JP2004165374A - Plasma treatment method and equipment thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma treatment method and a plasma treatment equipment which can control electron temperature of electron cyclotron resonance (ECR) plasma with high precision. <P>SOLUTION: In a chamber 20, a controller 12 sets magnetic field gradient over longitudinal of the chamber 20 in an ECR region and a region in the vicinity of the ECR region as a prescribed range, by using a main coil 40 and an auxiliary coil 41. The controller 12 so controls microwave power by a microwave oscillator 39 that plasma having a prescribed electron temperature is generated in a magnetic field configuration having a prescribed magnetic field gradient. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plasma processing method and a plasma processing apparatus for performing predetermined processing on an object to be processed such as a semiconductor wafer and a liquid crystal display substrate using electron cyclotron resonance plasma.
[0002]
[Prior art]
2. Description of the Related Art In a process of manufacturing an electronic device such as a semiconductor device and a liquid crystal display device, a process using plasma is widely used. Such plasma processing generates a plasma of a process gas or a carrier gas, and chemically reacts with a process gas active species or a process gas excited by contact with the carrier gas active species on a surface of an object to be processed such as a semiconductor wafer. Subject to physical or physical treatment.
[0003]
In recent years, plasma with a low electron temperature has been demanded in order to perform highly reliable plasma processing on an object to be processed. For example, when the electron temperature of the plasma is high, there are problems such as damage to the object to be processed and metal contamination of the object to be processed due to sputtering of a chamber member.
[0004]
As a method of generating plasma having a low electron temperature, a method of generating plasma at a relatively high vacuum pressure using microwaves has been developed. Such a low electron temperature plasma can be generated using a radial line slot antenna (RLSA), for example, as described in Patent Document 1 below.
[0005]
[Patent Document 1]
JP 2000-294550 A
[0006]
According to the above-described method, it is possible to perform a process that avoids damage to the object to be processed by plasma at a low electron temperature. However, on the other hand, a high gas pressure means that the concentration of a substance in the gas is high, and high-quality processing may not be performed in some cases, such as difficult etching with high anisotropy.
[0007]
[Problems to be solved by the invention]
In this regard, an electron cyclotron resonance (ECR) plasma can be generated at a relatively low pressure, and high-quality processing such as anisotropy can be performed. However, on the other hand, the ECR plasma has a larger variation in electron energy (electron temperature) distribution in the plasma than the RLSA plasma or the like. Therefore, when ECR plasma is used, processing stability is lower than when high-pressure plasma is used.
[0008]
As described above, the conventional processing method using the ECR plasma can generate plasma at a relatively low pressure and perform high-quality processing, but has a relatively large variation in plasma electron temperature and thus has a stable processing. Is difficult to obtain. Therefore, a method for controlling the electron temperature of the ECR plasma with high accuracy has been required in order to realize highly stable processing, but such a method has not been conventionally available.
[0009]
In view of the above circumstances, an object of the present invention is to provide a plasma processing method and a plasma processing apparatus capable of performing high quality and stable processing using ECR plasma.
Another object of the present invention is to provide a plasma processing method and a plasma processing apparatus capable of controlling the electron temperature of ECR plasma with high accuracy.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a plasma processing method according to a first aspect of the present invention includes:
A plasma processing method for performing a predetermined process on an object to be processed by utilizing a plasma generated based on electron cyclotron resonance by an interaction between a magnetic field and a microwave electric field,
In a region where electron cyclotron resonance occurs and a region in the vicinity thereof, a magnetic field forming step of forming a magnetic field having a predetermined gradient with respect to the traveling direction of the microwave,
A microwave control step of controlling the power of the microwave introduced into the magnetic field formed in the magnetic field forming step, such that a plasma having a predetermined electron temperature is generated;
including.
[0011]
In the above method, in the microwave control step, the microwave power may be controlled so as to generate a predetermined power absorption distribution of the electromagnetic wave.
[0012]
In the above method, in the magnetic field forming step, a magnetic field having a predetermined gradient is formed so that the power of the microwave is almost uniformly absorbed in a plane in a region where electron cyclotron resonance occurs and a region in the vicinity thereof. You may.
[0013]
In the above method, in the microwave control step, the microwave power may be controlled so that the electron temperature changes while the electron density of the generated plasma is kept constant.
[0014]
The method may further include an information acquisition step of acquiring information indicating a processing state of the processed object to be processed,
In the microwave control step, the power of the microwave may be controlled based on the information obtained in the information obtaining step.
