JP2009179826A - Ecr sputtering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize film-formation in a metal mode, which is an operation of forming a film by making a target discharge a metal element in a metal state. <P>SOLUTION: The ECR sputtering apparatus inhibits the surface of the target from being rapidly oxidized and promotes the oxidation reaction on the surface of a substrate to stabilize the film formation in the metal mode, by controlling a flow of active species of oxygen in plasma in a passage of the plasma which directs to the substrate from a plasma-generating chamber. A reaction chamber has a target electrode arranged along the passage in which the plasma flows toward the substrate, and a shield for controlling a flow of the plasma provided therein. The shield controls the flow of the active species of oxygen in the plasma. The sputtering apparatus alters a flowing ratio of the plasma directing toward the substrate to the plasma directing toward the target, thereby controls the amount of the active species of oxygen directing toward the surface of the target, thereby relatively increases the amount of the active species of oxygen directing toward the substrate to inhibit the surface of the target from being rapidly oxidized, and increases the amount of the active species of oxygen directing toward the substrate to promote the oxidation reaction on the surface of the substrate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sputtering apparatus using ECR plasma, and more particularly to metal mode film formation performed in a metal mode region.

The ECR sputtering apparatus is an apparatus that generates ECR (Electron Cyclotron Resonance) plasma, sputters a target with ions in the plasma, and deposits sputtered particles emitted by the sputtering on the surface of the substrate to be processed. . When a reactive gas is introduced into the processing chamber, the sputtered particles scattered from the target cause a chemical reaction with the reactive gas during the scattering or on the surface of the substrate to be processed. Deposit as a thin film. By this reactive ECR sputtering method, a thin film such as a compound semiconductor or a piezoelectric ceramic can be formed. Conventionally, there has been known an ECR sputtering apparatus that introduces O ₂ gas as a reactive gas into a processing chamber, sputters a metal zinc target with Ar ions, and reacts Zn particles from the target with O ₂ gas to form a ZnO film. (For example, refer to Patent Document 1).

  FIG. 7 is a diagram showing a schematic configuration of a conventional ECR sputtering film forming apparatus. In FIG. 7, the ECR sputtering film forming apparatus 101 includes a plasma generation chamber 102 and a reaction chamber 103. A microwave introduction hole 104 is provided in the wall of the plasma generation chamber 102. A microwave generated by a high-frequency power source (not shown) is impedance-matched by a transmitter and an EH tuner (not shown), and then guided through a microwave waveguide (not shown). The plasma is introduced into the plasma generation chamber 102 through a microwave introduction window (not shown) of the introduction hole 104. A magnetic field coil 105 is provided on the outer periphery of the plasma generation chamber 102.

  The reaction chamber 103 communicates with the plasma generation chamber 102 through an opening for extracting plasma. The reaction chamber 103 is provided with an exhaust port 106 and a gas introduction port 107. The exhaust port 106 evacuates the inside of the reaction chamber 103, and the gas introduction port 107 is connected to the gas supply source at the other end. A reaction gas or the like is introduced into 103.

  In the plasma processing, the reaction chamber 103 and the plasma generation chamber 102 are decompressed to a predetermined pressure by a vacuum exhaust device, a direct current is supplied to the magnetic field coil 105, and the reaction is performed from the gas inlet 107 into the reaction chamber 103 and the plasma generation chamber 102. A gas is introduced and a microwave is introduced into the plasma generation chamber 102. In the reaction gas, high-density plasma is generated by electron cyclotron resonance by a microwave electric field and a magnetic field of the magnetic field coil 105, and is separated into positive ions and electrons.

  In the plasma, since the electrons are light, they move at a high speed, get out of the plasma in a short time, collide with the walls, and disappear. On the other hand, positive ions have a large mass and a low speed compared to electrons, and therefore exist in plasma for a long time. Thereby, the plasma becomes a positive charge as a whole and forms an ion sheath. The substrate support 111 that supports the substrate 112 is attracted by the positive charge of the ion sheath, accumulates negative charges, and generates a negative self-bias voltage. The positive ions in the plasma are transported to the reaction chamber by the divergent magnetic field of the magnetic field coil 105, are accelerated by the negative self-bias voltage, collide with the substrate 112, and accumulate on the substrate 112 to form a film.

  Patent Document 2 points out that as a problem in the conventional ECR sputtering film forming apparatus, it may be difficult to ensure stability when a metal compound thin film is formed reactively. In the said patent document 2, it points out as follows.

