Semiconductor vapor etching device with intermediate chamber

Abstract

A semiconductor vapor etching apparatus is disclosed. The apparatus may include an intermediate chamber between a vapor source and a reaction chamber. Etching reactant vapor may be delivered from the intermediate chamber to the reaction chamber in a pulsed form to etch a substrate.

Description

[0001] Any priority application is incorporated by reference

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 875,910, filed June 18, 2019, the contents of which are incorporated herein by reference in their entirety and for all purposes. Technical Field

[0003] The technical field relates to semiconductor processing apparatus having an intermediate chamber, and more particularly, to an etching reactor having an intermediate chamber. Background Art

[0004] Controlled material removal in semiconductor processing is highly desirable. Chemical vapor etching (CVE) or atomic layer etching (ALE) can have advantages over plasma systems, but in both thermal and plasma etching, providing uniform etching action across large substrates can be challenging, especially when the substrate has significant topography. Summary of the Invention

[0005] According to one aspect, a semiconductor etching apparatus is disclosed. The apparatus may include: a reaction chamber; an intermediate chamber upstream of and in fluid communication with the reaction chamber, the intermediate chamber configured to deliver an etching reactant vapor to the reaction chamber; an etching reactant vapor source upstream of and in fluid communication with the intermediate chamber, the source configured to deliver the etching reactant vapor to the intermediate chamber; a first valve disposed along a reactant supply line between the source and the intermediate chamber, the first valve configured to regulate the flow of the etching reactant vapor to the intermediate chamber; and a second valve disposed along the reactant supply line between the intermediate chamber and the reaction chamber, the second valve configured to regulate the flow of the etching reactant vapor to the reaction chamber.

[0006] According to one aspect, a semiconductor etching apparatus is disclosed. The apparatus may include: a reaction chamber; an intermediate chamber upstream of and in fluid communication with the reaction chamber, the intermediate chamber configured to deliver etching reactant vapor to the reaction chamber; and a control system configured to deliver the etching reactant vapor from the intermediate chamber to the reaction chamber in pulses.

[0007] According to one aspect, a method of etching a substrate is disclosed. The method may include: supplying an etching reactant vapor to an intermediate chamber; and pulsing at least a portion of the etching reactant vapor from the intermediate chamber to a reaction chamber downstream of the intermediate chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] These and other features, aspects and advantages of the present invention will now be described with reference to the drawings of several embodiments, which are intended to illustrate and not to limit the present invention.

[0009] Figure 1 is a schematic system diagram of a semiconductor processing apparatus during a fill phase according to various embodiments.

[0010] Figure 2 is a schematic system diagram of a semiconductor processing apparatus during a first instance of a pulse mode, according to an embodiment.

[0011] Figure 3 is a schematic system diagram of a semiconductor processing apparatus during a second instance of a pulse mode, according to an embodiment.

[0012] Figure 4 is a schematic system diagram of a semiconductor processing apparatus during a third instance of a pulse mode, according to an embodiment. DETAILED DESCRIPTION

[0013] Sub-monolayer or more layers of material can be removed from substrate by chemical vapor etching (CVE). Delivery of gas-phase etching reactants (e.g., adsorbed reactants and / or etchants) in pulsed form can provide additional parameters to regulate and better control the etching process, thereby achieving the desired distribution on the large substrate used in the latest semiconductor processing. In some pulsed etching processes, one or more gas-phase reactants can be used in sequential pulses. For example, in one pulse, a reactant can be adsorbed, followed by a second reactant that forms a volatile by-product, the volatile by-product containing adsorbed atoms, the second reactant, and some atoms from the etching surface. In this way, the etching of the desired material on the substrate surface can be carefully controlled. Additional systems and methods for the pulsed and cyclic etching processes are shown and described in U.S. Patent No. 10,273,584, which is also incorporated herein by reference in its entirety for all purposes.

[0014] Thermochemical etching of microelectronic materials can have the benefit that is better than plasma etching process.But, in order to have the uniform etch rate on wafer, the partial pressure, residence time and temperature of etching reaction thing (such as etchant and / or other reactants) and by-product above wafer should not be spatially varied.In the case of lacking surface control in etching reaction, etching / secondary circulation (EPC) can still be controlled for example by insufficient dosage.Insufficient dosage relates to the molecular quantity injected in reactor in limiting each etching pulse or circulation, and this also limits the penetration depth in substrate.Therefore, pulse etching under accurate dosage control can play the effect that better etching process control is provided, no matter whether relate to multiple reactants all is like this.But, amount should preferably be evenly distributed in substrate so that uniformly etch large area substrate.

