JP2008311382A - Washing method for porous ceramic-made chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a washing method for a disk-like porous ceramic-made chuck by which a ground substrate having no dimple mark and superior surface gloss is obtained. <P>SOLUTION: The washing method for the porous ceramic-made chuck includes: applying rear surface grinding to a rear surface of the semiconductor substrate mounted on a surface of the porous ceramic-made chuck table 2; washing the ground surface of the semiconductor substrate w; removing the washed ground semiconductor substrate from on the porous ceramic-made chuck table; and washing the chuck table with washing liquid, wherein the washing liquid is supplied from a bottom surface side to a top surface side of the chuck table 2 and pressurized water is jetted to the chuck table surface from an injection nozzle 10 provided above the chuck table to remove sludge from the chuck table. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for cleaning a porous ceramic chuck installed in a back grinding apparatus for a semiconductor substrate. More specifically, the present invention relates to a chuck cleaning method that effectively removes grinding residues and particle debris buried or stuck in a porous ceramic chuck from a porous ceramic chuck.

  In a semiconductor substrate back surface grinding apparatus, the back surface of a semiconductor substrate placed on a porous ceramic chuck table is ground, and the substrate is cleaned by spraying a cleaning liquid onto the back ground substrate surface. A number of chuck cleaning methods have been proposed in which, after removal, grinding residues and particle debris buried or stuck in the porous ceramic chuck table are effectively removed from the porous ceramic chuck.

  For example, while supplying a cleaning liquid to the cleaning surface of a porous ceramic chuck, a plurality of ceramic rods radially supported by a rotating shaft are rotated while being in contact with the chuck, and partially bite into micropores on the surface of the porous ceramic chuck. This is a method for removing grinding scraps (for example, see Patent Document 1).

  Further, after supplying cleaning fluid (for example, pressurized air and pressurized water) from the bottom surface side to the surface side of the chuck table made of porous ceramic (back flush), the grinding waste entering the porous hole is ejected to the surface side, An oil stone (grinding stone member) is pressed against the surface of the porous ceramic chuck table and rubbed to remove grinding debris protruding from the surface of the porous ceramic chuck table, and then provided above the porous ceramic chuck table. There has been proposed a cleaning method in which pure water is sprayed onto the surface of the chuck table from the spray nozzle, and the sprayed pure water is guided to the bottom surface side of the chuck table through a hole (for example, see Patent Document 2).

  Further, the surface of the porous ceramic chuck table that is exposed by removing the semiconductor substrate from the porous ceramic chuck table that sucks and holds the semiconductor substrate is 3 to 10 Mpa, preferably from the spray nozzle provided obliquely above. Has proposed a cleaning method in which 7 Mpa of high-pressure water is jetted onto the surface of the chuck table in an amount of 5 to 20 liters / minute to remove grinding waste from the surface of the chuck table (see, for example, Patent Document 3).

  In addition, it is easy to separate the semiconductor substrate from the surface of the chuck table by ejecting (back flushing) pressurized air from the bottom surface side of the chuck table to the semiconductor substrate whose surface is held by the porous ceramic chuck table. After that, the semiconductor substrate is transferred to the next process stage by the transfer suction pad, and then the rotating ceramic table is lowered while supplying the cleaning liquid to the surface of the rotating chuck table while rotating the chuck table to lower the chuck table. There has also been proposed a cleaning method for removing sludge (grinding debris and abrasive grains) adhering to the chuck table surface by sliding on the surface (see, for example, Patent Document 4).

  In addition, the semiconductor substrate that has been brush-cleaned on the surface of the porous ceramic chuck table can be easily separated from the chuck table surface by ejecting pressurized air (back flushing) from the bottom surface side of the chuck table. After that, the semiconductor substrate is transferred to the next process stage by the transfer suction pad, and then the rotating ceramic table is lowered while supplying the cleaning liquid to the surface of the rotating chuck table while rotating the chuck table to lower the chuck table. Remove the sludge (grinding debris and abrasive grains) adhering to the chuck table surface by rubbing against the surface, then raise the ceramic iron, lower the rotating brush and rub against the chuck table surface to chuck A cleaning method to completely remove sludge adhering to the table surface is also proposed. Is (e.g., see Patent Document 5.).

