JP5939373B2 - Electronic material cleaning method and cleaning apparatus - Google Patents

Description

  The present invention relates to a resist on an electronic material in the field of electronic component manufacturing that requires extremely strict control in the manufacturing process, specifically in the field of manufacturing semiconductor substrates, liquid crystal substrates, organic EL substrates, photomask substrates, hard disk substrates, and the like. The present invention relates to a cleaning method and a cleaning apparatus for efficiently peeling and removing the water.

In recent years, as the miniaturization, higher functionality, and higher performance of products progress in the semiconductor manufacturing field, the manufacturing process becomes complicated, and the number of processes and time required for manufacturing have been increasing. For this reason, the amount of chemicals used in the manufacturing process, such as sulfuric acid and hydrogen peroxide solution, has been increasing, and the waste liquid treatment has become a problem.
Conventionally, resist cleaning on electronic materials in the manufacturing field of semiconductor substrates, liquid crystal substrates, organic EL substrates, photomask substrates, hard disk substrates and the like has been performed using a sulfuric acid solution containing persulfuric acid, which is a mixture of sulfuric acid and hydrogen peroxide. A certain SPM solution (Sulfuric acid / hydrogen peroxide mixture) is used, but the amount of SPM solution used in the resist stripping process tends to increase. If the SPM solution continues to be used, the concentration of persulfuric acid decreases due to decomposition. In the SPM solution, since hydrogen peroxide water is added as appropriate, water is generated, the sulfuric acid concentration is lowered, and the efficiency of persulfuric acid generation by hydrogen peroxide is reduced. Therefore, it is necessary to periodically replace the SPM solution.
Moreover, although the method of preventing the fall of the density | concentration of hydrogen peroxide by adding ozone to the said SPM solution and preventing it is proposed (for example, refer patent document 1), even if it can delay chemical solution exchange time, chemical solution exchange The necessity of cannot be avoided.
On the other hand, as an alternative technique to the conventionally used cleaning liquid (SPM solution), it has been proposed that the resist is stripped and decomposed using a sulfuric acid electrolyte, which is a persulfuric acid-containing sulfuric acid solution obtained by electrolyzing a sulfuric acid solution. (For example, Patent Documents 2 and 3). By using the sulfuric acid electrolytic solution, the sulfuric acid concentration is not lowered and the persulfuric acid concentration is stabilized, so that a high resist stripping / decomposing ability can be stably obtained. For this reason, it has been found that not only the conventional low-to-medium concentration ion-implanted resist but also the high-concentration ion-implanted resist can be stripped and decomposed by skipping the ashing process.

Japanese Patent Laid-Open No. 1-189921 JP 2006-114880 A JP 2007-266495 A

However, as described above, in the recent semiconductor manufacturing process, the manufacturing process becomes more complicated with the miniaturization, higher functionality, and higher performance of products, and higher resist stripping ability is required. With the increase in volume, the drainage treatment has become a problem. In addition, since the number of manufacturing steps has increased, the time required for manufacturing tends to be long. Therefore, it is strongly desired to reduce the time required for each step including the resist stripping step.
In addition, when resist removal cleaning is performed on an ashless substrate using sulfuric acid electrolyte, a large amount of resist is peeled off or dissolved in the sulfuric acid electrolyte, so it is desirable to decompose the resist in a short time. ing.

The present invention has been made in view of the above-described conventional circumstances, and an object of the present invention is to provide an electronic material cleaning method and an electronic material cleaning apparatus that can significantly reduce the time required for resist stripping processing of an electronic material.
Another object of the present invention is to provide a method and an apparatus for improving the resist stripping effect and for dissolving a dissolved resist in a short time in ashless cleaning.

That is, of the electronic material cleaning methods of the present invention, the first invention is to clean the electronic material by bringing a persulfuric acid-containing sulfuric acid solution obtained by electrolyzing a sulfuric acid solution of 70% by mass or more into contact with the electronic material. In the electronic material cleaning method
The cleaning by the contact is performed by immersing the electronic material in a cleaning tank in which the sulfuric acid solution containing persulfuric acid is contained, and during the cleaning, the liquid temperature is higher than 130 ° C. to 190 ° C. (however, the persulfuric acid content is included) The cleaning is performed so that ozone gas is in contact with the persulfuric acid-containing sulfuric acid solution supplied to the washing tank while the persulfuric acid-containing sulfuric acid solution is heated to a temperature equal to or lower than the boiling point of the sulfuric acid solution. It is characterized by supplying ozone gas into the tank .

The electronic material cleaning method of the second aspect of the present invention is the method of cleaning the electronic material according to the first aspect of the present invention, wherein the sulfuric acid solution used for the cleaning is electrolyzed again to regenerate the persulfuric acid-containing sulfuric acid solution. It is characterized by being reused.
The electronic material cleaning method of the third aspect of the present invention is characterized in that, in any of the first and second aspects of the present invention, the ozone gas supplied into the cleaning tank is heated to 50 ° C. or higher. And
According to a fourth aspect of the present invention, there is provided the electronic material cleaning method according to any one of the first to third aspects of the present invention, wherein the ozone gas bubbled into the persulfuric acid-containing sulfuric acid solution in the cleaning tank is supplied.
The electronic material cleaning method according to a fifth aspect of the present invention is the electronic material cleaning method according to any one of the first to fourth aspects, wherein at least an anode of the electrodes used for the electrolysis of the sulfuric acid solution is a conductive diamond electrode. And
The electronic material cleaning method of the sixth aspect of the present invention is characterized in that, in any one of the first to fifth aspects of the present invention, the electronic material is an electronic material that has not been subjected to an ashing treatment.

