JPH0766137A - Gas flow controller - Google Patents

Abstract

PURPOSE:To provide a gas flow controller in which flow control is effected correctly and a decision of abnormality can be made when the flow control is no effected correctly. CONSTITUTION:A flow decision section 3 comprises a first comparing circuit 15, a current control circuit 16, and a second comparing circuit 17. The first comparing circuit 15 compares a flow detection signal VA based on a detection result with a flow set signal VB and outputs a control current I required for equalization thereof. The current control circuit 16 is connected in parallel with the first comparing circuit 15 and outputs a maximum allowable current Imax corresponding to the flow set signal VB. The second comparing circuit 17 compares the control current I with the maximum allowable current Imax. If ¦I¦<=¦Imax¦, the control current I is fed as a drive signal to a flow control section 4 in order to open or close a gas channel 1 and if ¦I¦>¦Imax¦, an abnormality is displayed and the supply of control current I to the flow control section 4 is interrupted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas flow rate control device for controlling the flow rate of a process gas introduced into a manufacturing processing chamber.

[0002]

2. Description of the Related Art For example, in the process of manufacturing a semiconductor device, when supplying a process gas into a manufacturing process chamber, it is necessary that the flow rate of the supplied process gas is always controlled appropriately. For example, by CVD, epitaxial single crystal Si, polycrystalline Si, SiO
_2. When forming various thin films such as phosphorous glass and Si ₃ N _4, the flow rate of the raw material gas supplied to the manufacturing process chamber influences the characteristics and uniformity of the formed thin film.

Therefore, it has been conventionally practiced to use a gas flow rate control device to supply the process gas into the manufacturing processing chamber after the flow rate of the process gas is sufficiently controlled. As the gas flow rate control device, for example, a mass flow controller is used. (Ma
ss Flow Controller (hereinafter referred to as MFC) is used.

The MFC is a gas flow rate control device which captures the flow rate of the process gas by a mass flow rate which is not influenced by temperature and pressure. For example, as shown in FIG. And a flow rate control unit 104 that controls the flow rate of the gas based on the determination result.

The gas flow path 101 has a gas inlet 105.
On the downstream side of the detection line 106 and the bypass line 10
It is divided into 7. Then, the detection line 106
The bypass line 107 and the bypass line 107 merge further downstream so that the gas flows out from the gas outlet 108.

The flow rate detecting section 102 includes the above-mentioned detection line 1
The flow rate of the process gas passing through the inside of 06 is detected, and the heating resistors 109 and 110, the bridge circuit 111 and the amplifier circuit 1 which are wound around two points of the detection line 106.
It consists of 12. Then, in the flow rate detection unit 102, the process gas passing through the detection line 106 and the heating resistors 109, 11 held at a constant temperature.
Since heat exchange occurs between the two and 0, and this appears as a temperature difference between the two that is proportional to the mass flow rate, it can be detected as a voltage signal by the bridge circuit 111. The voltage signal is amplified by the amplifier circuit 112, is displayed on the display 113, and is input to the flow rate determination unit 103 as the flow rate detection signal V _A.

The flow rate judging section 103 comprises a comparison circuit 114 for comparing the input flow rate detection signal V _A with a preset flow rate setting signal V _B. In the comparison circuit 114, the flow rate detection signal V _A is compared with the flow rate setting signal V _B, and the control current I necessary for equalizing the two is supplied to the flow rate control unit 104. If V _A = V _B , the control current I currently being supplied may be continuously supplied to the flow rate control unit 104 as it is.

The flow control unit 104 includes a solenoid coil 1
15 and a plunger 116 connected to the solenoid coil 115. For example, the solenoid coil 115
The plunger 116 is pulled up by supplying an electric current to the. Therefore, as the control current I sent from the flow rate determination unit 103 changes, the plunger 116 moves up and down, and the gas flow path 101 is opened and closed.

Specifically, when the flow rate detection signal V _A is larger than the flow rate setting signal V _B , for example, the control current I which is smaller than the current value currently being supplied to the solenoid coil 115.
Is supplied, the plunger 116 electromagnetically coupled to the solenoid coil 115 is lowered to lower the gas flow path 1
01 is narrowed. On the contrary, when the flow rate detection signal V _A is smaller than the flow rate setting signal V _B , for example, the control current I larger than the current value currently being supplied to the solenoid coil 115 is supplied to connect to the solenoid coil 115. The plunger 116 that has been lifted up to lift the gas passage 101.
Widen.

