Chemical vapor deposition furnace, and method for depositing silicon nitride layer

Abstract

The disclosed invention pertains to a chemical vapor deposition furnace for depositing silicon nitride films. The furnace has a process chamber extending substantially vertically and a wafer boat for supporting a plurality of wafers within the process chamber. A process gas injector within the process chamber is provided with a plurality of vertically spaced gas injection ports to supply gas introduced at a feed end within one of the process gas injectors to the process chamber. A valve system connected to the feed end of the process gas injector is configured to connect a source of a silicon precursor and a nitrogen precursor to the feed end for depositing the silicon nitride layer. This valve system can connect the feed end of the process gas injector to a cleaning gas system to provide a cleaning gas for removing silicon nitride from the process gas injector and / or the processing chamber.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor processing equipment. More specifically, it relates to cleaning chemical vapor deposition furnaces with clean gases. Prior Technology

[0002] Chemical vapor deposition furnaces for depositing films on wafers may have a process chamber and a wafer boat for supporting multiple wafers within the process chamber. A process gas injector may be provided within the process chamber, extending along the wall of the process chamber. The process gas injector may have multiple vertically spaced gas injection holes to supply gas introduced at the feed end within the process gas injector into the process chamber for film deposition on the wafers.

[0003] The film produced by this process is deposited not only on the wafer but also on the process chamber, wafer boat, and process gas injector. The film can have high tensile stress, which can lead to significant particle contamination from the wafer flakes generated by the membrane in the reactor, wafer boat, and process gas injector. Wafer contamination can be prevented by cleaning or replacing the process chamber, wafer boat, and process gas injector before the film flakes begin to flake. For cleaning, etchant gases can be used to remove the film. If too much etchant gas is supplied, the components of the process chamber and process gas injector can be over-etched, potentially causing damage. If too little etchant gas is supplied, the components of the process chamber and process gas injector may still have the film on them.

[0004] It has been found that it is difficult to find the right balance during cleaning, enough to ensure that the parts are thoroughly cleaned while preventing over-etching. Summary of the Invention

[0005] This disclosure is provided in a simplified form to introduce a series of concepts. These concepts will be described in further detail in the embodiments described below. This disclosure is not intended to identify key or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0006] According to one objective, a chemical vapor deposition furnace with improved cleanliness can be provided.

[0007] According to one embodiment, a chemical vapor deposition furnace for depositing silicon nitride films on a plurality of wafers is provided. The furnace includes a process chamber extending substantially vertically and a wafer boat for supporting the plurality of wafers within the process chamber. The furnace may have a process gas injector extending substantially vertically along the wafer boat within the process chamber and having a plurality of vertically spaced gas injection holes to supply gas introduced at a feed end within one of the process gas injectors to the process chamber. The furnace may include a valve system operatively connected to the feed end of the process gas injector, the valve system being configured and configured to connect a source of a silicon precursor and a source of a nitrogen precursor to the feed end of the process gas injector for depositing the silicon nitride layer. This valve system can be constructed and configured to connect this feed end of the process gas injector to a clean gas system to provide a clean gas to the interior for removing silicon nitride from the process gas injector and / or processing chamber.

[0008] According to a further embodiment, a method for depositing a silicon nitride layer on a plurality of wafers is provided. The method includes: providing a plurality of wafers in a wafer boat and loading the wafer boat in a substantially vertical direction into a process chamber of a chemical vapor deposition furnace; flowing a process gas based on a silicon precursor and a nitrogen precursor into the interior of a process gas injector extending parallel to the wafer boat to a plurality of vertically spaced gas injection holes to supply the process gas across the wafers in the wafer boat to the process chamber for silicon nitride deposition; and removing the plurality of wafers from the wafer boat from the process chamber. The method may further include: providing a cleaning gas to the interior of the process gas injector and from the interior of the process gas injector to a processing chamber to remove silicon nitride from the process gas injector and / or the processing chamber.

