JP2006244891A - Microwave plasma processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave plasma processing device with small microwave power loss, hardly generating degradation of microwave power efficiency and abnormal discharge at an inside of an antenna. <P>SOLUTION: The microwave plasma processing device 100 forms a plasma of processing gas in a chamber by the microwave, and applies the plasma treatment on an object to be processed by the plasma. A flat antenna 31 and a microwave transmission plate 28 are formed so as to closely contact to each other, practically not interposing air in between. A wave delaying plate 33 and the microwave transmission plate 28 are made of identical material, and the wave delaying plate 33, the flat antenna 28, and an equivalent circuit formed by a plasma satisfy a condition for resonance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a microwave plasma apparatus that performs processing using microwave plasma on an object to be processed.

  Plasma processing is an indispensable technology for the manufacture of semiconductor devices. Recently, the design rules of semiconductor elements constituting LSIs have been increasingly miniaturized due to the demand for higher integration and higher speed of LSIs, and semiconductor wafers Along with this, there is a demand for plasma processing apparatuses that can cope with such miniaturization and enlargement.

  However, in parallel plate type and inductively coupled plasma processing apparatuses that have been widely used in the past, the electron temperature is high, resulting in plasma damage to the microelements, and because the region where the plasma density is high is limited, it is large. It is difficult to uniformly and rapidly plasma-treat the semiconductor wafer.

  Therefore, an RLSA (Radial Line Slot Antenna) microwave plasma processing apparatus that can uniformly form a plasma with a high density and a low electron temperature has attracted attention (for example, Patent Document 1).

  The RLSA microwave plasma processing apparatus is provided with a planar antenna (Radial Line Slot Antenna) in which a number of slots are formed in a predetermined pattern at the upper part of a chamber, and the microwave guided from the microwave generation source is transmitted to the slot of the planar antenna And is radiated into a chamber held in a vacuum through a microwave transmission plate made of a dielectric material provided below, and the gas introduced into the chamber is converted into plasma by this microwave electric field. An object to be processed such as a semiconductor wafer is processed by the plasma thus formed.

  In this RLSA microwave plasma processing apparatus, a high plasma density can be realized over a wide region directly under the antenna, and uniform plasma processing can be performed in a short time. Further, since the low electron temperature plasma is formed, the damage to the element is small.

  In this RLSA microwave plasma processing apparatus, a technique is known in which an air gap is provided between a planar antenna and a microwave transmission plate in order to adjust the microwave electric field distribution in the microwave transmission plate and stabilize the plasma mode. (Non-Patent Document 1).

However, when the air gap is provided between the planar antenna and the microwave transmission plate in this way, the impedance of the air gap is higher than that of the dielectric constituting the microwave transmission plate, so that the microwave power loss in the air gap is large. . As a result, the microwave power efficiency is lowered and abnormal discharge inside the antenna tends to occur.
JP 2000-294550 A Jpn. Appl. Phys. Vol.38 (1999) pp.2082-2088 Part l, No. 4A, April 1999

  The present invention has been made in view of such circumstances, and it is intended to provide a microwave plasma processing apparatus in which a loss of microwave power is small and a decrease in microwave power efficiency and an abnormal discharge inside an antenna are unlikely to occur. Objective.

  In order to solve the above problems, the present invention is directed to a chamber in which an object to be processed is accommodated, a microwave generation source for generating a microwave, and a microwave generated by the microwave generation source toward the chamber. A planar antenna comprising a waveguide means, a conductor having a plurality of microwave radiation holes that radiate microwaves guided to the waveguide means toward the chamber, and a top wall of the chamber, the planar antenna comprising A microwave transmitting plate made of a dielectric material that transmits microwaves radiated from the microwave radiating holes of the first and second microwaves provided on the opposite side of the planar antenna from the microwave transmitting plate and reaching the planar antenna A retardation plate made of a dielectric material and a processing gas supply means for supplying a processing gas into the chamber. A microwave plasma processing apparatus for forming a plasma of a processing gas in the chamber and performing plasma processing on the object to be processed by the plasma, wherein the planar antenna and the microwave transmitting plate substantially emit air. The slow wave plate and the microwave transmission plate are formed of the same material, and the equivalent circuit formed of the slow wave plate, the planar antenna, the microwave transmission plate, and plasma is A microwave plasma processing apparatus characterized by satisfying a resonance condition is provided.

