JP2928577B2 - Plasma processing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is particularly applicable to a semiconductor manufacturing apparatus for performing processes such as etching, ashing, and film formation, in which plasma is generated by a synergistic effect of a microwave and a magnetic field. The present invention relates to a microwave plasma processing apparatus for performing processing.

[Prior Art] In a process of manufacturing a semiconductor device, a dry process using plasma is used as an effective means in departments such as etching, ashing, and film formation. At present, this plasma is mainly generated by applying a high frequency (mainly 13.56 MHz) to two parallel opposing electrodes, but recently, Japanese Patent Application Laid-Open Nos. 56-155535 and 60 −12
Attention has been paid to those using higher frequency microwaves (eg, 2.45 GHz) as disclosed in No. 0525. As in the above two examples, those using microwaves for plasma generation require 500 to 100 to increase ionization efficiency.
In most cases, a magnetic field of about 0 Gauss is applied.
This is to apply a magnetic field to cause the electrons to perform cyclotron motion, to increase the probability of collision of the electrons, to limit the movement of the charged particles in the direction across the line of magnetic force, and to prevent diffusion.

Microwave plasma provides 1. high-density plasma (up to 10 ¹¹ / cm ³ or more) with respect to RF plasma. 2. Can be used at low pressure (10 ^-4 to 10 ^-2 Torr). 3. Less damage to the object. Etc. have great advantages in manufacturing semiconductor devices.

[Problems to be Solved by the Invention] However, the conventional microwave plasma processing apparatus has the above-mentioned disadvantages.

(1) In this device, a plasma is generated by a synergistic effect of a microwave and a magnetic field.
Alternatively, a non-uniform spatial distribution of the plasma density is easily generated due to the intensity distribution of the applied magnetic field. In addition, since the charged particles are bound by the lines of magnetic force and do not diffuse due to the action of the magnetic field, the non-uniformity of the plasma density is maintained as it is on the object. On the other hand, in recent semiconductor manufacturing processes, processing operations using ions are becoming important not only from the viewpoint of processing speed but also from the viewpoint of miniaturization and shape control, and there is also a tendency that the diameter of the workpiece is increased. However, the above disadvantages have become a serious problem.

(2) When processing is performed using ions in the plasma,
In order to perform processing speed adjustment, shape control, damage control, and the like, it is necessary to control the energy of incident ions. In a conventional parallel plate type apparatus using high frequency (RF waves), the voltage (V _DC ) generated in the holder to be processed can accelerate the ions incident on the sample to give energy, and the voltage (V _DC ) Can be controlled by the applied power. However, plasma generated by microwaves does not provide sufficient V _DC , and even if the power of microwaves is controlled, V _DC hardly changes. Therefore, in order to obtain a necessary V _DC , as disclosed in Japanese Patent Application Laid-Open No. 60-120525, a high-frequency power is separately applied to an object-holding device (holder).

According to this method, it is possible to independently control two parameters, that is, high-density plasma using microwaves and ion incident energy using high-frequency power. When power is applied, a high-frequency current flows between the treatment object holder and the surrounding processing chamber wall, so that the effect of ion incidence is stronger in the peripheral portion than in the central portion of the treatment object. There is a problem that it is.

In order to solve the above problems (1) and (2), the following configuration can be considered. That is, as shown in FIG. 8, the microwave is supplied to the discharge chamber through the holes 30 of the flat plate (antenna plate) 14 installed in parallel with the object holder 4.

In this case, it is possible to make the distribution of the plasma density in the radial direction of the antenna plate uniform by optimizing the shape and distribution of the holes formed in the antenna plate 14, and the antenna plate is positioned with respect to the workpiece holder. Since the electrodes are opposed to each other, a uniform high-frequency electric field can be formed over the entire target object.

However, even with this method, the following two problems remain. The microwave is absorbed by the plasma immediately after exiting the emission hole (hole) of the antenna plate, so that the pattern of the radiation hole is strongly reflected on the distribution of the plasma density. This effect is particularly pronounced when the distance between the microwave radiating plate (antenna plate) and the object holder is short, or when the divergence of the applied magnetic field is small and the lines of magnetic force are nearly perpendicular.

