Patent Application
20210057292
Embodiments of the present principles generally relate to semiconductor processes used in packaging semiconductor devices.
Advanced packaging has paved the way to produce semiconductor chip packages with improved performance for various applications, such as mobile communications, computing, and internet of things (IoT). To achieve this, wafer-level processing is no longer limited to standard silicon wafers, but also covers reconstituted wafers. The latter refers to the case where chips from different wafers may be combined together by placing the chips on a surface and overlaying the chips with a polymer material, typically epoxy mold compound (EMC). The chips often contain complex circuitry which needs to interact with external components. Lead outs are formed that are connected to the internal circuitry of the chip to a pad or solder ball that allows for external connections. Common building blocks to achieve the connection are through-silicon vias (TSV), Cu pillars (bumps), and redistribution layers (RDLs). In the case of RDLs, for example, as the technology node keeps scaling down, non-uniformities in the surface of the polymer layer, such as those caused by the embedded chips, limit the spacing of the connections. The inventors have found that the non-uniformities necessitate the use of chemical mechanical planarization (CMP) in the wafer-level process flow. In another example, one may use thick RDL or bump which requires a thick polymer or an EMC encapsulation layer. In the example, not only is a fast removal process required, but also the introduction of a heterogeneous material like EMC (epoxy filled with silica fillers) may present a new challenge in monitoring the thickness of the EMC material.
Thus, the inventors have provided an improved method and apparatus for reducing non-uniformities in the surface of the substrate.
Methods and apparatus for reducing non-uniformities of a surface of a substrate are provided herein.
In some embodiments, a method for chemical mechanical planarization (CMP) of a polymer or epoxy-based layer may comprise obtaining an endpoint for polymer or epoxy-based material for use in a CMP process, the CMP process configured to polish polymer or epoxy-based material; monitoring the polymer or epoxy-based layer with an endpoint detection apparatus configured to monitor polymer or epoxy-based material, polishing the polymer or epoxy-based layer with the CMP process; detecting when the polymer or epoxy-based layer has reached the endpoint for the CMP process; and halting the CMP process when the endpoint is detected.
In some embodiments, the method may further comprise using an optical detection apparatus as the endpoint detection apparatus, the optical detection apparatus is configured to operate at a wavelength of approximately 200 nm to approximately 1700 nm and is configured to reduce step height of the polymer or epoxy-based layer such that a surface of the polymer or epoxy-based layer has a uniformity that supports a redistribution layer with at least two lead outs with line and spacing of approximately greater than 0/0 μm to less than or equal to approximately 2/2 μm, using an optical detection apparatus as the endpoint detection apparatus, wherein the polymer or epoxy-based layer has at least one underlying redistribution layer or bump and the optical detection apparatus is configured to operate at a wavelength of approximately 200 nm to approximately 1700 nm and to planarize the polymer or epoxy-based layer; obtaining the endpoint for the polymer or epoxy-based layer from a combination of stored data and monitored data; using an optical detection apparatus as the endpoint detection apparatus, the optical detection apparatus is configured to operate at a wavelength of approximately 200 nm to approximately 1700 nm and is configured to detect a reveal of a metal-based material in the polymer or epoxy-based layer; using a laser detection apparatus as the endpoint detection apparatus, the laser detection apparatus is configured to detect metal clearance in a polymer damascene structure in the polymer or epoxy-based layer; using a motor torque detection apparatus as the endpoint detection apparatus, the motor torque detection apparatus is configured to detect metal reveals in the polymer or epoxy-based layer based on changes in torque applied to one or more motors of a CMP process chamber; using an eddy current detection apparatus as the endpoint detection apparatus, the eddy current detection apparatus is configured to detect a thickness of a metal-based material in the polymer or epoxy-based layer; using an X-ray detection apparatus as the endpoint detection apparatus, the X-ray detection apparatus is configured to non-destructively detect a thickness of the polymer or epoxy-based layer; and/or using more than one of an optical detection apparatus, a motor torque detection apparatus, an eddy current detection apparatus, and an X-ray detection apparatus as the endpoint detection apparatus.
