JP2007073686A - Polishing method of semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing method of a semiconductor wafer which polishes the semiconductor wafer appropriately. <P>SOLUTION: In a slurry adjustment process in a slurry adjustment 150, a secondary polishing slurry adjustment liquid is supplied to a secondary polishing section 132. The secondary polishing slurry adjustment liquid is adjusted so that an Si/O composition ratio becomes 50 wt.% to 60 wt.%/40 wt.% to 50 wt.%, modulus of elasticity becomes 1.4×10<SP>10</SP>Pa or higher, and the number of dry silica whose grain diameter is 1 μm or larger becomes 3,000/ml or smaller. In a secondary polishing process at the secondary polishing section 132, the secondary polishing slurry adjustment liquid supplied from the slurry adjustment 150 is utilized to perform the secondary polishing of a semiconductor wafer W. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor wafer polishing method for polishing a semiconductor wafer.

  Conventionally, as a method for polishing a semiconductor wafer using a polishing slurry, for example, a method including a primary polishing step, a secondary polishing step, and a final polishing step is used. In such a polishing method, in the primary polishing step and the secondary polishing step, the polishing slurry is appropriately reused from the viewpoint of manufacturing cost.

On the other hand, as a configuration applicable to, for example, a secondary polishing process, a polishing system that polishes a semiconductor wafer by reusing polishing slurry is known (see, for example, Patent Document 1).
In the device described in Patent Document 1, a new slurry supplied from an unused slurry supply unit and a regenerated slurry after filtration supplied from a regeneration unit are supplied to a buffer tank. The polishing slurry stored in the buffer tank is supplied to each polishing unit by a pump that is connected to each polishing unit and can be independently controlled.

JP 2000-237959 A (page 4 left column-page 5 right column)

  However, when the configuration as described in Patent Document 1 described above is applied to the secondary polishing step, that is, the rough polishing step immediately before the final polishing step, due to foreign matter that cannot be removed by filtration existing in the polishing slurry to be reused. There is a problem that a large number of minute protrusion defects may occur in the semiconductor wafer.

  An object of the present invention is to provide a semiconductor wafer polishing method capable of satisfactorily polishing a semiconductor wafer.

As a result of extensive research by the present inventors, the stock solution of the polishing slurry (hereinafter referred to as the polishing slurry stock solution) contains 1 of silica having a particle size distribution as shown in the graph of FIG. 14 and a maximum particle size of 0.1 μm. It was confirmed that secondary particles were present.
Further, the abrasive slurry to be reused (hereinafter referred to as the reuse slurry) has a particle size distribution as shown in the graph of FIG. 15 and an aggregate of silica in which primary particles are agglomerated by a high pressure applied during polishing ( In the following, it was confirmed that there was a silica crystal formed by drying the polishing slurry (hereinafter referred to as dry silica). And it was confirmed that the agglomerated silica and the dried silica have different Si / O composition ratios and elastic moduli, respectively.
Specifically, the agglomerated silica has a Si / O composition ratio of 40 wt% to 50 wt% / 50 wt% to 60 wt%, and an elastic modulus of less than 1.4 × 10 ¹⁰ Pa. Was 50 wt% to 60 wt% / 40 wt% to 50 wt%, and the elastic modulus was confirmed to be 1.4 × 10 ¹⁰ Pa or more.

Further, the agglomerated silica has a hardness lower than that of dry silica, and as shown in FIGS. 16 and 17, there is a correlation with the number of protruding defects (hereinafter referred to as minute defects) having a height of 10 nm or less generated by polishing. It was confirmed that it was smaller than dry silica.
Moreover, when the reused slurry used in the rough polishing step immediately before the final polishing step is filtered, when the solid content size that can be captured by filtration is small, the polishing rate is lowered because a large number of aggregated silica and dry silica are removed, When the size of the solid content that can be captured is large, the large dry silica is not removed, resulting in an increase in micro defects.
The present invention has been devised based on such knowledge.

That is, in the method for polishing a semiconductor wafer of the present invention, a polishing slurry containing silica is prepared by using a Si / O composition ratio of 50 wt% to 60 wt% / 40 wt% to 50 wt%, an elastic modulus of 1.4 × 10 ¹⁰ Pa or more, A slurry adjustment step for adjusting the silica having a diameter of 1 μm or more to 3000 pieces / ml or less is provided, and the polishing slurry adjusted in the slurry adjustment step is used in a rough polishing step immediately before the final polishing step. The wafer is polished.

According to such an invention, in the slurry adjustment step, the polishing slurry containing silica has a Si / O composition ratio of 50 wt% to 60 wt% / 40 wt% to 50 wt%, and an elastic modulus of 1.4 × 10 ¹⁰ Pa or more. , Adjusted to a state where the particle size is 1 μm or more of 3000 pieces / ml or less, that is, adjusted to a state where the particle size is 1 μm or more of dry silica is 3000 pieces / ml or less, and rough polishing just before the final polishing step In the process, the semiconductor wafer is polished using the polishing slurry adjusted in the slurry adjusting process.
This adjusts the content of dry silica in the polishing slurry used in the rough polishing step immediately before the final polishing step, that is, the content of components harder than the agglomerated silica, so that the content of the agglomerated silica and dry silica is adjusted. Compared to the above, it is possible to increase the polishing rate and reduce the number of minute defects generated in the rough polishing step.
Moreover, since the lower limit of the particle diameter for adjusting the content is set to 1 μm, which is the maximum value of the machining allowance in a general finish polishing process, compared with the configuration in which the lower limit is set to be larger than 1 μm, It becomes easy to make the height of the generated minute defect 1 μm or less, and efficient finish polishing is possible.
Furthermore, since the upper limit value of the content to be adjusted is 3000 pieces / ml or less, as shown in FIG. 16, the number of micro defects generated in the rough polishing step can be suppressed to a predetermined number or less.
Therefore, it becomes possible to polish the semiconductor wafer satisfactorily.

And in this invention, the said slurry adjustment process is a stock solution filtration process which filters the stock solution of the said polishing slurry with the 1st filter which can capture solid content of predetermined size, and the said polishing slurry filtered by this stock solution filtration process A slurry generation step for preparing the polishing slurry by mixing the stock solution with an additive, and the polishing slurry generated in the slurry generation step by a second filter capable of capturing solids having a size smaller than that of the first filter. It is preferable to include a preparation liquid filtration step of filtering the liquid.
According to such an invention, in the slurry adjustment step, the stock solution filtering step of filtering the stock solution of the polishing slurry (hereinafter referred to as the polishing slurry stock solution) with the first filter capable of capturing a solid content of a predetermined size, and this stock solution filtration A slurry generation step for preparing a polishing slurry by mixing the polishing slurry stock solution filtered in the step with an additive, and a preparation for filtering the polishing slurry by a second filter capable of capturing solids having a size smaller than that of the first filter. The liquid filtration step is included, so that the polishing slurry can be adjusted to the above-described state in which the semiconductor wafer can be polished satisfactorily by simply providing the first filter and the second filter in the slurry adjustment step. It becomes.
In addition, even if dry silica is generated during storage of the polishing slurry stock solution, the dry silica of a predetermined size or more is removed in the stock solution filtration step, so the number of dry silica contained in the polishing slurry generated in the slurry generation step And the size of the dry silica that cannot be removed can be minimized. Therefore, it is possible to reduce the number of dry silica trapped in the preparation liquid filtration step compared to the configuration without the stock solution filtration process, and clogging of the second filter in the preparation liquid filtration process is suppressed, and the polishing slurry is reduced. It can be adjusted efficiently.

Further, in the present invention, the first filter has a solid content capturing efficiency of 99.99% or more having a size of 50 times or more of the primary particles of silica contained in the stock solution of the polishing slurry, and the second filter. The filter preferably has a solid content capture efficiency of 99.99% or more having a size 10 times or more of the primary particles.
According to such an invention, a first filter having a solid content capture efficiency of 99.99% or more having a size of 50 times or more of the primary particles of silica is applied, and the primary filter is used as the second filter. Applying a solid content capture efficiency of 99.99% or more having a size of 10 times or more, the polishing slurry can be made more efficient compared to a configuration using another configuration having the ability to capture other solids. Adjustable.

Furthermore, in this invention, it is preferable that the said slurry adjustment process is equipped with the centrifugation process which centrifuges the said polishing slurry.
According to such an invention, since the slurry adjustment step includes a centrifugation step of centrifuging the polishing slurry, the semiconductor wafer is centrifuged by utilizing the density difference between the dried silica and the agglomerated silica. Thus, the polishing slurry can be adjusted to the above-described state where it can be polished well. In addition, the used polishing slurry can be reused in the rough polishing step immediately before the final polishing step, and the amount of the polishing slurry stock solution used can be reduced.