  The present invention also includes a chamber that accommodates an object to be processed, a microwave generation source that generates a microwave, a waveguide unit that guides the microwave generated by the microwave generation source toward the chamber, A planar antenna composed of a conductor having a plurality of microwave radiation holes for radiating microwaves guided to the waveguide means toward the chamber; and a top wall of the chamber; and a microwave radiation hole of the planar antenna A microwave transmitting plate made of a dielectric material that transmits the microwave that has passed through, and a function of shortening the wavelength of the microwave that reaches the planar antenna, provided on the opposite side of the planar antenna from the microwave transmitting plate. , A slow wave plate made of a dielectric, and a processing gas supply means for supplying a processing gas into the chamber. A microwave plasma processing apparatus that forms plasma of a processing gas and performs plasma processing on an object to be processed by the plasma, wherein the planar antenna and the microwave transmission plate are in close contact with each other substantially without air. The slow wave plate and the microwave transmission plate are formed of a material whose ratio of dielectric constants is 70% to 130%. The slow wave plate, the planar antenna, and the microwave Provided is a microwave plasma processing apparatus in which a transmission plate and an equivalent circuit formed of plasma satisfy a resonance condition.

  In any of the above inventions, the thickness of the microwave transmitting plate is in the range of 1/2 to 1/4 of the wavelength of the introduced microwave, more preferably in the range of 1/2 to 1/3. The microwave reflectance of the planar antenna is in the range of 0.4 to 0.8. Thereby, the equivalent circuit can satisfy the resonance condition.

  The waveguide means includes a rectangular waveguide that propagates the microwave generated from the microwave generation source in the TE mode, a mode converter that converts the TE mode into the TEM mode, and a microwave that is converted into the TEM mode. Having a coaxial waveguide that propagates toward the planar antenna can be employed.

  Further, the plurality of microwave radiation holes formed in the planar antenna have a long groove shape and are arranged so that adjacent microwave radiation holes intersect with each other, and the plurality of microwave radiation holes are arranged concentrically. What can be used suitably.

  Furthermore, a lid provided so as to cover the slow wave plate and the planar antenna can be further provided. In that case, the lid is provided with a refrigerant flow path, and the refrigerant flow path is provided in the refrigerant flow path. It is preferable that the slow wave plate, the planar antenna, and the microwave transmission plate are cooled by flowing a refrigerant.

  Furthermore, the frequency is 2.45 GHz, the relative dielectric constant of the slow wave plate and the microwave transmission plate is 3.5 to 4.5, and the slot can be doubled.

  Furthermore, when the slow wave plate and the microwave transmission plate are made of quartz, the microwave plasma device is preferably a plasma etching device or a plasma surface modification device.

  Furthermore, when the slow wave plate and the microwave transmission plate are made of alumina, the microwave plasma device is preferably a plasma CVD device.

  According to the present invention, the planar antenna and the microwave transmission plate are in close contact with each other, and no conventional air gap is formed, so that no microwave power loss occurs in the air gap, It is possible to make it difficult to reduce the microwave power efficiency and to generate abnormal discharge inside the antenna.

  Further, simply eliminating the air gap may increase the reflection of microwaves and may deteriorate the stability of the plasma. According to the present invention, a slow wave plate, a planar antenna, a microwave transmission plate, and The equivalent circuit formed by plasma resonates to minimize the reflection of the microwave, and the slow wave plate and the microwave transmission plate are made of the same material, or the ratio of the values of these dielectric constants is 70% to 130%. Therefore, it is possible to prevent the microwave power efficiency from decreasing and abnormal discharge inside the antenna from occurring while maintaining the plasma stably.

  Furthermore, a lid is provided so as to cover the slow wave plate and the planar antenna, a coolant channel is provided in the lid, and the coolant is passed through the coolant channel, whereby the slow wave plate, the planar antenna, When the microwave transmission plate is cooled, the microwave transmission plate, which has conventionally had a poor cooling efficiency due to the presence of the air gap having low thermal conductivity due to the absence of the air gap, can be sufficiently cooled.

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view schematically showing a microwave plasma processing apparatus according to an embodiment of the present invention.

  The microwave plasma processing apparatus 100 radiates a microwave guided from a microwave generation source into a chamber using a planar antenna (Radial Line Slot Antenna) in which a large number of slots are formed in a predetermined pattern, and plasma. Is configured as an RLSA microwave plasma processing apparatus.

