JP2005171328A - Plasma film deposition system, and film deposition method using the system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma film deposition system and a method therefor wherein a thin film is deposited on a substrate with a large area at high uniformity, and to provide a method wherein a metallic compound is stably deposited in a metal mode. <P>SOLUTION: The plasma film deposition system comprises: a sample stand for installing at least a sample substrate inside a vessel holdable to a reduced pressure; a target having a through hole and arranged with a fixed interval from the sample stand or one or more sets of targets arranged so as to be confronted each other; and a mechanism for controlling the distribution of particles flying from the target to the sample substrate. In the method, a thin film is deposited on the sample substrate using the system. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a plasma film forming apparatus for forming thin films of various materials on a sample substrate for the purpose of manufacturing electronic devices such as semiconductor integrated circuits and display devices, and a film forming method using the apparatus. In particular, the present invention relates to a plasma film forming apparatus and a film forming method for forming a high-quality metal or metal compound thin film at a low temperature.

  A method of forming a thin film by applying a voltage to a target facing in a decompression vessel and depositing target particles ejected by sputtering on a sample substrate placed in the vicinity is, for example, NFTS (New Faceting Targets Sputtering, a new counter target. It is known as a technique such as a sputtering method.

  Further, a so-called solid source electron cyclotron resonance (ECR) plasma film forming method is known, and this method has already been patented (Patent Documents 1 and 2). This method uses plasma generated by ECR, and applies a voltage to a target arranged around the plasma to accelerate and cause ions contained in the plasma to be incident on the target, thereby causing a sputtering phenomenon and emission. This is a technique for forming a thin film by depositing the target particles on a sample substrate placed nearby.

  In this type of conventional apparatus, the film thickness of the thin film adhering to the sample substrate is distributed, and it is difficult to form a film uniformly over the entire surface of the sample substrate.

  As one of means for reducing such a film thickness distribution and uniformly forming a film, there is a so-called tilt rotation film forming method in which a substrate is inclined with respect to a target and then rotated (Patent Document 3). This method is extremely effective in improving uniformity, and even within a large area substrate having a diameter of 30 cm, it is possible to sufficiently ensure uniformity within ± 5%. However, there are drawbacks such as the fact that the mechanism is complicated and the cost of the apparatus is increased due to the inclined arrangement and rotation in vacuum.

Another problem with conventional devices is that it may be difficult to ensure stability when a metal compound thin film is formed reactively. A major feature of the solid source 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. The 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.

Japanese Patent No. 1553959 Japanese Patent No. 1462543 Japanese Patent No. 3208439

As described above, in a conventional apparatus, it is necessary to use a mechanism having a complicated structure in order to uniformly form a film on a substrate, and an easy and highly uniform film forming method has been desired. In addition, there has been a demand for an apparatus that stably forms a thin film such as TiO ₂ in a metal mode.

  A first object of the present invention is to provide an apparatus and method for forming a thin film with high uniformity on a large-area substrate in a plasma deposition apparatus. A second object is to provide a method for stably depositing a metal compound in a metal mode.

  The first of the present invention relates to an improved plasma film forming apparatus. The plasma apparatus of the present invention includes at least a sample stage for placing a sample substrate in a container that can be maintained at a reduced pressure, and a target having a through groove disposed at a certain interval from the sample stage, or one or more sets. A target disposed opposite to each other, and a mechanism for controlling the distribution of particles flying from the target to the sample substrate.

  In one embodiment of the present invention, the mechanism for controlling the distribution of particles flying to the sample substrate is a shielding plate provided at an arbitrary position between the sample substrate and the target. In another embodiment of the present invention, the mechanism for controlling the distribution of particles flying to the sample substrate is a target having an inclination on the inner surface of the through groove or the opposite surface of the target, and this inclination is the inner surface of the through groove. Alternatively, it is characterized in that the opposing surface is inclined so as to separate from the side close to the sample substrate toward the side farthest from the sample substrate.

