JP2006120796A - Manufacturing method of solid state imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a solid state imaging device capable of preventing the breakage to a wafer caused by a transparent fragment generated during cut off grinding, in carrying out cut off grinding of the transparent plate of the solid state imaging device aggregate consisting of transparent plates and a wafer of a solid state image pickup device joined with a very narrow gap. <P>SOLUTION: The manufacturing method of a solid state imaging device is provided with a process for forming many solid state image pickup devices 11A in a wafer 11, a process for forming a spacer 13 in a shape surrounding each solid state image pickup device 11A on a transparent plate 12, a process for forming two or more penetration long holes 12B leaving only the edge 12C of the transparent plate 12 between fellow spacers 13 of the transparent plate 12, a process for carrying out alignment and junction of the wafer 11 and the transparent plate 12, a process for dividing the transparent plate 12 corresponding to each solid state image pickup device 11A by performing cut off grinding to the transparent plate 12, and a process for dividing the wafer 11 corresponding to each solid state image pickup device 11A. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a solid-state imaging device, and more particularly to a method for manufacturing a solid-state imaging device in which a large number of chip size package (CSP) type solid-state imaging devices manufactured at the wafer level are individually divided.

  A solid-state imaging device composed of a CCD or a CMOS used for a digital camera or a mobile phone is increasingly required to be downsized. For this reason, the conventional large package in which the entire solid-state image sensor chip is hermetically sealed in a ceramic package or the like has recently been shifted to a chip size package (CSP) type having a size substantially equal to the size of the solid-state image sensor chip. .

  Under such circumstances, a sealing member (transparent glass plate) made of a transparent material in which a frame portion (spacer) is integrally formed on the lower surface edge portion is disposed only for the light receiving area of the solid-state imaging device chip, and the frame portion (spacer ) Has been proposed (see, for example, Patent Document 1).

  When the solid-state imaging device described in Patent Document 1 is collectively manufactured at the wafer level, a large number of solid-state imaging elements are first formed on a wafer (semiconductor substrate). On the other hand, a large number of frame portions (spacers) surrounding the light receiving area of the solid-state imaging device are integrally formed on a sealing member (transparent glass plate) made of a transparent material.

Next, this sealing member (transparent glass plate) is bonded to the wafer via a frame portion (spacer) to seal the light receiving area of each solid-state imaging device, and a stack in which a large number of solid-state imaging devices are formed at the wafer level. Manufacture the body. Next, the solid-state imaging device described in Patent Document 1 is obtained by dividing the stacked body into individual solid-state imaging devices.
Japanese Patent Laid-Open No. 07-202152

    However, Patent Document 1 described above does not describe any method for dividing a stacked body in which a large number of solid-state imaging devices are formed at the wafer level into individual solid-state imaging devices. However, generally, in order to divide a large number of semiconductor devices formed on a wafer into individual semiconductor devices, grinding and cutting with a dicing device is used.

  For this reason, for example, using a dicing machine, a disc-shaped grindstone (dicing blade) having a width necessary to expose the pad surface of the wafer is used, and the lowest point of the grindstone is the wafer above the pad and the transparent glass plate. A method is conceivable in which the transparent glass plate is ground and cut so as to pass through the gap formed between the two, and then the wafer portion is ground and cut with another thin disc-like grindstone (dicing blade).

  However, in the case of the method of grinding and cutting using such a grindstone, for example, when the height of the gap formed between the wafer and the transparent glass plate is as narrow as about 100 μm, FIG. 7A, and FIG. 7B showing a partially enlarged view of FIG. 7A, the glass fragments 12A generated during the grinding and cutting of the transparent glass plate 12 are grindstones when discharged. There is a serious problem that the wafer 11 is damaged by being caught in the gap between the wafer 52 and the wafer 11, scratched, and extremely dragged.

  The present invention has been made in view of such circumstances, and is a transparent glass of a solid-state imaging device assembly composed of a wafer of a solid-state imaging element and a transparent glass plate that are joined with an extremely narrow gap. A method of manufacturing a solid-state imaging device with a high yield is provided by providing a solid-state imaging device assembly grinding method capable of preventing wafer damage caused by transparent glass plate fragments generated during grinding and cutting when grinding and cutting a plate. The purpose is to provide.

