JP3642773B2 - Plasma processing method and plasma processing apparatus - Google Patents

Description

[0001]
BACKGROUND 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 or a liquid crystal display substrate using electron cyclotron resonance plasma.
[0002]
[Prior art]
In the manufacturing process of electronic devices such as semiconductor devices and liquid crystal display devices, processing using plasma is widely used. Such plasma treatment generates a plasma of a process gas or a carrier gas, and chemically processes the surface of an object to be processed such as a semiconductor wafer with a process gas activated species or a process gas excited in contact with the carrier gas activated species. Apply physical or physical treatment.
[0003]
In recent years, plasma having a low electron temperature has been demanded in order to perform a highly reliable plasma treatment on an object to be processed. For example, when the electron temperature of the plasma is high, damage to the object to be processed, metal contamination of the object to be processed based on sputtering of the chamber member, and the like become problems.
[0004]
As a method of generating plasma having a low electron temperature, a method of generating plasma at a relatively high vacuum pressure using a microwave has been developed. Such a low electron temperature plasma can be generated using a radial line slot antenna (RLSA) as described in, for example, Patent Document 1 below.
[0005]
[Patent Document 1]
JP 2000-294550 A
[0006]
According to the above-described method, it is possible to perform processing while avoiding damage to the object to be processed by the low electron temperature plasma. However, a high gas pressure means that the concentration of the substance in the gas is high, and high-quality processing may not be performed, for example, it is difficult to perform highly anisotropic etching.
[0007]
[Problems to be solved by the invention]
In this respect, electron cyclotron resonance (ECR) plasma can be generated at a relatively low pressure, and high quality processing such as anisotropy is possible. On the other hand, the ECR plasma has a large variation in electron energy (electron temperature) distribution in the plasma compared to the RLSA plasma. For this reason, when ECR plasma is used, the processing stability is lower than when the high-pressure plasma is used.
[0008]
As described above, the conventional processing method using ECR plasma can generate plasma at a relatively low pressure and can perform high-quality processing. However, the variation in plasma electron temperature is relatively large, and the processing is stable. It is difficult to obtain sex. Therefore, in order to realize highly stable processing, a method for controlling the electron temperature of ECR plasma with high accuracy has been required, but there has been no such method in the past.
[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 using ECR plasma capable of processing with high quality and stability.
It is another object of the present invention 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 the first aspect of the present invention comprises:
A plasma processing method for performing a predetermined process on an object to be processed using a plasma generated based on electron cyclotron resonance by an interaction between a magnetic field and a microwave electric field,
A magnetic field forming step of forming a magnetic field having a predetermined gradient with respect to the traveling direction of the microwave in a region where electron cyclotron resonance occurs and in the vicinity thereof; and
A microwave control step for controlling the power of the microwave introduced into the magnetic field formed in the magnetic field formation step so that plasma of a predetermined electron temperature is generated;
including.
[0011]
In the above method, in the microwave control step, the microwave power may be controlled so that a power absorption distribution of a predetermined electromagnetic wave is generated.
[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 absorbed almost uniformly in a plane in a region where electron cyclotron resonance occurs and in the vicinity thereof. May be.
[0013]
In the above method, in the microwave control step, the microwave power may be controlled so that the electron temperature changes while maintaining the electron density of the plasma to be generated constant.
[0014]
The method may further include an information acquisition step of acquiring information indicating a processing state of the object to be processed.
In the microwave control step, the power of the microwave may be controlled based on the information acquired in the information acquisition step.
[0015]
In order to achieve the above object, a plasma processing apparatus according to the second aspect of the present invention provides:
A plasma processing apparatus that performs a predetermined process on an object to be processed using plasma generated based on electron cyclotron resonance by the interaction between a magnetic field and a microwave electric field,
In a region where electron cyclotron resonance occurs, magnetic field forming means for forming a magnetic field having a predetermined gradient with respect to the traveling direction of the microwave,
Microwave control means for controlling the power of the microwave introduced into the magnetic field formed by the magnetic field forming means so that plasma of a predetermined electron temperature is generated;
Is provided.