[0015] The system configuration of using pulse method in which the total amount and partial pressure during the pulse can be separately controlled can help to etch large area substrates uniformly. The amount can measure EPC during the process, and the partial pressure state during the pulse can measure etching uniformity. In certain embodiments, partial pressure / full pressure pulse is used instead of continuous flow etching. Etching reactants are delivered to the reactor in pulse form to increase the convection and diffusion transport speed in the reactor, and therefore can cause more conformal etching than continuous flow (steady state) etching process.

[0016] Figure 1-4 A system configuration 1 is described with various pulse methods. In some embodiments, the system configuration 1 includes a carrier gas line 2, a reactant source 3 downstream of the carrier gas line 2 and in fluid communication therewith, an intermediate chamber 4 downstream of the source 3, a reactor 5 downstream of the intermediate chamber 4, and a plurality of valves V1, V2, and V3. A reactant supply line 6 connects the source 3 with the intermediate chamber 4, wherein valve V1 is installed on the reactant supply line 6 between the source 3 and the intermediate chamber 4. The reactant supply line 6 connects the intermediate chamber 4 with the reactor 5, wherein a plurality of valves V2 and V3 are installed on the line 6 between the intermediate chamber 4 and the reactor 5. Valves V1, V2, and V3 can include any suitable type of valve. For example, in various embodiments, valves V1 and V2 can include adjustable valves having multiple flow conductances. In some embodiments, valves V1 and V2 can include binary on / off valves. In some embodiments, valve V3 can include a needle valve that can be adjusted to a desired flow conductivity. As Figure 1-4 As shown in , control system 7 may include an operation (such as opening and / or closing) and / or other components of the system configured to control valve V1, V2, V3, such as a processing circuit for the operation of a reactor assembly. Although not illustrated, control system 7 may also be electrically communicated with different types of sensors, including a pressure sensor configured to monitor the pressure of any other suitable component or gas line of intermediate chamber 4, source 3, reactor 5 or system. Control system 7 may be electrically communicated with other components such as heaters. Additionally, although not illustrated, a filter may be provided in system 1, such as the upstream of intermediate chamber 4 and / or any one of valves V1, V2, V3.

[0017] In some embodiments, source 3 comprises a vaporizer configured to convert a liquid or solid material into steam. For example, source 3 can include a bubbler, an evaporator, a liquid injector, a solid source sublimator, etc. Source 3 can supply gasified reactants to reactant supply line 6. In various embodiments, source 3 can contain etching process reactants (e.g., etchants). A carrier gas can be used together with the illustrated vaporizer and can also be used to carry / dilute natural gaseous reactants. In other embodiments, a carrier gas is not used.

[0018] In some embodiments, system configuration 1 does not include a plasma, free radical, or excited species source. In some embodiments, system configuration 1 does not include an RF, microwave, or ICP source for forming plasma, free radicals, or excited species. In some embodiments, system configuration 1 is not compatible with or cannot be used for plasma-based processes.

[0019] Figure 1 The system 1 is described in the filling phase in which the gasified reactants are supplied to and contained in the intermediate chamber 4. For example, Figure 1 In the embodiment of the present invention, valve V1 can be opened to fill the intermediate chamber 4 with a mixture of carrier gas and gasified reactants to reach a desired pressure. In some embodiments, valve V1 can be an adjustable valve that can control the conductivity of the gasified reactants. The intermediate chamber 4 can include a chamber that can ensure that the reactants remain in vapor form for delivery to the reactor 5. In some embodiments, the control system 7 can also measure or control the amount of the reactant vapor supplied to the reactor 5, for example, by opening and closing one or more of valves V1 and V2. Therefore, the control system 7 can be configured to control the pulse width and timing of the pulse delivery arriving at the reactor 5. In some embodiments, the pulse arriving at the reactor 5 can have a pulse width in the range of about 0.001 seconds to 60 seconds. For example, the pulse width can be in the range of about 0.01 seconds to 10 seconds, in the range of about 0.05 seconds to 10 seconds, or in the range of about 0.1 seconds to 5 seconds. In some embodiments, the partial pressure associated with the pulse height of the pulse can be in the range of about 0.001 millibar to 100 millibar. For example, the partial pressure associated with the pulse height of the pulse can be in the range of about 0.05 mbar to 50 mbar or in the range of about 0.1 mbar to 20 mbar. Valve V2 can be opened to supply a mixture of carrier gas and gasified reactants to reactor 5. In some embodiments, valve V2 can be an adjustable valve that can control the conductivity of the gasified reactants. In some embodiments, valve V3 can be a needle valve that controls the conductivity of the gasified reactants.

