JP2006100587A - Method of manufacturing solid-state imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a solid-state imaging device with a high yield by providing a grinding method which can prevent a wafer from being damaged by glass fragments, at the time of grind-cutting a transparent glass board of a solid-state imaging device assembly made by joining a solid-state imaging element wafer and the transparent glass board with a narrow space left in-between. <P>SOLUTION: The method of manufacturing a solid-state imaging device comprises processes of forming many solid-state imaging elements 11A on a wafer 11, forming a spacer 13 having such a shape as to surround individual solid-state imaging elements 11A on a transparent flat board 12, forming grooves 12B having a prescribed depth in the transparent flat board 12, aligning the wafer 11 and the transparent flat board 12 and joining them together, grinding the transparent flat board 12 to divide it in correspondence with individual solid-state imaging elements 11A, and dividing the wafer 11 in correspondence with individual solid-state imaging elements 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. As shown in FIG. 6 (b), which is a cross-sectional view taken along the line AA 'of FIG. 6 (a) and a partially enlarged view, the glass fragments 12A generated during the grinding and cutting of the transparent glass plate 12 are removed when the grinding glass is 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 in a shape surrounding each solid-state imaging device, and a step of forming a groove having a predetermined depth between the spacers on the lower surface of the transparent plate; Aligning and joining the wafer and the transparent flat plate through the spacer, grinding the transparent flat plate, and dividing the transparent flat plate so as to correspond to the individual solid-state imaging devices; And a step of dividing the wafer in correspondence with each solid-state image sensor.

  According to the present invention, since there is a step of forming a groove of a predetermined depth between the spacers on the lower surface of the transparent flat plate, when the transparent flat plate is ground and cut, there is sufficient clearance between the grinding wheel and the wafer surface. Therefore, the transparent flat plate fragments generated by grinding are easily discharged, and the damage of the wafer surface due to the broken pieces is mitigated.

  In the present invention, the step of dividing the transparent flat plate is characterized by grinding and cutting the transparent flat plate with a disk-shaped grindstone having a thickness dimension larger than the width dimension of the groove of the transparent flat plate.

  According to this, since the width of the grinding cut groove is wider than the groove width previously formed in the transparent flat plate, the receiving portion of the disc-shaped grindstone is formed in the transparent flat plate, and large pieces of the transparent flat plate are not easily generated. . Therefore, the surface damage of the wafer is alleviated.

  Further, in the present invention, in the step of dividing the transparent flat plate, a flowable material is previously filled in a gap formed by a groove of the transparent flat plate and a space between the spacers below the groove. A step of forming a protective layer.

  According to this, since the fluidity material is filled in the lower gap of the grinding cut portion of the transparent flat plate to form the protective layer of the wafer, the surface damage of the wafer due to the transparent flat plate fragments caused by grinding is prevented. The

  As described above, according to the method for manufacturing a solid-state image pickup device of the present invention, the solid-state image pickup device assembly constituted by the solid-state image pickup device wafer and the transparent glass plate bonded with an extremely narrow gap is transparent. When grinding and cutting the glass plate, since the grooves are formed in advance in the grinding and cutting portion of the transparent glass plate to increase the height of the gap, the pieces of the transparent glass plate generated during the grinding and cutting are easily discharged. Can prevent damage to the wafer and can provide a method for manufacturing a solid-state imaging device with a high yield.

  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 an explanatory view showing a manufacturing process of a CSP type solid-state imaging device. As shown in FIG. 1C, a large number of solid-state imaging devices 11 </ b> A 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. 1C, pads 11B, 11B,... For wiring with the outside are formed outside the solid-state imaging device 11A.

  In the process shown in FIG. 1, a transparent glass plate 12 (corresponding to a transparent flat plate) is pasted on the wafer 11 on which the above-described solid-state imaging device 11A is formed, and the light-receiving portion of the solid-state imaging device 11A is sealed, and then each solid state The process of dividing into the imaging device 21 is represented conceptually.

  First, as shown in FIG. 1A, a spacer 13 made of silicon having a predetermined thickness in a frame shape surrounding each solid-state imaging device 11A is formed on a transparent glass plate 12. The spacer 13 is formed by applying an adhesive 13A to the transparent glass plate 12 and bonding a silicon plate thereto. Next, a spacer 13 having a required shape is formed by using photolithography and dry etching technology.

  Next, as shown in FIG. 1B, grooves 12 </ b> B are formed between the frame-shaped spacers 13 and the spacers 13 of the transparent glass plate 12. The groove 12B may be formed by grinding or may be formed by etching. Next, the adhesive 13 </ b> B is transferred to the end surface portion of the spacer 13. The groove 12B may be formed before the silicon plate is bonded to the transparent glass plate 12.

  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, as shown in FIG.1 (c), the solid-state imaging device 21 of the structure which has the space | gap part 14 between the wafer 11 and the transparent glass plate 12, and the light-receiving part of solid-state image sensor 11A was sealed is wafer level. Thus, the laminate 20 formed in a large number is manufactured.

