JPS61159116A - Weighing equipment for liquid - Google Patents

Abstract

PURPOSE:To improve weighing accuracy of the titled equipment by providing an airtight weighing vessel, a platform scale, inlet pipes, an outlet pipe, an air flowing-in and discharging means, spiral pipe parts, etc. CONSTITUTION:The weighing equipment is composed of the weighing vessel 15 on the platform scale 14 put on a fixed base 19, the inlet pipes 37, 50, 54 to flow in a liquid, the outlet pipe 58 to discharge the liquid, a means to flow the air into the vessel 15 and discharge it therefrom with increase and decrease of the liquid within the vessel 15, the spiral pipe part 40, 48, 53, etc. Then, since the upstream ends are connected with the liquid sending pipings 36, 47, 52 and the lower ends of the inlet pipes 37, 50, 54 to flow in the liquid from the upper part are always immersed in the liquid of the vessel 15, there is no dropping load of the liquid and after a supply of the liquid is stopped, the surplus liquid is not supplied to the vessel 15 and the supplied amount to the vessel 15 can be weighed accurately. Further, since the upstream ends of the spiral pipe parts 40, 48, 53 are supported by the fixed frame 43, the large tensile load and compression load do not work on the vessel 15 and weighing accuracy can be more improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a measuring device used for measuring various liquids, such as cleaning liquids for wafers such as silicon, chemicals for preparing etching liquids, and the like.

[Prior art] For example, a processing solution for surface treatment (cleaning, etching, etc.) of silicon wafers etc. contains a cleaning agent such as ammonia, sulfuric acid, hydrochloric acid, etc. and an oxidizing agent such as hydrogen peroxide solution in a predetermined ratio. A mixed solution is used. In order to obtain good processing effects with such processing liquids, it is necessary to accurately adjust the mixing ratio.

By the way, many of the undiluted solutions used to prepare cleaning solutions are highly corrosive, so when such undiluted solutions are measured with a general-purpose flowmeter, metal ions etc. may be eluted into the solution from the flowmeter material. There is a problem that the liquid deteriorates.

There is also a method of supplying each stock solution at a constant flow rate to a mixing container in which each stock solution is mixed, and controlling the supply amount of each stock solution by adjusting the supply time. Since it is easy to change, accurate measurement is difficult.

Therefore, attempts have been made to measure the supply amount of the stock solution by weight, and as an example, as shown in FIG. and an inlet pipe 4 connected to the liquid feeding pipe 3, and the weight of the fed chemical solution is measured by the amount of change in the weight of the measuring container 2 before and after the feeding of the chemical solution. Are known.

However, in the above-mentioned measuring device, if the feeding speed of the drug solution is constant, the drug solution will increase to the level of the stored liquid 5 in the measuring container 2 after the start of feeding, as shown by the imaginary line in FIG. 3(b). The weight of the weighing container 2 is supposed to increase linearly after summer, at time T when it reaches the surface, but in reality, the dynamic load and falling load FM of the chemical solution
acts on the platform scale 1, so that the apparent weight change of the weighing container 2 measured by the platform scale 1 becomes larger than the actual weight change, as shown by the solid line, and the weight change is equal to the target value W. Even if the opening/closing valve 6 is closed when this point is reached, the chemical liquid that has already left the inlet pipe 4 will fall directly into the measuring container 2, so there is a problem that sufficient measuring accuracy cannot be obtained.

Furthermore, as shown in FIG. 4(a), a metering device may be considered in which an inlet pipe 8 fixed to a closed type metering container 7 is connected to the liquid feeding pipe 3. This is preferable in terms of preventing dust from entering.

However, in the metering device of FIG. 4(a), as shown in FIG. 4(b), after the start of liquid feeding, after the time T1 when the chemical liquid reaches the liquid level, the inlet pipe is closed due to the jetting of the chemical liquid. The reaction force F^ applied to 8 and the dynamic load and falling load F of the above-mentioned chemical solution, etc.
M is in equilibrium and the influence on the weight change temporarily disappears, but even if the on-off valve 6 is closed when the target value W0 is reached, the chemical liquid that has already left the inlet pipe 8 will still be in the measuring container 7 as described above. There is a problem that the amount of chemical solution supplied increases when the liquid drops to the surface, causing the measured value to falsify, and good measurement accuracy cannot be obtained. With the downward displacement of the platform scale 1, a large tensile load is applied from the liquid feed pipe 3 to the measuring container 7, which acts as a load on the platform scale 1, resulting in a further decrease in measurement accuracy.