  A more detailed embodiment of the apparatus of the present invention should form a plasma generation chamber configured to generate a plasma under reduced pressure using an electron cyclotron resonance discharge by the interaction of a microwave and a magnetic field, and a thin film. A sample chamber provided with a sample stage for installing a sample substrate; a plasma extraction window disposed between the plasma generation chamber and the sample chamber for extracting the plasma flow into the sample chamber; and the plasma generation chamber A magnetic field generating means having a magnetic field distribution of a divergent magnetic field whose magnetic field strength is weakened with a predetermined gradient from the sample chamber toward the sample chamber, and a sputtering material including a target, the target being between the plasma extraction window and the sample stage Are arranged so as to surround the plasma flow, the target is sputtered by some ions of the plasma flow, and sputtered particles The present invention relates to a plasma deposition apparatus that takes in the plasma flow, transports it to the sample substrate and makes it incident, and forms a thin film containing the sputtering material on the sample substrate. It has a mechanism for controlling.

  Another feature of the shielding plate of the present invention is that it has a structure that suppresses gas conductance between the sample stage side and the target side.

  The second of the present invention relates to a film forming method using a plasma film forming apparatus. In this method, a voltage is applied to a target arranged around the plasma generated by electron cyclotron resonance, thereby causing ions contained in the plasma to be accelerated and incident on the target, thereby causing a sputtering phenomenon and emitting the target. This is a film forming method for forming a thin film by attaching particles onto a sample substrate arranged in the vicinity, and is characterized in that the film is formed through a mechanism for controlling the particle distribution of flying target particles. Furthermore, the film forming method of the present invention can form a film in a mixed gas atmosphere of an inert gas and a reactive gas. The mechanism for controlling the distribution of particles flying on the sample substrate is preferably a shielding plate provided at an arbitrary position between the sample substrate and the target. Furthermore, it is preferable that the shielding plate has a structure for suppressing gas conductance between the sample stage side and the target side.

  In the apparatus and film forming method of the present invention, a large film thickness distribution can be suppressed and highly uniform film formation can be realized. In addition, the deposition rate of the thin film on the substrate can be lowered without lowering the sputtering rate of atoms on the target surface, and the metal mode margin during compound thin film deposition can be improved.

  Furthermore, the metal mode margin can be further increased by devising the structure of the shielding plate according to an embodiment of the present invention so as to reduce the gas conductance between the vicinity of the target and the sample chamber.

The first of the present invention is an improved solid source ECR plasma deposition apparatus. The present invention will be described below with reference to the drawings.
FIG. 1 shows a schematic structure of a solid source ECR plasma film forming apparatus. In the figure, the plasma generation chamber 1 and the sample chamber 2 are sealed spaces that are isolated from the atmosphere, and are connected via a plasma extraction window 3. In order to form a thin film on the sample substrate 5 placed on the sample stage 4, first, the plasma generation chamber 1 and the sample chamber 2 are evacuated by a vacuum pump through the exhaust path 6, and then the gas introduction port (A) 7. Alternatively, gas is introduced from (B) 8 and maintained at a predetermined pressure. Next, a current is passed through the two magnetic coils 9 placed around the plasma generation chamber 1 to generate a magnetic field, and then the microwave 11 guided to the rectangular waveguide 10 is introduced into the lower part of the plasma generation chamber. It introduces to the vacuum side through the window 12. As a result, electron cyclotron resonance occurs in the plasma generation chamber 1, and ECR plasma is generated. The plasma generated in the plasma generation chamber 1 flows as a plasma flow 13 from the plasma extraction window 3 to the sample substrate 5 along the divergent magnetic field. When the sputtering power supply 14 is turned on and a voltage is applied to the target 15 in this state, ions in the ECR plasma are accelerated toward the target 15 and target constituent atoms are released into the vacuum by the ion bombardment. The particles that have jumped out of the target 15 travel in all directions and form a thin film on the sample substrate 5.

