Low temperature thermal flow ratio controller

Abstract

Provided herein are methods and apparatus for a flow ratio controller. In some embodiments, the flow ratio controller includes an inlet, a plurality of channels extending from the inlet to a corresponding plurality of outlets, a bypass pipe extending from each of the plurality of channels to divert a small portion of the flow from that channel and then return the small portion of the flow to that channel, and a thermal mass flow meter coupled to the bypass pipe and having a first temperature sensor, a second temperature sensor, and a heating element disposed therebetween. The controller is configured to determine a flow rate through each of the plurality of channels based on a temperature difference measured between the first temperature sensor and the second temperature sensor.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure generally relate to substrate processing equipment and techniques. [Background technology]

[0002] Gas processing systems are often used in the semiconductor industry during processes such as Chemical Vapor Deposition (CVD), High-Density Plasma Chemical Vapor Deposition (HDPCVD), Atomic Layer Deposition (ALD), and etching. Typically, systems, apparatus, and methods for distributing process gas flows to a processing chamber in a desired ratio for processing a substrate use mass flow controllers (MFCs) that supply process gases to one or more Flow Ratio Controllers (FRCs) to precisely control the desired flow distribution. However, the inventors have observed decomposition and corrosion of certain process gases in the Flow Ratio Controllers, which prevents accurate flow measurement.

[0003] Accordingly, the inventors have developed an improved method and apparatus for distributing process gas to a process chamber. Summary of the Invention

[0004] Provided herein are embodiments of a flow ratio controller apparatus and method. In some embodiments, the flow ratio controller includes an inlet, a plurality of channels extending from the inlet to a corresponding plurality of outlets, a control valve on each of the plurality of channels, a bypass tube extending from each of the plurality of channels to divert a small portion of the flow from the channel and then return the small portion of the flow to the channel, a thermal mass flow meter coupled to the bypass tube and including a first temperature sensor, a second temperature sensor, and a heating element disposed between the first temperature sensor and the second temperature sensor, the heating element configured to heat the flow through the bypass tube to a predetermined temperature between about 40° C. and about 60° C., and a controller that determines a flow rate through each of the plurality of channels based on a measured temperature difference between the first temperature sensor and the second temperature sensor, and controls the control valve of each channel to provide a predetermined flow ratio of process gas between the plurality of channels.

[0005] In some embodiments, an apparatus for controlling gas distribution to an etch chamber includes a gas source, an etch chamber having a chamber body and a plurality of gas delivery zones, at least one flow ratio controller having an inlet coupled to the gas source, a plurality of channels from the inlet to a corresponding plurality of outlets, the plurality of outlets being fluidly coupled to respective gas delivery zones of the etch chamber, a bypass tube extending from each channel of the plurality of channels, the bypass tube diverting a small portion of the flow from the channel and then returning the small portion of the flow to the channel, a thermal mass flow meter coupled to the bypass tube and including a first temperature sensor, a second temperature sensor, and a heating element disposed between the first temperature sensor and the second temperature sensor, the heating element configured to heat the flow through the bypass tube to a predetermined temperature, and a controller providing a flow ratio of process gas from the gas source between the plurality of outlets and determining a flow rate through each of the plurality of outlets based on a measured temperature difference between the first temperature sensor and the second temperature sensor.

[0006] In some embodiments, a method of supplying process gases to a process chamber includes flowing one or more process gases through a flow ratio controller to supply one or more process gases at a first flow rate through a first channel to a first gas supply zone in the process chamber, one or more process gases at a second flow rate through a second channel to a second gas supply zone in the process chamber, and one or more process gases at a third flow rate through a third channel to a third gas supply zone in the process chamber; diverting a small amount of flow from each of the first, second, and third channels to a respective thermal mass flow meter having a heating element, a first temperature sensor disposed upstream of the heating element, and a second temperature sensor disposed downstream of the heating element; applying power to the heating element in each thermal mass flow meter to heat the heating element to a predetermined temperature that prevents corrosion of the one or more process gases; and calculating a measured temperature difference between the first and second temperature sensors of each thermal mass flow meter using the controller to determine a first flow rate, a second flow rate, and a third flow rate.

