Controlling the supply rate of low vapor pressure precursors
Patent Information
- Application Number
- JP2026513072
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-09-07
- Filing Date
- 2024-07-26
- Publication Date
- 2026-09-07
Smart Images
Figure 2026530241000001_ABST
Abstract
Description
Technical Field
[0001] The disclosure of the present application (hereinafter referred to as the present disclosure) generally relates to control of precursor supply amount in a substrate processing apparatus. In particular, it relates to adjusting the supply amount of low vapor pressure precursor pulses, but is not limited thereto. Background
[0002] It should be noted that this section describes useful background information, but does not constitute an admission that the technology described herein represents the state of the art.
[0003] In substrate processing, accurate control of precursor supply amount is important. Insufficient control of the supply amount degrades processing quality and increases resource consumption. Low vapor pressure precursors present difficult challenges in achieving and maintaining a desired pressure and supply amount throughout successive reactant pulses. Therefore, improved means for accurately controlling the supply amount of low vapor pressure precursors is desired. Abstract
[0004] The appended claims define the scope of protection. Matters not covered by the claims among examples and technical descriptions of apparatuses, products and / or methods in the description and / or drawings of the present specification are presented not as embodiments of the present invention, but as background art or examples useful for understanding the present invention.
[0005] According to a first exemplary aspect, the following apparatus is provided. The apparatus comprises: a processing chamber for processing a substrate; an inert gas supply system; a first introduction line connecting the inert gas supply system to the processing chamber; a (precursor) source container containing a low vapor pressure precursor; a second introduction line connecting the inert gas supply system to a buffer volume including the headspace of the source container; a third introduction line connecting the source container to the first introduction line via the buffer volume and a first pulse valve; The system is configured to adjust the pressure within the buffer volume to a predetermined level during the purging phase of the process cycle.
[0006] Advantageously, the control of the series of precursor pulses and pulse supply rates can be improved.
[0007] In some embodiments, the first pulse valve is a multi-leg (having multiple ports) pulse valve. In some embodiments, the first pulse valve is a three-leg (having three ports) pulse valve.
[0008] Depending on the embodiment, the apparatus includes a third introduction line that connects the source container to the first introduction line via the buffer volume through the first pulse valve.
[0009] In some embodiments, the apparatus is configured to adjust the pressure in the buffer volume to a predetermined level when the port of the first pulse valve downstream of the buffer volume is closed during the purging phase of the process cycle.
[0010] In some embodiments, the first introduction line is configured to supply a first inert gas flow to the processing chamber. In some embodiments, the second introduction line is configured to supply a second inert gas flow to the buffer volume. In some embodiments, the first introduction line is configured to supply a first inert gas flow to the processing chamber, and the second introduction line is configured to supply a second inert gas flow to the buffer volume.
[0011] In some embodiments, the first pulse valve has a first on / off timing cycle configured to control the amount of precursor supplied from the buffer volume to the first introduction line during a process cycle. Advantageously, the amount of precursor supplied to the processing chamber can be improved.
[0012] In some embodiments, the apparatus includes a second pulse valve in the second introduction line. In some embodiments, the second pulse valve is configured to control a second inert gas flow to the buffer volume. In some embodiments, the second pulse valve is configured to control a second inert gas flow to the buffer volume during purging in order to adjust the pressure in the buffer volume to a predetermined level during purging. In some embodiments, the apparatus includes a second pulse valve, which is configured to control a second inert gas flow to the buffer volume in order to allow the pressure in the buffer volume to be adjusted to a predetermined level during the purging phase of the process cycle. Advantageously, the pressure in the buffer volume can be precisely controlled. Furthermore, fluctuations in the amount of precursor supplied between a series of pulses can be minimized.
[0013] In some embodiments, the second pulse valve has a second opening / closing timing cycle that is coordinated with the first opening / closing timing cycle of the first pulse valve. Advantageously, this improves the control of the pressure and process of the apparatus.
[0014] In some embodiments, the second pulse valve is configured to open during the pulse of the first pulse valve. In some embodiments, the second pulse valve remains open even after the purging phase following the reactant pulse through the first pulse valve, and remains open until a predetermined pressure level is achieved within the buffer volume.
[0015] In some embodiments, the device is configured to enter an idle phase when a predetermined pressure level is achieved in the buffer volume during purging.
[0016] In some embodiments, the apparatus has a first limiting section between the first pulse valve and the buffer volume. Advantageously, control of the precursor flow rate and supply amount can be further improved.
[0017] In some embodiments, the buffer volume includes an additional gas storage space configured to provide an additional buffer volume. Advantageously, this can improve the control of precursor supply.
[0018] Depending on the embodiment, the apparatus may include a plurality of inert gas sources.
[0019] In some embodiments, the apparatus includes a first flow rate control means for controlling a first inert gas flow in the first introduction line upstream of the first pulse valve. In some embodiments, the first flow rate control means includes a mass flow controller. In some embodiments, the first flow rate control means includes a pressure transducer.
[0020] Depending on the embodiment, the first inert gas flow is constant.
[0021] In some embodiments, the apparatus includes a second flow rate control means configured to control the second inert gas flow in the second introduction line upstream of the second pulse valve.
[0022] In some embodiments, the second flow rate control means includes a mass flow controller. In some embodiments, the second flow rate control means includes a pressure transducer. In some embodiments, the second flow rate control means includes a second limiting unit.
[0023] In some embodiments, the second flow control means includes a pressure controller, which is configured to receive data from a pressure transducer located in the buffer volume and to adjust the second inert gas flow to the second pulse valve.
[0024] In some embodiments, the device includes a check valve upstream of the second pulse valve.
[0025] In some embodiments, the apparatus comprises a control unit. In some embodiments, the control unit is configured to control the apparatus. In some embodiments, the control unit is configured to control opening and closing timing cycles of the first pulse valve and the second pulse valve. In some embodiments, the control unit is configured to adjust opening and closing timing cycles of the first pulse valve and the second pulse valve. In some embodiments, the control unit is a computer-based system. In some embodiments, the control unit comprises at least one processor. In some embodiments, the control unit comprises at least one memory. In some embodiments, the control unit comprises a user interface. In some embodiments, the control unit is configured to operate as a valve controller.
[0026] In some embodiments, the control unit is connected to the first pulse valve. In some embodiments, the control unit is configured to control the first pulse valve.
