JP2002170793A - Method for manufacturing cmp slurry raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a CMP slurry having the satisfactorily small number of coarse particles with which a semiconductor wafer can be polished without generating scratches from a CMP slurry waste liquid. SOLUTION: In a method for manufacturing a CMP slurry raw material, the raw material of the CMP slurry is reproduced from the waste liquid of the CMP slurry by executing a step of removing the coarse particles in the CMP slurry waste liquid used for polishing to reduce the number of the coarse particles in the waste liquid and a step of concentrating the liquid to obtain the material by applying a centrifugal force to the liquid after the removing step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CMP (Chemical Mechanical Pos.) Used for flattening a semiconductor wafer or the like.
The present invention relates to a method for producing a raw material of a CMP slurry by regenerating a raw material of a CMP slurry from a waste liquid of the slurry.

[0002]

2. Description of the Related Art A CMP slurry such as an aqueous dispersion of fumed silica or colloidal silica is used for polishing a semiconductor wafer or the like. Since the CMP slurry used for polishing is diluted with a cleaning solution, it contains not less than a large number of coarse particles having a particle size of 5 μm or more, and these coarse particles cause scratches on the semiconductor wafer.
It cannot be reused as slurry, and is currently disposed of as waste liquid.

[0003]

There is a demand to reuse a waste liquid of a CMP slurry. SUMMARY OF THE INVENTION An object of the present invention is to make it possible to reuse a waste liquid of a CMP slurry used for polishing a semiconductor wafer or the like. That is, it is an object of the present invention to be able to regenerate a CMP slurry having excellent characteristics that does not generate scratches even when used for polishing a semiconductor wafer or the like due to a sufficiently small number of coarse particles from a waste liquid of the CMP slurry.

[0004]

According to the first aspect of the present invention, a CMP slurry raw material is regenerated from a waste liquid of a CMP slurry by performing the following steps (a) and (b). It is a manufacturing method of. (A) a removing step of removing coarse particles in a waste liquid of the CMP slurry used for polishing to reduce the number of coarse particles in the waste liquid; and (b) applying a centrifugal force to the waste liquid after the removing step. A concentration step of concentrating the waste liquid to obtain a CMP slurry raw material. In the above description, the coarse particles refer to inorganic particles and / or organic particles having a particle size of 5 μm or more. 5μm particle size in slurry
The above number of coarse particles is 500 in terms of a solid content concentration of 20 wt%.
If the number is less than 0 / mL, it is considered that no scratch is generated on the semiconductor wafer even when used as a CMP slurry.
It is defined as above. Further, the particles are inorganic particles and / or organic particles. Particles that exert CMP action
Hereinafter, it is called an abrasive grain. CM produced by the method of the present invention
The P slurry raw material is appropriately diluted to obtain a CMP slurry. In this CMP slurry, the number of coarse particles is 5,000 / mL or less, preferably 3,000 / mL or less, more preferably 1,000 / mL or less in terms of the solid content concentration of 20 wt%. The removal step (a) can be performed, for example, by centrifugation and / or filtration. The centrifugation will be described in the description of claim 3. When filtration is performed, for example, the filter is designed such that the pore structure of the filter medium is coarse on the inlet side, fine on the outlet side, and finer continuously or stepwise from the inlet side to the outlet side. Depth type filters can be used. By filtering through a depth-type filter, a CMP waste liquid having a reduced number of coarse particles can be obtained. In addition, even if it is not a depth type, any filter can be used as long as it has the same effect.

According to a second aspect of the present invention, in the first aspect, the abrasive grains in the CMP slurry used for polishing are silica (Si).
O ₂ ). When a silicon (Si) wafer is polished using a CMP slurry using silica as abrasive grains, various impurities such as metal ions and additives are not contained in the CMP waste liquid. Therefore, the CMP slurry raw material can be obtained without performing the step of removing the various impurities and the like. It should be noted that W, C, Ceria (CeO ₂ ), etc.
When the surface to be polished such as u or TiN is polished, the slurry raw material can be similarly regenerated by performing a step of removing impurities contained in the waste liquid.