[0007] Other and further embodiments of the present disclosure are described below.

[0008] Embodiments of the present disclosure, briefly summarized above and discussed in more detail below, can be understood by reference to exemplary embodiments of the present disclosure, which are depicted in the accompanying drawings, which, however, depict only typical embodiments of the present disclosure and should not be considered limiting in scope, as the present disclosure may admit of other equally effective embodiments. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a flow distribution system according to some embodiments of the present disclosure. [Diagram 2] FIG. 1 is a schematic diagram of a flow distribution system according to some embodiments of the present disclosure. [Diagram 3] FIG. 1 is a schematic diagram of a flow ratio controller according to some embodiments of the present disclosure. [Figure 4] 4 is a flow chart of a method for distributing process gas to multiple gas delivery zones according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] To facilitate understanding, the same reference numbers have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale and some have been simplified for clarity. Elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0011] Provided herein are embodiments of an apparatus and method for controlling gas distribution to multiple gas supply zones in an etch chamber. In some embodiments, the apparatus includes one or more flow ratio controllers that split a mass flow rate into multiple flow lines, or channels. Aggressive etching chemistries using certain process gases result in corrosion in the gas distribution lines. In some embodiments, the process gas includes one or more of hydrogen bromide (HBr), chlorine (Cl2), nitrogen trifluoride (NF3), tetrafluoromethane (CF4), silicon tetrachloride (SiCl4), argon (Ar), oxygen (O2), nitrogen (N2), and helium (He). Corrosion can be exacerbated when the one or more flow ratio controllers include a thermal mass flow meter with a heater. Advantageously, the one or more flow ratio controllers can reduce the heat provided by the heater to reduce corrosion.

[0012] FIG. 1 is a schematic diagram of a flow distribution system 102 coupled to a process chamber 100 according to some embodiments of the present disclosure. In some embodiments, the process chamber 100 is an etch chamber. However, other types of processing chambers can be used or modified with the embodiments of the flow distribution system 102 described herein. The process chamber 100 is a vacuum chamber adapted to maintain a sub-atmospheric pressure within an interior volume 120 of the process chamber 100 during substrate processing, such as high temperature substrate processing and / or high power substrate processing. The process chamber 100 includes a chamber body 106 that is closed by a lid 104 located on top of the interior volume 120 and enclosing a processing volume 122. The chamber body 106 and the lid 104 may be made of a metal, such as aluminum. The chamber body 106 may be grounded to a ground 116 via a fitting. The lid 104 may be electrically floating or grounded.

[0013] A substrate support 124 is provided within the interior volume 120 for supporting and clamping a substrate 108, such as, for example, a semiconductor substrate or other such substrate that can be electrostatically clamped. The substrate support 124 may generally include a pedestal 136 and a support shaft 112 that supports the pedestal 136. The support shaft 112 may be hollow and may provide, for example, a conduit for supplying process gases, gases, coolants, power, etc. to the pedestal 136.

[0014] In some embodiments, a bellows 110 is disposed about the support shaft 112 and coupled between the pedestal 136 and the bottom surface 126 of the process chamber 100, providing a flexible seal that allows the pedestal 136 to move up and down while preventing loss of vacuum from within the process chamber 100. Alternatively or in combination, a bellows (not shown) may be disposed about the support shaft 112 and coupled between a portion of the support shaft 112 disposed outside the process chamber 100 and the exterior bottom surface of the process chamber 100, providing a flexible seal that allows the pedestal 136 to move up and down while preventing loss of vacuum from within the process chamber 100.

[0015] The process chamber 100 is coupled to and in fluid communication with a vacuum system 114, for example, via an exhaust port 128 in the process chamber. The vacuum system 114 includes a throttle valve and a vacuum pump used to evacuate the process chamber 100. The pressure in the process chamber 100 can be adjusted, at least in part, by adjusting the throttle valve and / or the vacuum pump. In some embodiments, the vacuum system 114 is located to one side of the process chamber 100. In some embodiments, the vacuum system 114 is centrally located below the process chamber 100. In some embodiments, the vacuum pump of the vacuum system 114 is a turbopump located below the process chamber 100 and configured to symmetrically evacuate the interior volume 120.

