JP3199306B2 - Plasma processing apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a plasma processing apparatus and method.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, a thin film is formed on an object to be processed such as a semiconductor wafer or a glass substrate for an LCD using a reactive plasma excited by a high-frequency electric field obtained by applying a microwave or the like. And the etching process is performed. In these plasma processing steps, radicals in the reactive plasma play an important role.
In recent years, as the required processing precision has become extremely fine, a technique for controlling radicals in reactive plasma with higher precision and higher speed has been required.

[0003] In this regard, conventionally, it has been attempted to indirectly control radicals in reactive plasma by controlling various parameters such as power applied to a plasma source and pressure in a processing chamber. However, since these parameters change relative to each other, it has been difficult to control only radicals with high accuracy. In addition, because of the indirect control method, it has been difficult to quickly optimize the state of radicals. Furthermore, even under the same processing conditions,
Reproducibility of the process is difficult due to factors such as contamination of the reaction vessel wall, and from this point, it is difficult to control radicals with high accuracy.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional plasma processing apparatus and method, and has been developed in a reactive plasma or a remote plasma in a processing chamber. It is an object of the present invention to provide a new and improved plasma processing apparatus and method capable of controlling particles at a high speed with high reproducibility and high accuracy.

[0005]

According to a first aspect of the present invention, a reactive plasma excited by a pulse-modulatable high-frequency electric field in a plasma generation chamber is supplied to a plasma processing chamber. A plasma processing method for introducing and etching an object placed in a plasma processing chamber, wherein a particle density and / or a composition in plasma existing in a plasma generation chamber and / or a plasma processing chamber are measured by infrared light. A step of measuring the particle density and / or composition by absorption spectroscopy; and a step of pulse-modulating a high-frequency electric field in accordance with the measured particle density and / or composition to control the particle density and / or composition to a predetermined value. Is to change the period and / or output of the pulse ,
The measurement of the particle density and / or the composition of
The operation is performed at a position approximately 5 mm to approximately 10 mm above .

In the above-described plasma processing method, when controlling the pulse modulation, the control of the pulse modulation may be performed by controlling radicals in plasma in the plasma processing chamber and / or the plasma generation chamber. It is preferable to change the pulse period and / or duty ratio and / or power so that the composition is constant. Preferably, the reactive plasma is obtained by converting a reactive gas containing at least a fluorocarbon into a plasma as described in claim 3, and more specifically, as described in claim 4. , The reactive plasma is at least C
It is preferable to control the pulse modulation so that the radicals of F, CF2, CF3, F and CF + ions are included, and the composition of the radicals and ions of CF / F and CF + and / or CF2 / F and CF + is constant. .

According to a second aspect of the present invention, a high-frequency electric field capable of pulse modulation is applied to a plasma generation chamber for exciting a reactive plasma by a high-frequency electric field capable of pulse modulation and a mounting table communicating with the plasma generation chamber. A plasma processing apparatus is provided which includes a mechanism for performing a process and a plasma processing chamber for processing an object mounted on the mounting table. Then, the plasma processing apparatus, as claimed in claim 5, irradiating the plasma present in the upper space of the mounting table in the reactive plasma in the plasma generating chamber and / or plasma treatment chamber infrared light of a predetermined wavelength And an infrared absorption spectroscopy means for measuring the particle density and / or composition of the plasma, and a high frequency electric field and / or a radio frequency electric field for exciting the reactive plasma in accordance with the particle density and / or composition measured by the infrared absorption spectroscopy means. A controller for pulse-modulating a high-frequency electric field applied to the mounting table, wherein the pulse modulation changes a period and / or an output of a pulse, and the infrared absorption spectroscopy means comprises:
The plasm at a position of about 5 mm to about 10 mm immediately above
Installed to measure particle density and / or composition
It is characterized by that.

