Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/32—Gas-filled discharge tubes
  • H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
  • H01J37/3411—Constructional aspects of the reactor
  • H01J37/3447—Collimators, shutters, apertures
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/0021—Reactive sputtering or evaporation
  • C23C14/0036—Reactive sputtering
  • C23C14/0068—Reactive sputtering characterised by means for confinement of gases or sputtered material, e.g. screens, baffles
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/04—Coating on selected surface areas, e.g. using masks
  • C23C14/042—Coating on selected surface areas, e.g. using masks using masks
  • C23C14/044—Coating on selected surface areas, e.g. using masks using masks using masks to redistribute rather than totally prevent coating, e.g. producing thickness gradient
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/32—Gas-filled discharge tubes
  • H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/32—Gas-filled discharge tubes
  • H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
  • H01J37/3464—Operating strategies
  • H01J37/347—Thickness uniformity of coated layers or desired profile of target erosion

Definitions

• the present invention relates to sputter deposition and. more specifically, to reactive sputter deposition used to coat a substrate with a film that is a combination of the target material and a reactive gas.
• Sputter deposition is a generally known method of depositing a layer of material onto the surface of a substrate workpiece. such as a semiconductor wafer.
• a substrate to be coated is placed generally opposite a sputter target of the material to be deposited and an ionized gas plasma is formed in the area of the target.
• the target is electrically energized with a negative electrical polarity opposite the polarity of the ionized gas particles in the plasma, while the deposition chamber or enclosure is grounded so as to create an electric field at the target.
• the ionized plasma atoms under the influence of the electric field, bombard the target surface and dislodge or "sputter" particles of target material which travel away from the target. Since the substrate is usually positioned opposite the target, the sputtered panicles deposit on the substrate to form a deposition film layer of the target material on the substrate.
• Reactive sputter deposition is a form of sputter deposition which
• a chemically reactive gas such as nitrogen or oxygen
• an inert gas such as argon
• the plasma produces the ions that sputter the target ejecting particles that project onto the substrate.
• the target panicles As the target panicles are deposited on the substrate, they come into contact and react with the reactive gas at the surface of the substrate causing a film to fo ⁇ n on the substrate surface that is a product of the chemical reaction. Therefore, in reactive sputter deposition, the composition of the deposited film is a chemical combination of both the target material and the reactive gas.
• sputtering an aluminum target in the presence of inert argon gas will yield an aluminum film on the substrate.
• particles are reactively sputtered from an aluminum target in the presence of an argon-oxygen gas combination
• the film deposited on the substrate is the ceramic aluminum oxide.
• targets sputtered in the presence of other reactive gas combinations will yield various other reactant films on the substrate.
• a recurring problem with reactive sputtering is that the chemical reaction between the reactive gas and the target particles takes place not only at the surface of the substrate but also at the sputtering surface of the target. As a result, an undesired reactant film forms on the target.
• This problem is pa ⁇ icularly troublesome when the reactant film that is formed is an electrically insulating material, such as, for example, the ceramic aluminum oxide.
• an insulating reactant film is formed on the surface of the target, it causes plasma instabilities, - electrical arcing, and the generation of contaminating particles in the sputter deposition chamber. These results are undesirable in a sputter deposition chamber and adversely affect the proper deposition of a film on a substrate.
• the sputter target and the substrate be increased in order to reduce the tendency of the inert gas and the reactive gas to intermix and in order to physically isolate the target from the reactive gas.
• the deposition rate is reduced and the thickness uniformity of the film deposited on the surface of the substrate is also reduced. Uniform thickness of the deposition film
• Another way of reducing the formation of a reactant film on the surface of the target is to bias the target such that it is sputtered away at a rapid rate that is faster than the reaction rate of the reactive gas with the target. Rapidly sputtering the target yields a clean target surface and prevents the formation of a reactant layer on the target.
