JP2008244076A - Semiconductor device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, when a thin-plate part 4 is formed by polishing the center of a rear face 2b and a half-polished wafer 2 in which a ring-like thick part 6 is formed at a peripheral part is diced, diced semiconductor devices 22 are scattered. <P>SOLUTION: Pure water 34 is cooled after being poured into a half-polished region 6 in the half-polished wafer 2. Accordingly, ice 36 is formed in the half-polished region 6 so as to planarize the rear face 2b of the half-polished wafer 2. In this state, if the rear face 2b of the half-polished wafer 2 is fixed to a dicing ring 12 with a dicing tape 14, the thin-plate part 4 is fixed to the dicing ring 12 with the ice 36 and the dicing tape 14. Consequently, the diced semiconductor devices 22 are prevented from being scattered. It is possible to perform dicing by measuring a dicing line from the surface 2a of the half-polished wafer 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a plurality of semiconductor devices through a process of dicing a wafer.

A method of manufacturing a plurality of semiconductor devices from a single wafer by passing through a wafer dicing process has become widespread.
In the process of dicing the wafer, the back surface of the wafer is fixed to the dicing ring via a dicing tape, the wafer fixed to the dicing ring is fixed to the stage, and the dicing line passes between the semiconductor devices formed on the wafer. Dicing the wafer along.

A method of cooling and fixing a wafer on a stage instead of a dicing tape is disclosed in Patent Document 1. In this method, a stage in which a Peltier element is incorporated is used, water is supplied between the wafer and the stage, and the stage is cooled by using the Peltier element to freeze the water.
When a wafer for dicing is irradiated on the wafer surface with the backside of the wafer fixed to frozen stage on the stage, a large temperature difference occurs on the front and back of the wafer, and the initial crack formed on the wafer surface by the laser irradiation causes a temperature difference. Grow in the direction. As a result, it has been reported that accurate dicing is possible.

  Vertical semiconductor devices have been put into practical use. The vertical semiconductor device here refers to a semiconductor device in which electrodes are formed on both the front and back surfaces of a semiconductor substrate. In the vertical semiconductor device, the thickness of the semiconductor substrate (that is, the thickness of the wafer) is the distance between the electrodes, and thus the thickness of the wafer greatly affects the characteristics of the semiconductor device. Some vertical semiconductor devices require a very thin wafer.

  If the wafer is thinned to such a thickness that the characteristics required for the semiconductor device can be obtained, the strength of the wafer will not be maintained, and it may be necessary to thin the wafer to such an extent that the wafer is easily destroyed during the manufacturing process of the semiconductor device. Yes. In order to solve this problem, as shown in FIG. 1, the center part of the back surface of the wafer 2 is polished to reduce the thickness of the center part of the wafer 2 to a thickness that provides the characteristics required for the semiconductor device. At the same time, a technique for leaving the ring-shaped thick portion 8 in the peripheral portion of the wafer has been developed. According to this technique, in order to maintain the strength of the wafer 2 by the ring-shaped thick portion 8 at the peripheral portion, the central portion 4 of the wafer 2 is thinned to a thickness that provides the characteristics required for the semiconductor device. Can do.

JP 2004-25187 A

When dicing a wafer 2 whose center part on the back surface is thinned (hereinafter, sometimes referred to as a half-wafered wafer for simplicity), as shown in FIG. Is fixed to the dicing ring 12 via the dicing tape 14. In this case, since the back surface of the central portion of the half-cut wafer 2 is thinned, it is not in close contact with the dicing tape 14. FIG. 3 shows a state in which the half-cut wafer 2 fixed as shown in FIG. 2 is diced by the dicing blade 18. When dicing with the dicing blade 18, the dicing is often performed while the cooling water 20 is applied. As a result, the diced semiconductor device 22 is scattered by the momentum of the cooling water. Alternatively, the semiconductor device 22 diced by receiving force from the rotating dicing blade 18 is scattered. If the semiconductor device 22 scatters, the semiconductor device 22 may be damaged, and further handling work becomes difficult.
Even if the technique of fixing the back surface of the half-cut wafer 2 to the stage 16 with frozen ice is used, it is not fixed to the stage 16 because the back surface at the center of the half-cut wafer 2 is thinned. There is no effect on the phenomenon that the diced semiconductor device 22 is scattered.