According to a third aspect of the present invention, in the first aspect, in the removing step (a), a centrifugal force having an integrated value of the maximum centrifugal acceleration of less than 4,500,000 G · sec is applied to the waste liquid of the CMP slurry. The coarse particles are removed, and in the concentration step (b), the integrated value of the maximum centrifugal acceleration is 4,50 in the waste liquid after the removal step.
A method for producing a raw material for a CMP slurry, comprising applying a centrifugal force of 000 G · sec or more to concentrate the waste liquid. Here, G is the gravitational acceleration. The maximum centrifugal acceleration refers to the position of the maximum radius _Rmax from the rotation axis C when the CMP waste liquid is centrifuged / concentrated (the outermost position in the container in which the CMP waste liquid to be centrifuged / concentrated is placed). Means the centrifugal acceleration (see FIGS. 1 and 2). The rotor used in the centrifuge / concentrator is not particularly limited. Known angle rotors, swing rotors, continuous centrifugal rotors, and the like can be used. In the removal step (a), if the integrated value of the maximum centrifugal acceleration is 4,500,000 G · sec or more, not only coarse particles but also fine abrasive grains necessary for the intended CMP slurry are separated. Not preferred. A preferable range of the integrated value of the maximum centrifugal acceleration in the removing step (a) is 300,000 to 1,500,000.
G · sec, a more preferred range is 600,000 to 1,
200,000 Gsec. In the removal step (a), the integrated value of the maximum centrifugal acceleration was 300,000 G ·
If it is less than sec, the coarse particles cannot be sufficiently centrifuged. On the other hand, in the concentration step (b), if the integrated value of the maximum centrifugal acceleration is less than 4,500,000 G · sec, the CMP waste liquid cannot be concentrated. The preferred range of the integrated value of the maximum centrifugal acceleration in the concentration step (b) is 6,000,000 G · sec or more, and the more preferred range is 9,000,000 G · sec or more.

According to a fourth aspect of the present invention, in the third aspect, the maximum centrifugal acceleration of the centrifugal force in the removing step (a) is less than 2500 G, and the maximum centrifugal acceleration of the centrifugal force in the concentration step (b) is 2500 G or more. And a method for producing a CMP slurry raw material. In the removing step (a), when the maximum centrifugal acceleration is 2,500 G or more, coarse particles can be separated, but fine abrasive grains necessary for the target CMP slurry are not separated. Therefore, it is necessary to precisely control the application time of the centrifugal force, and such control is difficult in some cases, which is not preferable. A preferred range of the maximum centrifugal acceleration in the removing step (a) is 500 to 2,250 G, and a more preferred range is 1,000.
0 to 2,000G. If the maximum centrifugal acceleration is less than 500 G in the removing step (a), coarse particles cannot be sufficiently centrifuged within a practical time. on the other hand,
In the concentration step (b), when the maximum centrifugal acceleration is less than 2500 G, the CMP waste liquid cannot be concentrated, or the CMP waste liquid cannot be concentrated within a practical time. The maximum centrifugal acceleration in the concentration step (b) is preferably 3000 G or more, more preferably 5000 G or more.

(1) Abrasives: When a CMP slurry is used for polishing a semiconductor wafer or the like, the CMP target of the present invention is CMP.
Waste liquid is produced. As abrasive grains constituting the CMP slurry, inorganic particles and / or organic particles can be used. As inorganic particles, silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, antimony oxide,
Chromium oxide, germanium oxide, vanadium oxide, tungsten oxide, iron oxide, cerium oxide, manganese oxide,
Metal oxides such as zinc oxide can be exemplified. Among these, silicon oxide, aluminum oxide, titanium oxide and cerium oxide are particularly preferred. Further, these inorganic oxides are preferable because inorganic oxides synthesized by a gas phase method such as a fumed method (high-temperature flame hydrolysis method) or a nanophase technology method (metal evaporation oxidation method) have high purity. Also,
Inorganic oxides synthesized by the fumed method are more preferable because they have high purity and are relatively inexpensive. The inorganic oxides may be used as a mixture of one or more kinds. CMP
The slurry may be colloidal silica.

