JP5165635B2 - Etch solution regeneration system - Google Patents

Description

  The present invention relates to an etching solution regeneration system, and more particularly to an etching solution regeneration system that can regenerate an etching solution so that the content of dissolved substances in the etching solution in a processing tank in which an etching process is performed is accurately and uniformly controlled.

In recent years, in the field of semiconductor device manufacturing, among Si ₃ N ₄ film and SiO ₂ film formed on a semiconductor material such as a silicon wafer, the Si ₃ N ₄ film is selectively etched away leaving the SiO ₂ film, In addition, a precise etching process is required to maintain the selection ratio uniformly.

The etching selectivity of the Si ₃ N ₄ film and the SiO ₂ film is set in a mixed solution of phosphoric acid (H ₃ PO ₄ ) and pure water (H ₂ O) used as an etchant (hereinafter also referred to as “phosphoric acid aqueous solution”). Since it varies depending on the concentration of the silicon compound produced, in order to continue stable etching, the concentration of the silicon compound in the etching solution in the processing tank in which the etching process is performed is maintained at an optimal constant concentration. There is a need.

With regard to such a problem, the applicant of the present application has deposited a part of the dissolved silicon compound, which is generated as a by-product in the etching solution in the etching process of the Si ₃ N ₄ film, in the etching solution, The apparatus which collect | recovered by doing and can maintain the density | concentration of Si component (Si ion) in an etching liquid constant was proposed (patent document 1). This apparatus extracts a part of the etching solution from the processing tank, deposits and removes a part or all of the silicon compound produced by the etching process, and then returns the processing liquid to the processing tank again to regenerate the etching solution. The etching process can be performed while extending the life and maintaining the etching selectivity of the Si ₃ N ₄ film and the SiO ₂ film constant.

By the way, in the etching processing system as described above, in order to keep the etching selectivity of the Si ₃ N ₄ film and the SiO ₂ film constant with higher accuracy, the concentration of Si component (Si ions) in the etching solution is set. It is desirable to grasp the process in-line in real time and to perform feedback control of the precipitation removal / regeneration in the shortest possible cycle. However, the amount (concentration) of the Si component in the etching solution can be measured by atomic absorption analysis, ion chromatography, inductively coupled plasma mass spectrometry (ICP analysis), or the like (Patent Documents 2 and 2). 5), these methods are not suitable for in-line measurement because it is necessary to dilute or burn the etching solution for measurement. Further, Patent Document 6 proposes a concentration measuring method and measuring apparatus using ultraviolet absorption analysis capable of in-line measurement of a process. However, in this method, depending on the combination of the etching solution and the dissolved component (for example, phosphoric acid aqueous solution and silicon), a sufficient correlation coefficient cannot be obtained between the ultraviolet absorbance and the dissolved component concentration, and the measurement accuracy is sufficiently high. I can't get it. For this reason, the present applicant further proposed a new technique for quantifying the concentration of the Si component dissolved in the etching solution so that in-line measurement can be performed even in a combination of phosphoric acid and silicon (Patent Document 7). In this method, since the transmittance of the etching solution changes due to light scattering by the precipitate when the Si component dissolved in the etching solution exceeds the saturation solubility, the transmittance is first reduced while lowering the temperature of the etching solution. The concentration of the Si component is quantified by finding the temperature that changes to. However, this method also requires additional equipment and operation of sampling and cooling the phosphoric acid solution for measurement, and a simpler measurement method is desired.

  On the other hand, Patent Document 8 proposes an etching apparatus in which the processing time is adjusted according to the degree of deterioration of the etching solution so that an appropriate etching process can be performed even with the deteriorated etching solution. In other words, this device estimates the degree of deterioration of the etching solution from the usage history of the etching solution, and extends the processing time corresponding to the degree of deterioration of the etching solution from the relationship between the degree of deterioration and the processing rate that has been obtained in advance. Although the etching solution is not regenerated and used, the concentration of the silicon compound (Si ion) that affects the degree of deterioration of the etching solution cannot be measured. Has been. Therefore, it cannot be said that high-precision processing can be performed because it cannot cope with fluctuations in the actual processing environment. In Patent Document 9, the concentration of a predetermined substance in the etching solution is detected, and when the concentration of the predetermined substance reaches a predetermined concentration, a predetermined amount of the etching solution in the processing tank is discharged, and a new etching solution is prepared. An etching method and apparatus for replenishing a processing tank and adjusting the concentration of a predetermined substance in an etching solution are described. However, the concentration detection means (concentration detection sensor) for detecting the concentration of a predetermined substance in the etching solution is not specifically described, and the concentration control of the etching solution is a novel etching solution (a solute component thereof). It is performed by replenishment, and the etching solution is not regenerated.

Japanese Patent No. 3842657 Japanese Patent Laid-Open No. 7-21973 JP-A-7-280725 JP-A-10-267836 JP 11-326280 A JP 2004-294205 A JP 2009-58306 A JP 2004-288963 A JP 2001-23952 A

  The present invention has been made in view of the circumstances as described above, and the problem to be solved is that the content of dissolved substances in the etching solution is grasped in real time in the process, and the etching process is performed. Another object of the present invention is to provide an etching solution regeneration system that can regenerate the etching solution so that the content of dissolved substances in the etching solution in the treatment tank is accurately and uniformly controlled.

  In order to solve the above problems, the present inventors grasped the content (concentration) of dissolved substances in the etching solution in real time in the process, and regenerated the etching solution in a cycle as short as possible. When we examined feedback control, when the refractive index of the liquid and the prism in contact with the liquid is close, the reflectance of light at the boundary surface of the prism that forms the interface with the liquid indicates the inclusion of dissolved substances in the liquid. As a result of discovering that it changes with high sensitivity to the change in the refractive index of the liquid accompanying the change in the amount, and further researching based on such knowledge, the refractive index of the etching solution in the etching tank or circulation path is Reflected light obtained by bringing a prism close to the refractive index of the etching solution into contact with light and making light incident on the boundary surface of the prism that forms the interface with the etching solution at a predetermined incident angle. By knowing the strength, it is found that the content of dissolved substances (for example, Si ions) in the etching solution can be measured with high accuracy in a short time, and the above feedback control is possible, and the present invention is completed. It came.

