JP2000195878A - Wafer transfer / fixing jig and semiconductor device manufacturing method - Google Patents

Abstract

(57) [Summary] Dicing in a semiconductor device assembling process;
A wafer transfer / fixing jig that can be covered by a single transfer / fixing jig in each of the backside grinding and die bonding steps, and can easily cope with peeling of thin chips that was difficult in the die bonding step. To provide a method of manufacturing a semiconductor device. SOLUTION: A wafer transfer / fixing jig comprising a thin plate 1 having a diameter equal to or larger than that of a wafer 2 and having a plurality of holes 4 formed in a plate thickness direction, and an adhesive material 3 applied to one side of the thin plate. In the state where the thin plate is fixed by the adhesive material, a groove 6 deeper than the chip thickness at the time of completion is formed on the main surface where the semiconductor element is formed along the dicing line. Is ground and polished to the chip thickness at the time of completion to separate the wafer into individual chips, and the wafer separated into chips is transported to a die bonding apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer / fixing jig used for fixing a wafer in a process of assembling a semiconductor device and transferring a wafer to a next process after chip division, and more particularly to backside grinding after a dicing process. The present invention relates to a method for manufacturing a semiconductor device using a transfer / fixing jig used consistently in a process and a die bonding process.

[0002]

2. Description of the Related Art In general, a semiconductor device usually has a design process, a wafer forming process of cutting a wafer from a single crystal ingot,
A wafer processing step of forming semiconductor elements such as transistors and integrated circuits on the main surface of the wafer, an assembling step and an inspection step of separating chips on which semiconductor elements are formed from the wafer and sealing each chip in an envelope. After that, the product is completed. In a conventional semiconductor device assembly process, a tape is used for holding a wafer in each of a back surface grinding process, a dicing process, and a die bonding process. Here, the back side grinding step is for grinding the back side of the wafer,
This is performed after a tape for protecting the main surface of the wafer on which the semiconductor elements are formed is attached. The dicing process is to cut the dicing line formed on the semiconductor element with a diamond blade to divide the chips, to prevent scattering of the divided chips, and to a dedicated ring to transport the divided chips Secure the wafer with tape.

FIG. 14 shows a process up to die bonding in a conventional semiconductor device assembling process. First,
(1) A wafer such as a silicon semiconductor having semiconductor elements formed on a main surface in a wafer processing step is prepared. (2) A protective tape is attached to the main surface of the wafer on which the semiconductor elements are formed before the back surface grinding. Next, (3) the back surface of the wafer is ground to make the wafer into a chip thickness. Thereafter, (4) the protective tape attached to the main surface of the wafer is peeled off. Next, (5) the back surface of the wafer is fixed to a tape to which a dedicated ring is attached to prevent the divided chips from scattering and transport the divided chips. (6) Dicing is performed on the fixed wafer to separate it into individual chips, and the individual chips are fixed to a tape attached to a ring. Next, (7) the wafer is transferred to a die bonding apparatus (die bonder). (8) The separated chip is pushed up on the back surface of the tape by a pickup needle provided in the die bonding apparatus, penetrates through the chip, directly contacts the pickup needle on the back surface of the chip, and is further lifted to peel off the chip from the tape. . The surface of the peeled chip is sucked by a collet and mounted on the island of the lead frame in that state. And
By performing wire bonding, each pad of the chip is electrically connected to the inner lead portion of the lead frame, and these are sealed in an envelope.

FIG. 1 shows the flow of the dicing method proposed by the inventors (Japanese Patent Application No. 9-197291).
As shown in FIG. In the pre-dicing method, first, a wafer such as a silicon semiconductor having semiconductor elements formed on a main surface in a wafer processing step is prepared. And
(2) The main surface of the wafer, on which the semiconductor elements are formed, is first cut into notches having a thickness equal to or greater than the finishing thickness required by dicing. This notch dices (cuts) a dicing line formed in the wiring pattern on the main surface only for dicing. Next, (3) a protective tape is attached to the cut main surface of the wafer to protect the main surface of the wafer on which the semiconductor elements are formed at the time of grinding the back surface. (4) After attaching the protective tape, the wafer is ground from the rear surface side, and ground to the cut point formed by dicing to perform chip division. (5) Since the wafer, which is an aggregate of chips divided by the back surface grinding, is turned upside down, the back surface of the wafer is fixed to a dicing tape attached to a flat ring, and the protective tape on the main surface side is peeled off. Replacement (transfer) is performed. In the transfer, the back surface of the wafer is adhered and fixed to a dicing tape with the surface protection tape attached, and finally the surface protection tape is removed. This results in the same state as after completion of the conventional dicing process. Finally, (6) the chip is separated from the tape by die bonding and attached to a lead frame or bonded to a package.