[0015]
In order to achieve the above object, a plasma processing apparatus according to a second aspect of the present invention includes:
A plasma processing apparatus that performs a predetermined process on a target object using plasma generated based on electron cyclotron resonance by an interaction between a magnetic field and a microwave electric field,
In a region where electron cyclotron resonance occurs, a magnetic field forming unit that forms a magnetic field having a predetermined gradient with respect to the traveling direction of the microwave,
Microwave control means for controlling the power of microwaves introduced into the magnetic field formed by the magnetic field forming means, so that a plasma having a predetermined electron temperature is generated,
Is provided.
[0016]
In the above device, the microwave control means may control the microwave power so that a predetermined power absorption distribution of the electromagnetic wave is generated.
[0017]
In the above-mentioned apparatus, in the magnetic field forming step, a magnetic field having a predetermined gradient is formed so that the power of the microwave is substantially uniformly absorbed in a plane in a region where electron cyclotron resonance occurs and a region in the vicinity thereof. You may.
[0018]
In the above apparatus, the microwave control means may control the microwave power so that the electron temperature changes while keeping the electron density of the generated plasma constant.
[0019]
The apparatus may further include information acquisition means for acquiring information indicating a processing state of the processed object,
The microwave control means may control the power of the microwave based on the information obtained by the information obtaining means.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
A plasma processing method and a plasma processing apparatus according to an embodiment of the present invention will be described below with reference to the drawings.
In this embodiment, an electron cyclotron resonance (ECR) plasma processing apparatus will be described as an example. This ECR plasma processing apparatus forms a silicon nitride film on the surface of a semiconductor wafer as a processing target by CVD (Chemical Vapor Deposition).
[0021]
FIG. 1 shows a configuration of a plasma processing apparatus 11 according to the present embodiment.
As shown in FIG. 1, the plasma processing apparatus 11 includes a controller 12, a cassette chamber 13, a transfer chamber 14, a process chamber 15, and a measurement chamber 16.
[0022]
The controller 12 controls the entire operation of the plasma processing apparatus 11 including a film forming operation, a measuring operation, and the like described below.
[0023]
The cassette chamber 13 functions as a cassette loading / unloading port. The cassette chamber 13 includes a cassette table or the like (not shown), and is configured such that a predetermined number of cassettes can be disposed therein. The cassette contains a predetermined number of semiconductor wafers. The cassette chamber 13 is configured so that its internal atmosphere can be evacuated by an exhaust device (not shown) or the like.
[0024]
The transfer chamber 14 is connected to the cassette chamber 13, the process chamber 15, and the measurement chamber 16 via a gate valve 17, respectively. A transfer mechanism 18 is disposed in the transfer chamber 14, and the target object is transferred between the transfer chamber 14 and each of the chambers via the transfer chamber 14. The transfer chamber 14 is configured so that its internal atmosphere can be evacuated.
[0025]
The process chamber 15 is provided for performing plasma CVD (Chemical Vapor Deposition) on a semiconductor wafer using ECR plasma, as described later.
[0026]
The measurement chamber 16 is provided for measuring a processed semiconductor wafer and acquiring information on a formed film. In the measurement chamber 16, information on the thickness and quality of the formed film is obtained.
[0027]
The measurement is performed by a spectroscopic method. For example, light such as visible light and infrared light is made incident on the surface of the film, and the degree of interference between the reflected light and the incident light is determined. Through the measurement, for example, information on film formation uniformity indicating whether the film is uniformly formed on the entire surface of the semiconductor wafer is obtained.
As described later, the controller 12 controls the film forming operation in the process chamber 15 based on the information about the film obtained in the measurement chamber 16.
[0028]
FIG. 2 shows a configuration of the process chamber 15. The process chamber 15 includes a substantially cylindrical chamber 20 made of aluminum or the like, and the chamber 20 is set to a GND potential. The chamber 20 has, for example, a lower portion (bottom portion) having a larger diameter than an upper portion.
A substantially columnar mounting table 21 made of, for example, aluminum or the like stands upright from the bottom of the chamber 20.
[0029]
A flat electrostatic chuck 22 is provided on the upper surface of the mounting table 21. The electrostatic chuck 22 is configured by embedding a disc-shaped electrode plate 23 made of copper or the like inside an insulator such as polyimide or ceramic. A semiconductor wafer W is mounted on one surface of the electrostatic chuck 22.