[0016]
In the above apparatus, the microwave control means may control the microwave power so that a power absorption distribution of a predetermined electromagnetic wave is generated.
[0017]
In the above apparatus, in the magnetic field forming step, a magnetic field having a predetermined gradient is formed 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. May be.
[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 plasma to be generated constant.
[0019]
The apparatus may further include information acquisition means for acquiring information indicating a processing state of the object to be processed.
The microwave control unit may control the power of the microwave based on the information acquired by the information acquisition unit.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
A plasma processing method and a plasma processing apparatus according to embodiments of the present invention will be described below with reference to the drawings.
In the present 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 an object to be processed 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 and a measuring operation which will be described later.
[0023]
The cassette chamber 13 functions as a cassette loading / unloading port. The cassette chamber 13 includes a cassette stand (not shown) and the like, and is configured so that a predetermined number of cassettes can be arranged therein. A predetermined number of semiconductor wafers are accommodated in the cassette. The cassette chamber 13 is configured such that the internal atmosphere can be evacuated by an exhaust device (not shown).
[0024]
The transfer chamber 14 is connected to the cassette chamber 13, the process chamber 15, and the measurement chamber 16 via gate valves 17, respectively. A transfer mechanism 18 is disposed in the transfer chamber 14, and the object to be processed is transferred to and from the chambers via the transfer chamber 14. The transfer chamber 14 is configured so that the internal atmosphere can be evacuated.
[0025]
As will be described later, the process chamber 15 is provided for performing plasma CVD (Chemical Vapor Deposition) on a semiconductor wafer using ECR plasma.
[0026]
The measurement chamber 16 is provided for measuring the processed semiconductor wafer and acquiring information about the formed film. In the measurement chamber 16, information about the thickness of the deposited film and its quality is obtained.
[0027]
The measurement is performed by a spectroscopic method. For example, light such as visible light or infrared light is incident on the surface of the film, and the degree of interference between the reflected light and the incident light is obtained. By the measurement, for example, information on film formation uniformity indicating whether or not the film is uniformly formed on the entire surface of the semiconductor wafer is acquired.
As will be 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 the 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 at a GND potential. For example, the lower portion (bottom portion) of the chamber 20 has a larger diameter than the upper portion.
From the bottom of the chamber 20, for example, a substantially columnar mounting table 21 made of aluminum or the like stands.
[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 disk-shaped electrode plate 23 made of copper or the like in an insulator such as polyimide or ceramic. A semiconductor wafer W is placed on one surface of the electrostatic chuck 22.
[0030]
A DC power source 24 is connected to the electrode plate 23, and a high-frequency power source 25 for bias of, for example, 13.56 MHz is connected via the matching box 26 in parallel therewith. A DC voltage is applied from the DC power supply 24 to the electrostatic chuck 22, and an electrostatic force is generated between the semiconductor wafer W and the insulator, whereby the semiconductor wafer W is attracted and held by the electrostatic chuck 22.
[0031]
Further, 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]
Inside the mounting table 21, a heater 27 for heating the semiconductor wafer W on the mounting table 21 is provided. The heater 27 is composed of a resistor, for example.
Further, a cooling jacket 28 for preventing overheating of a connection portion between the stage and the chamber 20 is provided at the lower portion of the mounting table 21. The cooling jacket 28 includes a flow path through which a refrigerant having a predetermined temperature flows.
[0033]
A gate 29 is opened on the side wall of the chamber 20. The gate 29 can be opened and closed airtight 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 in the 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 rate controller (APC) 31 including a butterfly valve. By the exhaust device 32 and the APC 31, the inside of the chamber 20 is set to a predetermined pressure atmosphere, for example, a pressure of about 1 to 50 mTorr.
[0035]
A gas nozzle 33 is provided above the chamber 20, for example, above a main coil 40 described later. The gas nozzle 33 has nitrogen (N ₂ ) Supply gas. Nitrogen gas is supplied to the upper portion of the chamber 20 at a predetermined flow rate by a mass flow controller (not shown). Although there are two gas nozzles 33 in the figure, the number is not limited to this, and three or more may be provided. Moreover, you may make it supply nitrogen gas with inert gas, such as argon and neon.
