Chemical sensor for automatic flow compensation of mass flow controller

Abstract

Examples are disclosed that relate to automatic flow compensation for a reactant gas based on a detected concentration of a second gas flowing with the reactant gas. One example provides a substrate processing tool comprising a processing chamber. The substrate processing tool further comprises a conduit for flowing a mixture of a reactant gas with a second gas to the processing chamber. The substrate processing tool further comprises a chemical sensor configured to detect a concentration of the second gas in the conduit. The substrate processing tool further comprises a mass flow controller located along the conduit and downstream from the chemical sensor. The substrate processing tool further comprises a systems controller configured to receive a signal from the chemical sensor indicating a concentration of the second gas in the conduit and adjust the mass flow controller based on the signal and a set point for the reactant gas.

Description

CHEMICAL SENSOR FOR AUTOMATIC FLOW COMPENSATION OFMASS FLOW CONTROLLERBACKGROUND

[0001] Semiconductor device fabrication processes involve many steps of material deposition, patterning and removal to form integrated circuits on substrates. Various methods can be used to deposit films of materials onto a substrate. As an example, chemical vapor deposition (CVD) deposits a film by directing a continuous flow of reactant gas(es) over a substrate under conditions configured to convert the reactant gas(es) into a film. In various examples, the reactant gas(es) can be converted to a film using heat (thermal CVD) or plasma (plasma-enhanced CVD). In some examples, film deposition can be affected by the flow rate of the reactant gas(es) flowing into the processing chamber.SUMMARY

[0002] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.

[0003] Examples are disclosed that relate to automatic flow compensation for a reactant gas based on a detected concentration of a second gas flowing with the reactant gas. One example provides a substrate processing tool. The substrate processing tool comprises a processing chamber. The substrate processing tool further comprises a conduit for flowing a mixture of a reactant gas with a second gas to the processing chamber. The substrate processing tool further comprises a chemical sensor configured to detect a concentration of the second gas in the conduit. The substrate processing tool further comprises a mass flow controller located along the conduit and downstream from the chemical sensor. The substrate processing tool further comprises a systems controller configured to receive a signal from the chemical sensor indicating a concentration of the second gas in the conduit. The systems controller is furtherconfigured to adjust the mass flow controller based on the signal and a set point for the reactant gas.

[0004] In some such examples, the reactant gas comprises acetylene.

[0005] In some such examples, the second gas additionally or alternatively comprises a stabilizer.

[0006] In some such examples, the stabilizer additionally or alternatively comprises acetone.

[0007] In some such examples, the chemical sensor additionally or alternatively comprises an infrared sensor.

[0008] In some such examples, the chemical sensor additionally or alternatively comprises a visible light sensor.

[0009] In some such examples, the systems controller additionally or alternatively is configured to adjust the flow offset of the mass flow controller using a look-up table.

[0010] In some such examples, the substrate processing tool additionally or alternatively is configured to form a plasma using the reactant gas to deposit a film.

[0011] Another example provides a method of controlling a substrate processing tool. The method comprises, using a mass flow controller, controlling a flow of reactant gas and a second gas through a conduit towards a processing chamber of the substrate processing tool. The method further comprises, using a chemical sensor positioned along the conduit, detecting a concentration of the second gas flowing through the conduit. The chemical sensor is located upstream from the mass flow controller. The method further comprises adjusting the mass flow controller based at least on the concentration of the second gas detected.

[0012] In some such examples, detecting the concentration of the second gas comprises using an infrared sensor.

[0013] In some such examples, adjusting the mass flow controller additionally or alternatively comprises adjusting a flow offset of the mass flow controller.

[0014] In some such examples, adjusting the mass flow controller additionally or alternatively comprises using a lookup table.

[0015] In some such examples, adjusting the flow rate of the gas mixture additionally or alternatively is further based on a target deposition rate.

[0016] In some such examples, the reactant gas additionally or alternatively comprises a carbon-containing gas, and the method further comprises depositing a carbon-based film on a substrate disposed in the processing chamber.

[0017] In some such examples, the carbon-containing gas additionally or alternatively comprises acetylene.

[0018] In some such examples, the second gas additionally or alternatively comprises acetone.

[0019] Another example provides a substrate processing tool. The substrate processing tool comprises a processing chamber. The substrate processing tool further comprises a conduit for flowing a mixture of a reactant gas with a second gas to the processing chamber. The substrate processing tool further comprises a chemical sensor configured to detect a concentration of the second gas in the conduit. The substrate processing tool further comprises a mass flow controller located along the conduit and downstream from the chemical sensor. The substrate processing tool further comprises a systems controller configured to receive a signal from the chemical sensor indicating a concentration of the second gas in the conduit. The systems controller is further configured to use a lookup table to determine a flow offset for the mass flow controller based at least on the signal from the chemical sensor. The systems controller is further configured to adjust the mass flow controller based on the determined flow offset.

