JP4771049B2 - Sulfuric acid recycling cleaning system - Google Patents

Description

  The present invention relates to a sulfuric acid recycle type cleaning system that regenerates persulfuric acid and uses it for cleaning while repeatedly using a sulfuric acid solution when cleaning and peeling a contaminant attached to a silicon wafer or the like with a persulfuric acid solution having a high peeling effect. Is.

Wafer cleaning technology in the VLSI manufacturing process is a process for stripping and cleaning resist residues, fine particles, metals and natural oxide films, and ozone gas is blown into concentrated sulfuric acid and hydrogen peroxide mixed solution (SPM) or concentrated sulfuric acid. A solution (SOM) is frequently used. When hydrogen peroxide or ozone is added to high-concentration sulfuric acid, the sulfuric acid is oxidized to produce persulfuric acid. It is known that persulfuric acid has a high cleaning ability because it generates a strong oxidizing power when self-decomposing, and is useful for cleaning the wafer and the like.
As a method for producing persulfuric acid, in addition to the above method, there is also known a method in which an aqueous solution containing sulfate ions is electrolyzed in an electrolytic bath to obtain persulfuric acid-dissolved water and used for washing (Patent Documents 1 and 2). reference).

JP 2001-192874 A Special table 2003-511555 gazette

  By the way, in SPM, it is necessary to repeat the replenishment of the hydrogen peroxide solution in order to compensate for the decomposition when the persulfuric acid generated by the hydrogen peroxide solution is self-decomposed and the oxidizing power is reduced. When the sulfuric acid concentration falls below a certain concentration, it is exchanged with a new high concentration sulfuric acid. However, in the above method, since the persulfuric acid solution is diluted with water in hydrogen peroxide water, it is difficult to maintain a constant liquid composition. Further, the liquid is discarded and renewed every predetermined time or every processing batch. It is necessary to. For this reason, there are problems that the cleaning effect is not constant and a large amount of chemicals must be stored. On the other hand, in the SOM, the liquid is not diluted, and although the liquid renewal cycle can be generally longer than that of the SPM, the cleaning effect is inferior to that of the SPM. In these methods, there is a limit to the concentration of persulfuric acid produced, which leads to the limit of the cleaning effect.

  In addition, in SPM, the amount of persulfuric acid that can be generated by adding high-concentration sulfuric acid that has filled the washing tank once and hydrogen peroxide water several times is small and has a limit. Further, in the SOM method, the generation efficiency of persulfuric acid with respect to the ozone blowing amount is very low. Therefore, in these methods, there is a problem that the concentration of persulfuric acid produced is limited and the cleaning effect is also limited. For this reason, in the cleaning using the above-described SPM method or SOM method, as a pretreatment step of the SPM method or SOM method, dry etching or an ashing process is used to oxidize and ash the organic resist in advance. A process is incorporated. There is a problem that pre-processing such as dry etching or ashing process damages the wafer or increases the cost of the apparatus.

  Further, in each of the above methods, a rinsing tank is used when the suspended suspended matter (SS) that gradually remains and accumulates in the solution due to the resist peeling and dissolution is reattached to the cleaned wafer and rinsed with ultrapure water. There is a problem of being mixed in.

  The present invention has been made against the background of the above circumstances, and by reusing sulfuric acid by regenerating sulfuric acid by electrochemical action from an aqueous solution of sulfuric acid while repeatedly using sulfuric acid, the amount of sulfuric acid used is greatly reduced. It is an object of the present invention to provide a sulfuric acid recycle type cleaning system capable of continuously obtaining a good cleaning action and removing SS in the cleaning liquid to prevent reattachment to the material to be cleaned.

That is, in the sulfuric acid recycle type cleaning system of the present invention, the first invention is a cleaning apparatus for cleaning an electronic material substrate using a persulfuric acid solution heated to 120 ° C. or more as a cleaning liquid and removing a resist on the substrate, A persulfate solution is produced by using a conductive diamond electrode at least as an anode and generating a persulfate ion from a sulfate ion contained in a solution having a sulfuric acid concentration of 15 M or more and a temperature of 10 ° C. to 90 ° C. by electrolytic reaction. An electrolytic reaction device that recycles the solution, a circulation line that circulates the solution while performing the cleaning and electrolysis between the cleaning device and the electrolytic reaction device, and a circulation line that extends from the cleaning device to the electrolytic reaction device. A cooling means for cooling the solution to be liquefied, and whether the SS in the solution sent in the circulation line from the cleaning device to the cooling means is captured and And a SS removal device having a SS acquisition filter for removing,
The electronic material substrate is a semiconductor substrate to which a resist by pattern processing is attached, and is subjected to the cleaning without undergoing a pretreatment step in which the resist is oxidized and incinerated in advance.
The SS capture filter is characterized Rukoto which have a pore diameters of ≦ 0.1mm or 0.1 [mu] m.