[0027] In some embodiments, the control unit is connected to the second pulse valve. In some embodiments, the control unit is configured to adjust the second pulse valve based on a feedback loop. Herein, a control algorithm is used to adjust an opening mode of the second pulse valve during an opening cycle of the second pulse valve based on a detected pressure of the buffer volume. In some embodiments, the control unit adjusts (or is configured to adjust) an opening size of the second pulse valve during an opening cycle of the second pulse valve. In some embodiments, an opening frequency of the second pulse valve is adjusted. In some embodiments, an opening size of the second pulse valve is adjusted. In some embodiments, both the opening size and frequency of the second pulse valve are adjusted.
[0028] In some embodiments, the second pulse valve is closed in an idle phase to prevent backflow from the source container. In the idle phase, the first pulse valve allows a first inert gas flow into the processing chamber, but precursor pulses are blocked, and the pressure within the buffer volume is at the predetermined level. In some embodiments, in the idle phase, the first pulse valve allows a steady flow of inert gas into the processing chamber, but precursor pulses are blocked, and the pressure within the buffer volume is at the predetermined level.
[0029] In some embodiments, the apparatus comprises a shut-off valve for isolating the source container from any gas flow during maintenance purging. In some embodiments, the apparatus comprises a first shut-off valve arranged immediately upstream of the source container. In some embodiments, the apparatus comprises a second shut-off valve arranged immediately downstream of the source container.
[0030] In some embodiments, the apparatus comprises a bypass valve that allows a second inert gas flow to bypass the isolated source container during maintenance purging.
[0031] According to another exemplary aspect, there is provided the following apparatus. The apparatus comprises a first pulse valve configured to control the supply of precursor pulses into a first inert gas flow in a first introduction line connected to a processing chamber, a low vapor pressure reactant (precursor) in a source container, wherein the reactant is allowed to evaporate from the source container into a buffer volume, the buffer volume comprising the upper space of the source container, the buffer volume is connected to the first introduction line through the first pulse valve, the apparatus further comprises a second inert gas flow into the buffer volume, a second pulse valve arranged upstream of the source container, The second pulse valve is configured to adjust the second inert gas flow to the source vessel so as to adjust the pressure in the buffer volume to a predetermined pressure level during the purging phase of the process cycle.
[0032] According to a second exemplary aspect, a method is provided for controlling the supply of a low vapor pressure reactant. This method is The low vapor pressure precursor is supplied from the source container to a buffer volume located upstream of the first pulse valve that controls the precursor pulse to the processing chamber, The inert gas is supplied from the inert gas supply system to the buffer volume, including the upper space of the precursor container. During the purging phase of the process cycle, the pressure within the buffer volume is adjusted to a predetermined level. Includes.
[0033] In some embodiments, the method includes supplying a first inert gas flow to the processing chamber and a second inert gas flow to the buffer volume, wherein the precursor pulse passing through the first pulse valve is supplied to the first inert gas flow. In some embodiments, the method includes supplying a first inert gas flow to the processing chamber through a first introduction line and a second inert gas flow to the buffer volume through a second introduction line. In some embodiments, the method includes supplying a precursor pulse to the first introduction line upstream of the processing chamber via the first pulse valve. In some embodiments, the method includes supplying a precursor pulse to the first inert gas flow in the first introduction line upstream of the processing chamber via the first pulse valve.
[0034] In some embodiments, the first inert gas flow is constant. In some embodiments, the first inert gas flow is constant during the pulse and purge phases of the process cycle. In some embodiments, the method includes supplying a constant first inert gas flow during the pulse and purge phases of the process cycle.
[0035] In some embodiments, the method includes controlling the (second) inert gas flow to the buffer volume by a second pulse valve located upstream of the buffer volume.
[0036] In some embodiments, the method includes coordinating the opening and closing timing cycle of the second pulse valve with the opening and closing timing cycle of the first pulse valve. In some embodiments, the method includes opening the second pulse valve during the pulse phase of the process cycle. In some embodiments, the method includes keeping the second pulse valve open during the purge phase of the process cycle until a predetermined pressure level in the buffer volume is achieved.
[0037] In some embodiments, the method further includes adjusting the degree to which the second pulse valve opens during an opening cycle based on a feedback loop based on the detected pressure in the buffer volume. In some embodiments, the method includes adjusting the magnitude of the opening of the second pulse valve during purging. In some embodiments, the method includes adjusting the frequency of the opening of the second pulse valve during purging.
[0038] In some embodiments, the method further includes closing the first pulse valve to stop the precursor pulses to the processing chamber and, after a predetermined pressure in the buffer volume has been achieved, closing the second pulse valve to prevent backflow of the precursor and / or inert gas from the buffer volume, thereby entering an idle phase.
[0039] In some embodiments, the method further includes, outside of the process cycle, a) isolating the precursor source vessel from all gas flows by closing a shut-off valve and opening a bypass valve, and b) performing a maintenance purge by opening both the first pulse valve and the second pulse valve and flushing the gas line with an inert gas so that no inert gas enters the precursor source vessel.
[0040] In another exemplary aspect, a method is provided for controlling the supply of a precursor to a processing chamber in an apparatus in one exemplary aspect. Here, a first pulse valve is configured to regulate the precursor pulse to the processing chamber, and a second pulse valve is configured to regulate the pressure in a buffer volume upstream of the first pulse valve by controlling the flow of inert gas to a buffer volume. The method includes coordinating the opening and closing timing cycle of the second pulse valve with the opening and closing timing cycle of the first pulse valve, as follows. i) In the pulse stage in which the first pulse valve is opened to allow the precursor pulse to flow into the processing chamber, the second pulse valve is also opened. ii) During the purging phase in which the first pulse valve is closed to prevent precursor pulses from entering the processing chamber, the second pulse valve is kept open until a predetermined pressure level in the buffer volume is achieved.
