Scattered melting detection system and method of using the same

Abstract

A high-bandwidth time and spatial resolution scattered phase transition microscope system configured to detect the onset of melting in a wafer processed by a laser annealing system having a very short dwell time and spot size.

Description

[Technical Field]

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 337,714, filed on 3 May 2022, entitled “Scatter Melt Detection System and Method of Use thereof,” which is incorporated herein by reference in its entirety.

[0002] This disclosure generally relates to temperature measurement. In particular, this disclosure relates to phase transition microscopy. [Background technology]

[0003] Pulsed laser melt annealing systems are used in the manufacturing of advanced integrated circuit (IC) chips for rapid heat treatment of the chips. The heat treatment provided by such laser systems can be used for various effects, such as dopant activation, bond formation, and other modifications to the material and electrical properties of the chip. [Overview of the project] [Problems that the invention aims to solve]

[0004] However, accurate measurement and control of wafer temperature during annealing using pulsed laser systems is crucial, and this can become difficult as the duration of the laser's action on the wafer decreases and the surface area of ​​the wafer affected by the laser diminishes. Accurate measurement and control of wafer temperature is also important for calibrating the annealing system. [Means for solving the problem]

[0005] In one embodiment, the present disclosure relates to a method for determining the occurrence of a solid-to-liquid material phase transition in a semiconductor material during a laser annealing process. This method includes forming an annealing image on the surface of a semiconductor material using an annealing laser beam from an annealing laser, forming a scattering image of a region of the semiconductor surface including the annealing image, and identifying the solid-to-liquid material phase transition of the semiconductor material according to the intensity of light collected in the scattering image.

[0006] In another embodiment, the disclosure relates to a method for analyzing scattered image data. This method includes receiving scattered images of a region of a semiconductor surface captured during a laser annealing process of a semiconductor, and identifying a solid-to-liquid material phase transition of the semiconductor material from the images, wherein this identification includes identifying statistical, time-series, or geometrically nonlinear fluctuations of the image intensity as a function of one or more annealing process control parameters.

[0007] In yet another embodiment, the disclosure relates to a method for performing melt calibration for a laser annealing process of a semiconductor material. The method includes annealing a region of the semiconductor material with an annealing laser beam from an annealing laser, which includes stepwise changing the power level below and above a melt threshold power level at which a material phase transition from solid to liquid occurs in the semiconductor material; capturing a scattering image of the region of the semiconductor material during annealing; and determining at least one melt threshold setpoint power level of the annealing laser from the captured scattering image.

[0008] In yet another embodiment, the disclosure relates to a scattering melt detection system. This scattering melt detection system includes a stage configured to support a semiconductor wafer, an annealing laser configured to anneal the semiconductor wafer, a scattering melt detector including an image capture device including a focal plane array (FPA), and a scattering optical arrangement configured to block or avoid specular reflection of the beam formed by the annealing laser and to form a scattering image of the surface of the semiconductor wafer on the FPA.

[0009] In yet another embodiment, the disclosure relates to a laser annealing system. The system includes an annealing laser, a storage device containing at least one annealing laser melt threshold calibration setpoint that specifies the operating parameters of the annealing laser to raise the temperature of a local region of a semiconductor material to a melt threshold under a set of predetermined annealing process conditions, the annealing laser melt threshold calibration setpoint being derived from scattering images of the semiconductor material acquired during the laser annealing process of the semiconductor material, and a controller configured to control the annealing laser according to the annealing laser melt threshold calibration setpoint.

[0010] In yet another embodiment, the disclosure relates to a non-temporary machine-readable storage medium, which includes at least one annealing laser melt threshold calibration setpoint that specifies the operating parameters of an annealing laser for raising the temperature of a local region of a semiconductor material to a melt threshold under a set of predetermined annealing process conditions, the annealing laser melt threshold calibration setpoint derived from scattering images of the semiconductor material acquired during the laser annealing process of the semiconductor material.

[0011] In yet another embodiment, the disclosure relates to a method for forming non-melted reference images and parameters for use in a melt detection algorithm. This method includes annealing a wafer in a non-melted state, capturing an image frame using a scattering melt detector, recording the output level of the annealing laser, creating a non-melted reference image from the captured image frame, processing the non-melted reference image to generate a plurality of non-melted one-dimensional stage scanning intensity profiles, identifying a region of interest (ROIref) in the non-melted reference image, and creating an average one-dimensional stage scanning intensity profile.