[0008] Such a control unit of the plasma processing apparatus, as claimed in claim 6, as in the composition of the radicals in the plasma in the plasma processing chamber and / or plasma generation chamber is constant, the period of the pulse and / or It is preferable to change the duty ratio and / or the power. Also,
Reactive plasma, as described in claim 7, comprising at least SiH3 radicals and / or CH3 radicals and / or Cl radical, SiH3 radicals and / or C
It is preferable to control the pulse modulation so that the density of H3 radicals and / or Cl radicals becomes constant. Alternatively, as described in claim 8 , the reactive plasma contains at least CF, CF2, CF3, F radicals and CF + ions, and CF / F and CF + and / or CF + ions.
It is preferable to control the pulse modulation so that the composition of radicals and ions of 2 / F and CF + becomes constant .

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment in which the plasma processing apparatus and method according to the present invention are applied to an ECR plasma processing apparatus using microwaves will be described in detail.

FIG. 1 shows an example of the configuration of an ECR plasma processing apparatus to which the present invention is applied. In the figure, reference numeral 1 denotes a vacuum container forming a processing chamber, and an upper part of the vacuum container
A discharge chamber 2 for generating a CR discharge is connected. A waveguide 3 for introducing microwaves of, for example, 2.45 GHz is connected to the discharge chamber 2 through a window 3a made of a dielectric material such as quartz. Further, the waveguide 3 is connected to a microwave power supply 4. The microwave power supply 4 is connected to a pulse generator 5, whereby its output can be controlled arbitrarily from a pulse-like waveform to a continuous waveform. Further, for example, an inert gas such as He and methane trifluoride (CHF
A first inlet 6 for introducing a reactive gas (A) such as 3) is attached to the discharge chamber 2. Reference numeral 7 denotes a cooling mechanism provided for water-cooling the outer wall of the discharge chamber 2, and a magnetic coil 8 is attached to the outside of the cooling mechanism 7 so as to surround the discharge chamber 2. A discharge is generated by microwaves in the discharge chamber 2, and a magnetic field of, for example, about 875 gauss is applied by the magnetic coil 8 so that electrons move in a cyclotron during the discharge, thereby generating high-density plasma.

On the other hand, a mounting table 9 as an electrode is provided inside the vacuum vessel 1, and a wafer or the like as a workpiece W is mounted on the mounting table 9 via an adsorption means such as an electrostatic chuck 10. Is placed. The electrostatic chuck 10 has a plate-shaped electrode 10a interposed between thin films made of an insulating material such as a polyimide resin, and applies a DC high-voltage current from a power supply 10b to the electrode 10a to coulomb the workpiece W. It can be adsorbed by force. Further, the mounting table 9 is provided with a temperature control means including a cooling device 11 such as a cooling jacket and a heater 12 capable of circulating liquid nitrogen, and a temperature control means for controlling the temperature of the workpiece W to a desired temperature. can do. Reference numeral 13 denotes a heat transfer gas supply mechanism, which supplies a back cooling gas such as helium to the back surface of the workpiece W from a plurality of holes formed in the electrostatic chuck 10 so that the workpiece W This is a mechanism for increasing the efficiency of heat transfer to W.

A high frequency power supply 15 for applying a high frequency power for bias is connected to the mounting table 9 via a matching circuit 14. The high frequency power supply 15 includes a pulse generator 16
Is connected, whereby the high-frequency output of the high-frequency power supply 15 can be arbitrarily controlled from a pulse-like waveform to a continuous waveform.
Therefore, a bias of about minus several tens to about minus 300 V is generated in the electrode 9 by the application of the high frequency. In addition, a second inlet 17 for introducing an inert gas such as He and a reactive gas (B) such as methane trifluoride (CHF 3) is attached to the vacuum vessel 1. An exhaust pipe 18 connected to a vacuum exhaust device such as a vacuum pump is connected. A predetermined amount of a raw material gas, for example, a reaction gas containing fluorocarbon is introduced from each of the gas inlets 6 and 17, and exhausted through an exhaust pipe 18. Maintained at gas pressure.

