JP3175672B2 - Plasma processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus for supplying a high-frequency electric field to an antenna to generate an electric field, generating a plasma by the electric field, and performing a surface treatment such as etching of a substrate or thin film formation by the plasma. Related to
In particular, the present invention relates to a semiconductor processing apparatus that targets a semiconductor device as an object to be processed.

2. Description of the Related Art In a semiconductor processing apparatus in which a current is caused to flow through a coil-shaped antenna to generate plasma by induction, a vacuum vessel wall made of a non-conductive material surrounding a plasma generating portion is provided by a plasma to provide a vacuum atmosphere. The problem is that it is cut. To solve this problem, a method using an electric field shield called a Faraday shield has been considered as described in Japanese Patent Application Laid-Open No. 5-502971. However, if the Faraday shield is used, the plasma ignitability deteriorates, and the plasma will not ignite unless a high voltage of several tens of kV is supplied to the feeding portion of the coiled antenna. In such a device, there is a high possibility that an accident, such as discharge between the antenna and a conductive structure in the vicinity, will occur, and as a countermeasure, the antenna and the structure must be connected to each other in order to prevent discharge. A structure for insulating the space between them is required separately, which complicates the device. In addition, when the amount of shaving of the wall is reduced by using the Faraday shield, when foreign matter or the like adheres to the wall faster from the plasma, the foreign matter adheres to the wall, and the foreign matter easily comes out. Therefore, it is necessary to adjust the amount of shaving the wall according to the process. The plasma density distribution is mainly determined by the production rate distribution and the transport of ions and electrons. In the absence of an external magnetic field, plasma transport diffuses isotropically in each direction. At that time, the electron
Since the mass is less than 1/1000 of the ion, it reaches the vacuum wall instantaneously and tries to escape, but a sheath (ion sheath) is formed near the wall to repel electrons. As a result, the quasi-neutral condition of electron density to ion density is always satisfied in the plasma, and both ions and electrons escape to the wall by ambipolar diffusion. At this time, the potential of the plasma becomes maximum at the place where the plasma density, more precisely, the ion density becomes maximum. This potential is called the plasma potential Vp, and Te,
If mi, me is the electron temperature, the mass of the ion, and the mass of the electron, it is about Vp to Te × ln (mi / me). This V in plasma
The potential distribution is determined by p and the wall potential (usually 0V), and the density distribution is determined accordingly.
In this case, since the plasma is confined by its own electrostatic field, the shape of the density distribution is determined by the shape of the device, the location where the induced electric field is maximized, and the ratio of generation rate / ambipolar diffusion flux. become.

For example, when an antenna having several coils is wound around a vacuum vessel, the magnetic flux produced by the antenna is maximum at the center, and the induced electric field is maximum at the center. Moreover, the induced electric field is about skin depth, usually 1c
Since only about m can penetrate, both the ionization rate and the dissociation rate are maximum in the center of the radial direction (r direction), and directly below the dielectric (z direction). After that, the plasma diffuses to the wafer side (downstream side). Therefore, in the case of a normal cylindrical container, the plasma density becomes maximum at the center in the r direction, and the degree of concentration of the center increases toward the downstream, and the plasma density at the wafer setting portion becomes uneven. SUMMARY OF THE INVENTION It is a first object of the present invention to control the amount by which the wall of a vacuum vessel surrounding a plasma generating section is cut by plasma. It is a second object of the present invention to improve plasma ignitability.
A third object is to realize uniform high-density plasma.

