JPS6125769A - Residual thickness measuring device in grinder - Google Patents

Abstract

PURPOSE:To measure accurately in semiconductor wafer grinding machine, by contacting a contact element against the surface of an object on the holding table and corresponding the gap between the detector and an element to be detected with the residual thickness of the object. CONSTITUTION:Upon carrying of grinded semiconductor wafer W through a holding table 14 to the detecting area, the piston rod 144 will rise to the non- restricted position thus to turn a member 84 through shifting means 134 and to contact the contact element against the surface. The gap between the detection face 132 of contactless detector 124 and the surface of the element 122 to be detected is set to the level corresponding with the residual thickness of the wafer W thus to produce the output voltage. Here, quite low contacting pressure is required for the element 11 while only momentary contacting time is required to feed the output voltage from the detector 124 to the control circuit 146 without damaging the wafer W.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a grinding machine for grinding the surface of a flat object to be ground, particularly a semiconductor wafer. The present invention relates to a grinding object residual thickness measuring device for measuring the residual thickness of a grinding object.

BACKGROUND ART As is well known to those skilled in the art, in the manufacture of semiconductor devices it is necessary to grind the surface of a semiconductor wafer to bring the thickness of the semiconductor wafer to a desired value. As a grinding machine for grinding the surface of semiconductor wafers,
For example, JP-A-56-152562 and JP-A-57
A grinding machine such as that disclosed in Japanese Patent No. 156157 is widely used in practice. Such grinding machines include a rotatably mounted support disc and a plurality of grinding wheel assemblies disposed above the support disc. A plurality of holding tables are mounted on the support disk at appropriate intervals in the circumferential direction.

Each of the grinding wheel assemblies includes a grinding wheel rotatably and adjustable in axial position;
The grinding wheel has a grinding blade formed by bonding abrasive grains, typically superabrasive grains such as natural or synthetic diamond abrasive grains or cubic boron nitride abrasive grains.

A semiconductor wafer whose surface is to be ground is placed on the holding table and held on the holding table by, for example, vacuum suction. In each of the grinding wheel assemblies described above, the grinding wheel is rotated at high speed. Then, while the holding table and the semiconductor wafer held thereon are transported through the arc-shaped transport path by the rotation of the support disk, the grinding wheels in the plurality of grinding wheel assemblies sequentially act on the semiconductor wafer. Grind its surface.

In the grinding machine as described above, in order to grind the surface of the semiconductor wafer sufficiently well and to make the thickness of the semiconductor wafer to the required Wr value with sufficient precision, the axial position of the grinding wheel, more specifically, the grinding It is necessary to adjust the axial position of the blade tip with sufficient precision. Since the tip of the grinding blade is worn out when the grinding is performed, it is desirable to perform such adjustment in a so-called in-process manner as the grinding is performed.

Therefore, in order to satisfy the above requirements, the residual thickness of the semiconductor wafer ground by the grinding wheel must be sufficiently precisely measured in-process, and the axial position of the grinding wheel can be determined based on the measured value. It is important to adjust using a feedback control method. However, (a) there are grinding debris generated by the grinding around the ground conductor, and during grinding, a cooling liquid such as tap water is generally poured into the grinding blade of the grinding wheel and the semiconductor wafer. Because the liquid is injected into ..., there are droplets or liquid mist, so a precision measurement method that is not affected by grinding debris or droplets or liquid mist must be adopted. Do not cause damage (
c) Since the object to be measured for residual thickness is not a conductor but a semiconductor, a non-contact detector that is known per se, such as an eddy current type that functions when the object to be measured is a conductor, is used to measure the residual thickness. There are difficult problems to be overcome, such as the inability to act directly on objects, and therefore there is a technology to measure the residual thickness of semiconductor wafers ground by a grinding wheel with sufficient precision in-process. has not yet been established, and the above requirements could not be met.

