Method of determining plasma abnormality, method of manufacturing semiconductor device, and substrate processing apparatus

There is provided a technique that includes: imaging a gas supply hole configured to supply a plasma-converted gas into a process chamber by using an imaging device disposed in the process chamber; detecting a plasma emission intensity based on an image of the imaged gas supply hole; and determining at least one of whether abnormal plasma discharge has occurred and whether plasma flickering has occurred based on the detected plasma emission intensity.

TECHNICAL FIELD

The present disclosure relates to a method of determining a plasma abnormality, a method of manufacturing a semiconductor device, and a substrate processing apparatus.

BACKGROUND

As a semiconductor device manufacturing process, a substrate processing process is often carried out in which a substrate is loaded into a process chamber of a substrate processing apparatus, a precursor gas, a reaction gas and so on supplied into the process chamber are activated by using plasma, and various films such as an insulating film, a semiconductor film, a conductor film and the like are formed on the substrate or removed from the substrate. In the related art, the plasma is used for promoting the reaction of a deposited thin film, removing impurities from the thin film, or assisting the chemical reaction of a film-forming precursor.

However, when a plasma electrode deteriorates due to aging or unexpected causes, abnormal discharge such as arc discharge, or plasma flickering may occur in a plasma generation part or an excited species supply port around the plasma generation part. However, since methods for dealing with these abnormal states are different, there is a case where it is necessary to strictly determine the abnormality that has occurred.

SUMMARY

Some embodiments of the present disclosure provide a technique capable of determining a plasma abnormality.

According to an embodiment of the present disclosure, there is provided a technique including:

imaging a gas supply hole configured to supply a plasma-converted gas into a process chamber by using an imaging device disposed in the process chamber;

detecting a plasma emission intensity based on an image of the imaged gas supply hole; and

determining at least one of whether abnormal plasma discharge has occurred and whether plasma flickering has occurred based on the detected plasma emission intensity.

DETAILED DESCRIPTION

Embodiments of the Present Disclosure

A substrate processing apparatus according to one embodiment of the present disclosure will now be described with reference toFIGS. 1 to 9.

(1) Configuration of Substrate Processing Apparatus

A substrate processing apparatus according to one embodiment of the present disclosure includes a process furnace202, as illustrated inFIG. 1. The process furnace202is a so-called vertical furnace in which substrates can be accommodated in multiple stages in a vertical direction, and includes a heater207as a heating device (a heating mechanism). The heater207has a cylindrical shape and is supported by a heat base (not shown) serving as a support plate so as to be vertically installed. As will be described later, the heater207functions as an activation mechanism (an excitation part) configured to thermally activate (excite) a gas.

A reaction tube203is disposed inside the heater207to be concentric with the heater207. The reaction tube203is made of, for example, a heat resistant material such as quartz (SiO2), silicon carbide (SiC) or the like, and has a cylindrical shape with its upper end closed and its lower end opened. A manifold (inlet flange)209is disposed under the reaction tube203so as to be concentric with the reaction tube203. The manifold209is made of, for example, a metal material such as stainless steel (SUS) or the like, and has a cylindrical shape with both upper and lower ends thereof opened. The upper end portion of the manifold209engages with the lower end portion of the reaction tube203so as to support the reaction tube203. An O-ring220aserving as a seal member is installed between the manifold209and the reaction tube203. As the manifold209is supported by the heater base, the reaction tube203comes into a vertically installed state. A process vessel (reaction vessel) mainly includes the reaction tube203and the manifold209. A process chamber201is formed in a hollow cylindrical portion of the process vessel. The process chamber201is configured to be able to accommodate a plurality of wafers200as substrates. The process vessel is not limited to the above configuration, and only the reaction tube203may be referred to as the process vessel.

Nozzles249aand249bare installed in the process chamber201so as to penetrate a sidewall of the manifold209. Gas supply pipes232aand232bare connected to the nozzles249aand249b, respectively. In this manner, the two nozzles249aand249band the two gas supply pipes232aand232bare installed in the reaction tube203, thereby allowing plural kinds of gases to be supplied into the process chamber201. When the manifold209is not installed and only the reaction tube203is used as the process vessel, the nozzles249aand249bmay be installed so as to penetrate the sidewall of the reaction tube203.

Mass flow controllers (MFCs)241aand241b, which are flow rate controllers (flow rate control parts), and valves243aand243b, which are opening/closing valves, are installed in the gas supply pipes232aand232bsequentially from upstream sides of gas flow, respectively. Gas supply pipes232cand232dfor supplying an inert gas are connected to the gas supply pipes232aand232bat downstream sides of the valves243aand243b, respectively. MFCs241cand241dand valves243cand243dare respectively installed in the gas supply pipes232cand232dsequentially from upstream sides of gas flow.

As illustrated inFIG. 2, the nozzle249ais installed in a space between an inner wall of the reaction tube203and the wafers200so as to extend upward along a stacking direction of the wafers200from a lower portion to an upper portion of the inner wall of the reaction tube203. Specifically, the nozzle249ais installed at a lateral side of the wafer arrangement region (mounting region) in which the wafers200are arranged (mounted), namely in a region which horizontally surrounds the wafer arrangement region, so as to extend along the wafer arrangement region. That is, the nozzle249ais installed in a perpendicular relationship with the surfaces (flat surfaces) of the wafers200at a lateral side of the end portions (peripheral edge portions) of the wafers200, which are loaded into the process chamber201.

Gas supply holes250afor supplying a gas is formed on the side surface of the nozzle249a. The gas supply holes250aare opened toward the center of the reaction tube203so as to allow a gas to be supplied toward the wafers200. The gas supply holes250amay be formed in a plural number between a lower portion and an upper portion of the reaction tube203. The respective gas supply holes250amay be formed to have the same aperture area and may be formed at the same aperture pitch.