  The microwave plasma processing apparatus 100 includes a substantially cylindrical chamber 1 that is airtight and grounded. A circular opening 10 is formed at a substantially central portion of the bottom wall 1a of the chamber 1, and an exhaust chamber 11 that communicates with the opening 10 and protrudes downward is provided on the bottom wall 1a. . A susceptor 2 made of a ceramic such as AlN is provided in the chamber 1 for horizontally supporting a wafer W as a substrate to be processed. The susceptor 2 is supported by a support member 3 made of ceramic such as cylindrical AlN that extends upward from the center of the bottom of the exhaust chamber 11. A guide ring 4 for guiding the wafer W is provided on the outer edge of the susceptor 2. A resistance heating type heater 5 is embedded in the susceptor 2. The heater 5 is supplied with power from a heater power source 6 to heat the susceptor 2 and heats the wafer W as a processing object. To do. A cylindrical liner 7 made of quartz is provided on the inner periphery of the chamber 1.

  The susceptor 2 is provided with wafer support pins (not shown) for supporting the wafer W and moving it up and down so as to protrude and retract with respect to the surface of the susceptor 2.

An annular gas introducing member 15 is provided on the side wall of the chamber 1, and a processing gas supply system 16 is connected to the gas introducing member 15. The gas introduction member may be arranged in a shower shape. A predetermined processing gas is introduced from the processing gas supply system 16 into the chamber 1 through the gas introduction member 15. As the processing gas, an appropriate gas is used according to the type of plasma processing. For example, Ar gas, H ₂ gas, O ₂ gas, or the like is used when performing oxidation treatment such as selective oxidation treatment of a tungsten-based gate electrode.

  An exhaust pipe 23 is connected to the side surface of the exhaust chamber 11, and an exhaust device 24 including a high-speed vacuum pump is connected to the exhaust pipe 23. Then, by operating the exhaust device 24, the gas in the chamber 1 is uniformly discharged into the space 11 a of the exhaust chamber 11 and exhausted through the exhaust pipe 23. Thereby, the inside of the chamber 1 can be depressurized at a high speed to a predetermined degree of vacuum, for example, 0.133 Pa.

  On the side wall of the chamber 1, there are a loading / unloading port 25 for loading / unloading the wafer W to / from a transfer chamber (not shown) adjacent to the plasma processing apparatus 100, and a gate valve 26 for opening / closing the loading / unloading port 25. Is provided.

The upper portion of the chamber 1 is an opening, and a ring-shaped support portion 27 is provided along the peripheral edge of the opening. A dielectric such as quartz or Al ₂ O ₃ is provided on the support portion 27. A microwave transmitting plate 28 made of ceramics and transmitting microwaves is airtightly provided via a seal member 29. Therefore, the inside of the chamber 1 is kept airtight.

  A disk-shaped planar antenna 31 is provided above the microwave transmission plate 28 so as to face the susceptor 2. The planar antenna 31 is locked to the upper end of the side wall of the chamber 1. The planar antenna 31 is made of a conductor, for example, a copper plate or an aluminum plate whose surface is gold-plated, and has a configuration in which a number of microwave radiation holes (slots) 32 are formed in a predetermined pattern. That is, the planar antenna 31 constitutes an RLSA antenna. The microwave radiation holes 32 have, for example, a long groove shape as shown in FIG. 2 and are typically orthogonal to each other so that adjacent microwave radiation holes 32 intersect each other ("T"). The plurality of microwave radiation holes 32 are concentrically arranged. The length and arrangement interval of the microwave radiation holes 32 are determined according to the wavelength of the microwave and the like. In FIG. 2, an interval Δr between adjacent microwave radiation holes 32 formed concentrically (the distance from the center to the innermost microwave radiation hole 32 is also the same) in a slow wave plate 33 described later. Assuming that the wavelength is the microwave and the length from the center of the planar antenna 31 to the innermost microwave radiation hole 32 is also Δr, a strong electric field is preferably emitted from this, and in the illustrated example, four-turn microwave radiation is achieved. A hole is arranged. Further, the microwave radiation hole 32 may have another shape such as a circular shape or an arc shape. Moreover, the arrangement | positioning form of the microwave radiation hole 32 is not specifically limited, For example, it can also arrange | position in spiral shape and radial form other than concentric form.

  A slow wave plate 33 made of a dielectric material having a dielectric constant larger than that of a vacuum is provided on the upper surface of the planar antenna 31. The slow wave plate 33 has a function of making the wavelength of the microwave in the slow wave plate shorter than the wavelength of the microwave in vacuum.

  A shield lid 34 made of a metal material such as aluminum or stainless steel is provided on the upper surface of the chamber 1 so as to cover the planar antenna 31 and the slow wave plate 33. The upper surface of the chamber 1 and the shield lid 34 are sealed by a seal member 35.

  A cooling water flow path 34a is formed in the shield lid 34, and the planar antenna 31, the microwave transmission plate 28, the slow wave plate 33, and the shield lid 34 are cooled by passing cooling water therethrough. It is like that. The shield lid 34 is grounded.

