JP4164154B2 - Ionization sputtering equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sputtering apparatus for forming a predetermined thin film on the surface of a substrate, and more particularly to an ionization sputtering apparatus having a function of ionizing sputtered particles.
[0002]
[Prior art]
In semiconductor devices such as various memories and logics, a sputtering process is used when creating various wiring films and barrier films that prevent mutual diffusion of different layers, and sputtering devices are often used. There are various characteristics required for such a sputtering apparatus, but recently it has been strongly demanded that the inner surface of a hole formed on the surface of the substrate can be coated with good coverage.
More specifically, for example, in the case of a barrier film, there has recently been a strong demand for improvement in the bottom coverage ratio, which is the ratio of the film formation rate on the bottom surface of the hole with respect to the surface outside the hole. This is because the aspect ratio (ratio of the depth of the hole to the size of the hole opening) of the hole such as a contact hole has been increasing year by year due to the increase in the degree of integration. This is because the conventional sputtering technique often cannot form a film with good bottom coverage. When the bottom coverage rate decreases, the barrier film becomes thin on the bottom surface of the hole, which may cause a fatal defect in device characteristics such as a junction leak.
[0003]
As sputtering techniques for improving the bottom coverage rate, techniques such as collimated sputtering and low-pressure remote sputtering have been developed so far. Collimated sputtering is a technique in which a plate (collimator) with many holes in the direction perpendicular to the substrate is provided between the target and the substrate, and only the sputtered particles that fly almost perpendicular to the substrate are selectively delivered to the substrate. is there. Low-pressure remote sputtering increases the distance between the target and the substrate so that a relatively large amount of sputtered particles flying almost perpendicular to the substrate are incident on the substrate, and the pressure is lower than usual and the average freedom is reduced. This is a method of preventing the sputtered particles from being scattered by lengthening the stroke.
[0004]
However, in collimated sputtering, sputtered particles accumulate on the collimator and become lost, so there is a problem that the film formation speed decreases. In low-pressure remote sputtering, the pressure is lowered and the distance between the target and the substrate is increased. Therefore, there is a problem that the film forming speed is essentially lowered. Because of these problems, it is predicted that the limit is 64 megabits for collimated sputtering and the first generation of 256 megabits for low-pressure remote sputtering. A search for a new technique is underway.
[0005]
In order to meet such a demand, it is considered that an ionized sputtering technique is promising. Ionized sputtering is a method in which sputtered particles emitted from a target are ionized and the sputtered particles efficiently reach the holes by the action of ions. It has been confirmed that ionized sputtering can provide a much higher bottom coverage than collimated sputtering or low-pressure remote sputtering.
[0006]
[Problems to be solved by the invention]
However, according to the research of the inventors, it has been found that ionization sputtering has a problem that film formation is not uniform in the peripheral portion of the substrate. This problem was not observed in collimated sputtering or low-pressure remote sputtering, and is a problem specific to ionized sputtering.
The object of the present invention is to solve the problem of non-uniformity of film formation at the periphery of the substrate, which is characteristic of this ionization sputtering.
[0007]
[Means for Solving the Problems]
  In order to solve the above-mentioned problems, the invention described in claim 1 of the present application includes a sputtering chamber having an exhaust system, a gas introduction system for introducing a predetermined gas into the sputtering chamber, and a surface to be sputtered exposed in the sputtering chamber. A target provided in such a manner, a sputtering power source for sputtering the target by applying a high frequency voltage to the target, ionization means for ionizing the sputtered particles released from the target by sputtering, and a position where the ionized sputtered particles are incident And a substrate holder for holding the substrate and an electric field setting means for setting an electric field that allows ionized sputtered particles to be vertically incident on the substrate and increasing the film formation rate on the bottom surface of the fine hole formed on the surface of the substrate.Create a thin film on the inner surface of minute holes formed on the surface of the substrateAn ionization sputtering apparatus,
  The ionization means is for ionizing the sputtered particles by forming plasma in a sputtered particle flight space between the target and the substrate. Inside the sputter chamber, the sputtered particles released by the sputter are other than the substrate. An adhesion shield is provided to prevent it from adhering to the location.
  AboveThe deposition shield is within 50mm from the edge of the board in the direction of the board surface.AndIt has a configuration in which the size shape and the arrangement position do not occupy the forbidden area which is a space area within 50 mm on the side where the plasma is formed in the direction perpendicular to the surface of the substrate.