[0036]
A gas ring 34 is provided in the center of the chamber 20, for example, between a main coil 40 (described later) and the mounting table 21. For example, the gas ring 34 is formed to have a slightly larger diameter than the mounting table 21 and has a large number of gas holes 34a. From the gas hole 34a of the gas ring 34, silane (SiH ₄ ) The gas is controlled to a predetermined flow rate and supplied to the surface of the semiconductor wafer W on the mounting table 21.
[0037]
The ceiling portion of the chamber 20 is opened, and a microwave introduction window 35 is provided in the opening portion. 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 Inorganic films such as AlN and MgO, and organic films and sheets such as polyethylene, polyester, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide and polyimide. A connection portion between the microwave introduction window 35 and the opening is hermetically sealed by a seal member (not shown) such as an O-ring.
[0038]
A conical taper waveguide 36 is connected to the ceiling of the chamber 20 via a microwave introduction window 35. The taper waveguide 36 is connected to a rectangular waveguide 38 having a rectangular cross section through a conversion waveguide 37 that converts a microwave vibration mode. The end of the rectangular waveguide 38 is connected to the microwave oscillator 39. The microwave oscillated by the microwave oscillator 39 is generated in a predetermined mode, for example, TM. ₀₁ It is converted into a mode and introduced into the chamber 20 through the microwave introduction window 35.
An industrial frequency of 915 MHz is selected as the microwave frequency.
[0039]
A ring-shaped main coil 40 is provided on the outer side of the chamber 20 so as to surround the chamber 20. Similarly, a ring-shaped auxiliary coil 41 is disposed below the bottom of the chamber 20. 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 a cassette disposed in the cassette chamber 13 and loads it into the transfer chamber 14. Thereafter, the gate valve 17 that separates the cassette chamber 13 and the transfer chamber 14 is closed, and the inside of the transfer chamber 14 is depressurized 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 carries the semiconductor wafer W into the process chamber 15. After the semiconductor wafer W is mounted on the mounting table 21, the transport mechanism 18 is withdrawn 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 to fix 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 a predetermined degree of vacuum by the APC 31. Next, the controller 12 introduces nitrogen gas and silane gas at a predetermined flow rate from the gas nozzle 33 and the gas ring 34, respectively.
[0043]
Further, the controller 12 applies a bias voltage of, for example, 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 the top to the bottom in the axial direction of the cylindrical chamber.
[0045]
Further, the controller 12 oscillates a microwave of 915 MHz from the microwave oscillator 39. The microwave passes through the conversion waveguide 37 and the taper waveguide 36, thereby causing a predetermined mode, for example, TM. ₀₁ It is converted into a mode and 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 microwaves with such a power that plasma with a predetermined electron temperature is generated.
[0046]
Due to the interaction between the microwave electric field and the magnetic field, electron cyclotron resonance (ECR) occurs in a predetermined region on the upper portion of the chamber 20. In other words, due to the microwave electric field and the magnetic field, electrons in the magnetic field region receive a Lorentz force and perform a turning motion (cyclotron motion). In a magnetic field region (hereinafter referred to as an ECR region) in which the period of the swirl motion and the frequency of the microwaves substantially coincide with each other, the electrons are always accelerated, and electron cyclotron resonance occurs. Here, when the frequency of the microwave is 915 MHz, the magnetic field strength that satisfies 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 plasma state gas flows downward, activates the supplied silane gas, and generates radicals thereof. The activated silane and nitrogen collect on the surface of the semiconductor wafer W to which a bias voltage is applied, thereby forming a silicon nitride film.
[0048]
In the film forming step, the magnetic field configuration 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 the magnetic field so that the magnetic field gradient in the ECR region has a relatively small value, and oscillates the microwave with, for example, a relatively low microwave power. At this time, plasma having a relatively low electron temperature is generated in the chamber. By processing with plasma having a low electron temperature in this way, damage to the film, contamination of the chamber member due to sputtering, and the like can be kept low.