That is, the present invention includes the following contents.
(1) A high temperature etching solution in an etching tank in which the material to be etched is immersed and accommodated is taken out through the circulation path, filtered in the middle of the circulation path, and returned to the tank while being reheated. An etching solution regeneration system attached to an etching apparatus for performing an etching process on the material to be etched while repeating pumping circulation,
Etching solution regenerating means for forcibly separating the dissolved substance in the etching solution taken out from the etching tank or from the middle of the circulation path from the etching solution, and generating a regenerated etching solution in which the dissolved substance is removed or reduced, and
Dissolved substance content measuring means for measuring the content of a substance dissolved in the etching solution in the etching tank or the circulation path;
Control means for determining the amount of the etchant returned from the etchant regeneration means to the etching tank based on the dissolved substance content in the etchant measured by the dissolved substance content measurement means;
When the dissolved substance content measuring means is a prism, the absolute value (| N ₁ −N ₂ |) of the difference between the refractive index (N ₁ ) and the refractive index (N ₂ ) of the etching solution is 0.30 or less. An optical unit that uses a prism and makes light from a light source incident on the boundary surface of the prism that forms an interface with the etching solution, and detects the reflectivity of reflected light from the prism boundary surface, and a detection signal of the optical unit And a data processing unit for calculating the dissolved substance content in the etching solution based on the above.
(2) The material to be etched is a semiconductor material in which a silicon nitride film and a silicon oxide film are formed, and the etching process is an etching process for selectively removing the silicon nitride film on the semiconductor material, and the etching solution is The etching solution regeneration system according to (1) above, which is an aqueous phosphoric acid solution and the prism is a quartz prism.

  Examples of the “etching solution” in the present invention include acid solutions such as aqueous solutions of phosphoric acid, hydrofluoric acid, hydrochloric acid, acetic acid, nitric acid, sulfuric acid, etc .; aqueous ammonia solutions; aqueous hydrogen peroxide solutions, and mixtures thereof.

  The dissolved substance in the etching solution is a by-product by etching or a substance derived from the by-product. For example, aluminum (Al), magnesium (Mg), manganese (Mn), nickel (Ni), copper It is a metal element (ion) such as (Cu), silicon (Si), phosphorus (P) or the like, or a metal-like element (ion) exhibiting metallic properties.

In the process (system), the means (measuring substance content measuring means) for measuring the content of the dissolved substance in the etching liquid in the etching liquid regeneration system of the present invention may be substantially a light source, a prism, and a light receiving element. Can be easily integrated (that is, in-line measurement of the process is possible), and the dissolved substance content (concentration) in the etching solution can be measured in real time. For this reason, in the etching solution regenerating system of the present invention, the regenerated etching solution obtained by forcibly separating the etching residue dissolved in the etching solution by the etching solution regenerating apparatus is reused to dissolve dissolved substances in the etching solution. The etching solution regeneration process with a constant concentration can be performed with high accuracy in a short cycle. As a result, the life of the etching solution is extended, and the etching selectivity is maintained and maintained with high accuracy. Thus, an efficient etching process can be repeatedly performed. Further, since the dissolved substance content measuring means calculates the dissolved substance concentration in the etching solution based on the reflected light of the light incident on the boundary surface of the prism that forms the interface with the etching solution, for example, a Si ₃ N ₄ film And the light transmittance, scattered light intensity and dissolved components (such as phosphoric acid aqueous solution used in the etching process for selectively etching the Si ₃ N ₄ film while leaving the SiO ₂ film from the silicon wafer on which the SiO ₂ film is formed ( Even if the liquid does not have a sufficient correlation coefficient with the concentration of the silicon compound), the concentration of dissolved components in the etching solution can be detected with high accuracy, and the etching selectivity, etc. can be kept constant. A highly accurate and efficient etching process can be repeatedly performed while managing.

It is a schematic diagram of an example of an etching processing apparatus provided with the etching liquid reproduction | regeneration system of this invention. It is an enlarged view of the mounting part to the etching tank of the dissolved substance content measuring means in FIG. It is a system block diagram of the dissolved substance content measuring means in FIG. It is a schematic diagram of another Example of the optical part in a dissolved substance content measuring means. FIGS. 1A to 1D are schematic views of first to fourth embodiments of an etchant regeneration apparatus in an etchant regeneration system of the present invention. It is the schematic of 5th Embodiment of the etching liquid reproduction | regeneration apparatus in the etching liquid reproduction | regeneration system of this invention. It is the schematic of 6th Embodiment of the etching liquid reproduction | regeneration apparatus in the etching liquid reproduction | regeneration system of this invention. It is the schematic of 7th Embodiment of the etching liquid reproduction | regeneration apparatus in the etching liquid reproduction | regeneration system of this invention. It is the schematic of 8th Embodiment of the etching liquid reproduction | regeneration apparatus in the etching liquid reproduction | regeneration system of this invention. It is the schematic of 9th Embodiment of the etching liquid reproduction | regeneration apparatus in the etching liquid reproduction | regeneration system of this invention. It is the schematic of 10th Embodiment of the etching liquid reproduction | regeneration apparatus in the etching liquid reproduction | regeneration system of this invention.

Hereinafter, the present invention will be described with reference to preferred embodiments thereof.
FIG. 1 is a schematic view of an example of an etching processing apparatus provided with the etching solution regeneration system of the present invention. In the following description, an etching process using a phosphoric acid aqueous solution is performed on a semiconductor material on which a Si ₃ N ₄ film and a SiO ₂ film are formed as an example. The operation to be used will be described.

The etching tank 41 contains the etching liquid M, and a processing tank 41-1 in which an etching target material (not shown) is immersed and immersed in the etching liquid M to perform an etching process, and the processing tank 41-1. An overflow tank 41-2 for receiving the etching solution M overflowing from the tank. Specifically, the inside of the treatment tank 41-1 is filled with an aqueous phosphoric acid solution (H ₃ PO ₄ + H ₂ O) that is heated and controlled at 150 to 175 ° C. as an etching solution M, and Si ₃ N is filled therewith. _The semiconductor material (not shown) on which the _four films and the SiO ₂ film are formed is immersed and immersed so that the Si ₃ N ₄ film is selectively etched away from the semiconductor material and an etching process is performed to leave the SiO ₂ film. Is called. A silicon compound (etching residue) is generated as a by-product by the etching process, and the accumulation gradually increases, so that the Si ion concentration in the etching solution (phosphoric acid aqueous solution) M increases.

  The etching solution M overflows from the treatment tank 41-1 to the overflow tank 41-2, and the overflowed etching solution M is circulated by the pump 43 and returned to the treatment tank 41-1, during which foreign matter is removed. A filtration filter 44 to be removed and a line heater 45 for heating to 150 to 175 ° C. to keep the circulation path 42 at a constant temperature are attached. Further, a branch path 46 is formed from the circulation path 42 by branch piping, and a part of the etching solution M is taken out along the path and the silicon compound (etching residue) dissolved in the etching solution is forcibly separated from the etching solution. In addition, an etchant regenerator 47 that generates a regenerated etchant from which the silicon compound (etching residue) has been removed or reduced is attached.

  The processing tank 41-1 in the etching tank 41 is made of a desired material such as quartz, and has a bottomed box having a substantially rectangular shape in plan view and having a size capable of accommodating a plurality of semiconductor materials in a vertically parallel shape. A tank formed in a mold. A rectifying plate (not shown) is provided on the bottom side in the processing tank 41-1, and the etching solution fed and circulated from the bottom center is supported by all semiconductor materials supported and accommodated in a vertical parallel configuration. The material to be etched flows (increases) while contacting at an optimum flow rate (m / s) for effective etching.

