JP2009054799A - Chuck table - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chuck table which can prevent protective tape from sticking at high temperatures and achieve a sufficient suction force. <P>SOLUTION: The chuck table is used for bonding a die bonding film onto the backside of a wafer on which a plurality of devices are formed and protective tape is bonded thereon. The chuck table is made up of a holding table for holding the wafer by suction and a base table including a heater for heating the holding table. At the center or over the surface of the holding table, surface treatment is performed so as to apply a material mainly composed of one of fluorocarbon resin, fluorocarbon rubber, silicone resin, and silicone rubber. Surface roughness varies between the center of the holding table and the outer periphery around the center. The center of the holding table has higher surface roughness than the outer periphery. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a chuck table used for adhering a die bonding film to the back surface of a wafer.

  A wafer on which a plurality of devices such as IC and LSI are formed on the front surface side is divided into individual devices by a dicing apparatus, and the back surface of each device is die-bonded to a lead frame having a plurality of electrodes.

  In order to perform die bonding, a bonding film called a die attach film (DAF) is attached to the back surface of the wafer before dicing (see, for example, Japanese Patent Application Laid-Open No. 11-219962).

  The bonding film is formed of an epoxy resin or the like, and is bonded to the back surface of the wafer in a state where the wafer is heated to 130 to 180 ° C., and further cured (cured) at about 150 to 180 ° C.

  When the die bonding film is attached, a chuck table including a holding table that holds the wafer and a base table that has a heating unit that heats the holding table is used.

  In this chuck table, the wafer is supported by a holding table with the front side of the wafer to which a protective tape for device protection is attached facing down, and a die bonding film is attached to the back surface exposed upward.

  The holding table is heated by the heating unit to heat the held wafer, and the die bonding film is adhered to the back surface of the wafer by pressing the die bonding film against the holding table with a roller or the like, and further heating is continued. To obtain a wafer with a die bonding film. Therefore, in order to sufficiently conduct heat to the holding table, a metal having high thermal conductivity is used for the heating unit.

At present, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-317712, a protective tape for device protection is attached to the front surface, the back side is ground by a grinding device, and loaded from a thinned wafer state, A tape mount apparatus is also used that automatically attaches a die bonding film, fixes the wafer to the dicing frame with a dicing tape, and then peels off the protective tape.
Japanese Patent Laid-Open No. 11-219962 JP 2005-317712 A

  As described above, the holding table for adhering the die bonding tape to the wafer is set to a very high temperature of about 130 to 180 ° C. when the tape is applied and about 150 to 180 ° C. when thermosetting. Therefore, since the protective tape formed from resin contacts with the holding table set at high temperature, it is easy to soften, and there is a concern that it may stick to the holding table.

  In order to prevent this, the surface of the holding table was treated with a fluorine resin such as Teflon. However, because the temperature was too high, the protective tape was completely stuck even with this surface treatment. It did not come to prevent.

  As a result, when the wafer is transported to the next process, a wafer crack or a transport error occurs, the protective tape is fixed to the holding table, maintenance is required to remove it, and the bonding time is set. There was a problem that the limit was made.

  In order to improve this, there was a case where an unevenness was formed on the surface of the holding table, the degree of adhesion between the holding table and the protective tape was lowered, and a process for preventing the sticking of the protective tape (for example, a toxical process) was performed. On the other hand, since the degree of adhesion has decreased too much, a new problem has occurred that air leaks during vacuum suction, resulting in frequent suction errors.

  The present invention has been made in view of these points, and an object of the present invention is to provide a chuck table that is difficult to attach a protective tape even in a high temperature state and that has sufficient vacuum suction performance. .

  According to the present invention, a chuck table used for adhering a die bonding film to a back surface of a wafer having a protective tape attached to a surface on which a plurality of devices are formed, and a holding table for sucking and holding the wafer; And a base table provided with a heater for heating the holding table, and the surface of the holding table is either a fluororesin, a fluororubber, a silicone resin, or a silicone rubber at the center or the entire surface. A surface treatment is applied to which a material mainly composed of k is applied, and the surface roughness is different between the central portion of the holding table and the outer peripheral portion surrounding the central portion, and the central portion of the holding table is There is provided a chuck table characterized in that the surface roughness is rougher than that of the outer peripheral portion.

  Preferably, the surface roughness of the holding table is Ra: 3 to 10 μm, Rz: 25 to 60 μm at the center, Ra: 0.5 to 5 μm, Rz: 5 to 20 μm at the outer periphery.