And in this invention, it is preferable that the centrifugal force of the said centrifugation in the said centrifugation process is 5000G-10000G.
According to such an invention, since the lower limit value of the centrifugal force of the centrifugal separation is set to 5000 G, it is possible to remove the dry silica by centrifugal separation so that the number of minute defects can be reduced. In addition, since the upper limit value of the centrifugal force is set to 10,000 G, it is possible to minimize the number of the agglomerated silica removed by centrifugal separation, and polishing can be performed without reducing the polishing rate.

Moreover, in this invention, it is preferable that the said slurry adjustment process is equipped with the grinding | pulverization process which grind | pulverizes the said silica contained in the said polishing slurry with a bead mill.
According to such an invention, since the slurry adjustment step includes a pulverization step of pulverizing silica contained in the polishing slurry with a bead mill, the semiconductor wafer can be satisfactorily improved by pulverizing the dry silica present in the polishing slurry. The polishing slurry can be adjusted to the above-described state where polishing is possible. In addition, since a bead mill having the smallest energy per unit mass (hereinafter referred to as pulverization energy) given to an object to be pulverized is used, the aggregated silica produced by the pulverization energy is compared with a configuration using pulverization means other than the bead mill. The hardness becomes low and the polishing can be performed better. Then, the used polishing slurry can be reused in the rough polishing step immediately before the final polishing step, and the amount of the polishing slurry stock solution used can be reduced.

Furthermore, in this invention, it is preferable that the energy per unit mass given to the to-be-ground object in the said grinding | pulverization process is 20 kWh / dry kg or more.
According to such an invention, since the lower limit value of the powder energy is 20 kWh / dry kg, the content of dry silica in the polishing slurry can be efficiently reduced to 3000 pieces / ml or less.

[First Embodiment]
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings.

[Configuration of semiconductor wafer polishing equipment]
FIG. 1 is a block diagram showing a schematic configuration of a polishing apparatus 100 for a semiconductor wafer W according to the first embodiment.
The polishing apparatus 100 is an apparatus that polishes the surface of a semiconductor wafer W having a diameter of 200 mm using a polishing slurry containing silica. The polishing apparatus 100 may be a semiconductor wafer W having a diameter other than 200 mm. As illustrated in FIG. 1, the polishing apparatus 100 includes a stock solution supply unit 110, a primary polishing preparation solution supply unit 120, a polishing unit 130, a recovery unit 140, and a slurry adjustment unit 150.

The stock solution supply unit 110 is formed in a substantially box shape by, for example, PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), and is connected to the primary polishing preparation solution supply unit 120 and the slurry adjustment unit 150. .
This stock solution supply unit 110 is completely sealed and managed so that the humidity of the internal space becomes 99% or more. In addition, a polishing slurry stock solution having a particle size distribution as shown in FIG. 14 is stored in the internal space of the stock solution supply unit 110. The stock solution supply unit 110 appropriately supplies the polishing slurry stock solution stored in the internal space to the primary polishing preparation solution supply unit 120 and the slurry adjustment unit 150.

The primary polishing preparation liquid supply unit 120 is formed in a substantially box shape, for example, and is connected to the polishing unit 130 and the recovery unit 140.
The primary polishing preparation liquid supply unit 120 appropriately stores the polishing slurry stock solution supplied from the stock solution supply unit 110. Then, pure water is prepared in the polishing slurry stock solution to produce a polishing slurry preparation solution (hereinafter referred to as a primary polishing slurry preparation solution) used for primary polishing, which will be described later, and the primary polishing slurry preparation solution is polished. To the unit 130.
Further, the primary polishing preparation liquid supply unit 120 appropriately stores a polishing slurry recovery filtrate described later that is used for polishing in the polishing unit 130 and is supplied from the recovery unit 140, and stores the polishing slurry as a primary polishing slurry preparation liquid. To 130 as appropriate.

  The polishing unit 130 polishes the semiconductor wafer W. The polishing unit 130 includes a primary polishing unit 131, a secondary polishing unit 132, a finish polishing unit 133, and a transport unit (not shown). Since the primary polishing unit 131, the secondary polishing unit 132, and the finish polishing unit 133 have the same configuration, the primary polishing unit 131 will be described in detail, and the secondary polishing unit 132 and the finish polishing unit will be described. The description of the polishing unit 133 is simplified.

  The transfer unit includes a mounting unit on which the semiconductor wafer W is mounted, and a moving unit that moves the mounting unit. The transport unit moves the semiconductor wafer W placed on the placement unit by the moving unit, and sequentially transports the semiconductor wafer W to the primary polishing unit 131, the secondary polishing unit 132, and the finish polishing unit 133.

The primary polishing unit 131 performs a primary polishing process in which the semiconductor wafer W is roughly polished with a predetermined roughness. The primary polishing unit 131 includes a primary polishing pad, a primary polishing liquid supply unit, a primary polishing holding unit, and a primary discharge unit (not shown).
The primary polishing pad has a configuration in which a polyurethane resin is impregnated in a state where the semiconductor wafer W is primarily polished.
The primary polishing liquid supply section is connected to the primary polishing preparation liquid supply section 120 and supplies the primary polishing slurry preparation liquid from the primary polishing preparation liquid supply section 120 to the primary polishing pad.
The primary polishing holding unit holds the semiconductor wafer W transferred by the transfer unit.
The primary discharge unit is connected to the collection unit 140 and discharges the primary polishing slurry preparation liquid used in the primary polishing to the collection unit 140.
The primary polishing unit 131 uses the primary polishing slurry preparation liquid from the primary polishing preparation liquid supply part 120 supplied from the primary polishing liquid supply part by the primary polishing pad, and uses the primary polishing holding part. The semiconductor wafer W held in step 1 is subjected to primary polishing, and the used primary polishing slurry preparation liquid is discharged to the collection unit 140.

  Here, the primary polishing slurry preparation liquid discharged from the primary polishing unit 131 includes a large number of agglomerated silica generated by applying a high pressure to the primary polishing slurry preparation liquid during the primary polishing. ing. Moreover, many dry silica produced | generated by drying by exposing a primary polishing slurry preparation liquid to external air is contained.

The secondary polishing unit 132 performs a secondary polishing process in which rough polishing is performed with finer roughness than the primary polishing. Here, the secondary polishing process performed in the secondary polishing unit 132 corresponds to the rough polishing process immediately before the final polishing process of the present invention. The secondary polishing unit 132 includes a secondary polishing pad, a secondary polishing liquid supply unit, a secondary polishing holding unit, and a secondary discharge unit (not shown).
The secondary polishing liquid supply unit is connected to the slurry adjustment unit 150 and supplies a secondary polishing slurry adjustment liquid, which will be described later, adjusted by the slurry adjustment unit 150 to the secondary polishing pad.
The secondary discharge unit is connected to the recovery unit 140, and discharges the secondary polishing slurry adjusting liquid used in the secondary polishing to the recovery unit 140.
The secondary polishing unit 132 is held by the secondary polishing holding unit using the secondary polishing slurry adjustment liquid from the slurry adjustment unit 150 supplied from the secondary polishing liquid supply unit by the secondary polishing pad. The semiconductor wafer W is subjected to secondary polishing, and the used secondary polishing slurry adjustment liquid is discharged to the recovery unit 140.

Here, the allowance for secondary polishing is set to 2 μm or less, which is a general value.
Further, the secondary polishing slurry adjustment liquid discharged from the secondary polishing unit 132 includes a large number of agglomerated silica and dry silica generated by the same phenomenon as that of the primary polishing unit 131.

The finish polishing unit 133 performs a finish polishing process for finish polishing the semiconductor wafer W. The finish polishing unit 133 includes a finish polishing pad, a finish polishing liquid supply unit, and a finish polishing holding unit (not shown).
The finishing polishing liquid supply unit is connected to a slurry finishing liquid supply unit (not shown), and supplies the polishing slurry finishing liquid from the slurry finishing liquid supply unit to the finishing polishing pad.
The finish polishing unit 133 uses the finish polishing pad to finish polish the semiconductor wafer W held by the finish polishing holding unit using the polishing slurry finish solution supplied from the finish polishing solution supply unit. Here, the machining allowance for finish polishing is set to 1 μm or less, which is a general value.

  The recovery unit 140 processes the primary polishing slurry preparation liquid and the secondary polishing slurry adjustment liquid that have been used in the polishing unit 130 into a state where they can be reused in the primary polishing unit 131 to obtain a primary polishing slurry recovery filtrate. Supply to polishing preparation liquid supply unit 120. The collection unit 140 includes a collection device 141 and a collection filter 142.

