Patent Application
20190292662
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2018-058911, filed on Mar. 26, 2018, the entire contents of which are incorporated herein by reference.
The present disclosure relates to a technique for forming a silicon-containing nitride film on a substrate.
In forming a semiconductor device, a silicon-containing nitride film such as a silicon nitride (SiN) film is often formed on a substrate such as a semiconductor wafer (hereinafter, referred to as a “wafer”) by atomic layer deposition (ALD). In a film-forming apparatus that performs the ALD, there is a case where a wafer is mounted on a rotary table installed in a vacuum container, and the wafer that rotates by rotation of the rotary table repeatedly passes through an atmosphere to which a raw material gas is supplied and an atmosphere to which a reaction gas that reacts with the raw material gas is supplied so as to form a film.
An example of a specific process including the formation of an SiN film may include a process in which an SiN film is first formed on an underlying film, a pattern for etching the underlying film is formed on the SiN film, and then the underlying film is etched using the pattern as a mask. The pattern formed on the SiN film as such may have a relatively large height relative to its width. Since the pattern has such a shape, there is a possibility that the underlying film may not be etched due to its bending or collapsing in the case where the SiN film is not formed to have an appropriate film stress. Further, the aforementioned appropriate film stress may change under an influence of the stress of the underlying film. That is, in order to reliably etch the underling film, it is required that the stress of the SiN film formed in the ALD be adjusted.
In the related art, there is an apparatus which simultaneously supplies a silane gas, an ammonia gas and a hydrogen gas into a process container and plasmarizes these gases by a microwave to form an SiN film on a glass substrate by chemical vapor deposition (CVD). Although it is described that the stress of the SiN film is controlled and generation of pinholes in the SiN film is suppressed by controlling each of a power of the microwave and a flow rate of hydrogen, there is a desire for a technique capable of controlling the film stress to a desired value for the apparatus that performs the ALD.
Some embodiments of the present disclosure provide a technique capable of forming a silicon-containing nitride film so as to have a desired stress, in alternately supplying a raw material gas containing silicon and a nitriding gas for nitriding the raw material gas to a substrate to form the silicon-containing nitride film.
According to an embodiment of the present disclosure, there is provided a film-forming method, including: mounting a substrate on a mounting table installed in a vacuum container; adsorbing a raw material to the substrate by supplying a raw material gas containing silicon into the vacuum container; nitriding the raw material adsorbed to the substrate by supplying a nitriding gas to a plasma formation region inside the vacuum container so as to plasmarize a gas supplied to the plasma formation region and supply thus plasmarized gas to the substrate; forming a silicon-containing nitride film on the substrate by alternately and repeatedly performing the adsorbing a raw material and the nitriding the raw material; setting a stress of the silicon-containing nitride film before performing the adsorbing a raw material and nitriding the raw material; and adjusting a nitriding time during which nitriding the raw material is performed, the nitriding time having a length based on a first correspondence relationship between the stress of the silicon-containing nitride film and a parameter corresponding to the nitriding time in the plasma formation region, and the set stress of the silicon-containing nitride film.
According to an embodiment of the present disclosure, there is provided a film-forming apparatus, including: a vacuum container including therein a mounting table in which a substrate is mounted; a raw material gas supply part configured to supply a raw material gas containing silicon into the vacuum container to adsorb a raw material to the substrate; a plasma formation region located in the vacuum container so as to plasmarize a gas supplied to the plasma formation region and supply a plasmarized gas to the substrate; a nitriding gas supply part configured to supply a nitriding gas to the plasma formation region to generate a plasmarized nitriding gas and nitride the raw material adsorbed to the substrate, using the plasmarized nitriding gas; a controller configured to output a control signal such that a silicon-containing nitride film is formed by alternately and repeatedly supplying the raw material gas and supplying the plasmarized nitriding gas to the substrate; and a storage part configured to store a first correspondence relationship between a stress of the silicon-containing nitride film and a parameter corresponding to a nitriding time in the plasma formation region, wherein the controller is configured to output the control signal such that the plasmarized nitriding gas is supplied to the substrate during the nitriding time having a length that is based on a preset stress of the silicon-containing nitride film and the first correspondence relationship.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the present disclosure.
Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments.
A series of processing steps on a wafer W including a film-forming process according to the present disclosure will be described with reference to
An SiN film 15 as a thin film is formed so as to cover the amorphous Si film 13 and the underlayer film 12 along unevenness on the surface of the wafer W (
Subsequently, a film-forming apparatus 1 according to an embodiment of the present disclosure will be described with reference to a longitudinal sectional view of
In the drawing, reference numeral 21 denotes a flat, substantially circular vacuum container (process container), which is constituted by a container body 21A that forms a sidewall and a bottom portion, and a ceiling plate 21B. In the drawing, reference numeral 22 denotes a circular rotary table horizontally installed in the vacuum container 21. In the drawing, reference numeral 22A denotes a support part that supports a center of the rear surface of the rotary table 22. In the drawing, reference numeral 23 denotes a rotary mechanism which rotates the rotary table 22 clockwise in a circumferential direction, when viewed from the top side, through the support part 22A during the film-forming process. In the drawing, reference symbol X denotes a rotary shaft of the rotary table 22.
Six circular recesses 24 are provided on a top surface of the rotary table 22 along the circumferential direction (rotation direction) of the rotary table 22, and wafers W are stored in the respective recesses 24. That is, each wafer W is mounted on the rotary table 22 so as to be rotated by the rotation of the rotary table 22. In
A gas supply/exhaust unit 3, a modification region R1, a reaction region R2, and a modification region R3 are sequentially installed on the rotary table 22 toward a downstream side in a rotation direction of the rotary table 22 along the rotation direction. Hereinafter, the gas supply/exhaust unit 3 will also be described with reference to
A gas discharge port 31, an exhaust port 32 and a purge gas discharge port 33 are opened on a lower surface of the gas supply/exhaust unit 3. In
In this fan-shaped region 34, three sections 34A, 34B, and 34C are set from the center side of the rotary table 22 toward the peripheral side of the rotary table 22. Gas passages (not shown), which are partitioned from each other, are provided in the gas supply/exhaust unit 3 so that the DCS gas can be supplied independently to the respective gas discharge ports 31 provided in the sections 34A, 34B and 34C. In addition, the upstream sides of these gas passages are connected to a gas supply source (not shown) that supplies the DCS gas to the respective gas passages. Furthermore, the gas supply source that supplies the DCS gas, and each gas supply source as described hereinbelow include a valve for controlling the supply and disconnection of the gas to the downstream side, a mass flow controller for adjusting the flow rate of the gas to the downstream side, and the like.
The exhaust port 32 and the purge gas discharge port 33 are annularly opened to the periphery of the lower surface of the gas supply/exhaust unit 3 so as to surround the fan-shaped region 34 and face the top surface of the rotary table 22, and the purge gas discharge port 33 is located outside the exhaust port 32. A region inside the exhaust port 32 on the rotary table 22 forms an adsorption region RO where the adsorption of DCS to the surface of the wafer W is performed. An exhaust device (not shown) is connected to the exhaust port 32, and a gas supply part that supplies an inert gas such as an argon (Ar) gas, as a purge gas, to the purge gas discharge port 33 is connected to the purge gas discharge port 33.
During the film-forming process, the discharge of the raw material gas from the gas discharge ports 31, the exhaust from the exhaust port 32, and the discharge of the purge gas from the purge gas discharge port 33 are all performed. Thus, the raw material gas and the purge gas discharged toward the rotary table 22 are exhausted from the exhaust port 32 with a top surface of the rotary table 22 facing the exhaust port 32. By performing the discharge and the exhaust of the purge gas in this way, the atmosphere of the adsorption region RO is separated from an external atmosphere such that the raw material gas can be limitedly supplied to an adsorption region RO. That is, since the DCS gas supplied to the adsorption region RO and a gas supplied to the outside of the adsorption region RO by plasma formation units 4A to 4C as described hereinbelow and active species of the gas can be suppressed from being mixed with each other, the film-forming process by ALD can be performed on the wafer W. Further, in addition to such a role of separating the atmosphere in this way, the purge gas also has a role of removing the DCS gas excessively adsorbed to the wafer W from the wafer W.