The nozzle249bis installed within a buffer chamber237serving as a gas dispersion space. As illustrated inFIG. 2, the buffer chamber237is disposed in an annular space (in a plane view) between the inner wall of the reaction tube203and the wafers200such that the buffer chamber237extends upward along the stack direction of the wafers200from the lower portion to the upper portion of the inner wall of the reaction tube203. Specifically, the buffer chamber237is formed by a buffer structure300along the wafer arrangement region in a region horizontally surrounding the wafer arrangement region at the lateral side of the wafer arrangement region. The buffer structure300is made of an insulating material such as quartz. Gas supply holes302and304for supplying a gas or active species to be described later into the process chamber201are formed on an arc-shaped wall surface of the buffer structure300.

As illustrated inFIG. 2, the gas supply holes302and304are opened toward the center of the reaction tube203at positions facing plasma generation regions224aand224bbetween rod-shaped electrodes269and270(which will be described later) and between rod-shaped electrodes270and271(which will be described later) respectively, thereby allowing a gas or active species (which will be described later) to be supplied toward the wafers200. A plurality of gas supply holes302and304may be formed between the lower portion and the upper portion of the reaction tube203. The plurality of gas supply holes302and304may be formed to have the same aperture area at the same aperture pitch.

The nozzle249bis disposed so as to extend upward along the stack direction of the wafers200from the lower portion to the upper portion of the inner wall of the reaction tube203. Specifically, the nozzle249bis installed in a region horizontally surrounding the wafer arrangement region in which the wafers200are arranged at the lateral side of the wafer arrangement region inside the buffer structure300, along the wafer arrangement region. That is, the nozzle249bis installed in a perpendicular relationship with the surfaces of the wafers200at the lateral side of the end portions of the wafers200, which are loaded into the process chamber201.

A gas supply hole250bfor supplying a gas is formed on the side surface of the nozzle249b. The gas supply hole250bis opened toward a wall surface formed in the radial direction with respect to the arc-shaped wall surface of the buffer structure300, thereby allowing a gas to be supplied toward the wall surface. As a result, the reaction gas is dispersed in the buffer chamber237and is not directly blown to the rod-shaped electrodes269to271, thereby suppressing generation of particles. As with the gas supply hole250a, a plurality of gas supply holes250bmay be formed between the lower portion and the upper portion of the reaction tube203.

A precursor containing a predetermined element, for example, a silane precursor gas containing silicon (Si) as the predetermined element, is supplied from the gas supply pipe232ainto the process chamber201via the MFC241a, the valve243aand the nozzle249a.

An example of the silane precursor gas may include a precursor gas containing Si and a halogen element, that is, a halosilane precursor gas. The halosilane precursor is a silane precursor having a halogen group. The halogen element includes at least one selected from the group including chlorine (Cl), fluorine (F), bromine (Br) and iodine (I).

An example of the halosilane precursor gas may include a precursor gas containing Si and Cl, that is, a chlorosilane precursor gas. An example of the chlorosilane precursor gas may include a dichlorosilane (SiH2Cl2, abbreviation: DCS) gas.

A reactant containing an element different from the above-mentioned predetermined element, for example, a nitrogen (N)-containing gas as a reaction gas, is supplied from the gas supply pipe232binto the process chamber201via the MFC241b, the valve243band the nozzle249b. An example of the N-containing gas may include a hydrogen nitride-based gas. The hydrogen nitride-based gas is a substance including only two elements of N and H, and acts as a nitriding gas, that is, an N source. An example of the hydrogen nitride-based gas may include an ammonia (NH3) gas.

An inert gas, for example, a nitrogen (N2) gas, is supplied from the gas supply pipes232cand232dinto the process chamber201via the MFCs241cand241d, the valves243cand243d, the gas supply pipes232aand232band the nozzles249aand249b, respectively.

A precursor supply system as a first supply system mainly includes the gas supply pipe232a, the MFC241aand the valve243a. A reactant supply system as a second supply system mainly includes the gas supply pipe232b, the MFC241band the valve243b. An inert gas supply system mainly includes the gas supply pipes232cand232d, the MFCs241cand241dand the valves243cand243d. The precursor supply system, the reactant supply system and the inert gas supply system are collectively referred to simply as a gas supply system (gas supply part).

As illustrated inFIG. 2, three rod-shaped electrodes269,270and271, which are made of a conductor and have an elongated structure, are disposed in the buffer chamber237along the arrangement direction of the wafers200to span from the lower portion to the upper portion of the reaction tube203. Each of the rod-shaped electrodes269,270and271is installed parallel to the nozzle249b. Each of the rod-shaped electrodes269,270and271is covered with and protected by an electrode protection tube275over a region spanning from an upper portion to a lower portion thereof. Of the rod-shaped electrodes269,270and271, the rod-shaped electrodes269and271disposed at both ends are connected to a high frequency power supply273via a matching device272and an impedance measuring device274. The rod-shaped electrode270is grounded to the ground that is the reference potential. That is, the rod-shaped electrodes connected to the high frequency power supply273and the grounded rod-shaped electrode are alternately arranged. The rod-shaped electrode270interposed between the rod-shaped electrodes269and271connected to the high frequency power supply273is used in common for the rod-shaped electrodes269and271as the grounded rod-shaped electrodes. In other words, the grounded rod-shaped electrode270is disposed so as to be sandwiched between the rod-shaped electrodes269and271connected to the adjacent high frequency power supply273, and the rod-shaped electrode269and the rod-shaped electrode270, and, similarly, the rod-shaped electrode271and the rod-shaped electrode270are respectively configured to be paired to generate plasma. That is, the grounded rod-shaped electrode270is used in common for the rod-shaped electrodes269and271connected to two high frequency power supplies273adjacent to the rod-shaped electrode270. By applying high frequency (RF) power from the high frequency power supply273to between the rod-shaped electrodes269and271, plasma is generated in a plasma generation region224abetween the rod-shaped electrodes269and270and in a plasma generation region224bbetween the rod-shaped electrodes270and271.

