Patent Grant
8414357
Embodiments of the present invention relate to a chemical mechanical polisher having movable slurry dispensers and related methods.
In the fabrication of the integrated circuits (ICs) and displays, chemical-mechanical planarization (CMP) is used to smoothen the surface topography of a substrate for subsequent etching and deposition processes. A typical CMP polisher comprises a polishing head that oscillates and presses a substrate against a polishing pad while a slurry of abrasive particles is supplied to the polishing pad to polish the substrate. CMP can be used to planarize dielectric layers, deep or shallow trenches filled with polysilicon or silicon oxide, and metal films. It is believed that CMP polishing is a result of both chemical and mechanical effects, for example, a chemically altered layer is repeatedly formed at the surface of the material being polished and then polished away. For example, in metal polishing, a metal oxide layer can be formed and removed repeatedly from the surface of the metal layer during CMP polishing. In oxide polishing, the oxide layer is both chemically and physically eroded by the polishing slurry.
One type of conventional slurry dispenser comprises a fixed arm having a single slurry dispensing nozzle which releases slurry from a fixed point above the polishing pad. The slurry spreads across the polishing pad from the rotary or oscillating motion of the polishing pad and/or substrate carrier. However, because the slurry is dispensed from a single position above the platen, which is often at a mid-point of the radius of the platen, the resultant distribution of slurry across the surface of the platen is not always very uniform. Rotation of the underlying polishing platen and the resultant centrifugal forces causes the slurry to spread radially outward from the median point. However, a preferentially higher concentration of slurry forms in a circular strip that radiates outward from the median dispensing point due to these centrifugal forces, and a lower slurry concentration region forms between the point of dispensation and the radially inner region. This can result in uneven polishing rates across the diameter of the substrate being polished.
Multipoint slurry dispensers also been developed to provide a more uniform distribution of slurry for polishing single substrates, as for example, described in U.S. Pat. No. 6,284,092, entitled “CMP Slurry Atomization Slurry Dispense System”. A sweeping multipoint slurry dispenser has also been used to spread the slurry across the pad, as for example, described in U.S. Pat. No. 7,052,374, entitled “Multipurpose Slurry Delivery Arm for Chemical Mechanical Polishing”. However, while these slurry dispensing systems provide a better slurry distribution for single substrate polishers, they do not provide effective slurry distribution for newer generations of CMP polishers which use multiple carrier heads to polish several substrates at the same time or which are used for polishing large substrates. Thus it is desirable to have a chemical mechanical polisher with a slurry dispensing system that provides a more uniform distribution of slurry across the surface of the polishing pad for simultaneously polishing multiple substrates or for polishing large substrates.
A chemical mechanical polisher comprises a polishing platen capable of supporting a polishing pad, first and second substrate carriers that are each capable of holding a substrate against the polishing pad, and first and second slurry dispensers. First and second slurry dispensers each comprise (i) an arm comprising a pivoting end and a distal end, (ii) at least one slurry dispensing nozzle on the distal end, and (iii) a dispenser drive capable of rotating the arm about the pivoting end to swing the slurry dispensing nozzle at the distal end to dispense slurry across the polishing platen.
A chemical mechanical polishing method comprises rubbing first and second substrates against a polishing pad, and dispensing polishing slurry before each of the first and second substrates.
These features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings, which illustrate examples of the invention. However, it is to be understood that each of the features can be used in the invention in general, not merely in the context of the particular drawings, and the invention includes any combination of these features, where:
A chemical mechanical polisher 100 is useful for polishing a surface of a substrate. For example, the polisher 100 can be used to polish a surface of a substrate that comprises copper interconnect lines or vias. In another application, the polisher can be used to polish a surface of a silicon dioxide layer on a substrate. Many other polishing applications and uses, as would be apparent to those of ordinary skill in the art, are also within the scope of the present invention.
An embodiment of a polisher 100 suitable for polishing a surface of a substrate comprising a semiconductor wafer, display, or panel, is shown in
The polishing pad 112 mounted on the platen 110 typically comprises a planar disc having a radius that is sized sufficiently large to provide coverage for at least two substrates 140a,b. The polishing pad 112 contacts and rotates against the substrates 140a,b (which can also be rotated, oscillated or vibrated themselves) to polish each substrate 140a,b. The polishing pad 112 comprises a polishing surface 113 made of a material that is sufficiently abrasive to polish and remove undesired material from the substrates 140a,b without excessively scratching or otherwise damaging the substrate surface. For example, the polishing surface 113 may be made of a polymer, felt, paper, cloth, ceramic, or other such materials. The polishing surface 113 can also include more grooves (not shown) to enhance the flow of the polishing slurry over the polishing surface 113. For example, a suitable polishing pad 112 comprises a fixed abrasive polishing pad, manufactured by 3M Superabrasives and Microfinishing Systems Division, St. Paul, Minn., which contains abrasive particles, such as silica, embedded in a resin. In one version, the polishing pad 112 is adhered to the platen 110, which is about the same diameter as the polishing pad 112, using a pressure sensitive adhesive.