In some embodiments, a method for chemical mechanical planarization (CMP) of a polymer or epoxy-based layer may comprise obtaining an endpoint for polymer or epoxy-based material for use in a CMP process, the CMP process configured to polish polymer or epoxy-based material, monitoring the polymer or epoxy-based layer with an optical detection apparatus configured to monitor polymer or epoxy-based material and configured to operate at a wavelength of approximately 200 nm to approximately 800 nm or a wavelength of approximately 900 nm to approximately 1700 nm, polishing the polymer or epoxy-based layer with the CMP process, detecting when the polymer or epoxy-based layer has reached the endpoint for the CMP process, and halting the CMP process when the endpoint is detected.
In some embodiments, the method may further comprise wherein the optical detection apparatus is configured to reduce step height of the polymer or epoxy-based layer such that a surface of the polymer or epoxy-based layer has a uniformity that supports a redistribution layer with at least two lead outs with line and spacing of approximately greater than 0/0 μm to less than or equal to approximately 2/2 μm; wherein the polymer or epoxy-based layer has at least one underlying redistribution layer or bump and the optical detection apparatus is configured to planarize polymer or epoxy-based layer; obtaining the endpoint for the polymer or epoxy-based layer from a combination of stored data and monitored data; wherein the optical detection apparatus is configured to detect a reveal of a metal-based material in the polymer or epoxy-based layer; and/or using the optical detection apparatus and at least one of a motor torque detection apparatus, an eddy current detection apparatus, and an X-ray detection apparatus to detect the endpoint of the CMP process for the polymer or epoxy-based layer.
In some embodiments, a non-transitory, computer readable medium having instructions stored thereon that, when executed, cause a method for chemical mechanical planarization (CMP) of a polymer or epoxy-based layer to be performed, the method comprising obtaining an endpoint for polymer or epoxy-based material for use in a CMP process, the CMP process configured to polish polymer or epoxy-based material, monitoring the polymer or epoxy-based layer with an endpoint detection apparatus configured to monitor polymer or epoxy-based material, polishing the polymer or epoxy-based layer with the CMP process, detecting when the polymer or epoxy-based layer has reached the endpoint for the CMP process, and halting the CMP process when the endpoint is detected.
In some embodiments, method of the non-transitory, computer readable medium of may further comprise using an optical detection apparatus as the endpoint detection apparatus, the optical detection apparatus is configured to operate at a wavelength of approximately 200 nm to approximately 1700 nm and configured to reduce step height of the polymer or epoxy-based layer such that a surface of the polymer or epoxy-based layer has a uniformity that supports a redistribution layer with at least two lead outs with line and spacing of approximately greater than 0/0 μm to less than or equal to approximately 2/2 μm, using an optical detection apparatus as the endpoint detection apparatus, the optical detection apparatus is configured to operate at a wavelength of approximately 200 nm to approximately 1700 nm and configured to detect a reveal of a metal-based material in the polymer or epoxy-based layer, and/or using more than one of an optical detection apparatus, a motor torque detection apparatus, an eddy current detection apparatus, and an X-ray detection apparatus as the endpoint detection apparatus.
Other and further embodiments are disclosed below.
Embodiments of the present principles, briefly summarized above and discussed in greater detail below, can be understood by reference to the illustrative embodiments of the principles depicted in the appended drawings. However, the appended drawings illustrate only typical embodiments of the principles and are thus not to be considered limiting of scope, for the principles may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
A chemical mechanical planarization (CMP) process is used to enable fine pitch patterning of a polymer-based redistribution layer (RDL) for wafer level packaging. The fine pitch patterning is accomplished by planarizing or polishing a surface of a polymer-based layer on a substrate using CMP endpoints for polymer-based materials. The inventors discovered that polymer-based materials provide a higher level of uniformity after a CMP process, allowing for very close spacing of circuit interconnects, such as line and spacing of greater than 0/0 μm to approximately 2/2 μm or less. In current processes, the new polymer-based material may be polished based on timing and inspection. Timing-based polishing typically wastes material due to extra thicknesses used to prevent burn through of the polymer-based layer when using timing to polish the polymer-based layer. In addition, timing based polishing is subject to slurry removal rate stability. The slurry used in the CMP process may not have a linear removal rate, causing an unknown amount of material to be removed during the timed process. The inventors have discovered several CMP endpoint methods and apparatus that may be utilized to control the polishing of polymer or epoxy-based materials in place of time-based polishing, solving the lack of CMP endpoint systems available for the new class of polymer-based materials which include epoxy-based materials.
