JP3208995B2 - Plasma processing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method and apparatus, and more particularly to a plasma processing method and apparatus suitable for uniformly processing a sample by generating plasma by electromagnetic waves such as microwaves.

[0002]

2. Description of the Related Art An example of the prior art is an example in which a quartz discharge tube is used as an electromagnetic wave transmitting member.
l. 71-No. 5 (19899.5).

[0003]

In a semiconductor manufacturing process using plasma, it is necessary to uniformly process the workpiece without damaging it. As an example of a conventional semiconductor manufacturing apparatus, there is an apparatus using a hemispherical quartz discharge tube as an electromagnetic wave transmitting member. Therefore, the electromagnetic wave propagating in the waveguide is easily affected by the shape of the quartz discharge tube, and is introduced into the quartz discharge tube by repeating complicated reflection and refraction. As a result, various modes are excited as the propagation mode of the electromagnetic wave, and the state of the generated plasma tends to be unstable. Further, in the example where a flat plate is used as the electromagnetic wave transmitting member, the electromagnetic wave transmitting member having a diameter smaller than the diameter of the cavity resonance portion is provided, so that the electromagnetic wave reflection on the electromagnetic wave transmitting member side is not uniform, ie The reflection differs between the part and the peripheral part, and the energy distribution of the electromagnetic wave introduced into the discharge region tends to be non-uniform. Therefore, the distribution of the generated plasma becomes non-uniform, and it becomes difficult to uniformly process the object to be processed. As described above, the conventional method is disadvantageous in terms of stability and uniformity of generated plasma.

SUMMARY OF THE INVENTION It is an object of the present invention to generate a stable plasma by suppressing a mode transition of an electromagnetic wave introduced into a discharge region and to generate a uniform plasma by making the energy distribution of the electromagnetic wave introduced into the discharge region uniform. It is an object of the present invention to provide a plasma processing method and apparatus which can be used.

[0005]

In order to achieve the above object, an electromagnetic wave introducing section for introducing an electromagnetic wave into a device, a hollow section for transmitting an electromagnetic wave following the electromagnetic wave introducing section, and a discharge area connected to the hollow section are formed. A vacuum vessel to be provided, and an electromagnetic wave transmitting member that is provided between the cavity and the vacuum vessel, forms a part of the vacuum vessel, and transmits electromagnetic energy substantially all over the vacuum vessel. The diameter of the transmitting portion and the inner diameter of the vacuum vessel are substantially the same, and the diameter is 1.75 times or more the diameter of the material to be processed. to form a standing wave as a repeating TE ₀₁ mode reflected between the, a structure the apparatus as a mix with TE ₁₁ mode come to propagate electromagnetic wave introducing section for introducing the discharge region, a cavity Through the electromagnetic wave introduction section A method for plasma processing an object to be processed in the electromagnetic vacuum chamber is propagated to the discharge region of the vacuum vessel of the electromagnetic wave introducing portion to propagate electromagnetic waves in the TE ₁₁ mode, and the boundary surface of the electromagnetic wave electromagnetic wave transmission member and the discharge region Reflection is repeated between the cavity and the electromagnetic wave introduction side end face TE ₀₁
Mode becomes to form a standing wave, the electromagnetic wave introducing portion be mixed with the propagation of electromagnetic waves with TE ₁₁ came mode introduced into the discharge region, it is obtained by a method of generating a discharge in the vacuum vessel.

[0006]

According to the present invention, the energy of electromagnetic waves is transmitted through the entire surface of the vacuum vessel through an electromagnetic wave transmitting member provided between the cavity and the vacuum vessel. in substantially the same diameter and not less than 1.75 times the diameter of the material to be treated the該径, electromagnetic waves repeatedly reflected between the electromagnetic wave introducing end face of the boundary surface and the cavity portion of the electromagnetic wave transmission member and the discharge region TE ₀₁ mode becomes to form a standing wave, by a mix and TE ₁₁ modes which come to propagate electromagnetic wave introducing section so as to introduce the discharge region, the nature of the reflecting end of the electromagnetic wave of the electromagnetic wave transmission member side one As a result, the transition of the electromagnetic wave mode is suppressed and stable plasma can be generated, and the mode of the electromagnetic wave excited in the cavity is limited to make the energy distribution of the electromagnetic wave uniform in the part where the plasma is generated. To Rukoto can. Further, by combining a large-sized exhaust duct connected thereto as a vacuum vessel having a diameter of 1.75 times or more of the diameter of the object to be treated, the exhaust conductance can be increased, and a low-pressure process or a large-flow process can be realized.

