Treatment system having gate device for decompression chamber

A toggled gate device to be used for opening and closing a gate aperture leading to a magnetron plasma etching apparatus comprises a gate for being pressed against the wall defining the gate aperture to hermetically cover the gate aperture. The gate is supported by a support member such that the gate is movable in substantially the horizontal direction toward and away from the gate aperture. The support member is vertically driven by a cylinder. Stopper plates are arranged at an upper portion of the gate and provided with a surface inclined divergently from the edge remote from the gate aperture toward the edge close to the gate aperture. Rollers are arranged on the wall to abut the respective stopper plates. The stopper plates and the rollers are made of an iron or nickel-based double boride hard alloy. Part of the force applied to the rollers by the gate through the respective stopper plates is converted into a force moving and urging the gate toward the wall.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a treatment system having a gate device for a 
decompression chamber and, more particularly, it relates to a magnetron 
plasma etching apparatus, having a load-lock gate, used for treating ultra 
LSIs. 
2. Description of the Related Art 
An installation for manufacturing semiconductor devices normally comprises 
various apparatuses for processing semiconductor wafers in vacuum, where 
load-lock gate devices are applied to partition connected vacuum chambers 
or isolate the inside of vacuum chambers from atmosphere so as to treat 
wafers continuously. A toggled gate device is a type of these gate 
devices. 
A toggled gate device is so designed that it moves and aligns a gate with a 
gate aperture by means of rotatable gate rollers that come to abut or 
rather collide with the forward end of the gate. After the collision, the 
force that tends to drive the gate further in that direction is utilized 
to bring the gate in close contact with the gate aperture to make a seal 
as the rollers are rotated on the gate. 
The rollers that take part in the collision are normally made of stainless 
steel, whereas the gate including its upper portions that also take part 
in the collision is usually made of aluminum. Since the collision takes 
place under considerable pressure and, thereafter, the rollers are forced 
to rotate on the surface of the gate under that pressure, the upper 
portions of the gate against which the rollers are respectively pressed 
are scraped to produce dust that can be dispersed into and pollute the 
ambient atmosphere of the processing site. 
The process of manufacturing semiconductor devices, such as devices having 
an integration degree of more than 16M, requires accurate treatment. In a 
magnetron plasma etching apparatus that requires a high degree of vacuum 
and performs anisotropic etching for semiconductor devices of more than 
16M, the process can be seriously affected by the dust given off by 
scraping the metal gate in terms of yield and efficiency. Such dust did 
not cause problems when the etching apparatus was used for treating 
semiconductor devices of less than 16M. 
Besides, as the surface of the metal gate is scraped by the rollers, the 
toggled gate device tends to malfunction and adversely affect its 
reliability. 
Additionally, a gate device applied to a load-lock type vacuum chamber 
connected to a magnetron plasma etching apparatus can be selectively 
eroded by the air in the etching apparatus at the scraped area. 
While the above described problems are particularly remarkable at the 
portions of the gate against which the respective rollers collide, similar 
problems may be observed at other locations where friction takes place. 
SUMMARY OF THE INVENTION 
It is therefore the object of the present invention to provide a gate 
device for a decompression chamber that effectively prevents generation of 
dust and corrosion at locations where friction takes place and 
consequently enhance the yield of the related processing apparatus. 
According to a first aspect of the invention, the above object is achieved 
by providing a treatment system having a gate device to be used for 
opening and closing a gate aperture, through which an object to be treated 
is loaded and unloaded, of a decompression chamber, comprising: a wall 
means for defining the gate aperture arranged on it; a gate for being 
pressed against the wall means to hermetically cover the gate aperture; a 
support member for supporting the gate movable toward and away from the 
gate aperture in a first direction; means for driving the support member 
in a second direction substantially perpendicular to the first direction; 
a stopper plate arranged at an end of the gate in the second direction and 
having a surface inclined divergently from the edge remote from the gate 
aperture toward the edge close to the gate aperture, the stopper plate 
being made of a material selected from sapphire, ruby and an iron or 
nickel-based double boride hard alloy; a roller arranged to abut the 
stopper plate, the axis of the roller being stationary relative to the 
wall means; and converting means for converting part of the force applied 
to the roller by the gate through the stopper plate in the second 
direction into a force moving and urging the gate toward the wall means in 
the first direction. 