[0030]
A DC power supply 24 is connected to the electrode plate 23, and a 13.56 MHz bias high frequency power supply 25, for example, is connected to the electrode plate 23 via a matching box 26 in parallel. A DC voltage is applied from the DC power supply 24 to the electrostatic chuck 22 to generate an electrostatic force between the semiconductor wafer W and the insulator, whereby the semiconductor wafer W is suction-held by the electrostatic chuck 22.
[0031]
In addition, by applying a bias voltage from the high frequency power supply 25 to the electrode plate 23, ions are efficiently drawn into the surface of the semiconductor wafer W. Thereby, the semiconductor wafer W is efficiently processed.
[0032]
A heater 27 for heating the semiconductor wafer W on the mounting table 21 is provided inside the mounting table 21. The heater 27 is formed of, for example, a resistor.
Further, a cooling jacket 28 is provided below the mounting table 21 to prevent overheating of a connection portion between the stage and the chamber 20 and the like. The cooling jacket 28 is configured to include a flow path through which a coolant having a predetermined temperature flows.
[0033]
A gate 29 is provided on the side wall of the chamber 20. The gate 29 can be opened and closed hermetically by the gate valve 17. The semiconductor wafer W is transferred to and from the transfer chamber 14 via the gate 29 and the gate valve 17.
[0034]
An exhaust port 30 is provided on a lower side wall of the chamber 20. The exhaust port 30 is connected to an exhaust device 32 such as a turbo molecular pump via a flow controller (APC) 31 having a butterfly valve and the like. The inside of the chamber 20 is set to a predetermined pressure atmosphere, for example, a pressure of about 1 to 50 mTorr by the exhaust device 32 and the APC 31.
[0035]
A gas nozzle 33 is provided above the chamber 20, for example, above a main coil 40 described later. The gas nozzle 33 is provided with nitrogen (N ₂ ) Supply gas. The nitrogen gas is supplied to the upper part of the chamber 20 at a predetermined flow rate by a mass flow controller (not shown). Although two gas nozzles 33 are shown in the drawing, the number of gas nozzles is not limited to two, and three or more gas nozzles may be provided. Further, the nitrogen gas may be supplied together with an inert gas such as argon and neon.
[0036]
A gas ring 34 is provided at a central portion of the chamber 20, for example, between a main coil 40 and the mounting table 21 described later. The gas ring 34 is formed, for example, slightly larger in diameter than the mounting table 21 and has a number of gas holes 34a. From the gas hole 34a of the gas ring 34, silane (SiH ₄ The gas is controlled at a predetermined flow rate and supplied to the surface of the semiconductor wafer W on the mounting table 21.
[0037]
The ceiling of the chamber 20 is opened, and a microwave introduction window 35 is provided in the opening. The microwave introduction window 35 is made of a material that can transmit microwaves, for example, quartz, SiO ₂ Glass, Si ₃ N ₄ , NaCl, KCl, LiF, CaF ₂ , BaF ₂ , Al ₂ O ₃ , AlN, MgO and the like, and organic films and sheets such as polyethylene, polyester, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, and polyimide. The connection between the microwave introduction window 35 and the opening is hermetically sealed by a sealing member (not shown) such as an O-ring.
[0038]
A conical tapered waveguide 36 is connected to the ceiling of the chamber 20 via a microwave introduction window 35. The tapered waveguide 36 is connected to a rectangular waveguide 38 having a rectangular cross section via a conversion waveguide 37 for converting a vibration mode of microwaves. An end of the rectangular waveguide 38 is connected to a microwave oscillator 39. The microwave oscillated by the microwave oscillator 39 has a predetermined mode, for example, TM ₀₁ The mode is converted into a mode, and is introduced into the chamber 20 through the microwave introduction window 35.
As the microwave frequency, an industrial frequency of 915 MHz is selected.
[0039]
A ring-shaped main coil 40 is provided on the outer side of the chamber 20 so as to surround it. A ring-shaped auxiliary coil 41 is also arranged below and below the bottom of the chamber 20. Note that a permanent magnet may be used instead of the coil.
[0040]
Next, the operation of the plasma processing apparatus 11 configured as described above will be described.
First, the transfer mechanism 18 takes an unprocessed semiconductor wafer W from the cassette arranged in the cassette chamber 13 and carries it into the transfer chamber 14. Thereafter, the gate valve 17 separating the cassette chamber 13 and the transfer chamber 14 is closed, and the pressure in the transfer chamber 14 is reduced to a predetermined pressure. At this time, all the gate valves 17 are closed.
