region;
depositing a sacrificial layer that extends into the poly gate trench to define sacrificial sidewalls in the poly gate trench;
forming a drain contact trench through an opening defined between the sacrificial sidewalls in the poly gate trench and extending downwardly to a further depth in the epitaxy region than the poly gate trench;
filling the drain contact trench with a drain contact trench fill material;
removing the sacrificial sidewalls in the poly gate trench to define poly gate openings in the poly gate trench;
filling the poly gate openings with poly gate material to form poly gates in the poly gate trench;
etching a drain contact opening in the drain contact trench fill material; and
filling the drain contact opening with drain contact material to form a front-side drain contact in the drain contact trench, wherein the front-side drain contact is contained in the epitaxy region; and
forming a source region in the epitaxy region adjacent the poly gate;
wherein a drift region is defined from an intersection of the poly gate and source region to the front-side drain contact.