Anode assisted sputter etch and deposition apparatus

An anode assisted sputter etch and deposition apparatus having an electron source, a first anode adjacent the electron source and a second anode adjacent a negatively charged article to be sputter etched or sputter target in an ionizable gas atmosphere. Upon production of the electrons from said electron source a plasma is formed between the electron source, the first anode and the second anode, the plasma adjacent the second anode being capable of desorbing gases and other absorbed vapors from the surface of the article or target while positive ions from the plasma bombard the article or target with sufficient energy to eject material from the surface thereof.

BACKGROUND OF THE INVENTION 
This invention relates generally to sputter etch and deposition systems, 
and, more particularly to an etch and deposition apparatus which 
incorporates therein a centrally located anode in order to assist in the 
sputtering operation when utilized with concave surfaces. 
In recent years the demand in the electronics industry, for example, for 
films with qualities difficult or even impossible to attain by deposition 
techniques already available, has led to the utilization of sputtering as 
a method of depositing a thin film coating on a surface. In addition, the 
sputtering technique has been utilized for the cleaning and etching of 
surface contaminants or other layers of material which are not desired 
from the surface of an article. 
Unfortunately, a basic problem still exists in the sputter cleaning of the 
inside of a small hemispherical cavity. The standard technique for sputter 
cleaning was simply to apply a negative bias to the article to be cleaned 
in a glow discharge or plasma. It was then discovered that because of the 
shape of the cavity and its small size that the effectiveness of the 
sputtering technique decreased greatly when the effective diameter of the 
concave surface of the cavity is of the order of the Crookes dark space or 
smaller. For example, such sputter cleaning techniques of the past were 
relatively ineffective in cleaning the interior of a hemispherical cavity 
of 3/8 inches in diameter. Consequently, it can be seen that past sputter 
cleaning techniques utilized with articles having concave surfaces require 
substantial improvement to be effective. 
SUMMARY OF THE INVENTION 
The instant invention overcomes the problems encountered in the past by 
providing an anode assisted sputter etch and deposition apparatus which is 
capable of uniformly applying a bombarding plasma to the interior of a 
concave surface for the purpose of plasma cleaning which results in the 
removal from the surface of any contaminants or other layers of material 
which are not desired on the surface which may inhibit other processes 
such as the deposition of other material on the surface. In addition, the 
instant invention can be utilized for altering the size and shape or 
patterns of the concave surface by sputter etching the surface with the 
plasma until the desired size and shape or pattern are obtained. 
Furthermore, the instant invention can be utilized in conjunction with a 
conventional deposition process for the purpose of applying a voltage bias 
to the entire surface thereby causing the removal of gaseous impurities 
from the surface as well as permitting better adhesion to take place 
during the deposition process. In addition, the instant invention is 
capable of using the concave surface as a sputter target wherein the 
material is removed from the surface and deposited onto a nearby 
substrate, thereby forming a coating on the substrate. 
The sputter etch and deposition apparatus of this invention is made up of a 
housing which is capable of having a partial vacuum formed therein. A 
heated filament located within the housing provides a source of electrons 
in an argon or other suitable atmosphere at this partial vacuum. The 
electrons are accelerated toward an anode located within the housing and 
upon colliding with an atmospheric gas, such as argon, forms a plasma 
which consists of positive and negative ions and electrons. 
The concave surface of an article to be cleaned by the instant invention is 
secured in position by a holder intermediate the heated filament and anode 
while a negative voltage bias is applied to it. A positive electrode in 
the form of an anode pin is centrally located within the concave surface. 
The positive potential on the anode pin utilizes part of the available 
ions to form a plasma within the concave cavity, which in itself is 
effective in desorbing gases and other absorbed vapors from the surface. 
The negative potential applied to the concave surface attracts the 
positive ions of the plasma which then bombards the surface with 
sufficient energy to eject materials from the surface. 
The present invention has the advantage that a plasma is created within the 
cavity and that the Crookes dark space is established between the 
centrally located anode pin and the surface to be cleaned. Bombarding 
action takes place within the entire cavity. As a result thereof the 
present invention can plasma clean or etch smaller parts than was possible 
in the past, and can more uniformly clean or etch larger parts. 
It should also be realized that the present invention is not limited to 
merely the cleaning of concave surfaces, in that it can be used to change 
the size and shape of any surface by small controllable amounts by 
continuing to sputter etch the surface as long as desired. Such a system 
may also be used to form patterns or grooves in the surface, which could 
not be accomplished with prior art techniques. Furthermore, the instant 
invention has the advantage that it can be used in conjunction with a 
conventional deposition process to apply an effective bias to the entire 
surface when it is desired to bias sputter-deposit material onto the 
surface. Past attempts at such a procedure generally would not uniformly 
apply the bias to the surface and the deposited coating would not have the 
same uniformity and characteristics over the entire surface. 
In addition, since the instant invention can effectively remove material 
from the concave surface of an article, it follows that this removed 
material can be utilized for the purpose of deposition onto a nearby 
substrate in a deposition operation. In this mode of operation the 
hemispherical cavity becomes a small sputtering target. Since the plasma 
is mostly contained within the cavity substantial reduction can be made in 
substrate heating, a considerable advantage over small flat targets of the 
past. 
It is therefore an object of this invention to provide a sputter etch and 
deposition apparatus which incorporates therein a centrally located anode 
for the purpose of effectively removing material from a concave surface. 
It is another object of this invention to provide an anode assisted sputter 
apparatus capable of effectively depositing material on an adjacent 
substrate. 