First and second substrate carriers 120a,b are each adapted to hold a substrate 140a,b, respectively, against the polishing pad 112. The substrates 140a,b are held onto each substrate carrier 120a,b with a vacuum or surface tension. Each of the substrate carriers 120a,b apply a pressure while independently rotating and oscillating back-and-forth across the polishing pad 112 to achieve a uniformly polished surface on the substrates 140a,b. During polishing, a pneumatic system (not shown) lowers the substrate carriers 120a,b onto the polishing pad 112 to press the substrates 140a,b against the polishing pad 112 with a pre-determined loading force. The platen motor 117 rotates the platen 110 and polishing pad 112. At the same time, each substrate carrier 120a,b rotates a substrate 140a,b, while sliders (not shown) linearly drive the substrate carriers 120a,b back and forth to oscillate the substrates 140a,b laterally on the surface of the polishing pad 112. The substrate carriers 120a,b are driven by one or more carrier motors (not shown), which can also be a variable speed direct current motor, such as a servo-motor, that can provide variable substrate rotational speeds and can also move the substrate in a back and forth linear motion. The substrate carriers 120a,b abrade the surface of the substrates 140a,b by rubbing the substrates against two different regions of the polishing pad 112.
During, before or after polishing, first and second slurry dispensers 122a,b provide polishing slurry, neutralizing solution, and/or water to the surface of the polishing pad 112. In one version, the first and second slurry dispensers 122a,b are positioned abutting the polishing platen 110. The dispensers 122a,b can also be located across the platen 110 and diametrically opposing one another. The opposing pair of slurry dispensers 122a,b are each located so that they can rotate and be positioned between the first and second substrate carriers 120a,b. In one version, the dispensers 122a,b sweep in an arc across the polishing platen 110 while dispensing slurry. Each slurry dispenser 122a,b feeds fresh polishing slurry to a different region of the polishing pad 112 that is located immediately before one of the substrates 140a,b mounted on the substrate carriers 120a,b. In this manner, the first slurry dispenser 122a provides fresh slurry to the substrate 120b on the second substrate carrier 120b and the second slurry dispenser 122b provides fresh slurry to the substrate 120a on the first substrate carrier 120a, or vice versa, depending on the direction of rotation of the polishing platen 110. Advantageously, this allows the polisher 100 to polish both substrates 148a,b at approximately the same polishing rates because fresh polishing slurry is dispensed at different circumferential regions across the polishing pad 112 that each lie between the first and second substrate carriers 120a,b.
The first and second slurry dispensers 122a,b each comprise a dispenser arm 123a,b which has a pivoting end 126a,a′ and a distal end 126b,b′, respectively. Each pivoting end 126a,a′ of the slurry dispenser arms 123a,b is mounted on a rotatable axle 127a,b. A dispenser drive 128a,b powers the rotatable axle 127a,b to rotate each dispenser arm 123a,b about their pivoting ends 126a,a′ to swing the respective slurry dispensing nozzles at the distal ends of the arms 123a,b to dispense slurry across the polishing platen 110. The dispenser drives 128a,b can be operated to rotate the dispenser arms 123a,b so that the pivoting ends 126a,a′ rotates along a fixed arc across different regions of the polishing platen 110. The dispenser drives 128a,b are capable of rotating each arm 123a,b to sweep each arm in an arc across the polishing platen 110 while dispensing slurry. In one embodiment, each arc covers an arcuate distance that spans from about 0° to about 45°. The first and second fixed arcs can oppose one another across a diameter of the polishing pad 112.
At least one slurry dispensing nozzle 124a,b is provided between the pivoting end 126a,a′ and the distal end 126b,b′ of each of the dispenser arms 123a,b, respectively, as shown in
The slurry dispensers 122a,b can also comprise at least a first nozzle 124a,a′ and a second nozzle 124b′,b′, respectively. Each of the first and second nozzles 124a,a′ and 124b,b′ are spaced apart from one another, and can also be aligned along a common axis that is along the longitudinal direction of the arms 123a,b. The dispensing nozzles 124a,a′ and 124b,b′ direct fluid, such as polishing slurry, onto the polishing pad 112 to distribute polishing slurry across a larger surface of the polishing pad 112 in the desired spray coverage area 133a,b.