  In order to solve the above-mentioned problem, the invention according to claim 2 of the present application is the structure according to claim 1, wherein the deposition shield side of the ring-shaped holder that surrounds the periphery of the substrate held by the substrate holder. It has a configuration of being a shield.
  Further, in order to solve the above problems, the claims of the present application3The invention according to claim 1 is the configuration according to claim 1, wherein the deposition shield is a cylindrical main shield that surrounds a space between the target and the substrate holder, and an inner edge of the main shield is a substrate. It has the structure of being located in the position exceeding 50 mm from the periphery of a board | substrate in the direction of the surface of the board | substrate hold | maintained at the holder.
  In order to solve the above-mentioned problem, the invention according to claim 3 of the present application is the structure of claim 1, wherein two of the deposition shields are provided, one of which is the target and the substrate holder. Is a cylindrical main shield that surrounds the space between and the other is a ring-shaped holder side shield that surrounds the periphery of the substrate held by the substrate holder,
The holder-side shield is a member that prevents sputtered particles from passing through and adhering to the space between the main shield and the substrate holder,
The inner edge of the main shield is configured to be located at a position exceeding 50 mm from the periphery of the substrate in the direction of the surface of the substrate held by the substrate holder.
  Further, in order to solve the above problems, the claims of the present application5The invention described is the above claim.2 or 4In this configuration, the holder-side shield is configured to be provided apart from the substrate holder.
  In order to solve the above-mentioned problem, in the invention according to claim 6 of the present application, in the structure of claim 5, a fixed shield fixed to the substrate holder is provided, and the fixed shield occupies the prohibited area. It has a configuration in which it has a dimension shape and an arrangement position that do not occur and is provided apart from the holder side shield.
  In order to solve the above-mentioned problem, in the invention according to claim 7 of the present application, in the configuration of claim 6, the space formed between the holder side shield and the fixed shield is a bent bottleneck. It has the composition of being.
  In order to solve the above problem, the invention according to claim 8 of the present application is the structure of claim 1, wherein the portion of the deposition shield occupies within 50 mm from the periphery of the substrate in the direction of the surface of the substrate. The surface on which the plasma is formed has a configuration in which the surface is located within 15 mm on the opposite side to the side on which the plasma is formed from the same surface as the surface of the substrate.
  In order to solve the above-mentioned problem, the invention according to claim 9 of the present application is the structure of the above-mentioned claim 2, 4, 5, 6 or 7, on the side where plasma is formed in the holder side shield. The surface has a configuration in which the surface is located at a position within 15 mm opposite to the side where plasma is formed from the surface flush with the surface of the substrate.
  In order to solve the above-mentioned problem, according to a tenth aspect of the present invention, in the structure according to any one of the first to ninth aspects, the exhaust system has an inner space of 20 mTorr or more when the thin film is formed. Exhaust is performed so that the pressure is in the range of 100 mTorr or less.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 is a front sectional view showing a schematic configuration of an ionization sputtering apparatus according to an embodiment of the present invention. An ionization sputtering apparatus shown in FIG. 1 includes a sputtering chamber 1 provided with an exhaust system 11, a target 2 provided so as to expose a surface to be sputtered in the sputtering chamber 1, and a sputtering power source for sputtering the target 2. 3, a process gas introduction system 4 for introducing a predetermined process gas into the sputter chamber 1, ionization means for ionizing sputtered particles released from the target 2 by sputtering, and ionized sputtered particles (hereinafter referred to as ionized sputtered particles) Includes a substrate holder 5 that holds the substrate 9 at a position where the incident light enters, and an electric field setting unit that sets an electric field for vertical incidence in which ionized sputtered particles are vertically incident on the substrate 9.
[0009]
The sputter chamber 1 is an airtight container and is electrically grounded. The sputter chamber 1 is provided with a gate valve (not shown), and the substrate 9 is carried into and out of the atmosphere via a transfer chamber and a load lock chamber (not shown). The exhaust system 11 includes a vacuum pump such as a turbo molecular pump or a cryopump.^-8It is configured to be able to exhaust to about Torr.
[0010]
The target 2 is attached to the sputter chamber 1 via an insulating material 21. The material of the target 2 is titanium in this embodiment.
In the present embodiment, a high-frequency power source is employed as the sputtering power source 3. This high-frequency power source has, for example, a frequency of 13.56 MHz and an output of about 10 kW. In addition, an impedance matching circuit 31 is provided between the target 2 and the sputtering power source 3 in order to prevent the generation of reflected waves.