By arranging the outlet of the process gas near the electromagnetic wave transmitting member, the influence of the stagnation of the gas in the vacuum vessel can be reduced, and the distribution of the process gas in the portion where plasma is generated can be made uniform. it can. Also,
In order to generate stable plasma and uniformly process an object to be processed, the thickness of the ECR surface, which is a plasma generation unit, and E
It is necessary to optimize the distance between the CR surface and the workpiece and the distance between the ECR surface and the electromagnetic wave transmitting member. The thickness of the ECR surface is expressed as a function of the magnetic field gradient. By setting the value of the magnetic field gradient on the ECR surface within the range of 20 G / cm or more and 50 G / cm or less, stable and uniform plasma can be generated. Distance between ECR surface and workpiece, ECR
The distance between the surface and the electromagnetic wave transmitting member greatly affects the density and uniformity of the plasma. If the distance between the ECR surface and the processing object is too small, the diffusion of the plasma is not sufficient, and the uniformity of the plasma (saturated ion current density) reaching the processing object is deteriorated. Further, if the distance between the ECR surface and the electromagnetic wave transmitting member is too small, the distribution of the electromagnetic wave is greatly affected, and the uniformity of the plasma generated near the ECR surface is deteriorated. Current density) is deteriorated. 30mm distance between ECR surface and workpiece
As described above, by setting the distance between the ECR surface and the electromagnetic wave transmitting member to be 50 mm or more, the consumption of the electromagnetic wave transmitting member can be reduced, and the plasma (saturated ion current density) reaching the object to be processed can be made uniform. As a result, it is possible to improve the operating ratio and the yield in the mass production line.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an embodiment of the present invention. FIG. 2 shows FIG.
FIG. 3 is an enlarged view of a plasma generating portion in FIG. This embodiment is an example in which a microwave and a magnetic field are used as means for generating plasma. 1 is a magnetron that generates microwaves, 2
Is a waveguide for propagating microwaves, 3 is a circular-rectangular conversion waveguide, 4 is a hollow portion, 41 is a top plate of the hollow portion 4, 5 is a solenoid coil for generating a magnetic field, 51 is a topmost solenoid coil, 6 is an electromagnetic wave transmitting member (for example, a quartz flat plate), 7 is a vacuum vessel, 8 is a holder for mounting an object to be processed, 9 is a driving mechanism for moving the holder up and down, and 10 is applying an RF bias voltage for etching to the holder. A shower plate for introducing an etching gas into the vacuum vessel 7; a gas outlet 111 provided on the shower plate 11; a gas introduction path 112;
2 is a variable valve for adjusting the pressure of the vacuum vessel 7,
13 is a turbo molecular pump for depressurizing the vacuum vessel 7 to a vacuum, and 14 is a roughing vacuum pump. Reference numeral 15 denotes the generated plasma, and 151 denotes a boundary surface of the plasma 15, that is, a reflection surface of an electromagnetic wave (a surface having an electron density of> 1 × 10 ¹¹ / cm ^{3 in} the case of a magnetic field).

The inside of the vacuum vessel 7 is provided with a turbo molecular pump 13.
The pressure is reduced by the rough pump 14. When a sample is processed, a process gas is introduced between the electromagnetic wave transmitting member 6 and the shower plate 11 from the gas introduction path 112, and is guided to the vacuum vessel 7 from a gas outlet 111 provided in the shower plate 11. A similar effect can be obtained even if a gas outlet is provided around the lower surface of the electromagnetic wave transmitting member 6 without using the shower plate 11. A variable valve 12 is provided for adjusting the internal pressure of the vacuum vessel 7.