[0012] In yet another embodiment, the disclosure relates to a method for detecting whether wafer material has melted during an annealing process. This method includes annealing the wafer below a melting threshold, at a melting threshold, or above a melting threshold; capturing image frames using a scattering melt detector during annealing; recording the laser power level; creating an averaged image from the captured image frames; and creating a melted-detected image relating the averaged image to a corresponding non-melted control image of the same wafer type.

[0013] In yet another embodiment, the disclosure relates to a method for detecting whether a wafer material has melted during an annealing process. This method includes annealing the wafer below a melt threshold, at a melt threshold, or above a melt threshold; capturing an image frame during annealing using a scattering melt detector; calculating a statistical variation in pixel values ​​within a region of interest (ROIref) of the image frame, which is the area of ​​the image where the annealing laser image is formed on the wafer; and identifying the onset of melting by comparing the calculated statistical variation. [Brief explanation of the drawing]

[0014] For illustrative purposes, the drawings illustrate aspects of one or more embodiments of the present disclosure. However, it should be understood that the present disclosure is not limited to the exact arrangements and means shown in the drawings. [Figure 1] This is a schematic diagram of an exemplary laser annealing system having a scattering melt detector according to the present disclosure. [Figure 2] This is a top view of a semiconductor wafer illustrating an exemplary method of scanning the wafer surface using preheating line images and annealing images. [Figure 3A] This is a top view magnified of the preheating line image and annealing image formed on the wafer surface, showing the relative dimensions and scanning direction of the two images, as well as the scanning overlap region that defines the residence time of the melt annealing process. [Figure 3B]This is a top view of an alternative example without a preheating laser, showing the annealed image formed on the wafer surface, as well as the image sweeping direction and the stage scanning direction. [Figure 3C] This is a top view magnified of the annealing image sweep and the volume of the liquid phase semiconductor material, called the molten pool, which increases along the sweep of the annealing image. [Figure 4A] This is a schematic diagram illustrating an exemplary scattering melt detection system that utilizes a laser process beam as a light source probe. [Figure 4B] This is a schematic diagram of an exemplary scattering melt detection system, including a light source probe separated from a laser process beam. [Figure 5A] This is a schematic diagram of the optical arrangement of the scattering image system disclosed herein. [Figure 5B] This is a schematic diagram of another example of the optical arrangement of the scattering image system of the present disclosure. [Figure 6A] This diagram conceptually and visually illustrates the data captured within the image frame by the image capture device of a scattering melt detector during the sweeping of an annealed image when the wafer surface is in a non-melted state. [Figure 6B] This figure conceptually and visually illustrates the data captured within the image frame by the image capture device of a scattering melt detector during the sweep of an annealing image, when a pool of liquid phase material is formed along the sweep of the annealing image while the wafer surface is in a molten state. [Figure 6C] This data comes from image frames of an annealing image swept using an improperly calibrated annealing laser, resulting in a mixture of non-melted and molten areas in the sweep. [Figure 7A] The test data shows the results of gradually increasing the laser power, and an increase in the melting range was detected in the test data from the melting threshold calibration. [Figure 7B] The laser power was increased in stages, and the increase in the degree of melting was detected in the test data from the melting threshold calibration. [Figure 7C]The laser power was increased in stages, and the increase in the degree of melting was detected in the test data from the melting threshold calibration. [Figure 8] This shows the FPA cumulative intensity data for a series of annealing processes as the output level is increased below and above the melting threshold output level. [Figure 9A] This shows scattered image data of multiple consecutive annealing images swept along a semiconductor surface using an annealing laser operating at a melting threshold output level. [Figure 9B] This shows scattered image data of multiple consecutive annealing images swept along a semiconductor surface using an annealing laser operating at a melting threshold output level. [Figure 10] This is a functional block diagram of an example of a computing device. [Figure 11] A conceptual representation of some exemplary image frames captured by the ICD of the scattering melt detector during the annealing process is shown. [Figure 12] An exemplary method for generating a non-melted state reference image and associated parameters for use by one or more melt detection algorithms is illustrated. [Figure 13] This example demonstrates one melt detection algorithm in which melting is detected from the nonlinearity of the amplitude in an image frame. [Figure 14] This document presents an exemplary method of a melt detection algorithm that detects melting from statistical variations in melting images. [Modes for carrying out the invention]

[0015] Aspects of the present disclosure are configured to detect the onset of melting in semiconductor wafers processed by scanning CW or QCW (pulse time << residence time) laser annealing systems having very short residence times and small spot sizes, and include a phase transition microscope system having high bandwidth temporal and spatial resolution for calibrating such systems for the annealing process. In some examples, the melt detection systems of the present disclosure are configured to accurately and reliably detect the onset of melting for lasers having very short residence times in the range of 10 ns to 500 ns or 25 ns to 250 ns, and spot sizes in the range of 10 μm to 150 μm × 10 μm to 150 μm.