[0020] In some such examples, the systems controller is configured to use the lookup table to determine the flow offset for the mass flow controller further based on a target deposition rate.

[0021] In some such examples, the reactant gas additionally or alternatively comprises acetylene.

[0022] In some such examples, the second gas additionally or alternatively comprises acetone.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 schematically shows an example processing tool comprising a chemical sensor and mass flow controller located along a conduit leading to a processing chamber.

[0024] FIG. 2 shows a graph illustrating example adjustments of a flow offset for a mass flow controller at different acetone concentration levels.

[0025] FIG. 3 schematically shows an example substrate comprising a recessed feature.

[0026] FIG. 4 shows a flow diagram for an example method of performing flow control compensation for a reactant gas based on a detected concentration of a second gas.

[0027] FIG. 5 schematically shows a block diagram of an example computing system.DETAILED DESCRIPTION

[0028] The term “chemical sensor” generally represents a device configured to detect a concentration level of one or more processing gases. An example of a chemical sensor is an infrared sensor.

[0029] The term “chemical vapor deposition” (CVD) generally represents a process in which a solid phase film is formed on a substrate by directing a continuous flow of one or more precursor gases over the substrate surface under conditions configured to cause the chemical conversion of the precursor gases to the film. The term “plasma-enhanced chemical-vapor deposition” (PECVD) generally represents a CVD process in which a plasma is used to facilitate the chemical conversion of one or more precursor gases to a solid phase film on a substrate. Thermal CVD (TCVD) processes utilize thermal energy to facilitate film formation. The terms “growth”, “deposition”, and variants thereof, also can be used to refer to film formation.

[0030] The term “conduit” generally represents a fluidic path for a processing gas to flow from a processing gas source to a processing chamber. The term “downstream” refers to the direction along the fluidic path towards the processing chamber. The term “upstream” refers to the direction along the fluidic path towards the processing gas source.

[0031] The term “CVD tool” generally represents a machine comprising a processing chamber and other hardware configured to perform CVD processing. The term “PECVD tool” generally represents a CVD tool configured for PECVD processing.

[0032] The term “mass flow controller” generally represents a device configured to flow a gas or liquid at a desired rate based on a set point. The term “set point” generally represents a control input to a mass flow controller related to the desired flow rate. The mass flow controller is configured to adjust the flow rate of thegas or liquid to achieve the set point. In some examples, a mass flow controller can be calibrated to control a specific type of gas or liquid.

[0033] The term “processing chamber” generally represents an enclosure in which chemical and / or physical processes are performed on substrates. The pressure, temperature and atmospheric composition within a processing chamber are controllable to perform chemical and / or physical processes.

[0034] The term “processing tool” generally represents a machine including a processing chamber and other hardware configured to enable processing to be carried out in the processing chamber.

[0035] The term “reactant gas” generally represents a processing gas that participates in a chemical reaction within a processing chamber. Examples of reactant gases include precursor compounds that can be used to deposit films onto substrates. Examples of films include silicon oxide, silicon nitride, and carbon-containing films such as amorphous carbon, silicon carbide, silicon oxy carbide, silicon carbonitride, and silicon oxycarbonitride. Example carbon-containing reactant gases for depositing a carbon-containing film include alkynes, such as acetylene (C2H2). Further examples of carbon-containing reactant gases include alkanes, alkenes (such as propylene), cyclic hydrocarbons, aromatics, alkyl halides, alkyl amines, and alkyl diamines.

[0036] The term “showerhead” generally represents a processing gas outlet comprising a plurality of holes distributed across an area.

[0037] The term “stabilizer” generally represents a compound that is mixed with aa reactant gas to help avoid degradation of the reactant gas prior to use of the reactant gas. One example of a stabilizer is acetone (CsEfcO). Acetone can be used to stabilize acetylene. Further examples of stabilizers for acetylene include hydrogen bromide (HBr) and hydrogen iodide (HI). Further examples of stabilizers can include various ketones, ionic liquids, carbenes, silylenes, aldehydes, esters, amides, ethers, amines, and imines.

[0038] As mentioned above, chemical vapor deposition (CVD) uses a continuous flow of precursor compound(s) to deposit a film on a substrate. Plasma- enhanced CVD (PECVD) utilizes a plasma to facilitate chemical conversion of precursor compound(s) to form a film on the substrate. As an example, a carbon- containing film can be deposited using a PECVD process. During PECVD, a carbon- containing reactant gas is introduced into a deposition chamber and a plasma is formedto cause the reactant to form a film on a substrate surface. Thermal CVD (TCVD) processes utilize thermal energy to facilitate film formation.