To achieve the above object, the present invention provides an antenna for generating an electric field in a plasma generating unit, a high-frequency power supply for supplying high-frequency power to the antenna, and a method for forming a vacuum atmosphere. A vacuum vessel surrounding the plasma generating section, a Faraday shield provided around the vacuum vessel, a gas supply device for supplying gas into the vacuum vessel, a sample table for placing an object to be processed, and the sample A plasma processing apparatus that includes a high-frequency power supply for applying a high-frequency electric field to the table, accelerates electrons by an electric field generated by the antenna and collides and ionizes the gas to generate plasma to process the object, A load is provided on a ground portion of the antenna, so that the average potential of the antenna is increased so that ignition is improved during plasma ignition,
A feature of the plasma processing apparatus is that the load is adjusted so that the average potential of the antenna is close to the potential of the ground so that the amount of shaving of the wall of the vacuum vessel after plasma generation is reduced. Here, that the average potential of the antenna is close to the ground means that the potentials of 30a and 30b in FIG. 4 are almost equal in opposite phases, that is, that Va ≒ −Vb. The means for solving the above problem will be described with reference to FIG. FIG. 2 shows a general inductive type plasma generator, in which the way of grounding the Faraday shield and the way of grounding the antenna are changed, and the vacuum vessel wall surrounding the plasma generating unit is changed. A method for reducing the amount of shaving by the plasma and improving the ignitability of the plasma was investigated. In this device, a mixed gas of chlorine gas and boron trichloride gas is supplied from a gas supply device 4 into a vacuum container 2 made of alumina, and the mixed gas is wound around the vacuum container 2 into a two-turn coiled antenna. The plasma 6 is generated by being ionized by the electric field generated by 1. After the plasma is generated, the gas is exhausted out of the vacuum vessel by the exhaust device 7. 13. Generated by high frequency power supply 10
An electric field for plasma generation is obtained by supplying high-frequency power of 56 MHz to the antenna 1, but the impedance of the antenna 1 is matched with the output impedance of the high-frequency power supply 10 by using the impedance matching device 3 to suppress power reflection. Let me. As the impedance matching device, a device using two capacitors having a variable electric capacity called a general inverted L type is used. The other end of the antenna is grounded with the capacitor 9 in between,
A switch 21 is provided to short-circuit the capacitor 9. Further, a Faraday shield 8 for preventing the vacuum vessel 2 from being shaved by the plasma 6 is provided between the antenna 1 and the vacuum vessel 2, but the Faraday shield is grounded by opening and closing a plurality of switches 22. It can be both in a state where it is active and in a state where it is not active.
FIG. 3 is a perspective view showing a state where the Faraday shield is installed. The Faraday shield 8 is provided with a slit 14 so as to transmit an inductive electric field 15a generated by the coiled antenna 1 into the vacuum vessel and block a capacitive electric field 15b. Plasma is capacitive electric field 15b
However, when the Faraday shield is grounded to ground, the capacitive electric field from the antenna is hardly transmitted to the vacuum vessel, so that the ignitability of the plasma deteriorates. When the Faraday shield is not grounded to the ground, the potential of the Faraday shield is close to the average potential of the antenna because the antenna and the Faraday shield are capacitively connected. It is considered that the ignitability of the plasma does not deteriorate so much because a typical electric field is generated. The capacitive electric field 15b is an electric field perpendicular to the wall of the vacuum vessel 2, and the charged particles in the plasma are accelerated to collide with the wall and cut the wall. The light 16 generated by the plasma was observed using the spectroscope 20, and the amount of aluminum that was present in the plasma was measured by removing the alumina on the wall, thereby identifying the amount of the wall that was removed. First, in the experimental apparatus shown in FIG.
A method for optimizing the electric capacity of the device so as to reduce the shaving amount of the wall will be described. In the following, a state in which both ends of the switch are conductive is referred to as on, and a state in which both ends are closed is referred to as off.
The optimum value of the magnitude of the electric capacity of the capacitor 9 will be examined when the switch 21 is off, that is, when the capacitor 9 is not short-circuited. 2 can be written as shown in FIG. 4, where the antenna 1 acts as a primary coil of the transformer and the plasma 6
Next coil. The antenna 1 and the plasma 6 are capacitively coupled.
1a and 31b. The capacitance C of the capacitor 9 is determined such that the relationship between the potential Va at the position of the point 30a and the potential Vb at the position of the point 30b on the circuit is always Va = −Vb when the inductance of the antenna is L. . When this condition is satisfied, capacitors 31a and 3
Since the potential applied to both ends of 1b is minimized, the amount of wall shaving is also minimized. FIG. 5 is a further simplified version of FIG. 4 and is an approximation of the element 17 having one combined impedance by combining the antenna and the plasma. When the impedance Z1 of this element is experimentally obtained, Z1 = 2.4 + 114
j (Ω). Here, j represents a complex number. Such an impedance can be easily measured by measuring the current flowing through the object to be measured and the voltage across the both ends. The impedance Z2 of the capacitor 9 is 13.
Assuming that the angular frequency corresponding to 56 MHz is ω, Z2 = −
Since (1 / ωC) j, the real part of Z1 is small in order to satisfy Va = −Vb, so that Z1 + Z2: Z2 =
The relationship of 1: -1 only needs to be established. Therefore, according to calculation, the capacitance of the capacitor 9 is about 150 pF and Va = −Vb
The following relationship holds. FIG. 6 shows the amplitude of the potential generated at the point 30a (dotted line) and the point 30b (solid line) obtained by calculation. The horizontal axis indicates the capacitance of the capacitor 9, and the vertical axis indicates the amplitude of the generated potential. As a result, the amplitudes of the potentials generated near the capacitance of the capacitor 9 of 150 pF were equal, and the phase of the oscillating voltage at that time was shifted by 180 degrees, so that the relationship of Va = -Vb was established. . Therefore, by such a determination method, it is possible to determine the electric capacity of the capacitor placed on the ground side of the antenna that minimizes the amount of wall shaving. Next, FIG. 15 shows the results of investigating the amount of wall shaving and plasma ignitability when the switch 21 and the switch 22 are turned on or off with the capacitance of the capacitor 9 fixed at 150 pF in FIG. If the amount of wall shaving is large, switch 21 should be turned on,