The methods and apparatus of the present principles allow thinner polymer layers to be used, allow an increase in the patterning resolution window, and allow control of dishing to improve bonding performance of polymer-based materials, lowering processing costs. In some embodiments, the methods and apparatus may include endpoint determination based on optical systems that operate over a broadband (approximately 200 nm to approximately 1700 nm) for polymer or epoxy thickness and step height control. In some embodiments, the methods and apparatus may include endpoint determination based on lasers for metal clearance in polymer damascene structures. In some embodiments, the methods and apparatus may include endpoint determination based on motor torque control for copper or other metal reveals. In some embodiments, the methods and apparatus may include endpoint determination based on eddy current for metal thickness control in hybrid bonding applications. In some embodiments, the methods and apparatus may include endpoint determination based on electromagnetics (X-rays) for thick absorbing material such as epoxy molding compound (EMC). In some embodiments, multiple types of endpoint determination may be combined together to yield enhanced results.
The CMP apparatus 100 also includes a system controller 116. The system controller 116 controls the operation of the CMP apparatus 100 directly and/or indirectly by controlling other computers (or other controllers) associated with other subsystems of the CMP apparatus 100. In operation, the system controller 116 enables data collection and feedback from the subsystems to optimize performance of the CMP apparatus 100. The system controller 116 generally includes a central processing unit (CPU) 118, a memory 120, and a support circuit 122. The CPU 118 may be any form of a general purpose computer processor that can be used in an industrial setting. The support circuit 122 is conventionally coupled to the CPU 118 and may comprise a cache, clock circuits, input/output subsystems, power supplies, and the like. Software routines, such as the methods described below may be stored in the memory 120 or other computer readable media and, when executed by the CPU 118, transform the CPU 118 into a specific purpose computer (system controller 116). The software routines may also be stored and/or executed by a second controller (not shown) that is located remotely from the CMP apparatus 100. The memory 120 may also be utilized to store data for use with CMP processes associated with endpoints for polymer-based material planarization.
The CMP apparatus 100 may also include a polymer endpoint detection apparatus 126 that includes and is in communication with a polymer endpoint detector 128. In some embodiments, the polymer endpoint detector 128 may be embedded in the rotatable platen 102 near a bottom surface 136 of the rotatable platen 102 (shown), embedded in a center portion of the rotatable platen 102 approximately midway between the top surface 134 and the bottom surface 136, embedded near a top surface 134 of the rotatable platen 102, and/or positioned below the rotatable platen 102. The polymer endpoint detector 128 interacts 138 with the substrate 124 during planarization to obtain parameters associated with a polymer or epoxy-based layer on the substrate 124. In some embodiments, the polymer endpoint detector 128 may include transmitters and receivers to assist in obtaining parameters during CMP processes. In some embodiments, the polymer endpoint detection apparatus 126 may interact with the platen motor 106 and/or the carrier head motor 114 to detect torque parameters during the CMP process. In some embodiments, the polymer endpoint detector 128 may include apparatus for detecting eddy currents in the substrate 124. In some embodiments, the polymer endpoint detection apparatus 126 may be positioned with the polymer endpoint detector 128, may be positioned separate from the polymer endpoint detector 128 (shown), and/or may be part of the system controller 116.
