JP3775689B2 - Method and apparatus for ionizing sputtering of materials - Google Patents

Description

The present invention relates to sputter coating, and more particularly to a method and apparatus for ionizing a coating material onto a substrate and performing physical vapor deposition (IPVD).
Background of the Invention
In semiconductor manufacturing, the presence of submicron high aspect ratio formations such as biases, trenches and contact holes have caused various coating problems. In the manufacture of very large scale integrated semiconductor devices (VLSI and ULSI), the contacts at the bottom of such formations often need to be coated with a liner, and the formations often need to be filled with a conductive metal. is there. In the manufacturing context of many semiconductor devices to be film deposited, it is necessary or at least preferred to apply the coating using a physical vapor deposition (PVD) method. Film deposition on the bottom of a narrow, high aspect ratio formation (aperture) by physical methods requires achieving high orientation in moving the material to be deposited toward the substrate. Higher aspect ratio formations require greater directionality. For example, to effectively coat a contact at the bottom of a narrow, high aspect ratio hole on the surface of the substrate, the particles of coating material are not significantly larger than the angled opening of the formation, at an angle to a right angle. I need to exercise.
In semiconductor device manufacturing, the width is 0.25 to 0.35 microns, and the contact at the bottom of the trench or trench with a high aspect ratio that tends to become narrower as the device continues to shrink There is. Metallizing such contacts by physical vapor deposition, such as sputter coating, is an alternative method in film purity, and overall cost and simplification of the processing equipment, where PVD is achieved overall. This is preferred because of its technical and commercial advantages. For example, chemical vapor deposition (CVD) is sometimes used to deposit films in deep holes and trenches because chemical methods can form a film on the surface of the substrate inside the holes and trenches. However, CVD methods require more complex and expensive equipment than PVD equipment. Because of their chemical nature, CVD methods often include environmental elements and often employ chemical precursors that can provide a source of device contamination, and these devices are typically more Frequent protective maintenance work is required, thus resulting in unproductive downtime. For many types of films, the PVD method is faster and more productive than the CVD method, and thus costs are lower. Furthermore, CVD methods cannot survive for many deposition materials, i.e., cannot be practical, for example by requiring complex precursors and dispensing equipment that can eliminate CVD deposition. There are acceptable CVD processes for titanium, titanium nitride and tungsten. However, there is no CVD method for aluminum, copper, tantalum, and tantalum nitride, and if present, it is incomplete or commercially impractical. Further, in some methods, CVD may expose elements partially formed on the substrate to heat for extended periods of time, which may cause the material to move or diffuse at the material boundary, or It is possible to expose the device to other damaging heat or to exceed the heat supply for the process.
In order to reduce the size of the formation and increase the aspect ratio, in some applications it is preferable to apply the coating by physical vapor deposition to achieve an increasingly higher direction in moving the coating material on the substrate. Therefore, the demand for the sputtering method is increased. If the path of the sputtered material particles incident on the substrate cannot be kept very parallel and perpendicular to the plane of the substrate, the formation is attempted when sputter coating a high aspect ratio formation. This results in excessive deposition on the top of the object, or results in closing the mouth of the formation, in which case physical vapor deposition does not achieve satisfactory results.
Sputter coating is typically performed by placing a substrate and a high purity coating material target in a vacuum chamber filled with an inert gas such as argon and forming a plasma in the gas. . The plasma is typically generated by constantly or intermittently holding the target at a negative potential, so that the target excites the gas in the vacuum chamber and supplies the electrons that form the plasma near the surface of the target. Function as. Plasma generation is usually enhanced by a magnetron cathode assembly. In the magnetron cathode assembly, a magnet behind the target traps these electrons across the surface of the target, where they collide with atoms in the process gas, stripping the electrons from the gas atoms and making them positive. Convert to ions. The gas ions are accelerated towards the negatively charged target, where they collide with the surface and are emitted from atoms on the target surface, atomic clusters or particles of the target material, and secondary electrons. Secondary electrons play a major role in sustaining the plasma. The discharged particles of the target material are neutral in charge, propagate in various directions through the vacuum space, collide with the substrate to some extent, and adhere to the substrate to form a film. Increasingly narrower formations and higher aspect ratios on the substrate reduce the allowable angle of the opening, thereby protecting the sides of the formation and consequently being blocked by the sides of the formation and the area around it. Increasing the incident particles further reduces the number of particles available for vapor deposition at the bottom.
EP 593924 describes an apparatus for generating plasma by cathode sputtering. The apparatus includes a magnetron cathode positioned above the substrate to be coated. A coil is provided around the space above the substrate connected to the high frequency power source. The coil is disposed in a groove on the inner surfaces of the two insulators. Each cover plate that functions as an antenna extends above the inner surface of each insulator, and a shield covers the lower surface and outer surface of each insulator.
Various methods have been used to cause propagating particles to make a linear motion perpendicular to the plane of the substrate. One method distributes the incident angle normally and blocks particles introduced at a small angle with respect to the collimator so that the particles passing through the collimator are only perpendicular or nearly perpendicular to the substrate. Using a physical collimator plate between the target and the substrate to improve the directionality of the incident particles. Another method known as long-throw sputtering is that only particles moving at or near normal to the substrate move across the length of the vacuum chamber and collide with the substrate. Thus, it is necessary to increase the distance between the substrate and the target. The collimator provides a source of particle contamination as the blocked particles accumulate in the collimator where a film is formed and eventually falls off. Both collimated deposition and long throw methods achieve directionality by eliminating material moving at a small angle with respect to the substrate, thus dramatically increasing the percentage of sputtered material incident on the substrate, Therefore, the deposition rate is significantly reduced. It also increases maintenance work for protection, reduces the use of target materials and reduces production.
Another way to derive the newly studied sputtered material is an ionized sputtering process, often referred to as ionized physical vapor deposition or IPVD. According to IPVD, the coating material is sputtered from the target using magnetron sputtering or other conventional sputtering or vapor deposition techniques. In the sputter coating method, the sputtered particles are emitted from the target at a wide emission angle. IPVD attempts to improve directionality by ionizing particles so that the particles can be guided electrostatically or electrically in a direction perpendicular to the substrate.