Sulfuric acid recycle type cleaning system of the second invention, in the first invention, the SS capture filter is a detachable, characterized in that the captured SS is recycled ceramic filter capable of removing by combustion .

The sulfuric acid recycling type cleaning system according to a third aspect of the present invention is characterized in that, in the first or second aspect , the cleaning device includes a plurality of cleaning tanks for sequentially cleaning the material to be cleaned.

In a sulfuric acid recycle type cleaning system according to a fourth aspect of the present invention, in the first to third aspects, the SS removing device removes SS in the cleaning tank of one or more front side cleaning ranks including the first cleaning rank. It is connected to the washing tank as described above.

The sulfuric acid recycling type cleaning system according to a fifth aspect of the present invention is the sulfuric acid recycling type cleaning system according to the third or fourth aspect , wherein one of the plurality of cleaning tanks including one or more front cleaning ranks including the first cleaning rank The solution can be circulated with the electrolytic reaction apparatus independently of the washing tank, and two or more rear washing ranks including the final washing rank are connected in series to connect the electrolytic reaction apparatus. It is characterized in that the solution can be circulated.

The sulfuric acid recycle type cleaning system according to a sixth aspect of the present invention is characterized in that, in the fifth aspect , the cleaning tank connected in series has a higher cleaning order in the upstream side.

Seventh sulfuric acid recycle type cleaning system of the present invention, in the fifth aspect, in some or all of the cleaning tank which are connected in series, the filtration filter between the washing tank, characterized in that it is interposed.

The sulfuric acid recycle type cleaning system according to an eighth aspect of the present invention includes the heating device for heating at least the persulfuric acid solution in the cleaning tank of the first cleaning order among the cleaning tanks of the front side order in the fourth to seventh inventions. It is characterized by.

A sulfuric acid recycling type cleaning system according to a ninth aspect of the invention is characterized in that, in the first to eighth aspects of the invention, the sulfuric acid recycling type cleaning system further comprises heating means for heating the persulfuric acid solution used in the cleaning device .

  According to the present invention, a sulfuric acid cleaning solution containing persulfate ions is sent from the electrolytic reaction device to the cleaning device, and in the cleaning device, the persulfate ions in the cleaning solution self-decompose and generate oxidizing power, and the cleaning action by sulfuric acid. In addition, the contaminants of the cleaning material are effectively peeled and cleaned by the oxidizing power of persulfuric acid. For example, when cleaning a wafer, the resist adhering to the wafer is peeled off by the cleaning action and dissolved in the cleaning liquid. At this time, the dissolution rate of the resist in the sulfuric acid solution increases as the sulfuric acid concentration increases. The sulfuric acid concentration as the cleaning liquid is preferably 8M or more, more preferably 12M or more. Further, the dissolution rate of the resist in the sulfuric acid solution increases as the temperature of the sulfuric acid solution increases. Therefore, it is desirable that the temperature of the sulfuric acid solution as the cleaning liquid is 120 to 150 ° C. Examples of means for heating the cleaning liquid to the above temperature include a heater, a heater using heat exchange with hot water, steam, and the like, but the present invention is not limited to a specific one. The resist dissolved in the cleaning solution is further effectively decomposed by the oxidizing action by persulfate ions.

  During the cleaning and dissolution, the SS component generated as the resist is removed gradually accumulates in the solution. This SS component is removed by an SS removing device. As the SS removing device, an apparatus that removes SS while allowing a cleaning liquid to flow is desirable, and thus SS can be removed without stopping the system. In particular, by interposing it in the circulation line, it is possible to prevent SS from flowing into the electrolytic reaction apparatus described later. It is desirable that the SS removing device includes an SS capturing filter that captures SS and removes it from the solution while performing the above-described liquid passing. The capture filter is preferably a ceramic filter, and the pore diameter is preferably 1 mm or less, particularly 0.1 mm or less. The ceramic filter may be mainly composed of alumina and mixed with impurities such as siri force and magnesia. However, an alumina filter having a purity of 99.5% or more is desirable from the viewpoint of corrosion resistance. As another component of the SS removing device, a material such as tetrafluoroethylene which is not eroded by a sulfuric acid solution containing persulfuric acid having a high temperature of about 130 ° C. is desirable. The ceramic filter can be removed from the SS removing device, and can be removed by burning and ashing SS by heat treatment (preferably 400 to 1200 ° C.) with SS attached. The capture filter from which SS has been removed can be reused by being mounted on the SS removal device again.

  The cleaning liquid used in the cleaning apparatus is sent to the electrolytic reaction apparatus. In the cleaning liquid, the persulfate concentration gradually decreases due to self-decomposition of persulfate ions in the solution in the cleaning device. In an electrolytic reaction apparatus, an anode and a cathode are immersed in a solution containing sulfate ions, and a current is passed between the electrodes to perform electrolysis, whereby sulfate ions are oxidized to regenerate persulfate ions, and the concentration of persulfate is increased. The regenerated persulfuric acid solution is returned again to the cleaning device through the circulation line and is used for cleaning the material to be cleaned in the same manner as described above. In this way, effective cleaning can be continued while maintaining the persulfate composition by circulating the cleaning solution while regenerating the persulfate ions.