In order to prevent metal contamination, an earth electrode 72, which is a member having a ground potential, is provided near the inner surface of the vacuum vessel 7 and a cylindrical member made of quartz, ceramic or the like is provided inside the vacuum vessel 7. Is installed.
In this case, the insulator cover is dropped and held in a groove formed by the inner wall surface of the vacuum vessel 7 and the ground electrode 72. The insulator cover 72 is designed to have a thickness of, for example, 5 mm or more in consideration of strength and a maintenance cycle. In order to obtain electrical conductivity between the vacuum vessel 7 and the plasma 15, the insulator cover 71 is provided. An earth electrode serving also as a holding member for holding is provided. Other methods for breaking metal contamination include other insulators having plasma resistance (for example, quartz, Al ₂ F ₃ , mullite, and Cr _2).
O ₃ ) or a semiconductor (SiC or the like) may cover the inner surface of the vacuum vessel 7. When applying high-frequency bias power to the holder 8 for processing, it is preferable that the thickness of the above-mentioned plasma-resistant insulator be 1 mm or less so that the ground effect can be easily obtained.

The microwave generated by the magnetron 1 passes through the waveguide 2, the circular-rectangular conversion waveguide 3, the cavity 4, the electromagnetic wave transmitting member 6, the shower plate 11, and the vacuum vessel 7.
It is led to. A solenoid coil 5 is provided around the vacuum vessel 7.
Is provided, and a magnetic field exists inside the vacuum vessel 7. Electrons receive a Lorentz force from a magnetic field to perform a turning motion. When the frequency of the rotating motion and the frequency of the electromagnetic wave are almost the same, the electrons receive energy efficiently from the electromagnetic wave,
Electron cyclotron resonance phenomenon (Electron Cy)
A plasma 15 is generated by clotron resonance (hereinafter abbreviated as ECR). ECR in equipment
Magnetic field surface that satisfies the conditions that cause the noise
Is designed to exist inside the vacuum vessel 7.
FIG. 3 shows how the microwave guided to the cavity is reflected. The case where the reflection is repeated between the top plate 41 of the cavity 4 and the upper surface of the electromagnetic wave transmitting member 6 as shown by the standing wave a generated by the electromagnetic wave introduced into the device, and the case where the cavity is 4 and the lower surface of the shower plate 11 or the electromagnetic wave transmitting member 6, and the boundary between the top plate 41 of the cavity 4 and the generated plasma 15 as shown by the standing wave c. It is conceivable that the reflection is repeated between the reflected light and the reflected light 151. Although the boundary surface 151 of the plasma 15 actually has a certain thickness, the principle will be briefly described below. When the density of the generated plasma exceeds a certain density (in the case of a magnetic field condition, the electron density> 1 × 10 ¹¹ / cm ³ ), the standing wave c becomes dominant. Therefore, when the height of the cavity 4 is changed, the distance from the top plate 41 of the cavity 4 to the boundary surface 151 of the plasma 15 (equivalent distance to electromagnetic waves: L = ∫)
When √εr dx (integral of [0, l], εr = relative permittivity) becomes an integral multiple of の of the guide wavelength of a mode, the mode causes resonance and a standing wave Can exist between the top plate 41 of the cavity 4 and the boundary surface 151 of the plasma 15. Modes that do not satisfy the above conditions are attenuated and the boundary surface of the plasma 15 from the top plate 41 of the cavity 4 is attenuated. 151 cannot be present. By appropriately selecting the height of the hollow portion 4 in this manner, it becomes possible to guide a microwave of a specific single mode or a plurality of modes to the vacuum vessel 7 via the electromagnetic wave transmitting member 6 and the shower plate 11, Uniform and stable high-density plasma can be generated. In this embodiment, the cavity 4
Has a diameter of 405 mm and a height of 0 to 160 mm. The diameter of the electromagnetic wave transmitting member 6 was 404 mm, the diameter of the vacuum vessel 7 was 350 mm, and the distance between the lower surface of the electromagnetic wave transmitting member 6 and the upper surface of the holder 8 was 175 mm.