[0016] Melt annealing involves using an incident laser beam to locally raise the temperature of the wafer surface or subsurface until it melts. For example, if the wafer surface consists of a thin silicon layer on top of a layer of material having a lower melting temperature (e.g., germanium or germanium-silicon), the wafer surface may remain solid while the subsurface material melts. The melt detection system described herein may be configured to detect melting in a surface melting process where melting occurs on the wafer surface, and / or to detect melting in a subsurface melting process where the wafer surface remains solid and a volume of material beneath the wafer surface melts.

[0017] Figure 1 is a schematic diagram of an exemplary quasi-continuous wave (QCW) laser annealing system ("System") 100 into which the melt detection system of the present disclosure may be incorporated. As can be understood, System 100 is described and illustrated as an example, and the melt detection system of the present disclosure may be used in any of various other laser annealing systems. Specific aspects of exemplary embodiments of System 100 are described in U.S. Patent No. 10,083,843, entitled “Laser Annealing System and Method Having Very Short Residence Time,” issued September 25, 2018, the contents of which are incorporated herein by reference in their entirety. References incorporated in U.S. Patent No. 10,083,843, including U.S. Patents No. 8,309,474, No. 8,546,805, No. 8,865,603, and U.S. Patent Application No. 14 / 497,006, currently issued as U.S. Patent No. 9,343,307, are also incorporated herein by reference in their entirety.

[0018] System 100 includes a wafer stage 120 that operably supports a chuck 130 having a top surface 132. The wafer stage 120 is operably connected to a stage controller 124 and is configured to move in the XY plane via the operation of the stage controller, and optionally also in the Z direction. The chuck top surface 132 is configured to operably support a wafer 10 having a surface 12. In some examples, the wafer 10 may be processed and may contain patterns defined by semiconductor structures typically associated with various stages of manufacturing integrated circuit chips, often having optically deep, highly patterned multilayer structures. In other examples, the wafer 10 may be unprocessed and have no manufactured structures, and the surface 12 may be an extremely smooth, mirror-like surface. As will be described in more detail below, the unprocessed wafer 10 may be useful in the measurement systems disclosed herein for calibrating and tracking the performance of laser annealing tools. The measurement systems disclosed herein, when used in conjunction with a well-calibrated annealing system, can perform wafer-specific annealing laser power calibration and, for example, determine melt threshold setting power levels for specific materials or surfaces. In one example, the chuck 130 includes a heater that heats the wafer 10 to a temperature higher than the uniform ambient temperature. The wafer stage 120 is operably connected to the stage controller 124.

[0019] System 100 includes an annealing laser system 250 configured to generate a scanning laser beam 268 that forms an annealed image 270 (Figure 2) on the wafer surface 12. The annealing laser system 250 includes an annealing laser 260 that emits an initial laser beam 262, a modulator 264 operably connected to a modulator driver, and a scanning optical system 266 that receives the initial laser beam and generates the scanning laser beam 268. In one example, the annealing laser 260 may be a QCW fiber laser that emits a scanning laser beam 268 having a wavelength of, for example, 532 nm. The foregoing is provided as an example, and other annealing laser systems currently known or to be developed may be used with the measurement system disclosed herein. In one example, the modulator 264 is an acousto-optic modulator (AOM) used with the scanning optical system 266, which selectively and alternately cuts off and passes through the initial laser beam 262 to control the scanning of the annealed image 270, resulting in a sweeping motion of the annealed image across the entire wafer surface.

[0020] In some examples, system 100 may optionally also include a preheating laser system 150 configured to operate in conjunction with the annealing laser system 250 and generate a preheating laser beam 168. The preheating laser beam 168 is heated to a wafer surface (or sub-wafer surface) temperature T S melting temperature T M Lower pre-annealing temperature T PA It is used to preheat the wafer surface 12 by raising it to a certain temperature.

[0021] The preheating laser system 150 may include a preheating laser 160 and a line-forming optics system 166. The preheating laser 160 may include a diode laser, a fiber laser, or a CO2 laser such as a continuous-wave (CW) p-polarized 10.6-micron CO2 laser. In one example, the line-forming optics system 166 is configured such that the preheating laser beam 168 is incident at an incident angle that is nearly perpendicular to the wafer surface 12 or at a large oblique angle. In one example embodiment, the incident angle of the preheating laser beam 168 is approximately equal to the Brewster angle with respect to the wafer surface 12, thereby reducing or minimizing the adverse effect on pattern density due to non-uniform light absorption.