The collection device 141 is formed in a substantially box shape, for example, and is connected to the collection filter 142.
The recovery device 141 appropriately stores the primary polishing slurry preparation liquid used in the primary polishing unit 131 and the secondary polishing slurry adjustment liquid used in the secondary polishing unit 132, and supplies them to the recovery filter 142 as appropriate. . Here, when the primary polishing slurry preparation liquid and the secondary polishing slurry adjustment liquid that have been used are collectively described, they are referred to as a polishing slurry recovery liquid.

The recovery filter 142 is connected to the primary polishing preparation liquid supply unit 120.
The collection filter 142 removes the agglomerated silica and dry silica of a predetermined size or more contained in the polishing slurry collection liquid from the collection device 141 by filtration.
Here, as described above, the polishing slurry recovery filtrate supplied to the primary polishing preparation liquid supply unit 120 is used only for the primary polishing process and is not used for the secondary polishing process and the final polishing process. Further, even if a large number of micro defects are generated in the semiconductor wafer W in the primary polishing process, these micro defects are polished by the secondary polishing process and the finish polishing process, so that there is no problem. For these reasons, the size of the solid content to be removed by the recovery filter 142 is set to a predetermined size that can make the polishing rate in the primary polishing step equal to or higher than a predetermined level even if a large number of minute defects occur. Yes.
Then, the recovery filter 142 supplies the polishing slurry recovery liquid from which the agglomerated silica and the dried silica of a predetermined size or more are removed to the primary polishing preparation liquid supply unit 120 as a polishing slurry recovery filtrate.
As the recovery filter 142, any filter capable of filtering a liquid, such as a depth filter or a membrane filter, can be applied.

The slurry adjusting unit 150 is a dry silica having a particle diameter of 1 μm or more, that is, a Si / O composition ratio of 50 wt% to 60 wt% / 40 wt% to 50 wt%, an elastic modulus of 1.4 × 10 ¹⁰ Pa or more, and a particle diameter of 1 μm. The slurry adjustment process which produces | generates the secondary polishing slurry adjustment liquid adjusted to the state used as the above 3000 silica / ml or less is implemented. The slurry adjusting unit 150 includes a first filter 151, a secondary polishing preparation liquid generating unit 152, and a second filter 153.

The first filter 151 has a capability of capturing a solid content having a particle size of 5 μm or more and has a capacity of 99.99% or more, and is connected to the stock solution supply unit 110 and the secondary polishing preparation solution generation unit 152. .
Here, the maximum particle diameter of the primary particles of silica in the polishing slurry stock solution is 0.1 μm as shown in FIG. That is, the first filter 151 has a capability of capturing a solid content of 99.99% or more having a size of 50 times or more of the primary particles of silica contained in the polishing slurry stock solution.
The first filter 151 removes a solid content of 5 μm or more contained in the polishing slurry stock solution from the stock solution supply unit 110 by filtration, and supplies it to the secondary polishing preparation solution generating unit 152.
As the first filter 151, the same configuration as that of the recovery filter 142 can be applied.

The secondary polishing liquid preparation unit 152 is formed in a substantially box shape, for example, and is connected to the second filter 153.
The secondary polishing liquid preparation unit 152 appropriately stores the polishing slurry stock solution from which the solid content of 5 μm or more from the first filter 151 has been removed. Then, pure water is appropriately mixed with the polishing slurry stock solution to generate a secondary polishing slurry preparation solution, and this secondary polishing slurry preparation solution is supplied to the second filter 153.

The second filter 153 has a capability of capturing 99.99% or more of solids having a particle size of 1 μm or more, that is, solids having a size of 10 times or more of the primary particles of silica contained in the polishing slurry stock solution. And connected to the secondary polishing section 132.
The second filter 153 removes a solid content of 1 μm or more contained in the secondary polishing slurry preparation liquid from the secondary polishing preparation liquid generator 152 by filtration, and serves as a secondary polishing slurry adjustment liquid to the secondary polishing section 132. To supply.
As the second filter 153, the same configuration as the recovery filter 142 and the first filter 151 can be applied.

[Operation of semiconductor wafer polishing equipment]
Next, as an operation of the polishing apparatus 100 described above, a polishing process for the semiconductor wafer W will be described.

(Primary polishing process)
First, a primary polishing process will be described as a polishing process for the semiconductor wafer W.

The polishing apparatus 100 moves the semiconductor wafer W to be polished by the transport unit of the polishing unit 130 and holds the semiconductor wafer W in the primary polishing holding unit of the primary polishing unit 131.
The primary polishing preparation liquid supply unit 120 prepares the polishing slurry stock solution supplied from the raw solution supply part 110 to generate a primary polishing slurry preparation liquid, and supplies the primary polishing slurry preparation liquid to the primary polishing part 131. The primary polishing preparation liquid supply unit 120 supplies the polishing slurry collection filtrate supplied from the recovery unit 140 to the primary polishing unit 131 as a primary polishing slurry preparation liquid.
Thereafter, the primary polishing unit 131 primarily polishes the semiconductor wafer W with a primary polishing slurry preparation liquid containing a large number of agglomerated silica and dry silica from the primary polishing preparation liquid supply part 120 and is used 1 The next polishing slurry preparation liquid is discharged to the collection unit 140.
As described above, since a large number of dry silica exists in the primary polishing slurry preparation liquid, a large number of micro defects are generated by the primary polishing, but these micro defects are polished by the secondary polishing. Therefore, primary polishing using the polishing slurry recovery filtrate as the primary polishing slurry preparation liquid becomes possible.

(Slurry adjustment process)
Next, as a polishing process for the semiconductor wafer W, a slurry adjustment step will be described.
The polishing apparatus 100 supplies the polishing slurry stock solution to the slurry adjustment unit 150 at the stock solution supply unit 110.
The slurry adjusting unit 150 performs a stock solution filtering step of filtering the supplied polishing slurry stock solution with the first filter 151. Thereafter, the secondary polishing liquid preparation unit 152 performs a secondary polishing liquid preparation process as a slurry generation process for generating a secondary polishing slurry liquid from the polishing slurry stock solution filtered by the first filter 151. And the 2nd filter 153 implements the preparation liquid filtration process which filters the secondary polishing slurry preparation liquid produced | generated in the secondary grinding | polishing preparation liquid production | generation part 152, and 3000 pieces of dry silica with a particle size of 1 micrometer or more are carried out. / Ml is supplied to the secondary polishing section 132 as a secondary polishing slurry adjusting liquid adjusted to a state of not more than / ml.

(Secondary polishing process)
Next, a secondary polishing process will be described as a polishing process for the semiconductor wafer W.

The polishing apparatus 100 moves the semiconductor wafer W primarily polished by the primary polishing unit 131 by the transport unit of the polishing unit 130 and holds the semiconductor wafer W in the secondary polishing holding unit of the secondary polishing unit 132.
Then, the secondary polishing unit 132 secondary polishes the semiconductor wafer W with the polishing slurry adjustment liquid from the slurry adjustment unit 150 and discharges the used secondary polishing slurry adjustment liquid to the recovery unit 140.

(Finishing polishing process)
Next, a finish polishing process will be described as a polishing process for the semiconductor wafer W.

The polishing apparatus 100 moves the semiconductor wafer W secondary polished by the secondary polishing unit 132 by the transport unit of the polishing unit 130 and holds the semiconductor wafer W in the final polishing holding unit of the final polishing unit 133.
Then, the finish polishing unit 133 finish polishes the semiconductor wafer W with the polishing slurry finish solution from the finish polishing solution supply unit.

[Operational effects of semiconductor wafer polishing equipment]
According to the first embodiment described above, the following operational effects are obtained.
(1) The polishing apparatus 100 is a dry silica having a particle size of 1 μm or more, that is, a Si / O composition ratio of 50 wt% to 60 wt% / 40 wt% to 50 wt%, and an elastic modulus in a slurry adjusting step in the slurry adjusting unit 150. A secondary polishing slurry adjusting liquid adjusted to a state where the silica having a particle size of 1.4 × 10 ¹⁰ Pa or more and a particle size of 1 μm or more is 3000 particles / ml or less is supplied to the secondary polishing unit 132. Then, in the secondary polishing step in the secondary polishing unit 132, the semiconductor wafer W is secondarily polished using the secondary polishing slurry adjustment liquid supplied from the slurry adjustment unit 150.
For this reason, since the content of the dry silica in the secondary polishing slurry adjustment liquid used in the secondary polishing step immediately before the final polishing step is adjusted, the polishing rate is compared with the configuration in which the content of the aggregated silica and the dry silica is adjusted. In addition, the number of minute defects generated in the secondary polishing process can be reduced.
Moreover, since the lower limit value of the particle size for adjusting the content is set to 1 μm which is the maximum value of the machining allowance in the final polishing process, it occurs in the secondary polishing process as compared with the configuration in which the lower limit value is larger than 1 μm. It becomes easy to make the height of minute defects 1 μm or less, and finish polishing can be efficiently performed.
Furthermore, since the upper limit value of the content to be adjusted is 3000 pieces / ml or less, the number of micro defects generated in the secondary polishing step can be suppressed to a predetermined number or less.
Therefore, the semiconductor wafer W can be satisfactorily polished.