• the rate of sputtering is increased, the rate of deposition on the substrate is also increased. At an increased deposition rate, the sputter particles do not have time to sufficiently react with the reactive gas at the surface of the substrate, and the desired reactant film is not formed. It has also been proposed to rapidly sputter the target and increase the concentration of reactive gas at the substrate surface. However, an increased concentration of gas requires the introduction and evacuation of gas at a rate that may not be possible without the use of an increased number of pumps or larger
• the uniformity of the film thickness is a function of many factors, including the relative ion concentration and the shape of the gas plasma which sputters the target, such as that which results from the shape of the magnetic fields which may be used to enhance the plasma formation over the target.
• Other factors include the shape of the vacuum chamber containing the substrate, the spatial effects of any other structures or devices located within the chamber proximate the target and the substrate, as well as any external or internal electric or magnetic field effects associated with sputter deposition chamber.
• the shape of the target and its orientation with respect to the substrate may also result in a non-uniform film.
• an objective of the present invention to reduce the formation of a reactant film on the surface of the sputter target while providing the proper reaction conditions at the substrate surface for the deposition of the desired reactive material film on the substrate. It is a further objective of the present invention to provide a means for selectively controlling the rate of deposition on a substrate and selectively varying the thickness of a deposited film, such as to improve the uniformity of the thickness of a sputter deposited film.
• the present invention accomplishes these and other objectives by providing a stationary apermre plate which is mounted between and generally parallel to the sputter target and a substrate upon which a reactant material film is to be deposited.
• the stationary aperture plate includes a plurality of low aspect ratio apertures formed therein which have walls oriented generally perpendicularly to the target and substrate to intercept some of the sputter panicles traveling from the target. Other sputter panicles that are not intercepted by the plate pass through the plate and deposit themselves upon a surface of the substrate. The rate of sputtering from the target is therefore higher than the deposition rate due to the interception of the panicles by the plate.
• the rate of sputtering from the target may be kept sufficiently higher than the reaction rate of the reactive gas with the target so as to prevent the formation of a reactant film on the substrate surface while providing the desired film on the substrate.
• the apertures of the plate of the present invention have low aspect ratios, such that when placed between the sputter target and the substrate, the plate is generally non-collimating. Therefore, the sputter panicles are generally not focused into columns or beams of panicles, but rather are distributed at random flight paths onto the substrate surface. Further, the plate is spaced a sufficient distance from the substrate, preferably 0.5 to 1 inch, such that the plate is virtually shadowless. In this way, there is no masking of apertures of the plate onto the substrate surface. Due to the plate and the effect of the apermres, the deposition rate is maintained sufficiently low to allow complete reaction between the sputter
• the stationary aperture plate creates and maintains a difference between the sputter rate and the deposition rate in order to prevent the formation of a reactant film on the target.
• the target is sputtered away at a sufficiently high rate, keeping the target surface clean and free from the formation of a
• the cross-sectional area, depth and density of apermres of the plate may be selectively varied across the plate to achieve different deposition rates at different areas on the substrate.
• the apertures might be varied in cross-sectional area, depth and/or density to provide different deposition rates at different radii outwardly from the center of a circular substrate such as a traditional semiconductor wafer.
• the variation in deposition rates achieved by the apermre plate is a function of the cross-sectional area, depth and density of the apertures on the plate.
• the apertures are increased or decreased in cross-sectional area, or alternatively, increased or decreased in depth such as by changing the thickness of the plate in different areas, to achieve the desired deposition rates on different areas of the substrate.
• the dimensions of the aper res and their density determine the percentage of sputter particles that are intercepted by the plate, and the extent to which they are varied across the plate determines the effective variation in deposition rate that is achieved at different areas across the substrate or wafer. Therefore, using selective variation of the apermre dimensions and/or density, the deposition rates may be made selectively higher in some areas of the substrate relative to other areas on the substrate. By varying the deposition rates achieved
• the plate having apertures of varied cross- sectional area and depth also preferably has apertures of a low aspect ratio such that they are generally non-collimating. Further, the plate is preferably spaced a sufficient distance, at least approximately 0.5 inches, from the substrate so as not to leave a mask pattern of the apermre plate in the film layer deposited on the substrate. If collimation is desired, the aspect ratios of the plate might be adjusted to accomplish collimating as long as the varied deposition rates at the different areas of the substrate are also accomplished in accordance with this one feature of the present invention.
