JP3471385B2 - Plasma processing equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus used for a semiconductor process or the like, and relates to a process for processing a semiconductor substrate or the like by ions generated from generated plasma. Performs precise processing, such as etching and CVD, on the object. In particular, it uses magnetized plasma to generate high-density plasma by efficiently applying high-frequency energy to the plasma by generating electromagnetic waves (abnormal waves) in the plasma. To a plasma processing apparatus. 2. Description of the Related Art In recent years, the demand for high integration in semiconductor manufacturing and the need for economical efficiency have resulted in the necessity of fine processing and a large-diameter semiconductor substrate. There is a demand for high-density and uniform plasma generation with a caliber. As means for obtaining high-density plasma, it is effective to absorb high-frequency energy having a frequency exceeding the plasma frequency into the plasma, and the characteristics of a magnetized plasma for applying a magnetic field to the plasma are used. ECR (Electron Cyclotron Resonance) plasma and helicon wave plasma are known as such magnetized plasma. Although plasma processing equipment using ECR plasma has a reputation as a high-performance equipment, it requires a high magnetic field to obtain ECR conditions, and has problems such as control of this high magnetic field and enlargement of magnetic coils to obtain large-diameter plasma. There is. On the other hand, a plasma processing apparatus using helicon wave plasma is characterized by introducing high-frequency power from an RF antenna into a vacuum vessel to which a magnetic field is applied to generate plasma, and does not require a high magnetic field unlike an ECR plasma processing apparatus. , Can generate plasma under low magnetic field,
It is attracting attention as a source of large-diameter, high-density plasma required in the semiconductor process. FIG. 1 shows a conventional example of a plasma processing apparatus using this helicon wave plasma.
0 is shown. In FIG. 10, a helicon wave plasma processing apparatus 30 is provided with a high frequency power supply 3 inside the reaction chamber 31 at an outer peripheral position of a reaction chamber 31 formed in a cylindrical shape by quartz glass or the like.
An RF antenna 32 for applying a high frequency power from 9 is arranged, and a magnetic coil 33 for applying a magnetic field in the axial direction in the reaction chamber 31 is arranged. The reaction chamber 31 communicates with the process chamber 37, and is evacuated from an exhaust port 35 provided in the process chamber 37, and the reaction chamber 31 and the process chamber 37 form a vacuum vessel. The process chamber 37 has a gas introduction port 3 for introducing a processing gas.
4 and a mounting table 36 on which the object 38 is mounted. In the above configuration, the processing gas introduced into the process chamber 37 from the gas introduction port 34 by the magnetic field from the magnetic field coil 33 and the high frequency power from the RF antenna 32 is turned into plasma, and the application of the magnetic field and electric field is performed. Helicon waves (a kind of anomalous waves) are generated in the plasma when the conditions are met, and electrons in the plasma absorb energy from the Helicon waves due to Landau decay to generate high-density plasma. The ions and the like generated by the plasma are transported from the reaction chamber 31 to the process chamber 37 along the direction of the magnetic field, and the workpiece 38 is efficiently subjected to plasma processing such as etching. The helicon wave plasma device configured as described above generates an initial plasma by electric field excitation by electromagnetic induction, and an electromagnetic wave (helicon wave) generated in the plasma is excited by an applied magnetic field. Landau damping can effectively impart electric field energy to electrons in the plasma, and can generate high-density plasma even under a low magnetic field. [0004] However, the above-mentioned helicon wave plasma processing apparatus can efficiently obtain high-density plasma, but has the following problems. (1) In order to generate a helicon wave in the plasma, a cylindrical process tube (reaction chamber 3) having a length of at least a half wavelength of the helicon wave (usually 8 to 15 cm) or more in the direction of the line of magnetic force.
Since 1) is required, it is difficult to reduce the size of the entire device. (2) Since the RF antenna 32 is disposed at the outer peripheral position of the reaction chamber 31, R
An electric potential with respect to the plasma is generated in the F antenna 32, electrons are collected in the reaction chamber 31 near the RF antenna 32, and negative charges are accumulated.