[0039] Some CVD processes utilize acetylene to deposit carbon-containing films onto a substrate. Acetylene storage and handling can be challenging. For example, acetylene can react explosively with oxygen. Further, acetylene can undergo explosive decomposition in the absence of oxygen. Additionally, pure acetylene is explosive when pressurized. As such, acetylene can be dissolved in a stabilizer for safe storage. Example stabilizers for acetylene include acetone, hydrogen bromide, and hydrogen iodide. Use of a stabilizer helps avoid reactions with oxygen. Dissolving acetylene in a stabilizer helps reduce the pressure in the storage container. This helps avoid explosive decomposition. Further, stabilizers can help safely store large amounts of acetylene. In particular, acetone has the capacity to dissolve up to 25L acetylene per IL of acetone.

[0040] However, acetylene flow rates as a proportion of total gas flow rates from acetylene mixed with a stabilizer can vary over the lifetime of a storage container. Typically, an acetylene flow rate leaving a storage container decreases over time as a function of total gas flow rate. This is accompanied by an increase in stabilizer (e.g. acetone) flow rates. For example, acetone gas can comprise 0.5% of the total gas flowing out from the storage container at early stages of the storage container lifetime. At later stages of the storage container lifetime, acetone gas can increase to 5% or more of the outflowing gas. Consequently, the proportion of acetylene decreases over the lifetime of the storage container.

[0041] Changes to reactant gas concentration can affect film deposition rates on a substrate. Accordingly, examples are disclosed that relate to automatic flow compensation for a reactant gas based on a detected concentration of a second gas flowing with the reactant gas, such as a stabilizer gas. Briefly, a reactant gas flows from a gas source through a conduit towards a processing chamber. A mass flow controller can be used to control the flow of reactant gas. The gas source further comprises a second gas, such as a stabilizer, that is mixed with the reactant gas. A chemical sensor detects a concentration of the second gas flowing through the conduit. As the reactant gas is mixed with the second gas in a same storage container, the concentration of the second gas indicates a concentration of the reactant gas. Upon receiving a signal from the chemical sensor, a controller adjusts the mass flow controller to control the flow rate of the reactant gas. In this manner, the flow rate of the reactant gas can be increased to automatically compensate for changes to the relative concentrations of the secondgas and the reactant gas. This can help avoid processing issues, such as a decreasing film growth rate as a reactant gas concentration decreases.

[0042] Measuring the concentration of the second gas can provide a more accurate method of flow control compensation than measuring a concentration of reactant gas. This is because the second gas can comprise a relatively small concentration of the gas mixture compared to the reactant gas. For example, as discussed above, the proportion of acetone outflowing from a storage container can increase from 0.5% to 5% over the lifetime of the storage container. Thus, the proportion of acetylene can decrease from 99.5% to 95%. As a result, assuming constant pressure, the concentration of acetone can increase 1000% while the concentration of acetylene decreases by approximately 5%. Thus, a measurement of acetone can provide greater accuracy in determining the ratio of gases in the mixture. This helps provide a more accurate flow compensation adjustment than measurements of acetylene concentration.

[0043] While many of the examples herein are described in the context of acetylene gas mixed with acetone gas, the disclosed examples also can be applied to any other suitable combination of reactant gas and second gas.

[0044] FIG. 1 shows an example processing tool 100 that includes a sensor to facilitate automatic flow control compensation. Processing tool 100 comprises a processing chamber 102 and a substrate support 104 within processing chamber 102. Substrate support 104 is configured to support a substrate 106 disposed within processing chamber 102. Substrate support 104 comprises a substrate heater 108. In other examples, a heater can be omitted, or can be located elsewhere within processing chamber 102.

[0045] Processing tool 100 further comprises a showerhead 110 disposed in processing chamber 102. In other examples, a processing tool can comprise a nozzle or other apparatus for introducing gas into processing chamber 102, as opposed to or in addition to a showerhead. In some examples, processing tool 100 comprises a heater configured to heat showerhead 110.

[0046] Processing tool 100 further comprises a reactant gas source 112. Reactant gas source 112 stores a reactant gas 114 and a second gas 116. Reactant gas 114 can comprise any suitable compound that can be used for processing substrates in processing chamber 102. In some examples reactant gas comprises acetylene (C2H2). Second gas 116 can comprise any suitable gas that can be mixed with reactant gas 114.In some examples, second gas 116 comprises a stabilizer to help stabilize reactant gas 114. For example, in examples where reactant gas 114 comprises acetylene, second gas 116 can comprise acetone. As mentioned above, acetone helps stabilize acetylene. In some examples, acetone can dissolve 25X as much acetylene by volume or more. In other examples, a hydrogen halide, such as HBr or HI, can be used to stabilize acetylene. Further examples of stabilizers can include various ketones, ionic liquids, carbenes, silylenes, aldehydes, esters, amides, ethers, amines, and imines.

