JP5479781B2 - Slurry recovery method and recovery device - Google Patents

Description

  The present invention relates to a slurry recovery method and a recovery apparatus.

  In chemical mechanical polishing (CMP) in a semiconductor manufacturing process, a semiconductor wafer is rotated while being pressed against a polishing pad using a polishing apparatus, and at the same time, a slurry, which is an abrasive, is placed between the semiconductor wafer and the polishing pad. Supply and polishing is performed.

  According to CMP, in addition to the chemical action by the chemical components and abrasive grains (for example, alumina particles and silica particles) in the slurry, a synergistic polishing action by sliding contact between the semiconductor wafer and the polishing pad can be achieved.

  In order to perform the above CMP, for example, the polishing apparatus 1 schematically shown in FIG. 13 is used. The polishing apparatus 1 includes a platen 4 that has a polishing pad 2 attached to the upper surface and rotates around a main rotation shaft 3, and a rotation in which a semiconductor wafer 5 that is a polishing object is eccentric with respect to the main rotation shaft 3 of the platen 4. The polishing head 7 is configured to press the polishing pad 2 while rotating around the shaft 6. The slurry S flows down on the polishing pad 2 on the platen 4 from the slurry supply nozzle 8 disposed above the platen 4.

  The slurry supply nozzle 8 is connected to a slurry supply pipe 10 and a cleaning water (ultra pure water) pipe 11 via a switching valve 9, and after the polishing with slurry for a predetermined time, the switching valve 9 By switching, a large amount of cleaning water is discharged from the slurry supply nozzle 8 onto the platen 4, and rinsing and pad conditioning are performed while flowing the cleaning water. The slurry and washing water used here are all collected in the drainage tank through the common drainage discharge pipe 12. Slurries diluted with such a large amount of washing water are discarded because they are difficult to reuse.

  Conventionally, proposals have been made to recover useful components such as abrasive grains from waste liquid containing such slurry, and further, the slurry used in the polishing process and the cleaning water used in the cleaning process are separated and recovered, There has also been a proposal to increase the concentration of the slurry to be recycled (for example, Patent Document 1), but the slurry in the polishing process is still very small compared to the amount of cleaning water, so the recovered slurry has a low concentration, There was a problem that a complicated concentration process and a component adjustment process were required.

JP-A-11-010540

  The present invention solves such a conventional problem, and a useful used slurry is recovered at a high concentration and recovered by using a simple device by utilizing the difference in viscosity and the amount of use with washing water. It is an object of the present invention to provide a slurry recovery method and a recovery device that enable recovery at a high rate.

  That is, the slurry recovery method of the present invention is a method for recovering the slurry used in a polishing apparatus that repeatedly performs a polishing process using a slurry and a cleaning process using a cleaning water at a predetermined timing, and the slurry of the polishing apparatus and the slurry A step of attaching a slurry drainage recovery pipe provided with a slurry trapping pocket for trapping slurry flowing down along the inner wall to a discharge port commonly receiving the washing water, and a flow down along the inner wall of the slurry drainage recovery pipe It has a slurry collection process which collects slurry via the slurry catching pocket, and a drainage collection process which collects drainage liquid containing washing water discharged from the slurry drainage collection pipe.

  Switching from the slurry recovery step to the drainage recovery step is performed when the conductivity of the slurry recovered in the slurry catch pocket is measured and the conductivity of the slurry falls below the reference value. This indicates that the conductivity of a normal slurry stock solution is about 200 mS / m. Since the cleaning water is ultrapure water, it utilizes the fact that when the polishing process is completed and the cleaning process is entered and the cleaning water is mixed into the slurry, the conductivity of the slurry rapidly decreases.

  When a decrease in conductivity is detected, if a slurry recovered thereafter is accommodated in the drainage tank, a slurry having a composition closer to that of the original slurry can be recovered.

  Further, the slurry recovery device of the present invention is a slurry recovery device in a polishing device that repeatedly performs a polishing step with slurry and a cleaning step with cleaning water at a predetermined timing, and the slurry recovery device is suspended downward from an outlet of the polishing device. A slurry drainage recovery pipe having an inner diameter sufficient for the slurry used in the polishing process to flow down only through the inner wall, a slurry trapping pocket for trapping the slurry flowing down through the inner wall of the slurry drainage recovery pipe, and And a slurry suction tube having a suction port opened at the bottom of the slurry catching pocket.

  The slurry recovery apparatus of the present invention can be applied to either a single drainage discharge pipe or a plurality of drainage discharge pipes of a polishing apparatus.