[0011]
A magnet mechanism 22 is provided behind the target 2. The magnet mechanism 22 is provided for performing magnetron sputtering with high discharge efficiency. Specifically, the magnet mechanism 22 includes a central magnet 221, a peripheral magnet 222 that surrounds the central magnet 221 in a circumferential shape, and a disk-shaped yoke 223 that connects the central magnet 221 and the peripheral magnet 222.
[0012]
A process gas necessary for the sputter discharge is introduced by the process gas introduction system 4. The process gas introduction system 4 includes a gas cylinder 41 that stores a predetermined process gas, a pipe 42 that connects the sputter chamber 1 and the gas cylinder 41, and a pipe 42.EtThe valve 43 and the flow rate regulator 44 are mainly configured. A gas such as argon or nitrogen is used as the process gas.
[0013]
When the sputtering power supply 3 operates in a state where a predetermined process gas is introduced into the sputtering chamber 1 at a predetermined flow rate by the process gas introduction system 4, a high-frequency electric field is set in the sputtering chamber 1 via the target 2. . As a result, high-frequency discharge occurs in the introduced gas, and plasma is formed. At this time, an appropriate capacitance exists between the sputtering power source 3 and the target 2, and a negative self-bias voltage is generated in the target 2 due to this capacitance. By this negative self-bias voltage, positive ions are extracted from the plasma and bombard the target, and the target 2 is sputtered. This capacitance may correspond to a capacitor in the impedance matching circuit 31 or may be self-biased.VoltageIn some cases, a dedicated capacitor is provided. Note that when the discharge is maintained only by ionization of the sputtered particles emitted from the target 2, the process gas may not be introduced.
[0014]
On the other hand, the substrate holder 5 that holds the substrate 9 at a position where the sputtered particles emitted by the sputtering arrives has a trapezoidal shape as a whole, and the substrate 9 is placed and held on the upper surface. . The substrate holder 5 includes an electrostatic adsorption mechanism 53 for electrostatically adsorbing the substrate 9 to the substrate placement surface. The electrostatic adsorption mechanism 53 is mainly composed of an adsorption electrode 51 embedded in a dielectric block 531 provided as a part of the substrate holder 5 and an adsorption power source 52 for applying a negative DC voltage to the adsorption electrode 51. It is configured.
When a DC voltage of about 200 to 1000 V, for example, is applied to the suction electrode 51 by the suction power source 52, the dielectric block 531 is dielectrically polarized and static electricity is induced on the substrate mounting surface. The substrate 9 is electrostatically attracted to the dielectric block 531 by this static electricity.
[0015]
The substrate holder 5 includes a heater 54 for heating the substrate 9. As the heater 54, a configuration in which a resistance heating type heater is embedded in the substrate holder 5 can be employed. The substrate 54 is heated to a predetermined temperature from room temperature to about 500 ° C. by the heater 54. Another configuration of the heater 54 may be a radiant heating type.
[0016]
In the present embodiment, an ionization means that uses plasma to ionize sputtered particles is employed. In other words, the ionization means forms plasma in the flight path of the sputtered particles from the target 2 to the substrate 9 and causes the sputtered particles to ionize by colliding with electrons or ions in the plasma when the sputtered particles pass through the plasma. It has become. In the present embodiment, the above-described ionization can be performed by the plasma formed when the target 2 is sputtered, and the sputtering power source 3 and the process gas introduction system 4 described above are used as ionization means.
[0017]
Although the negative DC power supply may be used as the sputtering power supply 3, it is preferable to use a high-frequency power supply as in this embodiment in consideration of sharing the ionization means. In the case of a high-frequency power source, a high-frequency electric field is set between the target 2 and the substrate holder 5, and ions and electrons in the plasma are alternately accelerated in the reverse direction by the high-frequency electric field. For this reason, a periodic motion of charged particles called plasma oscillation occurs, and as a result, the frequency with which the charged particles collide with the neutral sputtered particles and ionize the neutral sputtered particles increases.
[0018]
Further, the process gas introduction system 4 that is also used as an ionization means is preferably capable of introducing the process gas into the sputtering chamber 2 while maintaining a relatively high pressure. That is, in order to perform ionization sputtering, it is necessary to increase the collision frequency between charged particles in plasma and neutral sputtered particles. For this purpose, it is preferable to perform sputter discharge at a relatively high pressure. Specifically, the range is about 20 to 100 mTorr. If it is less than 20 mTorr, ionization of neutral sputtered particles may not be sufficient. Further, when the speed is 100 mTorr or more, the number of process gas molecules becomes too large, and even if the sputtered particles are ionized, many of them are scattered due to collision with the process gas molecules, causing a problem that the substrate 9 cannot be sufficiently reached. As the flow rate regulator 44 of the process gas introduction system 4, one that can adjust the flow rate with sufficient accuracy within the above pressure range is used.