[0009] According to another further embodiment, a method for depositing a silicon nitride layer on a plurality of wafers is provided. This method includes: providing a plurality of wafers in a wafer boat and loading the wafer boat in a substantially vertical direction into a process chamber of a chemical vapor deposition furnace; flowing a process gas based on a silicon precursor and a nitrogen precursor into the interior of a process gas injector extending parallel to the wafer boat to a plurality of vertically spaced gas injection holes to supply the process gas across the wafers in the wafer boat to the process chamber for silicon nitride deposition; and removing the plurality of wafers from the process chamber. This method may include: providing a cleaning gas to the process gas injector and simultaneously providing an inert gas to the process chamber, thereby removing silicon nitride from the process gas injector; stopping the supply of the cleaning gas to the process gas injector; and providing the inert gas to the process gas injector and simultaneously providing the cleaning gas to the processing chamber, thereby removing silicon nitride from the processing chamber.

[0010] The various embodiments disclosed herein can be applied separately or in combination with each other. The embodiments disclosed herein will be further illustrated in the embodiments with reference to some examples shown in the drawings. Simple Explanation of the Diagram

[0011] It should be understood that the elements in the drawings are shown for simplicity and clarity and are not necessarily drawn to scale. For example, some elements in the drawings may be enlarged relative to other elements to help improve the understanding of the illustrated embodiments. Figure 1 is a cross-sectional side view of an example of a chemical vapor deposition furnace including a process furnace tube. Figure 2 shows the valve system, clean gas system, and controller of the chemical vapor deposition furnace in Figure 1. Implementation

[0012] While certain embodiments and examples are disclosed below, those skilled in the art will understand that this disclosure extends beyond the specific embodiments and / or uses disclosed herein, as well as obvious modifications and equivalents thereof. Therefore, it is intended that the scope of this disclosure be not limited to the specific disclosed embodiments described below. The illustrations presented herein are not intended to represent actual views of any particular material, structure, or device, but are merely idealized representations used to describe embodiments of this disclosure.

[0013] As used herein, the terms "substrate" or "wafer" can refer to any underlying material on which devices, circuits, or films can be formed or formed. The term "semiconductor device structure" can refer to any portion of a processed or partially processed semiconductor structure that is, includes, or defines at least a portion of the active or passive components of a semiconductor device to be formed on or in a semiconductor substrate.

[0014] Semiconductor substrates can be processed in batches in vertical furnaces. One example of this process is the deposition of various material layers on the substrate. For example, some processes may be based on chlorides and ammonia.

[0015] Figure 1 is a cross-sectional side view of an example of a chemical vapor deposition furnace, which includes a low-pressure process tube 1 defining a low-pressure process chamber 4. The furnace may include a vertically movable door 5 configured to close a central inlet opening 10 in the lower and / or upper flanges 3, and configured to support a wafer boat 6 configured to hold a plurality of substrates. The upper and lower flanges 3 may partially close the open ends of the process furnace tube 1. A liner 2 may extend along the process furnace tube 1 to protect the furnace tube 1.

[0016] Door 5 may be equipped with a drive 7 to allow rotation of wafer boat 6 within process chamber 4. A base 9 may be provided between the drive 7 and wafer boat 6. The base 9 may be equipped with a heater and / or thermal insulator to improve thermal uniformity of the wafers within the boat 6. The liner 2 may close at its higher end into, for example, a dome shape, and may be substantially closed above an opening at its bottom for gas. The lower flange 3 includes an inlet opening 10 configured for insertion and removal of the boat 6, which is configured to carry a plurality of substrates within process chamber 4.

[0017] A process gas injector 17 may be provided within the process chamber 4, extending substantially vertically across the height of the substantially wafer boat 6. A liner 2 extending along the furnace tube 1 may have radially outwardly extending protrusions for accommodating the process gas injector 17. The process gas injector 17 includes a feed end 18 operatively connected to a first feed line 19, which may be connected to a source of silicon precursor 20. The feed end 18 may also be operatively connected to a second feed line 21, which may be connected to a source of nitrogen precursor 22.