The impedance measuring device274is installed between the matching device272and the high frequency power supply273. The impedance measuring device274measures high frequency traveling and reflected waves, and the matching device272measures the load impedance and high frequency reflection state of the rod-shaped electrodes269and271. That is, the impedance measuring device274measures the high frequency traveling and reflected waves, feeds back the measured values to a controller121, and the controller121controls the high frequency power supply273so that the amount of plasma generated in the plasma generation regions224aand224bis controlled.

The information measured by the impedance measuring device274includes at least one of a voltage ratio or a power ratio of the high frequency reflected wave to the high frequency traveling wave, a difference in phase of the high frequency reflected wave with respect to the high frequency traveling wave, or resistance, reactance, conductance, susceptance, impedance, admittance and the like calculated from the voltage ratio or power ratio and the phase difference. Here, switches (not shown) may be interposed between the rod-shaped electrode269and the impedance measuring device274and between the rod-shaped electrode271and the impedance measuring device274. Thus, by providing a switch between the rod-shaped electrode269and the impedance measuring device274and by providing a switch between the rod-shaped electrode271and the impedance measuring device274, it is possible to specify one of the rod-shaped electrodes269and270, which causes an abnormality such as deterioration, disconnection or short circuit.

A plasma generation part mainly includes the rod-shaped electrodes269,270and271and the matching device272and generates plasma in the plasma generation regions224aand224b. The plasma generation part may include the electrode protection tubes275, the high frequency power supply273and the impedance measuring device274. As will be described later, the plasma generation part functions as a plasma excitation part (an activation mechanism) that plasma-excites a gas, namely, excites (activates) the gas into a plasma state.

Each electrode protection tube275has a structure in which each of the rod-shaped electrodes269,270and271can be inserted into the buffer chamber237while keeping each of the rod-shaped electrodes269,270and271isolated from the internal atmosphere of the buffer chamber237. When an O2concentration within the electrode protection tube275is substantially equal to an O2concentration in the ambient air (atmosphere), the rod-shaped electrodes269,270and271respectively inserted into the electrode protection tube275may be oxidized by the heat generated from the heater207. By charging the interior of the electrode protection tube275with an inert gas such as a N2gas or the like, or by purging the interior of the electrode protection tube275with an inert gas such as a N2gas or the like through the use of an inert gas purge mechanism, it is possible to reduce the O2concentration within the electrode protection tube275, thereby preventing oxidation of the rod-shaped electrodes269,270and271.

An exhaust pipe231for exhausting an internal atmosphere of the process chamber201is installed in the reaction tube203. A vacuum pump246, as a vacuum-exhausting device, is connected to the exhaust pipe231via a pressure sensor245, which is a pressure detector (pressure detecting part) for detecting an internal pressure of the process chamber201, and an auto pressure controller (APC) valve244, which is an exhaust valve (pressure adjustment part). The APC valve244is configured to perform or stop a vacuum-exhausting operation in the process chamber201by opening or closing the valve while the vacuum pump246is actuated, and is also configured to adjust the internal pressure of the process chamber201by adjusting an opening degree of the valve based on pressure information detected by the pressure sensor245while the vacuum pump246is actuated. An exhausting system mainly includes the exhaust pipe231, the APC valve244and the pressure sensor245. The exhausting system may include the vacuum pump246. The exhaust pipe231is not limited to being installed in the reaction pipe203, but may be installed in the manifold209in the same manner as the nozzles249aand249b.

A seal cap219, which serves as a furnace opening cover configured to hermetically seal a lower end opening of the manifold209, is installed under the manifold209. The seal cap219is configured to contact the lower end of the manifold209from the lower side in the vertical direction. The seal cap219is made of, for example, a metal material such as stainless steel (SUS) or the like, and is formed in a disc shape. An O-ring220b, which is a seal member making contact with the lower end of the manifold209, is installed on an upper surface of the seal cap219. A rotation mechanism267configured to rotate a boat217, which will be described later, is installed at the opposite side of the seal cap219from the process chamber201. A rotary shaft255of the rotation mechanism267, which penetrates through the seal cap219, is connected to the boat217. The rotation mechanism267is configured to rotate the wafers200by rotating the boat217. The seal cap219is configured to be vertically moved up or down by a boat elevator115which is an elevator mechanism vertically installed outside the reaction tube203. The boat elevator115is configured so as to load/unload the boat217into/out of the process chamber201by moving the seal cap219up or down. The boat elevator115is configured as a transfer device (transfer mechanism) which transfers the boat217, that is, the wafers200, into/out of the process chamber201. In addition, a shutter219s, which serves as a furnace opening cover configured to hermetically seal a lower end opening of the manifold209while the seal cap219is descended by the boat elevator115, is installed under the manifold209. The shutter219sis made of, for example, a metal material such as stainless steel (SUS) or the like, and is formed in a disc shape. An O-ring220c, which is a seal member making contact with the lower end of the manifold209, is installed on an upper surface of the shutter219s. The opening/closing operation (such as elevation operation, rotation operation or the like) of the shutter219sis controlled by a shutter opening/closing mechanism115s.

As illustrated inFIG. 1, the boat217serving as a substrate support is configured to support one or more wafers200, for example, 25 to 200 wafers, in such a state that the wafers200are arranged in a horizontal posture and in multiple stages along a vertical direction with the centers of the wafers200aligned with one another. That is, the boat217is configured to arrange the wafers200to be spaced apart from each other at predetermined intervals. The boat217is made of a heat resistant material such as quartz or SiC. A heat insulating region where heat insulating plates218made of a heat resistant material such as quartz or SiC are supported in multiple stages is formed below the boat217.

