JP3040313B2 - Low concentration adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-concentration adjusting device, and more particularly to a low-concentration adjusting device for adjusting a chemical solution to a low-concentration target concentration.

[0002]

2. Description of the Related Art In the manufacturing process of semiconductors and liquid crystal display devices,
A substrate processing step using a processing liquid such as etching, photoresist stripping after etching, and substrate cleaning after stripping is indispensable. In this type of substrate processing process, for example, an etching process or a cleaning process using a low concentration solution of hydrofluoric acid (HF) is performed.

[0003] In the case of preparing a low-concentration processing solution, conventionally, a chemical solution is prepared in a mixing tank to a desired concentration and then supplied to the processing tank, or a chemical solution is prepared in the processing tank to a desired concentration. ing. In the preparation of such a drug solution, first, the drug solution and the diluent are supplied in a fixed amount to each of the target concentrations, and the concentrations are measured by a concentration sensor. The chemical solution or the diluent is supplied by the difference between the target solution and the target concentration.

[0004]

In such a concentration sensor for measuring the concentration of a low-concentration chemical solution, a reproducibility and detection accuracy of the sensor are not good, so that a detection error in a predetermined range occurs. For example, when measuring the concentration of 1% hydrofluoric acid, a detection error of about 1% ± 0.01% occurs. Therefore, it is difficult to control the low-concentration processing solution to a constant concentration according to the detection concentration of the concentration sensor. For this reason, if the chemical solution and the diluent are supplied with the aim of the target concentration from the beginning, the chemical solution concentration may be too high. At this time, if a diluting solution is added so as to make the concentration thinner, it repeatedly becomes too thin and then becomes too dense, so that the concentration hardly quickly converges to the target concentration.

[0005] In addition, when the mixture is prepared in a processing tank, the concentration may decrease as the processing proceeds. In such a case, if a chemical solution is prepared for the target concentration, a similar problem occurs, and it is difficult to quickly converge to the target concentration. The purpose of the present invention is
An object of the present invention is to make a low-concentration chemical solution quickly converge to a target concentration.

[0006]

SUMMARY OF THE INVENTION A low concentration adjusting apparatus according to the present invention is an apparatus for adjusting a chemical solution to a low concentration target concentration, comprising a storage tank, a concentration detection means, a target value setting means, and a concentration control means. Adjusting means. The storage tank is for storing a chemical solution. The concentration detecting means intermittently detects the concentration of the chemical solution stored in the storage tank within a predetermined detection error range with respect to the target concentration. The target value setting means sets a density between the target density and the detected density to a new target value when the density detecting means detects a density different from the target density. The concentration adjusting means adjusts the chemical concentration such that the concentration of the chemical in the storage tank becomes the target value set by the target value setting means.

It is preferable that the target value setting means sets a half of the density between the detected density and the target density as the target value. A concentration adjusting unit configured to supply a chemical solution having a concentration higher than the target concentration to the storage tank; and a liquid supply unit configured to supply the chemical solution according to the target value set by the target value setting unit when the detected concentration is lower than the target concentration. It is preferable to have an operating means for operating.

The concentration adjusting means includes a diluting liquid supply means for supplying a diluting liquid for diluting the chemical to the storage tank, and a detecting means for adjusting the target concentration set by the target value setting means when the detected concentration is higher than the target concentration. It is preferable to have operating means for operating the diluting liquid supply means accordingly. Further, it is preferable that the apparatus further comprises a circulating means for discharging the chemical solution from the storage tank and returning it to the storage tank, and the concentration detecting means detects the concentration of the circulating chemical solution.

Preferably, the operating means operates the chemical liquid supply means and the diluent liquid supply means so that the concentration of the chemical liquid becomes lower than the lower limit of the detection error range of the target concentration when a new chemical liquid is prepared in the storage tank.

[0010]

In the low-concentration adjusting device according to the present invention, when the chemical is stored in the storage tank, the concentration detecting means detects the concentration of the chemical within a predetermined detection error range. When the detected density is different from the target density, the target value setting means sets a density between the target density and the detected density to a new target value. Then, the concentration adjusting means adjusts the concentration of the chemical so that the concentration of the chemical becomes the target value set by the target value setting means.

Here, since the density adjustment is not performed directly on the target density but on a target value between the target density and the detected density, the density detecting means detects the density within a predetermined detection error range. However, the density quickly converges to the target density without increasing or decreasing. When half the detected density and the target density are set to the target value, the target density can be converged more efficiently.