  The branch path (branch pipe) 46 normally has a pipe diameter smaller than the pipe diameter of the circulation path 42, and exhausts the air that enters the circulation path 42 together with the overflowed etchant to the outside, thereby It serves to maintain the flow rate and flow rate of the etching solution smoothly and at a constant flow rate. One end of a part of the circulation path 42 that connects between the filtration filter 44 and the treatment tank 41-1 is provided. The other end side is branched from the circulation path 42 in a released state with the other end facing the upper opening of the overflow tank 41-2 around the processing tank 41-1.

  A part of the etching solution overflowing the overflow tank 41-2 and taken out of the tank by the circulation pump 43 through the circulation path 42 and circulated by pressure flows into the branch path 46, and the etching solution M flowing into the path 46 is etched. It returns to the processing tank 41-1 from the open discharge port facing the upper opening of the tank 41. At this time, the air mixed in the etching solution M is separated from the etching solution by the flow in which the etching solution M is discharged back into the treatment tank 41-1. Then, an etchant regenerator 47 is connected in the middle of the branch path 46, and the silicon compound (etching residue) dissolved in the etchant M is separated from the etchant M by the etchant regenerator 47, Regenerate the etchant. In FIG. 1, the etchant regenerator 47 is attached in the middle of the branch path 46. However, the etchant regenerator 47 is attached so that a part of the etchant M is directly taken out from the etching tank and regenerated. Also good.

  Reference numeral 50 in the drawing is an open / close valve connected by piping to the connection side of the branch path 46 with respect to the circulation path 42, and this path 46 is temporarily used when performing maintenance and inspection of the etchant regenerator 47 and replacement thereof. To be able to close.

  The etchant regenerator (hereinafter also simply referred to as “regenerator”) 47 is manufactured from a desired material such as quartz or Teflon (registered trademark), and is the etchant M cooled by cold water or air cooling or oxidized? Alternatively, the silicon compound (etching residue) dissolved in the etching solution M introduced through the branch path 46 by atomization is forcibly precipitated and separated (recovered and removed) from the etching solution.

  FIG. 5A shows the regenerator 47 according to the first embodiment, in which a cooling pipe 52 that circulates a cooling medium such as cold water is spirally wound around a precipitation container 51 formed in a box shape having an appropriate size. In addition, the access port pipes 53 and 54 for detachably connecting to the branch path (branch pipe) 46 are respectively inserted into the container 51, and the container 51 contains an etching solution. A precipitation nucleus mesh 55 is provided for positively and efficiently depositing and recovering the silicon compound. Although not shown in the drawings, it is preferable to use a joint means such as a coupling that can be easily performed as a structure for attaching and detaching the connection port pipes 53 and 54 to the branch path 46.

  Thus, according to the regenerator 47, the etching solution M introduced into the deposition vessel 51 from the branch path 46 through the inlet connection pipe 53 is cooled. Then, the silicon compound in the etching solution M is forcibly precipitated and adheres to the precipitation nucleus mesh 55. As a result, the silicon compound is efficiently and reliably recovered and removed from the etching solution M. The etching solution M from which the silicon compound has been recovered and removed is returned from the outlet connection port tube 54 to the branch path 46 and is returned to the treatment tank 41-1 through the path 46.

  FIG. 5B shows a regeneration device 47 according to the second embodiment, which is connected to the discharge port in the container 51 of the inlet connection port pipe 53 inserted and connected to the precipitation container 51 described in detail in the first embodiment. By attaching a substantially trumpet-shaped discharge port 56 having an infinite number of small holes (not shown), a small discharge pump 57 is connected to the pipe portion of the inlet connection port pipe 53 located outside the container 51 by piping. The etching liquid M is diffused and discharged into the container 51 by the discharge pump 57. That is, the etching solution M is expanded and cooled by diffusing and discharging the etching solution M from the discharge port 56 into the container 51 by the discharge pump 57, and the precipitation nucleus mesh while forcibly depositing the silicon compound in the etching solution M. By adhering to 55, the silicon compound can be efficiently and reliably recovered and removed from the etching solution M. Note that the same reference numerals are used for the same components as those in the detailed description of the above-described embodiment, and redundant description is omitted.

  FIG. 5C shows a reproducing apparatus 47 according to the third embodiment, which is introduced from the connection port pipe 53 by inserting and connecting the inlet connection port pipe 53 described in detail in the first embodiment. The outlet connection port 54 described in the first embodiment is inserted and connected to a dilution container 58 for adding a diluent such as pure water to the stored etching solution M, and the mesh for precipitation nuclei. 55 is connected and equipped, and as described above, the etching solution M is cooled by air cooling (atmospheric temperature) in the precipitation vessel 60, so that the silicon compound in the solution M is forcibly removed. It is configured to be collected and removed by being deposited and attached to the precipitation nucleus mesh 55. In the figure, reference numeral 61 is a dilution replenishment pipe inserted into and connected to the dilution container 58, and 62 is a replenishment valve equipped with the replenishment pipe 61. The replenishment amount of the diluent can be arbitrarily changed and set.

  FIG. 5 (d) shows a regenerator 47 according to the fourth embodiment, which includes both inlet / outlet pipes 53 and 54, which are described in detail in the first embodiment, and a precipitation nucleus mesh 55. An air supply pipe 64 for blowing clean air toward the discharge port in the container 63 of the inlet connection port pipe 53 and an air cooling nozzle 65 connected to the supply pipe 64 are connected to the precipitation container 63 to be connected. At the same time, in order to maintain the internal pressure and the like of the deposition container 63 in a constant atmosphere, an air exhaust pipe 66 for exhausting excess air from the inside of the container 63 is connected with the blowing of air from the air supply pipe 64. . In the figure, reference numeral 67 denotes an air valve provided on the air supply pipe 64 so that the amount of air blown out can be arbitrarily changed and set by the valve 67. Reference numeral 68 denotes a gas-liquid separation filter that is present in the air exhaust pipe 66. The filter 68 does not drain the etching solution M to the outside, and only excess air is exhausted to the outside.

  Thus, according to the regeneration device 47 having such a configuration, clean air is supplied to the etching solution M discharged and introduced into the deposition vessel 63 from the branch path (branch pipe) 46 through the inlet connection pipe 53. Be sprayed. Then, the silicon compound (Si ions) in the etching solution M is forcibly deposited by oxidation, adheres to the precipitation nucleus mesh 55, and is recovered and removed from the etching solution M. The etching solution M from which the silicon compound has been recovered and removed is returned to the branch path 46 from the outlet connection pipe 54 inserted and connected near the bottom in the recovery container 63, and passes through the path 46 to the treatment tank 41-1. Returned to

  5A to 5D, the regenerator 47 is attached in the middle of the branch path 46, but a part of the etching solution M is directly taken out from the etching tank 41 (41-1) and regenerated. You may attach as follows.