[0022] The line-forming optics system 166 is configured to receive an initial laser beam 162 from the preheating laser 160 and from it to form a preheating line image 170 (Figures 2 and 3) on the wafer surface 12. The line-forming optics system 166 and the scanning optics system 266 may each include lenses, mirrors, apertures, filters, active optical elements (e.g., variable attenuators), and combinations thereof. In one example, one or both of the line-forming optics system 166 and the scanning optics system 266 may be configured to perform beam tuning, for example, to homogenize the respective laser beams 162 and 262 and / or to give the laser beams a selected cross-sectional shape. Optical systems as non-limiting examples suitable for performing such beam tuning are disclosed in U.S. Patents 7,514,305, 7,494,942, 7,399,945, and 6,366,308, the contents of which are incorporated herein by reference in their entirety. In one example, the initial laser beam 262 from the annealing laser 260 is of high quality (e.g., substantially Gaussian) and is used with little (or sometimes no) beam adjustment.

[0023] System 100 also includes a scattering melt detector 280 configured in a scattering optics arrangement for detecting scattered light from a region of interest on the wafer surface 12 and for detecting the onset of melting by temporally and spatially resolving the scattered light, as will be described in more detail below. The scattering optics arrangements of this disclosure include systems based on spatially resolved sensors or sensor arrays that do not have a far-field specular reflection diffraction limit for the probe beam and do not detect specular reflection from a flat wafer surface. One example of a scattering optics arrangement is dark-field imaging. Probe control (such as polarization and wavelength) and post-optical measurement selection (such as polarizing filters and birefringent crystals) can also be used to capture the same or similar scattering information.

[0024] An exemplary laser annealing system 100 further includes a controller 300. In one example, the controller 300 is or includes a computer, such as a personal computer or a workstation. Preferably, the controller 300 includes one of the commercially available microprocessors, a suitable bus architecture for connecting the processor to a storage device such as a hard disk drive, and suitable input devices (e.g., a keyboard) and output devices (e.g., a display). The controller 300 is programmable via instructions (software) recorded on a non-temporary computer-readable medium (e.g., memory, the processor, or both), which cause the controller to perform various functions of the system 100 to achieve wafer annealing 10.

[0025] The controller 300 is operably connected to the preheating laser system 150 and the scanning laser system 250, and controls the operation of these systems. The controller 300 is electrically connected to the modulator 264 and controls the operation of the modulator using the control signal SMod. In one example, the controller 300 includes digital signal processors (DSPs) (not shown) for controlling the scanning function in the preheating laser system 150 and the scanning laser system 250. In some examples, the controller 300 may also be operably connected to the scattering melt detector 280 and the scanning optics system 266, and may be configured to receive and process a melt signal SM generated by the scattering melt detector during the laser annealing process for use when controlling the annealing laser system 250 or the preheating laser system 150, as well as adjusting the output level of the scanning laser beam 268 to achieve desired process conditions. In other examples, the controller 300 may control the output level of the annealing laser system 250 according to a previously acquired annealing laser melt calibration setpoint 1024 stored in a computer-readable storage device 1016 (Figure 10). The controller 300 or another computing device may also be configured to control components of the scattering melt detector 280, such as controlling the image acquisition device (ICD) of the melt detector.

[0026] In one example of the operation of system 100, the system controller 300 transmits a first control signal S1 to the preheating laser 160, which in turn generates an initial laser beam 162. This initial laser beam 162 is received by the optical system 166, which forms a preheating laser beam 168 from it, and the preheating laser beam 168 forms a preheating line image 170 on the wafer surface 12. The system controller 300 also transmits a second control signal S2 to the annealing laser 260, which in turn generates an initial laser beam 262. This initial laser beam 262 is received by the scanning optical system 266, which, controlled by the control signal SS, forms a scanning laser beam 268, and the scanning laser beam 268 then forms an annealing image 270 on the wafer surface 12. The system controller 300 also transmits a third control signal S3 to the stage controller 124, causing the stage 120 to perform a controlled movement and move (scan) the wafer 10 relative to the preheating line image 170 and the annealing image 270. In an example where the chuck 130 performs wafer preheating, the system controller 300 may transmit another control signal (not shown) to the chuck controller to start or control wafer preheating. The typical chuck preheating range is from room temperature (25°C) to 400°C.