(2) In the slurry adjusting step, a stock solution filtering step of filtering the polishing slurry stock solution by the first filter 151 and a polishing slurry stock solution filtered in the stock solution filtering step by the secondary polishing preparation solution generating unit 152 are prepared for secondary polishing. A secondary polishing preparation liquid generation step for generating a slurry preparation liquid and a preparation liquid filtration step for filtering the secondary polishing slurry preparation liquid by the second filter 153 are provided.
Therefore, the semiconductor wafer W can be adjusted to the above-described state that can be satisfactorily polished with a simple configuration in which only the first filter 151 and the second filter 153 are provided in the slurry adjustment step.
Further, even if dry silica is generated during storage of the polishing slurry stock solution in the stock solution supply unit 110, since dry silica of a predetermined size or larger is removed in the stock solution filtration step, it is generated in the secondary polishing preparation solution generation step. The number of dry silica contained in the secondary polishing slurry preparation liquid can be reduced, and the size of dry silica that cannot be removed can be minimized. Accordingly, the number of dry silica captured in the preparation liquid filtration step can be reduced as compared with a configuration in which no stock solution filtration process is provided, and clogging of the second filter 153 in the preparation liquid filtration process is suppressed, and secondary polishing is performed. A slurry preparation liquid can be adjusted efficiently.

(3) As the 1st filter 151, what has the capture | acquisition efficiency of the solid content which has a size 50 times or more of the primary particle | grains of the silica contained in polishing slurry stock solution is 99.99% or more is applied. As the second filter 153, a filter having a solid content capturing efficiency of 99.99% or more having a size 10 times or more that of the primary particles is applied.
For this reason, since the 1st filter 151 and the 2nd filter 153 which have the capture capability as mentioned above are applied, compared with the composition which has the capability to capture other, the secondary polishing slurry preparation liquid is made more efficient. Can be adjusted.

(4) The stock solution supply unit 110 is managed so that the humidity of the internal space is 99% or more.
For this reason, generation | occurrence | production of the dry silica in the wall surface of the internal space in the stock solution supply part 110 and the boundary part of polishing slurry stock solution can be suppressed.
Therefore, the number of dry silicas contained in the secondary polishing slurry adjustment liquid can be further reduced.

[Second Embodiment]
Next, 2nd Embodiment of this invention is described based on drawing.
In the following description, the same structure and the same members as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted or simplified.

[Configuration of semiconductor wafer polishing equipment]
FIG. 2 is a block diagram showing a schematic configuration of a polishing apparatus 200 for a semiconductor wafer W according to the second embodiment.
As shown in FIG. 2, the polishing apparatus 200 includes a stock solution supply unit 210, a primary polishing preparation solution supply unit 220, a polishing unit 130, a recovery unit 140, and a slurry adjustment unit 250.

The stock solution supply unit 210 is formed in a substantially box shape by PFA, for example, and is connected to the primary polishing preparation solution supply unit 220.
In the stock solution supply unit 210, the humidity of the internal space is not specially managed. The stock solution supply unit 210 appropriately supplies the polishing slurry stock solution stored in the internal space to the primary polishing preparation solution supply unit 220.

The primary polishing preparation liquid supply unit 220 is formed, for example, in a substantially box shape, and is connected to the polishing unit 130, the recovery unit 140, and the slurry adjustment unit 250.
The primary polishing preparation liquid supply unit 220 prepares the primary polishing slurry preparation liquid by preparing the polishing slurry stock solution supplied from the raw solution supply unit 210 and supplies the primary polishing slurry preparation liquid to the polishing unit 130.
Further, the primary polishing preparation liquid supply unit 220 appropriately stores the polishing slurry recovery filtrate containing a large number of aggregated silica and dry silica from the recovery unit 140 and supplies the polishing slurry 130 appropriately as a primary polishing slurry preparation liquid. To do.
Further, the primary polishing preparation liquid supply unit 220 appropriately supplies the above-described primary polishing slurry preparation liquid to the slurry adjustment unit 250.

The primary polishing liquid supply part provided in the primary polishing part 131 of the polishing part 130 is connected to the primary polishing preparation liquid supply part 220 and supplies the primary polishing slurry preparation liquid to the primary polishing pad.
The secondary polishing liquid supply unit provided in the secondary polishing unit 132 of the polishing unit 130 is connected to the slurry adjustment unit 250, and the secondary polishing slurry adjustment liquid adjusted by the slurry adjustment unit 250 is used as a secondary polishing pad. Supply.
The recovery filter 142 provided in the recovery unit 140 is connected to the primary polishing preparation liquid supply unit 220, and supplies the polishing slurry recovery filtrate to the primary polishing preparation liquid supply unit 220.

  The slurry adjustment unit 250 performs a slurry adjustment step of generating a secondary polishing slurry adjustment liquid adjusted to a state in which the dry silica having a particle size of 1 μm or more is 3000 pieces / ml or less. The slurry adjustment unit 250 includes a centrifuge 251, an in-liquid particle counter (hereinafter referred to as PMS) 252, a secondary polishing adjustment liquid supply unit 253, and a centrifuge control unit 254.

The centrifuge 251 has a configuration capable of continuously processing fluid, and is connected to the primary polishing preparation liquid supply unit 220, the PMS 252, and the centrifuge control unit 254.
The centrifuge 251 is controlled by the centrifuge controller 254, and processes the primary polishing slurry preparation liquid appropriately supplied from the primary polishing preparation liquid supply section 220 with a centrifugal force of 5000G to 10000G, so that the particle size is 1 μm. A secondary polishing slurry adjustment liquid adjusted to a state in which the above dry silica is 3000 pieces / ml or less is generated. That is, the centrifugal separator 251 centrifuges the dry silica having a particle size of 1 μm or more mainly by centrifugal separation using the density difference between the aggregated silica and the dry silica contained in the primary polishing slurry preparation liquid. Next, a polishing slurry adjusting solution is produced.
Then, the centrifuge 251 supplies the secondary polishing slurry adjustment liquid to the PMS 252.

The PMS 252 is connected to the secondary polishing adjusting liquid supply unit 253 and the centrifuge control unit 254.
The PMS 252 counts the number of agglomerated silica and dry silica contained in the secondary polishing slurry adjustment liquid supplied from the centrifuge 251, for example, every predetermined time, and outputs a signal related to the counting result to the centrifuge controller 254. To do. Then, the PMS 252 supplies the measured secondary polishing slurry adjustment liquid to the secondary polishing adjustment liquid supply unit 253.

The secondary polishing adjusting liquid supply unit 253 is formed, for example, in a substantially box shape and is connected to the secondary polishing unit 132.
The secondary polishing adjustment liquid supply unit 253 stores the secondary polishing slurry adjustment liquid supplied from the centrifuge 251 via the PMS 252 and appropriately supplies it to the secondary polishing unit 132.

The centrifuge control unit 254 controls the operation of the centrifuge 251 based on the counting result in the PMS 252.
Specifically, when the centrifuge control unit 254 obtains a signal indicating that the count result is a number within a predetermined range from the PMS 252, the centrifuge control unit 254 dries the dried silica having a particle size of 1 μm or more to 3000 particles / ml or less. Judging that the silica is centrifuged, the centrifugal force of the centrifuge 251 is not changed.
Further, when the centrifugation control unit 254 obtains a signal indicating that the counting result is larger than the number in the predetermined range, the dried silica is centrifuged so that the dry silica having a particle size of 1 μm or more becomes 3000 pieces / ml or more. Therefore, the centrifugal force of the centrifuge 251 is changed to a state where more dry silica is centrifuged. That is, the state is changed to a state where the centrifugal force of the centrifuge 251 is increased.
Furthermore, when the centrifugation control unit 254 acquires a signal indicating that the counting result is smaller than the number in the predetermined range, the centrifugal separation control unit 254 determines that a large number of the aggregated silica is centrifuged in addition to the dry silica. And since the polishing rate falls by the reduction | decrease of agglomerated silica, the centrifugal force of the centrifuge 251 is changed to the state which reduces the agglomerated silica to centrifuge. That is, the state is changed to a state where the centrifugal force of the centrifuge 251 is reduced.