[0050]
The film formation 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 is completed, the controller 12 stops the microwave oscillation, the energization of the main coil 40 and the auxiliary coil 41, the supply of silane gas, the application of the bias voltage, and the heating by the heater 27. After purging with nitrogen gas for a predetermined time, the 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 the semiconductor wafer W is unloaded, the gate valve 17 is closed.
[0052]
At this time, the gate valve 17 that separates the measurement chamber 16 and the transfer chamber 14 is opened, and the transfer mechanism 18 carries the semiconductor wafer W into the measurement chamber 16. The semiconductor wafer is mounted on the mounting table 21, and the transport mechanism 18 leaves the measurement chamber 16. Thereafter, the gate valve 17 is closed.
[0053]
In the measurement chamber 16, information on the film thickness and film quality of the silicon nitride film formed on the surface of the semiconductor wafer W is acquired. The controller 12 controls the processing operation based on the information regarding the film.
[0054]
The controller 12 determines whether the film thickness is within a predetermined range. If it is within the predetermined range, the process is continued. If not, it is determined that the plasma processing apparatus 11 is not operating normally, an alarm is given to that effect, and the process is interrupted.
[0055]
After the film measurement is completed, the gate valve 17 is opened, and the semiconductor wafer W is unloaded into 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 transport mechanism 18 stores the semiconductor wafer W in the cassette of the cassette chamber 13. Thereafter, the transfer mechanism 18 carries 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 plasma processing on a large number of semiconductor wafers W.
[0056]
Here, in the above-described continuous processing, the controller 12 feeds back information on the film quality acquired in the measurement chamber 16 to control the plasma processing in the process chamber 15.
[0057]
That is, the controller 12 acquires information on the plasma generation state, particularly the electron temperature, from the information on the film quality. For example, the controller 12 obtains information on the electron temperature of plasma during film formation from the correlation obtained in advance through experiments or the like based on the acquired film quality information, for example, information related to film formation uniformity.
[0058]
The controller 12 controls the microwave power of the microwave oscillator 39 based on the obtained information about the electron temperature of the plasma. As will be described later, the plasma electron temperature depends on the microwave power in a predetermined magnetic field configuration. The controller 12 controls the microwave power so that plasma with a predetermined electron temperature is generated.
[0059]
For example, the controller 12 controls the microwave power according to a change in the electron temperature, and performs PID control on the electron temperature. The method for controlling the electron temperature is not limited to PID control, and the electron temperature may be controlled according to a difference from a predetermined threshold.
[0060]
As described above, by feeding back and controlling information on the state of the formed film, a high-quality film can be stably formed even when using ECR plasma with a relatively large variation in electron temperature. .
[0061]
Hereinafter, the result of examining the dependence of the electron temperature of ECR plasma on the magnetic field configuration will be described. FIG. 3 schematically shows the configuration of the apparatus 50 used in the experiment. The apparatus 50 shown in FIG. 3 has a configuration substantially similar to the configuration shown in FIG.
[0062]
The apparatus 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 on the upper portion of the container 51 so as to seal one end thereof. Through the microwave transmission window 53, microwaves are incident on the inside of the container 51 in parallel to the axial direction. The microwave has a frequency of 915 MHz and TM ₀₁ Incident in mode.
A coil 54 is provided around the upper portion 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 on the top of the container 51. From the gas supply nozzle 55, nitrogen gas is supplied into the container 51 at a predetermined flow rate.
[0065]
A disc-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, and can move up and down in the container 51 in the axial direction.
[0066]
The shaft 57 is hollow, and a Langmuir probe 58 is inserted through the shaft 57. The Langmuir probe 58 is arranged so that the tip thereof protrudes from the center of the substrate holder 56.
[0067]
The Langmuir probe 58 is used for detection of 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 plasma, detects changes in current according to the plasma state, and detects electron density and electron temperature from changes in DC voltage and current. Is the method.
[0068]
In the figure, z indicates the distance in the axial direction of the container 51 from the microwave transmission window 53. R represents a distance in the radial direction around the axis of the container 51.
