Patent Application
20070176119
The present invention generally relates to apparatuses and methods for analysis of semiconductor workpieces, such as semiconductor wafers or other semiconductor structures.
Semiconductor devices and other microelectronic devices are typically manufactured on a workpiece (e.g., a semiconductor wafer) having a large number of individual dies (e.g., chips). Each workpiece undergoes several different procedures to construct the switches, capacitors, conductive interconnects, and other components of a device. For example, a workpiece can be processed using lithography, implanting, etching, deposition, planarization, annealing, and other procedures that are repeated to construct a high density of features. One aspect of manufacturing microelectronic devices is evaluating the workpieces to ensure that the microstructures are within the desired specifications and do not include defects that can negatively affect the various microelectronic components that are formed in and/or on the workpieces.
Photoluminescence spectroscopy is a non-contact, nondestructive method of probing the electronic structure of the workpiece to evaluate the extent of impurities and defects. More specifically, when silicon is excited with laser irradiation at an energy above the band-gap of the material, free electron hole pairs are produced. The electron hole pairs can recombine in a manner that causes luminescence. More specifically, the electron hole pairs formed can be trapped at defects and impurities in silicon such that the photons emitted during the recombination process provide a characteristic of the defects/impurities. Thus, photoluminescence spectroscopy is useful for detecting surface or near surface defects and contamination in the workpieces.
Many workpieces also include small geometric features on their surfaces at various stages of fabrication, and various tools and methods have been used to rapidly and accurately analyze the surface geometry of the workpieces to identify portions that are outside specified tolerances. One useful method for analyzing such features is measuring the workpiece's topology. More particularly, a workpiece's topology is a three-dimensional optical measurement of a surface of the workpiece and/or material on the surface. The topology can be measured using a non-contact optical measurement to determine the condition of the workpiece's surface (e.g., roughness) and/or imperfections at the surface (e.g., scratches, pits, bumps, smears, droplets, particulates, and/or mottled portions).
One challenge of evaluating workpieces during manufacturing is correlating the data used to analyze the workpieces. Conventional techniques include measuring various characteristics of the workpieces, but this data is generally not combined or used together in an efficient manner. Furthermore, it can be extremely expensive and time-consuming to accurately align and measure the workpieces within a variety of different measurement tools. Accordingly, there is a need to improve the process for evaluating workpieces.
A. Overview
The present invention is directed toward apparatuses and methods for analyzing surfaces of semiconductor workpieces and other types microelectronic substrates or wafers. One embodiment of the invention, for example, is directed to an apparatus for analyzing a semiconductor workpiece. The apparatus can include a first metrology unit configured to measure photoluminescence from the workpiece and a second metrology unit configured to determine a topographical profile of the workpiece. The apparatus can further include a control unit operatively coupled to the first metrology unit and the second metrology unit to receive and associate data regarding the photoluminescence and the topographical profile to produce an integrated map of the workpiece.
The apparatus can have several different configurations. In one embodiment, for example, the first metrology unit and the second metrology unit can be housed in a single tool. Further, the first metrology unit and the second metrology unit may be components within a single optical assembly and/or be configured to use a single optics subsystem. In other embodiments, the first metrology unit and the second metrology unit may be in separate tools.
Another embodiment of an apparatus for analyzing a semiconductor workpiece includes a radiation source configured to irradiate at least a portion of the workpiece. The apparatus also includes a first metrology unit configured to measure photoluminescence from the workpiece. The metrology unit can include (a) a first detector to measure photoluminescence from the irradiated portion of the workpiece, and (b) a first processor operatively connected to the first detector to produce a photoluminescence map of the workpiece. The apparatus can further include a second metrology unit configured to determine a topographical profile of the workpiece. The second metrology unit can include (a) a second detector to measure radiation reflected from the irradiated portion of the workpiece and generate a condition signal in response thereto, and (b) a second processor operatively coupled to the second detector for evaluating the geometry of the surface of the workpiece based on the condition signal to produce a topographical profile of the surface of the workpiece. The apparatus can also include a control unit operatively coupled to the first metrology unit and the second metrology unit to receive and associate data from the photoluminescence map and the topographical profile to produce an integrated map of the workpiece.