[0016] During operation, a substrate 108 may enter the process chamber 100 through a selectively sealable opening, such as a slit valve 132, in the chamber body 106. The opening may be selectively sealed via a door in the slit valve 132 or other device that selectively provides access to the interior of the process chamber 100 through the opening. Also during operation, a plasma 118 may be created in the interior volume 120 to perform one or more processes. The plasma 118 may be created by coupling power from a plasma power source (e.g., an RF plasma power source 130) to one or more process gases proximate to or within the interior volume 120 and igniting the process gases to create the plasma 118.

[0017] Multiple process gases may be introduced into the interior volume 120 in multiple gas delivery zones. In some embodiments, the multiple gas delivery zones are three gas delivery zones. In some embodiments, for example, the multiple gas delivery zones correspond to regions on the substrate 108, such as a central region, an annular middle region surrounding the central region, and an annular edge location surrounding the annular middle region. The multiple process gases may be introduced into the interior volume 120 in any suitable manner, such as by one or more of a gas inlet, a nozzle, a showerhead, or the like. In some embodiments, the multiple process gases are introduced into the interior volume 120 via a showerhead 138 attached to an upper region of the process chamber 100, such as in or on the lid 104, opposite the pedestal 136. In some embodiments, the multiple process gases are introduced into the interior volume 120 through a sidewall of the chamber body 106. In some embodiments, the multiple process gases are introduced into the interior volume 120 through the showerhead 138 and through a sidewall of the chamber body 106.

[0018] In some embodiments, at least some of the multiple gas delivery zones are defined within the showerhead 138. For example, in some embodiments, the showerhead has a first gas delivery zone 172 and a second gas delivery zone 174. In some embodiments, a central region of the showerhead 138 coincides with the first gas delivery zone 172. In some embodiments, a peripheral region of the showerhead 138 coincides with the second gas delivery zone 174. In some embodiments, a plurality of openings 160 or nozzles on or through the sidewall of the chamber body 106 define a third gas delivery zone 176. The showerhead 138 is coupled to and in fluid communication with a flow distribution system 102 that delivers a plurality of process gases through the showerhead 138 to the process chamber 100 for processing a substrate disposed therein. The plurality of openings 160 are coupled to and in fluid communication with a flow distribution system 102, 202 that supplies a plurality of process gases through the plurality of openings 160 to the process chamber 100 for processing a substrate disposed therein.

[0019] In some embodiments, all of the multiple gas delivery zones are defined within the showerhead 138. For example, the showerhead can include a first gas delivery zone 172, a second gas delivery zone 174, and alternatively a third gas delivery zone 176 defined by the multiple openings 160, a third gas delivery zone 176'. In some embodiments, an edge region of the showerhead 138 coincides with the third gas delivery region 176'.

[0020] As shown in FIG. 1, the flow distribution system 102 controls the gas flow and gas composition for each of the first gas delivery zone 172, the second gas delivery zone 174, and the third gas delivery zone 176, 176'. In some embodiments, the gas flow may include a gas flow or gas droplets associated with the gas flow. In some embodiments, the flow distribution system 102 may be expanded in accordance with the principles disclosed herein to provide gas flow to additional gas delivery zones. In some embodiments, as shown in FIG. 1, the flow distribution system 102 includes a first flow ratio controller 144 with an inlet 141 and multiple outlets. In some embodiments, the inlet 141 is connected to a gas source that provides one or more process gases or gas mixtures to the first flow ratio controller 144.

[0021] In some embodiments, the gas source includes a first gas source 140 through a first mass flow controller (MFC) 142. The first MFC 142 is configured to control a total flow rate of a first process gas provided to a first flow ratio controller 144. In some embodiments, the gas source includes a second gas source 150 through a second mass flow controller (MFC) 152. The second MFC 152 is configured to control a total flow rate of a second process gas provided to the first flow ratio controller 144. In some embodiments, the first gas source 140 includes hydrogen bromide (HBr) and the second gas source 150 includes at least one of chlorine (Cl2), hydrogen bromide (HBr), nitrogen trifluoride (NF3), tetrafluoromethane (CF4), and silicon tetrachloride (SiCl4). In some embodiments, the first gas source 140 includes chlorine (Cl2) and the second gas source 150 includes hydrogen bromide (HBr). In some embodiments, the first and second process gases are combined upstream of the first flow ratio controller 144.