  In the apparatus of FIG. 1, the particles sputtered from the target are generally emitted according to the cosine law such that the component in the direction perpendicular to the target surface is the largest. For example, even in a cylindrical target, only the particles emitted from the entire target surface toward the sample substrate placed in the sample chamber contribute to the film formation. For this reason, in a normal arrangement relationship, the sample substrate has a concentric film thickness distribution in which the center of the sample substrate is thick and the periphery is thin. For example, when a film is formed using a target having an inner diameter of 100 mm and a height of 40 mm, the thickness of the thin film formed on the substrate is nearly 10% thinner than the center at a position 5 cm away from the center.

  As described above, in the solid source ECR plasma film forming apparatus, it is difficult to form a film uniformly on the sample substrate. The first feature of the present invention is that this problem of the apparatus shown in FIG. 1 is improved.

  In the present invention, the target is preferably a target having a through groove or a pair of targets arranged to face each other. Specific examples thereof include a cylindrical target having a cylindrical or prismatic through groove, or at least one pair of targets arranged to face each other. In the case of a target having a cylindrical or prismatic through groove, the through groove of the target faces a direction perpendicular to the sample substrate, and sputtered particles are emitted from the surface of the through groove. Further, in the case of a target arranged oppositely, the opposing surface is perpendicular to the sample substrate, and sputtered particles are emitted from this opposing surface.

  Any solid material can be used as the target material. Typical examples are silicon, aluminum, beryllium, magnesium, titanium, zirconium, hafnium, carbon, vanadium, tantalum, chromium, molybdenum, tungsten, niobium, cobalt, nickel, In addition to zinc, compounds such as STO and PZT are also used.

  The size of the target may be appropriately selected depending on the target material, film forming conditions, and the like. For example, in the case of a cylindrical target, a target having an inner diameter of 50 mm to 500 mm and a height of 10 mm to 100 mm can be used.

  In the present invention, a reactive gas such as oxygen, nitrogen, or fluorine can be used in combination with an inert gas such as argon or xenon when forming a film. If such a mixed gas is used, even if the target is a single metal, it is possible to form thin films of various compounds in addition to oxides and nitrides such as silicon oxide, silicon nitride, and alumina. There is an effect of the invention. In the present invention, the mixing ratio of the inert gas and the reactive gas such as oxygen, nitrogen or fluorine is variable in the range of 0% to 100%.

  The present invention is characterized in that it has a mechanism for controlling the distribution of particles flying on the sample substrate by suppressing the passage of sputtered particles between the target and the sample substrate. The first aspect of this mechanism is a shielding plate provided at an arbitrary position between the sample substrate and the target. The shielding plate is preferably ring-shaped with respect to the cylindrical target. In order to increase the metal mode margin during sputtering, it is also preferable to devise the structure of the shielding plate so as to reduce the gas conductance between the vicinity of the target and the sample chamber. Such a contrivance is to make the shielding plate into a ring shape and to ensure a sufficient sealing property between the outer periphery of the ring and its mounting periphery.

  When the shielding plate is ring-shaped, its inner diameter varies depending on the film forming conditions, but can be, for example, 50% to 90% of the inner diameter of the target. For the shielding plate, any metal such as SUS, titanium, and aluminum, an insulator such as quartz and alumina, and a semiconductor such as silicon can be used.

  The second aspect of the mechanism for controlling the distribution of particles flying on the sample substrate is an inclined structure provided on the surface of the through groove of the target or the opposing surface of the opposing target. The inclined structure of the present invention is preferably inclined so that the surface of the through groove or the opposing surface of the opposing target spreads from the side closer to the substrate toward the side farther from the substrate. The inclination angle is preferably 5 ° to 15 °.

  A second aspect of the present invention is a film forming method using the above apparatus. In the method of the present invention, a voltage is applied to a target arranged around a plasma generated by electron cyclotron resonance, thereby causing ions contained in the plasma to be accelerated and incident on the target, thereby causing a sputtering phenomenon and emission. In a film forming method for forming a thin film by attaching the target particles to a sample substrate arranged in the vicinity, the film is formed through a mechanism for controlling the particle distribution of the flying target particles.

  In the method of the present invention, an inert gas alone or a mixed gas of an inert gas and a reactive gas such as oxygen, nitrogen or fluorine can be used. When a mixed gas is used, the mixing ratio of the gas is variable in the range of 0% to 100%.