It is a further object of this invention to provide an anode assisted 
sputter apparatus capable of altering the size and shape of a surface by 
small controllable amounts. 
It is still a further object of this invention to provide an anode assisted 
sputter etch and deposition apparatus which is economical to produce and 
which utilizes conventional, currently available components that lend 
themselves to standard, mass producing, manufacturing techniques. 
For a better understanding of the present invention, together with other 
and further objects therein, reference is made to the following 
description taken in conjunction with the accompanying drawing and its 
scope will be pointed out in the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Reference is now made to FIG. 1 of the drawing which illustrates in 
schematic fashion the anode assisted sputter etch apparatus 10 of this 
invention. Apparatus 10 is made up of a housing 12 having side walls 13 
and base and cover plates 14 and 15, respectively, which form therein a 
vacuum chamber. Located at opposite ends of housing 12 and secured, as 
shown, to base plate 14 or to side walls 13 is a source of electrons, 
produced by, for example, a conventional heating filament 16, and an anode 
18, respectively. 
The various inputs and outputs to housing 12 are made at base 14 and are in 
the form of a duct 20 operably connected to a vacuum pump (not shown) and 
a duct 22 for admitting an inert ionizable gas such as argon into the 
housing chamber. Other connections (not shown) are made through cover or 
base plates 14 and 15, respectively, for electrical conductors supplying 
the required energizing potentials and controls and for any suitable 
cooling apparatus, if needed, within housing 12. 
Fixedly secured to cover plate 15 of housing 12 is a holder 26 which 
secures in any conventional manner such as by clamping therebeneath any 
article 28 which is to be sputter cleaned by the apparatus 10 of this 
invention. In addition, holder 26 incorporates therein a centrally located 
anode pin 30. In order to insulate anode pin 30 from holder 12, any 
suitable insulation such as ceramic insulation material 32 is interposed 
between holder 26 and anode pin 30. Any suitable positive bias source 31 
is electrically connected to anode pin 30 while any suitable negative bias 
source 33 is either formed integral with or electrically coupled to holder 
26 to provide a negative potential to holder 26. 
For proper operation of the embodiment of the instant invention shown in 
FIG. 1 of the drawing, an aperture 34 should be centrally located within 
the article 28 to be cleaned in order to allow anode pin 30 to protrude 
therethrough. Furthermore, although not limited thereto, the sputter etch 
apparatus 10 of this invention is extremely effective on an article 28 to 
be cleaned having a hemispherical internal configuration. 
Operation of the instant invention takes place by the evacuation of gas 
through duct 20 from within housing 12 and the controlled inlet of argon 
or any other suitable atmosphere which can be at a partial vacuum through 
duct 22. Heated filament 16 provides a source of electrons in the argon 
atmosphere and these electrons accelerate toward anode 18. Upon colliding 
with the atmospheric gas such as argon a plasma 36 is formed. Plasma 36 
consists of positive and negative ions and electrons. 
In addition, a positive potential is applied to anode 30 which utilizes 
part of the available ions to form an additional plasma within the concave 
cavity of article 28. This plasma in itself is effective in desorbing 
gases and other absorbed vapors from the surface of article 28. The 
negative potential which is applied to the surface of article 28 attracts 
the positive ions of the plasma which in turn bombards the inner surface 
of article 28 with sufficient energy to eject material from the surface in 
order to clean article 28. 
Reference is now made to FIG. 2 of the drawing which illustrates in 
schematic fashion an alternate embodiment of the instant invention. 
Apparatus 40, illustrated in FIG. 2 of the drawing, utilizes many of the 
same elements of apparatus 10 and shown in FIG. 1 of the drawing. 
Consequently, for purposes of simplicity of understanding of the 
invention, those identical elements will be denoted by the same numeral 
used within FIG. 1. 
The essential difference between apparatus 40, shown in FIG. 2, and 
apparatus 10 shown in FIG. 1, is that it is not required that the article 
28 to be cleaned have a centrally located aperture therein. Since 
apparatus 40 of FIG. 2 utilizes in place of anode pin 34 a ball-shaped 
anode 44 which is disposed centrally within the undersurface of 
hemispherical article 28, holder 42 may be of solid construction. 
Ball-shaped anode 44 is held in this position by an insulated housing 46 
thereby separating the positive potential of anode 44 from the negative 
potential applied to the article 28 to be cleaned. The operation of the 
anode assisted sputter etch apparatus 40 shown in FIG. 2 is otherwise 
identical to that of apparatus 10 shown in FIG. 1 of the drawing. 
As stated hereinabove, the sputter apparatus 10 or 40 of the instant 
invention is not limited merely to the cleaning or etching of surfaces, 
but can be utilized, if desired for the deposition procedure in which the 
sputter material from the article 28, is utilized for the purpose of 
depositing the material on a nearby substrate. To accomplish this end, 
reference is now made to FIG. 3 of the drawing which is identical to FIG. 
1 of the drawing except for the addition of a substrate holder 52 and the 
positioning thereon of the substrate 54. Operation of the deposition 
apparatus set forth in FIG. 3 is identical to the operation of the etching 
apparatus 10 set forth in FIG. 1 with the additional procedure that the 
material removed from article 28 is now deposited upon the substrate 54. 
It should be further realized, although not shown in the drawing, that 
substrate holder 52 in conjunction with substrate 54 can be utilized with 
apparatus 40 shown in FIG. 2 of the drawing. 
Although this invention has been described with reference to the particular 
embodiment, it will be understood to those skilled in the art that this 
invention is also capable of further and other embodiments within the 
spirit and scope of the appended claims.