Referring to
The embodiment of the slurry dispenser 122 shown in
The plurality of nozzles 124a-e can also be located in a slurry dispenser channel 137 that is affixed along the length of the dispenser arm 123 to disperse slurry across the polishing pad 112. The dispenser channel 137 comprises a hollow rectangular body that is disposed along the underside of the dispenser arm 123 such that the longitudinal axis of the channel is substantially parallel to the longitudinal axis of the hollow body. The dispenser channel 137 comprises one or more integral slurry dispensing nozzles 124a-e that can be formed, for example, by machining or drilling a nozzle shaped opening into the dispenser channel 137. Each shaped opening of the nozzles 124a-e can have, for example, a conical profile that tapers outward with a smaller first opening facing the internal volume of the channel 137 and a larger second opening at the exterior surface of the channel 137 (not shown). For example, the shaped opening can have a first opening diameter of less than 1 mm, and a second opening diameter of greater than about 1.1 mm. The shaped opening opens toward the platen surface and comprises a diameter of from about 1 mm to about 2 mm. The first opening of the dispenser channel can also be sufficiently large to fit over the diameter of a corresponding opening of the fluid supply tube 125a which supplies polishing slurry to the dispenser channel.
As a substrate 140 and polishing pad 112 are rotated against each other, measured amounts of polishing slurry supplied according to a selected slurry recipe are sprayed onto the polishing pad through the nozzles 124a-e. The polishing slurry contains a reactive agent and a chemically reactive catalyst. For example, an oxide substrate can be polished with polishing slurry comprising deionized water—which is used as the reactive agent, and potassium hydroxide—which serves as the catalyst. Suitable polishing slurries may also comprise, for example, abrasive particles comprising at least one of aluminum oxide, silicon oxide, silicon carbide, or other ceramic powders; and which are suspended in a solution comprising for example, one or more of water, alcohol, buffering agents and suspension chemicals.
The dispenser arm 123 of the slurry dispenser 122 also includes a separate set of rinsing nozzles 138a-g which provide a rinsing fluid for rinsing a substrate 140 after a polishing process. The rinsing nozzles 138a-g are spaced apart form one another, and which can provide a high-pressure fluid rinse of the polishing pad 112 at the end of each polishing and/or conditioning cycle. The rinsing fluid is supplied to the rinsing nozzles 138a-g through the supply tube 125c. A rinsing fluid such as deionized water can be used to clean a substrate 140 as it passes from one polishing station to another. The rinsing nozzles 138a-g can also direct streams of water toward the slowly rotating polishing pad 112 to rinse slurry from the polishing pad surface while a substrate 140 is being transferred back to a holding station. Water can also be supplied to the surface of the polishing pad 112 to rinse particles and chemicals from the pad surface between processing of substrates 140. The rinsing step can be performed after polishing a predetermined number of substrates 140 or at the beginning of the polisher operation as a pretreatment step, at the end of operation to remove reactants from the pad surface or on an as-needed basis to rinse particles and chemicals from the pad surface. The rinsing nozzles 138a-g can also comprise conical cross-sections to supply a conical spray section of water or other cleaning fluid to the polishing pad 112. A rinsing fluid shield (not shown) can be used to cover the sides of the rinsing nozzles 138a-g to contain the spray of the rinsing fluid over the substrate. The rinsing fluid shield can be made from Teflon®, DuPont de Nemours Co., Delaware.
The dispenser arm 123 of the slurry dispenser 122 can also include a chemical rinse nozzle 139 which disperses a chemical agent across the polishing pad 112 to neutralize the active agent of the polishing slurry after the polishing of one or more substrates 140 is completed. While the chemical rinse nozzle 139 is described as a separate nozzle from the slurry dispensing nozzle 124, it can also be the same nozzle structure. In one embodiment, the chemical rinse nozzle 139 is located at the distal end 126b of the dispenser arm 123. The composition of the chemical rinse is selected to stop the reaction of the chemically active components of the polishing slurry with the substrate 140 being polished, and can serve to neutralize the etchant or corrosive properties of the active slurry components. For example, in one embodiment, the chemical rinse comprises an acid or ammonia based neutralizing agent.
A controller 188 comprises suitable programming code 190 to control the CMP apparatus 100 and its various components, including the slurry dispenser 122, as shown in
In an alternate embodiment of a slurry dispenser 122, features of which can occur on its own or in combination with any other features described herein, the dispenser arm 123 comprises a distal end 131 that is movable in a linear motion with respect to a proximal end 141, as shown in
In this version, the segment of the dispenser arm 123 that includes the distal end 131 is connected to a dispenser drive 143 which can move the distal end 131 towards and away from the proximal end 141 of the dispenser arm 123 along a linear path. The dispenser drive 143 moves the distal end of the arm along a linear path to dispense slurry in a line across the polishing platen. The linear motion can match the line corresponding to the longitudinal axis of the dispenser arm 123. The dispenser drive 143 is controlled by the controller 188, which comprises program code to control the linear motion of the dispenser arm 123. The distal end 131 can travel a linear distance of from about 20% to about 90% of the length of the un-extended dispenser arm 123.
