# US 7,411,247 B2 · Twin insulator charge storage device operation and its fabrication method

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- Number: US 7,411,247 B2
- Document ID: US7411247B2
- Status: Granted
- Kind: B2
- Application number: 11/652,888
- Filed: 2007-01-12
- Published: 2007-05-24
- Granted: 2008-08-12
- Earliest claimed: 2002-10-15
- Assignees: Halo LSI, Inc.
- Inventors: Seiki Ogura; Kimihiro Satoh; Tomoya Saito
- Web page: https://patentgrep.com/patent/US7411247B2

## CPC

- G11C 16/0475: {comprising two or more independent storage sites which store independent data}
- G11C 16/0483: {comprising cells having several storage transistors connected in series}
- G11C 16/14: Circuits for erasing electrically, e.g. erase voltage switching circuits
- H10B 43/30: characterised by the memory core region
- 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
- H10D 30/69: IGFETs having charge trapping gate insulators, e.g. MNOS transistors
- H10D 30/694: {characterised by the shapes, relative sizes or dispositions of the gate electrodes}
- H10D 64/037: {comprising charge-trapping insulators}
- G11C: STATIC STORES (semiconductor memory devices H10B)
- H10B: ELECTRONIC MEMORY DEVICES
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

The invention proposes am improved twin MONOS memory device and its fabrication. The ONO layer is self-aligned to the control gate horizontally. The vertical insulator between the control gate and the word gate does not include a nitride layer. This prevents the problem of electron trapping. The device can be fabricated to pull the electrons out through either the top or the bottom oxide layer of the ONO insulator. The device also incorporates a raised memory bit diffusion between the control gates to reduce bit resistance. The twin MONOS memory array can be embedded into a standard CMOS circuit by the process of the present invention.

## Claims

### Claim 1

A twin MONOS memory embedded in a CMOS device comprising:
a memory area and a CMOS area separated by isolation regions in a substrate;
a deep N-well in said memory area;
polysilicon word gates having polysilicon control gates on sidewalls of said word gates having an oxide layer therebetween and not having an oxide-nitride-oxide (ONO) layer therebetween and having an ONO layer underlying said control gates wherein said nitride portion of said ONO layer underlying said control gates provides memory storage in said memory area;
raised polysilicon diffusions in said memory area between each two of said control gates and separated from said control gates by an oxide layer;
word lines overlying and crossing said word gates;
polysilicon CMOS gates in said CMOS area;
source and drain regions in said substrate adjacent to said gates in said CMOS area and in said memory area wherein said source and drain regions in said memory area are underlying and directly contacting said raised polysilicon diffusions;
diffusion contacts through a dielectric layer overlying said gates to said raised diffusions at an end of every other raised diffusion alternating in a memory block;
control gate contacts through a dielectric layer overlying said gates on an extension of said diffusion contacts or between diffusion contacts; and
word gate contacts at ends of said word lines alternately to complete said Twin MONOS memory device.

### Claim 2 (depends on 1)

The device according to claim 1 wherein said polysilicon word gates have a thickness of between about 100 and 200 nm.

### Claim 3 (depends on 1)

The device according to claim 1 wherein said oxide-nitride-oxide (ONO) layer comprises:
a base oxide layer having a thickness of between about 3 and 6 nm;
a nitride layer overlying said base oxide layer having a thickness of between about 3 and 6 nm; and
a top oxide layer overlying said nitride layer having a thickness of between about 4 and 7 nm.

### Claim 4 (depends on 3)

The device according to claim 3 wherein electrons stored in said nitride layer are to be erased through said base oxide layer and wherein said base oxide layer is thinner than said top oxide layer.

### Claim 5 (depends on 3)

The device according to claim 3 wherein electrons stored in said nitride layer are to be erased through said top oxide layer and wherein said top oxide layer is thinner than said base oxide layer.

### Claim 6 (depends on 1)

The device according to claim 1 further comprising salicided said memory gates, said CMOS gates, and said source and drain regions in said CMOS areas.