  A major feature of the ECR plasma film formation method is reactive film formation in which a compound thin film is formed using a metal target and an argon / oxygen mixed gas. In such a reactive film formation, if the oxygen flow rate is controlled within a very small range, the metal element is sputtered out from the target surface, adsorbed on the sample substrate, and then the oxygen adheres and reacts to form the metal oxide thin film. The thin film grows in the process as it is formed. On the other hand, when the oxygen flow rate is increased, oxygen adheres to the target surface and oxidizes, and a mode in which it is sputtered and jumps out in the oxide state. As in the former case, the case of jumping out from the target with the metal element as it is is called metal mode film formation, and the case of jumping out as an oxide is called oxide mode film formation. In metal mode film formation, since the sputtering efficiency of metal is overwhelmingly higher than that of oxide, there is a great advantage that the film formation speed can be increased.

On the other hand, it is difficult to always keep the target surface in a stable metallic state in an oxygen atmosphere, and there is a problem that the target surface is oxidized for some reason during film formation and shifts to an oxide mode. An oxygen flow rate range in which metal mode film formation can be stably maintained is called a metal mode margin, and the wider this range, the more stable film formation is possible. A sufficient margin can be secured by SiO ₂ film formation using an Si target or Al ₂ O ₃ film formation using an Al target, but other refractory metal oxide film formation is often not sufficient, especially TiO 2. _{In 2} film formation, stable metal mode film formation has been extremely difficult so far.

  In Patent Document 2, as a means for solving the above problem, a shielding ring mechanism for controlling the particle distribution is provided on the downstream side of the target, thereby lowering the film formation speed and extending the oxygen supply time to the sample substrate. In addition, it is described that the supply of oxygen from the sample chamber side to the target is suppressed, and oxidation of the target surface is prevented while supplying oxygen to the sample substrate. The shielding ring of Patent Document 2 is denoted by reference numeral 200 in FIG.

  Although the ECR sputtering film forming apparatus has different purposes, a configuration is proposed in which the flow of plasma or reactive gas is controlled by providing a shielding member.

  For example, as a configuration for controlling the flow of plasma, a configuration in which a plasma limiting cylinder is provided on the downstream side of the target has been proposed (see Patent Document 3). In this configuration, the spread of the plasma is limited, the plasma is prevented from being irradiated on the inner wall of the chamber, and the damage due to dust and abnormal plasma is suppressed.

  Further, as a configuration for controlling the flow of the reactive gas, a configuration in which a shielding member is installed on the downstream side of the target in the reaction chamber has been proposed (see Patent Document 4). In this configuration, a ring-shaped space surrounded by the shielding member and the substrate support is formed in the processing chamber, and the reactive gas is introduced into the ring-shaped space to restrict the flow of the reactive gas to the target. , Which suppresses oxidation and nitridation of the target.

Japanese Patent Laid-Open No. 10-030179 Japanese Patent Laying-Open No. 2005-171328 (paragraph 0006) JP 2003-129236 A (paragraph 0006) Japanese Patent Laying-Open No. 2005-226130 (paragraphs 0019, 0026, 0028)

  As described above, metal mode film deposition has an enormous advantage that the deposition rate can be increased because the metal sputtering efficiency is overwhelmingly higher than that of oxide, while the target surface is always stable in an oxygen atmosphere. However, as a means for solving this problem, Patent Document 2 provides a shielding ring mechanism for controlling the particle distribution on the downstream side of the target.

  This shield ring mechanism reduces the film formation rate to increase the oxygen supply time to the sample substrate, and suppresses the supply of oxygen from the reaction chamber (sample chamber) side to the target to oxidize the target surface. By preventing this, metal mode film formation is stabilized.

  However, stabilization of the metal mode film formation by this shielding ring mechanism is achieved by introducing a reactive gas into the reaction chamber (sample chamber) into which plasma flows in the configuration of the ECR plasma film formation apparatus, and in the vicinity of the substrate in the reaction chamber. This is effective in a configuration in which oxygen active species (radicals) are formed to form a target particle on a substrate, and is not necessarily effective in an ECR plasma film forming apparatus having another configuration.

  In the ECR plasma deposition system, reactive gas is introduced into the plasma generation chamber upstream of the target to form oxygen active species (radicals) and introduced into the reaction chamber (sample chamber) together with Ar ions. In the configuration in which the target particles are sputtered to generate sputtered particles and fly to the substrate, and the target particles are deposited on the substrate by sending oxygen active species (radicals) to the substrate. The effect of suppressing the supply of oxygen from the) side to the target cannot be applied, and the metal mode film formation cannot be stabilized.