<Object of the Invention> The present invention has been made in view of the above facts, and its main purpose is to skillfully solve the problems 0) to (c) above, and to provide a flat workpiece to be ground, especially a semiconductor. In a grinding machine that grinds the surface of a workpiece, the residual thickness of the workpiece held on a holding table and conveyed through a predetermined conveyance path can be measured with sufficient precision. An object of the present invention is to provide a residual thickness measuring device.

<Summary of the Invention> According to the present invention, in a grinding machine that grinds the surface of a flat plate-shaped workpiece, the residual thickness of the workpiece held on a holding table and conveyed through a straight conveyance path is measured. (7) a rotating member which is rotatably mounted around a predetermined rotational axis and has a contact element at one end and a detected element at the other end; biasing means for biasing the rotating member in a direction in which the rotating member projects into the conveying path of the object to be ground held on the holding table;
a non-contact detector disposed opposite to the detected element for detecting a distance from the detected element; By bringing the elements into contact, the distance between the detector and the detected element is made to correspond to the residual thickness of the object to be ground.
An apparatus for measuring the residual thickness of a ground object is provided.

<Preferred specific examples of the invention> A more detailed explanation will be given below with reference to the accompanying drawings.

FIG. 1 schematically illustrates an example of a grinding machine to which a grinding object residual thickness measuring device constructed according to the present invention is applied. The illustrated grinding machine, generally designated by the number 2, for grinding the surface of a semiconductor wafer has a support disk 4. Grinding wheel assemblies 6A, 6B and 6C, semiconductor wafer loading means8. It is also equipped with semiconductor wafer unloading means.

Referring to FIG. 2 together with FIG. 1, the illustrated support disk 4 is rotatable about a central axis @121 that extends substantially vertically (in FIG. 1, extends substantially perpendicular to the plane of the paper). It is installed.

On this support disk 4, at least one holding table 14, in the case shown, twelve holding tables 14 are arranged at equal intervals in the circumferential direction. Advantageously, the radial distance from said central axis 12 to each of the holding tables 14 is substantially the same. The support disk 4 is drive-coupled to a rotational drive source 16 such as an electric motor through a suitable transmission mechanism (not shown) 9 and is rotationally driven in the direction shown by the arrow 18, thus supporting the holding table. 14
each holding table 14 is moved in the direction shown by arrow 18 through a circular movement path shown by dash-dotted line 20.
Each has air permeability at least in its central portion, and is selectively communicated with a vacuum source (not shown), so that the semiconductor wafer Wt-
Holds by adsorption.

The grinding wheel assemblies 6A, 6B, and 6C are arranged opposite to and above the support disk 4. Although there may be one, two, or more than four grinding wheel assemblies, in the illustrated embodiment, three grinding wheel assemblies 6A, 6B, and 6C are arranged in the direction of rotation 18 of the support disk 40;
Therefore, the holding table 14 is spaced apart from each other in the direction of the circular movement path 20. Advantageously, the radial distance from the central axis 12 of the support disc 4 to each of the grinding wheel assemblies 6A, 6B and 6C is substantially the same. Each of the grinding wheel assemblies 6A, 6B, and 6C has support shafts 22A, 22B, and 22C attached to the grinding wheel assemblies 6A, 6B, and 6C so as to be movable in the vertical direction and rotatable about a central axis extending substantially vertically, and the support shafts 22A, 2
A grinding wheel 24A is detachably attached to the lower ends of 2B and 22C.

Contains 24B and 24C. Support shaft 22A.

Each of 22B and 22C is connected to a rotary drive source 26A, such as an electric motor, via an appropriate transmission mechanism (not shown).
26B and 26C, and is rotated at high speed in the direction shown by arrow 28. In addition, the support shaft 22A,
Each of 22B and 22C is also drivingly connected to a positioning drive source 30A, 30B and 30C, conveniently a pulse motor, via a suitable transmission mechanism (not shown) 1. Drive sources 30A, 30B and 3
Due to the action of 0C, it is moved finely in the vertical direction and positioned at the desired position. Grinding wheel 24A, 2
Grinding blade 32A, each of 4B and 24C is conveniently annular in shape formed by electrodepositing or otherwise bonding natural or synthetic diamond abrasive grains or superabrasive grains such as cubic boron nitride. , 32B and 32C.

