JP2711577B2 - Mass flow controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a mass flow controller capable of doubling the flow rate without changing the mounting dimensions of an existing mass flow controller.

(Prior art and its problems) In the semiconductor, especially VLSI manufacturing field,
To reduce cost, wafer sizes are increasing in diameter from 4 inches to 6 inches to 8 inches. Along with this, the flow rate of the gas used for the production of the VLSI has been increasing, and it is desired that the mass flow controller also cope with this trend.

◎ Problems (1) In general, mass flow controllers have a joint at the gas inlet (2) and gas outlet (3) of the mass flow controller in order to make the connections compatible between manufacturers. The dimensions between the joints are unified so that they are almost the same. For example, in a model having a mass flow controller, the flow rate is limited to 5 l / min, and in a model having a larger flow rate, the allowable limit of the flow rate of the same size is almost determined, such as 20 l / min.

Therefore, when a higher flow rate is required, a larger mass flow controller must be selected, and the size of the joint between the gas inlet (2) and the outlet (3) and the size between the joints must be increased. However, increasing the size of the mass flow controller requires a significant modification of the gas supply system of the semiconductor manufacturing apparatus. As the mass flow controller becomes larger, the cost increases sharply for the reasons described below.
Larger mass flow controllers not only become heavier,
The installation work to the piping and the maintenance are troublesome. Since the compatibility with the conventional model is lost, the number of models must be increased, and the management becomes complicated for both manufacturers and users, and the management cost also increases.

◎ Problem (2) Therefore, an attempt was made to increase the mass flow rate only by using the conventional model as it is, but the problems that occur in that case are as follows.

When a gas flow rate that is higher than a predetermined value flows through the mass flow controller, the relationship between the flow rate and the sensor output deviates from a proportional straight line, or at a certain flow rate or more, the output decreases, and control becomes impossible.

When the flow rate is increased by increasing the pressure difference between the inlet (2) and the outlet (3) of the bypass element (8), the state of gas flow changes from laminar flow to turbulent flow, and the characteristic of differential pressure to flow rate is proportional. It deviates significantly from the straight line, and the sensor flow rate and the bypass flow rate deviate from the proportional relationship.

In addition, the flow varies depending on the type of gas, and it is difficult to accurately control the flow rate.

Further, since the sensor flow rate and the bypass flow rate deviate from the proportional relation, the sensor flow rate is greatly affected by the temperature and the pressure, so that it cannot be put to practical use.

◎ Problem (3) Further, a factor that hinders an increase in mass flow rate also exists in the bypass structure of the conventional model. That is, the problems are as follows.

As shown in FIGS. 9 and 10, the bypass element (8) of the conventional model is formed by bundling a number of bypass capillaries (13) having the same inner diameter and length as the sensor tube (9) and filling the protection tube (34). Therefore, there is a problem that the bypass element (8) is not suitable for a large flow rate.

That is, in the mass flow controller, it is necessary that the relationship between the differential pressure and the flow rate at both ends of the bypass element (8) is substantially linear. For example, the flow rate of one bypass capillary (13) is 10 ml.
Assuming that the mass flow controller for 10 l / min has to bundle 1,000 capillaries (13), the mass flow controller for 20 l / min has 2,000 tubes and the mass flow rate for 50 l / min The controller must bundle a large number of 5,000 capillaries (3), which is very costly.

Conversely, it is not possible to flow 20 l / min to the mass flow controller for the maximum flow rate of 5 l / min because the cross-sectional area of the bypass is limited. Therefore, when trying to flow at a flow rate of 20 l / min, the cross-sectional area must be increased as much as necessary. However, as described above, a large amount of the capillary (13) is required, which is not practical because the cost increases.

(Object of the present invention) The present invention has been made in view of the related art, and the first object of the present invention is to expand a flow rate range without substantially changing the mounting dimensions of an existing mass flow controller. A second object of the present invention is to provide a mass flow controller which does not require a large number of bypass capillaries and can secure a large flow at a low cost.

(Means for Solving the Problems) The device of the present invention has the following features to attain the object.
In the above, an inlet (2) for gas inflow is provided at one end of the body (1), and an outlet (3) for gas outflow is provided at the other end of the body (1). A partition (5) is provided substantially parallel to the direction of the gas flow (4) flowing toward the outlet (3), and a primary communicating with the entrance (2) in front of the partition (5) through the partition (5). A secondary chamber (7) forming a chamber (6) and communicating with the outlet (3) behind the partition (5);
And a bypass element (8) for communicating the primary chamber (6) and the secondary chamber (7) is provided in the partition (5), and the primary chamber (6) and the secondary chamber (7) are connected to each other. A sensor tube (9) for gas flow measurement is connected between them.