When the switch 22 is turned off, the plasma ignitability under these conditions is excellent. Under other conditions, the shaving amount of the wall can be reduced, but the ignitability of the plasma is inferior. Therefore, it was found that there is no condition in which the amount of wall shaving is small and the plasma has excellent ignitability in this system. However, during plasma ignition, switch 21 is turned off.
n, after igniting the plasma under the condition that the switch 22 is turned off, it is possible to achieve both the objects by operating either the switch 21 or the switch 22 so as to reduce the shaving amount of the wall. Here, in order to simplify the device structure, it is better to use only the switch 21. It is necessary to reduce the potential of the Faraday shield to zero as much as possible in order to reduce the amount of shaving of the wall using the switch 22, so that a plurality of switches 22 are required, and the Faraday shield is grounded to the ground at the shortest distance. Therefore, the switch 22 needs to be installed immediately next to the antenna or the Faraday shield. Therefore, if a plurality of switches are provided in a portion adjacent to the antenna, the Faraday shield, and the like, the structure becomes complicated. In that respect, the switch 21 is simply provided on one side of the condenser 9 which is placed at a certain distance from the antenna, so that the device can be simplified. The state where the switch 21 is off is a state where a 150 pF capacitor is inserted between the antenna and the ground, and the state where the switch 21 is on is HF or
In a high-frequency band such as VHF, the value is equivalent to the fact that the capacitance of the capacitor 9 has changed to infinity. Thus, increasing the capacitance of the capacitor 9 from 150 pF increases the amount of wall shaving. Similarly, even if the capacitance of the capacitor 9 is set to be smaller than 150 pF, the amount of wall shaving increases. Therefore, the amount of wall shaving can be controlled by changing the electric capacity of the condenser 9. In the device shown in FIG. 7, the capacitance of the condenser 9 installed on the ground side of the antenna 1 is made variable. By changing the capacitance of the condenser 9, the amount of wall shaving by plasma is adjusted. Can do things. At the time of plasma ignition, the ignition capacity of the plasma can be significantly improved by making the electric capacity of the condenser 9 sufficiently larger or smaller than 150 pF. As mentioned above, by adjusting the capacitance of the capacitor placed on the ground side of the antenna,
The first object of the present invention can be achieved by adjusting the amount by which the plasma can cut the wall. In addition, the second object of the present invention can be achieved by changing the value of the capacitor placed on the ground side of the antenna when the plasma is ignited so as to obtain a state excellent in ignitability. Next, a method for generating uniform plasma will be discussed. When a coiled antenna is placed on the upper surface of the vacuum vessel, even if the intensity of the induced electric field is changed in the radial direction by changing the diameter of the antenna, an induced electric field is generated in the center, and as a result, the plasma density distribution is concentrated at the center, It becomes uneven.
Also, even if multiple antennas are arranged and the distance between each antenna and the dielectric is changed, the tendency of the plasma density to concentrate at the center does not change. FIG. 21 shows an example of calculating the plasma density distribution when the antenna is placed on a vacuum vessel (FIG. 21A). According to the figure, when the device height H / radius R ratio (aspect ratio) is as large as (b) H / R = 20/25, the plasma density just below the antenna (z = 2 cm) at the location where the antenna exists The absolute value of the density increases (z = 10 cm) toward the downstream side (z increasing direction), and the density decreases immediately above the substrate. At this time, it can be seen that it is uneven in the radial direction. When viewed in the z direction, the density becomes maximum at the center of the device z = 10 cm. When the aspect ratio is reduced (H / R = 15/25) as shown in FIG. 21C, the density distribution is essentially the same as that of FIG. 21B, but the distribution just above the substrate is smaller than that of FIG. Although it is moderate, it has a centralized distribution. The plasma density distribution is determined by the boundary condition that the plasma density is 0 at the vacuum vessel wall and the generation rate distribution, that is, the antenna position. However, as shown in FIG. 21D, the antenna position is changed or a plurality of antennas are placed. Changing the power distribution does not change the shape of the density distribution. When the antenna is placed on the top surface, the induced electric field generated by the antenna is maximized immediately below the antenna, so it is considered that the distribution will be centrally concentrated downstream. On the other hand, when the antenna is arranged beside the vacuum container (FIG. 22A), the induced electric field becomes maximum on the side of the container. A sheath is formed on the side of the container,
The R> degree becomes maximum slightly inside the sheath closest to the antenna. At this time, when viewed in a horizontal cross section, the potential is higher at the sheath end at the wall-sheath end, and the potential at the sheath end also becomes higher at the sheath end-plasma center, and plasma is transported from the sheath end to both sides. At the same time, since the plasma flows downstream from this position, there is a place where the density distribution becomes uniform in the horizontal cross section some distance in the z direction from the place where the density is maximum. For example, in the case of a cylindrical device, if the diameter of the device is R and the height is H, if the ratio of R / H is large, the distribution may be concave near the wafer. The plasma density distribution can be controlled to some extent, for example, the distribution (FIG. 22B). The biggest controlling factor is
It is the ratio of R / H, that is, the shape of the device. However, when the antenna is installed on the side surface, the coupling efficiency decreases due to the large antenna-plasma coupling area, and the plasma density decreases due to the large plasma loss because the location where the density is maximum is near the side wall. When the input power and the size of the vacuum vessel are the same, the plasma density in this case is smaller than that in the case where the antenna is installed above. As a result, there was a problem that the processing speed of the workpiece was reduced. As described above, in the inductively coupled plasma, the plasma density distribution changes depending on the shape of the apparatus and the antenna arrangement. However, the area of the upper surface of the vacuum vessel constituting the processing chamber is smaller than the area of the lower surface, and the upper surface is planar. The third object of the present invention is achieved. Preferably, in the above plasma processing apparatus, an angle between a ridge connecting the upper surface and the lower surface and a normal line of the upper surface is 5 degrees or more. More preferably, in the above plasma processing apparatus, a ratio of apparatus height (distance from an object to be processed to an upper surface) / radius of a lower surface is 1 or less.