[Operation of semiconductor wafer polishing equipment]
Next, a polishing process for the semiconductor wafer W will be described as an operation of the polishing apparatus 200 described above.
Since the primary polishing process, the secondary polishing process, and the final polishing process are the same as those in the first embodiment, only the slurry adjustment process will be described.

(Slurry adjustment process)
As a polishing process for the semiconductor wafer W, a slurry adjustment step will be described.
The polishing apparatus 200 supplies the primary polishing slurry preparation liquid to the slurry adjustment section 250 by the primary polishing preparation liquid supply section 220. Here, as described above, the primary polishing slurry preparation liquid contains a large number of agglomerated silica and dry silica.
The slurry adjusting unit 250 performs a centrifugal separation process in which the supplied primary polishing slurry preparation liquid is processed by the centrifugal separator 251. That is, the secondary polishing slurry adjustment liquid adjusted to a state in which the dry silica having a particle diameter of 1 μm or more is adjusted to 3000 pieces / ml or less is generated by centrifuging the dry silica mainly from the primary polishing slurry preparation liquid.
Thereafter, the slurry adjustment unit 250 supplies the secondary polishing slurry adjustment liquid to the secondary polishing adjustment liquid supply unit 253 via the PMS 252, and also includes aggregated silica and dry silica contained in the secondary polishing slurry adjustment liquid in the PMS 252. The centrifugal force of the centrifuge 251 is adjusted according to the number of Then, the secondary polishing slurry adjustment liquid is appropriately supplied to the secondary polishing part 132 by the secondary polishing adjustment liquid supply unit 253.

[Operational effects of semiconductor wafer polishing equipment]
According to 2nd Embodiment mentioned above, in addition to the effect similar to (1) of 1st Embodiment, there exist the following effects.

(5) The slurry adjustment step is provided with a centrifugation step of centrifuging the primary polishing slurry preparation liquid by the centrifuge 251.
For this reason, the dry silica having a particle size of 1 μm or more becomes 3000 pieces / ml or less by centrifuging the dry silica mainly from the primary polishing slurry preparation liquid using the density difference between the dry silica and the agglomerated silica. The secondary polishing slurry adjustment liquid adjusted to the state can be generated.
Further, the used polishing slurry recovery filtrate can be reused in the secondary polishing step, and the amount of the polishing slurry stock solution used can be reduced.

(6) The centrifugal force of the centrifuge 251 is set to 5000G to 10000G.
For this reason, since the lower limit of the centrifugal force of centrifugation is set to 5000 G, dry silica can be removed by centrifugation in a state where the number of micro defects can be reduced. Further, since the upper limit value of the centrifugal force is set to 10,000 G, the number of the aggregated silica removed by centrifugation can be minimized, and secondary polishing can be performed without lowering the polishing rate.

(7) PMS 252 that counts the number of agglomerated silica and dry silica contained in the secondary polishing slurry adjustment liquid generated by the centrifugal separator 251 in the slurry adjustment unit 250, and centrifugal separation based on the counting result of the PMS 252 And a centrifuge controller 254 for adjusting the centrifugal force of the machine 251.
For this reason, since the centrifugation state in the centrifuge 251 is controlled based on the production | generation state of a secondary polishing slurry adjustment liquid, the secondary polishing slurry adjustment liquid of the stable quality can always be supplied to the secondary polishing part 132. FIG.

[Third Embodiment]
Next, 3rd Embodiment of this invention is described based on drawing.
In the following description, the same reference numerals are given to the same structures and the same members as those in the first embodiment or the second embodiment, and the detailed description thereof is omitted or simplified.

[Configuration of semiconductor wafer polishing equipment]
FIG. 3 is a block diagram showing a schematic configuration of a polishing apparatus 300 for a semiconductor wafer W according to the third embodiment. FIG. 4 is a schematic diagram showing a schematic configuration of the bead mill.
As illustrated in FIG. 3, the polishing apparatus 300 includes a stock solution supply unit 210, a primary polishing preparation solution supply unit 120, a polishing unit 130, a recovery unit 340, and a slurry adjustment unit 350.

The stock solution supply unit 210 is connected to the primary polishing preparation solution supply unit 120 and appropriately supplies the polishing slurry stock solution stored in the internal space to the primary polishing preparation solution supply unit 120.
The primary polishing preparation liquid supply unit 120 is connected to the polishing unit 130 and the recovery unit 340, prepares the polishing slurry stock solution from the raw solution supply unit 210, and supplies the primary polishing slurry preparation liquid to the polishing unit 130. At the same time, a polishing slurry recovery filtrate containing a large number of aggregated silica and dry silica from the recovery unit 340 is appropriately supplied to the polishing unit 130 as a primary polishing slurry preparation.
The primary polishing liquid supply section provided in the primary polishing section 131 of the polishing section 130 is connected to the primary polishing preparation liquid supply section 120 and supplies the primary polishing slurry preparation liquid to the primary polishing pad.
The secondary polishing liquid supply unit provided in the secondary polishing unit 132 of the polishing unit 130 is connected to the slurry adjustment unit 350, and the secondary polishing slurry adjustment liquid adjusted by the slurry adjustment unit 350 is used as a secondary polishing pad. Supply.

  The recovery unit 340 processes the polishing slurry recovery liquid used in the polishing unit 130 so as to be reusable in the primary polishing unit 131 and supplies the polishing slurry recovery liquid to the primary polishing preparation liquid supply unit 120 as a polishing slurry recovery filtrate. . Further, the polishing slurry recovery liquid is supplied to the slurry adjusting unit 350. The recovery unit 340 includes a recovery device 341 and a recovery filter 142.

The collection device 341 is formed, for example, in a substantially box shape, and is connected to the collection filter 142 and the slurry adjustment unit 350.
The recovery device 341 appropriately stores the polishing slurry recovery liquid and supplies it to the recovery filter 142 and the slurry adjustment unit 350 as appropriate.

  The slurry adjustment unit 350 performs a slurry adjustment step of generating a secondary polishing slurry adjustment liquid adjusted to a state in which the dry silica having a particle diameter of 1 μm or more is 3000 pieces / ml or less. The slurry adjustment unit 350 includes a pump 351, a bead mill 360, an adjustment filter 353, and a secondary polishing adjustment liquid supply unit 253.

The pump 351 is connected to the recovery device 341 and the bead mill 360.
The pump 351 appropriately sends the polishing slurry recovery liquid stored in the recovery device 341 to the bead mill 360.

The bead mill 360 is adjusted so that the aggregated silica and dry silica of the polishing slurry recovery liquid sent from the recovery device 341 via the pump 351 are pulverized so that the dry silica having a particle size of 1 μm or more is 3000 pieces / ml or less. A secondary polishing slurry adjustment liquid is generated.
As shown in FIG. 4, the bead mill 360 includes a mill main body 370 and a drive unit 380.

  The mill body 370 is driven by the drive unit 380 to generate a secondary polishing slurry adjustment liquid. The mill main body 370 includes a main body 371, a recovered liquid introduction part 372, an adjustment liquid discharge part 373, and a stirring part 374.

The main body 371 is formed in a substantially cylindrical shape whose upper and lower surfaces are closed. Specifically, the main body 371 has a substantially cylindrical first cylindrical portion 371A, the same height as the first cylindrical portion 371A, and a smaller diameter than the first cylindrical portion 371A. A second cylindrical portion 371B provided inside the first cylindrical portion 371A, a top surface portion 371C closing the upper surface of the first cylindrical portion 371A, and a lower surface portion 371D closing the lower surface of the first cylindrical portion 371A. .
A space between the first cylindrical portion 371A and the second cylindrical portion 371B is a cooling water circulation space 371E in which the cooling water circulates. The internal space of the second cylindrical portion 371B is a pulverization space 371F filled with beads (not shown) for pulverizing dry silica or the like. Here, the beads are formed into particles having a diameter of 0.2 mm by zirconia.
A substantially cylindrical cooling water introduction portion 371G capable of introducing cooling water from the outside into the cooling water circulation space 371E is provided on the lower surface portion 371D side of the circumferential surface of the first cylindrical portion 371A. Further, a substantially cylindrical cooling water discharge portion 371H capable of discharging the cooling water introduced into the cooling water circulation space 371E to the outside is provided on the upper surface portion 371C side of the circumferential surface of the first cylindrical portion 371A.
A substantially circular insertion hole 371C1 is formed in the approximate center of the upper surface portion 371C.
A substantially circular fitting hole 371D1 is formed in the approximate center of the lower surface portion 371D.