  In the reproducing apparatus of the first to third embodiments described above (FIGS. 5A to 5C), the silicon compound (etching residue) in the etching solution is forcibly deposited by cooling the etching solution with cold water or air. Further, in the regenerating apparatus of the fourth embodiment (FIG. 5D), the silicon compound (etching residue) in the etching solution is forcibly precipitated by oxidizing the etching solution to separate (recover and remove the silicon compound). )doing. However, in these recycling apparatuses, in the process of etching a large amount of silicon wafers, accumulation of the silicon compound in the etching solution cannot be avoided, and it cannot be said that the removal efficiency of the silicon compound is sufficiently high. Therefore, eventually, the etching solution must be periodically replaced with a new etching solution, and problems remain with respect to the increase in processing cost and disposal of the etching solution that becomes industrial waste by using the new etching solution. The etching solution regenerating apparatus described below atomizes the etching solution taken out from the etching processing device (branch path, etching tank) (preferably temperature adjustment for adjusting the temperature of the etching solution taken out from the etching processing device) Having a means for atomizing the temperature-adjusted etching solution), and depositing and / or aggregating silicon compounds dissolved in the etching solution to separate them from the etching solution. The problems of the playback apparatus of the fourth embodiment can be solved.

  In the following description, the mounting position of the etching solution regenerating apparatus in the etching processing apparatus 100 is not specified, but it is attached in the middle of the branch path 46 as in the regenerating apparatus of the first to fourth embodiments. Alternatively, a part of the etching solution M is directly taken out from the etching tank 41 (41-1) and attached so as to be regenerated.

FIG. 6 shows an etching solution regenerating apparatus 10 according to the fifth embodiment. The regenerating apparatus 10 is added to the etching processing apparatus 100 shown in FIG. 1 in the etching processing tank 41 (41-1) or in the middle of the circulation path 42. An atomizing means 11 for atomizing an etching solution taken out from the substrate, and SiO ₂ in the etching solution deposited and / or agglomerated by the atomization by the atomizing means 11 is separated from the etching solution to obtain a regenerated etching solution. Separating means 12 is provided.

  The atomization means 11 performs atomization processing with respect to the etching solution taken out from the etching processing apparatus 100, and is provided in the atomization tank 11A and the atomization tank 11A as shown in FIG. A mixing atomization unit 11B and a gas supply unit 11C that supplies gas to the mixing atomization unit 11B at a set flow rate are provided.

  The mixing atomization part 11B is comprised by the spray nozzle of various structures, such as an external mixing system as shown in FIG. 6, and an internal mixing system not shown. The mixed atomization section 11B is connected to a liquid extraction path 13 from the etching processing apparatus 100 and a gas supply path 14 from the gas supply section 11C, and is supplied from the gas supply section 11C at a set flow rate. The gas to be mixed is mixed with the etching solution, and the atomized etching solution is sprayed.

Here, the type of the supply gas is not particularly limited, but dry dry gas or dust-cleaned gas is suitable, and nitrogen N ₂ , oxygen O _{2 and the} like are suitable.
The atomization state (miniaturization state) by the mixed atomization unit 11B can be set by the gas supply flow rate from the gas supply unit 11C and the etching solution supply flow rate. The gas supply flow rate can be set by adjusting the opening / closing of the open / close valve 15 provided in the gas supply path 14, and the etchant supply flow rate is discharged from the supply pump 16 provided in the liquid extraction path 13. It can be set according to the amount.

  Note that the supply of the etching solution taken out from the etching processing apparatus 100 to the mixed atomization unit 11 </ b> B may be performed via the supply pump 16 or may not be performed via the supply pump 16. Therefore, in this embodiment, as shown in FIG. 6, the liquid extraction path 13 has two paths, the supply pump 16 and the switching valve 18 are provided on one path 13a side, and the switching is performed on the other path 13b side. Only the valve 17 is provided.

  That is, when the etching solution from the etching processing apparatus 100 is taken out from the circulation path 42 in the vicinity of the circulation pump 43, the etching solution is mixed and atomized at a predetermined supply flow rate with the pumping force of the circulation pump 43. Since it can supply to the part 11B, it can carry out without letting the supply pump 16 pass. On the other hand, when it is performed by being connected to the etching treatment tank 41 (such as the bottom of the overflow tank 41-2), it is necessary to carry out through the supply pump 16 in order to obtain a predetermined supply flow rate of the etching solution to the mixed atomization section 11B. There is.

The separating means 12 includes a separator 12A made of a filter and the like, and a storage tank 12B for temporarily storing the etching solution that has passed through the separator 12A.
Thereby, the etching liquid in the atomization tank 11A is sent to the separator 12A by the pressure feed pump 20 of the communication path 19 that connects the atomization tank 11A and the separator 12A, and is deposited and / or aggregated by the atomization means 11. Thus, the silicon compound whose crystal is enlarged is separated and removed from the etching solution by the separator 12A. After the silicon compound is removed, the regenerated etching solution (phosphoric acid aqueous solution) having a low silicon compound concentration is stored (collected) in the storage tank 12B. The regenerated etching solution stored in the storage tank 12B is returned to the etching processing apparatus 100 by the liquid return pump 22 in the liquid return path 21 that connects the storage tank 12B and the etching processing apparatus 100 (etching processing tank 41).

  According to the etching solution regenerating apparatus 10 configured in this manner, most of the silicon compound dissolved in the etching solution taken out from the etching processing apparatus 100 is mixed with the gas in the mixed atomizing section 11B of the atomizing means 11. It can be efficiently enlarged and / or agglomerated by atomization by mixing. Thereby, the separation removal of the silicon compound (component crystal) from the etching solution by the separator 12A of the separation means 12 can be performed with a high removal rate.

FIG. 7 shows an etching solution regenerating apparatus 10-1 according to the sixth embodiment, and the regenerating apparatus 10-1 includes a temperature adjusting means 23 for adjusting the temperature of the etching solution taken out from the etching processing apparatus 100. . Since the other components are basically the same as those of the fifth embodiment, the same components are denoted by the same reference numerals, and redundant description is omitted.
That is, as shown in FIG. 7, the temperature adjusting means 23 is provided between the etching processing apparatus 100 and the atomizing means 11, and after adjusting the etching solution taken out from the etching processing apparatus 100 to a predetermined temperature, It is made to supply to the conversion means 11.

As shown in FIG. 7, the temperature adjusting means 23 includes a temperature adjusting tank 23A in which the etching solution taken out from the etching processing apparatus 100 by the liquid extraction path 13 is temporarily stored, and the temperature adjusting tank from the bottom of the temperature adjusting tank 23A. The temperature control / circulation pump 23B provided in the temperature control path 24 piped so that the etching solution is returned into 23A, and both the heating and cooling functions provided in the temperature control path 24 are combined. And a temperature controller 23C.
Thereby, the etching solution stored in the temperature control tank 23A is sent to the temperature controller 23C by the temperature control / circulation pump 23B, and the circulation returned to the temperature control tank 23A via the temperature controller 23C is repeated. Thus, the temperature of the etching solution is adjusted to a temperature that promotes precipitation and / or aggregation in the mixed atomizing portion 11B of the atomizing means 11.