[0027] Figure 2 is , Preliminary Examples of when the thermal laser system 150 is used in This is a top view of wafer 10 illustrating a method of scanning the wafer surface using an annealing image 270. Moving the preheating line image 170 relative to the wafer surface 12 can be achieved by moving the stage 120 in a first direction indicated by arrow AR1, for example, in the y direction, which is also referred to herein as the preheating scanning direction or stage scanning direction. The portion of the wafer surface 12 related to the preheating line image 170 is the wafer surface temperature T S The pre-annealing temperature is T PAThis represents a locally preheated portion of the wafer surface that is raised to this point. The annealed image 270 formed by the scanning laser beam 268 moves relative to the wafer surface 12 in a second direction orthogonal to the first direction, for example, in the x-direction, as indicated by the arrow AR2, and is referred herein to as the annealing scanning direction or sweeping direction.

[0028] The scanning optics system 266 is configured to scan or sweep the annealed image 270 over the preheating line image 170 in the x-direction over the length of the preheating line image. In one example, the scanning speed of the annealed image 270 is sufficiently fast compared to the movement of the preheating line image 170, so that the preheating line image remains substantially stationary while the annealed image is being scanned.

[0029] When the annealed image 270 reaches the edge of the preheating line image 170, the scanning laser beam 268 and the corresponding annealed image 270 are turned off by activating the modulator 264 (Figure 1), which in turn blocks the transmission of the initial laser beam 262. While the scanning laser beam 268 is "off," the preheating line image 170 moves in the y-direction, thereby allowing scanning of the next portion of the wafer surface 12. In one example, the movement of the preheating line image 170 may be continuous, for example, by continuously moving the stage 120 in the y-direction. Once the preheating line image 170 is positioned, the scanning laser beam 268 is turned on again by putting the modulator 264 into transmission mode, so that the scanning optics system 266 can direct the scanning laser beam 268 and the corresponding annealed image 270 to the starting position of the first edge of the newly positioned preheating line image 170. The scanning of the annealed image 270 is then performed on the newly positioned preheating line image 170. Figure 2 shows an exemplary method of scanning substantially the entire wafer surface 12 (e.g., at least the patterned portion) by repeating the scanning method described above. In other examples where the annealing system does not include a preheating laser, such as a preheating laser system 150, the preheating line image 170 is omitted, and the annealing image 270 can be scanned at high speed in the x direction while the wafer 10 is moved in the y direction by the stage 120.

[0030] Figure 3A is a top view enlargement of one of the preheating line image 170 and annealing image 270 formed on the wafer surface 12. The preheating line image 170 has a proximal end 172, a distal end 174, and opposing sides 173. The preheating line image 170 has a longitudinal direction (dimension) extending from the proximal end 172 to the distal end 174 and has a length L1. The preheating line image 170 also has a narrow direction (dimension) measured between the opposing sides 173, which have a width W1. In one example, the length L1 is in the range of 5 mm to 20 mm, and an exemplary length L1 is in the range of 7 mm to 12 mm. Also, in one example, the width W1 is in the range of 50 μm to 200 μm, and an exemplary width W1 is 150 μm. In one embodiment, the preheated laser beam 168 (Figure 1) has a Gaussian intensity profile in the scanning direction (e.g., y-direction) and a relatively flat upper distribution in the longitudinal (scanning transverse direction) direction (e.g., x-direction). The beam width W1 is 1 / e of the Gaussian profile. 2 It can be defined by intensity values ​​or the full width at half maximum (FWHM) of the Gaussian profile.

[0031] The anneal image 270 overlaps a part of the preheat line image 170, and the overlapping area is referred to as the scanning overlap area (SOR) in this specification. The anneal image 270 has a long dimension with length L2 and a narrow dimension with width W2. In the illustrated example, the anneal image 270 has a substantially Gaussian intensity distribution in the x and y directions. The long dimension L2 of the anneal image 270 is oriented in the direction of the short dimension W1 of the preheat line image 170. In one example, the length L2 ranges from 100 μm to 500 μm, the width ranges from 10 μm to 50 μm, and in some examples, the width ranges from 15 μm to 20 μm or from 16 μm to 18 μm. The scanning direction AR2 of the anneal image 270 is perpendicular (orthogonal) to its longitudinal direction. The scanning direction AR2 is also called the anneal scanning direction or the sweeping direction and is substantially orthogonal to the preheat scanning direction AR1. The width W2 of the anneal image 270 defines the width of the scanning overlap area SOR in the anneal scanning direction AR2. By rapidly scanning the anneal image 270 in the scanning direction AR2, the SOR forms an anneal irradiation line 272 having substantially the same size as the preheat line image 170, which is sequentially moved in the y direction (preheat scanning direction AR1) along the wafer surface 12 by the movement of the stage 120 in the y direction.

