Patent Application
20240131652
This disclosure is generally related to a method and device for improving chemical mechanical planarization (CMP) performance for the planarization of thin films using wafer carriers with planarized membranes.
During chemical mechanical planarization or polishing (CMP), an abrasive and either acidic or alkalinic slurry is applied via a metering pump or mass-flow-control regulator system onto a rotating polishing pad/platen. A substrate or wafer is held by a wafer carrier which is rotated and pressed against a polishing platen for a specified period of time. The slurry is normally brought to the polishing platen in a single-pass distribution system. The wafer is polished or planarized by both abrasion and corrosion during the CMP process.
The slurry particles in their media may not be distributed evenly between the rotating wafer and the rotating polishing pad/platen. At least some of the polishing slurry may not be effective nor productive because it is swept to the edge of the polishing pad/platen by centrifugal force, and also by the “squeegee” action of the wafer against the polishing pad/platen. Particles that do not contact the wafer surface don't contribute to planarization and are wasted, increasing cost and reducing efficiency of the CMP process. Aspects of the pad, such as its hydrophobic nature, contribute to variations in the distribution of the slurry and its sub-micron abrasive particles and corrosive chemicals.
There is a need to improve the slurry and pad performance to increase CMP efficiency and reduce the cost of manufacturing.
One aspect of the disclosed technology is a method for processing a resilient membrane for a substrate carrier. The method includes providing the resilient membrane, and planarizing a surface of the resilient membrane to form a planarized resilient membrane.
Another aspect of the disclosed technology is an apparatus for supporting a substrate. The apparatus includes a membrane comprising a planarized surface, a support plate configured to support the membrane, and a holding element configured to hold the membrane to the support plate.
Another aspect of the disclosed technology is a membrane for chemical mechanical planarization. The membrane includes a resilient membrane body comprising a substrate facing surface and a carrier facing surface, wherein the substrate facing surface is planarized.
The above, as well as additional objects, features and advantages of the present inventive concept, will be better understood through the following illustrative and non-limiting detailed description of embodiments of the present invention, with reference to the appended drawings. In the drawings like reference numerals will be used for like elements unless stated otherwise.
Although the following text sets forth a detailed description of numerous different embodiments of the invention, it should be understood that the legal scope of the invention is defined by the words of the claims set forth at the end of the patent. The detailed description is to be construed as exemplary only and does not describe every possible embodiment of the invention since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the invention.
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect or embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or embodiments. Various aspects of the novel systems, apparatuses, and methods are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the novel systems, apparatuses, and methods disclosed herein, whether implemented independently of, or combined with, any other aspect described. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosures set forth herein. It should be understood that any aspect disclosed herein may be embodied by one or more elements of a claim.
It should also be understood that, unless a term is expressly defined in this patent using the sentence “As used herein, the term ‘ ’ is hereby defined to mean . . . ” or a similar sentence, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to in this patent in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term be limited, by implication or otherwise, to that single meaning.
Chemical Mechanical Planarization (CMP)
The adoption and use of chemical mechanical planarization (CMP) for the planarization of thin films in the manufacture of semiconductor ICs, MEMS devices, and LEDs, among many other similar applications, is common among companies manufacturing “chips” for these types of devices. This adoption includes the manufacture of chips for mobile telephones, tablets and other portable devices, plus desktop and laptop computers. The growth in nanotechnology and micro-machining holds great promise for ever-widespread use and adaptation of digital devices in the medical field, in the automotive field, and in the Internet of Things (the “IoT”). Chemical mechanical planarization for the planarization of thin films was invented and developed in the early 1980's by scientists and engineers at the IBM Corporation. Today, this process is widespread on a global basis and is one of the truly enabling technologies in the manufacture of many digital devices.
Integrated circuits are manufactured with multiple layers and alternating layers of conducting materials (e.g., copper, tungsten, aluminium, etc.), insulating layers (e.g., silicon dioxide, silicon nitride, etc.), and semiconducting material (e.g., poly silicon). A successive combination of these layers is sequentially applied to the wafer surface, but because of the implanted devices on the surface, topographical undulations are built up upon the device structures, as is the case with silicon dioxide insulator layers. These unwanted topographical undulations are often flattened or “planarized” before the next layer can be deposited, to allow for proper interconnect between device features of ever decreasing size. In the case of copper layers, the copper is deposited on the surface to fill contact vias and make effective vertical paths for the transfer of electrons from device to device and from layer to layer. This procedure continues with each layer that is applied (usually applied by a deposition process). In the case of multiple layers of conducting material (multiple layers of metal), this could result in numerous polishing procedures (one for each layer of conductor, insulator, and semiconductor material) in order to achieve successful circuitry and interconnects between device features.