An electronic material cleaning apparatus according to a seventh aspect of the present invention includes an electrolysis unit that electrolyzes a sulfuric acid solution of 70% by mass or more;
A feed line for feeding a sulfuric acid solution containing persulfuric acid obtained by electrolysis in the electrolysis unit;
A washing tank containing a persulfuric acid-containing sulfuric acid solution which is fed by the feed line and heated to a liquid temperature of more than 130 ° C. to 190 ° C. (but not higher than the boiling point of the persulfuric acid-containing sulfuric acid solution);
An ozone generator for generating ozone;
A temperature of 130 ° C. to 190 ° C. (the boiling point of the persulfuric acid-containing sulfuric acid solution) that is connected to the cleaning tank and the ozone generated in the ozone generation unit is fed into the cleaning tank through the feed line. characterized in that it comprises a an ozone supply unit for supplying the cleaning tank so as to be in contact with the sulfuric acid solution containing persulfuric acid below).

According to an eighth aspect of the present invention, there is provided the electronic material cleaning apparatus according to the seventh aspect , further comprising a return line for returning the persulfuric acid-containing sulfuric acid solution in the cleaning tank to the electrolysis unit.
The electronic material cleaning apparatus according to a ninth aspect of the present invention is the electronic material cleaning apparatus according to the seventh or eighth aspect of the present invention, wherein the persulfuric acid-containing sulfuric acid in the cleaning tank is heated by heating the persulfuric acid-containing sulfuric acid solution accommodated in the cleaning tank. It is characterized by comprising a persulfuric acid heating section that heats the solution to a temperature higher than 130 ° C. to 190 ° C. (but not higher than the boiling point of the persulfuric acid-containing sulfuric acid solution).
An electronic material cleaning apparatus according to a tenth aspect of the present invention is the electronic device cleaning apparatus according to the ninth aspect , wherein the persulfuric acid heating section has an external heater for heating the persulfuric acid-containing sulfuric acid solution supplied into the cleaning tank. Features.
The electronic material cleaning apparatus according to an eleventh aspect of the present invention is the internal heater according to the ninth or tenth aspect of the present invention, wherein the persulfuric acid heating section heats the persulfuric acid-containing sulfuric acid solution accommodated in the cleaning tank. It is characterized by having.
The electronic material cleaning apparatus according to a twelfth aspect of the present invention is the ozone according to any one of the seventh to eleventh aspects, wherein the ozone supplied to the persulfuric acid-containing sulfuric acid solution in the cleaning tank is heated to 50 ° C or higher. A heating unit is provided.
In the electronic material cleaning apparatus according to a thirteenth aspect of the present invention, in any one of the seventh to twelfth aspects of the present invention, the ozone supply unit bubbles the ozone gas and supplies it to the persulfuric acid-containing sulfuric acid solution in the cleaning tank. A bubbling nozzle that is made of sintered glass, PTFE (polytetrafluoroethylene), or PFA (perfluoroalkoxyethylene copolymer resin). Features.
The electronic material cleaning device according to a fourteenth aspect of the present invention is the electronic material cleaning apparatus according to any one of the seventh to thirteenth aspects, wherein at least an anode of the electrodes provided in the electrolysis unit is composed of a conductive diamond electrode. And
The electronic material cleaning device according to a fifteenth aspect of the present invention is the electronic material cleaning apparatus according to any one of the seventh to fourteenth aspects, wherein the ozone supply unit supplies ozone to the persulfuric acid-containing sulfuric acid solution and the feed line supplies the ozone. The supply direction of the persulfuric acid-containing sulfuric acid solution into the cleaning tank intersects, and the ozone supply unit and the feed line are arranged so that the supplied ozone and the supplied persulfuric acid-containing sulfuric acid solution immediately exchange with each other. It is arranged.

According to the present invention, by supplying ozone gas to a persulfuric acid-containing sulfuric acid solution (sulfuric acid electrolytic solution) generated by electrolysis of a sulfuric acid solution, an SPM solution or a sulfuric acid electrolytic solution that has been conventionally used for resist stripping can be used alone. Compared to the time of use, it is possible to greatly reduce the time (liquid recovery time) required for resist stripping and decomposition from the electronic component material. This is probably because a higher oxidizing power, a larger amount of persulfuric acid, and more radicals are generated.
The reason why a large amount of radicals are generated is that the sulfuric acid radical further promotes the decomposition of ozone by the sulfuric acid radicals and OH radicals generated by the decomposition of persulfuric acid at the bubble interface where the persulfuric acid in the sulfuric acid electrolyte contacts the ozone gas bubbles. And OH radicals are presumed to be generated. Therefore, in the present invention, it is necessary to blow ozone into a place where radicals are generated. The details of the mechanism are not always clear.
Therefore, by supplying ozone gas to the sulfuric acid electrolyte (preferably bubbling), not only ashing wafers but also ashing-less wafers can be processed in a short time. For example, the number of wafers processed per hour (throughput) ) Can be greatly increased.

It is described in Patent Document 1 described above that ozone is supplied into a high-temperature SPM solution and reacted with sulfuric acid to suppress the consumption of hydrogen peroxide and extend the life of the SPM solution. However, in the present invention, ozone is supplied to the sulfuric acid electrolyte for the purpose of improving the oxidizing power rather than prolonging the life of the liquid, so the aim of both technologies is different. Also in the technique in Patent Document 1, when cleaning wastewater is reused as in conventional SPM cleaning, hydrogen peroxide is decomposed and water is generated, so the sulfuric acid concentration gradually decreases and the cleaning power decreases. The difference from the present invention is clear.
The present invention is further described below.