[0018] The silicon precursor provided at the feed end 18 of the process gas injector may contain silane. The silicon precursor may contain one or more compounds selected from the group consisting of monochlorosilane, dichlorosilane, trichlorosilane, tetrachlorosilane, disilane, and trisilane. The nitrogen precursor provided at the feed end 18 of the process gas injector may contain ammonia.

[0019] The nitrogen and silicon precursors begin to mix and react with each other when they enter the process gas injector 17 at the feed end 18. This mixing ensures good productivity and uniformity in the deposition process. The process gas flow rate through the process gas injector 17 into the process chamber 4 can be between 100 cubic centimeters per minute (SCCM) and 500 cubic centimeters per minute, preferably 250 cubic centimeters per minute.

[0020] Optionally, nitrogen and silicon precursors can be sequentially supplied to process chamber 4 in atomic layer deposition mode via valve system 31. The latter provides good feasibility for controlling layer thickness.

[0021] The process gas injector 17 may be provided with a plurality of vertically spaced gas injection holes 23 to uniformly supply the gas received inside the injector 17 across the length of the wafer boat 6 to the process chamber 4 at the feed end 18. These plurality of gas injection holes may extend across a portion of the height of the gas process gas injector 17. The first feed line 19 and the second feed line 21 may be partially provided as channels through one of the flanges 3, and further as pipes to the source of the nitrogen precursor 22 or the silicon precursor 20.

[0022] These plurality of gas injection holes may extend across a portion of the height of the process gas injector 17. Each gas injection hole 23 may have a gas injection hole diameter of at least about 1 millimeter (mm). The diameter of the gas injection hole may, for example, be about 3 millimeters. The diameters of all gas injection holes in the process gas injector 17 may be substantially equal. Each gas injection hole may have a gas injection hole area, wherein the total area of ​​all gas injection hole areas in the process gas injector 17 may be at least about 30 square millimeters (mm²). The total area of ​​all gas injection hole areas may be between about 200 square millimeters and 400 square millimeters.

[0023] The chemical vapor deposition furnace may be equipped with a purge gas injection system, which includes a purge line 24 to provide purge gas 25 to the process chamber 4 near the lower end of the process chamber 4. The purge line 24 may be partially provided as a passage through one of the flanges 3 and further serve as a furnace tube to the source of the purge gas 25. The purge gas injection system may be configured to provide an inert gas as the purge gas. The purge gas injection system may be configured to provide nitrogen as the inert purge gas. Nitrogen is an inexpensive inert gas readily available in wafer fabrication plants.

[0024] The purge gas injection system can be configured to provide purge gas at a rate between 15 and 100 cubic centimeters per minute (SCCM), preferably between 30 and 70 cubic centimeters per minute, and most preferably approximately 50 cubic centimeters per minute, into the process chamber. The purge gas injection system can be configured to provide an inert gas as purge gas within the processing chamber to improve the uniformity of silicon nitride deposition on the wafer across the wafer boat and at a certain height. The purge gas injection system may include a tuning knob to adjust the flow of purge gas within the processing chamber, thereby adjusting the uniformity of silicon nitride deposition on the wafer across the wafer boat and at a certain height.

[0025] The chemical vapor deposition furnace may be provided with a gas exhaust opening 8 for removing gas at the lower end of the process chamber 4. In this manner, by closing the gas supply to the liner 2 above the liner opening, supplying process gas via a process gas injector 17 and purge gas 25 via a purge gas injection system to the process chamber 4, and removing gas from the process chamber 4 at the lower end of the process chamber 4 via the gas exhaust opening 8, a downward flow 26 can be created in the process chamber 4. This downward flow can transport reaction byproducts, contaminants from the substrate, boat 6, liner 2, and / or the support area of ​​the liner 2 on the flange 3, downward and radially outward to the gas exhaust opening 8 away from the processed substrate W. The gas exhaust opening 8 for removing gas from the process chamber 4 can be operatively connected to a pump. The pump can be used to control the pressure in the process chamber 4 to between 20 mTorr and 500 mTorr, more preferably between 50 mTorr and 300 mTorr, and most preferably between 100 mTorr and 150 mTorr.

