JP2007266522A - Plasma treatment device and processing method employing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma treatment device and its working method capable of quickly removing reaction product and effecting etching high in uniformity with high speed, in plasma processing employing gas pulse. <P>SOLUTION: The plasma treatment device 9 is provided with a plasma producing chamber 1 for producing plasma, a processing chamber 5 in which a workpiece 6 is installed and a gas introducing unit (pulse nozzle) 101 which introduces gas for processing timely and intermittently into the plasma producing chamber 1. Impulse wave is generated by introducing the gas for processing timely and intermittently into the plasma producing chamber 1 from the gas introducing unit 101 to remove the reaction product stagnated on the surface of the workpiece 6 by the impulse wave. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a technique for performing microfabrication on a semiconductor device manufacturing, a glass substrate, etc., a MEMS (Micro-Electro Mechanical Systems) or NEMS (Nano-Electro Mechanical Systems) or a liquid crystal display or a micromachine, which applies the semiconductor manufacturing technique It relates to nanotechnology and μ-TAS (Total Analysis System). The present invention particularly relates to a plasma generation method for inductively coupled plasma, a plasma source that generates plasma using the plasma generation method, a processing apparatus (processing apparatus) using the plasma source, and a processing method.

In recent years, in the fields of semiconductor integrated circuits and nanotechnology, the processing pattern is remarkably miniaturized, and processing with high accuracy, high selectivity, and high aspect ratio is required. In processing in this field, processing apparatuses using plasma are widely used. “Processing” described here uses plasma or particles in plasma (including positive ions, negative ions, and electrons) and radicals or neutral particles generated by the generation or extinction of plasma. This means that etching is performed. Therefore, in this application, the expressions “etching” and “processing” are mixed, but both have the same meaning.
As a processing apparatus using such plasma (hereinafter, also referred to as a plasma processing apparatus in the present invention), plasma is generated in a vacuum vessel, and the positive ions, radical particles, and the like generated by the plasma are used for coating. A technique for processing a processed material, for example, a reactive ion etching (RIE) apparatus is used. In the processing technology using the plasma generated in the above vacuum vessel, high-density plasma is required to further improve productivity, and electron cyclotron resonance (ECR) plasma, Plasma generation methods such as inductively coupled plasma (ICP: Inductively Coupled Plasma) and TCP (Transformer Coupled Plasma) derived from ICP are used. Using these plasma generation methods, the electromagnetic field penetrates into the plasma easily, exceeding the so-called cut-off frequency (which cuts off the electromagnetic wave depending on the plasma density). High density plasma exceeding 10 ¹² / cm ³ can be generated.
Techniques for improving processing characteristics such as processing speed, processing accuracy, in-plane uniformity, etc. by making the gas in the plasma into a pulse form include the following.
Japanese Patent Application Laid-Open No. 5-299378 discloses a technique for providing means for increasing or decreasing or changing the pressure of a reactive gas medium periodically or vibrationally for generating and controlling non-equilibrium plasma. In the present invention, a vibration diaphragm is used as means for specifically varying the pressure. In other words, non-equilibrium plasma is effectively generated by temporally changing the pressure in the plasma generation chamber with a vibrating diaphragm, constantly maintaining high ionization rate and activity, improving the processing speed, etching and film formation processing Is effective.
In Japanese Patent Laid-Open No. 7-226397, in order to prevent abnormal formation of the sidewall protective film during trench etching, the supply flow rate of the sidewall protective film forming gas is repeatedly changed in a pulse shape among a plurality of types of gases. The technology is disclosed. By implementing these, abnormal formation of the sidewall protective film during etching is prevented, and proper etching is performed.
In JP-A-7-263353, in an apparatus for performing etching with a structure in which a plasma chamber and a processing chamber are separated, there is a problem that when the diameter of the processing apparatus is increased, a significant enhancement of the exhaust system is required. And a gas supply means for supplying gas in a pulsed manner to the plasma chamber in order to solve the problem that the electrode material that separates the plasma chamber and the processing chamber is sputtered by plasma and contamination by the electrode material occurs in the object to be processed The plasma processing apparatus provided with this is disclosed. By doing so, a large-diameter workpiece is uniformly processed by the large-area plasma while maintaining the pressure difference between the plasma generation chamber and the processing chamber.
In Japanese Patent Laid-Open No. 2000-306884, when trench etching is performed on an object to be processed such as a silicon wafer, the exhaust efficiency of the reaction product generated by the etching reaction is significantly higher in the central portion of the wafer than in the peripheral portion. The reaction product stays down, making it difficult for ions and radicals to reach the surface of the workpiece, while the reaction product is efficiently exhausted at the periphery of the workpiece regardless of the wafer diameter. A technique for solving the problem that ions, radicals, etc. easily reach the surface of the object and etching becomes non-uniform is disclosed. That is, in the present invention, a predetermined gas is supplied to the reaction chamber in a pulsed manner through the buffer chamber, thereby urging the etching reaction product in the central portion during the OFF period of the pulse gas valve, and thereby in the vicinity of the object to be processed. A technique for preventing the retention of the reaction product is disclosed.
It is known that by generating plasma in a pulse form, ion species and active species generated in the plasma change with time in accordance with the pulse period. This has long been studied as an unsteady plasma. Recently, research on applying this unsteady plasma to a plasma process has become active. For example, when an electromagnetic field is input to the plasma, electrons and positive ions are dominant in the particles constituting the plasma. However, when the input of the electromagnetic field to the plasma is stopped, the attachment of electrons to the residual gas does not occur. Since this occurs, it is known that a large amount of negative ions is generated (Japanese Patent Laid-Open No. 9-139364 (Patent No. 2842344)).
Japanese Patent Laid-Open No. 5-299378 Japanese Unexamined Patent Publication No. 7-26397 JP-A-7-263353 JP 2000-306884 A JP-A-9-139364

In the technique disclosed in Japanese Patent Laid-Open No. 5-299378, the amount of ions and radicals generated in the plasma cannot be intentionally controlled, so that it is not possible to cope with processing that is increasingly miniaturized. In addition, the processing uniformity cannot be ensured between the central portion and the peripheral portion of the workpiece having a large diameter. This is because the reaction product generated at the center of the workpiece cannot be effectively removed.
In Japanese Patent Laid-Open No. 7-263353, a large area of uniform processing is realized by providing a pressure difference between the plasma generation chamber and the processing chamber, but on the other hand, the processing speed decreases.
As described above, when the conventional RIE apparatus is used, there is a problem that the reaction product stays on the workpiece, for example, the wafer surface during the processing by the plasma, thereby preventing the processing. Therefore, as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2000-306884, a technique for promoting the removal of reaction products by introducing gas in a pulsed manner has been proposed, but it is not sufficient alone. This is because, in the case of wafers that will become larger in diameter in the future, the time until the reactive organisms in the central part will be exhausted will become longer, and the productivity may be significantly reduced. In some cases, attractive force may be generated between van der Waals force and electrical interaction with polarization between the reaction product and the workpiece). In such a case, simply introduce gas. This is because it is insufficient to remove reactive organisms simply by reducing the pressure on the surface of the workpiece by stopping. In addition, the wiring width will be further reduced in the future. However, when reactive organisms enter between the more reduced wirings, it becomes difficult to remove them by the conventional method.
Therefore, the object of the present invention is to quickly remove the reaction product including the central part even if the workpiece has a large diameter, and the van der Waals force and the electric attractive force act (workpiece and reaction product). In the case where it is difficult to remove the reaction product quickly and sufficiently, such as when the wiring is miniaturized, the reaction product is quickly and sufficiently removed. An object of the present invention is to provide a plasma processing apparatus and a processing method capable of realizing uniform and high-precision processing of a workpiece and maintaining a high processing speed by enabling the removal.