[0022] In some embodiments, each outlet of the first flow ratio controller 144 is coupled to a different gas delivery zone. In some embodiments, the plurality of outlets includes three outlets, e.g., a first outlet 146, a second outlet 147, and a third outlet 148. In some embodiments, the plurality of outlets includes only two outlets, e.g., the first outlet 146 and the second outlet 147. The first outlet 146 is fluidly coupled to the first gas delivery zone 172 via a first gas line 180. The second outlet 147 is fluidly coupled to the second gas delivery zone 174 via a second gas line 184. In some embodiments, the third outlet 148 is fluidly coupled to the third gas delivery zone 176' via a third gas line 188. In some embodiments, the third outlet 148 is fluidly coupled to a third gas supply zone 176 via a gas line 164 through a number of openings 160 or nozzles disposed through the sidewall of the chamber body 106 .

[0023] 2 is a schematic diagram illustrating a flow distribution system 202 according to some embodiments of the present disclosure. In some embodiments, the flow distribution system 202 includes a first flow ratio controller 244 and a second flow ratio controller 254. The first flow ratio controller 244 includes a first inlet 241 and a plurality of outlets. In some embodiments, the plurality of outlets includes a first outlet 246, a second outlet 247, and a third outlet 248. The first inlet 241 is coupled to a first gas source 240 that provides a first process gas (e.g., one or more process gases or a gas mixture) to the first flow ratio controller 244. In some embodiments, the first inlet 241 is fluidly coupled to the first gas source 240 through a first MFC 242. The first MFC 242 is configured to control the total flow rate of the first process gas provided to the first flow ratio controller 244.

[0024] The second flow ratio controller 254 includes a second inlet 251 and a plurality of outlets. In some embodiments, the plurality of outlets includes a first outlet 256, a second outlet 257, and a third outlet 258. The second inlet 251 is coupled to a second gas source 250 that provides a second process gas (e.g., one or more process gases or a gas mixture) to the second flow ratio controller 254. In some embodiments, the second inlet 251 is fluidly coupled to the second gas source 250 through a second MFC 252. The second MFC 252 is configured to control the total flow rate of the second process gas provided to the second flow ratio controller 254. In some embodiments, it is advantageous for the first and second process gases to mix downstream of the first and second flow ratio controllers 244 and 254 and upstream of the process chamber 100 to keep the first and second process gases as separated as possible before entering the process chamber 100.

[0025] In some embodiments, each outlet of the first and second flow ratio controllers 244, 254 is coupled to a different gas delivery zone. For example, in some embodiments, the first outlet 246 and the first outlet 256 are both coupled to the first gas delivery zone 172 via the first gas line 180. In some embodiments, the second outlet 247 and the second outlet 257 are fluidly coupled to the second gas delivery zone 174 via the second gas line 184. In some embodiments, the third outlet 248 and the third outlet 258 are fluidly coupled to the third gas delivery zone 176 via the third gas line 188. In some embodiments, the third outlet 248 and the third outlet 258 are fluidly coupled to the plurality of openings 160 via the gas line 164.

[0026] In some embodiments, as shown in FIG. 1, the first flow ratio controller 144 is coupled to the controller 170. In some embodiments, as shown in FIG. 2, the first flow ratio controller 244 and the second flow ratio controller 254 are coupled to the controller 170. The controller 170 facilitates a user to select and control a predetermined flow ratio for each of the flow ratio controllers 144, 244, 254. The controller 170 facilitates controlling the first, second, and third flow ratio controllers 144, 244, 254 to distribute the flow of process gases according to a predetermined flow ratio. The controller 170 may provide control of the flow distribution system using a predetermined process recipe selected by the user or as part of the fabrication procedure. Alternatively or in combination, the controller 170 may provide control of the flow division via manual input of desired flow rates, flow ratios, valve settings, etc. Control of the predetermined flow ratios for each of the flow ratio controllers 144, 244, 254 advantageously provides control of the flow rates and compositions of process gases provided to gas supply zones within the process chamber 100, such as the first gas supply zone 172, the second gas supply zone 174, the third gas supply zone 176, and the multiple openings 160.