[0026] A chemical vapor deposition (CVD) furnace can be used to deposit silicon nitride layers on a wafer W by providing a plurality of wafers in a wafer boat 6 and loading the wafer boat into the process chamber 4 of the CVD furnace in a substantially vertical direction; allowing process gases based on silicon precursor 20 and nitrogen precursor 22 to flow into a process gas injector 17 and then to a plurality of vertically spaced gas injection holes 23 to supply process gases to the process chamber 4 across the wafers in the wafer boat 6. Optionally, purge gas 25 and / or process gases can be supplied to the process chamber 4 near the lower end of the process chamber 4. During the deposition process, the pressure in the process chamber 4 can be controlled to be between 20 mTorr and 500 mTorr, more preferably between 50 mTorr and 300 mTorr, and most preferably between 100 mTorr and 150 mTorr.

[0027] The film produced by this deposition process is deposited not only on the wafer but also inside and outside the substrate 2 of the process chamber 4, the wafer boat 6, and the process gas injector 17. The film can have high tensile stress, which can lead to high-level wafer contamination from film shedding from the reaction chamber 4, the wafer boat 6, and the process gas injector 17. Process chamber 4, the wafer boat 6, and the process gas injector 17 can be cleaned or replaced before film shedding begins to prevent wafer contamination.

[0028] For cleaning, etchant gases can be used to remove the film. If too much etchant gas is supplied, the components of the process chamber and process gas injector may be over-etched, potentially damaging them. If too little etchant gas is supplied, the components of the process chamber and process gas injector may still have a film on them. It has been found that finding the correct balance during cleaning—enough to ensure components are adequately cleaned while preventing over-etching—is difficult. This is particularly true for the interior of process gas injector 17, due to the high concentration of process gases, which are especially sensitive to deposition.

[0029] Figure 2 illustrates the valve system 31 and cleaning systems 43, 33 used in conjunction with the chemical vapor deposition furnace of Figure 1. Figure 2 shows that the feed end 18 of the process gas injector 17 is connected to the second source 41 of the silicon precursor 20 via a second feed line 21 and a second valve 35. The feed end 18 of the process gas injector 17 can also be connected to the first source 39 of the nitrogen precursor 22 via a first feed line 19 and a second valve 37. As depicted, both the first valve 35 and the second valve 37 are closed for both the silicon precursor 20 and the nitrogen precursor 22. However, if both the first valve 35 and the second valve 37 are open for both the silicon precursor 20 and the nitrogen precursor 22, the feed end 18 of the process gas injector 17 will receive the process gas used to deposit the silicon nitride layer in the process chamber 4.

[0030] Valve system 31 can be further constructed and configured to connect the feed end 18 of process gas injector 17 to a clean gas system 43 equipped with a clean gas source. This can be accomplished by shutting off the second source 41 of silicon precursor 20 via the second feed line 21 using a first valve 35, as depicted in Figure 2. Simultaneously, the flow of nitrogen precursor 22 from the first source 39 via the first feed line 19 to the feed end 18 can be shut off by a second valve 37. In this way, clean gas 33 can be supplied from clean gas system 43 to the interior of process gas injector 17 to remove silicon nitride there, and later, when it leaves the interior of process gas injector 17 via gas injection port 23 into processing chamber 4, it can clean processing chamber 4. Since the interior of process gas injector 17 can be a first area where fresh clean gas 33 is supplied, the etching rate inside can be higher than the etching rate in reaction chamber 4. This is advantageous because the deposition rate inside the process gas injector 17 is also higher, so we can benefit particularly from the higher etching rate inside the process gas injector 17 there.

