JP3951003B2 - Plasma processing apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing apparatus and method.
[0002]
[Prior art]
In semiconductor manufacturing processes, thin films and etching processes are performed on workpieces such as semiconductor wafers and glass substrates for LCDs using reactive plasma excited by a high-frequency electric field obtained by applying microwaves. It has been broken. In these plasma processing steps, radicals in the reactive plasma play an important role. In recent years, as the required processing accuracy is highly refined, a technique for controlling the radicals in the reactive plasma with higher accuracy and at higher speed is required.
[0003]
However, in thin film formation and etching processes using other types of reactive gases as the processing gas, it is difficult to efficiently generate and control important radicals because the cross-sectional area of the processing gas used is energy dependent. is there. In order to improve such a point, a method has been proposed for dealing with each processing gas by using plasmas having different frequencies. However, it is difficult to control the electron temperature of plasma generated by a plurality of processing gases under the same pressure condition with high accuracy, and therefore it is difficult to control the radicals in the reactive plasma with high accuracy. It was. Further, in order to control the electron temperature and electron density of the reactive plasma with high accuracy by the conventional configuration, the apparatus configuration has to be complicated.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described problems of the conventional plasma processing apparatus and method. Even when a plurality of processing gases are used under the same pressure condition, It is possible to control the electron density and electron temperature in the reactive plasma and / or remote plasma generated according to the processing gas with high accuracy, and thus, radicals important for the process can be efficiently and simply obtained. It is an object of the present invention to provide a new and improved plasma processing apparatus and method which can be supplied to a processing surface of an object to be processed.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, according to a first aspect of the present invention, a plasma processing method for processing an object to be processed by plasma of a plurality of types of processing gases by the high frequency electric field is Ru are provided. The plasma processing method using a plurality of high-frequency electric field pulse modulation controllable into individual separate independently under the same pressure, and a high-frequency electric field varies depending on the type of processing gas is characterized in that pulse modulation. When performing such processing, it is preferable to perform pulse modulation to produce a reactive plasma and / or remote plasma electron temperature varies depending on the type of processing gas. Also, the higher the reactive plasma and / or remote plasma of electron temperature, it is preferable to perform processing to generate at a position spaced than the processing surface of the object to be processed. According to such a processing method, it is possible to select an optimum electron temperature and electron density according to each processing gas, so that important radicals can be efficiently supplied to the object to be processed. Therefore, the present invention can be suitably applied to the case where the object to be processed is placed in mainly remote plasma away from the reactive plasma and the object to be processed is processed by the radicals.
[0006]
Also, the hand when performing the plasma treatment, the particle density and / or composition in the flop plasma was measured by infrared absorption spectroscopy, according to the measured value, to adjust the pulse modulation applied to each high-frequency electric field May be. According to this, it is possible to select an optimum electron temperature and electron density according to each processing gas, and it is possible to control radicals with high accuracy in real time.
[0007]
In order to solve the above problems, according to the second aspect of the present invention, a plurality of plasma the plurality of process gas by the plasma source, the object to be processed placed in the processing chamber that is maintained at a predetermined pressure A plasma processing apparatus for plasma processing is provided . In this plasma processing apparatus , each plasma source is provided with pulse modulation means that can be controlled independently, and the pulse modulation means performs different pulse modulation on different plasma sources depending on the type of processing gas. ing. At that time , if each plasma source is arranged at a different position in the processing chamber and the processing gas is supplied to the processing chamber independently in the vicinity of each plasma source, the reactive plasma generated by each processing gas is generated. And / or the electron temperature of the remote plasma can be controlled more efficiently.
[0008]
Further, in the plasma processing apparatus, by processing the management chamber of the reactive plasma is irradiated with infrared light of a predetermined wavelength, for detecting infrared light that has passed through the reactive plasma and / or remote plasma, reactive plasma And / or an infrared absorption spectroscopic means for measuring particle density and / or composition in the remote plasma, and a controller for adjusting the pulse modulation applied to each plasma source in accordance with the measured value of the infrared absorption spectroscopic means; By providing this, it becomes possible to control radicals with high accuracy in real time.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which a plasma processing apparatus and method according to the present invention are applied to an ECR plasma processing apparatus using a microwave will be described in detail with reference to the accompanying drawings.