As illustrated inFIG. 2, a temperature sensor263serving as a temperature detector is installed in the reaction tube203. Based on temperature information detected by the temperature sensor263, a state of supplying electric power to the heater207is adjusted such that an interior of the process chamber201has a desired temperature distribution. The temperature sensor263is installed along the inner wall of the reaction tube203in the same manner as the nozzles249aand249b.

Next, a control device will be described with reference toFIG. 3. As illustrated inFIG. 3, a controller121, which is a control part (control device), is configured as a computer including a central processing unit (CPU)121a, a random access memory (RAM)121b, a memory device121cand an I/O port121d. The RAM121b, the memory device121cand the I/O port121dare configured to exchange data with the CPU121avia an internal bus121e. An input/output device122configured as, e.g., a touch panel or the like, is connected to the controller121.

The memory device121cis configured by, for example, a flash memory, a hard disk drive (HDD) or the like. A control program for controlling operations of a substrate processing apparatus and a process recipe, in which sequences and conditions of a film-forming process to be described later are written, are readably stored in the memory device121c. The process recipe functions as a program for causing the controller121to execute each sequence in the various processes (film-forming processes), which will be described later, to obtain an expected result. Hereinafter, the process recipe and the control program may be generally and simply referred to as a “program.” Furthermore, the process recipe may be simply referred to as a “recipe.” When the term “program” is used herein, it may indicate a case of including only the recipe, a case of including only the control program, or a case of including both the recipe and the control program. The RAM121bis configured as a memory area (work area) in which a program or data read by the CPU121ais temporarily stored.

The I/O port121dis connected to the MFCs241ato241d, the valves243ato243d, the pressure sensor245, the APC valve244, the vacuum pump246, the heater207, the temperature sensor263, the matching device272, the high frequency power supply273, the impedance measuring device274, the rotation mechanism267, the boat elevator115, the shutter opening/closing mechanism115sand the like.

The CPU121ais configured to read and execute the control program from the memory device121c. The CPU121aalso reads the recipe from the memory device121caccording to an input of an operation command from the input/output device122. In addition, the CPU121ais configured to control the rotation mechanism267, the flow rate adjustment operation of various kinds of gases by the MFCs241ato241d, the opening/closing operation of the valves243ato243d, the adjustment operation of the high frequency power supply273based on impedance monitoring by the impedance measuring device274, the opening/closing operation of the APC valve244, the pressure adjusting operation performed by the APC valve244based on the pressure sensor245, the actuating and stopping of the vacuum pump246, the temperature adjustment operation performed by the heater207based on the temperature sensor263, the forward/backward rotation, rotation angle and rotation speed adjustment operation of the boat217by the rotation mechanism267, the operation of moving the boat217up or down by the boat elevator115, and the like, according to contents of the read recipe.

The controller121may be configured by installing, on the computer, the aforementioned program stored in an external memory device (for example, a magnetic disk such as an HDD, an optical disc such as a CD, a magneto-optical disc such as an MO, or a semiconductor memory such as a USB memory)123. The memory device121cor the external memory device123is configured as a computer-readable recording medium. Hereinafter, the memory device121cand/or the external memory device123may be generally and simply referred to as a “recording medium.” When the term “recording medium” is used herein, it may indicate a case of including only the memory device121c, a case of including only the external memory device123, or a case of including both the memory device121cand the external memory device123. Furthermore, the program may be provided to the computer using communication means such as the Internet or a dedicated line, instead of using the external memory device123.

(2) Substrate Processing Process

Next, a film-forming process of forming a thin film on a wafer200, which is a substrate processing method using the substrate processing apparatus of the present embodiment, as one of processes for manufacturing a semiconductor device, will be described with reference toFIGS. 4 and 5. In the following descriptions, the operations of the respective parts constituting the substrate processing apparatus are controlled by the controller121.

Here, examples will be described in which a silicon nitride film (SiN film) is formed, as a film containing Si and N, on a wafer200by, non-synchronously, that is, without being synchronized, a predetermined number of times (once or more), performing a step of supplying a DCS gas as a precursor gas and a step of supplying a plasma-excited NH3gas as a reaction gas. Further, for example, a predetermined film may be formed in advance on the wafer200. Further, a predetermined pattern may also be formed in advance on the wafer200or the predetermined film.

In the present disclosure, for the sake of convenience, a process flow of a film-forming process flow illustrated inFIG. 5may be denoted as follows. The same denotation may be used in other embodiments to be described below.
(DCS→NH3*)×n⇒SiN

When the term “wafer” is used herein, it may refer to “a wafer itself” or “a laminated body of a wafer and a predetermined layer or film formed on the surface of the wafer”. In addition, when the phrase “a surface of a wafer” is used herein, it may refer to a surface of a wafer itself or a surface of a predetermined layer or the like formed on a wafer. In the present disclosure, the expression “a predetermined layer is formed on a wafer” may mean that a predetermined layer is directly formed on a surface of a wafer itself or that a predetermined layer is formed on a layer or the like formed on a wafer. In the present disclosure, when the term “substrate” is used herein, it may be synonymous with the term “wafer.”

If a plurality of wafers200is charged on the boat217(wafer charging), the shutter219sis moved by the shutter opening/closing mechanism115sto open the lower end opening of the manifold209(shutter opening). Thereafter, as illustrated inFIG. 1, the boat217supporting the plurality of wafers200is lifted up by the boat elevator115and is loaded into the process chamber201(boat loading). In this state, the seal cap219seals the lower end of the manifold209through the O-ring220b.