[0027] The controller 170 may include a central processing unit (CPU), memory, and support circuits. The CPU may be any form of general-purpose computer processor used in an industrial environment. The software routines may be stored in memory, such as random access memory, read-only memory, a floppy disk or hard disk, or other forms of digital storage. The support circuits are conventionally coupled to the CPU and may consist of cache, clock circuits, input / output subsystems, power supplies, and the like. The software routines, when executed, transform the general-purpose computer processor into a special-purpose computer (controller 170) that controls chamber operation such that the methods disclosed herein are performed.

[0028] The configuration of the flow distribution system 102 and the flow distribution system 202 may be determined based on the expected operating conditions and power requirements for a particular application. For example, in some embodiments, the flow ratio controllers 144, 244, 254 may each provide flow ratios from 1:1 to 6:1 in half ratio increments (i.e., 1 / 1, 1.5 / 1, 2 / 1, 2.5 / 1...6 / 1) and may be fully reversible between the first gas supply zone 172, the second gas supply zone 174, and the third gas supply zone 176, 176' (i.e., 1 / 1, 1 / 1.5, 2 / 1, 2.5 / 1...1 / 6). In some embodiments, the accuracy of the gas flow division may be within, for example, 5%, to match the performance of existing equipment.

[0029] 3 is a schematic diagram of a flow ratio controller 302 according to some embodiments of the present disclosure. The flow ratio controller 302 can be one or more of the flow ratio controllers 144, 244, 254 described above. The flow ratio controller 302 is configured to provide a flow ratio of a first process gas or process gas mixture between an inlet 351 and one or more outlets. In some embodiments, the flow ratio controller 302 includes a first outlet 346, a second outlet 347, and a third outlet 348. The first outlet 346 is fluidly coupled to the first gas delivery zone via a gas line (e.g., the first gas line 180). The second outlet 347 is fluidly coupled to the second gas delivery zone via a gas line (e.g., the second gas line 184). The third outlet 348 is fluidly coupled to the third gas delivery zone via a gas line (e.g., the third gas line 188 or the gas line 164). However, the flow ratio controller 302 may include more or less outlets fluidly coupled to a corresponding number of gas delivery zones.

[0030] The flow ratio controller 144, 244, 254 includes multiple channels corresponding to multiple outlets. In some embodiments, the multiple channels are two channels, three channels, or four channels. For example, as shown in FIG. 3, the flow ratio controller 302 includes a first channel 304 from an inlet 351 to a first outlet 346, a second channel 306 from the inlet 351 to a second outlet 347, and a third channel 308 from the inlet 351 to a third outlet 348. A first control valve 312 is disposed on the first channel 304 to control the flow rate of gas through the first outlet 346. A second control valve 314 is disposed on the second channel 306 to control the flow rate of gas through the second outlet 347. A third control valve 316 is disposed on the third flow path 308 to control the flow rate of gas through the third outlet 348. The first control valve 312, the second control valve 314, and the third control valve 316 may be any suitable valves for use in a semiconductor manufacturing environment. The first control valve 312, the second control valve 314, and the third control valve 316 may be coupled to a controller 370. The controller 370 facilitates user selection and control of a predetermined flow ratio between the first channel 304, the second channel 306, and the third channel 308 of the flow ratio controller 302. In some embodiments, the controller 370 is similar to the controller 170.

[0031] Each channel 304, 306, 308 of the flow ratio controller 302 includes a thermal mass flow meter for regulating gas flow through the respective channel 304, 306, 308. For example, the first channel 304 includes a first thermal mass flow meter 322, the second channel 306 includes a second thermal mass flow meter 324, and the third channel 308 includes a third thermal mass flow meter 326. The following discussion regarding the first channel 304 and the first thermal mass flow meter 322 may apply to the second channel 306 and the second thermal mass flow meter 324 and the third channel 308 and the third mass flow meter 326, respectively.