Embodiments of the present invention will be described below. FIG. 1 shows a first embodiment of a semiconductor processing apparatus according to the present invention. In the present apparatus, a raw material gas such as oxygen, chlorine, boron trichloride or the like used for semiconductor processing is supplied from a gas supply device 4 into a vacuum vessel, and the gas is supplied to the coiled antenna 1.
The plasma 6 is generated by ionization by the electric field generated by the above.
After the plasma is generated, the gas is exhausted out of the vacuum vessel by the exhaust device 7. 13.56 MHz, 27.12 MHz,
An electric field for plasma generation is obtained by supplying high-frequency power generated by a high-frequency power supply 10 such as 40.68 MHz to the antenna 1, but the impedance of the antenna 1 is reduced by using the impedance matching unit 3 to suppress power reflection. With the output impedance of the high-frequency power supply 10. Although what is called an inverted L type is shown as an impedance matching device, it is necessary to use an impedance matching device that can easily achieve matching depending on the frequency and the structure of the antenna. The other end of the antenna 1 is grounded via a capacitor 9 having a variable electric capacity. Further, a Faraday shield 8 for preventing the vacuum vessel 2 from being shaved by the plasma 6 is provided between the antenna 1 and the vacuum vessel 2, but the Faraday shield is not electrically grounded. As shown in FIG. 3, the Faraday shield 8 is provided with a slit so as to be orthogonal to the direction in which the coil antenna is wound. The semiconductor wafer 13 to be processed is
Place on electrode 5. An oscillating voltage is applied to the electrode 5 by a high-frequency power supply 12 in order to draw ions present in the plasma onto the wafer 13. It is important that the electric capacitance of the variable capacitor 9 be set to an electric capacitance value that minimizes the amount of wall shaving as described in the section for solving the problem. Reference numeral 29 in FIG. 1 indicates a constant temperature bath,
The temperature of the vacuum vessel 2 is controlled. Specifically, the temperature is controlled by providing a fan and a heater. In this embodiment, when the plasma 6 is ignited, the electric capacity of the condenser 9 is set to a value larger or smaller than a value at which the amount of wall shaving is minimized. By setting the value of the electric capacity at that time to about twice or half the electric capacity value at which the amount of wall shaving is minimized, the plasma can be ignited with a high frequency power of several tens of watts. After ignition of the plasma,
In order to reduce the amount of wall shaving, the electric capacity of the condenser 9 is approached to a value at which the amount of shaving is minimized. Set the capacitance of the capacitor 9 to the value. It is necessary to determine the optimum value by repeatedly performing the semiconductor process. FIG. 8 shows a second embodiment of the present invention.
It will be described according to. Although the basic device configuration of the present embodiment is the same as that of the first embodiment, the difference between the present embodiment and the first embodiment is the structure of the capacitor installed on the ground side of the antenna 1. In this embodiment, two capacitors 9a and 9b are inserted in parallel on the ground side of the antenna 1, the capacitor 9a is directly connected to the ground, and the capacitor 9b is connected to the ground by inserting the switch 21. . If the electric capacity of the capacitor 9a is set to a value that minimizes the amount of shaving, the electric capacity that enters the ground side of the antenna 1 by turning on the switch 21 at the time of plasma ignition is increased by the amount of the capacitor 9b. By setting the electric capacity of the capacitor 9b to be sufficiently large, the plasma ignitability is improved. After the plasma ignition, the switch 21 is turned off so that the amount of wall shaving is minimized. Also, as in the first embodiment, if it is desirable to cut the wall to some extent from the viewpoint of foreign matter, the value of the capacitor 9a may be set to a value that is the amount of cut of the wall to be obtained. A third embodiment of the present invention will be described with reference to FIG. The basic device configuration of this embodiment is the same as that of the second embodiment, but the difference between this embodiment and the second embodiment is that an inductor 19 is used instead of the capacitor 9b in FIG. is there. Assuming that the capacitance of the capacitor 9 is C, the inductance of the inductor 19 is L, and the high-frequency angular frequency output by the high-frequency power supply 10 is ω, the impedance Z between the ground side of the antenna and the ground is when the switch 21 is off. Z = − (1 / ωC) j, and when the switch 21 is on, Z = − (1 / (ωC−1 / ωL)) j. If the capacitance of the capacitor 9 is set so that the amount of wall shaving is minimized when the switch 21 is off, the value of Z can be changed by operating the switch 21 to improve the ignitability of the plasma. You can do it. Therefore, when plasma is ignited, the switch 21 is turned on to ignite the plasma, and after the plasma is ignited, the switch 21 is turned off to minimize the amount of wall shaving. Also, as in the first embodiment, if it is desirable to cut the wall to some extent from the viewpoint of foreign matter, the value of the condenser 9 may be set to a value that is the amount of cut of the wall to be obtained. In the third embodiment, the method of changing the impedance of the load inserted between the antenna and the ground by combining the capacitor, the inductor, and the switch has been described. By using means that can change the value of the impedance of the load other than in the above-described embodiment, it is possible to achieve a state in which the plasma ignitability is excellent and a state in which the shaving amount of the wall is small. A fourth embodiment of the present invention will be described with reference to FIG. The basic configuration of this embodiment is the same as that of the first, second and third embodiments, except that the Faraday shield 8 made of a conductive material is made of a non-conductive material. That is, it is embedded in the inside of the wall of the vacuum container 2 thus formed. Alumina, glass, or the like is used as the material of the vacuum vessel 2, but a metal such as chromium, aluminum, or the like is easily fused to the alumina, so that it is easy to form those patterns inside the alumina. . Also, it is possible to embed metal foil in glass like a heater for defrosting automobiles. Advantages of embedding the Faraday shield 8 in the wall of the vacuum vessel 2 as described above are that the insulating structure between the antenna 1 and the Faraday shield 8 is unnecessary, the distance between the vacuum vessel 2 and the antenna 1 can be reduced, and the apparatus is compact. What you can do. FIG. 11 shows a fifth embodiment of the present invention.