[0031] It is understood that "source" refers to a container containing gas or a gas supplying gas. As depicted, the first valve 35 can be a two-way valve that connects either the silicon precursor or the cleaning gas to the feed end 18. The valve system 31 can also be designed with two valves that perform this function separately.

[0032] A controller 50 may be provided, operably connected to the valve system 31 and the cleaning system 43. The controller 50 can control the first valve 35 and the second valve 37 during deposition and cleaning. The controller 50 may include a memory 50 and a processor 53. The controller 50 may include a clock, for example, as part of the processor 53, to run the formula as a function of time. The formula for deposition and / or cleaning may be stored in the memory 50.

[0033] Clean gas system 43 may be configured and configured to provide clean gas 33 mixed with inert gas received from inert gas source 45. Inert gas source 45 may provide argon, helium, or nitrogen as inert gas. Clean gas system 43 may be configured and configured to provide clean gas mixed with argon, helium, or nitrogen. Clean gas system 43 may be configured and configured to provide clean gas containing at least one halogen from clean gas source 33, wherein the at least one halogen is selected from the group consisting of fluorine, chlorine, bromine, and iodine. Clean gas system 43 may be configured and configured to provide clean gas containing nitrogen trifluoride (NF3) from clean gas source 33.

[0034] Clean gas system 43 can be configured and configured to mix clean gas from clean gas source 33 with inert gas from inert gas source 45. The clean gas can be mixed by clean gas system 43 to a mixture of 1% to 20%, preferably 3% to 10%, and most preferably about 5% in the inert gas. The mixing by clean gas system 43 can be controlled by controller 50 to achieve a partial pressure of clean gas within a required range. Over-etching can not occur within the required range. Clean gas system 43 can be configured and configured to supply clean gas (pure etchant) to valve system 31 at a flow rate between 10 and 300 cubic centimeters per minute (SCCM), preferably between 50 and 200 cubic centimeters per minute. Because it is mixed with an inert gas, this means (if using a 5% etchant concentration) a total flow rate of 0.2 liters per minute (SLM) to 6 liters per minute, preferably 1 liters per minute to 4 liters per minute.

[0035] The cleaning gas can be fluorine, and is mixed by the cleaning gas system 43 into a mixture of 1% to 20%, more preferably 3% to 10%, and most preferably about 5% in helium (as an inert gas).

[0036] A chemical vapor deposition furnace can be constructed and configured to provide clean gas within the process gas injector 17 using a clean gas system 43. The furnace can be constructed to provide clean gas within this furnace at a partial pressure between 0.01 Torr and 0.5 Torr, preferably 0.05 Torr. At this partial pressure, relatively thick layers of cleaning within the injector 17 can be achieved relatively quickly.

[0037] A chemical vapor deposition furnace can be constructed and configured to supply clean gas to the process chamber 4 via a process gas injector 17 using a clean gas system 43. A gas exhaust port 8 for removing gas from the process chamber 4 can be operatively connected to a pump. The pump can be connected to a controller 50 to control the pressure in the process chamber 4 to a partial pressure of the clean gas between 0.001 Torr and 0.1 Torr, and preferably approximately 0.02 Torr. At this partial pressure, relatively thin layers of cleaning can be achieved relatively slowly in the process chamber 4, avoiding over-etching of the process chamber 4. Over-etching can negatively impact the lifespan of the process gas injector 17, the furnace tube 1, or the liner 2, as it can roughen surfaces. The chemical vapor deposition furnace may be equipped with a purge gas injection system 24, which is constructed and configured to supply purge gas 25 to the process chamber 4 near the lower end of the process chamber 4 to reduce the particle pressure of the clean gas in the process chamber. The purge gas injection system 24 can be connected to the controller 50 to control the partial pressure of the cleaning gas to between 0.001 Torr and 0.1 Torr, and optimally to about 0.02 Torr, for cleaning the process chamber 4 while avoiding over-etching.