[0041] While various aspects and embodiments have been presented, these are not intended to limit the scope of the invention. These embodiments are merely used to illustrate specific aspects and steps that may be used in various implementations. Some embodiments may be presented only by reference to specific exemplary aspects. Corresponding embodiments may also apply to other exemplary aspects. [Brief explanation of the drawing]
[0042] Several embodiments will be described with reference to the following accompanying drawings. [Figure 1a] A schematic diagram of a device configured for pulsed stages according to one embodiment is shown. [Figure 1b] A schematic diagram of an apparatus configured for the purging phase, according to one embodiment, is shown. [Figure 1c] A schematic diagram of a device configured for the idle phase, according to one embodiment, is shown. [Figure 1d] A schematic diagram of a device configured for maintenance purging, according to one embodiment, is shown. [Figure 2]A schematic diagram of an apparatus configured for pulsed stages, according to another embodiment, is shown. [Figure 3] A schematic diagram of an apparatus configured for pulsed stages, according to yet another embodiment, is shown. [Figure 4] A schematic diagram of an apparatus configured for pulsed stages, according to yet another embodiment, is shown. [Figure 5] A schematic diagram shows a device comprising a control unit according to one embodiment. [Figure 6] A flowchart of a method for controlling the pulse supply amount in one embodiment is shown. [Figure 7] A flowchart of another method for controlling the pulse supply amount in one embodiment is shown. Detailed description
[0043] In the following description, similar symbols indicate similar elements or steps.
[0044] This disclosure aims to improve the supply control of low vapor pressure precursor pulses in a substrate processing apparatus 100. The substrate processing apparatus 100 is configured to utilize the principles of vapor deposition-based technology. In some embodiments, the substrate processing apparatus 100 is configured as an atomic layer deposition (ALD) apparatus.
[0045] In the description of this application, the term ALD encompasses all available technologies based on ALD, as well as all equivalent or closely related technologies. For example, it includes variants of ALD such as MLD (Molecular Layer Deposition), plasma-assisted ALDs such as PEALD (Plasma Enhanced Atomic Layer Deposition), and photon-enhanced ALDs, also known as flash-enhanced ALDs.
[0046] ALD (Automated Lamination Deposition) is a widely used technique for forming thin films by depositing a precursor layer onto a substrate from the gas phase. ALD is based on the alternating execution of multiple types of self-saturating surface reactions on the substrate. Specifically, several different reactants (precursors), supplied as chemical compounds or elements, are sequentially introduced in a pulsed manner into the reaction space containing the substrate using a non-reactive inert gas carrier. After the deposition of the reactants, the substrate is purged with an inert gas. The precursor pulse and purge cycle is repeated the number of times necessary to obtain a film of a predetermined thickness.
[0047] Apparatus 100 can be applied to other thin-film deposition technologies, such as physical vapor deposition (PVD) and plasma-enhanced chemical vapor deposition (PECVD) processes. It can also be applied to other applicable technologies, such as atomic layer etching (ALE).
[0048] In Figures 1a-5, the white (unshaded) triangles in the valve symbols indicate the open portion (flow is permitted through the triangle; that is, it can flow through the valve port represented by that triangle), and the black triangles indicate the closed portion (flow is not permitted through the triangle; that is, it cannot flow through the valve port represented by that triangle).
[0049] Figures 1a to 1d show a device 100 according to one embodiment, each representing the pulse, purge, idle, and maintenance purge states, respectively.
[0050] The substrate processing apparatus 100 includes a processing chamber 110. The processing chamber 110 is configured to accommodate a substrate to be processed within the apparatus 100 or a plurality of substrates.
[0051] The substrate processing apparatus 100 is equipped with an exhaust duct 115 downstream of the processing chamber 110. Gaseous substances in the processing chamber 110 are discharged from the processing chamber 110 through the exhaust duct 115. A pump 125 connected to the exhaust duct 115 is used to actively remove the gaseous substances. In some embodiments, the pump 125 is a vacuum pump.
[0052] The substrate processing apparatus 100 includes an inert gas supply system configured to supply inert gas. In some embodiments, the inert gas supply system includes a first inert gas source 120a. In some embodiments, the inert gas supply system includes a second inert gas source 120b. In some embodiments, the inert gas supply system includes a plurality of inert gas sources.
[0053] In some embodiments, as shown in Figures 1a to 1d, the inert gas supply system includes a first inert gas source 120a connected to the processing chamber 110 via a first introduction line 130. The first inert gas flow is configured to flow from the first inert gas source 120a to the processing chamber 110 along the first introduction line 130. In other words, the first introduction line constitutes the entire inert gas supply system, i.e., the line from the first inert gas source 120a to the processing chamber 110 in Figures 1a to 1d. In some embodiments, the inert gas is one of N2, Ar, or He. The inert gas is used, for example, to purge the processing chamber 110 between precursor pulses or to isolate subsequent precursor pulses from each other. In some embodiments, the inert gas source 120a is configured to supply the first inert gas flow to the processing chamber 110. In some embodiments, the flow rate of the inert gas is constant. In some embodiments, the flow rate of the inert gas is constant through the first introduction line 130 from the inert gas supply system to the processing chamber 110.
[0054] The substrate processing apparatus 100 includes a first flow rate control means 140 in the first introduction line 130 downstream of the first inert gas source 120a. The first flow rate control means 140 is shown by a dashed frame in Figures 1a to 1d. In some embodiments, the first flow rate control means 140 includes a mass flow controller 140a and a first pressure transducer 140b. The first flow rate control means 140 is configured to establish and maintain a stable first inert gas flow in the first introduction line 130 from the first inert gas source 120a to the processing chamber 110. In some embodiments, the pressure of the first inert gas flow in the first introduction line 130 downstream of the flow rate control means 140 is 5 to 15 hPa when the flow rate of the first inert gas is 500 to 2000 sccm.
[0055] The substrate processing apparatus 100 is equipped with a first pulse valve V1 in the introduction line 130. The opening and closing cycle of the first pulse valve V1 controls the precursor pulse-purge cycle to the processing chamber 110. In some embodiments, the first pulse valve V1 is a pneumatic valve. In some embodiments, the first pulse valve V1 is a diaphragm valve. The first pulse valve V1 is configured to allow the flow of a first inert gas in the first introduction line 130, and at the same time, to supply low vapor pressure reactant pulses from a reactant source to the inert gas flow in the first introduction line 130 upstream of the processing chamber 110. In some embodiments, the flow rate of the first inert gas flow is constant. In some embodiments, the first inert gas flow is maintained throughout the pulse, purge, and idle phases of the substrate processing cycle.
[0056] In some embodiments, the first pulse valve V1 is a pulse valve having three legs (ports). The three-leg valve V1 allows for the supply of precursor pulses from a precursor source container to the first inert gas flow in the first introduction line 130. In some embodiments, the first pulse valve V1 is a pulse valve having four legs. The four-leg valve V1 allows for the supply of precursor pulses from two different precursor source containers to the first inert gas flow in the first introduction line 130. This allows for pulse control by a single multi-port first pulse valve V1.