The said washing | cleaning apparatus shall wash | clean a to-be-cleaned material sequentially in these washing tanks as what has a some washing tank. Each of these cleaning tanks may be provided independently, or the independent cleaning tank may be partitioned by a filtration filter or a partition plate described later to form a plurality of cleaning tanks. In the case where a plurality of cleaning tanks are provided, it is desirable that the SS removing device is for a cleaning tank having a front cleaning order including the first cleaning order.
As described above, it is possible to reduce the burden on the apparatus by effectively removing the SS in the cleaning tank of the front cleaning order in which SS is likely to occur and making the SS removing device unnecessary in the cleaning tank of the rear cleaning order. In particular, in the SS removing device having the above-described trapping filter, pressure loss is likely to occur. Therefore, in order to smoothly circulate the cleaning liquid, it is desirable to target only a part of the cleaning tanks in the front cleaning order, and in particular, the first cleaning order. It is more desirable to target only the washing tank.

As described above, the cleaning liquid has a higher cleaning ability as the temperature is higher. However, if it exceeds 160 ° C., the self-decomposition rate of persulfuric acid becomes extremely high. When cleaning is performed in a plurality of cleaning tanks, if the cleaning liquid is heated to a high temperature in all the cleaning tanks, persulfuric acid is decomposed at an early stage as described above, resulting in insufficient resist decomposing ability. In this case, it is desirable to perform heating specifically for the cleaning liquid in one or more front side cleaning tanks including the first cleaning order. In the cleaning tank with the cleaning order on the front side, more contaminants are adhering like the resist of the wafer, and it is desirable to perform cleaning with a cleaning liquid that is specially heated to increase the cleaning power. On the other hand, in the cleaning tank in which the cleaning order is later, much of the object to be removed such as resist is removed, and the resist dissolved in the cleaning liquid can be sufficiently decomposed even at about 100 ° C., and the resist concentration can be reduced. Therefore, it is desirable to heat only the cleaning liquid in the cleaning tanks of the front cleaning order to a particularly high temperature, and in the cleaning tanks of the rear side, it is desirable to perform the cleaning efficiently without heating or suppressing the heating temperature. In addition, this configuration reduces the burden on the apparatus.

On the other hand, the electrolytic reaction apparatus differs from the cleaning apparatus in that the lower the solution temperature, the better the efficiency of producing persulfuric acid and the smaller the electrode wear. In the present invention, since the cleaning device and the electrolytic reaction device are separated, the temperature of the solution electrolyzed in the electrolytic reaction device can be kept lower than the temperature of the cleaning solution. Can increase the efficiency. For this reason, the solution electrolyzed by the electrolytic reaction apparatus can be cooled to an appropriate temperature by an appropriate cooling means. Examples of the cooling means include air coolers and water coolers. The appropriate temperature as the solution to be electrolyzed can be in the range of 10 to 90 ° C. When the temperature range is exceeded, the electrolysis efficiency decreases and the wear of the electrode also increases. On the other hand, when the temperature is lower than the above temperature, the heat energy for heating the cleaning tank to a temperature of 130 ° C. becomes enormous, and the piping path for heat exchange becomes significantly longer, which is not practical. For the same reason, it is more desirable to set the lower limit to 40 ° C. and the upper limit to 80 ° C.
The heating means and cooling means described above may be attached to a cleaning device or an electrolytic reaction device, or may be provided in a circulation line. Further, another line may be provided in the cleaning device or the electrolytic reaction device to heat or cool the solution. Moreover, heat exchange can be performed between the forward path and the return path of the circulation line so as to increase the temperature of the cleaning liquid and decrease the temperature of the electrolytic solution.

  Further, in the case of having a plurality of cleaning tanks, it is possible to circulate the solution with the electrolytic reaction device independently of the other cleaning tanks for the cleaning tank of the front cleaning order including the first cleaning order, and to set the final cleaning order. It is desirable that the two or more rear cleaning tanks to be included are connected in series so that the solution can be circulated with the electrolytic reaction apparatus. In the cleaning tank of the front cleaning order, a lot of dissolved substances such as resist and SS are generated, and when this is transferred to the cleaning liquid of the cleaning tank of the rear order and mixed, it is re-applied to the material to be cleaned. Adhere to. Therefore, it is desirable to prevent the SS and resist solution from being transferred to another cleaning tank by independently circulating the cleaning liquid in the cleaning tank of the front cleaning order. This prevents the resist melt and SS from re-adhering to the material to be cleaned in the cleaning tank of the rear cleaning order, and the resist solution is sufficiently removed with a cleaning solution having a high persulfuric acid concentration in the cleaning tank of the front cleaning order. Can be decomposed. Furthermore, the SS in the system can be effectively removed by connecting the SS removing device only to the cleaning tank of the front cleaning order that circulates the cleaning liquid independently. Note that one of the first cleaning tanks is usually sufficient as the cleaning tank of the front cleaning order. However, as the present invention, the number of cleaning tanks in the front cleaning order is not limited to one.