[0032] In some embodiments, the first channel 304 includes a bypass tube 332 that diverts a small portion of the flow from the first channel 304 and then returns the small portion of the flow to the first channel 304. In some embodiments, the bypass tube 332 is located upstream of the first control valve 312. The first thermal mass flow meter 322 is coupled to the bypass tube 332. The bypass tube 332 is sized to operate in a laminar flow regime over the entire operating range of the flow ratio controller 302. In some embodiments, the thermal mass flow meter 322 includes a first temperature sensor 336, a second temperature sensor 338, and a heating element 334 disposed between the first temperature sensor 336 and the second temperature sensor 338. In some embodiments, the first temperature sensor 336 and the second temperature sensor 338 are disposed substantially equidistant from the heating element 334.

[0033] The first temperature sensor 336 is configured to measure a first temperature T1 of the process gas upstream of the heating element 334. The second temperature sensor 338 is configured to measure a second temperature T2 of the process gas downstream of the heating element 334. In some embodiments, the first temperature sensor 336 and the second temperature sensor 338 are resistance temperature detectors (RTDs).

[0034] In use, the heater power supply 360 heats the heating element 334 to a predetermined temperature. When there is no flow through the bypass tube 332, the first temperature sensor 336 and the second temperature sensor 338 measure substantially similar temperatures. In other words, the measured temperature difference between T2 and T1 is substantially zero. In some embodiments, the heating element 334 can protrude into the gas flow of the bypass tube 332. In such embodiments, as the process gas flows through the bypass tube 332 and passes over the heating element 334, the process gas is heated. In some embodiments, the heating element 334 is external to the bypass tube 332, for example, wrapped around the bypass tube 332. In such embodiments, the heating element 334 heats a portion of the bypass tube 332, and as the process gas flows through the bypass tube 332, the process gas is heated. The gas molecules of the process gas carry the heat downstream, raising the second temperature T2 relative to the first temperature T1. The thermal mass flow meter 322 includes a Wheatstone bridge circuit 342 connected to terminals of the first temperature sensor 336 and the second temperature sensor 338. The Wheatstone bridge circuit 342 is configured to convert a measured temperature difference into a voltage difference calibrated for a known flow rate.

[0035] The small diameter of the bypass tube 332 is advantageous in minimizing power consumption by the heating element 334. However, the heat provided by the heating element 334 may also heat the bypass tube walls, increasing the corrosion rate of certain gases flowing through the bypass tube 332 and causing drift of the first and second temperature sensors 336, 338. Drift of the first and second temperature sensors 336, 338 may result in inaccurate temperature measurement readings. Advantageously, the predetermined temperature may be lowered to reduce heating of the bypass tube walls and, therefore, reduce the corrosion rate. The flow ratio controller 302 may be calibrated at a lower predetermined temperature. In some embodiments, the predetermined temperature is reduced from about 70°C to about 90°C to about 40°C to about 60°C. In some embodiments, the predetermined temperature is about 45°C to about 55°C.

[0036] In some embodiments, the first thermal mass flow meter 322, the second thermal mass flow meter 324, and the third thermal mass flow meter 326 are coupled to a controller 370. The controller 370 is configured to take readings from the temperature sensors of each of the thermal mass flow meters 322, 324, 326 and control the flow rates through each of the outlets 346, 347, 348. In some embodiments, the controller 370 is also coupled to a heater power supply 360 to control the amount of heat provided to the heating elements in each of the thermal mass flow meters 322, 324, 326. The heater power supply 360 can be one power supply that provides heat to the heating elements in each of the thermal mass flow meters 322, 324, 326.