Several embodiments of the invention are also directed to methods for analyzing semiconductor workpieces. For example, one embodiment of a method in accordance with the invention includes irradiating a portion of a workpiece. The method also includes measuring photoluminescence and a topographical profile from the irradiated portion of the workpiece. The method further includes forming an integrated map of the workpiece based on the measured photoluminescence and topographical profile.
The following disclosure describes apparatuses and methods for analyzing surfaces of semiconductor workpieces and other types of microelectronic substrates or wafers. The term “workpiece” is defined as any substrate or wafer either by itself or in combination with additional materials that have been implanted in or otherwise deposited over the substrate. For example, semiconductor workpieces can include substrates upon which and/or in which microelectronic circuits or components, epitaxial structures, data storage elements or layers, and/or vias or conductive lines are or can be fabricated. Semiconductor workpieces can also include patterned or unpatterned wafers. Many specific details of certain embodiments of the invention are set forth in the following description to provide a thorough understanding and enabling description of these embodiments. A person skilled in the art, however, will understand that the invention may be practiced without several of these details or additional details can be added to the invention. Well-known structures and functions have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments of the invention. Where the context permits, singular or plural terms may also include the plural or singular term, respectively. Moreover, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in reference to a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of items in the list.
B. Embodiments of Apparatuses for Analyzing Semiconductor Substrates
In the illustrated embodiment, the apparatus 10 includes a radiation source 20 configured to generate one or more beams 22 at a desired wavelength. The radiation source 20 can be any of a variety of radiation sources known in the art, such as laser systems and/or lamps. The nature of the source depends upon the intended application. In one embodiment, for example, the radiation source 20 can be a laser capable of producing (a) a beam 22 at a single wavelength, or (b) a plurality of beams 22 having different wavelengths. In the illustrated embodiment, a first beam 22a having a first wavelength and a second beam 22b having a second wavelength different than the first wavelength are produced by the radiation source 20. In other embodiments, the radiation source 20 may include multiple lasers or lamps that each produce one or more beams with a desired wavelength.
The beams 22a and 22b are directed to an optical assembly 30. The optical assembly 30 includes an optics subsystem 32 that conditions the beams 22a and 22b to form one or more conditioned beams 23 (illustrated as conditioned beams 23a and 23b, respectively). The optics subsystem 32 is an optical head that can include a variety of lenses, filters, and/or optical elements to condition the beams 22a and 22b. In several embodiments, for example, the optics subsystem 32 includes a beam expander, a beam splitter, and a plurality of lenses and/or filters. In other embodiments, the optics subsystem 32 can include other elements.
The conditioned beams 23a and 23b are directed from the optics subsystem 32 to one or more portions of the workpiece 12 carried by a support member 40. At least one of the support member 40 and the optical assembly 30 is adapted to move relative to the other to change the relative orientation of the workpiece 12 and the optical assembly 30. In the illustrated embodiment, for example, a motor 44 (shown in hidden lines) is operatively coupled to the support member 40 to move the workpiece 12 with respect to optical assembly 30 in the x-, y-, and/or z-directions. In this way, the conditioned beams 23a and 23b are directed onto the desired portions of the workpiece 12. Alternatively, the optical assembly 30 can be moved relative to the support member 40, or both the optical assembly 30 and the support member 40 can be moved relative to each other.
The optics subsystem 32 is also configured to receive radiation reflected or emitted from the workpiece 12 (also shown as beams 23a and 23b) and transmit the reflected radiation to a first metrology unit 50 and/or a second metrology unit 60 for analysis. In the illustrated embodiment, the first metrology unit 50 is configured to measure photoluminescence from the workpiece 12 and the second metrology unit 60 is configured to determine a topographical profile of the workpiece 12. In the embodiment shown in
The first metrology unit 50 can include a first detector 52 and a first processor 54 operatively coupled to the first detector 52. The first detector 52 includes lenses, filters, and/or other mechanisms to isolate certain wavelengths of the reflected radiation and measure the photoluminescence from the workpiece 12. The first processor 54 evaluates the photoluminescence data and forms a photoluminescence map of the workpiece 12. The second metrology unit 60 includes a second detector 62 and a second processor 64. The second detector 62 can also include a number of lenses, filters, and/or other mechanisms to evaluate the reflected radiation and produce a condition signal. The second processor 64 is operatively coupled to the second detector 62 and evaluates the geometry of the surface of the workpiece 12 based on the condition signal from the second detector 62 to produce a topographical profile of the workpiece's surface.