  Note that the space portion in which the groove 12B between the solid-state imaging elements 11A is formed is a gap portion 14A that is higher than the gap portion 14 by the amount of the groove 12B.

  Next, the transparent glass plate 12 is divided by cutting by cutting only the transparent glass plate 12 of the laminate 20 by cutting into the gap portion 14 </ b> A with a grindstone having a thickness of about 0.6 to 1.2 mm. The pads 11B, 11B,... Are exposed (FIG. 1 (d)).

  Next, a portion between the pad 11B and the pad 11B of the wafer 11 is ground and cut with another thin grindstone and divided into individual solid-state imaging devices 21 (FIG. 1 (e)). The laminate 20 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.

  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.

  In the grinding and cutting process of the transparent glass plate 12 shown in FIG. 1D, the height of the gap 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. For this reason, when the groove 12B is not formed in the transparent glass plate 12, as described with reference to FIGS. 6 (a) and 6 (b), the glass generated during the progress of grinding and cutting of the transparent glass plate 12. The debris 12A is caught in the gap between the grindstone 52 and the wafer 11, and is scratched or dragged to damage the wafer 11 side.

  In the present invention, the groove 12B is formed in the transparent glass plate 12, and the gap 14A between the transparent glass plate 12 and the wafer 11 in the ground cut portion is made large, so that the glass fragments 12A are easily discharged and the wafer 11 is removed. There is no damage.

Next, a specific example of grinding and cutting the transparent glass plate 12 will be described with reference to FIG. First, a groove 12B having a width of 900 μm and a depth of l ₂ = 300 μm is formed in advance on the transparent glass plate 12 having a thickness of l ₁ = 500 μm, and affixed to the wafer 11 via a spacer 13 having a thickness of l ₃ = 100 μm. A laminated body 20 that is an aggregate of the wafer level solid-state imaging device 21 is formed (FIG. 2A).

  2 (b) and 2 (c), the laminated body 20 is sucked and placed on the wafer table 51 of the dicing apparatus, and the lowest point of the cutting edge of the dicing blade (grinding stone) 52 is in the gap portion 14A. The transparent glass plate 12 was ground and cut at a position where it entered 50 μm to expose the pads 11B, 11B,. 2B represents a cross section in a direction orthogonal to the grinding cutting direction, and FIG. 2C represents an A-A ′ cross section in FIG.

  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. The dicing blade 52 has a diameter of 100 mm and a thickness of 1.0 mm, and has a rotational speed of 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.

  Thus, the transparent glass plate 12 is ground and cut using the dicing blade 52 having a thickness (1,000 μm) thicker than the width (900 μm) of the groove 12B formed in the transparent glass plate 12. Since the receiving part of the dicing blade 52 is formed therein and receives a grinding resistance, large pieces of the transparent glass plate 12 are unlikely to be generated during grinding and cutting.

  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 processed laminated body 20 is observed on a monitor screen using an observation optical system provided in the dicing apparatus, the surface of the wafer 11 has 1 to 2 scratches exceeding 10 μm in size per chip. However, there were no large and deep scratches that could break the circuit wiring, and there were about 20 to 30 scratches per chip, within the allowable range.

  Next, another embodiment of the present invention will be described with reference to FIGS. In this other embodiment, a process of forming a protective layer on the surface of the wafer 11 in the gap portion 14A is added to the above-described embodiment. In addition, although the laminated body 20 in FIG. 3 is actually manufactured at the wafer level, in the figure, for simplification, it is described with only one grinding portion.

  First, as shown in FIG. 3, a fluid material (including a gel-like material) for the protective layer 15 that protects the wafer 11 is formed in the gap 14 </ b> A of the laminate 20 in which the grooves 12 </ b> B are formed in the transparent glass plate 12. Fill. For this purpose, the laminate 20 is dipped in a tray 81A filled with the fluid material of the protective layer 15 and kept in the vacuum chamber 81 decompressed by the vacuum pump 82 for a predetermined time. Thereby, the air in the gap portion 14A of the laminate 20 is discharged, and the material of the fluid protective layer 15 is easily filled in the gap portion 14A.

  Next, as shown in FIG. 4, the laminated body 20 is fixed on the wafer table 51 of the dicing apparatus, and set to a position where the lowest point of the cutting edge of the dicing blade (grinding stone) 52 slightly enters the gap portion 14A. Then, the transparent glass plate 12 is ground and cut. At this time, even if the glass fragments 12A are generated while the transparent glass plate 12 is being ground and cut, the gap of the gap 14A is large and the protective layer 15 is present in the gap 14A, so that the wafer 11 is damaged. There is nothing.

  4A shows a cross section in a direction orthogonal to the grinding cutting direction, and FIG. 4B shows an A-A ′ cross section in FIG.

  Next, the wafer 11 is fully cut with another thin dicing blade, and finally the cleaning liquid is sprayed with a spin cleaner to remove the protective layer 15.

  Next, specific examples of the grinding and cutting of the transparent glass plate 12 in another embodiment will be described. The laminate 20 was immersed in a fluid material that will be the protective layer 15, and the vacuum chamber 81 was used to fill the void portion 14 </ b> A with the fluid material. The flowable material used was water or oil. Moreover, the vacuum degree of the vacuum chamber 81 at the time of filling was set to about 5 to 80 kPa.