  In order to achieve the object, a method of manufacturing a solid-state imaging device according to the present invention includes a step of forming a large number of solid-state imaging elements on a surface of a wafer, and the solid-state imaging element on a lower surface of a transparent flat plate bonded to the wafer. A step of forming a frame-shaped spacer having a predetermined thickness surrounding each solid-state image sensor at a corresponding location, and a through-hole that leaves only the peripheral edge of the transparent flat plate between the spacers of the transparent flat plate , A step of aligning the wafer and the transparent flat plate and joining them via the spacer, and grinding the peripheral edge of the previous transparent flat plate left when the through long hole is formed, Grinding the transparent flat plate in a direction perpendicular to the long holes, dividing the transparent flat plate so as to correspond to the individual solid-state image sensor, and dividing the wafer corresponding to the individual solid-state image sensor And that step, characterized in that it comprises a.

  According to the present invention, before joining a transparent flat plate on which a frame-shaped spacer surrounding the solid-state imaging device is formed to the wafer via the spacer, only the peripheral portion of the transparent flat plate is placed between the transparent flat plate spacers. Since the remaining through long hole is formed, it is not necessary to process the through long hole portion when grinding the transparent flat plate after joining. Therefore, at least the wafer surface below the through-hole portion is not damaged by glass fragments generated by grinding, and the yield reduction of the solid-state imaging device is suppressed.

  Further, the present invention is characterized in that, in the above invention, the step of forming a through hole in the transparent flat plate is performed by grinding. According to this, a through-hole can be easily formed in a transparent flat plate using the grinding device which divides | segments a transparent flat plate so that it may respond | correspond to each solid-state image sensor, without using a special apparatus.

  In the invention, the solid-state imaging device has wiring pads for external connection on two opposite sides outside the spacer, and the through-holes of the transparent flat plate expose the wiring pads. And a width necessary for exposing the wiring pad.

  According to this invention, since the wiring pad is exposed by the through hole of the transparent flat plate, there is no need to grind the transparent flat plate on the upper side of the wiring pad, and the wiring pad is damaged by the glass fragments generated by the grinding of the transparent flat plate. Is prevented.

  As described above, according to the manufacturing method of the solid-state imaging device of the present invention, the transparent glass plate of the solid-state imaging device assembly constituted by the solid-state imaging element wafer and the transparent glass plate joined with a narrow gap. Since the through-hole is formed in advance in the transparent glass plate, leaving only the peripheral edge of the transparent glass plate, at least the wafer surface below the through-hole portion is damaged by glass fragments generated by grinding. In other words, the yield reduction of the solid-state imaging device is suppressed.

  A preferred embodiment of a method for manufacturing a solid-state imaging device according to the present invention will be described below in detail with reference to the accompanying drawings. In each figure, the same number or symbol is attached to the same member.

  FIG. 1 is a flowchart showing a manufacturing process of a CSP type solid-state imaging device according to the present invention, and FIG. 2 is an explanatory diagram thereof. In the method for manufacturing a solid-state imaging device of the present invention, first, a large number of solid-state imaging elements 11A are formed on a semiconductor substrate (wafer) 11.

  A general semiconductor element manufacturing process is applied to manufacture the solid-state imaging device 11A. The solid-state imaging device 11A includes a photodiode that is a light receiving element formed on the wafer 11, a transfer electrode that transfers excitation voltage to the outside, and an opening. Light shielding film, interlayer insulating film, inner lens formed on the upper part of the interlayer insulating film, color filter provided on the upper part of the inner lens via an intermediate layer, provided on the upper part of the color filter via an intermediate layer The microelements composed of microlenses and the like are arranged in a planar array.

  Since the solid-state imaging device 11A is configured in this way, light incident from the outside is condensed by the microlens and the inner lens and irradiated to the photodiode, so that the effective aperture ratio is increased.

  Further, as shown in FIG. 2C, pads (wiring pads) 11B, 11B,... For wiring with the outside are formed on the two opposite sides of the solid-state imaging device 11A (step). S1).

  In parallel with the formation process of the solid-state imaging device 11A, a spacer 13 having a predetermined thickness in a frame shape surrounding each solid-state imaging device 11A is formed on a transparent glass plate (transparent flat plate) 12 as a sealing member.

  Since the wafer 11 is typically a single crystal silicon wafer, the material of the spacer 13 is preferably a material having physical properties similar to those of the wafer 11 and the transparent glass plate 12, such as a thermal expansion coefficient. Is preferred.