In IPVD, additional plasma is formed in the gas in the space between the target and the substrate through which the sputtered particles pass midway to the substrate. In the prior art, the additional plasma is formed in space by various methods, eg, capacitively coupling RF energy into a vacuum chamber downstream of the target, or electron cyclotron resonance (ECR) or other The microwave generation technology is formed away from the space and then flows into the space. Sputtered material particles passing through this space collide with metastable neutrons of electrons or ionized process gas. The collision strips the electrons from the atoms of the sputtered particles and leaves the particles in a positively charged state. These sputtered positive ions are then accelerated electrically, eg towards the substrate by applying a negative bias to the substrate.
The IPVD method in the prior art exhibits a number of drawbacks and problems that hinder the use of the particles in the manufacturing environment. Such a method, for example, has a low overall efficiency. In particular, the IPVD method typically has a low deposition rate. In addition, the prior art methods have a high level of film contamination. In particular, it has been found that in the prior art IPVD method, the filling of the high aspect ratio formation decreases as the sputtering power of the target increases. Such a fill reduction results in an aluminum alloy sputtering of 3 kW with a 304.8 millimeter (12 inch) magnetron target compared to the 12-30 kW typically achievable for target / magnetron assemblies. Limited to DC power. Low sputtering power results in a low deposition rate, resulting in reduced productivity and yield, and a sputtering time per wafer, eg, 10%, compared to typical wafer processing times of about 45 seconds to 1 minute. Increase contamination from 40 minutes to 40 minutes. Furthermore, it has been found that the fractional ionization of the sputtered material is low if the apparatus does not operate at a relatively high pressure, for example 20 to 40 mTorr, in the sputtering chamber. If an argon process gas is used, this pressure is typically 15 mTorr or higher than the desired sputtering pressure in the low milliTorr range. Higher pressures tend to reduce the quality of the deposited film properties and increase film contamination. Furthermore, higher pressures reduce process flat field uniformity and force a larger vacuum chamber structure, thus further reducing ionization efficiency. Another problem caused by the prior art IPVD method is unwanted sputtering of the RF electrode or element by plasma, flaking of the deposited sputtered material from the RF element by undesirable deposition, and deposition on the plasma or RF element. Short circuit of the RF element with the material formed, and other plasma and material interactions with the electrode or element used to couple RF energy into the plasma to ionize the sputtered material.
Accordingly, there is a need for an IPVD apparatus and method that overcomes the shortcomings and problems of the prior art. In particular, there is a need for a practical and effective IPVD device that results in acceptable overall efficiency, particularly high deposition rates, high sputtered material ionization efficiency, and low contamination of the deposited film. There is a particular need for an apparatus that forms a film of high uniformity and quality while providing high enough productivity to make the process commercially useful.
Summary of invention
Accordingly, the present invention is a process gas space sealed inside a vacuum chamber, a source of evaporated coating material, and located in the vacuum chamber opposite the source and facing the source. A physical vapor deposition method comprising providing a vacuum chamber having a substrate support for supporting a substrate, coupling RF energy to the chamber by a coil surrounding the space, and providing a shield in the chamber. Is oriented. In accordance with the present invention, the method provides ionized physical vapor deposition and provides a non-conductive protective structure between a coil and the space, wherein RF energy is passed through the protective structure. Coupled to the space, the shield being provided proximate to the protective structure, and physically protecting the protective structure from particles of coating material without electrically shielding the space from RF energy Shielding the plasma, energizing the plasma in the space with RF energy, ionizing particles of the coating material with the plasma, and directing ionized particles of the coating material from the space onto the substrate.
The present invention also provides a process gas space sealed in a vacuum chamber, to be kept at a low pressure level, a source of vapor deposition material in the vacuum chamber, and a source of vapor deposition material located in the chamber facing the source. A substrate support facing the source and supporting the substrate parallel to the supply source; at least one coil surrounding the chamber space between the substrate support and the surface of the supply source; and Directed to a physical vapor deposition apparatus that includes an RF energy source connected to and operable to energize the coil and a shield. According to the present invention, the device is an ionized physical vapor deposition device, further comprising a non-conductive protective structure disposed between the coil and a vacuum chamber space, wherein the RF energy source is the space. Operable to couple RF energy through a protective structure to energize the plasma in the gas within, with a shield circumferentially around the space of the vacuum chamber and outside the vacuum chamber Disposed and spaced inwardly from the protective structure to physically protect the protective structure from the sputtered material, the shield being at least partially sufficient to reduce circumferential current in the shield. Having at least one gap separating.
It is a principal object of the present invention to provide a method and apparatus for depositing thin films on narrow and high aspect ratio holes and trench bottoms and to some extent on the sides of VLSI and ULSI semiconductor wafers. In addition, the main object of the present invention is to provide a method and apparatus for performing ionized physical vapor deposition with high overall efficiency, and in particular, having high ionization efficiency of a coating material and providing a high vapor deposition rate over a wide range of pressures. . Yet another object of the present invention is to provide an IPVD method and hardware with low preventive maintenance requirements.
A particular object of the present invention is that the sputtering power at the target can be maintained at at least moderate levels and high RF energy coupling into the sputtered material without the need to keep the vacuum chamber at a relatively high sputtering pressure. It is to provide an IPVD apparatus and method that provides efficiency. Yet another object of the present invention is to adversely interact between the room plasma and the elements used to couple RF energy into the plasma to ionize the electrode or sputtered material, particularly sputtering from the electrode. It is to provide a method and apparatus that minimizes the possibility of sputtering, flaking or shorting of electrodes of the formed material.
In accordance with the principles of the present invention, the main plasma sputters material from the target while the RF element couples energy into the PVD process chamber and generates a secondary plasma in the chamber space between the main plasma and the substrate. In order to do so, an IPVD apparatus and method formed in the vicinity of a target is provided. The secondary plasma is typically an auxiliary to the main plasma confined in close proximity to the sputtering target. The secondary plasma generally fills the chamber, but mainly occupies at least a portion of the space between the target and the substrate, whereby particles of the sputtered material are deposited on the substrate with the aid of ions. The particles of the sputtered material are ionized while moving from the target so that they can be electrostatically accelerated towards the substrate.
The ionized and sputtered material is preferably accelerated towards the substrate by a negative bias applied to the substrate that can be controlled to optimally direct the moving ions without damaging the wafer surface. . Alternatively or additionally, the chamber is further between the substrate and the target to facilitate confinement of ionized and sputtered particles in a trajectory that is parallel to the chamber axis and perpendicular to the surface of the substrate. It can be surrounded by a permanent magnet or an electromagnet that forms an axial magnetic field in the room.