Claim (2) is a bypass element (8) and a sensor tube (9).
The relationship between the differential pressure of the sensor tube (9) and the bypass element (8)
Between the primary chamber (6) and the entrance (2) of the sensor tube (9) and between the exit (3) of the sensor tube (9) and the secondary chamber (7) to increase the differential pressure across the A line for increasing differential pressure (10) is provided.

The technical means of:

Claim (3) is a specific example of a bypass, in which a number of concave grooves (33) are formed in the surface of the band-shaped body (11) in the width direction, and the band-shaped body (11) is wound around to form a bypass hole in the axial direction. Is formed, and this is fitted into the partition wall (5).

The technical means of:

(Operation) When gas is supplied to the mass flow controller, the gas is supplied to the primary chamber (6).
Most of the gas flows into the secondary chamber (7) through the bypass hole, and only a small part of the gas flows through the sensor pipe (9) through the differential pressure increasing pipe (10). Subsequently, the gas flows into the secondary chamber (7) and merges with the gas on the bypass side.

At this time, the gas flowing through the sensor tube (9) deprives the upstream heater (27a) of heat and flows downstream, and the downstream heater (27)
b) The amount of heating is suppressed.

In the upstream heater (27a), the control circuit controls the upstream heater (27a) so as to supply the deprived heat and reach the equilibrium temperature. As a result, the balance between the power supplied to the heaters (27a) and (27b) is lost, and the mass flow of the gas flowing through the sensor tube (9) is detected by detecting and calculating the difference.

Since the bypass side is proportional to the flow rate of the sensor pipe (9), the total gas flow rate can be easily known by multiplying the flow rate of the sensor pipe (9) by a predetermined coefficient. Then, this output is fed back to the control valve section, and the control section (2
9) drives the control valve (30) to accurately control the mass flow rate flowing through the valve chamber (18).

Here, by using the differential pressure increase pipeline (10),
The differential pressure ΔP ′ at both ends of the bypass element (8) is the sensor pipe (9).
If the pressure difference ΔP is made (n) times larger than the differential pressure ΔP at both ends, the gas flow rate flowing through the bypass element (8) can be increased by (n) times, and the same type of model can flow (n) times the flow rate. It is something that will be.

Hereinafter, a first embodiment of the present invention will be described in detail with reference to the illustrated embodiments. 1 is a plan sectional view of one embodiment of a mass flow controller according to the present invention, FIG. 2 is a front sectional view thereof, and FIG. 3 is a longitudinal sectional view thereof. The mass flow controller mainly includes a body (1), a sensor unit (A) mounted on the body (1), and a control valve unit (B).

The body (1) is composed of a body body (16), an inlet flange (14) and an outlet flange (15) fixed to both ends thereof, and an inlet (15) for gas inflow is provided at the inlet flange (14). 2) is provided, and an outlet (3) for gas outflow is provided at the outlet flange (15).
A cylindrical hole (17) opening at one end is formed in the body body (16). The center of the bottom of the cylindrical hole (17) communicates with the valve chamber (18) of the control valve portion (B). Next side L-shaped hole (19)
And a secondary side L-shaped hole (20) communicating from the valve chamber (18) to the other end
And are drilled. A partition (5) partitioning the cylindrical hole (17) is fitted in the center of the cylindrical hole (17) in an airtight manner, and the cylindrical hole (17) is connected to the primary chamber (6) by the partition (5). Partitioned into secondary room (7). A circular flange (21) is provided at both ends of the partition wall (5), and a primary communication hole for communicating the entrance (2) and the primary chamber (6) to one of the flanges (21). (22) is provided with the secondary chamber (7) and the first
A secondary communication hole (23) communicating with the entrance (2) of the secondary L-shaped hole (19) is formed. Further, a plurality of (eight in the illustrated embodiment) through holes are formed in the partition wall (5), and a bypass element (8) described later is fitted into the through holes.
The partition (5) may be made of metal or resin.

The sensor section (A) is composed of a sensor tube (9) and a spacer (12) for increasing the differential pressure. The spacer (12) is mounted and fixed on the upper surface of the body (1). Two differential pressure increasing pipes (10) are bored in the spacer (12). The body (1) has a sensor side through-hole (24) opened from the primary chamber (6) and the secondary chamber (7) to the upper surface of the body (1). The path (10) and the sensor-side through hole (24) communicate with each other. A sensor block (25) is mounted and fixed on the upper surface of the spacer (12), and a sensor tube (9) is installed between sensor connection holes (26) formed in the sensor block (25). The gas on the primary side flows into the secondary chamber (7) through the space (9) between the sensors. Two heaters (27a) and (27b) are wound around the space between the sensors (9).