[0032] In one example, the length L2 is substantially larger than the width W1 (e.g., two to four times larger), and as a result, as shown in FIG. 3A, the ends of the anneal image 270 extend beyond the sides 173 of the preheat line image 170. This makes it relatively easy to align the preheat line image 170 and the anneal image 270 to define the scanning overlap area SOR. This configuration utilizes the high-intensity part in the center of the anneal image 270 to raise the wafer surface temperature T S to the melting temperature T M until it rises.

[0033] In one example, the width of the residence time t d of the scanning overlap area SOR is within the range of 10 ns ≤ t d ≤ 500 ns, and in another example, 25 ns ≤ t dIt is within the range of ≤250ns. When the width W2 = 15 μm and the residence time is 25 ns, the scanning speed of the annealed image 270 and thus the scanning overlap region SOR is 、6 It is 00 m / s. Residence time t d If the scan speed is 250ns, s The speed is 60 m / s. Residence time t d If the scan speed is 500ns, then v s The speed is 30 m / s. Residence time t d If the scan speed is 10 ns, s This is 1500 m / s. In one example, the scanning optical system 266 is configured to provide any speed in between these speeds.

[0034] Figure 3B is a top view enlargement of another exemplary embodiment of system 100 in which the preheating laser system 150 is omitted. The annealing laser system 250 heats the wafer surface temperature T S The system is designed and configured to raise the temperature to a desired annealing temperature. High-speed scanning of the annealing image 270 in scanning direction AR2 causes the stage 120 to move in the y direction, forming an annealing illumination line 272 that moves sequentially along the wafer surface 12 in the y direction (arrow AR1). In one example, the length L1 of the annealing illumination line 272 is in the range of 3 mm to 12 mm or less, the width W2 of the annealing image 270 is in the range of 10 μm to 50 μm, and the length L2 of the annealing image 270 is in the range of 100 μm to 500 μm.

[0035] Figure 3C is a top view of a portion of the wafer surface 12, showing three points in time (labeled a, b, and c) of the annealing image 270 moving in the scanning direction AR2 along the annealing irradiation line 272. Figure 3C conceptually illustrates a molten pool 310 formed by the scanning laser beam 268, in which a localized area of ​​the wafer surface 12 melts and partially or completely transitions from a solid phase to a liquid phase, resulting in the creation of an interface 312 between the solid and liquid phases. In the illustrated example, the size of the molten pool 310 increases along the scanning direction AR2, which is potentially due to the increasing optical power density of the laser beam 268 through the sweep of the annealing image 270 across the annealing irradiation line 272. The phase transition of the wafer material in the molten pool 310 is a first-order phase transition that results in a discontinuity in both the density of the wafer material and the form of interatomic or intermolecular interactions. The phase transition causes a significant change in the refractive index of the material due to differences in electromagnetic interactions between the two different phases of the material (solid and liquid). In one example, the refractive index of the liquid phase in the molten pool 310 is substantially higher than the refractive index of the wafer material of the solid phase outside the molten pool 310, for example, 100% to 300% higher than the refractive index of a typical IC semiconductor material.

[0036] The interface 312 between the molten pool 310 and the solid phase material surrounding it acts as the primary scattering source of incident light, and the magnitude of the wide-field structure factor is determined by the radius r of the molten pool 310. l The intensity increases accordingly. The scattering imaging systems disclosed herein are designed and configured to detect scattered light generated at the start of melting and when the molten pool 310 first begins to form. The intensity of the scattered light increases rapidly and nonlinearly as the size of the molten pool 310 increases, and the scattering imaging systems of this disclosure may be configured to detect the increasing intensity of scattered light resulting from the increasing extent of the molten wafer material.

[0037] In the non-molten state of the solid phase, the relationship between the intensity of the reflected light signal and the material temperature can be approximated as approximately linear, γT, where γ is the scaling factor and T is the material temperature. For a molten pool 310 with a wavelength smaller than the wavelength of the incident light, for example, the wavelength of the laser beam 268, the scattering intensity of the molten pool 310 and the interface 312 is approximately αV. 4 / 3 It is approximated by , where α is the scaling factor and V is the volume of the molten pool, or the fourth power of the radius of the molten pool, where the magnitude α >> γ. For a molten pool 310 that is much larger than the wavelength of the incident light, the radius r l The discontinuity on the molten pool becomes the main scattering source in the wide field of view, and its magnitude is approximately αV. 2 / 3 This is approximated as follows. Thus, the overall scaling relationship between the increase in optical output and the size of the molten pool is highly nonlinear and can eventually saturate the scattering imaging system. In the example shown in Figure 3C, the initial formation of the molten pool 310 results in a sharp discontinuity in the light detected by the scattering melt detector 280 due to a sharp increase in scattered light emitted from the region surrounding the molten pool. As the size of the molten pool 310 increases (e.g., the sizes of molten pools 310b and 310c compared to molten pool 310a), the intensity of the light detected by the scattering melt detector 280 increases nonlinearly on the order of the fourth power of the increase in the radius of the molten pool, which can rapidly saturate the melt signal SM generated by the melt detector. The scattering melt detector 280 and scattering imaging channel disclosed herein are designed and configured to be highly sensitive to the onset of melt, where the discontinuous increase in the intensity of the light captured by the melt detector occurs substantially instantaneously at the onset of melting, resulting in an increase of several orders of magnitude in the intensity of the optical signal.