The RF ionization energy coupling element may be an RF electrode, preferably a conductor element such as one or more coils surrounding the chamber. As will be described in detail below, the RF element is located within the chamber, and may preferably be isolated from the chamber process gas or located outside the chamber.
Preferred devices also include non-conductive, non-magnetic that protects or shields the RF element from adverse interactions with the plasma, such as, for example, with the main plasma or with a secondary plasma generated by the RF element. A protective structure made of a dielectric material is provided. The protective structure is such that the sputtered material impinging on it adheres to the structure so that it does not fall from the structure and become a source of contamination. The portion of the protective structure is preferably further configured to prevent eddy currents in the layer of sputtered material deposited therein or thereon and to prevent electrostatic shielding of the RF element.
Various forms of RF elements and protective structures are possible within the scope of the present invention. For example, in one embodiment, the RF coil surrounds the chamber behind the protective structure, and the protective structure covers the RF coil with an outer conductive seal so that a portion of the vacuum hermetic inner wall of the chamber surrounding the processing space. Form. Alternatively, the RF coil is in the processing chamber vacuum outside and downstream of the perimeter of the target, and a protective structure separates the RF coil from interaction with the plasma. In another embodiment, a slotted or segmented insulator with a solid insulator that completely covers the conductor of the coil or with a slot that is narrow enough to prevent plasma formation in the vicinity of the conductor. In addition, an RF coil coated with a protective insulating material is provided. It is preferable that the RF coil and the protective structure have a cylindrical shape and surround the processing space.
The preferred apparatus further includes a shield array provided to shield the protective structure such that the function of the protective structure is not offset by the effect of deposition of the sputtered material thereon. Various embodiments of the protective structure and the shield array can be utilized as described in the following examples.
First embodiment
In this embodiment, the RF element consists of a helical coil that surrounds the vacuum chamber behind a generally cylindrical quartz window used as a protective structure. The generally cylindrical quartz window can form part of the vacuum-tight inner wall of the chamber, or it can be in the form of an insulator surrounding the coil inside the chamber, or in some other form that shields the coil conductor from the process gas.
A generally cylindrical shield is provided that surrounds the chamber adjacent to the window separating the coil from the PVD processing chamber. The shield is slit in a direction that is preferably parallel to the axis of the chamber. The term “close” means separated from the window by a sufficiently short distance to prevent plasma formation between the shield and the window. The slit shield follows the shape of the dielectric window separating the coil from the vacuum chamber and process gas. The shield prevents coating material from depositing on the window. If the material is conductive, an electrical short circuit of the coil will occur, preventing RF energy from being transferred into the chamber. The shield does not provide a circumferential passage around the chamber where the shield consumes energy from the RF coil and a circumferential current can be introduced that reduces the efficiency of the energy coupled into the auxiliary plasma. It is preferred to be slit in a manner. The shield further extends far enough in the axial direction to a short axial electric field across the RF coil, thereby optimizing the efficiency of inductively coupling energy into the plasma and reducing the capacity of the combined energy. In addition, the shield is held in close proximity to the window to prevent the generation of plasma behind the shield so that the plasma is more efficiently generated in the space through which the sputtered particles travel. This separation of the shield from the window is less than the average free path of the process gas atoms, ie the minimum diffusion length of the plasma in space.
The slit in the shield is wide enough to allow the plasma to form therein, so that the plasma is continuous by resputtering the deposition of the coating material in the window as a result of the coating material from the source passing through the slit. Thus, the plasma is removed.
The position and shape of the shield relative to the protective coating of the coil contributes to highly efficient plasma generation in the chamber space and eliminates losses due to the generation of plasma between the shield and the coil. As a result, high ionization efficiency of the sputtered material is provided.
In this embodiment, the generation of plasma in the ineffective area of the chamber, for example between the shield structure and the coil protection insulator or window, is prevented, thus eliminating the loss of ionization efficiency.
Second embodiment
According to this embodiment, a sealing body, dielectric window and solid or segmented insulator are used alone or in combination to protect the RF elements from plasma and sputtered materials. The shield is preferably in the form of a plurality of shield portions that can be biased to control its sputtering by plasma. The shield array has a plurality of voids that at least partially electrically shield the shield portion to prevent induced vortices from consuming energy and resisting coupling of energy to the plasma. Furthermore, the individual shield portions are preferably electrically separated so as to be individually biased to optimize the uniformity of the coating and the directionality of the ionized material onto the substrate. The space between the shield segments facilitates plasma propagation from behind the shield into the process space.
Third embodiment
In this embodiment, a helical coil surrounds the chamber behind the protective structure. When so arranged, the coil is protected from contact with the plasma formed in the chamber. The chamber is provided with an array of shields that also enclose the space between the target and the substrate and are preferably biased to control its sputtering by plasma. The array of shields has a plurality of air gaps that at least partially electrically isolate the shield parts, and the induced eddy currents partially consume energy and counteract the coupling of energy to the plasma. To stop. The shield portion is configured and oriented so that the shield portion protects the protective structure from the target, while having minimal impact on the coupling of energy from the coil and the formation and location of the secondary plasma, Defined.
The array of shields is positioned relative to the protective structure so that no coating is formed thereon, supports vortices therein, and electrostatically shields the RF coil. It is preferable that no part of the target is visible from any part of the protective structure, the target can be seen from any part of the protective structure, and if a coating of conductive sputtering material is deposited, it is coated. The region is not shaped to support vortices or to significantly shield the coil.
In the illustrated example of the third embodiment, the protective structure comprises a dielectric window. The shield array is formed from angled portions that collectively and completely block all the passages between the target and the window. The portion is angled so that much of the volume of the space between the main plasma and the substrate is visible from the coil. As such, the window is protected from sputter deposition from the target, while providing the most efficient coupling of energy to form a secondary plasma that ionizes the sputtered material. The shield portion is preferably spaced from the window, and the portion of the coil has a space between adjacent portions sufficient to allow viewing of the room space in which the secondary plasma is to be formed. Therefore, it is possible for the plasma to form in the vicinity of the window and extend into the space where the sputtered material can be ionized.