[0069]
In the magnetic field configuration having a predetermined magnetic field gradient, the electron temperature and the 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, magnetic field configurations B having different magnetic field gradients in the ECR region, respectively. _a ~ B _d Was examined. The magnitude of the magnetic field gradient is B _a <B _b <B _c <B _d The order is
[0070]
Magnetic field configuration B shown in FIG. _b , B _c , B _d FIG. 5 shows the result of forming the magnetic field B, and the magnetic field configuration B _a The result when forming is shown in FIG. The experimental conditions were nitrogen gas 50-76 sccm, 0.1-1 Pa (approximately 1-10 mTorr), and measurement point z = 400 mm.
[0071]
FIG. 5 shows that the magnetic field configuration B has a relatively large magnetic field gradient in the ECR region. _b , B _c , B _d It can be seen that plasma with higher electron density is generated as the microwave power increases. On the other hand, it can be seen that the electron temperature does not depend on the magnitude of the microwave power and is substantially constant at a relatively high value.
[0072]
On the other hand, FIG. 6 shows that the magnetic field configuration B has a relatively small magnetic field gradient in the ECR region. _a It can be seen that plasma with higher electron temperature is generated as the microwave power increases. 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 can be seen that the electron density is almost constant without depending on the magnitude of the microwave power.
[0073]
From the results shown in FIG. 5 and FIG. 6, the magnetic field gradient in the ECR region and the vicinity thereof 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 the electromagnetic wave motion diverges when the microwave power is relatively high, and that the electromagnetic wave is focused when the microwave power is relatively low. In the following, the theory is given.
[0075]
7A and 7B show the magnetic field configuration B _a Fig. 5 shows the result of calculating the electromagnetic wave distribution in the radius r direction when the microwave power is 0.5 kW and 1.5 kW. FIGS. 8A and 8B similarly show the results of calculating the power absorption distribution in the radius r direction when the microwave power is 0.5 kW and 1.5 kW.
For the calculation, TASK described in Journal of Applied Physics No. 72 (1992), page 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 of the 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 is relatively divergent from the outside in the radial direction to the middle as shown by the arrows in the figure. I understand that. On the other hand, FIG. 7B shows that the electromagnetic wave distribution is relatively focused when the microwave power is high, that is, when the electron temperature is high.
[0078]
Further, FIG. 8A shows that when the electron temperature is relatively low, the power absorption distribution diverges in a relatively wide region. On the other hand, FIG. 8B shows that when the electron temperature is relatively high, the power absorption distribution is relatively focused in a region near the window 53 outside 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 are compared, it can be seen that the higher the electron temperature (the greater the microwave power), the greater the maximum value.
[0080]
From the above results, it is inferred that when the microwave power is large, the electromagnetic wave motion is focused, and at this time, the power absorption of the electromagnetic wave concentrates in a predetermined region, thereby increasing the electron temperature. On the other hand, when the microwave power is small, electromagnetic wave motion diverges and power absorption also diverges, so that the electron temperature is low.
[0081]
As described above, the power absorption distribution of electromagnetic wave motion is focused or diverged 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 the vicinity thereof to a predetermined value and controlling the magnitude of the microwave power.
[0082]
In addition, 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 is that 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. The measurement was conducted 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, it is understood that 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 Desirably, 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 in the vicinity of 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, magnetic field configuration B ₆ , The magnetic field strengths at z = 200 mm and 300 mm are 37 mT (3.7 G) and 28 mT (2.8 G), and the gradient is 90 mT / m (9 G / m). Magnetic field configuration B ₂ For z = 200 mm and 300 mm, the magnetic field strength 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 it is within the range, the electron temperature can be controlled by the microwave power while keeping the electron temperature relatively low.
[0088]
As described above, according to the above embodiment, the electron temperature can be controlled with high accuracy by forming a predetermined magnetic field configuration, in particular, a predetermined magnetic field gradient in the ECR region. For this reason, it is possible to stably form a high-quality film by using ECR plasma having a relatively large variation in electron temperature.
[0089]
Further, by changing the microwave power in a predetermined magnetic field gradient, in particular, a magnetic field configuration having a relatively small magnetic field gradient with respect to the z direction, the electron temperature of the generated plasma can be controlled with high accuracy.