In order to achieve the above object of the present invention, the invention described in each of the claims is provided.
The invention described in claim 1 is a plasma processing apparatus including a plasma generation chamber for generating plasma, a processing chamber in which a workpiece is installed, and a gas introduction unit for introducing gas intermittently in time. Then, using the shock wave generated by intermittently introducing the processing gas from the gas introduction part into the plasma generation chamber, the reaction product staying on or near the surface of the workpiece is ejected and removed. It is comprised so that it may do.
Generally, when a so-called normal temperature or normal pressure (for example, about 20 ° C., about 1 atm) gas is introduced into a vacuum (in the case of the present invention, a plasma generation chamber) via a nozzle or orifice, the nozzle or orifice exit. , The Mach number of the gas flow rate (ratio of the flow velocity to the speed of sound) is 1. The gas expands further downstream and the Mach number exceeds 1. At this time, a shock wave is generated. In the present invention, when the processing gas is introduced temporally, that is, intermittently with respect to the elapsed time, the following occurs. The pressure in the plasma generation chamber before introducing the processing gas is exhausted by a vacuum pump provided downstream of the processing chamber, and is approximately 10 ^-5 It is kept at high vacuum of Pa level. By intermittently introducing the processing gas into the plasma generation chamber in which such a vacuum is maintained, a shock wave is repeatedly generated in the plasma generation chamber in terms of time, that is, intermittently with respect to the elapsed time.
The shock wave thus generated propagates as follows. As an example, a description will be given of an embodiment in which the shape of the plasma generation chamber is an axisymmetric cylindrical shape, a processing chamber for storing a workpiece is disposed on the downstream side, and a vacuum pump is further disposed on the downstream side. Here, in order to describe the propagation of shock waves, the processing gas is simply referred to as gas, but this is the processing gas used in the plasma processing apparatus of the present invention. A gas introduction part is installed on the upstream side of the central axis of the plasma generation chamber, and the gas is intermittently introduced from the gas introduction part in time, and the gas is introduced to the downstream side opposite to the gas introduction part. Consider the case of exhausting. By introducing the gas intermittently into the plasma generation chamber in time, a shock wave is repeatedly generated in time intermittently at the gas introduction portion outlet. Each of the shock waves forms a thin disk shape perpendicular to the central axis of the plasma generation chamber and travels downstream at a speed of several hundred m / sec to several km / sec. Propagate.
The shock wave referred to here is a steep change in pressure from positive to negative that occurs within a very short time. More specifically, it can be stated as follows. For example, when the shock wave is observed at a certain position in the plasma generation chamber, the pressure rises to about several MPa (megapascal) within a short time of about several msec or less, and after that, about several tens of msec. It turns to a negative pressure and eventually returns to the same pressure as before the introduction of gas intermittently. Moreover, it is known that the pressure is the momentum of gas molecules. That is, the pressure has directionality (vector quantity). The shock wave viewed from the viewpoint of molecular motion is that molecules per unit volume corresponding to several MPa form a pressure surface (this is called a shock wave surface) in a very thin region, and this thin pressure surface is in a certain direction. It is a phenomenon that propagates at a speed exceeding the Mach number. The negative pressure in the present invention is a gas flow (gas molecule flow) in a direction opposite to the traveling direction of the shock wave generated by intermittently introducing the processing gas.
When the shock wave passes through the plasma generation chamber and propagates into the machining chamber and reaches the workpiece surface accommodated in the machining chamber, the shock wave has a steep pressure fluctuation and the workpiece surface or the vicinity thereof. The reaction product is ejected, and the reaction product is promoted to diffuse from the surface of the workpiece or the vicinity thereof into the space in the processing chamber. Note that the surface of the workpiece in the present invention is, for example, a semiconductor substrate, in addition to the geometrical outermost surface, in the uneven portion formed by resist, fine wiring, etc. Wall surfaces, more specifically, surface portions of side walls such as trenches and fine wiring.
By introducing the gas intermittently in time, the shock wave generated in the plasma generating chamber is repeatedly generated in time, that is, intermittently in time, and reaches the workpiece intermittently in time. The first shock wave reaches the bottom while repeatedly reflecting inside the trench and fine wiring. Therefore, the reaction product staying on or near the workpiece surface is repeatedly ejected intermittently from the workpiece surface or the vicinity thereof by the shock wave irradiated intermittently. In this way, the reaction product ejected intermittently from the surface of the workpiece and its vicinity intermittently leaves the surface of the workpiece and its vicinity and diffuses into the space in the processing chamber. For this reason, the reaction product that hinders the processing can be quickly and sufficiently removed from the surface of the workpiece and the vicinity thereof, so that the processing speed and processing accuracy are improved and the processing uniformity is maintained. Note that, for example, a wafer which is a workpiece by the shock wave is not damaged or broken. This is because the workpiece is held from the entire back surface by the stage, and there is no cause of damage to the wafer such as deformation. That is, it can be considered that the action by the shock wave acts only on the surface of the workpiece.
Further, by introducing the gas intermittently in time, there are the following merits at the time of plasma generation. In general, plasma generation has a suitable gas pressure range. The pressure region suitable for plasmatization is in the range of about 0.1 Pa to 20 Pa. In a pressure region where the maximum pressure reaches the MPa (Mega Pascal) range, such as a shock wave, the gas pressure (density) is too high with respect to the input discharge power, so that it is difficult to make it into plasma. However, in the process of increasing or decreasing the pressure, it passes through a pressure region suitable for plasmatization. Plasma is generated when it enters a pressure region suitable for this plasma formation. That is, there is a pressure region that is converted into plasma before and after the shock wave, and plasma is generated in that region. However, since the pressure rise time immediately before the shock wave is extremely short, such as several milliseconds or less, plasma generation may not be possible immediately before the shock wave. Therefore, since it may be considered that there is a region where plasma is generated substantially behind the shock wave, here, a stage in which the high pressure portion due to the shock wave passes and the pressure is reduced will be described. Immediately after the shock wave passes, the pressure rapidly decreases, enters a pressure region suitable for plasmatization, and plasma is generated. Since the processing gas is intermittently introduced into the plasma generation chamber in time, the plasma is generated in time, that is, intermittently with respect to the elapsed time. This is called gas pulse plasma.
However, since the pressure is further reduced thereafter, the discharge cannot be maintained as plasma. In other words, the generation and extinction of plasma occurs here. In general, the process of plasma losing energy and extinguishing is called afterglow. In the afterglow, electrons in the plasma collide with gas molecules and lose energy. In the process of losing energy, negative electrons such as radicals, chlorine, oxygen, and fluorine-based gases are formed in the process of losing energy. That is, in the plasma generated before and after the shock wave, chemically active species such as ions and radicals or negative ions in the negative gas are mixed.
Chemically active species such as negative ions constituting the shock wave reach the workpiece surface as the shock wave progresses. The processing speed is improved by the action of these chemically active species. That is, according to the plasma generating apparatus of the present invention, not only when the reactive organism is formed in a film shape on the entire surface of the workpiece, but also the reactive organism attached to the side wall such as the fine wiring portion or the trench is quickly and sufficiently obtained. Since it can be removed, not only the overall processing speed can be improved, but also the local processing speed non-uniformity can be corrected and the processing accuracy can be improved. There is a merit that the yield of the semiconductor device is improved.
Here, a pulse nozzle can be used as the gas introduction part used for intermittently introducing the processing gas in terms of time. In order to avoid a chemical reaction with the processing gas, the pulse nozzle has a metal surface that is in contact with the processing gas coated with a chemically stable substance, or more preferably a fluororesin such as Teflon (registered trademark). It is desirable to be made. Specifically, in the component parts of the gas introduction part, the material of the valve and the valve seat is made of a fluorine-based resin such as Teflon (registered trademark) as well as the flow path directly touched by the processing gas. It is desirable that it is coated with Teflon (registered trademark) or fluorine resin.
According to a second aspect of the present invention, the plasma processing apparatus of the first aspect has at least two gas introduction portions for introducing a processing gas, and the processing gas is constantly supplied from at least one of them. In the plasma processing apparatus, the gas is introduced into the plasma generation chamber and the gas is introduced into the plasma generation chamber intermittently in time from at least one other.
A processing gas is constantly introduced from one of the at least two gas introduction portions. This is called a steady gas introduction part. In addition, the processing gas is intermittently introduced in time from another one of the at least two gas introduction portions. This is called an intermittent gas introduction part. Needless to say, the stationary gas introduction part and the intermittent gas introduction part do not have to be one each, and a plurality of them may be provided. Here, for simplification, a plasma processing apparatus provided with one stationary gas introduction part and one intermittent gas introduction part will be described.