  An opening 36 is formed at the center of the upper wall of the shield lid 34, and a waveguide 37 is connected to the opening. A microwave generator 39 is connected to the end of the waveguide 37 via a matching circuit 38. Thereby, for example, a microwave having a frequency of 2.45 GHz generated by the microwave generator 39 is propagated to the planar antenna member 31 through the waveguide 37. Note that the microwave frequency may be 8.35 GHz, 1.98 GHz, or the like.

  The waveguide 37 has a circular cross-section coaxial waveguide 37a extending upward from the opening 36 of the shield lid 34, and a horizontal cross-section connected to the upper end of the coaxial waveguide 37a. And a rectangular waveguide 37b. A mode converter 40 is provided at the end of the rectangular waveguide 37b on the side where the coaxial waveguide 37a is connected. An inner conductor 41 extends in the center of the coaxial waveguide 37 a, and the lower end portion of the inner conductor 41 is connected and fixed to the center of the planar antenna 31.

  Each component of the plasma processing apparatus 100 is connected to and controlled by the process controller 50. The process controller 50 includes a user interface 51 including a keyboard for a process manager to input a command to manage the plasma processing apparatus 100, a display for visualizing and displaying the operating status of the plasma processing apparatus 100, and the like. It is connected.

  In addition, the process controller 50 includes a storage unit 52 that stores a recipe in which a control program, processing condition data, and the like for realizing various processes executed by the plasma processing apparatus 100 are controlled by the process controller 50. It is connected.

  Then, if desired, an arbitrary recipe is called from the storage unit 52 by an instruction from the user interface 51 and is executed by the process controller 50, so that a desired process in the plasma processing apparatus 100 can be performed under the control of the process controller 50. Is performed.

Next, the slow wave plate 33, the planar antenna 31, and the microwave transmission plate 28 in this embodiment will be described in more detail.
In the present embodiment, as shown in FIG. 1, the planar antenna 31 and the microwave transmission plate 28 are in close contact with each other, and no conventional air gap is formed. The slow wave plate 33 and the planar antenna 31 are also in close contact with each other. However, if the air gap is simply eliminated, the reflection of the microwave viewed from the mode converter 40 becomes large, the stability of the plasma is deteriorated, and the efficiency is inferior.

  Therefore, in this embodiment, the slow wave plate 33, the planar antenna 31, the microwave transmission plate 28, and the equivalent circuit as shown in FIG. 3 formed of plasma satisfy the resonance condition, and the slow wave plate 33 and the microwave transmitting plate 28 are made of the same material. By making the equivalent circuit satisfy the resonance condition, the reflection of the microwave can be minimized, and by making the slow wave plate 33 and the microwave transmission plate 28 the same material, the interface reflection of the microwave can be reduced. Can be prevented. Thereby, the efficiency of the microwave power can be maintained high while increasing the stability of the plasma.

ここで、Ｃは、Ｃ＝１／｛（１／Ｃ_１）＋（１／Ｃ_２）｝である。 The slow wave plate 33 and the plasma transmission plate 28 function as a capacitor, the planar antenna 31 functions as a resistor, the plasma functions as a coil, and the capacitance of the slow wave plate 33 is C _{1 as} shown in the equivalent circuit of FIG. When the capacitance of the plasma transmission plate 28 is C ₂ , the resistance of the planar antenna 31 is R, the inductance of the plasma is L, and the frequency of the microwave is f, the following equation (1) It needs to hold.

Here, C is C = 1 / {(1 / C ₁ ) + (1 / C ₂ )}.

  In order to satisfy such a resonance condition, the thickness of the microwave transmission plate 28 that defines the capacitance is set to 1/2 to 1/4 (1 / 2λ to 1) of the wavelength of the microwave in the microwave transmission plate 28. / 4λ) and the microwave reflectivity (power reflection coefficient) viewed from the mode converter 40 of the planar antenna 31 needs to be within a range of 0.4 to 0.8.

Regarding the thickness of the microwave transmitting plate 28, the above equation (1) defining the resonance condition includes a term of capacitance, and the magnitude of the capacitance is inversely proportional to the thickness. Here, the thinner the capacitance C ₁ (slow wave plate 33), the more efficiently the planar antenna 31 and the microwave transmission plate 28 can be cooled. Therefore, the capacitance C that becomes more dominant with respect to the size of the capacitance C. ₂ The thickness of the (microwave transmission plate 28) is defined within a range where resonance can occur. When the thickness of the microwave transmitting plate 28 is larger than 1/2 or smaller than 1/3 of the wavelength of the introduced microwave, the resonance condition region becomes narrower, and when it becomes smaller than 1/4, it becomes difficult to resonate. .