The interior of the process chamber201, namely the space in which the wafers200are located, is vacuum-exhausted (depressurization-exhausted) by the vacuum pump246to reach a desired pressure (degree of vacuum). In this operation, the internal pressure of the process chamber201is measured by the pressure sensor245. The APC valve244is feedback-controlled based on the measured pressure information. Furthermore, the wafers200in the process chamber201are heated by the heater207to a desired temperature. In this operation, the state of supplying electric power to the heater207is feedback-controlled based on the temperature information detected by the temperature sensor263such that the interior of the process chamber201has a desired temperature distribution. In addition, the rotation of the boat217and the wafers200by the rotation mechanism267begins. The exhaust of the interior of the process chamber201and the heating and rotation of the wafers200may be all continuously performed at least until the processing of the wafers200is completed.

Thereafter, a film-forming step is performed by sequentially performing steps S3, S4, S5and S6.

At step S3, a DCS gas is supplied to the wafer200in the process chamber201.

The valve243ais opened to allow the DCS gas to flow through the gas supply pipe232a. A flow rate of the DCS gas is adjusted by the MFC241a, and then the DCS gas is supplied from the gas supply hole250ainto the process chamber201via the nozzle249aand is exhausted through the exhaust pipe231. Simultaneously, the valve243cmay be opened to allow a N2gas to flow through the gas supply pipe232c. A flow rate of the N2gas is adjusted by the MFC241c, and the N2gas is supplied into the process chamber201together with the DCS gas and is exhausted through the exhaust pipe231.

In addition, in order to prevent the DCS gas from entering into the nozzle249b, the valves243dmay be opened to allow the N2gas to flow through the gas supply pipe232d. The N2gas is supplied into the process chamber201through the gas supply pipe232band the nozzle249band is exhausted through the exhaust pipe231.

A supply flow rate of the DCS gas, which is controlled by the MFC241a, is set to fall within a range of, e.g., 1 to 6,000 sccm, or 2,000 to 3,000 sccm in some embodiments. Each of supply flow rates of the N2gas, which are controlled by the MFCs241cand241d, are set to fall within a range of, e.g., 100 to 10,000 sccm. An internal pressure of the process chamber201is set to fall within a range of, e.g., 1 to 2,666 Pa, or 665 to 1,333 Pa in some embodiments. A supply time of the DCS gas is set to fall within a range of, e.g., 1 to 10 seconds, or 1 to 3 seconds in some embodiments.

The temperature of the heater207is set such that the temperature of the wafer200becomes a temperature which falls within a range of, for example, 0 to 700 degrees C., a room temperature (25 degrees C.) to 550 degrees C. in some embodiments, or 40 to 500 degrees C. in some embodiments. By setting the temperature of the wafer200to 700 degrees C. or lower, further to 550 degrees C. or lower, and furthermore to 500 degrees C. or lower as in the present embodiments, it is possible to reduce the quantity of heat applied to the wafer200, and to control the thermal history received by the wafer200.

By supplying the DCS gas to the wafer200under the aforementioned conditions, a Si-containing layer containing Cl is formed on the wafer200(a base film on its surface). The Si-containing layer containing Cl may be a Si layer containing Cl or an adsorption layer of DCS, or may include both of them. Hereinafter, the Si-containing layer containing Cl will be simply referred to as a Si-containing layer.

After the Si-containing layer is formed, the valve243ais closed to stop the supply of the DCS gas into the process chamber201. In this operation, the interior of the process chamber201is vacuum-exhausted by the vacuum pump246while maintaining the APC valve244opened. Thus, the DCS gas which has not reacted, the DCS gas which has contributed to the formation of the Si-containing layer, or reaction byproduct, or the like, which remains within the process chamber201, is removed from the interior of the process chamber201(S4). Furthermore, the supply of the N2gas into the process chamber201is maintained while maintaining the valves243cand243dopened. The N2gas acts as a purge gas. This S4may also be omitted.

As the inert gas, it may be possible to use a rare gas such as Ar gas, He gas, Ne gas, Xe gas, or the like, as well as the N2gas.

After the film-forming process is completed, plasma-excited NH3gas as a reaction gas is supplied to the wafer200in the process chamber201(S5).

In this step, the opening/closing control of the valves243bto243dis performed in the same procedure as the opening/closing control of the valves243a,243cand243din step S3. A flow rate of the NH3gas is adjusted by the MFC241b, and the NH3gas is then supplied into the buffer chamber237through the nozzle249b. At this time, high frequency power is supplied between the rod-shaped electrodes269,270and271. The NH3gas supplied into the buffer chamber237is plasma-excited (plasma-converted and activated), supplied as active species (NH3*) into the process chamber201, and exhausted through the exhaust pipe231.

The supply flow rate of the NH3gas controlled by the MFC241bis set at a flow rate which falls within a range of, for example, 100 to 10,000 sccm or 1,000 to 2,000 sccm in some embodiments. The high frequency power applied to the rod-shaped electrodes269,270, and271is set at electric power which falls within a range of, for example, 50 to 600 W. The internal pressure of the process chamber201is set at a pressure which falls within a range of, for example, 1 to 500 Pa. By using plasma, the NH3gas can be activated even when the internal pressure of the process chamber201is set to such a relatively low pressure range. The time, during which the active species obtained by plasma-exciting the NH3gas are supplied to the wafer200, namely the gas supply time (injection time), is set at a time which falls within a range of, for example, 1 to 180 seconds, or 1 to 60 seconds in some embodiments. Other processing conditions are similar to the processing conditions of S3described above.

By supplying the NH3gas to the wafer200under the aforementioned conditions, the Si-containing layer formed on the wafer200is plasma-nitrided. In this operation, Si—Cl bonds and Si—H bonds of the Si-containing layer are broken by the energy of the plasma-excited NH3gas. Cl and H, from which the bonds with Si are broken, are desorbed from the Si-containing layer. Then, Si in the Si-containing layer, which has dangling bonds due to the desorption of Cl or the like, is bonded to N contained in the NH3gas to form Si—N bonds. As this reaction proceeds, the Si-containing layer is changed (modified) into a layer containing Si and N, i.e., a silicon nitride layer (SiN layer).