[0019]
On the other hand, as an electric field setting means for setting an electric field for vertical incidence in which ionized sputtered particles are incident vertically by the substrate 9 as described above, in this embodiment, an appropriate sheath electric field is provided between the plasma and the substrate 9. What is being formed is used. Specifically, the electric field setting means is a part of the substrate holder 5 described above.DielectricThe block 531 is also used.
[0020]
More specifically, the plasma formed by sputtering discharge as described above diffuses in the sputtering chamber 1 and reaches the vicinity of the substrate holder 5. In particular, since a high-frequency power source is used as the sputtering power source 3, the plasma diffusion tends to be larger than that of the DC power source. Here, when the dielectric is disposed so as to be in contact with the plasma, the surface of the dielectric has a negative potential called a floating potential, as is well known, due to the difference in mobility between electrons and ions in the plasma. On the other hand, the space potential of the plasma is almost 0 V, and thus a sheath electric field is formed between the plasma and the dielectric.
[0021]
Also in this embodiment, the surface of the dielectric block 531 provided for electrostatic attraction of the substrate 9 has a floating potential when plasma is formed, and a sheath electric field is generated between the plasma and the dielectric block 531. It is formed. This sheath electric field is an electric field in which the potential gradually decreases toward the dielectric block 531 and has an effect of extracting positive ions from the plasma.
When the substrate 9 is placed on the surface of the dielectric block 531 as described above, the direction of the sheath electric field is substantially perpendicular to the substrate 9 and functions to cause the ionized sputtered particles to enter the substrate 9 perpendicularly. The specific numerical values will be described. If the pressure is 60 mTorr and the sputtering power source 3 has a frequency of 13.56 MHz and an output of 3 kW, the surface of the dielectric block 531 has a floating potential of about −10V.
When ionized sputtered particles are vertically incident on the substrate 9 as described above, a large number of sputtered particles can reach the bottom surface of a hole having a high aspect ratio. Therefore, film formation can be performed with a high bottom coverage even for holes with a high aspect ratio.
[0022]
A major feature of the apparatus of this embodiment is the configuration of an adhesion shield provided to prevent sputter particles from adhering to a place other than the substrate 9. When sputtered particles unnecessarily adhere to a place other than the substrate 9, it grows into a thin film over time. When the thickness of this thin film reaches a certain level, it peels off due to its own weight or internal stress. The thin film becomes particles with a certain size due to this peeling, and floats in the sputter chamber 1. When the particles reach the surface of the substrate 9, defects such as local film thickness anomalies are generated. For this reason, the apparatus of this embodiment is provided with an adhesion shield for preventing sputtered particles from unnecessarily adhering to locations other than the substrate 9.
[0023]
As shown in FIG. 1, the apparatus of this embodiment is provided with a plurality of deposition shields 61, 62, 63. One of the plurality of deposition shields is a deposition shield (hereinafter referred to as a main shield) 61 that surrounds the sputter particle flight space between the target 2 and the substrate holder 5. A ring-shaped deposition shield (hereinafter referred to as a target side shield) 62 is provided around the target 2. A ring-shaped deposition shield (hereinafter referred to as a “holder side shield”) 63 is also provided around the substrate holder 5.
On the surface of these deposition shields 61, 62, 63, irregularities are formed to prevent peeling of the deposited thin film. These deposition shields 61, 62, and 63 are all provided so as to be replaceable, and are replaced when the deposited thin film reaches a predetermined thickness.
[0024]
The major feature of the apparatus of the present embodiment is that the above-described deposition shields 61, 62, and 63 do not occupy a prohibited area set as a spatial area that causes the film forming process on the substrate 9 to be non-uniform. It is a point. In the present embodiment, the prohibited area is a space area within 50 mm from the periphery of the substrate 9 in the direction of the surface of the substrate 9 held by the substrate holder 5 (hereinafter referred to as a film formation surface direction), and in the film formation surface direction. A space region within 50 mm on the side (hereinafter referred to as plasma forming side) where plasma is formed in a direction perpendicular to the vertical direction (hereinafter referred to as vertical direction). This forbidden area is a cylindrical space area coaxial with the substrate 9.