[0047] Processing tool 100 optionally can comprise a storage container sensor 118. Optional storage container sensor 118 can be configured to detect a pressure in reactant gas source 112 or detect a weight of reactant gas source 112. For example, a detected weight of reactant gas source 112 can help estimate the amount of gas remaining in reactant gas source 112. Further, a detected pressure in reactant gas source 112 can help indicate a relative proportion of reactant gas 114 to second gas 116. As such, a detected weight and / or detected pressure can be used to estimate the amount of reactant gas 114 and an amount of second gas 116 remaining in reactant gas source 112. In some examples, processing tool 100 can comprise both a pressure sensor and a weight sensor for a reactant gas source. In other examples such sensors can be omitted.

[0048] Processing tool 100 further comprises a conduit 120 leading from reactant gas source 112 to processing chamber 102. In some examples, reactant gas source 112 comprises a regulator to help control the flow of gas into conduit 120. For example, a regulator can be used to flow reactant gas 114 and second gas 116 out from reactant gas source 112 at a selected flow rate and / or to achieve a selected pressure within conduit 120. In some examples, processing tool 100 can include one or more additional conduits for connecting additional processing gas source(s) to processing chamber 102. Further examples of processing gases include silicon-containing precursors (such as silane), inert gases (such as argon), oxygen gas, and hydrogen gas. In such examples, processing tool 100 can include one or more valves and additional mass flow controllers for controlling flow rates of other processing gases.

[0049] Processing tool 100 further comprises an exhaust system 132. Exhaust system 132 is configured to exhaust gases from processing chamber 102. Exhaust system 132 can comprise any suitable hardware, including one or more low vacuum pumps, one or more high vacuum pumps, and one or more valves for controlling an exhaust flow. In some examples, exhaust system 132 can be operated to achieve aselected pressure in processing chamber 102 during substrate processing. Further, exhaust system 132 can be operated to purge processing chamber 102.

[0050] Processing tool 100 further comprises a radiofrequency power source 134 that is electrically connected to showerhead 110. Radiofrequency power source 134 is configured to form a plasma in processing chamber 102 by supplying radiofrequency power to showerhead 110. For example, during PECVD, radiofrequency power source 134 can be operated to form a plasma using a reactant gas 114 to deposit a film (e.g., a carbon-containing film). In the depicted example, a capacitively coupled plasma can be formed in processing chamber 102 between showerhead 110 and substrate support 104. Radiofrequency power can be supplied to the showerhead electrode or substrate holder electrode in various examples. As shown in FIG. 1, the radiofrequency energy is provided to showerhead 110, and substrate support 104 is configured as a grounded opposing electrode. In other examples, radiofrequency power source 134 can supply radiofrequency power to substrate support 104, and showerhead 110 can be grounded.

[0051] Processing tool 100 further includes include a matching network 136 for impedance matching of the radiofrequency power source 134. Radiofrequency power source 134 can be configured to provide radiofrequency energy of any suitable frequency and power. Examples frequencies include 400 kHz, 13.56 MHz, 27 MHz, 60 MHz, and 90 MHz. Examples of radiofrequency power include power of 100W to 6500W. In other examples, a radiofrequency power outside this range can be used. In some examples, radiofrequency power source 134 is configured to operate at a plurality of different frequencies and / or powers.

[0052] Processing tool 100 further comprises a mass flow controller 140 positioned along conduit 120. Mass flow controller 140 is configured to control the flow rate of reactant gas 114 flowing into processing chamber 102. Mass flow controller 140 can control the flow rate of reactant gas 114 based on a set point, i.e., to achieve a selected flow rate indicated by the set point. In some examples, the set point is within a range of 10% to 90% of the flow capacity of the mass flow controller. In other examples, a set point outside this range can be used. In some examples, mass flow controller 140 can control the flow rate of reactant gas 114 further based on a flow offset to the set point. Mass flow controller 140 can comprise a thermal mass flow controller, in some examples. In other examples, any other suitable flow controller can be used.

[0053] Processing tool 100 further comprises a chemical sensor 142 positioned along conduit 120. Chemical sensor 142 is located upstream from mass flow controller 140. Upstream refers to a direction opposite to the flow of gas through conduit 120 from reactant gas source 112 to processing chamber 102. Downstream refers to the direction along the conduit towards processing chamber 102. As shown in FIG. 2, mass flow controller 140 is located along the conduit between chemical sensor 142 and processing chamber 102. Chemical sensor 142 is configured for detecting a concentration of second gas 116 in conduit 120. Chemical sensor 142 can comprise any suitable sensor. Examples include spectroscopic sensors, such as an infrared (IR) sensor. For example, an infrared sensor can be configured to detect infrared absorption corresponding to second gas 116. As absorption increases with increasing concentration of second gas 116, the infrared sensor output signal indicates the increasing concentration of second gas 116 flowing through conduit 120. In some examples, a different type of spectroscopic sensor can be used, such as a visible light sensor.