Although it is structurally symmetric with respect to the central axis, when actually creating the antenna plate, the processing accuracy, parallelism,
The uniformity of the microwave emission intensity may be deteriorated due to the center shift or the like.

The present invention provides a microwave plasma processing method and a method and apparatus having a novel configuration that solves the problems of the apparatus and the apparatus, which are considered to be improvements of the conventional technique.

[Means for Solving the Problems] A plasma processing apparatus according to the present invention that solves the above-mentioned problems includes:
In a plasma processing apparatus including a chamber into which a reaction gas is introduced, a flat plate antenna having holes for emitting microwaves for converting the reaction gas into plasma, and an object holder for mounting an object to be processed by generated plasma. A driving mechanism for rotating the antenna to relatively rotate the antenna and the object is provided. It is preferable that the plasma processing apparatus has a mechanism in which the holes of the antenna are arranged in a spiral shape and a mechanism for joining the rotating part and the fixed part in the rotation by a coaxial tube having a choke structure.

In the plasma processing method of the present invention, plasma is generated by microwave interaction,
In a plasma processing method for performing ashing or film formation, an in-plane density distribution of plasma generated by microwaves radiated from holes of a flat antenna provided at a predetermined distance from an object to be processed is determined by the flat antenna. By rotating the holes, the holes are relatively rotated with respect to the object to be processed and are also moved on the object to perform a desired process. In the plasma processing method, it is preferable that the holes are arranged in a vortex, and the in-plane density distribution of the plasma is moved in the radial direction on the object to be processed.

In addition, the plasma processing apparatus of the present invention includes a chamber for introducing a reaction gas, a holder for holding a processing object in the chamber, and a micro-cell for converting the reaction gas introduced into the chamber into plasma. A flat-plate antenna for radiating waves into the chamber, wherein the flat-plate antenna has a plurality of sets of a plurality of thin linear slits having different directions arranged concentrically or spirally. It is characterized by having been done. The plasma processing apparatus may further include a microwave transmission insulating plate provided on a surface of the flat antenna facing the object to be processed, for preventing contact between the flat antenna and plasma. The antenna is provided with a coaxial waveguide for introducing microwaves from the direction perpendicular to the flat antenna, and a beam for rotating the flat antenna in-plane relative to the object to be processed. It is preferable to have a structure.

Further, in the plasma processing method of the present invention, a chamber into which a reactive gas is introduced, a workpiece holder for holding the workpiece in the chamber, and a plasma for the reactive gas introduced into the chamber. A flat-plate antenna for radiating microwaves into the chamber, wherein the flat-plate antenna has a plurality of sets of a plurality of thin wire-like slits having different directions facing each other arranged in a concentric circle or a spiral shape. The object to be processed is processed by the plasma of the reaction gas using a plasma processing apparatus. In the plasma processing method, the processing is etching, ashing, or film formation; the processing is etching of a silicon oxide film; the processing is film formation of a silicon oxide film; It is preferable to arrange the surfaces to be processed of the object to be processed in parallel, and to perform the processing while relatively rotating the surfaces in the surface. According to the present invention, the density portion of the plasma density generated in the chamber for rotating the radiation plate is moved on the object to be processed, whereby the plasma density on the object to be processed can be averaged over time, Furthermore, even if high-frequency power is applied to the workpiece holder for ion energy control, the radiation plate becomes the electrode facing the workpiece holder, so that the electric field distribution due to high frequency is also uniform near the workpiece. This makes it possible to eliminate the non-uniformity of the processing speed such as film formation and etching, which has been a problem of the conventional apparatus, while keeping the processing speed high.

[Examples] The present invention will be specifically described below based on examples.

Embodiment 1 FIG. 1 is a schematic view showing one embodiment of an apparatus for carrying out the present invention.

That is, the apparatus basically applies a magnetic field to the discharge chamber 2 for introducing the reaction gas by the air-core coil 7 and further converts the reaction gas into a plasma by using the air provided on the flat radiation plate (antenna plate) 14. The processing target 3 mounted on the processing target holder 4 is subjected to predetermined processing by plasma generated by radiating from the hole (slit) and generating plasma.
Further, as a driving mechanism for rotating the antenna plate 14 and the object 3 relatively, a bevel gear that rotates a coaxial tube 8 (8a outer conductor, 8b inner conductor) connected to the antenna body 11 so that the antenna body 11 rotates. 16, 17 and a motor 18 are provided. In the present invention, to relatively rotate the antenna plate and the object to be processed means to rotate one of them without changing the positional relationship between the antenna plate and the object to be processed. You may rotate your body. This figure shows a configuration in which the antenna plate is rotated.

