Cleaning water producing device and cleaning water producing method

Abstract

To provide a cleaning water production device and a cleaning water production method capable of accurately and stably adjusting solute concentration of dilute cleaning water to a desired value.SOLUTION: A cleaning water production device produces cleaning water having constant concentration by adding a chemical agent containing a pH adjusting agent and / or an oxidation-reduction potential adjusting agent to ultrapure water. Retention time of the cleaning water from an addition position of the chemical agent to an outlet of the cleaning water production device is 30 seconds or more. A cleaning water production method produces cleaning water having constant concentration by adding the chemical agent containing the pH adjusting agent and / or the oxidation-reduction potential adjusting agent to ultrapure water using the cleaning water production device. A retention time of the cleaning water from the addition position of the chemical agent to the outlet of the cleaning water production device is set to be 30 seconds or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus for producing cleaning water for semiconductor wafers and the like by adding a pH adjuster, an oxidation-reduction potential adjuster, etc. to ultrapure water, and particularly to a cleaning water producing apparatus and method suitable for producing dilute cleaning water containing solutes such as a pH adjuster and an oxidation-reduction potential adjuster at very low concentrations. [Background technology]

[0002] In the cleaning and rinsing process for semiconductor wafers, dilute conditioned water (including rinse water) is sometimes used as cleaning water (including rinse water) by dissolving an acid or alkaline pH adjuster or an oxidation-reduction potential adjuster such as an oxidizing agent or reducing agent in ultrapure water at a very low concentration, the minimum necessary, in order to suppress wafer charging, metal corrosion and dissolution, and particle adhesion (see, for example, Patent Document 1). While one method for producing this dilute cleaning water involves dissolving reducing, oxidizing, acidic, or alkaline gases, such as H2, O2, O3, CO2, or NH3, in ultrapure water, a method in which a chemical solution containing a pH adjuster and / or an oxidation-reduction potential adjuster dissolved in water is often adopted due to its simple operation. Chemical solution injection methods include using a pump and pressurizing a sealed container with an inert gas, such as N2, both of which are in practical use.

[0003] Fluctuations in the solute concentration of cleaning water can lead to deterioration of the cleaning ability of semiconductor materials and corrosion, so it is necessary to stably supply cleaning water of the desired concentration to downstream equipment (cleaning machines, CMP equipment, wafer bonding equipment, etc.).

[0004] If the flow rate of ultrapure water is constant and the amount of solute added is sufficiently large, the ultrapure water (solvent) and the chemical solution (solute) are easily mixed, making it easy to achieve the desired solute concentration. However, because the amount of solute added to ultrapure water to produce diluted cleaning water is extremely small, simply adding the solute does not result in the ultrapure water and the solute being mixed sufficiently uniformly, and there is a risk that cleaning water with a quality that is significantly different from the desired solute concentration will be supplied to downstream equipment.

[0005] Furthermore, in downstream equipment that uses diluted cleaning water, the supply and stop of water poured onto the wafer is controlled by opening and closing multiple valves, causing the flow rate to fluctuate irregularly. Accordingly, the flow rate of the cleaning water produced by the cleaning water production equipment also fluctuates. Therefore, even if the ultrapure water and solutes are sufficiently mixed when the cleaning water flow rate is constant, repeated fluctuations in the flow rate can cause the solute concentration in the cleaning water to deviate significantly from the desired concentration.

[0006] Line mixers and the like are sometimes used to efficiently mix chemicals and other liquids in piping, but when the amount of solute is extremely small, mixing is insufficient using only a line mixer.

[0007] One simple method is to prioritize stabilizing the liquid quality and continue to produce and supply diluted cleaning water under constant conditions, but in this case, excess water will simply be discharged.In recent multi-chamber single-wafer cleaning machines, there is a large difference between the maximum and minimum flow rates required at any given time, so if a large flow of cleaning water is continuously supplied, a considerable amount of excess water will be discharged, which will cause problems in terms of burdening the water supply and drainage facilities and excessive use and discharge of chemicals.

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-139766 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a cleaning water producing apparatus and a cleaning water producing method that can accurately and stably adjust the solute concentration of diluted cleaning water to a desired value. [Means for solving the problem]

[0010] The gist of the present invention is as follows.

