JP6078236B2 - Processing waste liquid treatment equipment - Google Patents

Description

  The present invention relates to a processing waste liquid processing apparatus attached to a processing apparatus such as a cutting apparatus for cutting a workpiece such as a semiconductor wafer or a grinding apparatus for grinding a workpiece, and processing a waste liquid of a processing liquid supplied during processing. .

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a substantially wafer-shaped semiconductor wafer, and devices such as ICs, LSIs, etc. are partitioned in the partitioned regions. Form. By cutting the semiconductor wafer having the device formed on the surface in this way along the street, the region where the device is formed is divided to manufacture individual semiconductor devices.

  The above-described cutting along the street of the semiconductor wafer is usually performed by a cutting device called a dicer. This cutting apparatus includes a chuck table for holding a workpiece such as a semiconductor wafer, a cutting means having a cutting blade for cutting the workpiece held on the chuck table, and supplying cutting water to the cutting blade. A cutting water supply means for cooling the cutting blade by supplying the processing water to the rotating cutting blade by the processing water supply means and supplying the cutting water to the cutting portion of the workpiece by the cutting blade. Carry out cutting work.

  The wafer divided in this way is ground to a predetermined thickness by a grinding device before being cut along the street. The grinding apparatus includes a chuck table that holds a workpiece, and a grinding unit that grinds the workpiece held on the chuck table. The grinding means includes a rotating spindle, a wheel mount provided at the lower end of the rotating spindle, and a grinding wheel that is detachably attached to the lower surface of the wheel mount. And a plurality of grinding wheels mounted on the outer peripheral grinding wheel mounting portion on the lower surface of the wheel base, and the grinding wheel is held on the chuck table while rotating the grinding wheel and supplying processing water The workpiece is ground by pressing against the workpiece.

  As described above, silicon fine particles generated by cutting or grinding silicon are mixed in the processing water supplied during cutting by the cutting device or grinding by the grinding device. Since the processing waste liquid mixed with the silicon fine particles contaminates the environment, the processing waste liquid has to be treated and drained, resulting in a problem of waste liquid processing cost. In particular, in the grinding apparatus, the thickness of the wafer as a workpiece is ground from, for example, 600 μm to around 100 μm, so that the processing water used in one grinding apparatus is 2 to 3 t per day and the running cost. There is a problem that becomes expensive. Furthermore, although the wafer is formed of relatively expensive silicon, as described above, there is a problem that silicon is discarded by nearly 90% by grinding and cutting, and resources are not effectively utilized.

  In order to solve the above problem, a processing waste liquid treatment apparatus has been proposed in which processing waste liquid is filtered through a filter to produce fresh water, which is circulated and used as cutting water or grinding water. (For example, refer to Patent Document 1.)

JP 2009-95941 A

Thus, the above-described processing waste liquid treatment apparatus has to be replaced with a new filter, resulting in a new problem of poor productivity. In particular, in a processing waste liquid treatment apparatus attached to a grinding apparatus for grinding a silicon wafer having a thickness of about 600 μm to a thickness of about 100 μm, a large amount of grinding debris is generated, and therefore, the work of exchanging the filter is frequent.
In addition, since silicon fine particles as grinding waste are captured by the filter, it is possible to recover the silicon ingot by collecting the silicon fine particles from the filter, but it is difficult to efficiently recover the silicon fine particles that have penetrated the filter. It is.

  The present invention has been made in view of the above-mentioned facts, and the main technical problem thereof is that silicon fine particles can be separated from processing waste liquid containing silicon fine particles as cutting scraps or grinding scraps to generate clean water, and silicon An object of the present invention is to provide a processing waste liquid treatment apparatus capable of efficiently collecting fine particles.

In order to solve the main technical problem, according to the present invention, in a processing waste liquid treatment apparatus for separating processing waste liquid mixed with silicon fine particles into silicon fine particles and fresh water,
A waste liquid treatment tank provided at the bottom with a processing waste liquid inlet communicating with the processing waste liquid supply means, a negatively charged cathode means disposed in the waste liquid treatment tank, and a positive electrode disposed opposite to the negative electrode means. Positively charged anode means, fresh water suction means disposed above the cathode means for sucking fresh water , and pH adjusting means for adjusting the pH of the processing waste liquid flowing from the processing waste liquid supply means into the waste liquid treatment tank And comprising
The pH adjusting means adjusts the pH so that the trapping power of the silicon fine particles mixed in the processing waste liquid supplied to the waste liquid treatment tank is increased by the anode means.
A processing waste liquid treatment apparatus is provided.