[0020] In some embodiments, the system configuration 1 may include one or more hot zones maintained at various temperatures by heaters or other heating devices. In some embodiments, there may be separate hot zones for the vaporizer, the intermediate chamber 4, and the reaction chamber, each of which has a first, second, and third temperature, respectively. In some embodiments, the first temperature, the second temperature, and the third temperature are approximately equal. In some embodiments, the second temperature of the second hot zone may be higher than the first temperature of the first hot zone. In various embodiments, for example, the second temperature may be higher than the first temperature by a temperature difference in the range of 5°C to 50°C, in the range of 5°C to 35°C, or in the range of 10°C to 25°C. In some embodiments, the first temperature of the first hot zone may be higher than the second temperature of the second hot zone. In some embodiments, portions of the carrier gas line 2 may be provided with heater jackets to maintain the line 2 at or above the temperature of its corresponding hot zone and above the reactant condensation temperature.

[0021] The system 1 can be operated in various etching modes. Figure 1 In the embodiment of the present invention, the intermediate chamber 4 can be filled with vaporized reactants and carrier gas to reach a desired or set point pressure, which may be related to the desired reactant partial pressure. The reactant vapor can be vaporized at the source 3. When the valve V1 is open, the mixture of vaporized reactants and carrier gas can be carried along the reactant supply line 6 and delivered to the intermediate chamber 4. Figure 2-3 As shown in , the intermediate chamber 4 can be filled to reach the P1 pressure and then the valve V1 can be closed. The amount of gasified reactants in the intermediate chamber 4 can be determined by the equation nR=P1V / T.

[0022] Figure 2The first etching mode in which a pulse of a first type or shape is delivered to the reactor 5 is described. As explained above, valve V1 can be closed and valve V2 can be at least partially open. A portion of the reactant vapor contained in the intermediate chamber 4 can be transported to the reactor 5. The partial pressure of the reactant during the pulse period can be determined at least in part by the conductance of needle valve V3 and the pressure difference between the pressure P1 in the intermediate chamber 4 and the pressure P2 in the reactor 5. In some embodiments, pressure P1 can be within a range of about 0.001 mbar to 100 mbar. For example, pressure P1 can be within a range of about 0.05 mbar to 50 mbar or within a range of about 0.1 mbar to 20 mbar. In some embodiments, pressure P2 can be within a range of about 0.001 mbar to 100 mbar. For example, pressure P2 can be within a range of about 0.05 mbar to 50 mbar or within a range of about 0.1 mbar to 20 mbar. In various embodiments, the ratio of P1 to P2 can be less than about: 100:1, 50:1, 10:1, 5:1, 3:1, 2:1, 1.5:1, 1.25:1, or 1.1:1. The pressure difference is determined by the equation ΔP = P1 - P2. During operation, after opening valve V2, the pressure difference ΔP changes continuously as the pressure P1 decreases. Therefore, the partial pressure of the reactants in the reaction chamber 5 can also change with time and can also be linear if the conductivity remains constant during the pulse. Figure 2 As depicted in FIG, precursor tailing at the end of the pulse may be caused by exhausting the precursor gas from the volume between V2 and V3 after closing V2. In some embodiments, the partial pressure in the last half of the pulse is less than about 75% when compared to the maximum partial pressure in the first half of the pulse. In other embodiments, the partial pressure in the last half of the pulse is less than about 50% when compared to the maximum partial pressure in the first half of the pulse. In other embodiments, the partial pressure in the last half of the pulse is less than about 25% when compared to the maximum partial pressure in the first half of the pulse. The described pulses can be repeated cyclically in a pulsed or cyclic chemical vapor etching process.