A dielectric component of the reaction chamber 31 formed of a dielectric such as quartz glass is mixed into the plasma. For example, when oxygen, which is a component of quartz glass, is mixed during etching of aluminum, alumina (Al2
O3) is generated and the etching process is hindered by the strong alumina film. (3) Since plasma particles generated in the cylindrical reaction chamber 31 are transported to the process chamber 37, when performing a large-area plasma treatment, a diverging magnetic field causes a reduction in plasma density and disturbance of ion directionality. And uniform plasma processing is difficult. SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the conventional apparatus, and solves the above problems while taking advantage of the characteristics of a plasma generation process in which high-density plasma is generated by generating electromagnetic waves in plasma. It is an object to provide a plasma processing apparatus that can solve the above problem. Means adopted by the present invention to achieve the above object is to apply a magnetic field from a magnetic coil in the direction of the center axis of a cylindrical vacuum vessel,
A plasma processing apparatus for applying high-frequency power from an RF antenna to the vacuum container to convert a processing gas introduced into the vacuum container into plasma, and performing plasma processing on an object placed in the vacuum container with the plasma. In the above, a dielectric dome portion formed in a substantially hemispherical or conical shape toward the outside of the container is provided at one end in the central axis direction of the vacuum container, and is formed in a loop outside the vicinity of the tip of the dielectric dome portion. The plasma processing apparatus is provided with an RF antenna. In a conventional helicon wave plasma apparatus, an RF antenna for determining a wavelength of an electromagnetic wave generated in plasma is arranged at a position corresponding to a wavelength of the helicon wave, and generates a helicon wave by an electromagnetic induction action. Therefore, as shown in FIG. 2, the R formed in two loops that coincide with the current component wavelength L of the helicon wave with an interval between the electric field components of the helicon wave.
An F antenna is arranged. Due to the necessity of such an RF antenna arrangement, the reaction chamber had to be formed in a cylindrical shape. However, the present inventors have determined that the RF antenna does not need to be provided with the loop interval L for determining the wavelength of the helicon wave.
It has been found that electromagnetic waves can be generated in plasma by bringing an RF antenna formed in a loop close to a process tube (reaction chamber) formed of a dielectric. When high-frequency power is applied to the plasma by bringing the one-loop RF antenna close to the process tube, electromagnetic waves are generated in the plasma in a mode most stable according to the shape of the plasma reaction chamber. Therefore, it is possible to generate plasma in a vacuum vessel in which an object is disposed without forming a cylindrical reaction chamber required for helicon wave plasma generation. Therefore, in the present invention, a dielectric dome portion is formed at one end in the direction of the central axis of the vacuum container so as to protrude substantially hemispherically or conically outwardly of the vacuum container. By arranging an RF antenna formed in one loop at an outer position and applying high-frequency power to the vacuum vessel and applying a magnetic field in the central axis direction, plasma is generated on the central axis in the vacuum vessel. You. Ions generated from a high-density plasma with an electromagnetic wave motion which is generated in the vacuum vessel by the above-described configuration, but is transported in the direction of the magnetic field Ru is delivered to the object, since transport distance is short, uniformity, Plasma irradiation with excellent directivity is performed. Also,
Since the RF antenna can be arranged at a position outside the plasma generation area, the sputtering of the dielectric dome (corresponding to a conventional reaction chamber) caused by the potential difference between the plasma and the RF antenna is small, and the impurity is introduced into the vacuum chamber. Is reduced. An embodiment of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention. still,
The following embodiments are examples embodying the present invention and do not limit the technical scope of the present invention. Here, Figure 1
FIG. 2 is a schematic view showing a configuration of a plasma processing apparatus according to a first embodiment of the present invention. FIG. 2 shows a comparison between a one-loop RF antenna according to the embodiment and a conventional two-loop RF antenna, with respect to plasma density and impurity by ion sputtering. FIG. 3 is a graph showing the change in plasma density measured by the configuration shown in FIG. 2, and FIG. 4 is a graph showing the spatter of the dielectric dome portion measured by the configuration shown in FIG. FIG. 5 is an explanatory view showing a reduction effect, and FIG.
