Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J4/00—Measuring polarisation of light
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/21—Polarisation-affecting properties
  • G01N21/211—Ellipsometry
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/21—Polarisation-affecting properties
  • G01N21/211—Ellipsometry
  • G01N2021/213—Spectrometric ellipsometry

Definitions

• the disclosure generally relates to the field of surface inspection, and particularly to ellipsometry tools.
• Thin polished plates such as silicon wafers and the like are a very important part of modern technology.
• a wafer for instance, may refer to a thin slice of semiconductor material used in the fabrication of integrated circuits and other devices.
• Other examples of thin polished plates/films may include magnetic disc substrates, gauge blocks and the like. While the technique described here refers mainly to wafers, it is to be understood that the technique also is applicable to other types of polished plates and films as well.
• the term wafer and the term thin polished plate and/or film may be used interchangeably in the present disclosure.
• Ellipsometry is an optical technique for the investigation of the dielectric properties of the wafers. Upon the analysis of the change of polarization of light, which is reflected off a sample (e.g., a wafer surface), ellipsometry can yield information about the sample. Ellipsometry can probe the complex refractive index or dielectric function tensor, which gives access to fundamental physical parameters and is related to a variety of sample properties, including morphology, crystal quality, chemical composition, or electrical conductivity.
• Ellipsometry is commonly used to characterize film thickness for single layers or complex multilayer stacks ranging from a few angstroms or tenths of a nanometer to several micrometers.
• Spectroscopic ellipsometry is a type of ellipsometry that employs a broad band light source, which covers a certain spectral range (e.g., in the infrared, visible or ultraviolet spectral region). By covering a spectral range, the complex refractive index or the dielectric function tensor in the corresponding spectral region can be obtained, which gives access to a large number of fundamental physical properties.
• the present disclosure is directed an ellipsometry system.
• the ellipsometry system may include a support mechanism configured for supporting a wafer and an illumination source configured for delivering an incident beam towards the wafer. The incident beam may reflect off the wafer thereby forming a reflected beam.
• the ellipsometry system may also include an analyzer configured for polarizing the reflected beam. The polarization direction of the analyzer may be rotatable to a plurality of predetermined, discrete angular positions.
• a detector may be utilized to collect a set of spectrum data based on the reflected beam passing through the analyzer. Each spectrum data of the set of spectrum data being collected may correspond to one of the set of predetermined, discrete angular positions.
• a processor module may be utilized to perform simultaneous regression on the set of spectrum data.
• a further embodiment of the present disclosure is directed to an ellipsometry method for inspecting a wafer.
• the method may include: delivering an incident beam towards the wafer, wherein the incident beam reflects off the wafer thereby forming a reflected beam; polarizing the reflected beam utilizing an analyzer, the analyzer having a polarization direction rotatable to a set of predetermined, discrete angular positions; collecting a set of spectrum data based on the reflected beam passing through the analyzer, each spectrum data of the set of spectrum data being collected when the polarization direction of the analyzer is pointing to one of the set of predetermined, discrete angular positions; and performing simultaneous regression on the set of spectrum data collected.
• An additional embodiment of the present disclosure is also directed to an ellipsometry method for inspecting a wafer.
• the method may include: delivering an incident beam towards the wafer, wherein the incident beam reflects off the wafer thereby forming a reflected beam; polarizing the reflected beam utilizing an analyzer, the analyzer having a polarization direction pointing to a first predetermined, discrete angular position; collecting the reflected beam passing through the analyzer when the polarization direction of the analyzer is pointing to the first predetermined, discrete angular position; rotating the analyzer, wherein the polarization direction of the analyzer is rotated to point to a second predetermined, discrete angular position; collecting the reflected beam passing through the analyzer when the polarization direction of the analyzer is pointing to the second predetermined, discrete angular position; and performing simultaneous regression on spectrum data collected when the polarization direction of the analyzer is pointing to the first predetermined, discrete angular position and when the polarization direction of the
• FIG. 1 is an isometric view of an illustration depicting an ellipsometry system in accordance with the present disclosure
• FIG. 2 is an illustration depicting multiple predetermined, discrete angular positions with respect to a cross-sectional view of a reflected beam
• FIG. 3 is a flow chart illustrating an ellipsometry method for inspecting a wafer in accordance with the present disclosure.
• FIG. 4 is a flow chart illustrating a method for collecting spectrum data according to multiple predetermined, discrete angular positions.
• the present disclosure is directed to ellipsometry systems and ellipsometry data collection methods with improved stabilities.