[0037] 4 is a flow chart of a method 400 for distributing process gas to multiple gas delivery zones according to some embodiments of the present disclosure. In some embodiments, the flow distribution systems 102, 202 described above may be used to perform the method 400. In some embodiments, the method 400 for controlling gas distribution to multiple gas delivery zones includes, at 402, flowing one or more process gases through a first flow ratio controller (e.g., first flow ratio controller 144, 244, flow ratio controller 302) through a corresponding number of channels to a plurality of outlets, providing a predetermined flow rate of one or more process gases through each of the channels to a corresponding number of gas delivery zones of a process chamber. For example, a first flow rate of one or more process gases flows through a first channel (e.g., first channel 304) to a first gas supply zone (e.g., first gas supply zone 172) in the process chamber (e.g., process chamber 100), a second flow rate of one or more process gases flows through a second channel (e.g., second channel 306) to a second gas supply zone (e.g., second gas supply zone 174) in the process chamber, and a third flow rate of one or more process gases flows through a third channel (e.g., third channel 308) to a third gas supply zone (e.g., third gas supply zone 176, multiple openings 160) in the process chamber. In some embodiments, the one or more process gases include at least one of hydrogen bromide (HBr) or chlorine (Cl2), as described above with respect to the first gas source 140 and the second gas source 150. In some embodiments, the first flow ratio controller is fluidly coupled to a first gas source, such as first gas source 140, and a second gas source, such as second gas source 150. In some embodiments, the first flow ratio controller is fluidly coupled to a first gas source, such as first gas source 240, and the second flow ratio controller (e.g., second flow ratio controller 254) is fluidly coupled to a second gas source, such as second gas source 250.

[0038] At 404, the small streams are diverted from each of the first, second, and third channels via a bypass line or tube (e.g., bypass tube 332) to a respective thermal mass flow meter (e.g., thermal mass flow meter 322, 324, 326). At 406, power is applied to a heating element of each thermal mass flow meter 322, 324, 326 to heat the heating element to a predetermined temperature. The predetermined temperature is lowered to reduce or prevent corrosion of one or more process gases in the bypass line. For example, in some embodiments, the predetermined temperature is lowered to about 40° C. to about 60° C. In some embodiments, the predetermined temperature is about 45° C. to about 55° C. A first temperature sensor is disposed upstream of the heating element and a second temperature sensor is disposed downstream of the heating element.

[0039] At 408, a controller (e.g., controller 170, 370) calculates the measured temperature difference between the first and second temperature sensors. The controller is configured to determine the flow rates through the respective channels based on the measured temperature difference. For example, a Wheatstone bridge circuit (e.g., Wheatstone bridge circuit 342) is configured to convert the measured temperature difference into a voltage difference that is calibrated against known flow rates to determine the flow rates through the respective channels of the flow ratio controller. In some embodiments, during use, the controller is configured to maintain the temperature of each of the bypass tubes at or near a predetermined temperature by controlling the power provided to the respective heating elements.

[0040] At 410, the controller controls the control valves on each channel of the flow ratio controllers by sending electrical signals to the control valves to open or close the valves to regulate the flow rate through the respective channels to provide a desired amount of process gas to each outlet of the flow ratio controllers.

[0041] While the forgoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof.

Claims

1. The entrance and a plurality of channels extending from the inlet to a corresponding plurality of outlets; a control valve on each channel of the plurality of channels; a bypass tube extending from each channel of the plurality of channels, the bypass tube diverting a minor portion of the flow away from the channel and then returning the minor portion of the flow to the channel; a thermal mass flow meter connected to the bypass pipe and including a first temperature sensor, a second temperature sensor, and a heating element disposed between the first temperature sensor and the second temperature sensor, the heating element being configured to heat the flow through the bypass pipe to a predetermined temperature, the temperature being between about 40° C. and about 60° C.; a controller that determines a flow rate through each of the plurality of channels based on a temperature difference measured between the first temperature sensor and the second temperature sensor, and controls the control valve of each channel to provide a predetermined flow ratio of process gas between the plurality of channels; A flow ratio controller comprising:

2. 2. The flow ratio controller of claim 1, wherein the first temperature sensor and the second temperature sensor are disposed approximately equidistant from the heating element.