FIG. 8 shows a configuration in which ions and oxygen active species (radicals) are supplied from the plasma generation chamber into the reaction chamber (sample chamber). In this configuration, when the shielding ring 200 is provided between the substrate 113 and the downstream side of the target 113, the flow of oxygen active species (radicals) O ^* is limited by the shielding ring 200, and the oxygen active species supplied to the substrate 112. The flow rate of (radical) O ^* will decrease.

  As shown in FIG. 8, when a shielding ring mechanism is provided on the downstream side of the target, oxygen active species (radicals) in the plasma pass through the target surface and flow to the substrate side, so the oxygen flow rate is increased. The concentration of oxygen active species (radicals) on the target surface is increased, and the target surface is rapidly oxidized when the amount exceeds a predetermined amount, and the film formation rate is rapidly decreased to shift from the metal mode to the oxide mode. In this oxide mode, the substrate is deposited with oxide target particles. This oxide mode film formation is an incomplete oxide and does not lead to complete oxidation.

  Further, since the oxygen active species (radicals) supplied to the substrate are limited by the shielding ring mechanism, the concentration of oxygen active species (radicals) near the surface of the substrate may be lowered, and the film formation rate may be reduced.

  For this reason, in the conventional ECR sputtering apparatus, in the reactive sputtering for obtaining an oxide thin film, when the oxygen flow rate is increased to increase the film formation rate, the metal mode region shifts to the oxide mode. There is a problem that it is difficult to form a complete oxide film. In addition, since the oxide mode film formation is an incomplete oxide, the absorption coefficient k of the film formation increases, and there is a problem that high reflection characteristics cannot be obtained.

  Therefore, the present invention solves the above-mentioned conventional problems, introduces plasma generated by ECR plasma in the plasma generation chamber into the reaction chamber, and generates sputtered particles generated by sputtering of the target by ions in the plasma, An object of the present invention is to stabilize metal mode film formation in which an element is released from a target in a metal state in an ECR plasma film formation apparatus that forms a substrate with oxygen active species (radicals).

  More specifically, the oxidation of the target due to oxygen active species (radicals) is reduced, and the transition from metal mode film formation to oxide mode film formation is suppressed. An object is to release a metal element as target particles and promote oxidation of the target particles on the substrate surface.

  The present invention suppresses rapid oxidation at the target surface by controlling the flow of oxygen active species (radicals) in the plasma in the plasma flow path from the plasma generation chamber toward the substrate, and at the substrate surface. By promoting the oxidation reaction, the metal mode film formation is stabilized.

  Control of the flow of oxygen active species in the plasma according to the present invention is performed by changing the flow rate of plasma transported in the direction of the substrate by a magnetic field, lowering the rate toward the target surface, and increasing the rate toward the substrate. By changing the flow ratio of the plasma toward the substrate and the plasma toward the target, the amount of oxygen active species toward the target surface is suppressed, and the amount of oxygen active species toward the substrate is relatively increased.

  By suppressing the amount of oxygen active species toward the target surface, rapid oxidation on the target surface is suppressed, and by increasing the amount of oxygen active species toward the substrate, the oxidation reaction on the substrate surface is promoted.

  In the present invention, plasma generated by ECR plasma in a plasma generation chamber is introduced into a reaction chamber, a target is sputtered by ions in the plasma to generate sputtered particles, and a substrate is formed by the sputtered particles and oxygen active species in the plasma. In the ECR plasma film forming apparatus, the target chamber is provided with a target electrode arranged along a flow path where the plasma flows toward the substrate, and a shield for controlling the flow of the plasma.

  The shield of the present invention controls the flow of oxygen active species (radicals) in the plasma by changing the flow ratio of the plasma toward the substrate and the plasma toward the target. The shield surrounds the periphery of the target electrode except for the surface where the target electrode faces the substrate, and is disposed at a predetermined distance from the target electrode. Further, as a characteristic of the shield, the surface of the shield that faces the plasma flow path has a configuration in which the target electrode extends in the substrate direction from the face that faces the plasma flow path.

  The shield provided by the present invention has a configuration in which the surface facing the plasma flow path is configured such that the target electrode extends in the substrate direction more than the surface facing the plasma flow path, so that the plasma and the target direction toward the substrate direction The plasma flow rate toward the substrate is changed, the amount of plasma toward the target is reduced, and the amount of plasma toward the substrate is increased.

  This shield relatively reduces the amount of oxygen active species toward the target, but ions are attracted by the negative bias potential applied to the target in the plasma that sputters the target. A sufficient amount of target particles in the metal element state can be released to perform metal mode film formation.