[0041]
Next, the gate valve 17 separating the transfer chamber 14 and the process chamber 15 is opened, and the transfer mechanism 18 loads the semiconductor wafer W into the process chamber 15. The transfer mechanism 18 places the semiconductor wafer W on the mounting table 21 and then withdraws from the process chamber 15 and the gate valve 17 is closed.
Further, the controller 12 applies a DC voltage (chuck voltage) to the electrode plate 23 of the electrostatic chuck 22 and fixes the semiconductor wafer W on the electrostatic chuck 22 by electrostatic force.
[0042]
Subsequently, the controller 12 drives the exhaust device 32 to exhaust the inside of the chamber 20, and sets the APC 31 to a predetermined degree of vacuum. Next, the controller 12 introduces a nitrogen gas and a silane gas at a predetermined flow rate from the gas nozzle 33 and the gas ring 34, respectively.
[0043]
Further, the controller 12 applies, for example, a bias voltage of 13.56 MHz and 1.5 kW to the electrode plate 23, and heats the surface temperature of the mounting table 21 to the process temperature by the heater 27.
[0044]
On the other hand, the controller 12 energizes the main coil 40 and the auxiliary coil 41 to form a magnetic field in the upper part of the chamber 20. The magnetic field is formed from above to below in the axial direction of the cylindrical chamber.
[0045]
The controller 12 oscillates a 915 MHz microwave from the microwave oscillator 39. The microwave passes through the conversion waveguide 37 and the tapered waveguide 36, and thereby has a predetermined mode, for example, TM. ₀₁ The mode is converted into a mode, and is introduced into the chamber 20 through the microwave introduction window 35. An electric field is formed in the chamber 20 by the introduction of the microwave. As will be described later, the controller 12 controls the microwave oscillator 39 to oscillate the microwave with power such that plasma having a predetermined electron temperature is generated.
[0046]
Interaction between the microwave electric field and the magnetic field causes electron cyclotron resonance (ECR) to occur in a predetermined region above the chamber 20. That is, the electrons in the magnetic field region perform a gyrating motion (cyclotron motion) by receiving the Lorentz force by the microwave electric field and the magnetic field. In a magnetic field region (hereinafter, referred to as an ECR region) in which the cycle of the swirling motion and the frequency of the microwave substantially coincide with each other, electrons are constantly accelerated, and electron cyclotron resonance occurs. Here, when the frequency of the microwave is 915 MHz, the magnetic field strength satisfying the electron cyclotron condition is about 32.7 mT (327 G).
[0047]
The electrons accelerated in the ECR region collide with nitrogen molecules in the gas supplied into the chamber 20 to generate plasma. The gas in the plasma state flows downward, activates the supplied silane gas, and generates its radicals and the like. The activated silane and nitrogen gather on the surface of the semiconductor wafer W to which the bias voltage is applied, and form a silicon nitride film.
[0048]
In the film forming step, the configuration of the magnetic field in the chamber 20 and the power of the microwave are formed so that plasma having a predetermined electron temperature is generated. As will be described later, it has been found that the electron temperature of the ECR plasma can be controlled by controlling the magnetic field configuration and the microwave power.
[0049]
For example, the controller 12 forms a magnetic field such that a magnetic field gradient in the ECR region has a relatively small value, and oscillates a microwave with a relatively low microwave power, for example. At this time, plasma having a relatively low electron temperature is generated in the chamber. By treating with plasma having a low electron temperature in this manner, damage to a film, contamination of a chamber member due to sputtering, and the like can be suppressed to a low level.
[0050]
The film forming process in the process chamber 15 is performed so that a silicon nitride film having a predetermined thickness is formed. When the controller 12 determines that the process has been completed, the controller 12 stops the oscillation of the microwave, the energization of the main coil 40 and the auxiliary coil 41, the supply of the silane gas, the application of the bias voltage, and the heating by the heater 27. After purging with nitrogen gas for a predetermined time, supply of nitrogen gas is stopped.
[0051]
Thereafter, the pressure in the chamber 20 is returned to a predetermined pressure, and the gate valve 17 is opened. The electrostatic chuck 22 is released, and the semiconductor wafer W is unloaded from the process chamber 15 by the transfer mechanism 18. After unloading the semiconductor wafer W, the gate valve 17 is closed.
[0052]
At this time, the gate valve 17 separating the measurement chamber 16 and the transfer chamber 14 is opened, and the transfer mechanism 18 loads the semiconductor wafer W into the measurement chamber 16. The semiconductor wafer is mounted on the mounting table 21, and the transfer mechanism 18 moves out of the measurement chamber 16. Thereafter, the gate valve 17 is closed.