[Formation of persulfuric acid solution]
The persulfuric acid used in the present invention refers to peroxomonosulfuric acid (H ₂ SO ₅ ) and peroxodisulfuric acid (H ₂ S ₂ O ₈ ). These peroxomonosulfuric acid, peroxodisulfuric acid and ozone all have high oxidizing power.
Peroxomonosulfuric acid can be produced by the reaction of sulfuric acid and ozone as shown in the following reaction formula.
3H ₂ SO ₄ + O ₃ → 3H ₂ SO ₅
On the other hand, peroxodisulfuric acid can be produced by electrolytic oxidation of a sulfuric acid solution as shown in the following reaction formula.
2SO ₄ ²⁻ → S ₂ O ₈ ²⁻ + 2e ⁻
Or
2HSO ₄ ⁻ → S ₂ O ₈ ²⁻ + 2H ⁺ + 2e ⁻

When peroxodisulfate ion (S ₂ O ₈ ²⁻ ) is subjected to strong energy such as ultraviolet irradiation or high-temperature heating, it is excited and self-decomposed as shown in the following formula to generate a sulfate radical (SO ₄ .−).
S ₂ O ₈ ²⁻ → 2SO ₄・⁻
The generated sulfuric acid radical decomposes the resist dissolved in the solution, reacts with ozone at the gas-liquid interface between the ozone gas and the persulfuric acid solution, and promotes the decomposition of ozone to generate OH radical (OH.). The radical decomposition reaction proceeds in an accelerated (spiral form). Therefore, it is considered that the radical amount is remarkably increased as compared with the case where the sulfuric acid electrolyte is used alone, and the resist can be decomposed in a short time.

  The sulfuric acid concentration of the sulfuric acid solution to be electrolyzed is preferably about 70 to 96% by mass, particularly about 80 to 92% by mass. If the sulfuric acid concentration of the sulfuric acid solution is too low, the resist dissolving power of the sulfuric acid solution will be reduced, making it difficult to obtain a sufficient resist stripping effect. Further, if the sulfuric acid concentration of the sulfuric acid solution is higher than the above upper limit, it is not preferable because there is a risk of current efficiency reduction or electrode wear due to a decrease in ion flux.

In the present invention, the persulfuric acid-containing sulfuric acid solution (sulfuric acid electrolyte) used in the resist stripping step is a sulfuric acid solution (usually, a sulfuric acid dissolved in pure water or ultrapure water is used as this sulfuric acid solution). It is manufactured by electrolysis of It is preferable that the sulfuric acid solution in which the concentration of persulfuric acid in the solution is reduced by using it for resist stripping is regenerated by electrolysis and recycled. In this case, the sulfuric acid solution having a reduced persulfuric acid concentration is fed from the washing tank to the electrolysis unit through the circulation line.
In the electrolysis section, the anode and cathode are brought into contact with the sulfuric acid solution, and electrolysis is performed by passing an electric current between the electrodes to oxidize sulfate ions or hydrogen sulfate ions to generate peroxodisulfate ions. Regenerate high sulfuric acid solution. The regenerated persulfuric acid-containing sulfuric acid solution is returned to the cleaning tank through the circulation line and reused for resist stripping and cleaning. Thus, by repeatedly circulating the persulfuric acid-containing sulfuric acid solution between the cleaning tank and the electrolysis unit, the persulfate ion composition of the persulfuric acid-containing sulfuric acid solution used for the stripping cleaning can be obtained at a high concentration suitable for resist stripping cleaning. In this state, efficient cleaning can be continued.

In an electrolysis unit that performs electrolysis of a sulfuric acid solution (including a persulfuric acid-containing sulfuric acid solution), electrolysis is performed with a pair of an anode and a cathode. The material of the electrode is not particularly limited. However, when platinum, which is widely used as an electrode, is used as an anode, peroxodisulfate ions cannot be efficiently produced and platinum is eluted. is there. When peroxodisulfuric acid is produced by electrolytic oxidation of sulfuric acid solution, in order to prevent the elution of impurities from the electrode, a conductive diamond electrode having heat resistance, acid resistance and oxidation resistance is preferably used as at least the anode of the electrode. It is done. When a conductive diamond electrode is used at least for the anode, the conductive diamond electrode has the advantage that it is chemically stable and does not elute impurities in concentrated sulfuric acid or persulfuric acid-containing sulfuric acid solution, and the durability of the electrode can be increased. It has been reported that peroxodisulfate ions are generated from sulfate ions or hydrogen sulfate ions under conditions of a current density of about 0.2 A / cm ² with a conductive diamond electrode (Ch. Comninellis et al., Electrochemical and Solid- State Letters, Vol. 3 (2) 77-79 (2000)).

  As a conductive diamond electrode, a semiconductor material such as a silicon wafer is used as a substrate, and a conductive diamond thin film is synthesized on the surface of the substrate to a thickness of 20 μm or more. Mention may be made of stand-type conductive polycrystalline diamond. The conductive diamond thin film is one obtained by doping boron or nitrogen during synthesis of the diamond thin film to impart conductivity, and usually boron doped one. If the doping amount is too small, technical significance does not occur. If the doping amount is too large, the doping effect is saturated. Therefore, a doping amount in the range of 50 to 20,000 ppm with respect to the carbon amount of the diamond thin film is suitable. . In the present invention, the conductive diamond electrode is usually a plate-like one, but a network structure having a plate-like shape can also be used.

In the electrolytic treatment in the electrolysis section, the current density on the surface of the conductive diamond electrode is 10 to 100,000 A / m ² , the sulfuric acid solution is parallel to the diamond electrode surface, and the liquid flow rate is 10 to 10,000 m / hour. It is desirable to perform contact treatment with.