FIG. 6 is a schematic diagram illustrating a configuration of a plasma processing apparatus according to a second embodiment, and FIG. 7 is a schematic diagram illustrating a configuration of a plasma processing apparatus according to a second embodiment. FIG. 8 is a measurement data graph showing the effect of increasing the plasma density, FIG. 8 is a schematic diagram showing another embodiment of the RF antenna according to the embodiment, and FIG. 9 is a schematic diagram showing another embodiment of the dielectric dome portion according to the embodiment. . In FIG. 1, a vacuum vessel 2 formed in a cylindrical shape is configured to be evacuated from an exhaust port 8 to obtain a predetermined vacuum state, and one end of the vacuum vessel 2 on a central axis 11 is made of quartz glass. A dielectric dome portion 3 formed in a substantially hemispherical shape is attached. A magnetic coil 6 is arranged outside the dielectric dome portion 3 concentrically with the center axis 11, and applies a magnetic field in the direction of the center axis in the vacuum vessel 2. Further, an RF antenna 4 having a loop formed concentrically with the central axis 11 is disposed at an outer position near the distal end of the dielectric dome portion 3 (see FIG. 1B).
A high-frequency power from a high-frequency power source 5 is applied to the inside of the vacuum vessel 2. Further, a mounting table 9 on which a workpiece 10 is mounted is disposed on a central axis 11 in the vacuum vessel 2, and a gas introduction port 7 for introducing a processing gas into the vacuum vessel 2 is provided at a predetermined position of the vacuum vessel 2. Is connected. In the above configuration, when the processing gas is introduced into the vacuum vessel 2 from the gas introduction port 7 and the magnetic field from the magnetic coil 6 and the high-frequency power from the RF antenna 4 are applied, the processing gas is Is turned into plasma. The plasma particles such as ions generated by the plasma are transported in the direction of the magnetic field by the magnetic field, and are irradiated on the workpiece 10 mounted on the mounting table 9 to perform predetermined plasma processing. In a plasma processing apparatus, processing speed and processing accuracy are important points, and it is desired that the processing can be performed by a smaller apparatus. The processing speed is related to the plasma density, and the helicon wave plasma processing device described above was useful as a device capable of generating high-density plasma under a low magnetic field. As mentioned above, the use of tubes (reaction chambers) has problems in processing accuracy and miniaturization. As an apparatus for solving the problems while utilizing the effectiveness of a plasma processing apparatus utilizing an abnormal wave generated in the plasma, such as the helicon wave plasma processing apparatus, the above-described configuration shown in the present embodiment is used. The significance of the configuration of the above embodiment and its effectiveness will be described below while showing experimental results in comparison with the helicon wave plasma processing apparatus having the configuration (FIG. 10). (1) Elimination of the process tube and the location of the RF antenna 4 FIGS. 2 and 3 show the change of the plasma density depending on the location of the RF antenna. This is a comparison between the antenna and the one-loop RF antenna according to the present embodiment. The horizontal axis in FIG.
The distance from the end of the antenna to the process tube.
The unit is mm. The gas pressure in the process tube 20 is 3 mTorr, the magnetic field intensity at the center of the process tube 20 is 300 G (magnetic coils are not shown), and 13.56 M is applied to the RF antenna 21 or 22 having a diameter of 150 mm in one loop.
The plasma density on the downstream side (right side in the figure) of the plasma when high frequency power of 1 Hz and 1 Hz was supplied was measured. FIG.
In the conventional configuration shown in FIG.
Since the loop interval P determines the wavelength of the helicon wave, the distance L from the end of the process tube 20 of the two-loop RF antenna 22 is important for generating the helicon wave in the process tube 20 at an appropriate position. Fig. 3
As shown in (1), the fluctuation of the plasma density due to the distance L is remarkable. On the other hand, in the case of the one-loop RF antenna 21 according to the configuration of the present embodiment shown in FIG. 2B, a high plasma density can be obtained regardless of the arrangement position. Even if the position of the one-loop RF antenna 21 is displaced from the process tube 20, if the position is close to the end of the process tube 20, high-frequency power is introduced into the process tube 20.