[0005]

The tape used in the semiconductor device assembling process (back surface grinding to die bonding) described above is a spacer for the purpose of protecting and transporting the chip. Is an ancillary process, so the more the tape is attached, the higher the cost of the product. In addition, contradictory specifications that backside grinding requires an adhesive force that does not cause chip flying and die bonding requires an adhesive material that can be easily peeled off from the tape must be achieved. However, it is difficult to satisfy such contradictory requirements with the current tape, and there is a problem that the protection tape must be replaced. In particular, when changing the tape, it is necessary to have a difference in adhesive strength between the side to be transferred and the side to be transferred. In order to generate the difference, a UV (ultraviolet curing type) tape must be used. This has led to higher costs. In addition, die bonding has a problem that it is difficult to pick up a chip having a small thickness. The present invention has been made in view of such circumstances, and each of the steps of dicing, backside grinding, and die bonding in a semiconductor device assembling process requires one step.
A wafer transfer / fixing jig which can be covered by various kinds of transfer / fixing jigs and can easily cope with peeling of thin chips which has been conventionally difficult in a die bonding process, and a method of manufacturing a semiconductor device using the same I will provide a.

[0006]

SUMMARY OF THE INVENTION The present invention provides a thin plate having the same diameter as or larger than the wafer and having a plurality of holes formed in the thickness direction, and an adhesive material applied to one side of the thin plate. Using a wafer transfer / fixing jig having the above, in a state where the thin plate is fixed by the adhesive, the main surface on which the semiconductor element is formed along the dicing line is deeper than the chip thickness at the time of completion. A step of grinding and polishing the back surface of the wafer in which the grooves are formed to the chip thickness at the time of completion to separate the wafer into individual chips is performed, and the wafer separated into chips is transported to a die bonding apparatus. It is characterized by: In the prior art, a tape was used in each of a dicing process, a back surface grinding process, and a die bonding process, and various types of tapes were used according to applications.
All the steps can be covered by one kind of fixing jig, whereby the tape can be abolished and the additional steps when the tape is attached can be reduced. Further, it is possible to easily cope with peeling of a thin film chip, which has been difficult in the die bonding step.

That is, the wafer transfer / fixing jig of the present invention has the same diameter as or larger than the wafer.
And a thin plate having a plurality of holes formed in the plate thickness direction, and an adhesive applied to one side of the thin plate, the thin plate is formed by the adhesive on the main surface of the wafer on which the semiconductor elements are formed. In this state, the back surface of the wafer in which a groove deeper than the chip thickness at the time of completion is formed on the main surface on which the semiconductor element is formed along the dicing line, and the chip thickness at the time of completion is It is characterized in that a step of separating the wafer into individual chips by grinding and polishing is performed. The thin plate may be warped when carrying the wafer, and may be less bent. The holes formed in the thin plate may be smaller than at least each chip region formed in the wafer, and at least one hole may be arranged in each chip region.

