# US 5,346,851 A · Method of fabricating Shannon Cell circuits

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- Number: US 5,346,851 A
- Document ID: US5346851A
- Status: Granted
- Kind: A
- Application number: 07/979,117
- Filed: 1992-11-20
- Granted: 1994-09-13
- Earliest claimed: 1992-11-20
- Assignees: Texas Instruments Incorporated
- Inventors: John N. Randall; Gary A. Frazier; Rajni J. Aggarwal
- Web page: https://patentgrep.com/patent/US5346851A

## CPC

- H10D 84/01: Manufacture or treatment
- B82Y 10/00: Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
- H10D 84/05: using Group III-V technology
- H10W 10/00: Isolation regions in semiconductor bodies between components of integrated devices
- H10W 10/01: {Manufacture or treatment}
- Y10S 148/05: Etch and refill
- Y10S 148/051: Etching
- Y10S 148/169: Vacuum deposition, e.g. including molecular beam epitaxy
- Y10S 438/962: Quantum dots and lines
- Y10S 977/773: Nanoparticle, i.e. structure having three dimensions of 100 nm or less
- Y10S 977/774: Exhibiting three-dimensional carrier confinement, e.g. quantum dots
- Y10S 977/94: in a logic circuit
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A quantum effect device implementation of the Shannon Decomposition Function in the form of a Shannon Cell is provided in which a first quantum dot logic unit (50) is coupled between the X input and the output of the Shannon Cell. A second quantum dot logic unit (52) is coupled between the Y input and the output of the Shannon Cell. The control input to the Shannon Cell is coupled to both the first and second quantum dot logic units (50 and 52) such that current flows through the appropriate quantum dot logic unit (50 or 52) depending upon the logic state of the control input.

## Claims

### Claim 1

A method of fabricating a quantum-effect implementation of Shannon Cell, comprising the steps of:
providing a semiconductor substrate;
forming a first barrier layer overlying the substrate;
forming a quantum layer overlying the first barrier layer;
forming a second barrier layer overlying the quantum layer;
etching through said first and second barrier layers and said quantum layer to separate a first quantum dot logic unit area from a second quantum dot logic unit area;
etching three trenches in the first quantum dot logic unit area to define a first filter quantum dot and a first control quantum dot;
etching three trenches in the second quantum dot logic unit area to define a second filter quantum dot and a second control quantum dot;
regrowing heterojunction tunnel barriers in the trenches;
forming an X-input contact conductively coupled to the quantum well in the first quantum dot logic unit area;
forming a first control contact insulatively adjacent the first control quantum dot, such that potentials placed on the first control contact align or misalign electron energy states within the first control quantum dot with electron energy states of the first filter quantum dot;
forming a first output contact conductively coupled to the quantum well opposite the first filter quantum dot and the first control quantum dot from the X-input contact;
forming a Y-input contact conductively coupled to the quantum well in the second quantum dot logic unit area;
forming a second control contact insulatively adjacent the second control quantum dot and coupled to the first control contact, such that potentials placed on the second control contact align or misalign electron energy states within the second control quantum dot with electron energy states of the second filter quantum dot; and
forming a second output contact conductively coupled to the quantum well opposite the second filter quantum dot and the second control quantum dot from the Y-input contact, the second output contact coupled to said first output contact.

### Claim 2 (depends on 1)

The method of claim 1, and further comprising the steps of:
etching through said first and second barrier layers and said quantum layer to define a third quantum dot logic unit area and fourth quantum dot logic unit area;
etching three trenches in the third quantum dot logic unit area to define a third filter quantum dot and a third control quantum dot;
etching three trenches in the fourth quantum dot logic unit area to define a fourth filter quantum dot and a fourth control quantum dot;
regrowing heterojunction tunnel barriers in the trenches;
forming a source contact conductively coupled to the quantum well in the third quantum dot logic unit area;
forming a third control contact insulatively adjacent the third control quantum dot and coupled to the first and second output contacts, such that potentials placed on the first control contact align or misalign electron energy states within the third control quantum dot with electron energy states of the third filter quantum dot;
forming a first buffer output contact conductively coupled to the quantum well opposite the third filter quantum dot and the third control quantum dot from the source contact;
forming a sink contact conductively coupled to the quantum well in the fourth quantum dot logic unit area;
forming a fourth control contact insulatively adjacent the fourth control quantum dot and coupled to the third control contact, such that potentials placed on the fourth control contact align or misalign electron energy states within the fourth control quantum dot with electron energy states of the fourth filter quantum dot; and
forming a second buffer output contact conductively coupled to the quantum well opposite the fourth filter quantum dot and the fourth control quantum dot from the sink contact, the second buffer output contact coupled to the first buffer output contact.

### Claim 3

A method of fabricating a quantum-effect implementation of Shannon Cell, comprising the steps of:
providing a semiconductor substrate;
forming a first barrier layer overlying the substrate;
forming a first quantum layer overlying the first barrier layer;
forming a second barrier layer overlying the first quantum layer;
forming a second quantum layer overlying the second barrier layer;
etching a contact opening through the first and second barrier layers and the first and second quantum layers to the semiconductor substrate;
etching the second quantum layer to define an X-well and a Y-well, the X-well and Y-well having different thicknesses and spaced apart by etching through to the second barrier layer between the X-well and Y-well;
forming an insulating layer overlying the X-well, the Y-well, the contact opening, and the space between the X-well and Y-well;
forming a control contact conductively coupled to the semiconductor substrate at the contact opening;
forming an X-input contact insulatively adjacent to the X-well;
forming a Y-input contact insulatively adjacent to the Y-well; and
forming an output contact conductively coupled to the first quantum layer, such that potentials placed on the control contact affect electron energy states within the first quantum layer, thereby causing alignment or misalignment with the energy states within the X-well and Y-well, such that current flows either from the X-input contact or the Y-input contact to the output contact.