Generation of high density plasma is observed. However, no plasma is generated at a position distant from the process tube 20. In the plasma generation by the one-loop RF antenna as described above, when a predetermined high frequency is introduced into the plasma generation region, an electromagnetic wave (abnormal wave) that determines the wavelength of the plasma itself is generated, and the energy of the electromagnetic wave is converted into the plasma. High density plasma is generated because it is given to the electrons inside. From the results of the above experiments, in this embodiment, the configuration of the dielectric dome portion 3 instead of the process tube as shown in FIG. 1 and the one-loop RF antenna 4 arranged at a position close to the dielectric dome portion 3 are adopted. With this configuration, since the process tube can be omitted substantially, the overall size of the apparatus can be reduced. (2) Reduction of Impurity Mixing into Vacuum Vessel due to RF Antenna Potential In the conventional configuration, the inside of the process tube 20 at the position where the RF antenna 22 is provided is an outer peripheral portion where high-density plasma is generated. Therefore, the electrons in the plasma are accelerated by the high-frequency potential generated in the RF antenna 22,
The process tube below the RF antenna 22 is charged to generate a DC negative voltage. The ions in the plasma are accelerated toward the RF antenna 22 by the potential difference between the potential and the plasma, and as a result, the walls of the process tube 20 are sputtered by the ions. Since the process tube 20 is usually made of quartz glass, impurities such as silicon and oxygen in performing plasma processing are released into the vacuum vessel and affect the plasma processing. FIGS. 2 and 4 show that the incorporation of impurities into the vacuum chamber due to the potential generated in the RF antenna 22 can be reduced in the configuration of the present embodiment.
This will be described based on the experimental results shown in FIG. FIG. 2 (a),
In order to observe the state of ion sputtering on the tube wall of the process tube 20 when plasma is generated in the process tube 20 in each state of (b), oxygen ion emission when the tube wall is sputtered (4414) Was measured for strength. The processing gas is argon gas, and each RF antenna 2
FIG. 4 shows a graph in which the emission peak intensity was measured when the high-frequency power was increased to 1, 22. As shown in the drawing, it can be seen that oxygen ion emission is smaller in the case of the one-loop RF antenna 21 (b) than in the case of the two-loop RF antenna 22 (a), and the degree of sputtering is lower. In this embodiment, since a dielectric dome portion 3 instead of the process tube as shown in FIG. 1 and an RF antenna 4 arranged at a position close to the distal end thereof are formed,
The position of the F antenna 4 deviates from the center of the plasma generation region, the degree of spattering of the dielectric dome portion 3 by ions is further smaller than in the above experimental configuration, and the contamination of the vacuum vessel 2 with impurities is reduced. (3) Uniformity of Plasma Density Distribution and Directivity of Irradiation on Workpiece FIG. 5 shows the shape of a dielectric dome part in place of a conventional process tube (reaction chamber) and the arrangement position of an RF antenna. FIG. 9 shows an experimental result in which the optimum shape of the dielectric dome portion and the optimum position of the RF antenna were obtained from the change in the plasma density distribution when the change was made. Figure 5 shows the plasma density distribution.
(A), (b) and (c) as shown in FIG.
The measurement was performed by moving the measurement probe on a line A orthogonal to the central axis O on the mm plasma side and measuring the electron density distribution (Ne). The measurement graph is shown below each schematic diagram. In FIG. 5, dielectric dome portions 25a, 25b, and 25c having different shapes are attached to ends of a cylindrical vacuum vessel 23 on a central axis O, and a magnetic field is applied from a magnetic coil 27 and an RF antenna is provided. The arrangement positions of 26a, 26b, 26c are changed.
The position of the mounting table 24 arranged in the vacuum vessel 23 is common to each state. The state shown in FIG. 5A is a configuration close to the conventional configuration, and the plasma density distribution is not uniform.
Since the generation of the electromagnetic wave in the plasma by the antenna does not need to coincide with the wavelength of the wave, if the RF antenna 26b is disposed at the position shown in FIG. 5B, the uniformity of the plasma density distribution is improved. Since the electromagnetic wave is considered to determine a stable mode by the plasma itself depending on the shape of the plasma generation position and the position of the RF antenna, the height of the dielectric window 25 c is reduced as shown in FIG. 5C. However, a more uniform plasma density distribution was obtained. The height of the dielectric window 2 5 c at this time was 100 mm. FIG.