The concentration adjusting means includes a chemical liquid supply means for supplying a chemical liquid having a concentration higher than the target concentration to the storage tank, and when the detected concentration is lower than the target concentration, the concentration adjusting means is adapted to the target value set by the target value setting means. In the case of having the operating means for operating the chemical liquid supply means, when the detected concentration is low, the concentration is quickly controlled with respect to the target value, and the convergence with respect to the target concentration becomes more rapid.

A diluting liquid supply means for supplying a diluting liquid for diluting the chemical to the storage tank; and a diluting liquid supply means for supplying the diluting liquid according to the target value set by the target value setting means when the detected concentration is higher than the target concentration. When the means is operated and the operating means is provided, when the detected density is high, the density is quickly controlled with respect to the target value, and the convergence with respect to the target density is quicker. In addition, the apparatus further includes a circulating means for discharging the chemical solution from the storage tank and returning it to the storage tank, and when the concentration detecting means detects the concentration of the circulating chemical solution, the chemical solution is constantly circulating. More accurate detection is possible.

Further, when the operating means operates the chemical liquid supply means and the diluent liquid supply means such that the concentration becomes the lower limit of the detection error range of the target concentration when dispensing a new chemical liquid in the storage tank, Since the density adjustment is performed in a state where the density is set slightly, the density does not increase, and the density quickly converges to a desired target density.

[0015]

1, a substrate processing apparatus according to an embodiment of the present invention includes a diluent storage tank 1, a chemical storage tank 2, and a substrate processing tank 3. In the diluent storage tank 1, for example, pure water is stored as a diluent. Chemical storage tank 2
Contains, for example, hydrofluoric acid as a chemical solution. A diluent supply pipe 4 for supplying diluent to the substrate processing tank 3 is connected to the bottom of the diluent storage tank 1. In the middle of the diluent supply pipe 4, a metering pump P1 is arranged. Similarly, a chemical supply pipe 5 for supplying a chemical to the substrate processing tank 3 is connected to the bottom of the chemical storage tank 2.
A metering pump P2 is arranged on the way.

A substrate holding section 10 for holding a large number of substrates W with their main surfaces opposed to each other is provided inside the substrate processing tank 3. One end of a circulation pipe 6 is connected to the bottom of the substrate processing tank 3. The other end of the circulation pipe 6 is introduced into the substrate processing tank 3 from above. In the middle of the circulation pipe 6, a circulation pump P3, a heat exchanger 7 for temperature control, a concentration sensor 8, a filter 9, and a circulation valve V1 are arranged in this order from one end. Further, a discharge valve V2 is connected between the filter 9 and the circulation valve V1. The concentration sensor 8 has a low concentration of hydrofluoric acid (for example, 1
%) Can be detected within a detection error range of ± 0.01%, and includes, for example, a capacitance sensor and an optical sensor.

The substrate processing apparatus has a control unit 20 shown in FIG. The control unit 20 includes a microcomputer including a CPU, a RAM, and a ROM. The control unit 20 includes an operation panel 2 for inputting a target density and the like.
1 and a density sensor 8 are connected. Further, the control unit 20 is connected to the metering pumps P1 and P2, the circulation pump P3, the circulation valve V1, the supply valve V2, and other input / output units.

Next, the control operation of the control unit 20 will be described with reference to the control flowcharts shown in FIGS. When the program starts, first, initial settings are made in step S1. At this time, the respective pumps P1 to P3 are turned off, and the respective valves V
1, V2 is closed. Also, various set values are set to initial values.

In step S2, it is determined whether or not the target density Ct has been input from the operation panel 21. Step S
At 3, it is determined whether or not a blending command has been issued. In step S4, it is determined whether a substrate processing command has been issued.
In step S5, it is determined whether a discharge command has been issued. In step S6, it is determined whether another command has been issued. If it is determined that another command has not been issued, the process returns to step S2.

When it is determined that the target density Ct has been input, the process proceeds from step S2 to step S10. In step S10, the input target density Ct is set. This target density is set to, for example, 1%. The target density Ct is set with a certain width (for example, a width of about Ct ± 0.005%). If it is determined that a blending command has been issued, the process proceeds from step S3 to step S11. In step S11, a blending process (described later) is performed. When it is determined that the substrate processing command has been issued, the process proceeds from step S4 to step S12. In step S12, substrate processing (described later) is performed. When it is determined that the discharge command has been issued, the process proceeds from step S5 to step S13. In step S13, a discharging process (described later) is performed. When another command is issued, the process moves from step S6 to step S14.
In step S14, another process according to the command is performed.

