JP2012146868A - Processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing device capable of reliably measuring thickness of a workpiece regardless of a kind of a workpiece.SOLUTION: A processing device 10 presses a lower surface 37a of a grindstone 37 to an upper surface 4a of a ring reinforcing part 4 of a workpiece 1 held by holding means 20, and grinds it. Height of the lower surface 37a of the grindstone 37 is detected by measurement means 50, and the thickness of a workpiece 1 is measured while a height position of the lower surface 37a is a height position of an upper surface 4a of the workpiece 1.

Description

  The present invention relates to a processing apparatus for grinding a thin plate-like workpiece such as a semiconductor wafer.

  In the manufacturing process of a semiconductor device, in order to obtain a target thickness of a device, it is generally performed by grinding and thinning the back surface at the stage of a wafer before being divided into a large number of devices. Wafer grinding proceeds while measuring the thickness, but as a means of measuring the thickness in such a form, a contact type that detects the displacement of the thickness while bringing the measuring probe into contact with the work surface. One is known (Patent Document 1).

  On the other hand, in recent years, wafers have been processed even thinner due to the remarkable thinning of devices. However, since the rigidity decreases when the thickness is reduced, handling in the process after thinning becomes difficult or easily broken. Occurs. Therefore, the circular device formation area where a large number of devices are formed is ground from the back side to the desired thickness, and the outer peripheral part is relatively thick, and the entire wafer is processed into a substantially concave shape with the back side recessed. (Patent Document 2). In such a wafer, a thick outer peripheral portion serves as a ring reinforcing portion to ensure rigidity, and it is easy to handle and difficult to break.

JP 2000-6018 A JP 2007-19461 A

  The wafer processed into the substantially concave shape in the cross section is finally ground and removed from the ring reinforcing portion on the outer peripheral portion. Therefore, at the time of grinding, the probe of the contact-type thickness measuring means is used in contact with the back surface of the ring reinforcing portion. Therefore, it is necessary for the ring reinforcing portion to have a certain width in order to ensure contact with the probe. However, if the width of the ring reinforcing portion is increased, the device formation area is reduced and the width of the device is reduced from one wafer. Since the number of acquired devices is reduced, the width of the ring reinforcing portion is preferably as small as possible. However, if the width of the ring reinforcing portion is small, it is difficult to make the probe surely contact with each other, which causes a problem that thickness measurement becomes difficult. Further, when the optical non-contact thickness measuring means is used, there arises a problem that measurement becomes difficult when the detection surface of the workpiece does not sufficiently reflect the detection light. Thus, conventionally, even if the thickness measuring means is a contact type or a non-contact type, it may be difficult to measure the thickness depending on the type of workpiece.

  The present invention has been made in view of the above circumstances, and a main technical problem thereof is to provide a machining apparatus capable of reliably measuring the thickness of a workpiece regardless of the type of the workpiece.

  The processing apparatus of the present invention includes a holding means for holding the surface side of a workpiece, a tool for pressing the lower surface of the grindstone against the upper surface of the workpiece held by the holding means, and a spindle for rotatably supporting the tool And a measuring device for measuring the thickness of the workpiece during grinding, wherein the measuring means detects the height position of the lower surface of the grindstone, and the lower surface of the grindstone The thickness of the workpiece is measured with the height position of the workpiece as the height position of the workpiece upper surface.

  According to the present invention, the measuring means measures the thickness of the workpiece based on the height position of the lower surface of the grindstone that contacts the upper surface of the workpiece and grinds the upper surface. The thickness of the workpiece can be measured regardless of various factors that cause measurement difficulty by the conventional thickness measuring means such as the reflection state.

  In the present invention, the work has a back surface corresponding to the device formation region ground to form a ring reinforcing portion on the outer periphery, the work upper surface is the upper surface of the ring reinforcing portion, and the thickness of the work is the thickness of the ring reinforcing portion. Including the form that is. In this embodiment, even if the width of the ring reinforcing portion is narrow, the thickness of the ring reinforcing portion can be reliably measured.

The work referred to in the present invention is not particularly limited. For example, semiconductor wafers made of silicon, gallium arsenide (GaAs), silicon carbide (SiC), etc., ceramics, glass, sapphire (Al ₂ O ₃ ) -based inorganic materials Substrate, plate-like metal or resin ductile material, flatness of micron order to submicron order (TTV: total thickness variation-the entire work surface of the workpiece measured in the thickness direction based on the work surface of the work Examples of various processing materials that require a difference between the maximum value and the minimum value).

  According to the present invention, there is an effect that a machining apparatus capable of reliably measuring the thickness of a workpiece regardless of the type of workpiece is provided.