(2) Centrifugation / concentration: Centrifugation is a technique for separating a solid from a liquid in a centrifugal force field. In the present invention, centrifugal separation is used to remove coarse particles from the CMP waste liquid according to claims 3 and 4. In addition, centrifugal concentration is used to concentrate the CMP waste liquid after removing coarse particles according to claims 1 to 4. FIG. 1 schematically shows a cross section of a continuous centrifugal rotor set in a centrifugal separator. The continuous centrifugal rotor is used, for example, in the removal step (a), but may be used in the concentration step (b). When used in the removal step (a), as shown in the figure,
The CMP waste liquid is continuously supplied into the separation tank 505 from the fluid supply port 502 of the continuous centrifugal rotor 500 rotated at a predetermined speed through the introduction path 503. Since the supplied CMP waste liquid is subjected to centrifugal force due to rotation, the coarse particles in the CMP waste liquid settle outward (radially outward with the rotation axis C as the center). CMP
Since the waste liquid is continuously supplied as described above, the CMP waste liquid after the coarse particles are settled and separated is gradually pushed up, discharged to the outside via the outlet path 506, and collected. Thereby, the number of coarse particles is sufficiently reduced in C
Obtain MP waste liquid. FIG. 2 schematically shows a cross section of an angle rotor set in a centrifugal concentrator. The angle rotor is used, for example, in the concentration step (b), but may be used in the removal step (a). When used in the concentration step (b),
As shown in the figure, a pair of two tubes 55 in which the CMP waste liquid after the removal step (a) is sealed at a predetermined position in the angle rotor 50 are mutually moved 180 degrees from the axis C of the rotating shaft in a top view.
It is set so as to form an angle of °, and is rotated at a predetermined speed by a rotating shaft (the shaft center is indicated by C). CMP in tube
Since the centrifugal force due to rotation is applied to the waste liquid, the fine abrasive grains in the CMP waste liquid settle outward (radially outward with the rotation axis C as the center, left and right in the figure). . Thus, a CMP slurry raw material in which the abrasive grains are concentrated is obtained. Since the angle rotor can rotate at a very high speed, there is an advantage that a very large G can be applied to the CMP waste liquid. In the above description, the case where a continuous centrifugal rotor is used in the removal step (a) and the angle rotor is used in the concentration step (b) has been described. Same as above.

(3) Average particle size: The average particle size of the secondary particles of the CMP slurry obtained by diluting the CMP slurry raw material produced by the method of the present invention is 0.01 to 2 μm, preferably 0.02 to 2 μm. 1 μm, more preferably 0.03 to
0.8 μm. If it is less than 0.01 μm, the viscosity of the CMP slurry becomes extremely high, and good dispersion stability cannot be obtained. If it exceeds 2 μm, the stability becomes poor and sedimentation occurs. In order to make the average particle diameter of the secondary particles fall within the above range, it is only necessary to select the type of the abrasive material and adjust the conditions in the dilution step.