  In the film forming method of the present invention, the target is as described in the first invention. The first aspect of the mechanism for controlling the particle distribution of the target particles is a shielding plate. In particular, when the target has a cylindrical shape, the shielding plate is preferably ring-shaped. In such a cylindrical target, it is desirable that the shielding plate has a ring shape and has a structure that ensures sufficient sealing between the outer periphery of the ring and the periphery of the ring. The material, inner diameter, and the like when the shielding plate is a ring are as described in the first invention. Moreover, the 2nd aspect of this means is the inclination structure provided in the target. The inclined structure is as described in the first invention.

  By forming a film using a mechanism for controlling the particle distribution of these target particles, a thin film can be uniformly formed on the sample substrate. Further, by reducing the gas conductance between the vicinity of the target and the space where the sample substrate exists, even if a mixed gas is used, oxidation of the target surface can be suppressed and the metal mode margin can be increased.

Hereinafter, the present invention will be described in more detail with reference to examples.
(Example 1)
FIG. 2 shows an embodiment in which the thickness distribution formed on the sample substrate is made uniform by installing a shielding plate between the cylindrical target and the sample substrate. The target 15 shown in the figure has a cylindrical shape with an inner diameter of 100 mm and a height of 40 mm, and the upper and lower surfaces thereof are covered with a metal shield 16 that is electrically vacuum-insulated from the target. In addition, the outer peripheral surface of the target has a structure that is water-cooled through a metal back plate called a backing tube 17. For this reason, the region where the target atoms are sputtered out is only the inner peripheral surface of the target. The sample substrate is placed approximately 200 mm away from the upper end of the target with the center position coincident with the center of the cylindrical target. In such an arrangement-related apparatus, a ring-shaped shielding plate 18 having various inner diameters D was installed at a distance of 12 mm from the upper end of the target. The target is electrically insulated from the surroundings, and after generating ECR plasma, by applying RF power to the target, the target element is sputtered out.

  FIG. 3 shows the result of simulating the film thickness distribution of the thin film formed on the sample substrate in such an arrangement.

  Here, it is assumed that the density distribution of particles popping out from the target surface is proportional to cos θ, where θ is the angle formed with the perpendicular to the target surface. In the simulation, particles that reach the substrate surface after being emitted from one point on the target surface are integrated over the entire surface of the target. In addition, the scattering effect due to gas collision in the gas phase is also considered. As is apparent from the figure, when the inner diameter D of the shielding ring is set to 100 mm, which is the same as the target inner diameter, that is, a large film thickness distribution is seen when the shield is not shielded. Reduced and uniformity is improved. When the inner diameter D of the shielding ring is 86 mm, a substantially flat distribution is obtained. If the ring diameter is made smaller than that, the film thickness at the center becomes thin, resulting in a concave distribution.

  The mechanism by which the uniformity of the film thickness is improved by inserting the shielding ring can be explained using a simple model shown in FIG. For simplicity, paying attention to the sputtering phenomenon at the center of the target, the particles popping out from this point travel in all directions, but most of them are perpendicular to the target surface, and the other angular components follow the cosine law. Get smaller. The particles shown by solid line arrows in FIG. 2 are components that adhere to the periphery of the sample substrate after a certain amount of collision in the gas phase, while most of the particles traveling in the direction of the broken line arrows adhere to the center of the sample substrate. To do. When the shielding ring is inserted, the broken line component is blocked by the shielding ring and cannot reach the sample substrate, as is apparent from the figure. Such a phenomenon occurs in the same manner with respect to particles protruding from the entire surface of the target, so that a thin film is formed on the sample substrate with a film thickness distribution as if all of these were collected. By inserting the shielding ring, on average, the effect of cutting the amount of adhesion at the central portion of the sample substrate is obtained, and the uniformity is improved.