The plasma formation units 4A, 4B and 4C for forming plasma by activating the gases existing in the respective regions are installed in the modification region R1, the reaction region R2 and the modification region R3.
Hereinafter, the plasma formation unit 4B will be described. The plasma formation unit 4B supplies a gas onto the rotary table 22 and also supplies a microwave to the gas to generate plasma on the rotary table 22. The plasma formation unit 4B includes an antenna 41 for supplying the microwave, and the antenna 41 includes a dielectric plate 42 and a metallic waveguide 43.
The dielectric plate 42 has a substantially fan shape which widens from the center side toward the peripheral side of the rotary table 22 when seen in a planar view. A substantially fan-shaped through-hole is provided in the ceiling plate 21B of the vacuum container 21 so as to correspond to the shape of the dielectric plate 42. The inner peripheral surface of the lower end portion of the through-hole slightly protrudes to the center side of the through-hole to form the support part 44. The dielectric plate 42 closes the through-hole from above and is provided so as to face the rotary table 22, and the peripheral edge of the dielectric plate 42 is supported by the support part 44.
The waveguide 43 is installed on the dielectric plate 42 and has an internal space 45 extending along a radial direction of the rotary table 22. In the drawing, reference numeral 46 denotes a slot plate forming a lower portion of the waveguide 43. The slot plate is installed so as to make contact with the dielectric plate 42 and has a plurality of slot holes 46A. In
Further, the plasma formation unit 4B has gas discharge holes 51 in the support part 44 of the dielectric plate 42. A plurality of gas discharge holes 51 are located along the circumferential direction of the vacuum container 21, and the gas is discharged to the reaction region R2 from the peripheral side of the rotary table 22 toward the center side of the rotary table 22. In addition, the gas discharge holes 51 constituting a nitriding gas supply part are connected to an NH3 gas supply source 52 for supplying an NH3 gas and an Ar gas supply source 53 for supplying an Ar gas via a pipe system, and discharge these NH3 gas and Ar gas. The NH3 gas is a nitriding gas for nitriding the raw material gas, and the Ar gas is a gas for plasmarizing the NH3 gas. That is, the plasma formation unit 4B is a unit which plasmarizes the NH3 gas and performs a nitriding process in the reaction region R2.
Further, the NH3 gas and the Ar gas are also supplied from gas injectors 54 and 55 installed near the reaction region R2 to the reaction region R2. The gas injectors 54 and 55 constituting the nitriding gas supply part are respectively installed on the upstream side of the rotary table 22 in the rotation direction and on the downstream side thereof in the rotation direction. Hereinafter, the rotation direction when it is described as the upstream side in the rotation direction and the downstream side in the rotation direction is assumed to be the rotation direction of the rotary table 22 unless specifically specified. These gas injectors 54 and 55 horizontally extend from the outside of the vacuum container 21 along the edge of the reaction region R2, and the leading end side thereof is located near the center portion of the rotary table 22 and is formed as a closed elongated tube. Furthermore, the base end portions of the gas injectors 54 and 55 are respectively connected to the NH3 gas supply source 52 and the Ar gas supply source 53 via a pipe system. A plurality of discharge holes 56 are formed in the gas injectors 54 and 55 along the longitudinal direction of the gas injectors 54 and 55 so that the supplied NH3 gas and Ar gas can be supplied to the reaction region R2.
Subsequently, the plasma formation unit 4A and the plasma formation unit 4C will be described focusing on differences from the plasma formation unit 4B. The plasma formation units 4A and 4C are configured in the same manner, and the plasma formation unit 4A is illustrated as a representative in
As described above, the modification regions R1 and R3 and the reaction region R2 already described above are formed as a plasma formation region, and are set apart from the adsorption region RO that is a supply region of the raw material gas in the rotation direction. Among these modification region R1, reaction region R2 and modification region R3, partition of the atmosphere by the purge gas, such as partition between the adsorption region R0 and its external region, is not performed.