[0053]
In the measurement chamber 16, information on the thickness and quality of the silicon nitride film formed on the surface of the semiconductor wafer W is obtained. The controller 12 controls the processing operation based on the information about the film.
[0054]
The controller 12 determines whether the value of the film thickness is within a predetermined range. If it is within the predetermined range, the processing is continued. If not, it is determined that the plasma processing apparatus 11 is not operating normally, and an alarm is issued to that effect to interrupt the processing.
[0055]
After the film measurement is completed, the gate valve 17 is opened, and the semiconductor wafer W is carried out to the transfer chamber 14. Next, after the inside of the transfer chamber 14 is set to a predetermined pressure atmosphere, the gate valve 17 connected to the cassette chamber 13 is opened. The transfer mechanism 18 stores the semiconductor wafer W in a cassette in the cassette chamber 13. Thereafter, the transfer mechanism 18 loads a new semiconductor wafer W into the transfer chamber 14 and performs the same operation as described above. As described above, the plasma processing apparatus 11 continuously performs the plasma processing on a large number of semiconductor wafers W.
[0056]
Here, in the above continuous processing, the controller 12 controls the plasma processing in the process chamber 15 by feeding back the information on the film quality acquired in the measurement chamber 16.
[0057]
That is, the controller 12 obtains information about the plasma generation state, particularly, information about the electron temperature from the information about the film quality. For example, the controller 12 obtains information on the electron temperature of the plasma at the time of film formation from a correlation obtained in advance through experiments or the like based on the acquired film quality information, for example, information on film formation uniformity.
[0058]
The controller 12 controls the microwave power of the microwave oscillator 39 based on the obtained information on the electron temperature of the plasma. As will be described later, the electron temperature of the plasma in a predetermined magnetic field configuration depends on the microwave power. The controller 12 controls the microwave power so that plasma having a predetermined electron temperature is generated.
[0059]
The controller 12 controls the microwave power in accordance with a change in the electron temperature, for example, and performs PID control of the electron temperature. The control method of the electron temperature is not limited to the PID control, and the electronic temperature may be controlled according to a difference from a predetermined threshold.
[0060]
As described above, by feeding back and controlling the information on the state of the formed film, a high-quality film can be stably formed even when ECR plasma having relatively large variations in electron temperature is used. .
[0061]
Hereinafter, the result of examining the dependence of the electron temperature of the ECR plasma on the magnetic field configuration will be described. FIG. 3 schematically shows the configuration of the device 50 used in the experiment. Note that the device 50 shown in FIG. 3 has a configuration substantially similar to the configuration shown in FIG.
[0062]
The device 50 shown in FIG. 3 has a substantially cylindrical container 51 made of aluminum or the like. An exhaust port 52 is formed at the bottom of the container 51, and the inside of the container 51 is exhausted to a predetermined vacuum state via the exhaust port 52.
[0063]
A microwave transmission window 53 is provided at an upper portion of the container 51 so as to seal one end thereof. Microwaves enter the container 51 via the microwave transmission window 53 in parallel with the axial direction. The microwave has a frequency of 915 MHz and TM ₀₁ Mode.
A coil 54 is provided around the upper part of the container 51. The coil 54 forms a magnetic field in the axial direction of the container 51.
[0064]
A gas supply nozzle 55 is provided above the container 51. From the gas supply nozzle 55, nitrogen gas is supplied into the container 51 at a predetermined flow rate.
[0065]
A disk-shaped substrate holder 56 is provided inside the container 51. The substrate holder 56 is supported by a shaft 57 that can be moved up and down, so that the inside of the container 51 can be moved up and down in the axial direction.
[0066]
The shaft 57 is hollow, and a Langmuir probe 58 is inserted therein. The Langmuir probe 58 is arranged such that its tip projects from the center of the substrate holder 56.
[0067]
The Langmuir probe 58 is used for detecting the electron density and electron temperature of plasma using the Langmuir probe method. The Langmuir probe method applies a variable DC voltage to a probe placed in the plasma, detects a change in current according to the state of the plasma, and detects an electron density and an electron temperature from the change in the DC voltage and current. Is the way.
[0068]
In the drawing, z indicates the distance in the axial direction of the container 51 from the microwave transmission window 53. R indicates a distance in a radial direction about the axis of the container 51.
[0069]
In a magnetic field configuration having a predetermined magnetic field gradient, the electron temperature and electron density of the generated plasma when the microwave power was changed were examined using a Langmuir probe.