[0054] Processing tool 100 further comprises a systems controller 150 configured to control operation of the processing tool. Systems controller 150 is operatively coupled to substrate heater 108, exhaust system 132, radiofrequency power source 134, mass flow controller 140, chemical sensor 142, and optional storage container sensor 118. Systems controller 150 is configured to control various functions of processing tool 100 to perform chemical vapor deposition. For example, systems controller 150 is configured to control mass flow controller 140 to flow reactant gas 114 at a selected rate into processing chamber 102. Systems controller 150 also is configured to control processing tool 100 to operate substrate heater 108 to heat a substrate to a desired temperature. Systems controller 150 also is configured to operate exhaust system 132 to remove gases from processing chamber 102. Systems controller 150 also is configured to operate radiofrequency power source 134 to form a plasma, as well as to control any other suitable functions of processing tool 100.

[0055] Further, systems controller 150 also is configured to receive signals from chemical sensor 142 and adjust mass flow controller 140 based on signals received from chemical sensor 142. For example, systems controller 150 can determine an offset for mass flow controller 140 and adjust a set point for mass flow controller 140. As discussed above, the amount of reactant gas 114 flowing out from reactant gas source 112 can change in proportion to second gas 116 over the lifetime of the storage container. For example, towards the end of a storage container lifetime, acetyleneconcentration tends to decrease while acetone concentration tends to increase. The lower acetylene concentration in reactant gas flowing through conduit 120 can cause a decrease in the deposition rate of a film being deposited on substrate 106. As such, in response to a signal from chemical sensor 142, systems controller 150 can adjust a flow offset to the set point for mass flow controller 140 to maintain a target deposition rate.

[0056] The effect of flow offsets on deposition rates is shown schematically in FIG. 2. FIG. 2 shows a graph 200 of an example deposition rate for PECVD of a carbon- containing film using acetylene gas. Line 202 shows the deposition rate versus acetylene flow offset for a “lower acetone concentration” gas mixture. For example, acetylene dissolved in acetone can release a gas mixture comprising approximately 99.5% acetylene and 0.5% acetone at an early stage of the storage container lifetime. This gas mixture represents a relatively lower concentration of acetone. Later in the storage container lifetime, this proportion can change to 95% acetylene and 5% acetone in such an example. This represents a relatively higher concentration of acetone. Line 204 shows deposition rate versus acetylene flow offset for such a “higher acetone concentration” gas mixture.

[0057] Deposition rates can be adjusted by changing the flow offset for acetylene gas. As shown in graph 200, both line 202 and line 204 have a positive slope. This is because the deposition rate increases with increasing flow of acetylene gas. Further, line 204 shows lower deposition rates than line 202. This is because line 204 corresponds to a relatively lower proportion of acetylene (95% acetylene) than line 202 (99.5% acetylene). Thus, the deposition rate of line 204 is less than the deposition rate of line 202 for a selected flow offset.

[0058] Thus, the mass flow controller can be adjusted to help achieve a target deposition rate 206. As shown in graph 200, line 202 intersects the target deposition rate 206 at flow offset 208. As such, when the acetylene gas comprises a lower acetone concentration (line 202), the acetylene flow offset can be adjusted to flow offset 208. Further, when the acetylene gas comprises a higher acetone concentration (line 204), the acetylene flow offset can be adjusted to flow offset 210.

[0059] Referring again to FIG. 1, systems controller 150 can adjust mass flow controller 140 (e.g., adjust an offset) based on the detected concentration of second gas at chemical sensor 142. For example, upon detecting a low acetone concentration represented by line 202, systems controller 150 can adjust mass flow controller 140 to flow offset 208. This can help achieve target deposition rate 206. As the reactant gassource 112 empties, the acetone concentration of the gas mixture flowing through conduit 120 tends to increase. This is accompanied by a decrease in acetylene concentration. Upon detecting a high acetone concentration at chemical sensor 142 represented by line 204, systems controller 150 can adjust mass flow controller 140 to flow offset 210. This can help maintain the deposition rate a target deposition rate 206. In this manner, systems controller 150 can automatically maintain the deposition rate of a film deposited on substrate 106 in response to a detected concentration of second gas 116 at chemical sensor 142.

[0060] In some examples, adjustment of mass flow controller 140 can be performed using a lookup table. A lookup table can comprise a value for reactant gas flow offset for each of a plurality of values for a concentration of second gas 116. In such examples, systems controller 150 can reference a lookup table to determine a reactant gas flow offset based at least on a concentration of second gas detected at chemical sensor 142. In some examples, the values for reactant gas flow offset in the lookup table are further based on a reactant gas flow set point. In some examples, the values for reactant gas flow offset in the lookup table are further based on a target deposition rate (e.g., target deposition rate 206). In further examples, the values for reactant gas flow offset in the lookup table are further based on a pressure and / or weight detected by storage container sensor 118. A lookup table can be process dependent. More specifically, different lookup tables can be constructed for different processes. A pre-determined lookup table can be stored in memory (e.g., a storage subsystem) accessible by systems controller 150. Examples of computing systems and storage subsystems are described in more detail below with regard to FIG. 5.