It will be described according to. The basic device configuration of the present embodiment is the same as that of the fourth embodiment, but the difference from the present embodiment is that the vacuum vessel 2 made of a non-conductive material has a film of a conductive material as a Faraday shield. Due to coating on the wall. In the present embodiment, an example is shown in which the conductive Faraday shield 8 is coated on the plasma side inside the vacuum vessel, but the same effect can be obtained by coating the Faraday shield 8 on the atmosphere side of the vacuum vessel. In this embodiment, since the plasma 6 is in direct contact with the Faraday shield 8, the plasma 6 cuts the wall of the vacuum vessel 2 at the slit portion of the Faraday shield 8. Although depending on the process, in the oxide film etching process using oxygen or the like as a raw material gas, the Faraday shield 8 is made of conductive aluminum and the vacuum vessel 2 is made of aluminum, taking advantage of the excellent adhesion between alumina and aluminum. By using insulating alumina, a configuration in which an insulating material is coated with a conductive material can be achieved. In the case of a metal process using chlorine or boron trichloride as a source gas, the object can be achieved by using alumina as the insulating material and SiC as the conductive material. There are many other such combinations, but they have the ability to prevent the coated conductive material from peeling off when the vacuum vessel becomes hot,
In addition, the same effect can be expected in any combination as long as the insulating material and the conductive material are not easily removed by plasma. A sixth embodiment of the present invention will be described with reference to FIG. The basic device configuration of this embodiment is the same as that of the first, second, and third embodiments, but the difference between this embodiment and other embodiments is that the Faraday shield 8 is grounded by using the resistor 18. It is grounded. It is considered that a human often touches the Faraday shield 8 during work such as rearrangement of the device. At that time, a mechanism for preventing the Faraday shield from being charged is required. In this embodiment, the Faraday shield is grounded to the ground by using the resistor 18. The resistance value of this resistor is the impedance of the capacitance between the Faraday shield 8 and the ground at the frequency of the high frequency power supply 10 for generating plasma. It is necessary to have a larger impedance. To do so, the capacitance between the Faraday shield and ground must be C
Assuming that the resistance value of the ground resistor 18 is R and the high-frequency angular frequency output from the high-frequency power supply 10 is ω, R is set so that R> 1 / ωC. That is, at a high frequency for generating plasma, the load between the Faraday shield and the ground is coupled with a load having an impedance larger than the impedance of the capacitance between the Faraday shield and the ground, and the impedance of the load is reduced. In the case of direct current, the charge is reduced to prevent charging of the Faraday shield at the end of operation. A seventh embodiment of the present invention will be described with reference to FIG. Although the basic device configuration of the present embodiment is the same as that of the sixth embodiment, the difference between this embodiment and the sixth embodiment is that the effect of the Faraday shield is obtained by forming the vacuum vessel 2 with a conductive material. It depends on what you have. As described with reference to FIG. 3, the vacuum vessel serving as the Faraday shield cannot be provided with a slit for blocking an inductive electric field. Need to be able to pass through various electric fields. Here, the vacuum vessel has a structure in which it is electrically floated from the ground by an insulating flange 24. According to the present embodiment,
Since the work of providing the Faraday shield around the vacuum vessel is unnecessary, workability is improved. In this embodiment, a circuit for adjusting the average potential of the antenna 1 to be near the ground and as an absolute value larger than the ground is the same as that of the sixth embodiment. FIG. 14 is a perspective view showing the state of the eddy current flowing in the vacuum vessel in the present embodiment. The eddy current for canceling the transmission of the inductive electric field 15 a described in FIG. 3 into the vacuum vessel 2 flows in the circumferential direction of the cylindrical vacuum vessel 2 as indicated by an arrow 25. Assuming that the resistance in the eddy current flow path is R, the inductance is L, and the high-frequency angular frequency output by the high-frequency power supply 10 is ω, the eddy current attenuation due to the resistance increases if the relationship of R> ωL is satisfied. Then, an inductive electric field is transmitted into the vacuum vessel. Since the material of the vacuum vessel 2 is directly facing the plasma as in the case of the fifth embodiment, it is necessary that the material be hardly cut by the plasma. Since the thickness of the wall of the vacuum vessel is usually about 2 cm, for example, the frequency is 13.56 MHz.
In order to make the skin thickness at that level in z, 0.02Ω
It is sufficient to use a material having an electrical resistivity of about m.
The vacuum vessel 2 has an insulating flange 2 to insulate it from the ground.
4, but a resistor 18 for preventing charging is provided as in the sixth embodiment. As described in the sixth embodiment, the resistance of the resistor 18 needs to have an impedance greater than the impedance between the Faraday shield and the ground at the frequency of the high-frequency power supply 10 for generating plasma. In the semiconductor processing, a bias voltage is applied to the electrode 5 by the high-frequency power supply 12, but if the plasma is electrically floating with respect to the ground, the bias voltage will not be generated strongly between the plasma and the electrode. In order to prevent this, it is necessary to lower the potential of the plasma by bringing the plasma into contact with the ground as much as possible.