[0011] [1] A cleaning water producing apparatus that produces cleaning water of a certain concentration by adding a chemical agent containing at least one of a pH adjuster and an oxidation-reduction potential adjuster to ultrapure water, A cleaning water producing device in which the residence time of cleaning water from the point where the chemical is added to the outlet of the cleaning water producing device is 30 seconds or more.

[0012] [2] A sensor for detecting the chemical concentration of the cleaning water; a control unit that controls the amount of drug added so that the detection result of the sensor falls within a predetermined range; The cleaning water producing device according to [1], comprising:

[0013] [3] The cleaning water producing device according to [1], which is provided with a tank for retaining the cleaning water.

[0014] [4] The cleaning water producing apparatus according to [1], wherein the chemical agent contains ammonia, and the ammonia concentration of the cleaning water at the outlet of the cleaning water producing apparatus is 50 ppm or less.

[0015] [5] A cleaning water producing method for producing cleaning water of a certain concentration by adding a chemical agent containing at least one of a pH adjuster and an oxidation-reduction potential adjuster to ultrapure water using a cleaning water producing apparatus, A cleaning water producing method in which the residence time of cleaning water from the location where the chemical is added to the outlet of the cleaning water producing device is 30 seconds or more. [Effects of the Invention]

[0016] The solutes in dilute cleaning water are generally supplied by adding EL-grade chemicals, such as alkalis such as NH3, acids such as HCl, and oxidants such as H2O2. These are all added in amounts on the order of ppm at most to adjust the liquid quality, so the amount added is extremely small, about 1 / 10,000 to 1 / 100,000 of the ultrapure water flow rate.

[0017] Simply adding a small amount of this solute to ultrapure water will not result in sufficient mixing, making it impossible to supply homogeneous cleaning water of the desired concentration.In the present invention, the residence time from the addition of the solute to the outlet of the cleaning water production device is set to 30 seconds or more, so even if only a small amount of solute is added, it is possible to supply sufficiently mixed, stable cleaning water of the desired concentration to downstream equipment.

[0018] According to the cleaning water producing device and method of the present invention, cleaning water of a desired concentration can be produced accurately and stably, even if the amount of solute added is extremely small, regardless of fluctuations in the amount of water used. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a configuration diagram of a cleaning water producing device according to an embodiment. [Figure 2] 10 is a graph showing experimental results. [Figure 3] 10 is a graph showing experimental results. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be described in further detail below.

[0021] In the present invention, cleaning water of a certain concentration is produced by adding an agent containing at least one of a pH adjuster and an oxidation-reduction potential adjuster to ultrapure water.

[0022] Examples of pH adjusters include, but are not limited to, acids such as CO2, acetic acid, hydrochloric acid, nitric acid, sulfuric acid, hydrogen fluoride, citric acid, lactic acid, and phosphoric acid, and alkalis such as NH3, sodium hydroxide, potassium hydroxide, and TMAH. Examples of oxidation-reduction potential adjusters include, but are not limited to, oxidizing substances such as H2O2 and O3, and reducing substances such as H2 and hydrazine.

[0023] The upper limit of the concentration of the pH adjuster or redox potential adjuster in the produced cleaning water is preferably 500 ppm or less, more preferably 50 ppm or less. The lower limit of the concentration of the pH adjuster or redox potential adjuster is preferably 0.1 ppm or more, more preferably 1 ppm or more. When the concentration is within the above range, the properties of the cleaning water can be stabilized.

[0024] In one aspect of the present invention, the agent is ammonia, and the upper limit of the ammonia concentration of the cleaning water at the outlet of the cleaning water producing device is preferably 50 ppm or less, more preferably 40 ppm or less. Also, the lower limit of the ammonia concentration is preferably 0.1 ppm or more, more preferably 0.5 ppm or more. When the ammonia concentration is within the above range, the properties of the cleaning water can be stabilized.

[0025] The addition of chemicals such as acids, alkalis, oxidizing agents, and reducing agents can be achieved using conventional chemical injection or gas dissolution mechanisms. For chemical injection, the desired solute concentration can be achieved by pumping or using an inert gas such as N2. The amount of solute added can be controlled using proportional control based on the ultrapure water flow rate or PID control using a monitor installed near the injection point.