Note that the tendencies of FIGS. 4 to 8 described below are not limited to the dimensions described above. In an apparatus for processing a sample by generating plasma by electromagnetic waves,
An electromagnetic wave introduction unit for introducing an electromagnetic wave into the device, a vacuum container forming a discharge region, and a cavity configured to propagate the electromagnetic wave, a member that hermetically separates the discharge region from the cavity, A member for transmitting the electromagnetic wave energy in the cavity substantially all over the discharge region, wherein the member covers a surface to be processed of the sample, and has a surface substantially perpendicular to a traveling direction of the electromagnetic wave. This is the property common to all devices that do.

FIG. 4 shows the magnitude and uniformity of the ion current density reaching the object when the height of the cavity 4 is changed, and FIG. 5 shows an example of the behavior of the reflected microwave wave at that time. Show. It can be seen from FIGS. 4 and 5 that the size and uniformity of the saturated ion current density and the microwave reflected wave are changed by changing the dimensions of the cavity 4. Here, FIG.
Applying the condition (range of l _{1 to} l ₂ ) of the upper cavity size where the saturated ion current density is large and the uniformity is good in FIG. 5, the condition where the reflected wave becomes 0 and the condition where the reflected wave becomes the maximum are obtained. It is not in the middle of both conditions, that is, the condition that a certain amount of reflected wave is returned. The microwave at this time is considered to be a combination of a plurality of modes rather than a single mode. By providing a matching means such as a stub tuner at the waveguide 2 or the circular / rectangular conversion waveguide 3, an electromagnetic wave can be effectively input to the plasma even in a place where the reflected wave is large in FIG.

FIG. 6 shows the magnitude of the saturated ion current density that reaches the surface to be processed when the distance between the electromagnetic wave transmitting member 6 and the ECR surface is changed while keeping the distance between the ECR surface and the holder 8 on which the object to be processed is fixed. FIG. 7 shows the saturation ion current density that reaches the surface to be processed when the distance between the ECR surface and the holder 8 on which the object is mounted is changed while keeping the distance between the electromagnetic wave transmitting member 6 and the ECR surface constant. Shows the size and uniformity of FIG. 6 shows that the uniformity of the saturation ion current density distribution improves as the distance between the electromagnetic wave transmitting member 6 and the ECR surface increases. According to another experiment, in order to make the uniformity of the saturated ion current density 10% or less, the electromagnetic wave transmitting member 6 and the EC
It turned out that the distance of the R-plane needs to be 50 mm or more.
Further, it can be seen from FIG. 7 that the uniformity of the saturation ion current density distribution improves as the distance between the ECR surface and the holder 8 on which the workpiece is mounted increases. According to another experiment, if the distance between the ECR surface and the holder 8 on which the object to be processed is made smaller than 30 mm, the uniformity suddenly deteriorates, so that the uniformity of the saturated ion current density distribution is reduced to 10% or less. It was found that the distance between the ECR surface and the holder 8 on which the object was mounted was required to be 30 mm or more.