As long as the apparatus of the present invention has the above-described basic configuration, other configurations may be appropriately set according to the processing purpose. For example, in FIG. A high-frequency power supply 22 for applying high-frequency power to increase ion energy is provided, and FIG. 7 shows a configuration suitable for ion beam processing, and an electrode group 26 for extracting ions from plasma and accelerating to a predetermined energy is provided. Is provided.

Next, the apparatus shown in FIG. 1 will be described in more detail. In the figure, reference numeral 1 denotes a vacuum vessel for maintaining a vacuum in the reaction chamber 2,
Reference numeral 2 denotes a reaction chamber (discharge unit), 3 denotes an object to be processed (sample), 4 denotes an object holder that holds the object to be processed and includes a cooling mechanism (not shown), and 5 depressurizes the inside of the vacuum vessel 1. Exhaust system for
Reference numeral 6 denotes a gas inlet for introducing a reaction gas used for the processing reaction, 7 denotes an air-core coil which is a magnetic field generator for applying a magnetic field to the reaction chamber 2, and 8 denotes a coaxial which introduces a microwave into the microwave output antenna unit 11. In the waveguide, 8a is an outer conductor and 8b is an inner conductor. 9a and 9b are choke flanges for electrically connecting the upper and lower coaxial waveguides 8, 10 is a taper for suppressing reflection of microwaves, 11 is a microwave output antenna body, and 12 is a two-layer antenna. The conductive plate 13 is made of a dielectric material such as quartz, alumina, boron nitride, and forsterite. Numeral 14 denotes a conductor flat plate (antenna plate) made of, for example, a copper thin film or the like having a slit for radiating microwaves to the discharge part 2, and 15 denotes a microwave transmission insulation for preventing the conductor flat plate 14 from directly contacting the plasma. Plate, 16 is a bevel gear fixed to the coaxial waveguide, for rotating the microwave radiating antenna 11, 17 is a bevel gear paired with the bevel gear 16, 18 is a motor for driving the bevel gear 17 , 19 is a microwave oscillator, 20 is an isolator, 21 is a coaxial converter with a tuner for matching an antenna, 22 is a high-frequency power supply for supplying high-frequency power to the workpiece holder 4, and 23 is a discharge chamber 2. A surface 24 for vacuum sealing between the inside of the microwave radiating antenna 11 and a connecting surface 24 of the flanges 9a and 9b connecting the upper and lower coaxial tubes 8 is provided.

An embodiment in which the present invention is applied to etching of a silicon oxide film in the above configuration will be described.

First, the inside of the vacuum vessel 1 is evacuated by the exhaust system 5. The pressure at this time is desirably 10 ⁻⁶ Torr or less, but is appropriately adjusted depending on the processing purpose. Next, a silicon oxide film substrate (workpiece 3), which is a sample to be etched, is transported from a sample exchange chamber (preliminary exhaust chamber) (not shown) to the workpiece holder 4 and mounted. In order to suppress the temperature rise of the substrate, the substrate is brought into thermal contact with the object holder 4 by an adsorption mechanism (not shown) such as electrostatic adsorption, and the object holder is cooled by a cooling system (not shown). .

Next, a reaction gas used for etching the silicon oxide film,
For example, C ₂ F ₆ , CHF _3, or H ₂ , C ₂ H ₂ ,
O ₂ or the like is introduced into the reaction chamber 2 through the gas inlet 6, and the internal pressure is controlled by adjusting the flow rate and the pumping speed, which is 1 × 10 ^{−3 to} 5 × 10 ⁻³ Torr. To
A current is supplied from a power supply (not shown) to the air-core coil 7 to form a magnetic field of about 500 to 1000 Gauss in the reaction chamber 2.

