Apparatus for the treatment of semiconductor wafers by plasma reaction

An apparatus for the treatment of semiconductor wafers by plasma reaction is disclosed. The apparatus comprises a first wafer carrying means for a wafer to be treated, a reaction chamber, a second wafer carrying means for a treated wafer, and a control means for driving respective elements thereof in linkage motion. The first wafer carrying means has a first arm type wafer carrying means, which comprises a pair of guide rails, a pair of sliders mounted on the guide rails, respectively, and a pair of first arms for carrying the wafer to be treated. The reaction chamber is provided with a pair of slits for taking the wafer into and out of the reaction chamber, a pair of open-close type vacuum sealing devices mounted on the slits, respectively. Similarly, the second wafer carrying means has a second arm type wafer carrying means. The first and second wafer carrying means are preferably placed in a preliminary vacuum chamber, whereby a high vacuum in the reaction chamber can readily be obtained to be suitable for use in an etching device for aluminum wiring, and the like.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
This invention relates to an apparatus for the automatic sheet treatment of 
wafers by plasma reaction, and more particularly to an apparatus for the 
treatment of the wafer by plasma reaction with an improved wafer carrying 
means. 
(2) Description of the Prior Art 
Recently, etching of a semiconductor wafer, as well as removal by ashing of 
a photoresist by use of an apparatus for the treatment of wafer materials 
by gas plasma reaction, has become widely available in semiconductor wafer 
production processes. The apparatus for the treatment of wafer by plasma 
reaction can be classified into two major types, that is, a batch type in 
which 10 to 25 sheets of wafers are set in a horizontal reaction tube for 
the simultaneous treatment thereof, and an in-line type in which wafers 
are subjected to the automatic one-by-one treatment thereof. Recently, the 
latter type has become widely available with the advantages such as a 
narrow scatter of results from the treatment of respective wafers, high 
processing precision, and a short treating time for each sheet of wafer. 
Further, various kinds of automatic wafer carrying means have been 
proposed. 
U.S. Pat. No. 4,208,159 discloses a wafer carrying system using an arm 
provided with a pick up, and further discloses a wafer carrying system 
using a belt conveyor. 
Japanese utility Model Application No. 124709/1979 discloses a wafer 
carrying system of a wire conveyer type, which is widely used for 
practical apparatuses because of its excellent advantages. 
These wafer carrying systems described above are all of such a type that 
the vacuum of the reaction chamber is broken every time a wafer is taken 
in or out of the reaction chamber, and are unsuitable for such an 
apparatus as used in etching of an aluminium wiring, where a preliminary 
vacuum chamber is required to be provided for obtaining a high vacuum in 
the reaction chamber. However, it is very difficult to place the only 
wafer carrying means in the preliminary vacuum chamber due to the 
structure of the apparatus for the treatment of wafers by plasma reaction. 
Thus, the apparatus for the treatment of wafers by plasma reaction must be 
wholly placed in the preliminary vacuum chamber. This is very complicated 
and economically undesirable. Therefore, the wafer carrying means placed 
in the preliminary chamber is required to be compact and simplified in 
structure in order to obtain a high vacuum in the reaction chamber. 
U.S. Pat. No. 4,149,923 also discloses an automatic apparatus for the 
treatment of wafer materials by plasma reaction, in which a preliminary 
vacuum chamber is provided before and behind the reaction chamber and all 
elements of the apparatus are installed on an inclined base table to 
effect the downward movement of the wafer as a wafer carrying means, where 
the wafer is stopped as required by a wafer stopper. Accordingly, there is 
the disadvantage that the wafer is liable to be damaged by the stopper 
upon stopping the wafer. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide an apparatus for the treatment 
of semiconductor wafers by plasma reaction, in which the wafer carrying 
means and the reaction chamber are compact and simple in structure 
thereof. 
It is another object of this invention to provide an apparatus for the 
treatment of semiconductor wafers by plasma reaction, in which a high 
vacuum in the reaction chamber can readily be obtained by placing the 
wafer carrying means in a preliminary vacuum chamber. 
It is yet another object of this invention to provide an apparatus for the 
treatment of semiconductor wafers by plasma reaction which has such 
advantages as a narrow scatter of results from the treatment of respective 
wafers, high processing precision, and a short treating time for each 
sheet of wafer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention provides an apparatus for the treatment of 
semiconductor wafers by plasma reaction, which apparatus is substantially 
composed of a first wafer carrying means for a wafer to be treated, a 
reaction chamber, a second wafer carrying means for a treated wafer, and a 
control means for driving the first wafer carrying means, the reaction 
chamber, and the second wafer carrying means in linkage motion. 