  In addition, there is no particular limitation on the time for resist removal and cleaning with this persulfuric acid-containing sulfuric acid solution, the resist adhesion state of the material to be cleaned, the presence or absence of ashing treatment prior to this cleaning, the persulfuric acid concentration of Although it varies depending on the solution temperature, the conditions of the subsequent wet cleaning process, etc., it is usually preferably 5 to 30 minutes, particularly about 10 to 20 minutes in batch cleaning.

  As described above, the temperature suitable for the resist peeling and cleaning with the sulfuric acid solution containing persulfuric acid is more than 130 ° C. to 190 ° C. However, if the above-mentioned electrolysis temperature is excessively high, the electrolysis efficiency decreases, The electrode wear also increases. However, if the electrolysis temperature is excessively low, the heating energy when used for resist stripping and cleaning increases, so the temperature of the solution electrolyzed in the electrolysis part is 10 to 90 ° C, particularly 40 to 80 ° C. It is preferable.

  Therefore, when the sulfuric acid solution is circulated between the washing tank and the electrolytic section, a heat exchanger is provided in the circulation line, the sulfuric acid solution fed to the electrolytic section is cooled and the persulfuric acid-containing sulfuric acid fed to the washing apparatus is cooled. The solution can be heated. However, a heating unit that heats the sulfuric acid solution and a cooling unit that cools the sulfuric acid solution may be provided.

[Temperature of persulfuric acid-containing sulfuric acid solution]
The persulfuric acid-containing sulfuric acid solution desirably has a liquid temperature of more than 130 ° C. to 190 ° C. during washing. The liquid temperature is adjusted by heating a sulfuric acid solution containing persulfuric acid. When the liquid temperature of the sulfuric acid solution containing persulfuric acid in the washing tank is 130 ° C. or lower, not only the amount of sulfuric acid radicals and OH radicals generated by the decomposition of persulfuric acid is small, but not enough oxidizing power can be obtained. In addition, the effect of promoting ozone decomposition cannot be obtained sufficiently. On the other hand, if it exceeds 190 ° C., the persulfuric acid-containing sulfuric acid solution is likely to boil, and the member may be deformed by heat, which is not preferable. Therefore, it is desirable that the lower temperature of the persulfuric acid-containing sulfuric acid solution is over 130 ° C and the upper limit is 190 ° C. However, if the sulfuric acid concentration is low, it may boil even below 190 ° C, so it should be 190 ° C or lower and below the boiling point.

  The means for heating the persulfuric acid-containing sulfuric acid solution is not particularly limited, but the persulfuric acid-containing sulfuric acid solution supplied to the washing tank is heated with an external heater, and the persulfuric acid-containing sulfuric acid solution in the washing tank is internally contained. What heats with a heater is mentioned. In order to perform the treatment quickly and to perform cleaning while circulating the sulfuric acid solution containing persulfuric acid between the washing tank and the electrolysis unit, the sulfuric acid solution containing persulfuric acid supplied by an external heater is heated. It is desirable to provide an internal heater if desired. There is no particular limitation on the internal heater that heats the sulfuric acid solution containing persulfuric acid in the washing tank, but a heating heater can be used, and when installed in the washing tank, a quartz casting heater is used. It may be used, or a Teflon (registered trademark) -coated heater may be used. Although there is no restriction | limiting in particular also in the external heater installed in the feed line which supplies the persulfuric acid containing sulfuric acid solution to a washing tank, The heater etc. which used the infrared lamp made from quartz can be used.

[Ozone gas generation]
There is no restriction | limiting in particular in the generation mechanism of the ozone gas used by this invention. Ozone gas generated by silent discharge of oxygen gas may be used, or ozone gas generated by electrolyzing water may be used.
The purity of the oxygen gas used in the silent discharge method is not particularly limited, but it is more preferable to use an oxygen gas having a purity of 99.99% by volume or more.
Although there is no restriction | limiting in particular in the purity of the water used by an electrolysis system, More preferably, it is desirable that the water quality is 18 MΩ · cm or more.
Although there is no restriction | limiting in particular in the density | concentration of ozone gas, It is desirable that it is 100 g / Nm < ³ > or more, More preferably, it is 200 g / Nm < ³ > or more. The ozone gas is usually about 20 ° C. However, in order to increase the oxidation reaction efficiency when supplied to the persulfuric acid-containing sulfuric acid solution, and in order not to make the temperature of the persulfuric acid-containing sulfuric acid solution uneven, use a heater or the like beforehand. The temperature may be increased by heating. The O ₃ gas concentration in the discharge method is about 14% by volume, and if this level of O ₃ gas is used, the risk of explosion is low, and the temperature can be raised up to 100 ° C. An excessively high temperature is not preferable because the half life of O ₃ gas is short in addition to safety.
By supplying relatively low-temperature ozone gas into the persulfuric acid solution, the internal heater can be effectively used for adjusting the temperature of the persulfuric acid solution.

[Ozone gas bubbling]
Further, in the present invention, by using a nozzle capable of efficiently bubbling ozone gas with fine bubbles in the cleaning tank, radicals are efficiently generated at the interface between the bubbles and the sulfuric acid electrolyte, so that a higher cleaning effect is obtained. Can be obtained.
In the present invention, due to its excellent cleaning effect, the cleaning method of the present invention can be applied to an electronic material that has not been subjected to an ashing treatment, and even in this case, the resist remains on the electronic material. In addition, the sulfuric acid electrolyte treatment with ozone gas bubbling can be performed reliably and in a short time, and the time required for a series of resist stripping treatments can be further shortened to perform efficient cleaning.

[Bubbling nozzle shape]
There is no particular limitation on the bubbling method of ozone gas in the cleaning tank. Although the pipe may be left in a cut shape, a bubbling nozzle is more preferable. The material of the bubbling nozzle is not particularly limited as long as it has heat resistance, acid resistance and oxidation resistance, but it is desirable to use a nozzle made of sintered glass, PTFE, PFA or the like.