According to one illustrated example of this third embodiment, the shield array is located inside the window and is spaced apart in a plurality of axial directions inclined at an angle generally perpendicular to the path from the target to the window. It is formed from a frustoconical portion. The shield part may be inclined at the same angle relative to the chamber axis, or the part may be inclined at a different angle, for example the part may be inclined at a smaller angle relative to the axis at a further distance from the target. Is possible. The portion reduces overlap of the sputtered particles that have been diffused with minimal overlap, but preferably does not protect adjacent portions from points of the target. The shield part is preferably further segmented in the circumferential direction by a gap in the part to interrupt the potential induced current path.
According to another illustrative example of the third embodiment, the shield array has a plurality of flat or slightly curved rectangular extensions extending axially within the window and circumferentially spaced around the chamber. It is formed from a blade. These blades are spaced from the window and are inclined at an angle with respect to the radius of each chamber to protect the window centrally, or at least the portion of the window generally within the region of the coil from the entire area of the target However, a certain part of the coil is visible from the space of the room where the plasma is to be formed. Thus, the secondary plasma can be formed in the vicinity of the window and can immediately extend into the space through which the sputtered particles pass. The shielding part of this embodiment is preferably inclined at the same angle with respect to the radius of the chamber. Although minimal overlap is effective to further reduce window coating, it is preferred that the shielding portion does not protect the vicinity of the portion from any point on the target. The shielding portions are preferably spaced circumferentially relative to each other and separated from the target and the substrate by a distance equal to at least the mean free path of the gas molecules in the vacuum chamber.
When the present invention is used in a sputtering coating system, the sputtering power can be kept at a high level, thus maintaining a high deposition rate and a high ionization rate of the sputtered material. These results are achieved without the occurrence of many problems such as, for example, shorting of the RF coil or increased contamination and thus degradation of the deposited film. As a result, high aspect ratio formation can be effectively and efficiently filled by sputtering with a high directivity of the incident sputtered material normal to the plane of the substrate. The dense sputtering plasma is prevented from shorting or adversely affecting the RF plasma coupling element that generates the plasma that ionizes the sputtering material, thus eliminating the need to reduce the sputtering power of the prior art. The plasma formed by the RF element itself is prevented from shorting the element. The sputtering gas pressure is kept low, i.e. at normal sputtering levels, to prevent loss of directionality due to diffusion. The adverse effects from sputtering of the RF coupling element are eliminated. These advantages are achievable at processing times comparable to conventional sputtering methods that do not provide the high quality, high aspect ratio formation coatings provided by the present invention.
In addition to improving PVD processes, particularly sputter coating processes that deposit coatings in high aspect ratio formations, the present invention also provides an evaporation source or other source of evaporation material that is generally deposited by physical techniques. Offers advantages in the PVD process employed. Reaction methods and physical methods that are enhanced by chemical vapor deposition of materials or that include chemical vapor deposition may also be advantageous by the present invention. While the present invention is particularly useful in connection with the deposition of metal films, it can provide advantages in the deposition of other materials, particularly oxides and nitrides.
The above and other objects and advantages of the present invention will be readily apparent from the following detailed description of the preferred embodiments of the present invention.
[Brief description of the drawings]
FIG. 1 is a side view of an IPVD sputtering apparatus according to an embodiment of the present invention.
FIG. 1A is an enlarged side view of the protocol of FIG. 1 showing an alternative form of coil protection;
FIG. 2 is a perspective view of the shield of the apparatus shown in FIG.
FIG. 3 is a diagram of an IPVD sputtering apparatus according to an embodiment of the present invention.
4A to 4D are diagrams showing alternative coil configurations of the apparatus shown in FIG.
FIG. 5 is a diagram of an IPVD sputtering apparatus having an alternative form of secondary plasma RF coupling element and protective structure as opposed to that shown in FIG.
6 is a diagram of an IPVD sputtering apparatus having another alternative form of secondary plasma RF coupling element and protection structure as opposed to that shown in FIGS. 3 and 5;
7A to 7D are diagrams showing the form of the coil insulation protection structure in an alternative to the one shown in the embodiment shown in FIG.
FIG. 8 is a diagram of an IPVD sputtering apparatus according to an embodiment of the present invention.
FIG. 9 is a partial diagram of FIG. 8, showing an alternative form of the shield array,
10 is a cross-sectional view of the embodiment of the shield array shown in FIG. 9 taken along line 3-3 of FIG.
Detailed description of the invention
FIG. 1 shows diagrammatically a sputter coating apparatus 10 according to the principles of the present invention. The apparatus 10 includes a vacuum-tight processing space 11 sealed in a chamber 12. The chamber 11 is mounted with a substrate support, that is, a susceptor 14 that supports the semiconductor wafer 15 mounted thereon at one end. When mounted on the substrate support 14, the wafer 15 is parallel to and faces the target 16. Target 16 is formed from a sputter coating material that is deposited as a thin film of wafer 15. The processing space 11 is a generally cylindrical space, maintained at an ultra-high vacuum pressure level and filled with a processing gas such as argon during processing. The space 11 is located in the chamber 12 between the substrate support 14 and the target 16.
The target 16 is a part of the cathode assembly 17 that is mounted in the chamber 12 at the end facing the substrate support 14. The cathode assembly 17 includes a target holder 18 on which the target 16 is fixed. The magnet structure 19 is typically provided behind the target holder 18 on the side opposite the substrate support 14. A dark space shield 13 can be provided around the target 16. The magnet structure 19 is the surface of the target 16 that captures electrons emitted into the chamber 12 by the cathode assembly 17 when electrically energized to a negative potential as is well known to those skilled in the art. Preferably, it includes a magnet that generates a magnet tunnel closed above 21. The magnet structure 19 may include a fixed or rotating or otherwise moving magnet that may be any one of the permanent magnets or electromagnets of a number of magnetron sputtering assemblies known in the art.
When switched ON, the electrical energy source 20, which remains constant or pulsed, typically a DC power source, is connected between the cathode assembly 17 and the wall of the chamber 12, which is normally grounded and serves as the system anode. Has been. The cathode assembly 17 is insulated from the wall of the chamber 12. The power supply 20 is preferably connected to the cathode assembly 17 via the RF filter 22. An auxiliary energy source such as an RF generator 24 can also optionally be connected to the cathode assembly 17 via the matching network 25. A bias circuit 27 is also provided and connected to the substrate support 14 via a matching network 28. The bias circuit 27 supplies a bias to the wafer 15 mounted on the substrate support 14. A bipolar DC power supply or RF source can be used for this purpose. Stationary or pulsed power supply 20 and / or RF generator 24 generates a negative potential at surface 21 that causes electrons to be emitted from surface 21 of target 16. The emitted electrons collide with the atoms of the processing gas in the vicinity of the surface 21 of the target 16, are ionized, and are surfaced by the magnetic field generated by the magnet structure 19 until the main plasma 23 is formed in the vicinity of the target surface 21. Stays captured on 21. This main plasma 23 becomes a positive ion source of gas accelerated toward and against the negatively charged surface 21 that ejects particles from the target 16.
