JPH11304687A - Method and instrument for quantitatively measuring fine particles mixed in silicon wafer treating slurry - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and instrument by which the components and quantities of fine particles mixed in slurry can be measured quantitatively on a production line. SOLUTION: An instrument for quantitatively measuring quantity of fine particles mixed in slurry used for a silicon wafer treating process is provide with a circulating passage 22 which is constituted in such a way that part of the slurry can be taken out from the passage 22, a separating device 27 composed of a rotating body 30 in which a slurry storing layer having a prescribed thickness is formed of a transparent member 32 provided on at least one side and which is connected to the passage 22 and rotates in the direction normal to the thickness direction of the slurry storing layer, and a color discriminating sensor 41 which detects the color of the slurry storing layer in the thickness direction in the radial direction. Since the instrument is constituted to quantitatively fine the kinds (components) and mixed amounts (concentrations) of the fine particles mixed in the slurry on the production line by separating the fine particles from the liquid in the direction normal to the thickness direction of the slurry storing layer and measuring the colors of the separated layers of the fine particles and liquid and the position of the separating area by means of the sensor 41 from the thickness direction of the slurry storing layer, the components of the slurry can be adjusted to the optimum mixing ratio and, therefore, the treatment of silicon wafers can be performed efficiently by using the slurry containing the fine particles to the optimum mixing ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to fine particles (swarf and abrasive grains) contained in a slurry for processing a silicon wafer.
The present invention relates to a method and an apparatus for quantitatively measuring fine particles in a slurry for processing silicon wafers, each of which is capable of being independently and quantitatively measured in a production line.

[0002]

2. Description of the Related Art Waste slurry after use in a silicon wafer processing step includes liquids such as waste liquid (oil), waste water (eg, waste liquid and waste water from wafer cutting, lapping, various cleaning steps, etc.), and fine particles. Fine particles such as silicon (Si) and abrasive grains (SiC) having an average particle diameter of several microns to several tens of microns are included.

To quantitatively control and control the components of the waste slurry from the silicon wafer processing step so that the waste slurry can be used again in the silicon wafer processing step, it is necessary to reduce waste liquid and effectively use resources. It is strongly desired.

At present, fine-grained mixed liquid, which is waste slurry discharged from the above-described silicon wafer processing step, is mechanically and physically separated using a centrifuge, a liquid cyclone, various filters (membranes) and the like. And silicon (S) by gravity precipitation using chemicals
i) and fine particles composed of abrasive grains (SiC) and liquid,
Measure the reuse of active ingredients, waste liquid (oil) and waste water,
We are working to minimize the environmental impact of waste liquid disposal.

[0005] However, for example, in a cutting slurry used in a cutting process of a silicon wafer, in order to maintain cutting efficiency and cutting quality, the content of silicon chips (Si) and abrasive grains (SiC) contained in the cutting slurry. You need to control the amount.

Therefore, in order to reuse the waste slurry, it is necessary to know the components of the particles contained in the waste slurry or the cutting slurry and their contents. As a method for detecting the concentration, generally, the following measurement was performed.

(A) The collected waste slurry is pumped out of a storage tank or the like into a test tube or the like, and the collected slurry is centrifuged in a table-top type centrifuge. After separation in the test tube, visual measurement is performed.

(B) The mixing ratio of abrasive grains, chips and the like is indirectly estimated by automatically measuring the specific gravity and viscosity of the recovered waste slurry.

(C) The weight and volume of the recovered waste slurry are automatically measured, the specific gravity is determined, and the mixing ratio of abrasive grains, chips and the like is indirectly estimated from the specific gravity value.

[0010]

However, the method (A) is a manual sampling method, and has a problem that continuous measurement cannot be performed and the method cannot be applied to a production line. .

Further, the methods (B) and (C) cannot quantitatively measure the contaminants themselves in the waste slurry. In particular, it is not possible to directly and quantitatively measure the amount of silicon mixed in, which is a problem in waste slurry of wire saws. Therefore, it is impossible to know the true content of each component, and the estimation of the component amount from the measured value has a large error. Therefore, it is difficult to apply this method to a production line.

In view of the above circumstances, the present invention provides a method and an apparatus for quantitatively measuring the amount of fine particles in a silicon wafer processing slurry capable of quantitatively measuring the components and the amount of fine particles in the slurry on a production line. It is intended to provide.