The CMP process is an enabling technology in the manufacture of multi-layer circuitry that makes this all possible.
A major cost contributor in the CMP process is made up of the collective costs associated with the consumable set, such as the polishing slurries, the polishing pads and the wafer carrier membranes. The polishing slurries are typically colloidal suspensions of abrasive particles, i.e. colloidal silica, colloidal alumina, or colloidal ceria, in a water based medium.
The polishing pads are typically polyurethane based. The typical CMP polishing pad is usually from 18″ to 24″ in diameter; this dimension dictated by the size of the polishing platen (table) on the popular polishing machines in use around the world. However, in some applications they may be larger in diameter even up to 48″ and larger (precision optical applications for example). These polishing pads are attached to a very flat polishing platen (polishing table) by pressure sensitive adhesive.
Modern CMP carriers typically incorporate certain components for precision polishing of generally flat and round workpieces such as silicon wafers and/or films deposited on them. These components include: 1) a resilient membrane consisting of one or more separate zones, with compressed gas applied to the top surface or back side of the membrane; said pressure is then transmitted via the membrane to the top surface or back side of the workpiece in order to effect the material removal during CMP; 2) one or more rigid support components which provide means for: fastening the membrane to its mating components, holding the membrane to its desired shape and dimension, and/or clamping the membrane to provide a sealed volume for sealing and containing the controlled gas pressure.
During the CMP process, the slurry is applied via a metering pump or mass-flow-control regulator system onto the rotating polishing pad. The substrate or wafer is held by a wafer carrier which is rotated and pressed, generally via a resilient membrane within the wafer carrier, against the polishing platen for a specified period of time. The slurry is normally brought to the polishing platen in a single-pass distribution system. The normal expectation is that the slurry particles in their media will be distributed evenly between the rotating wafer, and the rotating polishing pad/platen.
A force is applied to the backside of the wafer by the wafer carrier membrane to press it into the pad and both may have motion to create a relative velocity. The motion and force leads to portions of the pad creating abrasion by pushing the abrasive against the substrate while it moves across the wafer surface. The corrosive chemicals in the slurry alter the material being polished on the surface of the wafer. This mechanical effect of abrasion combined with chemical alteration is called chemical mechanical planarization or polishing (CMP). The removal rate of the material can be easily an order of magnitude higher with both the chemical and mechanical effects simultaneously compared to either one taken alone. Similarly, the smoothness of the surface after polishing is also optimized by using chemical and mechanical effects together.
During the polishing process, material such as copper, a dielectric, or polysilicon is removed from the surface of the wafer. These microscopic particles either remain in suspension in the slurry or become embedded in the polishing pad or both. These particles cause scratches on the surface of the film being polished, and thus catastrophic failures in the circuitry rendering the chip useless, thus becoming a major negative effect upon yield.
Yield is the driving force in determining success at the manufacturing level for many products including integrated circuits, MEMS, and LEDs. The surface quality tolerances for a CMP process within semiconductor manufacturing facilities (“fabs”) and foundries are measured in nanometers and even Angstroms. The ability to remove material as uniformly as possible from the surface of a wafer or film during CMP is important. Therefore, carrier design technology is constantly evolving toward improving this capability. Small non-uniformities in the flatness of a wafer that has been processed in a CMP system can result in decreased yield and increased waste. The accumulated costs of manufacturing a solid state device are together termed the “Cost-of-Ownership” (CoO) and this term is also applied to each of the required manufacturing steps. The CoO of the CMP process is one of the highest CoO figures in the 500 to 800 individual manufacturing steps required to make a semiconductor “chip” and its associated digital device.
While carrier designs incorporating various embodiments of resilient membrane concepts work well in terms of uniform material removal, there remain some non-optimum characteristics in their typical process performance. Essentially, despite substantial efforts to minimize them, certain practical deficiencies and anomalies still exist, which cause non-uniform pressure application to the wafer and associated non-uniform material removal.