  On the other hand, in the rear rank cleaning tanks, a plurality of cleaning tanks are connected in series to obtain a row of cleaning tanks in which the persulfuric acid concentration gradually decreases toward the downstream side. These cleaning tanks can be selected and the materials to be cleaned can be sequentially cleaned with cleaning liquids having different cleaning performances. In particular, it is desirable that the upstream cleaning tank is set so that the cleaning order is earlier. As a result, the material to be cleaned can be initially cleaned with a cleaning solution having a high persulfuric acid concentration and then sequentially with a cleaning solution having a lower persulfate concentration.

  Further, it is desirable to provide a filtration filter between the series of washing tanks. As a result, convection is effectively generated in the cleaning liquid containing the resist solution in each cleaning tank, and the cleaning material is effectively cleaned and the resist solution is effectively decomposed. Examples of the pore diameter of the filtration filter include those having a diameter of 1 mm or less. Further, it is desirable that the filter on the upstream side has a filtration surface having a larger retained particle diameter. As a result, it is possible to move the dissolved resist, etc. to the downstream side so that each cleaning tank can be in the same convection state, and the dissolution burden of the dissolved resist, etc. in each cleaning tank is not excessive or insufficient. Can be adjusted. The filter is preferably made of tetrafluoroethylene which is not easily damaged by persulfuric acid.

  Further, in the electrolytic reaction apparatus, electrolysis is performed with a pair of an anode and a cathode. The material of these electrodes is not limited to a specific one in the present invention. However, when platinum, which is widely used as an electrode, is used as an anode, there is a problem that platinum is eluted. On the other hand, the diamond electrode can efficiently generate persulfate ions and has little electrode wear. Therefore, among the electrodes of the electrolytic reaction apparatus, it is desirable that at least the anode that generates sulfate ions is composed of a diamond electrode, and it is more desirable that both the anode and the cathode are composed of diamond electrodes.

The conductive diamond electrode is a semiconductor material such as a silicon wafer used as a substrate, and after synthesizing a conductive diamond thin film on the wafer surface, the wafer is dissolved or synthesized in a plate shape under the condition that the substrate is not used. Mention may be made of self-standing conductive polycrystalline diamond. In addition, a laminate formed on a metal substrate such as Nb, W, or Ti can be used. However, when the current density is increased, there is a problem that the diamond film is peeled off from the substrate.
An electrode having a diamond thin film supported on a metal substrate has a problem that the diamond film is peeled off and the effect disappears in a short period of time. Therefore, a self-standing type conductive diamond electrode in which the substrate is removed after being deposited on the substrate is desirable.

In the cleaning system of the present invention, cleaning processing can be performed on various materials to be cleaned, but cleaning processing is performed on electronic material substrates such as silicon wafers, glass substrates for liquid crystals, and photomask substrates. It is suitable for the use to do. More specifically, it can be used for a peeling process of an organic compound such as a resist residue attached on a semiconductor substrate. Further, it can be used for a foreign matter removing process such as fine particles and metal adhering to the semiconductor substrate.
Conventionally, prior to a cleaning process, a process for processing a semiconductor substrate usually includes a step of pre-oxidizing and ashing an organic resist using a dry etching or ashing process as a pre-processing step. Yes. This process has a problem of increasing the apparatus cost and the processing cost. By the way, in the system of the present invention, an excellent cleaning effect can be obtained. Therefore, even when a cleaning process is performed without incorporating a pretreatment process such as the above-described dry etching or ashing process, the resist is sufficiently removed. Is obtained. That is, the present invention makes it possible to establish a process in which these pretreatment steps are omitted.

As described above, according to the sulfuric acid recycling type cleaning system of the present invention, the cleaning apparatus for cleaning the electronic material substrate using the persulfuric acid solution heated to 120 ° C. or higher as the cleaning liquid and removing the resist on the substrate, A persulfate solution is produced by generating persulfate ions from sulfate ions contained in a solution having a sulfuric acid concentration of 15 M or more and a temperature of 10 ° C. to 90 ° C. by an electrolytic reaction using a conductive diamond electrode at least as an anode. The electrolytic reaction apparatus to be regenerated, the circulation line for circulating the solution while performing the cleaning and the electrolysis between the cleaning apparatus and the electrolytic reaction apparatus, and the liquid supply in the circulation line from the cleaning apparatus to the electrolytic reaction apparatus A cooling means for cooling the solution, and SS in the solution sent by the circulation line from the cleaning device to the cooling means to capture the SS And a SS removal device having a SS acquisition filter for removing, said electronic material substrate is a semiconductor substrate on which the resist by patterning are attached, without a pretreatment step of ashing in advance oxidizing the resist The SS trapping filter is used for the cleaning, and the SS trapping filter has a pore size of 0.1 μm or more and 0.1 mm or less. Therefore, the sulfuric acid solution is repeatedly used, and a persulfuric acid solution for enhancing the peeling effect is used as an electrolytic reactor. Can be regenerated on-site and used for cleaning. In addition, efficient cleaning can be continued without requiring addition of a chemical solution such as hydrogen peroxide or ozone from the outside. Further, SS generated by the system is effectively removed by the SS removing device.