[0057] In some embodiments, the apparatus 100 includes one or more first pulse valves V1. Thus, multiple different precursors from multiple different precursor source containers may be connected to different parts of the first introduction line 130 through multiple first pulse valves V1. In some embodiments, the apparatus 100 includes one, two, or three multi-port first pulse valves V1. Alternatively, in some embodiments, the apparatus includes multiple introduction lines similar to the first introduction line 130, each introduction line including a multi-port pulse valve V1.
[0058] The first pulse valve V1 has a predetermined opening and closing timing cycle. Preferably, in all configurations, the first inert gas flow in the first introduction line 130 is not obstructed as it passes through the first pulse valve V1. The first inert gas flow is preferably regulated by the first flow rate control means 140. In some embodiments, the first inert gas flow is constant.
[0059] During the pulse phase of the process cycle of apparatus 100 (Figure 1a), the first pulse valve V1 enters a state for the pulse phase. In this state, the first pulse valve V1 is configured to allow a low vapor pressure precursor pulse to the first inert gas flow in the first introduction line 130. That is, during the pulse period, a precursor pulse is supplied to the first inert gas flow and then supplied to the processing chamber 110. The process cycle alternates between the pulse phase and the purge phase until the surface treatment is completed. In some embodiments, the process cycle includes an idle phase between the purge phase and the pulse phase. In some embodiments, maintenance purging is performed outside of the process cycle.
[0060] During the purge phase of the process cycle of apparatus 100 (Figure 1b), i.e., before and after the precursor pulse passes through the first pulse valve V1, the first pulse valve V1 is in a state for the purge phase. In the purge state, the first pulse valve V1 allows the first inert gas to flow in the first introduction line 130 from the inert gas supply system to the processing chamber 110, but blocks the low vapor pressure precursor pulse to the first introduction line 130. In other words, purging is the phase between one precursor pulse and the next precursor pulse, during which only the first inert gas flow enters the processing chamber 110, washing away the residue from the previous pulse from the processing chamber.
[0061] In the idle phase of device 100 (Figure 1c), the device is prepared for the next precursor pulse. The pressure in the buffer volume 180 upstream of the first pulse valve V1 is at a preset level for the next precursor pulse (i.e., pulse phase). The state of the first pulse valve V1 for the idle phase is the same as the state for the purge phase.
[0062] During the maintenance purge of apparatus 100 (Figure 1d), apparatus 100 is cleaned with an inert gas, except for the source container 150. During the maintenance purge, the first pulse valve V1 is set to a maintenance purge state. In this state, the first pulse valve V1 is kept fully open, allowing the inert gas flow to pass through all ports.
[0063] Depending on the embodiment, the pulse phase, purge phase, and idle phase are repeated periodically. Maintenance purging is performed, for example, to clean the gas lines between runs of individual processes. The settings of other components of the apparatus 100 in each of the aforementioned phases will be detailed in the description of those components below.
[0064] The substrate processing apparatus 100 includes a source container 150. The source container 150 contains a low vapor pressure precursor 160. The low vapor pressure precursor 160 can evaporate into the upper space 155 of the source container 150. The evaporation of the low vapor pressure precursor is indicated by dashed arrows in the upper space 155 in Figures 1-4. The low vapor pressure precursor 160 may be, for example, tris(dimethylamino)cyclopentadienylzirconium (ZyALD), tris(dimethylamide)cyclopentadienylhafnium (HyALD), tetrakis(dimethylamide)titanium (TDMAT), hafnium tetrachloride (HfCl4), zirconium tetrachloride (ZrCl4), tetrakis(ethylmethylamino)hafnium (TemaHf), or tetrakis(ethylmethylamino)zirconium (TemaZr).
[0065] The source container 150 is connected to the multi-port first pulse valve V1 by the third introduction line 170. The evaporated low vapor pressure precursor 160 proceeds from the upper space 155 to the third introduction line 170. The first pulse valve V1 is configured to control the flow of the low vapor pressure precursor 160 from the third introduction line 170 to the first introduction line 130 and the processing chamber 110.
[0066] The source container 150 is located downstream of the inert gas supply system. The source container 150 is connected to the inert gas supply system through a second introduction line 185. In some embodiments, the inert gas supply system is configured to supply, preferably a constant second inert gas flow, to the upper space 155 (part of the buffer volume 180) of the source container 150 through the second introduction line 185. In some embodiments, the inert gas supply system includes a second inert gas source 120b. In some embodiments, the source container 150 is connected to the second inert gas source 120b as shown in Figures 1a to 1d. The inert gas is, for example, N2 or Ar. Preferably, the inert gas of the second inert gas flow is the same as the inert gas of the first inert gas flow. In some embodiments, the second introduction line 185 is connected to the same inert gas supply system as the first introduction line 130. The second pulse valve V2 is located in the second introduction line 185 between the inert gas supply system and the source container 150.
[0067] The upper space 155 and the third introduction line 170 (and a short section of the second introduction line 185 downstream of the second pulse valve V2) together form a buffer volume 180 (shown as an inverted L-shaped structure enclosed by a dashed polygon in Figure 1a). In some embodiments, the volume of the buffer volume is at least 100 cm³.
[0068] In some embodiments, the apparatus 100 is configured to adjust the pressure in the buffer volume 180 to a range of 1 to 50 hPa. The pressure of the low vapor pressure precursor 160 in the buffer volume 180 affects the amount of precursor 160 pulses supplied through the first pulse valve V1. In some embodiments, the amount of low vapor pressure precursor 160 supplied in the precursor pulses through the first pulse valve V1 is controlled by adjusting the pressure in the buffer volume 180.
[0069] In some embodiments, the buffer volume 180 includes an additional gas storage space 175. In some embodiments, the additional gas storage space 175 is located within a third introduction line 170. The additional gas storage space 175 increases the buffer volume 180. A larger buffer volume 180 allows for better maintenance of the pressure difference across the first pulse valve V1 during the precursor pulse.
[0070] The apparatus 100 includes a first limiting section R1 between the buffer volume 180 and the first pulse valve V1. The first limiting section R1 forms a flow limit to control the flow of the low vapor pressure precursor 160 from the buffer volume 180 to (and through) the first pulse valve V1 during the pulse phase. The amount of precursor supplied is affected by the gas pressure in the buffer volume 180 and the limiting section R1. Thus, the limiting section R1 partially determines the amount of precursor supplied in the pulse. In some embodiments, the first limiting section R1 is configured to keep the flow rate from the buffer volume 180 to the first pulse valve V1 constant. This has the advantage of minimizing pressure spikes in the precursor pulse and differences between consecutive precursor pulses.