[Washing tank]
The washing tank can be composed of one tank, but it can be constructed by arranging two or more washing tanks containing persulfuric acid-containing sulfuric acid solution, and ozone gas is supplied in the second and subsequent washing tanks. It may not be. Further, rinsing may be performed between these cleaning steps.
This peeling cleaning method is suitable for a batch method in which a plurality of electronic materials are cleaned at once. Batch cleaning is usually performed by immersing a plurality of electronic materials in a cleaning liquid in a cleaning tank.

[Electronic materials]
The electronic material to be cleaned in the present invention is an electronic material in which a resist pattern is formed in the manufacturing process of a semiconductor substrate, a liquid crystal display, an organic EL display, a photomask thereof, and the like.
Usually, the thickness of the resist film on the electronic material is about 0.1 to 5.0 μm, but is not limited to this thickness.

  As described above, according to the present invention, ozone gas is bubbled into a sulfuric acid solution containing persulfuric acid generated by the electrolysis of sulfuric acid, thereby greatly reducing the time required for stripping and decomposing the resist from the electronic material to be cleaned. Can be shortened.

It is a figure which shows the electronic material washing | cleaning apparatus of one Embodiment of this invention. Similarly, it is a figure which shows the electronic material washing | cleaning apparatus of other embodiment.

Embodiments of an electronic material cleaning method and an electronic material cleaning apparatus according to the present invention will be described below.
(Embodiment 1)
FIG. 1 shows an embodiment of an electronic material cleaning apparatus 1 according to the present invention, which includes a sulfuric acid electrolysis apparatus 10 and a cleaning machine 20.
The sulfuric acid electrolysis apparatus 10 includes an electrolysis unit 11, and an anode and a cathode (not shown) made of a boron-doped diamond electrode are arranged inside, and a power source (not shown) is connected to both electrodes. In addition to the anode and the cathode, a bipolar electrode may be provided.

An electrolytic solution storage tank 12 is connected to the electrolytic unit 11 through a circulation line 13 so as to be able to circulate. A gas-liquid separation unit 14 is interposed in the circulation line 13 on the liquid discharge side of the electrolysis unit 11. The gas-liquid separator 14 contains a persulfuric acid-containing sulfuric acid solution containing gas, separates gas such as nitrogen gas, oxygen gas, ozone, etc. in the persulfuric acid-containing sulfuric acid solution and discharges it out of the system. A known one can be used, and the configuration of the present invention is not particularly limited as long as gas-liquid separation is possible.
A circulation pump 15 for circulating the persulfuric acid-containing sulfuric acid solution is interposed on the feed side of the circulation line 13. In the above description, the gas-liquid separation unit 14 and the electrolytic solution storage tank 12 are provided. However, the electrolytic solution storage tank 12 may also serve as the gas-liquid separation unit 14.

The electrolyte storage tank 12 is connected to a feed circulation line 17 in which a liquid feed pump 16 and a feed automatic valve 17a are sequentially provided. Further, a return circulation line 18 in which a return automatic valve 18 a and a cooler 19 are sequentially provided is connected to the electrolytic solution storage tank 12. The cooler 19 cools the sulfuric acid solution to a liquid temperature of 40 to 80 ° C., and the configuration thereof is not particularly limited as the present invention.
The sulfuric acid electrolysis apparatus 10 is comprised by the above structure.

The cleaning machine 20 includes a batch-type cleaning tank 21, in which the drainage side and the liquid inlet side are connected by a circulation line 22. The drain side of the circulation line 22 is connected to the overflow part 21 a of the cleaning tank 21, and the liquid inlet side of the circulation line 22 is connected upward to the bottom part of the cleaning tank 21.
On the drain side of the circulation line 22, a liquid feed pump 23, a filter 24, and an inline heater 25 are interposed. The inline heater 25 corresponds to the external heater of the present invention.
A return circulation line 18 is branchedly connected to the circulation line 22 on the downstream side of the liquid feed pump 23 and the upstream side of the in-line heater 25.
In addition, a sulfuric acid supply unit 29 is connected to the return circulation line 18 so that sulfuric acid can be supplied to the electronic material cleaning apparatus through the return circulation line 18 at the time of initial operation or when necessary.

The feed circulation line 17 connected to the electrolytic solution storage tank 12 is connected so as to merge with the circulation line 22 on the upstream side of the inline heater 25. The feed circulation line 17 can also join the circulation line 22 on the downstream side of the inline heater 25.
The in-line heater 25 corresponds to the external heater of the persulfuric acid heating part of the present invention as described above. The structure is not particularly limited, and a known heater can be used. However, it is preferable to heat the sulfuric acid solution in a transient manner.

The electrolytic solution storage tank 12 is provided with a bubbling nozzle 27 made of sintered glass or PTFE (polytetrafluoroethylene). The bubbling nozzle 27 bubbles and discharges ozone gas. The discharge direction intersects with the supply direction of the persulfuric acid-containing sulfuric acid solution supplied in the circulation line 22 and immediately exchanges with the circulation line 22. It is installed near the supply port. The bubbling nozzle 27 is connected to the distal end side of an ozone supply pipe 26, the ozone supply pipe 26 extends to the outside of the cleaning tank 21, and the base end thereof is connected to the ozone generator 28. The ozone generator 28 corresponds to the ozone generator of the present invention.
Since the ozone supply pipe 26 is in contact with a high-temperature persulfuric acid-containing sulfuric acid solution, it is desirable that the ozone supply pipe 26 has heat resistance, acid resistance, and oxidation resistance, and may be made of sintered glass, PTFE, PFA, or the like. In addition, you may comprise only the site | part which the ozone supply pipe | tube 26 contacts with a persulfuric acid containing sulfuric acid solution with a heat resistant acid resistant and oxidation resistant material.
The ozone supply pipe 26 and the bubbling nozzle 27 constitute the ozone supply unit of the present invention.
Moreover, the washing machine 20 is configured by the above-described configurations.

