An automatic wafer etching method and apparatus

Abstract: An automatic wafer etching apparatus including a first elevator (33) and a second elevator (34) each having a top surface whose vertical cross-section is circularly concaved having a curvature equal to that of the wafers and adapted to reciprocate vertically such that the top surface can pass through the etching drum (31), and an etching drum having a main housing consisting of a pair of vertical parallel side plates opposing each other, a horizontal shaft integral with the main housing side plates; a plurality of rollers borne between the main housing side plates in a manner such that they are freely rotatory; the rollers having annular grooves in their surfaces to receive edges of wafers in a manner such that the wafers are supported vertically at suitable intervals in a horizontal row; small-diameter gears locked at those ends of the rollers.

Description: Background of Invention The present invention relates to an automatic wafer etching method and an apparatus therefor, adopted in the field of semiconductor wafer manufacturing, and in particular the invention concerns such a method and an apparatus wherein a plurality of wafers contained in a basket are automatically transferred to another container all at a time to thereby attain completely automatic etching operation. Description of the Prior Art A semiconductor wafer to be made into substrates for semiconductor electronic devices is produced in the following manner: a single crystal ingot of a semiconductor material such as silicon is sliced into thin plates by cutting it in a direction substantially normal to the axis of the ingot; then, the faces of the plates are lapped, etched, annealed and polished and eventually the plates are rendered thin round disks having a mirror face on one side of them. After the lapping, the wafers are contained in a wafer basket which carries them to a location where etching is conducted, and there the wafers are transferred from the basket to an etching drum, and the etching drum together with the wafers is submerged into an etchant so that the surfaces of the wafers are wetted and etched by the etchant, whereby the surface irregularities and the lapping abrasive powder rubbed into the surfaces of the wafers, which is caused during the surface lapping, are removed. Although the etching operation itself is conducted automatically, the transfer operation of the wafers from the lapping location to the etching location, and that from the etching location to the annealing and polishing locations were not automatic, nor were they conducted in an in-line manner. Problems the Invention seeks to solve Since the transportation of wafers from one location to another, or from one container to another was not automatic, the overall etching operation required much time and a constant attention of a human operator. Also, when the wafers were brought to a container by a transfer means, the transfer means by itself inserts the wafers into the wafer racks of the container and lets the wafers fall onto the racks so that the wafers are liable to chip as their edges collide with the frames of the wafer racks. Thus, it has been desired that the series of operations in the etching apparatus are all conducted automatically on end, and that in a manner such that the wafers are not allowed to hit upon any part of the containers. To realise this it was necessary to automatise the wafer transportation operations, and the wafers ought to be transferred from one container to another by a means more sophisticatedly designed than the conventional transfer means is. For example, when a basketful of wafers already polished and housed in the wafer basket are to be automatically etched at the etching location, the wafers in the basket must be automatically transported into the etching drum of the etching machine, and this must be conducted harmlessly. The present invention was made in view of these problems, and it is, therefore, an object of the invention to provide an automatic wafer etching method and an apparatus therefor wherein a basketful of wafers are automatically conveyed from one location (container) to another all at once and without letting the wafers hit upon the frames of the wafer receiving bodies. Means to solve the Problems In order to attain the object of the invention, there is provided an automatic wafer etching apparatus, having a plurality of tanks of which one contains an etchant and others pure water, a first wafer container having an opening, for containing a number of wafers to immerse them in pure water contained in said pure water tanks, a second wafer container having an opening, for containing as many wafers as said first wafer container to immerse the wafers in the etchant in said etchant tank, and an automatic wafer transfer mechanism for transferring said wafers from said first wafer container to said second wafer container, and vice versa, within pure water; characterised by: means for transferring said first wafer container; means for holding stationary either one of said first wafer container or said second wafer container; means for bringing either one of said first wafer container or said second wafer container that is not held stationary to the other wafer container in a manner such that the opening of one container enters the opening of the other container; and means for chucking and rotating either one of said first wafer container or said second wafer container which is held stationary by said holder means, whereby said wafers are transferred between said first and second containers. Preferably, said first wafer container is a wafer basket and said second wafer container is an etching drum which comprises: a main housing consisting of a pair of vertical parallel side plates opposing each other; a horizontal shaft means integral with said main housing side plates; a plurality of rollers borne between said main housing