Further, a liquid supply path 25 branched from between the temperature control / circulation pump 23B and the temperature controller 23C in the temperature control path 24 and connected to the mixed atomizing section 11B of the atomizing means 11 is provided. Switching valves 26 and 27 are provided in the temperature control path 24 and the liquid supply path 25 between the branch portion of the liquid supply path 25 and the temperature regulator 23C, respectively.
As a result, the etching solution stored in the temperature control tank 21A with the switching valve 26 opened and the switching valve 27 closed is sent to the temperature controller 23C by the temperature control / circulation pump 23B, and passes through the temperature controller 23C. Then, the temperature control circulation returned to the temperature control tank 23A is repeated. Then, by opening the switching valve 27 and closing the switching valve 26, the etching solution in the temperature control tank 23 </ b> A adjusted to a constant temperature suitable for precipitation and / or aggregation in the atomizing means 11 is controlled by the temperature control / circulation pump. 23B is sent to the mixing and atomizing unit 11B of the atomizing means 11 at a predetermined supply flow rate.

  According to the etching solution regenerating apparatus 10-1 according to the sixth embodiment configured as described above, the temperature adjusting means 23 and the atomizing means 11 are effectively combined to perform the atomization process at a constant temperature state. As a result, most of the supersaturated component of the silicon compound can be enlarged and / or aggregated more effectively. Thereby, the separation and removal of the silicon compound (component crystal) from the etching solution by the separator 12A of the separation means 12 can be adjusted to a controlled residual concentration.

FIG. 8 shows an etching solution regenerator 10-2 according to the seventh embodiment, and the regenerator 10-2 includes a concentration control unit 28 as shown in FIG. Since the other components are basically the same as those of the sixth embodiment, the same components are denoted by the same reference numerals, and redundant description is omitted.
That is, as shown in FIG. 8, the concentration control unit 28 selects the temperature regulator 23C, the temperature adjustment / circulation pump 23B, or the gas supply adjustment unit 29 that adjusts the supply speed of the gas supply unit 11C by setting human power. Can be controlled.

According to the etching solution regenerating apparatus 10-2 according to the seventh embodiment configured as described above, for example, by controlling the temperature of the temperature adjuster 23C of the temperature adjusting means 23 or by the temperature adjustment / circulation pump 23B. The atomizing means 12 is controlled by controlling the supply flow rate of the etching liquid to the mixed atomizing section 11B of the atomizing means 11 or by controlling the gas supply flow rate to the mixed atomizing section 11B by the gas supply adjusting section 29. The atomization state of the etching solution in the mixed atomization unit 11B can be controlled. And the silicon compound density | concentration of reproduction | regeneration etching liquid can be controlled by controlling one or both of these.
That is, it becomes possible to arbitrarily control the silicon compound concentration of the regenerated etching solution by setting input to the concentration control unit 28. By controlling the silicon compound concentration, it is possible to arbitrarily adjust the silicon compound concentration without adding a new etching solution or partially discarding the etching solution. For example, it becomes possible to adjust each silicon compound concentration according to the etching selectivity of each processor performing the etching process of the silicon wafer W.

FIG. 9 shows an etching solution regenerating apparatus 10-3 according to the eighth embodiment. In the regenerating apparatus 10-3, as shown in FIG. 9, the separation of the silicon compound from the etching solution by the separating means 12 is repeated several times. I am doing so. Since the other components are basically the same as those of the sixth embodiment, the same components are denoted by the same reference numerals, and redundant description is omitted.
That is, as shown in FIG. 9, the etching processing apparatus includes an intermediate part of the communication path 19 that connects the atomizing tank 11 </ b> A of the atomizing hand 11 and the separator 12 </ b> A of the separating means 12, and the storage tank 12 </ b> B of the separating means 12. The intermediate part of the liquid return path 21 is connected by a separation circulation path 30.

One end side of the separation circulation path 30 is branched and connected between the pressure feed pump 20 in the communication path 19 and the separator 12A of the separation means 12, and the other end side is etched by the liquid return pump 22 in the liquid return path 21. Branch connection is made on the 100 side.
Then, as shown in FIG. 9, both paths 19, 30 near the branch connection part of the separation circulation path 30 from the communication path 19 and both paths 21 near the branch connection part of the separation circulation path 30 from the liquid return path 21. , 30 are provided with switching valves 31-34, respectively.
Thus, the etching liquid stored in the storage tank 12B through the separator 12A is separated and circulated by operating the liquid return pump 22 with the switching valves 31 and 33 closed and the switching valves 32 and 34 opened. It is repeatedly sent through the path 30 to the separator 12A and returned to the storage tank 12B. That is, the separation and removal of the silicon compound from the etching solution by the separator 12A is repeated.

According to the etching solution regenerating apparatus 10-3 according to the eighth embodiment configured as described above, the etching solution taken out from the etching processing apparatus 100 is sprayed as in the fifth to seventh embodiments. Most of the silicon compound dissolved in the etching solution is precipitated and / or agglomerated by the atomization by the mixing atomization unit 11B of the conversion means 11 and the folded silicon compound is etched by the separator 12A of the separation means 12. Etching the deposited and / or agglomerated silicon compound by repeating the circulation of the etching solution stored in the storage tank 12B of the separation means 12 through the separation circulation path 30 after being separated and removed from the solution. Separation and removal from the liquid can be repeated.
Thereby, the removal rate of the silicon compound deposited and / or aggregated in the etching solution by the atomizing means 11 can be made close to 100%.

FIG. 10 shows an etching solution regenerating apparatus 10-4 according to the ninth embodiment. In the reproducing apparatus 10-4, pressure is applied to the etching solution taken out from the etching processing apparatus 100 as the atomizing means 11-1. By this, the compression atomization part 11-1 which atomizes etching liquid is provided. Since the other components are basically the same as those of the sixth embodiment, the same components are denoted by the same reference numerals, and redundant description is omitted.
That is, as shown in FIG. 10, the atomization tank 11-1A, the compression atomization part 11-1B that is provided in the atomization tank 11-1A and into which the etching solution is fed, and the mixed atomization part 11- And a liquid pressurizing pump 11-1C for supplying an etching liquid by applying a pressure set to 1B.

The compression atomization unit 11-1B is configured by spray nozzles or orifices having various structures. And the supply path 25 branched from the temperature control path | route 24 provided with the liquid pressurization pump 11-1C and the switching valve 27 is connected to this compression atomization part 11-1B.
As a result, after the temperature is adjusted by the temperature adjusting means 23, the etching liquid applied with pressure by the liquid pressurizing pump 11-1C and sent to the compression atomizing unit 11-1B is compressed into the compression atomizing unit 11-1B. Atomized by.