[0026] The location where the chemical solution is added is determined so that the retention time of the cleaning water from the chemical solution addition location to the outlet of the cleaning water production equipment is at least 30 seconds. The retention time can be calculated from the ultrapure water flow rate and the total volume of the equipment components (pipes, tanks, membranes, etc.) from the chemical solution addition location to the outlet of the cleaning water production equipment. If the amount of cleaning water used in the downstream equipment fluctuates, it is desirable to determine the retention time based on the ultrapure water flow rate when the amount of water used is the highest.

[0027] If the equipment alone does not provide sufficient residence time, some of the piping may be enlarged or a tank may be installed. A line mixer may also be installed. If a tank is installed, it is preferable that the water flow direction be upward to improve mixing.

[0028] 1 shows an example of a cleaning water production apparatus of the present invention. Ultrapure water is delivered to a tank 2 through a pipe 1. A chemical solution in a chemical tank 3 is added to this pipe 1 via a chemical injection pump 4 and a pipe 5.

[0029] The chemical solution and ultrapure water mix together while flowing through pipe 1 and while remaining in tank 2, becoming diluted cleaning water. This diluted cleaning water is sent from tank 2 through pipe 6, filter 7, and pipe 8 to downstream equipment such as a wafer cleaner. A solute concentration control monitor 9 is installed in pipe 8.

[0030] The solute concentration control monitor 9 used is one suited to the type of chemical solution, such as an oxidation-reduction potential meter (ORP meter), a conductivity meter, etc. The chemical injection pump 4 is controlled based on the detection value of the solute concentration control monitor 9 and the ultrapure water flow rate.

[0031] In FIG. 1, a chemical injection pump 4 is used, but a method of applying pressure to an inert gas such as N2 inside the chemical tank 3 to pump and inject the chemical may also be used.

[0032] In this cleaning water production system, the location where the chemical is added, i.e., the connection point A between pipe 5 and pipe 1, has a residence time up to the outlet of the cleaning water production system that is preferably 30 seconds or more, and more preferably 60 seconds or more. The upper limit of the residence time up to the outlet of the cleaning water production system is preferably 300 seconds or less, more preferably 120 seconds or less, and particularly preferably 90 seconds or less. Within this residence time range, the solute can be homogenized with the ultrapure water, allowing cleaning water to be produced efficiently. In this embodiment, the outlet of the cleaning water production system is position B on pipe 8 where the solute concentration control monitor 9 is installed. The upper limit of the flow rate of ultrapure water is preferably 300 L / min or less, more preferably 100 L / min or less. The lower limit of the flow rate of ultrapure water is preferably 0.5 L / min or more, more preferably 2 L / min or more, and particularly preferably 5 L / min or more. Within this flow rate range, the solute can be homogenized with the ultrapure water, allowing for efficient production of cleaning water. The water pressure of the ultrapure water is in the range of 0.01 to 10 MPa. [Example]

[0033] [Example 1] Using the apparatus shown in FIG. 1, cleaning water with an ammonia concentration of 1 ppm was produced.

[0034] The inner diameter of pipe 1 is 16.2 mm. The distance L from the connection point A between pipes 1 and 5 to tank 2 is 800 mm. Tank 2 has an inner diameter of 99.4 mm, a height of 627 mm, a volume of 4.86 L, and an upward flow system. The inner diameter of pipe 6 is 16.2 mm and the length is 500 mm. The volume of filter 7 is 2.1L The distance from the filter 7 to the solute concentration control monitor 9 is 100 mm. Solute concentration control monitor 9 is a conductivity meter Ammonia water concentration in chemical tank 3 is 28 wt% It was decided.

[0035] The volume from the connection point A between the pipes 1 and 5 to the installation point B of the solute concentration control monitor 9 on the pipe 8 is 7.25 L.

[0036] When ultrapure water was flowed through this cleaning water production apparatus 1 at 14.5 L / min, the residence time between points A and B was 30 seconds. With the residence time set to 30 seconds (ultrapure water flow rate 14.5 L / min) and the chemical feed rate from pump 4 set to 0.057 mL / min, cleaning water with a target ammonia concentration of 1 ppm (electrical conductivity 6.65 μS / cm) was produced.