• apertures of larger cross-sectional area around the periphery of the aper re plate than at its center will provide a greater deposition efficiency at the center of the substrate relative to the substrate edges.
• This, in m may cause a greater film thickness at the edge of the substrate than at the substrate center, or the higher deposition rate may be necessary to compensate for the common tendency of the deposition rate of sputter deposition to be greater at the substrate center.
• apermres shallower in depth at the periphery of the plate than at its center.
• the wall depth of the aper re is shortened, and the probability that a sputter particle will strike a wall and deposit thereon is reduced. Reducing the probability of capmring sputter particles with a particular aperture increases the probability that a sputter particle will be deposited beneath that apermre on the substrate. Therefore, a shallower apermre means a higher deposition rate beneath that apermre than beneath a deeper aperture.
• the aperture cross-section might be made larger and/or the aperture shallower at the center of the plate to provide a greater deposition rate at the center relative to the periphery of the substrate.
• the aperture plate of the present invention is used to selectively vary the deposition rates in different areas of the substrate to achieve either a generally uniform film thickness on the plate, or to achieve a film of selected, varying thickness across the substrate. Therefore, the apermre plate of the present invention reduces the formation of a reactant film layer on the target surface while allowing sufficient chemical reaction at the substrate surface.
• the aperture plate of the present invention provides selective variation of the deposition rate across the surface of the substrate to achieve variable film thicknesses or a more uniform film thickness on a substrate, as desired.
• FIG. 1 is a front elevational view, in cross-section, of a reactive sputter deposition chamber showing use of the stationary aperture plate of the
• Fig. 2 is a diagrammatic cross-sectional view along lines 2-2 of Fig. 1 of the stationary aperture plate and substrate.
• Fig. 3 is a fragmentary top plan view of an embodiment of the stationary apermre plate.
• Fig. 4 is a cross-sectional view similar to that of Fig. 2, of an alternative embodiment of the stationary apermre plate of the present invention.
• a reactive sputter deposition chamber 5 includes a vacuum housing 10 containing a sputter target 12 mounted to a mounting structure 14 and a substrate workpiece or wafer 16 mounted to a support 18 generally opposite the target 12.
• An ionizable inert gas such as argon, is introduced into the housing 10 in the proximity of the target 12 through a gas inlet, such as nozzle 20.
• the ionizable gas is ionized into a gas plasma which contains positively ionized gas atoms.
• the gas may be ionized into a plasma through any of the commonly acceptable methods. For example, by energizing the target 12 negatively through power, source 11 with respect to
• the positively ionized plasma atoms of the gas plasma are then attracted to cathode target 12 under the influence of an electric field, and the positive gas ions bombard the target 12 to dislodge or "sputter" the target particles 22 from the target 12.
• the dislodged target particles 22 travel away from target 12 and assume various flight paths, as indicated by the arrow 23.
• the panicles 22 predominately travel generally perpendicular to the bottom target surface 28; however, various other flight directions are also assumed by the panicles 22.
• Preferably a majority of the sputter particles 22 travel in a vertically downward direction as shown in Fig. 1, or in a direction generally perpendicular to the planar surface 24 of substrate 16 so that a large percentage of the particles 22 are deposited upon surface 24 of substrate 16 to form a film 27 on the substrate surface 24.
• a reactive gas such as oxygen or nitrogen is introduced into the housing 10 in proximity to the substrate 16 through appropriate means, such as a nozzle 26.
• the reactive gas (not shown) reacts with the sputter particles 25 which deposit on the substrate surface 24, and the gas chemically alters the particles 25 to yield a film layer 27 on surface 24 which is a chemical combination of the target material and the reactive gas (see Fig. 2).
• the sputter particles 22 are aluminum, and in the absence of a reactive gas, a film of aluminum is deposited upon substrate 16.
• a reactive gas such as oxygen
• a stationary apermre plate 30 in accordance with the principles of the present invention is positioned in housing 10 generally between target 12 and substrate 16.
