# US 7,611,953 B2 · Bipolar transistor with isolation and direct contacts

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- Number: US 7,611,953 B2
- Document ID: US7611953B2
- Status: Granted
- Kind: B2
- Application number: 11/677,776
- Filed: 2007-02-22
- Published: 2007-06-28
- Granted: 2009-11-03
- Earliest claimed: 2004-06-04
- Assignees: International Business Machines Corporation
- Inventors: David C. Ahlgren; Gregory G. Freeman; Francois Pagette; Christopher M. Schnabel; Anna W. Topol
- Web page: https://patentgrep.com/patent/US7611953B2

## CPC

- H10D 10/021: {of heterojunction BJTs [HBT]}
- H10D 10/891: {comprising lattice-mismatched active layers, e.g. SiGe strained-layer transistors}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A bipolar transistor has a collector that is contacted directly beneath a base-collector junction by metallization to reduce collector resistance. A conventional reach-through and buried layer, as well as their associated resistance, are eliminated. The transistor is well isolated, nearly eliminating well-to-substrate capacitance and device-to-device leakage current. The structure provides for improved electrical performance, including improved fT, Fmax and drive current.

## Claims

### Claim 1

A method of fabricating a device, comprising:
depositing a base layer on a first side of a collector layer;
depositing an emitter layer on the base layer;
depositing a silicide layer on a second side of the collector;
depositing a first oxide layer on the silicide layer on the second side of the collector layer;
etching a via through the first oxide layer from a top surface of the first oxide layer to the silicide layer on the second side of the collector layer;
filling the via with a conductor to form an electrical pathway to the collector through the first oxide layer;
bonding the second side of the collector layer to a first substrate prior to the deposition of the first oxide layer;
prior to the bonding step depositing an oxide layer around at least one side of the collector layer;
depositing a passivation layer on the oxide layer and base layer and emitter layer; and
depositing at least one metal contact on the passivation layer and bonding the at least one metal contact to a substrate and removing at least a portion of the first substrate.

### Claim 2 (depends on 1)

The method of claim 1, further comprising forming an electrical pathway to the emitter layer, and forming an electrical pathway to the base layer.

### Claim 3 (depends on 1)

The method of claim 1, further comprising depositing the silicide layer between the second side of the collector layer and the first oxide layer, wherein the via is etched through the first oxide layer from a top surface of the first oxide layer to the silicide layer already deposited.

### Claim 4 (depends on 3)

The method of claim 3, further comprising forming metal contacts on a passivation layer, the first oxide layer, and the base and emitter layers.

### Claim 5 (depends on 3)

The method of claim 3, further comprising forming a via through the another oxide layer to the base layer.

### Claim 6

A method of fabricating a device, comprising:
depositing a base layer on a first side of a collector layer;
depositing an emitter layer on the base layer;
depositing a first oxide layer on the second side of the collector layer;
etching a via through the first oxide layer from a top surface of the first oxide layer to the second side of the collector layer;
filling the via with a conductor to form an electrical pathway to the collector through the first oxide layer;
bonding the second side of the collector layer to a first substrate prior to the deposition of the first oxide layer;
prior to the bonding step depositing a oxide layer around at least one side of the collector layer;
depositing a passivation layer on the oxide layer and base layer and emitter layer; and
depositing at least one metal contact on the passivation layer and bonding the at least one metal contact to a substrate and removing at least a portion of the first substrate.

### Claim 7 (depends on 6)

The method of claim 6, further comprising forming a conductive pathway between the metal contact and the base by forming a via through the first oxide layer and a second oxide layer.

### Claim 8 (depends on 1)

The method of claim 1, further comprising forming a substrate which is electrically isolated from the collector region.