[0038] When the interior of the process gas injector 17 is thoroughly cleaned, the partial pressure of the cleaning gas can be increased by the controller 50 to clean the process chamber 4.

[0039] Optionally, the purge gas injection system 24 can be constructed and configured to provide cleaning gas to the process chamber 4 near the lower end of the process chamber 4. This can be implemented as an additional or separate solution for cleaning gas via the process gas injector. This helps to clean the process chamber 4 in a timely manner.

[0040] In one embodiment, the cleaning of the process gas injector 17 and the process chamber 4 can be decoupled from each other. This can be achieved through a two-step cleaning process. Therefore, the chemical vapor deposition furnace can be constructed and configured to provide cleaning gas to the interior of the process gas injector 17 in the first step using a cleaning gas system 43, while inert gas from an inert gas source 45 can be directly supplied to the process chamber 4. This allows for modulation of the partial pressure in the process chamber 4. Etching of the film produced by the deposition process also occurs in the process chamber 4 as the cleaning gas exits the interior of the process gas injector 17 through the gas injection port 23 into the process chamber 4. Providing inert gas to the process chamber 4 can thus provide a way to reduce the partial pressure of the cleaning gas in the process chamber 4. This can result in a reduced etching rate of the film produced by the deposition process in the process chamber 4. This advantageously allows for the avoidance of over-etching of the process chamber 4 while cleaning the process gas injector 17, thereby not jeopardizing the service life of the process chamber 4.

[0041] Therefore, decoupling the cleaning of gas injector 17 from the cleaning of process chamber 4 can result in the gas injector 17 being cleaned during the first step.

[0042] During the first step, the partial pressure of the cleaning gas in the process gas injector 17 can be configured such that the ratio of the etching rate of the film produced by the deposition process in the process gas injector 17 to that in the process chamber 4 can be about 2 or more, so as to achieve cleaning of the main process gas injector 17 during the first step cleaning.

[0043] Then, a pump connectable to controller 50 can adjust the partial pressure of the cleaning gas in process chamber 4 to less than 0.2 Torr during the first step, while simultaneously adjusting the partial pressure of the cleaning gas in process gas injector 17 to above 0.2 Torr. This advantageously allows for a higher selectivity in providing cleaning of process gas injector 17 compared to cleaning of process chamber 4 during the first step.

[0044] In one embodiment, the partial pressure of the cleaning gas in the process gas injector during the first step can be in the range of 0.2 Torr to 0.5 Torr.

[0045] In one embodiment, the inert gas can be supplied directly from the inert gas source 45 to the process chamber 4 during the first step via a bottom inlet.

[0046] In one embodiment, the direct supply of inert gas to process chamber 4 during the first step can be accomplished by another process gas injector 17, which may be present in process chamber 4. This can be the case when multiple process gas injectors are used, each directed to the individual supply of different precursors that may be included in the process gas.

[0047] After the cleaning of the process gas injector 17 is completed during the first step, the supply of cleaning gas to the gas injector 17 can be stopped, and during the second step, inert gas from the inert gas source 45 can be used instead. Then, only the cleaning gas can be supplied to the process chamber 4, thereby performing the second cleaning step. This allows the cleaning of the process chamber 4 to be decoupled from the cleaning of the process gas injector 17. Decoupling allows the process gas injector 17 and the process chamber 4 to be cleaned independently, thereby minimizing the risk of over-etching of the process gas injector 17 and / or the process chamber 4.

[0048] In one embodiment, the clean gas can be supplied to the process chamber 4 directly through the bottom inlet. In another embodiment, the clean gas can be supplied to the process chamber 4 through another process gas injector 17 that may be present in the process chamber 4.

[0049] A pump that can be connected to controller 50 can adjust the partial pressure of the cleaning gas in process chamber 4 to be equal to or higher than 0.2 Torr during the second step. This advantageously allows for the cleaning of process chamber 4 while providing inert gas to process gas injector 17.

