Low-voltage single-layer polysilicon eeprom memory cell

• US 7,144,775 B2
• Filed: 05/18/2004
• Issued: 12/05/2006
• Est. Priority Date: 05/18/2004
• Status: Active Grant

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Carver, Damian A., Chaudhry, Muhammad I.
• Primary Examiner(s): Whitehead, Jr., Carl
• Assistant Examiner(s): Rodgers, Colleen E.
• Application Number:
  US10/848,763
• Publication Number:
  US 20050258492A1
• Time in Patent Office: 931 Days
• Field of Search: 438/164, 438/223, 438/258
• US Class Current: 438/258
• CPC Class Codes: G11C 16/0433 comprising cells containing a single floating gate transistor and one or more separate select transistors
• CPC Class Codes: H01L 29/66825 with a floating gate H01L29/6684 takes precedence
• CPC Class Codes: H01L 29/7881 Programmable transistors with only two possible levels of programmation H01L29/7888 takes precedence
• CPC Class Codes: H10B 41/30 characterised by the memory core region
• CPC Class Codes: H10B 41/60 the control gate being a doped region, e.g. single-poly memory cell
• CPC Class Codes: H10B 69/00 Erasable-and-programmable ROM [EPROM] devices not provided for in groups H10B41/00 - H10B63/00, e.g. ultraviolet erasable-and-programmable ROM [UVEPROM] devices

Abstract

The present invention is an electronic memory cell and a method for the cell'"'"'s fabrication comprising a first transistor configured to be coupled to a bit line. The first transistor has an essentially zero voltage drop when activated and is configured to control an operation of the memory cell. A second transistor is configured to operate as a memory transistor and is coupled to the first transistor. The second transistor is further configured to be programmable with a voltage about equal to a voltage on the bit line.

Claims

1. A method of fabricating an electronic memory cell comprising:

producing a first drain dopant region and a first source dopant region in an uppermost side of a semiconducting substrate, the first drain and first source dopant regions being doped to provide donor sites;

producing a second drain dopant region and a second source dopant region in an uppermost side of a semiconducting substrate, the second drain and second source dopant regions being doped to provide acceptor sites;

constructing a shallow trench isolation region substantially between the first drain/first source dopant regions and the second drain/second source dopant regions;

coupling the first drain dopant region to the second drain dopant region to communicate electrically;

fabricating a PMOS transistor from the second drain and second source dopant regions, the PMOS transistor serving as a select transistor in the memory cell, the PMOS transistor being further configured to have an essentially zero voltage drop between the second source and second drain regions when the PMOS transistor is in an activated state; and

fabricating an NMOS transistor from the first drain and first source dopant regions, the NMOS transistor configured to serve as a memory transistor in the memory cell.

2. The method of fabricating an electronic memory cell of claim 1 further comprising fabricating a tunnel diode window wherein the tunnel diode window is about 7 nanometers in thickness.

3. The method of fabricating an electronic memory cell of claim 1 wherein all the dopant regions are formed within an epitaxial p-type layer which is an uppermost side of the semiconducting substrate.

4. The method of fabricating an electronic memory cell of claim 1 wherein the memory transistor is configured to operate with a programming voltage of about 10 volts.

5. The method of fabricating an electronic memory cell of claim 1 further comprising fabricating an n-well which forms a portion of the select transistor.

6. The method of fabricating an electronic memory cell of claim 1 wherein the shallow trench isolation region is formed from undoped silicate glass.

7. The method of fabricating an electronic memory cell of claim 1 wherein the shallow trench isolation region is formed from silicon dioxide.

8. The method of fabricating an electronic memory cell of claim 1 wherein the second drain dopant region and the second source dopant region are produced in an n-well fabricated within the uppermost side of the semiconducting substrate.

9. A method of fabricating an electronic memory cell comprising:

depositing a p-type epitaxial layer on an uppermost side of a semiconducting substrate;

producing a first drain dopant region and a first source dopant region in the epitaxial layer, the first drain and first source dopant regions being doped to provide donor sites;

producing a second drain dopant region and a second source dopant region in the epitaxial layer, the well being doped with donor sites and large enough to surround the second drain dopant region and the second source dopant region;

constructing a shallow trench isolation region substantially between the first drain/first source dopant regions and the second drain/second source dopant regions;

coupling the first drain dopant region to the second drain dopant region to communicate electronically;

fabricating a PMOS transistor from the second drain and second source dopant regions, the PMOS transistor serving as a select transistor in the memory cell, the PMOS transistor being further configured to have an essentially zero voltage drop between the second source and second drain regions when the PMOS transistor is in an activated state; and

fabricating an NMOS transistor from the first drain and first source dopant regions, the NMOS transistor configured to serve as a memory transistor in the memory cell, the memory transistor being configured to operate with a programming voltage of about 10 volts.

10. The method of fabricating an electronic memory cell of claim 9 wherein the shallow trench isolation region is formed from undoped silicate glass.

11. The method of fabricating an electronic memory cell of claim 9 wherein the shallow trench isolation region is formed from silicon dioxide.

12. The method of fabricating an electronic memory cell of claim 9 wherein the memory cell is fabricated without a threshold voltage dopant region.