FR2643843A1 - DEVICE FOR THE REPERAGE OF CRYSTALLINE ORIENTATION AND THE RECTIFICATION OF A BAR - Google Patents

Abstract

Device for locating the crystalline orientation and rectifying a bar comprising: a guide piece 30 having a first housing 32 capable of receiving said bar 18 and having a planar face 34 intersecting the first housing 32 so as to provide a opening 36 of width determined along the first housing 32; a fixing means suitable for fixing the bar 18 inside the housing 32 of the guide piece 30. Application to the production of the locating flats on bars of semiconductor and monocrystalline material intended for the production of wafers (wafers ).

Description

DEVICE FOR THE TRACKING OF THE ORIENTATION

  CRYSTALLINE AND THE RECTIFICATION OF A BAR.

Description

  The present invention relates to a device for the identification of the crystalline orientation and the correction of a bar. It applies in particular to the realization of locating flats on cylindrical bars of semiconductor and monocrystalline material intended for the production of wafers (wafers in English terminology). A bar of monocrystalline semiconductor material (gallium arsenide for example) is produced by known crystalline growth processes. A crude monocrystalline drawing bar has two extreme faces which, once erected, are oriented along defined crystalline planes

  and known (ioo00 plans for AsGa, for example).

  The bar is then lapped to make it cylindrical, the generatrices of the cylinder being perpendicular to the end faces. The diameter of the cylinder is normalized: it can be equal to 2

  inches (5.08 cm) or 3 inches (7.62 cm).

  FIG. 1 diagrammatically represents an exploded view of a device making it possible to

prepare the break-in operation.

  This device comprises a support 10 for aligning along an axis AA, two end pieces 12. One of the end pieces 12 rests on the support 10 and is centered with respect to the axis AA. The translation along AA of the other endpiece 12 is free. This translation is guided by a part 14 fixed on one end of the support 10. This part 14 has an orifice through which a cylinder 16 on which the end piece 12 is fastened. The axis of revolution of the cylinder 16 coincides with the axis AA. The translation of the cylinder 16 causes the translation of the tip

12 along the AA axis.

  FIG. 2 diagrammatically represents a lapping bar introduced into the device represented in FIG. 1. The end pieces 12 are hot-glued, at 50 ° C., for example, using a resin, on the end faces 20, 21 of the 18. A pressure is applied (symbolized by a arrow in Figure 2) on the end pieces 12 through the cylinder 16 for a time depending on the nature of the resin. This duration is set by the manufacturer. FIGS. 3A to 3C show the operation

lapping proper.

  There is therefore a bar 18 crude draft but pre-sentant two end faces 20, 21 planes and oriented (Figure 3A). On these faces 20, 21 are glued the end pieces 12 along an axis which

  defines the axis of revolution of the set.

  Figure 3B schematically shows the running-in operation. The assembly comprising the bar 18 and the end pieces 12 is placed between the centering points 22 of a lapping machine (not shown in FIG. 3B). The centering is ensured by conical holes 13 made in the end pieces 12 and able to receive the centering points 22 of the

lapping machine.

  The bar 18 is rotated.

  A grinding wheel 24 is brought into contact with the bar 18.

  The longitudinal displacement of the wheel 24 allows

  a setting to the desired diameter of the bar 18.

  Figure 3C shows schematically

  the bar 18 once the break-in operation is completed.

  The axis of revolution of the cylindrical bar 18 is

  coincides with the axis of alignment of the tips 12.

  Once this shaping is completed, two flats are made along two generatrices of the bar 18. These flats standardized width, 8 mm for one and 16 mm for the other, are arranged in planes perpendicular to each other. In the

  Following the description, the flat of width 8 mm

  is called small flat and the flat of width 16 mm is called large flat. These planes correspond to certain crystalline orientations (Eo10)

  - for the small flat of the AsGa, for example).

  These flats make it possible to identify the crystalline orientations of the slices cut in the bar during the production operations.

electronic circuits.