  The slurry catching pocket is configured by a flange member having an outer peripheral wall in close contact with the inner wall of the slurry drainage collecting pipe and arranged in an annular shape, for example, a U-shaped cross-section and a V-shaped cross-section having a circular bottom. Is done.

  1 to 3 show an example of such a slurry catching pocket 15, and the slurry catching pocket 15 collects and discharges slurry and washing water scattered around the bottom plate of the polishing apparatus. 13 has a structure in which a slurry drainage recovery pipe 16 is inserted. The slurry catching pocket 15 has a cylindrical shape as a whole, and a lower portion wraps inward to form a flange portion 17 having a U-shaped cross section. A slurry suction pipe 18 that is sucked by a pump is attached to the bottom of the flange portion 17.

  The slurry suction pipe 18 is connected to a suction pump, sucks the slurry collected in the slurry catching pocket 15 by the suction force of the pump, and collects it in the slurry collection tank.

The suction pump is always driven through the polishing process and the cleaning process in order to prevent the slurry from solidifying in the slurry absorption tube 18 or the flanges 17 and 19 of the slurry catching pocket 15. When the slurry suction tube is used in the upper portion as shown in FIG. 4 , the cross section of the collar portion may be arcuate.

  The slurry suction pipe 18 is branched downstream of the suction pump into a slurry recovery tank side and a cleaning waste liquid recovery tank side via a switching valve. For the control of this switching valve, a slurry concentration detector for measuring the slurry concentration, for example, a conductivity meter is arranged upstream of the switching valve, and when the measured value of the conductivity meter is equal to or higher than a predetermined set value, The switching valve can be switched to the slurry collection tank side.

  This prevents the switching valve from being switched from the slurry recovery tank side to the cleaning drainage recovery tank side before the cleaning drainage comes to the switching valve following the slurry, and prevents the cleaning water from entering the slurry recovery tank. It is.

 The slurry used in the polishing step of the polishing apparatus is as disclosed in JP-A-10-265766 and JP-A-11-116948, and specifically, for example, a particle size distribution of 0.02 μm or more. (Median diameter) A volume of about 0.15 μm of fumed silica fine particles and components such as oxidizer such as hydrogen peroxide, ferric nitrate, organic acid, amino acid, etc. are dispersed or dissolved in water. .

  In addition, it is desirable to provide a mesh member for preventing entry of foreign matters such as a broken breakage of the semiconductor wafer and an aggregate of the slurry at the inlet of the slurry drainage collection pipe.

  Further, in order to detect the blockage of the mesh member, for example, the flow rate of the slurry drainage was measured with a flow meter provided between the slurry suction pipe and the recovery tank, and the output of the flow meter became lower than a predetermined set value. It is desirable to provide a warning device that issues a warning and / or a control device that stops the operation of the pump.

  When the slurry suction tube is blocked by foreign matter or the like that has passed through the mesh member, the flow meter can detect the decrease in the flow rate and notify the monitoring staff by an alarm or a pump stop.

  The used slurry collected in the slurry collection tank was reused after its components were adjusted, and the waste liquid sent to the cleaning waste liquid collection tank side was accommodated in the waste liquid tank and subjected to the necessary processing. Discarded later.

It is sectional drawing which shows the principal part of one Embodiment of this invention roughly. It is a perspective view which shows the principal part of one Embodiment of this invention. It is sectional drawing which follows the III-III line of FIG. It is sectional drawing which shows schematically the principal part of other embodiment of this invention. It is a figure which shows other embodiment of this invention. It is sectional drawing which expands and shows the principal part of FIG. FIG. 7 is a perspective view of the slurry catching pocket of FIG. 6. It is the perspective view shown from the other direction of the slurry capture | acquisition pocket of FIG. It is a perspective view which shows the slurry acquisition pocket of FIG. 6 in a partial cross section. FIG. 7 is a plan view of the slurry catching pocket of FIG. 6. FIG. 7 is a side view of the slurry catching pocket of FIG. 6. It is a flowchart of one Embodiment of this invention. It is sectional drawing which shows the conventional grinding | polishing apparatus schematically.

  FIG. 5 shows an entire polishing system using the present invention. Reference numeral 101 denotes a polishing apparatus having two polishing units (not shown). A liquid discharge pipe is provided.

  A drainage discharge pipe 103 shown in an enlarged view in FIG. 6 is vertically connected to the discharge port 102, and a slurry catching pocket 105 connected to a slurry suction pipe 104 is connected to the drainage inflow port. It is inserted in close contact with the inner wall of the discharge pipe 103.

