Apparatus for transferring a substantially circular article

Abstract: Apparatus for transferring substantially circular article from a first unloading position to a second loading position. To obtain exact positioning in the second loading position means are proposed to compensate for misalignment of the article on a support arm portion. During movement of the support arm portion the position of the periphery of the circular article with regard to the support arm portion is detected. Based on that a correction of the movement of the support arm portion is generated.

Description: Background of the invention: During wafer processing in a reactor wafers are transferred from a processing station or feed station to a (further) processing station or discharge station. At this end a transferring apparatus is used. US-A-5,407,449 describes an apparatus being able to pick-up wafers from one station and to transfer them to another station. This apparatus is adjustable in vertical direction to be able to transfer wafers from a stack from one station to another. The transferring apparatus comprises an arm having three arms portions of which one portion is the support portion on which the wafer is loaded. During loading, unloading and processing wafers will slightly move from their starting position. If no correction is effected this deviation from the original position will be transferred in the next stage, i.e. this deviation will also be present in a next station. If several processing steps are undertaken this will mean that at the end of a series of processing steps a stack of wafers comprises a number of wafers having different positions. Because some processes are very critical with regard to the position of the wafer this is highly undesirable. To prevent misalignment of the wafer with regard to the supporting arm portion it has been proposed to provide video cameras above or in the apparatus for transferring the wafers in order to obtain a correction. Such cameras are relatively complicated with regard to recognizing the wafers and determining the correction desired. Furthermore only a reliable determination of the position of the several components can be made if there is no movement of the arm. Instead of cameras it is also proposed to use a sensor array at the top of the system. Also this system functions best if the wafer is in a stationary position. EP-A-0 597 637 discloses an apparatus for transferring a substantially circular article including an array of light sensitive means for determining the position of said article an the transfer means. Summary of the Invention: The invention aims to determine the position of the wafer with regard to the supporting arm position in a dynamic way i.e. during movement of the transfer robot to keep the time for transferral as short as possible. The invention furthermore aims to simplify the method for determining the position of the wafer on the supporting arm portion. Furthermore the invention aims to obtain a correction for deviations in speed of the several arm portions of the arm of the apparatus for transfering the wafer. The invention aims to provide a system for determining the position of the wafer with regard to the supporting arm position which is independent from the position in height direction of the supporting arm portion. This is realized with an apparatus for transferring a substantially circular article from a first unloading position to a second loading position according to claim 1. Detailed description of the Invention: The invention will be further elucidated referring to the drawings, in which: Figure 1 shows a side elevation of the device according to the invention; Figure 2 shows a plan view of the device according to figure 1; Figure 3 shows a detail in side view and partially exploded of a device according to the invention; Figure 4 shows a perspective view of the device according to figures 1-3 incl. and Figure 5 shows a block diagram. In Figure 1 a robot 1 is shown comprising a lower fixed part 2 and an upper part 3. Upper part 3 can be moved with regard to lower fixed part 2 in vertical direction by telescoping means which are not further shown. On upper part 3 an arm 4 is provided comprising first, second and third support arm portions indicated by 5,6,7 respectively. Support arm portion 7 is embodied to receive a wafer 8. Wafer 8 has to be transferred from storage 9 to storage 10. Supporting arm portion 7 is provided with a vacuum suction supporting face 26. With this vacuum suction support 26 it is possible to lock the wafer to the supporting arm portion during transversal and to release it at unloading. Storages 9 and 10 can e.g. be processing stations of a device for treating micro circuit wafers. Reference is made to US-A-5,407,449 wherein a robot is shown transferring wafers from one station to another. Arm portion 7 is provided with comb reference means 11. These reference means are provided with an serrated extremity indicated by 12. Upper part 3 is provided with an elongated member 13 in which a number of light reflective sensors 14 are provided. Operation of first arm portion 5, second arm portion 6 and support arm portion 7 is such that the center of support arm portion 7 will follow dashed line 15. This means that the serrated extremity 12 will move over light sensitive diodes 14. On elongated member 13 an U-shaped member 16 is provided which is shown more in detail in Figure 3. In this member opposed sets of light emitting and light sensitive diodes 17, 18 respectively are provided. The gap between the legs of the U-shaped member 16 are sized as to receive wafer 8 therebetween during its movement along dashed line 15 without any contact between both the upper and the lower leg of U-shaped member 16. For operating arm 4 three motors 19, 20 and 21 (for R, T and Z direction respectively) are provided as is schematically shown in Figure 5. Operation of the several motors is through control means 23. Control means 23 receive input from a main processing unit 24 controlling the sequence of discharging, charging of storages 9, 10 respectively. The signal from array of light sensitive means 17, 18 is input in calculating means 25. The same is true for the signal obtained from the light sensitive diodes 14. From this calculating means a correction signal is introduced in control means 23. The device described above functions as follows. During movement of a wafer from the position shown in Figure 2 along dash line 15 the serrated extremity 12 of reference means 11 will pass one of the light sensitive means of U-shaped member 18 (the most right one in Figure 3) and the light sensitive diodes 14 on elongated member 13. Based on the signals from these diodes the calculating means 25 are able to calculate the speed of serrated extremities 12 and so speed of support arm portion 7. At the same time wafer 8 will move between the legs of U-shaped member 16. One or more of the light emitting diode / light sensitive diodes 17, 18 respectively will subsequently from the right to the left be activated, deactivated respectively. From this array of light sensitive diodes information can be obtained with regard to the position of wafer 8 on support arm portion 7 in the direction of dashed line 15 as well as its position perpendicular thereto. This is calculated based on the output of the signal of U-shaped member 16 input to calculating means 25. Through the provision of e.g. six dents of the serrated extremity in combination with four sensors it is possible to affect 48 measures for returning the speed of supporting arm portion 7. Knowing the speed is of importance for determining the shape of the circle of article 8. Based on the speed of support arm portion 7 and the position of wafer 8 on support arm portion 7 it is possible to provide a correction signal to control means 23 to correct the position of support arm portion 7 by adjusting the control of the two motors 19, 20. Although the invention has been described above relating to a preferred embodiment it has been understood that many variations can be introduced without leaving the scope of protection as defined in the appended claims. Except from using all light emitting diodes and light sensitive diodes 17,18 for determining the position of wafer 8 it is also possible to only use for example the first and last set of calculating and to use the other one as a check.