[Object of the Invention] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to improve the measurement accuracy of a type of measuring device that uses a platform scale to measure liquid by weight.

[Structure of the Invention] Therefore, in the present invention, a liquid measuring device includes: a measuring container whose upper part is sealed by a lid member; a platform scale placed on a fixed table to support the measuring container; and a liquid feeding device. The upstream end is connected to the piping, and there is an inlet pipe that allows liquid to flow into the measuring container from above, an outlet pipe that discharges the liquid in the measuring container, and an air pipe that flows into the measuring container as the liquid in the measuring container increases or decreases. The inlet pipe has a middle portion fixed by a lid member of the measuring container such that its lower end is located near the bottom of the measuring container, and a portion above the lid member. is formed as a spiral tube section that can expand and contract following the vertical movement of the measuring container, and the upstream end of the spiral tube section is fixedly attached to seven fixed frames. Note that as the platform balance, for example, an electromagnetic force self-balancing electronic balance or a load cell type balance can be used.

[Effect of the Invention J According to the present invention, since the lower end of the inlet pipe is constantly immersed in the liquid in the measuring container, the falling load of liquid such as medicinal solution is eliminated.
Further, the dynamic load of the liquid jetted from the lower end of the inlet pipe is always balanced with the reaction force applied to the inlet pipe. Furthermore, since excess liquid is not supplied to the measuring container after the liquid supply is stopped, the amount of liquid supplied to the measuring container can be accurately measured.

In addition, a spiral tube portion is formed in a portion above the lid member of the inlet pipe, and expands and contracts according to the vertical movement of the weighing container on the platform balance as the liquid in the weighing container increases and decreases. Since the upstream end is supported by a fixed frame, the weight of the inlet pipe can be supported by the fixed frame, and even if the weighing container moves up and down due to fluctuations in the platform scale, the vertical movement is absorbed by the expansion and contraction of the spiral tube. Therefore, there is no possibility that a large tensile load or compressive load will be applied to the measuring container.
Therefore, measurement accuracy can be further improved.

Furthermore, since the measuring container is sealed, it is possible to prevent foreign matter such as dust from entering the liquid in the measuring container.
This prevents the liquid from deteriorating during metering.

"Example" Examples will be described below.

FIG. 1 shows a compounding device for preparing a cleaning solution for wafers such as silicon. A sealed and movable first replenishment container 13 for replenishing ammonia 11, a second storage container (not shown) for storing hydrogen peroxide solution, and a second storage container for replenishing the second storage container with hydrogen peroxide solution. A replenishment container (not shown) and a closed weighing/mixing container 15 are placed on a platform scale 14 (electromagnetic force self-balancing electronic balance or load cell type balance) placed on a fixed table 19, and the above-mentioned A measuring/mixing device 17 that measures and mixes the ammonia 11, hydrogen peroxide solution, and pure water supplied from the first storage container 12, the second storage container, and the pure water supply port 16, respectively, and the inside of the measuring/mixing container 15. and a third closed storage container 20 for storing the cleaning liquid 18 prepared in the above.

Note that the cleaning liquid 18 may be directly supplied from the measuring/mixing container 15 to a wafer cleaning tank (not shown).

Detection devices 21 and 22 are installed in the first storage container 12 to detect the preset upper limit level L1 and lower limit level L2 of the ammonia 11 liquid level, so that the ammonia 11 liquid level is always at the upper limit level L, Ammonia 11 is supplied from the first replenishment container 13 so as to be located between the lower limit level L2 and the lower limit level L2.
Ammonia 11 is supplied by a liquid feeding pump 25 (air-driven bellows pump) through a liquid feeding pipe 24 having a liquid detector 23 for detecting the flow condition of the liquid. The liquid feeding pump 25 has a driving air supply port 26.
The pressure regulator 27 and pressure gauge 28 are driven by compressed air supplied from the air pipe 30 through an interposed air pipe 30.

