JP4474950B2 - Polishing equipment - Google Patents

Description

The present invention relates to a polishing apparatus that performs polishing by immersing a polishing object in a polishing liquid and injecting a gas onto the surface of the polishing object.

  Conventionally, a method of polishing a surface of an object to be polished by spraying a polishing liquid obtained by mixing a liquid such as water and an abrasive from an injection nozzle is known. In this case, since the abrasive directly passes through the passage of the injection nozzle, there is a problem that the abrasive adheres to the tip of the injection nozzle and causes clogging. In addition, since the abrasive passes through the narrow passage of the injection nozzle at a high speed, it causes wear of the inner wall of the passage, and when the inner wall of the passage is worn, the diameter of the passage of the injection nozzle changes. When polishing is performed under such circumstances, the surface of the object to be polished becomes uneven due to a change in the polishing rate accompanying a change in the flow rate of the polishing liquid.

On the other hand, a liquid surface processing apparatus described in Patent Document 1 is disclosed as an apparatus for deburring a workpiece. Here, in this apparatus, a workpiece is placed in an abrasive mixed liquid in a tank, and a machining fluid is jetted from a nozzle device toward the surface of the workpiece to be processed at a high pressure. It is described that various liquids and gases can be used as the processing fluid. However, in this patent document 1, the embodiment using gas as a processing fluid is not described.
JP 2002-113663 A

  However, since the device described in Patent Document 1 is a deburring device, it is difficult to apply it to polishing of optical elements and the like that require high-precision surface polishing.

  Therefore, the inventors have applied for a patent on a polishing apparatus that immerses a polishing object in a polishing liquid tank filled with a polishing liquid consisting of a polishing material and a liquid such as water and injects a gas from an injection nozzle (however, , Not yet published). By injecting the gas from the injection nozzle, the polishing liquid entrained in the gas collides with the surface of the object to be polished, whereby the surface is polished.

  At this time, depending on various conditions such as the material and particle size of the abrasive particles in the polishing liquid and the energy of the abrasive particles to be sprayed, the surface of the object to be polished is affected by the mechanical wear action caused by the collision of the abrasive particles. Highly flexible polishing that can be applied to a wide range of fields, allowing various polishing effects to be exerted on the surface of the object to be polished, up to the action of high chemical reactivity resulting from the solid-phase reaction with the surface of the abrasive particles Has been studied by the present inventors.

  In particular, in polishing processing that requires high-precision shape processing and good surface roughness, such as processing of precision optical components used in semiconductor exposure equipment, the polishing processing proceeds mainly due to a highly reactive polishing action. Is preferred.

  However, in such a case, since polishing proceeds mainly due to a chemical reaction, there is a problem that if the chemical characteristics of the polishing liquid change during the polishing process, the polishing rate also changes accordingly. . In particular, the polishing rate was greatly changed by the change in the viscosity of the polishing liquid (the concentration of abrasive particles) and the PH value of the polishing liquid during the polishing process. Thus, the inventors have found that the fact that the polishing rate gradually changes during the polishing process results in a large processing error when performing high-precision shape creation polishing of the optical element. .

In view of such a situation, an object of the present invention is to provide a polishing apparatus capable of keeping a polishing rate constant by suppressing a change in chemical characteristics.

The invention according to claim 1 includes a polishing liquid filled in a container, and an injection nozzle that introduces a gas into the polishing liquid, and causes the polishing liquid and the gas to collide with an object to be polished. A polishing apparatus for polishing the object to be polished, wherein the viscosity is adjusted to a desired viscosity value by adding a viscosity adjusting agent while monitoring the viscosity value of the polishing liquid during polishing of the object to be polished The polishing apparatus is provided with the means as a polishing liquid adjusting means.

The invention according to claim 2 includes a polishing liquid filled in a container, and an injection nozzle that introduces a gas into the polishing liquid, and causes the polishing liquid and the gas to collide with an object to be polished. A polishing apparatus for polishing the object to be polished, the polishing apparatus including a gas component removal mechanism for removing a component that deteriorates polishing characteristics from the gas.