  The slurry catching pocket 105 is a molded product of vinyl chloride resin and has a shape shown in FIGS.

  In these drawings, reference numeral 105a denotes a rubber ring locking portion that seals a slurry drainage recovery pipe having a drainage drainage pipe and a slurry supplement pocket, 105b is a flange part, 105c is a threaded part of the suction pipe 104, 105d Is a passage for drainage diluted with wash water.

  In the embodiment shown in FIG. 5, the outlet side of the drainage discharge pipe 103 (shown by a chain line) is connected to the collecting drain pipe 106. Slurry suction pipe 104 (shown by a solid line) is always sucked by suction pumps P-1 and P-2, and is 20L through switching valves AV-101, AV-102, AV-201, and AV-202. The slurry recovery tanks 107 and 108 and the collecting drain pipe 106 are connected.

  Conductivity meters CT-1 and CT-2 are arranged on the inlet side of the suction pumps P-1 and P-2, and flow sensors FS-1 and FS-2 are arranged on the outlet side. . Reference numeral 109 denotes a control panel.

  This polishing apparatus is operated according to the flow of FIG.

  That is, at the start of operation, the switching valves AV-101 and AV-201 are normally open, and the switching valves AV-102 and AV-202 are normally closed.

  First, the suction pumps P-1 and P-2 are driven, while the polishing apparatus is driven by another control system.

  In the polishing apparatus, for example, CMP is performed at a slurry supply rate of 200 ml / min for 45 seconds, rinsing while supplying cleaning water (ultra pure water) at a flow rate of 8000 ml / min, and then cleaning water (ultra-clean water at a flow rate of 8000 ml / min). The pad conditioning cycle while supplying pure water) is repeated.

  First, prior to the CMP process, the polishing apparatus sends a slurry supply signal to the control device (control panel 109), and then starts supplying slurry to the pad. The slurry supplied in the CMP process is supplied between the semiconductor wafer and the pad and used for polishing, then sent to the edge of the platen by centrifugal force and collected in the drainage discharge pipe. The slurry that has entered the drainage discharge pipe travels along the inner wall of the slurry drainage collection pipe due to its viscosity, enters the slurry trap pocket 105, and is sucked into the slurry suction pipe.

  The flow sensors FS-1 and FS-2 detect the flow of the slurry, the conductivity meters CT-1 and CT-2 detect the predetermined conductivity, and the slurry supply signal from the polishing apparatus is received. As a result, AV-102 and AV-202 are opened, AV-101 and AV-201 are closed, and the slurry is collected in the slurry collection tank.

  When the polishing process of the polishing apparatus is completed and a large amount of cleaning water is discharged to the drain receiver, the slurry in the slurry catching pocket is diluted with the cleaning water and measured by the conductivity meters CT-1 and CT-2. The rate drops rapidly. When the conductivity falls below the reference value, the switching valve returns to the state in which the original AV-101 and AV-201 are normally open and AV-102 and AV-202 are normally closed. The slurry concentration in the slurry collection tank is released to the collecting water distribution pipe and is maintained in a predetermined range.

(Example)
An example in which the present embodiment is applied to a process of chemical mechanical polishing (hereinafter referred to as W-CMP) of a tungsten film formed on a silicon wafer using the system shown in FIG. 5 will be described.

The polishing cycles of the examples are as shown in Table 1.

  The used suction pump can be a small bimol pump (maximum flow rate 500ml / min) manufactured by Nitto Kohki.

  The recovery rate of the slurry recovered in this example was 60% or more by calculated value. In addition, the dilution rate is about 2 to 5 times that of the stock solution, including residual water from the pad and the apparatus.

  For comparison, the slurry and the cleaning liquid were separated under the conditions shown in Table 1 by the method of distributing the collection and disposal to the existing drainage pipe with a valve without using the slurry trapping pocket. It was impossible to recover the used slurry up to 5-fold dilution.

  In the comparative example, since the polishing time is as short as 45 seconds, it is difficult to collect only the slurry having a high concentration, and the washing water is mixed before the slurry arrives at the switching valve 300 cm ahead.

  That is, in the comparative example, when the polishing time is 45 seconds and the cleaning water is mixed, the flow rate is increased to 28 cm / second. For this reason, high-concentration slurry drainage is carried up to about 30 cm of the slurry drainage collection tube, but the remaining 270 cm is carried while mixing the slurry and washing water, resulting in a dilution factor of 30 times or more. It is considered a thing.