  If the surface 2a of the half-cut wafer 2 is fixed to the dicing ring 12 via the dicing tape 14, the dicing tape 14 can be brought into close contact with the entire surface 2a of the half-cut wafer 2, so that the diced semiconductor device 22 is provided. Can be prevented from scattering. However, when the surface 2a of the half-cut wafer 2 is fixed to the dicing ring 12, the position of the dicing line passing between adjacent semiconductor devices must be specified by observing from the back side of the half-cut wafer 2. This specific work becomes troublesome.

  If the stage 16 is devised to prepare the stage 16 that comes into the inside of the ring-shaped thick portion 8 of the half-wafered wafer 2 and contacts the back surface 4b of the thinned central portion 4, the above-mentioned problem occurs. Seems to be resolved. However, for this purpose, it is necessary to prepare a stage 16 that matches the shape of the half-cut wafer 2, which also becomes troublesome. Moreover, in the present dicing tape attaching apparatus, the dicing tape cannot be brought into close contact with the thinned back surface 8b inside the ring-shaped thick portion 8.

  If a Peltier element is incorporated in the stage that comes into the inner side of the ring-shaped thick portion 8 of the half-cut wafer 2 and contacts the thin back surface 4b of the central portion, the thin back surface 4b of the central portion is placed on the stage. There is a possibility that it can be fixed to. However, even if possible, this technique requires the work of freezing water in the dicing machine and the work of melting ice in the dicing machine after dicing, and it takes time to detach the wafer from the dicing machine. It will take. The operation rate of the dicing apparatus is reduced as compared with the case where the wafer is detached and attached in a short time using the dicing tape.

The present invention comprehensively solves the above problems. That is, the following problems are solved all at once.
(1) If the internally-cut wafer is fixed and normally diced, the diced semiconductor device will be scattered.
(2) When the surface of the half-cut wafer is fixed, it is difficult to observe the dicing line.
(3) It is not necessary to separately prepare a stage having a shape that enters the central portion of the half-cut wafer.
(4) The wafer can be detached in a short time using a dicing tape.

  In the present invention, the back surface of the half-cut wafer is flattened and fixed to the dicing ring. In order to flatten the back surface of the half-cut wafer, a liquid that solidifies when cooled is used. If this idea is used, the above problems will be solved at once.

The present invention relates to a method of manufacturing a plurality of semiconductor devices through a process of dicing a wafer.
The manufacturing method of the present invention includes the following steps.
(1) A plurality of semiconductor devices are formed on a wafer.
(2) By polishing the central portion of the back surface of the wafer, the central portion of the wafer is thinned until the thickness required for the performance of the semiconductor device is obtained, and a ring-shaped thick portion is formed on the peripheral portion. leave.
(3) A solidifying liquid is injected into the thinned region surrounded by the ring-shaped thick part.
(4) The wafer and liquid are cooled to solidify the liquid.
(5) Fix the back surface of the ring-shaped thick portion of the wafer and the exposed surface of the back surface of the solidified solidified liquid to the dicing ring via a dicing tape.
(6) Fix the dicing ring to the stage.
(7) The wafer fixed to the dicing ring is diced along a dicing line passing between adjacent semiconductor devices.