In the method of manufacturing a semiconductor device according to the present invention, a groove deeper than a completed chip thickness is formed along a dicing line of a wafer on which a semiconductor element is formed on a main surface on which the semiconductor element is formed. And a step of attaching a wafer transfer / fixing jig to the main surface of the wafer on which the semiconductor elements are formed, and grinding and polishing the back surface of the wafer to the chip thickness at the time of completion to separate the wafer into individual wafers. A step of separating the wafer into chips, wherein the wafer transfer / fixing jig has the same diameter as or larger than the wafer, and has a plurality of holes formed in the thickness direction, and a thin plate. And an adhesive applied to one side. The holes formed in the thin plate may be smaller than at least each chip region formed in the wafer, and at least one hole may be arranged in each chip region. The wafer whose back surface has been ground and polished to the chip thickness at the time of completion, after a predetermined chip area is held by a collet, air is blown to the predetermined chip area through a hole formed in the thin plate. Alternatively, the chips may be separated from the thin plate.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. First, a series of dicing steps, a back surface grinding step, and a die bonding step in the assembling step of the present invention will be described with reference to a manufacturing process flow chart shown in FIG. First, (1) formed in the wafer processing step,
A wafer such as a silicon semiconductor having semiconductor elements such as transistors and integrated circuits formed on a main surface is prepared. (2) The main surface of the wafer on which the semiconductor elements are formed is first cut into a notch having a thickness equal to or greater than a finish thickness required by dicing. This cut dices the dicing line formed in the wiring pattern on the main surface exclusively for dicing. Next, (3) the wafer diced in the above step is fixed using a wafer transfer / fixing jig. The main surface of the wafer on which the semiconductor elements are formed is fixed to a jig. Next, (4) the wafer fixed to the wafer transfer / fixing jig is ground from the back side by using a back side grinding device, and is ground to a cutting point formed by dicing to perform chip division. (5) The wafer, which is an aggregate of chips divided by the back grinding, is used for wafer transfer /
It is transported to a die bonding device (die bonder) while being fixed to the fixing jig. (6) The separated chip pushes up the chip main surface from the back surface of the jig via a through hole by an air pin generated from an air device provided in the die bonding apparatus, and peels off the chip from the jig. The surface of the peeled chip is sucked by a collet and mounted on the island of the lead frame in that state. Then, perform wire bonding,
Each pad of the chip is electrically connected to the inner lead portion of the lead frame, and these are sealed in an envelope. The chip can be directly bonded to the package.

Next, each step described with reference to the manufacturing process flow chart will be described in detail with reference to FIGS. FIG. 2 is a wafer cross-sectional view showing a step of making a cut in the wafer. Semiconductor elements such as transistors and integrated circuits formed in a wafer processing step are patterned on the main surface of the wafer 2. Cuts not less than the finish thickness required by dicing from the wafer main surface 6
Insert This cut is for dicing a dicing line formed in the wiring pattern on the main surface exclusively for dicing. The wafer 2 is sucked and fixed to the chuck table 5 of the dicing apparatus by vacuum or other method. In this state, the dicing blade 7 is rotated at a predetermined number of rotations, and the groove 6 is cut to a predetermined depth while applying cutting water. The depth of the groove 6 should be at least 5 μm larger than the chip thickness at the time of completion to enable complete chip separation.
m deeper. After that, the cleaning process and the drying process of the wafer 2 are performed.

Next, the wafer diced in the above step is fixed using a wafer transfer / fixing jig. FIG.
FIG. 3 is a perspective view of a wafer transfer / fixing jig. The shape of this jig is determined according to the size and shape of the wafer. As shown in FIG. 3, for example, a disk-shaped thin plate (hereinafter, referred to as a plate) 1 having this size or a slightly larger size is used so as to fit a 6-inch (15.24 cm) wafer. The plate is made of, for example, S
US, 303, 304, etc., stainless steel, other iron or alloys thereof, metals other than iron and alloys thereof, or hardened resins (plastics and the like) can be used. The thickness of the plate 1 is about 1 mm in consideration of its mechanical strength. The plate 1 has a plurality of through holes 4 formed in the thickness direction. This serves as a suction hole for sucking the wafer and is used as a hole through which air pins for pushing up the wafer pass. The diameter of the through hole 4 is about 0.1 to 0.8 mm, preferably 0.3 to 0.8 mm.
About 6 mm is appropriate. If the through-hole is too small, it is not preferable. Even if the through-hole is large beyond the range, the suction force becomes large, and the force is locally applied to the wafer, and the wafer often breaks. The through holes are arranged uniformly over substantially the entire surface of the plate.