  On the other hand, since the oxygen active species in the plasma are in an electrically neutral state, they are guided toward the substrate along the shield without being attracted by the negative bias potential of the target.

  The shield is disposed at a predetermined distance from the target electrode, and is insulated or grounded. The distance between the shield and the target electrode can be set to a distance at which arc discharge does not occur. By suppressing the arc discharge between the shield and the target electrode, the generation of fine particles released by the arc discharge can be suppressed, and damage to the target electrode can be prevented.

  In one embodiment of the present invention, the target electrode has a trapezoidal cross-sectional shape having an inner diameter surface on the plasma flow path side, an outer diameter surface larger than the diameter of the inner diameter surface, and an inclined surface that faces the substrate. The shield surrounds the periphery of the target electrode excluding the inclined surface, and the surface facing the inner diameter surface of the target electrode extends in the substrate direction from the inner diameter surface of the target electrode facing the surface. The configuration.

  In another embodiment of the present invention, the target electrode is an annular electrode having a rectangular cross-sectional shape having an inner diameter surface on the plasma flow path side and a plane that faces the substrate, and the shield is the target electrode excluding this plane. The surface surrounding the periphery and facing the inner diameter surface of the target electrode is configured to extend in the substrate direction from the inner diameter surface of the target electrode facing the surface. Further, the inner diameter of the shield electrode can be the same in the direction of the plasma flow path.

  Each form of the present invention is such that the surface of the shield facing the plasma extends in the substrate direction from the inner diameter surface of the target electrode, thereby reducing the amount of plasma toward the target direction and toward the substrate direction. Increase the amount of plasma.

  In addition, according to the embodiment of the present invention, even when the oxygen flow rate is increased, the target surface is not rapidly oxidized because the shield suppresses an increase in the amount of oxygen active species toward the target surface. Metal target particles are released, and an oxide film can be obtained in the metal mode region where the film formation rate is high on the substrate surface.

  According to the present invention, a plasma generated by ECR plasma in a plasma generation chamber is introduced into a reaction chamber, and a substrate is formed by sputtered particles generated by sputtering of a target by ions in the plasma and oxygen active species (radicals) in the plasma. In an ECR plasma film forming apparatus for forming a film, metal mode film formation in which a metal element is released from a target in a metal state to form a film can be stabilized.

  More specifically, the oxidation of the target due to oxygen active species (radicals) is reduced, and the transition from metal mode film formation to oxide mode film formation is suppressed. Metal elements can be released as target particles, and oxidation of the target particles on the substrate surface can be promoted.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram for explaining a configuration example of an ECR sputtering apparatus of the present invention.

  The ECR sputtering apparatus 1 includes a plasma generation chamber 2 for generating ECR plasma and a reaction chamber 3 in which a substrate 12 that is a film formation target is accommodated. The plasma generation chamber 2 and the reaction chamber 3 communicate with each other through a plasma extraction opening 2a, and the reaction chamber 3 is evacuated from an exhaust port 6 by a vacuum pump (not shown).

  The plasma generation chamber 2 is provided with a microwave introduction hole 4, a gas introduction port 7, and an air core magnetic field coil 5. The microwave generated by the high-frequency power supply 8 is impedance-matched by an oscillator and an EH tuner 9, guided through the microwave waveguide 10, and plasma through a microwave introduction window (not shown) of the microwave introduction hole 4. It is introduced into the generation chamber 2.

  The plasma generation chamber 2 is configured to function as a cavity resonator with respect to a microwave of 2.45 GHz. A magnetic field of 87.5 (mT) is generated by the magnetic field coil 5, and a microwave with a frequency of 2.45 GHz is introduced from the microwave introduction window.

  Gas is supplied to the gas inlet 7 of the plasma generation chamber 2 through the gas lines L1 and L2. The gas line L1 supplies argon gas, and the gas line L2 supplies oxygen gas. The gas line L1 is provided with a valve B1, and the supply of argon gas is controlled by opening and closing the valve B1. The gas line L2 is provided with a valve B2, and the supply of oxygen gas is controlled by opening and closing the valve B2. The mass flow controller M1 and the mass flow controller M2 control the flow rates of argon gas and oxygen gas.