The recovered liquid introduction part 372 is formed in a substantially cylindrical shape, and one end side is fitted into the fitting hole 371D1 of the lower surface part 371D, and the other end side is connected to the pump 351.
The recovery liquid introduction unit 372 introduces the polishing slurry recovery liquid supplied via the pump 351 into the grinding space 371F.

The adjustment liquid discharger 373 discharges the polishing slurry recovery liquid obtained by pulverizing dry silica or the like as a secondary polishing slurry adjustment liquid. The adjustment liquid discharger 373 includes a discharge cylinder 373A and a sentry separator 373B.
The discharge cylindrical portion 373A is formed in a substantially cylindrical shape, and one end side is connected to the adjustment filter 353. Further, the discharge cylindrical portion 373A is inserted into the insertion hole 371C1 of the upper surface portion 371C in a state where the other end side is located in the pulverizing space 371F and is rotatable around the axis of the discharge cylindrical portion 373A. A substantially ring plate-shaped mill belt receiving portion 373A1 is provided at a substantially axial center in a portion of the discharge cylindrical portion 373A located outside the main body 371.
The sentry separator 373B separates the beads from the polishing slurry recovery liquid in the grinding space 371F and discharges the beads as a secondary polishing slurry adjusting liquid through the discharge cylindrical portion 373A. The sentry separator 373B includes a ring plate portion 373B1, a plurality of blades 373B2, and a disc portion 373B3.
The ring plate portion 373B1 is formed in a substantially ring plate shape that protrudes outward from the other end of the discharge cylindrical portion 373A.
The blade 373B2 has a rectangular plate shape whose long side is shorter than the width of the ring plate portion 373B1. The blades 373B2 are attached to the outer edge side of the ring plate portion 373B1 at predetermined intervals in the circumferential direction with the long side direction substantially coincident with the radial direction.
The disc portion 373B3 is formed in a substantially disc shape having substantially the same diameter as the outer diameter of the ring plate portion 373B1, and is attached to the blade 373B2 so as to be substantially parallel to the ring plate portion 373B1.

The stirring unit 374 is provided in the pulverization space 371F, and agitates the polishing slurry recovery liquid to pulverize dry silica or the like using beads. The stirring portion 374 includes a stirring shaft portion 374A and a plurality of rotor pins 374B.
The stirring shaft portion 374A is formed in a substantially rod shape, and is fixed to the lower surface of the disc portion 373B3 of the sentry separator 373B so as to extend vertically downward.
The rotor pins 374B are formed in a substantially rod shape, and are provided in a state of projecting radially from the circumferential surface of the stirring shaft portion 374A and in a state of being juxtaposed at predetermined intervals in the axial direction.

The drive unit 380 drives the mill main body 370. The drive unit 380 includes a motor main body 381 connected to a motor control unit (not shown). A substantially cylindrical drive belt receiving portion 382 is provided at the tip of the rotation shaft 381 </ b> A of the motor main body 381. Further, the belt 383 is stretched over the circumferential surface of the drive belt receiving portion 382 over the mill belt receiving portion 373A1 of the mill main body portion 370.
Then, the drive unit 380 drives the motor body 381 under the control of the motor control unit, and rotates the adjustment liquid discharge unit 373 and the stirring unit 374 via the belt 383. Specifically, the drive unit 380 rotates the stirring unit 374 in a state where the pulverization energy becomes 20 kWh / dry kg or more.

The adjustment filter 353 has the same capability as the second filter 153 of the polishing apparatus 100 of the first embodiment, and is connected to the secondary polishing adjustment liquid supply unit 253.
The adjustment filter 353 filters the secondary polishing slurry adjustment liquid discharged from the bead mill 360 and supplies it to the secondary polishing adjustment liquid supply unit 253.

[Operation of semiconductor wafer polishing equipment]
Next, a polishing process for the semiconductor wafer W will be described as the operation of the polishing apparatus 300 described above.
Since the primary polishing process, the secondary polishing process, and the final polishing process are the same as those in the first embodiment, only the slurry adjustment process will be described.

(Slurry adjustment process)
As a polishing process for the semiconductor wafer W, a slurry adjustment step will be described.
The polishing apparatus 300 sends the polishing slurry recovery liquid stored in the recovery device 341 of the recovery unit 340 to the bead mill 360 by the pump 351 of the slurry adjustment unit 350. Here, as described above, the abrasive slurry recovery liquid contains a large number of aggregated silica and dry silica.
The bead mill 360 carries out a pulverization step of pulverizing dry silica and the like contained in the sent polishing slurry recovery liquid. That is, the bead mill 360 introduces the polishing slurry collection liquid into the pulverization space 371F of the main body 371 via the collection liquid introduction unit 372. Then, the adjustment liquid discharger 373 and the agitation unit 374 are rotated by the driving unit 380, and the dry silica and the like of the polishing slurry recovery liquid are pulverized using the beads filled in the pulverization space 371F. Thereafter, the beads are separated from the polishing slurry recovery liquid by the sentry separator 373B of the rotating adjustment liquid discharger 373, and adjusted to a state where the dry silica having a particle diameter of 1 μm or more is 3000 pieces / ml or less. The secondary polishing slurry adjustment liquid is discharged from the discharge cylindrical portion 373A.
Further, the slurry adjustment unit 350 supplies the secondary polishing slurry adjustment liquid to the secondary polishing adjustment liquid supply unit 253 via the adjustment filter 353. Then, the secondary polishing slurry adjustment liquid is appropriately supplied to the secondary polishing part 132 by the secondary polishing adjustment liquid supply unit 253.

[Operational effects of semiconductor wafer polishing equipment]
According to 3rd Embodiment mentioned above, in addition to the effect similar to (1) of 1st Embodiment, there exist the following effects.

(8) The slurry adjusting step is provided with a pulverizing step of pulverizing dry silica or the like of the polishing slurry recovery liquid by the bead mill 360.
Therefore, by pulverizing the dry silica of the polishing slurry recovery liquid, it is possible to generate a secondary polishing slurry adjustment liquid adjusted to a state in which the dry silica having a particle size of 1 μm or more is 3000 pieces / ml or less.
In addition, since the bead mill 360 having the smallest pulverization energy is used, the hardness of the agglomerated silica generated by the pulverization energy can be reduced and the polishing can be performed more satisfactorily than the configuration using the pulverization means other than the bead mill 360.
Then, the used polishing slurry recovery liquid can be reused in the secondary polishing step, and the amount of the polishing slurry stock solution used can be reduced.

(9) The powder energy in the bead mill 360 is set to 20 kWh / dry kg or more.
For this reason, since the lower limit value of the energy to be powdered is 20 kWh / dry kg, the content of dry silica in the secondary polishing slurry adjustment liquid can be effectively 3000 pieces / ml or less.

[Other Embodiments]
Note that the present invention is not limited to the above embodiment, and various improvements and design changes can be made without departing from the scope of the present invention.

That is, in the first embodiment, instead of the first filter 151 and the second filter 153, a filter having a capturing capability different from that of the first filter 151 and the second filter 153 may be applied.
In the second embodiment, the centrifugal force of the centrifuge 251 may be larger than 10000G. In such a configuration, although the polishing rate is lowered, the number of minute defects generated in the secondary polishing step can be suppressed to a predetermined number or less.
And it is good also as a structure which combines slurry adjustment part 150,250,350 arbitrarily.
Furthermore, it is good also as a structure which supplies the secondary polishing slurry adjustment liquid produced | generated by the slurry adjustment parts 150,250,350 to the primary polishing part 131. FIG. In such a configuration, the primary polishing step has a larger allowance than the secondary polishing step, but the primary polishing can be performed without lowering the polishing rate by adjusting the polishing time or the load applied to the primary polishing pad.

Although the best configuration for carrying out the present invention has been disclosed in the above description, the present invention is not limited to this. That is, the invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of materials, quantity, and other detailed configurations.
Therefore, the description limited to the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such is included in this invention.

Next, the effect of this invention is demonstrated based on a specific Example.
In the following description, a protrusion defect larger than a minute defect will be referred to as a scratch defect.

[First embodiment]
First, a first example for explaining the effect of the first embodiment will be described.
FIG. 5 is a graph showing the relationship between the storage time of the polishing slurry stock solution stored at each humidity and the number of dry silica contained in this polishing slurry stock solution. FIG. 6 is a graph showing the number of micro defects generated in the secondary polishing using the polishing slurry liquids of Example 1, Comparative Example 1, and Comparative Example 2. FIG. 7 is a graph showing the number of scratch defects generated in secondary polishing using the polishing slurry liquid of Example 1, Comparative Example 1, and Comparative Example 2.