Further, as illustrated in
A controller 60 including a computer is installed in a film-forming apparatus 2.
These processing parameters are revolutions per minute (rpm) of the rotary table 22 and a flow rate of the H2 gas from the H2 gas supply source 57 to the modification regions R1 and R3 during the film-forming process. In this example, since the flow rate of the H2 gas is selectively determined from 0 and predetermined values other than 0, the flow rate of the H2 gas as the processing parameters may more specifically refer to the presence or absence of supply of the H2 gas from the H2 gas supply source 57 to the regions R1 and R3. A graph illustrated in
In the case where the H2 gas is supplied, the stress of the SiN film 15 increases as the rpm of the rotary table 22 increases in a range of 3 to 20 rpm. In the case where the H2 gas is not supplied, the stress of the SiN film 15 decreases as the rpm of the rotary table 22 increases in a range of 3 to 5 rpm, and the stress of the SiN film 15 increases as the rpm of the rotary table 22 increases in a range of 5 to 20 rpm. In addition, when the rpm of the wafer W has an arbitrary value, the stress of the SiN film 15 becomes larger in the case where the H2 gas is supplied than in the case where the H2 gas is not supplied.
Further, according to this graph, it can be seen that the stress of the SiN film 15 can be changed within a range of −0.8 to 0.08 GPa by adjusting the rpm of the rotary table 22 within the range of 3 to 20 rpm and selecting the presence or absence of supply of the H2 gas to the modification regions R1 and R3. That is, when forming the SiN film 15 having a desired stress within the range of −0.8 to 0.08 GPa, the rpm of the rotary table 22 and the presence or absence of supply of the H2 gas from the H2 gas supply source 57 to the modification regions R1 and R3 can be determined based on this graph. In addition, when the stress of the SiN film 15 is set, there is a case where two rpms of the rotary table 22 for obtaining the set stress can be set from this graph, but in this case, for example, it is determined in advance which one of the higher value and the lower value is to be set. Further, it is considered that the reason why the stress of the SiN film 15 is changed by changing the rpm of the rotary table 22 is that the nitriding time during which the nitriding process is performed during a time period in which the wafer W is exposed to the plasmarized NH3 gas, i.e., in one cycle of ALD, is changed. In the film-forming apparatus 2, this nitriding time is adjusted by adjusting the rpm of the rotary table 22.
Subsequently, the program 64 will be described. Regarding the program 64, a group of steps are configured to cause the film-forming process as described later to be executed by transmitting a control signal to each part of the film-forming apparatus 2 to control its operation. Specifically, the rpm of the rotary table 22 by the rotary mechanism 23, the flow rates and the supply and disconnection of the respective gases by the respective gas supply parts, the exhaust amount by the exhaust port 59, the supply and disconnection of the microwave from the microwave generator 47 to the antenna 41, the power supply to the heater 25, and the like are controlled by the program 64. The control of the power supply to the heater 25 is the control of the temperature of the wafer W, and the control of the exhaust amount by the exhaust port 59 is, i.e., the control of the pressure of the interior of the vacuum container 21.
The control of the rpm of the rotary table 22 by the program 64 is performed based on the stress of the SiN film 15 set by the setting part 65 and the graph illustrated in
Hereinafter, the film-forming process performed by the film-forming apparatus 2 will be described. First, when the user sets a desired value for the stress of the SiN film 15 from the setting part 65, the controller 60 determines the rpm of the rotary table 22 and the presence or absence of supply of the H2 gas from the H2 gas supply source 57 to the modification regions R1 and R3 based on the set value and the graph of
Subsequently, when six wafers W whose surfaces are formed as illustrated in
The wafers W are sequentially and repeatedly moved over to the adsorption region R0, the modification region R1, the reaction region R2, and the modification region R3 by the rotation of the rotary table 22, and the supply of the DCS gas, the supply of active species of the H2 gas, the supply of active species of the NH3 gas, and the supply of active species of the H2 gas, when viewed from the wafers W, are sequentially repeated. As a result, an island-shaped SiN layer is grown on the surface of the wafers W so as to be modified and widened. Even thereafter, SiN is deposited on the surface of the wafer W by continuing the rotation of the rotary table 22, and a thin layer grows to become the SiN film 15 to increase the thickness of the SiN film 15. Then, as illustrated in
The film-forming process in the case where it is determined that the supply of the H2 gas from the H2 gas supply source 57 to the modification regions R1 and R3 is not performed as a result of setting the desired value for the stress of the SiN film 15 from the setting part 65 by the user will also be described. In this case, except that the supply of the H2 gas is not performed as such, the film-forming process is performed in the same manner as in the case where it is determined that the supply of the H2 gas is performed.