In the frequency band 2, it can be achieved by having an impedance smaller than the impedance between the Faraday shield and the ground. The present embodiment is a case where the entire vacuum vessel is made of a conductive material.However, in the other embodiments, the slit is not provided in the Faraday shield, and only the thickness of the conductive material is adjusted as in the present embodiment. Can obtain the same effect. In the above-described embodiment, the vacuum vessel 2 has been described as having a cylindrical shape. However, the vacuum vessel 2 is provided with a coil and a Faraday shield in a vacuum vessel 2 having a trapezoidal cross section with a side surface having an inclination. In any case, the above-described embodiment can be similarly applied. An eighth embodiment of the present invention will be described with reference to FIG. The basic device configuration of the present embodiment is the same as the first, second, and third embodiments, but the difference between this embodiment and other embodiments is that the upper surface of the vacuum vessel Distant one) 2a
Is characterized in that the area of the lower surface of the vacuum vessel is small. Preferably, the upper surface is planar. In the present invention configured as described above, the degree and position of coupling between the plasma and the antenna can be changed depending on the arrangement of the antenna, the number of turns of the antenna, the distance between the antenna and the vacuum vessel, and the like. For example, when the antenna is wound one side horizontally, FIG.
As shown in (a), the coupling location changes depending on whether the antenna is up or down. In the case of a plurality of windings, the coupling state can be changed depending on the vertical position of the antenna and the distance between each winding and the vacuum vessel (FIG. 23 (b)). In order to increase the density in the central part, the antenna is moved upward. On the other hand, when the distribution is high in the periphery, the antenna is moved downward. The position of the coupling can be changed because the shape of the device is inclined due to the small area of the upper surface and the large area of the lower surface. In the case of inductively coupled plasma, the distribution of electrons and ions is affected by the shape of the container because the electrons and ions are diffused isotropically toward the container wall. Therefore, if the top surface is planar, the plasma distribution is also easily flattened. It is easy to control the plasma density distribution by antenna arrangement and characteristic device shape. Also, due to the electrostatic field generated by the antenna 1, foreign substances and reaction products generated by the interaction between the plasma and the vacuum vessel wall 2 increase in the vicinity of the antenna. Since a flow path is formed and flows easily along the wall, the amount of the flow toward the wafer 13 can be reduced, and good processing can be realized. Reference numeral 191 in FIG. 16 denotes a means for moving the position of the coil, and the height of the coil can be adjusted to adjust the plasma density distribution. FIG. 17 shows a ninth embodiment of the present invention. Although the basic device configuration of this embodiment is the same as that of the eighth embodiment, the difference between this embodiment and the other embodiments is that the ridge line connecting the upper surface 2a and the lower surface 2b of the vacuum vessel 2 and the method of the upper surface are different. The angle between the line and the line is 5 degrees or more. FIG. 24 shows the distribution of ion current density incident on the surface of the workpiece when the radius of the upper surface Ru: the radius of the lower surface Rd = 4: 5, for example, the shape of the vacuum vessel according to the present invention. The ion current is flat up to φ300 (r = 15cm) when the height of the vacuum vessel is H = 13cm. When H is increased, the central part has a slightly higher distribution. It has also been confirmed that if H is smaller than this, the surrounding height will increase. tan-1 {(Rd-Ru) / H} ≧ 5
If it is a degree, distribution of flatness, center height and peripheral height can be realized.
FIG. 18 shows a tenth embodiment of the present invention. The basic device configuration of this embodiment is the same as that of the eighth embodiment, but the difference between this embodiment and the other embodiments is the height H of the vacuum vessel 2 (the distance from the electrode 5 to the upper surface 2a). And the diameter of the vacuum vessel 2, that is, the radius Rd of the lower surface, satisfies the relationship of H / Rd ≦ 1. For example, the vacuum container shape shown in FIG. 24 satisfies this relationship. FIG. 19 shows an eleventh embodiment of the present invention.
Although the basic device configuration of this embodiment is the same as that of the eighth embodiment, the difference between this embodiment and other embodiments is that a magnetic field generating means 26 is provided outside the vacuum vessel 1. I do. FIG. 25 shows the distribution of the plasma density n immediately above the substrate in the presence of a magnetic field. According to this, as the magnetic field is increased, the plasma density distribution becomes higher around the periphery, and it can be understood that this is an auxiliary means that can control the distribution. In FIG. 25, Dl, which is a parameter, represents the diffusion coefficient in the direction of the line of magnetic force, and Dp represents the diffusion coefficient in the direction perpendicular to the line of magnetic force. FIG. 20 shows a twelfth embodiment of the present invention. The basic device configuration of this embodiment is the same as that of the eighth embodiment, but the difference between this embodiment and the other embodiments is that the surface facing the electrode 5, the conductor inside the upper surface 2a of the vacuum vessel, Alternatively, a plate 27 made of a semiconductor is provided. Preferably, a high frequency voltage applying means 28 is connected to the plate 27 to apply a high frequency. The high frequency here may be a pulsed DC voltage. The plate 27 may be grounded.