According to the above method, the back surface of the wafer is flattened in order to inject and solidify the solidified liquid into the thinned central portion prior to attaching the dicing tape to the back surface of the wafer. The The back surface of the flattened wafer can be fixed to a dicing ring via a dicing tape. The thin plate portion in which the semiconductor device is built can be fixed to the dicing ring via the solidified product and the dicing tape. For this reason, the diced semiconductor device does not scatter.
According to the above method, the back surface of the wafer is fixed to the dicing ring, the dicing ring is fixed to the stage, and dicing can be performed with the surface of the wafer exposed. The dicing line is not difficult to observe.
In the above method, the step of solidifying the liquid injected into the thinned central portion and the step of melting the solidified liquid can be performed outside the dicing apparatus. In the dicing apparatus, the wafer can be attached and detached in a short time using a dicing tape. The operating rate of the dicing apparatus is not reduced.

When the liquid solidifies, it is preferable that the back surface of the ring-shaped thick portion and the back surface (exposed surface) of the solidified product are aligned on the same surface. For this purpose, it is preferable to perform a step of specifying the volume of the thinned region surrounded by the ring-shaped thick portion before the step of injecting the liquid. In the step of injecting the liquid, it is preferable to inject an amount of liquid obtained by dividing the specified volume by the volume expansion rate at the time of solidification of the liquid.
For example, when pure water is used as the solidifying liquid, the volume of the pure water expands 1.09 times when solidifying. Therefore, it is preferable to freeze by injecting pure water that is an amount obtained by dividing the volume of the thinned region by the volume expansion coefficient, that is, 91.75% of the volume of the thinned region. The liquid injected into the range surrounded by the ring-shaped thick part is not limited to pure water. Other solidifying liquids can also be used.
In addition, it is possible to adjust the back surface of the ring-shaped thick part and the back surface of the solidified material to the same surface later, and the above quantitative relationship is preferable but not indispensable.

  In the dicing step, dicing is preferably performed using an antifreeze liquid having a solidification temperature lower than the solidification temperature of the solidifying liquid. The liquid that cools the dicing blade does not melt the solidified material that fixes the wafer to the dicing ring.

After the dicing process, it is preferable to carry out the following process to take out the semiconductor device.
(8) The dicing ring is removed from the stage with the wafer and the solidified product adhered to the dicing tape and the dicing ring.
(9) The separation wall formed in the spacer is inserted into the dicing groove formed in the dicing process by superimposing the spacer on which the separation wall is formed on the wafer.
(10) An opening is formed in a range in close contact with the solidified product of the dicing tape.
(11) The wafer and the solidified product are heated to melt the solidified product.

According to the above method, since the solidified product is melted in a state where the danced semiconductor device is positioned by the spacer, the semiconductor device that has been danced does not move without permission when the solidified product is melted. Since the liquid in which the solidified product is melted is discharged from the opening formed in the dicing tape, the diced semiconductor device does not float and sink in the liquid.
The danced semiconductor device groups are aligned in the same positional relationship as when a normal wafer (wafer with a flat back surface) is diced. The semiconductor device can be recovered using an existing die pick device.

  According to the present invention, it is possible to dice a ground wafer in the same manner as a normal wafer (a wafer having a flat back surface). The dicing semiconductor device does not scatter, it is difficult to observe the dicing line, and there is no need to separately prepare a stage according to the shape of the machined wafer. Furthermore, the wafer can be detached from the dicing apparatus in a short time using the dicing tape. Using well-established technology with high reliability and productivity, it is possible to efficiently and accurately dice a half-cut wafer.

The main features of the embodiments described below are first organized.
(Feature 1) Pure water is injected inside the ring-shaped thick part.
(Feature 2) At that time, a predetermined amount of pure water is injected by measuring the injection amount with a flow meter and performing feedforward control.
(Feature 3) After dicing, the wafer is removed from the stage in the same manner as a normal wafer by using a dicing ring.