When the wafer is divided into chips, all chips are arranged so as to always face at least one through hole. The distance between the through holes of the plate is preferably 0.1 to 0.15 mm. With such a configuration, the wafer can be sucked without being damaged, and the chips can be efficiently pushed up by the pressing force of the air (air pin). Further, although a wafer having a thickness of about 140 to 200 μm is used, a wafer having a small thickness, for example, a wafer having a thickness of 10 to 50 μm can be transported and fixed using this jig. FIG. 4 is a cross-sectional view showing a state where the wafer is fixed using the wafer transfer / fixing jig. At this time, the wafer 2 has the cut groove 6 formed in the main surface on which the semiconductor elements are formed, and the back surface faces upward. The main surface of the wafer 2 and the plate 1 are joined by an adhesive layer 3 such as an epoxy resin or a polyimide interposed therebetween. Since the wafer is held by the weakly viscous adhesive layer applied on the plate, the wafer is prevented from dropping from the plate during wafer transfer.

Next, in order to divide the chips by back surface grinding, the wafer is fixed to a grinding chuck table.
FIG. 5 is a cross-sectional view of the chuck table for grinding in a state where the wafer before back surface grinding is fixed. The fixing of the wafer in the backside grinding device is performed by vacuum suction on the entire surface by a suction body made of a ceramic porous plate. A grinding chuck table 9 which fixes the plate 1 on which the wafer 2 is fixed and forms a back surface grinding device is made of ceramics, and includes a ceramic porous plate 8 which is an adsorbent of a support surface.
The grinding chuck table 9 has a suction hole 11 at the bottom, and the inside thereof is evacuated as shown by an arrow in the drawing to evacuate the inside. The plate 1 is suction-fixed by the vacuum force. The back surface grinding is performed after fixing the wafer in this way. The wafer is attracted by the holes formed in the plate and firmly fixed on the plate, so that the chip does not fly due to the load during grinding.

FIG. 10 is a sectional view of the back surface grinding step.
The wafer 2 supported by the plate 1 is fixed by a chuck table 9 for grinding. In this state, the grinding chuck table 9 and the grinding wheel 10 are rotated,
The grinding wheel 10 descends while rotating, and grinds the back surface of the wafer 2. As a grinding method, any of in-field grinding and through-feed grinding may be used. When the back surface of the wafer 2 is shaved until it reaches the cut groove 6, the wafer 2 is divided into chips. Here, grinding may be continued even after the wafer 2 is divided into individual chips, and grinding and polishing may be continued for at least 5 μm or more. As a result, even if chipping occurs at a portion where the surface formed by dicing and the surface formed by grinding and polishing intersect, this region can be removed by grinding and polishing. The amount of grinding and polishing can be arbitrarily set in consideration of the thickness of the wafer, the thickness of the completed chip, and the like.

FIG. 6 is a sectional view showing a state in which the wafer separated for each chip region by back surface grinding is fixed to a grinding chuck table. Grinding chuck table 9
A suction hole 11 is provided at the bottom, and a vacuum is drawn from the suction hole 11 to evacuate the inside as shown by the arrow in the figure. The plate 1 is suction-fixed by the vacuum force. A plurality of chips 12 constituting the wafer are individually bonded to the plate 1 by the adhesive layer 3.
The assembly of the chips 12 divided by the back surface grinding is released from the grinding chuck table 9 of the back surface grinding device by the vacuum break. Then, the plurality of chips 12 are transported to the die bonding apparatus while being fixed on the plate 1 with the adhesive layer 3. At this time, each chip
The chip is fixed only by the weakly viscous adhesive layer on the plate to prevent the chip from flying during transport. In a die bonding apparatus, a chip is separated from a plate, and the chip is bonded to a lead frame or a package.