If the processing gas is only introduced intermittently from the intermittent gas introduction part in time, that is, with respect to the elapsed time, the gas may not be converted into plasma. Therefore, this problem can be solved by always introducing a constant flow of processing gas into the plasma generation chamber from the stationary gas introduction section and intermittently introducing the processing gas into the plasma generation chamber from the intermittent gas introduction section. To solve. A processing gas having a constant flow rate is introduced into the plasma generation chamber from the stationary gas introduction section, the pressure in the plasma generation chamber is maintained at about 0.1 to several Pa, and plasma is generated continuously in time. Next, the processing gas is intermittently introduced into the plasma generation chamber temporally from the intermittent gas introduction unit. Due to the processing gas introduced intermittently in time, shock waves are repeatedly generated in the plasma generation chamber intermittently in time. In this way, plasma can be easily and reliably generated even under conditions that have not been converted to plasma only by the processing gas introduced from the intermittent gas inlet, and further, the action and effect of shock waves that are intermittently repeated in time are also combined. Can be obtained. Further, there is an advantage that the processing speed can be improved because the workpiece can be always processed by constantly converting the processing gas at a constant flow rate into plasma as described above.
The action and effect of the shock wave generated by the processing gas introduced from the intermittent gas introduction part is the same as the contents described in the first aspect. This is because the pressure in the plasma generation chamber is higher than the case where the processing gas is not introduced by the processing gas introduced from the stationary gas introduction unit, but the maximum pressure is different only in the thickness of the shock wave. This is because there is no significant difference in the pressure rise time or the fall time. Therefore, detailed description of the action and effect of the shock wave is omitted here.
Note that the gas introduced from the stationary gas introduction part and the gas introduced from the intermittent gas introduction part both have the same notation as “processing gas”, but these processing gases are of the same type. A gas may be used, but a different gas may be used.
A third aspect of the present invention is the plasma processing apparatus according to the first or second aspect, wherein the plasma generated in the plasma generation chamber is inductively coupled plasma.
In order to improve the processing speed, it is necessary to increase the etching rate on the substrate surface by increasing the amount of chemically active species such as radicals and negative ions. In order to increase the amount of chemically active species such as radicals and negative ions, it is necessary to generate a high-density plasma in the plasma generation chamber. In order to generate high-density plasma in the plasma generation chamber, inductively coupled plasma (ICP) which is high-density plasma can be used. By using this inductively coupled plasma and its generation mechanism, the plasma density can be increased, so that not only the surface of the workpiece and reaction products in the vicinity thereof can be removed quickly and sufficiently, but also the processing speed itself. Improvements can also be made.
The inductively coupled plasma described here includes not only ICP but also TCP (Transformer Coupled Plasma) and similar systems.
According to a fourth aspect of the present invention, the plasma is generated using a high frequency power source for plasma generation, and is generated in a pulse form intermittent in time by performing time modulation operation of the high frequency power source. The plasma processing apparatus according to any one of claims 1 to 3, wherein the plasma processing apparatus is plasma. The time-modulated operation refers to a method for operating a plasma generating high-frequency power source that repeatedly turns on and off the power output in a short time period. This short time period is called a modulation period or a modulation frequency.
As an example, the ON frequency when the oscillation frequency of the high frequency power source for plasma generation is 13.56 MHz, the modulation frequency is 10 kHz, and the output ON / OFF time ratio, that is, the total time of ON and OFF is set to the reference value 1 is 0. Consider the case of .5. The ON / OFF ratio of the output is called a duty ratio, and is abbreviated as DR hereinafter. Since DR is 0.5, the time when the power supply output is ON and the time when it is OFF are the same, each 50 μsec. That is, plasma is generated in the previous 50 μsec, and in the next 50 μsec, there is no energy input for maintaining the discharge, resulting in afterglow. The plasma generated by time-modulating the plasma generating high frequency power supply is called pulse plasma or pulse discharge plasma, and the plasma generated using the plasma generating high frequency power supply in continuous wave is called continuous wave discharge plasma. Sometimes called and distinguished from each other.
The plasma shown in claim 4 is a pulsed plasma. In the pulsed plasma, the ion species and active species constituting the plasma change with a period corresponding to the modulation period. This is chlorine and SF ₆ When applied to a negative gas such as the above, a large amount of negative ions are formed in the afterglow. Generally, the particle types constituting the plasma are electrons and positive ions, but in the case of pulse plasma using a negative gas as described above, the plasma is composed of positive ions and negative ions. This is called ion-ion plasma. The use of ion-ion plasma has the following advantages. In general, processing by plasma is characterized in that processing is accelerated by colliding ions with a site where a chemical reaction between a radical and a workpiece occurs. However, when positive ions such as those found in conventional reactive ion etching are used, the damage to the substrate is significant due to the energy of positive ions being too large and charging due to positive ion charges. When plasma processing is performed using ion-ion plasma containing a large amount of negative ions, negative ions can be used instead of positive ions. Negative ions are generated by the attachment of electrons to gas molecules, so that the kinetic energy is small. Therefore, when plasma processing is performed using negative ions, damage to the substrate can be reduced. As described above, according to the present invention, not only the reaction product on the workpiece surface and its vicinity can be removed quickly and sufficiently, but also the machining speed can be greatly improved and machining with less damage to the workpiece can be performed. I can do it.
The invention according to claim 5 is characterized in that one or more potential control electrodes for controlling plasma potential are provided in the plasma generation chamber. It is.
When processing by plasma, it may be necessary to give energy to ions in the generated plasma or to reduce energy. Ions in the plasma have potential energy about the plasma potential. When the workpiece is set to the ground potential, energy corresponding to the difference between the plasma potential and the ground potential is given to the ions. For example, when monovalent positive ions are considered, when the plasma potential is 100 V and the workpiece is at ground potential, the energy of positive ions reaching the workpiece is approximately 100 eV (electron volts or electron volts). Become.
The potential of the plasma is determined by the interaction with the wall in contact with the plasma. Since the plasma generation chamber is generally made of a dielectric material such as quartz, the plasma potential in contact with the plasma generation chamber wall surface is a floating potential. The floating potential is determined by the quantity ratio of annihilation on the wall surface of electrons and ions. However, if a conductor having a sufficient size with respect to the plasma is inserted so as to be in contact with the plasma, the potential of the plasma is dragged to the potential of the conductor, that is, the potential of the plasma is affected. It becomes almost equal to the body potential. Therefore, when a voltage is applied to the conductor, the plasma potential can be controlled within a range of an appropriate voltage value. Here, this electrode is called a potential control electrode. When an appropriate potential is applied to the potential control electrode, the plasma potential can be controlled. That is, the ion energy can be controlled. Therefore, not only can the reaction product on and near the workpiece surface be removed quickly and sufficiently, but the ion energy can be controlled to improve the machining speed and machining accuracy, and to damage the workpiece. Can be suppressed. Alternatively, in some cases, the energy of ions can be intentionally increased and used for applications such as thin film formation by sputtering.
The power source connected to the potential control electrode may be a DC power source, an AC power source, or a 1 kHz to 1 MHz high frequency power source. More preferably, a bipolar power supply of 1 kHz to 1 MHz is used.
In the invention according to claim 6, at least one of the potential control electrodes is formed in a flat plate shape so as to partition the plasma generation chamber and the processing chamber and to face the workpiece. The at least one potential control electrode includes a plurality of small holes formed in a direction toward the workpiece, and the small holes have a rectangular shape in a cross section including the central axis of the small holes, or The plasma processing apparatus according to claim 5, wherein the plasma processing apparatus has a trapezoidal shape spreading toward a workpiece.
The plasma processing apparatus according to this aspect is the plasma processing apparatus according to claim 6, wherein at least one potential control electrode has a flat plate shape, which partitions the plasma generation chamber and the processing chamber and faces the workpiece. Is in position. By partitioning the plasma generation chamber and the processing chamber by the potential control electrode, the pressure difference between both the plasma generation chamber and the processing chamber can be maintained. A plurality of small holes are formed in the potential control electrode toward the workpiece. From these small holes, in addition to charged particles, radicals and neutral particles in the plasma, plasma is generated in the plasma generation chamber. Gas molecules that have not been released are released. In other words, the particles and molecules are irradiated from the small holes toward the workpiece.
The small hole may have a straight shape toward the work piece, that is, the cross-sectional shape of the small hole may be a rectangular shape, but the shape widened toward the work piece, that is, the cross-sectional shape of the small hole may be It may have a shape. The “trapezoidal shape” here includes not only the normal trapezoidal shape but also the shape of a Laval tube or a supersonic nozzle, and these shapes have a relatively high pressure such that the pressure in the plasma generation chamber exceeds several Pa. If it is high, there is an effect of smoothing the gas flow from the plasma product to the processing chamber, which is a preferable shape in a relatively high pressure region.