  According to the chuck table of the present invention, the surface of the holding table is subjected to a surface treatment for applying a fluorine-based resin or the like, and further the surface roughness of the central portion is processed to be rougher than that of the outer peripheral portion. In order to prevent sticking of the protective tape by lowering the degree of adhesion and to prevent air leakage at the outer periphery, it is difficult for the protective tape to stick even when the table is at a high temperature and can exhibit sufficient suction performance There is an effect.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an exploded perspective view showing a state where a die bonding film is attached to a semiconductor wafer. A plurality of devices such as IC and LSI are formed on the surface of the semiconductor wafer 2, and a protective tape 4 for protecting the device is attached to the entire surface.

  A die bonding film 6 called a die attach film (DAF) is attached to the back surface 2 a of the wafer 2. The die bonding film 6 is formed of an epoxy resin which is a thermosetting resin, and is bonded to the back surface 2a of the wafer 2 in a state where the wafer 2 is heated to 130 to 180 ° C., and then predetermined temperature is set to 150 to 180 ° C. By being held for a period of time, it is cured (cured) and firmly fixed to the back surface 2a of the wafer 2.

  Referring to FIG. 2, a sectional view of the chuck table 8 according to the first embodiment of the present invention is shown. The chuck table 8 is used as a mount table for adhering the die bonding film 6 to the back surface 2 a of the wafer 2.

  The chuck table 8 includes a base table 10, a heater 14 attached to the base table 10 via a heat insulating plate 12, and a holding table 16 fixed to the heat insulating plate 12 with a plurality of screws 18. The heater 14 is made of a metal such as stainless steel.

  The holding table 16 is also fixed to the heater 14 with screws 20. The holding table 16 is made of, for example, aluminum or an aluminum alloy, and a plurality of small holes in the vertical direction are drilled over the entire area.

  A vacuum hole 22 for vacuum suction is communicated with each small hole formed in the holding table 16. Reference numeral 24 denotes a wiring connected to the heater 14, and the temperature of the heater 14 is detected by a thermocouple 26.

  The surface of the holding table 16 is roughened so as to have a large number of convex portions and concave portions. As the rough surface processing method, a blasting method, a thermal spraying method or the like can be employed. In the blast method, a large number of irregularities are formed on the surface of the holding table 16 by spraying a granular or spherical metal body or ceramic body onto the surface of the holding table 16 with a predetermined blast pressure.

  The feature of the present invention is that the surface roughness of the holding table 16 by the roughening is made different between the central portion 16a shown in FIG. 3 and the outer peripheral portion 16b surrounding the central portion 16a. That is, the surface roughness of the central portion 16a is set to be rougher than that of the outer peripheral portion 16b.

  In FIG. 3, the code | symbol 19 has shown the hole for inserting the screw 18 for fastening. The holding table 16 of this embodiment has a diameter of 300 mm, a central portion 16a has a diameter of, for example, 280 mm, and an outer peripheral portion 16b has a width of 10 mm.

  Thus, after the surface of the holding table 16 is roughened, a coating layer made of a desired coating material is formed on the surface of the holding table 16. Since it is desirable that the surface of the holding table 16 has releasability, wear resistance, etc., the coating material is a fluorine resin, a fluorine rubber, a silicone resin, or a material mainly composed of a silicone rubber. Is preferred.

  Preferably, before the coating layer is formed on the surface of the holding table 16, the surface of the holding table 16 that has been roughened is flattened. As the flattening process, a method of compressing the top of the convex portion of the holding table 16, a method of cutting the top of the convex portion, a method of polishing the top of the convex portion, or the like can be employed.

  By performing the flattening process on the surface of the holding table 16 that has been roughened in this way, the thickness of the coating layer can be reduced. The film thickness of the coating layer is desirably about 10 μm to 50 μm.

  As for the surface roughness of the holding table 16 after forming the coating layer, the central portion 16a has an arithmetic average roughness Ra: 3 to 10 μm, a ten-point average roughness Rz: 25 to 60 μm, and the outer peripheral portion 16b has Ra: 0.5. It is desirable that it is ˜5 μm and Rz: 5 to 20 μm.

  Here, the arithmetic average roughness Ra is defined as an average value of absolute value deviations from the average line. Further, the ten-point average roughness Rz is defined as the average height of five points selected from the highest of the peaks for each reference length and five points from the lowest of the valley bottoms.

In FIG. 2, in order to attach the die bonding film 6 to the back surface 2 a of the wafer 2, the wafer having the protective tape 4 attached to the surface of the holding table 16 heated to 130 to 180 ° C. by the heater 14. 2 is placed with the protective tape 4 facing downward.

  Then, the die bonding film 6 attached to the release sheet 7 is pressed against the back surface 2 a of the wafer 2 by the roller 28, so that the die bonding film 6 is attached to the back surface of the wafer 2. When the die bonding film 6 is attached to the back surface of the wafer 2, the release sheet 7 is peeled from the die bonding film 6.