BRIEF DESCRIPTION OF THE DRAWINGS (a) The perspective view which shows the back surface side of the workpiece | work ground by the processing apparatus which concerns on one Embodiment of this invention, (b) The top view which shows the surface side, (c) It is sectional drawing which turned up the back side. . 1 is an overall perspective view of a processing apparatus according to an embodiment. It is a side view which shows the state which grinds the workpiece | work while measuring the thickness of a workpiece | work with the same processing apparatus. It is a side view for demonstrating the principle which measures the thickness of a workpiece | work with the measurement means which concerns on one Embodiment.

Hereinafter, a processing apparatus according to an embodiment of the present invention will be described.
(1) Workpiece FIG. 1 shows a disk-shaped work 1 such as a semiconductor wafer whose back surface is ground by the processing apparatus 10 of this embodiment shown in FIG. First, the workpiece 1 will be described. As shown in FIG. 1B, a large number of devices 2 on which electronic circuits are formed are partitioned on the surface 1 a of the workpiece 1 by the division lines 3. In the workpiece 1, most of the circular shape excluding the outer periphery is a device formation region 2 </ b> A in which a rectangular device 2 that is effective as a product is formed. As shown in FIGS. 1A and 1C, the workpiece 1 in this case is formed in a substantially concave shape in cross section by grinding a portion corresponding to the device formation region 2A of the back surface 1b, and forming a device on the outer periphery. A ring reinforcing portion 4 that is thicker than the region 2A and protrudes toward the back surface 1b is formed. For the purpose of protecting the electronic circuit, the workpiece 1 is transported by holding the ring reinforcing portion 4 with the protective tape 5 attached to the surface 1a (not attached in FIG. 1B).

(2) Processing Device The processing device 10 will be described with reference to FIGS.
In the processing apparatus 10, as shown in FIG. 2, the workpiece 1 is conveyed by an operator or the like as indicated by an arrow to the disk-shaped holding means 20 provided on the base 11, and is placed on the upper surface of the holding means 20. On the formed circular holding surface 21, the back surface 1 b side is exposed upward, and the front surface 1 a side is placed concentrically via the protective tape 5.

  The holding means 20 is supported on a movable table 22 provided on the base 11 so as to be movable in the X direction so as to be rotatable about the Z direction (vertical direction) as the rotation axis direction. The holding means 20 is of a generally well-known vacuum chuck type, and holds and holds the workpiece 1 on the holding surface 21 set horizontally by negative pressure action via the protective tape 5.

  The workpiece 1 held on the holding surface 21 of the holding means 20 is moved in the X direction by the moving table 22, so that the front side (X1 side) loading / unloading position and the rear (X2 side) machining position in FIG. 2. Can be reciprocated between. The base 11 is provided with a moving mechanism for moving the moving base 22 in the X direction, and the moving base 22 is provided with a rotation driving mechanism for rotating the holding means 20 (all not shown). On both sides of the moving table 22 in the moving direction, a telescopic bellows-like cover 24 that covers the moving path 23 of the moving table 22 and prevents grinding scraps from falling into the base 11 is provided.

  A column 12 is erected on the rear side of the processing position of the base 11. A slider 14 is attached to the front surface of the column 12 via a pair of Z-axis guides 13 so as to be movable up and down along the Z direction, and a grinding means 30 is fixed to the slider 14.

  The grinding means 30 has a spindle 31 whose axial direction extends in the Z direction. The spindle 31 has a rotating shaft 33 incorporated in a cylindrical housing 32. A flange-shaped mount 34 is formed at the lower end of the rotating shaft 33, and a grinding tool 35 is detachably fixed to the mount 34. A motor unit 38 that rotationally drives the rotating shaft 33 is provided at the upper end of the housing 32.

  The tool 35 is a tool in which a number of grindstones 37 are annularly arranged and fixed to the outer peripheral portion of the lower surface of a grinding wheel 36 that is detachably fixed to the lower surface of the mount 34. The grindstone 37 corresponds to the workpiece 1, for example, a diamond grindstone formed by solidifying diamond abrasive grains with a binder such as metal bond or resin bond. The tool 35 is rotationally driven integrally with the rotary shaft 33 by the motor unit 38.

  In the grinding means 30, the housing 32 is fixed to the slider 14 via the holder 39 with the mount 34 disposed below. The slider 14 is provided with a ball screw 41 that is disposed between the pair of Z-axis guides 13 and is coupled to the slider 14 so as to be screwed together, and a motor 42 that rotationally drives the ball screw 41. It is driven up and down by the feeding means 40. That is, the grinding means 30 is moved up and down integrally with the slider 14 by the processing feed means 40.

  The workpiece 1 positioned at the processing position is ground by the grinding means 30 until the upper surface 4a of the ring reinforcing portion 4 exposed upward is removed, and the whole is formed with the device forming region 2A. Processed to the same thickness. Grinding by the grinding means 30 rotates the holding means 20 in one direction to rotate the workpiece 1, operates the motor unit 38 to rotate the tool 35, and rotates the tool 35 together with the slider 14 by the work feeding means 40. It is made by pressing the lower surface 37a of the grindstone 37 of the tool 35 that feeds and rotates against the upper surface 4a of the ring reinforcing portion 4. In grinding, a grinding fluid is supplied to the workpiece 1 from a grinding fluid supply means (not shown) for the purpose of lubrication, cooling, cleaning, and the like.