  FIG. 4 shows the result of simulating the film thickness distribution when the distance from the upper end of the target is varied between 0 and 32 mm while the inner diameter D of the shielding ring is fixed at 80 mm. Even if the inner diameter is the same, the effect of homogenization is strengthened by reducing the distance, but the film formation rate is significantly reduced accordingly. In the case of an inner diameter of 80 mm, the positions separated by about 20 mm are the most uniform.

FIG. 5 shows the result of actually forming the SiO ₂ film using the Si target. As conditions for the film formation, a gas flow rate (gas: argon) was set to 20 SCCM under a pressure of about 0.1 Pa, and 500 W was used for both microwave power and RF power. The distance H between the shielding ring (material: SUS) and the target was fixed at 12 mm, and the ring diameter D was variable. The conventional structure without a shield ring has a film thickness distribution of ± 4.61% within a plane of ± 30 mm from the center of the substrate, but is improved to ± 1.39% by using a shield ring with an inner diameter of 80 mm. ing. FIG. 6 shows the result of depositing Al ₂ O ₃ using an Al target (deposition conditions are the same as above). Similar to the SiO ₂ film, it is confirmed that the film thickness distribution is improved from ± 5.75% of the conventional structure to ± 1.26%. Although there is a slight difference between the film thickness distribution obtained in the experiment and the simulation result, the tendency that the center becomes concave as the ring diameter is reduced is consistent. One possible reason for the difference from the simulation is that the entire surface of the target is not oxidized in metal mode film formation, and only a certain region is oxidized. In addition, particles emitted from the target are generally proportional to cos ⁿ θ, the value of n varies depending on the crystal structure and surface state of the target, and the scattering effect in the gas phase depends on the gas pressure. There may be a simulation problem. About these, it is possible to improve the precision of simulation further by combining parameters.

  As can be seen from the results shown above, the film thickness distribution on the sample substrate can be made uniform by changing the inner diameter D of the shielding ring and the distance H from the target. However, the optimum uniform condition varies depending on various film forming conditions such as the target material, gas type, gas pressure, microwave power, and RF power. Further, when the film formation is continued, the target material is consumed and the inner diameter is increased, and the required inner diameter of the ring is slightly changed. In order to cope with such a situation, it is possible to prepare several shielding rings having various inner diameters and replace them as necessary. Instead of exchanging the ring, the distribution can be optimized by adding a vertical mechanism to the ring and changing the distance from the target. In order to change the inner diameter, the parts must be replaced. However, the vertical mechanism can be changed even while the film is formed, which is highly convenient. In ECR plasma, it is desirable that the shield ring be electrically floating, and it is preferable that the shield ring is made of an insulating material such as quartz or alumina, or the holding portion is made of an insulating material.

  In the above embodiment, the case where a cylindrical target is used in the solid source ECR plasma film forming method has been described. However, even in a general sputtering method that does not use ECR plasma, the emission distribution from the target is the same in principle. The effect equivalent to the above can be obtained. In addition, regardless of the plasma generation means, the cross-sectional structure is also shown in FIG. 2 in the case where the target shape is not a cylindrical shape but two plate-like targets are arranged to face each other. Therefore, the same effect can be obtained. The opposing targets do not necessarily need to be arranged in parallel, and in some cases, the film formation speed may be improved and the condition may be better if the interval on the sample substrate side is somewhat widened. It has been experimentally confirmed that the cylindrical target also has a structure that is opened in a trumpet shape on the sample substrate side by several degrees to improve the film forming speed.

  Any solid material can be used as the target material. Typical examples are silicon, aluminum, beryllium, magnesium, titanium, zirconium, hafnium, carbon, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, and zinc. In addition, compounds such as STO and PZT are also used. In addition, when a reactive gas such as oxygen, nitrogen, or fluorine is used in combination with an inert gas such as argon, helium, neon, krypton, or xenon when forming a film, silicon oxide or In addition to oxides and nitrides such as silicon nitride and alumina, any compound thin film can be formed.