[0071] The amount of precursor supplied in a pulse passing through the first pulse valve V1 is proportional to Δp × pi, where pi is the partial pressure of the precursor 160 in the buffer volume 180 and Δp is the pressure difference at the first limiting section R1. Δp can be changed by controlling the pressure in the upper space 155 of the container. In some embodiments, as pi decreases over time, Δp is increased to compensate for the change. Advantageously, even if pi in the buffer volume 180 is not constant, the amount of precursor 160 supplied in a precursor pulse remains constant.
[0072] In some embodiments, the flow of a second inert gas stream into the source container 150 increases the pressure in the buffer volume 180 during the purging phase, restoring a preset pressure level. In some embodiments, the second inert gas stream enables a stable pulse supply of a low vapor pressure precursor through the first pulse valve V1. In some embodiments, pressure loss in the buffer volume due to precursor pulses through the first pulse valve V1 is compensated by the second inert gas stream. Advantageously, the pressure in the buffer volume and the supply rate of low vapor pressure precursor pulses can be controlled by the second inert gas during and / or between successive precursor pulses.
[0073] The first shut-off valve SV1 is located upstream of the source container 150 and very close to the source container 150 in the second inlet line 185. The second shut-off valve SV2 is located downstream of the source container 150 and very close to the source container 150 in the third inlet line 170. In some embodiments, the shut-off valves SV1 and SV2 are manual valves. In some embodiments, the shut-off valves SV1 and SV2 are closed during maintenance purging to isolate the source container 150 from any gas flow during maintenance purging.
[0074] In some embodiments, the apparatus 100 has a bypass line 195 equipped with a bypass valve BV. In some embodiments, the bypass line 195 connects a second inlet line 185 and a third inlet line 170. In some embodiments, the bypass valve BV is a manual valve. In some embodiments, the bypass valve BV is closed during the pulse phase, purge phase, and idle phase. In some embodiments, the bypass valve BV is opened for maintenance purging. This causes the second inert gas flow to bypass the source vessel and flow directly from the second inlet line 185 along the bypass line 195 to the third inlet line 170, flushing the gas line with inert gas.
[0075] The apparatus 100 has a second pulse valve V2 in a second introduction line 185 upstream of the source vessel 150. In some embodiments, the second pulse valve V2 is a pneumatic valve. In some embodiments, the second pulse valve V2 is a diaphragm valve. The second pulse valve V2 is configured to control the flow rate of the second inert gas from the second inert gas source 120b to the buffer volume 180. The second pulse valve V2 has an opening and closing timing cycle that is coordinated with the opening and closing timing cycle of the multi-port first pulse valve V1. This is to adjust the pressure in the buffer volume 180 to a predetermined level for each reactant pulse of the multi-port first pulse valve V1 in order to control the amount of low vapor pressure precursor supplied to the first inert gas flow. Advantageously, the pressure in the buffer volume can be actively controlled according to the opening and closing timing cycle of the first pulse valve V1.
[0076] In some embodiments, the second pulse valve V2 is opened during the purge phase between two consecutive reactant pulses of the first pulse valve V1. In some embodiments, this is to raise the pressure in the buffer volume 180 to a predetermined level during each precursor pulse, i.e., during the purge before the opening of the first pulse valve V1. During the purge phase, a continuous flow of a constant first inert gas stream is permitted through the first pulse valve V1, while low vapor pressure reactant pulses to the inert gas stream are blocked.
[0077] In some embodiments, the second pulse valve V2 is open during the precursor pulse period of the first pulse valve V1. During the pulse phase, the first pulse valve V1 opens and supplies a low vapor pressure precursor pulse from the buffer volume 180 to the first inert gas flow in the first introduction line 130. In some embodiments, the first pulse valve V1 allows a constant first inert gas flow through the first pulse valve V1 during the purge, pulse, and idle phases. In some embodiments, the second pulse valve V2 opens simultaneously with the precursor pulse of the first pulse valve V1 to minimize pressure loss in the buffer volume 180 during the precursor pulse phase. Advantageously, this improves the maintenance of the pressure difference across the first pulse valve (and throttling section R1).
[0078] In some embodiments, the second pulse valve V2 opens during a low vapor pressure reactant pulse passing through the multiport first pulse valve V1, and remains open during the transition to the purge phase until a predetermined pressure level in the buffer volume is achieved. In some embodiments, this is to restore the pressure in the buffer volume to a predetermined level during the purge before the next precursor pulse. Advantageously, this compensates for the pressure drop in the buffer volume caused by the precursor pulse.
[0079] In some embodiments, the pulse valve V2 prevents backflow of evaporated precursor and / or second inert gas during the idle phase. During the idle phase, the first pulse valve is in a purging state (i.e., the precursor pulse is blocked), and the pressure in the buffer volume 180 is at a predetermined level. That is, the device 100 is prepared for another precursor pulse through the first pulse valve V1. In some embodiments, the pressure in the buffer volume 180 is passively maintained by the second pulse valve V2, which prevents backflow, without requiring continuous and active pumping of the second inert gas from the second inert gas source 120b.
[0080] In some embodiments, the second pulse valve V2 is fully opened during maintenance purging. In some embodiments, this is to allow the flow of inert gas through the second pulse valve V2 to proceed without obstruction in order to clean the gas lines 185, 195, and 170.
[0081] The apparatus 100 includes a second flow rate control means 190 in the second introduction line 185 downstream of the second inert gas source 120b. In some embodiments, the second flow rate control means 190 has a pressure controller. In some embodiments, the second flow rate control means 190 has a second limiting section R2, as shown in Figures 2 and 3. In some embodiments, the second flow rate control means 190 is configured to receive pressure data from within the buffer volume 180 or from the upper space 155 of the source container and adjust the flow rate of the second inert gas to the second pulse valve V2 accordingly. Preferably, the pressure and flow rate of the second inert gas flow to the second pulse valve V2 are kept constant during substrate processing. In some embodiments, the pressure within the buffer volume 180 is controlled by adjusting the opening and closing timing cycle of the second pulse valve V2.
