KR20070049349A - Wafer back grinding apparatus having sawing unit - Google Patents

Abstract

The present invention relates to a wafer backside polishing apparatus having a sawing unit. Wafers that have passed through the conventional wafer backside polishing apparatus have been difficult to handle due to deformations such as thinning and warpage caused by stress during backside polishing. In order to solve such a problem, the present invention provides a wafer backside polishing apparatus having a sawing unit for cutting a wafer fixed to a chuck table into individual semiconductor chips in addition to the polishing unit. The wafer backside polishing apparatus according to the present invention is sawed together with backside polishing in the backside polishing apparatus. According to the present invention, a separate sawing device is not required, which reduces the installation space in the production line. And since the sawing is done immediately after polishing, TAT (Turn Around Time) is reduced. In addition, since the wafer is discharged in the sawed state in the back polishing apparatus, a problem due to warpage of the wafer as in the prior art does not occur. Therefore, productivity and reliability of the work can be improved. Furthermore, by sawing on the back surface of the wafer, damage to the circuit pattern formation surface can be prevented and the reliability of the product can be improved.

Wafer Polishing Device, Wafer, Laser, Sawing, Handling

Description

Wafer back grinding apparatus having sawing unit

1 is a plan view schematically showing a wafer backside polishing apparatus according to the prior art.

Figure 2 is a plan view schematically showing a wafer backside polishing apparatus according to the present invention.

3A to 3D are sectional views showing the operation of the wafer backside polishing apparatus of FIG.

Explanation of symbols on the main parts of the drawings

100,200; Wafer back grinding apparatus

11; Turntable

12,212; Chuck table

13a, 213a; Rough grinding wheel

13b, 213b; Fine grinding wheel

13c, 213c; Polishing Grinding Pad

14; Laser sawing unit

15a, 15b, 15c, 15d; Cleaning Liquid Spray Nozzle

20; Wafer

21; Lamination tape

101,201; Wafer Supply

30,230; Cassette

102,202; Wafer Alignment

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor package manufacturing apparatus, and more particularly, to a backside polishing apparatus for a wafer.

After a series of wafer fabrication processes are completed, the wafer is subjected to back grinding before being separated into individual chips. The back surface polishing process is a process for making the thickness of the wafer thin by mechanically polishing the back surface of the wafer. In this case, the final thickness of the target wafer may vary depending on the type of semiconductor product or the customer's requirements.

1 is a plan view schematically showing a wafer backside polishing apparatus according to the prior art.

Referring to FIG. 1, the conventional wafer back surface polishing apparatus 200 is provided with four chuck tables 212a to 212d on a turn table 211, and a polishing unit 213a to back surface of the wafer 220. 213c are provided on the turntable 211. The wafer 220 that has passed through the wafer alignment unit 202 in the wafer supply unit 201 is loaded into the chuck table 212d. By the rotation of the turntable 211, the chuck tables 212a to 212d are moved in units of 90 °. Then, the roughing wheel 213a, the finishing wheel 213b, and the polishing polishing pad 213c provided at each position are polished to the final thickness targeted for the wafer 220.

In recent years, thinning of wafers of 80 mu m or less in thickness is accelerating with wafer large diameter. By the way, the back surface polishing apparatus of the mechanical polishing method by the grinding wheel (grind wheel) as described above has a limitation due to the thinning of the wafer. Wafer deformation and damage due to stress applied to the wafer during the back polishing process for wafers less than 50 μm thick and subsequent sawing tape mount and lamination tape removal processes. This is because there is a problem with the handling of.

For example, a wafer thinned after backside polishing generates wafer warpage due to thermal stress. This is because the thinned silicon layer cannot withstand the shrinkage force acting toward the wafer surface due to the difference in thermal expansion coefficient between the metal wiring and the silicon layer. Warped wafers cause various handling problems, such as difficult pick-ups and falling during the transfer process.

On the other hand, the wafer on which backside polishing is completed is sawed by a wafer sawing apparatus. As a wafer sawing apparatus, in order to prevent chipping, cracks, etc., which may occur in a mechanical sawing method using a blade, a laser sawing apparatus of a cutting method using a laser sawing unit is provided. Recently introduced. However, residues during laser sawing contaminate the wafer's pattern portion or fine debris remains after cleaning, and the wafer circuit is subjected to instantaneous thermal shock of the laser when laser sawing from the wafer circuit pattern forming surface. There is a problem in that the pattern portion is delaminated or peeled.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wafer backside polishing apparatus which can minimize wafer warpage after backside polishing to prevent wafer damage due to warpage and thus facilitate handling of the wafer.

Another object of the present invention is to provide a wafer backside polishing apparatus that can prevent wafer damage due to contamination and heat shock on the wafer circuit pattern forming surface during wafer sawing.

In order to achieve the above object, the present invention provides a wafer backside polishing apparatus in which sawing is performed without further handling after wafer backside polishing, and sawing proceeds from the backside of the wafer.