• multiple predetermined, discrete analyzer angles are utilized to collect ellipsometry data for a single measurement, and data regression is performed based on the ellipsometry data collected at these predetermined, discrete analyzer angles. Utilizing multiple discrete analyzer angles for a single measurement improves the stability of the ellipsometry system.
• FIGS. 1 and 2 illustrations depicting an ellipsometry system 100 in accordance to one embodiment of the present disclosure are shown.
• the ellipsometry system 100 may include a support mechanism 102 configured for supporting a wafer 104.
• the ellipsometry system 100 may also include an illumination source 106 configured for delivering an incident beam 108 through a polarizer 1 10 towards the wafer 104, illuminating at least a portion of the wafer 104.
• the incident beam 108 may be reflected off the wafer 104, forming a reflected beam 1 12 as shown in FIG. 1.
• the incident beam 108 and the reflected beam 1 12 span a plane commonly referred to as the plane of incidence.
• the reflected beam 112 then passes a second polarizer, which is called an analyzer 114, and falls into a detector 1 16.
• the analyzer 114 and the detector 116 may be jointly referred to as the analyzer module, which is positioned along the optical path of the reflected beam 1 12 in the plane of incidence.
• multiple analyzer angles are utilized to collect ellipsometry data for a single measurement, therefore improving the stability of the ellipsometry system.
• ellipsometry data may be collected when the polarization direction of the analyzer 114 (vector A in FIG. 1 ) points to various predetermined, discrete angular positions.
• the direction of the analyzer 114 may be stepped /rotated from one discrete position to the next for each of the fixed angular positions, allowing the detector 116 to collect ellipsometry data at each fixed angular positions.
• a pair of analyzer angles a and -a offset symmetrically on either side of the plane of incidence may be defined as the predetermined, discrete angular positions.
• the analyzer 114 may first be rotated so that the direction of the analyzer 1 14 (vector A) is pointing to the analyzer angle a.
• the detector 116 may collect the spectrum reflected off the wafer 104 passing through the analyzer 1 14 when vector A is pointing to the analyzer angle a.
• the direction of the analyzer 1 14 (vector A) may remain unchanged (i.e., pointing to the analyzer angle a) for a predetermined duration while the detector 1 16 is collecting the spectrum.
• the analyzer 1 14 may be rotated with respect to the reflected beam 112 so that the direction of the analyzer 1 14 (vector A) is pointing to the analyzer angle -a.
• the detector 116 may then collect the spectrum reflected off the wafer 104 passing through the analyzer 114 when vector A is pointing to the analyzer angle -a.
• the direction of the analyzer 114 (vector A) may remain unchanged (i.e., pointing to the analyzer angle -a) for the predetermined duration while the detector 116 is collecting the spectrum.
• the value of a may vary and may be determined for each specific application without departing from the spirit and scope of the present disclosure.
• the analyzer angles i.e., the angular positions
• the angular positions are not limited to two depicted in the example above. More than two discrete angular positions may be defined without departing from the spirit and scope of the present disclosure.
• the analyzer 1 14 is not required to be stepped from one discrete point to the next.
• the analyzer 114 may continuously rotate through the range of angles and the detector 116 may collect the spectra reflected off the wafer 104 when the direction of the analyzer 1 14 (vector A) points to one of the predetermined analyzer angles.
• the analyzer 114 may continuously rotate through the range of angles and the detector 116 may collect the spectrum data reflected off the wafer 104, but only the data collected when the direction of the analyzer 114 (vector A) is pointing to one of the predetermined analyzer angles may be used/feed to subsequent processing steps (i.e., the data collected from other angles are not used).
• the ellipsometry data collected in accordance with the present disclosure may be processed utilizing a processor module communicatively coupled with the detector 116.
• the processor module may be implemented as a processing unit, a computing device, an integrated circuit, or any control logic (stand-alone or embedded) in communication with the detector 1 16.
• the processor module may be located in proximity to the detector 116, or located elsewhere and communicate with the detector 1 16 via wired or wireless communication means.
• the processor module may be configured for performing simultaneous regression of the ellipsometry data collected utilizing multiple analyzer angles as described above.
• model based measurement is the typical approach.
• the multiple spectra with different analyzer angle positions may be processed simultaneously for the better accuracy instead of averaging the measurement results with single analyzer angle spectrum.
• One of the advantages of the dual/multi analyzer angle measurements in accordance with the present disclosure is to minimize the systematic errors present in the optical design and mathematical model of the system such that the resultant errors after the model fit are symmetrically distributed around the ideal state of zero error, improving the stability of the ellipsometry system 100.