Such anomalies include, but are not necessarily limited to, the following: variations in membrane thickness across the membrane; variations in tension across the membrane; and variations in flatness of any rigid components contacting the membrane.
In order to reduce the presence, magnitude and effects of such anomalies, the present application discloses embodiments of systems, apparatus and methods that implement a planarized membrane for use in a substrate carrier for a CMP apparatus. These improve the flatness tolerances and substrate surface quality, when implemented in a CMP apparatus, resulting in increased yield and decreased CoO. It will be understood that although embodiments of the planarized membranes described herein are disclosed within the context of CMP equipment, they can be similarly implemented within other applications.
Detailed embodiments of the present invention will now be described with reference to the drawings.
In the system 100 of
The slurry delivery system 140 can deliver a slurry containing sub-micron abrasive and corrosive particles to a surface of the treated polishing pad 130. The polishing slurries are typically colloidal suspensions of abrasive particles, i.e. colloidal silica, colloidal alumina, or colloidal ceria, in a water based medium. In various embodiments, the slurry delivery system 140 includes a metering pump or a mass-flow-control regulator system, or other suitable fluid delivery components.
The wafer carrier 150 can hold wafer 155, for example, with a vacuum, so that the surface of the wafer 155 to be polished faces towards polishing pad 110. Abrasive particles and corrosive chemicals in the slurry deposited by the slurry delivery system 140 on the polishing pad 110 mechanically and chemically polish the wafer through abrasion and corrosion, respectively. The wafer carrier 155 and polishing pad 110 can move relative to each other in any of a number of different ways, to provide the polishing. For example, the wafer carrier can apply a downward force against the platen 120 so that the wafer 155 is pressed against the polishing pad 110. The wafer 155 can be pressed against the polishing pad 110 with a pressurized membrane (not shown), as will be described further herein. Abrasive particles and corrosive chemicals of the slurry between the wafer 155 and the polishing pad 110 can provide chemical and mechanical polishing as the polishing pad 110 and wafer carrier 155 move relative to each other. The relative motion between polishing pads and wafer carriers can be configured in various ways, and either or both can be configured to oscillate, move linearly, and/or rotate, counter clockwise and/or clockwise relative to each other.
Pad conditioning arm 160 conditions the surface of polishing pad 110, by pressing against polishing pad 110 with a force, with relative movement therebetween, such as the relative motion described above with respect to the polishing pad and wafer carrier 150. The pad conditioning arm 160 in the illustrated embodiment can oscillate, with a rotating pad conditioner at its end, which contacts the polishing pad 110.
The membrane assembly 305 may include a support plate 310, a resilient membrane 320, a membrane clamp 330, and an outer pressure ring 340, as shown. The support plate 310 can be any suitable configuration to attach membrane assembly 305 to support base 380. For example, the support plate 310 may be mounted to the support base 380 using one or more bolts or other suitable attachment elements. The support plate 310 may be mounted to the support base 380 at various locations, such as along the outer perimeter of the support base 380.
The support plate 310 can be any suitable configuration to support the resilient membrane 320. The resilient membrane 320 may be secured to the support plate 310 in a number of different ways. The resilient membrane 320 may be secured to the support plate 310 before or after the support plate 310 is secured to the support base 380. The resilient membrane 320 may be secured to the support plate 310 through use of any of a number of suitable different holding elements, such as the membrane clamp 330. In some embodiments, the membrane clamp 330 may be spring loaded. In other embodiments, the membrane clamp 330 may tighten securely through the use of a fastening mechanism (e.g., nuts and bolts, etc.).
The resilient membrane 320 can be secured to the support plate 310 such that the membrane 320 can hold a wafer 370 against a polishing pad and process the wafer, for example, as described above with reference to
In some embodiments, the cavity 360 can be formed by spacing the membrane 320 from the support plate 310. For example, the support plate 310 can included a recessed inner portion to form a cavity. In the illustrated embodiment, the membrane assembly 305 can include an outer pressure ring 340 to form the cavity 360. In other embodiments, the membrane assembly may be assembled without pressure rings. For example, the membrane 320 may rest directly against the support plate 310 without a cavity 360 separating the membrane 320 from the support plate 310. In some embodiments, the membrane assembly may include one or more pressure rings 340 arranged in concentric circles.