In the experiment, as shown in FIG. 4, each of the magnetic field configurations B having different magnetic field gradients in the ECR region. _a ~ B _d Was considered. The magnitude of the magnetic field gradient is B _a <B _b <B _c <B _d It is in order.
[0070]
Magnetic field configuration B shown in FIG. _b , B _c , B _d Is shown in FIG. 5, and the magnetic field configuration B _a FIG. 6 shows the results in the case of forming. The experimental conditions were as follows: nitrogen gas 50 to 76 sccm, 0.1 to 1 Pa (about 1 to 10 mTorr), and measurement point z = 400 mm.
[0071]
FIG. 5 shows that the magnetic field configuration B in which the magnetic field gradient is relatively large in the ECR region _b , B _c , B _d It can be seen that the higher the microwave power, the higher the plasma with a higher electron density. On the other hand, it can be seen that the electron temperature does not depend on the magnitude of the microwave power and is relatively constant at a relatively high value.
[0072]
On the other hand, from FIG. 6, the magnetic field configuration B in which the magnetic field gradient in the ECR region is relatively small _a It can be seen that the higher the microwave power, the higher the plasma temperature of the electron. In FIG. 6, when the microwave power is changed from about 0.5 kW to about 1.3 kW, the electron temperature changes from about 2 eV to about 7 eV. On the other hand, it is understood that the electron density does not depend on the magnitude of the microwave power and is almost constant.
[0073]
From the results shown in FIG. 5 and FIG. 6, the magnetic field gradient in the ECR region and the region near the ECR region is generated by forming a magnetic field configuration such that the magnetic field gradient has a predetermined magnitude, particularly a relatively small value. It can be seen that the electron temperature of the plasma can be controlled by the microwave power while keeping the electron density constant.
[0074]
As described above, the reason why the electron temperature depends on the microwave power is that when the microwave power is relatively large, the electromagnetic wave diverges, and when the microwave power is relatively small, the electromagnetic wave is focused. The following is the theory.
[0075]
FIGS. 7A and 7B show the magnetic field configuration B _a Shows the results of calculating the electromagnetic wave distribution in the radius r direction when the microwave power is set to 0.5 kW and 1.5 kW. FIGS. 8A and 8B show the results of calculating the power absorption distribution in the radius r direction when the microwave power is set to 0.5 kW and 1.5 kW.
For the calculation, TASK described in Journal of Applied Physics No. 72 (1992), p. 2652 (Fukuyama et al.) Was used.
[0076]
Here, the electron temperature when the microwave power was 0.5 kW was about 2 eV, and the electron temperature when the microwave power was 1.5 kW was about 7 eV. Therefore, the results at microwave powers of 0.5 kW and 1.5 kW indicate a case where the electron temperature is relatively low and a case where the electron temperature is high, respectively.
[0077]
First, from FIG. 7A, when the microwave power is small, that is, when the electron temperature is low, the electromagnetic wave distribution relatively diverges from the outside to the middle in the radial direction as shown by the arrow in the figure. You can see that there is. On the other hand, FIG. 7B shows that when the microwave power is large, that is, when the electron temperature is high, the electromagnetic wave distribution is relatively focused.
[0078]
FIG. 8A shows that when the electron temperature is relatively low, the power absorption distribution diverges in a relatively wide area. On the other hand, FIG. 8B shows that when the electron temperature is relatively high, the power absorption distribution is relatively focused on a region near the window 53 on the outer side in the radial direction.
[0079]
FIGS. 9A and 9B are spatial distribution diagrams showing the power absorption distributions shown in FIGS. 8A and 8B together with their sizes. 9A and 9B, it can be seen that the maximum value increases as the electron temperature increases (the microwave power increases).
[0080]
From the above results, it is inferred that when the microwave power is large, the electromagnetic wave converges, and at this time, the power absorption of the electromagnetic wave is concentrated in a predetermined region, so that the electron temperature increases. On the other hand, when the microwave power is small, the electromagnetic wave diverges and the power absorption also diverges, so that the electron temperature becomes low.
[0081]
Thus, the power absorption distribution of the electromagnetic wave converges or diverges depending on the microwave power. Therefore, the electron temperature of the ECR plasma can be controlled by setting the magnetic field gradient in the ECR region and its vicinity to a predetermined value and controlling the magnitude of the microwave power.