According to a second aspect of the invention, the above object is achieved 
by providing a treatment system having a gate device to be used for 
opening and closing a gate aperture, through which an object to be treated 
is loaded and unloaded, of a decompression chamber, comprising: wall means 
for defining the gate aperture arranged on it; a gate for being pressed 
against the wall means to hermetically cover the gate aperture; a support 
member for supporting the gate movable toward and away from the gate 
aperture in a first direction; means for driving the support member in a 
second direction substantially perpendicular to the first direction; and 
converting means for converting movement of the movable support member in 
the second direction to movement of the gate in the first direction to 
close or open the gate aperture; wherein whole or part of each of its 
components directly subjected to friction between a part stationary 
relative to the wall means and part movable relative to the wall means is 
made of a material selected from sapphire, ruby and an iron or 
nickel-based double boride hard alloy. 
Sapphire, ruby or a double boride hard alloy to be used for components 
which are subjected to friction is very hard and highly abrasion-resistive 
so that the components may hardly be scraped and produce dust if they are 
hit by considerable force. Moreover, since the above cited materials 
provide a highly smooth surface, they are by far less liable to abrasion 
than the materials that have been conventionally used. 
Additional objects and advantages of the invention will be set forth in the 
description which follows, and in part will be obvious from the 
description, or may be learned by practice of the invention. The objects 
and advantages of the invention may be realized and obtained by means of 
the instrumentalities and combinations particularly pointed out in the 
appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1 illustrating a preferred embodiment of the invention, 
magnetron plasma etching apparatus 100 (having a configuration as shown in 
greater detail in FIG. 2) is hermetically connected to a first load-lock 
type decompression chamber 152 at the wafer loading side and to a second 
load-lock type decompression chamber 156 at the wafer unloading side so as 
to perform etching treatment continuously. By turn, the chamber 152 is 
connected to a loading section 154 in which a wafer is pre-positioned on 
the basis of a portion thereof, such as a orientation flat, while the 
chamber 156 is connected to an unloading section 158. Both sections 154 
and 158 contain unprocessed and processed wafer cassettes 172a and 172b 
respectively. 
The load-lock type decompression chambers 152 and 156 can be independently 
evacuated in a known manner and contain respective wafer transfer robots 
160, 160b of the same type. While the inside is illustrated in FIG. 1 and 
will be described beow only for the chamber 152 for the purpose of 
simplicity, the illustration and the description are equally applicable to 
the robot 160b in the chamber 156. 
The robot 160 is provided with a circular rotary support 162. A pair of 
reciprocating linkages 164 and 166 are pivoted at respective points which 
are located close to each other near the outer periphery of the support 
162. The movable members of the linkages 164 and 166 are connected to a 
fork 168 at the remote ends so that it may be driven back and forth to 
move a wafer W carried by it as the linkages fold and extend themselves. 
The fork 168 may change its direction by turning the support 162. 
An embodiment of the gate device 180 according to the present invention is 
arranged in the chamber 152 in juxtaposition with the gate aperture 12 of 
the etching apparatus 100. Gate devices 180b, 180c and 180d of the same 
type as that of the gate device 180 are arranged respectively between the 
etching apparatus 100 and the chamber 156, between the chamber 152 and the 
section 154 and between the chamber 156 and the section 158 in a similar 
manner. The gate device 180 is a so called load-lock gate which is opened 
when a wafer is passing by, while it is hermetically closed in general to 
form a vacuum space. 
Now, how the operation of processing wafers by a system for magnetron 
plasma etching as schematically illustrated in FIG. 1 proceeds will be 
described. Note that, in the course of this procedure, the gate devices 
180 through 180d are so operated and the chambers 152 and 156 are so 
evacuated by a know technique that the air intake/discharge level of the 
etching apparatus 100 is minimized. 