The above-mentioned circuits are connected to a common power source 117, and necessary power is supplied from the power source 117.

As described above, the MFC has the gas inlet 10
The total flow rate of the process gas is determined and controlled by detecting the mass flow rate of a part of the process gas flowing into No. 5, that is, the part that has passed through the detection line 106, and a desired flow rate of the process gas is passed. It flows out from the outlet 108.

[0012]

Generally, when a process gas is supplied to a semiconductor device manufacturing process chamber, the process gas is highly filtered (about 0.01 μm) in order to prevent foreign matter from entering. It is carried out after passing through the above filter in advance and then flowing into the MFC. However, due to long-term use, particles will be generated from the piping material and self-dusting of the above-mentioned filter will occur.
Foreign matter may be mixed in C and, for example, foreign matter may be accumulated in the detection line 106 in the gas flow path 101 of the MFC shown in FIG. Further, when supplying the liquefied gas, the liquefied gas may be condensed in the detection line 106. Then, in such a state, the flow rate of the process gas passing through the inside of the detection line 106 decreases.

When the flow rate of the process gas passing through the detection line 106 is reduced as described above, even if the process gas having a sufficient flow rate actually flows out from the outlet 108, the comparison circuit 114 outputs the process gas. Is determined that the flow rate detection signal V _A is smaller than the flow rate setting signal V _B. Further, in such a state, even if the gas flow path 101 is widened, it is continuously determined that the flow rate detection signal V _A is smaller than the flow rate setting signal V _B. When the control current I based on this determination is applied to the solenoid coil 115, a large amount of process gas will flow out from the outflow port 108 while the gas flow path 101 is kept open more than necessary.

That is, in the MFC, since the flow rate of the process gas that has passed through the detection line 106 is detected, if an abnormality occurs in the detection line 106, the flow rate of the process gas can be properly controlled. Disappear. When the flow rate control is improper as described above, a process gas having a flow rate significantly different from the desired flow rate is supplied to the semiconductor manufacturing processing chamber, which significantly improves the quality of the elements processed in this processing chamber. It also lowers the product quality, and in some cases causes product defects.

In the case where the flow passage 101 is almost closed and the flow rate of the process gas supplied to the manufacturing processing chamber is insufficient even if the plunger 116 is pulled up to the maximum, the inside of the manufacturing processing chamber is Although the device that controls the process can recognize the abnormality in the flow rate, the MFC has no means for recognizing the abnormality even when such an abnormality occurs.

Therefore, the present invention has been proposed in view of such conventional circumstances, and the gas flow rate control is performed so that the flow rate control is properly performed, and when the flow rate control is improper, an abnormality can be determined. The purpose is to provide a device.

[0017]

DISCLOSURE OF THE INVENTION The present invention has been proposed in order to achieve the above-mentioned object, and is based on a flow rate detecting means for detecting the flow rate of gas and a detection result of the flow rate detecting means. _A first comparison circuit for comparing the detected flow rate detection signal V _A with the flow rate setting signal V _B output from the flow rate setting means; a current control circuit connected in parallel with the first comparison circuit; A second comparison circuit that compares the output signals of the first comparison circuit and the current control circuit, and a flow rate control unit that controls the flow rate of gas based on the determination result of the second comparison circuit. Is.

In practice, it is effective to use the output signal of the current control circuit as a signal representing the maximum allowable value of current (maximum allowable current I _max ) corresponding to the value of the input flow rate setting signal V _B. Is. In this case, the second comparison circuit outputs the value of the output signal of the first comparison circuit (control current I).
Is the value of the output signal of the current control circuit (maximum allowable current I
When it is less than or equal to _max ), the drive signal can be output to the flow rate control means, and in other cases, the output of the drive signal can be stopped and the abnormality detection signal can be output.