3. The process gas is hydrogen bromide (HBr), chlorine (Cl ２ ), nitrogen trifluoride (NF ３ ), tetrafluoromethane (CF ４ ), or silicon tetrachloride (SiCl ４ 3. The flow ratio controller of claim 1, further comprising at least one of:

4. 3. The flow ratio controller according to claim 1, wherein the control valve is provided downstream of the bypass pipe.

5. 3. The flow ratio controller of claim 1, wherein the first temperature sensor and the second temperature sensor are resistive temperature sensing elements.

6. The flow ratio controller of claim 1 or 2, wherein the heating element is external to the bypass pipe.

7. 1. An apparatus for controlling gas distribution to an etch chamber, comprising: A gas source; an etch chamber having a chamber body and a plurality of gas delivery zones; 3. At least one flow ratio controller according to claim 1 or 2, each of the at least one flow ratio controller having an inlet connected to the gas source; An apparatus comprising:

8. The process gas is hydrogen bromide (HBr), chlorine (Cl ２ ), nitrogen trifluoride (NF ３ ), tetrafluoromethane (CF ４ ), or silicon tetrachloride (SiCl ４ 8. The apparatus of claim 7, further comprising at least one of:

9. 8. The apparatus of claim 7, wherein the at least one flow ratio controller comprises a first flow ratio controller and a second flow ratio controller, and the gas source includes a first gas source having a first process gas coupled to the inlet of the first flow ratio controller and a second gas source having a second process gas coupled to the inlet of the second flow ratio controller, the first gas source and the second gas source being separate.

10. 10. The apparatus of claim 9, wherein the first process gas and the second process gas are combined downstream from the first flow ratio controller and the second flow ratio controller and upstream from the etch chamber.

11. The apparatus of claim 7 , wherein the plurality of channels comprises three channels.

12. 8. The apparatus of claim 7, wherein the plurality of gas delivery zones comprises three gas delivery zones, and the plurality of outlets comprises three outlets, a first outlet fluidly coupled to the first gas delivery zone via a first gas line, a second outlet fluidly coupled to the second gas delivery zone via a second gas line, and a third outlet fluidly coupled to the third gas delivery zone via a third gas line.

13. 13. The apparatus of claim 12, wherein the third gas supply zone is defined by a plurality of openings disposed around the chamber body through a sidewall of the chamber body.

14. 1. A method for delivering a process gas to a process chamber, comprising: flowing one or more process gases through a flow ratio controller to supply the one or more process gases at a first flow rate through a first channel to a first gas delivery zone in the process chamber, supply the one or more process gases at a second flow rate through a second channel to a second gas delivery zone in the process chamber, and supply the one or more process gases at a third flow rate through a third channel to a third gas delivery zone in the process chamber; diverting a small amount of flow from each of the first, second, and third channels to a respective thermal mass flow meter having a heating element, a first temperature sensor disposed upstream of the heating element, and a second temperature sensor disposed downstream of the heating element; applying power to the heating element in each thermal mass flow meter to heat the heating element to a predetermined temperature that prevents corrosion of the one or more process gases; and calculating, using a controller, a measured temperature difference between the first temperature sensor and the second temperature sensor of each thermal mass flow meter to determine the first flow rate, the second flow rate, and the third flow rate.

15. The one or more process gases may include hydrogen bromide (HBr), chlorine (Cl ２ ), nitrogen trifluoride (NF ３ ), tetrafluoromethane (CF ４ ), or silicon tetrachloride (SiCl ４ 15. The method of claim 14, comprising at least one of:

16. 15. The method of claim 14, wherein applying power to the heating element comprises heating the heating element to a predetermined temperature of about 40°C to about 60°C.

17. 17. The method of any one of claims 14 to 16, wherein determining the first flow rate, the second flow rate, and the third flow rate includes converting the measured temperature difference into a voltage difference calibrated to a known flow rate using a Wheatstone bridge circuit.

18. 17. The method of any one of claims 14 to 16, further comprising using the controller to control a control valve on each channel to provide a desired amount of process gas to each outlet of the flow ratio controller.

19. 17. The method of any one of claims 14 to 16, wherein flowing one or more process gases into the third gas supply zone comprises flowing the one or more process gases through a sidewall of the process chamber.

Images