  In the usual way, a rough registration of the two generators to be machined is carried out in order to obtain the two flats. This identification is made from surface details observable with the naked eye on the raw drawing bar. Benchmarks are written on the end faces 20, 21 of the bar 18, in ink

indelible for example.

  In a known manner, a blank of one of the flats is made according to one of the marks. Then we perform successive machining followed by orientation checks of the plane of the flat by X-ray diffraction, so as to obtain the good width of the flat and the good

orientation.

  The second flat is made using the same technique in a plane perpendicular to that

the first flat.

  In known manner, the realization of the flats is manual: the bar 18 is manually applied to a rotating grinding wheel, the generatrix previously identified facing the grinding wheel. This way

  to operate has many disadvantages.

  The respect of the crystalline orientation During the successive machining forces the operator to numerous X-ray measurements, considering the rough precision of the preliminary identification and the uncertainty of the manual work. Despite numerous round trips between the X-ray measuring machine and the machining station, the accuracy thus obtained is not satisfactory. The present invention overcomes these disadvantages; it allows to obtain a greater precision on the width of the flats and on the crystalline orientation during manual machining

  of the Bar while making only one

  X-ray diffraction. Thanks to the device recommended by the invention, the identification of the second

  flat is easy once spotted the first flat.

  Specifically, the present invention relates to a device for adjusting the crystalline orientation and the rectification of a crystalline bar of cylindrical shape, said bar having a normalized diameter. This device comprises: a guide piece having a first housing adapted to receive said bar. This first home

  has a longitudinal central axis.

  The guide piece has a flat face intersecting the first housing so as to provide an opening of determined width along the first housing. The device according to the invention further comprises a fastening means adapted to fix the bar

  inside the housing of the guide piece.

  According to a particular embodiment, said bar being of cylindrical shape and having a standardized diameter, the first housing is

  cylindrical of revolution around the central axis.

  The diameter of the first housing is then substantially

  equal but greater than the normalized diameter.

  According to a preferred embodiment, the fastening means consists of: a bar disposed in a second recess formed in the guide piece and opening on the first housing, at least one clamping screw exerting a pressure on said bar, through a threaded hole made for this purpose in the room

guidance.

  This bar may have a concave face. In this way, for a cylindrical bar the concave face is suitable for

  marry the cylindrical shape of the bar.

  The device further comprises means for rotating said bar around the axis

  central of the first housing of the guide piece.

  Preferably, these means for rotating said bar comprise: a hollow plate rotating about an axis of revolution, this plate being supported by a hollow body adapted to be fixed at one end of the guide piece; Link piece secured to the turntable, - a centering tip adapted to be fixed to an end face of the bar, a raised end of the connecting piece being adapted to fit into a recess of the endpiece so as to ensure a centering of the bar inside the first housing, this end being secured to the connecting piece by a fastening means so that a rotation of the turntable causes rotation of the bar, the end piece having a bulk such that a introduced into the guide piece, the tip has no overflowing portion of

the opening of the first housing.

  The bar is introduced into the first housing of the guide piece. In the case of a cylindrical bar, it is carried out a marking of the generator of the bar according to which one wants to machine

a flat.

  This identification is obtained by X-ray diffraction on the bar. The selected generator is brought into position in the guide piece by rotation of the bar which is secured to the turntable. Once in position the bar is fixed inside the guide piece by means

of fixation.

  The machining is done manually after disassembling the turntable of the guide piece. The flat face of the guide piece serves as a reference plane. The part of the bar overhanging the opening of the first housing is ground until the plane face comes flush with the surface

of the grinding wheel.

  With this flat face, the crystalline orientation and the width of the flat are

  guaranteed with great precision.

  The device according to the invention further comprises: two flanges able to be fixed by fastening means at each end of the guide piece and each having a planar face of predetermined width, and overflowing the guide piece, positioning means capable of positioning the flat face of each flange parallel to the flat face of the guide piece. According to one embodiment, the positioning means consist of two pins per flange to be positioned, each pin being adapted to fit into housings for this purpose.

  in each flange and in the guide piece.