• the processor module may also be configured to facilitate a calibration process to select the optimal angles for the analyzer 1 14.
• the analyzer 1 14 may be supported by a movable /rota table mechanism. Initially, the direction of the analyzer 1 14 (vector A) may be setup to point to the angle a, then carefully tuning the second angle from the starting position of -a, in such a fashion as to maximize the symmetry of residual errors after the measurement model fit. That is, the two analyzer angles are not required to be exactly symmetric with respect to the plane of incidence.
• an elUpsometry system may include more than one illumination source as described above for delivering additional incident beam(s) towards the wafer.
• Each illumination source may have a corresponding analyzer modules arranged in accordance with the present disclosure. It is understood that the arrangement of measurements with analyzer angles as described above may be independently configured for each illumination source. That is, if the elUpsometry system includes multiple ellipsometers each with a distinctive optical design, then it is appropriate for each subsystem to determine the optimum measurement analyzer angles in order to maximize its own sensitivity.
• the polarizer 110 may be configured as a continuously rotating polarizer.
• a continuously rotating polarizer may polarize the incident beam delivered to the wafer, effectively providing a spectroscopic elUpsometry system.
• the spectroscopic elUpsometry system may also utilize the multi-angle analyzer module in accordance with the present disclosure in order to improve its stability and sensitivity.
• the elUpsometry and spectroscopic elUpsometry systems in accordance with the present disclosure may provide improved stability, precision and sensitivity for inspecting various types of wafers including materials with high dielectric constant (also referred to as high-k applications).
• high-k applications the value of a may range between 25° and 37°. However, it is understood that such a range may vary and may be determined for each specific application without departing from the spirit and scope of the present disclosure.
• Step 302 may deliver an incident beam towards the wafer.
• the incident beam may reflect off the wafer thereby forming a reflected beam as described above.
• the reflected beam may be polarized in step 304 utilizing an analyzer.
• the polarization direction of the analyzer may be rotatable to a set of predetermined, discrete angular positions.
• Step 306 may collect a set of spectrum data based on the reflected beam passing through the analyzer. Each spectrum data of the set of spectrum data being collected may correspond to one of the set of predetermined, discrete angular positions.
• step 308 may perform simultaneous regression on the set of spectrum data collected at these predetermined, discrete angular positions.
• step 402 may rotate the analyzer so that its polarization direction is pointing to a first predetermined, discrete angular position.
• step 404 may then collect the reflected beam passing through the analyzer when the polarization direction of the analyzer is pointing to the first predetermined, discrete angular position.
• step 406 may rotate the analyzer so that its polarization direction is pointing to a second predetermined, discrete angular position.
• step 408 may collect the reflected beam passing through the analyzer when the polarization direction of the analyzer is pointing to the second predetermined, discrete angular position.
• Step 410 may perform simultaneous regression on spectrum data collected when the polarization direction of the analyzer is pointing to the first predetermined, discrete angular position and when the polarization direction of the analyzer is pointing to the second predetermined, discrete angular position.
• the analyzer is not required to step from one discrete point to the next.
• the analyzer may continuously rotate through the range of angles and the detector may collect the spectrum data when the direction of the analyzer points to one of the predetermined analyzer angles.
• the analyzer may continuously rotate through the range of angles and the detector may collect the spectrum data reflected off the wafer, but only the data collected when the direction of the analyzer is pointing to one of the predetermined analyzer angles may be used for simultaneous regression.
• wafer inspections the systems and methods in accordance with the present disclosure are applicable to other types of polished plates as well without departing from the spirit and scope of the present disclosure.
• wafer used in the present disclosure may include a thin slice of semiconductor material used in the fabrication of integrated circuits and other devices, as well as other thin polished plates such as magnetic disc substrates, gauge blocks and the like.
• the methods disclosed may be implemented as sets of instructions, through a single production device, and/or through multiple production devices. Further, it is understood that the specific order or hierarchy of steps in the methods disclosed are examples of exemplary approaches.

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• 2012
  • 2012-07-03 JP JP2014519266A patent/JP2014524028A/ja active Pending
  • 2012-07-03 EP EP12807285.7A patent/EP2729789A4/en not_active Withdrawn
  • 2012-07-03 WO PCT/US2012/045436 patent/WO2013006637A1/en active Application Filing
  • 2012-07-06 TW TW101124514A patent/TWI558975B/zh active

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