Claims: Apparatus for transferring a substantially circular article (8) from a first unloading position (9) to a second loading position (10), comprising displaceable transferring means (5-7) for engaging said article at said first unloading position, transferring it and discharging it in said second loading position; means for determining the position of said article on said displaceable transferring means comprising a first array of light sensitive means (17, 18) sensitive to the presence of said article and being positioned in the path (15) of the article from said first unloading position to said second loading position and extending in a direction non-parallel to said path and wherein the output of said first array of light sensitive means is connected to calculating means (25) for determining the position of said article on the displaceable means; reference means (11, 12) on the displaceable transferring means; characterized in that said means for determining the position of said article on said displaceable transferring means further comprise: a second array of light sensitive means (14) positioned in said path (15) of the article and extending in a direction parallel to said path, said second array of light sensitive means cooperating with said reference means (11, 12) so as to detect said reference means as the displaceable transferring means passes said second array of light sensitive means, wherein the output of said second array of light sensitive means is connected to said calculating means (25) for determining the speed of said displaceable transferring means. An apparatus according to claim 1, characterized in that said apparatus further comprises motors (19, 20) for driving the displaceable transferring means and control means (23) adapted to control said motors, wherein said calculating means provide a correction signal to the control means (23). An apparatus according to claim 1 and 2, wherein said first and second arrays of light sensitive means have at least one common light sensitive means. An apparatus according to claim 1 to 3 in which the reference means (11) on the displaceable transferring means comprise a serrated extremity (12) cooperating with said second array of light sensitive means. An apparatus according to claim 1 to 4, wherein said first array of light sensitive means extends substantially perpendicular to the path of said article.

Inventors: HAANSTRA KORNELIUS, SCHIMMEL RUDI, ZINGER JAN, HAANSTRA, KORNELIUS, SCHIMMEL, RUDI, ZINGER, JAN
Applicants: ASM INT, ASM INTERNATIONAL N.V.
Application year: 1996
Main classification: H01L21
IPC codes: B65G49, B25J9, H01L21