side plates in a manner such that they are freely rotatory; said rollers having annular grooves in their surfaces to receive edges of wafers in a manner such that the wafers are supported vertically at suitable intervals in a horizontal row; small diameter gears locked at those ends of said rollers which extend beyond one of the main housing side plates; a movable housing having a pair of vertical parallel side plates opposing each other and borne by said rotary shaft in a manner such that said movable housing can rotate freely about said rotary shaft; a set bar borne between said movable housing side plates in a manner such that said set bar is freely rotatory about its centre line; a small diameter gear locked about that end of said set bar which extends beyond said movable housing; and a large diameter gear which is borne about said rotary shaft and meshes with each of said small diameter gears. Preferably also, said etching drum is supported between first and second axially adjustable chucks adapted to be rotated by first and second drive means; the apparatus further including: a basket support assembly for supporting said wafer basket relative to said etching drum, said basket support assembly being connected to said chucks and having a basket set mount adapted to be driven in a radial direction (c) with respect to said chucks by third drive means. Preferably also, the apparatus, further includes basket stopper means for locating said wafer basket on said basket set mount; basket pusher means connected to said basket set mount for urging said wafer basket into abutment with one of said stopper means; and basket positioning means for urging said wafer basket into abutment with another of said stopper means when said basket set mount is in a lowermost radial position relative to said chucks. According to the invention there is also provided a method for automatically etching a plurality of wafers in an automatic wafer etching apparatus having a plurality of tanks of which one contains an etchant and others pure water, a first wafer container for containing a number of wafers to immerse said wafers in pure water contained in said pure water tanks, and a second wafer container for containing as many wafers as said first wafer container to immerse the wafers in the etchant in said etchant tank, the method comprising the steps of: automatically transferring the wafers from said first wafer container to said second wafer container within pure water contained in one of said pure water tanks; having said second wafer container steeped in the etchant contained in said etchant tank; and transferring the wafers from said second wafer container to said first wafer container within pure water contained in one of said pure water tanks; characterised in that: said first wafer container is a wafer basket and said second wafer container is a wafer drum; said method further comprising the steps of causing said wafer basket containing said wafers to approach said wafer drum in a manner such that an opening of said wafer basket enters an opening of the wafer drum; and rotating said wafer drum together with said wafer basket such that the wafers roll from said wafer basket into said wafer drum due to gravitation. GB-A-213875 discloses apparatus for automatically transferring semiconductor wafers between carriers in which the wafers are raised from the first carrier by an elevator mechanism to be gripped by a pair of jaws which transport the wafers to the second carrier. US-A-4899768 discloses apparatus in which semiconductor wafers are automatically transported from a chemical cleaning bath to a rinse bath by a first transport mechanism prior to being transferred to a second transport mechanism, by means of an elevator mechanism, to be transported to a drying unit. Effects According to the invention, the wafers are automatically transferred from one wafer container to another wafer without colliding with any part of the containers. These and other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings. Brief Description of the Drawings Fig 1 is a side view of a wafer transfer assembly according to the invention; Fig 2 is a front view of the wafer assembly of Fig 1; Fig 3 is a side view of a wafer drum (seen in the direction of arrows A of Fig 4); Fig 4 is a cross-sectional view of the drum taken along the sectional lines B-B of Fig 3; Fig 5 is a schematic drawing showing how the wafer transfer operation is carried on; Fig 6 is a schematic drawing showing how the wafer transfer operation is carried on; Fig 7 is a schematic drawing showing how the wafer transfer operation is carried on; Fig 8 is a schematic drawing showing how the wafer transfer operation is carried on; Fig 9 is a schematic drawing showing how the wafer transfer option is carried on; Fig 10 is a schematic drawing showing how the wafer transfer operation is carried on; Fig 11 is a schematic drawing showing how the wafer transfer operation is carried on; and Fig 12 is a schematic drawing showing how the wafer transfer operation is carried on. Embodiments Next, embodiments of the invention will be described with reference to the attached drawings. Fig 1 is a side view of an automatic etching apparatus having a wafer transfer assembly 101 of an embodiment of the invention; Fig 2 is a front view of the same assembly 101. The wafer transfer assembly 101 of this embodiment is adapted to automatically transfer the plurality of lapped wafers W contained in a wafer basket 102 to a wafer etching drum 103 of an etching machine all at once, and this assembly 101 is submerged in the pure water contained in a transfer tank 104. In Fig 2, the reference numerals 105 and 106 designate a pair of coaxial drum chucks whose heads are opposed to each other; driven by drive means 107 and 108, respectively, these drum chucks 105, 106 are adapted to reciprocate axially as indicated by horizontal double-pointed arrows, and also turn about their