JP2000310630A - Evaluation method of slurry for wire saw slicing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To preliminarily grasp a change in the physical properties of a slurry at a time of slicing without actually performing troublesome and expensive slicing. SOLUTION: Impalpable powder-like silicon is added to an evaluating slurry and the physical properties of the slurry are measured while the slurry is circulated and fluidized by a small-sized impeller pump 20. As the slurry 11, an oily or aq. one may be used and, pref., impalpable powder-like silicon with a particle size of 0.05-50 μm is added.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating characteristics of a slurry used for slicing an ingot with a wire saw in advance.

[0002]

2. Description of the Related Art An ingot manufactured by a pulling method or the like is cut into a top and a tail, and then sliced into a wafer having a predetermined thickness through processes such as outer diameter grinding and orientation flat processing. As the slicing, a slicer having an inner peripheral blade is known, but recently, cutting with a wire saw such as a piano wire has been adopted as the diameter of a wafer increases. The wire saw cutting device generally has three groove rollers 1 to 3 as shown in FIG.
, One of which is connected to the drive motor 4. The multi-wire 5 configured by making the groove rollers 1 to 3 make multiple turns is unwound from one wire reel 6 and wound up on the other wire reel 7. A tension is applied to the multi-wire 5 by the tensioner 8 so as to go around the rollers 1 to 3 in a pulled state.

An ingot 9 to be sliced is mounted on a holder 10 via an adhesive jig, disposed between the groove rollers 1 and 2, and sliced into a plurality of wafers by a multi-wire 5. At this time, the slurry 11 is supplied to the multi-wire 5 in order to smoothly perform the slicing operation. The slurry 11 is supplied from the slurry tank 12 to the multi-wire 5 from the nozzle 14 via the supply pipe 13, then collected by the pan 15 and returned to the slurry tank 12. In order to cool the slurry 11, the slurry 11 is circulated between the heat exchanger 16 and the slurry tank 12.

[0004]

SUMMARY OF THE INVENTION Slurry 1 to be used
For cutting a large number of wafers from the ingot 9 with the multi-wire 5, it is required that the abrasive grains 1 be sent to the inside of the ingot 9 in a state of being dispersed in the coolant. It is also important that the various physical properties such as the dispersion state of the slurry 11 and the viscosity and pH are stable so that the cutting conditions do not change during slicing. Further, the slurry 1 remaining on the surface of the wafer cut out from the ingot 9
It is one of the characteristics required for the slurry 11 that the slurry 1 is easily removed and that the amount of abrasive grains deposited in the apparatus is small. The slurry has abrasive particles having a particle size of about 20 μm added to the coolant. As the coolant, an oil-based coolant or a water-based coolant containing a mineral oil as a main component is used.

[0005] Oily slurries based on oily coolants are widely used because they have the advantages of being able to stably disperse and retain abrasive grains and have a relatively low cost, but they are flammable and can be used for long periods of unmanned operation. However, it is not easy to clean a sliced wafer or an apparatus, and there is a concern that the used slurry is finally incinerated, which may affect the environment. On the other hand, an aqueous slurry in which abrasive grains are suspended in an aqueous coolant is not flammable, and the cut wafers and equipment can be easily washed only with water, and the used slurry can be biodegraded. The state is unstable. In any of the slurries, the ingot can be sliced without wire breakage or wafer breakage, the wire can be removed after slicing, the sliced wafer can be easily peeled off, no abrasive grains accumulate inside the apparatus, Good wafer accuracy such as thickness and TTV, and small changes in the viscosity of the slurry during slicing are required.

[0006] The coolant is improved daily to satisfy the slicing characteristics required for the slurry 11,
There is an increasing need for a method for easily and inexpensively evaluating the slurry 11 using a newly developed coolant. At present, only the properties of the slurry before use are evaluated based on viscosity, density and pH. The viscosity is generally measured by a rotary cylindrical viscometer 30 (B-type viscometer) shown in FIG. That is, the inner cylinder 31 and the container 32 (outer cylinder) suspended from the stator 34 via the metal wire 33.
The sample A is put in between, and the container 32 is rotated at a constant rotation speed. Then, a force is also applied to the inner cylinder 31 in the rotation direction according to the viscosity of the sample A, and as a result, a torsional moment (torque) is applied to the metal wire 33. Since the scale disk 35 attached in the middle of the metal wire 33 rotates according to the amount of twist, the viscosity can be obtained by reading the rotation angle. The density is measured by a floating type densitometer, and the pH is measured by an electrode type pH meter.

[0007] The physical properties of the slurry 11 when the ingot 9 is actually sliced are far from the characteristic values measured in this way because silicon dust generated by slicing is mixed with the slurry 11. This may cause defects such as breakage of the wire 5, breakage of the wafer, mutual adhesion of wafers cut from the ingot 9, and accumulation of slurry 11 in the apparatus.
The H value is not effective for predicting the cutting performance. In particular, the viscosity tends to fluctuate, and the change in the viscosity greatly affects the deposition of abrasive grains from the slurry 11. Therefore, at present, a slicing test of the ingot 9 is actually performed to examine whether or not the wire 5 is broken, and to evaluate the suitability of the slurry 11. However, slicing the ingot 9 to test the cutting condition requires a great deal of time and cost, and the slicing ingot 9 tends to have a large diameter, which imposes a heavy burden.