  On the other hand, in the reaction chamber 3, a target electrode 13, a shield 20 that surrounds the surface excluding a part of the surface of the target electrode 13, and a substrate support portion 11 that holds the substrate 12 are provided. The target electrode 13 is, for example, an annular electrode having a trapezoidal cross-sectional shape having an inner diameter surface on the plasma flow path side, an outer diameter surface larger than the inner diameter surface, and an inclined surface on the surface facing the substrate. In addition to the cone shape with a through-hole formed in the central part, the cross-sectional shape having an inner diameter surface on the plasma flow path side and a plane facing the substrate is a rectangular annular electrode, and the through-hole is formed in the central part. The formed disk shape can be used.

  The through-hole formed in the center portion of the target electrode 13 is disposed between the plasma extraction opening 2a of the plasma generation chamber and the substrate 12, and the plasma from the plasma extraction opening 2a flows to form a flow path.

  As the material of the target electrode 13, for example, aluminum is used. The target electrode 13 can be connected to a DC power source 14 and a DC pulse voltage can be applied to the target electrode 13. In this case, for example, a voltage of −200 to −800 V is applied to the target electrode 13 so that the potential of the electrode becomes a negative potential with respect to the plasma. Instead of the DC pulse voltage, a high frequency voltage may be applied to the target electrode 13 using a high frequency power source in which the positive electrode side is grounded and the negative electrode side is connected to the target electrode 13.

  The substrate support unit 11 may be provided with a drive mechanism that rotates the substrate 12. In addition, a high frequency power supply 15 is connected to the substrate support unit 11 and a high frequency voltage is applied so that the potential of the substrate support unit 11 is a negative potential with respect to plasma. If arcing does not occur, a DC power source may be used instead of the high frequency power source.

  In the plasma processing, the reaction chamber 3 and the plasma generation chamber 2 are depressurized to a predetermined pressure by an evacuation apparatus (not shown), a direct current is supplied to the magnetic field coil 5 to generate a magnetic field of 87.5 mT in the plasma generation chamber 2. Then, a reactive gas is introduced into the reaction chamber 3 and the plasma generation chamber 2 from the gas inlet 7, oscillated by the high frequency power source 8, and impedance-matched by the oscillator and the EH tuner 9. The gas is introduced into the plasma generation chamber 2 from the window of the introduction hole 4.

  The reactive gas generates a high-density plasma by electron cyclotron resonance by setting the microwave electric field and the magnetic field of the magnetic field coil 5 to 875 Gauss, and separates them into positive ions and electrons.

  In the plasma generation chamber 2, argon gas is ionized by ECR, and high-density plasma is generated. When oxygen gas is further supplied to the plasma generation chamber 2, the oxygen gas is activated by ECR and oxygen active species (radicals) are generated. In the plasma, there are electrons, argon ions, excited argon, argon atoms, oxygen active species, and oxygen atoms.

  In the plasma, electrons having high mobility move into the reaction chamber 3 from the extraction opening 2 a along the magnetic field lines of the divergent magnetic field formed by the magnetic field coil 5. Since the electrons are lightweight, they move at a high speed, get out of the plasma in a short time, collide with the walls and disappear. On the other hand, positive ions have a large mass and a low speed compared to electrons, and therefore exist in plasma for a long time. Thereby, the plasma becomes a positive charge as a whole and forms an ion sheath. The substrate support 11 that supports the substrate 12 is attracted by the positive charge of the ion sheath, accumulates negative charges, and generates a negative self-bias voltage.

  As a result, the space in which the electrons in the reaction chamber 3 exist has a negative potential when viewed from the plasma in the plasma generation chamber 2, so that the argon ions in the plasma move along the magnetic field lines of the diverging magnetic field of the magnetic field coil 5. Move to. Further, oxygen active species (radicals) move to the reaction chamber 3 by diffusion. In this way, plasma is drawn out into the reaction chamber 3.

  When a voltage is applied to the target electrode 13 so as to have a negative potential, the argon ions are accelerated in the direction of the target electrode 13 by the electric field generated by the target voltage, and enter the surface of the target electrode 13. When accelerated argon ions are incident on the target electrode 13, sputtered aluminum particles are released from the target electrode 13 toward the substrate 12 due to a sputtering phenomenon.

  On the substrate 12, there are non-oxidized metal particles of aluminum released from the target electrode 13 and oxygen active species (radicals) in the plasma, which react to form a metal mode film. An aluminum thin film is formed on the surface of the substrate 12.

  The shield 20 surrounds the periphery of the target electrode 13 except for the surface where the target electrode 13 faces the substrate 12, and is disposed with a predetermined distance between the target electrode 13.

  FIG. 2 shows a configuration example of the shield 20.

