WO1995000291A1 - Appareil de rodage de haute precision - Google Patents

Appareil de rodage de haute precision Download PDF

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Publication number
WO1995000291A1
WO1995000291A1 PCT/US1994/006881 US9406881W WO9500291A1 WO 1995000291 A1 WO1995000291 A1 WO 1995000291A1 US 9406881 W US9406881 W US 9406881W WO 9500291 A1 WO9500291 A1 WO 9500291A1
Authority
WO
WIPO (PCT)
Prior art keywords
lapping
wafers
dimension
wafer
trajectory
Prior art date
Application number
PCT/US1994/006881
Other languages
English (en)
Inventor
Charles M. Carman, Jr.
Steven C. Moore
Original Assignee
Carman Charles M Jr
Moore Steven C
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Carman Charles M Jr, Moore Steven C filed Critical Carman Charles M Jr
Priority to AU71749/94A priority Critical patent/AU7174994A/en
Publication of WO1995000291A1 publication Critical patent/WO1995000291A1/fr

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/04—Lapping machines or devices; Accessories designed for working plane surfaces
    • B24B37/07—Lapping machines or devices; Accessories designed for working plane surfaces characterised by the movement of the work or lapping tool
    • B24B37/10—Lapping machines or devices; Accessories designed for working plane surfaces characterised by the movement of the work or lapping tool for single side lapping
    • B24B37/105—Lapping machines or devices; Accessories designed for working plane surfaces characterised by the movement of the work or lapping tool for single side lapping the workpieces or work carriers being actively moved by a drive, e.g. in a combined rotary and translatory movement