[0023] Figure 3 A second etching mode is described in which a second type or shape of pulse is delivered to the reactor 5. Figure 2 The first mode is different. Figure 3 In the second mode, the reactant vapor that completely or substantially completely fills the intermediate chamber 4 can be used, for example, to be delivered to the reaction chamber 5. Figure 3As shown in , valve V1 can be closed. Valve V2 can be opened and can transport at least a portion of the amount of reactant vapor contained in the intermediate chamber 4 to the reactor 5 until the pressure between the filling volume (e.g., the intermediate chamber 4) and the reactor 5 is the same (ΔP=0). The partial pressure of the vaporized reactant during this pulse period can be determined by the conductivity of the needle valve V3 and the pressure difference between the pressure P1 in the intermediate chamber 4 and the pressure P2 in the reactor 5. The pressure difference is determined by the equation ΔP=P1-P2. During operation, after opening valve V2, the pressure difference ΔP can continuously change as the pressure P1 can decrease. Therefore, the partial pressure of the reactant delivered to the reaction chamber 5 can also change over time, and it can also be linear if the conductivity remains constant. As Figure 3 As depicted in FIG, after valve V2 is opened, the partial pressure of the vaporized reactant may decrease in a linear manner. In some embodiments, the partial pressure may decrease at a rate exceeding 10% / second. For example, the partial pressure may decrease at a rate greater than about 25% / second, at a rate greater than about 50% / second, or at a rate greater than about 75% / second. In various embodiments, after valve V2 is opened, the partial pressure of the vaporized reactant may decrease in a substantially linear manner. Figure 2 Unlike the first mode shown in Figure 3 In the second mode, there may be no partial pressure tail in this pulse mode. The amount of vaporized reactant can be determined by the equation [P1(0)-P2]V / T, where P1(0) is the intermediate chamber 4 pressure before opening V2, and P2 is the reactor pressure. The described pulses can be repeated cyclically in a pulsed or cyclic chemical vapor etching process.

[0024] Figure 4 A third etching mode is described in which a third type or shape of pulses is delivered to the reactor 5. Figure 4 In the third mode shown in FIG, both V1 and V2 are open during the pulse period, which transfers the vaporized reactant from the source 3, through the intermediate chamber 4, and to the reactor 5. The partial pressure of the reactant during the pulse time can be determined at least in part by the pressure in the source container 3 and the conductance of the needle valve V3. If the vaporization rate and conductance of the precursor in the source container 3 are constant during the pulse, the partial pressure can also be kept constant during the pulse. Figure 4 As described in the Figure 2Precursor tailing at the end of the pulse may also be present for reasons similar to those explained for precursor tailing in the embodiment of the present invention. The described pulses may be cyclically repeated in a pulsed or cyclic chemical vapor etching process. Operation of this third etch mode may not be affected by the presence of the intermediate chamber relative to an apparatus that does not have such a chamber, but exhibits the operational flexibility of the apparatus to achieve these and other desired modes and provide additional adjustment variables for achieving desired etching distributions and effects on the substrate within the reaction chamber. In other embodiments, operation of this third etch mode may be affected by the presence of the intermediate chamber relative to an apparatus that does not have such a chamber, but exhibits the operational flexibility of the apparatus to achieve these and other desired modes and provide additional adjustment variables for achieving desired etching distributions and effects on the substrate within the reaction chamber.

[0025] Advantageously, the systems and methods disclosed herein can provide improved spatial uniformity and conformality in various types of etching processes, such as ALE. The use of an intermediate chamber 4 between the source 3 and the reactor 5, along with valves V1, V2, and V3, can provide both total and partial pressure control during pulsing. Different pulsing modes can also be selected to provide a desired pulse shape to the reactor 5.

[0026] Although certain embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the present disclosure. In fact, the novel methods and systems described herein can be embodied in various other forms. In addition, various omissions, substitutions, and changes can be made to the systems and methods described herein without departing from the spirit of the present disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications that would fall within the scope and spirit of the present disclosure. Therefore, the scope of the present invention is defined solely with reference to the appended claims.

[0027] Features, materials, characteristics or groups described in conjunction with a particular aspect, embodiment or example are to be understood to be applicable to any other aspect, embodiment or example described in that section or elsewhere in this specification unless incompatible therewith. All features disclosed in this specification (including any accompanying claims, abstract and drawings) and / or all steps of any method or process so disclosed may be combined in any combination, except where at least some of the features and / or steps are mutually exclusive. Protection is not limited to the details of any foregoing embodiments. Protection extends to any novel feature or any novel combination of the features disclosed in this specification (including any accompanying claims, abstract and drawings) or to any novel step or any novel combination of the steps of any method or process so disclosed.

[0028] Furthermore, certain features described in this disclosure in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of individual embodiments may also be implemented in multiple embodiments individually or in any suitable subcombination. Furthermore, although features may be described above as functioning in a particular combination, in some cases, one or more features from a claimed combination may be deleted from the combination, and the combination may be claimed as a subcombination or variations of a subcombination.

