Mass flow controller

A mass flow controller includes a base having a passage that allows a fluid to pass through the passage. A first control valve controls a mass flow of a fluid passing through the passage. A second control valve controls a full scale of the mass flow of the fluid. A bypass portion is disposed in the passage through which the fluid passes. A mass flow sensor measures the mass flow of the fluid passing through the bypass portion. The second control valve is connected to the passage adjacent to the bypass portion for controlling the full scale of the mass flow of the fluid passing through the bypass portion.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119 to Korean Patent Application No 2003-19596, filed on Mar. 28, 2003, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, generally, to a mass flow controller, and more particularly to a controller for controlling a mass flow of a fluid by measuring the mass flow of the fluid and then by comparing the measured mass flow to a standard flow.

2. Description of the Related Art

Generally, various kinds of gases are used in semiconductor fabricating processes. A mass flow controller controls mass flows of the gases. As semiconductor devices have become more highly integrated, requirements for controls to accurately measure and control the mass flows of gases to semiconductor fabricating processes have increased.

FIG. 1is a sectional view illustrating a conventional mass flow controller, andFIG. 2is a partially enlarged view illustrating a mass flow sensor of the conventional mass flow controller ofFIG. 1.

Referring toFIGS. 1 and 2, a base110of a conventional mass flow controller100has a passage112through which a fluid passes, an inlet portion114for introducing the fluid into the passage112and an outlet portion116for releasing the fluid from the passage112.

A bypass portion120through which the fluid passes is formed in the passage112adjacent to the inlet portion114. A sampling pipe132is connected to the passage112. Particularly, the sampling pipe132is connected between a first portion adjacent to an inlet end of the bypass portion120and a second portion adjacent to an outlet portion of the bypass portion120, thereby allowing a sample of the fluid passing through the bypass portion120to pass through the sampling pipe132.

A mass flow sensor130measures a mass flow of the fluid passing through the bypass portion120. The mass flow sensor130includes a first thermal resistance134aand a second thermal resistance134b,wherein the first thermal resistance134aand the second thermal resistance134bare wound around the sampling pipe132. The first thermal resistance134aand the second thermal resistance134bcomprising Pt or other metals similar to Pt are connected to a bridge circuit136. A control valve140, e.g., a solenoid valve, is connected between the bypass portion120and the outlet portion116.

When the first thermal resistance134aand the second thermal resistance134bare heated, a temperature difference proportional to the mass flow of the fluid is generated between an upper stream and a lower stream of the sampling pipe132. Therefore, resistance values of the first thermal resistance134aand the second thermal resistance134bare different from each other. The bridge circuit136detects the different resistance values as an electric signal. The detected signal is amplified through an amplifier (not shown). The compensator compensates the amplified signal to correspond to the mass flow of the fluid.

The measured signal indicating the mass flow of the fluid is transmitted to a valve controller (not shown). The valve controller compares the measured signal to a predetermined standard flow. The valve controller controls operations of a control valve140to correspond the measured signal to the standard signal.

Full scale of the mass flow of the fluid is determined according to a volume of the bypass portion120. The full scale may not be readily controlled. In the meantime, the semiconductor fabricating processes contain various kinds of lot processes. Also, various kinds of gases are used in the fabricating processes. In addition, the gases supplied to a semiconductor substrate to perform the fabricating processes have different mass flows from one other. Accordingly, there exists a problem that the conventional mass flow controller100may not be applied to the various processes.

Therefore, a need exist for a mass flow control that can control a full scale of a mass flow and the mass flow of the various kinds of gases used in the various processes of semiconductor fabrication.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention include a mass flow controller that is capable of controlling a full scale of a mass flow and the mass flow of a fluid.

According to an exemplary embodiment of the present invention, a mass flow controller includes a base having a passage through which a fluid passes, an inlet portion for introducing the fluid into the passage and an outlet portion for releasing the fluid from the passage. A mass flow sensor is connected to the passage adjacent to the inlet portion, which measures a mass flow of the fluid passing through the passage. A first control valve is connected to the passage adjacent to the outlet portion, which controls the mass flow of the fluid passing through the passage. A valve controller compares the mass flow measured by the mass flow sensor to a standard flow, and then controls the first control valve to correspond the measured mass flow to the standard flow. A second control valve is connected to the passage adjacent to the inlet portion, which controls a full scale of the mass flow of the fluid passing through the passage.