[0061] In some examples, a signal from storage container sensor 118 alternatively or additionally can be used to adjust mass flow controller 140. For example, storage container sensor 118 can comprise a weight sensor. As reactant gas source 112 empties, storage container sensor 118 can detect a decrease in weight of reactant gas source 112. As the weight corresponds to the amount of chemicals remaining in the storage container, the weight can be used to estimate the amount of reactant gas in proportion to second gas outflowing from reactant gas source 112. For example, the values for a reactant gas flow offset (or other adjustment to a mass flow controller) in a lookup table can be further based on a pressure within conduit 120. Similarly, a pressure detected also can be used to estimate the amount of reactant gas in proportion to second gas outflowing from reactant gas source 112. As such, a signalfrom storage container sensor 118 can be used to estimate the concentration of reactant gas 114 flowing through conduit 120. Thus, in some examples, systems controller 150 is configured to adjust mass flow controller 140 based at least on a signal detected from storage container sensor 118. In some examples, a signal from chemical sensor 142 and a signal from storage container sensor 118 both can be used to adjust mass flow controller 140. However, due to variations in supply of reactant gas sources, chemical sensor 142 can provide a more accurate determination of second gas concentration than storage container sensor 118.

[0062] In some examples, relatively slow film growth can be at least partially compensated by control adjustments other than flow rate of the reactant gas. Examples include increasing temperature or increasing radiofrequency power supplied to a plasma. For example, systems controller 150 can operate substrate heater 108 to heat substrate 106 to a different temperature in response to a signal from chemical sensor 142. As another example, systems controller 150 can operate radiofrequency power source 134 to supply a different radiofrequency power in response to a signal from chemical sensor 142. However, in some examples, these control adjustments can lead to different film growth rates at different locations of a feature on a substrate. These issues are discussed in regard to FIG. 3, which shows an example substrate 300 comprising a feature 302. Substrate 300 further comprises a film 303 deposited on the substrate and surfaces in feature 302. Film 303 is shown schematically with a reentrant profile. In various example CVD processes, techniques such as etching or inhibition can be employed to deposit a film that is more conformal or less conformal than film 303. In some examples, increasing radiofrequency power can help increase a film growth rate at surface 304 near the opening of feature 302. However, even with increased radiofrequency power, film growth rate on an upper sidewall surface 306 can be relatively slower than the film growth rate at surface 304. Further, film growth rate on a lower sidewall surface 308 near the bottom of feature 302 can be even slower. Uneven growth rates can lead to varying film thickness and / or a film with a conformality outside of the tolerances of a selected process. This can affect device performance. Further, in some examples, adjustments to temperature, pressure and / or radiofrequency power can affect film quality.

[0063] Accordingly, the disclosed examples for performing automatic flow compensation of reactant gas can help maintain film growth rates without uneven deposition caused by varying proportions of a reactant gas and a second gas (e.g. astabilizer). For example, by adjusting mass flow controller 140 to increase the flow rate of reactant gas 114, the film growth rates at surface 304, upper sidewall surface 306, and lower sidewall surface 308 can all be controlled according to a desired process. This helps to avoid film growth outside of the tolerances of a selected process. Further, by compensating for decreased reactant gas concentration with increased flow rates, a desired film growth can be maintained without affecting film quality.

[0064] FIG. 4 shows a flow diagram of an example method 400 for adjusting a flow rate of a reactant gas based on a detected concentration of a second gas. Method 400 can be used to control a processing tool, such as processing tool 100. Method 400 can be implemented by systems controller 150, for example.

[0065] At 402, method 400 comprises, using a mass flow controller, controlling a flow of a reactant gas and a second gas through a conduit towards a processing chamber. At 404, method 400 further comprises, using a chemical sensor positioned along the conduit, detecting a concentration of the second gas flowing through the conduit. The chemical sensor is located upstream from the mass flow controller. As such, the mass flow controller is positioned along the conduit between the chemical sensor and the processing chamber. For example, chemical sensor 142 is positioned along conduit 120 and is located upstream from mass flow controller 140. In some examples, at 406, the method comprises using an infrared sensor to detect the concentration of the second gas. In other examples, any other suitable chemical sensor can be used.

[0066] At 408, method 400 further comprises adjusting the mass flow controller based at least on the concentration of the second gas detected. In some examples, at 410, the method comprises adjusting a flow offset of the mass flow controller. In some examples, at 412, the method comprises adjusting the mass flow controller further based on a target deposition rate. In some examples, at 414, adjusting the mass flow controller comprises using a lookup table. For example, a lookup table can be used to determine the flow offset based on the concentration of the second gas detected. In some such examples, the flow offset is further based on a target deposition rate. For example, as described above regarding FIG. 2, a deposition rate of a carbon-containing film can be relatively lower for a mixture of acetylene gas and acetone gas comprising a relatively higher acetone concentration (line 204) than a mixture comprising a relatively lower acetone concentration (line 202). Thus, the flow offset of the mass flow controller can be adjusted to flow offset 210 based on target deposition rate 206.