Japanese Patent Publication No. 5-9229 Japanese Patent Publication No. 5-55207 JP 2004-095771 A Japanese Patent Laying-Open No. 2005-044874 JP 2006-237108 A

  The cleaning method of washing away grinding scraps and abrasive grains stuck into the holes of the porous ceramic chuck with a grinding wheel such as a ceramic rod or an oil stone that uses the back flush described in Patent Documents 1 and 2 and Patent Document 4, When the surface of a porous ceramic chuck surface is heavily worn and an ultrathin semiconductor substrate with a thickness of 20-50 μm is ground by backside grinding, the porous ceramic chuck table is sometimes removed and the chuck table surface is ground or lapped to flatten it. It needs to be regenerated and placed on the rotary table. For example, an index table type back grinding apparatus having three porous ceramic chuck tables is used, and a 300 mm diameter silicon wafer is run for 6 weeks (2400 on the porous ceramic chuck of the first grinding stage). (7200 on the second grinding stage) Since the wear at the center of the chuck when grinding is about 3 μm, it is necessary to correct the spindle tilt angle for bearing the grinding wheel in the machining program once a week. It was.

  The cleaning method of the porous ceramic chuck table in which the number of brush cleaning steps in Patent Document 5 is increased, compared with the cleaning method described in Patent Document 4, the degree of wear on the surface of the porous ceramic chuck is reduced. Has the advantage of extending the time. However, a semiconductor substrate processing manufacturer demands the appearance of a chuck cleaning method that can further extend the period for regenerating the porous ceramic chuck table.

  In the chuck cleaning method using only high-pressure jet cleaning disclosed in Patent Document 3, it is difficult to completely remove grinding debris and abrasive grains stuck in the holes of the porous ceramic chuck table, and the mirror gloss of the back surface of the ground semiconductor substrate is processed. Are gradually reduced, and the back surface of the semiconductor substrate becomes semi-glossy on the 2400th ground substrate.

  An object of the present invention is to reduce the degree of wear of a porous ceramic chuck table over time, to delay the opportunity over time to correct the spindle tilt angle in a machining program, and to maintain the gloss. The object is to provide a method for cleaning a ceramic chuck table.

  According to the first aspect of the present invention, the back surface of the semiconductor substrate placed on the surface of the disk-shaped porous ceramic chuck table is ground, the ground surface of the ground semiconductor substrate is cleaned, and then the cleaned ground semiconductor substrate is In the method for cleaning a porous ceramic chuck table, which is removed from the cylindrical ceramic ceramic chuck table and cleaned with a cleaning liquid, the disk-shaped porous ceramic chuck table is moved from the bottom side to the front side of the porous ceramic chuck table. .2 to 2.5 Mpa of cleaning fluid is supplied, and 0.4 to 3 Mpa of pressurized water is sprayed onto the surface of the chuck table from the spray nozzle provided above the porous ceramic chuck table to sludge the porous ceramic chuck. It is characterized by removing from the table That is to provide a cleaning method.