The apparatus of the present invention will be further described in detail 
with reference to the accompanying drawings. 
In FIGS. 1 and 3, the first wafer carrying means substantially consists of 
a first cassette elevator 9, a first wafer cassette 8 for the wafer to be 
treated which is mounted on the first cassette elevator 9, a first belt 
conveyer 10 for carrying the wafer to be treated and disposed adjacent to 
the first wafer cassette 8, a second belt conveyer 5 for carrying the 
wafer to be treated and disposed adjacent to the first belt conveyer 10, 
and a first arm type wafer carrying means which is composed of a pair of 
guide rails 11, 11, a pair of sliders 17, 17, slidably mounted on the 
guide rails 11, 11, respectively, in the horizontal direction, and a pair 
of first arms 4, 4, for carrying the wafer to be treated which are fixed 
to said sliders 17, 17, extended horizontally along said second belt 
conveyer 5 and are shaped to be a pair of parallel rods spaced at a 
certain distance to each other with a certain length to be movable 
horizontally with the sliders 17, 17. A pair of wire conveyers may also be 
used instead of the belt conveyer. 
In FIG. 1, the reaction chamber 1 is opened to a preliminary vacuum 
chambers 13, 13' through a pair of slits 14, 14', in which a pair of 
vacuum sealing devices 3, 3', incorporating therein a pair of gate valve 
type shutters 20, 20', respectively. The slits 14, 14' are opened and 
closed as the shutters 20, 20' are opened and closed respectively. The 
reaction chamber 1 is provided with a first electrode 2 which is connected 
to a power source (not shown). The reaction chamber 1 is further provided 
with a wafer table 6 serving as a second electrode, which is faced to the 
first electrode 2 and insulated from the surrounding environment, a 
sub-table 7 which is fittable vacuum-tightly in the center of the wafer 
table 6 along with a shaft 7' integral therewith and is vertically movable 
by means of an elevator cylinder 7", a plasma gas nozzle 15, and a vacuum 
line 16. The slits 14, 14' may have such a size that arms 4, 4, and 4', 
4', with the wafer 12 mounted thereon may pass therethrough, respectively, 
the smaller the better. 
In FIGS. 1 and 4, the second wafer carrying means substantially consists of 
a second arm type wafer carrying means which is composed of a pair of 
guide rails 11', 11', a pair of sliders 17', 17', slidably mounted on the 
guide rails 11', 11', respectively, in the horizontal direction, and a 
pair of second arms 4', 4', for carrying the treated wafer which extends 
horizontally along a third belt conveyer 5' for carrying the treated wafer 
and are shaped to be a pair of parallel rods spaced at a certain distance 
to each other with a certain length to be movable horizontally with the 
sliders 17', 17', the third belt conveyer 5', a fourth belt conveyer 10' 
for carrying the treated wafer and disposed adjacent to the third belt 
conveyer 5', a second cassette elevator 9', and second wafer cassette 8' 
which is mounted on the second cassette elevator 9' and is disposed 
adjacent to the fourth belt conveyer 10'. 
In FIG. 1, the first wafer carrying means, and the second wafer carrying 
means are all placed in a preliminary vacuum chambers 13, 13'. In FIGS. 1, 
3 and 4, the arms 4, 4 and 4', 4' are spaced to each other such that the 
wafer to be treated and the treated wafer may be safely placed thereon 
respectively, and have such a length that the wafer to be treated may be 
carried to the center of the reaction chamber by the arms 4, 4 so as to be 
put on the sub-table elevated thereon, and that the treated wafer may be 
carried from the center of the reaction chamber to the third belt conveyer 
5' by the arms 4', 4', respectively. 
The first arm type wafer carrying means and the second arm type wafer 
carrying means are disposed outside the second belt conveyer 5 and the 
third belt conveyer 5', respectively. 
The sub-table 7 should have such a size that the wafer can be safely 
mounted thereon and that it can pass between a pair of arms. 
The control means of the apparatus in the present invention is 
substantially composed of a microcomputer (not shown) located in the drive 
control. That is, the control means for bringing the individual parts into 
a harmonized linkage motion may be a programmed control means well-known 
in the control of various kinds of machine tools for automatic machining. 