Here, the thickness of the microwave transmitting plate 28, as shown in FIG. 4 (a), when the shape is flat, its actual thickness d ₁ is used, the microwave at that time When the capacitance of the transmission plate 28 is C _F , its relative dielectric constant is ε ₀ , and the surface area is S ₁ , the following equation (2) is established.
C _F = ε ₀ (S ₁ / d ₁ ) (2)
On the other hand, when the microwave transmission plate 28 of complicated shape, the thickness thereof, using an equivalent thickness d ₂ obtained from a calculation of the capacitance. That is, when the capacitance of the microwave transmission plate 28 having a complicated shape is C _C and the surface area is S ₂ , the following equation (3) is established. Here, since the surface area S ₂ is always obtained, if it is difficult to obtain d _{2 due} to a complicated shape, the equivalent thickness d ₂ is calculated as the thickness of the microwave transmitting plate 28 by calculating backward from this equation after measuring _CC. Can do.
C _C = ε ₀ (S ₂ / d ₂ ) (3)
Note that equivalent thickness d ₂ at this time, corresponding to an average thickness of uneven as shown in FIG. 4 (b).

  The reason why the microwave reflectivity of the planar antenna 31 is set within the range of 0.4 to 0.8 is that if the reflectivity is lower than 0.4, the change in phase when the frequency changes is large, so the resonance condition is adjusted. This is because it is difficult to satisfy the resonance condition.

  The slow wave plate 33 and the microwave transmission plate 28 are preferably made of the same material. However, even if they are different materials, they can always resonate if their dielectric constant ratio is in the range of 70% to 130%. This is confirmed by simulation.

  In the plasma processing apparatus 100 configured as described above, first, the gate valve 26 is opened, and the wafer W as the object to be processed is loaded into the chamber 1 from the loading / unloading port 25 and placed on the susceptor 2.

Then, a predetermined processing gas is introduced from the gas supply system 16 into the chamber 1 through the gas introduction member 15 and maintained at a predetermined pressure. For example, when performing an oxidation process such as a selective oxidation process of a tungsten-based gate electrode, Ar gas, H ₂ gas, O ₂ gas or the like is introduced into the chamber 1 as a processing gas, and the pressure in the chamber 1 is set to, for example, Set to 3 to 700 Pa.

  Next, the microwave from the microwave generator 39 is guided to the waveguide 37 through the matching circuit 38. Microwaves are sequentially supplied to the planar antenna member 31 through the rectangular waveguide 37b, the mode converter 40, the coaxial waveguide 37a, and the slow wave plate 33, and from the planar antenna member 31 through the microwave transmission plate 28. Radiated into the space above the wafer W in the chamber 1. The microwave propagates in the rectangular waveguide 37b in the TE mode, and the TE mode microwave is converted into the TEM mode by the mode converter 40, and the coaxial waveguide 37a is directed toward the planar antenna member 31. Propagated.

  The processing gas introduced into the chamber 1 is turned into plasma by the microwave radiated from the planar antenna member 31 through the microwave transmitting plate 28 into the chamber 1, and predetermined processing such as oxidation processing is performed by this plasma.

The microwave plasma processing apparatus 100 of the present embodiment can realize high electron density of about 10 ¹² / cm ³ or more and low electron temperature plasma of about 1.5 eV or less. For this reason, it is possible to perform plasma processing at a low temperature and in a short time, and there are advantages such as small plasma damage such as ions to the base film.

  In the present embodiment, as shown in FIG. 1, the planar antenna 31 and the microwave transmission plate 28 are in close contact with each other, and no conventional air gap is formed. There is no microwave power loss in the gap. Further, it is possible to prevent a decrease in microwave power efficiency and an abnormal discharge that tends to occur between the gaps of the microwave radiation holes (slots) 32 inside the antenna and around the slow wave plate 33.

  However, if the air gap is simply eliminated, the reflection of the microwave viewed from the mode converter 40 becomes large, and the stability of the plasma may be deteriorated. On the other hand, in this embodiment, the slow wave plate 33, the planar antenna 31, the microwave transmission plate 28, and the equivalent circuit formed of plasma are resonated to minimize the reflection of the microwave, and Since the slow wave plate 33 and the microwave transmission plate 28 are made of the same material so as to prevent the reflection of the microwave interface, the microwave power efficiency is lowered and abnormal discharge is generated inside the antenna while maintaining the plasma stably. Can be difficult. The planar antenna 31 and the microwave transmission plate 28 may be in close contact with each other substantially without air. Even if there is a slight gap due to an adhesion error or thermal expansion, the planar antenna 31 and the microwave transmission plate 28 are 0.1 mm or less. If allowed.