According to this film-forming apparatus 1, the rpm of the rotary table 22 and the presence or absence of supply of the H2 gas to the modification regions R1 and R3 are determined according to the set stress, and the SiN film 15 can be formed so as to have the set stress. Therefore, when the SiN film 15 is formed in a vertically elongated pattern as illustrated in
Meanwhile, assuming that the correspondence relationship between the stress of the SiN film 15 and the rpm of the rotary table 22 is a first correspondence relationship, both the first correspondence relationship when the H2 gas is supplied as indicated by a solid line graph in
Further, the film-forming apparatus 1 may be configured so as to perform the film-forming process at a predetermined rpm regardless of the setting of the stress of the SiN film 15 by the user such that only the presence or absence of supply of the H2 gas by setting the stress of the film by the user is determined. For example, it is assumed that the rotary table 22 is determined to rotate at 20 rpm during the film-forming process. Further, the stress of the SiN film is stored in the memory 66 for both when the H2 gas is supplied and when the H2 gas is not supplied in the case where it is rotated at 20 rpm as such. The presence or absence of supply of the H2 gas may be determined so that the stress becomes a value close to the stress set by the user using the setting part 65. That is, assuming that the correspondence relationship between the presence or absence of supply of the H2 gas and the stress of the SiN film to be formed is a second correspondence relationship, both the first correspondence relationship and the second correspondence relationship are included in the memory 66 in the configuration example described with reference to
Further, in the configuration example of the aforementioned apparatus, it is illustrated that the data of the graph of
Further, the film-forming apparatus of the present disclosure is not limited to being configured as a batch-type film-forming apparatus such as the film-forming apparatus 2 which stores a plurality of wafers W in the vacuum container 21 and processes them in batch, but it may be configured as a single-wafer-type film-forming apparatus 7 which stores and processes only one wafer W in the vacuum container 21 as illustrated in
A mounting table 71 on which a wafer W is mounted is installed in a vacuum container 21 of the film-forming apparatus 7, and a high-frequency power supply 72 for applying a high-frequency bias power (e.g., 13.56 MHz) is connected to the mounting table 71 via a matching unit 73. A heater 25 is installed in the mounting table 71 to heat the wafer W mounted on the mounting table 71. A ceiling part of the vacuum container 21 is configured as a microwave supply part 74. A microwave of TE mode of, e.g., 2.45 GHz, generated by a microwave generator 47 is supplied to a mode converter 76 via a waveguide 75 to convert it into a TEM mode and then supplied into the vacuum container 21 via a coaxial waveguide 77, a slot plate 46 having a slot hole 46A formed therein, and a dielectric plate 42 forming the ceiling surface of the vacuum container 21. Thus, each gas supplied into the vacuum container 21 can be plasmarized.
For example, an NH3 gas and an H2 gas are introduced into the vacuum container 21 using the mode converter 76 and a gas supply line 78 formed in the coaxial waveguide 77. Further, for example, a DCS gas and an Ar gas are supplied into the vacuum container 21 via the gas supply pipe 79. This Ar gas is also used as a purge gas for purging the interior of the vacuum container 21, in addition to plasmarizing the NH3 gas. In the drawing, reference numeral 81 denotes a DCS gas supply part, and in the drawing, reference numeral 82 denotes an exhaust mechanism connected to an exhaust port 59.