axes. A basket set assembly 109 is connected to the drum chucks 105, 106 in one body, and a basket set mount 111 is included in the assembly 109 and is adapted to shift in a radial direction of the drum chucks 105, 106 (as indicated by the double-pointed arrow c), driven by a drive means 110. To the bottom of the basket set mount 111 are attached stoppers 112 and 113, and on the floor of the basket set mount 111 is installed a basket stopper device 114, which has a basket pusher 115 adapted to reciprocate in the direction indicated by the double-pointed arrow d so that it can hold the basket 102 between itself and the stopper 112. In Fig 1, the reference numeral 116 designates a basket-positioning device, and this device 116 has a rod 117 adapted to reciprocate in the direction indicated by the double-pointed arrow e, which is normal to the direction d, so that when the basket set mount 111 comes right below the drum 103, the rod 117 engages with the stopper 113 of the basket set mount 111. The drum 103 is supported and transferred by means of a drum carrier robot 120, and is detachably chucked by means of the drum chucks 105, 106, see Figs 3 and 4 for reference numerals of elements of the drum 103. The end face of the rotary shaft 132 of the movable housing 127 and that of the rotary shaft 123 of the housing 121 are respectively formed with generally rectangular parallelepiped recesses 132a and 123a so that the thus shaped end faced engage and interlock with the opposing end faces of the drum chucks 105, 106 which are formed with rectangular parallelepiped protrusions 105a, 106a (ref Fig 2). Next, the manner of automatically transferring the wafers W from the basket 102 to the etching drum 103 will be explained with reference to Figs 5 through 12. Incidentally, Fig 5 through Fig 12 are schematic drawings showing how the wafer transferring operation is conducted. First, the drive means 107 and 108 are operated so as to turn the drum chucks 105, 106 and thereby the basket set mount 111 of the basket set assembly 109 interlocked with the drum chucks 105, 106 is turned from the position drawn in broken line to the position drawn in solid line, as shown in Fig 5. Next, the basket 102 containing a plurality (twenty, for example) of wafers W which have already been lapped and cleaned in preparation for etching in the foregoing stage, is mounted on the basket set mount 111, as shown in Fig 6; then, as shown in Fig 7, the basket-positioning device 116 is driven so that the rod 117 pushes the basket 102 until the basket 102 is stopped by the stopper 113, whereby the basket 102 is positioned. Thereafter, the basket stopper device 114, as shown in Fig 2, is driven to cause the basket pusher 115 to push the basket 102 to hold it between itself 115 and the stopper 112. Meanwhile, the empty drum 103 is removed from the etching machine, not shown, and conveyed to the wafer transfer assembly 101 by means of the drum carrier robot 102, where it is horizontally supported at its ends by the drum chucks 105, 106. In particular, when the drum 103 is duly positioned, as shown in solid line in Fig 2, the drum chucks 105, 106, which have heretofore assumed the withdrawn positions, advance and mesh with the ends of the rotary shafts 132, 123, that is, the protrusions 105a, 106a of the drum chucks 105, 106 engage with the recesses 132a and 123a formed at the respective end faces of the rotary shafts 132, 123. While the basket 102 is firmly fitted on the basket set mount 111, as shown in Fig 7, the movable housing 127 of the drum 103 is turned prostrate on the housing 121 such that the drum 103 opens downwardly. At this juncture, the drive means 110 for the basket set assembly 109 is driven in a manner such that the basket set mount 111 is caused to ascend together with the basket 102 in the direction indicated by the arrow in Fig 8, whereby the upper open portion of the basket 102 enters the opening of the drum 103, hence the docking of the two bodies 102 and 103. Next, the drive means 107, 108 are driven such that the drum 103 and the basket 102 are turned together through a clockwise angle  1 , as seen in Fig 9, and as the bodies 102 and 103 turn, the wafers W in the basket 102 roll into the drum 103 due to the gravitation, and are each received the wafer receivable grooves 124b formed of the rotary shafts in a manner such that the wafers W are vertically supported at suitable intervals in a horizontal row. Thereafter, the basket set assembly 109 is driven again such that, as shown in Fig 10, the empty basket 102 is removed radially from the drum 103 and then turned anticlockwise to assume the former position, as indicated in broken line; then, the drive means 107, 108 are driven again in a manner such that the drum 103 is caused to turn clockwise through an angle of  2 to assume the position it is assuming in Fig 11. Finally, the drive means 107 is driven to thereby cause the movable housing 127 to turn through a clockwise angle  3 as shown in Fig 12, and as the result, the drum 103 assumes its closed state, whereby the wafers W housed in the drum 103 are prevented by the set bar 128 from dropping, and thus the transfer operation of the wafers W from the basket 102 to the drum 103 is completed. Now, the drum 103, in which the wafers W have been housed, is detached from the drum chucks 105, 106, and is transported to the etching machine, not shown, by means of the drum carrier robot 120. As described above, this embodiment of the invention also enables automatic transfer of the wafers W from the basket 102 to the drum 103, and that all at once, so that the entire wafer production line becomes more automatized. Incidentally, in this embodiment, the drum 103 is removed from the etching machine and transported to the transfer tank 104 by means of the drum carrier robot 120, it is alternatively effective if the basket 102 is brought to the drum 103, without removed the drum 103 from the etching machine.