According to a third aspect of the present invention, in addition to the configuration of the second aspect , the component that deteriorates the polishing characteristics is carbon dioxide gas.

According to a fourth aspect of the present invention, in addition to the configuration of the second aspect , the gas component removing mechanism is a filter.

  According to the first aspect of the present invention, the apparatus includes a polishing liquid filled in a container and an injection nozzle that introduces a gas into the polishing liquid, and causes the polishing liquid and the gas to collide with an object to be polished. A polishing apparatus for polishing the object to be polished, comprising: a polishing liquid adjusting means for keeping the physical property value constant while monitoring the physical property value of the polishing liquid during polishing of the polishing object Since it is provided, the polishing rate can be kept constant during the polishing step, so that high-precision polishing is possible.

Further , as the polishing liquid adjusting means, there is provided a viscosity adjusting means that adjusts to a desired viscosity value by adding a viscosity adjusting agent while monitoring the viscosity value. Can be maintained at a constant value, and the polishing rate can be maintained constant, so that highly accurate polishing is possible.

According to invention of Claim 2 , it is equipped with the polishing liquid with which the container was filled, and the injection nozzle which introduce | transduces gas in the said polishing liquid, and makes the said polishing liquid and said gas collide with a grinding | polishing target object. Thus, the polishing apparatus for polishing the object to be polished is equipped with a gas component removing mechanism for removing components that deteriorate polishing characteristics from the gas, so that the PH value of the polishing liquid fluctuates during the polishing process. Therefore, since the polishing rate does not fluctuate, there is an advantage that high-precision polishing is possible and the configuration of the apparatus is simplified.

According to the third aspect of the invention, in addition to the effect of the second aspect , since the component that deteriorates the polishing characteristics is carbon dioxide gas, the gas component removal mechanism is used to reliably remove the carbon dioxide gas. can do.

According to the fourth aspect of the present invention, in addition to the effect of the second aspect , the gas component removing mechanism is a filter, so that it is possible to provide a polishing apparatus having a simple configuration and a low cost.

Embodiments of the present invention will be described below.
Embodiment 1 of the Invention

  Hereinafter, Embodiment 1 of the present invention will be described with reference to FIG. 1 and FIG.

  FIG. 1 is a schematic diagram of a polishing apparatus 10 according to Embodiment 1 of the present invention.

  First, the configuration will be described. The polishing apparatus 8 includes a polishing liquid 3 filled in a container 13, a jet nozzle 1 for introducing a gas 4 into the polishing liquid 3, a viscosity sensor 5 having blades 7 as polishing liquid adjusting means, and viscosity adjustment. And a liquid device.

  The container 13 has a rectangular box shape with a size capable of storing a predetermined volume of the polishing liquid 3, and the polishing object 2 is placed on a mounting table 14 provided in a substantially central portion inside the container 13. The polishing object 2 is configured to be immersed in the polishing liquid 3.

The polishing liquid 3 is a mixture of abrasive particles and pure water. Here, colloidal silica was used as the abrasive particles. Note that an oxide-based (CeO ₂ , ZrO ₂ , Al ₂ O ₃ ) abrasive or the like can also be used. In addition to pure water, alcohol may be used as the solvent.

  As the polishing object 2, fluorite, quartz, multicomponent glass for ultraviolet rays, low thermal expansion glass, silicon, electroless nickel, or the like is used.

  Further, the injection nozzle 1 is connected to a tank (not shown), and a compressed gas 4 is sent from the tank to the surface of the polishing object 2 in the polishing liquid 3 from the injection port 1a of the injection nozzle 1. It is comprised so that it may inject toward.

  The injection nozzle 1 can also be configured to perform shape generating polishing by driving an NC (Numerical Control) up and down, left and right, front and back in the drawing by an injection nozzle moving mechanism (not shown).

  Furthermore, the viscosity sensor 5 includes a rotatable blade 7, detects the torque applied to the blade 7 by rotating the blade 7 at a predetermined rotational speed, and based on the torque value, the polishing liquid. The viscosity value of 3 (= viscosity) is calculated.