  According to the etching regenerator 10-4 according to the ninth embodiment configured as described above, the temperature adjusting means 23 and the atomizing means 11-1 are effectively combined to perform the atomization process at a constant temperature state. By doing so, most of the supersaturated component of the silicon compound can be more effectively enlarged and precipitated and / or aggregated. Thereby, the separation and removal of the silicon compound (component crystal) from the etching solution by the separator 12A of the separation means 12 can be adjusted to a controlled residual concentration.

FIG. 11 shows an etching solution regenerating apparatus 10-5 according to the tenth embodiment. Here, description will be made with reference to FIG. 7 as appropriate.
In the tenth embodiment, as the atomizing means 11-2, an ultrasonic atomizing unit (11-) that atomizes the etching solution by applying ultrasonic vibration to the etching solution taken out from the etching processing apparatus 100. 2B-11-2C). Since the other components are basically the same as those of the sixth embodiment, the same components are denoted by the same reference numerals, and redundant description is omitted.
That is, as shown in FIG. 11, the atomizing means 11-2 has an ultrasonic vibrator 11-2B and a drive source 11-2C that drives the ultrasonic vibrator 11-2B in the atomizing tank 11-2A. And an etchant supply unit 11-2D.

According to the etching solution regenerating apparatus 10-5 according to the tenth embodiment configured as described above, the etching solution supplied from the temperature adjusting unit 24 shown in FIG. 7 is supplied to the etching solution supply unit 11-2D. Then, the ultrasonic vibration is applied to the etching liquid by the ultrasonic vibrator 11-2B, so that the etching liquid is atomized. The atomized etching solution is temporarily stored in the atomization tank 11-2A and is sent to the separation means 12 by the pump 20 shown in FIG.
That is, atomization of the fine potential of the etching solution can be realized using ultrasonic vibration.
Thereby, the silicon compound dissolved in the etching solution can be efficiently precipitated and / or aggregated. Moreover, the optimal atomization state can be obtained by adjusting the drive frequency by appropriately changing the drive frequency of the drive source 11-2C.
Moreover, the atomization state of the atomization means 11-2 includes controlling the refinement | miniaturization of fog, and in the said 6th and 7th embodiment, the supply flow rate of the gas supplied to the mixing atomization part 12B. However, in the tenth embodiment, it can be controlled by the vibration frequency of the ultrasonic transducer 11-2B and its applied energy.

  According to the etching solution regenerating apparatus of the fifth to tenth embodiments described above, the etching solution regenerating apparatus 10 (10-1 to 10-4) is branched from the circulation path 42 of the etching processing apparatus 100 to the circulating path 42. In the case where the etching solution regenerating apparatus 10 (10-1 to 10-4) is directly incorporated in the circulation path 5 of the etching processing apparatus 100, the etching process is performed in the etching solution. The dissolved silicon compound can be easily and precisely removed from the phosphoric acid aqueous solution during the etching process. Therefore, when applied to the etching processing apparatus 100 as shown in FIG. 1, the filtration filter 3 is not clogged, and the etching processing apparatus can be continuously operated even for a large amount of continuous processing. The working efficiency of the processing apparatus 100 can be improved.

  In particular, by incorporating it into the circulation path 42 of the etching apparatus 100, the silicon compound concentration of the phosphoric acid aqueous solution during the etching process can be maintained constant, and a large number of lots can be continuously etched with a constant etching selectivity. can do. Therefore, it becomes possible to continue the etching process with high uniformity over many lots.

  Furthermore, since the regeneration to a high purity phosphoric acid aqueous solution can be performed during the etching process, the replacement work with a new phosphoric acid aqueous solution can be reduced, the stop time of the etching processing apparatus 100 can be reduced, and the productivity can be reduced. A high etching process can be realized. In particular, the reuse of the etching solution reduces the discarding of the etching solution, which is preferable from the viewpoint of protecting the natural environment. Since there is little replacement with a new etching solution, an economically advantageous operation is possible.

  Further, when the etching solution is regenerated by batch processing, a regenerated etching solution in which the silicon compound concentration is optimized can be generated under the control of the concentration control unit 28. As a result, the etching process from the beginning can be performed with a desired etching selection ratio without performing dummy etching, and the efficiency of the etching process can be improved.

  In the etching solution regenerating system of the present invention, the regenerated etching solution regenerated by the above-described etching solution regenerating apparatus is returned to the etching tank 41 of the etching processing apparatus 100 and reused, but in the processing tank in which the etching process is performed. In order to control the concentration (content) of the silicon compound dissolved in the etching solution accurately and uniformly, the concentration (content) of the silicon compound dissolved in the etching solution is grasped in real time in the process and etched. The supply amount (return amount) of the regenerated etching liquid regenerated by the liquid regenerating apparatus to the etching tank 41 is determined.

  In other words, the overflow tank 41-2 of the etching tank 41 is equipped with the dissolved substance content measuring means 310, and the measurement apparatus 310 uses the etching solution M (phosphoric acid aqueous solution) in the overflow tank 41-2. The content of the dissolved silicon compound (Si ion) is measured, and the supply amount (return amount) of the regenerated etching solution regenerated by the etching solution regenerating apparatus to the etching tank 41 is determined based on the content.

The dissolved substance content measuring means 310 in FIG. 1 always calculates the Si ion content (Si ion concentration) of the etching solution M (phosphoric acid aqueous solution) by the operation described in detail later, and calculates the calculated Si Based on the ion concentration, the amount of the etching solution regenerated by the regenerating apparatus 47 (regenerated etching solution) to be returned to the etching tank 41 is determined. That is, an electronic control valve 70 is attached to the outlet connection pipe of the regenerator 47 provided in the branch path 46, and the content of Si ions calculated by the dissolved substance content measuring means 3 (calculation data C). Is sent to the CPU 61, and from the reproducing device 47, the CPU 61 sets the Si ion concentration in the etching solution M in the processing tank 41-1 to a constant concentration based on the content of Si ions and information stored in advance. The amount of the etching solution to be returned to the etching tank 41 is determined, a control signal S is sent to the electronic control valve 70, and a valve opening / closing command is issued. As a result, the amount of the regenerated etching solution determined by the CPU 61 is returned from the regenerating device 47 to the processing tank 41-1 of the etching tank 41. By repeating this operation in a short time, the Si ion concentration in the etching solution M in the processing tank 41-1 is controlled accurately and constantly, the etching rate is maintained and managed, and the lifetime of the etching solution is also increased. become longer. Specifically, it is possible to perform efficient etching with the Si ₃ N ₄ film and the Si ₃ N ₄ film precision while managing kept constant etching selectivity with respect to the SiO ₂ film.

  FIG. 2 is an enlarged view of a portion where the dissolved substance content measuring means 310 is mounted on the etching tank 41 (overflow tank 41-2), and FIG. 3 is a system configuration diagram of the dissolved substance content measuring means 310.