FIG. 1A shows a perspective view of the internally-cut wafer 2 from the back surface 2b side, and FIG. 1B shows a cross-sectional view of the internally-cut wafer 2 along the line bb.
The half-cut wafer 2 includes (1) a step of forming a plurality of semiconductor devices 10a, 10b, 10c,... In a region (center portion) other than the peripheral portion of the wafer having a uniform thickness, and (2) a uniform thickness. Is manufactured through a process of thinning the central portion of the back surface of the wafer to a thickness that provides the characteristics required for the semiconductor devices 10a, 10b, 10c,. . The half-cut wafer 2 includes a thin plate portion 4 formed in the center portion and a thick portion 8 surrounding the periphery thereof in a ring shape. The half-cut wafer 2 includes a recess 6 having a thin plate portion 4 as a bottom surface and a ring-shaped thick portion 8 as a side wall. Hereinafter, the recess 6 is referred to as a half-cut region 6. The ring-shaped thick portion 8 formed in the peripheral portion of the thin plate portion 4 is thick and has high mechanical strength. Even if the thin plate portion 4 is very thin, the half-cut wafer 2 is broken. It has strength that is not possible.

  While the surface 2a of the half-cut wafer 2 is flat, the height of the back surface 8b of the ring-shaped thick portion 8 is different from the height of the back surface 4b of the thin plate portion 4 on the back surface 2b. When the dicing tape 14 is attached to the back surface 2b, the height of the back surface 4b is different. When the dicing tape 14 is attached to the back surface 2b, the thin plate portion 4 is not fixed to the dicing tape 14 as shown in FIG. When dicing in this state, the diced semiconductor device 22 is scattered as shown in FIG. Here, the semiconductor device before dicing is indicated by reference numeral 10, and the semiconductor device after dicing is indicated by reference numeral 22.

  In this embodiment, as shown in FIG. 5, pure water 34 is injected into the shaving region 6 and frozen, thereby filling the shaving region 6 with ice. The height of the back surface 8b of the ring-shaped thick portion 8 and the exposed surface 36b on the back surface side of the ice 36 are matched. If the dicing tape 14 is attached to the back surface 2b of the half-cut wafer 2 in this state, the back surface 4b of the thin plate portion 4 is fixed to the dicing ring 12 via the ice 36 and the dicing tape 14 as shown in FIG. . If dicing is performed in this state, the diced semiconductor device 22 is fixed to the dicing ring 12 via the ice 36 and the dicing tape 14 as shown in FIG.

In this embodiment, before the pure water 34 is injected into the mid-cut region 6 of the mid-cut wafer 2, the volume of the mid-cut region 6 is first measured. For this purpose, as shown in FIG. 4, the ring-shaped thick portion 8 of the half-cut wafer 2 is measured by an optical shape measuring device 32. That is, by measuring the width 8 c and height 8 d of the ring-shaped thick part 8 and the shape of the R part 8 e at the base of the ring-shaped thick part 8, the volume of the mid-cut region 6 is measured.
The method for measuring the ring-shaped thick portion is not limited to a specific method. The thickness distribution of the wafer 2 may be measured. Alternatively, the shape of the ring-shaped thick portion may be measured by a stylus type shape measuring device.
After measuring the volume of the intermediate cutting region 6, the amount of pure water 34 is calculated based on the measurement result. Pure water expands to 1.09 times its volume when it solidifies into ice. Pure water in an amount obtained by dividing the volume of the medium-cutting region 6 by the expansion coefficient at solidification (1.09 in the case of pure water) (91.75% of the volume of the medium-cutting region 6 in the case of pure water) If 34 is injected and frozen, the height of the back surface 8b of the ring-shaped thick part 8 and the exposed surface 36b on the back surface side of the ice 36 coincide with each other, and the back surface 2b of the half-cut wafer 2 is flattened.
When injecting pure water, measure the injection volume while injecting, perform the feed-forward control method based on the measured injection volume, and inject when a pre-calculated amount of pure water is injected. It is preferable to stop.