The apparatus 10 further includes a controller 70 operatively coupled to the first metrology unit 50 and the second metrology unit 60. The controller 70 of this embodiment is configured to associate the data from the first metrology unit 50 and the second metrology unit 60. The controller 70, for example, can include a computer-readable medium that receives and associates data regarding the photoluminescence (e.g., the photoluminescence map) and topology (e.g., the topographical profile) of the workpiece 12 to produce an integrated map of the workpiece. The method used by the controller to associate the data is described in greater detail below in Section C. In this embodiment, the controller 70 is also operatively coupled to the radiation source 20 to operate and/or monitor the output of the radiation source 20. In alternative embodiments, the controller 70 may also control operation of the optics subsystem 32 and/or other portions of the apparatus 10.
One advantage of the apparatus 10 described above is that the first metrology unit 50 and the second metrology unit 60 are both configured to use the same optics subsystem 32 or at least share a portion of the same optics subsystem 32. The lenses, filters, and/or other optical elements that make up the optics subsystem 32 can be complex and extremely sensitive components of the apparatus 10. Therefore, the use of a single set of optics is expected to substantially reduce the complexity of the apparatus 10 compared to conventional systems having separate photoluminescent and topology tools.
Another advantage of the apparatus 10 is that the use of a single optics subsystem 32 is expected to quickly perform the analysis process with a high degree of accuracy. For example, after measuring the photoluminescence from a desired portion of the workpiece 12, the topography of that same portion of the workpiece 12 can be measured without moving the workpiece to a different tool and realigning the workpiece. Moving a workpiece to a different tool as required by conventional systems is time consuming and can introduce contamination or cause damage to the workpiece. Moreover, the realignment process required by conventional systems is further time consuming because the workpiece 12 and the optical assembly 30 must be aligned precisely to avoid potential errors. Accordingly, the apparatus 10 is expected to (a) significantly reduce the time for analyzing both the photoluminescence and topography of a workpiece, and (b) eliminate a source of potential errors resulting from misalignment.
Yet another advantage of the apparatus 10 is that the integrated map produced by the apparatus can be used to accept or reject individual workpieces or entire batches of workpieces if they fall outside of desired specifications. This feature can prevent the processing and/or testing of unacceptable workpieces, which in turn will reduce costs and increase throughput for processing and fabrication.
The various components of the first and second tools 210a and 210b can be generally similar to those described above with respect to
In several embodiments, for example, the workpiece 212 can be positioned within the first tool 210a to form a photoluminescence map of the workpiece 212. The workpiece 212 can then be moved to the second tool 210b and realigned using methods known to one of ordinary skill in the art. The second metrology tool 260 determines a topographical profile of the workpiece 212. A controller 280 operatively coupled to both the first tool 210a and the second tool 210b can then associate the photoluminescence data and the topographical profile from the workpiece 212 to form an integrated map of the workpiece. In alternative embodiments, the first tool 210a and/or the second tool 210b may have different combinations of components. Furthermore, the topographical profile of the workpiece 212 may be determined before measuring the photoluminescence.
C. Embodiments of Methods for Analyzinq a Semiconductor Workpiece
Referring to
The method 300 also includes determining a topographical profile of the workpiece at stage 320. The topographical profile describes the surface features and flaws on the workpiece. The topographical data is correlated to form a topographical map 420 (
The method 300 further includes associating the photoluminescence data and topographical profile at stage 330 to form an integrated map 430 (
One advantage of the integrated map 430 is that the topographical information provides the ability to look more deeply into the photoluminescence data. For example, the photoluminescence map can highlight an anomaly, but it can be difficult to determine whether the anomaly is a particle on the surface of the workpiece or a defect within the workpiece. The topographical profile provides additional information about the anomaly so that the characteristics of the anomaly can be quickly determined (e.g., surface particle or embedded defect). In this way, the particle can either be removed before it contaminates the workpiece or the workpiece can be scrapped before wasting additional manufacturing resources.
From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the invention. For example, aspects of the invention described in the context of particular embodiments may be combined or eliminated in other embodiments. Accordingly, the invention is not limited except as by the appended claims.
