Highly Selective Photoresist Ashing by Addition of Ammonia to Plasma Containing Carbon Tetrafluoride

Makoto Saito, Hideo Eto, Kayoko Omiya, Tetsuya Homma, Takao Nagatomo

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

A highly selective photoresist ashing process performed at low temperature using a downflow plusma consisting of a carbon tetrafluoride/oxygen (CF4/O2) gas mixture was developed for the fabrication of thin film transistor liquid crystal displays (TFTLCDs). Although the ashing rate was increased by using the CF4/O2 gas mixture plasma, the etching selectivity for underlying amorphous silicon (a-Si:H) films containing hydrogen decreased. The etching rate of a-Si:H films was decreased by the addition of ammonia (NH3). Since the etching rate of a-Si:H films decreased to zero at NH3 flow rates higher than 15 standard cubic centimeters per minute, an infinitely high etching selectivity for the photoresist films was achieved at room temperature. On the basis of the surface analysis results for a-Si:H films, a mechanism for the high etching selectivity of the photoresist films was proposed. Reaction products that were formed on a-Si:H films by the addition of NH3 gas to CF4/O2 gas mixture plasma obstructed the etching of a-Si:H films by fluorine (F) radicals, resulting in the high selectivity, It was found that the NH3, gas that was added to CF4/O2 gas mixture plasma reacted with a-Si:H. resulting in the formation of a protective reaction product which is considered to be an ammonium salt such as (NH4)2 SiF6

Original languageEnglish
JournalJournal of the Electrochemical Society
Volume148
Issue number2
DOIs
Publication statusPublished - 2001

Fingerprint

carbon tetrafluoride
Photoresists
Ammonia
photoresists
ammonia
Plasmas
Etching
Carbon
etching
Gas mixtures
gas mixtures
selectivity
Reaction products
reaction products
Hydrogen
Gases
Fluorine
Surface analysis
Thin film transistors
Amorphous silicon

ASJC Scopus subject areas

  • Electrochemistry
  • Surfaces, Coatings and Films
  • Surfaces and Interfaces

Cite this

Highly Selective Photoresist Ashing by Addition of Ammonia to Plasma Containing Carbon Tetrafluoride. / Saito, Makoto; Eto, Hideo; Omiya, Kayoko; Homma, Tetsuya; Nagatomo, Takao.

In: Journal of the Electrochemical Society, Vol. 148, No. 2, 2001.

Research output: Contribution to journalArticle

@article{b9cc4844058e453d87631c018ddc7d97,
title = "Highly Selective Photoresist Ashing by Addition of Ammonia to Plasma Containing Carbon Tetrafluoride",
abstract = "A highly selective photoresist ashing process performed at low temperature using a downflow plusma consisting of a carbon tetrafluoride/oxygen (CF4/O2) gas mixture was developed for the fabrication of thin film transistor liquid crystal displays (TFTLCDs). Although the ashing rate was increased by using the CF4/O2 gas mixture plasma, the etching selectivity for underlying amorphous silicon (a-Si:H) films containing hydrogen decreased. The etching rate of a-Si:H films was decreased by the addition of ammonia (NH3). Since the etching rate of a-Si:H films decreased to zero at NH3 flow rates higher than 15 standard cubic centimeters per minute, an infinitely high etching selectivity for the photoresist films was achieved at room temperature. On the basis of the surface analysis results for a-Si:H films, a mechanism for the high etching selectivity of the photoresist films was proposed. Reaction products that were formed on a-Si:H films by the addition of NH3 gas to CF4/O2 gas mixture plasma obstructed the etching of a-Si:H films by fluorine (F) radicals, resulting in the high selectivity, It was found that the NH3, gas that was added to CF4/O2 gas mixture plasma reacted with a-Si:H. resulting in the formation of a protective reaction product which is considered to be an ammonium salt such as (NH4)2 SiF6",
author = "Makoto Saito and Hideo Eto and Kayoko Omiya and Tetsuya Homma and Takao Nagatomo",
year = "2001",
doi = "10.1149/1.1339870",
language = "English",
volume = "148",
journal = "Journal of the Electrochemical Society",
issn = "0013-4651",
publisher = "Electrochemical Society, Inc.",
number = "2",

}

TY - JOUR

T1 - Highly Selective Photoresist Ashing by Addition of Ammonia to Plasma Containing Carbon Tetrafluoride

AU - Saito, Makoto

AU - Eto, Hideo

AU - Omiya, Kayoko

AU - Homma, Tetsuya

AU - Nagatomo, Takao

PY - 2001

Y1 - 2001

N2 - A highly selective photoresist ashing process performed at low temperature using a downflow plusma consisting of a carbon tetrafluoride/oxygen (CF4/O2) gas mixture was developed for the fabrication of thin film transistor liquid crystal displays (TFTLCDs). Although the ashing rate was increased by using the CF4/O2 gas mixture plasma, the etching selectivity for underlying amorphous silicon (a-Si:H) films containing hydrogen decreased. The etching rate of a-Si:H films was decreased by the addition of ammonia (NH3). Since the etching rate of a-Si:H films decreased to zero at NH3 flow rates higher than 15 standard cubic centimeters per minute, an infinitely high etching selectivity for the photoresist films was achieved at room temperature. On the basis of the surface analysis results for a-Si:H films, a mechanism for the high etching selectivity of the photoresist films was proposed. Reaction products that were formed on a-Si:H films by the addition of NH3 gas to CF4/O2 gas mixture plasma obstructed the etching of a-Si:H films by fluorine (F) radicals, resulting in the high selectivity, It was found that the NH3, gas that was added to CF4/O2 gas mixture plasma reacted with a-Si:H. resulting in the formation of a protective reaction product which is considered to be an ammonium salt such as (NH4)2 SiF6

AB - A highly selective photoresist ashing process performed at low temperature using a downflow plusma consisting of a carbon tetrafluoride/oxygen (CF4/O2) gas mixture was developed for the fabrication of thin film transistor liquid crystal displays (TFTLCDs). Although the ashing rate was increased by using the CF4/O2 gas mixture plasma, the etching selectivity for underlying amorphous silicon (a-Si:H) films containing hydrogen decreased. The etching rate of a-Si:H films was decreased by the addition of ammonia (NH3). Since the etching rate of a-Si:H films decreased to zero at NH3 flow rates higher than 15 standard cubic centimeters per minute, an infinitely high etching selectivity for the photoresist films was achieved at room temperature. On the basis of the surface analysis results for a-Si:H films, a mechanism for the high etching selectivity of the photoresist films was proposed. Reaction products that were formed on a-Si:H films by the addition of NH3 gas to CF4/O2 gas mixture plasma obstructed the etching of a-Si:H films by fluorine (F) radicals, resulting in the high selectivity, It was found that the NH3, gas that was added to CF4/O2 gas mixture plasma reacted with a-Si:H. resulting in the formation of a protective reaction product which is considered to be an ammonium salt such as (NH4)2 SiF6

UR - http://www.scopus.com/inward/record.url?scp=0002621020&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0002621020&partnerID=8YFLogxK

U2 - 10.1149/1.1339870

DO - 10.1149/1.1339870

M3 - Article

VL - 148

JO - Journal of the Electrochemical Society

JF - Journal of the Electrochemical Society

SN - 0013-4651

IS - 2

ER -