(4) Filtration: Filtration is a technique for collecting and removing coarse particles with a filter. In the present invention, in the removal step (a), a filtration technique is used before or after centrifugation, or alone instead of centrifugation. As the filter used for the filtration, for example, a cartridge type depth filter (manufactured by Advantech Toyo Co., Ltd., manufactured by Nippon Pall Co., Ltd.) or a bag type depth filter (manufactured by ISP, etc.) can be used. Also, a pleated type filter can be used. Among them, a depth filter is preferable. The depth type filter is a filter capable of collecting a large amount of foreign substances from a fluid passing through the filter medium, the filter medium being sufficiently thick (eg, 0.2 to 2 cm). In a depth type filter, for example, the pore structure is coarse on the fluid entry (inlet) side, fine on the discharge (outlet) side,
In addition, a filter material having a certain thickness is used which is designed to be continuously or stepwise (steps may be one step or two or more steps) from the entry side to the discharge side. I have. In such a structure, relatively large particles among the coarse particles are collected near the entry side, and relatively small particles are collected near the discharge side.As a whole, the coarse particles are collected at each part in the thickness direction of the filter. Collected. As a result, there is an effect that the collection of the coarse particles is sufficiently performed, the filter is hardly clogged, and the life of the filter can be extended. In the depth type filter, preferably,
Filtration in which the porosity is substantially uniform between the fluid entry side and the discharge side by designing the fiber thickness to be thicker on the fluid entry (inlet) side and thinner on the discharge (outlet) side Use materials.
The porosity is the ratio of the porosity per unit cross-sectional area in a plane orthogonal to the direction in which the fluid passes. When the porosity is substantially uniform, the pressure loss at the time of filtration becomes small, and the conditions for collecting coarse particles become substantially uniform in the thickness direction. Therefore, a relatively low-pressure pump can be used. The cartridge type hollow cylindrical depth filter has an advantage that the thickness of the filter medium can be designed to a desired thickness. The bag-type depth filter has an advantage that the filter can be removed together with the filter at the time of replacement by installing the filter inside the filter device so that the fluid passes from the inside of the bag to the outside of the bag.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. In the following description, “%” represents “% by weight”. In addition, coarse particles before and after centrifugation and after filtration (particle diameter 5 μm)
The particle counter (RION)
The measurement was performed using a model name (KL-11) manufactured by the company. (1) Concentration target: In the following examples, a CMP waste liquid generated by subjecting a silicon wafer to chemical mechanical polishing using the following CMP slurry is treated (Examples 1, 3, 3).
5) Polishing was performed using a CMP slurry prepared from a CMP slurry raw material regenerated from the CMP waste liquid (Examples 2, 4, and 6). The solid content concentration of the above-mentioned CMP waste liquid is 2%. Note: Fumed silica (Aerosil # 50, manufactured by Nippon Aerosil Co., Ltd.) was dispersed in water, and the pH (pH) was adjusted to 10.6 using KOH (potassium hydroxide). 10% slurry.

(2) Outline of Embodiment: Embodiments 1 and 3
In the removal step, centrifugal separation was performed using a Hitachi high-speed cooling centrifuge CR22E manufactured by Hitachi Koki Co., Ltd., and using a continuous rotor R18C for the centrifuge as the rotor. FIG. 1 shows a principle diagram of the centrifugation. In the removal step of Example 1, only centrifugation was performed, and in Example 3, filtration was performed after centrifugation. The filter used in this filtration is the same as the filter used in Example 5 below. In the concentration steps of Example 1 and Example 3, a centrifuge CR26H manufactured by Hitachi Koki Co., Ltd. was used, and an angle rotor R26A for the centrifuge was used as a rotor.
(Or 24A) for concentration. FIG. 2 shows a principle diagram of the centrifugal concentration. In the removing step of Example 5, a depth cartridge filter (profile, made of MCY1001Y050 / polypropylene, manufactured by Nippon Pall Co., Ltd., cartridge length 25 cm, filter thickness through which the liquid passes 2 cm, 5 μm particle capturing performance 100
%) To perform a filter treatment. That is, in the removal step of Example 5, only filtration was performed.

(3) Example 1 (Example of treatment of CMP waste liquid): (a) Removal step (centrifugation): The number of coarse particles in the CMP waste liquid before centrifugation was 2% TSC (solids concentration 2%). , The same applies hereinafter), 4,450 pcs / mL, and 4
It was 4,500 pieces / mL. The conditions for centrifugation are as follows: flow rate: 400 mL / min, maximum centrifugal acceleration: 1,000
G, rotation time is 10 minutes, and the integrated value of the maximum centrifugal acceleration is 60
It is 0000 G · sec. The number of coarse particles in the CMP waste liquid after centrifugation (the CMP waste liquid discharged from the outlet path 506) was 122 particles / mL at 1.9% of TSC, and
It was 1,284 / mL in terms of%. (B) Concentration step: TSC before centrifugal concentration is 1.9% as described above. The conditions for the centrifugal concentration are that the maximum centrifugal acceleration is 26,600 G, the rotation time is 30 minutes, and the integrated value of the maximum centrifugal acceleration is 47,880,000 G · sec. The TSC of the CMP waste liquid after the centrifugal concentration, that is, the TSC of the CMP slurry raw material was 35%, and most of the silica particles in the CMP waste liquid were concentrated.