Upper Symbol p H adjusting means, an acid supply means for supplying an acid to the machining waste, and the electrical resistance measuring means for measuring the electrical resistance value of the processing effluent flowing into the waste liquid treatment tank, measured from the electric resistance measuring means Control means for controlling the acid supply means based on the signal.

A processing waste liquid treatment apparatus according to the present invention comprises a waste liquid treatment tank provided at the bottom with a processing waste liquid inlet communicating with a processing waste liquid supply means, a cathode means disposed in the waste liquid treatment tank and negatively charged, and the cathode A positive means that is disposed to face the means and is positively charged, a fresh water suction means that is disposed above the cathode means and sucks fresh water , and a processing waste liquid that flows into the waste liquid treatment tank from the processing waste liquid supply means. pH adjusting means for adjusting pH, and the pH adjusting means has a pH value that increases the trapping power of the silicon fine particles mixed in the processing waste liquid supplied to the waste liquid treatment tank by the anode means. so as to adjust to Runode, processed waste which has flowed from the machining waste inlet provided in the waste liquid treatment tank to the waste liquid treatment tank, and silicon particles are attracted to the anode means is separated into fresh water. Thus, the separated silicon fine particles are adsorbed and deposited on the plurality of anode means, and fresh water is mainly generated on the upper part of the cathode means. The fresh water generated at the upper part of the cathode means is conveyed to the fresh water tank through the fresh water suction means provided at the upper part of the cathode means. The silicon ingot can be regenerated by collecting the silicon fine particles adsorbed and deposited on the anode means. Therefore, silicon fine particles can be separated efficiently and fresh water can be easily generated from the processing waste liquid by flowing a predetermined amount of the processing waste liquid from the processing waste liquid inlet provided on one side wall of the waste liquid treatment tank. .

The perspective view of the processing waste liquid processing apparatus comprised according to this invention. The perspective view which decomposes | disassembles and shows the member which comprises the process waste liquid processing apparatus shown in FIG. Sectional drawing of the processing waste liquid processing apparatus shown in FIG. The block diagram of the pH adjustment means with which the process waste liquid processing apparatus shown in FIG. 1 is equipped.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a processing waste liquid treatment apparatus configured according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view of a processing waste liquid treatment apparatus constructed according to the present invention, and FIG. 2 is a perspective view showing an exploded view of members constituting the processing waste liquid treatment apparatus shown in FIG. Yes. The processing waste liquid treatment apparatus in the illustrated embodiment includes a waste liquid treatment tank 2, a cathode means 3 that is disposed in the waste liquid treatment tank 2 and is negatively charged, and is disposed so as to face the cathode means 3 and is positively charged. The anode means 4 is provided. As shown in FIG. 2, the waste liquid treatment tank 2 includes a bottom wall 21 having a large length with respect to the width direction, side walls 22 and 23 erected from both side edges of the bottom wall 21, and the bottom wall 21. Formed by end walls 24 and 25 erected from both side edges in the longitudinal direction, the upper side is released. A processing waste liquid inlet 241 is provided below one end wall 24 constituting the waste liquid treatment tank 2, and this processing waste liquid inlet 241 is a processing waste liquid supply pipe 51 of the processing waste liquid supply means 5 as shown in FIG. It is communicated to.

  A plurality of first support grooves 221 and 231 for supporting the cathode means 3 and a plurality of second support grooves for supporting the anode means 4 are formed on the inner surfaces of the side walls 22 and 23 constituting the waste liquid treatment tank 2. 222, 232 are provided. The plurality of first support grooves 221 and 231 and the plurality of second support grooves 222 and 232 are alternately provided in the arrangement direction. The waste liquid treatment tank 2 configured as described above is formed of an insulating member such as a synthetic resin.

  The cathode means 3 is composed of a plurality of cathode plates 31 made of a conductive member such as copper or stainless steel. The plurality of cathode plates 31 are fitted in the plurality of first support grooves 221 and 231 provided in the side walls 22 and 23 in the longitudinal direction in the waste liquid treatment tank 2. The anode means 4 is composed of a plurality of anode plates 41 made of a conductive member such as copper or stainless steel, and a handle 411 is provided at the center of the upper end. The plurality of anode plates 41 formed in this way are fitted into the plurality of second support grooves 222 and 232 provided in the side walls 22 and 23 in the longitudinal direction in the waste liquid treatment tank 2. In this way, the cathode fitted into the plurality of first support grooves 221 and 231 and the plurality of second support grooves 222 and 232 provided in the side walls 22 and 23 in the longitudinal direction in the waste liquid treatment tank 2. The plate 31 and the anode plate 41 are disposed alternately facing each other as shown in FIG. The anode plate 41 arranged in this way is connected to the plus (+) of the DC power source 6, and the cathode plate 31 is connected to the minus (−) of the DC power source 6.