  In such a configuration, there is an advantage that the polishing liquid 3 is agitated by the blades 7. However, the present invention is not limited to this configuration, and the viscosity of the polishing liquid 3 may be measured using a known technique used for viscosity measurement. .

  Further, the viscosity adjusting liquid adding device 6 is configured to appropriately add a viscosity adjusting agent for keeping the viscosity value of the polishing liquid 3 constant based on the measurement result by the viscosity sensor 5. Yes.

  In such a case, the gas 4 is injected from the injection nozzle 1, and the polishing liquid 3 entrained in the gas 4 collides with the surface of the polishing object 12, whereby the surface of the polishing object 12. Is polished.

  At this time, the air around the apparatus is used as the gas 4, and the humidity of the air compressed by the compressor or the like is significantly lower than that of normal air. Therefore, when the low humidity air (gas 4) is injected into the polishing liquid 3, the gas 4 deprives the polishing liquid 3 of moisture. Deprivation of moisture increases the concentration of abrasive particles in the polishing liquid 3 and increases the viscosity of the polishing liquid 3.

  FIG. 2 is a diagram showing the relationship between the viscosity of the polishing liquid and the polishing rate. As shown in FIG. 2, it was found that the polishing rate increases as the viscosity increases. That is, the polishing rate increases from about 50 nm / min to about 118 nm / min while the viscosity of the polishing liquid increases from about 1.8 cst to 3.4 cst. As described above, when the viscosity of the polishing liquid 3 increases, the polishing rate increases, and there arises a problem that a predetermined accuracy cannot be maintained in the high-precision correction polishing. Moreover, the surface roughness of a processed surface may deteriorate with the increase in a viscosity. Therefore, the polishing apparatus 8 is configured to include a viscosity sensor 5 and a viscosity adjusting agent adding apparatus 6 that works in conjunction with the viscosity sensor 5 in order to keep the viscosity of the polishing liquid 3 constant during the polishing process.

  Thus, during the polishing process, the viscosity of the polishing liquid 3 is kept constant, and the polishing speed is kept constant, so that a highly accurate polishing surface with good surface roughness can be obtained. Combining with driving enables highly accurate shape creation polishing.

  In addition, when using the polishing liquid 3 which is a mixture of abrasive particles and pure water, the viscosity adjusting agent added by the viscosity adjusting agent adding device 6 is pure water, but the polishing liquid 3 is made of other substances. In this case, the present invention is not limited to this, and the most suitable viscosity adjusting agent is selected in accordance with the characteristics of the polishing liquid 3.

In the above description, the case where the viscosity of the polishing liquid 3 increases during the polishing step has been described. On the contrary, the viscosity of the polishing liquid 3 may decrease with time. In this case, a highly viscous solvent may be added as a viscosity modifier.
[ Reference Example 1 ]

Hereinafter, Reference Example 1 will be described with reference to FIGS. 3 and 4.

FIG. 3 is a schematic view of a polishing apparatus according to Reference Example 1 .

Compared with Embodiment 1 of the present invention, Reference Example 1 is different in that a PH sensor 9 is provided instead of the viscosity sensor 5 and a PH adjuster adding device 10 is provided instead of the viscosity adjuster adding device 6. ing. Since other components are the same as those of the first embodiment of the present invention, the same components are denoted by the same reference numerals, and description thereof is omitted.

The gas 4 obtained by compressing external air with a compressor (not shown) contains carbon dioxide (CO ₂ ) gas, though in a small amount. When the gas 4 is injected into the polishing liquid 3, the carbon dioxide gas contained in the gas 4 dissolves into the polishing liquid 3, so that the pH of the polishing liquid 3 gradually changes to the acidic side.

  FIG. 4 is a diagram showing the relationship between the PH value of the polishing liquid and the polishing rate. As shown in FIG. 4, when PH changes from 10.16 to 9.25 on the acidic side, the polishing rate increases from approximately 55 nm / min to 118 nm / min. In polishing applied mainly to the processing of precision optical elements mainly due to chemical reaction, the polishing rate is greatly changed due to the change in PH of the polishing liquid 3, which becomes a significant error factor for the accuracy of polishing processing.