Definitions

  • This invention relates to lapping apparatus, and particularly to such apparatus in which a workpiece rotates about an axis normal to a planar lapping surface while the axis translates along the surface.
  • the wafer is rotated in a spinning motion about a short-radius axis normal to and between the disks, and also together with its axis in a translating motion about the central axis of the disks, in the manner of an orbiting "planet". From this action comes the term "planetary lapping apparatus" which charaterizes such machinery as used in this art.
  • the abrasive or lapping disks of a planetary apparatus are held rotationally stationary, but with the lower disk fixed and the upper disk free to move up or down along the disk axis, so as to provide with its own weight the pressure needed on both sides of the wafer for the abrasive removal of material.
  • the wafers usually rectangular and nearly square in outline, are held in one or more conforming openings of a circular holder, which is much thinner than the eventual thickness of the wafer, and is provided with gear teeth around its circumference.
  • the holder teeth engage the teeth of an outer ring gear, which may be stationary, and of an inner pinion gear, which is co-axial with the lapping disks and fits within the circular axial or inner openings of the flat-toroidal or ring-shaped lapping disks.
  • the pinion gear is driven by a motor to both rotate and circulate the wafer in its spinning and orbiting planetary motion between the disks. It is usual to ensure that some corners of the wafer, on each rotation about the wafer axis, swing beyond the inner and outer peripheries of the lapping disks so as to avoid leaving periperal ridges on the disks as they themselves wear down in repeated use. The reason why the wafer is rotated about its own axis as well as that of the disks, is to avoid the production of arcuate ridges (centered on the disk axis) in the disks and wafer.
  • This circular trace of wear has an undesirable effect upon the lapping disk when the wafer is orbiting in the ordinary way: greater wear takes place along portions of the mid-width of the lapping disk than at its inner and outer radii, for it is remote from the disk that the circular trace of wear has its maximum dimensions - the center of the wafer if it is a single wafer centrally located on the holder - or at two or more radii between the disk edges if several wafers are arranged in a ring around the holder axis.
  • Wafer blanks are presently produced from crystal blocks that are grown in autoclaves from seeds of pure quartz, over a period of weeks or months, and the blocks are then sawn into rectangular slices having typical thicknesses of from six to ten mils (.15 to .25 mm). The wafer is then lapped to a final thickness dimension of from 2.5 to four mils (.06 mm to .1 mm), with a maximum thickness variation of one ten-millionth to one twenty- millionth of a meter (0.1-O.O5 micron).
  • the prior-art dressing remedy comprises substituting gear- toothed steel dressing rings for the wafer holders; but these rings are much thicker than the holders, so that production cannot continue while the dressing takes place.
  • the re-dressing remedy represents expensive down-time during which the machine is not available for production. The thinner the wafer to be ground, and the more strict the tolerances, the more often re-dressing must take place, and the more expensive is the production process.
  • the present invention is an improvement upon a previous invention (U.S. Patent 4,996,797) of one of the present inventors (Moore), and also substantially eliminates the need for re- dressing.
  • the present invention accomplishes this object by the attainment of theoretically perfect flat surfaces, in a true precision operation, even in the "sub-micron" range
  • the first nor any other wafer that is lapped between the disks of the present invention comes out with a systematic variance from perfect flatness. Any variations must be accidental and random - and therefore substantially self-cancelling over the long run.
  • the way is opened for an advance of the first magnitude in this and associated arts of forming, dimensioning and precision-finishing objects of all kinds.
  • lapping member that may be either rectilinear or disk-shaped with " e. mid- width portion formed to abrade at the same or a lesser rate than the radially inner and outer portions thereof.
  • the holder axis is centered ,
  • the axis of the lapping disk for a dimension inversely proportional to the radius of the disk.
  • means are provided for supporting the portions of the wafers that overhang and project beyond the edges of the lapping member.
  • FIGURE 1 is a plan view of a simple planetary lapping apparatus, with a cover portion and the upper lapping disk removed above the plane of lines 1- 1 of FIGURE 2 so as to show the wafers and one form of the structure of the invention;
  • FIGURE 2 is a front view of the apparatus of FIGURE 1, broken away partly on the plane 2-2 of FIGURE 1;
  • FIGURE 3 is a schematic view to an enlarged scale illustrating a portion of the apparatus shown in FIGURE 1;
  • FIGURE 4 is a schematic view illustrating part of the theory and structure of the invention.
  • FIGURE 5 is a table further illustrating part of the theory and structure of the invention.
  • FIGURE 6 is a table further illustrating part of the theory and structure of the invention.
  • FIGURE 7 is a schematic view further illustrating part of the theory and structure of the invention.
  • FIGURE 8 is a schematic view further illustrating part of the theory and structure of the invention:
  • FIGURE 9 is a schematic view further illustrating part of the theory and structure of the invention.
  • FIGURES 1 and 2 there is shown a simple lapping machine of the type used in the art of grinding piezoelectric quartz crystal wafers for the , 0-_U_- T_-C_i_. -___- ⁇ ___? S** ⁇ CMd r- electronics industry.
  • the wafers ⁇ are shown under the reference numerals ⁇ " '! 1. 12. 13. 14* A,21. 22. 23. 24 * />-31. ' 32. 33. 34. ' " A41. 42. 43, • 44,.51. 52. 53. 54, ⁇ 61, 62, 63. 64..71. 72, 73. 74. 81. 82. 83. 84, ⁇ "'
  • the machine includes a housing 111 containing a driving motor (not shown), and defining a recessed well 113 constituting a sump for collecting overflow or used abrasive-carrying fluid, as well as the debris resulting from lapping and grinding, which is also carried away by the fluid.
  • each holder ⁇ * has four rectangular openings which conform to and snugly fit around four of the rectangular flat quartz wafers or workpieces 11-94.
  • a ring gear 124. mounted on stanchions 126. also engages the teeth 119 of the holders.
  • the pinion gear may be driven to rotate, e.g.. in the direction of arrow 127, so as to cause the holder £ ⁇ f to spin about its own central axis in the direction of arrow 128, and concurrently to translate the holder bodily about the central axis of the apparatus (i.e., the axis of shaft 117), and in the same direction as arrow 127.
  • the upper lapping disk 114a (shown only in Figure 2) rests with the force of gravity upon the workpieces 11 -94. and is generally positioned horizontally by the shaft 117. but is free to slide axially (vertically) with respect to the shaft, and does not rotate therewith.