The polymer endpoint detection apparatus 126 processes data relating to polymer or epoxy-based materials to determine endpoints for the CMP processing of the substrate 124. Polymer and epoxy (e.g., EMC) have a higher absorption rate and lower reflection intensity than other dielectrics. The polymer endpoint detection apparatus 126 may alter the transmitter and receiver parameters (e.g., transmission power, receiver sensitivity, transmission signal wavelength, etc.) of the polymer endpoint detector 128 to optimize results obtained by the polymer endpoint detector 128 for the polymer-based material on the substrate 124. The polymer endpoint detection apparatus 126 may also adjust detection parameters and/or polymer CMP endpoints based on the composition of the polymer-based material on the substrate 124 and/or the type of CMP process to be accomplished. Some polymer-based layers on the substrate 124 may contain chip die and/or metallic structures (e.g., vias, contact pads, etc.) that may be revealed (exposed) during the CMP process. Other CMP processes may have hidden or in-film structures that are to remain overlaid with polymer material and are not to be exposed during the CMP process. The process purpose, composition of the polymer-based layer, stored historical data for a given CMP process (e.g., removal rates, variations, etc.), and/or absorption rate of transmitted signals used by the polymer endpoint detector 128 may affect the determination of the polymer CMP endpoint by the polymer endpoint detection apparatus 126.
In
In a first scenario, the polymer endpoint detector 128a transmits an optical light beam 408 at a surface 406 of the polymer-based layer 308 at a location without an embedded chip die. A first portion 410 of the optical light beam 408 is reflected back to the optical light receiver 432a. A second portion 412 penetrates through the polymer-based layer 308 and reflects off of a surface 402 of the EMC of the substrate 302 as a third portion 414 of the optical light beam 408 that penetrates back through the polymer-based layer 308 and to the optical receiver 432a as a fourth portion 418. The inventors found that the polymer-based layer 308 and the EMC of the substrate 302 have different absorption and reflective properties than other dielectrics. For the case of thick polymer, the power and intensity of the optical light transmitter 430a may be increased so that the optical light beam 408 can penetrate the polymer-based layer 308 and to compensate for the absorbing property of the polymer and/or reduced reflective properties of the EMC. The sensitivity of the optical light receiver 432a may also be adjusted to account for the difference in reflective properties of the polymer-based layer 308 and the EMC of the substrate 302. In the first scenario, the polymer endpoint detection apparatus 126 may include compensation for the differences in the absorption and/or reflective properties. The compensation may include referencing historical information to assist in determining if an endpoint has been reached.
In a second scenario, the polymer endpoint detector 128b transmits an optical light beam 420 at a surface 406 of the polymer-based layer 308 at a location that includes an embedded chip die. A first portion 422 of the optical light beam 420 is reflected back to the optical light receiver 432b. A second portion 424 penetrates through the polymer-based layer 308 and reflects off of a surface 404 of the embedded chip die 312 in the substrate 302 as a third portion 426 of the optical light beam 420 that penetrates back through the polymer-based layer 308 and to the optical receiver 432b as a fourth portion 428. In the example, the reflected intensity power is sufficiently high to be processed by the polymer endpoint detector 128b and processed by the polymer endpoint detection apparatus 126. For the case of thick polymer or epoxy (EMC), power and intensity of the optical light transmitter 430b may still need to be increased. The inventors have found that the same endpoint technique can be generalized to endpoint polymer CMP with underlying metallization (e.g., RDL or bump), as shown in
In
The inventors have found that due to the uniqueness of polymer and/or epoxy-based materials that utilizing one or more of the above described techniques may assist in better determining an endpoint for the CMP process. In some embodiments, the polymer endpoint detection apparatus 126 may use more than one of an optical detection, a motor torque detection, an eddy current detection, and an X-ray detection for various endpoint detections in CMP processes where polymer and/or epoxy-based materials are involved.
Embodiments in accordance with the present principles may be implemented in hardware, firmware, software, or any combination thereof. Embodiments may also be implemented as instructions stored using one or more computer readable media, which may be read and executed by one or more processors. A computer readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing platform or a “virtual machine” running on one or more computing platforms). For example, a computer readable medium may include any suitable form of volatile or non-volatile memory. In some embodiments, the computer readable media may include a non-transitory computer readable medium.
While the foregoing is directed to embodiments of the present principles, other and further embodiments of the principles may be devised without departing from the basic scope thereof.