  The spacer 13 is formed by applying an adhesive 13A to the transparent glass plate 12, bonding a silicon plate as a spacer base material thereto, and performing surface grinding with a grindstone to reduce the thickness of the silicon plate to about 100 μm. To do. Next, a spacer 13 having a necessary shape is formed on the thinned silicon plate by using photolithography and dry etching technology (step S2). FIG. 2A shows the transparent glass plate 12 on which a large number of spacers 13 are thus formed.

  Next, as shown in FIG. 2 (b), only the peripheral edge of the transparent glass plate 12 is left between the adjacent spacers 13 of the transparent glass plate 12 in the direction in which the pads 11B, 11B,. A plurality of the long holes 12B, 12B,... Are formed only in one direction in the manner shown in FIG. The width of the through long hole 12B is formed to be a width necessary to expose the pad 11B.

  3A and 3B are explanatory views of a method of processing the through long hole 12B. FIG. 3A is a front sectional view, and FIG. 3B is an A-A ′ sectional view in FIG. The through holes 12B, 12B,... Are formed as follows. First, the transparent glass plate 12 is suction-mounted on the wafer table 51 of the dicing apparatus with the dicing sheet 53 attached to the lower surface with the surface on which the spacers 13 are formed facing upward.

  Next, a rotating dicing blade (grinding stone) 52 having a thickness of about 0.6 to 1.2 mm is lowered from the upper surface in the vicinity of the peripheral edge on one side of the transparent glass plate 12, and the cutting edge of the dicing blade 52 is moved to the dicing sheet 53. Cut feed to the position where it is slightly cut. Next, the dicing sheet 53 is ground and fed in the horizontal direction relative to the transparent glass plate 12 and is raised in the vicinity of the peripheral edge on the other side of the transparent glass plate 12.

  At this time, the relative movement of the dicing blade 52 with respect to the transparent glass plate 12 is as indicated by an arrow M in FIG. In addition, the uncut part is formed in the peripheral part of the transparent glass plate 12 by controlling the position of the start and end of the through long hole 12B.

  In this way, one through long hole 12B is formed, and then the dicing blade 52 is indexed by one pitch in the direction orthogonal to the grinding feed to form the next through long hole 12B. A number of through holes 12B, 12B,... Are formed on the entire surface of the glass plate 12 (step S3).

  FIG. 4 is a plan view showing the transparent glass plate 12 in which the through long holes 12B, 12B,. As shown in FIG. 4, a plurality of through-holes 12B, 12B,... Are formed on the entire surface of the transparent glass plate 12 by leaving uncut portions in the peripheral edge portion 12C.

  Next, the adhesive 13 </ b> B is applied to the end surfaces of the spacers 13 formed in large numbers on the transparent glass plate 12. The adhesive 13B is applied by a transfer method in which the spacer 13 of the transparent glass plate 12 is pressed against the adhesive 13B applied on a flat plate and the adhesive 13B is transferred to the end surface of the spacer 13.

  Next, the transparent glass plate 12 provided with the spacer 13 on one surface in this way is opposed to the wafer 11 and aligned with the wafer 11. The alignment is performed by providing an alignment mark on each of the wafer 11 and the transparent glass plate 12 in advance and overlaying the alignment mark on the transparent glass plate 12 on the alignment mark on the wafer 11.

  Next, the transparent glass plate 12 aligned with the wafer 11 is bonded to the wafer 11 via the spacer 13 and the adhesive 13B. Thereby, the solid-state imaging device 21 having a structure in which the gap portion 14 as shown in FIG. 2C is provided between the wafer 11 and the transparent glass plate 12 and the light-receiving portion of the solid-state imaging device 11A is sealed is obtained at the wafer level. A large number of formed laminates are manufactured (step S4).

  Next, the cutting edge of the dicing blade 52 having a thickness of about 0.6 to 1.2 mm is set to a height at which the cutting edge is cut into the gap 14 between the transparent glass plate 12 and the wafer 11, and as shown in FIG. A grinding groove 12E is formed in the peripheral portion left uncut when the through long hole 12B of the plate 12 is formed, and the uncut portion of the peripheral portion is ground and cut. At this time, the processing stroke is set to be equal to or larger than the diameter of the transparent glass plate 12, and the inside of the through long hole 12B is cut open.