[0082]
FIG. 11 shows the result of examining the relationship between the magnetic field gradient in the ECR region and the microwave power. The result shown in FIG. 11 shows a plurality of magnetic field configurations B having different magnetic field gradients in the ECR region shown in FIG. ₁ ~ B ₇ Shows the plasma electron temperature when the microwave power is changed. In addition, the measurement was performed in the same manner as in the above measurement, using nitrogen gas, the measurement point Z = 400 mm, and the microwave power set to 750 W, 1 kW, 1.25 kW, and 1.5 kW.
[0083]
As shown in FIG. 10, the magnitude of the magnetic field gradient is B ₁ <B ₂ <… <B ₇ It has become. As can be seen from FIG. 11, the electron temperature of the plasma can be changed by changing the microwave power in a predetermined magnetic field configuration.
[0084]
In particular, the magnetic field configuration B ₂ ~ B ₆ , Preferably the magnetic field configuration B ₂ ~ B ₅ It can be seen that a relatively low electron temperature (about 3 eV or less) can be obtained even when the microwave power is different.
[0085]
The magnetic field gradient near the ECR region can be approximated, for example, by calculating the slope of the curve from the magnetic field strength at z = 200 mm and z = 300 mm.
[0086]
For example, the magnetic field configuration B ₆ , The magnetic field strength at z = 200 mm and 300 mm is 37 mT (3.7 G) and 28 mT (2.8 G), and the gradient is 90 mT / m (9 G / m). In addition, magnetic field configuration B ₂ For, the magnetic field strength at z = 200 mm and 300 mm is 34 mT (3.4 G) and 31 mT (3.1 G), and the gradient is 30 mT / m (3 G / m).
[0087]
From this, the value of the magnetic field gradient in the ECR region and the vicinity thereof is, for example, 30 to 90 mT / m (3 to 9 G / m), preferably 0.3 to 0.5 mT / cm (3 to 5 G / m). When the electron temperature is within the range, the electron temperature can be controlled by the microwave power while keeping the electron temperature at a relatively low value.
[0088]
As described above, according to the above-described embodiment, the electron temperature can be controlled with high accuracy by forming a predetermined magnetic field configuration, particularly a predetermined magnetic field gradient in the ECR region. Therefore, a high-quality film can be stably formed using ECR plasma having relatively large variations in electron temperature.
[0089]
Further, by changing the microwave power in a predetermined magnetic field gradient, particularly in a magnetic field configuration in which the magnetic field gradient is relatively small in the z direction, the electron temperature of the generated plasma can be controlled with high accuracy.
[0090]
Further, in the above embodiment, information on the quality of the formed film is obtained, and the electron temperature of the plasma at the time of processing is estimated based on the information. In the continuous processing, the estimated electron temperature information is fed back, and the microwave power is adjusted to control the electron temperature of the plasma. As described above, by controlling the plasma generation by feedback, it is possible to suppress a relatively large variation in the electron temperature in the ECR plasma and to stably form a high-quality film.
[0091]
The present invention is not limited to the above embodiment, and various modifications and applications are possible. Hereinafter, modifications of the above embodiment to which the present invention is applicable will be described.
[0092]
In the above embodiment, the 915 MHz microwave is used. However, the frequency used is not limited to this, and may be any frequency such as 2.45 GHz.
[0093]
In the above-described embodiment, an example in which the present invention is applied to a single-wafer apparatus has been described. However, the present invention is of course applicable to a batch-type apparatus.
In the above example, one process chamber 15 and one measurement chamber 16 are provided. However, the number of each chamber may be any number.
Furthermore, the measurement of the film thickness and film quality may be performed in the transfer chamber 14 without providing the measurement chamber 16. In this case, for example, an optical measurement unit may be provided on the ceiling of the transfer chamber 14 and the measurement light may be applied to the semiconductor wafer W held by the transfer mechanism 18 through the light transmission window.
[0094]
In the above embodiment, in the measurement chamber 16, the film quality is inspected by a spectroscopic method. However, the measuring method is not limited to this, and an electrical method such as energizing the insulating film may be used.
Further, in the above example, the inspection in the measurement chamber 16 is performed on each of the processed wafers one by one. However, the inspection may be performed every predetermined number of wafers.
[0095]
In the above embodiment, the case where a silicon nitride film is formed by CVD using a silane gas and a nitrogen gas has been described. However, the type of gas used and the type of film to be generated are not limited to the above examples. Of course, the present invention can be applied to a processing apparatus such as MOCVD.
Further, the present invention is not limited to CVD, and can be applied to a case where plasma processing such as PVD is performed. Further, the present invention can be applied to any plasma processing using ECR plasma, such as etching, surface modification, ashing, annealing, etc., without being limited to the film formation processing.