Further, at least two windows 19 made of a light transmissive material such as quartz are provided on the side wall of the processing vessel 1 at positions facing each other. A laser light source 20a that emits an infrared semiconductor laser of a predetermined wavelength through these windows
And the vacuum processing vessel 1 emitted from the laser light source 20a.
A detection device 20b for detecting the infrared semiconductor laser that has passed through the inside (accordingly, in the reactive plasma) is provided.
The laser light source 20a and the detection device 20b constitute an infrared semiconductor laser absorption spectrometer 20, and the detection device 20b
It is possible to measure the density and composition of plasma particles, for example, radicals, ions, atoms, molecules, etc., in the vacuum processing container 1 by a change in the spectrum of the infrared semiconductor laser detected by the method. Then, the detection device 20b
The measurement data relating to the density and composition of the particles measured by the above is sent to the main controller 21 for pulse modulation of the microwave output or the high frequency output for bias by the pulse generator 5 or 16 as described later. Can be used for

The methane trifluoride (CHF 3) introduced into the discharge chamber 2 through the gas inlet 6 becomes a reactive plasma P due to a high frequency electric field generated by microwaves.
Radicals such as F, CF2 and CF3 and ions such as CF + are generated. In the illustrated example, the reactive plasma P is developed from the discharge chamber 2 into the vacuum vessel 1. Radicals contained in the reactive plasma P are polymerized on the target object W, and a polymer thin film grows. Alternatively, if a high-frequency output is applied to the object W from the high-frequency power supply 15, a self-bias voltage is induced on the surface of the object W by the high frequency, and ions are extracted from the plasma by the bias voltage, and the substrate W is processed. Shocked. Therefore, the workpiece W is etched by the ion bombardment. Also,
By appropriately adjusting the output of the high-frequency power supply 15, it is possible to generate plasma by applying a high frequency to the surface of the workpiece W.

According to the plasma processing apparatus having the above configuration, the microwave output generated from the microwave power supply 4 is modulated by the pulse generator 5 or the high frequency output generated from the high frequency power supply 15 is modulated by the pulse generator 16. The density and composition of the radicals in the vacuum vessel 1 can be controlled by modulating the temperature, or by time-sharing the application of the microwave output and the high-frequency output and appropriately combining them. At this time, according to the present invention, the infrared semiconductor laser absorption spectrometer 20 measures the density and composition of particles, for example, radicals, ions, atoms and molecules in the reactive plasma, and compares the measured values with the controller 21. Through
Pulse generator 5 for microwave power supply 4 and high frequency power supply 1
While feeding back to the pulse generator 13 for 5
The microwave output or the high-frequency output can be pulse-modulated so that the density or composition of particles, for example, radicals, ions, atoms, and molecules in the reactive plasma have desired values. That is, according to this embodiment, the radical composition that has an important effect on etching and thin film formation can be measured in real time, and only radicals can be controlled with high accuracy while feeding back the measured value to pulse modulation. Excellent high-precision etching and thin film formation are possible.

The density and composition of the reactive plasma particles, which are the target values of the feedback control according to the present invention, vary greatly depending on the type of the object to be processed, the type of the process, the process conditions, and the like. It is preferable to set by experiment or the like. The method of pulse modulation includes not only the cycle and duty ratio of the microwave output of the microwave power supply 4 or the high-frequency output of the high-frequency power supply 15 and ON / OFF, but also the power Hi /
Lo and the like can be changed, and an optimal pulse modulation method can be adopted according to the process. The pulse waveform is not limited to a square wave, but may be a triangular wave or a sawtooth wave.

The infrared semiconductor laser absorption spectrometer 20
Thereby, the position in which the density or composition of particles in the reactive plasma, for example, radicals, ions, atoms and molecules is measured, is preferably immediately above the reaction surface of the target object W, for example,
By measuring the density and composition of the particles in the reactive plasma 5 mm to 10 mm above the target object W, it becomes possible to measure a value closer to the true value of the radical that strongly affects the process, and a higher value is obtained. Accurate process control becomes possible.