[0013]

According to the first aspect of the present invention,
A method for quantitatively measuring fine particles in a slurry used in a silicon wafer processing step, wherein a part of the slurry is taken out through a circulation path, and the slurry is held in a slurry storage layer having a predetermined thickness to give a centrifugal force. Thereby, the fine particles and the liquid are separated in a direction orthogonal to the thickness direction of the slurry storage layer, and the color and the separation area of the separation layer of the fine particles and the liquid are separated by a color determination sensor from the thickness direction of the slurry storage layer. The present invention relates to a method for quantitatively measuring fine particles in a silicon wafer processing slurry, wherein a mixed amount according to the type of fine particles is measured by measuring a position.

According to a second aspect of the present invention, there is provided an apparatus for quantitatively measuring the amount of fine particles in a slurry used in a silicon wafer processing step, wherein a circulating system through which a part of the slurry is taken out, A separating device including a rotating body that forms a slurry storage layer having a predetermined thickness inside by a transparent member connected to at least one side and that rotates in a direction perpendicular to the thickness direction of the slurry storage layer; And a color discriminating sensor for detecting a color in a thickness direction of the slurry storage layer in a radial direction of the slurry.

According to the first and second aspects of the present invention,
The following operation is obtained.

The slurry taken out by the circulation path is held in a slurry storage layer having a predetermined thickness and subjected to centrifugal force to separate the slurry into fine particles and liquid in a direction perpendicular to the thickness direction of the slurry storage layer. The type (component) and mixed amount (concentration) of the mixed fine particles can be determined by measuring the color of the separation layer between the fine particles and the liquid and the position of the separation area from the thickness direction of the slurry storage layer using a color determination sensor. Since it is determined quantitatively in the production line, the components of the slurry can be adjusted to the optimum ratio.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. For example, a cutting slurry is supplied to a wire saw which is one of silicon wafer processing steps, and the waste slurry used for cutting is collected by the wire saw. Fig. 3 shows a cutting slurry supply device that adjusts the slurry and supplies the cutting slurry again to the wire saw. In FIG. 1, reference numeral 1 denotes a waste slurry storage tank that receives and stores waste slurry 3 (slurry) from the wire saw 2, and 4 denotes a slurry supply tank that adjusts the cutting slurry 5 (slurry) and supplies the slurry to the wire saw 2.

The waste slurry storage tank 1 is provided with a mixing blade 6 therein so as to stir the particles in the waste slurry 3 so as not to settle, and a waste slurry supply pipe 8 provided with a pump 7 on the way. One end is connected to the bottom of the waste slurry storage tank 1, the other end of the waste slurry supply pipe 8 is branched into two branches, one branch pipe 8a is connected to the slurry supply tank 4, and the other branch is used. The pipe 8 b is connected to the waste slurry storage tank 1 via an automatic quantitative valve 9, and a predetermined amount of the waste slurry 3 can be supplied to the slurry supply tank 4 by adjusting the automatic quantitative valve 9.

The slurry supply tank 4 is provided with a mixing blade 10 therein so as to stir so that particles in the cutting slurry 5 do not settle.
Is provided with a new abrasive supply device 11. A new abrasive supply device 11 includes an abrasive hopper 12 containing new abrasives, and a screw feeder 13 provided below the abrasive hopper 12.
And a motor 1 for driving the screw feeder 13 to rotate.
The new abrasive grains in the abrasive hopper 12 can be supplied to the slurry supply tank 4 by a predetermined amount via a new abrasive grain supply pipe 15 by driving the motor 14.

A new liquid (oil or water) storage tank 16 is provided above the slurry supply tank 4, and a predetermined amount of new liquid is supplied through an automatic metering valve 18 provided in a new liquid supply pipe 17. Can be supplied to the slurry supply tank 4.

In FIG. 1, 19 is an automatic metering valve 9, a motor 1
4 and the automatic metering valve 18 are adjusted so that the slurry supply tank 4
A controller for controlling the concentration of the cutting slurry 5 in the inside, so that the cutting slurry 5 adjusted in the slurry supply tank 4 is supplied to the wire saw 2 via a pipe 21 by a pump 20. Has become.