The control valve section (B) is composed of a valve housing (28) and a control section (29).
The primary side L is inserted into the valve chamber (18) of the lower surface opening formed in 8).
The exit of the character hole (19) and the entrance of the secondary side L-shaped hole (20) are open. A control valve (30) is housed in the valve chamber (18) so as to be movable up and down, and is connected to a drive section (3) arranged on the upper surface of the valve housing (28). Control valve (3
The lower surface of (0) coincides with the exit of the primary side L-shaped hole (19), and is constantly urged upward by a spring (32) in the separating direction.

As shown in FIG. 4, the bypass element (8) is a strip (11).
A large number of concave grooves (33) are formed in the surface in the width direction by etching, and this band-shaped body (11) is wound around a core rod (35) to form a bypass having a bypass hole in the axial direction. An element (8) is formed. Needless to say, the band-shaped body (11) in which the concave groove (33) is formed may be a resin molded body. As shown in FIGS. 7 and 8, the end of the bypass element (8) is slightly tapered, so that the shape of the winding is circular.

In this case, as can be seen from FIG. 8, the flow rate is accurately set by defining the number of the concave grooves (33) since there is no through-hole except for the concave grooves (33). On the other hand, in the case of the conventional capillary (13), the number of the capillaries (13) is small even if the number of the capillaries (13) is specified unless a narrow gap formed between the capillaries (13) and the capillaries (13) is closed. Will flow at a flow rate higher than the specified amount, and the accuracy will decrease. The shape of the groove (33) may be a half-moon shape or a shape close to a rectangle with an arc-shaped corner, and may have substantially the same cross section so that all the grooves (33) have substantially the same flow rate. Desirably, the cross-sectional shape of the opening does not matter.

In the bypass hole in FIG. 8, the concave groove (33) is wound outward, but it goes without saying that it may be wound inward as shown in FIG. The bypass element (8) thus formed is used by being fitted into the through hole of the partition (5) as shown in FIG. The number of bypass holes is determined by using a partition wall (5) in which the number of through holes is reduced in accordance with the flow rate, or by using a valve in which the through holes are closed and the bypass element (8) is fitted into a required number of through holes. .

Here, the gas flow rate per one bypass element (8) was changed to 10 ml / min, 100
If four types are manufactured: ml / min, 1 / min, and 10 l / min, various types of flow can be covered by selecting them appropriately according to the flow rate and fitting them into the partition wall (5). Things. On the other hand, in the conventional bypass element (8), 10 ml /
Min, 20ml / min, 50ml / min, 100ml / min, 200ml / min, 500ml /
Min, 1 / min, 2l / min, 5l / min, 10l / min, 20l / min
Eleven types of bypass elements (8) were required, and management was troublesome. Moreover, in the mass flow controller of the present invention, by setting the differential pressure of the bypass element (8) higher than the differential pressure of the sensor pipe (9), the maximum flow rate is 2.5 to 4 times the conventional flow rate.
It can be doubled.

Thus, when the mass flow controller according to the present invention is connected to a gas supply system of a precision equipment such as a semiconductor manufacturing apparatus and the gas flows, the gas flows into the primary chamber (6), and most of the gas flows. Flows into the secondary chamber (7) through the bypass hole,
Only a part of the gas flows through the sensor pipe (9) via the differential pressure increasing pipe (10), and then flows into the secondary chamber (7) to join the gas on the bypass side. Now, the gas flowing through the sensor tube (9) deprives the upstream heater (27a) of heat and flows downstream, suppressing the amount of heating of the downstream heater (27b). In the upstream heater (27a), the control circuit controls the upstream heater (27a) so as to supply the deprived heat and reach the equilibrium temperature. As a result, the balance between the power supplied to the heaters (27a) and (27b) is lost, and the mass flow of the gas flowing through the sensor tube (9) is detected by detecting and calculating the difference. Since the bypass side is proportional to the flow rate of the sensor pipe (9), the total gas flow rate can be easily known by multiplying the flow rate of the sensor pipe (9) by a predetermined coefficient. Then, this output is fed back to the control valve section, and the control valve (30) is driven by the control section (29) to accurately control the mass flow rate flowing through the valve chamber (18).