Continuing the explanation with reference to FIG. 1, the semiconductor wafer loading means 8 has a swing arm 34 and a suction device 36 attached to the tip of the swing arm 34. The swing arm 34 is reciprocated and pivoted between an adsorption position shown by a two-dot chain line and a detachment position shown by a solid line, and the adsorption device 36 is selectively communicated with a vacuum source (not shown). Semiconductor wafer wt-adsorbs to the lower surface. Semiconductor wafers W whose surfaces are to be ground are sequentially fed, for example, from a storage cassette (not shown) onto the carry-in table 38 by a belt conveyor mechanism (not shown) or the like. Then, the semiconductor wafer carrying means 8 transfers the support disk 4 from the carrying table 38 to the loading area indicated by the number 40 by the arrow 18.
It is carried in in synchronization with the rotation in the direction indicated by the required rotation, and is placed on the holding table 14.

The semiconductor wafer unloading means 10 has a rotating arm 42 and a suction device 44 attached to the tip of the rotating arm 42. The rotating arm 42 is reciprocally pivoted between an adsorption position shown by a two-dot chain line and a detachment position shown by a solid line, and the adsorber 44 is selectively communicated with a vacuum source (not shown) so that its A semiconductor wafer W is attracted to the lower surface. Such a semiconductor wafer transport means lO has a rotating arm 4.
2 is reciprocally rotated in synchronization with the rotation of the support disk 4 in the direction shown by the arrow 18, and the semiconductor wafer W whose surface has been ground is held on a holding table in the take-out area shown by number 46. 14 and carry it out to the pedestal 48. The semiconductor wafer WFi placed on the pedestal 48 is cleaned by an appropriate cleaning means (not shown), thereby removing grinding debris. Thereafter, the semiconductor wafer 1 is removed from the pedestal 48 by means of a suitable transfer means (not shown) which may consist of a belt conveyor mechanism or the like.
W is transported, for example into a storage cassette (not shown)
will be stored in.

In the grinding machine 2 as described above, the following actions are sequentially performed in accordance with the rotation of the support disk 4, which is rotated in the direction indicated by the arrow 18. First, in a cleaning zone indicated by the number 50, the surface of the holding table 14 is cleaned (by which grinding is removed from the surface of the holding table 14) by suitable cleaning means (not shown) which may be of a form known per se. debris is removed). Next, in the above-described placement area 40, the semiconductor wafer/%W is placed on the holding table 14 and held there by the semiconductor wafer loading means 8 with the surface to be ground facing upward. The semiconductor wafer W is thus moved along with the holding table 14 substantially parallel to its surface in a predetermined direction, ie in the direction indicated by the arrow 18 along the circular movement path 20 of the holding table 14. Thereafter, in a first grinding zone indicated by numeral 52, the grinding blade 32A of the rotating grinding wheel 24A in the grinding wheel assembly 6A acts on the surface of the semiconductor wafer W to grind it; In a second grinding zone, indicated at 54, the grinding blade 32B of the rotating grinding wheel 24B in the grinding wheel assembly 6B acts on the surface of the semiconductor wafer/%W to further grind it, and In the third grinding zone indicated by numeral 56, the grinding blade 32C of the rotating grinding wheel 24C in the grinding wheel assembly 6C cuts the semiconductor wafer/%W.
The above-mentioned 1. acts on the surface to further grind it. Second
When the semiconductor wafers W are ground in the third grinding zones 52, 54 and 56, appropriate coolant injection means (not shown) attached to the grinding wheel assemblies 6A, 6B and 6C are used. A cooling liquid such as tap water is injected from the grinding blade 32A.