  • the disk 114a is more precisely positioned horizontally by means of a mandrel 131 (shown only in phantom in Figure 1), which fits into the central opening of the disk, and is in turn supported by an integral spider member 132 extending diametrically into conforming recesses in the top of housing 111.
  • the composite member formed by disk 114a and extensions 115, 115a is also free to slide vertically with respect to mandrel 131 as the wafer grows thinner, but the disk is restrained against rotation by means of a stop member 133 (shown only in phantom in Figure 1), which extends from the disk 114a and engages the spider member 132.
  • the spider 132, mcindrel 131 and lapping disk 114a can all be lifted off the axle 117 by hand, as indeed they have been in the showing of Figure 1 , when it is desired to get at the workpieces 11 -94.
  • the lapping disks 114, 114a are formed differently than are those generally used in the art, which are meant to directly (or indirectly through abrasive particles carried by fluid) engage the workpieces 11-94 with confronting cast-iron faces. Instead, the disks 114, 114a shown here for the present invention are considerably narrower in radial dimension, as will be explained more fully in relation to other drawing Figures. Suffice it here to say that these disks 114, 114a are particularly shaped to wear evenly at all points when exposed to the abrading action of wafers shaped, dimensioned and mounted as shown for wafers 11-94.
  • the extensions 115, 115a are made of more rapidly abrading material than the disks 114, 114a, and are shown here as mounted on the peripheral faces of the disks 114, 114a by any suitable means, such as adhesives or machine-screw fasteners, not here illustrated.
  • the extensions 115, 115a may be formed integrally with the disks 114, 114a, as by merely machining or cutting away some of the peripheral material of the disks for perhaps 50 mils or about 1 millimeter in an axial direction, to form a support for the wafers as they circulate portions beyond the peripheries of the lapping surface.
  • the substance may even be plastic, but in any case must be capable of wearing more rapidly than the members 114, 114a, and therefore in practice must wear at precisely the same rate - for of course they cannot wear faster without coming out of pressurized relationship with the wafers and ceasing thereby to wear.
  • the faster-wearing material is said to "follow", in effect, the slower wear- rate of the steel or iron surface of the members 114. 114a, and consequently the members 115. 115a cannot interfere with the wear-stabilization operation of the invention.
  • a well-known feature of the cast-iron lapping disks of the prior art is a set of circumferentially and radially spaced distribution grooves on the confronting disk faces, which help to distribute the abrasive- carrying fluid from input orifices (not here shown) evenly across the surfaces of the disks in contact with the workpieces 11-94, and to wash away the used abrasive and debris particles to the sump of well 113.
  • Another function of such distribution grooves is to help in gently breaking the adherence between plate and workpieces. induced primarily by ambient atmospheric pressure, when it is time to remove the workpiece from the machine, thus avoiding tearing or breaking the very thin and brittle quartz wafers.
  • Such grooves may of course be provided in the disks of the present invention, but are not here shown, for greater clarity of illustration of the structure that is more closely relevant to the invention.
  • the point 341 schematically represents the axis of the drive shaft 117 and therefore the central axis of the entire apparatus; and the twenty- two arcuate locii 201- 222 shown centering on axis 341 represent the paths swept by twenty-two points of the holders and wafers on the surface of the lapping disk 114 at different radii.
  • the locus 201 represents the inner periphery of the disk
  • locus 222 represents the outer periphery.
  • the point 345 is the center of rotation of a ring-shaped wafer array, square or trianglar as the case may be.
  • w ic is t e same as 9 degrees in this case.
  • the nine wafer sets of Figure 3 represent nine different angularly equispaced stages of a full 90-degree rotation of a wafer set with respect to the set of locii 201-222. And since there are four wafers in each set, the total of nine sets represents the equivalent of a full 360- degree rotation of a ⁇ wa ⁇ er «et with respect to the locii
  • the design process begins with the - generatp ⁇ on of a bifurcate pattern 351 as oh ⁇ wn in Figure 4-, wherein all of the arcs that are subtended by all of the wafers on each circular locus 201-222 as shown in Figure 3, are added together, or laid end-to-end. on the respective locus in Figure 4.
  • the "W” shape represents generally the cross -sectional hollowed- profile that the wafers attempt to gouge out of the lapping disks over an extended series of runs with different wafers, which result in turn causes the later runs of wafer-sets to be formed to increasingly domed shapes on both sides, like the playing pieces in the Japanese game of Go (Wei-chi in China). If a set of four wafers is formed to this domed shape, as an assembly but not necessarily individually, then it follows that each individual wafer is formed with its radially most-outward corner too thin and its most-inward corner too thick, and planarity is impossible.
  • the disk surface is constrained to remain in a plane with points 352, 357 and 358, because the wafer-sets are rotating while moving (translating) along a circumferential ridge (or "potential-ridge") represented by point 352.
  • a circumferential ridge or "potential-ridge” represented by point 352.
  • the "potential- ridges" and “potential-valleys" remain potential only, and never wear out-of-flat.
  • a wafer-lapping apparatus of the type in which a lapping member is mounted to present a lapping surface that is planar at least within a predetermined lapping zone and therein has a lapping relationship with a number of wafer-holders each of which carries a number of wafers and spins the wafers about a holder axis normal to the lapping surface while concurrently causing said wafers to have a relative translational motion with respect to said planar lapping surface in a path that is parallel to a pair of first and second parallel edges of the lapping surface, said path having a predetermined width between said edges and a shape parallel to the edges that is chosen from the range circular-to-rectilinear, wherein:
  • the centroids of said wafers in each holder have a characteristic mean circular trajectory centered on the holder axis;
  • said trajectory having a major portion arranged to span at least a portion of the width of said path with the remaining minor portion of the trajectory overhanging and protruding laterally beyond the lapping surface first edge for a first dimension that is inversely proportional to the radius of curvature of said path;
  • said first dimension other than zero being taken from the trajectory minor portion toward the first edge and toward the centers of curvature of said path and of said trajectory.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
  • Mechanical Treatment Of Semiconductor (AREA)