A mass flow controller according to an embodiment of the invention controls the full scale of the mass flow of the fluid and can be employed in semiconductor fabricating processes using various kinds of gases.

These and other exemplary embodiments, features, aspects, and advantages of the present invention will be described and become readily apparent from the following detailed description of exemplary embodiments when read in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 3is a schematic sectional view illustrating a mass flow controller according to an exemplary embodiment of the invention, andFIG. 4is a perspective view illustrating a bypass portion and a second valve body ofFIG. 3.

ReferringFIGS. 3 and 4, a mass flow controller200according to an exemplary embodiment is connected to a fluid pipe (not shown) for supplying a fluid. For example, the mass flow controller200is connected to the fluid pipe for supplying semiconductor fabricating equipment with processing gases, thereby controlling the mass flow of the gases. The mass flow controller200includes a base210, a mass flow sensor230, a first control valve250, a valve controller260and a second control valve270.

The base210is connected to the fluid pipe. The base210has a long passage212through which the fluid passes, an inlet portion214for introducing the fluid into the passage212from the fluid pipe and an outlet portion216for releasing the fluid from the passage212.

The mass flow sensor230is connected to the passage212adjacent to the inlet portion214, thereby measuring the mass flow of the fluid passing through the passage212. The mass flow sensor230includes a sampling pipe232, a first thermal resistance234aand a second thermal resistance234bcoiled around the sampling pipe232, respectively, a bridge circuit236connected to the first thermal resistance234aand the second thermal resistance234b, an amplifier238connected to the bridge circuit236and a compensator connected to the amplifier238.

Particularly, a bypass portion220through which the fluid passes is disposed in the passage212adjacent to the inlet portion214. The sampling pipe232for sampling the fluid passing through the bypass portion220is connected between a first portion of the passage212between the inlet portion214and the bypass portion220and a second portion of the passage212between the bypass portion220and the first control valve250.

The first thermal resistance234ais wound (as a coil) on an upper stream of the sampling pipe232and the second thermal resistance234bis wound on a lower stream of the sampling pipe232. When the first thermal resistance234aand the second thermal resistance234bare heated, the bridge circuit236generates an electric signal corresponding to a temperature difference between the upper stream and the lower stream of the sampling pipe232.

The amplifier238amplifies the electric signal detected by the bridge circuit236. The compensator230compensates the amplified electric signal to correspond to the mass flow of the fluid passing through the bypass portion220.

The first control valve250includes a valve seat252, a first valve body254and a first driving unit256. The valve seat252is disposed in the passage212between the lower stream of the sampling pipe232and the outlet portion216of the base210. Preferably, the first valve body254has a valve head having a disk shape. The first driving unit256drives the first valve body254to properly adjust the opening of the first control valve250. The first driving unit256may include a solenoid. In addition, the first valve body254may have a poppet valve head having a cone shape.

The configuration of the first control valve250may be varied depending upon the kind of first driving unit256employed. For example, the first control valve250may include a thermal valve including a thermal type driving unit or a piezoelectric valve having a piezoelectric stack composed of a plurality of piezoelectric elements.

The valve controller260controls the operation of the first control valve250. In particular, the valve controller260receives the signal compensated by the compensator240. The valve controller260compares a standard signal corresponding to a predetermined standard flow with the compensated signal, and then controls the operation of the first control valve250to correspond the mass flow measured by the mass flow sensor230to the predetermined standard flow.

The second control valve270is connected to the passage212adjacent to the inlet portion214. Particularly, the second control valve270is connected to the passage212between the bypass portion220and a releasing end of the sampling pipe232, thereby controlling a full scale of the mass flow of the fluid passing through the bypass portion220. The second control valve270includes a second valve body for controlling an opened sectional area of the passage212and a second driving unit274traversing the passage212with the second valve body272.

The passage212has a circular section. The second valve body272has a disk shape corresponding to the circular section of the passage212. The second driving unit274having a solenoid provides a driving force to the second valve body272. The second valve body272makes contact with the releasing end of the bypass portion220. Alternatively, the second valve body272may be disposed apart from the releasing end of the bypass portion220. Also, the second control valve270may be adjacently disposed at the inlet end of the bypass portion220.

To stabilize the fluid passing through the passage212to the sampling pipe232, it is preferred that the fluid passing through the passage212is under a laminar flow condition. As shown inFIG. 5, to create the laminar flow condition with in the passage212, a second valve body272aincluding a plurality of holes272bmay be employed. On the other hand, the valve controller260may control the second control valve270.