  2 and 3, the processing waste liquid treatment apparatus in the illustrated embodiment includes fresh water suction means 7 disposed at the upper ends of a plurality of cathode plates 31 constituting the cathode means 3. doing. The fresh water suction means 7 includes a fresh water suction pipe 71 attached along the upper ends of the plurality of cathode plates 31 and closed at both ends. The side surface of the fresh water suction pipe 71 is provided with a plurality of fresh water suction ports 711 along the longitudinal direction, and a fresh water delivery port 712 is provided at the end. The fresh water delivery port 712 of the fresh water suction pipe 71 configured as described above is in communication with the fresh water feed pump 72.

  4, the processing waste liquid treatment apparatus in the illustrated embodiment includes pH adjusting means 8 for adjusting the pH of the processing waste liquid flowing from the processing waste liquid supply means 5 into the waste liquid treatment tank 2. ing. The pH adjusting means 8 includes an acid supply means 81 for supplying an acid to the processing waste liquid, an electric resistance measuring means 82 for measuring an electric resistance value of the processing waste liquid flowing into the waste liquid treatment tank, and an electric resistance measuring means 82 And control means 83 for controlling the acid supply means 81 based on the measurement signal. The processing waste liquid supply pipe 51 of the processing waste liquid supply means 5 is provided with a bypass pipe 52, and an acid is supplied to the bypass pipe 52 from an acid supply means 81 constituting the pH adjusting means 8. Note that the ratio of the diameter of the processing waste liquid supply pipe 51 to the diameter of the bypass pipe 52 is set to 50: 1 in the illustrated embodiment. In the illustrated embodiment, the acid supply means 81 is a mixture of carbon dioxide and water supplied by the carbon dioxide supply means 811, the water supply means 812, the carbon dioxide supply means 811 and the water supply means 812, and carbonated water. And a flow rate control valve 814 disposed in a pipe connecting the mixing chamber 813 and the bypass pipe 52. The electrical resistance measuring means 82 is disposed downstream of the bypass pipe 52 in the machining waste liquid supply pipe 51 of the machining waste liquid supply means 5 and is supplied with acid by the acid supply means 81 and flows into the waste liquid treatment tank 2. The pH is measured and a measurement signal is sent to the control means 83. The control means 83 controls the flow rate control valve 814 based on the detection signal from the electrical resistance measuring means 82 that constitutes the pH adjusting means 8, so that the pH of the processing waste liquid flowing into the waste liquid treatment tank 2 has a predetermined value. Act to maintain. Although hydrochloric acid may be used as the acid supplied to the processing waste liquid, it is preferable to use carbonated water for safety.

The processing waste liquid treatment apparatus in the illustrated embodiment is configured as described above, and the operation thereof will be described below.
The processing waste liquid sent from the processing waste liquid sending means installed in a processing apparatus such as a grinding apparatus (not shown) and stored in a waste liquid tank (not shown) is provided on one end wall 24 of the waste liquid treatment tank 2 by the processing waste liquid supply means 5. Then, it is supplied to the waste liquid treatment tank 2 from the processing waste liquid inlet 241. At this time, the pH adjusting means 8 is operated to supply carbon dioxide and water to the processing waste liquid. Then, the pH adjusting means 8 adjusts so that the measurement signal from the electric resistance measuring means 82 is 1 MΩcm, that is, the processing waste liquid supplied to the waste liquid treatment tank 2 maintains pH 5. According to the experiments by the present inventors, it has been found that when the negative (−) zeta potential charged in the silicon fine particles is adjusted, the capturing power of the silicon fine particles by the anode plate is increased. That is, if the negative (−) zeta potential charged in the silicon fine particles is high, the silicon fine particle capturing force by the anode plate does not increase, but the silicon fine particles mixed in the processing waste liquid supplied to the waste liquid treatment tank. It was found that when the zeta potential of the negative electrode is about minus (−) 40 mV, the trapping power of the silicon fine particles by the anode plate increases most. The pH at which silicon exhibits a zeta potential of about minus (−) 40 mV is about pH 5, and the electrical resistance of the processing waste liquid at this time is 1 MΩcm.