FIG. 8 shows the magnitude and uniformity of the saturated ion current density that reaches the object when the magnetic field gradient at the center of the ECR plane is changed. When changing the value of the magnetic field gradient from FIG. 8, 50 G / cm, 40 G / cm, 30 G / cm
cm, there is no significant difference in discharge stability.
When it is set to 20 G / cm, the discharge tends to be slightly unstable. According to another experiment, a magnetic field gradient of 15 G /
cm, it was found that the discharge was not stable. Further, when the value of the magnetic field gradient is increased from FIG. 8, there is no large difference in the average value of the saturated ion current density in the sample, but the uniformity tends to deteriorate. From the above,
In order to obtain stable and uniform high-density plasma, ECR
The value of the magnetic field gradient at the center of the surface is 20 G / cm or more,
It is effective to set within the range of 0 G / cm or less.
In order to obtain a more uniform plasma, it is necessary to make the iso-magnetic surface satisfying the condition for causing ECR a substantially flat surface with respect to the processing surface of the processing object. As shown in FIG. 1, the inner diameter of the upper solenoid coil 51 or the inner diameter (Dy) of the yoke is made smaller than the diameter of the object to be processed or the electromagnetic wave transmitting member 6, thereby easily increasing the magnetic field strength on the central axis. Thus, a flat magnetic field with a magnetic field gradient of 20 G / cm or more and 50 G / cm or less and in a plane parallel to the surface of the object can be easily obtained. Further, if the diameter of the vacuum container 7 is set to +50 mm or more with respect to the diameter of the object to be processed, it is possible to secure uniformity of 10% or less. In order to perform such control, the main magnetic flux electromagnetic coil and the control electromagnetic coil are arranged without providing a large gap.

FIG. 9 shows a second embodiment of the present invention. This embodiment is an example in which only electromagnetic waves are used as means for generating plasma. In this figure, the same reference numerals as in FIG. 1 denote the same members, and a description thereof will be omitted.

In this embodiment, since there is no magnetic field, only the point that the microwave does not enter the plasma when the electron density exceeds 7 × 10 ¹⁰ / cm ³ is different from the above-mentioned embodiment. Is the boundary surface 151 of the plasma 15
Therefore, the operation other than the physical phenomenon caused by the magnetic field is the same as that of the above-described embodiment.

Until now, microwaves (eg 2.45)
GHz), but the present invention is not limited to this. In a method of processing a sample by generating plasma by electromagnetic waves, the method comprises an electromagnetic wave introduction part for introducing the electromagnetic waves into the apparatus, a vacuum vessel serving as a discharge region, and a cavity part for resonating the electromagnetic waves. A member that separates and transmits the electromagnetic wave energy in the cavity almost entirely to the discharge region, the member covers a surface to be processed of the sample, and has a surface substantially perpendicular to a traveling direction of the electromagnetic wave. A similar effect can be expected if the device has the same.

[0019]

As described above, according to the present invention, it is possible to make the energy distribution of electromagnetic waves uniform in a portion where plasma is generated, to generate uniform plasma, and to realize a vacuum vessel. Metal contamination due to plasma in the inside can be prevented. Therefore, by applying the present invention to a semiconductor manufacturing apparatus, a large-diameter wafer can be processed uniformly and with good yield.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a magnetic field microwave plasma etching apparatus showing an embodiment of the present invention.

FIG. 2 is a detailed view showing details of a gas introduction unit in the apparatus of FIG.

FIG. 3 is an enlarged view of a plasma generation portion in the apparatus of FIG.

FIG. 4 is a diagram showing the magnitude and uniformity of an ion current density that reaches a workpiece when the size of a cavity in the apparatus of FIG. 1 is changed.

FIG. 5 is a diagram showing reflected waves of microwaves when the dimensions of a cavity in the apparatus of FIG. 1 are changed.

FIG. 6 is a diagram showing the magnitude and uniformity of the ion current density reaching the object when the distance between the electromagnetic wave transmitting member and the ECR surface in the apparatus of FIG. 1 is changed.

FIG. 7 is a diagram showing the magnitude and uniformity of the ion current density reaching the object when the distance between the ECR surface and the holder for mounting the object is changed in the apparatus of FIG. 1;

FIG. 8 is a diagram showing the magnitude and uniformity of the ion current density reaching the object when the magnetic field gradient in the apparatus of FIG. 1 is changed.