The microwave generated by the microwave oscillator 19 passes through an isolator 20 and is supplied by a waveguide. The microwave is converted to a coaxial tube 8 by a coaxial converter 21 having a tuning mechanism for matching. Supplied to The output power of the microwave is about 400 to 1000 W.

The outer conductor 8a of the coaxial tube 8 is located below the outer conductor 8a, which is vertically separated on the way, and the inner conductor 8b is connected to the antenna main body 11a.
, And is rotated together with the antenna body 11 by the motor 18 and the bevel gears 16 and 17. Here, the coaxial tube 8
It is necessary that the joint surface of the outer conductor 8a does not leak microwaves and is capable of rotating motion. However, by providing a flange 9 having a choke structure, the leakage of microwaves is mechanically prevented. Since it can be prevented in a non-contact state, high durability against rotation of the joint surface can be obtained.

The microwave entering the antenna 11 is finally emitted into the discharge chamber 2 from a slit hole provided in the microwave radiating plate 14. By the microwave and the magnetic field, a strong plasma of about 10 ¹¹ / cm ³ is formed in the discharge chamber 2. It moves along this plasma magnetic field line. When the magnetic field is diverging, the object can be separated from the discharge part because the plasma can be accelerated downward by this. When plasma acceleration by a magnetic field is not used, the object to be processed is directly placed on the discharge part. In any case, the reactive gas plasma generated in the discharge chamber is irradiated onto the silicon oxide film substrate 3 as the object on the object holder 4. A high frequency is applied to the object holder 4 from a high frequency power supply 22,
The etching of the silicon oxide film proceeds by the plasma irradiated from the discharge unit 2 and the bias voltage by the high-frequency power. The etching speed varies depending on the high-frequency power applied to the holder 4, but it is 3000 to 4000 mm at a high-frequency power of 100 W.
/ min etching rate.

Next, the microwave radiation antenna plate which is the main feature of the present invention
The method of making the etching uniform by the rotation of 14 will be described below.

FIG. 2 is a schematic plan view showing an example of a conductor plate (antenna 14) having slits used in the present invention. here,
Reference numeral 30 denotes a spiral slit having a width S and an interval d. In the configuration shown in FIG. 1 using this, the microwave transmitted through the coaxial waveguide 8 propagates the upper layer partitioned by the conductor 12 toward the outer periphery and the lower layer partitioned by the conductor plate 12. , The microwave radiating plate 14
2 (slit 30 shown in FIG. 2) gradually radiates into the discharge chamber. In addition, the plasma is directly
In order to prevent the metal from being sputtered on 14 and contaminating the sample with the metal, 15 insulators are provided. The microwave radiation intensity distribution that determines the in-plane distribution of the processing reaction can be controlled by changing the width S and interval d of the slit 30 formed in the antenna plate 14. For example, if the microwave radiation intensity at the central portion is high, it can be dealt with by increasing the slit interval d at the central portion and decreasing it at the peripheral portion. or,
By changing the slit width S, the radiation characteristics of the microwave can also be changed. However, microwaves are absorbed by the plasma as soon as they are emitted from the slit. Therefore, there is a difference in the plasma density between the portion where the slit of the antenna plate is provided and the portion where the slit is not provided. FIG. 4 shows the second
The example of the distribution of the plasma density generated by performing the microwave radiation without rotating the antenna plate 14a in the figure is shown corresponding to the cross section of the antenna plate. The strength appears, and this is reflected in the in-plane distribution of the processing speed. Here, when the antenna plate 14a is rotated by the drive motor 18 and the gear 16 attached to the coaxial tube 8 together with the antenna main body 11, the plasma density corresponding to, for example, the fourth density shown in the plan view of the antenna plate shown in FIG. As can be seen from the figure focusing on one of the regions having a high plasma density, this region moves from the outer periphery to the center. In this manner, if the region where the plasma density is high (or low) is scanned by rotation, the unevenness of the plasma density at each point can be averaged over time as shown in FIG. It can be seen that the uniformity can be improved. Further, even when there is unevenness in the circumferential direction, averaging can be performed by rotation. Normally, S and d are conventional S = about 2 mm, d = 10-20 mm
And may be set as appropriate according to the state of microwave radiation.