[0082] In some embodiments, the apparatus 100 has a third pulse valve V3 in the third introduction line 170. The third pulse valve V3 is shown in Figure 1a, but is applicable to other embodiments as well. In some embodiments, the third pulse valve V3 is provided in the precursor source container 150. In some embodiments, the third pulse valve V3 controls the flow of precursor from the upper space 155 along the third introduction line 170 to the additional gas storage space 175 and the first pulse valve V1. Advantageously, the pressure (supply conditions) upstream of the first pulse valve V1 can be controlled more precisely. In some embodiments, the third pulse valve V3 is a pneumatic valve.
[0083] Figures 2-4 schematically show the apparatus 100 according to other embodiments in the state for the pulse stage. In addition to the teachings described later regarding the embodiments according to Figures 2-4, the embodiments shown in Figures 1a-1d can also be applied here, and vice versa.
[0084] In the embodiments shown in Figures 2-4, the buffer volume 180 of the substrate processing apparatus 100 consists of the upper space 155 of the source container and the third introduction line 170 (and a short section of the second introduction line 185 downstream of the second pulse valve V2). That is, in these embodiments, there is no additional gas storage space 175 in the third introduction line 170 upstream of the first pulse valve V1. In some embodiments, the absence of an additional gas storage volume makes the apparatus 100 more compact. Advantageously, the size of the apparatus and the amount of material used can be reduced.
[0085] In one embodiment according to Figure 2, the second flow rate control means 190 has a second limiting section R2. In some embodiments, the second flow rate control means 190 consists only of the second limiting section R2. In some embodiments, the limiting section R2 does not include any moving parts. In some embodiments, the second limiting section R2 provides flow rate restriction so that the flow rate of the second inert gas reaching the second pulse valve V2 is constant. Thus, in some embodiments, the opening and closing timing cycle of the second pulse valve V2 regulates the flow rate of the second inert gas to the buffer volume 180. Advantageously, the second flow rate control means 190 is kept simple, for example, reducing the need for maintenance.
[0086] In some embodiments, the absolute pressure of the second inert gas flow is the same as the absolute pressure of the first inert gas flow from the first inert gas source 120a.
[0087] In one embodiment according to Figure 3, the second intake line 185 is directly connected to the third intake line 170. Here, one end of the third intake line 170 is connected to the source container 150, and the other end is connected to the first pulse valve V1. That is, unlike the embodiments according to Figures 1-2, in some embodiments, the second inert gas flow does not enter the buffer volume 180 via the upper space 155 of the source container. In any case, in some embodiments according to Figure 3, the second inert gas flow increases the pressure in the buffer volume 180 (the space including the upper space 155, the third intake line 170, and a short section of the second intake line 185 downstream of the second pulse valve V2). As a result, in some embodiments, the device 100 also lacks a bypass line 195. Therefore, in some embodiments, the source container 150 has only one shut-off valve SV. In some embodiments, the second intake line 185 and the third intake line 170 can be separated using a bypass valve BV. The advantages include a reduction in the number of gas lines and valves required, which can reduce the risk of leakage, for example. Additionally, the source container 150 can be easily separated from the gas line.
[0088] In one embodiment according to Figure 3, the apparatus 100 includes a check valve 310. The check valve 310 permits fluid flow in only one direction, namely, the second inert gas flow toward the source container 150. Thus, in some embodiments, the pressure downstream of the check valve 310 is easily maintained, and backflow of the second inert gas flow and / or low vapor pressure precursor is effectively prevented. In some embodiments, the check valve 310 provides a backup in case of failure of backflow prevention in the second pulse valve V2. Advantageously, the operational reliability of the substrate processing apparatus 100 can be improved.
[0089] In one embodiment according to Figure 4, the device 100 includes a valve controller 420. In some embodiments, the device includes a second pressure transducer 410 configured to monitor the pressure in a buffer volume 180. In some embodiments, the second pressure transducer 410 is located in the upper space 155. In some embodiments, the valve controller 420 controls the second pulse valve V2 based on pressure data received from the second pressure transducer 410. In some embodiments, a control unit 510 (see Figure 5) functions as the valve controller 420. In some embodiments, the valve controller 420 uses a feedback loop in which a control algorithm adjusts the opening (degree of opening and / or frequency of opening) of the second pulse valve V2 during its opening cycle based on the detected pressure in the buffer volume 180 or the upper space 155. In some embodiments, the valve controller 420 is configured to identify when a predetermined pressure in the buffer volume has been achieved and, accordingly, instruct the closing of the second pulse valve V2, for example, during the purge phase. In some embodiments, the valve controller 420 is a general-purpose computing device such as a personal computer. In some embodiments, the valve controller 420 is also configured to control the second flow rate control means 190, and thus controls the flow rate and pressure of the second inert gas flow reaching the second pulse valve V2.
[0090] Figure 5 schematically shows an apparatus comprising a control unit according to one embodiment. In some embodiments, the control unit is a computer-based system configured to control the apparatus 100. In some embodiments, the control unit 510 operates the apparatus 100 autonomously (without user input) during board processing. That is, board processing is automatically controlled by the control unit 510. In some embodiments, the user defines the processes and parameters monitored and executed by the control unit.
[0091] In some embodiments, the control unit 510 controls the first pulse valve V1. That is, in some embodiments, the control unit 510 opens and closes the first pulse valve V1 according to a predetermined opening and closing timing cycle. Therefore, by controlling the first pulse valve V1, the control unit 510 controls the discharge and supply of precursor pulses passing through the first pulse valve from the third introduction line 170 to the first introduction line 130.
[0092] In some embodiments, the control unit 510 controls the second pulse valve V2. In some embodiments, the control unit controls the opening and closing timing cycle of the second pulse valve V2 in accordance with the opening and closing timing cycle of the first pulse valve V1. In some embodiments, the control unit 510 opens the second pulse valve V2 simultaneously with the first pulse valve V1. As a result, in some embodiments, the pressure drop in the buffer volume 180 during the precursor pulse (pulse stage) passing through the first pulse valve V1 is minimized.
[0093] In some embodiments, the control unit opens the second pulse valve V2 during a pulse (simultaneously with the first pulse valve V1) and keeps the second pulse valve V2 open during purging (after closing the first pulse valve V1) until the pressure in the buffer volume 180 is adjusted to a predetermined level. In this way, in some embodiments, the control unit 510 ensures that the pressure in the buffer volume 180 is adjusted to a predetermined level during purging before each precursor pulse. Advantageously, the control unit 510 ensures a stable and accurate precursor supply during pulses. In some embodiments, the control unit 510 closes the second pulse valve V2 during purging after the predetermined pressure level in the buffer volume 180 has been adjusted. That is, the control unit 510 sets the device to idle by closing the second pulse valve V2 after the pressure in the buffer volume has been adjusted to a predetermined level. Advantageously, the predetermined pressure level in the buffer volume 180 is passively maintained because the closed second pulse valve V2 prevents gas backflow. Therefore, it is not necessary to constantly and actively supply inert gas to the buffer volume 180 through the second pulse valve V2.