A correspondence relationship between the stress of the SiN film 15 and the nitriding time in one cycle of ALD is stored in a memory 66 of a controller 60 provided in the film-forming apparatus 7 is stored for each of the case where the H2 gas is supplied into the vacuum container 21 and the case where the H2 gas is not supplied into the vacuum container 21. The nitriding time in one cycle of the ALD may indicate the time required for the wafer W to pass through the reaction region R2 in the film-forming apparatus 2, and thus can be calculated by multiplying the rpm of the rotary table 22 by a predetermined coefficient. That is, the data corresponding to the memory 66 of the film-forming apparatus 2 is stored in the memory 66 of the film-forming apparatus 7.
When performing the film-forming process in the film-forming apparatus 7, the stress of the SiN film 15 is input by the user in the same manner as in the case where the film-forming process is performed by the film-forming apparatus 2, and the presence or absence of supply the H2 gas, and the nitriding time described above are determined based on the already described data stored in the memory 66. When it is determined that the supply of the H2 gas is performed, a cycle which performs the supply of the DCS gas, the supply of the purge gas (Ar gas), the supply of the H2 gas, the supply of the purge gas, the supply of the NH3 gas and the supply of the Ar gas, the supply of the purge gas, the supply of the H2 gas, and the supply of the purge gas into the vacuum container 21 is repeatedly implemented to thus form an SiN film 15 having a desired film thickness. When the H2 gas is supplied and when the NH3 gas and the Ar gas are supplied, the microwave is supplied into the vacuum container 21 to plasmarize the aforementioned gases.
On the other hand, when it is determined that the H2 gas is not supplied, a cycle which performs the supply of the DCS gas, the supply of the purge gas (Ar gas), the supply of the NH3 gas, the supply of the Ar gas, and the supply of the purge gas into the vacuum container 21 is repeatedly implemented to thus form an SiN film 15 having a desired film thickness. When the NH3 gas and the Ar gas are supplied, the microwave is supplied into the vacuum container 21 to plasmarize these gases. In both when it is determined that the H2 gas is supplied and when it is determined that the H2 gas is not supplied, the time at which the NH3 gas and the Ar gas are supplied, i.e., the aforementioned nitriding time, is controlled to be equal to the time determined as described above.
However, the present disclosure is not limited to the aforementioned embodiments, and the aforementioned embodiments may be appropriately combined or modified. For example, in the film-forming apparatus 2, the reaction region R2, and the modification regions R1 and R3 are not limited to the examples described above, but the modification regions R1 and R3 and the reaction region R2 may be sequentially arranged in the clockwise direction. Furthermore, the method of plasmarizing the H2 gas or the NH3 gas in the film-forming apparatus 2 described above is not limited to the example using the microwave, but inductively coupled plasma (ICP) may be generated using an antenna. In addition, a silicon-containing nitride film formed by the film-forming apparatus 2 is not limited to the SiN film, but may be, for example, a carbon-containing silicon nitride film (SiCN film) or the like. In order to form the SiCN film, for example, a nozzle for supplying a gas containing carbon such as methane or the like is installed in the reaction region R2, and the carbon-containing gas may be supplied together with the NH3 gas and the Ar gas to the reaction region R2 to plasmarize these gases in the region R2.
Next, evaluation tests conducted in connection with the present disclosure will be described.
The series of processes described with reference to
A schematic view of
According to the present disclosure in some embodiments, a nitriding time is adjusted based on a first correspondence relationship between a stress of a silicon-containing nitride film and parameters corresponding to the nitriding time in a plasma formation region or a hydrogen gas is supplied based on a second correspondence relationship between the stress of the silicon-containing nitride film and a flow rate of a hydrogen gas supplied to the plasma formation region, in alternately and repeatedly supplying a raw material gas containing silicon and a plasmarized nitriding gas to a substrate to form a silicon-containing nitride film. Thus, it is possible to form the stress of the silicon-containing nitride film so as to have a desired stress.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-058911 | Mar 2018 | JP | national |