• Fig. 2 shows an enlarged diagrammatic cross-sectional view of a region of the stationary aper re plate 30.
• Apermre plate 30 has a plurality of openings or apermres 32 extending through the plate.
• the apermres 32 are defined by opposing aperture walls 34 as discussed hereinabove.
• sputter particles travel toward substrate 16 and, if unhindered, will strike the exposed surface 24 of substrate 16 to form film 27.
• some of the sputter particles such as those particles having a flight path similar to arrow 38, impact with an aperture wall 34 and will be deposited thereon instead of substrate 16.
• Other sputter particles such as those having a path similar to arrow 40, pass through the apermres 32, avoiding walls 34, and are deposited upon substrate surface 24.
• the accumulation of sputter particles 22 intercepted by the walls 34 of apermre plate 30 is indicated by reference numeral 42.
• the interception of sputter particles 22 by the walls 34 of aperture plate 30 reduces the number of sputter particles 25 which make it past the aperture plate 30 to be deposited on substrate surface 24. That is, the number of particles 22 incident upon the top plane 41 of plate 30 is greater than the number of particles 25 which pass through the bottom plane 46 of the plate 30 to deposit on substrate 16.
• the sputter rate is defined as the number of particles that are sputtered from target 12 per unit time
• the deposition rate is defined as the number of sputtered particles which deposit on the upper exposed surface 24 of substrate 16 per unit time.
• the rate of production of sputter particles 22 from target 12, i.e., the sputter rate, is indicated by the relatively large number of arrows 23 that are incident on the top plane 41 of the plate 30 compared with the smaller number of arrows 44 which pass through the plate 30 and through the bottom plane 46 of the plate 30. Since a percentage of sputter particles 22 are intercepted by the aper re walls 34 of plate 30. the number of sputter particles 25 deposited on substrate surface 24 per second, i.e., the deposition rate, is less than the sputter rate as illustrated by the smaller number of arrows 44 on the bottom side of plate 30.
• the apertures 32 of plate 30 have relatively low aspect ratios.
• high aspect ratio apermres intercept a large percentage of sputter particles and focus the sputter particles into generally highly defined columns or beams of sputter particles. Such focusing by high aspect ratio apertures is referred to as collimation.
• the aperture plate 30 of the present invention is substantially non-collimating. That is, the apermres 32 of the plate 30 do not substantially focus or collimate the incident sputter particles 22 into focused beams or columns by eliminating all particles 22 incident to the plate 30 except those having a generally perpendicular flight path with respect to the plate 30 and substrate 16.
• the substantially non-collimating plate 30 generally intercepts only a relatively small percentage of sputter particles. Utilizing low aspect ratio apertures, the rate reduction between the sputter rate and the deposition rate achieved by plate 30 is between approximately 20 and 40 percent, and preferably between 25 and 35 percent. That is, using the plate 30 of the present invention, the deposition rate is generally only 25 to 35 percent less than the sputter rate. Commercial collimators, on the other hand, with high aspect ratio apertures, achieve a reduction in the rate of deposition from the rate of sputtering in the range of approximately 90 to 95 percent. Such a rate reduction is undesirable due to the waste of deposition material and the increased amount of time associated with depositing a film 27 of predetermined thickness on
• plate 30 is spaced from the substrate 16 a sufficient distance so that there is no sharp delineation of the apermre pattern on the surface of substrate 16. That is, plate 30 is virtually shadowless. In this way, the plate 30 does not mask the apermres onto the substrate 16 to produce a film layer which reflects the apermre pattern, but rather provides sufficiently equal deposition rates across the substrate surface 24 to achieve a generally uniformly thick layer on substrate 16 as may be desired.
• the plate 30 is spaced from the substrate 16 approximately 0.5 to 1 inch, or more, to reduce or eliminate any masking or shadowing effects that may occur on substrate surface 24.
• the target 12 may be sputtered away at a first rate, but the effective deposition rate on substrate 16 which is achieved below plate 30 is at a second rate which is less than the sputter rate or first rate.