In another embodiment, the membrane 320 used may be a multi-zoned membrane. For example, the membrane 320 may have grooves (e.g., indentations) and/or raised portions of the membrane 320 that effectively segregate various zones of the membrane 320. In a non-limiting example, the grooves may be arranged in a series of concentric circles originating from the center of the membrane. In another example, the grooves and raise portions may be irregularly shaped (e.g., interconnecting circles, non-circular indentations, circular patterns scattered across the surface of the membrane) in order to improve distribution of pressure applied across the wafer 370 when attached to the membrane assembly.
The membrane 320 may be flexible such that it conforms to a structure that it surrounds. In some instances, the membrane 320 may be convex. For example, the membrane 320 may sag in the center. The membrane 320 may even be shaped like a cone such that a small area of the membrane 320 would be in contact with the wafer surface for finer precision polishing.
The membrane material may be any resilient material suitable for planarization, as described herein, and for use, for example, within a carrier head for a CMP process. In some embodiments, the membrane material may be one of rubber or a synthetic rubber material. The membrane material may also be one of Ethylene propylene diene monomer (M-class) (EPDM) rubber or silicone. Alternatively, it may be one or more combinations of vinyl, rubber, silicone rubber, synthetic rubber, nitrile, thermoplastic elastomer, fluorelastomers, hydrated acrylonitrile butadiene rubber, or urethane and polyurethane formas.
One or more membrane assemblies can be implemented within a single CMP system. The CMP system may have controls utilizing feedback from the system while operating to more accurately control the CMP process (e.g., variable speed motor controls, etc.).
In an exemplary embodiment, the membrane 320 may be planarized. For example, the membrane 320 can be made flat within a desired tolerance, and/or made to conform to a surface roughness within a desired tolerance. For example, the membrane 320 may undergo a planarization procedure wherein the membrane is subjected to a polishing pad. In addition, the membrane 320 may be introduced to a chemical slurry that causes the membrane 320 to become planarized. Furthermore, the surface roughness of the membrane 320 can be improved throughout this planarization process. Surface roughness can be important for membranes used within the context of a CMP process for at least two reasons: sealing and stiction. Through the planarization process, the surface roughness may be lowered in order to provide improved sealing between the wafer 370 and the membrane 320 for handling purposes. At the same time, the surface roughness may be increased in order to prevent stiction (i.e., the wafer sticking to the membrane from surface tension), and improve wafer release from the membrane after processing. Control mechanisms may be used during the planarization process (described below) in order to achieve a desired balance between low and high surface roughness. The control mechanism may be external to the device used to planarized the membrane.
A specialized tool or device may be used to planarize a membrane 320. For example, a conditioning tool 400 (described in reference to
In some examples, only a portion or section of the surface of the membrane need be planarized. For example, it may be more advantageous to planarize only the outer diameter of the membrane. A single surface or both surfaces of the membrane can be planarized.
For example, the conditioning tool 400 may include a plate 410, an arm 420, one or more rollers 430a, 430b, and a conditioning tool base 450. In an exemplary embodiment, a membrane 320 may be placed on the top surface of the plate 410. The moving contact between the membrane 320 and the plate 410 can provide the planarization to the surface of membrane 320. The planarization can include introducing an abrasive material, such as sand, and/or other chemicals, such as a chemical slurry, to remove material and planarize membrane 320. The planarization can be performed with the membrane 320 pressurized, to press it against the plate 410. Other types of forces can be implemented to press the membrane 320 against the plate 410 and provide planarization. For example, arm 420 and/or plate 410 can move relative to each other to press membrane 320 against the plate 410. The arm 420 and/or plate 410 can be configured in other ways to provide similar function. For example, the arm 420 can be configured similarly to a wafer carrier, and move linearly to provide force between the plate 410 and the membrane 320 for planarization. The plate 410 can include a polishing pad or other components or treatments on its surface to provide planarization to the membrane 320.