FIG. 7 is a sectional view for explaining a state in which a chip is peeled from a plate in a die bonding apparatus. Of the plurality of chips 12, the backup holder 1 is located in the region of the plate 9 where the predetermined chip 12 'is arranged.
4 is adhered. The backup holder 14 is provided with an air-permeable ceramic porous plate 15 on the contact surface with the plate 1 and has a through hole 16 on the bottom surface. When air generated from an air device (not shown) provided in the die bonding device is blown from the outside into the backup holder 14 as shown by an arrow, the air is
7 passes through the porous ceramic plate 15 having air permeability, pushes up the main surface of the chip 2 through the through hole 4 of the plate 1, and peels the chip 2 from the plate 1. The chip 12 ′ separated from the plate 1 is sucked on the front side (that is, the back side) by the collet 13. The collet 13 is provided with a chip reversing mechanism, and reverses so that the downward suction surface faces upward. In this state, the tip 12 'is separated by another collet (not shown) by using the tip air transfer mechanism.
Will be changed to As a result, the chip 12 'sucked by another collet has its main surface sucked by this collet and its back surface faces downward. This other collet mounts the chip 12 'on a lead frame.

FIG. 11 is a plan view of the lead frame 18 on which the chip 12 'separated from the plate 1 is mounted. The lead frame 18 includes an island 19 supported by square hanging pins 20 supported by the frame,
Similarly, a lead 21 having one end supported by the frame and the other end facing the island 19 is provided. The surface of the island 19 is coated with a conductive paste supplied from a dispenser. Chip 12 '
Are mounted on the island 19 and fixed by a conductive paste.

FIG. 12 is a sectional view of a semiconductor device obtained by the method of manufacturing a semiconductor device according to the present invention. As shown in FIG. 11, the chip 12 'is die-bonded to an island 19 to which a conductive paste for bonding and fixing is applied in advance.
It is also possible to mount using a gold-silicon eutectic, or mount a metal thin film on the back surface of the wafer by vacuum evaporation and further use solder. Each pad of the chip 12 ′ fixed to the island 19 by using the conductive paste 22 and each lead 21 of the lead frame 18 are electrically connected by a bonding wire 23. Then, the chip 12 ', the island 19, a part of the lead 21, and the conductive paste 22 are sealed in a resin sealing body 24 such as an epoxy resin. Thereafter, the lead frame 18 connected to the resin sealing body 24 is cut and removed, and lead forming is performed to complete a product. The chip can be directly bonded to the package.

FIG. 13 is a sectional view of another semiconductor device obtained by the method of manufacturing a semiconductor device according to the present invention. The semiconductor device is applied to a LOC (Lead On Chip) package. In the case of the LOC package, as shown in FIG. 7, the chip 12 ′ attracted to the collet is fixed to the lead 26 of the lead frame 25 by the adhesive tape 27. Each pad of the chip 12 'and each lead 26 of the lead frame 25 are electrically connected by bonding wires 28, respectively. Then, the chip 12 ', the adhesive tape 27, a part of the lead 26, and the bonding wire 28
Is sealed in a resin sealing body 29 such as an epoxy resin.
Thereafter, the lead frame 2 connected to the resin sealing body 29
5 is cut and removed, and lead forming is performed to complete a product. In the conventional method, the pick-up needle was used to push up from the back, but in this method stress is concentrated at the contact point and chip breakage easily occurs, but air is blown from the hole opened in the plate as in the present invention In this method, concentration of stress can be avoided by applying a uniform pressure to the entire surface of the hole formed in the plate.

At the same time, since the collet is vacuum-adsorbed from above the chip, the chip can be easily separated from the plate. Further, in the present invention, the wafer transfer /
Holes (through holes) formed in the plate that is the fixing jig
May meet in a cross shape as shown in a circular diagram 8 as shown in FIG. 3 or a square shape as shown in FIG. Further, the shape of the hole such as an ellipse is not particularly limited.

[0021]

According to the prior art, a protective tape was used in each of the steps of dicing, backside grinding, and die bonding in the semiconductor assembly process, and various types of tapes were used according to the application. Process of one type
It can be covered by a fixing jig. As a result, it is possible to abolish the tape and to reduce the number of ancillary processes for attaching the tape, thereby facilitating the manufacturing process. Further, it is possible to easily cope with the separation of a thin chip which has been difficult in the die bonding step.

[Brief description of the drawings]

FIG. 1 is a process flowchart illustrating an assembly process of a semiconductor device according to the present invention.

FIG. 2 is a cross-sectional view illustrating a dicing step of the semiconductor device of the present invention.