FIG. 9 is a configuration diagram of a non-magnetic field microwave plasma etching apparatus showing another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... magnetron, 2 ... waveguide, 3 ... circular rectangular conversion waveguide, 4 ... hollow part, 41 ... hollow part top plate, 5 ... solenoid coil, 51 ... solenoid coil, 6 ... electromagnetic wave transmission member,
7 ... Vacuum container, 8 ... Holder, 9 ... Drive mechanism, 10 ... High frequency power supply, 11 ... Shower plate, 111 ... Gas outlet, 112 ... Gas introduction path, 12 ... Variable valve, 13 ... Turbo molecular pump, 14 ... rough quote vacuum pump, 15 ... plasma, 151 ... plasma boundary surface, 71 ...
Insulator cover, 72 ... ground electrode.

Continuation of front page (56) References JP-A-5-74592 (JP, A) JP-A-6-104096 (JP, A) JP-A-1-222446 (JP, A) JP-A-5-190501 (JP) JP-A-5-266992 (JP, A) JP-A-6-53170 (JP, A) JP-A-4-302429 (JP, A) JP-A-5-190501 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/3065 C23F 4/00

Claims (9)

(57) [Claims] 1. A method for plasma processing an object to be processed in said vacuum chamber to propagate in the discharge region of the vacuum vessel electromagnetic waves from the electromagnetic wave introducing part via the cavity, the TE ₁₁ mode to the electromagnetic wave introducing part electromagnetic waves And the electromagnetic wave repeats reflection between the boundary surface of the electromagnetic wave transmitting member and the discharge region and the end surface on the electromagnetic wave introduction side of the cavity to form a standing wave in a TE ₀₁ mode, and the electromagnetic wave introduction unit the plasma processing method characterized by causing the electromagnetic wave and to mix the TE ₁₁ mode came propagated and introduced into the discharge region, cause discharge in the vacuum vessel. 2. The plasma processing method according to claim 1, wherein the electromagnetic wave in the cavity is transmitted to substantially the entire surface of the discharge region. 3. The electron cyclotron resonance phenomenon according to claim 1, wherein the discharge uses an electromagnetic wave and a magnetic field, and accelerating the electrons by matching the cycle of the Larmor swirling motion of the electrons in the magnetic field with the frequency of the electromagnetic wave. Plasma processing method. 4. An electromagnetic wave introducing section for introducing an electromagnetic wave into the device, a cavity for transmitting the electromagnetic wave following the electromagnetic wave introducing section, a vacuum vessel connected to the cavity to form a discharge region, and An electromagnetic wave transmitting member that is provided between the vacuum container and forms a part of the vacuum container and transmits the energy of the electromagnetic wave through substantially the entire surface of the vacuum container; and an effective transmitting portion diameter of the electromagnetic wave transmitting member. And the inner diameter of the vacuum vessel are substantially the same, and the diameter is set to 1.75 times or more of the diameter of the material to be processed, and the electromagnetic wave is introduced into the cavity through the electromagnetic wave transmitting member and the boundary between the discharge region and the cavity. It is configured to form a standing wave that repeats reflection with the side end face and becomes a TE ₀₁ mode, and introduces the electromagnetic wave introduction part into the discharge region in a mixed state with the TE ₁₁ mode that has propagated. And Zuma processing apparatus. 5. The apparatus according to claim 4, wherein said discharge is means using an ECR effect of an electromagnetic wave and a magnetic field, and said magnetic field is generated by using a solenoid coil, and an inner diameter of said solenoid coil or a yoke of a coil case is provided. A plasma processing apparatus in which the inner diameter of the substrate is smaller than the diameter of the object to be processed and the electromagnetic wave transmitting member. 6. The plasma processing apparatus according to claim 5, wherein a distance between said electromagnetic wave transmitting member and said ECR surface is 50 mm or more. 7. The plasma processing apparatus according to claim 5, wherein a distance between the ECR surface and the object is 30 mm or more. 8. The plasma processing apparatus according to claim 5, wherein a value of a magnetic field gradient on the ECR surface is set in a range from 20 G / cm to 50 G / cm. 9. The plasma processing apparatus according to claim 4, wherein the outlets of the process gas into the vacuum vessel are installed in a vicinity of the electromagnetic wave transmitting member so as to be distributed in parallel with the object to be processed.