32B and 32C and the semiconductor Ueno-W are cooled. The grinding direction, i.e. the circular movement path 2 of the holding table 14
The grinding blades 32A, 32B, and 32C of the grinding wheel assemblies 6A, 6B, and 6C, which are sequentially located in the direction indicated by the arrow 18 along 0, have smaller grain sizes as they are located downstream in the grinding direction. Formed from abrasive grains9
(Therefore, the grain size of the abrasive grains in the grinding blade 32B is smaller than that of the abrasive grains in the grinding blade 32A, and the grain size of the abrasive grains in the grinding blade 32C is smaller than that of the abrasive grains in the grinding blade 32A.
It is advantageous that the grinding roughness of the surface of the semiconductor wafer W is gradually reduced toward the downstream side when viewed in the grinding direction.

It is convenient that the grinding depth of the surface of the semiconductor wafer W is also gradually reduced toward the downstream side when viewed in the grinding direction. After passing through the third grinding zone 56, the holding table 14 is communicated with a source of liquid, such as water (not shown), and the liquid flowing onto the holding table 14 causes the semiconductors on the holding table 14 to be The wafer W is levitated.

Then, in the take-out area 46, the semiconductor wafer carry-out means 10 takes out the semiconductor wafer W whose surface has been ground from the holding table 14.

The above-described configuration and operation of the illustrated grinding machine 2 are merely an example of a grinding machine to which a grinding object residual thickness measuring device configured according to the present invention is applied, and therefore,
Details regarding the configuration and operation of the illustrated grinding machine 2 as described above are omitted in this specification.

In the grinding machine 2 as described above, in order to make the thickness of the semiconductor wafer W whose surface has been ground to a required value with sufficient precision, the grinding wheel disposed in the third grinding area 56 must be used. It is important to adjust the vertical position of the grinding wheel 24C in the assembly 6C, and more specifically, the vertical position of the lower end of the grinding blade 32C, with sufficient precision. Moreover, the grinding blade 32A can be used without causing cracks or grinding defects on the semiconductor wafer W.

In order to sufficiently grind the surface of the semiconductor wafer W without causing damage to 32B and 32C, the grinding wheel 24A in the grinding wheel assembly 6AK disposed in the first grinding area 52 must be The vertical position and the vertical position of the grinding wheel 24B in the grinding wheel assembly 6B disposed in the second grinding area 54 are also
It is desirable to make adjustments with sufficient precision. Adjustment of the vertical positions of the grinding wheels 24A, 24B, and 24C can be performed in a so-called in-process process depending on the grinding process, since the grinding blades 32A, 32B, and 32C are damaged by the grinding process. desired. In order to meet such demands, in the illustrated grinding machine 2, a downstream portion of each of the first to third grinding zones 52, 54 and 56, as viewed in the direction of rotation of the support disk 4 as indicated by the arrow 18, is provided. The first to third detection areas 58, 60 and 62 on the side
A grinding object residual thickness measuring device 64A, 64B, and 64C constructed according to the present invention is disposed in each of the ground objects.

These measuring devices 64A, 64B and 64C measure the residual thickness of the semiconductor wafer W after being ground by the grinding wheels 24A, 24B and 24C, respectively, and therefore the vertical positions of the grinding wheels 24A, 24B and 24C.

Measuring devices 64A, 64B, and 64C may have substantially the same configuration, and therefore only the configuration of measuring device 64A will be described in detail below.