In order to modify the Si-containing layer into the SiN layer, the NH3gas may be plasma-excited and supplied. This is because, even if the NH3gas is supplied under a non-plasma atmosphere, the energy needed for nitriding the Si-containing layer may be insufficient in the aforementioned temperature range and it may be difficult to sufficiently desorb Cl and H from the Si-containing layer, to sufficiently nitride the Si-containing layer, and to increase the Si—N bonds.

After the Si-containing layer is modified into the SiN layer, the valve243bis closed to stop the supply of the NH3gas. Furthermore, the supply of the high frequency power to between the rod-shaped electrodes269,270and271is stopped. Then, the NH3gas or reaction byproduct, which remains within the process chamber201, is removed from the interior of the process chamber201under the same processing procedures and processing conditions as those of S4(S6). S6may also be omitted.

As a nitriding agent, i.e., a plasma-excited NH3-containing gas, it may be possible to use, diazene (N2H2) gas, hydrazine (N2H4) gas, N3H8gas, or the like, as well as the NH3gas.

As the inert gas, it may be possible to use, for example, various kinds of rare gases exemplified at S4, as well as the N2gas.

A process that performs the foregoing S3, S4, S5, and S6in this order non-simultaneously, i.e., non-synchronously, is set as one cycle, and this cycle is performed a predetermined number of times (n times), namely once or more (S7). As a result, a SiN film having a predetermined composition and a predetermined thickness can be formed on the wafer200. The aforementioned cycle may be repeated multiple times. That is, the thickness of the SiN layer formed per one cycle may be set smaller than a desired thickness, and the aforementioned cycle may be repeated multiple times until the thickness of the SiN film formed by laminating the SiN layer becomes the desired thickness.

After the film-forming process described above is completed, the N2gas as an inert gas is supplied from the respective gas supply pipes232cand232dinto the process chamber201and is exhausted from the exhaust pipe231. Thus, the interior of the process chamber201is purged with an inert gas and the gas or the like remaining within the process chamber201is removed from the interior of the process chamber201(inert gas purge). Thereafter, the internal atmosphere of the process chamber201is substituted by an inert gas (inert gas substitution). The internal pressure of the process chamber201is returned to an atmospheric pressure (S8).

Thereafter, the seal cap219is moved down by the boat elevator115to open the lower end of the manifold209. The processed wafers200supported on the boat217are unloaded from the lower end of the manifold209to the outside of the reaction tube203(boat unloading) (S9). After the boat unloading, the shutter219sis moved so that the lower end opening of the manifold209is sealed by the shutter219sthrough the O-ring220c(shutter closing). The processed wafers200are unloaded to the outside of the reaction tube203and are subsequently discharged from the boat217(wafer discharging).

(3) Plasma Abnormality Determination

In the above-described film-forming process and etching process, the active species (ions and radicals) obtained by plasma-converting the reaction gas are used to promote the chemical reaction particularly on the substrate surface, thereby forming and removing a dense film. However, by repeatedly performing the processes, the plasma characteristics may change due to the deterioration of the plasma electrodes (rod-shaped electrodes in this embodiment) and the influence of the surrounding environment, and the film formation characteristics and etching characteristics may not be stable.

In this embodiment, in order to optically monitor the plasma state in the substrate processing apparatus, after the substrate processing such as the above-described film-forming process and etching process are performed a predetermined number of times as one of the above-described semiconductor device manufacturing processes using the above-described substrate processing apparatus, an empty boat217that does not hold a wafer is loaded into the process chamber201, a plasma monitor10configured to be installed in the process chamber201(to be described later) is installed in the process chamber201. Then, the reaction gas supplying step S5of the above-described substrate processing process is performed, the gas supply holes302and304for supplying the plasma-converted gas are imaged, and a plasma emission intensity is monitored and recorded. Then, the captured image is analyzed, and the abnormal discharge and flickering of the plasma are distinguished and determined.

As illustrated inFIG. 6, the plasma monitor10that has an elongated structure extending from the lower portion to the upper portion of the reaction tube203and that can be attached to and detached from the seal cap219or the shutter219sis inserted into the process chamber201.

The plasma monitor10is disposed at a position where the gas supply holes302and304formed on the arc-shaped wall surface of the buffer structure300can be imaged. Further, the plasma monitor10is disposed substantially parallel to the rod-shaped electrodes269to271installed in the buffer chamber237.

The plasma monitor10includes an endoscope camera12as an imaging device that images the plasma emission intensity, and a tube-shaped protective tube14. The protective tube14is formed of, for example, a quartz member. The endoscope camera12is configured to be movable in the vertical direction and the rotational direction within the protective tube14.

The endoscope camera12is connected to an image reception device16installed outside the reaction tube203via a cable, or the controller121via the image reception device16. The endoscope camera12is equipped with a lens18. Further, as illustrated inFIG. 7, a periphery of the endoscope camera12is covered and protected by a metal net20as a noise removal member such as a metal mesh or a metal foil. When the endoscope camera12is affected by the high frequency power supply273that is a plasma generation source, it receives a lot of noise. By covering the endoscope camera12with the metal net20in this manner, electromagnetic waves generated from the high frequency power supply273are shielded to remove electrical noise. An opening is formed in the metal net20so as not to obstruct the lens18that is at an imaging position, and the endoscope camera12is disposed inside the protective tube14with the metal net20covering a periphery thereof. The metal net20is not limited to a net shape as long as noise from the plasma can be removed, but may have any shape such as a plate shape or a cylindrical shape.

That is, the endoscope camera12is movable in the vertical direction and the rotational direction within the protective tube14, and the lens18of the endoscope camera12maintains an arbitrary rotation angle with respect to the gas supply holes302and304. In this state, the entire area extending from the lower portion to the upper portion of the gas supply holes302and304is moved at a constant speed in the vertical direction to take an image and acquire image data.