[0008]

SUMMARY OF THE INVENTION The present invention has been devised in order to solve such a problem. The present invention circulates and flows using a slurry to which fine powder silicon is added, and performs a chemical reaction and a chemical reaction which occur during slicing. By imitating physical phenomena,
An object of the present invention is to omit a troublesome and costly ingot slicing operation of an ingot and to grasp characteristics required for a slurry in advance. The slurry evaluation method of the present invention measures various physical properties of a slurry by adding fine powdered silicon to the slurry for evaluation and circulating and flowing the slurry along a flow path passing through a slurry container and a pump in order to achieve the object. It is characterized by doing. A small impeller pump is used as the pump, and the flow rate is 100 to 1000 ml / min.
It is preferable that the zero-hour evaluation slurry is circulated and fluidized. As the slurry, either oily or aqueous can be used,
Preferably, finely divided silicon having a particle size of 0.05 to 50 μm is added. The physical properties to be measured include viscosity, pH, sedimentation, density, liquid temperature, surface tension, affinity with wire, etc. When detecting physical property changes by continuous or intermittent measurement, actual ingot slicing is performed. The behavior of the slurry inside can be predicted more accurately.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the slurry 11 used for slicing the ingot 9, silicon chips generated by slicing the ingot 9 are mixed. The mixed cutting chips cause the physical properties of the slurry 11 to be changed every moment. In particular, in the case of an aqueous slurry, the chemical components in the slurry 11 react with the silicon cuttings, and the slurry 11
Greatly change the physical property values of Fluctuations in physical properties due to the mixing of cutting chips make it difficult to predict the performance and behavior of the new slurry during actual slicing from physical properties measured in advance. Therefore, in the present invention, finely divided silicon having a particle size of about 0.05 to 50 μm corresponding to silicon chips is added to the slurry. When the slurry to which fine silicon powder is added is fluidized and circulated under certain conditions, a chemical reaction between the chemical components in the slurry 11 and the fine silicon powder is promoted, and a slurry whose characteristics change during actual slicing may be imitated. it can. Further, since a heat balance due to heat generation from the pump, frictional heat in the piping system, or the like can be obtained close to the actual state at the time of actual slicing, a result independent of the type of coolant serving as the base of the slurry 11 can be obtained.

Specifically, the viscosity, p
H, density, liquid temperature, surface tension, and affinity with wire are continuously measured. The circulation flow is 100 to 10 by the pump.
The evaluation slurry is circulated at a flow rate of 00 ml / min for 1 to 10 hours. As the pump, a small impeller pump is used, and a pump of the type used in a slicing device is preferable. For example, a centrifugal impeller pump as shown in FIG. 3 is generally used for a slicing device. The flow rate should be close to the actual slicing device, and should be set to 100 ml / min or more. On the other hand, if the flow rate is higher than 1000 ml / min, the change of the evaluation sample slurry is too fast to allow sufficient observation. The time required for the circulation and flow is 1 to 10 hours, and a necessary and sufficient evaluation can be made.

For pH measurement, an electrode type pH meter is suitable for continuous measurement. The viscosity is measured by taking a sample and using a rotating cylinder viscometer. The density is measured by a floating-type densitometer, and the surface tension is measured by, for example, a Wilhelm method for vertically pulling a ring or plate immersed in a sample slurry and determining a maximum force when the ring or plate is separated. The sedimentability is measured by the amount of the settled abrasive grains after standing in a measuring cylinder for 24 hours. The affinity with the wire is measured by dropping the slurry on the wire running at a low speed and measuring the amount of the slurry carried by the wire.
It can be measured by, for example, a method of measuring the weight of the slurry attached to the wire piece. The finely divided silicon to be dispersed has a particle size of 0.05 to 0.05 in order to approximate silicon particles separated as cutting chips from a silicon ingot during actual slicing.
Adjusted to 50 μm. If the particle size is smaller than 0.05 μm, the chemical reaction is promoted too much, and if it is larger than 50 μm, the chemical reaction is slowed down, and a result that accurately represents the behavior of the slurry during actual slicing cannot be obtained.

[0012]

EXAMPLE 1 An aqueous slurry A in which SiC abrasive grains having a particle size of about 20 μm were dispersed in an aqueous coolant containing glycol and a glycol ester at a ratio of 1: 1 by weight was evaluated according to the present invention. This aqueous slurry A
Is a slurry with a track record of slicing, and the initial physical properties are: density: 1.6 g / cm ³ , viscosity: 180 mPa ·
Seconds, pH: 9.0. In addition, 2
After standing for 4 hours, no condensation of the abrasive grains was observed. As shown in FIG. 2, the lower outlet of the slurry container 22 having a diameter of 200 mm and the height of 160 mm and the inlet of the impeller pump 20 are connected to a vinyl hose 23 having a diameter of 12 mm and a length of 200 mm.
Connected with. Diameter 12 at the outlet of impeller pump 20
mm, a 300 mm long vinyl hose 24 is connected,
The other end of the vinyl hose 24 was exposed 100 mm above the liquid surface of the slurry 11 contained in the slurry container 22.