  According to another embodiment, the positioning means consist of a pin per flange to be positioned, this pin being able to fit into housings provided for this purpose in each flange and in the guide piece, and in a relief of flaccid able to fit into

  the first housing of the guide piece.

  Once the bar is oriented by means of the turntable and fixed in its position, the flanges are put in place and a grinding of the bar is carried out to obtain the flat. The machining is done manually, the portion of the bar overflowing the opening of the first housing and protruding beyond the flat faces of the flanges is kept in contact with a grinding wheel until the flat faces of the flanges.

  flush the surface of the grinding wheel.

  The two flats of desired width and crystalline orientation are thus obtained using a single exposure to X-rays and avoiding

  the imprecision of successive machining.

  In any case, the features and advantages of the invention will appear better after

  the following description given for explanatory purposes

  and in no way limiting. This description refers to

  to the accompanying drawings in which: - Figure 1, already described, schematically shows an exploded view of a device for preparing a lapping operation; FIG. 2, already described, schematically represents a front view of this same device with a raw draft bar positioned in its interior; FIGS. 3A to 3C, already described, schematically represent the steps of setting the diameter of a FIG. 4A and 4B schematically represent a cutaway view and a cross-section of a device according to the invention; FIG. 5A schematically represents an exploded view of a device according to the invention used for 5B schematically represents an alternative embodiment of a flange for machining a small flat, - Figures 6A to 6D show schematically The various steps of the realization of the flats on a bar, - FIG. 7 schematically represents a bar

  once both flats are made.

  Figure 4A shows schematically

  an exploded view of a device according to the invention.

  This device is particularly suitable for machining a standard diameter cylindrical rod 18 of standardized diameter for the realization of the two locating flats. The device comprises a guide piece having a first housing 32 cylindrical in revolution about a central axis CC. This housing 32 is intended to receive the bar 18 to rectify, its diameter is substantially equal to but greater than the normalized diameter of the bar 18. For example, for a standard diameter of 2 inches

  (5.08 cm) The diameter of the housing 32 is 5.1 cm.

  The guide piece 30 has a flat face 34 intersecting the diameter of the housing 32 so as to provide an opening 36. This opening 36 has a determined width which corresponds to the width of the large flat to be machined on the bar 18

  (that is, a width of 18 mm).

  The bar 18 introduced inside the first housing 32 of the guide piece 30 must be oriented for the machining of the flats. To do this, thanks to a centering tip 12 hot-glue on an end face of the bar 18, is secured the bar 18 with a rotating hollow plate 42, via a connecting piece 44 integral with the turntable 42 A raised end 46 of the connecting piece 44 engages in a recess 38 of the nozzle 12. The size of the tip 12 is such that once introduced into the guide piece, the tip 12 has no overflowing part

  The opening 36 of the first housing 32.

  The turntable 42 is supported by a hollow body 40. The turntable 42 and the hollow body 40 may be of the type TR80 manufactured by La

  Socity. Micro-Control, for example.

  The link piece 44 is fixed to the turntable 42 by two screws 48; eltte traverse The turntable 42 and the hollow body 40 to be secured

with the endpiece 12 by two screws 54.

  Advantageously, the centering tip 12 is one of those already attached to the bar 18 during the setting of the diameter, thus ensuring perfect concordance between the central axes of the bar

18 and the tip 12.

  The rod 18 is introduced into the first housing 32 of the guide member 30. The hollow body is then fixed to one end of the guide piece 30 by means of two screws 50. These screws 50 are fed to the end. of the guide piece 30 by a passage 52 machined over the entire height

  of the guide piece 30, for example.

  Optionally, the centering of the assembly consisting of the turntable 42 and its body 40 can be improved by the use of a centering ring (not shown) interposed between the piece

30 and the body 40.

  The bar 18 is then properly oriented inside the first housing 32 by X-ray diffraction on the portion of the bar 18 projecting through the opening 36. The orientation is obtained by rotating the axis CC about the bar 18 inside the housing 32, by actuating a coupled screw system 43

  to a wheel setting in motion The turntable 42.