[Relationship between the storage time of the polishing slurry stock solution stored at each humidity and the number of dry silica contained in this polishing slurry stock solution]
First, the relationship between the storage time of the polishing slurry stock solution stored at each humidity and the number of dry silica contained in this polishing slurry stock solution will be described.

<experimental method>
The polishing slurry stock solution is stored for 0 hours, 6 hours, 12 hours, 24 hours in PFA storage tanks (hereinafter referred to as PFA storage tanks) set to a humidity of 50%, 80%, and 99%, respectively. The number of dry silica of 1 μm or more present per 1 ml was counted using the following method.
Specifically, a membrane filter (Whatman, product name: NucleporeTrack-EtchMembrane) with a mesh size of 3 μm is set at the bottom of the holder (Whatman, product name: Swin-Lok Holder 25 mm), and 1 ml with a syringe. Pour ~ 5 ml of polishing slurry stock solution into holder. Then, the treatment of injecting 20 ml of water into the holder with a syringe and washing the membrane filter was carried out three times. The washed membrane filter was observed with an SEM (scanning electron microscope), and the number of dry silica of 1 μm or more was observed. Were counted.

<Experimental result>
As shown in FIG. 5, it was confirmed that the number of dry silica of 1 μm or more present per ml increases as the humidity decreases and the storage time increases.
In particular, when the polishing slurry stock solution was stored in an atmosphere with a humidity of 99%, it was confirmed that the number of dry silica of 1 μm or more present per ml was less than 1000 even after 24 hours had passed.

    [Number of micro-defects and scratch defects generated by secondary polishing using each polishing slurry]

  Next, the number of micro defects generated in the secondary polishing using the polishing slurry liquid of Example 1, Comparative Example 1, and Comparative Example 2 and the number of scratch defects will be described.

<Example 1>
The polishing slurry liquid of Example 1 is a liquid generated by processing the polishing slurry stock solution in the slurry adjusting unit 150 of the first embodiment. The number of dry silica of 1 μm or more contained in the polishing slurry of Example 1 was 1700 / ml.

<Comparative example 1>
The polishing slurry liquid of Comparative Example 1 is a liquid prepared by adding pure water to a polishing slurry stock solution stored in a PFA storage tank having a humidity of 99% for 24 hours. The number of dry silica of 1 μm or more contained in the polishing slurry liquid of Comparative Example 1 was 2600 / ml.

<Comparative example 2>
The polishing slurry liquid of Comparative Example 2 is a liquid prepared by mixing pure water with a polishing slurry stock solution stored in a PFA storage tank having a humidity of 75% for 24 hours. The number of dry silica of 1 μm or more contained in the polishing slurry liquid of Comparative Example 2 was 5400 / ml.

<experimental method>
By using the polishing slurry liquid of Example 1 described above, the polishing slurry liquid of Comparative Example 1, and the polishing slurry liquid of Comparative Example 2, two semiconductor wafers W were polished under the same polishing conditions as the secondary polishing step in the secondary polishing unit 132. Subsequent polishing was performed to compare the number of minute defects and the number of scratch defects per sheet.

<Experimental result>
As shown in FIG. 6, it was confirmed that the number of minute defects per sheet was the smallest in the polishing slurry liquid of Example 1 and the largest in the polishing slurry liquid of Comparative Example 2. That is, it was confirmed that the smaller the number of dry silica of 1 μm or more contained in the polishing slurry liquid, the smaller the number of minute defects per sheet generated in the secondary polishing.
Further, as shown in FIG. 7, it was confirmed that the number of scratch defects per sheet was the smallest in the polishing slurry liquid of Example 1 and the largest in the polishing slurry liquid of Comparative Example 2.

[Evaluation]
From the above, the secondary polishing slurry adjustment liquid generated by the configuration of the first embodiment, that is, the secondary polishing slurry adjustment liquid obtained by treating the polishing slurry stock solution stored in an environment with a humidity of 99% by the slurry adjustment unit 150. However, it was confirmed that the number of minute defects can be particularly reduced.

[Second Embodiment]
Next, a second example for explaining the effect of the second embodiment will be described.
FIG. 8 is a graph showing the relationship between the centrifugal force when the polishing slurry recovery filtrate is centrifuged and the number of dry silica and aggregated silica contained in the polishing slurry recovery filtrate. FIG. 9 is a graph showing the relationship between the centrifugal force when the polishing slurry recovery filtrate is centrifuged and the number of micro defects generated in the secondary polishing using the polishing slurry recovery filtrate. FIG. 10 is a graph showing the relationship between the centrifugal force when the polishing slurry recovery filtrate is centrifuged and the polishing rate in secondary polishing using this polishing slurry recovery filtrate.

[Relationship between centrifugal force when the polishing slurry recovery filtrate is centrifuged and the number of dry silica and agglomerated silica contained in the polishing slurry recovery filtrate]
First, the relationship between the centrifugal force when centrifuging the polishing slurry recovery filtrate and the number of dry silica and agglomerated silica contained in the polishing slurry recovery filtrate will be described.

<experimental method>
The polishing slurry recovery filtrate processed in the recovery unit 140 was subjected to centrifugal separation with a centrifugal time of 3 min / L with each centrifugal force. Then, the number of dry silica and agglomerated silica of 1 μm or more present in this centrifuged slurry recovery filtrate is determined by the method using the above-mentioned SEM, and the particle counter (product name: KS71, manufactured by Rion). ).

<Experimental result>
As shown in FIG. 8, it was confirmed that the number of dry silica and agglomerated silica of 1 μm or more decreases as the centrifugal force increases.
In particular, when the centrifugal force is 5000 G to 10000 G, it was confirmed that more dry silica can be removed compared to the agglomerated silica. Further, it was confirmed that when the centrifugal force is 5000 G or less, it is difficult to set the number of dry silicas of 1 μm or more to 3000 pieces / ml or less.

[Relationship between centrifugal force when the polishing slurry recovery filtrate is subjected to centrifugal separation and the number of micro defects generated in secondary polishing using the polishing slurry recovery filtrate]
Next, the relationship between the centrifugal force when the polishing slurry recovery filtrate is centrifuged and the number of micro defects generated in the secondary polishing using the polishing slurry recovery filtrate will be described.

<experimental method>
The semiconductor wafer W was secondarily polished using the polishing slurry recovery filtrate that had been subjected to centrifugal separation for 3 min / L with each centrifugal force, and the number of micro defects per sheet was compared.

<Experimental result>
As shown in FIG. 9, it was confirmed that the number of minute defects per sheet decreases as the centrifugal force increases.
In particular, it was confirmed that the number of micro defects is extremely reduced when the centrifugal force is 5000 G or more.

[Relationship between Centrifugal Force when Centrifugating Polishing Slurry Recovery Filtrate and Polishing Rate in Secondary Polishing Using Polishing Slurry Recovery Filtrate]
Next, the relationship between the centrifugal force when the polishing slurry recovery filtrate is centrifuged and the polishing rate in secondary polishing using the polishing slurry recovery filtrate will be described.

<experimental method>
The semiconductor wafer W was secondarily polished using the polishing slurry recovery filtrate subjected to centrifugal separation at each centrifugal force for a centrifugation time of 3 min / L, and the polishing rates were compared.

<Experimental result>
As shown in FIG. 10, it was confirmed that the polishing rate was almost the same from 0G to 8000G. Moreover, in the case of 8000 G or more, it was confirmed that it falls, so that centrifugal force is large.
In particular, it was confirmed that the polishing rate was greatly reduced when the centrifugal force ranged from 8000 G to 14000 G. It was confirmed that the number of micro defects is extremely small.

[Evaluation]
From the above, it was confirmed that the configuration for performing the centrifugal separation process with the centrifugal force of 5000G to 10000G set in the second embodiment is appropriate from the viewpoint of the number of minute defects and the polishing rate. In particular, in the case of 8000G, it was confirmed that only dry silica can be selectively removed and the number of minute defects can be reduced without lowering the polishing rate, which is most appropriate.

[Third embodiment]
Next, a third example for explaining the effect of the third embodiment will be described.
FIG. 11 is a graph showing the relationship between the pulverization energy when pulverizing the polishing slurry recovery liquid and the number of dry silica and aggregated silica contained in the polishing slurry recovery liquid. FIG. 12 is a graph showing the relationship between the size and the number of dry silica contained in the polishing slurry recovery liquid before and after the pulverization treatment. FIG. 13 is a graph showing the relationship between the pulverization energy when pulverizing the polishing slurry recovery liquid and the number of micro defects generated in the secondary polishing using the polishing slurry recovery liquid.