• the target 12 may be sputtered away at a rate that is greater than the rate of reaction between the reactive gas and the target 12 so that the target surface 28 remains "clean" and free from the formation of a reactant film on the target 12. Since the deposition rate, or second rate, is less than the sputter rate, there is a sufficient amount of time for the particles on the surface 24 of substrate 16 to react with the reactive gas and form reactant film 27, despite the relatively high sputter rate.
• the desirable reaction between the deposited particles 25 and the reactive gas may be achieved without the necessity of boosting the concentration of reactive gas in proximity to substrate 16, thus eliminating the need for an increased number of larger pumps for evacuating the gas.
• Reactive sputter deposition is achieved using plate 30 without the undesired formation of a reactant layer on the target which may cause plasma instabilities, electrical arcing and the generation of contaminants in the sputter deposition chamber. Further, since the plate 30 is substantially non-collimating, there is not a lot of waste of sputter material that occurs due to the plate, and a layer may be deposited on substrate 16 quickly and more efficiently.
• the apermre dimensions of the apermres 32 of plate 30 may be tailored to achieve the desired reductions in deposition rate required in accordance with the principles of the present invention as just described.
• the dimensions of the apertures 32 determine the number or percentage of sputter particles 22 which pass through the apermre 32 and are deposited on substrate 16. Both the cross- sectional area of apermre 32, as indicated by reference numeral 50, and the depth, as indicated by reference numeral 51.
• the ratio of the depth 51 of apermre 32 to the cross-sectional area 50 of the aper re determines the percentage of incident sputter particles 22 which pass through plate 30.
• the ratio of aper re depth 51 to apermre cross-sectional area 50 is sometimes referred to as the "aspect ratio".
• an aspect ratio of 1 corresponds to those apertures which have the same depth 51 as diameter 50.
• the apermres 32 are generally in the range from 0.05 to 0.5, which correspond to apermre depth to diameter ratios of 1:20 and 1:2, respectively.
• the plate 30 of the present invention is substantially non-collimating as discussed above. In this way, the sputter deposition is maintained generally non-focused over the area of die substrate. Further, due to its substantially non-collimating nature, the plate 30 sufficiently reduces the deposition rate from the sputter rate in order to provide a clean target surface in accordance with one of the objectives of the present invention without blocking too large a percentage of the sputter material from the substrate. Therefore, the substrate may be coated with a film at a sufficient rate to have desirable substrate throughput in the deposition chamber, despite the reduction in the sputter rate to reduce and/or eliminate the undesirable target reactant film.
• the uniformity of the film 27 deposited upon the exposed surface 24 of the substrate 16 is often an important parameter.
• Non-uniform thickness of a layer deposited upon a substrate may reduce the yield of devices from the substrate and may also degrade the operation of the electrical devices which are yielded from the substrate.
• the apermre plate includes apermres of selectively varied cross-sectional areas and depth and various different aspect ratios in selected areas of the plate, as well as different aperture densities in selected areas of the plate. The selectively varied aperture dimensions and densities on the plate act to selectively vary the deposition rate in selected areas of the substrate.
• Fig. 3 shows a top view of one embodiment of an apermre plate with apertures having various different aspect ratios in accordance widi the principles of the present invention.
• Plate 49 has a series of circular openings or apertures 52 arranged around the circular plate 49.
• the apertures 52 are arranged concentrically around the plate 49; however, the size and spacing of the apertures may dictate that an arrangement other than concentric be used. This is especially true toward d e center of plate 49 where space constraints are higher.
• the apermres 52 of plate 49 are shown to be generally circular in Fig. 3, other shapes may readily be used to accomplish the results of the apermre plate 49 as mentioned above.
• the plate is divided into two regions according to the size of the apermres 52 as noted by imaginary line 55 and reference numerals 54 and 58. Additionally, other regions might be noted rather than just a center region 58 and a peripheral region 54 surrounding center region 58.
• the apermres, such as aperture 53 in the peripherai region 54 of plate 49 have larger diameters than the diameters of the apermres, such as apermre 56. located in the center region 58 of apermre plate 49.
