Process for etching by gas plasma

Details Process for etching by gas plasma Process for etching by gas plasma

1989-11-15

1991-09-10

Powell, William A.

Adhesive bonding and miscellaneous chemical manufacture

Delaminating processes adapted for specified product

Delaminating in preparation for post processing recycling step

156646, 156656, 156657, 1566591, 156662, 156345, 20419237, 252 791, H01L 21306, B44C 122, C03C 1500, C23F 100

Patent

active

050471155

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a process for etching by plasma usable for etching layers of a random nature (insulating, condutive, semiconductive) on random substrates (conductors, semiconductors, insulants) and in particular for producing large relief structures in silicon.
The invention more particularly applies to the microelectronics field, especially for producing magnetic recording heads and hybrid circuits, as well as in the optronics and sensor fields.
In known manner, for producing etchings by plasma, said plasma is produced by reacting an appropriate gaseous medium with ultra-high frequency and/or radio-frequency waves. The interaction of the ultra-high frequency or radio-frequency waves with the gaseous medium makes it possible to split up the gaseous medium into ionized species (ions, electrons) and into neutral species (atoms, molecules). These different species constitute the plasma and initiate chemical reactions on the layer to be etched.
Thus, J. Electrochem. Soc., Vol. 132, December 1985 discloses an etching process using a plasma produced by radio-frequency waves, in which the gaseous medium is constituted by a fluorinating gas formed by CF.sub.4 or SF.sub.6, to which is optionally added argon, oxygen or nitrogen. This document demonstrates that the addition of oxygen is prejudicial for the selectivity of the etching, because it increases the etching rate of the mask and decreases the etching rate of the substrate, no matter what the fluorinating gas used. In addition, the gaseous medium recommended is a mixed CF.sub.4 /N.sub.2 or SF.sub.6 /N.sub.2 system.
An apparatus making it possible to produce a plasma by ultra-high frequency waves is e.g. described in French patent application FR-A-2 534 040 and an apparatus making it possible to create a plasma by ratio-frequency waves is e.g. described in French patent application FR-A-2 538 987.
U.S. Pat. No. 4,298,419 discloses a process for etching by plasma produced by ultra-high frequency waves, in which the gaseous medium is constituted by a mixture of C.sub.2 F.sub.6 and H.sub.2 an a.c. voltage in the radio-frequency field is applied to the substrate to be etched in order to obtain a high etching rate when the substrate is insulating or covered insulating or covered with an insultant. However, the etching rates obtained with this process remain low, below 0.1 .mu.m/min. In this process, the plasma is produced by coupling between a waveguide and a gas column without a preferred direction and focussed onto the substrate by creating a magnetic field. For high values of this magnetic field cyclotron resonance of the electrons is obtained, which increases the dissociation of the plasma. This requires the use of relatively low pressures below 6.5 Pa (50 mTorr) and high pumping rates.


BACKGROUND OF THE INVENTION

EP-A-0 180 020 and Microelectronic Engineering, Vol. 3, No. 1/4, 1985, pp. 397-410 discloses plasma etching processes simultaneously using ultra-high frequencies and radio-frequencies with a gaseous medium chosen from among halogens, rare gases, etc., in the case of EP-A-0 180 020, or a mixture of CF.sub.4 and oxygen in the case of the document.
These plasma etching processes simultaneously using ultra-high frequencies and radio-frequencies generally make it possible to obtain an improved result compared with that obtained with plasmas produced solely by radio-frequencies.
However, for producing deep structures in certain substrates, e.g. in silicon, in an industrial manner and with a good definition with respect to the geometry defined by the mask, it is necessary to further improve the results, particularly the etching speed or rate in order to have a high industrial production rate adapted to the etched depth and the control of the etched profile or anisotropy and the selectivity of the etching.
The characteristics of an etching made in a layer with the aid of a plasma are the speed or rate Vg, the anisotropy A and the selectivity S of the etching. The anisotropy of an eching A is determined by the ratio b

REFERENCES:
patent: 4579623 (1986-04-01), Suzuki et al.
patent: 4581100 (1986-04-01), Hatzakis et al.
Journal of the Electrochemical Society, vol. 132, No. 12, Dec. 1985, S. Adachi et al.: "Reactive Ion Etching of Tungsten Films Sputter Deposited on GaAs", pp. 2980-2989.
Microelectronic Engineering, vol. 3, No. 1/4, Dec. 1985, Elsevier Science Publishers B.V., J. Paraszczak et al.: "Methods of Creation and Effect of Microwave Plasmas Upon the Etching of Polymers and Silicon", pp. 397-410.

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