Referring to FIG. 3, the illustrated measuring device 64A includes an abbreviated mounting bracket 66. As shown in FIG. The upper end of this mounting bracket 66 is attached to a stationary support frame 67 (a third
(only a portion of which is shown in the figure). A support block 68 is attached to the lower end of the mounting bracket 66 by an appropriate mounting means (not shown) so that its position can be freely adjusted in the downward direction. The lower end ttX of the support block 68 is also made to protrude downward, and a box-shaped measuring device frame 70 with an open bottom is fixed to the lower end of the support block 68. This frame body 70 includes an upper wall 72 identified at the lower end of the support block 68, and a front wall 74. Rear wall 76 and both side walls 78 (
(Only one side wall is shown in FIG. 3). A substantially rectangular connecting block 80 is installed on the lower surface of the curved end of the earthen wall 72.
are connected by a fastening screw 82.

A pivot member, generally designated by the number 84, is attached to the connection block 80. Although the pivot member 84 can be formed from a single piece, the illustrated pivot member 84 is
and a second arm 90 fixed to the lower surface of the front end of the first arm 86 with a fastening screw 88. The upper surface of the front end of the first arm 86 is attached to the connecting block 80 via two mutually orthogonal leaf springs 92 and 94. Referring to FIG. 4 as well as FIG. 3, a rectangular notch 96 is formed in the center of the upper half of the leaf spring 92 which is arranged substantially vertically, and the leaf spring 94 is inserted into the rectangular notch 96. extends practically horizontally through the bottom edge of. The upper half of the leaf spring 92 is held between the rear surface of the connecting block 80 and the presser plate 100 fixed thereto by the fastening screw 98, and the lower half S of the leaf spring 920 is held between the front surface of the first arm 86 and It is held between a presser plate 104 fixed thereto by a fastening screw 102. The rear half of the plate spring 94 is held between the upper surface of the first arm 86 and a presser plate 108 fixed thereto by a fastening screw 106, and the front half of the plate spring 94 is held between the upper surface of the first arm 86 and a presser plate 108 fixed thereto by a fastening screw 106. and a presser plate 1]2 fixed thereto by fastening screws IIO, and thus the pivoting member 84 having the first arm 86 and the second arm 90 is placed under the plate spring 92. Due to the elastic deflection of the half part and the elastic deflection of the rear half of the leaf spring 94, the leaf spring 9
The connecting block 80 is attached to the connecting block 80 so as to be pivotable over a certain angular range about the mutually orthogonal axes 114 of the leaf springs 94 and 2 and the leaf springs 94 as the pivot axis.

In order to rotatably mount the rotating member 84, a normal mounting method such as using a bearing and a swivel shaft rotatably supported by the bearing can also be adopted. However, when such a mounting method is adopted, the detection area 58 (FIG. 1) where the measuring device 64A is placed contains grinding debris generated by grinding and droplets or liquid mist generated by the injection of coolant. Because of the existence of
40 There is a possibility that turning as required may be obstructed.

On the other hand, according to the unique mounting method using two leaf springs 92 and 94 that are orthogonal to each other as described above, it can be used for a long period of time regardless of the presence of grinding debris and liquid droplets or liquid mist. The required functions can be stably maintained.

The lower end of the front wall 74 of the frame body 70 is connected to the rear wall 76 and both side walls 7.
The second arm 90 of the pivoting member 84 passes below the front wall 74 and projects forward. Such second arm 9
The front end of the detection area 58 is located above and opposite to the holding table 14 passing therethrough and the semiconductor wafer W held thereon. A contact element 116 that hangs downward is screwed onto the front end of the second arm 90. This contact element 116 has a ball 118 mounted at its lower end, which ball 118 is brought into contact with the surface of the semiconductor wafer W whose residual thickness is to be measured, as will be mentioned later, if desired. Instead of forming the contact element 116 and the arm 90 of w, 2 from separate pieces, they can also be formed in one piece.