That is, the gas flow controller according to the present invention
Is, for example, a mass flow controller that controls the mass flow rate.
Can be used as a roller (MFC), the first comparison time
Flow rate detection signal V_AAnd flow rate setting signal V_BAnd
By comparing, the control current I required to make both equal
It has the same configuration as the conventional MFC up to the output.
It is something. However, in the present invention, the control current I
Is not directly supplied to the flow rate control means, but the second
In the comparison circuit, the control current I is supplied from the current control circuit.
Maximum allowable current I output_maxThe control current I is
Maximum allowable current I _maxIs less than or equal to
Only when the control current I is used as a drive signal.
It is supplied to the stage.

[0020]

In the gas flow rate control device according to the present invention, for example, when the control current I supplied to the flow rate control means increases, the flow path is widened to increase the flow rate of gas supplied to the manufacturing processing device.
On the contrary, if the control current I supplied to the flow rate control means decreases, the flow rate is controlled so that the flow path is narrowed to reduce the flow rate of the gas supplied to the manufacturing processing apparatus.

Control current I output from the first comparison circuit
Is the difference between the flow rate detection signal V _A and the flow rate setting signal V _B (V
_B - _VA ), the differential voltage ΔV is calculated, this is converted into a differential current ΔI, and the differential current ΔI is added to the control current I ′ currently being supplied to the flow rate control means (I =
I ′ + ΔI).

Therefore, for example, V_A= V_Bin the case of,
Since ΔV = 0 and ΔI = 0, the control current currently being supplied is
I'may be continuously supplied to the second comparison circuit. one
One, V _A> V_B, ΔV is negative and ΔI is also negative.
Therefore, a negative ΔI is added to the control current I ′ currently supplied.
The calculated control current I, that is, the control current I'currently being supplied.
To supply a smaller control current I to the second comparison circuit
Become. Conversely, V_A<V_B, ΔV is positive and ΔI
Is also positive, the control current I ′ currently being supplied is positive ΔI.
Control current I, that is, the control current currently being supplied
A control current I larger than I'is supplied to the second comparison circuit.
It will be.

Further, the control current I input to the second comparison circuit as described above is compared with the maximum allowable current I _max corresponding to the magnitude of the flow rate setting signal V _B , and the maximum allowable current I _max. In the following cases, the control current I is supplied to the flow rate control means as a drive signal. The flow rate control means operates so as to widen the flow passage when the supplied control current I increases and narrow the flow passage when the supplied control current I decreases.

On the other hand, when the control current I input to the second comparison circuit is larger than the maximum allowable current I _max , the supply of the control current I to the flow rate control means is stopped and the abnormality detection signal is output.

The control current I is the maximum allowable current I _max.
In the case of a larger flow rate, for example, foreign matter is accumulated in the detection line in the flow path, and the gas flow rate in the detection line is decreasing. Even if the water flows out, it is possible that the determination that the detected flow rate is less than the set flow rate is continuously made.

In such a case, in the first comparison circuit, the control current I larger than the control current I'currently being supplied is output according to the judgment that V _A <V _B, but the flow path is widened. However, the judgment that V _A <V _B is not resolved,
The operation of outputting a larger control current I is repeated. As a result, the control current I input to the second comparison circuit continues to increase and the maximum allowable current I _max.
Over.

In the conventional gas flow rate control device, the increased control current I is continuously supplied as a drive signal to the flow rate control means, and a large amount of gas is discharged while keeping the flow path open more than necessary. However, in the gas flow rate control device of the present invention, when the control current I exceeds the maximum allowable current I _max , the supply of the control current I to the flow rate control means is stopped and an abnormality detection signal is output. .

Therefore, the abnormality of the gas flow rate control device can be recognized, and a large amount of gas greatly different from the desired flow rate does not continue to flow into the manufacturing processing chamber on the downstream side of the gas flow rate control device. Further, even when the gas supply from the gas supply source is stopped for some reason, the abnormality can be recognized by the similar operation.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described below with reference to the drawings. In the present embodiment, the gas flow rate control device according to the present invention controls the flow rate of the process gas when the process gas is supplied into the processing chamber of the semiconductor manufacturing apparatus (for example, CVD apparatus, dry etching apparatus, etc.). Applied to.