Further, the ammonia 11 in the first storage container 12 is fed under pressure from a gas supply port 31, a pressure regulator 32, and a gas filter 33.
A high pressure gas (air, nitrogen, etc.) is supplied through the gas pipe 35 in which the pressure gauge 34 is installed.
and is supplied to the measuring/mixing container 15 through an inlet pipe 37.

The inlet pipe 37 connects the lower end of a spiral pipe 40 provided above a lid member 38 that seals the upper part of the measuring/mixing container 15 and the upper end of a straight pipe 41 disposed inside the measuring/mixing container 15. It is connected by a pipe joint 42 fixed to a member 38,
The spiral tube 40 is made of a resin such as thiamin and is expandable and retractable so as to absorb vertical movement of the weighing/mixing container 15 on the platform scale 14 due to an increase or decrease in the liquid in the weighing/mixing container 15.

The longitudinal center line of the spiral tube 40 is oriented in the vertical direction, and the upper end of the spiral tube 40 is connected to seven fixed frames 43.
It is connected to the liquid feeding pipe 36 via a pipe joint 45 on a bar 44 suspended horizontally therebetween, and the upper and lower ends of the spiral pipe 40 are located on the center line.

On the other hand, the lower end of the straight pipe 41 forming the injection nozzle is immersed in the liquid in the metering/mixing container 15 at all times.
It is located near the bottom ISa of the mixing container 15. In other words, the lower limit level L, which is higher than the lower end of the straight pipe 41 of the inlet pipe 37, is set in the weighing/mixing container 15, and the platform scale is set so that the liquid level in the weighing/mixing container 15 does not fall below the lower limit level L. 14 output signals, i.e. measuring and mixing container 15
Based on the weight of the liquid, the amount of liquid discharged from the measuring/mixing container 15 is limited.

In this embodiment, the amount of ammonia 11 supplied from the first storage container 12 to the weighing/mixing container 15 is measured by the platform scale 14 as the amount of change in the weight of the weighing/mixing container 15 before and after the ammonia 11 is supplied. , since the lower end of the straight pipe 41 of the inlet pipe 37 is constantly immersed in the liquid in the metering/mixing container 15,
When ammonia 11 is supplied, the falling load of ammonia 11 disappears, and the dynamic load of ammonia 11 and the reaction force applied to the straight pipe 41 cancel each other out. The weight of the mixing container 15 increases linearly as shown in FIG.
When the amount of weight change reaches the target value W0, the liquid feeding pipe 36
When the opening/closing valve 46 interposed therein is closed, the supply of ammonia 11 to the measuring/mixing container 15 is immediately stopped, and the supply amount can be accurately measured.

On the other hand, the hydrogen peroxide solution is transferred from the second storage container to an inlet pipe 50 consisting of a liquid feeding pipe 47, a first spiral IF 48, and a straight pipe 49.
Further, pure water is supplied from the pure water supply port 16 to the measuring/mixing container 15 via a pure water pipe 52 having a pressure regulator 51 and an inlet pipe 55 consisting of a spiral pipe 53 and a straight pipe 54, respectively. , ammonia 11, hydrogen peroxide solution, and pure water are mixed at a predetermined mixing ratio, each being weighed in the same manner as described above. The lower ends of both the straight pipes 49 and 54 are located below the lower limit level L, similarly to the straight pipe 41.

The above-mentioned mixed liquid is continuously transferred to the measuring/mixing container 15 and the third storage container 20 through an outlet pipe 58 consisting of a straight pipe 56 and a spiral pipe 57.
A circulation/discharge pump (bellows pump) 64 is installed in a circulation path 63 including a metering/mixing container 15 formed by a part of a discharge pipe 60 communicating with the spiral pipe 61 and a return flow pipe 62 connected to a spiral pipe 61. The cleaning liquid 18 is circulated and stirred by the suction force and discharge force of the heat exchanger, and a cleaning liquid 18 having a uniform composition is prepared.During the circulation, the cleaning liquid 18 is filtered by a fluid filter 65 to remove impurities. 66 adjusts the temperature of the cleaning liquid 18. The thoroughly stirred and filtered cleaning liquid 18 is then transferred to the third storage container 20 or the aforementioned cleaning tank through the discharge pipe 60. Cleaning from the measuring/mixing container 15 to the third storage container 20 or cleaning tank
The daily supply amount is measured by a platform scale 14.