(Embodiment 1)
Below, one Embodiment of this invention is described based on FIG.
The cleaning device 1 of the present invention is divided into three cleaning tanks (a first cleaning tank 1a, a second cleaning tank 1b, and a third cleaning tank 1c) with a volume equal to three, and the first cleaning tank 1a is The other cleaning tanks 1b and 1c are isolated by the quartz plate 2. On the other hand, the 2nd washing tank 1b and the 3rd washing tank 1c are divided by filtration filter 3 which can permeate, and the thing made from tetrafluoroethylene is used for the material of this filtration filter 3. As shown in FIG. The first cleaning tank 1a is provided with a heater 9 as a heating device for heating the cleaning liquid in the tank.

An electrolytic reaction tank 20 corresponding to the electrolytic reaction apparatus of the present invention is connected to the cleaning apparatus 1 by a return pipe 4 and a feed pipe 5. The return pipe 4 and the feed pipe 5 each have at least an inner surface made of tetrafluoroethylene, and the feed pipe 5 is provided with a liquid feed pump 6 for feeding a persulfuric acid solution. A heat exchanger 7 is interposed between the return pipe 4 and the feed pipe 5 as heat exchange means of the present invention. The solution flowing through the return pipe 4 and the feed pipe 5 are connected by the heat exchanger 7. Heat exchange is possible with the flowing solution. It is desirable that at least the inner surface of the flow path (not shown) in the heat exchanger 7 is made of tetrafluoroethylene.
The return pipe 4 is branched into two on the side of the cleaning device 1 via the flow rate adjusting valve 8, and one return branch pipe 4 a is connected to the entrance side of the first cleaning tank 1 a, and the other one The return branch pipe 4b is connected to the entry side of the second cleaning tank 1b. The feed pipe 5 is connected to the outlet side of the third cleaning tank 1c, and the second cleaning tank 1b and the third cleaning tank 1c are connected in series.

In the first washing tank 1a, a feed pipe 10 is connected to the outlet side, and a suction pump 11 and an SS removing device 12 are interposed in the feed pipe 10, and the other end side of the feed pipe 10 is connected to the feed pipe described above. It joins the pipe 5. As a result, the first cleaning tank 1a can circulate the solution with the electrolytic reaction tank 20 independently of the other cleaning tanks 1b and 1c. The SS removing device 12 includes an alumina ceramic filter 13. The ceramic filter 13 preferably has a pore diameter of 0.1 mm or less, and the cleaning liquid introduced into the SS removing device 12 passes through the filter 13. It is configured as follows.
The return line 4, the return branch pipe 4a, the return branch pipe 4b, the feed pipe 5, the liquid feed pump 6, the feed pipe 10, and the suction pump 11 constitute the circulation line of the present invention.

  On the other hand, an anode 21 and a cathode 22 are disposed in the electrolytic reaction tank 20, and bipolar electrodes 23... 23 are disposed at a predetermined interval between the anode 21 and the cathode 22. Note that the present invention is not limited to the bipolar type, and may include only an anode and a cathode as electrodes. A DC power source 24 is connected to the anode 21 and the cathode 22, thereby enabling DC electrolysis in the electrolytic reaction tank 20.

  In this embodiment, the electrodes 21, 22, 23 are constituted by diamond electrodes. The diamond electrode is manufactured by forming a diamond thin film on a substrate and doping boron in a range of preferably 50 to 20,000 ppm with respect to the carbon content of the diamond thin film. Alternatively, a self-stand type may be used by removing the substrate after forming the thin film.

Next, the operation of the sulfuric acid recycling type cleaning system having the above configuration will be described.
In the first washing tank 1a, the second washing tank 1b, and the third washing tank 1c, sulfuric acid having a sulfuric acid concentration of 10 to 18M is accommodated, and ultrapure water is mixed with the sulfuric acid so that the volume ratio is 5: 1. To make a sulfuric acid solution. This is sequentially sent to the electrolytic reaction tank 20 by the liquid feed pump 6 and the suction pump 11.
In the electrolytic reaction tank 20, when the anode 21 and the cathode 22 are energized by the DC power source 24, the bipolar electrodes 23 ... 23 are polarized, and the anode and the cathode appear at predetermined intervals. The solution sent to the electrolytic reaction tank 20 is passed between these electrodes. At this time, it is desirable to set the outputs of the liquid feed pump 6 and the suction pump 11 so that the linear flow rate is 1 to 10,000 m / hr. In the above energization, it is desirable to control the energization so that the current density on the diamond electrode surface is 10 to 100,000 A / m ² .