On the other hand, a detected element 122 is fixed to the upper surface of the rear end of the first arm 86 of the rotating member 84 with a fastening screw 120 . If desired, sensed element 122 can be integrally formed with first arm 86. The above detected object 513
Corresponding to 122, a non-contact detector 124 is mounted on the upper wall 72 of the frame 70. This detector 124 is a cylindrical casing 12 having a male thread formed on its outer circumferential surface.
6, and is attached to the upper wall 72 at 11 positions in the vertical direction by screwing the fixing nuts 128 and 13 (1) into the casing 126 from the upper surface side and the lower surface side of the upper wall 72. The detector 124 has a detection surface 132 located close to the surface of the detected element 1220 at its lower end, and detects the distance between the surface of the detected element 122 and the detection surface 132.Such detection As the detector 124, a well-known eddy current type non-contact detector is suitable, which functions properly even in an environment where droplets or liquid mist generated by the injection of coolant exists. In the case of an eddy current non-contact detector, it is important that the detected element 122 is made of a conductive material such as stainless steel. and the surface of the detected element 1220 made of conductive material.In the illustrated example, as will become clear from the description later, the semiconductor wafer W to be measured is Corresponding to the residual thickness of
Contact element 11 provided on the front note of second arm 90
6 is defined in the vertical direction, and therefore the first arm 86
and the pivot axis M of the pivot member 84 consisting of the second arm 90
A pivot angle about 114 is defined and thus the second
The vertical position of the detected element 122 provided at the rear end of the arm 90, and therefore the distance between the detection surface 132 of the detector 124 and the surface of the detected element 122 is defined. Therefore, in order to measure the residual thickness of the semiconductor wafer W with sufficient precision, the detection surface 13 of the detector 124 should be adjusted sufficiently precisely in response to changes in the vertical position of the contact element 116.
It is important that the distance between the detected element 1220 and the detected element 1220 surface is varied.

In order to satisfy such requirements, the surface of the detected element 1220 is made spherical, and its curvature is similar to that of the rotating member 8.
It is set to a value that compensates for variations in the distance between the detection surface 132 of the detector 124 and the surface of the detected element 122 caused by the change in the rotation angle itself.

In addition, the distance t1 from the pivot axis 114 to the center of the lower surface of the contact element 116 and the distance t1 from the pivot axis 114 to the detected element 122
The distance t2 to the center of the surface is made equal. Therefore, when the contact element 116 moves in the vertical direction, the distance between the detection surface 132 of the detector 124 and the surface of the detected element 122 is changed with sufficient precision by a distance equal to the distance of the movement.

The measuring device 64A#'i further moves the rotating member 84 to the third
In the figure, the contact element 116 is optically clockwise, so that the contact element 116 is aligned with the holding table 14 and the semiconductor wafer WL7 held thereon.
It includes a biasing means 134 that protrudes into the conveyance path, contacts the semiconductor wafer W, and biases in the wetting direction. The illustrated small chewing means 134 is comprised of a tension coil spring member connected at its upper end to the upper wall 72 of the enclosure 70 and at its lower end to the first arm 86 of the pivot bracket 84. If desired, the biasing means 134 can be constructed from a suitable hydraulic cylinder mechanism or the like.