[0067] In some examples, at 416, the reactant gas comprises a carbon- containing gas and method 400 further comprises depositing a carbon-containing film onto a substrate. Examples of carbon-containing films include silicon carbide, silicon oxycarbide, silicon carbonitride, and silicon oxycarbonitride. Examples of carbon- containing gases for forming such films include alkanes, alkenes (e.g. propylene), alkynes (e.g., acetylene), cyclic hydrocarbons, aromatics, alkyl halides, alkyl amines, and alkyl diamines. In some examples, at 418, the carbon-containing gas comprises acetylene. In other examples, any other suitable reactant gas can be used to deposit a carbon-containing film. In some such examples, at 420, the second gas comprises acetone. As discussed above, acetone can be used as a stabilizer to stabilize acetylene. In other examples, any other suitable reactant gas can be used to deposit a film.

[0068] Thus, the disclosed examples can provide for automatically compensating the flow rate of a reactant gas based on a detected concentration of second gas. Adjusting the flow rate of the reactant gas can help maintain a film deposition rate at a target deposition rate. This can help avoid processing issues, such as slow film growth. By adjusting the flow rate at a mass flow controller, the examples can avoid adjustments to temperature, pressure, radiofrequency power, or other processing conditions. This can help maintain deposition rates while avoiding uneven film growth in some examples. This also can help preserve film quality.

[0069] FIG. 5 schematically shows an example of a computing system 500 that can enact one or more of the methods and processes described above. Computing system 500 is shown in simplified form. Computing system 500 can take the form of one or more personal computers, workstations, computers integrated with substrate processing tools, and / or network accessible server computers.

[0070] Computing system 500 includes a logic subsystem 502 and a storage subsystem 504. Computing system 500 can optionally include a display subsystem 506, input subsystem 508, communication subsystem 510, and / or other components not shown in FIG. 5. Systems controller 150 is an example of computing system 500.

[0071] Logic subsystem 502 includes one or more physical devices configured to execute instructions. For example, the logic subsystem can be configured to execute instructions that are part of one or more applications, services, programs, routines, libraries, objects, components, data structures, or other logical constructs. Such instructions can be implemented to perform a task, implement a data type, transformthe state of one or more components, achieve a technical effect, or otherwise arrive at a desired result.

[0072] The logic subsystem can include one or more processors configured to execute software instructions. Additionally or alternatively, the logic subsystem can include one or more hardware or firmware logic subsystems configured to execute hardware or firmware instructions. Processors of the logic subsystem can be single-core or multi-core, and the instructions executed thereon can be configured for sequential, parallel, and / or distributed processing. Individual components of the logic subsystem optionally can be distributed among two or more separate devices, which can be remotely located and / or configured for coordinated processing. Aspects of the logic subsystem can be virtualized and executed by remotely accessible, networked computing devices configured in a cloud-computing configuration.

[0073] Storage subsystem 504 includes one or more physical devices configured to hold instructions 512 executable by the logic subsystem to implement the methods and processes described herein. When such methods and processes are implemented, the state of storage subsystem 504 can be transformed — e.g., to hold different data.

[0074] Storage subsystem 504 can include removable and / or built-in devices. Storage subsystem 504 can include optical memory (e.g., CD, DVD, HD-DVD, Blu- Ray Disc, etc.), semiconductor memory (e.g., RAM, EPROM, EEPROM, etc.), and / or magnetic memory (e.g., hard-disk drive, floppy-disk drive, tape drive, MRAM, etc.), among others. Storage subsystem 504 can include volatile, nonvolatile, dynamic, static, read / write, read-only, random-access, sequential-access, location-addressable, file- addressable, and / or content-addressable devices.

[0075] It will be appreciated that storage subsystem 504 includes one or more physical devices. However, aspects of the instructions described herein alternatively can be propagated by a communication medium (e.g., an electromagnetic signal, an optical signal, etc.) that is not held by a physical device for a finite duration.

[0076] Aspects of logic subsystem 502 and storage subsystem 504 can be integrated together into one or more hardware-logic components. Such hardware-logic components can include field-programmable gate arrays (FPGAs), program- and application-specific integrated circuits (PASIC / ASICs), program- and applicationspecific standard products (PSSP / ASSPs), system-on-a-chip (SOC), and complex programmable logic devices (CPLDs), for example.