  In FIG. 2, the target electrode 13 has a cross-sectional shape having an inner diameter surface 13 a on the plasma flow path side, an outer diameter surface 13 b larger than the diameter of the inner diameter surface 13 a, and an inclined surface 13 c facing the substrate 12. It is a trapezoidal annular electrode. On the other hand, the shield 20 surrounds the periphery of the target electrode 13 excluding the inclined surface 13c, and the inner diameter surface 20a facing the inner diameter surface 13a of the target electrode 13 is larger than the inner diameter surface 13a of the target electrode 13 facing the inner diameter surface 20a. Is also formed extending in the direction of the substrate. The extended length of the inner diameter surface 20a is such that the total length D is at least longer than the length d of the inner diameter surface 13a of the target electrode 13, for example, an intermediate length between the inner diameter surface 13a and the outer diameter surface 13b. Make it long.

  The extending length of the inner diameter surface 20a can be determined according to the formation of the target electrode 13, the diameter of the channel through which the plasma flows, the speed at which the plasma moves, and the like. The inner diameter of the inner diameter surface 13a can be the same along the plasma flow path.

FIG. 3 is a view for explaining the action of the shield 20, particularly the action of the extending surface. FIG. 3A shows the case of a shield having an extending surface, and FIG. 3B shows the case of a shield having no extending surface. Note that FIG. 3 shows a case where argon ions (Ar ⁺ ) and oxygen radicals (O ^* ) as oxygen active species are contained in the plasma from the plasma generation chamber toward the substrate 12. Here, “ ^* ” indicates an active species.

In FIG. 3A, argon ions (Ar ⁺ ) in the plasma are attracted to the target electrode 13 applied to a negative potential by the DC power source 14 while moving in the direction of the substrate 12. At this time, since the target electrode 13 is surrounded by the shield 20 except for the inclined surface 13c, and the shield 20 is insulated or grounded, argon ions (Ar ⁺ ) enter only the inclined surface 13c. Argon ions (Ar ⁺ ) are incident on the inclined surface 13c of the target electrode 13, and the inclined surface 13c is sputtered to release metal atoms of the target.

On the other hand, oxygen radicals (O ^* ) in the plasma are guided by the inner diameter surface 20 a of the shield 20 facing the inner diameter surface 13 a of the target electrode 13 and move in the direction of the substrate 12. Since the oxygen radical (O ^* ) is electrically neutral, it moves in the direction of the substrate 12 without being attracted by the target electrode 13. At this time, the inner diameter surface 20a of the shield 20 is guided toward the substrate 12 by the portion extending in the direction of the substrate 12 without diffusing oxygen radicals (O ^* ) toward the target electrode 13 side.

This changes the flow ratio of oxygen radicals (O ^* ) flowing in the direction of the target electrode and the substrate, relatively reduces the oxygen radicals (O ^* ) that reach the surface of the target electrode 13, and the surface of the substrate 12 The oxygen radical (O ^* ) that reaches

Since the arrival amount of oxygen radicals (O ^* ) relatively decreases on the surface of the target electrode 13, even if the oxygen flow rate is increased, the target electrode due to oxygen radicals (O ^* ) is rapidly oxidized. This prevents the target particles released from the surface of the target electrode from remaining in a metal state and an oxide state.

Further, since the amount of oxygen radicals (O ^* ) that reach the surface of the substrate 12 relatively increases, the concentration of oxygen radicals (O ^* ) increases, and the target particles released from the target electrode 13 are completely discharged in the metal mode region. The film can be formed by oxidation.

On the other hand, in FIG. 3B, argon ions (Ar ⁺ ) in the plasma are attracted to the target electrode 13 applied to a negative potential by the DC power source 14 while moving in the direction of the substrate 12. Attraction operation of the argon ions (Ar ^+), and release operation of the target particles by sputtering argon ions (Ar ⁺⁾ is the same as the case of FIG. 3 (a).

On the other hand, oxygen radicals (O ^* ) in the plasma diffuse after passing through the inner diameter surface 20 a ′ of the shield 20 facing the inner diameter surface 13 a of the target electrode 13. At this time, when the inner diameter surface 20 a ′ of the shield 20 is long enough to face the inner diameter surface 13 a of the target electrode 13, oxygen radicals (O ^* ) pass through the inner diameter surface 20 a ′ of the shield 20. In addition to moving in the direction of the substrate 12, it also diffuses in the direction of the inclined surface 13 c of the target electrode 13. Therefore, the diffused plasma flows into the inclined surface 13 c of the target electrode 13, and oxygen radicals (O ^* ) that reach the surface of the target electrode 13 relatively increase, and oxygen radicals that reach the surface of the substrate 12. (O ^* ) decreases.