  The dissolved substance content measuring means 310 used in the present invention is substantially composed of the optical unit 1 and the data processing unit 2.

  The optical unit 1 includes a light source 311, a prism 312, and a light receiving element 313. As the light source 311, for example, an ultraviolet LED that emits single wavelength light having a predetermined wavelength, a deuterium lamp that emits continuous wavelength light, a halogen lamp, a xenon lamp, or the like is used. When a light source that emits continuous wavelength light such as a deuterium lamp, a halogen lamp, or a xenon lamp is used, an ultraviolet spectrometer (grating) or the like for extracting light with a predetermined wavelength is usually used. Moreover, the wavelength of ultraviolet rays is usually selected from the range of 120 to 400 nm.

  A part of the bottom wall 48 of the overflow tank 41-2 is cut out and a prism 132 is embedded therein (that is, a part of the bottom wall 48 of the overflow tank 41-2 is a window portion by the prism 312. ). The ultraviolet ray R1 incident on the prism 312 from the light source 311 arranged on the surface 312a on one side of the prism 312 is reflected by the transmitted light R2 transmitted through the boundary surface 312b of the prism 312 that forms the interface with the etching solution M and the boundary surface 32b. And reflected light R3. The reflected light R3 is received by the light receiving element 313 disposed on the other surface 312c of the prism 312, converted into a photocurrent corresponding to the intensity thereof, and output as an electrical signal.

By Snell's law, one of the medium (refractive index: n ₁₎ of the refractive index is different from the two media from the other medium (refractive index: n ₂₎ If the light on the incident, the incident angle n _1> n ₂ is When the angle is smaller than the total reflection angle or when n ₁ <n ₂ , the light is not totally reflected and the light is transmitted and the reflectance is extremely reduced. However, the present inventors have fixed the light incident angle. When n ₁ and n ₂ are close to each other, the reflectance increases when the refractive index difference between n ₁ and n ₂ increases, and the refractive index difference decreases. In the state where the reflectance decreases, that is, in the state where the total reflection condition is not satisfied, the light reflectance (transmittance) changes sensitively to the change in the refractive index of both media, and the silicon in the phosphoric acid aqueous solution changes. The change in the content of (Si) is a change in the reflectance of light at the interface between the phosphoric acid aqueous solution and the prism. We, the correlation between them was found to be very high.

  The dissolved substance content measuring means 310 is completed and arranged based on such knowledge, and the change in the content (concentration) of Si ions in the etching solution M (phosphoric acid aqueous solution) is determined by the etching solution M ( This is expressed as a change in the reflectance of light at the boundary surface 312 b between the phosphoric acid aqueous solution) and the prism 312. That is, a prism 312 having a refractive index close to the refractive index is brought into contact with the etching solution M, and light is incident on the boundary surface 312b of the prism 312 that forms an interface with the etching solution M at a predetermined incident angle (θ). The content (concentration) of Si ions in the etching solution M can be detected from the intensity of the obtained reflected light R3.

Here, the prism 312 has a refractive index (N ₁ ) having a relationship of N ₁ <N ₂ with the refractive index (N ₂ ) of the etching solution M, or a relationship of N ₁ > N _2. (N ₁ and N ₂ here are the refractive index at the temperature of the measurement system and the wavelength of the light source (the wavelength of the incident light R 1)).

When N ₁ <N ₂ , the reflected light R3 is obtained regardless of the incident angle (θ) of the incident light R1, but in this case, the incident angle (θ) is effective in terms of the apparatus configuration. Generally, it is set to about 75 to 15 ° due to restrictions on the arrangement of optical components. On the other hand, when N ₁ > N ₂ , the incident angle (θ) of the incident light R1 needs to be smaller than the total reflection angle. In this case, the incident angle (θ) of the incident light R1 is It is desirable that the angle difference from the total reflection angle is approximately within 45 °.

However, in the prism 312, the absolute value (| N ₁ −N ₂ |) of the difference between the refractive index (N ₁ ) and the refractive index (N ₂ ) of the etchant M is 0.30 or less (preferably 0.15 or less). , More preferably 0.05 or less). This is because, when the absolute value of the refractive index difference (| N ₁ −N ₂ |) exceeds 0.30, a slight change in the refractive index of the etching solution M hardly appears as an intensity change of the reflected light R3. Because.

  When the etching solution M is a phosphoric acid aqueous solution, for example, a quartz prism is used as the prism 312. When the light source wavelength (incident light R1 wavelength) is 250 nm, the refractive index (25 ° C.) of the phosphoric acid aqueous solution (phosphoric acid concentration: 86 ± 0.5 wt%) is 1.469, and the refractive index of the quartz prism (25 ° C.) is 1.508, and the total reflection angle of light is 77 degrees. In this case, when the incident angle (θ) of the incident light R1 is 75 degrees, the reflectance is 10%, and the amount of change in absorbance calculated from the change in reflectance when the refractive index of phosphoric acid changes by 0.001 is 0.046.

  When the material of the prism is quartz, if the wavelength of the incident light R1 is 190 nm or less, the difference in refractive index between quartz and the phosphoric acid aqueous solution becomes small, and the change in reflectance can be observed with higher sensitivity. For example, when the wavelength of the incident light R1 is 187 nm, the refractive index (25 ° C.) of the phosphoric acid aqueous solution (phosphoric acid concentration: 86 ± 0.5 wt%) is 1.548, and the refractive index (25 ° C.) of the quartz prism is At 1.571, the total reflection angle is 80 degrees. In this case, when the incident angle of the incident light R1 is 75 degrees, the reflectivity is 1.6%, and the change in absorbance calculated from the change in reflectivity when the refractive index of phosphoric acid is changed by 0.001 is 0. .057.

  Further, when the wavelength of the incident light R1 is 190 nm or less, the refractive index of water contained in the phosphoric acid aqueous solution increases, and the change in the moisture content and the change in the water temperature are reflected according to the measurement result. Accordingly, a plurality of incident lights R are selected with a wavelength of 190 nm as a boundary (that is, two or more wavelengths including at least one within a wavelength range of 170 to 190 nm and at least one outside the wavelength range (greater than 190 nm) are selected. ), Measurement errors due to changes in moisture content or changes in the temperature of the sample can be corrected using the spectral changes observed in these lights.

  When the material of the prism is sapphire, the total reflection angle when the wavelength of the incident light R1 is 250 nm is 53 degrees. In this case, when the incident angle (θ) of the incident light R1 is 45 degrees, Similar to the embodiment using the quartz prism, the reflectance is 10% or less. However, since the difference between the refractive index of sapphire and the refractive index of the sample is as large as 0.377, the refractive index of phosphoric acid changed by 0.001. The amount of change in absorbance calculated from the change in reflectance in this case is as small as 0.004, and a slight change in refractive index of the sample tends not to appear as a significant change in absorbance.