[0010]
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 vessel forming a processing chamber. A discharge chamber 2 for generating ECR discharge by microwaves is connected to the upper portion of the vacuum vessel 1 as a first plasma source. For example, a waveguide 3 for introducing a microwave of 2.45 GHz is connected to the discharge chamber 2 via a window 3a made of a dielectric such as quartz. Furthermore, the waveguide 3 is connected to a microwave power source 4. The microwave power source 4 is connected to a pulse generator 5, and the output thereof can be arbitrarily controlled from a pulse waveform to a continuous waveform. Further, a first inlet 6 for introducing a first reactive gas (A) such as an inert gas such as He, hydrogen (H 2), and trifluoromethane (CHF 3) is attached to the discharge chamber 2. It has been. Reference numeral 7 denotes a cooling mechanism provided for water cooling the outer wall of the discharge chamber 2. A magnetic coil 8 is attached to the outside of the cooling mechanism 7 so as to surround the discharge chamber 2. According to such a configuration, by introducing a microwave into the discharge chamber 2 via the waveguide 3, a discharge occurs in the discharge chamber 2, and the magnetic coil 8 causes the electrons to perform cyclotron movement in the discharge. For example, a high-density plasma is generated by applying a magnetic field of about 875 Gauss.
[0011]
On the other hand, a part of the side wall of the vacuum vessel 1 is composed of an annular band 9 made of a dielectric material such as quartz, and a high-frequency antenna 10 is disposed so as to surround the outside of the annular band 9. A high frequency power supply 12 is connected to the high frequency antenna 10 via a matching circuit 11. The high-frequency power source 12 is connected to a pulse generator 13 so that its output can be arbitrarily controlled from a pulse waveform to a continuous waveform. The high-frequency antenna 10 excites inductively coupled plasma into the vacuum vessel 1 as a second plasma source. In the illustrated example, the one-turn high-frequency antenna 10 is arranged outside the annular band 9, but it is of course possible to arrange a high-frequency antenna of several turns.
[0012]
In addition, a mounting table 14 as an electrode is installed inside the vacuum container 1, and a wafer or the like as the object to be processed W is mounted on the mounting table 14 via suction means such as an electrostatic chuck 15. Yes. The electrostatic chuck 15 has a plate-like electrode 15a interposed between thin films made of an insulating material such as polyimide resin. By applying a DC high voltage current from a power source 15b to the electrode 15a, the workpiece W is coulombed. It can be adsorbed by force. Further, the mounting table 14 is provided with temperature adjusting means including a cooling device 16 such as a cooling jacket capable of circulating liquid nitrogen, a heater 17, and the like, and the temperature of the object to be processed W is adjusted to a desired temperature. can do. Reference numeral 18 denotes a heat transfer gas supply mechanism, which supplies a back cooling gas such as helium from a plurality of holes formed in the electrostatic chuck 10 to the back surface of the object W to be processed from the mounting table 14. This is a mechanism for increasing the efficiency of heat transfer up to W.
[0013]
A high frequency power source 20 for applying bias high frequency power is connected to the mounting table 14 via a matching circuit 19. A pulse generator 21 is connected to the high-frequency power source 20, whereby the high-frequency output of the high-frequency power source 20 can be arbitrarily controlled from a pulse waveform to a continuous waveform. Therefore, a bias of about minus several tens to minus 300 V is generated in the electrode 14 by the application of the high frequency. In addition, a second inlet 22 for introducing a reactive gas (B) such as octafluorobutane (C4F8), for example, as a second processing gas is attached to the vacuum vessel 1 and a vacuum (not shown) is attached. An exhaust pipe 18a leading to a vacuum exhaust device such as a pump is connected. A fixed amount of different kinds of first and second source gases are introduced from the first and second gas inlets 6 and 22, and exhaust is performed through the exhaust pipe 18a, whereby the apparatus vacuum vessel 1 and the discharge are discharged. The inside of the chamber 2 is kept at a predetermined gas pressure.