[0038] During the annealing process, a scattering melt detector 280 can be used to capture light from the surrounding region, including light diffracted, reflected, or refracted by optical structures within the region of the annealed image 270. In one example, the scattering melt detector 280 generates a melt signal SM representing the detected light and transmits the melt signal to a controller 300. In one example, the controller 300 receives the melt signal SM and can use the signal to create a feedback loop that controls one or more characteristics, such as the output level of the annealing laser system 250 and, in some examples, the preheating laser system 150, resulting in the wafer surface temperature T S This can be controlled. In some examples, the scattering melt detector 280 may be used to calibrate and track the optical performance of the annealing laser system 250. Also in some examples, the scattering melt detector 280 may be used to develop wafer-specific laser power calibrations that provide melt threshold laser power setpoints corresponding to a set of predetermined annealing process conditions.

[0039] Figure 4A shows a side view of one embodiment of the scattering melt detector 280. In the illustrated example, the melt detector 280 receives light from the wafer surface 12 along a scattering detector path 402 having an angle α1 with respect to the surface normal N that is different from the angle α2 of the scanning laser beam 268. In the illustrated example, the scanning laser beam 268 is used simultaneously as a probe for scattering temperature measurement and as an annealing laser beam. In other examples, a light source other than the scanning laser beam 268 can be used as a probe. Using the scanning laser beam 268 as a light source for scattering measurement offers the advantage of a simpler array because no additional light source is required, and it illuminates only a field of view around a small annealing image 270 that can travel rapidly across the wafer surface 12, for example, up to about 1 km / s. Using the scanning laser beam 268 as the light source for scattering measurements eliminates the need for additional light sources and offers the advantage of a simpler setup, as it illuminates only the field of view around a small annealed image 270 that can travel across the wafer surface 12 at high speeds of, for example, up to approximately 1 km / s.

[0040] The scanning laser beam 268 has an incidence angle α2 that is different from angle α1 with respect to the surface normal N, and forms an annealed image 270 on the wafer surface 12. The angle α1 of the scattering detector path 402 is designed so that the specular reflection 268R of the scanning laser beam 268 from the surface 12 of the wafer 10 does not enter the scattering detector path 402, thereby enabling scattering observation by the melt detector 280.

[0041] The melt detector 280 includes an optical element 404 and an image capture device (ICD) 406. The ICD 406 includes, or is electrically connected to, at least one pixelated two-dimensional CCD or CMOS focal plane array (FPA) and associated electronic equipment known in the art of image capture devices, including a processor and storage unit for storing captured images. The optical element 404 is configured to image the wafer surface 12 onto the FPA. In one example, the ICD 406 is configured to capture scattered images at an exposure time frame relatively long compared to the residence time of the laser beam 268, for example, at an image frame capture rate of about 50 us, thereby capturing at least one entire sweep of the annealed image 270 across the annealing irradiation line 272 in a single image frame.

[0042] The optical element 404 may include one or more lenses, mirrors, filters, diffraction gratings, apertures, or other components. Light collected along the scattering detector path 402, for example, scattered light, is collected by the optical element 404, optionally reflected, and / or filtered, and imaged onto the FPA of the image acquisition device 406. The field of view (FOV) of the optical element 404 may include the entire or a portion of the wafer surface 12. For example, the FOV optical element 404 may have a width in the scanning direction AR2 (see Figure 3B) that is approximately equal to the length L1 of the annealing irradiation line 272, or a width in direction AR2 that is about 5% to about 50% greater than the length L1 of the annealing irradiation line. The width of the FOV of the optical element 404 in the stage scanning direction AR1 (see Figure 3B) may be the same as, or greater than or less than, the width of the FOV in the annealing image scanning direction AR2. In one example, the width of the field of view (FOV) of the optical element 404 in the stage scanning direction AR1 is at least twice the diameter or outer range of the annealed image 270 in the stage scanning direction, so that the portion of the wafer surface 12 that is in a non-melted state and outside the annealed image is captured within the same image as the portion inside the annealed image. The FOV of the optical element 404 in the sweep direction AR2 may be at least 10% larger than the length L1 of the illumination line 272, and in some examples, it may be at least 20% larger. The spatial resolution of the ICD 406 may be from 10 μm / pixel to 50 μm / pixel, and in some examples, it may be about 30 μm / pixel.