FIG. 8is a block diagram showing a control system of the controller when performing plasma abnormality determination. The controller121as a control means (control part) includes a detection logic circuit22as a detection means (detection part), and a determination logic circuit24as a determination means (determination part). The detection logic circuit22detects a plasma emission intensity based on the image data of the periphery of the gas supply holes302and304imaged by the endoscope camera12. Based on the plasma emission intensity detected by the detection logic circuit22, the determination logic circuit24determines at least one of whether abnormal plasma discharge has occurred and whether plasma flickering has occurred.

Specifically, in a logic circuit storing the plasma emission intensity in advance in the memory device121cor the external memory device123based on the trimmed image data, the plasma emission intensity is read into the RAM121band is detected by the detection logic circuit22, which is operated by the CPU121a. Further, in a logic circuit storing data in advance as to whether or not the detected emission intensity is equal to or larger than a threshold value in the memory device121cor the external memory device123, the plasma emission intensity is read into the RAM121band is determined by the determination logic circuit24, which is operated by the CPU121a.

Then, when the emission intensity detected by the detection logic circuit22is equal to or larger than the threshold value, the determination logic circuit24determines that abnormal discharge has occurred. When the emission intensity detected by the detection logic circuit22is smaller than the threshold value, the determination logic circuit24determines whether or not there is a preset range or more between the maximum value and the minimum value of the detected emission intensity, for example, whether there is a difference of ±10% or more. Then, when it is determined that there is a difference of ±10% or more between the maximum value and the minimum value of the detected emission intensity, the determination logic circuit24determines that flickering has occurred. When it is determined that there is no difference of ±10% or more, the determination logic circuit24determines that the emission intensity is normal. Then, when it is determined that the emission intensity is normal (that there is no occurrence of the abnormal discharge and flickering), the boat217holding the wafers is loaded into the process chamber201and a substrate processing process such as the above-described film-forming process is performed.

FIG. 9is a flowchart showing an operation for performing the plasma abnormality determination. The operation for performing the plasma abnormality determination includes an operation to be described later and is mainly controlled by the controller121as the control part in the same manner as the substrate processing operation.

First, as illustrated inFIGS. 6 and 7, the plasma monitor10incorporating the endoscope camera12is inserted into the process chamber201(step S10).

Then, the same control as the reaction gas supplying step S5of the above-described substrate processing process is performed to generate plasma, and the lens18of the endoscope camera12maintains an arbitrary rotation angle with respect to the gas supply holes302and304. In this state, the plasma monitor10moves the entire area extending from the lower portion to the upper portion of the gas supply holes302and304at a constant speed in the vertical direction to take an image. A signal acquired by the endoscope camera12is transmitted as image data to the image reception device16, and the plasma emission state is stored as a moving image (step S11).

Then, a region of the image data where the plasma is strongly generated is trimmed (step S12). As a result, a signal-to-noise (SN) ratio, which is a ratio between a noise component and a signal component of the emission intensity, is improved.

Then, based on the trimmed image data, the plasma emission intensity is detected by the detection logic circuit22(step S13), and it is determined by the determination logic circuit24whether or not the detected plasma emission intensity is equal to or larger than a threshold value (step S14).

When the detected plasma emission intensity is equal to or larger than the threshold value (Yes in step S14), it is determined by the determination logic circuit24that abnormal discharge has occurred (step S15).

Then, when it is determined that abnormal discharge has occurred, the frequency is increased, or the reaction tube203is replaced with a new one.

On the other hand, when the detected plasma emission intensity is smaller than the threshold (No in step S14), it is determined by the determination logic circuit24whether or not there is a preset range or more between the maximum value and the minimum value of the detected plasma emission intensity, for example, whether there is a difference of ±10% or more (step S16).

Then, when it is determined that there is a difference of ±10% or more between the maximum value and the minimum value of the detected plasma emission intensity (Yes in step S16), it is determined by the determination logic circuit24that the flickering has occurred (step S17).

Then, when it is determined that the flickering has occurred, the frequency is controlled, or the rod-shaped electrodes269to271are replaced with new ones.

When it is determined that there is no difference of ±10% or more between the maximum value and the minimum value of the detected plasma emission intensity (No in step S16), it is determined by the determination logic circuit24that the plasma emission intensity is normal (step S18), the boat217holding the wafers is loaded into the process chamber201, and a substrate processing process such as the above-described film-forming process is performed.

Next, an Example will be described in detail. In this Example, in the reaction gas supplying step S5of the substrate processing process using the above-described substrate processing apparatus, the temperature of the process chamber201is set to room temperature, the internal pressure of the process chamber201is set to 66 Pa, and the frequency f of the high frequency power supply273is set to 13.56 MHz. Then, using the rod-shaped electrodes269,270and271having a length of about 0.6 m, a diameter of about 12 mm and a DC resistance of less than 1Ω, a CCP (Capacitively Coupled Plasma) mode plasma of NH3gas is generated and supplied into the buffer chamber237. Then, the gas supply holes302and304are imaged using the plasma monitor10.

In this Example, the rotation angle of the endoscope camera12of the plasma monitor10is fixed toward the gas supply holes302and304, and the plasma monitor10moves within the protective tube14from the lower portion to the upper portion thereof at a constant speed, and a moving image (30 frames per minute) is acquired.

InFIGS. 10A and 10B, a broken line frame indicates a region to be trimmed. That is, in this Example, a region of each frame image where the plasma is strongly generated is trimmed, and a determination is made with the improved S/N ratio of the plasma emission intensity.

As illustrated inFIG. 10B, when the plasma is in an abnormal state, it can be seen that strong emission is locally generated at a plurality of locations as compared with the normal state of the plasma illustrated inFIG. 10A. Such a state occurs when the shape of the gas supply holes302and304changes due to wear or deterioration of the reaction tube203and abnormal discharge occurs at the gas supply holes302and304whose shapes have changed.