[0014]
Further, on the outside of the light-transmitting annular band 9 of the processing container 1, a laser light source 23a that emits an infrared semiconductor laser having a predetermined wavelength, and the inside of the vacuum processing container 1 that is emitted from the laser light source 23a (accordingly, A detection device 23b for detecting the infrared semiconductor laser that has passed through the reactive plasma) is installed. The laser light source 23a and the detection device 23b constitute an infrared semiconductor laser absorption spectroscopic device 23, and plasma particles in the vacuum processing chamber 1, for example, due to a change in the spectrum of the infrared semiconductor laser detected by the detection device 23b. It is possible to measure the density and composition of radicals, ions, atoms and molecules. Then, the measurement data relating to the density and composition of the particles measured by the detection device 23b is sent to the main controller 24. As will be described later, the pulse generators 5, 13, and 21 use the microwave output, the high frequency output or the bias data. It can be used to pulse modulate the high frequency output. In the example shown in the figure, quartz is a dielectric and has optical transparency, so that infrared light is introduced into the vacuum vessel 1 through a band-shaped annular body 9 for the high-frequency antenna 10 that generates inductively coupled plasma. However, it goes without saying that it is possible to employ a configuration in which a transmission window for the infrared semiconductor laser absorption spectrometer 23 is separately provided.
[0015]
In the plasma processing apparatus having such a configuration, the first processing gas introduced into the discharge chamber 2 through the first gas inlet 6, for example, an inert gas such as trifluoromethane (CHF 3) and He, is discharged into the discharge chamber. 2 is introduced. The first processing gas becomes the first reactive plasma P1 by the high-frequency electric field generated by the microwave that is the first plasma source in the discharge chamber 2, and radicals such as F, CF, CF2, and CF3, and CF +, CF3 +, and the like. Ions are generated. In the present embodiment, the first reactive plasma P1 is generated as high energy plasma (and hence high electron temperature plasma) by controlling the pulse modulation by the pulse generator 5. One processing gas is decomposed to a low-order atom with a high decomposition rate. Also, ionization proceeds and a large amount of ions are generated. As described above, in the present embodiment, the reactive plasma P1 having a relatively high energy (and hence a relatively high electron temperature) can be obtained from the first plasma source.
[0016]
On the other hand, the second processing gas introduced into the vacuum vessel 1 through the second gas inlet 22, for example, a gas such as C 4 F 8, is generated by the high-frequency electric field generated by the high-frequency antenna 10 that is the second plasma source. Reactive plasma P2 is generated, and radicals such as CF2 are mainly generated. In the present embodiment, the second reactive plasma P2 is controlled by the pulse generator 13 to control the pulse modulation, so that the second reactive plasma P2 has a relatively low decomposition rate compared to the decomposition of the first processing gas. Generated as reactive plasma. As described above, in the present embodiment, it is possible to obtain the reactive plasma P2 having a relatively low energy (and hence a relatively low electron temperature) from the second plasma source.
[0017]
As described above, according to the present embodiment, by performing pulse modulation on the outputs of the first and second plasma sources, reactive plasmas (that is, electrons) having different energies from the first and second processing gases, respectively. Plasmas having different temperatures can be obtained. Therefore, a desired reaction can be selectively generated by introducing these reactive plasmas to the processing surface of the workpiece W. For example, ions and radicals contained in the reactive plasmas P1 and P2 are polymerized on the workpiece W, and a polymer thin film grows. Alternatively, when a high frequency output is applied to the object to be processed W from the high frequency power supply 20 via the mounting table 14, a self-bias voltage is induced on the surface of the object to be processed W by this high frequency, and ions are extracted from the plasma by this bias voltage. As a result, the substrate W is impacted. Therefore, the workpiece W is etched by this ion bombardment. When a bias was applied and the silicon oxide film (SiO2) was selectively etched with respect to silicon (Si), the SiO2 film could be etched at a high selectivity with respect to Si and at a high etching rate. Further, by appropriately adjusting the output of the high frequency power supply 20, it is possible to generate plasma by applying high frequency on the surface of the workpiece W.