[0077] When included, display subsystem 506 can be used to present a visual representation of data held by storage subsystem 504. This visual representation can take the form of a graphical user interface (GUI). As the herein described methods and processes change the data held by the storage subsystem, and thus transform the state of the storage subsystem, the state of display subsystem 506 can likewise be transformed to visually represent changes in the underlying data. Display subsystem 506 can include one or more display devices utilizing virtually any type of technology. Such display devices can be combined with logic subsystem 502 and / or storage subsystem 504 in a shared enclosure, or such display devices can be peripheral display devices.

[0078] When included, input subsystem 508 can comprise or interface with one or more user-input devices such as a keyboard, mouse, or touch screen. In some examples, the input subsystem can comprise or interface with selected natural user input (NUI) componentry. Such componentry can be integrated or peripheral, and the transduction and / or processing of input actions can be handled on- or off- board. Example NUI componentry can include a microphone for speech and / or voice recognition, and an infrared, color, stereoscopic, and / or depth camera for machine vision and / or gesture recognition.

[0079] When included, communication subsystem 510 can be configured to communicatively couple computing system 500 with one or more other computing devices. Communication subsystem 510 can include wired and / or wireless communication devices compatible with one or more different communication protocols. As non-limiting examples, the communication subsystem can be configured for communication via a wireless telephone network, or a wired or wireless local- or wide-area network. In some examples, the communication subsystem can allow computing system 500 to send and / or receive messages to and / or from other devices via a network such as the Internet.

[0080] It will be understood that the configurations and / or approaches described herein are exemplary in nature, and that these specific examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein can represent one or more of any number of processing strategies. As such, various acts illustrated and / or described can be performed in the sequence illustrated and / or described, in other sequences, in parallel, or omitted. Likewise, the order of the above-described processes can be changed.

[0081] The subject matter of the present disclosure includes all novel and non- obvious combinations and sub-combinations of the various processes, systems and configurations, and other features, functions, acts, and / or properties disclosed herein, as well as any and all equivalents thereof.

Claims

CLAIMS:

1. A substrate processing tool, comprising: a processing chamber; a conduit for flowing a mixture of a reactant gas with a second gas to the processing chamber; a chemical sensor configured to detect a concentration of the second gas in the conduit; a mass flow controller located along the conduit and downstream from the chemical sensor; and a systems controller configured to: receive a signal from the chemical sensor indicating a concentration of the second gas in the conduit; adjust the mass flow controller based on the signal and a set point for the reactant gas.

2. The substrate processing tool of claim 1, wherein the reactant gas comprises acetylene.

3. The substrate processing tool of claim 2, wherein the second gas comprises a stabilizer.

4. The substrate processing tool of claim 3, wherein the stabilizer comprises acetone.

5. The substrate processing tool of claim 1, wherein the chemical sensor comprises an infrared sensor.

6. The substrate processing tool of claim 1, wherein the chemical sensor comprises a visible light sensor.

7. The substrate processing tool of claim 1, wherein the systems controller is configured to adjust the flow offset of the mass flow controller using a look-up table.

8. The substrate processing tool of claim 1, wherein the processing tool is configured to form a plasma using the reactant gas to deposit a film.

9. A method of controlling a substrate processing tool, the method comprising: using a mass flow controller, controlling a flow of reactant gas and a second gas through a conduit towards a processing chamber of the substrate processing tool; using a chemical sensor positioned along the conduit, detecting a concentration of the second gas flowing through the conduit, the chemical sensor located upstream from the mass flow controller; and adjusting the mass flow controller based at least on the concentration of the second gas detected.

10. The method of claim 9, wherein detecting the concentration of the second gas comprises using an infrared sensor.

11. The method of claim 9, wherein adjusting the mass flow controller comprises adjusting a flow offset of the mass flow controller.

12. The method of claim 9, wherein adjusting the mass flow controller comprises using a lookup table.

13. The method of claim 12, wherein adjusting the flow rate of the gas mixture is further based on a target deposition rate.

14. The method of claim 9, wherein the reactant gas comprises a carbon-containing gas, and further comprising depositing a carbon-based film on a substrate disposed in the processing chamber.

15. The method of claim 14, wherein the carbon-containing gas comprises acetylene.

16. The method of claim 15, wherein the second gas comprises acetone.

17. A substrate processing tool, comprising:a processing chamber; a conduit for flowing a mixture of a reactant gas with a second gas to the processing chamber; a chemical sensor configured to detect a concentration of the second gas in the conduit; a mass flow controller located along the conduit and downstream from the chemical sensor; and a systems controller configured to: receive a signal from the chemical sensor indicating a concentration of the second gas in the conduit, use a lookup table to determine a flow offset for the mass flow controller based at least on the signal from the chemical sensor, and adjust the mass flow controller based on the determined flow offset.

18. The substrate processing tool of claim 17, wherein the systems controller is configured to use the lookup table to determine the flow offset for the mass flow controller further based on a target deposition rate.

19. The substrate processing tool of claim 17, wherein the reactant gas comprises acetylene.

20. The substrate processing tool of claim 19, wherein the second gas comprises acetone.

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