The gas flow controller according to the present embodiment is an MFC for measuring the flow rate of a process gas by a mass flow rate (hereinafter, simply referred to as the MFC according to the present embodiment). For example, as shown in FIG. , A gas flow path 1, a flow rate detection unit 2, a flow rate determination unit 3, and a flow rate control unit 4.

The gas flow path 1 is divided into a detection line 6 and a bypass line 7 on the downstream side of the gas inlet 5. Further, the detection line 6 and the bypass line 7 join at a further downstream side, and the process gas flows out at the gas outlet 8.

The flow rate detector 2 detects the flow rate of the process gas passing through the detection line 6, and the heating resistors 9 and 10 and the bridge circuit 11 wound around the detection line 6 at two positions. And an amplifier circuit 12. And
In the flow rate detection unit 2, heat exchange occurs between the process gas passing through the detection line 6 and the heating resistors 9 and 10 held at a constant temperature,
Since this appears as a temperature difference between the two that is proportional to the mass flow rate, it can be detected as a voltage signal by the bridge circuit 11.

The voltage signal detected by the bridge circuit 11 is normally set to be in the range of DC0 to 5V, and the detected voltage signal is amplified by the amplifier circuit 12, It is displayed on the display 13 and is input to the flow rate determination unit 3 as the flow rate detection signal V _A.

The flow rate determination unit 3 is provided with the flow rate detection signal V
_AAnd the preset flow rate setting signal V _BFirst to compare with
And the first comparison circuit 15 connected in parallel
From the current control circuit 16 and the first comparison circuit 15
Control current I output and output from the current control circuit 16
Maximum allowable current I_maxSecond comparison circuit for comparing with
It consists of 17.

The flow rate detection signal V _A output from the detection unit 2 and a preset flow rate setting signal V _B are input to the first comparison circuit 15, where: The flow rate detection signal V _A and the flow rate setting signal V _B are compared with each other, and a control current I required to equalize them is output. Specifically, the difference (V _B −V _A ) between the flow rate detection signal _VA and the flow rate setting signal V _B is calculated, the difference voltage ΔV is calculated, and the difference voltage ΔV is converted to obtain the difference current ΔI. Then, the control current I obtained by adding the difference current ΔI to the control current I ′ currently being supplied to the flow rate control unit 4
Is output.

Further, the current control circuit 16 includes the first
Of the flow rate setting signal V
_The maximum allowable current I _max corresponding to _B is output. That is, if you enter the flow rate setting signal V _B to the current control circuit 16, a voltage based on the correlation stored in advance - perform current conversion, the flow rate setting signal V _B to be compatible output control current The maximum value of I is the maximum allowable current I
It is designed to be output as _max .

The second comparison circuit 17 is a digital circuit composed of an arithmetic circuit 21, a latch circuit 22, and a switching circuit 23, for example, as shown in FIG. Output control current I
And the maximum allowable current I output from the current control circuit 16
_max is input, and it is determined whether or not | I | ≦ | I _max |.

Specifically, first, in the arithmetic circuit 21,
When the maximum allowable current I _max of 0 to x (A) and the control current I of 0 to y (A) are input, if the current signal is x ≧ y, logically “1”, x < If y, logically "0"
Then, the control signal Sc is output. The control signal Sc is supplied to the switching circuit 23 via the latch circuit 22 in the subsequent stage. The control signal Sc from the arithmetic circuit 21 is
Is held by the latch circuit 22 for a certain period of time so that the continuity of the logic signal (control signal Sc) is compensated.

The switching circuit 23 has two switches s1 and s2 therein, and the first switch s1 has a movable contact a to which a fixed potential Vr is constantly applied, and a fixed contact b to which error processing is performed. A processing circuit (for example, an input stage to the display device 20 for displaying an abnormality, a controller (not shown), or the like) is connected. Also, the second switch s2 is
The movable contact c is wired so that the control current I of 0 to y (A) is supplied, and the fixed contact d is electrically connected to the lead wire of the solenoid coil.

Then, these two switches s1 and s2
ON / OFF is continuously operated based on the control signal Sc from the latch circuit 22. That is, when the control signal Sc is logically "0", the first switch s1 is turned on and the second switch s2 is turned off. As a result, the fixed potential Vr applied to the movable contact a is supplied to the various processing circuits for error processing as an abnormality detection signal, error processing is performed, and the control current I is supplied to the solenoid coil 18. Be cut off.