The circulation line 13, the feed circulation line 17, and the downstream circulation line 22 after the joining position of the feed circulation line 17 connected to the liquid discharge side of the electrolysis unit 11 constitute the feed line of the present invention.
The return circulation line 18 and the circulation line 13 connected to the liquid inlet side of the electrolysis unit 11 up to the branch position of the circulation line 22 connected to the cleaning tank 21 constitute the return line of the present invention.
In the electronic material cleaning apparatus 1, each part of the sulfuric acid electrolysis apparatus 10 and the cleaning machine 20 is controlled by the control unit 2.

Next, an electronic material cleaning method will be described based on the operation of the electronic material cleaning apparatus configured as described above.
In the electrolytic solution storage tank 12, a sulfuric acid solution having a sulfuric acid concentration of 70% by mass or more and a liquid temperature of 40 to 80 ° C. is stored. The sulfuric acid solution is supplied through the return circulation line 18 by the sulfuric acid supply unit 29. The sulfuric acid solution can be supplied from the sulfuric acid supply unit 29 while the apparatus is in operation or stopped as required.
The sulfuric acid solution stored in the electrolytic solution storage tank 12 is fed through the circulation line 13 by the circulation pump 15 and introduced into the liquid inlet side of the electrolysis unit 11 at a temperature suitable for electrolysis. In the electrolysis unit 11, current is passed between the anode and the cathode by a DC power source (not shown), and the sulfuric acid solution introduced into the electrolysis unit 11 is electrolyzed. The electrolysis unit 11 generates an oxidizing substance containing persulfuric acid on the anode side and generates oxygen gas, and generates hydrogen gas on the cathode side.
These oxidizing substances and gases are discharged from the electrolysis unit 11 in a mixed state with the sulfuric acid solution, gas components are separated by the gas-liquid separation unit 14, and discharged outside the system system to be a catalyst device (not shown). ) And so on.

The sulfuric acid solution from which the gas has been separated contains persulfuric acid, and after returning to the electrolyte solution storage tank 12 through the return side of the circulation line 13, it is repeatedly sent to the electrolysis unit 11 to increase the concentration of persulfuric acid by electrolysis. . When the persulfuric acid concentration becomes moderate, the feed automatic valve 17 a is opened and a part of the persulfuric acid-containing sulfuric acid solution in the electrolyte solution storage tank 12 is fed by the feed pump 16 through the feed circulation line 17. The automatic feed valves 17a and 18a are opened and closed under the control of the control unit 2.
A sulfuric acid solution containing persulfuric acid (persulfuric acid-containing sulfuric acid solution) fed in the feed circulation line 17 joins the circulation line 22 on the upstream side of the in-line heater 25 and is introduced into the cleaning tank 21 through the circulation line 22.

In the circulation line 22, the persulfuric acid-containing sulfuric acid solution in the cleaning tank 21 is circulated by the liquid feed pump 23 and is heated by the in-line heater 25 and introduced into the cleaning tank 21.
In the in-line heater 25, the sulfuric acid solution containing persulfuric acid is heated while passing through the flow path. At this time, when mixed with the persulfuric acid-containing sulfuric acid solution sent in the feed circulation line 17 and supplied into the washing tank 21, it is in the range of more than 130 ° C to 190 ° C (but below the boiling point of the persulfuric acid-containing solution). Heating is performed to have a liquid temperature.

In the cleaning tank 21, for example, an electronic material substrate such as a silicon wafer provided with a resist ion-implanted at a concentration of 1 × 10 ¹² atoms / cm ² or more as the semiconductor material 100 can be targeted for cleaning.
The semiconductor material 100 is processed by being immersed in a sulfuric acid solution containing persulfuric acid in the cleaning tank 21. At this time, ozone gas is generated by the ozone generator 28, and ozone gas is supplied to the bubbling nozzle 27 through the ozone supply pipe 26. Then, the bubbling ozone gas is released from the bubbling nozzle 27 and immediately comes into contact with the persulfuric acid-containing sulfuric acid solution supplied through the circulation line 22.

As a result, the sulfuric acid solution containing persulfuric acid exhibits the oxidizing power by the self-decomposition of persulfuric acid and the oxidizing power by sulfuric acid, and the generated sulfuric acid radical comes into contact with the ozone gas at the gas-liquid interface to promote the decomposition of ozone, and the OH radical (OH.) Is generated, and the oxidizing power is further increased.
In the semiconductor material 100, the resist on the surface is peeled and removed in a short time by the oxidizing power by the self-decomposition of persulfuric acid, the oxidizing power of sulfuric acid, the oxidizing power by ozone decomposition, etc., and the resist transferred into the solution is also easily decomposed. The

  The sulfuric acid solution used for the washing is taken out from the overflow part 21a of the washing tank 21 to the circulation line 22, and is fed through the circulation line 22 by the liquid feed pump 23, and the fine particles contained in the sulfuric acid solution are removed by the filter 24. After that, it is heated by the in-line heater 25 and returned to the cleaning tank 21. The remaining portion of the sulfuric acid solution taken out in the circulation line 22 is returned to the electrolyte storage tank 12 through the return circulation line 18 in which the return automatic valve 18a is opened. The return automatic valve 18 a is controlled to open and close by the control unit 2 as necessary, and may have a step of circulating the entire amount of the sulfuric acid solution taken out by the circulation line 22 to the cleaning tank 21.