In the configuration shown in (c), since the transport distance of the plasma particles is short, the incident directionality of the plasma particles to the processing object mounted on the mounting table 24 is improved, and the accuracy of etching and film formation is improved. Plasma processing can be performed. The configuration of the present embodiment shown in FIG. 1 is configured based on the experimental results described in each of the above items (1), (2) and (3), and a helicon wave plasma processing capable of obtaining a high density plasma under a low magnetic field. In addition to further improving the advantages of the device, it was also possible to achieve the downsizing of the entire device by mixing impurities into the vacuum vessel and improving the plasma density distribution and directionality, which were problems of the device. . Next, a description will be given of a second embodiment configuration in which a higher-density plasma can be obtained by changing the configuration of the above embodiment (FIG. 1). Note that the same reference numerals are given to the same components as those in the configuration of the first embodiment, and description thereof will be omitted. FIG.
In the configuration of the second embodiment shown in FIG.
It is arranged close to the side. The effect of increasing the plasma density by this configuration will be described based on actual measurement data shown in FIG. In FIG. 6, the position of the magnetic coil 6 indicated by the broken line is the arrangement position in the configuration of the previous embodiment (FIG. 1), and the position of the magnetic coil 6a indicated by the solid line is the arrangement position in the configuration of the present embodiment. FIG. 7 is a graph in which the electron density (Ne) in the plasma on the central axis 11 at the positions where the magnetic coils 6 and 6a of the two examples are disposed is measured. In the measurement graph shown in FIG. 7, the mounting position of the RF
The electron density was measured on the central axis 11 in the direction. The plasma generation conditions under which the measurement data were collected were the argon gas pressure Ar = 3 mTorr introduced into the vacuum vessel 2, and the high frequency power 1.2 kW (13.56 M) introduced from the RF antenna 4.
Hz), the magnetic field strength on the central axis 11 by the magnetic coil 6 or 6a is 260 Gauss. It is confirmed that the electron density when the magnetic coil 6 is disposed at the position indicated by the broken line shows the distribution indicated by the dotted line in FIG. 7, and at the position of the magnetic coil 6a according to the present embodiment, the distribution indicated by the solid line. Was. High-density plasma generation is also observed at the position where the magnetic coil 6 is disposed in the first embodiment configuration indicated by the dotted line. Obtained. The location of the magnetic coil 6 or 6a is determined in consideration of the optimum plasma density and density distribution or the influence of magnetism on the workpiece depending on the type of plasma processing. Next, another embodiment of the RF antenna and the dielectric dome for introducing high-frequency power from the RF antenna into the vacuum vessel according to the present invention will be described. First, the embodiment of the RF antenna shown in FIG. 8 aims at increasing the radiation area of the high frequency power from the RF antenna to the inside of the vacuum vessel and obtaining a large-diameter plasma in the vacuum vessel. . In the embodiment shown in FIG. 8A, a conical dielectric dome portion 12 whose top is aligned with the central axis of the vacuum vessel 2a is attached to the vacuum vessel 2a.
An RF antenna 4a having a plate surface formed in a one-loop conical shape is provided along the conical portion of the dielectric dome portion 12 . Configuration of such an RF antenna 4 a is effective in the production process of a semiconductor integrated circuit in which the plasma processing is required in the state of recently Tomini large diameter wafer. Further, the embodiment of the dielectric dome portion shown in FIG. 9 changes the shape of the plasma generated in the vacuum vessel, as a result, changes the wavelength distribution of the electromagnetic wave (abnormal wave) generated in the plasma, The purpose of the present invention is to obtain an optimum state of the density distribution corresponding to the purpose of use of the plasma processing. In the embodiment shown in FIG. 9A, a concave portion is formed on the side of the vacuum container 2a of the dielectric dome portion 12a having a conical dome portion. In this mode, the density distribution of the generated plasma has a high distribution at the center (recess position). In the embodiment shown in FIG. 9B, a convex portion is formed on the side of the vacuum container 2a of the dielectric dome portion 12b having a conical dome portion. In this mode, the distribution density of the generated plasma is high in the peripheral portion centering on the convex portion. By appropriately changing the form of the RF antenna and the dielectric dome, the state of plasma generation corresponding to the purpose of the plasma processing can be controlled. As described above, in the plasma processing apparatus according to the present invention, it is possible to adjust the distribution of the wavelength and the velocity of the electromagnetic wave gravity induced in the plasma by changing the plasma shape, the magnetic field shape, the antenna shape, and the high-frequency output. Indicated. Therefore, each condition can be appropriately changed and optimized in accordance with the state of the applied plasma processing. As described above, according to the present invention, high-frequency power is applied to the inside of the vacuum vessel from the RF antenna formed in one loop to generate plasma in the vacuum vessel and to generate plasma in the plasma. Induces electromagnetic waves (abnormal waves). High-density plasma can be generated by the plasma generation accompanied by the electromagnetic wave. Unlike the conventional helicon wave (a kind of anomalous wave) plasma generation, there is no need to configure an RF antenna and a reaction chamber that match the helicon wave wavelength, so it is possible to generate plasma directly in a vacuum vessel that performs plasma processing. It becomes possible. Therefore, ions and the like generated from the high-density plasma accompanied by electromagnetic waves generated in the vacuum vessel are transported in the direction of the magnetic field and irradiated on the object to be processed.