The type of the slit of the antenna may be not only a spiral type as shown in FIG. 2, but also a type in which a plurality of fine slits are arranged in a spiral as shown in FIG. In this case, the control of the microwave radiation intensity is based on the circumferential interval S _の of the slit,
In addition to the radial spacing S _ρ , the slit length S _l (or its shape) can be used, and the in-plane distribution of the microwave radiation intensity can be more finely controlled than the pattern shown in FIG. Becomes In the case where there is non-uniformity only in the circumferential direction, the uniformity can be improved by rotating the antenna plate other than the above-mentioned spiral pattern (for example, concentric). The same effect can be obtained by plating the above-mentioned pattern on the surface of the dielectric 13 on the side of the reaction chamber 2 instead of the conductor plate by plating or metallizing.

Here, the rotation speed of the antenna plate depends on the non-uniformity of the in-plane distribution of the plasma density and the shape of the slit (d, S, S _l , S _Ψ , S _ρ, etc.).
For example, the rotation speed may be relatively low as long as the spiral slit d is small even if the distribution is non-uniform, but it is usually about 5 to 20 rpm. The moving speed of the plasma density distribution in the direction may be about 1 mm / sec to 7 mm / sec. In addition, not only the antenna plate but also the object to be processed may be rotated simultaneously, or the object to be processed alone may be rotated.

The measurement of the plasma density can be performed by a movable Langmuir probe.

As described above, according to the present invention, the non-uniformity of the plasma density, which has been a problem of the conventional magnetic field applying type microwave processing apparatus, can be solved and the etching can be made uniform.

Although the present invention has been described by taking the case where the present invention is applied to the etching of a silicon oxide film as an example, this effect is obtained by etching silicon using SF ₆ or Cl-based gas or amorphous silicon or silicon oxide using a gas such as SiH _4. The same effects can be suitably applied to other etching, ashing, and film forming processes such as film formation.

It should be noted that the silicon oxide film treated in this embodiment has an in-plane uniformity of the etching rate of 6 ″ as compared with the case of the silicon oxide film formed in the same manner without rotating the antenna plate as shown in Table 1, for example. It was reduced from 20% to 6% in the wafer.

Embodiment 2 FIG. 7 is a schematic view showing another embodiment of the device for carrying out the present invention. 7, 25 is an ion source chamber, 26 is an ion extraction electrode group, 27 is a plasma generation chamber, 28 is a reaction chamber, and other symbols are the same as those in FIG.

This is an example in which the present invention is applied to an ion beam processing apparatus using a microwave ion source, and also targets etching, ashing, film formation, and the like.

The difference from the first embodiment is that the plasma generation chamber 27 is separated from the reaction chamber 28, and the plasma generation chamber 27 is used as the ion source chamber 25.
This means that an ion extraction electrode group 26 composed of several sheets connected to a power supply (not shown) is arranged. This electrode group
By applying an appropriate voltage from a power supply to 26, ions can be extracted from the plasma generated in the plasma generation chamber 27, accelerated to a predetermined energy, and irradiated to the object 3 to be processed. In the case of this ion beam processing apparatus, even if the plasma in the plasma generation chamber 27 is uniform, the ion beam extracted by the extraction electrode group 26 tends to be non-uniform in the radial direction. The method of changing the distribution is more effective. In this embodiment, as in the first embodiment, uniform processing of the object 3 can be performed by rotating the antenna main body 11 by the driving systems 16 to 18.