According to the present embodiment, the amount of the vacuum vessel wall surrounding the plasma generating portion cut by the plasma can be controlled, and the plasma ignitability can be improved. Also, by changing the degree and position of the coupling between the plasma and the antenna depending on the arrangement of the antenna, the number of turns of the antenna, the distance between the antenna and the vacuum vessel, the distribution of the plasma can be controlled, and a uniform plasma can be obtained. it can.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing an experimental system used for verifying the present invention.

FIG. 3 is a perspective view showing a state where a Faraday shield is installed.

FIG. 4 is an equivalent circuit diagram of an experimental system used to verify the present invention.

FIG. 5 is an equivalent circuit diagram of an experimental system used to verify the present invention.

FIG. 6 shows the amplitude of a potential generated at both ends of the antenna.

FIG. 7 is a configuration diagram of an experimental system used to verify the present invention.

FIG. 8 is a configuration diagram showing a second embodiment of the present invention.

FIG. 9 is a configuration diagram showing a third embodiment of the present invention.

FIG. 10 is a configuration diagram showing a fourth embodiment of the present invention.

FIG. 11 is a configuration diagram showing a fifth embodiment of the present invention.

FIG. 12 is a configuration diagram showing a sixth embodiment of the present invention.

FIG. 13 is a configuration diagram showing a seventh embodiment of the present invention.

FIG. 14 is a perspective view showing a flow of an eddy current in a seventh embodiment of the present invention.

FIG. 15 is a diagram summarizing the amounts of scraping of the switches 21 and 22, the wall of the vacuum vessel, and RF power required for ignition of plasma.

FIG. 16 shows a plasma processing apparatus according to an eighth embodiment of the present invention.

FIG. 17 shows a plasma processing apparatus according to a ninth embodiment of the present invention.

FIG. 18 shows a plasma processing apparatus according to a tenth embodiment of the present invention.

FIG. 19 shows a plasma processing apparatus according to an eleventh embodiment of the present invention.

FIG. 20 shows a plasma processing apparatus according to a twelfth embodiment of the present invention.

FIG. 21 is a diagram showing a plasma density distribution in a case where the antenna is placed on an antenna.

FIG. 22 is a diagram showing a substrate incident ion current density distribution when the antenna is placed on the side surface.

FIG. 23 is a schematic view illustrating the principle of the present invention.

FIG. 24 is a diagram showing a substrate incident ion current density distribution in the case of the present invention.

FIG. 25 is a diagram showing the effect of the fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Antenna, 2 ... Vacuum container, 2a ... Upper surface of vacuum container, 2b
... Vacuum container, 2c ... Vacuum ridge, 3 ... Impedance matching device, 4 ... Gas supply device, 5 ... Electrode, 6 ... Plasma, 7 ... Gas exhaust device, 8 ... Faraday shield, 9 ...
Capacitor, 10 high-frequency power supply, 11 electric field shield, 12 high-frequency power supply, 13 wafer, 14 slit, 15a inductive electric field, 15b capacitive electric field, 1
6 ... light generated by plasma, 17 ... element having combined impedance, 18 ... ground resistance of Faraday shield, 1
9 ... Inductor, 20 ... Spectroscope, 21 ... Switch, 22
... Switch, 23 ... Switch, 24 ... Insulation flange, 2
5: Eddy current flow. 26 ... magnetic field generating means, 27 ... plate, 28
... High frequency voltage applying means, 29 ...