  Moreover, in a certain kind of polishing liquid 3, the dispersion state of the abrasive particles in the polishing liquid 3 can be stabilized by setting the pH of the polishing liquid 3 to a predetermined value. When such a polishing liquid 3 is used, if the pH of the polishing liquid 3 changes, the dispersion state of the abrasive particles may change, and the surface roughness of the processed surface may deteriorate.

  Therefore, the polishing apparatus 8 includes a PH sensor 9 and a PH adjuster addition device that works in conjunction therewith, so that the PH value is detected by the PH sensor 9 during the polishing process, and a PH adjusting liquid is determined according to this value. A pH adjusting agent can be added by the adding device 10 to keep the pH of the polishing liquid 3 constant. When the gas 4 injected from the injection nozzle 1 contains carbon dioxide gas and the polishing liquid 3 is a mixture of abrasive particles and water, the PH adjuster is preferably sodium hydroxide, which is a strong alkaline aqueous solution. Although a 50% aqueous solution is used, a suitable pH adjusting agent is appropriately selected when polishing in other situations.

  In addition, the case where the polishing liquid 3 changes to the acidic side with time has been described so far. On the contrary, the polishing liquid 3 may change to the alkaline side with time. In that case, a strongly acidic aqueous solution is added as a pH adjuster.

According to the polishing apparatus 8 described in Reference Example 1 , since the PH of the polishing liquid 3 is kept constant and the polishing speed is kept constant during the polishing process, a high-precision polishing surface with good surface roughness. In addition, by combining with NC driving, highly accurate shape creation polishing can be performed.
[ Reference Example 2 ]

Hereinafter, Reference Example 2 will be described with reference to FIG.

FIG. 5 is a schematic view of the polishing apparatus 8 according to Reference Example 2 .

The polishing apparatus 8 of this reference example 2 introduces a polishing liquid 3 filled in a container 13, an injection nozzle 1 that introduces a gas 4 into the polishing liquid 3, and an inert gas that is a gas 4. And a gas supply system 11 serving as a “gas supply means”. Here, nitrogen gas was used as the inert gas.

  The inert gas stored in the gas supply system 11 is compressed by a compressor (not shown), is pumped to the injection nozzle 1, and is injected into the polishing liquid 3 from the injection port 1 a of the injection nozzle 1. The injected inert gas collides with the polishing object 2 while entraining the polishing liquid 3 around the injection port 1 a of the injection nozzle 1. The surface of the polishing object 2 is polished by the impregnated polishing liquid 3 colliding with the surface of the polishing object 2.

In Reference Example 2 , the use of an inert gas as the gas 4 ejected from the ejection nozzle 1 can prevent the pH of the polishing liquid 3 from changing.

According to the reference example 2 , since the pH of the polishing liquid 3 can be kept constant only by using an inert gas as the gas 4, the PH sensor 9 and the PH adjusting liquid adding device 10 are not necessary. There is an advantage that the configuration of FIG. In Reference Example 2 , nitrogen gas is used as the inert gas, but it is needless to say that helium, argon, krypton, or xenon gas may be used without being limited thereto.
[Embodiment 2 of the Invention]

Hereinafter, Embodiment 2 of the present invention will be described with reference to FIG.

FIG. 6 is a schematic diagram of a polishing apparatus according to Embodiment 2 of the present invention.

The polishing apparatus 8 according to the second embodiment removes from the gas 4 the polishing liquid 3 filled in the container 13, the injection nozzle 1 that introduces the gas 4 into the polishing liquid 3, and components that deteriorate the polishing characteristics. And a removal filter 12 as a “gas component removal mechanism” that can be used.

  In such a case, the air taken in from the outside as the gas 4 is compressed by a compressor (not shown), and is sent to the injection nozzle 1 via the removal filter 12 for removing carbon dioxide. The pressure-fed air is injected into the polishing liquid 3 from the injection port 1 a of the injection nozzle 1 and collides with the polishing object 2 while entraining the polishing liquid 3 around the injection port 1 a of the injection nozzle 1. As the entrained polishing liquid 3 collides with the surface of the polishing object 2, the surface of the polishing object 2 is polished.