  Here, when using a material having a particularly large atomic weight, for example, a target such as zirconium, molybdenum, hafnium, tantalum, or tungsten, it may be difficult to obtain a flat film thickness distribution as shown in FIGS. It is necessary to pay attention. This is a case where the emitted particles from the target are heavy, so that there is a strong tendency to go straight without being sufficiently scattered by the sputtering gas argon. Will occur. In order to reduce such a phenomenon, there is a method of using a rare gas such as krypton or xenon having a large scattering effect as a sputtering gas. Since the scattering effect is greatly affected by the size and weight of the colliding particles, it is preferable to select the most efficient sputtering gas for the target material. Since xenon or the like is an expensive gas, it may be diluted to, for example, about 50% with argon gas in order to achieve the minimum required consumption.

  As another method for making the film thickness distribution more uniform, it is conceivable to devise the shape of the ring. For example, the film thickness distribution can be made smoother by providing protrusions having a height and width of about 4 mm at intervals of 4 mm over the entire inner circumference of the ring having an inner diameter of about 80 mm and forming a gear shape. The height and width of the protrusions can be selected so that the distribution is optimal, for example, in the range of about 1 mm to about 10 mm. Further, the shape may be a triangle instead of a rectangle. Furthermore, a mesh of around several mm may be arranged without making the inner peripheral portion of the ring into a gear shape. In short, any means can be set with a shielding property of about 10 to 90% without clearly separating the shielding property inside the ring of emitted particles from the target to 0 to 100% at the inner boundary. It may be a mechanism.

(Example 2)
In the second example, a TiO ₂ film was formed using the same device structure as that in FIG. 2 in which a shielding ring (material: high-purity alumina (purity 99.99%)) was installed. FIG. 7 shows the TiO ₂ film thickness distribution on the substrate when the inner diameter D of the shielding ring is changed from the conventional 100 mm to 80 mm. The distance H between the shielding ring and the target was fixed to 12 mm, the argon flow rate was set to 7 SCCM under a pressure of about 0.03 Pa, and the microwave power and the RF power were set to 600 W for film formation. The result of the film thickness distribution shows the same tendency as in the first embodiment, but the optimum uniformity is when the ring inner diameter D is 84 mm.

The conventional TiO ₂ film formation without a shielding ring has several major problems in addition to uniformity. The first point is that the metal mode margin is small. FIG. 8 shows how the DC potential component Vdc of the target changes with respect to the oxygen flow rate when a TiO ₂ film is formed using a Ti target. In a state where argon gas was flowed at 20 SCCM and the pressure was maintained at about 0.1 Pa, both microwave power and RF power were applied. In the case where the oxygen flow rate is 0 SCCM, that is, only argon gas is used, titanium atoms jumping out of the target reach the sample substrate as they are to form a titanium thin film. However, when oxygen is added, TiO ₂ is used at a certain oxygen flow rate or higher. A thin film will be formed. On the other hand, when focusing on the target surface, titanium metal is exposed on the target surface while the oxygen flow rate is low, but as the oxygen flow rate is increased, excess oxygen is adsorbed on the target surface and covered with an oxide film. It becomes like this. When the surface is covered with an oxide, the impedance decreases due to the difference in secondary electron emission coefficient and the like, and when the power is constant, the absolute value of the voltage Vdc decreases accordingly. The change can also be read in the figure, and | Vdc | slightly decreases around 4.5 SCCM. Thus, by examining the change in Vdc, it is possible to determine the oxidation state of the target surface. In FIG. 8, when the oxygen flow rate is increased, | Vdc | shifts from a high value to a low value, and in other regions, the value is almost constant with respect to the oxygen flow rate. When the oxygen flow rate is decreased from the larger one, | Vdc | does not necessarily return to a high value in the vicinity of 4.5 SCCM, but finally returns to about 2 SCCM. In this way, once the target surface is covered with oxygen, the sputtering efficiency is low and the state where it is not removed is maintained and exhibits hysteresis characteristics. If this hysteresis is large, that is, if the product of the difference in oxygen flow rate and the | Vdc | variation is large, the metal mode margin becomes high and film formation is stably maintained. However, in the characteristics of FIG. 8, the difference in Vdc is small and the margin is not sufficient. FIG. 9 shows the same characteristics when using a shielding ring (D = 80 mm) and optimizing the film formation conditions with an argon flow rate of 7 SCCM and a microwave power / RF power of 600 W. The amount of change in Vdc increases to about 100 V, and a sufficient metal mode margin is obtained.