Coiled supply tubes 145a,b extend through the length of the dispenser arm 123 to supply polishing slurry, suspension or other fluids to the nozzles 124a-c, as shown in
In a prospective embodiment, the controller 188 comprises program code 190 to control the movement of the distal end 131 of the dispenser arm 123 in relation to the movement of a substrate carrier 120. For example, the distal end 131 of the dispenser arm 123 can be moved into position and slurry dispensed to a substrate contact region 147 of the polishing pad 112 immediately prior to contact of this region of the pad, with a substrate 140 held by a substrate carrier 120 (not shown). The distal end 131 of the dispenser arm 123 can be positioned out of the path of the substrate carrier 120 to avoid collision with the carrier assembly. The dispenser arm 123 can supply polishing slurry to a larger area of the polishing pad 112 using a linear sweep that traverses the entire length, or a substantial portion of the radial length, of the platen or pad, as compared to a non-mobile arm.
The linear sweep arm can be configured to supply a polishing slurry along a liner path that traverses from the central region of the polishing pad 112 to the perimeter of the pad. Further, since the nozzles 124a-c located about the distal end 131 of the polishing arm 123 can be moved into a radial feeding position above the polishing pad 120, the flow requirements on the polishing slurry are not as stringent. For example, partial clogging of the nozzles 124a-c and sputtering of slurry from the dispenser nozzles, which would result in uneven distribution of polishing slurry, does not have as much of an effect because the nozzles 124a-c are located closer to the target area and slurry dispensed by the nozzle, however uneven, will still land on the polishing pad 112 in the substrate contact region 147.
The polishing system can comprise first and dispenser arms 123a, 123b as shown for example in
In one prospective embodiment, a first dispenser arm 123a is configured to dispense a polishing slurry and a second dispenser arm 123b is configured to dispense a rinsing fluid and a neutralizing chemical fluid. In this prospective embodiment the first dispenser arm 123a can be removed from the chamber for cleaning of dispenser valves that are clogged with polishing slurry without necessitating removal of the remaining dispenser arm 123b or disconnection of the other fluid supply lines.
In another prospective embodiment, a first slurry dispenser and dispenser arm 123a is provided to supply polishing slurry or other fluids to a first substrate contact region and a second slurry dispenser and dispenser arm 123b is provided to supply polishing slurry or other fluids to a second substrate contact region, the first and second contact regions being different from each other. A first substrate carrier contacts a substrate to the first substrate contact region and a second substrate carrier contacts a substrate to the second substrate contact region. In this manner the first and second slurry dispenser arms 123a,b supply slurry to first and second substrate carriers.
The slurry dispensers 122, 122a,b described herein can be used in a CMP polisher. One embodiment of a chemical mechanical polisher 100 that can be used to planarize a surface of a semiconductor wafer substrate, is shown in
Each polishing station 108a can also have one or more pad conditioners 114a which has a rotatable arm 118 that holds an independently rotating conditioner head 119. The pad conditioner 114a maintains the condition of the polishing pad 112a to allow the pad to effectively polish the substrates 40. Each pad conditioner head 119 comprises a platen 121 that holds an abrasive disc (not shown). The platen is a support structure, such a carbon steel plate, which provides structural rigidity to the abrasive pad. The abrasive disc comprises an exposed abrasive face of a metal alloy, such as a nickel or cobalt alloy, having abrasive particles embedded in the metal alloy. The polishing stations 108b having fixed-abrasive pads do not require a pad conditioner since fixed-abrasive pads generally do not require conditioning. The conditioner head 119 sweeps the abrasive disc across the polishing pad 112 with a reciprocal motion that is synchronized with the motion of the substrate carrier 120 across the polishing pad.
The pad conditioner 114a is mounted at a first height from the tabletop 106 that is higher than a second height of the first and second slurry dispensers, as shown in
Referring back to
As shown in
The present invention has been described with reference to certain preferred versions thereof; however, other versions are possible. For example, the pad conditioner can be used in other types of applications, as would be apparent to one of ordinary skill, for example, as a sanding surface. Other configurations of the CMP polisher can also be used. Furthermore, alternative channel configurations equivalent to those described can also be used in accordance with the parameters of the described implementation, as would be apparent to one of ordinary skill. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.
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