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsutomu Tsujiro 502 Kandatecho, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratory, Hitachi, Ltd. (72) Inventor Kenji Maeda 502-Kindachicho, Tsuchiura-shi, Ibaraki Pref. Inside the research laboratory (72) Inventor Takeshi Yoshioka 794, Higashi-Toyoi, Oji, Kudamatsu City, Yamaguchi Prefecture Inside the Kasado Plant, Hitachi, Ltd. (72) Inventor Saburo Kanai 794, Higashi-Toyoi, Katsumatsu City, Yamaguchi Prefecture Inside the Kasado Plant, Hitachi, Ltd. (72) Inventor Hideyuki Kazumi 7-1-1, Omikamachi, Hitachi City, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. In-house (72) Inventor Ryoji Nishio 502 Kandate-cho, Tsuchiura-shi, Ibaraki Pref. (56) Reference Patent flat 6-196446 (JP, A) JP flat 10-83898 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) H05H 1/46 C23C 16 / 50 C23F 4/00 H01L 21/3065

Claims (11)

(57) [Claims] An antenna for generating an electric field in a plasma generator, a high-frequency power supply for supplying high-frequency power to the antenna,
A vacuum vessel surrounding the plasma generation section to form a vacuum atmosphere, a Faraday shield provided around the vacuum vessel, a gas supply device for supplying gas into the vacuum vessel, and a A sample stage and a high-frequency power source for applying a high-frequency electric field to the sample stage are provided, and the electric field generated by the antenna accelerates electrons and collides and ionizes the gas to generate plasma to process the object. In the plasma processing apparatus, a load is provided on the grounding portion of the antenna so that the average potential of the antenna is increased so that ignition is improved during plasma ignition. A plasma processing apparatus characterized in that the load is adjusted so that the average potential of the antenna is close to the potential of the ground so as to reduce the potential. 2. The plasma processing apparatus according to claim 1, wherein said antenna is a coil. 3. The plasma according to claim 1, wherein the load is changed by using a variable capacitance capacitor or a variable inductance inductor as a load inserted into the ground side of the antenna. Processing equipment. 4. The load according to claim 1 or 2, wherein a load or a load is inserted into the ground side of the antenna by combining a capacitor or an inductor having a fixed capacitance and a switch so that the load has two or more types of load values. A plasma processing apparatus characterized in that: 5. A plasma processing apparatus according to claim 1, wherein, even after plasma generation, the average potential of the entire antenna is controlled to control the amount of wall shaving. . 6. The plasma processing apparatus according to claim 1, wherein the Faraday shield is embedded in a vacuum vessel wall made of a non-conductive material. 7. The plasma processing apparatus according to claim 1, wherein a Faraday shield effect is provided by coating a surface of the vacuum vessel wall with a conductive material. 8. The method according to claim 7, wherein the conductive material is coated on a surface of the vacuum vessel wall which is in contact with the plasma, and the conductive material is made of a material which is hard to be cut by the plasma to reduce the amount of wall shaving. A plasma processing apparatus characterized by the above-mentioned. 9. The Faraday shield and the load according to claim 1, wherein the Faraday shield and the load have an impedance greater than an impedance of an electric capacity between the Faraday shield and the ground at a high frequency for generating plasma. A plasma processing apparatus, wherein the Faraday shield is prevented from being charged at the end of the operation by coupling with a ground and reducing the impedance of the load in direct current. 10. An antenna for generating an electric field in the plasma generation unit, a high-frequency power supply for supplying high-frequency power to the antenna, a vacuum container surrounding the plasma generation unit for forming a vacuum atmosphere, and an inside of the vacuum container A gas supply device for supplying gas to the sample stage, a sample stage for placing an object to be processed, and a high-frequency power supply for applying a high-frequency electric field to the sample stage, and the electric field generated by the antenna accelerates electrons to generate gas. In a plasma processing apparatus that generates plasma by impact ionization, the material of the vacuum vessel is a conductive material,
The structure in which the potential of the vacuum vessel is electrically floated from the ground, and the thickness of the wall of the conductive vacuum vessel is adjusted so that the capacitive electric field generated by the antenna is not transmitted into the vacuum vessel, A semiconductor processing apparatus wherein an inductive electric field is transmitted. 11. An antenna for generating an electric field in the plasma generation unit, a high-frequency power supply for supplying high-frequency power to the antenna, a vacuum container surrounding the plasma generation unit for forming a vacuum atmosphere, and An antenna provided with a provided Faraday shield, a gas supply device for supplying gas into the vacuum vessel, a sample table for placing an object to be processed, and a high-frequency power supply for applying a high-frequency electric field to the sample table; In a plasma processing apparatus for processing an object by accelerating electrons by an electric field generated and impacting and ionizing the gas, the potential of the Faraday shield is changed between before and after plasma generation. A plasma processing apparatus characterized by the above-mentioned.