Now, here the pipeline (10) for increasing the differential pressure of the spacer (12)
The function of is explained. The schematic diagram of FIG. 13 shows a conventional mass flow controller. Assuming that the gas pressures at both ends of the bypass hole are P ₁ and P ₂ , respectively, the differential pressure ΔP is ΔP = P ₁ −P _2. ... (1).

On the other hand, the schematic diagram of FIG. 14 shows a mass flow controller according to the present invention (however, for convenience of drawing, two bypass elements (8) are directly opposed to the gas flow (4)). Although it is described as being disposed, the bypass element (8) is disposed at a right angle to the gas flow (4).) And the differential pressure increasing pipe (10) , The differential pressure at both ends of the bypass hole becomes higher than the differential pressure at both ends of the sensor tube (9).

Now, if the differential pressure ΔP at both ends of the sensor tube (9) is set to P ₁ and P _{2 at} the both ends of the sensor tube (9), as in the above conventional example, the same expression as the expression (1) is obtained. .

Next, due to the effect of the differential pressure increasing pipe (10), the gas pressures P ₁ and P ₂ at both ends of the sensor pipe (9) and the differential pressure ΔP thereof are different from the differential pressure of the bypass element (8). Therefore, assuming that the differential pressure of the bypass element (8) is ΔP ′ and the differential pressures at both ends are P ′ ₁ , P ′ ₂ , the following equation is obtained: ΔP ′ = P ′ ₁ −P ′ ₂ (2) Now, due to the pipe resistance of the differential pressure increase pipe (10),
Assuming that ΔP ′ becomes a (n) medium of ΔP, the following relationship is established: ΔP ′ = n · ΔP (3) Here, since the flow rate Q is proportional to the differential pressure at both ends, Q ₁ (the flow rate of the sensor tube) = K · ΔP (4) Q ₂ (the flow rate of the bypass element) = K · ΔP ′ (5) ∴Q ₂ / Q ₁ = ΔP ′ / ΔP = (n) The relationship of (6) holds, whereby the flow rate of the bypass element (8) can be increased to the (n) medium.

On the other hand, the maximum flow rate flowing through the sensor tube (9) is proportional to ΔP = P ₁ −P ₂ , which is the same as the flow rate flowing through the conventional sensor tube (9).

Therefore, even if the differential pressure of the bypass element (8) is increased by the differential pressure increasing pipe (10), the characteristic of the differential pressure versus the flow rate in the sensor pipe (9) does not change.

For example, when the differential pressure increasing pipe (10) having the same inner diameter as the sensor pipe (9) and twice the length is used, the differential pressure of the bypass element (8) is (l ₀ + 2 × l ₁ ) ÷ ( l ₀ ) = (l ₀ + 2 × 2l ₀ ) ÷ (l ₀ ) =
Therefore, the flow rate can be controlled five times with the same dimensions (in other words, the same type of model).

The height of the spacer (12) and the thickness of the differential pressure increasing pipe (10) can be appropriately changed depending on the flow rate.
Since the differential pressure of the bypass element (8) is increased, the opening area is widened so that the bypass element (8) does not become turbulent, and the flow velocity is reduced. The etching plate is suitable for this, and the present invention has a bypass structure in which these are arranged in parallel.

In addition, since the bypass element (8) is formed of an etching plate, the concave grooves (33) having substantially the same cross-sectional area can be mass-produced at a time, so that the cost can be reduced. There is no burr generated on the end face at the time of mechanical cutting of the tube unlike a capillary tube. Since the wall thickness can be reduced, there are various advantages such as a large effective sectional area and compactness.

FIG. 16 shows another embodiment of the present invention. That is, a primary communication hole (22) connecting the entrance (2) to the primary chamber (6).
A secondary communication hole (23) connecting the first chamber (7) and the primary L-shaped hole (19) is formed in the body body (16), and the primary chamber (6) and the secondary chamber ( 7) are respectively opened at the center of the first and second communication holes (22).
The direction of the gas flow (4) flowing through (23) is parallel to the partition (5).

(Effect) According to a first aspect of the present invention, a gas flow inlet is provided at one end of a body and a gas outlet is provided at the other end of the body. A partition is provided substantially parallel to the direction, a primary chamber communicating with the entrance is formed in front of the partition via the partition, and a secondary chamber communicating with the outlet is formed behind the partition, and a primary chamber is formed. A bypass element that connects the chamber and the secondary chamber is provided on the partition wall, and a sensor tube for measuring the gas flow rate is connected between the primary chamber and the secondary chamber. It is sufficient to increase or decrease the number of bypass elements of the partition wall. Further, since the partition wall is disposed substantially parallel to the gas flow direction of at least one of the inlet and the outlet inside the body, the partition wall is parallel to the gas flow of the mass flow controller. Effective use of dimensions in various directions Since the bypass elements are arranged in parallel in a direction substantially perpendicular to the gas flow, the gas can be passed through the bypass elements in the laminar flow region, and the differential pressure and flow characteristics are impaired. The flow rate can be increased as needed without any problems. In addition, there is an advantage that the type of the bypass element can be reduced to one because the bypass element is simply fitted into the partition wall in accordance with the flow rate.