[0018]
According to the present embodiment, the density and composition of particles such as radicals, ions, atoms and molecules in the reactive plasma are measured by the infrared semiconductor laser absorption spectroscopic device 23, and the measured values are controlled by the controller 24. The pulse generator 5 for the microwave power source 4 that is the first plasma source, the pulse generator 13 for the high-frequency power source 12 that is the second plasma source, or the pulse generator for the bias high-frequency power source 20 While feeding back to the apparatus 21, the microwave output or the high-frequency output can be pulse-modulated so that the density and composition of particles, for example, radicals, ions, atoms and molecules in the reactive plasma have a desired value. That is, according to the present embodiment, the radical composition that has an important influence on etching and thin film formation is measured in real time, and only the radicals important for the process can be controlled with high accuracy while the measured value is fed back to pulse modulation. Therefore, it is possible to perform highly accurate etching and thin film formation with excellent reproducibility without changing the pressure conditions as in the prior art.
[0019]
Note that 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 object to be processed, the type of process, the process conditions, etc. It is preferable to set. As a pulse modulation method, the microwave output of the microwave power source 4 or the cycle and duty ratio of the high frequency output of the high frequency power sources 12 and 20 can be changed. A scheme can be adopted.
[0020]
In addition, as a position for measuring the density and composition of particles, for example, radicals, ions, atoms and molecules in the reactive plasma by the infrared semiconductor laser absorption spectrometer 23, the position immediately above the reaction surface of the workpiece W is preferable. For example, by measuring the density and composition of the particles in the reactive plasma 5 mm to 10 mm above the workpiece W, it becomes possible to measure a value closer to the true value of the radical that strongly affects the process, More accurate process control is possible.
[0021]
Also, the type of reaction gas introduced into each plasma source or the electron temperature of the plasma obtained by the reaction gas varies greatly depending on the type of object to be processed, the type of process, the process conditions, etc. Accordingly, it is preferable to set by experiment or the like each time. Furthermore, in the present embodiment, in order to suppress damage to the object to be processed W, a configuration in which plasma having a high electron temperature is generated at a position separated from the object to be processed W is adopted, but depending on the type of process, A configuration in which plasma having a high electron density is generated on the workpiece W side may be employed.
[0022]
In the above embodiment, the microwave plasma generator is used as the first plasma source and the inductively coupled plasma generator is used as the second plasma source. However, the plasma processing apparatus according to the present invention is It is not limited to such an example. The plasma processing apparatus may employ any plasma source as long as it can control the electron temperature of the plasma to be generated (or the particle density and composition in the reactive plasma) by pulse modulation. Is possible.
[0023]
For example, as shown in FIG. 2, parallel plate plasma and inductively coupled plasma can be combined. Briefly describing the configuration of this plasma processing apparatus, a mounting table 32 also serving as a lower electrode is installed in the vacuum vessel 31, and an object to be processed W, for example, a semiconductor wafer is electrostatically chucked on the mounting table 32. It is adsorbed and held by the adsorbing means 33. A high frequency power source 35 is connected to the lower electrode 32 via a matching circuit 34. This high frequency power supply 35 can pulse-modulate its output by a pulse generator 36. An upper electrode 37 is installed on the ceiling of the vacuum container 31 so as to face the workpiece W. A high frequency power supply 39 is connected to the upper electrode 37 via a matching circuit 38. The high-frequency power source 39 is capable of pulse-modulating its output by the pulse generator 40. The upper electrode 37 also serves as the first processing gas supply means 41, and a predetermined flow rate of processing gas can be introduced into the vacuum vessel 1 from the first processing gas source 41 a via the flow rate control device 41 b. As described above, in the present embodiment, the first plasma can be generated by generating glow discharge between the upper electrode 37 and the lower electrode 32.
[0024]
Furthermore, a part of the side wall of the vacuum vessel 1 is composed of a belt-like annular body 42 made of a dielectric such as quartz. And the high frequency antenna 43 which comprises a 2nd plasma source is installed in the outer side of this strip | belt-shaped annular body 42 so that the circumference | surroundings may be enclosed. A high frequency power supply 45 is connected to the high frequency antenna 43 via a matching circuit 44. The high-frequency power source 45 can pulse-modulate its output by a pulse generator 46. A second processing gas supply means 47 is provided in the vicinity of the belt-shaped annular body 42, and a processing gas having a predetermined flow rate is supplied from the second processing gas source 42a to the vacuum vessel 31 via the flow rate controller 42b. Can be introduced. As described above, in the present embodiment, it is possible to excite the second plasma by the second processing gas by introducing a high-frequency electric field into the vacuum vessel 1 by the high-frequency antenna 43.