It can be considered that the space 11 between the target surface 21 and the substrate support 14 is formed by the two portions. One part of the space is mainly blocked by the plasma 23 and shaped to create a desired erosion pattern on the sputtering surface 21 of the target 1, while the second part of the space 11 is the remaining volume. And, it is located between the plasma 23 and the substrate 15 on the substrate support 14. The sputtered material particles from the target 16 are generally, but not entirely, electrically neutral, which can propagate only through momentum through the space 11 where they pass through the plasma 23 and volume 26 and strike the substrate 15. As particles. In the conventional sputtering apparatus, the neutral sputtered particles passing through the plasma 23 occupy a small volume near the target, and the neutral sputtered particles and the plasma 23 particles at the target operating pressure. Since there are few collisions between the two, they are not sufficiently ionized. Thus, in conventional sputtering, the neutral sputtered particles exit the plasma 23 in a nearly neutral state and remain neutral until deposited as a thin film on the substrate 15.
In VLSI and ULSI device manufacturing, particles are applied to the substrate in order to metallize the holes by coating the contacts at the bottom of the high aspect ratio holes and formation and filling the holes with sputtered conductive material. Collides on the surface of the substrate with a narrow angular distribution around the normal, so that the particles travel directly into the formation and onto the bottom of the formation, colliding with the sides of the formation or being shadowed. It is highly preferred that there is no occurrence. Such vertical impingement of particles on the substrate is facilitated by the apparatus 10 by ionizing the sputtered particles as they pass through the volume 26, thus causing the particles to generate a charge. The Once charged, the particles are either electrostatically accelerated into a trajectory that is parallel to the chamber axis and perpendicular to the plane of the substrate 15, or otherwise electrically or magnetically guided. sell. Such methods are known in the art as ionized physical vapor deposition (IPVD) or ion assisted sputter coating.
In accordance with a preferred embodiment of the present invention, ionization during the suspension of sputtered particles in the space 26 surrounds the space 26 but provides RF energy into the space 26 by providing RF elements that do not occupy the space 11. It is carried out by reacting, preferably by induction binding. Although it is possible to use coil shapes other than helical, the RF element is preferably in the form of a helical coil assembly 30. Examples of possible configurations of coil assemblies 30a-30d are shown in FIGS. 4A-4D. Further, the form of the coil assembly 30 should include coils, windings and / or devices consisting of coils and windings. In addition, RF energy can be pumped into the coil in ways other than shown, for example by adding a center tap to the center of the coil and installing the other two leads or vice versa. Is possible. The coil assembly 30 totally fills the space 26 by inductively coupling energy into the processing gas in the space 26, thereby forming a secondary plasma 29 that is distinct from the main plasma 23. Although not limited, an RF generator 32, preferably operating in the range of 0.1 to 0.2 MHz to 60 or 80 MHz, is connected to the coil assembly 30 via a matching network 33 to transfer energy to the coil assembly 30. A secondary plasma 29 is formed in the space 26 provided.
A processing gas source 40 is connected to the chamber 11 via a flow rate control device 41. The feed gas 40 for the sputtering process is typically an inert gas such as argon. For the reaction process, additional gases such as nitrogen and oxygen can be introduced via an auxiliary flow controller. A high vacuum pump 39 is also connected to the chamber 12 and draws the chamber 12 to a vacuum level in the range of milliTorr or sub-milliTorr. A pressure in the range of 5 to 50 milliTorr is preferred. Pump 39 maintains a very high vacuum with process gas at a flow rate in the range of 5 to 300 standard cubic centimeters (sccm) per second. The apparatus 10 also includes a main controller 50 which is preferably a microprocessor based programmable controller that operates to sequence and control the operation of the elements described above. The control device 50 includes cathode power sources 20 and 24, a substrate bias power source 27, an RF generator 32 for energizing a secondary plasma generating element as a coil assembly 30, a gas flow rate control device 41, a pump 39, and other devices 10 of the present invention. Has an output energizing the controllable element.
Via the matching network 28 to provide a force to accelerate positively ionized and sputtered particles toward and above the surface of the substrate to achieve the orientation of the ionized sputtered particles. The potential gradient may be maintained in the sheath of the plasma in front of the substrate support 14 by negatively biasing the substrate 15 with respect to the secondary plasma 29 by the bias power source 27 connected to the substrate support 14. A dipole DC power supply or an RF power supply can be used for this purpose.
Additionally or alternatively, a magnet 80 can be provided around the chamber 12 to generate a magnetic field in the axial direction in the chamber 12. The magnet 80 may be an electromagnet or may be formed of one or more permanent magnets. The magnetic field from the magnet 80 causes the charged particles to swirl around the line, thereby increasing radial confinement. In the presence of an axial electric field, the charged particles can be guided axially and move towards the substrate, minimizing radial losses.
A protective structure is provided between the coil assembly 30 and the space 11 to prevent the plasmas 23 and 29 from coming into contact with the coil assembly 30 and from interacting electrically. This structure is a non-conductive material that does not interfere with the magnetic field surrounding the coil assembly so that the coil assembly 30 does not enter the space 26. One preferred form of the protective structure is a dielectric material compatible with a vacuum, such as quartz, in the wall of the chamber 12 that is mounted to form a vacuum tight seal against the wall of the chamber 12. The structure of the window 60 made of The window 60 may be a single piece of electrically insulating and permeable material, or may be formed in joined segments to form a generally cylindrical protective structure. The coil assembly 30 described in the previous embodiment is preferably wound around the chamber 12 outside the window 60. The outer side of the coil assembly 30 is covered with a conductive metal sealing body 61, which shuts off the coil assembly 30, and electromagnetic energy from the coil assembly 30 and from the inside of the chamber 12 to the chamber. A sealed cavity 62 is formed so as not to be radiated to the outside of 12. Cavity 62 is sealed from chamber 11 but communicates with the external environment or is filled with an inert gas at atmospheric or lower pressure, and plasma formation occurs within cavity 62 when coil assembly 30 is energized. It may not be encouraged by gas.