[0094] In some embodiments, the control unit 510 opens the second pulse valve V2 only during purging (i.e., when the first pulse valve V1 is closed). In other words, in some embodiments, the second pulse valve V2 is closed during the pulse phase. This method allows a predetermined pressure level in the buffer volume 180 to be reached before each pulse, and thus allows for precise control of the amount of subsequent pulses supplied.
[0095] In some embodiments, the control unit 510 controls the third pulse valve V3.
[0096] In some embodiments, the control unit 510 receives data from the flow rate control means (140, 190) and / or the pressure transducers 140b, 410, and controls the inert gas flow rate of the device 100 according to the received data in order to provide a constant flow rate. In some embodiments, the control unit 510 is connected to an inert gas supply system. In some embodiments, the control unit 510 controls the flow rate of the inert gas within the device 100.
[0097] Figure 6 shows a flowchart of a method for controlling the pulse supply amount in one embodiment. This method may be implemented in any embodiment of the substrate processing apparatus 100 described above, for example. Details regarding apparatus to which this method can be applied have already been described with reference to the embodiments shown in Figures 1 to 5.
[0098] This method includes the following:
[0099] 610. The low vapor pressure precursor 160 is supplied from the source vessel 150 to a buffer volume 180 located upstream of the first pulse valve V1. Here, the first pulse valve V1 controls the precursor pulse from the buffer volume 180 to the processing chamber 110. The low vapor pressure precursor 160 is constantly evaporating within the source vessel 150, supplying the precursor 160 to the buffer volume 180. During the purging and idle phases, the evaporation of the precursor 160 causes the precursor to accumulate in the buffer volume for the next pulse. The buffer volume 180 helps reduce pressure fluctuations during pulse supply of the precursor 160 and maintain the pressure difference across the first pulse valve V1. In some embodiments, during maintenance purging, the precursor source vessel 150 is isolated from the rest of the apparatus 100 by closing shut-off valves SV, SV1, and SV2. This prevents the evaporated precursor 160 from being discharged from the source vessel 150 and prevents the inert gas flow from entering the source vessel.
[0100] 620. An inert gas stream is supplied to the buffer volume 180. In some embodiments, the inert gas is N2 or Ar. However, other inert gases can also be used. In some embodiments, the inert gas stream allows for more efficient control of the pressure in the buffer volume 180 than if it were based solely on the evaporation rate of the low vapor pressure precursor 160. In some embodiments, an inert gas is supplied to the buffer volume 180 during a pulse phase to reduce the pressure drop in the buffer volume 180 during the pulse phase. In some embodiments, an inert gas is supplied to the buffer volume between one pulse phase and the next to restore the pressure in the buffer volume 180 to a predetermined level during the purge phase. In some embodiments, an inert gas is supplied to the buffer volume 180 both during and after the pulse phase until a predetermined pressure level is reached. In some embodiments, the device 100 enters an idle phase. Here, when a predetermined pressure level is reached in the buffer volume 180 during the purge phase, i.e., when the device 100 is ready for the next pulse phase, the supply of inert gas to the buffer volume 180 is stopped.
[0101] 630. During the purging phase of the process cycle, the pressure in the buffer volume is adjusted to a predetermined level. In some embodiments, during the purging phase (when the first pulse valve V1 is closed to prevent precursor pulses), the pressure conditions in the buffer volume 180 are controlled by controlling the flow of inert gas to the buffer volume 180. Thus, in some embodiments, the low evaporation rate of the low vapor pressure precursor 160 (which affects the supply amount) is compensated for by adjusting the pressure in the upper space 155 of the container using the inert gas flow rate.
[0102] In some embodiments, the second opening / closing timing cycle of the second pulse valve V2 is coordinated with the first opening / closing timing cycle of the first pulse valve V1. This adjusts the pressure in the buffer volume 180 to a predetermined level during the purge phase between pulse phases of the first pulse valve. In some embodiments, the opening of the second pulse valve V2 during the pulse phase is synchronized with that of the first pulse valve V1 to further minimize the pressure drop during the precursor pulse. As a result, pressure fluctuations during substrate processing can be minimized, improving processing quality.
[0103] In some embodiments, the second pulse valve V2 follows the opening and closing timing cycle of the first pulse valve V1 (i.e., the opening and closing timing cycle of the second pulse valve V2 is similar to that of the first pulse valve V1). That is, in some embodiments, while the first pulse valve V1 is open, the second pulse valve V2 is also open during the pulse phase. Then, when the first pulse valve V1 closes, the second pulse valve V2 also closes. In this way, in some embodiments, the pressure drop in the buffer volume 180 during a pulse is minimized.
[0104] In some embodiments, the second pulse valve V2 opens during the pulse phase but remains open during the purge phase until the pressure in the buffer volume 180 is adjusted to a predetermined level. This allows for precise control of the supply amount and pressure profile of consecutive pulses. Advantageously, the pressure in the buffer volume 180 is adjusted to a predetermined level before each consecutive pulse passing through the first pulse valve V1.
[0105] In some embodiments, the second pulse valve closes during the pulse phase (when the first pulse valve V1 is open) and opens during the purge phase (when the first pulse valve V1 is closed). That is, in some embodiments, the opening and closing timing cycle of the second pulse valve V2 is the opposite of the opening and closing timing cycle of the first pulse valve V1. In this manner, in some embodiments, after the pressure drops during the pulse phase, the pressure in the buffer volume 180 recovers to a predetermined level during the purge phase. In some embodiments, once the predetermined pressure is achieved in the buffer volume 180, the second pulse valve V2 closes to prevent backflow of inert gas and maintain the pressure in the buffer volume 180 until the next pulse phase (idle phase).
[0106] In some embodiments, both the first pulse valve V1 and the second pulse valve V2 are kept fully open during maintenance purging. This maximizes the inert gas flow rate within the device 100.
[0107] Figure 7 shows a flowchart of another method for controlling the pulse supply amount in one embodiment. Similar to the method in Figure 6, this method can be implemented in any embodiment of the substrate processing apparatus 100 described above. Furthermore, the teachings and embodiments described above with respect to Figures 1-5 are applicable to this method, and vice versa.