[0029] In addition, although the operations may be depicted in the drawings or described in the specification in a particular order, it is not necessary to perform the operations in the particular order shown or in a sequential order, or to perform all of the operations, to achieve the desired result. Other operations not depicted or described may be incorporated into the example methods and processes. For example, one or more additional operations may be performed before, after, simultaneously, or between any of the described operations. In addition, in other embodiments, the operations may be rearranged or reordered. Those skilled in the art will appreciate that, in some embodiments, the steps actually taken in the illustrated and / or disclosed processes may be different from the steps shown in the figures. Depending on the embodiment, some steps described above may be removed and other steps may be added. In addition, the features and properties of the specific embodiments disclosed above may be combined in different ways to form additional embodiments, all of which fall within the scope of the present disclosure. In addition, the spacing of the various system components in the embodiments described above should not be understood as requiring the spacing in all embodiments, and it should be understood that the components and systems described may be integrated together in a single product or packaged into multiple products.

[0030] For purposes of this disclosure, certain aspects, advantages, and novel features are described herein. Not all of the described advantages may be realized according to any particular embodiment. Thus, for example, one skilled in the art will recognize that the present disclosure may be embodied or implemented in a manner that realizes one advantage or group of advantages taught herein without necessarily realizing other advantages that may be taught or suggested herein.

[0031] Unless specifically stated otherwise or otherwise understood in the context of usage, conditional language such as "can / could / might / may" is generally intended to convey that some embodiments include, while other embodiments do not, certain features, elements, and / or steps. Thus, such conditional language is generally not intended to imply that features, elements, and / or steps are in any way required by one or more embodiments, or that the one or more embodiments must include logic for determining, with or without user input or prompting, whether such features, elements, and / or steps are included in any particular embodiment or will be performed in any particular embodiment.

[0032] Unless specifically stated otherwise, linking language such as the phrase "at least one of X, Y, and Z" is generally understood to convey, in the context of usage, that an item, item, etc. can be X, Y, or Z. Thus, such linking language is generally not intended to imply that certain embodiments require the presence of at least one of X, at least one of Y, and at least one of Z.

[0033] Language of degree, such as the terms "substantially," "about," "generally," and "substantially," as used herein, refers to a value, amount, or characteristic that is approximately the same as the stated value, amount, or characteristic and still functions as intended or achieves the desired result. For example, the terms "substantially," "about," "generally," and "substantially" may refer to an amount that is within less than 10%, less than 5%, less than 1%, less than 0.1%, and less than 0.01% of the stated amount. As another example, in certain embodiments, the terms "generally parallel" and "substantially parallel" refer to a value, amount, or characteristic that deviates from exact parallelism by less than or equal to 15 degrees, 10 degrees, 5 degrees, 3 degrees, 1 degree, or 0.1 degrees.

[0034] The scope of the present disclosure is not intended to be limited by the specific disclosure of the preferred embodiments in this section or elsewhere in this specification, and may be defined by the claims presented in this section or elsewhere in this specification or presented in the future. The language of the claims is to be interpreted broadly based on the language employed in the claims and not limited to the examples described in this specification or during the prosecution of the application, which examples are to be construed as non-exclusive.

Claims

1. A semiconductor etching apparatus for removing a material layer from a substrate, comprising: reaction chamber; an intermediate chamber upstream of and in fluid communication with the reaction chamber, the intermediate chamber configured to deliver an etching reactant vapor into the reaction chamber; a source of etching reactant vapor upstream of and in fluid communication with the intermediate chamber, the source configured to deliver the etching reactant vapor into the intermediate chamber; a first valve disposed along a reactant supply line between the source and the intermediate chamber, the first valve configured to regulate a flow of the etching reactant vapor to the intermediate chamber; a second valve disposed along a reactant supply line between the intermediate chamber and the reaction chamber, the second valve configured to regulate a flow of the etching reactant vapor to the reaction chamber; a third valve between the second valve and the reaction chamber, the third valve having a plurality of adjustable conductivities, wherein the third valve comprises a needle valve configured to adjust to a desired conductance; and a control system configured to control operation of the first valve, the second valve, and the reaction chamber, the control system configured to control a partial pressure of the etching reactant vapor based at least in part on a conductance of the third valve; wherein the control system is configured to control the removal of the material layer from the substrate by delivering the reactant vapor into the reaction chamber in a pulsed form; Wherein, in the first etching mode, the control system is configured as follows: instructing the first valve to close and the second valve to open in each pulse to transfer only a portion of the etching reactant vapor in the intermediate chamber to the reaction chamber, the portion being substantially less than the entire amount, linearly increasing the pressure of the etching reactant vapor in the reaction chamber to a first pressure level, and After reaching a first pressure level, linearly reducing the pressure of the etching reactant vapor in the reaction chamber; Wherein, in the second etching mode, the control system is configured to: instructing the first valve to close and the second valve to open during each pulse to transfer substantially all of the etching reactant vapor in the intermediate chamber to the reaction chamber, linearly increasing the pressure of the etching reactant vapor in the reaction chamber to a second pressure level higher than the first pressure level, and After reaching the second pressure level, linearly reducing the pressure of the etching reactant vapor in the reaction chamber; and Wherein, in the third etching mode, the control system is configured to: simultaneously directing the first valve to open and the second valve to open during each pulse, each pulse having a third type different from the first type and the second type, each pulse increasing the pressure of the etching reactant vapor in the reaction chamber to a third pressure level, After reaching the third pressure level, maintaining the pressure of the etching reactant vapor in the reaction chamber at the third pressure level for a period of time, and The pressure of the etching reactant vapor in the reaction chamber is reduced.