FIG. 3 is a perspective view of a plate constituting the wafer transfer / fixing jig of the present invention.

FIG. 4 is a cross-sectional view of a wafer fixed by the plate of the present invention.

FIG. 5 is a cross-sectional view of a back surface grinding apparatus for mounting a wafer before grinding fixed by a plate according to the present invention.

FIG. 6 is a cross-sectional view of a back surface grinding apparatus for mounting a ground wafer fixed by the plate of the present invention.

FIG. 7 is a cross-sectional view illustrating chip peeling in the die bonding apparatus of the present invention.

FIG. 8 is a perspective view of a plate constituting the wafer transfer / fixing jig of the present invention.

FIG. 9 is a perspective view of a plate constituting the wafer transfer / fixing jig of the present invention.

FIG. 10 is a cross-sectional view illustrating a back surface grinding step of the semiconductor device of the present invention.

FIG. 11 is a plan view of a lead frame on which the chip of the present invention is mounted.

FIG. 12 is a sectional view of a semiconductor device obtained by the manufacturing method of the present invention.

FIG. 13 is a sectional view of a semiconductor device obtained by the manufacturing method of the present invention.

FIG. 14 is a process flowchart for explaining a conventional semiconductor device assembling process.

FIG. 15 is a process flowchart for explaining a conventional semiconductor device assembling process.

[Explanation of symbols]

1 ... thin plate (plate (wafer transfer / fixing jig)), 2 ... wafer, 3 ... adhesive layer,
4 ... Hole (through-hole), 5 ... Dicing chuck table, 6 ... Cut groove, 7 ... Dicing blade, 8 ... Ceramic porous plate,
9: Grinding chuck table, 10: Grinding wheel, 11: Suction hole, 12, 12 ': Tip, 13: Collet, 14: Backup holder, 15: Ceramic porous plate, 1
6 ... through-hole, 17 ... air pin, 18, 2
5 ... lead frame, 19 ... island,
20: hanging pin, 21, 26: lead, 2
2 ... conductive paste, 23, 28 ... bonding wire, 24, 29 ... resin sealing body, 27 ...
Adhesive tape.

Claims (6)

[Claims] 1. A semiconductor device comprising: a thin plate having a diameter equal to or larger than that of a wafer and having a plurality of holes formed in a thickness direction thereof; and an adhesive applied to one side of the thin plate. The thin plate is fixed to the main surface on which the element is formed by the adhesive material, and in this state, the main surface on which the semiconductor element is formed is deeper than the chip thickness at the time of completion along the dicing line. A jig for transporting and fixing between wafer processes, wherein a step of grinding and polishing the back surface of the grooved wafer to the chip thickness at the time of completion to separate the wafer into individual chips is performed. 2. The wafer transfer / fixing jig according to claim 1, wherein the thin plate is less warped and bent less when performing wafer transfer. 3. The semiconductor device according to claim 1, wherein the holes formed in the thin plate are smaller than at least each chip region formed in the wafer, and at least one hole is arranged in each chip region. Wafer transfer described in
fixing jig. 4. A step of forming a groove deeper than a completed chip thickness in a main surface on which the semiconductor element is formed along a dicing line of the wafer on which the semiconductor element is formed; Attaching a wafer transfer / fixing jig to the formed main surface, and grinding and polishing the back surface of the wafer to the chip thickness at the time of completion to separate the wafer into individual chips. The wafer transfer / fixing jig has a thin plate having the same diameter as or larger than the wafer, and having a plurality of holes formed in a thickness direction, and an adhesive applied to one side of the thin plate. A method for manufacturing a semiconductor device, comprising: 5. The device according to claim 4, wherein the holes formed in the thin plate are at least smaller than each chip region formed in the wafer, and at least one hole is arranged in each chip region. Of manufacturing a semiconductor device. 6. The wafer whose back surface has been ground and polished to the chip thickness at the time of completion, after a predetermined chip area is held by a collet, air is blown through the hole formed in the thin plate to the predetermined chip thickness. 6. The method according to claim 4, wherein the chip is separated from the thin plate by spraying the chip region.