[0050] In an exemplary embodiment of the two-step cleaning removal of silicon nitride, a 5% F2 gas mixed with He can be used as the cleaning gas at 550°C. During the first step, the cleaning gas can be supplied to the process gas injector 17 at approximately 0.3 Torr. During the second step, the cleaning gas can be supplied to the process chamber 4 at approximately 0.2 Torr.

[0051] It should be understood that as the thickness of the film to be cleaned and the percentage of inert gas in the cleaning gas change, the partial pressure of the cleaning gas and the cleaning time required for etching films produced by the deposition process can be altered.

[0052] The chemical vapor deposition furnace may be equipped with a heater 11 to heat the wafer in the wafer boat 6. The chemical vapor deposition furnace may also be equipped with a temperature measurement system mounted on the flange 3 and extending along the outer surface of the liner 2 toward the top of the liner to measure temperature. The temperature measurement system may include a beam with a plurality of temperature sensors provided along the length of the beam to measure temperature at different heights. The heater 11 and the temperature measurement system may be connected to a controller 50 to control the temperature of the process chamber 4 during cleaning and deposition.

[0053] Heater 11, controlled by controller 50, heats the top of process chamber 4 to a temperature higher than the bottom of process chamber 4 during the cleaning initiation phase. While providing the first cleaning gas, the top portion 4 of process chamber 4 is initially heated to 625 degrees Celsius by heater 11, and the lower portion of process chamber 4 is heated to below 575 degrees Celsius. This prevents the consumption of cleaning gas at the bottom of process gas injector 17 and enables etching at the top of process gas injector 17. Subsequently, under the control of controller 50, heater 11 can slowly increase the temperature at the center of process chamber 4 and later at the bottom to increase etching in the lower portion of process gas injector 17.

[0054] Preferred embodiments are particularly suitable for chemicals in which a chlorine-containing precursor is used in combination with a nitrogen precursor such as ammonia (NH3). Examples of chlorine-containing precursors are: TiCl4, SiCl2H2, HfCl4, and AlCl3. It must be understood that the nitrogen precursor may not be nitrogen. The nitrogen precursor may be reactive, while nitrogen may be non-reactive.

[0055] Although illustrative embodiments of this disclosure have been described above with reference to the accompanying drawings, it should be understood that this disclosure is not limited to these embodiments. Variations of the disclosed embodiments can be understood and practiced by those skilled in the art in the course of practicing the claimed invention through study of the drawings, this disclosure, and the appended claims.

[0056] Throughout this specification, the reference to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in that embodiment is included in at least one embodiment disclosed herein. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing in different places throughout this specification do not necessarily all refer to the same embodiment. Furthermore, it should be noted that particular features, structures, or characteristics of one or more embodiments can be combined in any suitable manner to form novel embodiments not explicitly described.

[0057] 1: Low-pressure furnace tube 2: Liner 3: Flange 4: Low-pressure process chamber 5: Door 6: Wafer Boat 7: Drive components 8: Gas exhaust opening 9: Base 10: Entrance opening 11: Heater 17: Process Gas Injector 18: Feed end 19: First feed line 20: Silicon precursors 21: Second feed line 22: Nitrogen precursors 23: Gas injection port 24: Purge lines, purging gas injection system 25: Purge gas 26: Flowing downwards 31: Valve System 33: Cleaning System 35: First valve 37: Second valve 39: The First Source 41: The Second Source 43: Cleaning system, clean gas system 45: Inert gas source 50: Controller 51: Memory 53: Processor W: substrate