Firstly, the fork 168 of the robot 160 is directed toward the section 154 
and a wafer W is taken up by the 168 is fork 168 from the cassette 172a. 
As the fork 168 is folded to draw the wafer W into the chamber 152, it is 
turned and directed to the etching apparatus 100. Then, the fork 168 is 
extended and the wafer W is sent into the etching apparatus 100, where it 
undergoes an etching process as described later. The processed wafer W is 
then taken up by the robot 160b of the chamber 156 and stored in the 
cassette 172b in the section 158. 
Referring now to FIG. 2 illustrating in greater detail the etching 
apparatus 100, it is of the RIE type and comprises a housing 102 
constituted by an upper frame 104 and a lower frame 106. Insulator frames 
107 and 109, and a jacket 108 are arranged in the housing 102 and a 
susceptor 112 is placed on the insulator frame 109. As the upper frame 104 
is grounded and the susceptor 112 is supplied with RF power, a pair of 
oppositely arranged electrodes are established there. 
Facing the wafer W in the apparatus and above the upper frame 104, there is 
provided a disc 124 that carries under it permanent magnets 122. The disc 
124 is securely fitted to the shaft 128 of an electric motor 126. As the 
disc is driven to revolve by the motor 126, the magnets 122 under the disc 
124 rotate to generate a magnetic field found near the wafer W and 
parallel to its surface. 
Etching gas is introduced into the housing 102 in such a manner that the 
inner gas pressure of the housing 102 is always maintained at a relatively 
low level between 10.sup.-2 and 10.sup.-3 Torr by appropriately 
discharging the gas within the housing 102 by way of a discharge port 114. 
The introduced etching gas is turned to plasma by the effect of the 
electric charge applied to it between the opposite electrodes. Because of 
the interaction between the magnetic field and the electric field produced 
there by the plasm sheath and directed perpendicular to the magnetic field 
in a magnetron plasma etching apparatus, electrons are caused to move 
cycloidally and eventually collide against gas molecules to increase the 
total number of times of ionization within the apparatus, making it 
possible to produce a hiqh etching speed with a relatively low pressure as 
cited above. 
For etching operation, wafers W are normally cooled to approximately 
-60.degree. C. A room 116 is arranged within the jacket 108 to contain 
liquefied nitrogen for cooling wafers. 
Referring to FIGS. 3 through 5, the decompression chamber 152 is provided 
with a gate aperture 12, which is covered by a cover 14 of the gate device 
180 as illustrated in FIGS. 4 and 5. A bracket 16 is rigidly fitted to the 
lower end of the chamber 152 and a air cylinder 18 to be used for opening 
and closing the gate 50 is securely fitted to the bracket 16. 
The cover 14 contains within it a gate fitting plate 30 connected to 
cylinder shaft 18a and supported by guide rails 32, 32 by way of bearings 
34, 34 so that it may be vertically movable along the rails 32, 32. The 
gate 50 is supported by the gate fitting plate 30 by means of a link 
mechanism, which will be described later. 
The bearings 34, 34 are made of a double boride hard alloy prepared by 
using iron as a principal ingredient. KH Hard Alloy (trade name; available 
from Toyo Kohan Co., Ltd. and disclosed in Japanese Patent No. 1329953 
etc.), an iron-based and sintered double boride hard alloy containing Cr, 
Mo, Ni and W, may be among the materials that are advantageously used for 
the bearings 34, 34. Alternatively, a nickel-based alloy containing the 
above mentioned elements may also be used. 
A stopper frame 20 is rigidly fitted to the inside of the cover 14 and a 
pair of rollers 24, 24 are rotatably supported by respective shafts at two 
locations on the surface of the stopper frame 20 facing the upper surface 
of the gate 50. These rollers 24, 24 are used to align the gate 50 with 
the gate aperture 12. 