The measuring/mixing container 15 is equipped with a supply/exhaust pipe 68 in which a ventilation filter 67 is interposed, and air is supplied to the measuring/mixing container 15 as liquid is supplied to the measuring/mixing container 15. It is designed to be ejected.

In addition, the platform scale 14 by supplying liquid to the weighing/mixing container 15
Although the amount of vertical displacement depends on the capacity of the weighing/mixing container 15, it is usually only a few - at most when an electromagnetic force self-balancing type electronic balance or a load cell type balance is used as the platform scale 14 (electromagnetic force Self-balancing electronic balances have a reference height,
It is controlled to maintain this height at all times, but if there is a large load fluctuation, slight fluctuations will be repeated until equilibrium is reached. No tensile or compressive loads are applied to the measuring/mixing container 15 from the water pipe 52, the discharge pipe 6o, and the return pipe 62, and each spiral pipe 40.48, 53.57.
Since only a weak tensile or compressive load is applied from 61, the vertical displacement of platform scale 14 has very little effect on the measurement accuracy. 6 In the above embodiment, ammonia 11 and Although we have described the case where hydrogen peroxide solution and pure water are mixed to prepare a cleaning liquid for the surface of a silicon wafer, the measuring/mixing device 17 is used not only for preparing a processing liquid for silicon wafers but also for preparing various other chemical liquids. It goes without saying that it can be used for compounding, and can also be used not only when mixing multiple medicinal solutions, but also as a measuring device for a single medicinal solution.

[Brief explanation of drawings]

Fig. 1 is an overall explanatory diagram of a silicon wafer cleaning liquid preparation device equipped with a measuring/mixing device according to the present invention, and Fig. 2 shows the time after the start of measurement in the measuring/mixing device shown in Fig. 1 and the length of the measuring container. Graph showing the relationship with weight change, Figure #13 (
a) is an explanatory diagram of the first conventional example, FIG. 3(b) is a graph corresponding to FIG. 2 of the first conventional example, FIG. 4(a) is an explanatory diagram of the second conventional example, FIG. (b) is a graph corresponding to FIG. 2 of the second conventional example. 11... Ammonia (liquid), 14... Platform scale,
15...Measuring container, 15a...Bottom, 19...
・Fixing stand, 36, 47.52...Liquid delivery piping,
37°50.54...Inlet pipe, 40,48,53.
...Spiral tube part, 43...Fixed frame, 58
... Outlet pipe, 68... Supply and exhaust pipe. Patent applicant: Kurashiki Boseki Co., Ltd. Agent
Patent attorney Maeda Ao and 2 others Figure 2 *m

Claims (2)

[Claims] (1) A measuring container whose upper part is sealed by a lid member, a platform scale placed on a fixed stand and supporting the measuring container, and a scale whose upstream end is connected to a liquid supply pipe, and which supplies liquid upward into the measuring container. An inlet pipe for allowing air to flow in from the measuring container, an outlet pipe for discharging the liquid in the measuring container, and a means for causing air to flow into or discharge from the measuring container as the liquid in the measuring container increases or decreases, and the inlet pipe is , the middle part is fixed by the lid member of the measuring container so that the lower end is located near the bottom of the measuring container, while the part above the lid member is a spiral that can expand and contract following the vertical movement of the measuring container. A liquid metering device, characterized in that it is formed as a tube section, and the upstream end of the spiral tube section is fixedly attached to a fixed frame. (2) Claim No. 1, characterized in that the platform scale is an electromagnetic force self-balancing electronic balance or a load cell type balance.
1) The liquid measuring device described in item 1).