In the above configuration, the slurry supply tank 4
A circulation path 22 (branch pipe) is branched in the middle of a pipe 21 for supplying the cutting slurry 5 to the wire saw 2.
Is connected to one end of a measuring device 25 via an automatic opening / closing valve 23 such as a solenoid valve and a check valve 24, and the other end of the measuring device 25 is connected to a circulating system having an automatic opening / closing valve 26 such as a solenoid valve. Road 2
2 and connected to the slurry supply tank 4 by adjusting the automatic opening / closing valves 23 and 26 by the control signal of the controller 19 so that a certain amount of the cutting slurry 5 can be circulated and supplied to the measuring device 25. ing.

FIG. 2 shows an example of the measuring device 25. The measuring device 25 includes a separating device 27 which is connected to the circulation path 22 so as to form a slurry storage layer having a predetermined thickness inside. Have.

The separating device 27 includes a shaft 29 rotatably supported by a bearing 28, and a rotating body 30 having a center fixed to the shaft 29. The rotating body 30 has, for example, a disk shape inside. A measuring chamber 31 for forming a slurry storage layer having a required thickness (for example, about 5 to 15 mm), and one side of the measuring chamber 31 is provided with a plastic cover or the like so that the color of the contents can be determined. The transparent member 32 of FIG.

The cutting slurry 5 introduced from the circulation path 22 is supplied from one end of the shaft 29 to the inlet flow path 33 formed inside the shaft 29 and the radial direction formed on the rotating body 30 on the side opposite to the transparent member 32. The cutting slurry 5 in the measuring chamber 31 is supplied from the inner peripheral part of the measuring chamber 31 to the outer periphery of the measuring chamber 31 through an opening 35 through a plurality of extending flow paths 34. The fluid flows out from the other end of the shaft 29 through the outlet flow path 36 inside the 29. FIG.
Reference numeral 37 denotes a rotary joint provided at an end of the shaft 29.

The measuring chamber 31 of the rotating body 30 may be a small measuring chamber 31a divided in the circumferential direction as shown in FIG. 3 depending on required accuracy.

The shaft 29 and the rotating body 30 are
8 and the power of the drive motor 38 is
The shaft 29 is rotated by transmitting it to the shaft 29 via a transmission mechanism such as a zero or a gear.

At the position facing the transparent member 32 of the rotator 30, the color of the separation layer of fine particles and liquid from which the cutting slurry 5 has been separated in the measurement chamber 31, and the position of the separation area are detected. The color determination sensor 41 described above is provided so as to be movable in the radial direction of the rotating body 30. The color discriminating sensor 41 performs a measurement either during the rotation of the rotating body 30 or after the rotation is stopped, and irradiates using a specific light source as necessary (depending on the type of contaminants in the cutting slurry 5). The measurement may be performed by performing the measurement.

In FIG. 1, reference numeral 42 denotes a cleaning liquid storage tank provided at the inlet of the measuring device 25 in the circulation path 22, and the inlet of the measuring device 25 via an on-off valve 43, a check valve 44 and a pump 45. A cleaning liquid discharge pipe 47 having an opening / closing valve 46 is provided at the outlet of the measuring device 25 to discharge the cleaned liquid to the waste slurry storage tank 1. It is supposed to.

The operation of the above embodiment will be described.

The automatic opening / closing valve 2 is controlled by the controller 19 shown in FIG.
A portion of the cutting slurry 5 supplied to the wire saw 2 from the slurry supply tank 4 via the pump 20 is supplied to the measuring device 25 via the circulation path 22 and the slurry supply tank 4 is controlled. It is circulating by being returned to.

The case where the circulation of the cutting slurry 5 is stopped to perform the quantitative measurement of the fine particles of the cutting slurry 5 will be described. The timer provided in the controller 19 or the inlet and outlet of the measuring device 25 is operated by an operator's push button operation. Are closed, the circulation of the temporary cutting slurry 5 is stopped.

Next, the drive motor 38 of the measuring device 25 is started, and the rotating body 30 containing the cutting slurry 5 is rotated at a high speed (for example, about 500 to 1000 rpm) for 30
Rotate for about 60 seconds. Then, the slurry storage layer of the cutting slurry 5 formed in the measurement chamber 31 is separated in the circumferential direction according to the specific gravity difference, the fine particles having a large specific gravity are separated in the outer peripheral direction, and the liquid is separated in the inner diameter direction. When two or more types of fine particles having different specific gravities are mixed, a separation layer is formed in accordance with the specific gravity difference.