[0037] The change over time in the conductivity detected by the solute concentration control monitor 9 is shown in Figure 2. As shown in Figure 2, the conductivity of the cleaning water was maintained at a constant value that was almost in line with the target value.

[0038] [Comparative Example 1] Cleaning water with a target ammonia concentration of 1 ppm (conductivity of 6.65 μS / cm) was produced under the same conditions as in Example 1, except that the ultrapure water flow rate and chemical injection amount were not changed, the height of tank 2 was increased to 160 mm, thereby reducing the volume of tank 2 to 1.24 L, and the residence time was set to 15 seconds. Figure 2 shows the change over time in the conductivity detected by the solute concentration control monitor 9.

[0039] As shown in Figure 2, the conductivity of the cleaning water varied widely between 5.5 and 7.5 μS / cm, sometimes falling outside the range of ±10% of the target value.

[0040] [Example 2, Comparative Example 2] The ultrapure water flow rate was switched between 15 L / min and 5 L / min every 1000 seconds, and the connection point A of the pipes 1 and 5 was changed to set the residence time to 30 seconds (Example 2) or 15 seconds (Comparative Example 2). The target ammonia concentration was the same as in Example 1. The change over time in the detected conductivity of the solute concentration control monitor 9 is shown in Figure 3.

[0041] As shown in Figure 3, when the residence time was set to 15 seconds, the conductivity at the outlet of the cleaning water production system fluctuated significantly when the ultrapure water flow rate fluctuated, significantly deviating from the range of ±10% of the set value. Furthermore, it was found that once a fluctuation in the ultrapure water flow rate occurred, the conductivity at the outlet of the cleaning water production system was difficult to stabilize and continued to fluctuate, even if the ultrapure water flow rate stabilized. On the other hand, when the residence time was set to 30 seconds, although the conductivity at the outlet of the cleaning water production system fluctuated slightly when the ultrapure water flow rate fluctuated, it did not deviate from the range of ±10% of the set value and quickly settled to the set concentration value.

[0042] The above results show that by ensuring sufficient residence time, the ultrapure water and ammonia are thoroughly mixed, making it possible to stably supply cleaning water with a uniform ammonia concentration, regardless of changes in the amount of water used in downstream equipment.

[0043] In semiconductor materials and manufacturing processes, where even slight dissolution can have a significant impact on semiconductor performance, fluctuations in the ammonia concentration in cleaning water that exceed a range of ±10% of the set value mean a decrease in semiconductor manufacturing yield. Therefore, in order to stably supply cleaning water with a uniform ammonia concentration, it is necessary to ensure a residence time of at least 30 seconds after adding ammonia. [Explanation of symbols]

[0044] 2 Tanks 3 Chemical tank 4 Chemical injection pump 7 Filters 9 Solute concentration control monitor

Claims

1. A cleaning water producing apparatus for producing cleaning water of a certain concentration by adding a chemical agent containing at least one of a pH adjuster and an oxidation-reduction potential adjuster to ultrapure water, The capacity of the device is set based on the maximum usage flow rate of the downstream device so that the residence time of the cleaning water from the addition position of the chemical to the outlet of the cleaning water producing device is 30 to 120 seconds, a tank for retaining the cleaning water, the water flowing in the tank being an upward flow; The cleaning water producing apparatus, wherein the chemical agent contains ammonia, and the ammonia concentration of the cleaning water at the outlet of the cleaning water producing apparatus is 0.1 to 1 ppm.

2. a sensor for detecting the chemical concentration of the cleaning water; a control unit that controls the amount of drug added so that the detection result of the sensor falls within a predetermined range; The cleaning water producing device according to claim 1, comprising:

3. A cleaning water producing method for producing cleaning water of a certain concentration by adding a chemical agent containing at least one of a pH adjuster and an oxidation-reduction potential adjuster to ultrapure water using a cleaning water producing apparatus, comprising: The residence time of the cleaning water from the adding position of the agent to the outlet of the cleaning water producing device is set to 30 to 120 seconds, The cleaning water is passed through an upward flow tank disposed between the chemical addition position and the outlet of the cleaning water producing device, The cleaning water producing method, wherein the chemical agent contains ammonia, and the ammonia concentration of the cleaning water at the outlet of the cleaning water producing device is 0.1 to 1 ppm.

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