By making the small holes straight or wide, various particles emitted from the small holes can have a direction toward the workpiece. In this way, the particles emitted from the small holes can be effectively irradiated onto the workpiece, and according to the present invention, not only the surface of the workpiece and the reaction products in the vicinity thereof can be removed quickly and sufficiently. , Machining speed and machining accuracy are improved.
The invention according to claim 7 is a processing method of a workpiece using a plasma processing apparatus, wherein an introduction step of intermittently introducing a processing gas into a plasma generation chamber from a gas introduction portion in time, and the above time Generated in the above-mentioned processing step, the plasma-forming step of converting the processing gas introduced intermittently into plasma, the processing step of irradiating the workpiece with the plasma-ized processing gas and processing the workpiece And a removal step of removing the reaction product by a shock wave generated by intermittently introducing the processing gas with respect to time.
By intermittently introducing the processing gas into the plasma generation chamber from the gas introduction portion in time, a shock wave is repeatedly generated in the plasma generation chamber in time, that is, intermittently with respect to the elapsed time. In the step of converting the introduced processing gas into plasma, plasma is generated before and after the shock wave, but substantially in particular on the rear side, and the plasma is applied to a workpiece such as a semiconductor substrate by the propagation of the shock wave. Is irradiated toward the workpiece in the machining chamber, and machining is performed. The plasma is a gas pulse plasma generated intermittently in time, that is, intermittently with respect to elapsed time, by intermittently introducing a processing gas into the plasma generation chamber.
Next, propagation of shock waves, effects of shock waves, and processing by gas pulse plasma will be described.
A first wave of the shock wave generated in the plasma generation chamber reaches the workpiece. At this time, since the workpiece is not processed, there is no reaction product on the surface or in the vicinity thereof, and there is no effect of ejecting reactive organisms by the shock wave. However, in the unlikely event that fine dust of about submicron or less adheres to the surface of the workpiece, there is an effect that the fine dust is ejected by the shock wave of the first wave.
Immediately after the shock wave of the first wave, the first gas pulse plasma reaches the workpiece, whereby the workpiece is subjected to predetermined machining.
Subsequently, the second shock wave reaches the workpiece. The reaction product staying on the surface of the workpiece or in the vicinity thereof is ejected by the shock wave of the second wave and quickly and sufficiently removed. Immediately thereafter, the second gas pulse plasma reaches and the workpiece is processed. At this time, since the reaction product is removed from the surface of the workpiece or the vicinity thereof by the second shock wave, high-accuracy machining as per the design drawing is performed. Thereafter, the effect by the shock wave of the second wave and the processing by the second gas pulse plasma are repeated intermittently with respect to time, that is, the elapsed time.
In the gas pulse plasma, a large amount of negative ions are generated when radicals or negative gases generated during the generation and extinction process of the plasma are used, and these also reach the workpiece surface. As a result, the processing speed is improved.
The invention according to claim 8 is a processing method of a workpiece using a plasma processing apparatus provided with at least two gas introduction units, and at least one gas introduction unit out of at least two gas introduction units. An introduction step of constantly introducing a processing gas into the plasma generation chamber and intermittently introducing the processing gas in time from another at least one gas introduction portion; A plasma forming step for converting the processing gas intermittently introduced into the plasma into a plasma, a processing step for processing the workpiece by irradiating the workpiece with the plasma processing gas, and the processing And a removing step of removing the reaction product generated in the step by a shock wave generated by intermittently introducing a processing gas in time.
Here, for simplification of description, a processing method in a plasma processing apparatus provided with one stationary gas introduction part and one intermittent gas introduction part will be described.
A processing gas having a constant flow rate is continuously introduced into the plasma generation chamber from the stationary gas introduction unit, and a temporally continuous plasma is generated by this gas. Although the workpiece is constantly and continuously processed by the processing gas that is constantly introduced, reactive organisms may stay on or near the surface of the workpiece and deteriorate the processing characteristics. Note that the surface of the workpiece in the present invention is, for example, a semiconductor substrate, in addition to the geometrical outermost surface, in the uneven portion formed by resist, fine wiring, etc. Wall surfaces, more specifically, surface portions of side walls such as trenches and fine wiring.
There, the processing gas is intermittently introduced in time from the intermittent gas introduction part. As a result, shock waves are repeatedly generated in the plasma generation chamber intermittently in time. This shock wave propagates into the processing chamber, reaches the workpiece, and ejects or peels off the reaction product from the surface of the workpiece, thereby causing a local delay in processing, that is, non-uniform processing. Since the reaction product which is the cause is quickly and sufficiently removed, it is possible to improve the processing speed and the processing accuracy. The processing accuracy includes an overall one that covers the entire surface of the workpiece and a local one that is, for example, inside the fine wiring. For example, the current problem in semiconductor manufacturing lines is often the local area such as the inside of fine wiring, and the reaction products remaining in such areas greatly increase the yield of semiconductor devices. It is a factor that influences. Therefore, according to the present invention, the reaction product remaining in the fine wiring can be quickly and sufficiently removed, so that, for example, in semiconductor manufacturing, the yield of semiconductor elements can be improved.
In addition, even when the plasma is not generated only by the introduction of the intermittent gas as shown in claim 7, the plasma is continuously generated by the processing gas introduced from the steady gas introduction section, so that the intermittent gas is generated. Since the processing gas introduced from the introduction part can be reliably converted into plasma, the above-described problem can be solved.
The invention described in claim 9 is the workpiece processing method according to claim 7 or 8, wherein an inductively coupled plasma is used as the plasma.
In order to improve the processing speed, it is necessary to increase the etching rate on the surface of the workpiece (for example, a semiconductor substrate) by increasing the amount of chemically active species such as radicals and negative ions. In order to increase the amount of chemically active species such as radicals and negative ions, it is necessary to generate a high-density plasma in the plasma generation chamber. In order to generate high-density plasma in the plasma generation chamber, inductively coupled plasma (ICP) which is high-density plasma can be used. As described above, high-density plasma can be generated by the inductively coupled plasma generation mechanism, so that not only the reaction product staying on and near the workpiece surface can be removed quickly and sufficiently, but also the processing speed. Can be obtained.
According to a tenth aspect of the present invention, the plasma used for processing the workpiece is plasma generated using a high frequency power source for generating plasma, and the high frequency power source is time-modulated to perform intermittent operation. 10. The processing method for a workpiece according to claim 7, wherein the plasma is generated in a pulse shape.
In plasma generated by time-modulated operation, in addition to positive ions generated by normal operation, a large amount of negative ions is generated when radicals or negative gases are used. These radicals and negative ions reach the workpiece by the propagation of shock waves, not only quickly and sufficiently remove the reaction products staying on and near the workpiece surface, but also improve the processing speed and processing accuracy, Furthermore, the processing method which reduces the damage to a workpiece is obtained.
The invention described in claim 11 is characterized in that one or more potential control electrodes are provided in the plasma generation chamber to control the potential of the plasma. It is a processing method of a workpiece.
When an appropriate voltage is applied to the potential control electrode, the plasma potential can be controlled, so that the energy of ions in the plasma can be controlled. If the ion energy can be controlled, a processing method in which damage to the workpiece is suppressed can be obtained. For example, if the voltage applied to the potential control electrode is limited to a range of plus 1 kV to minus 1 kV, preferably plus 500 V to minus 500 V, more preferably plus 100 V to minus 100 V, for a device formed on the object to be processed, etc. A processing method that avoids damage caused by ions or the like can be obtained. Therefore, if the processing method of the present invention is used, not only the reaction product can be removed quickly and sufficiently, but also processing with reduced damage to the workpiece can be performed.
The invention according to claim 12 is a processing method of a workpiece using a plasma processing apparatus having a plate-like potential control electrode as at least one of the potential control electrodes, the potential control electrode Is installed at a position that separates the plasma generation chamber from the processing chamber and faces the workpiece, and the potential control electrode has a plurality of small holes formed in the direction toward the workpiece. The small hole uses a potential control electrode of a mode in which the shape in a cross section including the central axis of the small hole is a rectangular shape or a shape that spreads toward the workpiece in a trapezoidal shape, thereby 12. The processing method for a workpiece according to claim 7, wherein the particles emitted from the plasma generation chamber are irradiated with a direction toward the workpiece.
According to the method of processing a workpiece by installing a flat plate-like potential control electrode having a small hole as described above at a position separating the plasma generation chamber and the processing chamber as described above, plasma is generated from the small hole. Since the particles, radicals, and neutral particles inside can be directed toward the workpiece while being directed, processing at higher speed and higher accuracy is possible.