[0090]
Furthermore, in the above embodiment, information on the quality of the formed film is acquired, and based on this, the electron temperature of plasma during processing is estimated. In continuous processing, the estimated electron temperature information is fed back and the microwave power is adjusted to control the electron temperature of the plasma. Thus, by controlling the plasma generation by feedback, it is possible to suppress a relatively large variation in electron temperature in 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-described embodiment to which the present invention is applicable will be described.
[0092]
In the above embodiment, the microwave of 915 MHz is used, but the frequency to be 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 type apparatus has been described. However, the present invention is naturally 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 chamber 16 may not be provided, and the film thickness and film quality may be measured in the transfer chamber 14. 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 irradiated onto the semiconductor wafer W held by the transfer mechanism 18 through the light transmission window.
[0094]
In the above embodiment, the film quality is inspected by the spectroscopic method in the measurement chamber 16. However, the measurement method is not limited to this, and an electrical method such as energizing the insulating film may be used.
In the above example, the inspection in the measurement chamber 16 is performed one by one on the processing wafer. However, the inspection may be performed every predetermined number of sheets.
[0095]
In the above embodiment, the case where the silicon nitride film is formed by CVD using silane gas and 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 example. Of course, the present invention can also be applied to a processing apparatus such as MOCVD.
Moreover, it is applicable not only to CVD but also to the case of performing plasma processing such as PVD. Furthermore, the present invention is not limited to the film formation process, and can be applied to any plasma process using ECR plasma such as etching, surface modification, ashing, annealing, and the like.
[0096]
In the above embodiment, the case of processing a semiconductor wafer 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 using ECR plasma capable of high quality and stable processing are provided.
The present invention also provides a plasma processing method and a plasma processing apparatus capable of controlling the electron temperature of ECR plasma with high accuracy.
[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.
2 is a diagram showing a configuration of a process chamber shown in FIG. 1. FIG.
FIG. 3 is a diagram showing a configuration of an experimental apparatus.
FIG. 4 Magnetic field configuration B _a ~ B _d FIG.
Fig. 5 Magnetic field configuration B _b ~ B _d It is a figure which shows the relationship between electron temperature and electron density.
FIG. 6: Magnetic field configuration B _a It is a figure which shows the relationship between electron temperature and electron density.
FIG. 7 is a diagram showing the relationship between electron temperature and electromagnetic wave motion distribution.
FIG. 8 is a diagram showing the 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 FIG.
FIG. 11: Magnetic field configuration B ₁ ~ B ₇ It is a figure which shows the relationship between the microwave power and electron temperature in FIG.
[Explanation of symbols]
11 Plasma processing equipment
12 Controller
15 Process chamber
16 Measuring 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 using a plasma generated based on electron cyclotron resonance by an interaction between a magnetic field and a microwave electric field,
A magnetic field forming step of forming a magnetic field having a predetermined gradient with respect to the traveling direction of the microwave in a region where electron cyclotron resonance occurs and in the vicinity thereof; and
A microwave control step for controlling the power of the microwave introduced into the magnetic field formed in the magnetic field formation step so that plasma of 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 power absorption distribution of a predetermined 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 absorbed almost uniformly in a plane in a region where electron cyclotron resonance occurs and 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, the microwave power is controlled so as to change an electron temperature while maintaining a constant electron density of plasma to be generated. 5. . An information acquisition step of acquiring information indicating a processing state of the object to be processed;
5. 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 an object to be processed using plasma generated based on electron cyclotron resonance by the interaction between a magnetic field and a microwave electric field,
A magnetic field forming means for forming a magnetic field having a predetermined gradient with respect to the traveling direction of the microwave in a region where electron cyclotron resonance occurs and a region in the vicinity thereof;
Microwave control means for controlling the power of the microwave introduced into the magnetic field formed by the magnetic field forming means so that plasma of a predetermined electron temperature is generated;
A plasma processing apparatus comprising: The plasma processing apparatus according to claim 6, wherein the microwave control unit controls the microwave power so that a power absorption distribution of a predetermined 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. The 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 plasma to be generated constant. . It further comprises information acquisition means for acquiring information indicating the processing state of the object to be processed,
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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