According to a second aspect of the present invention, the back surface of the semiconductor substrate placed on the surface of the disk-shaped porous ceramic chuck table is ground, the ground surface of the ground semiconductor substrate is cleaned, and then the cleaned ground semiconductor substrate is In the method for cleaning the porous ceramic chuck table, the cylindrical ceramic ceramic chuck table is removed from the cylindrical ceramic ceramic chuck table, and the disc-shaped porous ceramic chuck table is cleaned with a cleaning liquid.
In the first round of cleaning the disc-shaped porous ceramic chuck table, after performing backflush cleaning for supplying a cleaning fluid of 0.2 to 2.5 Mpa from the bottom surface side to the front surface side of the porous ceramic chuck table, The surface of the porous ceramic chuck table is rubbed against the surface of the porous ceramic chuck table to form the surface of the porous ceramic chuck table, and then the back surface of the semiconductor substrate placed on the porous ceramic chuck table is ground and the ground semiconductor substrate is ground. After cleaning the ground surface, remove the cleaned ground semiconductor substrate from the disk-shaped porous ceramic chuck table, and then clean the disk-shaped porous ceramic chuck table from which the ground semiconductor substrate has been removed. Number of cleanings set from the second time onwards m is an integer of 2 or more and 10,000 or less.) After the cleaned ground semiconductor substrate is removed from the disc-shaped porous ceramic chuck table, the bottom surface side of the porous ceramic chuck table is changed to the front surface side. Back flush cleaning is performed to supply a cleaning fluid of 0.2 to 2.5 Mpa toward the surface, and 0.4 to 3 Mpa of pressurized water is sprayed onto the surface of the chuck table from the spray nozzle provided above the porous ceramic chuck table. The present invention provides a method for cleaning a porous ceramic chuck table, wherein sludge is removed from the porous ceramic chuck table.

  According to the invention of claim 1, since the back flush and the pressurized jet water washing are used together as means for removing the sludge from the disc-shaped porous ceramic chuck table, the known oil swoon or ceramic soot is used together with the back flush. The wear time of the surface of the porous ceramic chuck table can be extended compared with the cleaning method.

  According to the second aspect of the present invention, in the first cleaning step, a flattening step of forming the disc-shaped porous ceramic chuck table surface with a truing grindstone is added. If the number of times of grinding k when dimples and claws are generated is confirmed based on empirical rules or previous experiments, an integer number of times s smaller than k is recorded in the numerical control recording unit as the time to resume truing (m = s). Then, when the cleaning number m of the machining program stored in the storage unit reaches s, the value of the cleaning number m is returned to 1, and the first cleaning step of performing the molding process with the truing grindstone is resumed. Therefore, the continuous back surface grinding of the semiconductor substrate can be performed continuously without interruption.

Hereinafter, the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a view for explaining a cleaning apparatus for a porous ceramic chuck table of a substrate back grinding apparatus.

In FIG. 1, 1 is a semiconductor substrate holder of a semiconductor substrate back grinding apparatus, 2 is a disk-shaped porous ceramic chuck table, 3 is a rotary table, 4 is a hollow main shaft that supports the rotary table, 4a is an air bearing, and 5 is a hollow main shaft. A drive servomotor, 5a is a pulley, 5b is a belt, 6 is a fluid supply pipe, its left tip extends into the hollow main shaft 6 and its right tip is a decompression pipe 6a connected to the vacuum pump 7, a compressor 8 is branched into a pressurized air supply pipe 6b connected to 8 and a pure water supply pipe 6c connected to a pump 6d. 6e is a rotary universal joint, 6f is a switching valve, and 9 is a pressure gauge.

Reference numeral 10 denotes a pressurized washing water jet nozzle housing provided with three nozzles 10a. 11 is an injection nozzle cover, 12 is an injection nozzle up / down lifting / rotation guide device, 13 is a constant temperature water unit, 14 is a pipe for supplying pure water to the constant temperature water unit, 15 is a truing grindstone, 16 is a support plate for the grindstone, and 17 A grindstone spindle, an 18 grindstone spindle drive motor, 19 is a grindstone spindle lifting device, 20 is a grindstone linear motion guide device, and 21 is a cleaning water supply nozzle. As the truing grindstone 15, an alkane stone stone, a ceramic rod, an oil stone or the like can be used.

The semiconductor substrate that has been subjected to back grinding and whose ground surface has been brush-washed is supplied with 0.1 to 1.1 Mpa of pressurized cleaning liquid or pressurized air via the fluid supply pipe 6 provided in the hollow spindle 4. After supplying the porous ceramic chuck table 2 to the bottom surface side from the hollow shaft 6 for 1 to 5 seconds to facilitate the peeling of the semiconductor substrate w from the chuck table 2, the bottom surface of the transport suction pad 22a attached to the tip of the transport device arm 22 is applied. It is adsorbed and transferred from the porous ceramic chuck table 2 to the next process stage.