[0025]
The configuration of the plasma processing apparatus according to the second embodiment of the present invention has been briefly described above. In this plasma processing apparatus as well, the first process generated by the first plasma source (parallel plate type plasma) is used. Electron temperature of reactive plasma by gas (or density and composition of particles in reactive plasma) and electron of reactive plasma by second processing gas generated by second plasma source (inductively coupled plasma) The temperature (or the density and composition of particles in the reactive plasma) can be individually controlled with high precision by pulse modulation control, so that radicals important to the process can be selectively generated and the process can be performed. It can be controlled with high accuracy. In the plasma processing apparatus having such a configuration, the first processing gas, for example, silane (SiH 4) introduced through the first gas inlet 41 is generated by the high-frequency power source 40 between the upper electrode 37 and the lower electrode 32. To be decomposed in the first plasma. This plasma is generated into a reactive plasma having a relatively low electron temperature by controlling the pulse modulation by the pulse unit 38. In this plasma, SiH3 radicals are mainly generated.
Furthermore, a part of the side wall of the vacuum vessel 1 generates a second plasma by applying a high frequency power supply 45 to a band-like annular body 42 made of a dielectric material such as quartz. The high-frequency power source 45 can generate plasma having a relatively high electron temperature by pulse-modulating the output with a pulse generator 46.
The second processing gas introduced through the second gas inlet 47, for example, hydrogen (H2) is decomposed by the second plasma, and H radicals are efficiently generated. Therefore, since the SiH 3 radical and the H radical are mainly transported and react efficiently on the workpiece W, the microcrystalline silicon thin film can be synthesized at a low temperature.
Although the infrared semiconductor laser absorption spectrometer is omitted in the illustrated example, the particle state in the reactive plasma is measured in real time and fed back as in the embodiment shown in FIG. Needless to say, it can be used for pulse modulation control.
[0026]
As mentioned above, as the second embodiment of the present invention, the example in which the parallel plate type plasma and the inductively coupled plasma are combined has been shown. However, by combining various plasma sources capable of pulse modulation control, the same pressure can be obtained. Even underneath, it is possible to control the electron temperatures of a plurality of types of processing gases individually, thereby controlling the process with high accuracy.
[0027]
【The invention's effect】
As described above, according to the present invention, a plurality of plasma sources are provided for a plurality of process gases, and the output of each plasma source is pulse-modulated to increase the electron density and electron temperature of each reactive plasma. Since it is possible to control with high accuracy, it is possible to efficiently introduce radicals important for the process onto the object to be processed by selecting the optimum electron temperature and electron density for each processing gas. Become. Therefore, the present invention can be suitably applied to a case where the object to be processed is placed in a remote plasma mainly away from the reactive plasma and the object to be processed is processed by the radicals.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a plasma processing apparatus combining microwave plasma and inductively coupled plasma according to a first embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of a plasma processing apparatus combining parallel plate type plasma and inductively coupled plasma according to a second embodiment of the present invention.