• Plate 49 has a generally uniform thickness throughout so that the apertures 52 are
• the larger diameter peripheral apertures 53 have a lower aspect ratio than the center apertures 56 because the depth to diameter ratio is smaller for the larger diameter apermres 53.
• the apermres 53 wim lower aspect ratios intercept a lower percentage of sputter particles than apermres 56 which have higher aspect ratios because of their smaller diameter, as will be further illustrated below. Therefore, the peripheral apermres 53 allow a greater number of incident sputter particles to pass through plate 49 during a sputter deposition process than do the center apertures 56. This, in turn, causes a relatively higher deposition rate at the periphery of a substrate located below the plate than is achieved at the center area of the substrate.
• the deposition rate proximate the center region 58 of plate 49 is also defined by the apertures 56 at the center of the plate 49 and their associated aspect ratios.
• the apertures 52 of the aperture plate 49 in Fig. 3 are shown to gradually decrease in diameter and thus increase in aspect ratio from the outer peripheral region 54 to the center region 58.
• the deposition rate is gradually reduced from the outer peripheral area of the substrate, which experiences the highest deposition rate because it underlies the peripheral region 54 of plate 49, to the center area of the substrate which underlies plate center area 58.
• the plate 49 of the present invention by creating a higher deposition rate at the peripheral area of the substrate, compensates for the often occurring tendency in many sputter deposition chambers and applications to have a higher deposition rate, and hence, a greater film thickness, at the center area of the substrate than at the peripheral edges.
• Deposition variations and resulting film thickness variations are caused by such factors as plasma density and the shape of the target, as well as the orientation of the substrate with respect to the target.
• Plate 49 may thus be utilized to achieve a more uniform thickness of the deposition film on a substrate. It may further be used to achieve a thicker film thickness around the periphery of a substrate than at its center if that is a desirable result. It has been empirically found that a deposition rate variance of approximately 10% between the center area and peripheral area of a substrate is all that is necessary to achieve an uniform film thickness in many, but not all cases. However, with the plate of the present invention, any rate variance may be achieved, as is required.
• the apermre plate may be utilized to decrease the deposition rate around the periphery of a substrate while increasing the deposition rate around the center area of the substrate, if so desired.
• center apermres 56 would be increased in diameter and peripheral apertures 53 decreased in diameter so that the larger apermres with lower aspect ratios are proximate center region 58 of plate 49 while the smaller apermres are located in peripheral region 54.
• the diameters and aspect ratios of the apermres 52 of plate 49 may be selectively varied in order to achieve other different deposition rates in selected areas of a substrate. In this way, the aper re plate 49 may be utilized to selectively vary the thickness of the deposited film across the surface of the substrate or to achieve a
• the apertures in the peripheral area would be positioned closer together than those in the center area.
• various deposition rates may be achieved by selectively varying the density of apermres around the plate.
• peripheral region 54 and center region 58 are not specific and may be redefined by moving imaginary line 55 to define different region boundaries. Further, omer regions might be defined on me plate having additional apermres of still different aspect ratios than the center apertures 58 and peripheral aper res 53. Additionally, while d e apermres 53, 56 are shown to taper in diameter within me regions moving toward the center of the plate 49, each region might contain aper res of all one aspect ratio unique to that plate region and different from me other plate regions. As discussed hereinabove, the aspect ratio of the aperture plate is defined as the ratio of the cross-sectional dimension of the aperture, such as diameter, to the depth of the aper re.
• a high aspect ratio apermre will generally have a longer depth and/or a smaller diameter d an a low aspect ratio apermre, which generally has a shorter depth and/or larger diameter.
• High aspect ratio aper res capmre a greater percentage of incident sputter particles man low aspect ratio apermres and thus reduce the sputter deposition rate to a greater extent than low aspect ratio apermres.
• the aspect ratios of the apermres are selectively varied by varying the thickness of the plate, i.e., by varying the depth of the apertures instead of varying the diameter of the apertures as shown in Fig . 3.
• stationary apermre plate 64 has a series of
• apertures 66 therein through which sputtered particles pass to be deposited upon a substrate.
• aper res 66 have aperture walls 68 which capmre a percentage of the incident sputtered particles such as particles indicated by arrows 70.