In the blending process of step S11, a value obtained by subtracting the detection error range α from the target density Ct in step S21 of FIG. 4 is set as the target value Cs. In step S22, the metering pumps P1, P2
Turn on. For example, the target density Ct is set to 1%,
If the detection error range is ± 0.01%, the target value C
0.99% is set as s. The discharge amounts of the pumps P1 and P2 are respectively controlled in accordance with the target value Cs, and the diluent and the chemical are supplied from the diluent storage tank 1 and the chemical storage tank 2 to the substrate processing tank 3, respectively. Here, since the capacity of the substrate processing tank 3 is predetermined, here,
The pumps P1 and P2 are controlled so that the concentration of the target value Cs according to the displacement is obtained. As a result, the density becomes as shown in FIG.

In step S23, the process waits until the time T1 has elapsed. During this time T1, the diluting liquid and the processing liquid are
Is enough time to be supplied to In step S24, the circulation valve V1 is opened. In step S25, the circulation pump P3 is turned on. As a result, the chemical in the substrate processing tank 3 is circulated by the circulation pipe 6. In step S26, the process waits for the lapse of time T2. This time T2 is for determining the circulation time. After the elapse of the predetermined time T2, the process proceeds to step S27.

In step S27, the output of the density sensor 8 is fetched and the density Cm is measured. In step S28, it is determined whether or not the detected density Cm falls within the range of the target density Ct. If it is within the range of the target density Ct, the process returns to the main routine. If it deviates from the target density Ct, the process moves to step S29. In step S29, as shown in FIG. 7, a half of the target density Ct and the detected density Cm is set as a new target value Cs. In step S30, the detected density Cm is set to the target density Ct.
Determine if it is greater than. If the detected concentration Cm is smaller than the target concentration Ct, the concentration is too low, so the flow shifts to step S31 to turn on the metering pump P2 in accordance with the difference between the detected concentration Cm and the target value Cs.
To supply. If it is determined that the detected density Cm is higher than the target density Ct, the density is too high, so that step S
The flow then proceeds to 32, where the metering pump P1 is turned on according to the difference between the detected concentration Cm and the target value Cs, and the diluent is supplied to the substrate processing tank 3. When these processes are completed, the process returns to the step S26. The operation from step S26 is repeated until the detected density Cm falls within the allowable range of the target density Ct.

In the substrate processing in step S12, the valve V1 is opened and the valve V2 is closed in step S40 in FIG. In step S41, the circulation pump P3 is turned on.
In step S42, the process waits for the elapse of time T3. This time T3 is a time for determining a detection interval by the density sensor 8. In step S43, the output of the density sensor 8 is fetched and the density Cm is measured. In step S44, it is determined whether or not the detected density Cm falls within the range of the target density Ct. If not, the process proceeds to step S45. In step S45, similarly to step S29, a half amount of the detected density Cm and the target density Ct is set as a new target value Cs.

In step S46, it is determined whether the detected density Cm is higher than the target density Ct. If the detected density Cm is higher than the target density Ct, the process proceeds to step S47. In this case, since the density is too high, step S4
In step 7, the pump P is set according to the difference between the target value Cs and the detected concentration Cm.
1 is turned on and the diluent is supplied. Further, the detected concentration Cm
Is smaller than the target density Ct, the process proceeds to step S48. In this case, since the density is too low, step S
At 48, the pump P2 is turned on in accordance with the difference between the target concentration Cs and the detected concentration Cm to supply the chemical. When these processes are completed, the process moves to step S49. Step S
At 49, it is determined whether or not a substrate end command has been issued. The operations from step S42 to step S49 are repeated until a substrate end command is issued. When a substrate end command is issued, the process returns to the main routine.

In the unloading process at step S13, the valve V1 is closed and the valve V2 is opened at step S51 in FIG. 6, and the circulation pump P3 is turned on at step S52. In step S53, the process waits for the lapse of time T4. This time T
Reference numeral 4 denotes a sufficient time for the chemical solution to be discharged from the substrate processing tank 3 with a slight amount remaining. In step S54,
The circulation pump P3 is turned off. As a result, the slightly remaining chemical liquid is discharged by natural fall. In step S55, both valves V1 and V2 are closed.