Further, in claim (2) of the present invention, in order to increase the differential pressure at both ends of the bypass element from the differential pressure at both ends of the sensor tube,
Since the differential pressure increasing pipe is provided between the entrance of the primary chamber and the entrance of the sensor pipe and between the exit of the sensor pipe and the secondary chamber, a large amount of gas can be flowed by the bypass pipe, and the same The advantage is that the capacity can be doubled in size to (n) medium.

In claim (3) of the present invention, since a large number of concave grooves are formed in the width direction on the surface of the strip, and the bypass element formed by winding the strip is fitted in the partition wall, it is almost the same. Mass production of bypass elements with grooves with a cross-sectional area of
As a result, the cost can be reduced, and since it is manufactured by etching, burrs are not generated on the end face at the time of mechanical cutting of the tube unlike a capillary tube. Furthermore, the etching has various advantages, such as a reduced thickness, a large effective area, and a compact size.

[Brief description of the drawings]

FIG. 1 is a schematic plan sectional view of an embodiment of the present invention. FIG. 2 is a longitudinal sectional view in the center of FIG. 1. FIG. 3 is a sectional view in a direction perpendicular to FIG. FIG. 5 is an enlarged view of an arrow X in FIG. 4. FIG. 6 is a perspective view showing a winding state of a bypass element used in the present invention. FIG. 7 is a bypass element used in the present invention. FIG. 8: Enlarged view of reverse bypass of bypass element used in the present invention FIG. 9: Cross-sectional view of bypass used in conventional example FIG. 10: Front view of FIG. 9 FIG. Schematic perspective view of a small flow bypass element. FIG. 12: Schematic perspective view of a conventional large flow bypass element. FIG. 13: Schematic front view of a conventional mass flow controller. FIG. 14: Schematic front view of a mass flow controller of the present invention. Fig. 15 ... Plan sectional view of another embodiment of the mass flow controller according to the present invention (1) ... Body, (2) ... Mouth (3) ... Exit, (4) ... Gas flow (5) ... Partition wall, (6) ... Primary chamber (7) ... Secondary chamber, (8) ... Bypass element (9) ... Sensor tube, (10 ... Differential pressure increase line (11) ... Band, (12) ... Spacer (13) ... Bypass capillary tube (14) ... Inlet flange (15) ... Outlet flange , (16) Body body (17) Cylindrical hole, (18) Valve chamber (19) Primary L-shaped hole, (20) Secondary L-shaped hole (21) ... Flange, (22) ... Primary side communication hole (23) ... Secondary side communication hole, (24) ... Sensor side through hole (25) ... Sensor block, (26) ... Sensor pipe connection Hole (27a) (27b) ... heater, (28) ... housing block (29) ... control unit, (30) ... control valve (31) ... drive unit, (32) ... spring (33) ... groove, (34) ... protection tube (35) ... mandrel

Claims (3)

(57) [Claims] An inlet for gas inflow is provided at one end of the body, an outlet for gas outflow is provided at the other end of the body, and a partition wall is provided in the body substantially parallel to a gas flow direction flowing from the inlet to the outlet. A primary chamber communicating with the entrance is formed in front of the bulkhead via the bulkhead, and a secondary chamber communicating with the outlet is formed behind the bulkhead to communicate the primary chamber with the secondary chamber. A mass flow controller characterized in that a bypass element is provided on a partition wall and a sensor tube for measuring gas flow is connected between the primary chamber and the secondary chamber. 2. The mass flow controller according to claim 1, wherein
In order to increase the differential pressure at both ends of the bypass element from the differential pressure at both ends of the sensor tube, a differential pressure increasing conduit is provided between the inlet of the primary chamber and the sensor tube and between the outlet of the sensor tube and the secondary chamber. A mass flow controller characterized by being installed. 3. The mass flow controller according to claim 1, wherein a number of grooves are formed in the surface of the band in the width direction, and the band is wound around the surface to form a bypass hole in the axial direction. A mass flow controller characterized in that a bypass element configured as described above is fitted into a partition wall.