The energy (electron temperature) of the plasma differs between the plasma discharge chamber 2 and the vacuum vessel 1 (that is, the plasma energy of the former is higher than that of the latter). Therefore, in the illustrated embodiment, various types of plasma conditions can be generated by introducing different types of gases from the gas inlets 6 and 17 to plasmas having different energies. . However, the present invention is not limited to such an example, and it goes without saying that a single processing gas may be introduced and the processing gas may be converted into plasma.

Next, using an ECR plasma processing apparatus shown in FIG. 1, an object to be processed such as a semiconductor wafer having a silicon oxide film formed on a silicon or silicon nitride film is turned into a plasma with a reaction gas containing at least fluorocarbon. An embodiment for performing an etching process will be described.

First, a reaction gas containing at least a fluorocarbon is introduced into the discharge chamber 2, and the pressure is maintained at 0.4 Pa.
The microwave has a cycle of 50 μsec, the microwave generator output is time-divided by the pulse generator 5, and the microwave power is modulated by changing the duty ratio from 1 to 100% (continuous) at a microwave power of 1000 W. Was.
In this case, an object to be processed W having a suitable etching pattern formed on SiO 2 was used. A high frequency of 400 KHz was applied to the object to be processed W, and a voltage of 250 V bias was applied to the surface of the object to be processed W. Further, using an infrared semiconductor laser absorption spectrometer 20 installed in the vacuum vessel 1,
CF, CF2, CF at 10 mm above the workpiece W
3. Radical density of F and CF + ion density were measured.

The infrared semiconductor laser absorption spectrometer 2
The cycle of the microwave output and the duty ratio are changed so that the composition of the radical (CF / F, CF2 / F) in the reactive plasma or the composition of the radical and the composition of the ion in the reactive plasma are constant according to the measured value of 0. I let it. As a result, according to the present embodiment, it was possible to feedback-control only the radical composition in the reactive plasma with high accuracy and high speed.

When the etching characteristics were evaluated, it was found that the silicon oxide film could be etched at a high etching rate of 6000 angstroms / sec with a high etching selectivity of 50 to silicon etching and 25 to silicon nitride film. SE etching pattern of silicon oxide film
Observation with M revealed that the pattern was almost perpendicular to a fine pattern of up to 0.3 μm.

Further, the etching characteristics of the oxide film / silicon were evaluated for the wafers (5000 wafers) in order to examine the change with time. When the feedback of the radical composition was not performed, the etching rate and the selection ratio were reduced from about 1000 wafers. Variation occurred, and a decrease in etching reproducibility was observed. On the other hand, if you provide feedback,
Good etching characteristics can be obtained for all 5000 wafers, and high reproducibility can be obtained.

The embodiment of the present invention applied to a microwave plasma processing apparatus has been described above, but the present invention is not limited to such an example. It is needless to say that the present invention can be applied to various plasma processing apparatuses capable of performing pulse modulation control of reactive plasma in a vacuum vessel, for example, a parallel plate plasma processing apparatus, an inductively coupled plasma processing apparatus, and the like.

[0025]

According to the present invention, the density and composition of radicals in reactive plasma, which have an important effect on etching and thin film formation, are measured in real time by an infrared semiconductor laser absorption spectrometer, and the measured values are fed back. Since pulse modulation is controlled while controlling only radicals with high accuracy, highly accurate etching and thin film formation with excellent reproducibility can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment in which the present invention is applied to a microwave plasma processing apparatus.