  Next, as shown in FIG. 5, grinding grooves 12D, 12D,... Are formed between the spacers 13 in a direction orthogonal to the grinding grooves 12E, and the transparent glass plate 12 is divided corresponding to each solid-state imaging device 11A (see FIG. 5). Step S5).

  In FIG. 5, the grinding grooves 12E and the grinding grooves 12D are shown to the outside of the transparent glass plate 12 so that the trajectory of the dicing blade 52 can be easily understood, but the actual grinding grooves 12E and the grinding grooves 12D are transparent glass plates. The grooves described on the outside of the transparent glass plate 12 only in the plane of 12 describe the trajectory of the dicing blade 52.

  FIG. 2C shows a state where the transparent glass plate 12 is ground and cut in this way and the pads 11B, 11B,... On the wafer 11 are exposed.

  Next, the portion between the pad 11B and the pad 11B of the wafer 11 is ground and cut by another thin dicing blade, and is divided into individual solid-state imaging devices 21 as shown in FIG. Note that a laminate in which a large number of solid-state imaging devices 21 are formed at the wafer level is ground and cut by attaching a dicing sheet (not shown) to the back surface of the wafer 11. Therefore, even if it is divided into individual solid-state imaging devices 21, it does not fall apart (step S6).

  In the above-described grinding and cutting process of the transparent glass plate 12, the height of the gap portion 14 between the wafer 11 and the transparent glass plate 12 is extremely narrow, about 100 μm, due to the thinning of the solid-state imaging device 21, and the above-described FIG. As described with reference to a) and FIG. 7B, the glass fragments 12A generated during the grinding and cutting of the transparent glass plate 12 are caught in the gap between the grindstone 52 and the wafer 11 and stirred. As a result, the wafer 11 is damaged.

  However, in the method for manufacturing a solid-state imaging device according to the present invention, since the through long holes 12B are formed in the transparent glass plate 12 in the direction in which the pads 11B of the wafer 11 are arranged in advance, the transparent glass plate 12 and the wafer 11 are bonded. Since it is not necessary to grind and cut this part later, the pads 11B, 11B,... Are not damaged by the glass fragments 12A generated by grinding the transparent glass plate 12.

  Although glass fragments 12A are generated in forming the grinding groove 12E formed in the uncut portion when the through long hole 12B is formed and the grinding groove 12D perpendicular to the through long hole 12B, the lower portion of the peripheral edge 12C of the transparent glass plate 12 is generated. Since the solid-state imaging device is not formed on the wafer 11 and the pad 11B is not formed below the grinding groove 12D, the probability that the solid-state imaging device 21 is defective due to the glass fragments 12A is greatly reduced. .

[ Example ]
Next, specific examples of grinding and cutting of the transparent glass plate 12 will be described. First, a through-hole 12B having a width of 900 μm is formed in advance in the transparent glass plate 12 having a diameter of 200 mm and a thickness of 500 μm (the remaining portion of the peripheral edge portion 12C of the transparent glass plate 12 is about 20 mm), and a spacer 13 having a thickness of 100 μm is formed. The laminated body which is an aggregate | assembly of the solid-state imaging device 21 of a wafer level is affixed on the wafer 11 via this.

  This laminated body is suction-mounted on a wafer table 51 of a dicing apparatus, and the lowest point of the cutting edge of a dicing blade (grinding stone) 52 is set at a position where it enters 50 μm into the gap portion 14 and shown in FIG. Such grinding grooves 12E and 12D were formed, and the transparent glass plate 12 was ground and cut so as to correspond to each solid-state imaging device 21. In addition, the inside of the through-hole 12B was empty.

  The dicing blade 52 is a metal bond blade in which diamond abrasive grains having a particle diameter of 8 to 40 μm are bonded with nickel and has a diameter of 100 mm and a thickness of 0.9 mm for grinding the through-hole 12B and the grinding grooves 12E and 12D. The rotation speed was 4,000 to 6,000 rpm. Further, the feeding speed of the wafer table 51 was set to 0.2 to 1.0 mm / sec.

  The dicing blade 52 is a resin-bonded blade in which diamond abrasive grains are bonded with a phenol resin or the like. However, since the wear is fast, it is necessary to frequently adjust the height in order to secure the depth of cut, so a metal bond blade was used in the examples.