According to another exemplary embodiment, the second control valve270controls the full scale of the mass flow of the fluid passing through the mass flow controller200. For example, when the full scale of the mass flow of the fluid is set to about 100 sccm by the second control valve270, the first control valve250controls the mass flow of the fluid to be below about 100 sccm. When the full scale of the mass flow of the fluid is set to about 1,000 sccm by the second control valve270, the first control valve250controls the mass flow of the fluid to be below about 1,000 sccm.

Since the second control valve270previously determines the full scale of the mass flow of the fluid, the mass flow controller270may be employed in semiconductor fabricating processes using various kinds of gases.

FIG. 6is a schematic sectional view illustrating a second valve body according to another variation ofFIG. 3.

ReferringFIG. 6, a second control valve270aincludes a valve body272afor controlling the full scale of the mass flow of the fluid passing through the passage212and a driving unit274afor moving the valve body272a. The driving unit274aincludes a motor274b, a driving screw274cand a driven screw274d.

The valve body272amay have a disk shape and may also include a plurality of holes, as shown inFIG. 5. The valve body272amakes contact with the releasing end of the bypass portion220. Alternatively, the valve body272amay be spaced apart from the releasing end of the bypass portion220.

The motor274bprovides a driving force to the valve body272a. The motor274bmay include a step motor capable of controlling a rotation angle of the valve body272a. The driving screw274cis connected to the motor274b, thereby transmitting the driving force to the driven screw274d. The driven screw274dis connected between the driving screw274cand the valve body272a. The driving force is applied to the driven screw274dso that the drive screw274dis reciprocally moved.

FIG. 7is a schematic sectional view illustrating a mass flow controller according to another exemplary embodiment of the invention.

Referring toFIG. 7, a mass flow controller300according to another exemplary embodiment includes a base310, a mass flow sensor330, a first control valve350, a valve controller360and a second control valve370.

The base310connected to a fluid pipe has a long passage312through which a fluid passes, an inlet portion314for introducing the fluid from the fluid pipe into the passage312and an outlet portion316for releasing the fluid from the passage312. A capillary bypass portion320is disposed in the passage312adjacent to the inlet portion314. The capillary bypass portion320forms a laminar flow condition in the passage312.

A mass flow sensor330includes a sampling pipe332, a first thermal resistance334a, a second thermal resistance334b, a bridge circuit336, an amplifier338and a compensator340. The sampling pipe332is connected between a first portion of the passage312adjacent to an inlet end of the capillary bypass portion320and a second portion of the passage312adjacent to a releasing end of the capillary bypass portion320. Another capillary bypass portion322may be further installed between the inlet portion314of the base310and the capillary bypass portion320.

The valve controller360compares a signal corresponding to the mass flow measured by the mass flow sensor330with a standard signal corresponding to a standard flow, and then controls the operation of the first control valve350. The valve controller360properly controls the mass flow of the fluid passing through the passage312.

The first control valve350includes a valve seat352, a first valve body354for controlling the mass flow of the fluid passing through the passage312and a first driving unit356for driving the first valve body354. The second control valve370includes a second valve body372for controlling the full scale of the mass flow of the fluid passing through the capillary bypass portion320and a second driving unit374for driving the second valve body. Here, the second valve body372may include a plurality of holes, as shown inFIG. 5. According to another exemplary embodiment, the second control valve270aofFIG. 6may be employed in the mass flow controller300ofFIG. 7.

Since the elements according to another embodiment are previously described in relation to the mass flow controller200ofFIG. 3, illustrations of the elements are omitted.

FIG. 8is a schematic sectional view illustrating a mass flow controller according to still another exemplary embodiment of the invention, andFIG. 9is a perspective view illustrating a bypass portion ofFIG. 8.

Referring toFIGS. 8 and 9, a mass flow controller400according to still another exemplary embodiment includes a base410, a mass flow sensor430, a first control valve450, a valve controller460and a second control valve470.

The base410connected to a fluid pipe has a long passage412through which a fluid passes, an inlet portion414for introducing the fluid from the fluid pipe to the passage412and an outlet portion416for releasing the fluid from the passage412.

A porous bypass portion420is disposed in the passage412adjacent to the inlet portion414. The porous bypass portion420formed of a cylindrical shape has a plurality of second passages420a, as shown inFIG. 9. The second passages420aform a laminar flow condition in the passage412.