When pure water is injected, both the half-cut wafer 2 and the pure water 34 are cooled to cool the pure water 34. Then, the height of the back surface 8b of the ring-shaped thick portion 8 and the exposed surface 36b on the back surface side of the frozen ice 36 coincide with each other, and the back surface 2b of the half-cut wafer 2 is flattened.
This step can be performed independently of the dicing apparatus. Since the half-cut wafer 2 in which the pure water 34 has been frozen outside the dicing apparatus may be set in the dicing apparatus, the use efficiency of the dicing apparatus does not decrease.
The liquid injected into the half-cutting region 6 is not limited to pure water. Any liquid that solidifies when cooled and melts when heated may be used.

In this embodiment, as shown in FIG. 7, the dicing tape 14 is attached to the back surface 8 b of the ring-shaped thick portion 8 and the exposed surface 36 b on the back surface side of the ice 36, and the dicing tape 14 is attached to the dicing ring 12. wear.
Since the back surface 8b of the ring-shaped thick portion 8 and the exposed surface 36b on the back surface side of the ice 36 are located on the same plane, both can be fixed entirely. As a result, the thin plate portion 4 on which the plurality of semiconductor devices 10 are formed is fixed to the dicing ring 12 via the ice 36 and the dicing tape 14.

  After fixing the half-cut wafer 2 affixed to the dicing ring 12 to the stage 16, as shown in FIG. 8, the dicing line passing between the adjacent semiconductor devices 10 and 10 is measured by the measuring device 24. Measure the position. Next, while the dicing blade 18 is cooled by the antifreeze liquid 26, the half-cut wafer 2 and the ice 36 are diced along the measured dicing line. Antifreeze is used after cooling to a negative temperature. In order to use the antifreeze liquid whose freezing temperature is below the freezing point below the freezing point, the antifreeze liquid 26 does not melt the ice 36 fixing the thin plate portion 4, and the thin plate portion 4 is fixed to the dicing ring 12 by the ice 36. Can be diced. The semiconductor device 22 after dicing is not scattered. When dicing, dicing grooves 38 are formed between the semiconductor devices 22 after dicing.

After dicing, the dicing ring 12 is removed from the stage 16. At this time, as shown in FIG. 9, the diced semiconductor device 22 is peeled off from the stage 16 while being fixed to the dicing tape 14 via the ice 36.
Thereafter, the spacer 40 is fitted into the dicing groove 38 formed by dicing. The spacer 40 is formed with a separation wall 40 a that enters the dicing groove 38, and the separation wall 40 a enters the dicing groove 38 when the spacer 40 is superimposed on the half-cut wafer 2.
Further, an opening 42 is formed in the area of the dicing tape 14 where the ice 36 is stuck. In this state, the wafer 2 and the ice 36 are heated to raise the temperature to about 80 degrees. Then, the ice 36 melts and returns to the pure water 34 and is discharged 44 from the opening 42. The diced semiconductor device 22 is guided by the separation wall 40 a of the spacer 40 and moves to a position where it directly contacts the dicing tape 14. The position of the semiconductor device 22 after dicing is shifted, and the semiconductor devices 22 do not contact each other and are not damaged.

  After the pure water 34 is completely discharged 44 from the shaving area 6, the spacer 40 is removed. As a result, as shown in FIG. 10, the semiconductor device 22 after dicing is disposed on the dicing tape 14. The semiconductor device 22 after dicing maintains the positional relationship before dicing. That is, the same result as that obtained by dicing a wafer having a flat back surface can be obtained. For this reason, the diced semiconductor device 22 can be collected in the tray 48 by using an existing die pick device.

  In the present embodiment, the process of solidifying the liquid to flatten the back surface of the half-cut wafer and the process of melting and removing the solidified product are performed outside the dicing apparatus. A dicing machine uses a dicing tape to detach a half-cut wafer. The procedure performed by the dicing apparatus is the same as that when a wafer having a flat back surface is processed, and does not reduce the operating rate of the dicing apparatus.