Claims

1. A chemical vapor deposition furnace for depositing silicon nitride films on a plurality of wafers, comprising: A process chamber extending in a vertical direction; a wafer boat for supporting the wafers within the process chamber; A process gas injector extends along the wafer boat in the vertical direction within the process chamber and has a plurality of vertically spaced gas injection holes to supply gas introduced at a feed end inside one of the process gas injectors to the process chamber; a liner accommodates the process gas injector and extends along the vertical direction to radially surround the wafer boat, the liner including a cover that covers the end of the wafer boat opposite to the feed end of the process gas injector in the vertical direction; A valve system operatively connected to the feed end of the process gas injector and configured to connect a source of a silicon precursor and a source of a nitrogen precursor to the feed end of the process gas injector for depositing a silicon nitride layer; wherein the valve system is further configured to connect the feed end of the process gas injector to a cleaning gas system to provide a cleaning gas to the interior for removing silicon nitride from the process gas injector and / or the process chamber; A purging system is disposed near the lower end of the process chamber and is completely below the liner. The purging system is configured to supply an inert gas directly to the lower end of the process chamber below the liner. A controller is operatively connected to the valve system, the cleaning gas system, and the purging system to control the purging system to supply a purging gas to dilute the cleaning gas in the process chamber during the supply of the cleaning gas, and to control the purging system to supply the inert gas directly to the process chamber, decoupled from the inert gas supplied to the process chamber via the vertically spaced gas injection holes.

2. The chemical vapor deposition furnace of claim 1, wherein the gas injection holes of the process gas injector extend across a height of the wafer boat.

3. The chemical vapor deposition furnace of claim 1, wherein the clean gas system is connected to a clean gas source.

4. The chemical vapor deposition furnace of claim 1, wherein the clean gas system is constructed and configured to provide the clean gas mixed with the inert gas.

5. The chemical vapor deposition furnace of claim 4, wherein the clean gas system is constructed and configured to provide the clean gas mixed with argon, helium or nitrogen as the inert gas.

6. The chemical vapor deposition furnace of claim 1, wherein the clean gas system is configured and configured to provide the clean gas comprising at least one halogen selected from the group consisting of fluorine, chlorine, bromine and iodine.

7. The chemical vapor deposition furnace of claim 1, wherein the clean gas system is constructed and configured to provide the clean gas including nitrogen trifluoride (NF3).

8. The chemical vapor deposition furnace of claim 1, wherein the clean gas system is constructed and configured to provide the clean gas including fluorine (F2).

9. The chemical vapor deposition furnace of claim 1, wherein the clean gas system is constructed and configured to provide the clean gas as a mixture of 1% to 20% helium as the inert gas.

10. The chemical vapor deposition furnace of claim 1, wherein the clean gas system is constructed and configured to provide the clean gas at a flow rate between 10 cubic centimeters per minute (SCCM) and 300 cubic centimeters per minute.

11. The chemical vapor deposition furnace of claim 1, wherein the furnace is constructed and configured to supply the clean gas at a partial pressure between 0.01 Torr and 0.5 Torr within the process gas injector using the clean gas system.

12. The chemical vapor deposition furnace of claim 1, wherein the furnace is constructed and configured to provide the clean gas in the process chamber by the clean gas system at a partial pressure between 0.001 Torr and 0.1 Torr.

13. The chemical vapor deposition furnace of claim 1, wherein the purging system is disposed below the wafer boat and configured to directly supply the inert gas to the lower end of the process chamber below the wafer boat.

14. The chemical vapor deposition furnace of claim 1, wherein the chemical vapor deposition furnace is provided with: a heater for heating the process chamber, wherein, The controller is operatively connected to the valve system, the cleaning gas system, the purging system, and the heater to control the heater to heat the process chamber during cleaning.

15. The chemical vapor deposition furnace of claim 14, wherein the heater is constructed and configured to create a temperature difference across the process chamber in the vertical direction, and the controller controls the heater to provide a higher temperature in the top of the process chamber than the bottom of the process chamber during cleaning, to improve cleaning in the top.

16. The chemical vapor deposition furnace of claim 1, wherein the chemical vapor deposition furnace is provided with: a pump for removing gas from the process chamber; and wherein the controller is operatively connected to the valve system, the cleaning gas system, the purging system, and the pump to control the pump to remove gas from the process chamber during cleaning.

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