When the solution is energized in the electrolytic reaction tank 20, the sulfate ions in the solution undergo an oxidation reaction to generate persulfate ions, thereby regenerating the persulfate solution. The persulfuric acid solution is fed from the return pipe 4 toward the cleaning device 1. At this time, heat is exchanged with the solution fed from the cleaning device 1 through the feed pipe 5 through the heat exchanger 7 and the temperature is raised. The persulfuric acid solution transferred through the return pipe 4 is branched into the return branch pipe 4a and the return branch pipe 4b after the branch flow rate is adjusted by the flow rate adjusting valve 8. The persulfuric acid solution flowing through the return branch pipe 4a is introduced into the first cleaning tank 1a, and the persulfuric acid solution flowing through the return branch pipe 4b is introduced into the second cleaning tank 1b.
Thereby, a high-concentration persulfuric acid solution is obtained in the 1st washing tank 1a and the 2nd washing tank 1b. In the first cleaning tank 1a, the persulfate ion concentration gradually decreases by autolysis, but the solution circulates between the electrolytic reaction tank 20 and is electrolyzed in the electrolytic reaction tank 20 to generate persulfate ions. A high persulfate ion concentration is maintained.

  The persulfuric acid solution in the 1st washing tank 1a is heated by the heater 9, and is heated at 120-150 degreeC. In the first cleaning tank 1a, the cleaning of the semiconductor wafer as the material to be cleaned is started. That is, the first cleaning tank 1a is assigned to the first cleaning order. When a semiconductor wafer is immersed in the first cleaning tank 1a, a high oxidation action is obtained by self-decomposition of persulfate ions in the first cleaning tank 1a, and contaminants on the semiconductor wafer are effectively peeled off. Removed and transferred into persulfuric acid solution. Further, SS is generated in accordance with this peeling and removal. The semiconductor wafer immersed in the first cleaning tank 1a for a predetermined time is transferred to the next cleaning tank. Further, the subsequent semiconductor wafer can be continuously immersed in the first cleaning tank 1a for cleaning. The persulfuric acid in the cleaning tank 1a is transferred to the SS removing device 12 by the feed pipe 10 and the suction pump 11, and the SS is captured by the capturing filter 13 and removed from the cleaning liquid. The cleaning liquid passes through the capture filter 13, merges from the feed pipe 10 to the feed pipe 5, and is sent to the electrolytic cell 20 by the liquid feed pump 6. The resist dissolved in the first cleaning tank 1a is decomposed by the action of persulfuric acid even when the feed tube 10 is moved.

When liquid is fed through the feed pipe 5, heat is exchanged with the cleaning liquid fed from the electrolytic reaction tank 20 through the return pipe 4 through the heat exchanger 7, and the temperature is lowered.
In the electrolytic reaction tank 20, persulfate ions are generated from sulfate ions in the same manner as described above, and the persulfate concentration reduced by the self-decomposition is increased to regenerate the persulfate solution, and returned to the cleaning device 1 through the return pipe 4 again. Washed away.
Further, when the persulfuric acid solution moves from the cleaning device 1 toward the electrolytic reaction tank 20, the persulfuric acid solution moves between the persulfate solution that is subjected to the electrolytic treatment in the electrolytic reaction tank 20 and moves through the return pipe 4. In the heat exchanger 7, heat exchange is performed.

  Next, in the second washing tank 1b, the introduced persulfuric acid solution flows into the third washing tank 1c through the filtration filter 3 while convection in the tank due to the presence of the filtration filter 3. In the third cleaning tank 1c, convection similarly occurs and flows from the outlet side of the third cleaning tank 1c to the feed pipe 5. In the feed pipe 5, the cleaning liquid is sent to the electrolytic reaction tank 20 by the liquid feed pump 6 while being heat-exchanged by the heat exchanger 7 as described above, and is electrolyzed. In the second washing tank 1b, although the persulfate ion concentration gradually decreases due to autolysis, the solution circulates between the electrolytic reaction tank 20 and is electrolyzed in the electrolytic reaction tank 20 to generate persulfate ions. A high persulfate ion concentration is maintained, and in the third cleaning tank 1c, the cleaning solution has a reduced persulfate concentration due to the progress of self-decomposition.