Claims: An automatic wafer etching apparatus, having a plurality of tanks of which one contains an etchant and others (104) pure water, a first wafer container (102) having an opening, for containing a number of wafers (W) to immerse them in pure water contained in said pure water tanks, a second wafer container (103) having an opening, for containing as many wafers as said first wafer container to immerse the wafers in the etchant in said etchant tank, and an automatic wafer transfer mechanism for transferring said wafers from said first wafer container to said second wafer container, and vice versa within pure water; characterised by: means for transferring said first wafer container; means (120) for holding stationary either one of said first wafer container or said second wafer container; means (109) for bringing either one of said first wafer container or said second wafer container that is not held stationary to the other wafer container in a manner such that the opening of one container enters the opening of the other container; and means (105-108) for chucking and rotating either one of said first wafer container or said second wafer container which is held stationary by said holder means (120), whereby said wafers are transferred between said first and second containers. The automatic wafer etching apparatus as claimed in Claim 1, wherein said first wafer container (102) is a wafer basket and said second wafer container (103) is an etching drum which comprises: a main housing (121) consisting of a pair of vertical parallel side plates (121a, 121b) opposing each other; a horizontal shaft means (122, 123) integral with said main housing side plates; a plurality of rollers (124) borne between said main housing side plates in a manner such that they are freely rotatory; said rollers having annular grooves (124b) in their surfaces to receive edges of wafers in a manner such that the wafers are supported vertically at suitable intervals in a horizontal row; small diameter gears (126) locked at those ends of said rollers which extend beyond one of the main housing side plates; a movable housing (127) having a pair of vertical parallel side plates (127a, 127b) opposing each other and borne by said rotary shaft in a manner such that said movable housing can rotate freely about said rotary shaft; a set bar (128) borne between said movable housing side plates in a manner such that said set bar is freely rotatory about its centre line; a small diameter gear (129) locked about that end of said set bar which extends beyond said movable housing; and a large diameter (130) gear which is borne about said rotary shaft and meshes with each of said small diameter gears (126, 129). The automatic wafer etching apparatus as claimed in Claim 2, wherein said etching drum (103) is supported between first and second axially adjustable chucks (105, 106) adapted to be rotated by first and second drive means (107, 108); the apparatus further including: a basket support assembly (109) for supporting said wafer basket (102) relative to said etching drum, said basket support assembly being connected to said chucks and having a basket set mount (111) adapted to be driven in a radial direction (c) with respect to said chucks by third drive means (110). The automatic wafer etching apparatus as claimed in Claim 3, further including basket stopper means (112, 113) for locating said wafer basket on said basket set mount; basket pusher means (114, 115) connected to said basket set mount for urging said wafer basket into abutment with one of said stopper means (112); and basket positioning means for urging said wafer basket into abutment with another of said stopper means (113) when said basket set mount is in a lowermost radial position relative to said chucks. A method for automatically etching a plurality of wafers in an automatic wafer etching apparatus having a plurality of tanks of which one contains an etchant and others (104) pure water, a first wafer container (102) for containing a number of wafers to immerse said wafers in pure water contained in said pure water tanks, and a second wafer container (103) for containing as many wafers as said first wafer container to immerse the wafers in the etchant in said etchant tank, the method comprising the steps of: automatically transferring the wafers from said first wafer container to said second wafer container within pure water contained in one of said pure water tanks; having said second wafer container steeped in the etchant contained in said etchant tank; and transferring the wafers from said second wafer container to said first wafer container within pure water contained in one of said pure water tanks; characterised in that: said first wafer container is a wafer basket and said second wafer container is a wafer drum; said method further comprising the steps of causing said wafer basket containing said wafers to approach said wafer drum in a manner such that an opening of said wafer basket enters an opening of the wafer drum; and rotating said wafer drum together with said wafer basket such that the wafers roll from said wafer basket into said wafer drum due to gravitation.

Inventors: HASEGAWA FUMIHIKO, SATO SHINJI, HASEGAWA, FUMIHIKO, SATO, SHINJI
Applicants: SHINETSU HANDOTAI KK, SHIN-ETSU HANDOTAI COMPANY LIMITED
Application year: 1992
Main classification: H01L21
IPC codes: H01L21