Bipolar transistor structures with cavity below extrinsic base and methods to form same
The disclosure provides bipolar transistor structures with a cavity below an extrinsic base, and methods to form the same. A structure of the disclosure provides a bipolar transistor structure including an extrinsic base protruding from an intrinsic base of a bipolar transistor. The extrinsic base extends over a cavity. An insulator is horizontally adjacent the cavity and below a portion of the extrinsic base. A collector extension region of the bipolar transistor structure extends laterally below the insulator and the cavity.
1 . A structure comprising:
a bipolar transistor structure including an extrinsic base protruding from an intrinsic base of the bipolar transistor structure, wherein an upper surface of the extrinsic base includes a notch;
an insulator below a portion of the extrinsic base, wherein a collector extension region of the bipolar transistor structure extends laterally below the insulator; and
a cavity encapsulated within the insulator, wherein the cavity is vertically between the collector extension region and the portion of the extrinsic base, and horizontally offset from the notch.
2 . The structure of claim 1 , wherein the extrinsic base includes a monocrystalline semiconductor.
3 . The structure of claim 1 , wherein the collector extension region includes a silicide region extending laterally below the cavity to the insulator such the cavity is vertically between the silicide region and the extrinsic base.
4 . The structure of claim 1 , wherein the insulator includes:
a nitride encapsulating the cavity, and
an oxide below a portion of the nitride and adjacent a portion of the collector.
5 . The structure of claim 4 , wherein the oxide includes a lower portion adjacent the collector and an upper portion between the nitride and the intrinsic base.
6 . The structure of claim 1 , further comprising a void within the extrinsic base above the insulator, wherein the void electrically separates an emitter of the bipolar transistor structure from an adjacent emitter.
7 . The structure of claim 1 , further comprising a spacer material within the notch on the upper surface of the extrinsic base.
8 . A structure comprising:
a vertical bipolar transistor structure including:
a collector on a substrate,
an intrinsic base on the collector,
an extrinsic base protruding from the intrinsic base,
wherein an upper surface of the extrinsic base includes a notch, and
an emitter on a portion of the intrinsic base;
an insulator below a portion of the extrinsic base, wherein a collector extension region of the bipolar transistor structure extends laterally below the insulator; and
a cavity encapsulated within the insulator, wherein the cavity is vertically between the collector extension region and the portion of the extrinsic base, and horizontally offset from the notch.
9 . The structure of claim 8 , wherein the intrinsic base includes silicon germanium (SiGe), and wherein the extrinsic base includes a monocrystalline semiconductor.
10 . The structure of claim 8 , wherein the collector includes a silicide region extending laterally below the cavity to the insulator such the cavity is vertically between the silicide region and the extrinsic base.
11 . The structure of claim 8 , wherein the insulator includes:
a nitride encapsulating the cavity, and
an oxide below a portion of the nitride and adjacent a portion of the collector.
12 . The structure of claim 11 , wherein the oxide includes a lower portion adjacent the collector and an upper portion between the nitride and the intrinsic base.
13 . The structure of claim 8 , further comprising a void within the extrinsic base above the insulator, wherein the void electrically separates an emitter of the vertical bipolar transistor structure from an adjacent emitter.
14 . The structure of claim 8 , further comprising a silicide material on an upper surface, a sidewall, and a lower surface of the extrinsic base.
15 . A method comprising:
forming a bipolar transistor structure including an extrinsic base protruding from an intrinsic base of the bipolar transistor structure, wherein an upper surface of the extrinsic base includes a notch;
forming an insulator and below a portion of the extrinsic base, wherein a collector extension region of the bipolar transistor structure extends laterally below the insulator; and
forming a cavity encapsulated within the insulator, wherein the cavity is vertically between the collector extension region and the portion of the extrinsic base, and horizontally offset from the notch.
16 . The method of claim 15 , further comprising forming a silicide region within the collector, the silicide region extending laterally below the cavity to the insulator such the cavity is vertically between the silicide region and the extrinsic base.
17 . The method of claim 15 , wherein forming the insulator includes:
forming a nitride to encapsulate the cavity, and
forming an oxide below a portion of the nitride and adjacent a portion of the collector.
18 . The method of claim 17 , wherein the oxide includes a lower portion adjacent the collector and an upper portion between the nitride and the intrinsic base of the bipolar transistor structure.
19 . The method of claim 15 , wherein forming the insulator includes forming a spacer material to fill the notch within an upper surface of the extrinsic base.
20 . The method of claim 15 , further comprising forming a void within the extrinsic base above the insulator, wherein the void electrically separates an emitter of the bipolar transistor structure from an adjacent emitter.