The color of the separation layer and the radial position of the separation area are measured by the color discrimination sensor 41, and the type (component) and the amount (concentration) of the mixed fine particles are determined based on the color of the separation layer and the position of the separation area. ) Can be obtained by calculation.

After the measurement is completed, the automatic opening / closing valves 23 and 26 before and after the measuring device 25 shown in FIG. 1 are opened, and the cutting slurry 5 in the pipe 21 is circulated again through the circulation path 22 to remove the cutting slurry 5 in the measuring chamber 31. It is discharged into the slurry supply tank 4 and returned to the normal operation.

According to the measurement result by the color discrimination sensor 41,
The motor 14 is automatically or manually operated by the controller 19 to adjust the flow rate of the new abrasive to be mixed into the slurry supply tank 4 and adjust the automatic quantitative valve 18 so that the new liquid in the new liquid storage tank 16 The amount of the liquid (oil) supplied to the supply tank 4 is adjusted. At this time, adjusting the amount of the cutting slurry 5 in the slurry supply tank 4 is also performed.

As described above, the fine particle concentration of the cutting slurry 5 supplied to the wire saw 2 can be adjusted optimally.
Therefore, operation at a point with high cutting efficiency and high quality control can be realized.

Also, periodically or as necessary, the automatic on-off valves 23 and 26 are closed and the on-off valves 43 and 46 are opened, and the cleaning liquid in the cleaning liquid storage tank 42 is forcibly forced by the pump 45 into the measuring device 25. To clean the measurement chamber 31 and the piping system.

In the above description, the measurement is performed in a state where the circulation of the cutting slurry 5 in the circulation path 22 is stopped. However, the measurement can be performed while the cutting slurry 5 is circulated.

It should be noted that the present invention is not limited to the above-described embodiment, but can be applied to measurement of waste slurry or other slurry in addition to cutting slurry. Can be arbitrarily changed, and various changes can be made without departing from the spirit of the present invention.

[0042]

As described above, according to the method and apparatus for quantitatively measuring particles in a silicon wafer processing slurry of the present invention, the slurry taken out by the circulation path is held in the slurry storage layer having a predetermined thickness. By applying centrifugal force to separate the fine particles and the liquid in a direction orthogonal to the thickness direction of the slurry storage layer, and from the thickness direction of the slurry storage layer by the color discrimination sensor of the separation layer of the fine particles and the liquid. By measuring the color and the position of the separation area, the type (component) and mixed amount (concentration) of the mixed fine particles are determined quantitatively in the production line, so that the components of the slurry can be adjusted to the optimum ratio. Therefore, an excellent effect that the silicon wafer can be efficiently processed with the slurry in a suitable ratio can be obtained.

[Brief description of the drawings]

FIG. 1 is an overall schematic side view showing an embodiment of the present invention.

FIG. 2 is a cut-away side view showing an example of the measuring device.

FIG. 3 is a cross-sectional view showing an example when viewed from a III-III direction in FIG. 2;

[Explanation of symbols]

 3 Waste Slurry (Slurry) 5 Cutting Slurry (Slurry) 22 Circulation System 27 Separator 30 Rotating Body 32 Transparent Member 41 Color Discrimination Sensor

Claims (2)

[Claims] 1. A method for quantitatively measuring fine particles in a slurry used in a silicon wafer processing step, wherein a part of the slurry is taken out through a circulation path, and the slurry is held in a slurry storage layer having a predetermined thickness. By applying centrifugal force to separate the fine particles and the liquid in a direction orthogonal to the thickness direction of the slurry storage layer, and from the thickness direction of the slurry storage layer by the color discrimination sensor of the separation layer of the fine particles and the liquid. A method for quantitatively measuring fine particles in a silicon wafer processing slurry, comprising measuring a mixed amount according to a type of fine particles by measuring a color and a position of a separation area. 2. A device for quantitatively measuring fine particles in a slurry used in a silicon wafer processing step, comprising: a circulation path for extracting a part of the slurry; and a circulation path connected to the circulation path. A separating device including a rotating member that forms a slurry storage layer having a predetermined thickness inside the transparent member provided therein and rotates in a direction orthogonal to a thickness direction of the slurry storage layer; and a thickness of the slurry storage layer in the separation device. A color discriminating sensor for detecting a color in a vertical direction in a radial direction.