  As described above, silicon fine particles are mixed in the processing waste liquid whose pH is adjusted and sent to the waste liquid treatment tank 2, and the silicon fine particles are charged to about minus (−) 40 mV. In order to separate the silicon fine particles mixed in the processing waste liquid stored in the waste liquid treatment tank 2 in this way, a positive (+) of the DC power source 6 is applied to the anode plate 41 of the anode means 4 and the cathode means. The negative (−) of the DC power source 6 is applied to the three cathode plates 31. As a result, the silicon fine particles mixed in the processing waste liquid and charged negative (−) are repelled from the negative (−) charged cathode plate 31 and adsorbed on the positive (+) charged anode plate 41. At this time, the processing waste liquid supplied to the waste liquid treatment tank 2 is adjusted to about pH 5 as described above, and the zeta potential of the silicon fine particles mixed in the processing waste liquid is maintained at about minus (−) 40 mV. The fine particles are efficiently captured by the anode plate 41.

  As described above, the processing waste liquid flowing into the waste liquid treatment tank 2 from the processing waste liquid inlet 241 provided on one end wall 24 of the waste liquid treatment tank 2 is separated into silicon fine particles adsorbed on the anode plate 41 and fresh water. Is done. In this way, the separated silicon fine particles are adsorbed and deposited on the plurality of anode plates 41, and fresh water is mainly generated on top of the plurality of cathode plates 31 constituting the cathode means 3. The fresh water generated on the top of the plurality of cathode plates 31 constituting the cathode means 3 is supplied from a plurality of fresh water suction ports 711 provided in a plurality of fresh water suction pipes 71 respectively disposed at the upper ends of the plurality of cathode plates 31. The water is sucked into the plurality of fresh water suction pipes 71, sent out from the fresh water feed ports 712 of the plurality of fresh water suction pipes 71, and conveyed to the fresh water tank (not shown) via the fresh water feed pump 72. Therefore, silicon fine particles can be separated efficiently by flowing a predetermined amount of processing waste liquid from a processing waste liquid inlet 241 provided on one end wall 24 of the waste liquid treatment tank 2, and clean water can be easily generated from the processing waste liquid. can do.

  If the processing process of the processing waste liquid described above is performed for a predetermined time and silicon fine particles are deposited on the plurality of anode plates 41 constituting the anode means 4, the plurality of anode plates 41 on which the silicon fine particles are deposited is placed on the side wall of the waste liquid treatment tank 2. A plurality of second support grooves 222 and 232 formed in 22 and 23 are extracted and conveyed to a silicon fine particle recovery process. In the silicon fine particle collecting step, the silicon fine particles deposited on the plurality of anode plates 41 are separated and collected. The silicon fine particles collected in this way are regenerated into a silicon ingot.

2: Waste liquid treatment tank 241: Processing waste liquid inlet 3: Cathode means 31: Cathode plate 4: Anode means 41: Anode plate 5: Processing waste liquid supply means 51: Processing waste liquid supply pipe 52: Bypass pipe 6: DC power supply 7: Shimizu Suction means 71: Fresh water suction pipe 72: Fresh water feed pump 8: pH adjusting means 81: Acid supply means 82: Electrical resistance measuring means 83: Control means

Claims (2)

In processing waste liquid treatment equipment that separates processing waste liquid mixed with silicon fine particles into silicon fine particles and fresh water,
A waste liquid treatment tank provided at the bottom with a processing waste liquid inlet communicating with the processing waste liquid supply means, a negatively charged cathode means disposed in the waste liquid treatment tank, and a positive electrode disposed opposite to the negative electrode means. Positively charged anode means, fresh water suction means disposed above the cathode means for sucking fresh water , and pH adjusting means for adjusting the pH of the processing waste liquid flowing from the processing waste liquid supply means into the waste liquid treatment tank And comprising
The pH adjusting means adjusts the pH so that the trapping power of the silicon fine particles mixed in the processing waste liquid supplied to the waste liquid treatment tank is increased by the anode means.
A processing waste liquid treatment apparatus characterized by that. The pH adjusting means includes an acid supply means for supplying an acid to the processing waste liquid, an electrical resistance measuring means for measuring an electrical resistance value of the processing waste liquid flowing into the waste liquid treatment tank, and a measurement signal from the electrical resistance measuring means. The processing waste liquid treatment apparatus according to claim 1, further comprising a control unit that controls the acid supply unit based on the control unit.

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