[0025]
The setting of the prohibited area is based on the inventor's research described below. The inventor has found that there is a problem of non-uniformity of film formation in the peripheral portion of the substrate 9 that was not seen in normal sputtering in the process of performing various experiments using an experimental apparatus of an ionization sputtering apparatus. . This point will be described first with reference to FIG.
FIG. 2 is a diagram showing the non-uniformity of film formation at the periphery of the substrate when using an experimental ionization sputtering apparatus, and shows the distribution of sheet resistance values of a thin film formed on the substrate. . In the experiment shown in FIG. 2, a titanium thin film was made on a semiconductor wafer having a diameter of 100 mm using a titanium target. The dotted line in FIG. 2 is the distribution of the sheet resistance value when the experimental machine is used.
[0026]
As shown in FIG. 2, the sheet resistance value of the titanium thin film prepared by the experimental machine is high in the peripheral portion of the substrate 9. Considering that titanium is a conductor, according to the experimental machine, it is determined that the thickness of the titanium thin film is thin at the periphery of the substrate 9.
The inventor diligently studied the cause of the decrease in the film thickness in the peripheral portion of the substrate 9 and found that it is caused by the arrangement of the members around the substrate holder 5. This point will be described with reference to FIGS. FIG. 3 is a front sectional partial view showing the arrangement of the substrate holder and the members around the substrate holder in the experimental machine. FIG. 4 is a diagram showing a plasma diffusion state in the experimental machine shown in FIG.
[0027]
As shown in FIG. 3, in the experimental machine, the holder-side shield 63 is positioned slightly higher than the height of the surface of the substrate 9, that is, on the target 2 side. According to the inventor's research, when a member such as the holder-side shield 63 exists at such a position, the spread of the plasma P is spatially restricted, and this causes uneven film formation on the periphery of the substrate 9. It has been found that
[0028]
More specifically, as described above, in the ionization sputtering apparatus using the high frequency power source, the plasma P diffuses widely to the vicinity of the substrate holder 5. At this time, if the holder-side shield 63 is disposed at the above-described position, the diffusion of the plasma P toward the outside in the radial direction of the substrate 9 is spatially restricted by the holder-side shield 63. Therefore, the plasma P does not diffuse so much in the vicinity of the substrate 9 and outside the peripheral edge of the substrate 9, and has a diffusion region shape as shown in FIG.
[0029]
On the other hand, as described above, in the ionization sputtering apparatus, the bottom coverage rate is increased by causing the ionized sputtered particles to be drawn vertically and made incident by the substrate 9. Since the ionized sputtered particles are ions, they constitute the plasma P together with process gas ions. In this case, the distribution of ionized sputtered particles incident on the substrate 9 depends on the distribution of ionized sputtered particles present in the plasma P. The distribution of ionized sputtered particles in the plasma P depends on the plasma density distribution. Therefore, the non-uniformity of film formation around the substrate 9 as shown in FIG. 2 is caused by the distribution of plasma density in the direction of the surface of the substrate 9.ofThis is thought to be due to non-uniformity. That is, the plasma density is low near the periphery of the substrate 9 and the number of sputtered particles incident on the substrate 9 is small.
[0030]
Further, as described above, the ionized sputtered particles in the plasma P are accelerated by the sheath electric field E formed at the boundary portion of the plasma and enter the substrate 9. In this case, in the state where the diffusion region is limited as shown in FIG. 3, the direction of the sheath electric field E is substantially perpendicular to the substrate 9 in the central portion of the substrate 9, but in the peripheral portion of the substrate 9, The direction is obliquely outward. For this reason, the ionized sputtered particles are accelerated by the sheath electric field E in this direction and proceed obliquely outward, and cannot reach or reach the substrate 9, but do not enter the substrate 9 perpendicularly, and therefore reach the bottom surface of the hole. It may be impossible. For this reason, it is considered that the film forming speed is reduced in the peripheral portion of the substrate 9 and this causes film forming non-uniformity such as an increase in sheet resistance value.
[0031]
Based on such considerations, the inventor of the present application sets a prohibited area as a spatial area that regulates the diffusion of the plasma P and affects the film formation on the periphery of the substrate 9, and prevents this area from being attached. Improvements have been made so that the shield does not occupy. FIG. 5 shows the main part of the ionization sputtering apparatus improved in this way, and is a front sectional partial view showing the arrangement of the substrate holder and members around the substrate holder in the apparatus of this embodiment shown in FIG. . FIG. 6 is a diagram showing a plasma diffusion state in the apparatus of the present embodiment.