FIG. 11Ais a graph showing a distribution of plasma emission intensity from the lower portion to the upper portion of the gas supply holes302and304when the plasma ofFIG. 10Ais normal and the plasma ofFIG. 10Bis abnormal, showing an example where the emission intensity is detected without trimming an acquired image.FIG. 11Bis a graph showing a case where the emission intensity of a trimmed region is averaged and plotted every 10 frames.FIG. 11Cis a graph showing a case where the maximum value and the minimum value of the emission intensity of the trimmed region are plotted every 10 frames.

That is, as illustrated inFIG. 11A, when the acquired image is not trimmed, it has a noise level distribution, and it is difficult to determine whether or not plasma abnormality has occurred. On the other hand, as illustrated inFIGS. 11B and 11C, when the acquired image is trimmed, the S/N ratio is improved, and, when the plasma is abnormal, the plasma emission intensity is sharpened.

Then, as illustrated inFIGS. 11B and 11C, when the plasma emission intensity is equal to or larger than the threshold value, it is determined that a peak position thereof is an abnormal discharge occurrence point. Further, as illustrated inFIG. 11C, when the maximum value and the minimum value of the plasma emission intensity are plotted for each frame, it is determined that the flickering has occurred when a difference between the maximum plot and the minimum plot is, for example, ±10% or more.

That is, as illustrated inFIG. 11C, a portion where a large difference appears in a plot curve of the maximum value and the minimum value means that there is the flickering.

The above-described controller121also functions as a plasma control device that controls plasma generation and plasma abnormality determination. That is, the controller121can monitor the plasma emission intensity imaged by the endoscope camera12built in the plasma monitor10and can determine whether the plasma is normal or abnormal even by computer algorithm processing.

Then, when it can be determined that the plasma is normal, since the plasma emission intensity is quantified, it can be managed as an index representing an amount of active species generated, and the amount of active species generated, in other words, plasma characteristics, can be maintained by adjusting the power and frequency of the high frequency power supply.

(5) Effects According to the Present Embodiment

According to the present embodiment, one or more effects set forth below may be achieved.

(a) According to the present embodiment, it is possible to determine a plasma abnormality with high accuracy.

(b) According to the present embodiment, it is possible to distinguish between abnormal plasma discharge and plasma flickering, and it is possible to take measures against each of the abnormal plasma discharge and the flickering.

(c) According to the present embodiment, even when an electrode and its surrounding environment are changed, by adjusting a power value and a frequency value of the high frequency power supply based on the image data, it is possible to maintain the plasma characteristics and stabilize the film formation characteristics and etching characteristics.

(d) According to the present embodiment, by maintaining the plasma characteristics, it is possible to stabilize the film formation characteristics and etching characteristics and improve the productivity and stability for wafer processing.

The embodiments of the present disclosure have been specifically described above. However, the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit and scope of the present disclosure.

For example, in the above-described embodiments, the arrangement position (insertion position) of the plasma monitor10is as shown inFIGS. 6 and 7. However, the present disclosure is not limited thereto. If such conditions where the entire object can be imaged, there is a sufficient space, the endoscope camera12is focused on the object, and the plasma monitor10does not contact other members such as the reaction tube203and the boat217are satisfied, the plasma monitor10may be disposed anywhere.

In the above-described embodiments, the configuration in which an empty boat217is loaded into the process chamber201and the plasma abnormality is determined after the above-described film-forming process and etching process are performed a predetermined number of times has been described. However, the present disclosure is not limited to such a configuration. For example, it may be possible to perform the plasma abnormality determination in a state where the boat holding the wafers is loaded, or to perform the plasma abnormality determination at the time of setting up the apparatus.

In the above-described embodiments, the case where one buffer structure is provided has been described. However, the present disclosure is not limited to such a case. The present disclosure may be applied to a case where two or more buffer structures are provided. When it is determined that the flickering has occurred in the two or more buffer structures, a trigger signal can be synchronized between two high frequency power supplies for improvement.

In the above-described embodiments, the example in which the reaction gas is supplied after the precursor is supplied has been described. However, the present disclosure is not limited to such an example. The supply order of the precursor and the reaction gas may be reversed. That is, the precursor may be supplied after the reaction gas is supplied. By changing the supply order, a film quality and a composition ratio of the formed film may be changed.

In the above-described embodiments, the example in which the plasma abnormality determination is performed after the film-forming process is performed a predetermined number of times has been described. However, the present disclosure is not limited to such an example. The present disclosure may also be applied to other substrate processing using plasma, such as performing plasma abnormality determination after performing an etching process a predetermined number of times. Thus, the plasma characteristics can be maintained and the etching characteristics can be stabilized.

Recipes used in the film-forming process and the etching process may be prepared individually according to the processing contents and may be stored in the memory device121cvia a telecommunication line or the external memory device123. Moreover, at the beginning of various types of processes, the CPU121amay properly select an appropriate recipe from the recipes stored in the memory device121caccording to the contents of the processing. Thus, it is possible for a single substrate processing apparatus to form thin films of various kinds, composition ratios, qualities, and thicknesses for general purpose and with enhanced reproducibility. In addition, it is possible to reduce an operator's burden and to quickly start the various processes while avoiding an operation error.

The recipes mentioned above are not limited to newly-prepared ones but may be prepared, for example, by modifying existing recipes that are already installed in the substrate processing apparatus. Once the recipes are modified, the modified recipes may be installed in the substrate processing apparatus via a telecommunication line or a recording medium storing the recipes. In addition, the existing recipes already installed in the substrate processing apparatus may be directly changed by operating the input/output device122of the substrate processing apparatus.

In the above-described embodiments, the substrate processing apparatus has been described. However, the present disclosure can be applied to all semiconductor manufacturing apparatuses.

According to the present disclosure, it is possible to provide a technique capable of determining plasma abnormality.