Gas separation: processes – Solid sorption – Inorganic gas or liquid particle sorbed
Reexamination Certificate
2001-11-29
2003-04-01
Simmons, David A. (Department: 1724)
Gas separation: processes
Solid sorption
Inorganic gas or liquid particle sorbed
C095S117000, C095S900000
Reexamination Certificate
active
06540814
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to an integrated system for ion implantation and scrubbing treatment of the resulting ion implantation effluent for abatement of selected components therein, e.g., components which are hazardous or otherwise undesirable in the effluent stream discharged from the ion implant chamber.
2. Description of the Related Art
Ion implantation is progressively widely used for the introduction of dopant species into substrates for the manufacturing of semiconductor device structures.
The increasingly high levels of microelectronic device integration require shallow junction depths and low temperature process conditions, which are well accommodated by ion implantation. Ion implantation provides a high degree of control and reproducibility, and the ability to incorporate the dopant species into buried substrate regions of the microelectronic device structure.
Typical dopant species for silicon-based microelectronic applications include boron as a p-type dopant, and phosphorus, arsenic and antimony as n-type dopants. Silicon, germanium and oxygen are also used as dopant species in some applications. Dopant species are typically formed from source gases, such as boron trifluoride, arsine, boron trichloride, and phosphine, which entail significant safety and handling issues.
The dopant source gases are introduced to an ionizer where the high voltage arc discharges are employed to form a mixture of ionized species of the source gas. Magnetic field separation is employed for the subsequent separation of the specific ionic species to be implanted, which are then accelerated, focused and directed by a scanner mechanism in an ion beam onto the substrate to be implanted, to introduce the implant species into the crystal lattice of the substrate material being bombarded by the ion beam.
Ion implanters typically use BF
3
, AsH
3
and PH
3
as primary dopant gases. Other gases, such as SiF
4
, GeH
4
, etc. are also used.
Due to the hazardous character of these commonly used dopant gases, significant safety issues are raised. The dopant gases are supplied in conventional practice from high pressure gas cylinders. There is thus a substantial safety threat posed by the danger of leakage of the dopant source gas from the high pressure cylinder, or rupture of the cylinder in use.
The effluent from the ion implantation system thus contains the aforementioned source gases used in the specific application, as well as their ionization decomposition products. Due to their toxicity and hazardous character, it is generally desirable to scrub the effluent gas from the ion implant operation to remove such gases and decomposition products.
The effluent scrubbing operation can be carried out using a variety of wet and/or dry scrubbing operations.
Wet scrubbing of the effluent stream involves contacting the effluent gas from the ion implantation system with a scrubbing liquid to cause the undesired effluent stream components to be absorbed by the liquid, or to react with the liquid (e.g., a caustic solution for contacting with an acid gas effluent) to effect removal of the undesired components from the gas phase.
Dry scrubbing involves contacting the effluent gas with a solid material which functions to chemisorb or react with the undesired components to effect their removal.
In general, wet scrubbing requires the consumption of significant chemical reagents, and thus is less preferred than dry scrubbing, in which a bed of solid-phase scrubbing materials is employed, through which the ion implantation effluent gas is flowed.
It is important to note that for dry scrubbing purposes, the chemical requirements to scrub acid gases such as BF
3
and SiF
4
are entirely different than the chemical requirements to scrub hydride gases such as AsH
3
, PH
3
and GeH
4
.
Available data show that BF
3
passes through an ion implanter largely intact, PH
3
is largely broken down to its elements while passing through the ion implanter, and AsH
3
is broken down to a moderate level while passing through the implanter.
It is expected that other fluorinated acid gases will behave similarly to BF
3
and pass through an ion implant system largely intact. Thus, the large flowrates of intact acid gas dopants mandate effluent stream treatment for removal of acid gases. While hydride source gases pass through only moderately intact, their high toxicity and low levels of permissible personnel exposure (for example, the threshold limit value (TLV) for AsH
3
is 0.05 ppm, or a &OHgr; IDLH of 3 ppm) mandate abatement. Thus, the scrubber employed for treatment of the ion implantation system effluent gas must be capable of handling both acid gases and hydride gases. Such scope of scrubbing utility is difficult to achieve with a single dry scrubbing composition. Multiple beds of different dry scrubbing compositions, split beds of different dry scrubbing compositions, and dry scrubbing composition blends can be used, but these approaches all suffer from the deficiency of being cumbersome in their application and use.
In addition to the foregoing issues incident to the use and operation of ion implantation systems, empirical characterization of ion implant process exhaust streams reveal significant emissions of hazardous gases in the process system from source gas pumps, roughing pumps and from cryogenic pump regeneration cycles.
It would therefore be a significant advance in the art, and accordingly is an object of the present invention, to provide an ion implantation system which eliminates or at least ameliorates the aforementioned hazards of conventional ion implantation processes.
It is another object of the invention to provide an improved system for the treatment of ion implantation process effluents.
Other objects and advantages will be more fully apparent from the ensuing disclosure and appended claims.
SUMMARY OF THE INVENTION
The present invention relates generally to an ion implantation process system having an improved safety character relative to ion implantation process systems of the prior art.
In one aspect, the invention relates to an ion implantation process system, comprising a supply of source gas for the ion implantation process, joined in flow communication with an ion implanter apparatus, with the ion implanter apparatus discharging an effluent gas stream to an effluent abatement apparatus, for removing hazardous effluent species from the effluent gas stream.
The invention in a preferred embodiment includes an ion implantation process system in which the effluent abatement apparatus is positioned in the ion implanter apparatus as a unitary and integrated process arrangement.
In another embodiment, such integrated ion implantation process system further comprises the source gas supply in the integrated arrangement, with the source gas supply, ion implanter apparatus and the effluent abatement apparatus being in a unitary housing.
In accordance with another aspect of the invention, the ion implantation process system comprises one of the following feature sets:
features (a) and (b);
features (a) and (c);
features (a), (b) and (c);
feature (b); and
features (b) and (c). of the features:
(a) the supply of source gas including a storage and dispensing vessel containing a physical sorbent medium having the source gas physically adsorbed thereon, with means for dispensing source gas from the vessel by desorbing source gas from the physical sorbent medium and discharging same from the vessel to the ion implanter apparatus;
(b) the effluent abatement apparatus including a dry scrubbing composition for contacting with the effluent gas stream to remove hazardous effluent species therefrom, in which the dry scrubbing composition is selected from the group consisting of the compositions:
(i) Fe
2
O
3
(ii) Fe
2
O
3
impregnated with a base;
(iii) Ca(OH)
2
;
(iv) Ca(OH)
2
impregnated with a base;
(v) Fe
2
O
3
and MnO
x
, wherein x is from 1 to 2 inclusive;
(vi) Fe
2
O
3
and MnO
z
impregnated with a base, wherein x is from 1 to 2 inclusive;
(vii) CuO a
Arno Jose I.
Hayes Michael W.
Holst Mark R.
Tom Glenn M.
Advanced Technology Materials, Inc
Hultquist Steven J.
Lawrence Frank M.
Simmons David A.
Zitzmann Oliver A.
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