The semiconductor wafer cleaned in the first cleaning tank 1a is then immersed in the second cleaning tank 1b on the upstream side of the second cleaning tank 1b and the third cleaning tank 1c connected in series, and further Washing is done. While the feed pipe 5 from the first cleaning vessel 1a, and the first cleaning vessel 1a, electrolytic reactor 20, the return pipe 4 passing liquid, resist dissolution contained in the cleaning liquid is sufficiently degraded by persulfate acid Therefore, the resist concentration in the cleaning liquid in the second cleaning tank 1b is low. In addition, when the material to be cleaned is immersed in the second cleaning tank 1b, the resist reattached when the material to be cleaned is lifted from the first cleaning tank 1a is dispersed in the cleaning liquid. to decompose the persulfate acid while reaching the 3 washing tank 1c, resist concentration in the washing liquid of the third washing tank 1c is kept very low. The resist dissolved in the second cleaning tank 1b is gradually decomposed by the cleaning solution having a high persulfuric acid concentration. The slightly dissolved resist melt passes through the filtration filter 3 and moves to the third cleaning tank 1c. The semiconductor wafer cleaned in the second cleaning tank 1b is immersed in the third cleaning tank 1c assigned to the final cleaning order and cleaned. Since the resist concentration in the cleaning liquid of the third cleaning tank 1c is very low, the resist does not adhere again even if the material to be cleaned is pulled up from the third cleaning tank 1c. Therefore, the material to be cleaned can be cleaned in detail. The slightly dissolved resist melt is also decomposed when the cleaning liquid moves through the feed pipe 5. The semiconductor wafers cleaned by the cleaning tanks 1a to 1c are free from adhesion of SS and dissolved resist, and contaminants are effectively removed. This semiconductor wafer can be rinsed with ultrapure water or the like as in the prior art. At this time, the rinse solution is not contaminated by the deposits on the semiconductor wafer.

  By cleaning the semiconductor wafer with the sulfuric acid recycling type cleaning system, it is possible to effectively clean the persulfuric acid solution by repeatedly using the persulfuric acid solution without requiring the addition of hydrogen peroxide or ozone. Can continue. In addition, when SS accumulates in the capture filter 13 and the filter performance deteriorates, only the capture filter 13 is removed, and the captured SS is burned and ashed by heating to 400 to 1200 ° C. Thereafter, it can be reused by being mounted on the SS removing device 12.

  Although the present invention has been described based on the first embodiment, the present invention is not limited to the description of the above embodiment, and can be changed without departing from the scope of the present invention.

Next, an example using the system of the first embodiment will be described.
In this embodiment, tetrafluoroethylene having a pore diameter of 0.5 mm was used for the filter 3 and each cleaning tank had about 17 liters of solution. As the cleaning liquid, a total of 50 liters of 15M concentrated sulfuric acid was used for cleaning, and the cleaning liquid was heated and maintained at 130 ° C. by the heater 9 in the first cleaning tank 1a.

Between the cleaning device 1 and the electrolytic reaction tank 20, the cleaning liquid is circulated at a flow rate of about 3 liters / min so that the residence time in each cleaning tank is 5 minutes. The amount of solution returning to the first cleaning tank 1a and the amount of solution returning to the second cleaning tank 1b were adjusted to be 1: 2.
As the SS trapping filter 13 of the SS removing device 12 connected to the first cleaning tank 1a, an alumina filter having a pore diameter of 0.1 μm, a diameter of 10 cm, and a length of 30 cm was used. Moreover, in the heat exchange by the heat exchanger 7, thermal energy was added with the boiler about the amount of heat radiation.

On the other hand, in the electrolytic reaction tank 20, ten conductive diamond electrodes doped with boron on a Si substrate having a diameter of 15 cm and a thickness of 1 mm were incorporated. Effective anode area for electrolysis is 15dm ^2, by setting the current density 60A / dm ^2, and electrolysis at 40 ° C..
As a pretreatment, 10 100-nm patterned resist-coated 5-inch silicon wafers that were not subjected to ashing were immersed in the first cleaning tank 1a for 5 minutes to remove the resist. In the first washing tank 1a, the solution in the tank was initially colored light brown and the TOC concentration was 18 mg / liter, but became colorless and transparent with time. The ten silicon wafers immersed in the first cleaning tank 1a for 5 minutes are sequentially immersed in the second cleaning tank 1b and the third cleaning tank 1c for 5 minutes, respectively, and the resist reattached at the time of pulling up in the first cleaning tank 1a is removed. Removed. Although SS floats in the sulfuric acid solution in the first cleaning tank 1 a, the solution after the wafer cleaning is sucked up by the pump 11 to the SS removing device 12 and captured by the capturing filter 13. Finally, it was rinsed with ultrapure water and spin-dried.
When the organic residue was measured on the cleaned wafer with a wafer analyzer, the residue was about 100 to 200 pg / cm ² , and it was confirmed that a highly clean wafer could be obtained.
Such a cleaning operation was repeated at 120 wafers / hr, and the trapping filter was replaced after a total of 8 hours of cleaning work (960 wafers). About the filter after use, attached SS was removed by heating to 800 ° C. in an air atmosphere, and recycling was possible.