(A) is the figure which looked at the half-cut wafer 2 from the back surface 2a side, (b) is the sectional drawing. FIG. 3 is a view in which a back surface 2b of the half-cut wafer 2 is fixed to a dicing ring 12 by a dicing tape 14; The problem of the prior art is shown. FIG. 3 shows the state of dicing the fixed shaving wafer 2 as shown in FIG. The problem of the prior art is shown. It is a figure which measures the shape of the ring-shaped thick part 8 of the half-cut wafer 2. FIG. 3 is a view in which pure water 34 is injected into the medium cutting region 6 of the medium cutting wafer 2. FIG. 6 is a view of the mid-cut wafer 2 in FIG. 5 cooled. FIG. 3 is a view in which a back surface 2b of a half-cut wafer 2 in which a half-cut region 6 is filled with ice 36 is fixed to a dicing ring 12 by a dicing tape 14; FIG. 8 shows a state in which the half-cut wafer 2 fixed as shown in FIG. 7 is diced. A state where the spacer 40 is fitted in the dicing groove 38 and the opening 42 is formed in the dicing tape 14 is shown. FIG. 6 is a diagram in which the semiconductor device 22 is collected in a tray 48.

Explanation of symbols

2... Half-cut wafer 2 a... Surface 2 b of the half-cut wafer... Back side 4 of the half-cut wafer... Thin plate portion 4 a. -Back surface 6 of thin plate part ... Medium-cutting region 8 ... Ring-shaped thick part 8a ... Surface 8b of ring-shaped thick part ... Ring-shaped thick part Back surface 8c of the ring-shaped thick part 8d Width of the ring-shaped thick part 8e ・ ・ ・ R shape of the ring-shaped thick part 10 Semiconductor device 10a, 10b, 10c, 10d, 10e ... Semiconductor device 12 ... Dicing ring 14 ... Dicing tape 16 ... Stage 18 ... Dicing blade 20 ... Cooling water 22 ... ... Semiconductor device 24 after dicing ... Dicing line measuring device 26 ... Anti-freezing 32 ... Shape measuring device 34 ... Pure water 36 ... Ice 36b ... Ice back surface 38 ... Dicing groove 40 ... Spacer 40a ... Spacer separation wall 42 ... Opening 44 ... Pure water discharge 48 ... Tray

Claims (4)

It is a method of manufacturing a plurality of semiconductor devices through a process of dicing a wafer,
Forming the plurality of semiconductor devices on the wafer;
Polishing the central portion of the back surface of the wafer, thinning the central portion of the wafer to a thickness required for the semiconductor device, and leaving a ring-shaped thick portion in the peripheral portion; and
Injecting a solidifying liquid into the thinned region surrounded by the ring-shaped thick part; and
Cooling the wafer and the liquid to solidify the liquid;
Fixing the back surface of the ring-shaped thick part of the wafer and the exposed surface of the back side of the solidified solidified liquid to a dicing ring via a dicing tape;
Fixing the dicing ring to a stage;
Dicing the wafer fixed to the dicing ring along a dicing line passing between adjacent semiconductor devices;
A method for manufacturing a semiconductor device, comprising: Before the step of injecting the liquid, comprising the step of identifying the volume of the thinned region surrounded by the ring-shaped thick part,
2. The method of manufacturing a semiconductor device according to claim 1, wherein in the step of injecting the liquid, an amount of the liquid obtained by dividing the volume specified in the step by the volume expansion coefficient at the time of solidification of the liquid is injected.   The manufacturing method according to claim 1 or 2, wherein in the dicing step, an antifreeze liquid having a solidification temperature equal to or lower than a solidification temperature of the liquid is used. After the dicing process,
A step of peeling the dicing ring from the stage in a state where the wafer and the solidified product are adhered to the dicing tape and the dicing ring;
Inserting the spacer separation wall into the dicing groove formed in the dicing step by superimposing the spacer on which the separation wall is formed on the wafer;
Forming an opening in a range in close contact with the solidified product of the dicing tape;
Heating the wafer and the solidified product to melt the solidified product;
The method of manufacturing a semiconductor device according to claim 1, further comprising:

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