[0032]
According to the research of the inventors of the present application, in order to prevent the diffusion of the plasma P that causes the non-uniformity of the film formation as described above from being regulated, the film surface is within 50 mm from the periphery of the substrate 9 in the direction of the film formation surface. It has been found that it suffices if no member that restricts plasma is arranged in the space region within 50 mm on the plasma forming side in the vertical direction. The area set in this way is the above-described prohibited area, and is hatched in FIG.IndicationIs a region a.
[0033]
In the space region exceeding 50 mm from the periphery of the substrate 9 in the film formation surface direction, the deposition shield 61, 62, 63 is located at a position away from the substrate 9. Is hardly affected. In addition, even if the region is within 50 mm from the periphery of the substrate 9 in the direction of the film formation surface, if it exceeds 50 mm on the plasma forming side in the vertical direction, it is still a position away from the substrate 9, and thus the deposition shield is located at any position. Even if 61, 62, and 63 are arranged, there is no influence of making the film formation uneven in the peripheral portion of the substrate 9. When any of the deposition shields 61, 62, 63 is disposed in a columnar space with the surface of the substrate 9 on which the film is formed as the bottom surface and the height of the plasma forming side in the vertical direction as the height, the substrate 9 from the target 2 is disposed. As a matter of course, the deposition shields 61, 62 and 63 are arranged so as not to occupy this space.
[0034]
The dimensional shape and arrangement position of the deposition shields 61, 62, and 63 will be described in more detail. The main shield 61 is cylindrical and is arranged coaxially with an axis penetrating the center of the substrate 9 in the vertical direction. When the substrate 9 is a semiconductor wafer having a diameter of 200 mm, the inner diameter of the main shield 61 is about 300 mm. That is, the inner surface of the main shield 61 is located at a position exceeding 50 mm from the peripheral edge of the substrate 9 when viewed in the film forming surface direction.
[0035]
The holder-side shield 63 has a ring shape with a cross-sectional shape as shown in FIG. In this cross-sectional shape, the inner edge of the ring is tapered slightly downward (opposite to the plasma forming side). In addition, a protrusion protruding toward the plasma forming side in the vertical direction is formed on the outer edge of the ring. The protrusion is located outside the main shield 61 and is therefore located at a position exceeding 50 mm from the peripheral edge of the substrate 9.
In the cross-sectional shape of the holder-side shield 63 shown in FIG. 5, the central portion is located within 50 mm from the peripheral edge of the substrate 9. However, as shown in FIG. 5, the upper surface (surface on the plasma forming side in the vertical direction) of the portion is located at a position slightly lower (for example, a position lower by about 15 mm) than the film formation surface. Therefore, the holder-side shield 63 has a dimensional shape and arrangement that does not occupy the prohibited area a. Note that the target shield 62 does not occupy the prohibited area a because it is a position surrounding the target 2 away from the substrate 9.
[0036]
Thus, in the apparatus of the present embodiment, since the deposition shields 61, 62, and 63 do not occupy the prohibited area a, the diffusion of the plasma P is not regulated, and the plasma P is generated on the substrate 9 as shown in FIG. It spreads widely to the outside away from the periphery. Therefore, the sheath electric field E does not face obliquely outward as shown in FIG. 4 in the peripheral portion of the substrate 9, and the sheath electric field E is oriented perpendicular to the substrate 9 as in the central portion. is there. Accordingly, the same amount of ionized sputtered particles as the central portion is incident on the peripheral portion of the substrate 9 to form a uniform film.
[0037]
The result of the experiment confirming the effect of improving the film formation uniformity is also shown in FIG. The solid line in FIG. 2 shows the distribution of the sheet resistance value of the titanium thin film prepared using the apparatus of the embodiment. As can be seen from this result, according to the apparatus of the present embodiment, an abnormal increase in the sheet resistance value in the peripheral portion of the substrate 9 is not seen, and uniform film formation can be performed.
[0038]
As shown in FIG. 5, the substrate holder 5 includes a fixed shield 55. The fixed shield 55 is fixed to the substrate holder 5. The fixed shield 55 prevents the side end surface of the dielectric block 531 and the exposed surface of the substrate holder 5 from being exposed to plasma.
The holder-side shield 63 is provided so as to be close to the fixed shield 55 that is a part of the substrate holder 5, but not in contact with the fixed shield 55. That is, the holder-side shield 63 is fixed by a support 631 provided separately from the substrate holder 5. Note that when the substrate 9 is loaded / unloaded, the holder-side shield 63 may be raised so that the substrate 9 is loaded / unloaded from the lower side of the holder-side shield 63.