  Cleaning the disc-shaped porous ceramic chuck table 2 from which the cleaned semiconductor substrate w has been removed is performed by the drive servo motor 5 of the hollow main shaft 4 that supports the rotary table 3 on which the porous ceramic chuck table 2 is mounted. Rotation 4 is rotated at a rotational speed of 10 to 100 rpm by driving, and a cleaning fluid (pressurized air or pressurized cleaning solution) of 0.2 to 2.5 Mpa from the bottom surface side to the front surface side of the porous ceramic chuck table 2. In addition, the cleaning liquid supplied from the constant temperature water unit 13 is pressurized by the pressure pump 6d to form pressurized water, and 0.4-3 Mpa of pressurized water is supplied from the pressurized cleaning water jet nozzle 10a to the disc-shaped porous ceramic chuck table 2. Porous sera by injecting sludge onto the surface at a flow rate of 2-10 liters / minute for 5-10 seconds Tsu to remove than click-made chuck table 2. The pressure washing water spray nozzle 10 may be swung linearly by 10 to 25 mm in the radial direction of the disc-shaped porous ceramic chuck table 2.

Example 1
The number m of cleaning of the chuck table was input to 2,400 times. After backflush cleaning to supply a cleaning fluid of 0.7 Mpa from the bottom side to the surface side of the 305 mm diameter porous ceramic chuck table, the porous ceramic chuck table surface is rubbed with an alkane suston stone. The surface of the ceramic chuck table was molded.

Next, a semiconductor substrate having a diameter of 300 mm and a thickness of 120 μm was placed on a porous ceramic chuck table, and backside grinding was performed using a diamond cup wheel type grindstone to remove the thickness of 70 μm from the backside of the substrate. After supplying 0.4 Mpa of pressurized cleaning water to the bottom side of the porous ceramic chuck table via the fluid supply pipe provided in the hollow main shaft for 1 second to facilitate peeling of the semiconductor substrate from the chuck table Then, the substrate was adsorbed to the bottom surface of the conveyance suction pad attached to the tip of the conveyance device arm, and transferred to the next process stage from the porous ceramic chuck table.

Next, the cleaning of the 305 mm diameter porous ceramic chuck table was carried out from three nozzles of pressurized cleaning water jet nozzles at a rotation speed of 20 rpm, a back flush of 2.2 Mpa of pressurized air for 2 seconds and a pitch of 40 mm. The cleaning was performed under the condition of spraying 2.0 Mpa of pressurized pure water at a flow rate of 3 liters / minute for 7 seconds.

A new semiconductor substrate having a thickness of 120 μm and a diameter of 300 mm is placed on a cleaned porous ceramic chuck table, and back surface grinding is performed in the same manner as described above, and the porous ceramic chuck table is cleaned and ground. Was removed from the porous ceramic chuck table, and the same porous ceramic chuck table as above was rotated at 20 rpm, 2.2 Mpa of pressurized air backflushing for 2 seconds, and three pressurized cleaning water jet nozzles at 40 mm pitch intervals. The cleaning was performed under the condition of cleaning a porous ceramic chuck table in which 2.0 Mpa of pressurized pure water was sprayed at a flow rate of 3 liters / minute for 7 seconds.

Thereafter, in the same manner, backside grinding of the semiconductor substrate, removal from the porous ceramic chuck table, and cleaning of the porous ceramic chuck table were performed 2,399 times. When 2,400 wafers were ground on the semiconductor substrate, the surface wear amount of the porous ceramic chuck table was 0.8 μm, and the number of dimples generated was 1. This amount of wear was smaller than the amount of wear of 3.1 μm and the number of generated dimples of 11,400 in the 2,400 cleaning method using the oil stone described in Patent Document 2 each time.

As another aspect of the present invention, a molding process using a truing grindstone is not performed at the first time before the back surface grinding of the semiconductor substrate, for example, once after 499 back grindings (the number of cleanings is 500), molding with a truing grindstone. A process may be included.