  When the laminated body after processing was observed on a monitor screen using an observation optical system provided in the dicing apparatus, the surface of the wafer 11 was scratched with 1 to 2 scratches exceeding 10 μm in size per chip. There were no large and deep scratches that could break the circuit wiring, and there were about 20 to 30 scratches of 10 μm or less per chip, which was within the allowable range.

  Further, when the transparent glass plate 12 is ground and cut, as shown in FIG. 6, the glass piece is cut by grinding and cutting while supplying a grinding liquid to which ultrasonic vibration is applied from a grinding liquid nozzle 55 with an ultrasonic vibrator. Since vibration is transmitted to 12A itself and the glass fragments 12A are discharged more smoothly, damage to the surface of the wafer 11 by the glass fragments 12A is further alleviated.

  As an embodiment in this case, for example, a model MSG-331 manufactured by Megasonic Systems is used as the oscillation device, the oscillation frequency of the oscillator 56 is about 1.5 to 3.0 MHz, and the ultrasonic output is 10 to 40 W. The degree is preferred.

  In addition, since the ultrasonic energy is most effectively applied to the grinding fluid immediately before discharge from the grinding fluid nozzle, the ultrasonic vibrator of the grinding fluid nozzle with ultrasonic vibrator 55 is incorporated at the tip of the nozzle as much as possible. The closer one is preferable.

  In the above-described embodiment, the step of forming the through-hole 12B in the transparent glass plate 12 is formed by grinding with the dicing blade 52, but the present invention is not limited to this, and various processes such as laser processing are performed. You may form using a known processing method.

  As described above, according to the present invention, the solid-state imaging device assembly constituted by the wafer 11 of the solid-state imaging device and the transparent glass plate 12 which are joined with a very narrow gap 14 of about 100 μm. When the transparent glass plate 12 is ground and cut, the transparent glass plate 12 is previously formed with the through long hole 12B in which only the peripheral edge portion 12C of the transparent glass plate 12 is left in one direction, so at least the lower portion of the through long hole 12B portion. The surface of the wafer 11 is not damaged by glass fragments 12A generated by grinding, and a method for manufacturing the solid-state imaging device 21 with a high yield can be obtained.

Process drawing showing the manufacturing method of the solid-state imaging device explaining embodiment of this invention Explanatory drawing showing the manufacturing method of the solid-state imaging device explaining embodiment of this invention Conceptual diagram for explaining a method of forming a through hole A plan view showing a transparent glass plate in which a through-hole is formed A plan view showing a transparent glass plate with grinding grooves formed Conceptual diagram showing a grinding and cutting method in which ultrasonic vibration is applied to the grinding fluid Conceptual diagram explaining grinding and cutting of a conventional transparent glass plate

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Wafer, 11A ... Solid-state image sensor, 11B ... Pad (wiring pad), 12 ... Transparent glass plate (transparent flat plate), 12A ... Glass fragment, 12B ... Through-hole, 13 ... Spacer, 14 ... Gap part, 21 ... Solid-state imaging device, 52 ... dicing blade

Claims (3)

Forming a large number of solid-state imaging devices on the surface of the wafer;
Forming a frame-shaped spacer having a predetermined thickness in a shape surrounding each solid-state image sensor at a position corresponding to the solid-state image sensor on the lower surface of the transparent flat plate to be bonded to the wafer;
Forming a plurality of through-holes leaving only the peripheral edge of the transparent flat plate between the spacers of the transparent flat plate;
Aligning the wafer and the transparent flat plate and bonding them via the spacer;
Grinding the peripheral edge of the transparent flat plate left at the time of forming the through-hole, and grinding the transparent flat plate in a direction perpendicular to the through-hole, so that the transparent flat plate is adapted to correspond to the individual solid-state imaging device. Dividing, and
Dividing the wafer in correspondence with each solid-state imaging device;
A method for manufacturing a solid-state imaging device.   The method of manufacturing a solid-state imaging device according to claim 1, wherein the step of forming a through hole in the transparent flat plate is performed by grinding. The solid-state imaging device has wiring pads for external connection on two opposite sides outside the spacer,
The through hole of the transparent flat plate is formed in a direction that exposes the wiring pad, and is formed with a width necessary for exposing the wiring pad. Manufacturing method of solid-state imaging device.

Images