(4) Example 2 (Example of polishing): The CMP waste liquid (= CMP slurry raw material) obtained in Example 1 was diluted, the pH was adjusted to 10.6 with KOH, and TSC 10%
CMP slurry. Using this CMP slurry, a silicon wafer was polished. Polishing machine specifications and polishing conditions are as follows. That is, the polishing machine was a lap master (LM-15, manufactured by SFT, surface plate diameter: 380 nm), the pad mounted on the surface of the polishing machine was a pad IC1000 (manufactured by Rodel-Nitta), the polishing pressure was 233 g / cm ² , The platen rotation speed is 60 rpm, the head rotation speed is 60 rpm, C
The supply rate of the MP slurry is 2 g / sec. The polishing rate was 400 Å / min. After polishing, the presence or absence of scratches on the surface to be polished was measured, but no scratches were found. The scratch was measured using Surfscan 6420 (KLA Tencor Co., Ltd.).

(5) Example 3 (Example of treatment of CMP waste liquid): (a) Removal step: (a-1) Centrifugation: The same centrifugation as in the removal step of Example 1 was performed. (a-2) Filtration: After the above centrifugation, filtration was performed. The number of coarse particles in the CMP waste liquid before filtration was 12% at TSC 1.9%.
The number is 2 / mL, and 1,284 / mL in terms of TSC 20% (see Example 1). Filtration is performed by putting the CMP waste liquid after the centrifugation into a 100 L pressure-resistant container, and 0.8 kg / cm
^The filtration was carried out with a filtration device equipped with the above-mentioned depth cartridge filter while pressurizing with nitrogen. CMP after filtration
The number of coarse particles in the waste liquid was 49 particles / m at 1.7% TSC.
L was 576 / mL in terms of TSC 20%. (B) Concentration step: TSC before centrifugal concentration is 1.7% as described above. The conditions of the centrifugal concentration are a maximum centrifugal acceleration of 26,600 G, a rotation time of 30 minutes, and an integrated value of the maximum centrifugal acceleration of 47,880,000 G · sec. The TSC of the CMP waste liquid after the centrifugal concentration, that is, the TSC of the CMP slurry raw material was 35%, and most of the silica particles in the CMP waste liquid were concentrated.

(6) Example 4 (Example of polishing): The CMP waste liquid (= CMP slurry raw material) obtained in Example 3 was diluted, the pH was adjusted to 10.6 with KOH, and TSC 10%
CMP slurry. Using this CMP slurry, a silicon wafer was polished. The specifications of the polishing machine are the same as in the second embodiment. The polishing conditions are as follows. That is, the polishing pressure is 233 g / cm ² , the platen rotation speed is 60 rpm,
The head rotation speed is 60 rpm, and the supply speed of the CMP slurry is 2 g / sec. The polishing rate was 400 Å / min. After polishing, the presence or absence of scratches on the surface to be polished was measured, but no scratches were found. The equipment used for the measurement of the scratch is the same as that of the second embodiment.