In the electrolytic solution storage tank 12, the sulfuric acid solution is sent to the electrolytic unit 11 through the circulation line 13 by the circulation pump 15 to generate persulfuric acid, and is returned to the electrolytic solution storage tank 12.
By repeating the circulation of the sulfuric acid solution, the electronic material 100 can be cleaned while the persulfuric acid concentration is stable, and the cleaning time can be sufficiently shortened by bubbling ozone gas.

In addition, after washing | cleaning the electronic material 100 with the washing tank 21, it is also possible to provide a rinse process. When performing the rinsing process, ultrapure water is usually used as the rinsing water.
In addition, as ultrapure water, the pure water which satisfy | fills all the following conditions is desirable.
Electrical specific resistance: 18 MΩ · cm or more Metal ion concentration: 5 ng / L or less Residual ion concentration: 10 ng / L or less Number of particles: 5 particles of 0.1 μm or more in 1 mL TOC: 0.1 to 10 μg / L

  In the rinsing step, if the temperature of the rinsing water to be used is too low, a sufficient rinsing effect cannot be obtained, and if it is too high, it is inefficient in terms of energy efficiency. It is preferable to set it as 60-80 degreeC.

  The time required for the rinsing process varies depending on the types of processes before and after the rinsing process. For example, in the case of ashing-less cleaning, the rinsing process after the separation cleaning with the persulfuric acid-containing sulfuric acid solution is 5 to 30 minutes, particularly 10 It is preferable to be about -20 minutes. When washing is performed after the ashing treatment, it is preferably 3 to 20 minutes, particularly about 5 to 10 minutes in the rinsing step after the separation and washing with a persulfuric acid-containing sulfuric acid solution.

<Dry>
After the cleaning, when the rinsing step is performed, a series of resist peeling cleaning removal processing can be completed by spin drying and IPA drying according to a conventional method. The electronic material from which the resist is removed is sent to the next process.

[Ashing process]
Prior to the resist peeling and cleaning according to the present invention, an ashing process may be performed. The ashing process is performed by ashing the resist on the electronic material with oxygen plasma or the like according to a conventional method.
However, in the present invention, if the sulfuric acid electrolyte solution bubbled with ozone gas is used, the resist can be surely cleaned and removed without causing a problem of resist residue even if the ashing process is omitted. By omitting the ashing process, the time and cost required for a series of resist stripping processes can be greatly reduced.

(Embodiment 2)
Next, another embodiment will be described with reference to FIG.
The second embodiment has the same configuration as that of the first embodiment except that the ozone supply pipe 26 includes an ozone gas heater 30 that heats ozone gas. Hereinafter, the same configuration as that of the first embodiment will be described by omitting or simplifying the configuration.
The ozone gas heater 30 corresponds to the ozone gas heating section of the present invention, and heats the ozone gas supplied by the ozone supply pipe 26. In that case, when supplying the persulfuric acid containing sulfuric acid solution with the washing tank 21, it heats so that ozone gas may be heated to 50 degreeC or more.
By supplying ozone gas heated appropriately in the sulfuric acid solution containing persulfuric acid, the temperature distribution in the sulfuric acid solution containing persulfuric acid can be kept uniform, and ozone gas is generated by sulfuric acid radicals generated by the self-decomposition of persulfuric acid. Is more effectively decomposed, and the oxidizing power is increased to enable the semiconductor material 100 to be cleaned in a shorter time.
In addition, the structure of the ozone gas heater 30 is not specifically limited as this invention, A well-known thing etc. can be used. The point is that any ozone gas can be heated to an appropriate temperature.

Examples of the present invention will be described below. Of course, the present invention is not limited to the following examples.
A cleaning test was performed under the following conditions, and the processing times of the respective experimental methods were compared. The test results are shown in Table 1.

<Conditions>
Wafer size: 150 mm (dose amount: 5 × 10 ¹⁴ atoms / cm ² , dose element: B dose product)
Resist coating thickness: 1.7 μm
Ashing presence / absence: Number of treatments per ashless process: 50 sheets / number of lots processed: 4 lots / hour to 6 lots / hour Processing temperature in washing tank: 140 ° C.
Sulfuric acid: Electronics industry grade 96% by mass
Hydrogen peroxide: Electronics industry grade 30% by mass

In the case of SPM cleaning, an SPM solution with a mixing ratio of sulfuric acid: hydrogen peroxide = 5: 1 (volume ratio) is used, and hydrogen peroxide is appropriately supplemented for each lot and reused (sulfuric acid concentration is 85 mass at the initial stage) From a little less than%).
-In the case of sulfuric acid electrolyte containing persulfuric acid, the collected solution is passed through the electrolytic cell again and reused. The sulfuric acid concentration is constant at 85% by mass.
-As for the resist peeling time, the time until the resist was peeled off from the wafer was visually confirmed.
-The liquid recovery time is visually (the time until the processing liquid returns to transparent).
・ Since the time was slightly different depending on the lot processed, the minimum and maximum values were listed.

  When the SPM solution is a new solution, both the stripping time and the liquid color recovery time are short. However, as the number of treatment lots increases, both the stripping time and the liquid color recovery time tend to increase. The value range is large.

When considering application in a mass production factory, the process time needs to be adjusted to the maximum value, [SPM solution or SPM solution + ozone gas or SOM solution (solution in which ozone gas is blown into hot concentrated sulfuric acid)] and [sulfuric acid electrolyte] And sulfuric acid electrolyte + ozone gas], the treatment time, the maximum value of the liquid recovery time, and the minimum value range are clearly smaller in [sulfuric acid electrolyte and sulfuric acid electrolyte + ozone gas]. Can be applied to processes while maintaining performance.
Further, in this example, the maximum value is shorter than the other conditions, so that a great advantage in improving the throughput was recognized.
Therefore, the resist stripping time can be shortened by washing with the sulfuric acid electrolyte solution bubbled with ozone gas, and the time required for resist stripping can be shortened from 15 minutes to 10 minutes by shortening the liquid recovery time. As a result, the number of sheets that can be processed per hour was changed from 200 sheets / hour to 300 sheets / hour, and the processing efficiency per unit time was improved by 50%.