Since the transport distance is short, plasma irradiation with excellent uniformity and directionality is performed. In addition, since the RF antenna can be arranged at a position outside the plasma generation region, the sputtering of the dielectric window (corresponding to the conventional reaction chamber) caused by the potential difference between the plasma and the RF antenna is small, and the impurity inside the vacuum chamber is reduced. Contamination is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a configuration of a plasma processing apparatus according to a first embodiment of the present invention. FIG. 2 is a comparative explanatory view of an experimental configuration for comparing a one-loop RF antenna according to an embodiment with a conventional two-loop RF antenna to verify differences in plasma density and impurity contamination due to ion sputtering. FIG. 3 is a graph showing a change in plasma density measured by the configuration shown in FIG. FIG. 4 is an explanatory view showing the effect of reducing spatter of the dielectric dome portion measured by the configuration shown in FIG. 2; FIG. 5 is a schematic configuration diagram and a plasma density distribution graph illustrating an experimental result for determining a shape of a dielectric dome portion and an arrangement position of an RF antenna. FIG. 6 is a schematic diagram showing a configuration of a plasma processing apparatus according to a second embodiment of the present invention. FIG. 7 is a measured data graph showing the effect of increasing the plasma density by the configuration of the second embodiment in comparison with the configuration of the first embodiment. FIG. 8 is a schematic diagram showing a configuration of another embodiment of the RF antenna. FIG. 9 is a schematic diagram showing the configuration of another embodiment of the dielectric dome. FIG. 10 is a schematic diagram showing a configuration of a plasma processing apparatus according to a conventional example configuration. [Description of Signs] 1,15 Plasma processing device 2, 2a Vacuum container 3, 12, 12a, 12b, 25c Dielectric dome portion 4, 4a, 4b, 13a, 13b, 26c RF antenna 5 RF power source 6, 6a magnetic coil 7 gas introduction port 8 exhaust port 9 mounting table 10 workpiece 11 central axis

Continuation of the front page (72) Inventor Tetsu Narai 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Kobe Steel, Ltd. Kobe Research Institute (56) References JP-A-6-232055 (JP, A JP-A-6-267903 (JP, A) JP-A-7-142450 (JP, A) JP-A-6-283471 (JP, A) JP-A-6-506084 (JP, A) Makoto Koto, Gaito 6 Name, Recent Developments in Plasma Etching Research, IEICE Technical Report, Japan, 1992, EP-92, 52-54.56-62, 65-70 (58) Int.Cl. ⁷ , DB name) C23C 16/00-16/56 H05H 1/46 H01L 21/302 H01L 21/205

Claims (1)

(57) [Claim 1] A magnetic field is applied from a magnetic coil in a central axis direction of a cylindrical vacuum vessel, and a high frequency power is applied from an RF antenna into the vacuum vessel. A plasma processing apparatus for plasma-treating a processing gas introduced into the vacuum vessel and performing plasma processing on an object to be processed disposed in the vacuum vessel by the plasma; Substantially hemispherical or conical in the direction
A plasma processing apparatus, comprising: a dielectric dome portion formed in a shape ; and an RF antenna formed in one loop disposed outside a vicinity of a tip of the dielectric dome portion.