(7) Example 5 (Example of treatment of CMP waste liquid): (a) Removal step: coarse particles were removed from the CMP waste liquid by filtration. The number of coarse particles in the CMP effluent before filtration is TS
4,450 particles / mL at C2%, 4 in TSC20% conversion
It is 4,500 pieces / mL. That is, it is the same as before centrifugation in Example 1. Filtration is carried out in a 100 L pressure vessel with the above C
The MP waste solution was charged, and the filtration was performed with a filtration device equipped with the depth cartridge filter while pressurizing with 0.8 kg / cm ² of nitrogen. The number of coarse particles in the CMP waste liquid after filtration was 592 particles / mL at TSC 1.9% and 6232 particles / mL at TSC 20% conversion. (B) Concentration step: TSC before centrifugal concentration is 1.9% as described above. The conditions for the centrifugal concentration are that the maximum centrifugal acceleration is 26,600 G, the rotation time is 30 minutes, and the integrated value of the maximum centrifugal acceleration is 47,880,000 G · sec. The TSC of the CMP waste liquid after the centrifugal concentration, that is, the TSC of the CMP slurry raw material was 35%, and most of the silica particles in the CMP waste liquid were concentrated.

(8) Example 6 (Example of polishing): The CMP waste liquid (= CMP slurry raw material) obtained in Example 5 was diluted, the pH was adjusted to 10.6 with KOH, and TSC 10%
CMP slurry. Using this CMP slurry, a silicon wafer was polished. The specifications of the polishing machine are the same as those of the second and fourth embodiments. The polishing conditions are as follows. That is, the polishing pressure is 233 g / cm ² , and the platen rotation speed is 60 r.
pm, the head rotation speed is 60 rpm, and the supply speed of the CMP slurry is 2 g / sec. The polishing rate was 400 Å / min. After polishing, the presence or absence of scratches on the surface to be polished was measured, but no scratches were found. The equipment used for the scratch measurement is the same as in Examples 2 and 4.

[0020]

According to the first aspect of the present invention, the number of coarse particles in the waste liquid is reduced by removing coarse particles in the waste liquid of the CMP slurry used for polishing, and centrifugal force is applied to the waste liquid. Since the slurry is concentrated to obtain a CMP slurry raw material, it is possible to regenerate a CMP slurry having excellent characteristics that does not generate scratches even when used for polishing a semiconductor wafer or the like from a waste liquid of the CMP slurry. According to the second aspect of the present invention, since the abrasive grains in the original CMP slurry are silica in the first aspect, when polishing a silicon wafer, various impurities are not contained in the CMP waste liquid. Therefore, a CMP slurry raw material can be obtained without performing the step of removing the various impurities and the like.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing the principle of a continuous centrifugal rotor used in a removing step of an embodiment.

FIG. 2 is an explanatory view schematically showing the principle of an angle rotor used in a concentration step of an example.

[Explanation of symbols]

 500 Continuous centrifugal rotor 50 Angle rotor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ichiro Iwama 2--11-24 Tsukiji, Chuo-ku, Tokyo Inside JSR Corporation (72) Inventor Yoshihisa Nakase 2-11-24 Tsukiji, Chuo-ku, Tokyo JSR Co., Ltd. F term (reference) 3C047 FF08 FF09 GG14 GG17

Claims (4)

[Claims] 1. A method of producing a raw material of a CMP slurry, comprising regenerating a raw material of a CMP slurry from a waste liquid of the CMP slurry by performing the following steps (a) and (b): Removing the coarse particles in the waste liquid of the CMP slurry to reduce the number of coarse particles in the waste liquid; (b) applying a centrifugal force to the waste liquid after the removing step to concentrate the waste liquid to remove the CMP slurry; A concentration step for obtaining raw materials. 2. The method according to claim 1, wherein the abrasive grains in the CMP slurry used for polishing are silica. 3. The method according to claim 1, wherein in the removing step (a), a centrifugal force with an integrated value of the maximum centrifugal acceleration of less than 4500000 G · sec is applied to the waste liquid of the CMP slurry to remove coarse particles. In b), a method for producing a CMP slurry raw material, comprising applying a centrifugal force with an integrated value of a maximum centrifugal acceleration of 4500000 G · sec or more to the waste liquid after the removing step to concentrate the waste liquid. 4. The method according to claim 3, wherein the maximum centrifugal acceleration of the centrifugal force in the removing step (a) is 2500G.
The maximum centrifugal acceleration of the centrifugal force in the concentration step (b) is 2500 G
It is the above, The manufacturing method of the CMP slurry raw material characterized by the above-mentioned.