[0039]
Further, since the holder-side shield 63 is not in contact with the fixed shield 55, it can take any potential regardless of the substrate holder 5. For this reason, for example, the holder-side shield 63 can be set to the ground potential to have a function as a discharge shield. According to the experiments by the inventors, it has been confirmed that the effect of the uniform film formation described above hardly changes even when the holder-side shield 63 is grounded or insulated from the ground potential.
[0040]
Further, as shown in FIG. 5, the space formed between the holder side shield 63 and the fixed shield 55 is a complicatedly bent bottleneck. For this reason, even if sputtered particles come into this space, it is difficult to pass through this space, and it is effective that the sputtered particles pass through this space and reach the inner surface of the sputter chamber 1 to deposit a thin film. It is prevented.
[0041]
Next, the overall operation of the ionization sputtering apparatus of this embodiment will be described.
In a state where the transfer chamber (not shown) or the load lock chamber and the sputter chamber 1 are evacuated to a predetermined pressure, the gate valve (not shown) is opened and the substrate 9 is carried into the sputter chamber 1. The substrate 9 is placed on the substrate holder 5 and the gate valve is closed. The electrostatic adsorption mechanism 53 operates, and the substrate 9 is electrostatically adsorbed to the substrate holder 5. The heater 54 in the substrate holder 5 is operated in advance, and the substrate 9 is heated to a predetermined temperature by being electrostatically attracted to the substrate holder 5.
[0042]
In this state, the process gas introduction system 4 operates and a predetermined process gas is introduced into the sputtering chamber 1. Then, the sputtering power source 3 is operated to form high frequency discharge plasma as described above, and the target 2 is sputtered by the self-bias voltage generated in the target 2. Sputtered particles emitted from the target 2 by sputtering reach the substrate 9, and a predetermined thin film is formed on the surface of the substrate 9. At this time, the sputtered particles are ionized when passing through the plasma, and are extracted vertically by the substrate 9 by the above-described normal incidence electric field and enter the substrate 9. As a result, a film is efficiently deposited on the bottom surface of the hole formed on the surface of the substrate 9, and film formation with a high bottom coverage rate can be performed. Since plasma diffusion is not restricted in the vicinity of the peripheral portion of the substrate 9, film formation can be performed uniformly up to the peripheral portion of the substrate 9.
[0043]
An example of film formation will be described. For example, when an intervening barrier film is formed in order to prevent mutual diffusion of different layers, argon is first introduced as a process gas to form a titanium thin film. After that, sputtering is performed by switching to nitrogen gas, and a titanium nitride thin film is formed while utilizing the reaction between titanium and nitrogen. Thereby, a barrier film structure in which a titanium nitride thin film is laminated on a titanium thin film is obtained.
[0044]
After film formation for a predetermined time in this way, the operations of the sputtering power source 3 and the process gas introduction system 4 are stopped. Then, the inside of the sputtering chamber 1 is evacuated again and the operation of the electrostatic adsorption mechanism 53 is stopped, and then the substrate 9 is unloaded from the sputtering chamber 1. Thereafter, the substrate 9 is taken out to the atmosphere side through the transfer chamber and the load lock chamber. By repeating such an operation, the film forming process is performed on the substrate 9 one by one.
[0045]
In the description of the embodiment described above, the ionization means is the sputtering power source 3 that applies a high frequency voltage to the target 2. However, the ionization means is ionized by forming plasma with a high frequency power source provided separately from the sputtering power source 3. Also good. In this case, for example, a configuration may be adopted in which a cylindrical or coiled electrode is provided between the target 2 and the substrate holder 5 and a high frequency voltage is applied thereto.
In addition to using a floating potential generated in the dielectric block 531 as the electric field setting means, a high frequency voltage is applied to the entire substrate holder 5 and a self-bias voltage is applied to the substrate 9 to set the vertical incident electric field. In some cases, a configuration is employed.
[0046]
【The invention's effect】
As described above, according to the invention of the present application, the problem of non-uniformity of film formation at the periphery of the substrate, which is unique to ionization sputtering, is solved, and the effect of film formation with a high bottom coverage ratio for holes with a high aspect ratio is eliminated. Can be obtained uniformly over the entire surface of the substrate.