  According to the present invention, the reaction product staying on or near the workpiece surface can be quickly and sufficiently removed, so that highly uniform etching can be performed at high speed. Furthermore, according to the present invention, a workpiece having a large caliber (large area) or a work in which van der Waals force or electric attractive force acts between the workpiece and the reaction product, or Since a similar effect can be obtained for a workpiece such as a semiconductor wafer in which the wiring is miniaturized, the productivity of the semiconductor element can be improved mainly by improving the yield of the semiconductor element.

    Hereinafter, embodiments of a plasma processing apparatus and a processing method according to the present invention will be described in detail with reference to the drawings.

    FIG. 1 is a diagram showing an overall configuration of a plasma processing apparatus 9 according to an embodiment of the present invention. As shown in FIG. 1, a plasma processing apparatus 9 includes a plasma generation chamber 1 that generates plasma therein, and a processing chamber in which a workpiece 6 made of a semiconductor substrate, glass, organic matter, ceramic, or the like is disposed. 5 is a vacuum device. This vacuum apparatus includes a high-frequency power source 4 provided with a time modulation function for plasma generation, a potential control electrode 103 for controlling the plasma potential, and a gas for intermittently introducing a processing gas. It has an introduction part (pulse nozzle) 101, a vacuum pump 8 for exhausting gas, and a stage 7 for holding the workpiece 6.

    An inductively coupled coil 2 is disposed on the outer periphery of the plasma generation chamber 1. The coil 2 is obtained by winding a copper water-cooled pipe having an outer diameter of, for example, about 8 mmφ for two turns in a coil shape. The coil 2 is installed so as to surround the outer periphery of the plasma generation chamber 1. The coil 2 is connected to a high frequency power source 4 via a matching box 3, and a high frequency voltage of 13.56 MHz is applied to the coil 2 in this example. The oscillation frequency of the high-frequency power source 4 used for plasma generation is not limited to 13.56 MHz, and a frequency in the range from 100 kHz to 10 GHz can be appropriately selected according to the processing process.

    A processing gas is flowed (introduced) into the plasma generation chamber 1, and plasma is generated in the plasma generation chamber 1 by the coil 2 and the high-frequency power supplied from the high-frequency power source 4. By applying a high frequency current to the coil, a magnetic field is generated in the plasma generation chamber 1, and the time change of the magnetic field induces an electric field, and electrons are accelerated by the electric field to generate plasma. This is called inductively coupled plasma (ICP: Inductively Coupled Plasma). Note that the number of turns (number of turns) of the coil 2 shown here is not limited to 2, and can be appropriately selected from about 1 to 20 turns depending on the size of the plasma generation chamber 1 and process conditions. When the workpiece 6 is a φ300 mm wafer, it is preferably 1 to 3 turns.

In the upper part of the plasma generation chamber 1, there is a gas introduction part for introducing gas. This gas introduction unit employs a pulse nozzle 101 in order to introduce the processing gas into the plasma generation chamber 1 in terms of time, that is, intermittently over time. The pulse nozzle 101 is connected to a gas supply source (not shown) via a gas supply pipe (not shown). Processing gases such as SF ₆ , CHF ₃ , CF ₄ , Cl ₂ , Ar, O ₂ , N ₂ , C ₄ F ₈ , CF ₃ I, and C ₂ F ₆ are supplied from a gas supply source (not shown). It is supplied to the plasma generation chamber 1 through the pulse nozzle 101.