Here, at the time of the first blending, blending is performed aiming at the density of the lower limit of the detection error range, and during blending or during substrate processing, the target value is set to a half amount of the detected density and the target density. Replenished liquid or diluent.
For this reason, even if the concentration sensor has a detection error range as compared with the case where the chemical solution is prepared from the beginning to the target concentration, the concentration does not increase or decrease and quickly converges to the target concentration. [Other Embodiments] (a) Setting the target value to a half of the detected density and the target density is an example, and the target value is set to any density between the target density and the detected density. May be set. (B) At the time of the blending process, the blending may be performed only aiming at the lower limit of the detection error range of the target density, and the density measurement and the accompanying control may be omitted. In this case, step S in FIG.
It is only necessary to skip the processing from step 26 onward and return to the main routine. Thereby, the blending process is completed in a short time. (C) At the time of substrate processing, the target value is not always set to a half of the detected density and the target density. If the detected density is out of the detection error range of the target density, the boundary density of the detection error range is set. (For example, Ct ± α) may be set as a new target value, and the half-amount control may be performed only when the detected density is within the detection error range. (D) During the blending process, the supply of the diluent or the supply of the chemical solution can be omitted by intentionally reducing or increasing the concentration of the chemical solution supplied to the substrate processing tank.

[0028]

In the low density adjusting apparatus according to the present invention, the density adjustment is performed not on the target density directly but on the target value between the target density and the detected density. However, even if the density is detected within a predetermined detection error range, the density quickly converges to the target density without increasing or decreasing.

When a half of the detected density and the target density is set as the target value, the target density can be converged more efficiently. In addition, when the concentration adjusting unit has the chemical solution supply unit and the operating unit, when the detected concentration is low, the concentration is quickly controlled with respect to the target value, and the convergence with respect to the target concentration is quickened.

When the concentration adjusting means has a diluting liquid supply means and an operating means, when the detected concentration is high, the concentration is quickly controlled with respect to the target value, and the convergence with respect to the target concentration is improved. Be quick. In addition, a circulation means is further provided,
When the concentration detecting means detects the concentration of the circulating drug solution, the drug solution is constantly circulating, so that the drug solution concentration can be detected with higher accuracy.

Further, when the operating means operates the chemical liquid supply means and the diluent liquid supply means so as to adjust the concentration to the lower limit of the detection error range of the target concentration when dispensing a new chemical liquid in the storage tank, Since the density adjustment is performed in a state where the density is set slightly, the density does not increase, and the density quickly converges to a desired target density.

[Brief description of the drawings]

FIG. 1 is a block diagram of a substrate processing apparatus employing one embodiment of the present invention.

FIG. 2 is a block diagram of the control system.

FIG. 3 is a flowchart showing a control operation of a control unit.

FIG. 4 is a control flowchart of the blending process.

FIG. 5 is a flowchart of the substrate processing.

FIG. 6 is a control flowchart of the discharging process.

FIG. 7 is a schematic diagram showing a change in density during preparation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diluent storage tank 2 Chemical storage tank 3 Substrate processing tank 4 Diluent supply pipe 5 Chemical supply pipe 6 Circulation pipe 8 Concentration sensor P1, P2 Metering pump P3 Circulation pump W Substrate

Claims (6)

(57) [Claims] 1. A low-concentration adjusting device for adjusting a chemical solution to a low-concentration target concentration, comprising: a storage tank for storing the chemical solution; and a storage tank for storing the target solution with respect to the target concentration. Concentration detecting means for intermittently detecting the concentration of the chemical solution within a predetermined detection error range, and when the concentration detecting means detects a concentration different from the target concentration, a concentration between the target concentration and the detected concentration Target value setting means for setting a new target value, and concentration adjusting means for adjusting the concentration of the chemical so that the concentration of the chemical in the storage tank becomes the target value set by the target value setting means. Low concentration adjustment device provided. 2. The low-concentration adjusting device according to claim 1, wherein said target value setting means sets half the density between said detected density and said target density as said target value. 3. A chemical liquid supply means for supplying a chemical liquid having a concentration higher than the target concentration to the storage tank,
3. An operating means for operating the chemical liquid supply means according to the target value set by the target value setting means when the detected concentration is lower than the target concentration.
The low-concentration adjusting device according to 1. 4. The concentration adjusting means comprising: a diluting liquid supply means for supplying a diluting liquid for diluting the chemical liquid to the storage tank; and a target value setting means when the detected concentration is higher than the target concentration. Operating means for operating said diluting liquid supply means in accordance with said set target value.
4. The low-concentration adjusting device according to any one of items 1 to 3. 5. The method according to claim 1, further comprising circulating means for discharging the chemical from the storage tank and returning the chemical to the storage tank, wherein the concentration detecting means detects the concentration of the circulating chemical. The low-concentration adjusting device according to the above. 6. The operating means operates the chemical liquid supplying means and the diluting liquid supplying means such that when a new chemical liquid is prepared in the storage tank, the concentration becomes a lower limit of a detection error range with respect to the target concentration. The low-concentration adjusting device according to any one of claims 1 to 5, wherein