[Explanation of symbols]

 W Object to be processed (semiconductor wafer) 1 Vacuum vessel (processing chamber) 2 Plasma discharge chamber 3 Microwave waveguide 4 Microwave generator 5 Pulse generator 6 Gas inlet 8 Magnetic coil 9 Electrode (mounting table) 14 Matching circuit 15 High frequency power supply 16 Pulse generator 17 Gas inlet 18 Exhaust hole 19 Transmission window 20 Infrared semiconductor laser absorption spectrometer 20a Laser source 20b Detector 21 Main controller P Reactive plasma

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Koshimizu Shioji 5-3-6 Akasaka, Minato-ku, Tokyo Inside Tokyo Electron Co., Ltd. (56) References JP-A-1-149965 (JP, A) JP-A JP-A-7-94130 (JP, A) JP-A-7-122543 (JP, A) JP-A-63-20484 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21 / 3065 C23C 16/52 C23F 4/00 G01N 21/35 H01L 21/205

Claims (8)

(57) [Claims] 1. Pulse modulation is possible in a plasma generation chamber
Reactive plasma excited by a high-frequency electric field
Into the plasma processing chamber and placed in the plasma processing chamber.
A plasma processing method for etching a processed object.
Therefore, it exists in the plasma generation chamber and / or the plasma processing chamber.
Particle density and / or composition in the changing plasma
Measuring by an optical method, and according to the measured particle density and / or composition,
The high frequency electric field is pulse modulated to obtain the particle density and / or
Controlling the composition to a predetermined value, wherein the pulse modulation comprises changing the period and / or output of the pulse.
To changeWith The measurement of the particle density and / or composition in the plasma
Performed at a position approximately 5 mm to approximately 10 mm directly above the object to be processed
,  A plasma processing method characterized by the above-mentioned. 2. The control of the pulse modulation is to change a pulse period and / or a power so that a composition of radicals in plasma in the plasma processing chamber and / or the plasma generation chamber is constant. The plasma processing method according to claim 1, wherein: 3. The plasma processing method according to claim 1, wherein the reactive plasma is obtained by converting a reactive gas containing at least fluorocarbon into plasma. 4. The reactive plasma comprises at least C
The control of the pulse modulation is performed so that the composition of the radicals and ions of CF / F and CF + and / or CF2 / F and CF + includes the radicals of F, CF2, CF3, and F +. The plasma processing method according to claim 2 or 3, wherein 5. A reaction by a high-frequency electric field capable of pulse modulation.
A plasma generation chamber for exciting a reactive plasma;
High-frequency electric field that can be pulse-modulated on the mounting table communicating with the generation chamber
And a mechanism for applying
Plasma processing equipment with a plasma processing chamber for processing
In and / or before the reactive plasma in the plasma generation chamber
Plas present in the upper space of the mounting table in the plasma processing chamber
Irradiates the plasma with infrared light of a predetermined wavelength to generate particles of the plasma.
Infrared absorption spectroscopy means for measuring density and / or composition, and particle density and / or
Or, depending on the composition, a high frequency to excite the reactive plasma
The wave electric field and the high-frequency electric field applied to the
A pulse controller for controlling the pulse period and / or output.
To changeWith The infrared absorption spectroscopy unit is located approximately 5 mm directly above the object to be processed.
Particle density in the plasma at a position approximately 10 mm from
And / or installed to take compositional measurements; That
Characteristic plasma processing equipment. 6. The controller according to claim 1, wherein the controller changes a pulse period and / or a power so that a radical composition in plasma in the plasma processing chamber and / or the plasma generation chamber becomes constant. The plasma processing apparatus according to claim 5 , wherein 7. The reactive plasma includes at least Si.
H3 radical and / or CH3 radical and / or Cl
7. The plasma processing apparatus according to claim 5 , wherein the pulse modulation is controlled such that the density of the SiH 3 radicals and / or the CH 3 radicals and / or the Cl radicals is constant. 8. The reactive plasma may include at least C
The control of the pulse modulation is performed so that the composition of the radicals and ions of CF / F and CF + and / or CF2 / F and CF + includes the radicals of F, CF2, CF3, and F +. Claim 5 or
7. The plasma processing apparatus according to 6 .