  Further, since there is no air gap between the planar antenna 31 and the microwave transmission plate 28 with low thermal conductivity, the cooling water is passed through the cooling water flow path 34a formed in the shield lid 34, When the planar antenna 31, the microwave transmission plate 28, the slow wave plate 33, and the shield cover 34 are cooled, the microwave transmission window 28 that has been poor in cooling efficiency can be efficiently cooled.

Next, an experiment for confirming the effect of the present invention will be described.
Here, the slow wave plate 33, the planar antenna 31, and the plasma transmission plate 28 are set as follows.
Slow wave plate: Quartz, diameter φ329mm, thickness 7mm
Planar antenna: Diameter φ344mm, thickness 0.3mm
Plasma transmission plate: Quartz, diameter φ362mm, thickness 31.3mm (= 1 / 2λ),
Flat type, integrated type with flat antenna

The electrical characteristics were as follows.
Frequency: 2.45GHz
Power density: 2.67 W / cm ² (at 2750 W), 2.91 W / cm ²
(At 3000W)
Input impedance: 50Ω (2.45 GHz)
Power reflection coefficient: 0.75 (2.45 GHz)

Under the above conditions, the electric field distribution in the plasma transmission plate was simulated. As analysis conditions, plasma radiation holes (slots) are formed in two turns as shown in FIG. 5 and adjacent microwave radiation holes 32 having a long groove shape are arranged in an “L” shape. The holes 32 are arranged concentrically, and the plasma density is 1 × 10 ¹² / cm ³ . As a result, as shown in FIG. 5, the electric field distribution is relatively uniform, there are many portions with a high electric field strength of 3 × 10 ² V / m or more, and a portion of 4 × 10 ² V / m or more is also seen. It was confirmed that there was little loss of microwave power.

  Plasma was actually formed under the above conditions, and electron temperature distribution and electron density distribution were obtained. At that time, Ar was used as a processing gas, the pressure in the chamber was 1 Torr (133 Pa), and the microwave power was 2750 W. FIG. 6 shows the electron temperature distribution, and FIG. 7 shows the electron density distribution.

As shown in FIG. 6, the electron temperature is 1.6 eV or less and the distribution variation is small, and as shown in FIG. 7, the electron density is approximately 1 × 10 ¹² / cm ³ or more and the distribution variation. It was also confirmed that a plasma with a low electron temperature and a high density was stably formed.

Next, the result of simulating the microwave electric field intensity in the microwave transmission plate using the microwave plasma processing apparatus according to the present invention and the conventional microwave plasma processing apparatus provided with an air gap will be described. In the case of the present invention, the conditions are the same as in the experiment for confirming the effect of the slow wave plate 33, the planar antenna 31, the plasma transmission plate 28, and the electrical characteristics, and the plasma density is 1 × 10 ¹⁰ / cm ^3. In the case of the example, in addition to these, the length of the air gap was 20 mm. The results at this time are shown in FIGS. 8 (a) and 8 (b). As shown in (a), in the device of the present invention, a high microwave electric field strength of 1.75 × 10 ¹ V / m or more is seen, but as shown in (b), in the prior art, 5 V / m. It was found that there are many low portions below, and the microwave electrolysis strength is remarkably increased by the present invention as compared with the prior art. It was also found that there is no significant difference in the uniformity of the microwave electric field strength between the present invention and the prior art.

As a suitable semiconductor manufacturing apparatus based on the idea of the present invention as described above, an apparatus in which the microwave transmission plate 28 and the retardation plate 33 are made of alumina (Al ₂ O ₃ ), or these are quartz ( A device composed of SiO ₂ ) can be mentioned.

  As an example in which an apparatus in which the microwave transmission plate 28 and the slow wave plate 33 are made of alumina is preferably applied, a plasma CVD apparatus can be exemplified. This is because when the microwave transmitting plate 28 reacts with active species of plasma and the like and a gas containing an element constituting the microwave transmitting plate 28 is generated, this is taken into the film formed on the object to be processed. This is because, if the microwave transmitting plate 28 is made of alumina, the alumina is dense, so that the amount of released oxygen is about one digit lower than that of quartz or the like. . Further, for example, the microwave transmission plate 28 and the slow wave plate 33 may be made of different materials having a dielectric constant close to that of alumina formed by laminating alumina and other materials. In this case, various combinations of materials having a relative dielectric constant of 7.4 to 9.6 are combined so that the ratio of the values of these dielectric constants is between 70% and 130% that can satisfy the resonance condition. Can be configured.