The membrane may be secured to the rollers 430a, 430b, with a fastener (e.g., magnets, screws, bolts, etc.). As shown in
In some embodiments, the plate 410 may move (e.g., rotate, orbit, oscillate, reciprocate, etc.) in any way to provide planarization while the membrane 320 is held stationary. In other embodiments, the membrane 320 may be moved while the plate 410 is stationary. In other embodiments, the membrane 320 and the plate 410 may both move to provide relative motion therebetween. The rotating velocity of the plate may be controlled by a variable speed drive which receives input from the system in order to accurately adjust the velocity of the plate in real-time. In another embodiment, the velocity may be kept at a low constant velocity. In addition, the arm 420 may be actionable such that it may apply pressure to the membrane to produce a sufficiently conditioned membrane.
In other embodiments, the membrane may be stretched around the outside of a temporary membrane holder. In some examples, this holder may stretch the membrane such that the membrane body experiences tension before or during the planarization process. In some embodiments, the membrane can be held in place with a membrane assembly that includes additional support components, such as the membrane assembly 305 in
A planarized surface is a substantially flat surface (e.g., a planar surface). One method of testing the planarization of a surface is to test the uniformity of the surface such that all points along the surface are on a single two-dimensional plane or within a specified margin of error of the single two-dimensional plane.
The process of planarizing includes conditioning a surface such that it becomes planarized. This may be done, for example, using a polishing pad, wherein polishing is sought that planarizes the membrane surface to a predetermined uniformity over the surface area of the portion of the membrane being planarized. In some embodiments, the approximate thickness of the planarized membrane between a first planarized surface, and a second opposing surface of the membrane is within a range of about 0.005 to 0.100 inches. In some embodiments, the overall thickness of the membrane after it has been planarized is reduced, relative to the thickness of the membrane prior to planarization, by about 10 to 50%. In some embodiments, the planarized membrane comprises a planarized surface with a roughness within a predetermined range. In some embodiments, the roughness of the planarized surface of the planarized membrane may be decreased or increased by some percentage relative to the same surface prior to planarization.
In another example, testing the planarity of a membrane may involve reflecting light off the membrane surface at a known angle and measure whether the light is reflected at the same or substantially the same angle at all points along the surface and how the reflected angle relates to the known angle. For example, an acceptable difference may be within two degrees. Alternatively, the angle may be 0.7-1.0 degrees on average.
It will be understood that embodiments of the planarized CMP membranes described herein can be formed through any of a number of different configurations, and should not be limited to the example shown in
In block 1010 a resilient membrane is provided. In block 1020, the surface of the membrane provided in block 1010 is planarized. Block 1020 may be performed, for example, by the conditioning tool system 400 (
It will be understood that the membrane planarization methods and equipment described herein can be implemented without the full CMP systems shown. For example, the membrane may be planarized prior to being brought within the context of the remainder of the CMP systems shown in
Another aspect of the present disclosure can include planarizing one or more of the components that support the resilient membranes described herein. For example, some embodiments can include methods of planarizing the supporting ring, such as the outer pressure ring 2020. The outer pressure ring may be made from poromeric urethane, or other suitable materials such as Eminess DF200 or WB20. Some materials used to form the pressure ring may exhibit imperfections, such as variations in thickness and/or local compressibility. In addition, the surface to which the outer pressure ring 2020 is mounted may have similar anomalies, such as out-of-flatness condition and/or surface defects (e.g., bumps, pits, etc.). Such imperfections can transfer a non-uniform application of pressure through the membrane to the substrate. As such, the outer pressure ring 2020 may be planarized before or after being applied to the support plate 2040. It will be understood that the rotational speeds and pressures for such planarization of the outer pressure ring 2020 may be in a similar range as would be used for a membrane.
Evidence has been obtained to demonstrate the improved non-uniformity of a wafer that may result through use of a planarized wafer carrier membrane. In one demonstration, the improved non-uniformity was especially apparent near the edge of the wafer. In that demonstration, a modified 150 mm Titan polishing head was used. The results of that demonstration are shown in
As shown in
Additionally, as shown in
This application is a continuation of U.S. Non-Provisional application Ser. No. 16/758,794, filed Apr. 23, 2020, which is a national phase under 35 U.S.C. § 371 of PCT/US2018/058024, filed Oct. 29, 2018, which claims the benefit of the U.S. Provisional Application No. 62/582,187 filed Nov. 6, 2017, each of which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62582187 | Nov 2017 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16758794 | Apr 2020 | US |
| Child | 18322374 | US |