  The data processing unit 2 amplifies the light intensity signal output from the light receiving element 313 of the optical unit 1 and corresponding to the intensity of the reflected light R3, and converts the analog signal output from the amplifier 14 into a digital signal. An A / D converter 15 and a data processing device 16 that receives a digital signal from the A / D converter 15 are provided.

  The data processing device 16 substantially includes a microprocessor 17, a RAM 18, a ROM 19, and an input device 210, and the microprocessor 17 performs an operation for deriving the content of dissolved substances in the etching solution M. I do. The RAM 18 stores a calibration curve type and various data. The ROM 19 stores a program for operating the microprocessor 17 and the like. The input device 20 includes a keyboard for inputting data and various commands.

Data processing in the data processor 16 is performed as follows.
When the light source 311 emits ultraviolet light having a predetermined wavelength, the light receiving element 313 outputs a signal proportional to the intensity of the reflected light R3 reflected by the boundary surface 312b of the prism 312 that forms an interface with the etching solution M in the overflow tank 41-2. Generate. This signal is amplified by the amplifier 14, converted to a digital signal by the A / D converter 15, and input to the microprocessor 17 of the data processing device 16.

The microprocessor 17 performs a calculation process according to the following expression 1 on the digital signal input from the A / D converter 15 to calculate the absorbance S (the intensity of the reflected light R3).
[Equation 1]
S = -log ₁₀ A / B ..................... Formula 1

  In Equation 1, A is a reflection intensity value (measured value) obtained from the etching solution M, and B is a reflection intensity value obtained from a reference solution that does not contain dissolved substances. B is data measured in advance, and is stored in the RAM 18 of the data processing device 16. When the etching solution M is an aqueous phosphoric acid solution, the reference solution is an unused aqueous phosphoric acid solution that has not been subjected to an etching process.

Next, based on the absorbance (reflection intensity) S obtained by Expression 1, the following Expression 2 is calculated to calculate the content (concentration) C of the dissolved substance in the etching solution M.
[Equation 2]
C = F (S) …………………… Formula 2

In Formula 2, F (S) is a calibration curve formula of a dissolved substance (for example, silicon (Si)), includes a first-order term and a higher-order term for S, and is represented by the following Formula 3, for example.
[Equation 3]
C = ΣαS + ΣβS ² + ΣγS ³ + …… + Z ₀ ……………………

In Equation 3, S is data obtained by Equation 1. α, β and γ are coefficients of the calibration curve equation. Z ₀ is a constant term. Each data included in Equation 3 is obtained in advance by the measurement device 3 using a standard sample of a sample solution with a known dissolved substance content, and is stored in the RAM 18 of the data processing device 16.

  Data of the dissolved substance content (concentration) C calculated in this way by the data processing device 16 is sent to the CPU 61 that controls the opening and closing of the electronic control valve 70 provided in the outlet connection pipe of the regeneration device 47 described above. The CPU 61 determines the amount of the regenerated etching solution to be returned from the regenerating device 47 to the etching tank 41 as described above, sends a control signal to the electronic control valve 70, and issues a valve opening / closing command.

  By repeating the above operation in a short time, the Si ion concentration in the etching solution M in the processing tank 41-1 is controlled precisely and constantly.

  In the present invention, the optical part 1 ′ shown in FIG. 4 may be used as the optical part of the dissolved substance content measuring means 3. 4, the same reference numerals as those in FIG. 1 denote the same or corresponding parts.

  In the optical unit 1 ′, ultraviolet rays incident on the prism 312 are subjected to multiple reflection between a boundary surface 312b that forms an interface with the etching solution M of the prism 312 and a facing surface 312d that faces the boundary surface 312b. Yes. With such a configuration, the intensity change of the reflected light R3 'with respect to the change in the refractive index of the etching solution M can be increased, and the measurement accuracy can be increased.

  As described above, in the etching solution regeneration system of the present invention, the dissolved substance in the etching solution used for the etching process is forcibly separated from the etching solution, and the regenerated etching liquid from which the dissolved substance is removed or reduced is subjected to the etching process again. In the circulating use of the etching solution used, the concentration of the dissolved substance in the etching solution in the processing tank in which the etching process is performed is controlled precisely and constantly, so that the etching rate is maintained and controlled at a high precision and efficiency. An etching process can be performed.

  In the apparatus of FIG. 1, the dissolved substance content measuring means 310 is incorporated in the bottom wall portion of the overflow tank 41-2 of the etching tank 41 so that the dissolved substance content (concentration) in the etching solution in the processing tank 41-1. ) Is measured, but the dissolved substance content measuring means 310 is incorporated in a part of the circulation path 42 to measure the content (concentration) of the dissolved substance in the etching solution flowing through the circulation path 42. Also good.

DESCRIPTION OF SYMBOLS 1 Optical part 2 Data processing part 10, 10-1, 10-2, 10-3, 10-4, 10-5, 47 Etching liquid reproduction | regeneration apparatus 14 Amplifier 16 Data processing apparatus 17 Microprocessor 41-1 Processing tank 41- 2 Overflow tank 42 Circulation path 46 Branch path 48 Bottom wall 61 CPU
70 Electronic control valve 310 Dissolved substance content measuring means 311 Light source 312 Prism 312b Prism boundary surface 313 Light receiving element R1 Ultraviolet R2 Reflected light M Etching solution

Claims (2)

A high-temperature etching solution in an etching tank that contains the material to be etched is immersed and accommodated through a circulation path, and is filtered and re-heated in the circulation path while being recirculated. An etching solution regeneration system attached to an etching apparatus for performing an etching process on the material to be etched while repeating,
Etching solution regenerating means for forcibly separating the dissolved substance in the etching solution taken out from the etching tank or from the middle of the circulation path from the etching solution, and generating a regenerated etching solution in which the dissolved substance is removed or reduced, and
Dissolved substance content measuring means for measuring the content of a substance dissolved in the etching solution in the etching tank or the circulation path;
Control means for determining the amount of the etchant returned from the etchant regeneration means to the etching tank based on the dissolved substance content in the etchant measured by the dissolved substance content measurement means;
When the dissolved substance content measuring means is a prism, the absolute value (| N ₁ −N ₂ |) of the difference between the refractive index (N ₁ ) and the refractive index (N ₂ ) of the etching solution is 0.30 or less. An optical unit that uses a prism and makes light from a light source incident on the boundary surface of the prism that forms an interface with the etching solution, and detects the reflectivity of reflected light from the prism boundary surface, and a detection signal of the optical unit And a data processing unit for calculating the dissolved substance content in the etching solution based on the above.   The material to be etched is a semiconductor material in which a silicon nitride film and a silicon oxide film are formed, and the etching process is an etching process for selectively removing the silicon nitride film on the semiconductor material, and the etching solution is a phosphoric acid aqueous solution. The etching solution regeneration system according to claim 1, wherein the prism is a quartz prism.

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