The illustrated measuring device 64AK also includes a limiting means [36] for limiting the pivoting of the pivoting member 84, which is biased clockwise in FIG. It is being This restriction means 1
36 screw members 138 are screwed onto the upper wall 72 of the frame 70. The screw member 138 has an upper JI of 1.72
84 and extends downwardly beyond the
By contacting the upper surface of the first arm 86 of the member 84, the rotation of the member 84 in the clockwise direction [
The movement is measured: R. Swivel part 84C] Swivel F) 1 - For the open position, loosen the stopper 140 and tighten the screw 1 of material 138.
- Can be adjusted to 9.1 by adjusting the downward position. It is convenient that the turning limit position is set such that the residual thickness of the semiconductor wafer W is zero, and therefore the contact element 116 is in contact with the surface of the holding table 14 that does not hold the # conductor wafer w'6. . Even at such a turning limit position, the detection surface 132 of the detector 124 and the surface of the detected element 1220 do not come into contact with each other, and a gap of about 0.1 clear exists between them. The illustrated measuring device 1lt64A further includes a restraining means 142.
Contains. This restraint means 142 is composed of a fluid pressure cylinder mechanism screwed onto the earthen wall 72 of the frame 70, and its piston rod 144 is connected to the earthen wall 721i-
It extends downward beyond. The hydraulic cylinder mechanism is connected to a source of pressure fluid (not shown) via a suitable control valve (not shown). When pressure fluid is supplied to the head side of the hydraulic cylinder mechanism, the piston rod 144
is lowered to the restraining position shown by the two-dot chain line. Thus, the piston rod 144 presses against the upper surface of the first arm 86 of the pivot member 84, thereby causing the pivot member 84 to
is pivoted to a non-detection position shown by a two-dot chain line 84' against the biasing action of the biasing means 134. In this non-detection position, the contact element 116 is moved upwardly away from the transport path of the semiconductor wafer W held on the holding table 14, and is moved toward the head side of the fluid pressure cylinder mechanism without interfering with the semiconductor wafer W. When the supply of pressure fluid is stopped, the piston rod 144 is raised to the unrestrained position shown in solid line by the elastic biasing action of a built-in spring member (not shown). Thus, the piston rod 144
is separated from the first arm 86 of the rotating member 84, and thus the restriction of the rotating member 84 to the non-detection position is released.

Instead of constructing the restraint means 142 from a hydraulic cylinder mechanism, the restraint means 142t-could also be constructed from any other suitable mechanism, such as a solenoid mechanism, if desired.

Next, referring to FIG. 1 together with FIG. 3, the operation of the measuring device 64A as described above will be summarized and explained. Normally, the restraint means 142 is in the activated state, i.e. the piston rod 144
is lowered to a restraining position shown by a two-dot chain line, and the rotating member 84 is placed at a non-detection position shown by a two-dot chain line 84. However, when the semiconductor wafer . condition, i.e. piston rod l 44
is raised to the unrestrained position shown by the solid line, and is forced into a restrained state. In this way, the restraint of the swinging part +484 to the non-detection position is released, and the swinging member 84 is pivoted clockwise in FIG. The lower surface of element 116 is brought into contact with the surface of semiconductor wafer W. Thus, the distance between the detection surface 132 of the detector 124 and the surface of the detected element 122 is set to a value corresponding to the residual thickness of the semiconductor wafer W, more specifically, the rotation limit of the rotation member 84 is indicated by the solid line in FIG. The value is set to be the sum of the initial gap between the two when in position plus the residual thickness of the semiconductor wafer and W. At this point, detector 124 is activated to measure the distance between its surface 132 and the surface of detected element 122 and generate an output voltage indicative of the residual thickness of semiconductor wafer W.

Since the contact pressure between the contact element 116 and the semiconductor wafer W may be sufficiently small, and the contact time may be a little, there is no risk that the semiconductor wafer W will be damaged by this. The output voltage generated by the detector 124 is supplied to the control circuit 146.

The control circuit 146 compares the supplied voltage with a predetermined reference voltage, and energizes the position adjustment drive source 30A by a required amount as necessary, thus increasing the support shaft 2 of the grinding wheel assembly 6A.
2Ai is lowered (or raised) to finely adjust the vertical position of the grinding wheel 22A with sufficient precision.

The measuring device 64B measures the residual thickness of the semiconductor wafer W ground by the grinding wheel 24B of the grinding wheel assembly 6B in the second detection area 60. Then, the vertical position of the grinding wheel 24B is finely adjusted with sufficient precision according to the measured value by the above-described continuous feedback method. The measuring device 64C measures the residual thickness of the semiconductor wafer W ground by the grinding wheel 24C of the grinding wheel assembly 6C in the third detection area 62. Then, according to the measured value, the grinding wheel/2
The vertical position of 4C is finely adjusted with sufficient precision by the above-mentioned feedback method.