[0096]
In the above embodiment, a case where a semiconductor wafer is processed has been described, but a liquid crystal display substrate may be used.
[0097]
【The invention's effect】
As described above, according to the present invention, a plasma processing method and a plasma processing apparatus capable of performing high quality and stable processing using ECR plasma are provided.
Further, according to the present invention, a plasma processing method and a plasma processing apparatus capable of controlling the electron temperature of ECR plasma with high accuracy are provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a plasma processing apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a process chamber shown in FIG.
FIG. 3 is a diagram showing a configuration of an experimental apparatus.
FIG. 4 Magnetic field configuration B _a ~ B _d It is a figure showing the shape of.
FIG. 5: Magnetic field configuration B _b ~ B _d FIG. 4 is a diagram illustrating a relationship between the electron temperature and electron density.
FIG. 6: Magnetic field configuration B _a FIG. 4 is a diagram illustrating a relationship between the electron temperature and electron density.
FIG. 7 is a diagram illustrating a relationship between an electron temperature and an electromagnetic wave distribution.
FIG. 8 is a diagram showing a relationship between electron temperature and power absorption distribution.
9 is a diagram showing a spatial distribution of the power absorption distribution shown in FIG.
FIG. 10: Magnetic field configuration B ₁ ~ B ₇ It is a figure showing the shape of.
FIG. 11: Magnetic field configuration B ₁ ~ B ₇ FIG. 3 is a diagram showing a relationship between microwave power and electron temperature in FIG.
[Explanation of symbols]
11 Plasma processing equipment
12 Controller
15 Process chamber
16 Measurement chamber
20 chambers
21 Mounting table
33 gas nozzle
34 Gas Ring
35 Microwave introduction window
39 Microwave oscillator
40 main coil
41 Auxiliary coil

Claims (10)

A plasma processing method for performing a predetermined process on an object to be processed by utilizing a plasma generated based on electron cyclotron resonance by an interaction between a magnetic field and a microwave electric field,
In a region where electron cyclotron resonance occurs and a region in the vicinity thereof, a magnetic field forming step of forming a magnetic field having a predetermined gradient with respect to the traveling direction of the microwave,
A microwave control step of controlling the power of the microwave introduced into the magnetic field formed in the magnetic field forming step, such that a plasma having a predetermined electron temperature is generated;
A plasma processing method comprising: The plasma processing method according to claim 1, wherein in the microwave control step, the microwave power is controlled so that a predetermined power absorption distribution of the electromagnetic wave is generated. In the magnetic field forming step, a magnetic field having a predetermined gradient is formed so that the power of the microwave is almost uniformly absorbed in a plane in a region where electron cyclotron resonance occurs and a region in the vicinity thereof. The plasma processing method according to claim 1. 4. The plasma processing method according to claim 1, wherein in the microwave control step, microwave power is controlled such that an electron temperature changes while maintaining a constant electron density of generated plasma. 5. . Further comprising an information acquisition step of acquiring information indicating the processing state of the processed object subjected to the processing,
The plasma processing method according to claim 1, wherein in the microwave control step, the power of the microwave is controlled based on the information acquired in the information acquisition step. A plasma processing apparatus that performs a predetermined process on a target object using plasma generated based on electron cyclotron resonance by an interaction between a magnetic field and a microwave electric field,
Magnetic field forming means for forming a magnetic field having a predetermined gradient with respect to the traveling direction of microwaves in a region where electron cyclotron resonance occurs and a region in the vicinity thereof;
Microwave control means for controlling the power of microwaves introduced into the magnetic field formed by the magnetic field forming means, so that a plasma having a predetermined electron temperature is generated,
A plasma processing apparatus, comprising: The plasma processing apparatus according to claim 6, wherein the microwave control means controls the microwave power so that a predetermined power absorption distribution of the electromagnetic wave is generated. The magnetic field forming means forms a magnetic field having a predetermined gradient so that the power of the microwave is absorbed almost uniformly in a plane in a region where electron cyclotron resonance occurs and a region in the vicinity thereof. A plasma processing apparatus according to claim 6. 9. The plasma processing apparatus according to claim 6, wherein the microwave control unit controls the microwave power so that the electron temperature changes while keeping the electron density of the generated plasma constant. . Further provided with information acquisition means for acquiring information indicating the processing state of the processed object to be processed,
10. The plasma processing apparatus according to claim 6, wherein the microwave control unit controls the power of the microwave based on the information acquired by the information acquisition unit.

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