Since the arrival amount of oxygen radicals (O ^* ) relatively increases on the surface of the target electrode 13, if the oxygen flow rate is increased, the target electrode is rapidly oxidized by the oxygen radicals (O ^* ), and the target On the electrode surface, the metal mode region shifts to the oxide mode region, and the target particles emitted from the inclined surface 13c of the target electrode 13 become oxide.

In addition, since the amount of oxygen radicals (O ^* ) that reach the surface of the substrate 12 relatively decreases, the concentration of oxygen radicals (O ^* ) decreases, and the target particles emitted from the target electrode 13 are reduced in the metal mode region. It becomes difficult to form a film by complete oxidation.

  FIG. 4 shows another configuration example of the shield 20. This configuration example is an example of a shield corresponding to a flat target electrode.

  In FIG. 4, the target electrode 13 is an annular electrode having a substantially rectangular cross section having an inner diameter surface 13a on the plasma flow path side and a flat surface 13d facing the substrate 12, and the example shown in FIG. 4B is an arrangement example in which the plane 13d of the target electrode 13 is installed in parallel with the substrate 12, and the example shown in FIG. 4B is an arrangement example in which the plane 13d of the target electrode 13 is installed obliquely with respect to the substrate 12. It is.

  The shield 20 surrounds the periphery of the target electrode 13 excluding the flat surface 13d, and the inner diameter surface 20a facing the inner diameter surface 13a of the target electrode 13 is more in the substrate direction than the inner diameter surface 13a of the target electrode 13 facing the inner diameter surface 20a. It is formed to extend. The length D of the extended length of the inner diameter surface 20 a is longer than at least the length d of the inner diameter surface 13 a of the target electrode 13. Moreover, when arrange | positioning the target electrode 13 inclining, it is made longer than the intermediate length of the internal diameter surface 13a and the outer diameter surface 13b, for example.

  The extending length of the inner diameter surface 20a can be determined according to the formation of the target electrode 13, the diameter of the flow path through which the plasma flows, the speed at which the plasma moves, and the like. The inner diameter of the inner diameter surface 13a can be the same along the plasma flow path.

FIG. 5 is a diagram for explaining the effect of the shield structure of the present invention. In FIG. 5, the horizontal axis indicates the flow rate of oxygen introduced into the plasma generation chamber, and the oxygen flow rate sccm indicates the flow rate cc (cm ³ ) / min expressed per minute normalized at a constant temperature. The vertical axis represents the film formation rate (Å / sec) and the film formation absorption coefficient k.

  In FIG. 5, when the oxygen flow rate is small, the film is formed in the metal mode region, and shows a high film formation rate indicated by C in FIG. On the other hand, when the oxygen flow rate is increased, film formation is performed from the metal mode region to the oxide mode region, and the film formation rate is lowered as indicated by D in FIG. Further, the absorption coefficient k for evaluating the optical characteristics of film formation decreases as the oxygen flow rate increases.

  Therefore, in order to reduce the absorption coefficient k of the oxide thin film formed on the substrate and realize a high film formation rate, it is necessary to increase the oxygen flow rate in the metal mode region indicated by C in the figure. However, when the oxygen flow rate is increased, the film formation rate is lowered by shifting from the metal mode region to the oxide region. Therefore, it is desirable that the oxygen flow rate be as high as possible when shifting from the metal mode region to the oxide region.

  Comparing the characteristics of A and B, according to the characteristic B that shifts from the metal mode region to the oxide region at a large oxygen flow rate, both a high film formation rate and an absorption coefficient k can be satisfied.

  The broken line A in FIG. 5 indicates the oxygen flow rate in the configuration in which the length of the inner surface 20a of the shield 20 is substantially the same as the length of the inner surface 13a of the target electrode 13, as shown in the configuration of FIG. It shows the change in the film formation rate when increasing. 5 indicates that the inner diameter surface 20a of the shield 20 is set to be longer than the inner diameter surface 13a of the target electrode 13, as shown in the configuration of FIG. In the configuration in which 20a is extended to the substrate side, the change in the deposition rate when the oxygen flow rate is increased is shown.

  Therefore, by having a configuration in which the inner diameter surface 20a of the shield 20 is extended to the substrate side, characteristics satisfying both a high film formation rate and a low absorption coefficient k can be obtained.

