Patent Application
20080199281
The present invention relates principally to a system for handling wafers within a treatment apparatus according to the preamble of claim 1.
An apparatus for treating wafers where the present invention advantageously finds an application is described in U.S. Pat. No. 6,648,974, which is incorporated herein by reference.
In that patent there in also described a tool suitable for handling wafers and for holding them by suction; the tool is connected to a suction pipe which is in turn connected to a suction system.
The tool is configured in such a manner that the suction effect on the wafer is low; in this way, there is no risk of deforming the wafer; however, situations may arise in which it is difficult for the tool to hold or grip the wafer.
US Patent Application 2004/0191029 describes a tool suitable for handling wafers and for holding same by suction and which is an improvement of the tool according to the patent mentioned above.
That patent application is incorporated herein by reference.
The improved tool is configured in such a manner that the suction effect on the wafer is high; in this way, there is no difficulty in gripping or holding the wafer; moreover, it has been found that in most cases the wafer is not deformed in a harmful manner; however, situations may arise in which the suction becomes harmful.
If a suction system is used in which the suction can be set, it is possible to adapt the suction to the various operating conditions of the wafer handling system. However, it is not possible to take into account unforeseeable factors such as, for example, the degree of alignment of the wafer with respect to the tool, the deformation of the wafer and/or of the tool and/or of the support for the wafer.
A common method of solving this problem is that of setting a suction much higher than the theoretical minimum required.
It is a general aim of the present invention to remedy the drawbacks of the prior art.
A more specific aim of the present invention is that of providing a system for handling wafers which is capable of gripping and holding the wafers properly but which avoids excessive suction effects in a simple manner.
These and other aims are achieved by means of the wafer handling system having the features recited in the claims appended hereto.
The idea underlying the present invention is that of using a simple valve which succeeds in regulating the pressure in a simple, reliable, effective and rapid manner; the presence of the valve does not however exclude a suction system of the type that can be set, for example computerised, by means of which sophisticated strategies can be carried out.
Moreover, according to another aspect, the present invention also relates to a method for regulating the pressure in a wafer handling system.
Finally, according to another aspect, the present invention also relates to an apparatus for treating wafers.
The present invention will become clearer from the following description to be considered together with the appended drawings, in which:
Both the description and the drawings are to be regarded solely as for purposes of example and therefore non-limiting.
The apparatus 1 comprises a reaction chamber 2, a transfer chamber 3, a flushing chamber 4, and a storage zone not shown in the drawing.
Placed in the transfer chamber 3 is the arm of a robot 5 which provides, before the treatment, for the wafers to be extracted one at a time from the flushing chamber 4 and to be inserted into the reaction chamber 2, and, after the treatment, for the wafers to be extracted one at a time from the reaction chamber 2 and to be inserted into the flushing chamber 4.
Placed in the reaction chamber 2 is a support 21 for the wafers to be treated. In the example of
In order to carry out the required movements, the robot 5 is equipped with an arm comprising members suitably articulated with one another; in the example of
The suction pipe 7 is composed of a flexible tube 71 followed by a rigid tube 73 connected to the flexible tube via a rotatable joint 72.
In the apparatus 1, outside the transfer chamber 3, in the immediate vicinity thereof, is placed a device 8 for regulating the pressure in the suction pipe 7; the device 8 is connected to the suction pipe 7, in particular to the rigid tube 73, and to a tube 9 which opens into the transfer chamber 3.
Referring now to
The tool 6 comprises a body 61 configured and dimensioned for contacting the edge of a wafer W so as to form a suction chamber 60 between the body 61 and the wafer W. A tool of this type is very efficient for gripping a wafer since it is capable of exerting a high suction effect on the wafer owing to the suction chamber (substantially closed) which forms when the wafer is in good contact with the body of the tool.
Moreover, the body 61 is mounted on the tube 51 so that the suction chamber 60 communicates with the suction pipe 7.
The device 8 contained in the system of
The valve 8 comprises a passage 80 equipped with an inlet 81 connected to the tube 9 and an outlet 82 connected to the tube 73; there is a movable member, constituted by a disc 83 joined to a rod 84, which can slide in an internal seat of the valve; a first end of a spring 85, within the seat, presses on the disc 83 of the movable member so as to keep the passage 80 closed; a second end of the spring 85 presses on a screw 86, screwed into the seat; the screw 86 is accessible from outside the valve so as to regulate the force which it exerts on the movable member.