When external air is introduced into the polishing liquid 3 as the gas 4 and injected, trace components such as carbon dioxide contained in the air change the pH of the polishing liquid 3 over time, and hinder precision polishing. This has already been described in Reference Example 1 .

Therefore, in Embodiment 2 of the present invention, the air compressed by the compressor is passed through the removal filter 12 and then pumped to the injection nozzle 1. Since compressed air from which carbon dioxide has been removed by the removal filter 12 is jetted into the polishing liquid 3, the PH of the polishing liquid 3 is not changed.

According to the second embodiment of the present invention, since the removal filter 12 is merely arranged, the polishing apparatus 8 having a simple configuration and low cost can be provided.

  FIG. 7 is a schematic diagram showing the overall configuration of the semiconductor exposure apparatus.

As shown in FIG. 7, the semiconductor exposure apparatus 21 includes a light source 22, an illumination optical system 23, a mask unit 24, a projection optical system 25, and a wafer unit 26. The optical element polished by using the polishing apparatus 8 described in the first and second embodiments and reference examples 1 and 2 of the present invention is incorporated into the illumination optical system 23 and the projection optical system 26 and used. Therefore, it is possible to provide the semiconductor exposure apparatus 21 capable of performing optical exposure with high accuracy.

  Table 1 shows the polishing rate when the values of viscosity and PH at a temperature of 18 ° C. are fixed values.

  As shown in Table 1, the polishing rate is 48.13 nm / min when there is a variation of PH 9.63 to 10.14 and a variation of viscosity 1.850 cst to 3.412 cst even when the temperature is constant. It was found that the variation was in the range of ˜117.23 nm / min.

If the polishing apparatus described in Embodiments 1 to 2 and Reference Examples 1 to 2 of the present invention is used, the viscosity and PH value can be kept constant, so that the polishing rate can be kept constant.

1 is a schematic view of a polishing apparatus according to Embodiment 1 of the present invention. It is a figure which shows the relationship between the viscosity of polishing liquid, and polishing rate. 1 is a schematic view of a polishing apparatus according to Reference Example 1. FIG. It is a figure which shows the relationship between PH of polishing liquid, and polishing rate. 5 is a schematic diagram of a polishing apparatus according to Reference Example 2. FIG. It is the schematic of the grinding | polishing apparatus which concerns on Embodiment 2 of this invention. It is the schematic of a semiconductor exposure apparatus .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection nozzle 1a Injection port 2 Polishing object 3 Polishing liquid 4 Gas 5 Viscosity sensor 6 Viscosity adjustment liquid addition apparatus 7 Blade 8 Polishing apparatus 9 PH sensor 10 PH adjustment liquid addition apparatus 11 Gas supply system 12 Removal filter 13 Container 14 Mounting stand DESCRIPTION OF SYMBOLS 21 Semiconductor exposure apparatus 22 Light source 23 Illumination optical system 24 Mask part 25 Projection optical system 26 Wafer part

Claims (4)

Polishing comprising a polishing liquid filled in a container and an injection nozzle for introducing a gas into the polishing liquid, and polishing the polishing object by causing the polishing liquid and the gas to collide with the polishing object A device,
During polishing of the object to be polished, while monitoring the viscosity value of the polishing liquid, and characterized in that the addition of viscosity control agent comprises a polishing liquid adjustment means the viscosity adjusting means for adjusting the desired viscosity value Polishing equipment. Polishing comprising a polishing liquid filled in a container and an injection nozzle for introducing a gas into the polishing liquid, and polishing the polishing object by causing the polishing liquid and the gas to collide with the polishing object A device,
A polishing apparatus comprising a gas component removal mechanism for removing a component that deteriorates polishing characteristics from the gas . The polishing apparatus according to claim 2 , wherein the component that deteriorates the polishing characteristics is carbon dioxide gas . The polishing apparatus according to claim 2 , wherein the gas component removing mechanism is a filter .

Images