  Once oriented, the bar 18 is held in position inside the housing 32 thanks to

fastening means.

  FIG. 4B schematically represents a transverse section along a plane perpendicular to the axis CC. This figure shows an embodiment of the rod fixing means 18 to

inside the dwelling 32.

  This fixing means is constituted by a bar 60 disposed in a second housing 62 practiced in the guide piece 30 and opening

on the first dwelling 32.

  This bar 60 has a concave face

  64 adapted to fit the cylindrical contour of the bar 18.

  When it is desired to fix the bar 18 inside the first housing 32 is actuated clamping screws 66 to exert pressure on said bar 60 through the threaded orifices made for this purpose in the guide piece 30. In L ' embodiment shown in Figure 4A and shown in section in Figure 4B, we see that the bar 60 is actuated by three setscrews 66, which allows to balance

  the pressure exerted on the bar 18.

  Once the bar 18 is perfectly oriented in the first housing 32 of the guide piece, that is to say that the selected crystalline planes ([110] for AsGa, for example) are parallel to the flat face 34 of the guide piece, we perform

then machining the small flat.

  For this, the bar 18 is detached from the turntable 42 by unscrewing the screws 54 and

the screws 50.

  FIG. 5A schematically represents an exploded view of a device according to the invention

  used to make the small m4plat.

  On each end of the guide piece containing the bar 18 suitably oriented and fixed by the fastening means, a flange having a flat face 72 of determined width and overflowing the guide piece 30 is fixed. Each flange is for example fixed by screws 74. The flat face 72 of each flask 70 is positioned parallel to the face 34 of the guide piece 30 by means of a set of two pins 76 fitting into housings 78, 79 designed for this purpose.

  effect in the flanges and in the guide piece 30.

  FIG. 5B schematically represents a variant embodiment of a flange allowing

to machine a small flat.

  In FIG. 5B, it can be seen that the flat face 72 of the flange 70 is positioned parallel to the face 34 of the guide piece 30 by means of a single pin 76 fitting into housings 78, 79 designed for this purpose. effect in the flange 70 and in the guide piece 30. The flange 70 also has a relief 75 adapted to fit together

  in the first housing 32 of the guide piece 30.

  Whatever the variant of embodiment, the flat faces 72 of the flanges 70 are included in a plane intersecting the diameter of the bar 18 projecting out of the opening 36. The section generated has an equal width. to the width of the small

flat.

Figures 6A-6D represent-

  schematically the different stages of the realization of the flats on a bar. The references used are the same as those used during

  from the description of FIGS. 1 to 5. In this example,

  the small flat is machined first.

  FIG. 6A schematically represents the orientation of the bar by the X-ray diffraction referenced RX. The bar 18 is introduced into the first housing of the guide piece 30 and

  secured to the turntable 42.

  The bar 18 is subjected to the beam RX through the opening 36 made in the first housing 32 of the guide piece 30. By rotating the bar 18, by acting on the rotating plate 42, the crystalline planes ([110] are oriented to the AsGa for example) parallel to the flat face 34 of the piece of

guidance 30.

  The bar 18 is fixed in this orientation by acting on the screws 66. The turntable 42 is then detached from the bar 18 and removed, as well as the body 40 and the connecting piece 44,

of the guide piece 30.

  FIG. 6B schematically represents the device according to the invention enabling the

realization of the small flat.

  The flanges 70 are fixed on the guide piece 30, their flat face 72 parallel to the

flat face 34.

  Holding the bar 18 against a grinding wheel

  (not shown) allows the machining of the flat 17.

  The machining is stopped when the me-ule comes into contact with the plane faces 72. The parallelism between the faces 72 of the flanges 70 and the flat face 34 of the guide piece 30 guarantees the orientation of the

flat 17.

  FIG. 6C schematically represents the device according to the invention making it possible, after the production of the small flat 17, to orient the

  bar 18 for the realization of the large flat.