[Relationship between grinding energy when grinding polishing slurry recovered liquid and the number of dry silica and agglomerated silica contained in this abrasive slurry recovered liquid]
First, the relationship between the pulverization energy when pulverizing the polishing slurry recovery liquid and the number of dry silica and aggregated silica contained in the polishing slurry recovery liquid will be described.

<experimental method>
The polishing slurry recovery liquid recovered by the recovery unit 140 is processed with each grinding energy using a bead mill (hereinafter referred to as an example bead mill) having a volume of 30 L and filled with zirconia beads having a diameter of 2 mm. The pulverization was performed for a time of 3 min / L. Then, the number of dry silica and agglomerated silica of 5 μm or more present in the pulverized polishing slurry recovery liquid was counted by a method using the above-described SEM and in-liquid particle counter.

<Experimental result>
As shown in FIG. 11, the number of dry silica of 5 μm or more may decrease corresponding to the size of the grinding energy because the number of dry silicas corresponding to the size of the grinding energy is ground by the beads. confirmed. That is, it was confirmed that the number of dry silicas less than 5 μm increased corresponding to the magnitude of the grinding energy.
On the other hand, it was confirmed that the number of agglomerated silica having a size of 5 μm or more increases corresponding to the magnitude of the crushing energy because the agglomeration of silica is promoted by the crushing energy.

[Relationship between size and number of dry silica contained in polishing slurry recovery liquid before and after pulverization]
Next, the relationship between the size and the number of dry silica contained in the polishing slurry recovery liquid before and after the pulverization treatment will be described.

<experimental method>
Example The number of dry silicas of each size contained in the polishing slurry recovery liquid before and after pulverization using a bead mill was examined by a method using the above-described SEM and in-liquid particle counter. Here, the pulverization process was performed under the conditions of a pulverization energy of 80 kWh / dry kg and a processing time of 3 min / L.

<Experimental result>
As shown in FIG. 12, it was confirmed that the number of 3 μm or more dry silica contained after the pulverization treatment was reduced from that before the pulverization treatment. Further, it was confirmed that the number of 1 μm and 2 μm dry silica after the pulverization treatment was increased from that before the pulverization treatment because the dry silica of 3 μm or more was pulverized by the pulverization treatment.

[Relationship between grinding energy when grinding polishing slurry recovered liquid and number of micro defects generated in secondary polishing using this abrasive slurry recovered liquid]
Next, the relationship between the pulverization energy when pulverizing the polishing slurry recovery liquid and the number of micro defects generated in the secondary polishing using the polishing slurry recovery liquid will be described.

<experimental method>
Example The semiconductor wafer W was secondarily polished using a polishing slurry recovery liquid that was pulverized with each pulverization energy for a processing time of 3 min / L using a bead mill, and the number of minute defects per sheet was compared.

<Experimental result>
As shown in FIG. 13, it was confirmed that the number of minute defects per sheet decreases as the grinding energy increases.

[Evaluation]
From the above, it was confirmed that the configuration in which the pulverization process is performed with the pulverization energy of 20 kWh / dry kg or more set in the third embodiment can reduce the number of minute defects.

  Since the semiconductor wafer can be satisfactorily polished when polishing the semiconductor wafer, the polishing method of the present invention can be used for a semiconductor wafer polishing apparatus.

1 is a block diagram showing a schematic configuration of a semiconductor wafer polishing apparatus according to a first embodiment of the present invention. It is a block diagram which shows schematic structure of the polishing apparatus of the semiconductor wafer which concerns on 2nd Embodiment of this invention. It is a block diagram which shows schematic structure of the polishing apparatus of the semiconductor wafer which concerns on 3rd Embodiment of this invention. It is a schematic diagram which shows schematic structure of the bead mill in the said 3rd Embodiment. It is a graph which shows the relationship of the storage time of the polishing slurry stock solution stored in each humidity in 1st Example, and the number of the dry silica contained in this polishing slurry stock solution. It is a graph which shows the number of the micro defects which generate | occur | produced by the secondary grinding | polishing using the polishing slurry liquid of Example 1, the comparative example 1, and the comparative example 2 in the said 1st Example. It is a graph which shows the number of scratch defects which generate | occur | produced by the secondary grinding | polishing using the grinding | polishing slurry liquid of Example 1, the comparative example 1, and the comparative example 2 in the said 1st Example. It is a graph which shows the relationship between the centrifugal force at the time of carrying out the centrifugation process of the grinding | polishing slurry collection | recovery filtrate in 2nd Example, and the number of the dry silica and the aggregation silica contained in this grinding | polishing slurry collection | recovery filtrate. It is a graph which shows the relationship between the centrifugal force at the time of carrying out the centrifugation process of the grinding | polishing slurry collection | recovery filtrate in the said 2nd Example, and the number of micro defects which generate | occur | produced by the secondary grinding | polishing using this grinding | polishing slurry collection | recovery filtrate. It is a graph which shows the relationship between the centrifugal force at the time of carrying out the centrifugation process of the grinding | polishing slurry collection | recovery filtrate in the said 2nd Example, and the grinding | polishing rate in the secondary grinding | polishing using this grinding | polishing slurry collection | recovery filtrate. It is a graph which shows the relationship between the grinding | pulverization energy at the time of grind | pulverizing the grinding | polishing slurry collection liquid in 3rd Example, and the number of the dry silica and the aggregation silica contained in this grinding | polishing slurry collection liquid. It is a graph which shows the relationship between the size and number of dry silica contained in the grinding | polishing slurry collection | recovery liquid before and behind the grinding | pulverization process in the said 3rd Example. It is a graph which shows the relationship of the grinding | pulverization energy at the time of grind | pulverizing the grinding | polishing slurry collection | recovery liquid in the said 3rd Example, and the number of micro defects which generate | occur | produced by the secondary grinding | polishing using this grinding | polishing slurry collection liquid. It is a graph which shows the particle size distribution of the silica which exists in the conventional polishing slurry stock solution. It is a graph which shows the particle size distribution of the silica which exists in the conventional reuse slurry. It is a graph which shows the relationship between the number of dry silica contained in the conventional polishing slurry, and the number of micro defects generated when polishing with this polishing slurry. It is a graph which shows the relationship between the number of the agglomerated silica contained in the conventional polishing slurry, and the number of micro defects generated when polishing with this polishing slurry.

Explanation of symbols

151: First filter 153: Second filter 360: Bead mill W: Semiconductor wafer

Claims (7)

The polishing slurry containing silica has an Si / O composition ratio of 50 wt% to 60 wt% / 40 wt% to 50 wt%, an elastic modulus of 1.4 × 10 ¹⁰ Pa or more, and 3000 silica particles / ml having a particle size of 1 μm or more. Provided with a slurry adjustment step to adjust to the following state,
A method for polishing a semiconductor wafer, comprising polishing the semiconductor wafer by using the polishing slurry adjusted in the slurry adjustment step in a rough polishing step immediately before the final polishing step. A method for polishing a semiconductor wafer according to claim 1,
The slurry adjustment step
A stock solution filtration step of filtering the stock solution of the polishing slurry by a first filter capable of capturing a solid content of a predetermined size;
A slurry generation step of preparing the polishing slurry by preparing a stock solution of the polishing slurry filtered in the stock solution filtering step with an additive,
A preparation liquid filtration step of filtering the polishing slurry produced in the slurry production step by a second filter capable of capturing a solid having a size smaller than that of the first filter;
A method for polishing a semiconductor wafer, comprising: A method for polishing a semiconductor wafer according to claim 2,
The first filter has a solid content capture efficiency of 99.99% or more having a size of 50 times or more of the primary particles of silica contained in the stock slurry slurry.
The method for polishing a semiconductor wafer, wherein the second filter has a solid content capture efficiency of 99.99% or more that is 10 times or more the size of the primary particles. A method for polishing a semiconductor wafer according to claim 1,
The slurry adjustment step
A method for polishing a semiconductor wafer, comprising: a centrifugation step of centrifuging the polishing slurry. A method for polishing a semiconductor wafer according to claim 4,
The method of polishing a semiconductor wafer, wherein the centrifugal force of the centrifugal separation in the centrifugal separation step is 5000G to 10,000G. A method for polishing a semiconductor wafer according to claim 1,
The slurry adjustment step
A method for polishing a semiconductor wafer, comprising: a pulverizing step of pulverizing the silica contained in the polishing slurry with a bead mill. A method for polishing a semiconductor wafer according to claim 6,
The method for polishing a semiconductor wafer, wherein an energy per unit mass given to the object to be crushed in the pulverization step is 20 kWh / dry kg or more.

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