  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. The dicing blade 52 has a diameter of 100 mm and a thickness of 1.0 mm, and has a rotational speed of 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.

  In processing, the periphery of the wafer table 51 of the dicing apparatus is surrounded by a weir and filled with water or oil, and the laminated body 20 is soaked and fixed inside, and the transparent glass plate 12 is ground while being soaked at room temperature. It cut | disconnected and the pad 11B, 11B, ... was exposed.

  When the laminated body 20 after processing was observed on a monitor screen, the scratches on the surface of the wafer 11 due to the glass fragments 12A were not found to be large and deep so as to break the circuit wiring. The number was less than the allowable range.

  The air gap 14A of the laminate 20 is filled with a fluid material that solidifies at a temperature below room temperature, and the laminate 20 is stored in the refrigerator in this state to solidify the fluid material to form the protective layer 15. You can also. In this state, the transparent glass plate 12 is cut by grinding. In this case, it is used below the melting point of the material solidified by filling the temperature of the grinding water.

  For example, when a silicone oil polymer solution frozen at 10 ° C. is used as a fluid material that solidifies at a temperature below room temperature, the laminate 20 is filled with the solution after filling the voids 14 </ b> A of the laminate 20. Is stored in a refrigerator (about 0 to 6 ° C.) to freeze and solidify the solution. In this case, the laminated body 20 is chucked by using a table having a cooling function such as a freezing chuck table (table surface temperature of about 0 to 6 ° C.) as the wafer table 51 of the dicing apparatus.

  Further, by supplying grinding water cooled to about 0 to 6 ° C., the laminated body 20 and its surroundings are kept below the melting point of the solution, and the transparent glass plate 12 is ground and cut in this state.

  In addition, when a material that solidifies under minus temperature, such as water, is used as the fluid material to be filled, ethylene glycol, an antifreeze solution, is mixed with the grinding water to prevent freezing and maintain liquidity even under minus temperature. To do.

  In addition, as a fluid material to be the protective layer 15, a material containing gelatin or agar is used, and once the material is cooled and solidified at a low temperature, it is difficult to fluidize even if it is returned to a normal temperature environment. The protective layer 15 can also be formed by cooling the body 20 in a refrigerator (about 4 to 8 ° C.) and solidifying the fluid material into a pudding shape.

  In any case, in addition to the height of the gap portion 14A being increased by the groove 12B, the protective layer 15 is formed by filling the gap portion 14A with a fluid material. Even if glass fragments 12A are generated during the grinding and cutting, they are easily discharged and the damage to the wafer 11 is suppressed.

  Further, when the transparent glass plate 12 is cut by grinding, as shown in FIG. 5, the glass fragments are obtained 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. Closer is better.

  As described above, according to the present invention, the transparent glass plate of the solid-state imaging device assembly composed of the solid-state imaging device wafer and the transparent glass plate joined with a very narrow gap of about 100 μm is ground. When cutting, since the height of the gap portion of the grinding cut portion is increased by forming grooves in the transparent glass plate in advance, damage to the wafer due to transparent glass plate fragments generated during grinding cutting is prevented. Therefore, a method for manufacturing a solid-state imaging device with a high yield can be obtained.

The conceptual diagram showing the assembly process of the solid-state imaging device explaining embodiment of this invention The conceptual diagram of the grinding cutting process explaining embodiment of this invention The conceptual diagram of the protective film formation process explaining another embodiment of this invention The conceptual diagram of the grinding cutting process explaining another embodiment of this invention Conceptual diagram explaining grinding and cutting with ultrasonic vibration applied to the grinding fluid Conceptual diagram explaining conventional grinding and cutting

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Wafer, 11A ... Solid-state image sensor, 12 ... Transparent glass plate (transparent flat plate), 12A ... Glass fragment, 12B ... Groove, 13 ... Spacer, 14, 14A ... Gap part, 15 ... Protective layer, 20 ... Laminate, 21 ... Solid-state imaging device, 52 ... Dicing blade (disc-shaped grindstone)

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 groove of a predetermined depth between the spacers on the lower surface of the transparent flat plate;
Aligning the wafer and the transparent flat plate and bonding them via the spacer;
Grinding the transparent flat plate, and dividing the transparent flat plate so as to correspond to the individual solid-state imaging devices;
Dividing the wafer in correspondence with each solid-state imaging device;
A method for manufacturing a solid-state imaging device.   2. The solid-state imaging according to claim 1, wherein in the step of dividing the transparent flat plate, the transparent flat plate is ground and cut with a disc-shaped grindstone having a thickness larger than a width of a groove of the transparent flat plate. Device manufacturing method.   In the step of dividing the transparent flat plate, a fluid material is previously filled in a gap formed by a groove of the transparent flat plate and a space between the spacers below the groove to form a protective layer of the wafer. The manufacturing method of the solid-state imaging device according to claim 1, further comprising a step.

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