On the other hand, a plasma etching apparatus or a plasma surface modification apparatus can be cited as an example in which an apparatus in which the microwave transmission plate 28 and the slow wave plate 33 are made of quartz is suitably applied. This is because the microwave transmission plate 28 is sputtered by ion bombardment under the process conditions for etching and surface modification. At this time, if the element constituting the microwave transmission plate 28 contains metal, the object to be processed is contaminated with metal. This is because alumina or the like cannot be used. In such a case, if the microwave transmitting plate 28 is made of quartz, in many cases, the object to be processed is a silicon wafer or a glass substrate, and these and quartz are mainly composed of the same element Si, so that the metal contamination. Will not cause.

  Further, in the apparatus in which the microwave transmitting plate 28 and the slow wave plate 33 are made of quartz, the interval between the adjacent microwave radiation holes 32 formed concentrically and the innermost microwave from the center of the planar antenna 31 is used. When the length to the radiation hole 32 is Δr (see FIG. 2) and Δr = (wavelength of microwave in the slow wave plate), when the microwave frequency is 2.45 GHz, the microwave radiation hole 32 is 2 A turn is formed. Here, the planar antenna 31 is assumed to be an apparatus that processes a 300 mm wafer, which is the mainstream of the present apparatus, and the diameter of the planar antenna 31 is also approximately 300 mm. On the other hand, if the microwave transmission plate 28 and the slow wave plate 33 are alumina, the microwave radiation hole 32 is formed in three turns. Comparing these two, it is extremely difficult to design and adjust the slot of the 3-turn device as compared to the 2-turn device. For example, in a 3-turn device, just because the number of slots in the intermediate turn is increased, the plasma density directly below it does not increase, but the density at the center of the plasma space decreases and the outer periphery density increases, The reverse is also possible. This is because the microwaves radiated from the slots of the intermediate turns interfere with the electromagnetic waves radiated from the slots of the inner and outer turns. From such a viewpoint, quartz in which the microwave radiation holes 32 are formed in two turns is preferable as a material constituting the microwave transmitting plate 28 and the slow wave plate 33. Further, for example, the microwave transmitting plate 28 and the slow wave plate 33 may be formed of different materials having a dielectric constant close to that of quartz formed by laminating quartz and other materials. In this case, various combinations of materials having a relative dielectric constant of 3.5 to 4.5 are used in combination so that the ratio of the values of these dielectric constants is between 70% and 130% that can satisfy the resonance condition. Can be configured. Also in this case, similarly to the case where the microwave transmitting plate 28 and the slow wave plate 33 are made of quartz, when the microwave frequency is 2.45 GHz, the microwave radiation hole 32 is formed in two turns.

  The present invention can be variously modified without being limited to the above embodiment. For example, the configuration of the processing apparatus is not limited to the above embodiment as long as the configuration requirements of the present invention are satisfied. Further, the target plasma treatment is not limited to the oxidation treatment, and can be applied to various treatments such as a film formation treatment and an etching treatment. Further, the object to be processed for plasma processing is not limited to a semiconductor wafer, but may be another object such as a flat panel display substrate.

  The present invention is suitable for plasma processing that requires low electron temperature and high-density plasma, such as oxidation processing, film formation processing, and etching processing in the manufacturing process of semiconductor devices.

1 is a cross-sectional view schematically showing a microwave plasma processing apparatus according to an embodiment of the present invention. The figure which shows the structure of a planar antenna. The figure which shows the equivalent circuit formed with a slow wave board, a planar antenna, a microwave permeation | transmission board, and plasma. The figure for demonstrating the thickness of a microwave permeation | transmission board. The figure which shows the simulation result of the electric field distribution of the plasma permeation | transmission board surface in the microwave plasma processing apparatus of this invention. The graph which shows the measurement result of the electron temperature distribution in the microwave plasma processing apparatus of this invention. The figure which shows the electron density distribution in the microwave plasma processing apparatus of this invention. The figure which shows the result of having simulated the microwave electric field intensity on the surface of a microwave permeation | transmission board with the microwave plasma processing apparatus which concerns on this invention, and the conventional microwave plasma processing apparatus.