The working gas introduced intermittently from the pulse nozzle 101 forms a shock wave 206 in the plasma generation chamber 1. When the shock wave 206 is observed at a certain observation point in the plasma generation chamber 1 or the processing chamber 5, the pressure at the observation point, which was about 10 ⁻⁵ Pa until just before that, is within a very short time of milliseconds or less. Increases to a high pressure of several MPa at a stroke, and immediately after that, turns to a negative pressure, and eventually the pressure before the processing gas is introduced intermittently in time (in the present application, the absolute pressure is on the order of 10 ⁻⁵ Pa). And a vacuum state of about 1 Pa, and a phenomenon in which the internal pressure of the plasma generation chamber 1 and the processing chamber 5 other than the state in which the internal pressure fluctuates is restored by intermittently introducing gas over time. When observed as the plasma processing apparatus 9, it can be said to be a wavefront having a high pressure surface that travels at supersonic speed from the outlet of the pulse nozzle 101 toward the processing chamber 5. This is the shock wave 206.

    Next, the shock wave 206 and the gas pulse plasma 102 generated in the plasma product 1 will be described with reference to FIG. In the shock wave 206, a portion that is in a pressure region suitable for being converted into plasma is converted into plasma by the high-frequency power supplied from the high-frequency power source 4 for generating plasma. This is called gas pulse plasma 202. The gas pulse plasma 202 represents one of the gas pulse plasmas 102 generated intermittently in FIG. The gas pulse plasma 202 is a plasma having a substantially disk-shaped region, and propagates by forming a shock wave 206 on the front edge side thereof. In the gas pulse plasma 202, a large amount of negative ions are generated when a large amount of radicals or negative gas that cannot be obtained by plasma by continuous discharge is used in addition to ions. These radicals and negative ions reach the workpiece by the propagation of the gas pulse plasma 202 following the shock wave 206, and a chemical reaction occurs. The next shock wave 206 arrives at the site where this chemical reaction takes place, and the reaction product staying on or near the workpiece surface is ejected. Subsequently, the gas pulse plasma 202 reaches the workpiece surface, and the processing speed is significantly improved by the energy of ions in the gas pulse plasma 202. As described above, after the reaction product is ejected by the shock wave 206, the chemical reaction by radicals and the processing promotion by ions are repeated, thereby enabling higher-speed and high-precision processing.

    Further, the shock wave 206 generated in the plasma generation chamber 1 has the following effects. The processing gas introduced from the pulse nozzle 101 into the plasma generation chamber 1 reaches supersonic speed at the pulse nozzle outlet, and further expands in the plasma generation chamber 1 to form a shock wave 206. The pressure of the shock wave 206 reaches several MPa, and the propagation speed reaches several km / sec. Since the shock wave 206 reaches the workpiece 6 and ejects the reaction product staying on the workpiece surface and inside the fine wiring formed on the surface, natural sublimation, which is a general method for removing the reaction product, is used. On the other hand, the removal can be performed at higher speed and sufficiently. The retention mentioned here means that the reaction product is physically attached to the workpiece surface or a structure such as fine wiring, or is attracted or drifted by van der Waals force or electrical attraction. This includes cases where When the shock wave 206 reaches the workpiece surface, the reaction product staying on the workpiece surface is ejected by the ultrahigh pressure of the shock wave 206. Thereafter, when the pressure is rapidly reduced on the surface of the workpiece and becomes a negative pressure, the ejected reaction product is pulled away from the surface of the workpiece toward the plasma generation chamber side. The reaction product separated from the workpiece 6 diffuses into the processing chamber 5 and is exhausted to the outside of the plasma processing apparatus by a vacuum pump 8 provided in the processing chamber 5. That is, the reaction product can be efficiently and sufficiently removed from the workpiece 6 by the shock wave 206 formed in the plasma generation chamber 1.

    The pulse nozzle 101 is preferably installed toward the workpiece 6. This is because the shock wave 206 directly hits the workpiece 6. Although it does not necessarily have to be on the central axis of the plasma generating apparatus, it is preferably arranged on the central axis of the plasma generating chamber 1 in order to prevent the influence of reflected waves on the inner walls of the plasma generating chamber 1 and the processing chamber 5.

    As described above, in the plasma processing apparatus 9 according to the present invention, the reaction wave staying on or near the workpiece surface can be efficiently and sufficiently removed by the shock wave 206 and the gas pulse plasma 202. In addition, high-precision processing becomes possible. This is because if the reaction product remains on the surface of the workpiece or in the vicinity thereof, the processing is locally hindered, so that high-precision processing such as processing with a high aspect ratio has been difficult. According to the method, the reaction product can be sufficiently removed, so that high-speed and high-precision processing as described above is possible.

    The conditions for introducing the processing gas introduced intermittently over time will be described as follows, for example. In a processing apparatus for processing a semiconductor substrate having a diameter of 300 mm, when the inner diameter of the plasma generation chamber is 350 mm, the period for intermittently introducing the processing gas is called the gas introduction period, and the introduction of the gas The period is preferably 1 Hz to 1 kHz, and more preferably 10 Hz to 100 Hz, in the plasma processing apparatus 9 equipped with the vacuum pump 8 having an effective exhaust speed of 1000 L / sec.

Next, the opening time of the pulse nozzle 101 that determines the absolute flow rate is called a gas pulse width, and the gas pulse width is 0.1 msec to 10 msec, and more preferably 0.5 msec to 2 msec. In the gas introduction cycle, one gas introduction is called one gas pulse, and the gas amount per gas pulse is 0.5 cm ^{3 to} 100 cm ³ in the standard state (0 ° C., 1 atm), more preferably 1 cm ^3. To 10 cm ³ .

    In FIG. 1, a potential control electrode 103 made of a conductor is disposed at the upper end inside the plasma generation chamber 1. The potential control electrode 103 need not satisfy the requirement of controlling the potential of the gas pulse plasma 102 or 202 generated in the plasma generation chamber 1 and therefore does not necessarily have to be above the plasma generation chamber 1. . For example, the shape may be cylindrical or rectangular along the inner wall of the plasma generation chamber 1, and may not necessarily be the shape along the inner wall of the plasma generation chamber 1.

    The potential control electrode 103 is connected to a potential control power source 104. The potential control electrode 103 may be made of metal, silicon, or graphite having no holes other than passing through the pulse nozzle 101. Alternatively, the potential control electrode 103 may be formed with a large number of holes from which gas is introduced in pulses. It may be formed. In this case, a mechanism for controlling the gas introduction period, the gas pulse width, and the like may be required separately. By applying a voltage to the potential control power supply 104, a predetermined voltage can be applied between the stage 7 on which the workpiece 6 is placed. As the potential control power supply 104 to be connected, in the case of direct current, it is preferable to use a bipolar power supply capable of flowing a reverse current. This is because a reverse current may flow because electrons have a higher mobility than ions, and this prevents damage to the power supply. By applying a DC voltage to the potential control electrode 103, energy in a certain direction can be given to charged particles in the plasma. For example, for positive ions, when a positive voltage is applied to the potential control electrode 103, the plasma potential rises by that amount, and the workpiece has a difference energy between the plasma potential and the stage 7 (ground potential). Positive ions are incident on. For negative ions, if a negative voltage is applied to the potential control electrode 103, the plasma potential is lowered by that amount, and the workpiece has a difference energy between the plasma potential and the stage 7 (ground potential). Negative ions are incident. At this time, when the voltage applied to the potential control electrode 103 is replaced with an AC power supply, a bipolar power supply operated by frequency modulation, or a high-frequency power supply, positive ions and negative ions can be irradiated alternately. This is particularly effective in a semiconductor manufacturing process such as gate poly silicon oxide film processing, and an alternating current or high frequency frequency applied at this time can be used in a wide range from about 1 Hz to about 10 MHz. The frequency is preferably 1 kHz to 5 MHz, more preferably 100 kHz to 1 MHz. Note that a method of reducing substrate damage by applying an AC voltage or a high frequency to the stage may be used.