The rollers 24, 24 are made of a double boride hard alloy prepared by using 
iron as a principal ingredient. KH Hard Alloy (trade name; available from 
Toyo Kohan Co., Ltd.) as mentioned earlier may also be among the materials 
that are advantageously used for the rollers. 
Three dampers are arranged on the stopper frame 20, one between the rollers 
24, 24 and the remaining two at respective positions off the rollers, in 
order to dampen the shock imparted to the frame when the fitting plate 30 
collides against it. 
Now, the link mechanism for fitting the gate to the fitting plate 30 will 
be described. A first link shaft 40 is rigidly fitted to the fitting plate 
30 to rotatably support an end of a link 42 by way of a bearing (not 
shown). On the other hand, a second link shaft 58 is rigidly fitted to the 
rear side of the gate 50 to rotatably support the other end of the link 42 
by any of a link bearing 60. A tension coil spring 44 is provided to bias 
the gate 50 away from the side of the decompression chamber 152 where the 
gate aperture 12 is arranged. An end of the spring 44 is anchored to a 
spring stopper arranged on the fitting plate 30, while its other end is 
securely held to the second link shaft 58 fitted to the gate 50. 
The gate 50 is large enough to entirely cover the gate aperture 12 and 
provided on its front surface with an O-ring receiving groove 52a running 
exactly to match the periphery of the gate aperture 12 and a sealing 
O-ring 52b is press fit into the groove 52a. A pair of stopper plates 56, 
56 designed as stoppers for the gate 50 are arranged on the upper surface 
of the gate 50 at locations that correspond to the respective positions of 
the rollers 24, 24 supported on the stopper frame 20 as shown in FIG. 4. 
The stopper plates 56, 56 are rigidly fitted into respective grooves 54, 54 
arranged on the upper surface of the gate 50. Each of the bottoms of the 
grooves 54, 54 is so inclined that the upper surface of the related 
stopper plate 56 shows a slope rising from the rear side toward the front 
side of the gate 50. The gradient of the slopes formed by the upper 
surfaces of the stopper plates 56, 56 is determined as a function of the 
locus of movement of the inclined upper surfaces of the plates 56, 56 when 
the gate is moved to completely abut the periphery of the gate aperture 12 
and the data concerning the wear of the corresponding area of the upper 
surface of a gate collected for conventional installations where stopper 
plates are not used. In other words, the gradient may be approximated to 
that of the profile of the corresponding area of the upper surface of a 
gate which is originally made flat but worn and deformed after use in a 
comparable apparatus. 
The stopper plates 56, 56 are made of a double boride hard alloy prepared 
by using iron as principal ingredient. KH Hard Alloy (trade name; 
available from Toyo Kohan Co., Ltd.) as mentioned earlier may also be 
among the materials that ar advantageously used for the stopper plates. 
The gate device as described above operates in the following manner. 
When the gate aperture 12 of the decompression chamber 152 is open and free 
for passage, the gate 50 is found below the gate aperture 12 as shown in 
FIG. 4. To close the gate aperture 12 of the chamber 152, the air cylinder 
18 is driven to push up the fitting plate 30 by way of the cylinder shaft 
18a. 
As the fitting plate 30 is g ided by the two rails 32, 32, it moves only 
vertically when it is driven by the air cylinder 18. Since no external 
force is directly applied to the gate 50 at this stage, the link 42 is 
urged to move clockwise in FIG. 4 by the biasing force of the tension coil 
spring 44 and, therefore, the gate 50 is lifted upward without touching 
the corresponding surface of the decompression chamber 152. 
A the gate 50 is driven upward by the air cylinder 18, the stopper plates 
56, 56 arranged at two different location of the gate 50 come to abut the 
respective rollers 24, 24 which are rotatably supported by the stopper 
frame 20. Since the air cylinder continues its driving operation after the 
abutment, the stopper plates 56, 56 consequently hit the respective 
rollers 24, 24 with considerable impact. 