  The thickness of the workpiece 1 in this case is the thickness of the ring reinforcing portion 4, and the thickness is disposed between the moving path 23 on the upper surface of the base 11 and the column 12 in the vicinity of the processing position. It is measured by the measuring means 50. The machining feed operation of the grinding means 30 by the machining feed means 40 is controlled based on the thickness measurement value measured by the measurement means 50. When the thickness measurement value reaches the target value, the grinding operation is terminated. Thereafter, the movable table 22 moves in the X1 direction, and the workpiece 1 is returned to the loading / unloading position. Then, the workpiece 1 is unloaded from the holding means 20 and moved to the next step (for example, the step of dividing the device 2).

(3) Measuring means Next, the measuring means 50 according to the present invention will be described.
The measuring means 50 is disposed between the moving path 23 and the column 12 on the upper surface of the base 11 as described above, but the measuring means 50 is directly below the grindstone 37 of the grinding wheel 36 as shown in FIG. Is positioned. The measuring means 50 irradiates the measurement object with the detection light beam, receives the reflected light from the measurement object, evaluates and calculates the received light, and converts it into a distance by a generally known non-contact optical distance. It is a sensor. In this embodiment, the object to be measured is the lower surface 37a of the grindstone 37, and the detection light beam is irradiated toward the lower surface 37a vertically above.

  In the measurement means 50, as shown in FIG. 4, the detection light beam L is irradiated vertically upward from the measurement means 50 toward the lower surface 37a of the grindstone 37. Then, the distance D to the height position of the lower surface 37a of the grindstone 37 pressed against the upper surface 4a of the ring reinforcing portion 4 of the workpiece 1 is detected as the height position of the lower surface 37a of the grindstone 37. Then, the thickness of the workpiece 1 is measured with the height position of the lower surface 37 a of the grindstone 37 as the upper surface height position of the workpiece 1. That is, as shown in FIG. 4, the distance D, the distance H from the measurement means 50 that is a constant value to the height position of the holding surface 21 of the holding means 20, and the thickness P of the protective tape 5 that is grasped. Based on the above, the thickness T of the workpiece 1 being ground is determined. Specifically, the thickness of the work 1 is obtained by T = D− (H + P). In this way, the thickness of the ring reinforcing portion 4 of the workpiece 1 that gradually decreases during grinding is measured one by one by the measuring means 50, and the grinding is finished when the thickness reaches the thickness of the device forming region 2A. .

  According to the measuring means 50 of the processing apparatus 10 of the present embodiment, the workpiece 1 is adjusted based on the height position of the lower surface 37a of the grindstone 37 that contacts the upper surface 4a of the ring reinforcing portion 4 of the workpiece 1 and grinds the upper surface 4a. The thickness is measured. For this reason, even when the width of the ring reinforcing portion 4 is small and it is difficult to contact the probe of the contact-type thickness measuring means, for example, the thickness of the workpiece 1 can be reliably measured. As a result, it is possible to contribute to increasing the number of devices acquired from one work by making the device formation region 2A as large as possible.

  Further, according to the measuring means 50 of the present embodiment, the lower surface of the grindstone 37, for example, even if the thickness of the workpiece is difficult to measure with the optical non-contact thickness measuring means, the upper surface of the workpiece is difficult to reflect light. Since the thickness is measured based on the height position of 37a, the thickness of the workpiece 1 of that kind can be measured. That is, according to this embodiment, the thickness of the workpiece can be reliably measured regardless of the type of workpiece.

DESCRIPTION OF SYMBOLS 1 ... Work, 1a ... Work surface, 1b ... Back surface of work, 2A ... Device formation area, 4 ... Ring reinforcement part, 10 ... Processing apparatus, 20 ... Holding means, 30 ... Grinding means, 31 ... Spindle, 35 ... Tool 37 ... Whetstone, 37a ... Lower surface of the grindstone, 50 ... Measuring means.

Claims (2)

Holding means for holding the surface side of the workpiece;
A grinding means having a tool for grinding by pressing the lower surface of the grindstone against the work upper surface held by the holding means, and a spindle for rotatably supporting the tool;
Measuring means for measuring the thickness of the workpiece during grinding,
The measuring means includes
A processing apparatus for detecting the height position of the lower surface of the grindstone and measuring the thickness of the workpiece with the height position of the lower surface of the grindstone as the workpiece upper surface height position. The workpiece is ground on the back surface corresponding to the device formation area, and a ring reinforcement is formed on the outer periphery.
The upper surface of the workpiece is the upper surface of the ring reinforcing portion,
The processing apparatus according to claim 1, wherein a thickness of the workpiece is a thickness of the ring reinforcing portion.

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