The window 60 itself is not conductive, but is sensitive to the deposition of a coating of conductive material sputtered from the target 16. Conductivity in or on the window 60 aids in the induction of current around the chamber and reduces or eliminates the effectiveness of RF coupling of energy from the coil assembly 30 to the secondary plasma 29 in the space 26. Or inhibit. Such conductivity of the coating of the window 60, particularly in the azimuthal direction (circumferential direction), i.e. the direction extending around the chamber 12, creates an inductively coupled short circuit, and all of the energy inductively coupled into the space 26. Or many invalidations.
In order to prevent such deposition of conductive sputtered material in the window 60, suitable apparatus includes various embodiments of shield arrays as further described below.
First embodiment
FIG. 1 shows a slit cylindrical shield 100 provided between the space 11 and the window 60 in proximity to the inner surface of the window 60. The shield 100 preferably protects the window 60 from the material sputtered from the target 16 and blocks any direct line of sight between any portion of the surface 21 of the target 16 and the window 60. Furthermore, according to the present embodiment, the shield 100 has a longitudinal slit 103 that is parallel to the axis of the chamber 12. It is also possible to use a shield provided with one or a plurality of slits shaped to cut off current in the circumferential direction. This prevents the induction of current in the circumferential direction, that is, the azimuthal direction in the shield 100.
Further, the shield 100 has an axial extent beyond the axial extent of the coil assembly 30 that generally reaches the entire effective axial extent of the electric field from the coil assembly 30. As a result, the conductive shield 100 effectively suppresses the electric field in the secondary plasma 29 that is parallel to the axis of the chamber 12 and capacitively shields the coil assembly 30 from the space 26, so that the coil assembly 30. To prevent an electric field in the axial direction from decreasing the efficiency of energy coupling to the space 26. The shield 100 preferably extends axially from behind the surface 21 of the target 16 beyond the window 60 and the coil assembly 30. In such a configuration, the shield 100 more effectively shorts the axial electric field in the secondary plasma 29, thereby improving inductive coupling of energy from the coil assembly 30 into the secondary plasma 29.
The preferred embodiment of the present invention also provides a highly efficient coupling of energy from the coil assembly 30 because the shield 100 is closely spaced from the window 60. This distance is kept at a preferable distance that is smaller than the mean free path of the atoms or molecules of the gas or smaller than the minimum diffusion length of the secondary plasma 29 in the chamber 12. This close spacing from the shield to the window allows plasma formation adjacent to the non-conductive structure that protects the window or coil and behind any of the structures provided below. In contrast to the other examples. Eliminating the formation of plasma behind the window tends to increase the rate of energy from the coil or other plasma generating electrode into the space through which the sputtered particles pass, so that the effective plasma and hence sputtering Increase the ionization efficiency of the deposited material. It is planned to use a process gas pressure in the apparatus 10 in the range of about 5 to 50 milliTorr. The mean free path of argon gas at such pressure is 11 millimeters to 1.0 millimeter, respectively. As a result, the preferred spacing from the window 60 to the shield is about 1.0 to 15 millimeters.
On the other hand, the slit 103 is preferably made wider than about 15 millimeters. The width of the slit 103 is two to clean the sputtered material that may deposit on the edge of the shield 100 near the slit 103 or on the window 60 as a result of the sputtered material passing through the slit 103. Wide enough to allow the next plasma 29 to be formed by the slit 103. Such plasma 29 formed in the slit 103 extends to the window 60 in the vicinity of the slit 103 and is continuously removed by resputtering the material deposited in the window 60 in the slit 103.
Instead of the window 60, the coil assembly 30 can alternatively be embedded in an insulating block 66 within the chamber 12, as shown in FIG. 1A. Insulation block 66 functions in a manner similar to that of window 60 and shields coil assembly 30 from the plasma in chamber 11 and from the sputtered material. The shield 100 is configured for the insulating block 66 in the same manner as configured for the window 60 shown in FIG.
Many of the details of the first embodiment are useful for the embodiments described below, but are omitted to simplify the description so that differences between the embodiments can be emphasized.
Second embodiment
FIG. 3 shows an alternative to the shield 100 shown in FIG. 1, but shows a shield array 200 provided between the space 11 and the window 60 with less proximity to the inner surface of the window 60. . The shield array 200 protects the window 60 from material sputtered from the target 16 at least in part, but has sufficient space or voids 204 to facilitate coupling of energy from the coil assembly 30 into the space 26. .
The shield array 200 is a plurality of individual shields or shield segments 202 that protect at least the axial strips of the window 60 so that circumferential conductive paths are not formed by a coating of sputtered material. Is preferred. The gap 204 is shaped to substantially block the circumferential current path in the shield array 200 and is shaped to extend entirely or partially over the axial dimension of the array 200. The shield segment 202 must be made from a metal or other material selected to retain such a coating when a coating of sputtered material is formed on the shield shield 202. Otherwise, such coatings will fall and contaminate the chamber 12 and the wafer 15 being processed. In order to control the deposition of evaporated material on the shield segment 202 and thereby reduce the risk of contamination, the shield segment 202 may be electrically biased. The segment 202 is also biased to be used, for example, to optimize the coating uniformity on the substrate 15 and the orientation of the ionized material relative to the substrate, thereby optimizing the distribution of the film deposited on the substrate. It is also preferable to individually bias each of these to be individually controllable. In such a configuration, the air gap 204 completely isolates and electrically shields each individually biased shield segment 202 from each other. The bias is provided by a generator 206 connected through a filter or matching network 207 with each shield individually connected through a current limiting resistor 208. Resistor 208 may be variable, or other means for individually controlling the bias of shield segment 202 in response to controller 50 may be provided.
FIG. 5 shows an alternative embodiment for the device 10 in which the coil assembly 30 is inside the wall of the chamber 12 but is still located in the vacuum chamber 12 outside the space 11. The protective structure is between the coil assembly 30 and the space 11 and is in the form of a window 60a in a sealed body 61a that seals the coil assembly 30 inwardly from the interior of the chamber 12 wall. The sealing body 61 a includes a port 62 that vents from the inside of the sealing body where the coil assembly 30 is located to the vacuum of the chamber 12. The shield array 200 is positioned so as to protect the window 60a from the target 16 as in the previous embodiment.