Explanation of symbols

1 ... Chamber (Processing room)
2 ... susceptor 3 ... support member 5 ... heater 15 ... gas introduction member 16 ... gas supply system 23 ... exhaust pipe 24 ... exhaust device 25 ... carry-in / out port 26 ... gate valve 28 ... microwave transmission plate 29 ... seal member 31 ... planar antenna 32 ... Microwave radiation hole 33 ... Slow wave plate 37 ... Waveguide 37a ... Coaxial waveguide 37b ... Rectangular waveguide 39 ... Microwave generator 40 ... Mode converter 50 ... Process controller 100 ... Plasma processing device W ... Semiconductor wafer (object to be processed)

Claims (10)

A chamber in which an object is accommodated;
A microwave source for generating microwaves;
Waveguide means for guiding the microwave generated by the microwave source toward the chamber;
A planar antenna made of a conductor having a plurality of microwave radiation holes for radiating the microwave guided to the waveguide means toward the chamber;
A microwave transmitting plate made of a dielectric material that constitutes the top wall of the chamber and transmits microwaves that have passed through the microwave radiation holes of the planar antenna;
A slow wave plate made of a dielectric, provided on the opposite side of the planar antenna to the microwave transmitting plate, and having a function of shortening the wavelength of the microwave reaching the planar antenna;
A processing gas supply means for supplying a processing gas into the chamber;
A microwave plasma processing apparatus that forms a plasma of a processing gas in the chamber by microwaves and performs plasma processing on an object to be processed by the plasma,
The planar antenna and the microwave transmission plate are formed in close contact with each other substantially without air,
The slow wave plate and the microwave transmission plate are formed of the same material,
A microwave plasma processing apparatus, wherein an equivalent circuit formed of a slow wave plate, a planar antenna, a microwave transmission plate, and plasma satisfies a resonance condition. A chamber in which an object is accommodated;
A microwave source for generating microwaves;
Waveguide means for guiding the microwave generated by the microwave source toward the chamber;
A planar antenna made of a conductor having a plurality of microwave radiation holes for radiating the microwave guided to the waveguide means toward the chamber;
A microwave transmitting plate made of a dielectric material that constitutes the top wall of the chamber and transmits microwaves that have passed through the microwave radiation holes of the planar antenna;
A slow wave plate made of a dielectric, provided on the opposite side of the planar antenna to the microwave transmitting plate, and having a function of shortening the wavelength of the microwave reaching the planar antenna;
A processing gas supply means for supplying a processing gas into the chamber;
A microwave plasma processing apparatus that forms a plasma of a processing gas in the chamber by microwaves and performs plasma processing on an object to be processed by the plasma,
The planar antenna and the microwave transmission plate are formed in close contact with each other substantially without air,
The slow wave plate and the microwave transmission plate are formed of a material such that a ratio of values of these dielectric constants is 70% to 130%,
A microwave plasma processing apparatus, wherein an equivalent circuit formed of a slow wave plate, a planar antenna, a microwave transmission plate, and plasma satisfies a resonance condition.   The thickness of the microwave transmission plate is in the range of ½ to ¼ of the wavelength of the introduced microwave, and the microwave reflectance of the planar antenna is in the range of 0.4 to 0.8. The microwave plasma processing apparatus according to claim 1 or 2, wherein   The waveguide means includes a rectangular waveguide for propagating the microwave generated from the microwave generation source in the TE mode, a mode converter for converting the TE mode to the TEM mode, and the microwave converted to the TEM mode. The microwave plasma processing apparatus according to any one of claims 1 to 3, further comprising a coaxial waveguide that propagates toward the planar antenna.   The plurality of microwave radiation holes formed in the planar antenna have a long groove shape, are arranged so that adjacent microwave radiation holes intersect with each other, and the plurality of microwave radiation holes are arranged concentrically. The microwave plasma processing apparatus according to any one of claims 1 to 4, wherein:   The microwave plasma processing apparatus according to claim 1, further comprising a lid provided so as to cover the slow wave plate and the planar antenna.   The coolant is provided in the lid body, and the slow wave plate, the planar antenna, and the microwave transmission plate are cooled by allowing the coolant to flow through the coolant channel. 6. The microwave plasma processing apparatus according to 6.   The frequency of the microwave is 2.45 GHz, the relative dielectric constant of the slow wave plate and the microwave transmission plate is 3.5 to 4.5, and the slots are doubled. The microwave plasma processing apparatus according to any one of claims 1 to 7.   9. The micro of claim 1, wherein the slow wave plate and the microwave transmission plate are made of quartz, and the microwave plasma device is a plasma etching device or a plasma surface modification device. Wave plasma processing equipment.   The microwave plasma processing apparatus according to any one of claims 1 to 7, wherein the slow wave plate and the microwave transmission plate are alumina, and the microwave plasma apparatus is a plasma CVD apparatus.

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