A wafer backside polishing apparatus according to the present invention includes a plurality of chuck tables on which a wafer is mounted and fixed so as to open opposite backsides of a circuit pattern forming surface, and rotates a wafer, at least one polishing unit for polishing a wafer backside on a chuck table; It has a sawing unit for sawing a wafer polished to a final wafer thickness on a chuck table into individual semiconductor chips.

In the wafer backside polishing apparatus according to the present invention, the polishing units are preferably polished by a predetermined thickness unit up to the target final wafer thickness.

In the wafer backside polishing apparatus according to the present invention, the chuck tables are preferably formed in the same number as the sum of the number of polishing units and the number of sawing units.

In the wafer backside polishing apparatus according to the present invention, the chuck tables may be radially installed and may include a turntable for rotating the chuck tables collectively.

In the wafer backside polishing apparatus according to the present invention, there are four chuck tables, three polishing units, and three polishing units are roughing wheels for primary polishing thicker than the final thickness of the wafer, which targets the backside of the wafer, 1 It is preferable that it is a finishing wheel for secondary polishing to the final thickness of the wafer targeted for the secondary polished wafer back surface, and a polishing polishing pad for mirror- mirroring the back surface of the secondary polished wafer.

In the wafer backside polishing apparatus according to the present invention, the sawing unit is preferably a laser sawing unit.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the accompanying drawings, some of the components are somewhat exaggerated, schematically illustrated or omitted to facilitate a clear understanding of the drawings, and the actual size of each component is not entirely reflected.

Example

2 is a plan view schematically showing a wafer back surface polishing apparatus according to the present invention, and FIGS. 3A to 3D are cross-sectional views showing the operation of the wafer back surface polishing apparatus of FIG.

2 and 3, the wafer backside polishing apparatus 100 according to the present invention comprises four chuck tables 12a, 12b, 12c, 12d and three grinding units 13a, 13b, 13c) and a cleaning liquid jet nozzles 15a, 15b, 15c, 15d, comprising a sawing unit 14 for sawing the wafer 20 immediately after backside polishing without additional handling. It is characterized by

The chuck tables 12a-12d are radially installed on the turn table 11 at 90 ° intervals, respectively. The positions of the chuck tables 12a to 12d are changed by the rotation of the turntable 11. The chuck tables 12a to 12d suck and fix the wafer 20 under vacuum pressure on the circuit pattern formation surface side of the wafer 20. Here, for convenience, the chuck tables 12a to 12d are referred to as first to fourth chuck tables in a process order. At the end of each process step, the four chuck tables 12a-12d mounted on the turntable 11 rotate by 90 °.

The polishing units 13a to 13c are positioned on the first to third chuck tables 12a to 12c to polish the back surface of the wafer 20 by a predetermined thickness unit up to the target final wafer 20 thickness, respectively. do. The polishing units 13a to 13c are roughing wheels 13a, finishing wheels 13b and polishing polishing pads 13c. The roughing wheel 13a has a particle size of 300 to 350 mesh, for example, 325 mesh, and is primarily about the back surface of the wafer 20 to be 20 to 30 μm thicker than the final thickness of the target wafer 20. Polish The finishing wheel 13b has a particle size of 1500 to 2500 mesh, for example 2000 mesh, and precisely polishes the back surface of the primary polished wafer 20 to the final target thickness. The polishing polishing pad 13c has a conventional structure in which a bottom surface is covered with a material such as cloth, and a slurry supply part is formed therein. The polishing polishing pad 13c mirrors the back surface of the secondary polished wafer 20 using the slurry.

The laser sawing unit 14 is located on the fourth chuck table 12d. The laser sawing unit 14 sawes the wafer 20 subjected to primary and secondary polishing and mirroring into individual semiconductor chips. At this time, since the back surface of the wafer 20 is adsorbed to face upward, sawing proceeds from the back surface side of the wafer 20. Here, the sawing unit is not limited to the structure using the laser sawing unit 14. For example, a structure for sawing a wafer using a blade or other sawing unit is possible.

The protective tape 21 is attached to the circuit pattern formation surface of the wafer 20. The protective tape 21 is used in a conventional wafer 20 back surface polishing process, and is temporarily attached to protect a circuit pattern formed on the surface of the wafer 20 during the process. The shifting of the individual semiconductor chips due to sawing is prevented by the protective tape 21.

The roughing wheel 13a, the finishing wheel 13b, the polishing polishing pad 13c and the laser sawing unit 14 are each disposed at 90 ° intervals. As described above, the chuck tables 12a to 12d are radially installed on the turntable 11 at 90 ° intervals. The polishing units 13a to 13c and the laser sawing unit 14 are located on the chuck tables 12a to 12d, respectively. Rotation of the turntable 11 and the chuck tables 12a-12d results in primary and secondary polishing, mirroring and sawing of the wafer 20.