• the deposition rate below the bottom plane 72 of plate 64 is lower than the sputter rate above the upper plane 74 of plate 64.
• the particle flight path may be characterized by a "flight angle" which is defined herein as the angle ⁇ of the particle flight with respect to an imaginary line 77 that extends generally parallel to the plane of plate 64.
• a sputter panicle which assumes a flight path that is essentially perpendicular to surface 74 of plate 64 and parallel to line 77, would have a flight angle of approximately 0"
• a sputter particle having a flight angle of 45 * or 135 * with respect to plate surface 74 is assigned a flight angle of 45 * .
• a particle having a flight path that is 10° above the horizontal plane of plate 64 is assigned a flight angle of 80" , and so on. Therefore, the flight angle of a sputter panicle as defined herein generally falls into the range of 0-90" with respect to die plate 64. Lower flight angles signify particles which are close to parallel with line 77 and perpendicular to plate 64,
• Each apermre in turn, has an associated critical angle that is determined by the dimensions of the apermre and is also defined with respect to line 77.
• the apermre critical angle indicates the maximum flight angle that a
• sputter particle 70 may assume and still pass through the apermre when it is incident upon the aper re at one of the farthestmost ends of the apermre.
• Particle path 80 and apermre 76 of Fig. 4 illustrate the critical angle of the apermre 76. If a sputter particle has a flight angle greater than the critical angle of the apermre or if it is incident upon die aperture somewhere in the middle of me apermre and has a flight angle close to or equal the critical angle, it will generally strike the walls of the aperture and be collected thereon.
• particle 82 of Fig. 4 has an angle greater than the critical angle of apermre 64 and strikes the aperture wall.
• sputter particles with flight angles below the critical angles will pass through the aperture and deposit upon die substrate.
• the higher the critical flight angle of the aperture the greater the percentage of particles mat will pass through the aperture, because a high critical angle, such as 80 * , means that the apermre will allow all particles having an angle below 80 * to pass through the aperture, and will intercept only that percentage of particles having angles between 80 * and 90' .
• the critical flight angle of the aperture is determined by me depth and cross- sectional dimensions of the apermre, i.e. , by the aspect ratio of the aperture. In Fig. 4, the angle ⁇ represents the greatest flight angle that a sputter particle, such as a particle indicated by arrow 80, may have and pass through apermre 76.
• Angle ⁇ is therefore the critical angle of the apermre 76.
• me critical angle would be smaller, signifying a higher aspect ratio, and a greater percentage of sputter particles would be intercepted. Therefore, the aspect ratio of an apermre is inversely proportional to the critical angle defined by that apermre.
• a high aspect ratio corresponds to a small critical angle and a greater percentage of blocked particles.
• a low aspect ratio apermre defines a high critical angle so that a greater percentage of particles pass through the apermre.
• a circular apermre with an aspect ratio of 1 has a diameter which is generally equal to the apermre dep i and a critical flight angle of 45 " .
• an aspect ratio of 1/5 or 0.2 corresponds to a critical flight angle of approximately 79" .
• the critical flight angle assumes, as discussed above, Uiat the particle is incident upon d e apermre at one of the farthermost sides of the apermre.
• Particle flight path 82 of Fig. 4 shows such a particle incident upon die plate at the farthestmost side of apermre 76.
• the flight angle distribution of sputter particles is not generally equally distributed over die range of angles from 0-90° due to such factors as me shape of the deposition chamber, me relative density and shape of the plasma and die location and shape of the target with respect to the substrate. For example, there may be more particles with a flight angle of 75° than 45° and so forth. Further, each of the sputter particles will not strike an apermre at the farthestmost side of d e aperture. As a result, the effective reduction in deposition rate achieved by a plate having apermres of a specific aspect ratio cannot always be
• a high reduction of the deposition rate is generally undesirable using me aperture plate of the present invention.
• the aspect ratios chosen for apertures in me plates 49. 64 of d e present invention are generally low, less than 1 and preferably between 0.5 and 0.05, to be substantially non-collimating.