A mass flow sensor430includes a sampling pipe432, a first thermal resistance434a, a second thermal resistance434b, a bridge circuit436, an amplifier438and a compensator440. The sampling pipe432is connected between a first portion of the passage412adjacent to an inlet end of the porous bypass portion420and a second portion of the passage412adjacent to a releasing end of the porous bypass portion420. In addition, another porous bypass portion422may be installed between the inlet portion414of the base410and the porous bypass portion420.

The valve controller460compares a signal corresponding to the mass flow measured by the mass flow sensor430with a standard signal corresponding to a standard flow, and then controls the operation of the first control valve450. The valve controller460properly controls the mass flow of the fluid passing through the passage412.

The first control valve450includes a valve seat452, a first valve body454for controlling the mass flow of the fluid passing through the passage412and a first driving unit456for driving the first valve body454. The second control valve470includes a second valve body472for controlling the full scale of the mass flow of the fluid passing through the porous bypass portion420and a second driving unit474for driving the second valve body472. The second valve body472has a plurality of holes corresponding to the second passages420aof the porous bypass portion420as shown inFIG. 8.

The second driving unit474moves the second valve body472to control the full scale of the mass flow of the fluid passing through the second passages420aof the porous bypass portion420and the holes of the second valve body472. The second driving unit474varies relative positions between the porous bypass portion420and the second valve body472so that the opened sectional area of the second passages420ais altered.

The second driving unit474includes a solenoid. The step motor type of the second driving unit274aofFIG. 6may be employed in the second control valve470. Since the moving distance of the second valve body472is relatively shorter than that of the second valve body272or372, the second driving unit474may further include a thermal type or a piezoelectric type of driving unit.

Since the elements according to still another exemplary embodiment are previously described in relation to the mass flow controller200ofFIG. 3, illustrations of the elements are omitted.

FIG. 10is a schematic sectional view illustrating a mass flow controller according to yet another exemplary embodiment of the invention.

Referring toFIG. 10, a mass flow controller500according to yet another exemplary embodiment includes a base510, a mass flow sensor530, a first control valve550, a valve controller560and a second control valve570.

The base510connected to a fluid pipe has a long passage512through which a fluid passes, an inlet portion514for introducing fluid from the fluid pipe into the passage512and an outlet portion516for releasing the fluid from the passage512. A bypass portion520is disposed in the passage512adjacent to the inlet portion514.

A mass flow sensor530includes a sampling pipe532, a first thermal resistance534a, a second thermal resistance534b, a bridge circuit536, an amplifier538and a compensator540. The sampling pipe532is connected between a first portion of the passage512adjacent to an inlet end of the bypass portion520and a second portion of the passage512adjacent to a releasing end of the bypass portion520. In addition, another capillary bypass portion (not shown) may be installed between the inlet portion514of the base510and the bypass portion520.

The valve controller560compares a signal corresponding to the mass flow measured by the mass flow sensor530to a standard signal corresponding to a standard flow, and then controls the operation of the first control valve550. The valve controller560properly controls the mass flow of the fluid passing through the passage512.

The first control valve550includes a valve seat552, a first valve body554for controlling the mass flow of the fluid passing through the passage512and a first driving unit556for driving the first valve body554.

The second control valve570includes a second valve seat571connected to the releasing end of the bypass portion520, a second valve body572for controlling the full scale of the mass flow of the fluid passing through the porous bypass portion520and a second driving unit574for driving the second valve body572to control the opening between the second valve seat571and the second valve body572.

The second valve seat571has a ring shape. Preferably, the second valve body572has a disc valve head including a disc shape corresponding to the shape of the second valve seat571. Also, a poppet valve head having a cone shape may be employed in the second valve body572.

Since the elements according to yet another exemplary embodiment are previously described in relation to the mass flow controller200ofFIG. 3, illustrations of the elements are omitted.

According to the exemplary embodiments of the present invention, the first control valve controls a mass flow of a fluid passing through the passage of the mass flow controller and the second control valve controls a full scale of the mass flow. Accordingly, the mass flow controller according to the embodiments of the present invention can be employed in different processes, e.g., semiconductor fabricating processes, using various kinds of gases.

Having described the exemplary embodiments for the stocker and the transfer system, it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. It is therefore to be understood that changes may be made in the exemplary embodiments of the present invention disclosed which is within the scope and the spirit of the invention outlined by the appended claims.