DESCRIPTION OF SYMBOLS 1 Electronic material washing | cleaning apparatus 10 Sulfuric acid electrolysis apparatus 11 Electrolysis part 12 Electrolyte storage tank 13 Circulation line 17 Feed circulation line 18 Return circulation line 19 Cooler 20 Washing machine 21 Washing tank 22 Circulation line 25 In-line heater 26 Ozone supply pipe 27 Bubbling nozzle 28 Ozone generator 100 Electronic materials

Claims (15)

In the electronic material cleaning method of cleaning the electronic material by bringing a persulfuric acid-containing sulfuric acid solution obtained by electrolyzing a sulfuric acid solution of 70% by mass or more into contact with the electronic material,
The cleaning by the contact is performed by immersing the electronic material in a cleaning tank in which the sulfuric acid solution containing persulfuric acid is contained, and during the cleaning, the liquid temperature is higher than 130 ° C. to 190 ° C. (however, the persulfuric acid content is included) The cleaning is performed so that ozone gas is in contact with the persulfuric acid-containing sulfuric acid solution supplied to the washing tank while the persulfuric acid-containing sulfuric acid solution is heated to a temperature equal to or lower than the boiling point of the sulfuric acid solution. An electronic material cleaning method comprising supplying ozone gas into a tank .   2. The electronic material cleaning method according to claim 1, wherein the sulfuric acid solution used for the cleaning is electrolyzed again to regenerate persulfuric acid, and the persulfuric acid-containing sulfuric acid solution is reused for the cleaning.   The electronic material cleaning method according to claim 1 or 2, wherein the ozone gas supplied into the cleaning tank is heated to 50 ° C or higher.   The electronic material cleaning method according to any one of claims 1 to 3, wherein the ozone gas bubbled into the persulfuric acid-containing sulfuric acid solution in the cleaning tank is supplied.   5. The electronic material cleaning method according to claim 1, wherein at least an anode of the electrodes used for the electrolysis of the sulfuric acid solution is a conductive diamond electrode.   The electronic material cleaning method according to claim 1, wherein the electronic material is an electronic material that has not been subjected to an ashing process. An electrolysis unit for electrolyzing a sulfuric acid solution of 70% by mass or more;
A feed line for feeding a sulfuric acid solution containing persulfuric acid obtained by electrolysis in the electrolysis unit;
A washing tank containing a persulfuric acid-containing sulfuric acid solution which is fed by the feed line and heated to a liquid temperature of more than 130 ° C. to 190 ° C. (but not higher than the boiling point of the persulfuric acid-containing sulfuric acid solution);
An ozone generator for generating ozone;
A temperature of 130 ° C. to 190 ° C. (the boiling point of the persulfuric acid-containing sulfuric acid solution) that is connected to the cleaning tank and the ozone generated in the ozone generation unit is fed into the cleaning tank through the feed line. below) electronic material cleaning apparatus characterized by comprising, an ozone supply unit for supplying the cleaning tank so as to be in contact with the sulfuric acid solution containing persulfuric acid of.   The electronic material cleaning apparatus according to claim 7, further comprising a return line that returns the sulfuric acid solution in the cleaning tank to the electrolysis unit.   The persulfuric acid-containing sulfuric acid solution contained in the washing tank is heated so that the liquid temperature of the persulfuric acid-containing sulfuric acid solution in the washing tank exceeds 130 ° C. to 190 ° C. (however, below the boiling point of the persulfuric acid-containing sulfuric acid solution) The electronic material cleaning apparatus according to claim 7, further comprising a persulfuric acid heating unit that heats and raises the temperature.   The electronic material cleaning apparatus according to claim 9, wherein the persulfuric acid heating unit includes an external heater that heats the persulfuric acid-containing sulfuric acid solution supplied into the cleaning tank.   The electronic material cleaning apparatus according to claim 9 or 10, wherein the persulfuric acid heating unit includes an internal heater that heats a persulfuric acid-containing sulfuric acid solution accommodated in the cleaning tank.   The electronic material cleaning apparatus according to any one of claims 7 to 11, further comprising an ozone heating section that heats and raises the ozone supplied to the persulfuric acid-containing sulfuric acid solution in the cleaning tank to 50 ° C or higher. .   The ozone supply unit has a bubbling nozzle for bubbling the ozone gas and supplying it to the persulfuric acid-containing sulfuric acid solution in the cleaning tank, and the bubbling nozzle is made of sintered glass or PTFE (polytetrafluoroethylene). Or it is a product made from PFA (perfluoroalkoxyethylene copolymer resin), The electric material washing | cleaning apparatus of any one of Claims 7-12 characterized by the above-mentioned.   14. The electronic material cleaning apparatus according to claim 7, wherein at least an anode of the electrodes provided in the electrolysis unit is formed of a conductive diamond electrode.   The supply direction of ozone to the persulfuric acid-containing sulfuric acid solution by the ozone supply unit and the supply direction of persulfuric acid-containing sulfuric acid solution to the cleaning tank by the feed line intersect and are supplied with the supplied ozone. The electronic material cleaning apparatus according to any one of claims 7 to 14, wherein the ozone supply unit and the feed line are arranged so that the persulfuric acid-containing sulfuric acid solution immediately exchanges with the sulfuric acid solution. .

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