    A second embodiment of the present invention is shown in FIG. As shown in FIG. 3, in addition to the intermittent gas introduction part (pulse nozzle 301), a steady gas introduction for always introducing a constant amount of processing gas separately from the plasma processing apparatus 9 of FIG. Part 305. A plasma is steadily generated by constantly introducing gas from the stationary gas introduction unit 305, and the gas is intermittently and temporally introduced from the pulse nozzle 301. A shock wave 206 is generated intermittently in time in the plasma generation chamber 1 by the processing gas introduced intermittently in time, and propagates into the processing chamber 5. By this shock wave, the reaction product staying on the surface of the workpiece or in the fine wiring is efficiently and sufficiently removed.

    The potential control electrode 303 is the same as that described with reference to FIG.

    However, in addition, the following method can be further applied to the steady gas introduction method. A slight gap is provided between the potential control electrode 303 and the plasma generation chamber 1, and gas can be introduced into the plasma generation chamber 1 through this slight gap. Alternatively, a large number of holes can be formed in the potential control electrode 303 or a porous (porous) material can be produced, and the gas can be uniformly introduced into the plasma generation chamber 1 from the entire surface of the electrode.

    The gas flow rate to be constantly introduced is preferably 1 sccm to 500 sccm, more preferably 5 sccm to 50 sccm. The conditions for introducing the gas are the same as those described with reference to FIG. 1. However, since the pressure in the plasma generation chamber 1 and the processing chamber 5 is increased by constantly introducing the gas, the gas introduced in a pulsed manner. The introduction period, gas pulse width and gas amount per gas pulse are reduced individually or independently by 10% to 50%, an exhaust pump having an effective exhaust speed of 1500 L / sec to 3000 L / sec, or a combination thereof. Is good.

    A third embodiment of the present invention is shown in FIG. In the present embodiment, in addition to the potential control electrode 403 provided at the upper part of the plasma generation chamber 1, another potential control electrode 405 is disposed downstream of the plasma generation chamber 1 of the plasma processing apparatus 9 shown in FIG. Is. This other potential control electrode 405 will be referred to as a potential control lower electrode. The potential control power supply 404 has one pole connected to the potential control electrode 403 provided on the upper side and the other pole connected to the potential control lower electrode 405. By doing so, a potential difference is generated between the potential control electrode 403 and the potential control lower electrode 405, and energy can be given to the charged particles in the plasma. In this example, an example is shown in which one potential control power source 404 is used, but independent power sources may be connected to the potential control electrode 403 and the potential control lower electrode 405, respectively. A DC power supply can be used as these potential control power supplies, but a bipolar power supply is preferably used. This is because, since the mobility of electrons in the plasma is larger than that of ions, a reverse current may flow, and in the case of a DC power supply, this may be damaged. Alternatively, an AC power source or a high frequency power source can be used as these potential control power sources.

    The material of the potential control lower electrode 405 may be a conductor such as metal or graphite. It is even better if these surfaces are subjected to corrosion prevention treatment or spatter prevention treatment.

Next, a structural example of the potential control lower electrode is shown. FIG. 5 shows an example of a mesh-like potential control lower electrode 501. Note that the mesh shape means a mesh shape. The mesh-like potential control strain electrode 50 is effective when a relatively thin plasma having a density of plasma generated in the plasma generation chamber 1 of, for example, less than 10 ¹¹ cm ⁻³ is used. The mesh interval depends on the plasma density, but if a fine mesh is used, the effect of the shock wave 206 is reduced. Therefore, it is preferable to use a mesh interval of about several mesh / inch to 100 mesh / inch.

    FIG. 6 shows an example of a potential control lower electrode 601 which is plate-shaped and has a large number of holes. The potential control lower electrode may have any of these shapes, and can take all shapes similar to these.

    In addition, among the potential control lower electrode 601 shown in FIG. 6, the shape of the small hole 602 opened in the potential control lower electrode 601 is straight toward the workpiece as shown in FIG. In this case (in the case of the small hole 701), fast neutral atoms (including molecules) can be obtained by charge exchange between ions and residual gas molecules in the hole 701. Since the high-speed neutral atoms (including molecules) have a direction toward the workpiece, the processing speed and processing accuracy are improved. Further, as shown in FIG. 8, even if a large number of small holes are formed in a trapezoidal shape toward the workpiece (in the case of the small holes 801), the radicals are converted into radicals by the principle of the Laval tube. Since the effect of giving direction to the workpiece is obtained, the processing speed and the processing accuracy are improved.

    Next, the operation of the plasma processing apparatus in the present embodiment will be described with reference to FIG. In this embodiment, a semiconductor substrate is taken as an example of a workpiece, and a case where poly silicon formed on a silicon oxide film of the semiconductor substrate is etched (gate etching) will be described as an example.

First, the plasma generation chamber 1 and the processing chamber 5 are evacuated by operating an exhaust pump, and then, for example, SF ₆ gas is introduced from the pulse nozzle 101 into the plasma generation chamber 1. For example, a high frequency voltage of 13.56 MHz is applied to the coil by a high frequency power source for 50 μsec. By applying this high frequency voltage, a high frequency electric field is formed in the plasma generation chamber 1. The gas introduced into the plasma generation chamber 1 is ionized by electrons accelerated by the high-frequency electric field, and high-density plasma is generated in the plasma generation chamber 1. The plasma formed at this time is a plasma mainly composed of positive ions and heated electrons.

    Then, the application of the high frequency voltage by the high frequency power supply is stopped for 50 μsec. The plasma generated in the plasma generation chamber 1 is cut off from the input of energy, and shifts to a process of natural annihilation with diffusion. This is called afterglow. After the high frequency voltage from the high frequency power source is stopped for 50 μs as described above, the high frequency voltage is again applied by the high frequency power source 4 to heat the electrons in the plasma in the plasma source, and the above-described cycle is repeated. That is, the application of the high-frequency voltage (50 μsec) and the application stop (50 μsec) are repeated alternately. The high-frequency voltage application stop time (50 μsec) is sufficiently longer than the time required for electrons in the plasma to adhere to the remaining processing gas and generate negative ions, and in the plasma This is a time sufficiently shorter than the time when the electron density of the plasma decreases and the plasma is extinguished. The application time of the high frequency voltage (50 μsec) There is enough time to restore energy. This is called pulse plasma or pulse modulation plasma.

When a negative gas such as SF ₆ gas is used in the pulsed plasma, electrons in the afterglow undergo an inelastic collision, the electron temperature decreases, and adhere to residual gas molecules to generate negative ions. That is, plasma in a state where negative ions coexist with positive ions can be efficiently formed. This is particularly called ion-ion plasma. Although an example in which the stop time of high-frequency voltage application is set to 50 μs has been described here, a large amount of negative ions as well as positive ions is generated in the plasma by setting it to 50 μs to 100 μs. be able to.

    Here, in FIG. 1, when a voltage of −50 V is applied to the potential control electrode 103 by the potential control power source 104, a potential difference is generated between the potential control electrode 103 and the stage 7 holding the workpiece 6. Therefore, negative ions in the plasma source are accelerated toward the stage by this potential difference.