[Effects of the Invention] As described above, the present invention rotates a conductor plate (antenna plate) having microwave radiation holes (slits), thereby performing etching, ashing, or plasma etching using plasma generated by a microwave and a magnetic field. In semiconductor processing equipment that performs film formation, the in-plane uniformity of the processing speed, which was a drawback of this method, is improved at a high processing speed, and the uniformity is greatly improved by using spirally arranged slits. It has the effect of improving.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing one embodiment of the device of the present invention, and FIGS. 2 and 3 are plan views each showing an example of a pattern of an antenna plate 14 which can be used in the present invention. FIG. 4 is a schematic diagram showing the plasma density distribution of the discharge chamber when the antenna plate (14b) shown in FIG. 2 is used, and FIG. 5 is rotated using the antenna plate (14b) shown in FIG. FIG. 6 is a schematic diagram for explaining the movement of the plasma density in the case of FIG. 6, FIG. 6 is a schematic diagram showing a state where the plasma density distribution is scanned and overlapped with time according to the present invention, and FIG. FIG. 8 shows an example of a type in which microwaves are radiated from an antenna plate having a slit, (a) is a schematic diagram of an apparatus,
(B) is a plan view of the antenna plate. DESCRIPTION OF SYMBOLS 1 ... Vacuum device, 2 ... Discharge chamber 3 ... Workpiece 4 ... Workpiece holder 5 ... Exhaust system, 6 ... Gas introduction system 7 ... Air-core coil, 8 ... Coaxial tube 8a ... ... outer conductor, 8b ... inner conductor 9 ... choke flange 10 ... taper, 11 ... antenna body 12 ... conductor plate 13 ... microwave transmitting dielectric 14 ... conductor plate with slit (antenna plate) 15 ... ... Insulator, 16,17 ... Bevel gear 18 ... Motor, 19 ... Microwave generator 20 ... Isolator 21 ... Coaxial converter with tuner 22 ... High frequency power supply 23 ... Vacuum sealing surface 25 ... ... Ion source chamber 26 ... Ion extraction electrode group 27 ... Discharge chamber, 28 ... Reaction chamber 30,31 ... Vacancy (slit)

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/3065 H01L 21/205

Claims (14)

(57) [Claims] An apparatus includes: a chamber into which a reaction gas is introduced; a flat plate antenna having holes for emitting microwaves for converting the reaction gas into plasma; and a workpiece holder for mounting a workpiece to be processed by the generated plasma. The plasma processing apparatus according to claim 1, further comprising a driving mechanism for rotating the antenna to relatively rotate the antenna and the object to be processed. 2. Apparatus according to claim 1, wherein the holes of the antenna are arranged in a spiral. 3. The apparatus according to claim 1, further comprising a mechanism for joining the rotating part and the fixed part in the rotation by a coaxial tube having a choke structure. 4. A plasma processing method for generating plasma by the interaction of microwaves and etching, ashing, or forming a film on an object to be processed, wherein a flat antenna provided at a predetermined distance from the object to be processed is provided. The in-plane density distribution of the plasma generated by the microwaves radiated from the holes is moved relative to the object and rotated on the object by rotating the flat antenna. A plasma processing method comprising: 5. The plasma processing method according to claim 4, wherein the holes are arranged in a vortex shape, and an in-plane density distribution of the plasma is moved in a radial direction on the object to be processed. 6. A chamber into which a reaction gas is introduced, an object holder for holding the object in the chamber, and a microwave for plasma-forming the reaction gas introduced into the chamber. A flat-plate antenna for radiating into the chamber, wherein the flat-plate antenna includes a plurality of sets of a plurality of thin wire-shaped slits having different orientations arranged concentrically or spirally. A plasma processing apparatus. 7. A microwave transmitting insulating plate for preventing contact between said flat antenna and plasma is provided on a surface of said flat antenna facing said object to be processed.
An apparatus according to claim 1. 8. The apparatus according to claim 6, wherein the flat antenna is provided with a coaxial waveguide for introducing microwaves from a direction perpendicular to the flat antenna. 9. The apparatus according to claim 6, further comprising a beam for rotating said flat antenna relative to the object to be processed. 10. A chamber into which a reaction gas is introduced, an object holder for holding the object in the chamber, and a microwave for plasma-forming the reaction gas introduced into the chamber. And a flat antenna for radiating into the chamber, the flat antenna includes:
Plasma processing characterized by performing processing of an object to be processed by plasma of the reactive gas using a plasma processing apparatus in which a plurality of sets of a plurality of thin linear slits having different directions are arranged concentrically or spirally. Method. 11. The plasma processing method according to claim 10, wherein the processing is etching, ashing, or film formation. 12. The plasma processing method according to claim 11, wherein said processing is etching of a silicon oxide film. 13. The plasma processing method according to claim 11, wherein said processing is the formation of a silicon oxide film. 14. The plasma processing according to claim 10, wherein the processing surface of the processing object is arranged in parallel with the plane of the flat plate antenna, and the processing is performed while rotating these relatively in-plane. Method.