Instead of the window 60 or 60a, the alternative embodiment shown in FIG. 6 utilizes a protective structure in the form of an insulating coating 86 that covers the conductors of the coil assembly 30. In this embodiment, the coil assembly 30 is located in the chamber 12 outside the space 11 and surrounds the space 26. The shield array 200 is positioned to protect the insulating layer 86 from the target 16 as in the previous embodiment. The insulating layer 86 may be in any of a number of forms, such as a solid insulator 86a that covers the entire conductor surface of the coil assembly 30 as shown in FIG. 7A, or a plurality of intermittent as shown in FIG. 7B. Insulator segment 86b may be used. In the segmented insulator 86b, the air gap 87 between the segments increases the effectiveness of the coil assembly 30, while the plasma is coiled by narrowing the air gap 87 below the mean free path of gas molecules in the chamber 12. It is preferable not to communicate with the conductor of the solid 30. Instead of the insulating coating on the coil assembly 30, insulating material may cover the coil assembly 30, such as insulators 86c and 86d shown in FIGS. 7C and 7D, respectively. Many other alternatives and protection structures for isolating the coil assembly 30 from these features and plasmas can be used in connection with other embodiments.
Third embodiment
FIG. 8 shows a shield array 300 provided between the space 11 and the window 60 in the vicinity of the inner surface of the window 60. The shield array 300 preferably protects the window 60 from material sputtered from the target 16 and blocks all direct line-of-sight between any portion of the surface 21 of the target 16 and the window 60. However, according to this embodiment of the invention, the shield array 300 provides a generally uninterrupted region between the coil assembly 30 behind the window 60 and the space 26 to which the plasma 29 is coupled, which Provides a space or gap 305 that facilitates coupling of energy from the coil assembly 30 and the propagating plasma into the space 26.
The shield array 300 is preferably in the form of a plurality of shields or shield segments 302 that collectively protect the window 60 from any location on the target 16. This protection almost eliminates the tendency of the sputtered film to accumulate and form on the window 60. Therefore, neither conductive paths nor electrostatic shielding occurs.
In one preferred embodiment of the invention, the shielding segment 302 is frustoconical and forms an angle .theta. With an inner surface parallel to the surface 21 of the target 16 and to the substrate 15 on the support 14. . The angle θ of each shielding segment 302 is the same, but the effectiveness of the shielding segment 302 can be improved, i.e. optimized, by decreasing the angle θ as the distance between the segment 302 and the target 16 increases. The top surface 303 of 302 faces the target 16 directly, providing maximum protection of the target 16 from the window 60 for a given segment area. The shielding segments 302 are located outside the space 11, surround the space 11 in the circumferential direction, and are separated from each other in the axial direction by a circumferential gap or space 305. The maximum width of the gap 305 is the largest gap S that still completely covers the surface of the target 16 from the window 60 as indicated by line 79, thus the circumferential band region of the window 60 is an annular conductive band around the window 60. It is not exposed to the toget 16 so as to deposit a piece. Accordingly, the maximum width S of the gap 305 can be increased at a greater distance from the target 16. The air gap 306 may be narrower, but should not be less than the mean free path of the process gas atoms at the chamber 12 temperature and pressure, but is most efficient for RF plasma into the space 26 in a given process state. Should be optimally spaced to promote proper diffusion. For the same reason, each segment 302 has a height H that can be the same for each segment 302 or can be modified to optimize the protection and space between segments 302. Good.
The ideal number of shielding segments 302 depends on the shape of the chamber 12. A single shielding segment 302 may be used, but typically 2 to 6 segments 302 are employed. In order to minimize RF plasma loss, the number of segments 302 is limited and the area of the accumulated shielding segment should be minimized. Further, in order to prevent the formation of closed circumferential passages for eddy currents or other currents induced by the RF coil assembly 30, the segments 302 have at least one air gap 304 that blocks each segment. Should. The gaps 304 in adjacent segments 302 can be straight as shown, or can preferably be staggered to prevent the deposition of continuous lines of film axially across the window 60. The air gap 304 should be wide enough to prevent arching and requires a width of about 1/4 to 1 inch, depending on processing parameters.
The air gap 304 is shaped to generally block current paths in the shield array 300 and to extend entirely or partially across the axial dimension of the array 300. The shielding segment 302 was selected to retain such coating when a coating of vacuum compatible inductive or sputtered material such as metal, ceramic or quartz was formed on the shielding segment 302. It can be made from other compatible materials. Otherwise, such deposits will fall and contaminate the chamber 12 and the wafer 15 being processed. In order to control the deposition of the material deposited on the shield array 300 and thereby reduce the risk of contamination, the shield segment 300 may be electrically biased and made of metal for its purpose. The shielding segment 302 is also used to optimize the distribution of the film being deposited on the substrate, for example by optimizing the coating uniformity of the substrate 15 and the orientation of the ionized material onto the substrate 15. Thus, it is preferable that each bias is individually controlled so that it can be controlled individually. In such a configuration, the air gap 304 completely separates and electrically shields the individually biased shielding segments 302 from each other. Bias is provided by a generator 306 connected through a filter or matching network 307, and each blocking segment 302 is individually connected through a current limiting resistor 308. Resistor 308 may be variable and may provide other means for individually controlling the bias of shielding segment 302 in response to controller 50.
The advantages of the shield array 300 described above can be implemented by an alternative embodiment having a shield array 300a, as shown in FIGS. The array 300a is formed from a plurality of flat or slightly curved rectangular segments 302a arranged as an array of blades or vanes around the periphery of the space 11 within the window 60. The segments 302a are circumferentially separated from each other by axial space or slots 304a. The slots provide space between the segments 302a that allow the plasma to couple into the space 26 and block potential circumferential current paths around the array 300a. The directions of the segments 302 a are such that each defines an angle φ with respect to the radial plane 311 through the axis 312 of the chamber 12. The spacing W between adjacent segments of the shielding segment 302a and between the shielding segment 302a and the window 60 is such that plasma is effectively formed in the vicinity of the window 60 and propagates into the space 26 of the air gap 304a between the segments 302a. It should not be less than the mean free path of gas in the chamber 12 as possible. The segments 302a are long enough in the axial direction to prevent the circumferential strip of coating from forming on the window 60 at the end of the segment 302a and are angled relative to each other to protect the entire target 16 at the window 60. It is preferable to set to φ and space W.