Next, FIG. 6 shows a film formation example according to the present invention. Here, the film forming conditions are as follows.
Film-forming material: Al ₂ O ₃
Target: High-purity aluminum Introduced gas: Ar, O ₂
Deposition pressure: 0.1-0.3 Pascal microwave power: 500-1000 W
Target bias power: 100-200W

  In FIG. 6, the horizontal axis represents the oxygen flow rate sccm introduced into the plasma generation chamber, and the vertical axis represents the film formation rate (レ ー ト / sec), the film formation absorption coefficient k, and the refractive index n.

  As shown in the configuration of FIG. 3B, when the length of the inner diameter surface 20a of the shield 20 is substantially the same as the length of the inner diameter surface 13a of the target electrode 13, it is indicated by E in FIG. While the film formation rate decreases from the metal mode region to the oxide region around the oxygen flow rate, it extends from the metal mode region to the oxide by extending to the substrate side as in the shield configuration of the present invention. The flow rate of oxygen transferred to the region can be increased, and the film formation absorption coefficient k can be lowered.

It is the schematic for demonstrating the structural example of the ECR sputtering apparatus of this invention. It is a figure which shows the structural example of the shield of this invention. It is a figure for demonstrating the effect | action by the shield of this invention. It is a figure which shows another structural example of the shield of this invention. It is a figure for demonstrating the effect by the shield structure of this invention. It is a figure which shows the relationship between the oxygen flow rate and the film-forming rate of the film-forming example by this invention. It is a figure which shows schematic structure of the conventional ECR sputtering film-forming apparatus. It is a figure which shows schematic structure of the ECR sputtering film-forming apparatus provided with the conventional shielding ring.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... ECR sputtering device, 2 ... Plasma generation chamber, 2a ... Plasma extraction opening, 3 ... Reaction chamber, 4 ... Microwave introduction hole, 5 ... Magnetic coil, 6 ... Exhaust port, 7 ... Gas introduction port, 8 ... High frequency power supply 9 ... Transmitter and EH tuner, 10 ... Waveguide, 11 ... Substrate support, 12 ... Substrate, 13 ... Target electrode, 13a ... Inner diameter surface, 13b ... Outer diameter surface, 13c ... Inclined surface, 13d ... Flat surface, DESCRIPTION OF SYMBOLS 14 ... Bias power supply, 15 ... High frequency power supply, 20 ... Shield, 20a, 20a '... Inner diameter surface, 101 ... Sputter film-forming apparatus, 102 ... Plasma production chamber, 103 ... Reaction chamber, 104 ... Microwave introduction hole, 105 ... Magnetic field Coil, 106 ... exhaust port, 107 ... gas inlet port, 111 ... substrate support, 112 ... substrate, 113 ... target, 200 ... shielding ring, B1 ... valve, B2 ... valve, L1, L2 ... Surain, M1, M2 ... mass flow controller, k ... absorption coefficient, n ... refractive index.

Claims (4)

Plasma generated by ECR plasma in the plasma generation chamber is introduced into the reaction chamber, a target is sputtered by ions in the plasma to generate sputtered particles, and a substrate is formed by the sputtered particles and oxygen active species in the plasma. In the ECR plasma film forming apparatus, in the reaction chamber,
A target electrode disposed along a flow path through which the plasma flows toward the substrate;
The target electrode surrounds the periphery of the target electrode excluding the surface facing the substrate, and includes a shield disposed with a predetermined distance between the target electrode and the target electrode,
An ECR sputtering apparatus, wherein the surface of the shield facing the plasma flow path extends in the substrate direction than the surface of the target electrode facing the plasma flow path. The target electrode is an annular electrode having a trapezoidal cross section having an inner diameter surface on the plasma flow path side, an outer diameter surface larger than the diameter of the inner diameter surface, and an inclined surface on the surface facing the substrate. Yes,
The shield surrounds the periphery of the target electrode excluding the inclined surface, and the surface facing the inner diameter surface of the target electrode extends in the substrate direction from the inner diameter surface of the target electrode facing the surface. The ECR sputtering apparatus according to claim 1. The target electrode is an annular electrode having a substantially rectangular cross-sectional shape having an inner diameter surface on the plasma flow path side and a plane facing the substrate,
The shield surrounds the periphery of the target electrode excluding the plane, and the surface facing the inner diameter surface of the target electrode extends in the substrate direction from the inner diameter surface of the target electrode facing the surface. The ECR sputtering apparatus according to claim 1.   4. The ECR sputtering apparatus according to claim 1, wherein a diameter of an inner diameter surface of the shield electrode is the same along a flow direction of the plasma. 5.

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