2. The apparatus of claim 1, wherein the etching reactant vapor comprises a vaporized liquid or solid.

3. The device of claim 1, further comprising a filter upstream of the intermediate chamber. 4 . The apparatus of claim 1 , further comprising a heater connected to the intermediate chamber, the heater being configured to heat the intermediate chamber in a first thermal zone.

5. The apparatus of claim 4, wherein the source is disposed in a second thermal zone at a second temperature that is higher than a first temperature of the first thermal zone.

6. The apparatus of claim 1, further comprising a liquid reactant source that delivers a liquid reactant to the source, wherein the source comprises a liquid vaporizer.

7. The apparatus of claim 1, further comprising a carrier gas line to deliver a carrier gas to the source of the etching reactant vapor. 8 . The apparatus of claim 1 , wherein the control system is configured to control the partial pressure of the etching reactant vapor based at least in part on a pressure difference between a first pressure in the intermediate chamber and a second pressure in the reaction chamber. 9 . The apparatus of claim 1 , wherein the apparatus is configured to deliver two different reactants alternately into the reaction chamber in a pulsed form for a controlled etching process.

10. An atomic layer etching apparatus for removing a material layer from a substrate, comprising: reaction chamber; an intermediate chamber upstream of and in fluid communication with the reaction chamber, the intermediate chamber configured to deliver an etching reactant vapor into the reaction chamber; a source of etching reactant vapor upstream of and in fluid communication with the intermediate chamber, the source configured to deliver the etching reactant vapor into the intermediate chamber; an adjustable needle valve having a plurality of adjustable conductivities, the adjustable needle valve being configured to control a flow of the etching reactant vapor to the reaction chamber; a first valve disposed along a reactant supply line between the source and the intermediate chamber, the first valve configured to regulate a flow of the etching reactant vapor to the intermediate chamber; a second valve disposed along a reactant supply line between the intermediate chamber and the reaction chamber, the second valve being configured to regulate a flow of the etching reactant vapor to the reaction chamber, the adjustable needle valve being disposed between the second valve and the reaction chamber; and a control system configured to control removal of the material layer from the substrate by pulsing the etching reactant vapor from the intermediate chamber into the reaction chamber, the control system configured to control a partial pressure of the etching reactant vapor based at least in part on a conductance of the adjustable needle valve, wherein the control system is configured to control the removal of the material layer from the substrate by delivering the reactant vapor into the reaction chamber in a pulsed form; Wherein, in the first etching mode, the control system is configured as follows: instructing the first valve to close and the second valve to open in each pulse to transfer only a portion of the etching reactant vapor in the intermediate chamber to the reaction chamber, the portion being substantially less than the entire amount, linearly increasing the pressure of the etching reactant vapor in the reaction chamber to a first pressure level, and After reaching a first pressure level, linearly reducing the pressure of the etching reactant vapor in the reaction chamber; Wherein, in the second etching mode, the control system is configured to: instructing the first valve to close and the second valve to open during each pulse to transfer substantially all of the etching reactant vapor in the intermediate chamber to the reaction chamber, linearly increasing the pressure of the etching reactant vapor in the reaction chamber to a second pressure level higher than the first pressure level, and After reaching the second pressure level, the pressure of the etching reactant vapor in the reaction chamber is linearly reduced.

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