[0108] Figure 7 shows a method in the apparatus 100 for controlling the supply amount of the low vapor pressure precursor 160 to the processing chamber 110, as described above. In the apparatus, a multi-port first pulse valve V1 is configured to regulate the pulse of the precursor 160 to the processing chamber 110, and a second pulse valve V2 is configured to regulate the pressure in the buffer volume 180 upstream of the first pulse valve V1 by controlling the inert gas flow from the source container 150 to the buffer volume 180. The method then includes the following: 710. The opening and closing timing cycle of the second pulse valve V2 is coordinated with the opening and closing timing cycle of the first pulse valve V1. Specifically, 720. During the pulse phase in which the first pulse valve V1 opens and supplies a precursor pulse to the processing chamber 110, an inert gas is supplied to the buffer volume 180, and the second pulse valve V2 also opens to minimize the pressure drop in the buffer volume 180 during the pulse phase. Purge is performed following the precursor pulse. In some embodiments, the second pulse valve V2 opens simultaneously with the first pulse valve V1 and remains open. That is, both pulse valves have similar opening and closing timing cycles. 730. During the purging phase, the first pulse valve V1 is closed to prevent the precursor pulse from entering the processing chamber 110, and inert gas is flowed through the second pulse valve V2 until a predetermined pressure is achieved in the buffer volume. The second pulse valve V2 remains open or continues to pulse until the predetermined pressure is reached. Once the predetermined pressure is reached, the device 100 prepares for the next pulse or transitions to the idle phase. 740. In some embodiments, during the idle phase, the first pulse valve V1 is closed to stop the precursor pulse from entering the processing chamber 110, and after a predetermined pressure in the buffer volume is achieved, the second pulse valve V2 is closed to prevent backflow of the precursor 160 and / or inert gas from the buffer volume 180, thereby entering the idle phase. 750. Depending on the embodiment, a maintenance purge is performed. Specifically, i) the source container is separated from the gas flow by closing shut-off valves SV1 and SV2 and opening bypass valve BV, and ii) both the first pulse valve V1 and the second pulse valve V2 are opened to flush the gas line with an inert gas flow without the inert gas flow entering the source container 150.
[0109] Without limiting the technical scope and interpretation of the claimed invention, one or more technical effects of the exemplary embodiments disclosed herein are listed below. One technical effect is the improvement of substrate processing conditions. A further technical effect is the reduction of fluctuations in the low vapor pressure precursor pulse. Yet another technical effect is a more accurate and reliable supply of the low vapor pressure precursor.
[0110] We have presented various embodiments. The words "to have," "to possess," and "to include" should be interpreted in an open-ended manner and do not exclude the existence of other elements.
[0111] The above description provides a complete and useful description of the best mode for carrying out the present invention as currently envisioned by the inventors, using non-limiting examples of specific implementations and embodiments. However, as will be apparent to those skilled in the art, the details of the embodiments described above are not limiting to the present invention and may be implemented in other embodiments using equivalent means or various combinations of embodiments without departing from the features of the present invention.
[0112] Furthermore, the features of the exemplary embodiments disclosed above may be used without the use of other corresponding features. However, the above description should be understood as merely an example to illustrate the principles of the present invention and not as a limiting factor. The scope of the present invention is limited only by the appended claims.
Claims
1. A processing chamber for processing substrates, Inert gas supply system, A first introduction line connecting the inert gas supply system to the processing chamber, A source container for containing a low vapor pressure precursor, A second introduction line connects the inert gas supply system to a buffer volume including the upper space of the source container, A third introduction line connects the source container to the first introduction line via the buffer volume through the first pulse valve, A device comprising a mechanism configured to adjust the pressure in the buffer volume to a predetermined level during the purging phase of a process cycle.
2. The apparatus according to claim 1, wherein the first introduction line is configured to supply a first inert gas flow to the processing chamber, and the second introduction line is configured to supply a second inert gas flow to the buffer volume.
3. The apparatus according to claim 1, further comprising a first flow rate control means for controlling a first inert gas flow in the first introduction line upstream of the first pulse valve.
4. The apparatus according to claim 1, configured to enter an idle phase when a predetermined pressure level is achieved in the buffer volume during the purge phase.
5. The apparatus according to claim 1, further comprising a first limiting section between the first pulse valve and the buffer volume.
6. The apparatus according to claim 1, wherein the buffer volume includes an additional gas storage space configured to provide an additional buffer volume.
7. The apparatus according to any one of claims 1 to 6, wherein the second introduction line is provided with a second pulse valve, the second pulse valve is configured to control a second inert gas flow to the buffer volume so as to enable the pressure in the buffer volume to be adjusted to a predetermined level during the purging phase of the process cycle.
8. The apparatus according to claim 7, further comprising a second flow rate control means configured to control a second inert gas flow in the second introduction line upstream of the second pulse valve.
9. The apparatus according to claim 7, further comprising a control unit configured to control the opening and closing timing cycles of the first pulse valve and the second pulse valve.
10. The control unit is configured to adjust the second pulse valve based on a feedback loop, wherein a control algorithm is used to adjust the degree to which the second pulse valve opens during the opening cycle of the second pulse valve based on the detected pressure of the buffer volume, as in the apparatus according to claim 9.
11. A method for controlling the supply of low vapor pressure reactants, The low vapor pressure precursor is supplied from the source container to a buffer volume located upstream of the first pulse valve that controls the precursor pulse to the processing chamber, The inert gas is supplied from the inert gas supply system to the buffer volume, including the upper space of the source container. During the purging phase of the process cycle, the pressure within the buffer volume is adjusted to a predetermined level. Methods that include...
12. The method according to claim 11, comprising supplying a first inert gas flow to the processing chamber and supplying a second inert gas flow to the buffer volume, wherein the precursor pulse passing through the first pulse valve is supplied to the first inert gas flow.
13. The method according to claim 12, further comprising controlling the flow of a second inert gas to the buffer volume with a second pulse valve located upstream of the buffer volume.
14. The method according to claim 13, further comprising coordinating the opening and closing timing cycle of the second pulse valve with the opening and closing timing cycle of the first pulse valve.
15. The method according to claim 14, further comprising closing the first pulse valve to stop the precursor pulse to the processing chamber and, after a predetermined pressure in the buffer volume has been achieved, closing the second pulse valve to prevent backflow of the precursor and / or inert gas from the buffer volume, thereby entering an idle phase.