Although one specific example of the residual thickness measuring device for a workpiece constructed according to the present invention has been described in detail in relation to a specific type of grinding machine, the present invention is not limited to such specific example. Needless to say, various changes and modifications can be made without departing from the scope of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a simplified plan view showing an example of a grinding machine to which a grinding object residual thickness measuring device configured according to the present invention is applied. 2 is a simplified side view of the grinding machine shown in FIG. 1; FIG. FIG. 3 is a side view, partially in cross section, of a specific example of the residual thickness measuring device for a ground workpiece constructed according to the present invention. FIG. 4 is a perspective view showing two mutually orthogonal leaf springs used in the apparatus for measuring the residual thickness of a ground object shown in FIG. 3. 2...Grinding machine 4...Support discs 6A, 6B and 6C...Grinding wheel assembly 8...Semiconductor wafer/carrying means 10...Semiconductor wafer/carrying means 14...Holding table 24A, 24B and 24C... grinding wheel 64A,
64B and 64C...Grinded object residual thickness measuring device 70...Measuring device frame 84...Swivel members 92 and 94...Plate spring 116...Contact element 122...Detected element 124 ... Non-contact detector 134 ... Biasing means 136 ... Limiting means 142 ... Restraining means W ... Semiconductor wafer...

Claims (1)

[Claims] 1. In a grinding machine that grinds the surface of a flat plate-shaped object to be ground,
A residual thickness measuring device for a ground workpiece held on a holding table and conveyed through a predetermined conveyance path; a pivoting member having a contact element at one end and a detected element at the other end; biasing the pivoting member in a direction in which the contact element projects into the transport path of the workpiece held on the holding table; and a non-contact detector disposed opposite to the detected element for detecting a distance between the detected element and the object to be ground held on the holding table. A residual thickness of a workpiece, characterized in that the distance between the detector and the detected element is made to correspond to the residual thickness of the workpiece by bringing the contact element into contact with the surface of the workpiece. Measuring device. 2. The device for measuring the residual thickness of an object to be ground according to claim 1, wherein the object to be ground is a semiconductor wafer. 3. The detected element is made of a conductive material, and the detector is an eddy current non-contact detector whose output voltage changes depending on the distance from the detected element. or second
A device for measuring the residual thickness of a workpiece described in Section 1. 4. A limiting means for limiting the pivoting of the pivoting member in the direction in which the contact element protrudes into the conveyance path of the workpiece held on the table to a predetermined limit position. The device for measuring the residual thickness of a ground object according to any one of items 1 to 3. 5. The predetermined limit position corresponds to zero residual thickness of the workpiece;
A residual thickness measuring device for a workpiece to be ground according to claim 4. 6. A restraint that releasably restrains the rotating member against the biasing action of the biasing means in a non-detection position where the contact element is separated from the conveyance path of the object to be ground held on the holding table. An apparatus for measuring residual thickness of a workpiece according to any one of claims 1 to 5, comprising means. 7. The apparatus for measuring the residual thickness of a ground object according to claim 6, wherein the restraint means temporarily releases the restraint of the rotating member when the ground object is transported to a predetermined measurement position. 8. The apparatus for measuring the residual thickness of a ground object according to claim 6 or 7, wherein the restraining means includes a fluid pressure cylinder mechanism. 9. The device for measuring the residual thickness of a ground object according to any one of claims 1 to 8, wherein the detected element has a spherical surface with a predetermined curvature. 10. Claim 1, wherein the pivoting member is attached to the frame via two leaf springs that are orthogonal to each other, and the pivot axis is the orthogonal line between the two leaf springs. The apparatus for measuring the residual thickness of a ground object according to any one of items 9 to 9. 11. The device for measuring the residual thickness of a ground object according to any one of claims 1 to 10, wherein the biasing means is constituted by a spring member.