The cleaning liquid spray nozzles 15a, 15b, 15c, and 15d are positioned on the first and fourth chuck tables 12a to 12d. First spray nozzle 15a and roughing wheel 13a, second spray nozzle 15b and finishing wheel 13b, third spray nozzle 15c and polishing polishing pad 13c, and fourth spray nozzle 15d And the laser sawing unit 14 are located adjacent to each other. The cleaning liquid spray nozzles 15a to 15d spray the cleaning liquid onto the back surface of the wafer 20 to remove foreign substances such as silicon debris or slurry remaining on the wafer 20.

3A to 3D, the operation of the wafer backside polishing apparatus 100 according to the present invention will be described. First, the wafer 20 loaded on the first chuck table 12a is predetermined thickness from the backside by the roughing wheel 13a. As much as primary polishing. When the primary polishing of the wafer 20 is completed, the turntable 11 is rotated 90 degrees. The first chuck table 12a on which the wafer 20 is adsorbed is moved to the position where the finishing wheel 13b is located.

By the finishing wheel 13b, the back surface of the wafer 20 on which primary polishing is completed is secondarily polished. When the secondary polishing of the wafer 20 is completed, the turntable 11 is rotated 90 ° so that the chuck table 12a on which the wafer 20 is adsorbed is moved to the position where the polishing polishing pad 13c is located.

The back surface of the wafer 20 polished secondary by the polishing polishing pad 13c is mirrored. As a result, a wafer 20 having a target thickness is obtained. When the mirroring of the wafer 20 is completed, the turntable 11 is rotated 90 degrees. The chuck table 12a on which the wafer 20 is adsorbed is moved to the position where the laser sawing unit 14 is located.

The mirrored wafer 20 is sawed by the laser sawing unit 14. As a result, the wafer 20 is separated into individual semiconductor chips. Unlike the general sawing process, the sawing process of the wafer 20 in the wafer backside polishing apparatus 100 according to the present invention is sawed on the backside of the wafer 20.

When the sawing of the wafer 20 is completed, the wafer 20 at the position where the laser sawing unit 14 is located is discharged. The chuck table 12a is rotated 90 degrees to move to the position where the roughing wheel 13a is located. The wafer 20 discharged from the wafer backside polishing apparatus 100 is unloaded and then transferred to the apparatus for the next process.

When the turntable 11 is rotated by 90 °, the first chuck table 12a on the roughing wheel 13a is in the position of the second chuck table 12b with the finishing wheel 13b, and at the position with the finishing wheel 13b. The second chuck table 12b was in the position with the polishing polishing pad 13c, the third chuck table 12c in the position with the polishing polishing pad 13c was in the position with the laser sawing unit 14, The fourth chuck table 12d in the position where the laser sawing unit 14 is located is moved to the position where the roughing wheel 13a is located.

When the primary and secondary polishing, mirroring, and sawing of the wafer 20 proceed, the cleaning liquid spray nozzles 15a to 15d spray the cleaning liquid. Thus, foreign substances remaining on the wafer 20 are removed.

According to the wafer backside polishing apparatus according to the present invention as described above, wafer sawing proceeds immediately after the backside polishing without further handling. The wafer is separated into each individual semiconductor chip. Therefore, warpage in the wafer state is minimized and wafer handling is easy, thereby ensuring workability on the thin wafer.

In addition, since wafer sawing is performed together with wafer backside polishing in a wafer backside polishing apparatus, a separate wafer sawing apparatus is not required, equipment occupied space is reduced, and TAT is reduced.

Moreover, since the sawing unit saws from the backside of the wafer, contamination and damage of the circuit pattern forming surface of the wafer is minimized. In particular, when the laser sawing unit is used, contamination of the wafer pattern forming surface due to fine debris generated during the sawing process can be minimized, and delamination or peeling of the wafer circuit pattern portion due to thermal shock of the laser can be minimized. can do.

Claims (6)

A plurality of chuck tables on which the wafer is mounted and fixed so as to open the reverse surface of the wafer opposite to the circuit pattern formation surface and rotate the wafer; At least one polishing unit corresponding to the chuck table and polishing the back surface of the wafer with a target final wafer thickness; And a sawing unit for sawing the wafer polished to a final wafer thickness on the chuck table into individual semiconductor chips. According to claim 1, And the polishing units each polish by a predetermined thickness unit to a target final wafer thickness. According to claim 1, And the chuck tables are formed in the same number as the sum of the number of polishing units and the number of sawing units. According to claim 1, The chuck tables are radially installed, further comprising a turntable for rotating the chuck tables collectively. The method of claim 2, The chuck table is four, the polishing units are three, and the three polishing units are aimed at the roughing wheel to first polish thicker than the final thickness of the wafer to target the backside of the wafer, the backside of the first polished wafer. And a polishing wheel for secondary polishing to a final thickness of the wafer, and a polishing polishing pad for mirror-mirroring the back surface of the secondary polished wafer. According to claim 1, And said sawing unit is a laser sawing unit.

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