  The reason why the metal mode margin is improved by the shielding ring is as follows. In the metal mode film formation, it is a requirement to reliably prevent oxidation of the target surface while supplying sufficient oxygen to the sample substrate side to promote oxidation. As a first effect when the shielding ring is installed, the sputtering rate on the target surface is not changed at all, whereas the deposition rate on the sample substrate is reduced to about half. As a result, oxygen can be supplied onto the sample substrate for a longer time while keeping the target surface in the metal state as in the conventional case, and the oxide film can be more reliably formed. The second effect of the shielding ring is that the gas conductance is suppressed by installing the shielding ring between the sample chamber side and the target. That is, the supply of oxygen from the sample chamber side to the target is suppressed by the shielding ring, and it becomes possible to prevent the target surface from being oxidized while sufficiently supplying oxygen to the sample substrate side.

Due to the above-described effect of the shielding ring, the film quality of TiO ₂ is greatly improved. The conventional TiO ₂ film formed in the normal metal mode has insufficient insulation properties and exhibits conductivity. However, an insulating thin film can be reliably obtained by using a shielding ring. Conventionally, the crystallinity is almost amorphous, but a more stable rutile or anatase crystal structure can be obtained. Further, due to the difference in crystallinity, the optical refractive index has been varied in the range of 2.3 to 2.4 so far, but can be stably controlled to 2.5 or more. In addition, until now, the reproducibility of film formation for each sheet has been a problem, but as shown in FIG. 10, it is possible to form a film stably on a large number of substrates without large fluctuations in film formation speed and refractive index. It became so.

  In the above embodiment, the case where a cylindrical target is used in the solid source ECR plasma film forming method has been described. However, even in a general sputtering method that does not use ECR plasma, the emission distribution from the target is the same in principle. The effect equivalent to the above can be obtained. In addition, regardless of the plasma generation means, the cross-sectional structure is also shown in FIG. 2 in the case where the target shape is not a cylindrical shape but two or more plate-like targets are arranged to face each other. Therefore, an equivalent effect can be obtained.

  The target material is effective for all metal targets, and representative examples include silicon, aluminum, beryllium, magnesium, titanium, zirconium, hafnium, carbon, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, Zinc is used. Further, as an inert gas for film formation, helium, neon, krypton, xenon and the like other than general argon are effective in the present invention, and nitrogen and fluorine are used as a reactive gas in addition to oxygen. be able to.

(Example 3)
FIG. 11 shows an embodiment in which the film thickness distribution on the sample substrate is made uniform by providing an inclination to the targets facing each other. In this figure, instead of using the shielding ring 18 in FIG. 2 showing the first embodiment, an inclined target 19 is used. Dimensions such as the inner diameter and height of the target are the same as those in the first embodiment. The film forming conditions are the same as those in the first embodiment. FIG. 12 shows the result of simulating the film thickness distribution of the thin film formed on the sample substrate in such an arrangement. The angle of the tilt target was 0 degree when there was no tilt, and was varied up to 15 degrees. According to this result, it can be seen that the most uniform distribution is obtained when the inclination of the cylindrical target is 10 degrees. As can be understood from FIG. 11, the direction component as shown by a broken line, for example, which protrudes from the target surface without inclination is directed toward the outer periphery of the sample substrate by the inclination as shown by the solid line. As a result, the film thickness at the central portion of the substrate is reduced and highly uniform.

  However, the simulation has some preconditions (for example, the particle emission distribution from the entire target surface, the scattering effect in the gas phase), and these parameters vary depending on the film forming conditions. Therefore, it is needless to say that the optimum inclination angle needs to be optimized depending on the target material, the film forming pressure, and the like.