  In the present embodiment, since the holding table 16 has a surface roughness that is set so that the central portion 16a is rougher than the outer peripheral portion 16b, the degree of adhesion is lowered at the central portion 16a of the holding table 16 and the protective tape 4 is attached to the holding table 16. Since the outer peripheral portion 16b has a fine surface roughness, the outer peripheral portion 16b can prevent air leakage at the time of suction and can prevent a wafer transport error. .

  A holding table having the same surface roughness as the central portion 16a over the entire area of the holding table 16 was created as a comparative example, and the difference in vacuum pressure from the holding table 16 of the embodiment of the present invention shown in FIG. 3 was measured. .

  In the comparative example having a uniform surface roughness, the vacuum pressure was 60 kPa and a wafer conveyance error occurred. However, in the holding table 16 of the embodiment of the present invention, the vacuum pressure was 83 kPa, and no wafer conveyance error occurred. there were.

  Referring to FIG. 4, a cross-sectional view of the chuck table 30 according to the second embodiment of the present invention is shown. The chuck table 30 of this embodiment is used as a cure table for curing (thermosetting) the die bonding film 6 adhered to the back surface of the wafer 2.

  A heater 36 is mounted on the base table 32 via a heat insulating plate 34. The heater 36 is fixed to the base table 32 by a plurality of screws 38. A holding table 40 is placed on the heater 36 and fixed to the heater 36 or the base table 32 by fastening means (not shown).

  The holding table 40 is made of aluminum or an aluminum alloy, and a large number of small holes extending in the vertical direction are drilled in the same manner as the holding table 16 of the first embodiment shown in FIG. The surface of the holding table 40 is subjected to the same surface treatment as the surface of the holding table 16 of the first embodiment shown in FIG.

  That is, a coating layer mainly composed of any one of fluororesin, fluororubber, silicone resin, or silicone rubber is formed on the entire surface of the holding table 40, and the surface roughness of the central portion 40a is Ra: 3. 10 μm, Rz: 25 to 60 μm, and the surface roughness of the outer peripheral portion 40 b is set to Ra: 0.5 to 5 μm and Rz: 5 to 20 μm.

  Reference numeral 42 denotes a vacuum hole communicating with a small hole drilled in the holding table 40, and 44 denotes a wiring connected to the heater 36. The temperature of the heater 36 is detected by a temperature sensor such as a thermocouple (not shown). An annular housing 46 is fixed to the base table 32.

  On the holding table 40 heated to about 150 to 180 ° C. by the heater 36, the wafer 2 having the protective tape 4 adhered on the surface thereof is placed with the protective tape 4 facing downward, and is held in this state for a predetermined time. Then, the die bonding film 6 adhered to the back surface of the wafer 2 is thermally cured (cured) and firmly fixed to the back surface of the wafer 2.

  Also in the chuck table 30 of the present embodiment, the surface of the holding table 40 is processed so that the central portion 40a is rougher than the peripheral portion 40b. Therefore, the degree of adhesion is lowered at the central portion 40a of the holding table 40 and the protective tape is used. 4 can be prevented and air leakage at the time of suction can be prevented at the outer peripheral portion 40b, so that a sufficient suction effect can be exhibited, and when the wafer 2 is transported to the next process It is possible to prevent cracks in the wafer 2 and conveyance errors.

It is a disassembled perspective view which shows a mode that a die-bonding film is stuck on the back surface of a wafer. It is sectional drawing of the chuck table which concerns on 1st Embodiment of this invention, and is suitable for utilizing as a mount table. It is a top view of a holding table. It is sectional drawing of the chuck table which concerns on 2nd Embodiment of this invention, and is suitable for utilizing as a cure table.

Explanation of symbols

2 Semiconductor wafer 4 Protective tape 6 Die bonding film 8, 30 Chuck table 10, 32 Base table 14, 36 Heater 16, 40 Holding table 16a, 40a Central part 16b, 40b Outer peripheral part 22, 42 Vacuum hole

Claims (2)

A chuck table used for adhering a die bonding film to the back surface of a wafer having a protective tape attached to a surface on which a plurality of devices are formed,
A holding table for sucking and holding the wafer, and a base table provided with a heater for heating the holding table;
The surface of the holding table is subjected to a surface treatment in which a material mainly composed of any one of a fluorine-based resin, a fluorine-based rubber, a silicone-based resin, and a silicone-based rubber is applied to the central portion or the entire surface.
The chuck table is characterized in that the central portion of the holding table is different in surface roughness from the outer peripheral portion surrounding the central portion, and the central portion of the holding table is rougher than the outer peripheral portion. .   The surface roughness of the holding table is such that the central portion is Ra: 3 to 10 μm, Rz: 25 to 60 μm, the outer peripheral portion is Ra: 0.5 to 5 μm, and Rz: 5 to 20 μm. Item 2. The chuck table according to item 1.

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