(Comparative Example 1)
The quartz plate 2, the filtration filter 3, the feed pipe 10, the suction pump 11 and the SS removing device 12 of the cleaning device used in Example 1 were removed, 50 liters of 15M concentrated sulfuric acid was put in the cleaning tank, and the entire sulfuric acid solution was added by the heater 9. Was heated and maintained at 130 ° C.
As in Example 1, 10 5-inch silicon wafers with 100 nm patterned resist that had not been subjected to ashing treatment as a pretreatment were immersed in this solution for 10 minutes to remove the resist. The resist removal effect on the wafer was good, and the sulfuric acid solution was colored light brown immediately after immersion, but became colorless and transparent in less than 10 minutes, and the TOC concentration became the detection limit.
When the organic substance residue was measured for the cleaned wafer using a wafer analyzer, the residue was about ²⁰⁰ to 300 pg / cm ² , and it was confirmed that a wafer having cleanliness that can be advanced to the next process can be obtained. did.
In addition, when wafer cleaning is repeated at 120 wafers / hr, after 8 hours (the number of wafers to be cleaned is 960 wafers), the amount of SS in the sulfuric acid solution in the cleaning tank increases, and the frequency with which SS is most adhered to the wafer is high. It became high. Once the apparatus was stopped, the sulfuric acid solution was cooled and transferred to the outside of the washing tank, and it was necessary to restart the apparatus after removing SS with a filtration apparatus having a tetrafluoroethylene filter. Furthermore, the tetrafluoroethylene filter used for removing SS is difficult to regenerate and needs to be replaced with a new one each time.

It is the schematic which shows the system in one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cleaning apparatus 1a 1st washing tank 1b 2nd washing tank 1c 3rd washing tank 2 Quartz plate 3 Filter 4 Return pipe 4a Return branch pipe 4b Return branch pipe 5 Feed pipe 6 Liquid feed pump 7 Heat exchanger 9 Heater 10 Feed tube 11 suction pump 12 SS remover 13 SS capture filter 20 electrolytic reactor 21 anode 22 cathode 23 bipolar electrodes 24 DC power supply

Claims (9)

A cleaning apparatus that cleans an electronic material substrate by using a persulfuric acid solution heated to 120 ° C. or higher as a cleaning solution and removes the resist on the substrate, and at least an anode uses a conductive diamond electrode. An electrolytic reaction device that generates sulfuric acid ions from sulfuric acid ions contained in a solution having a sulfuric acid concentration and a temperature of 10 ° C. to 90 ° C. to regenerate the persulfuric acid solution, and between the cleaning device and the electrolytic reaction device A circulation line for circulating the solution while performing the washing and the electrolysis, a cooling means for cooling the solution sent in the circulation line from the washing device to the electrolytic reaction device, and the cooling from the washing device An SS removal device having an SS capture filter that captures and removes SS in the solution sent in the circulation line leading to the means ,
The electronic material substrate is a semiconductor substrate to which a resist by pattern processing is attached, and is subjected to the cleaning without undergoing a pretreatment step in which the resist is oxidized and incinerated in advance.
The SS trapping filter, sulfuric acid recycle type cleaning system according to claim Rukoto which have a pore diameters of ≦ 0.1mm or 0.1 [mu] m.   2. The sulfuric acid recycling type cleaning system according to claim 1, wherein the SS trapping filter is a recyclable ceramic filter that is detachable and capable of removing the trapped SS by combustion.   The sulfuric acid recycling type cleaning system according to claim 1, wherein the cleaning device includes a plurality of cleaning tanks for sequentially cleaning the material to be cleaned.   The SS removing device is connected to the washing tank so as to remove SS in the washing tank of one or more front side washing ranks including the first washing rank. The sulfuric acid recycling type cleaning system according to any one of the above.   Among the plurality of cleaning tanks, one or two or more front cleaning order cleaning tanks including the first cleaning order enable solution circulation with the electrolytic reaction device independently of other cleaning tanks. 5. The two or more rear washing order washing tanks including the final washing order are connected in series so that the solution can be circulated with the electrolytic reaction apparatus. The sulfuric acid recycling type cleaning system described in 1.   6. The sulfuric acid recycle type cleaning system according to claim 5, wherein the cleaning tanks connected in series are set upstream in order of upstream cleaning.   6. The sulfuric acid recycling type cleaning system according to claim 5, wherein a filtration filter is interposed between the cleaning tanks in a part or all of the cleaning tanks connected in series.   The sulfuric acid recycling type cleaning system according to any one of claims 4 to 7, further comprising a heating device that heats the persulfuric acid solution of at least the first cleaning order of the cleaning tanks in the front order.   The sulfuric acid recycle type cleaning system according to any one of claims 1 to 8, further comprising heating means for heating a persulfuric acid solution used in the cleaning device.

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