For example, each of a plurality of cams fixed to a revolving shaft serves 
to start and stop the motion of one of the individual parts in a 
predetermined schedule. Alternatively, the linkage motion can be 
controlled by a series of electric relays. The microcomputer is 
incorporated in a drive control as shown in FIG. 1. 
In FIG. 1, wafers to be treated are stored in a first wafer cassette 8 
mounted on a first cassette elevator 9. A lowermost wafer 12 stored in the 
first wafer cassette 8 is carried by the first belt conveyor 10 and by the 
second belt conveyer 5 successively to the tip sections of the arms 4, 4 
to be mounted thereon. Then the shutter 20 of the vacuum sealing device 3 
is opened so that the wafer 12 may be carried through the slit 14 to the 
center of the reaction chamber 1 by means of the first arm type wafer 
carrying means as shown in FIG. 2(B). As another embodiment, a wafer to be 
treated may be supplied directly from a preceding step by a conveyer (not 
shown) without being stored in the first wafer cassette 8, where another 
vacuum sealing device may be provided for the preliminary vacuum chamber 
13. The sub-table 7 is extended upward with the wafer 12 mounted thereon 
and taken up to a predetermined position above the arms 4, 4 as shown in 
FIG. 2(C). The arms 4, 4 are returned to the original position and the 
shutter 20 of the vacuum sealing device 3 is closed while the sub-table 7 
is returned to the original position so that the wafer 12 may be placed on 
the wafer table 6. The reaction chamber 1 is evacuated to a predetermined 
vacuum by the vacuum line 16 connected to a vacuum pump (not shown), and a 
gas for plasma treatment is introduced thereinto through a plasma gas 
nozzle 15. A plasma is generated under vacuum with a radio frequency 
generator (not shown) by the application of the high voltage electrode 2 
for the treatment of the wafer 12 by plasma reaction. After completion of 
the treatment, the wafer 12 is elevated to the predetermined position in 
the same manner as in FIG. 2(C) while being mounted on the sub-table 7. 
The shutter 20' of the vacuum sealing device 3' is then opened and the 
arms 4', 4' extend through the slit 14' so that the tip sections thereof 
reach the center of the reaction chamber 1 beneath the wafer 12 mounted on 
the sub-table 7 elevated as above. The sub-table 7 with the wafer 12 
mounted thereon is returned to the original position, while the wafer 12 
is placed on the tip sections of the arms 4', 4' on the way. The wafer 12 
is carried out of the reaction chamber 1 by the second arm type wafer 
carrying means to the third belt conveyer 5' so as to be carried to the 
fourth belt conveyer 10', and the shutter 20' of the vacuum sealing device 
3' is closed. The wafer 12 is further carried to be stored in the second 
wafer cassette 8' mounted on the second cassette elevator 9'. As another 
embodiment, the treated wafer may be supplied directly to a succeeding 
step by a conveyer (not shown) without being stored in the second wafer 
cassette 8', where another vacuum sealing device may be provided for the 
preliminary vacuum chamber 13. On the other hand, another wafer to be 
treated is being taken out of the first wafer cassette 8 to be carried for 
the treatment in the same manner as described above. All the procedures 
described above are controlled by a microcomputer in linkage motion. 
In accordance with the apparatus of the present invention, the first wafer 
carrying means, the reaction chamber, and the second wafer carrying means 
can be made compact and simplified in structure such that the reaction 
chamber and the preliminary vacuum chamber can be greatly reduced in size. 
The compact and simplified structure of the first wafer carrying means, 
the reaction chamber, and the second wafer carrying means combines with 
the reduced size of the slits in the reaction chamber to make it possible 
to obtain a high vacuum in the reaction chamber, which makes the apparatus 
of the present invention suitable for use in an etching device of aluminum 
wiring and the like, where a high vacuum in the reaction chamber is 
required. 
In accordance with the apparatus of the present invention, a highly 
efficient apparatus for the treatment of semiconductor wafers by plasma 
reaction can be provided with little trouble due to simplified driving 
mechanisms thereof. 
Further, the present invention can provide an apparatus for the treatment 
of semiconductor wafers by plasma reaction with excellent advantages such 
as a narrow scatter of results from the treatment of respective wafers, 
high processing precision, and short treating time per one sheet of wafer 
without causing any damage to the wafer.