6 g / l of finely divided silicon having an average particle size of about 3 μm is dispersed in the slurry A for evaluation,
Preliminary stirring was performed at 0 rpm for 15 minutes. Next, the evaluation slurry A was put into a 5 liter slurry container 22 and immediately circulated by the impeller pump 20. Sampling slurry was extracted from the vinyl hose 23, and the temperature, viscosity and pH of the slurry were collected at 10 minute intervals.
Was measured. The viscosity was evaluated by a rotating cylinder viscometer (B-type viscometer), the pH was measured by an electrode type pH meter, and the sedimentation was evaluated by taking a sample in a measuring cylinder and allowing it to stand for 24 hours.

The results obtained are shown in graphs in FIGS. 4 and 5 in comparison with data previously obtained by actual slicing of a silicon ingot. However, the abscissa represents the circulation flow time T as the depth of cut D, which is expressed as D = 5.0 × T. That is, the circulation flow for one minute corresponds to a cutting depth of 5 mm in actual slicing. The viscosity change of the slurry obtained in the simulation test decreases at a constant gradient in the initial stage of cutting as shown in FIG. 4 and becomes almost constant at 70 m from the time when the cutting depth reaches 150 mm.
Pa · sec. This change in viscosity was in good agreement with the result obtained by actually slicing the silicon ingot. The pH change was also in good agreement with the data obtained in actual slicing. The sedimentability of the abrasive grains was determined as follows. The sedimentability of the abrasive grains was measured by taking the sample slurry after circulating for 80 minutes in a measuring cylinder and allowing the settled abrasive grains to stand for 24 hours.
00 g / l, which was also in good agreement with 800 g / l of data obtained in actual slicing. Other, specific gravity,
The liquid temperature, the surface tension, and the affinity with the wire also followed the same changes as in the actual slicing.

Example 2: SiC abrasive grains having a particle size of about 20 μm were added to an aqueous coolant containing glycol as a main component in a weight ratio of 1.
Aqueous slurry B dispersed at a ratio of 0: 1.0 was evaluated according to the present invention. This aqueous slurry B is a newly developed slurry, having a density of 1.6 g / cm ³ and a viscosity of:
The initial values of physical properties of about 160 mPa · s and pH: 7 were shown. Further, the abrasive grains were left standing in the measuring cylinder for 24 hours, and no condensation of the abrasive grains was observed. This slurry B was evaluated in the same manner as in Example 1. With the slurry B, stable viscosity change data as shown in FIG. 5 was obtained. Also in this case, it can be seen that the data matches well with the data obtained by actual cutting. Thus, from the high consistency of the test results, it can be said that the simulation test according to the present invention accurately mimics the behavior of the slurry during actual ingot slicing.

[0016]

As described above, according to the evaluation method of the present invention, changes in physical properties such as viscosity, pH, and sedimentation of abrasive grains during slicing of a silicon ingot can be grasped by a simple simulation test. . Therefore, without actually slicing the silicon ingot, it is possible to evaluate the slurry or the coolant that is the raw material of the slurry.・ Efficient response is possible.

[Brief description of the drawings]

FIG. 1 shows an example of a slicing device.

FIG. 2 shows an example of a fluid circulation device.

FIG. 3 is a diagram illustrating an impeller pump.

FIG. 4 is a graph showing a change in viscosity of a slurry A obtained by the method of the present invention in comparison with actual cutting data.

FIG. 5 is a graph showing a change in viscosity of a slurry B obtained by the method of the present invention in comparison with actual cutting data.

FIG. 6 is a diagram illustrating a rotating cylindrical viscometer.

[Explanation of symbols]

9: Ingot 11: Slurry 20: Impeller pump 21: Impeller 2
2: Slurry container 23, 24: Vinyl hose

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Keiichiro Asakawa 555-1, Nakanoya, Annaka-shi, Gunma Inside the Super Silicon Research Laboratories Co., Ltd. (72) Inventor Junichi Matsuzaki 555-1, Nakanoya, Annaka-shi, Gunma (72) Inventor Akio Ashida 2-17-10 Yahiro, Sumida-ku, Tokyo F-term (reference) 3C047 FF06 FF09 FF11 GG13 GG15 GG20 3C069 AA01 BA06 BC02 CA04 CB01 DA06 EA02

Claims (3)

[Claims] 1. A method for evaluating a slurry, comprising adding finely divided silicon to a slurry for evaluation, and measuring various physical properties of the slurry while circulating and flowing the slurry along a flow path passing through a slurry container and a pump. 2. Using a small impeller pump,
The method for evaluating a slurry according to claim 1, wherein the evaluation slurry is circulated at a flow rate of 1000 ml / min for 1 to 10 hours. 3. The particle size of the finely divided silicon is 0.05 to 50.
3. The method for evaluating a slurry according to claim 1, wherein the particle size is μm.