[Explanation of symbols]
W Object to be processed (semiconductor wafer)
1 Vacuum container (processing chamber)
2 Plasma discharge chamber 3 Microwave waveguide 4 Microwave generator 5 Pulse generator 6 First processing gas inlet 8 Magnetic coil 9 Dielectric 10 High frequency antenna 12 High frequency power source 13 Pulse generator 14 Mounting table 19 High frequency power source 21 Pulse Generator 22 Second processing gas inlet 23 Infrared semiconductor laser absorption spectrometer 23a Laser source 23b Detector 24 Main controller P1 First reactive plasma P2 Second reactive plasma

Claims (19)

A plasma processing method for processing an object to be processed by converting a plurality of types of processing gases into plasma by a high-frequency electric field,
The high-frequency waves respectively output from the first and second plasma sources are separately pulse-modulated by the first and second pulse generators,
Different electrons at different positions from the first and second process gases supplied from the first and second gas inlets due to the high frequency electric field energy of the first and second plasma sources controlled by the pulse modulation. A plasma processing method characterized in that plasma having temperature is generated and desired processing is performed on a processing surface of an object to be processed by the plasma having different electron temperatures . The first plasma source is a microwave plasma power source;
The plasma processing method according to claim 1, wherein the second plasma source is an inductively coupled plasma power source. The first plasma source is a parallel plate plasma power source;
The plasma processing method according to claim 1, wherein the second plasma source is an inductively coupled plasma power source. The plasma processing method according to claim 2, wherein the plasma having a higher electron temperature and / or the remote plasma is generated at a position separated from the processing surface of the object to be processed. 5. The plasma processing method according to claim 1, wherein the pulse modulation generates plasma and / or remote plasma having different electron temperatures depending on the type of processing gas. Measuring the particle density and / or composition in the generated plasma and / or remote plasma by infrared absorption spectroscopy;
The plasma processing method according to claim 1, wherein pulse modulation applied to the high frequency is adjusted according to a measurement value obtained by the infrared absorption spectroscopy. The plasma processing method according to claim 6, wherein the measurement by the infrared absorption spectroscopy is performed by an infrared semiconductor laser absorption spectrometer. The pulse modulation is adjusted by independently changing the period or duty ratio of the high frequency output from each of the first and second plasma sources using the first and second pulse generators. The plasma processing method according to claim 1, wherein the plasma processing method is performed. The plasma processing method according to claim 1, wherein a desired bias voltage is induced in the object to be processed by a high-frequency power source. The plasma processing method according to claim 9, wherein the high frequency output from the high frequency power source is pulse-modulated by a third pulse generator. The first and second plasma sources irradiate high frequencies to different positions in the processing chamber, respectively, and the first and second processing gases are irradiated with high frequencies from the first and second plasma sources, respectively. The plasma processing method according to claim 1, wherein the plasma processing method is supplied in the vicinity of a position. The plasma processing method according to claim 1, wherein the object to be processed is electrostatically adsorbed by an adsorption unit.   The plasma processing method according to claim 1, wherein the plasma processing is etching processing or film formation processing. A plasma processing apparatus that converts a plurality of processing gases into plasma by a high-frequency electric field and plasma-processes an object to be processed placed in a processing chamber maintained at a predetermined pressure,
First and second plasma sources;
First and second pulse generators that independently and independently modulate the high-frequency waves respectively output from the first and second plasma sources;
Due to the high-frequency electric field energy of the first and second plasma sources controlled by the respective pulse modulations, at different positions from the first and second processing gases supplied from the first and second gas inlets. Plasma processing comprising: first and second plasma generating means for generating plasma having different electron temperatures and performing desired processing on a processing surface of a workpiece by the plasma having different electron temperatures apparatus. The first and second plasma sources irradiate high frequencies to different positions in the processing chamber, respectively, and the first and second processing gases are irradiated with high frequencies from the first and second plasma sources, respectively. The plasma processing apparatus according to claim 14, wherein the plasma processing apparatus is supplied in the vicinity of a position. Further, by irradiating the plasma and / or remote plasma generated in the processing chamber with infrared light of a predetermined wavelength and detecting the infrared light that has passed through the plasma and / or remote plasma, An infrared absorption spectroscopic means for measuring particle density and / or composition in the plasma generated in
And a controller for controlling the first and second pulse generators for adjusting the pulse modulation applied to the first and second plasma sources, respectively, in accordance with the measurement value of the infrared absorption spectroscopic means. The plasma processing apparatus according to claim 14, wherein the plasma processing apparatus is characterized by. The first plasma source is a microwave plasma power source;
The plasma processing apparatus according to claim 14, wherein the second plasma source is an inductively coupled plasma power source. The first plasma source is a parallel plate plasma power source;
The plasma processing apparatus according to claim 14, wherein the second plasma source is an inductively coupled plasma power source.   The plasma processing apparatus according to claim 14, wherein the plasma processing is etching processing or film formation processing.

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