Instead of the window 60, the aforementioned shield array can be used for a dielectric window provided inside the chamber or for a coil in the chamber that is protected from plasma by insulation.
Those skilled in the art will recognize that the practice of the invention described herein can be varied and that the invention has been described with reference to the preferred embodiments. Accordingly, additions and modifications can be made without departing from the principles and intent of the present invention, and the details of the various embodiments can be interchanged.

Claims (8)

A sputtering apparatus (10-10b), the apparatus comprising:
A vacuum chamber (12) having a process gas space (11) enclosed within the vacuum chamber (12) and maintained at a low pressure level;
A source of sputtering material (16) having a sputtering surface in said chamber (12) ;
Supporting base plate (15), a substrate support in the chamber (12) and (14),
Sputtered material passes flying, volume of the chamber (12) and at least one coil (30 ~ 30d) on the outside (26),
Connected to said coil (30 ~ 30d) operates to bias the coil, an induced coupled to form the RF energy to the volume to form a secondary plasma, sputtered to fly through said volume An RF energy source (32) for ionizing the substance ;
Before Symbol coils (30 ~ 30d) and the non-conductive protective structure sandwiched between said volume (26) and (60,60a, 66,86 ~ 86d),
And RF energy is inductively coupled through the front Symbol protective structure (60,60a, 66,86 ~ 86d),
To physically shielded from the sputtered material protection structure, the outside of the volume in a vacuum chamber (12) (26), and said protective structure (60, 60a, 66, 86 ~ 86d ) In a sputtering apparatus including a shielding body (100, 300, 300a) disposed inside
Said shield (100,200,300,300a) is adapted to block the definitive circumferential direction of current to the shield around said chamber (100,300,300a), at least one extending in the axial direction One of a gap (103,204,304,304a),
The distance between the shield (100, 300, 300a) and the protective structure (60, 60a, 66, 86-86d) is such that the gas atoms in the volume of the space (11) in the chamber (12) Sputtering apparatus that is below the mean free path . The source (16) includes a sputtering target having a sputtering surface in the chamber (12), and the apparatus is configured to bias the target so that the apparatus generates a main plasma (23) in proximity to the sputtering surface. A cathode power supply (20, 24) connected to (16) and means (27) for electrically guiding ions of the material sputtered in a direction perpendicular to the substrate (15), the vacuum chamber ( 12) has dielectric windows (60, 60a) having opposite ends and sidewalls extending around the chamber between the ends, the sidewalls extending around the chamber (12) to provide a protective structure. The shield (300, 300b) surrounds the chamber (12) outside the volume (26) and is at least one inclined shielding segment inside the window and spaced apart from the window. (302), each segment facing the target (16), tilted at a fixed angle with respect to the sputtering surface of the target (16) and with respect to the axis of the target, It has a surface (303) that covers almost all points of the window (60, 60a) from the sputtering surface, and at least one gap (103, 204, 304, 304a) is around the chamber (12). in blocking a circumferential current path, wherein the shield is secondary plasma according to claim 1, characterized in that it is shaped to easily extend from the vicinity of the window to the volume (26) within the apparatus. The shield (300, 300a) includes a plurality of segmented shielding segments (302, 302a), and the shielding segments (302, 302a) are electrically separated by gaps (304, 304a). 3. A device according to claim 1 or claim 2 , wherein the devices are spaced apart. The shield (300) includes a plurality of axially spaced frustoconical shield segments (302), wherein the shield segment (302) is inclined to generally face the target (16); And spaced apart from each other so as to generally cover substantially all of the windows (60, 60a) from the target (16), each segment blocking at least a circumferential current path around the chamber (12). Having an axial gap (304), the axial spacing of the segments (302) is effective to facilitate secondary plasma extending from the window and into the volume (26). apparatus according to any one of claims 1 to 3, characterized in that the spatial from the window (60, 60a) defining the said volume (26) within. The shield includes a plurality of circumferentially spaced bladed shield portions (302a) having spaces extending in the axial direction therebetween, the shield (300a) surrounding the volume portion (26) from each other. Formed by a plurality of axially extending blades, each blade passing through the blade and at an angle relative to a radial plane (311) passing through the central axis (312) of the chamber (12) Tilted at (θ), the blades are oriented so as to generally cover almost all points of the window (60) from the target (16) and are spaced apart from each other, the blade (302a) Each of the shields (100, 20) is spaced apart from each other to define a space effective to facilitate the secondary plasma to extend into the volume (26) from the window into the volume (26). 300, 300a) covers the window (60, 60a) from the source of material (16) and extends sufficiently axially to electrically short out almost all axial electric fields in the plasma. The shield extends at least one axial length of the shield so as to block a circumferential conductive passage in the shield (100, 200, 300, 300a) around the chamber (12). A plurality of axial slits (103, 204, 304, 304a), wherein at least one slit (103, 204, 304, 304a) in the shield allows the formation of plasma in the slit. chamber (12) sufficiently wider than the mean free path of the gas atoms, said shield (100,200,300,300A) of at least the coils (30 ~ 30d Has a high a axial length of the of the non-conductive protective structure comprises a dielectric window (60, 60a) in the wall of the chamber (12), said coil (30 ~ 30d) said chamber (12) the apparatus according to that which is located behind the windows outside the preceding claims, characterized in any one of up to claims 4. Ions of sputtered means for guiding ions of the material is sputtered in a direction perpendicular to the substrate by electrically biased substrate (15) on a connected said support to said support (14) Materials apparatus according to any one of up to claims 1 to 5, characterized in that it comprises biasing energy generator (27) accelerates. Preparing a sputtering apparatus (10 to 10b) according to any one of claims 1 to 6,
Inductively coupling RF energy into the chamber (12) through the non-conductive protective structure (60, 60a, 66, 86-86d) by the coil (30-30d);
Physically shielding the protective structure from flying sputtered material by the shield (100, 300, 300a) without electrically shielding the space (11) from RF energy;
Energizing the plasma in the space (11) with RF energy;
Energizing the source (16) to sputter sputtering material;
Ionizing the sputtering material particles with plasma. Further comprising the step of biasing the shield (100,200,300,300a) to control the distribution of a material being sputtered, the step of subjecting said bias plurality of electrical said shield (300 and 300a) the method of claim 7 to the classified partial (302,302a) individually and selectively comprising biasing.

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