Since the stopper plates 56, 56 are made of a double boride hard alloy, 
which is highly anti-abrasive and capable of lubricating its surface, the 
surface of the stopper plates 56, 56 would not be scraped to produce dust 
that can be scattered into ambient atmosphere to pollute the latter, nor 
would it be selectively corroded in the atmosphere in the etching 
apparatus 100. 
Thus, the stopper plates 56, 56 are driven by the air cylinder 18 to go 
upward after they collide against the rollers 24, 24 and the gate fitting 
plate 30 is also lifted upward with the cylinder shaft 18a. Meanwhile, as 
the stopper plates 56, 56 abut the respective rollers 24, 24, the upward 
movement of the gate 50 is abated by the resistance of the rollers 24, 24. 
In other words, the stopper plates 56, 56 of the gate 50 are subjected to 
a force exerted by the rollers 24, 24 trying to push them down. As a 
result, the link 42 is rotated counterclockwise, or in the direction 
indicated by arrow A in FIG. 4, around the first link shaft 40. 
As the link 42 is rotated in the direction of arrow A, the gate 50 is 
driven to move toward the gate aperture 12 of the decompression chamber 
152 under the condition where the rollers 24, 24 are rotatably pressed 
against the respective stopper plates 56, 56. The rotation of the rollers 
24, 24 facilitates the movement of the gate 50 toward the gate aperture. 
Note here that this movement is further helped by the fact that the upper 
surfaces of the stop plates 56, 56 are inclined. 
Considering that the rollers 24, 24 are pressed against the respective 
stopper plates 56, 56 by a considerable force applied to them by the air 
cylinder 18, it may be clearly understood that the conventional 
arrangement of bringing a gate and rollers into direct contact as in the 
case of existing comparable etching apparatus/decompression chamber 
assemblies can easily result in a scraped gate surface and faulty 
operation of the assemblies. Since the gate of a decompression chamber 
according to the invention is provided with stopper plates 56, 56 which 
are made of a double boride hard alloy, the rollers 26, 26 can smoothly 
rotate on the respective stopper plates 56, 56 and the gate 50 can be 
smoothly moved relative to the gate aperture 12 without causing damages on 
the stopper plates due to scraping motion. 
The operation of air cylinder 18 to drive the fitting plate 30 upward is 
stopped when the plate 30 abuts the damper 26 arranged on the stopper 
frame 20 and the sealing O-ring 52b comes to closely contact with the 
outer surface of the decompression chamber 152 where the gate aperture 12 
is arranged so that the gate aperture 12 is hermetically sealed along its 
outer periphery. 
When the gate 50 is opened, on the other hand, the air cylinder 18 is 
driven to lower the cylinder shaft 18a. As the cylinder shaft 18a comes 
down, the fitting plate 30 is lowered with it to release the contact 
between the rollers and the respective stopper plates 56, 56 so that the 
tension coil spring 44 urges the link 42 to rotate clockwise as indicated 
in FIG. 4 and separate the gate 50 from the surface of the chamber 152 
where the gate aperture 12 is arranged. As the air cylinder 18 is driven 
further, the gate 50 is eventually returned to its original stand-by 
position. 
The use of a double boride hard alloy is not limited to the bearings 34, 
34, rollers 24, 24 and stopper plates 56, 56. Such a material is 
advantageously used also for other components of the gate device which are 
subjected to abrasion and collision. Besides, an abrasion-resistive hard 
and smooth material other than a double boride hard alloy, sapphire or 
ruby for instance, may be advantageously used for those components. 
The present invention can be applied to other treating apparatuses using a 
decompression condition, such as a CVD apparatus, a sputtering apparatus 
and an ion-implanting apparatus, other than a magnetron plasma etching 
apparatus described as an embodiment. 
Additional advantages and modifications will readily occur to those skilled 
in the art. Therefore, the invention in its broader aspects is not limited 
to the specific details, and representative devices shown and described 
herein. Accordingly, various modifications may be made without departing 
from the spirit or scope of the general inventive concept as defined by 
the appended claims and their equivalents.