[Brief description of the drawings]
FIG. 1 is a front sectional view showing a schematic configuration of a sputtering apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing non-uniformity of film formation at the periphery of a substrate when using an experimental apparatus of an ionization sputtering apparatus, and showing a distribution of sheet resistance values of a thin film formed on the substrate. .
FIG. 3 is a front sectional partial view showing the arrangement of a substrate holder and members around the substrate holder in the experimental machine.
FIG. 4 is a diagram showing a plasma diffusion state in the experimental machine shown in FIG. 3;
5 is a front sectional partial view showing the arrangement of a substrate holder and members around the substrate holder in the apparatus of the present embodiment shown in FIG. 1; FIG.
FIG. 6 is a diagram showing a plasma diffusion state in the apparatus of the present embodiment.
[Explanation of symbols]
1 Sputter chamber
2 Target
3 Sputtering power supply
4 Process gas introduction system
5 Board holder
61 Main shield
62 Target side shield
63 Holder side shield
631 Prop
9 Board
P Plasma
E Sheath electric field

Claims (10)

A sputtering chamber equipped with an exhaust system, a gas introduction system for introducing a predetermined gas into the sputtering chamber, a target provided with the surface to be sputtered exposed in the sputtering chamber, and a high-frequency voltage applied to the target Sputtering power source for sputtering the target, ionizing means for ionizing the sputtered particles released from the target by sputtering, a substrate holder for holding the substrate at a position where the ionized sputtered particles are incident, and the ionized sputtered particles perpendicular to the substrate A thin film on the inner surface of the fine holes formed on the surface of the substrate, and an electric field setting means for setting an electric field that increases the deposition rate on the bottom surface of the fine holes formed on the surface of the substrate. An ionization sputtering apparatus that
The ionization means is for ionizing the sputtered particles by forming plasma in a sputtered particle flight space between the target and the substrate. Inside the sputter chamber, the sputtered particles released by the sputter are other than the substrate. An adhesion shield is provided to prevent it from adhering to the location.
The deposition shield may occupy a forbidden region which is a space region within 50 mm from the periphery of the substrate in the direction of the surface of the substrate and within 50 mm on the side where the plasma is formed in a direction perpendicular to the surface of the substrate. An ionization sputtering apparatus having no dimensional shape and arrangement position.  The ionization sputtering apparatus according to claim 1, wherein the deposition shield is a ring-shaped holder-side shield surrounding the periphery of the substrate held by the substrate holder.   The deposition shield is a cylindrical main shield that surrounds a space between the target and the substrate holder, and an inner edge of the main shield is oriented toward the surface of the substrate held by the substrate holder. The ionized sputtering apparatus according to claim 1, wherein the ionized sputtering apparatus is located at a position exceeding 50 mm from the periphery. Two of the deposition shields are provided, one of which is a cylindrical main shield surrounding the space between the target and the substrate holder, and the other is a substrate held by the substrate holder. Is a ring-shaped holder-side shield that surrounds
  The holder-side shield is a member that prevents sputter particles from passing through and adhering to the space between the main shield and the substrate holder,
  2. An ionization sputtering apparatus according to claim 1, wherein the inner edge of the main shield is located at a position exceeding 50 mm from the periphery of the substrate in the direction of the surface of the substrate held by the substrate holder. 5. The ionization sputtering apparatus according to claim 2 , wherein the holder side shield is provided apart from the substrate holder. A fixed shield fixed to the substrate holder is provided, and the fixed shield has a dimensional shape and an arrangement position that does not occupy the prohibited area, and is provided apart from the holder side shield. An ionization sputtering apparatus according to claim 5. The ionized sputtering apparatus according to claim 6, wherein a space formed between the holder-side shield and the fixed shield is a bent bottleneck. Of the portion of the deposition shield that occupies 50 mm or less from the periphery of the substrate in the direction of the surface of the substrate, the surface on which plasma is formed is the side on which the plasma is formed from the same surface The ionized sputtering apparatus according to claim 1, wherein the ionized sputtering apparatus is located at a position within 15 mm on the opposite side to the above. The surface of the holder side shield on the side where plasma is formed is located within a position within 15 mm opposite to the side where the plasma is formed from the surface flush with the surface of the substrate. The ionized sputtering apparatus according to claim 2, 4, 5, 6, or 7. Place. The ionization according to any one of claims 1 to 9, wherein the exhaust system exhausts the inside of the sputtering chamber when the thin film is formed to a pressure in a range of 20 mTorr to 100 mTorr. Sputtering equipment.

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