On the other hand, when the control signal Sc is logically "1", the operation opposite to the above operation is performed. That is, the first switch s1 is turned off and the second switch s2 is turned on based on the input of the control signal Sc, whereby various processing circuits for error processing of the fixed potential Vr (abnormality detection signal) are performed. To the solenoid coil 18, and the control current I is supplied to the solenoid coil 18.

The first switch s1 and the second switch s2 are MO with the control signal Sc as the gate potential.
It can be easily manufactured with an S-type FET. Further, the second comparison circuit 17 may be an analog circuit including a comparator and a switching circuit.

The flow rate control unit 4 includes a solenoid coil 18
And a plunger 19 electromagnetically coupled to the solenoid coil 18, and the plunger 19 is moved up and down by a change in the control current I supplied from the flow rate determination unit 3 to the solenoid coil 18. For example, in this embodiment, when the control current I increases, the plunger 1
When 9 is pulled up to widen the gas flow path 1 and the control current I decreases, the plunger 19 is lowered and the gas flow path 1 becomes narrow.

Each of the circuits described above is connected to a common power source 14, and the necessary power is supplied from the power source 14. In addition, the MF according to the present embodiment
C is connected to a gas supply source (not shown) through a filter with high filtration accuracy (about 0.01 μm), and on the other hand, C is connected to a manufacturing processing chamber (not shown) such as a CVD device. ing.

The operation of the MFC according to this embodiment having the above-mentioned structure will be described below with reference to the flowchart of FIG.

First, in the detection section 2, the detection line 6
The flow rate of the process gas passing through the inside is detected (step S1), and the flow rate detection signal V _A based on the detection result is output.

Then, in the first comparison circuit 15, the flow rate detection signal V _A is compared with the flow rate setting signal V _B (step S2), and the difference (V _B between the flow rate detecting signal V _A and the flow rate setting signal V _B is calculated. take a -V _a), and calculates the difference voltage ΔV.

Further, the differential voltage ΔV is converted into a differential current ΔI, and the control current I obtained by adding the differential current ΔI to the control current I ′ currently being supplied to the solenoid coil 18 is output (step S3).

Then, in the second comparison circuit 17, the control current I output from the first comparison circuit 15 and the maximum allowable current I output from the current control circuit 16 in response to the flow rate setting signal V _B. Compared with _max , | I | ≦ | I
It is determined whether or not _max | (step S4).

When | I | ≦ | I _max | (YES), the control current I input from the first comparison circuit 15 is supplied to the solenoid coil 18 as a drive signal (step S5), and the plan The jar 19 is operated to control the flow rate (step S6). On the other hand, | I | ≦ | I _max
If it is not | (NO), as an error process (step S7), an abnormality detection signal is output to display an abnormality on the display 20, and the supply of the control current I to the flow rate control unit 4 is stopped.

Therefore, for example, a process with a desired flow rate is
If Sgas is detected, V_A= V _BTherefore, ΔV
= 0 and ΔI = 0. That is, in step S3, I = I '
(Current value of current supply) is output, and at this time | I |
| I_maxSince | is satisfied, the control current I = I ′ is driven.
It is supplied to the solenoid coil 18 as a signal,
The position of the charger 19 is maintained as it is.

If more process gas than the desired flow rate is detected, V _A > V _B , and therefore ΔV is negative and ΔI is also a negative value, and the current solenoid coil 18 is supplied in step S3. A control current I smaller than the inside control current I ′ is output. At this time, | I | ≦ | I
_{Since max} | is satisfied, the control current I is supplied to the solenoid coil 18 as a drive signal, the plunger 19 is lowered, and the gas passage 1 is narrowed.

On the contrary, when the detected process gas is less than the desired flow rate, V _A <V _B , and therefore ΔV is positive,
ΔI also has a positive value, and outputs a control current I larger than the control current I ′ currently being supplied to the solenoid coil 18.
At this time, if | I | ≦ | I _max | is satisfied, it is supplied to the solenoid coil 18 as a drive signal, the plunger 19 is pulled up, and the gas flow path 1 is expanded.