When the difference between the pressure at the inlet 81 of the valve (that is to say, the pressure in the transfer chamber 3) and the pressure at the outlet 82 of the valve (that is to say, the pressure in the suction pipe 7, which is substantially uniform along the length of the pipe) exceeds a predetermined value, the spring 85 can no longer keep the passage 80 closed via the disc 83 and therefore a flow of gas takes place between the inlet 81 and the outlet 82; the predetermined value depends on the elastic constant of the spring 85 and on the position of the screw 86 and therefore on how far the screw 86 is screwed into the seat of the valve.
In
It should be noted that a valve such as that shown diagrammatically in
In general, the handling system according to the present invention comprises:
This general definition of the present invention may be easily understood by referring by way of example to
Owing to the valve, a rather simple device (even though for the type of application it is necessary to provide a device of good quality), it is possible to avoid the formation of an excessive under-pressure in the suction pipe and therefore excessive suction by the tool; moreover, the valve has a rather reduced response time; finally, the valve can advantageously effect a substantially proportional regulation.
For the purposes of the present invention, in general, the valve may comprise a passage, a spring and a movable member capable of closing the passage under the action of the spring; obviously, the passage opens when the pressure which acts on the movable member overrides the action of the spring.
This general definition of the valve may be easily understood by referring by way of example to
It is advantageous to enable the valve to be calibrated and for the pressure value at which it opens to depend on such calibration; in this way, it is possible to compensate for constructional variations of the valve, and also of the components which constitute the suction circuit (body of the tool, parts of the suction pipe, etc.) and variations of the climatic conditions of operation of the apparatus (for example, the temperature).
A simple method for making calibration possible is that of providing a calibrating screw which acts on the spring; the valve is calibrated by rotation of the screw; this is the case in the example of
The use of a pressure regulating valve does not in the least exclude the handling system from being provided with a suction system with a suction that can be set or regulated; in fact the settings (regulation with open ring) or the regulation (regulation with closed ring) will be used in the case of normal operation and the valve will intervene only in case of need, typically when anomalous situations occur. Moreover, a valve such as that defined in general above cuts out automatically and autonomously when there is no longer any need for it, typically when the anomalous situations have come to an end.
If a suction system with a suction that can be regulated is used, the handling system according to the present invention is equipped with two regulating means; the regulation effected by the valve is rapid, simple and reliable; the regulation effected by the suction system, typically by means of an electronic system, often computerised, is slower, more complex and dependent upon the correction functioning of the electronic system.
A suction system (that can be set) that is very advantageous for use in combination with the pressure regulating valve comprises an ejection device fed by a flow of inert gas; the flow of inert gas is controlled by a mass flow controller, known in English by the acronym MFC, of the type that can be programmed. There are currently on the market ejection devices of the single-stage type and of the multi-stage type; in these devices, the pressure difference is not constant but depends on the suction capacity.
The handling system according to the present invention is advantageously of the automatic type; to this end, it comprises a robot with articulated arm on which is mounted the tool for handling the wafers.
In general, the suction pipe of the handling system will be composed of several parts; in particular, a flexible tube may be basically provided, followed preferably by a rigid tube connected to the flexible tube via a rotatable joint. Such a configuration lends itself particularly well to being used in combination with the robot with articulated arm, as in the example of
The handling system with regulating valve lends itself especially well to being used with a tool of a particular type. The tool comprises a body configured and dimensioned for contacting the edge of a wafer so as to form a suction chamber between the body and the wafer, and means are provided for placing the suction chamber in communication with the suction pipe; this is the case with the tool shown diagrammatically in
As already stated, the present invention also has as its subject an apparatus for treating wafers, in particular an epitaxial reactor, which comprises a wafer handling system having the technical characteristics described above.
If the apparatus comprises a transfer chamber, it is of advantage to provide for the valve of the regulating device of the handling system to be connected to the transfer chamber.
Moreover, if the handling system is equipped with a robot having an arm it is of advantage to provide for at least the arm of the robot to be housed within the transfer chamber.
From the methodological point of view, the teaching of the present invention is fundamentally to connect a valve to the suction pipe and to open the valve when the pressure in the suction pipe falls below a predetermined value.
Advantageously, the opening of the valve is gradual, so as to provide a substantially proportional type of control.
Moreover, still from the methodological point of view, it is good to connect the suction pipe to a suction system with a suction that can be set or regulated.
Finally, still from the methodological point of view, it is good to use a tool comprising a body configured and dimensioned for contacting the edge of a wafer so as to form a suction chamber between the body and the wafer, and means for placing said suction chamber in communication with said suction pipe.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IT05/00301 | 5/26/2005 | WO | 00 | 10/26/2007 |