  The flanges 70 are disassembled is the bar

  18 and again secured with the turntable 42.

  After having loosened the clamping screws 66, the bar 18 is subjected to a rotation of 90, then

tightens the clamping screws 66.

  The turntable 42 is then detached from the bar 18 and removed, as well as the body 40 and the connecting piece 44, the piece of

guidance 30.

  Figure 6D shows the device according to

  the invention to achieve the large flat.

  Once the rod 18 is properly oriented and fixed inside the guide piece 30, its portion protruding from the opening is brought into contact

a wheel (not shown).

  The machining is stopped when the wheel comes into contact with the flat face 34 of the guide piece 30. In this way, the orientation and

The Width of the Large Metal 19.

  Figure 7 schematically shows the bar 18 once The two flats 17, 19 made. The device according to the invention makes it possible to guarantee an angular precision of at least +5 'and a precision on the widths of the flats 17, 19

of +0,5 mm.

  The different manipulations involved are simple and reproducible. In addition, only one x-ray exposure is used

  limitation of the risks of irradiation.

Claims (9)

claims   1. Device for the adjustment of the crystalline orientation and the grinding of a bar (18), characterized in that it comprises: - a guide piece (30) having a first housing (32) adapted to receive said bar (18), said first housing (32) having a central longitudinal axis (CC), said guide member (30) having a planar face (34) intersecting the first housing (32) so as to provide an opening (36); along the first housing (32), this opening (36) being of determined width, - a fastening means adapted to fix the bar (18) inside the housing (32) of the piece of guiding (30).   2. Device according to claim 1, said bar being of cylindrical shape and having a standardized diameter, characterized in that the first housing (32) is cylindrical of revolution about the central axis (CC), the first housing having a substantially equal diameter but greater than the normalized diameter.   3. Device according to claim 1, characterized in that the fixing means consists of: - a bar (60) disposed in a second housing (62) formed in the guide piece (30) and opening on the first housing (32), - at least one clamping screw (66) exerting a pre-ssion on said bar (60), through a threaded orifice made for this purpose in La guide piece (30).   4. Device according to claim 3, characterized in that said bar (60) has a face (64) of concave shape.   5. Device according to claim 1, characterized in that it further comprises means for rotating said rod (18) about the central axis CC) of the first housing (32) of the guide piece (30). . 6. Apparatus according to claim 5, characterized in that the means for rotating said bar (18) comprise: - a rotating hollow plate (42) about a revolution axis, this plate (42) being supported by a body (40) adapted to be fixed at one end of the guide piece (30), - a connecting piece (44) integral with the turntable (42), - a centering tip (12) adapted to be fixed to a face end of the bar (18), a raised end (46) of the connecting piece (44) being adapted to fit into a recess (38) of the end piece (12) so as to ensure centering of the bar ( 18) inside the first housing (32), this end piece (18) being secured to the connecting piece (44) by a fastening means so that rotation of the turntable (42) causes rotation of the bar (18), this nozzle (12) having a size such that once introduced into the guide piece (30), the tip (12) has no part d bordering the opening (36) of the first Housing (32).   7. Device according to claim 1, characterized in that it comprises: - two flanges (70) adapted to be fixed by fastening means (74) at each end of the guide piece and each having a flat face (72). ) of determined width, and projecting over the guide piece (30), 26438L4   positioning means capable of positioning the flat face (72) of each flange (70)   at the flat face (34) of the guide piece (30).   8. Device according to claim 7, characterized in that the positioning means consist of two pins (76) per flange (70) to be positioned, each pin (76) being adapted to fit into housings (78, 79). performed for this purpose in each flange (70) and in the room guide (30).   9. Device according to claim 7, characterized in that the positioning means consist of a pin (76) for a flange (70) to be positioned, this pin being able to embellish in housings (78, 79) made to this effect in each flange (70) and in the guide piece (30) and in a relief (75) adapted to fit into   the first housing (32) of the guide piece (30).