It is the schematic which shows the structure of an ECR film-forming apparatus. It is the schematic which shows the structure of the principal part of the apparatus in a 1st Example. It is a figure which shows the simulation result of the film thickness distribution when changing the internal diameter of a shielding ring. It is a figure which shows the simulation result of the film thickness distribution when changing the distance of a shielding ring and a target. Is a graph showing measurement results of the film thickness distribution of the time of forming the SiO ₂ film in the first embodiment. Is a graph showing measurement results of the film thickness distribution of the time of forming an Al ₂ O ₃ film in the first embodiment. In the present invention is a diagram showing a measurement result of the film thickness distribution of the time of forming the TiO ₂ film. Shows a _{Vdc-O 2} flow rate characteristics in a conventional TiO ₂ deposition. Shows a _{Vdc-O 2} flow characteristic in TiO ₂ film formation using the present invention. The measurement results of the deposition rate and refractive index when the deposited TiO ₂ number on a substrate using the present invention. FIG. It is the schematic which shows the structure of the principal part of the apparatus in a 3rd Example. It is a simulation result of film thickness distribution when changing the tilt angle of the target.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plasma production chamber 2 Sample chamber 3 Plasma extraction window 4 Sample stand 5 Sample substrate 6 Exhaust path 7 Gas inlet (A)
8 Gas inlet (B)
9 Magnetic coil 10 Rectangular waveguide 11 Microwave 12 Microwave introduction window 13 Plasma flow 14 Sputtering power source 15 Target 16 Shield 17 Backing tube 18 Shielding ring 19 Inclined target

Claims (9)

  In a container that can be maintained at a reduced pressure, at least a sample stage for placing a sample substrate, and a target having a through-groove disposed at a certain distance from the sample stage or at least one set of each other are arranged opposite to each other. And a mechanism for controlling the distribution of particles flying from the target to the sample substrate.   2. The plasma film forming apparatus according to claim 1, wherein the mechanism for controlling the distribution of particles flying to the sample substrate is a shielding plate provided at an arbitrary position between the sample substrate and the target.   The mechanism that controls the distribution of particles flying to the sample substrate is a target with an inclination on the inner surface of the through groove or on the opposite surface of the target, and this inclination is such that the surface of the through groove or the opposite surface is close to the sample substrate. 2. The plasma film forming apparatus according to claim 1, wherein the inclination is such that it is separated from the side toward the side farthest from the sample substrate.   Equipped with a plasma generation chamber configured to generate plasma under reduced pressure using electron cyclotron resonance discharge by the interaction of microwave and magnetic field, and a sample stage for installing a sample substrate on which a thin film is to be formed A sample chamber, a plasma extraction window disposed between the plasma generation chamber and the sample chamber, for extracting a plasma flow of the generated plasma to the sample chamber, and from the plasma generation chamber toward the sample chamber A magnetic field generating means having a magnetic field distribution of a divergent magnetic field whose magnetic field strength is weakened at a predetermined gradient; and a target disposed so as to surround the plasma flow between the plasma extraction window and the sample stage. The target is sputtered by some of the ions, the sputtered particles are taken into the plasma flow and transported to the sample substrate for incidence. A plasma film forming apparatus for forming a thin film containing the target material on the sample substrate, the plasma film forming apparatus having a mechanism for controlling the particle distribution of the sputtering material flying on the sample substrate .   The plasma film-forming apparatus according to claim 2, wherein the shielding plate has a structure that suppresses a gas conductance between the sample stage side and the target side.   By applying a voltage to the target placed around the plasma generated by electron cyclotron resonance, the ions contained in the plasma are accelerated and incident on the target, causing a sputtering phenomenon, and the released target particles are in the vicinity. A film forming method for forming a thin film by adhering to a sample substrate disposed in a film, wherein the film is formed through a mechanism for controlling a particle distribution of flying target particles.   The film formation method according to claim 6, wherein the film formation is performed in a mixed gas atmosphere of an inert gas and a reactive gas.   8. The film forming method according to claim 6, wherein the mechanism for controlling the distribution of particles flying on the sample substrate is a shielding plate provided at an arbitrary position between the sample substrate and the target. The film forming method according to claim 8, wherein the shielding plate has a structure for suppressing a gas conductance between the sample stage side and the target side.

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