Abstract

Mécanisme pour l'entraînement en rotation et la translation de pièces à usiner (11) en relation de rôdage avec un élément de rôdage (114, 115) dont une partie (114) située à mi-largeur est conçue pour abraser à la même vitesse ou moins vite que les parties internes et externes (115). Dans un mode de réalisation, une pluralité de tranches est disposée dans une couronne placée dans un montage de support (121), un axe de support est centré (345) sur l'élément de rôdage rectiligne (fig. 7 & 8), une surface de rôdage est formée sur une largeur uniforme n'excédant pas le diamètre de la trajectoire circulaire moyenne des centres de gravité (361) des tranches en rotation. Dans un autre mode de réalisation, un élément de rôdage à disque annulaire (314, 315) est prévu, la largeur (C) de la surface de rôdage équivaut approximativement au diamètre de la trajectoire du centre de gravité des tranches (361), l'axe de support est radialement décalé vers l'extérieur par rapport à l'axe du disque de rôdage d'une distance inversement proportionnelle au rayon du disque (D). Un moyen de support des parties en saillie des tranches est prévu pour les deux modes de réalisation.
PCT/US1994/006881 1993-06-24 1994-06-16 Appareil de rodage de haute precision WO1995000291A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU71749/94A AU7174994A (en) 1993-06-24 1994-06-16 Ultra-precision lapping apparatus

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US8372293A 1993-06-24 1993-06-24
US98765493A 1993-06-24 1993-06-24
US08/083,722 1993-06-24

Publications (1)

Publication Number Publication Date
WO1995000291A1 true WO1995000291A1 (fr) 1995-01-05

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1994/006881 WO1995000291A1 (fr) 1993-06-24 1994-06-16 Appareil de rodage de haute precision

Country Status (1)

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2309080A (en) * 1941-12-06 1943-01-19 Grover C Hunt Work holder for grinding machines
US2314787A (en) * 1941-12-06 1943-03-23 Grover C Hunt Grinding machine
US3968598A (en) * 1972-01-20 1976-07-13 Canon Kabushiki Kaisha Workpiece lapping device
US4535567A (en) * 1983-08-26 1985-08-20 Seaborn Development, Inc. Computer magnetic media burnisher
US4656790A (en) * 1984-12-04 1987-04-14 Fuji Photo Film Co., Ltd. Burnishing method and apparatus for magnetic disk
US4805348A (en) * 1985-07-31 1989-02-21 Speedfam Co., Ltd. Flat lapping machine
US4996798A (en) * 1989-05-31 1991-03-05 Moore Steven C Ultra-precision lapping apparatus

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2309080A (en) * 1941-12-06 1943-01-19 Grover C Hunt Work holder for grinding machines
US2314787A (en) * 1941-12-06 1943-03-23 Grover C Hunt Grinding machine
US3968598A (en) * 1972-01-20 1976-07-13 Canon Kabushiki Kaisha Workpiece lapping device
US4535567A (en) * 1983-08-26 1985-08-20 Seaborn Development, Inc. Computer magnetic media burnisher
US4656790A (en) * 1984-12-04 1987-04-14 Fuji Photo Film Co., Ltd. Burnishing method and apparatus for magnetic disk
US4656790B1 (fr) * 1984-12-04 1989-01-10
US4805348A (en) * 1985-07-31 1989-02-21 Speedfam Co., Ltd. Flat lapping machine
US4996798A (en) * 1989-05-31 1991-03-05 Moore Steven C Ultra-precision lapping apparatus

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
IBM TECHNICAL DISCLOSURE BULLETIN, Vol. 23, No. 4, September 1980, J. BRUN et al., "Lapping Method to Adapt the Silicon Wafer Bow", pages 1467-1469. *

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