    The fluorine atoms or fluorine ions activated by the plasma are emitted into the processing chamber 5. The fluorine atoms and the like are irradiated to the workpiece 6 (semiconductor substrate) placed on the stage. Irradiated fluorine atoms and the like spontaneously sublimate as SiF4 in a processed layer (Poly silicon layer) of the workpiece 6 by a thermal chemical reaction of Si + 4F → SiF4 ↑. In this way, the poly silicon layer etching not covered with the mask proceeds. Here, the mask is a resist made of an organic material.

    In the processing chamber 5, a stage 7 for holding a workpiece 6 (wafer, that is, a semiconductor substrate) is disposed, and the workpiece 6 is placed on the upper surface of the stage 7. The processing chamber 5 is connected to an exhaust pump (vacuum pump 8) for exhausting gas. A valve such as a gate valve (not shown) is preferably disposed between the processing chamber 5 and the vacuum pump 8. The processing chamber 5 is maintained at a predetermined pressure by the vacuum pump 8. As the vacuum pump 8 used here, it is preferable to use a thread groove turbo molecular pump or a dry pump subjected to corrosion prevention treatment. Moreover, it is preferable to arrange | position the end point detection part which measures an etching state and detects an etching end point in the processing chamber 5. FIG. For example, a quadrupole mass analyzer can be used as the end point detection unit. More preferably, on-wafer monitoring (in-situ observation on the wafer) is performed using laser interference, ellipsometry, or the like. Is good.

    In the above-described embodiment, it is preferable to form a high-density plasma using an ICP type coil. However, TCP (Transformer Coupled Plasma), ECR (Electron Cyclotron Resonance), helicon wave, microwave, etc. It is good also as producing | generating a plasma using. Further, the oscillation frequency of the high-frequency power source that generates the plasma is not limited to 13.56 MHz described above, and any frequency from 1 MHz to 20 GHz can be used depending on the machining process, and frequency modulation is possible. May be used.

    Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.

The schematic diagram which shows the plasma processing apparatus in the 1st Embodiment of this invention. The schematic diagram which shows the gas pulse plasma and shock wave in this invention. The schematic diagram which shows the plasma processing apparatus in the 2nd Embodiment of this invention. The schematic diagram which shows the plasma processing apparatus in the 3rd Embodiment of this invention. The schematic diagram which shows the electric potential control lower electrode made into the mesh form in this invention. The schematic diagram which shows the electric potential control lower electrode provided with the some small hole in the plate shape in this invention. The schematic diagram which shows the electric potential control lower electrode which the some small hole in this invention made the structure straight toward the workpiece. The schematic diagram which shows the electric potential control lower electrode which made the structure where the several small hole in this invention spreads conically toward a workpiece.

Explanation of symbols

1 Plasma generation chamber 2 Coil (for plasma generation)
3 Matching box 4 High frequency power supply (for plasma generation)
5 Processing chamber 6 Work piece 7 Stage 8 Vacuum pump 9 Plasma processing apparatus 101, 301, 401 Pulse nozzle 102, 202, 302, 402 Gas pulse plasma 103, 303, 403 Potential control electrodes 104, 304, 404 Potential control power source 206 Shock wave 305 Gas introduction section 405 for constantly introducing gas Potential control lower electrode 501 Mesh-shaped potential control lower electrode 601 Plate-shaped potential control lower electrode 602 Plurality of holes opened in plate-shaped potential control lower electrode Small hole and enlarged view 701 viewed from above 701 A plurality of small holes in the potential control lower electrode and a cross-sectional enlarged view 801 having a straight structure toward the workpiece 801 expands in a trapezoidal shape toward the workpiece Structure of the small holes of the potential control lower electrode and enlarged view of the cross section

Claims (12)

  A plasma generation chamber for generating plasma; a processing chamber in which a workpiece is installed; and a gas introduction section for intermittently introducing a processing gas into the plasma generation chamber from the gas introduction section. A shock wave is generated by intermittently introducing a processing gas into the plasma generation chamber, and a reaction product staying on the workpiece surface is removed by the shock wave. Plasma processing equipment.   At least two gas introduction portions for introducing a processing gas into the plasma generation chamber are provided, and at least one of the gas introduction portions steadily introduces the processing gas into the plasma generation chamber. 2. The plasma processing apparatus according to claim 1, wherein the processing gas is intermittently introduced into the plasma generation chamber from time to time.   The plasma processing apparatus according to claim 1, wherein the plasma generated in the plasma generation chamber is inductively coupled plasma.   The plasma is plasma generated using a high frequency power source for plasma generation, and is generated in a pulsed manner intermittent in time by performing time modulation operation of the high frequency power source. The plasma processing apparatus according to claim 1.   The plasma processing apparatus according to claim 1, further comprising a potential control electrode for controlling one or a plurality of plasma potentials in the plasma generation chamber.   At least one of the potential control electrodes has a flat plate shape, partitions the plasma generation chamber and the processing chamber, and is disposed so as to face the workpiece. The at least one potential control electrode includes: A plurality of small holes formed in a direction toward the workpiece are provided, and the small holes have a rectangular shape in a cross section including the central axis of the small holes, or have a trapezoidal shape toward the workpiece. 6. The plasma processing apparatus according to claim 5, wherein the plasma processing apparatus has an expanding shape.   A processing method of a workpiece using a plasma processing apparatus, wherein an introduction step of intermittently introducing a processing gas from a gas introduction portion into a plasma generation chamber in time and the processing introduced intermittently in time A plasma forming step for converting the working gas into plasma, a processing step for processing the workpiece by irradiating the plasma processing gas to the workpiece, and a reaction product generated in the processing step. And a removing step of removing by a shock wave generated by intermittently introducing the working gas with respect to time.   A method of processing a workpiece using a plasma processing apparatus having at least two gas introduction units, wherein the processing unit is steadily processed from at least one gas introduction unit into at least one gas introduction unit into a plasma generation chamber. An introduction step of introducing a gas and intermittently introducing a processing gas from another at least one gas introduction portion, and the constantly introduced processing gas and the temporally introduced processing gas. A plasma forming step for converting the processed gas into plasma, a processing step for processing the workpiece by irradiating the plasma processing gas to the workpiece, and a reaction product generated in the processing step. And a removing step of removing by a shock wave generated by intermittently introducing the processing gas over time.   The method for processing a workpiece according to claim 7, wherein an inductively coupled plasma is used as the plasma.   The plasma is plasma generated using a high frequency power source for plasma generation, and is generated in a pulsed manner intermittent in time by performing time modulation operation of the high frequency power source. The processing method of the workpiece in any one of Claims 7 thru | or 9.   11. The workpiece processing method according to claim 7, wherein one or more potential control electrodes are provided in the plasma generation chamber to control the plasma potential.   A processing method for a workpiece using a plasma processing apparatus having a plate-like potential control electrode as at least one of the potential control electrodes, wherein the potential control electrode is installed at a plasma generation chamber. And the processing chamber are arranged at a position facing the workpiece, and the potential control electrode includes a plurality of small holes formed in a direction toward the workpiece, and the small holes are the small holes. Using the potential control electrode of a mode in which the shape in the cross section including the central axis of the hole is rectangular or trapezoidally widened toward the workpiece, the particles emitted from the plasma generation chamber are thereby collected. The method for processing a workpiece according to claim 7, wherein the irradiation is performed with directivity toward the workpiece.

Images