In contrast, in this embodiment, a small amount of undiluted slurry drainage is stored in the slurry supplement pocket of the slurry drainage collection pipe, and is immediately sucked by the pump and carried to the slurry drainage collection tank. Within 45 seconds of time, it becomes possible to carry a slurry having a high concentration to a recovery tank 300 cm ahead.

  DESCRIPTION OF SYMBOLS 1 ... Polishing apparatus, 2 ... Polishing pad, 3 ... Main rotating shaft, 4 ... Platen, 5 ... Semiconductor wafer, 6 ... Rotary shaft, 7 ... Polishing head 7, 8 ... Slurry supply nozzle, DESCRIPTION OF SYMBOLS 9 ... Switching valve, 10 ... Slurry supply piping, 11 ... Washing water piping, 101 ... Polishing apparatus, 102 ... Discharge port, 103 ... Drainage discharge pipe, 104 ... Slurry suction pipe, 105 ... Slurry catching pocket, 105a ....... rubber ring locking part, 105b... Collar part, 105d... Drainage passage part, P-1, P-2 ... suction pump, AV-101, AV-102, AV -201, AV-202 ... Switching valve, 107, 108 ... Slurry recovery tank, 106 ... Collective drain, CT-1, CT-2 ... Conductivity meter, FS-1, FS-2 ... Flow Sensor 109 ... Control panel.

Claims (10)

In the method of recovering the slurry used in the polishing apparatus that repeatedly performs the polishing step with the slurry and the cleaning step with the cleaning water at a predetermined timing,
Attaching a slurry drainage recovery pipe provided with a slurry trapping pocket for trapping slurry flowing down along an inner wall to a drainage port commonly receiving the slurry and the washing water of the polishing apparatus;
The slurry flows down along the inner wall of the slurry drainage recovery pipe, collected in the bottom of the slurry catching pocket, a slurry recovery step of recovering the slurry suction pipe having a suction port at the bottom of the slurry catching pocket,
A drainage recovery step for recovering the drainage containing the cleaning water used in the cleaning step discharged from the slurry drainage recovery pipe;
I have a,
Switching from the slurry recovery step to the drainage recovery step is performed when the conductivity of the slurry collected in the slurry catch pocket is measured and the conductivity of the slurry falls below a reference value. A method for recovering the slurry. In the slurry recovery apparatus in the polishing apparatus that repeats the polishing process with the slurry and the cleaning process with the cleaning water at a predetermined timing,
A slurry drainage collecting pipe having an inner diameter sufficient to allow the slurry used in the polishing step suspended downward from the drainage port of the polishing apparatus to flow down only through the inner wall;
A slurry catching pocket for catching the slurry flowing down along the inner wall of the slurry drainage collecting pipe;
Have a, a slurry suction pipe having a suction port at the bottom of the slurry catching pocket,
The slurry suction pipe branches downstream of the suction pump via a switching valve, and a slurry concentration detector that measures the slurry concentration provided on the upstream side of the switching valve, and an output of the slurry concentration detector And a control means for switching the switching valve according to a signal . The slurry recovery apparatus according to claim 2, wherein the slurry concentration detector is a conductivity meter. 4. The slurry collecting apparatus according to claim 2 , wherein the slurry suction pipe is provided with an inlet port opened at a bottom portion of the slurry catching pocket. 4. The slurry recovery apparatus according to claim 2 , wherein the slurry suction tube is provided at an upper portion of the slurry catching pocket. The slurry catching pocket, the outer peripheral wall, according to any one of claims 2 to 5, characterized in that an annular gutter member by tightly fixed to the inner wall to the inner wall of the slurry drainage recovery pipe Slurry recovery equipment. The slurry catching pocket includes an inner wall of the slurry drainage recovery pipe, a cylindrical portion inserted concentrically at an interval to the slurry drainage recovery pipe, an inner wall of the slurry drainage recovery pipe, and the cylinder The slurry recovery apparatus according to any one of claims 2 to 5 , wherein the slurry recovery apparatus includes a bottom member configured to liquid-tightly connect a lower portion of the shape portion. The slurry collecting apparatus according to any one of claims 2 to 7 , wherein the slurry suction pipe is connected to a suction pump and discharges the slurry captured in the slurry capturing pocket by a suction force of the pump. The slurry suction pipe includes a flow meter, and an alarm device that issues an alarm and / or a control device that stops the operation of the pump when an output signal of the flow meter becomes lower than a predetermined value. The slurry recovery apparatus according to claim 8 . The slurry recovery apparatus according to any one of claims 3 to 9, wherein a mesh member that prevents entry of foreign matter is disposed at an inlet of the slurry drainage recovery pipe.

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