As long as | I | ≦ | I _max | is satisfied, the above operation is repeated, so that the flow rate of the process gas supplied to the manufacturing processing chamber is controlled to a desired flow rate. . Although not shown in the flow chart of FIG. 3, the operation can be ended by giving an end request during the operation of the flow rate control as described above.

However, for example, when the flow rate detection signal V _A is smaller than the flow rate setting signal V _B due to the accumulation of foreign matter in the detection line, the control current I currently being supplied to the solenoid coil 18 is reached. Since the operation of outputting the control current I obtained by adding a positive ΔI to 'is repeated, the control current I increases and exceeds the maximum allowable current I _max . In this case, as seen from the flowchart of FIG. 3, in step S4, the process branches to step S7, and an abnormality detection signal is output as error processing, and an abnormality is displayed on the display 20, and the like. The supply of the control current I to the solenoid coil 18 is stopped.

As described above, the MFC according to this embodiment is
When the control current I exceeds the maximum allowable current I _max , the supply of the control current I to the flow rate control means is stopped and the abnormality detection signal is output, so that the abnormality can be recognized. Therefore, for example, even when foreign matter is accumulated in the detection line 6, an excessive control current I is supplied to the flow rate control unit 4 as a drive signal to keep the gas passage 1 open more than necessary. Absent. That is, a large amount of process gas that greatly differs from the desired flow rate does not continue to flow into the manufacturing processing chamber such as the CVD apparatus. Further, even when the supply of the process gas from the gas supply source is stopped for some reason, the abnormality can be recognized by the similar operation.

[0057]

As is apparent from the above description, the gas flow rate control device according to the present invention can recognize an abnormality in the flow rate control, so that the gas flow rate control device can generate a large amount of gas greatly different from the desired flow rate. Will not continue to flow into the manufacturing process chamber on the downstream side. Further, even when the gas supply from the gas supply source is stopped, the abnormality can be recognized by the same operation.

Therefore, the gas whose flow rate is properly controlled is supplied into the manufacturing process chamber on the downstream side of the gas flow rate control device according to the present invention, and a high quality element can be manufactured.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing a main part of an MFC according to this embodiment.

FIG. 2 is a block diagram showing an operation of a second comparison circuit in the MFC according to this embodiment.

FIG. 3 is a flowchart showing the operation of the MFC according to this embodiment.

FIG. 4 is a configuration diagram schematically showing a main part of an MFC according to a conventional example.

[Explanation of symbols]

1 ... Gas flow path 2 ... Flow rate detection unit 3 ... Flow rate determination unit 4 ... Flow rate control unit 5 ... Gas inlet 6 ... Detection line 7 ... Bypass line 8 ... ..Gas outlet 9,10 ... Heating resistor 11 ... Bridge circuit 12 ... Amplification circuit 13, 20 ... Indicator 14 ... Power supply 15 ... First comparison circuit 16 ... comparator circuit 18 ... solenoid coil 19 of · the current control circuit 17 ... second ... plunger V _a ... flow rate detection signal V _B ... flow rate setting signal I ... control current I _max ... Maximum allowable current

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location G05D 7/06 Z 9324-3H

Claims (4)

[Claims] 1. A first flow rate detecting means for detecting a flow rate of gas, and a first flow rate detecting signal generated based on a detection result of the flow rate detecting means and a flow rate setting signal output from the flow rate setting means. A comparison circuit; a current control circuit connected in parallel with the first comparison circuit; a second comparison circuit for comparing output signals of the first comparison circuit and the current control circuit; and a second comparison circuit. A gas flow rate control device comprising: a flow rate control means for controlling a gas flow rate based on a judgment result of a comparison circuit. 2. The gas flow rate control device according to claim 1, wherein the output signal of the current control circuit represents a maximum allowable value of the current corresponding to the value of the input flow rate setting signal. 3. The second comparison circuit outputs a drive signal to the flow rate control means when the value of the output signal of the first comparison circuit is less than or equal to the value of the output signal of the current control circuit. 3. The gas flow rate control device according to claim 2, wherein the gas flow rate control device outputs the signal, and otherwise outputs the drive signal and outputs the abnormality detection signal. 4. The gas flow rate control device according to claim 1, wherein the flow rate is a mass flow rate.