• a plate having low aspect ratio apertures in that range is generally non-collimating and will not substantially focus the sputter particles into columns of sputter beams to deposit on die substrate.
• the aspect ratios may be chosen to accomplish me collimation objectives, as long as various different aspect ratio apermres are utilized in accordance wid the objectives of the invention. Plates 49, 64 are also preferably
• the aper re plate 64 may be used to selectively capmre different percentages of sputter particles at different regions of the plate in order to achieve the desired deposition rate.
• die aspect ratio of apermre 76 is chosen so that it generally passes sputter particles which have a flight angle approximately less than or equal to ⁇ .
• particle 80. incident upon apermre 76 will pass through apermre 76, while particle 82, which is incident upon apermre 76 at me same point as particle 80, has a flight angle greater than the critical angle 0, and will strike wall 79 and be intercepted.
• apermre plate 64 has apertures which are varied in dep i rather than diameter in order to achieve the desired deposition rates at chosen areas on a substrate.
• aperture plate 64 has apermres located in d e center region 90 widi higher aspect ratios dian the apermres located in the peripheral region 88. Therefore, a larger percentage of sputter particles 70 are intercepted by die apermres in center region 90 of plate 64 than at peripheral region 88 of die plate because of the higher aspect ratios. Plate 64 thus yields a greater deposition
• An alternative embodiment of me plate of the present invention may have apermres of greater aspect ratios at the peripheral region 88 than at the center region 90 by providing deeper apertures in die peripheral region 88 and shallower apermres in the center region 90 to increase deposition at the center of a substrate. Since the apermres 66 of plate 64 are generally of equal diameter, the aspect ratios are varied in plate 64 by varying the depth of the apermres such as by varying the corresponding diickness of plate 64. That is, apertures with lower aspect ratios at the peripheral region 88 of plate 64 correspond to a d inner plate in that region dian in center region 90. As may be seen in Fig.
• the length of one wall of an apermre such as wall 79 of apermre 76 is longer than wall 78 when the apertures are located in the tapered or thinner peripheral area 88 of plate 64.
• the taper of plate 64 at peripheral area 88 or at any area on die plate 64 is such that the effective aspect ratios are approximately equal from one side of the apermre to the other side.
• the varying aspect ratio plates 49, 64 are spaced sufficiently from the substrate so as to be generally non-shadowing. That is, they are preferably maintained at a distance from the substrate of approximately 0.5 to
• die deposition rate is selectively varied to obtain a more uniform film thickness or a selectively variable film iickness as may be desired.
• the apermres may be varied in diameter or cross-
• the aspect ratios of the stationary apermre plate of the present invention may be varied by varying both the depdi and diameter of me apermres. Further, die density of apermres on me plate might also be varied.
• the diameter of the apermres and/or die density of the apermres in different regions of the stationary aper re plate are selectively varied to produce a desired result, such as a more uniform film thickness across the surface of die substrate.
• the apertures might be chosen to yield
• apermre plate thus disclosed will generally utilize apermres which are dimensioned to have aspect ratios between 0.05 and 0.5, apermres of other aspect ratios might be utilized as well widiout departing from me scope of me invention, keeping in mind me objectives of the present inventions. Still further, different apermre shapes as well as different plate shapes might be used instead of the circular apermres and circular plates utilized in the preferred embodiments of d e invention.

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• 1993
  • 1993-07-22 US US08/095,950 patent/US5415753A/en not_active Expired - Lifetime
• 1994
  • 1994-03-12 TW TW083102149A patent/TW285752B/zh active
  • 1994-06-13 CA CA002164975A patent/CA2164975A1/en not_active Abandoned
  • 1994-06-13 WO PCT/US1994/006716 patent/WO1995003436A1/en not_active Ceased
  • 1994-06-13 EP EP94920200A patent/EP0710299A1/en not_active Withdrawn
  • 1994-06-13 AU AU71079/94A patent/AU7107994A/en not_active Abandoned
  • 1994-06-13 JP JP7505135A patent/JPH09500690A/ja not_active Withdrawn
  • 1994-07-13 SG SG1996003680A patent/SG47675A1/en unknown

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