If the number of times of cleaning s by the truing grindstone is recorded in the numerical control recording unit as the time to resume truing (m = s), when the number of cleanings m of the machining program stored in the storage unit reaches s. The value of the number of cleanings m is returned to 1, and the initial cleaning process of performing the truing process with the alkane stone stone is resumed, so that the continuous back grinding of the semiconductor substrate can be performed continuously without interruption. .

The rotational speed of the rotary spindle 18 of the truing grindstone 16 is 10 to 30 rpm, the porous ceramic chuck table 2 surface rubbing time of the truing grindstone 16 is 1 to 4 seconds, and the cleaning liquid supply amount is 1 to 10 liters / minute. is there.

  The backflush cleaning from the bottom side of the porous ceramic chuck table of the present invention and the pressurized jet water cleaning from the surface side of the porous ceramic chuck table are used in combination with conventional backflush cleaning and oil stone or ceramic scissors. Compared with cleaning, there is an advantage that the amount of wear on the surface of the porous ceramic chuck table is small. In particular, when the porous degree of the porous ceramic chuck table is as high as 100 to 120, it is washed with pressurized fluid from both the front side and the bottom side of the porous ceramic chuck table. Or it is excellent in the effect of removing the sludge stuck in the chuck.

It is a figure explaining the washing | cleaning apparatus of the porous ceramic chuck tables.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate holder 2 Disc-shaped porous ceramic chuck table 3 Rotary table 4 Hollow spindle 5 Servo motor 6 Fluid supply pipe 6a Pressure reducing pipe 6b Pressurized air supply pipe 6c Pure water supply pipe 10a Pressurized cleaning water jet nozzle 15 Truing grindstone

Claims (2)

  After grinding the back surface of the semiconductor substrate placed on the surface of the disk-shaped porous ceramic chuck table and cleaning the ground surface of the ground semiconductor substrate, the cleaned ground semiconductor substrate is placed on the disk-shaped porous ceramic chuck table. In the cleaning method for the porous ceramic chuck table, the disk-shaped porous ceramic chuck table is removed with a cleaning liquid, and the cleaning fluid is 0.2 to 2.5 MPa from the bottom surface side to the front surface side of the porous ceramic chuck table. And 0.4-3 Mpa of pressurized water is sprayed onto the chuck table surface from the spray nozzle provided above the porous ceramic chuck table to remove sludge from the porous ceramic chuck table. , Cleaning method. After grinding the back surface of the semiconductor substrate placed on the surface of the disk-shaped porous ceramic chuck table and cleaning the ground surface of the ground semiconductor substrate, the cleaned ground semiconductor substrate is placed on the disk-shaped porous ceramic chuck table. In the method of cleaning the porous ceramic chuck table, removing the disk-shaped porous ceramic chuck table with a cleaning liquid,
In the first round of cleaning the disc-shaped porous ceramic chuck table, after performing backflush cleaning for supplying a cleaning fluid of 0.2 to 2.5 Mpa from the bottom surface side to the front surface side of the porous ceramic chuck table, The surface of the porous ceramic chuck table is rubbed against the surface of the porous ceramic chuck table to form the surface of the porous ceramic chuck table, and then the back surface of the semiconductor substrate placed on the porous ceramic chuck table is ground and the ground semiconductor substrate is ground. After cleaning the ground surface, remove the cleaned ground semiconductor substrate from the disk-shaped porous ceramic chuck table, and then clean the disk-shaped porous ceramic chuck table from which the ground semiconductor substrate has been removed. Number of cleanings set from the second time onwards m is an integer of 2 or more and 10,000 or less.) After the cleaned ground semiconductor substrate is removed from the disc-shaped porous ceramic chuck table, the bottom surface side of the porous ceramic chuck table is changed to the front surface side. Back flush cleaning is performed to supply a cleaning fluid of 0.2 to 2.5 Mpa toward the surface, and 0.4 to 3 Mpa of pressurized water is sprayed onto the surface of the chuck table from the spray nozzle provided above the porous ceramic chuck table. And removing the sludge from the porous ceramic chuck table.

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