[0043] As shown in the figure, the light source, here in the case of an annealing laser system 250, generates a scanning laser beam 268 that forms an annealing image 270 on the wafer surface 12. The first portion of the light from the scanning laser beam 268 is specularly reflected by the wafer surface 12 and does not reach the melt detector 280. If the temperature of the wafer surface 12 along the annealing irradiation line 272 is below the melting temperature and the wafer material is in the solid phase, the scattering melt detector 280 may detect a certain amount of background light, such as light from photoluminescence and scattered light due to defects on the wafer surface 12, such as small variations in thickness, or large defects such as scratches or dust, or, in the case of a processed wafer, light diffracted, reflected, and / or refracted from optical discontinuities in the wafer, such as fabricated patterns on or beneath the wafer surface. Therefore, in the case of an untreated and highly polished wafer 10, the melt detector 280 may detect little to no light along the scattering detector path 402, and the field of view of the melt detector 280 is substantially dark. In the case of processed wafers, scattered light related to the non-molten solid phase state may be captured to some extent.

[0044] The power density of the scanning laser beam 268 is equal to the melting threshold energy density E mAs the temperature rises, a phase transition occurs in the wafer material at or below the wafer surface 12, resulting in a volume of molten liquid phase material located near the annealing image 270. The reflectivity of the molten liquid phase material is substantially different from that of the material in the solid phase. The interface between the solid and liquid phases of the newly formed liquid volume (e.g., interface 312 (Figure 3C)) creates a new optical discontinuity on the wafer surface that strongly scatters light to a hemisphere of angle 2π above the molten region of the wafer. The reflection observed in the molten region (e.g., molten pool 310) is diffuse reflection, and in some examples approaches Lambertian reflection. The resulting intensity of the imaging thermal reflection signal in the molten region is substantially increased compared to the solid phase, for example, by 50%. On the other hand, the change in intensity of the scattering imaging thermal reflection signal along the scattering detector path 402 due to the phase transition of the material from solid to liquid is extreme, for example, on the order of 100,000% higher intensity, providing excellent sensitivity for detecting the onset of melting.

[0045] For example, ICD406 detects the corresponding frequency f ≤ 1 / t over a period longer than the residence time of annealed image 270. d The scattering image is captured by the scattering melt detector 280. The annealed image 270 moving at velocity v and x=v * Using t, time is resolved along the annealing laser sweep direction AR2. In this way, the captured scattering image is obtained by f = 1 / t, where the scattering signal data along the x direction (sweep direction AR2) is f = 1 / t d It can be used to decompose output variation spectral measurements in bandwidths up to . Using a scattering image frame containing the entire sweep of the annealed image 270 or multiple sweeps, the scattering melt detector 280 can be used to measure the uniformity of the process across the entire annealed image sweep stripe in a single image frame. In one example, the scattering melt detector 280 can measure all points x=v·(t±t) in a single frame. d By supplementing spatially resolvable scattering images for the frequency f ≤ 1 / t dIt is configured to measure the melting behavior and uniformity, which is very practical and useful in optimizing the annealing laser system 250.

[0046] Figure 4B shows another exemplary embodiment of the scattering melt detector 280 in which a probe light source 410, separate from the annealing laser system 250, is used as a probe for scattering measurements. The illustrated example has a similar configuration to the example shown in Figure 4A and includes a detector including an optical element 412 which may include the same or similar components as the optical elements 404 and ICD 406. The probe light source 410 may be a pulsed light source that emits probe light 420 incident on the wafer surface 12 in a region overlapping with the annealing image 270. Similar to the example shown in Figure 4A, the scattering melt detector 280 in Figure 4B has a scattering detector path 416 such that the optical element 412 does not capture the specular reflection 420R of the probe light 420 or the specular reflection 268R of the scanning laser beam 268. In the illustrated example, the melt detector 280 receives light from the wafer surface 12 along the scattering detector path 416 which has an angle α1 with respect to the surface normal N that is different from the angle α2 of the scanning laser beam 268 and the angle α3 of the probe light 420. The probe light source 410 may be a diode or an optical fiber connected to a laser source, and may emit narrowband light such as green, blue, or NIR, or communication band light such as between 1260 nm and 1675 nm. The optical element 412 may be configured to filter out wavelengths of light other than the probe light 420. The probe light source 410 may be configured to emit pulses of the probe light 420 at a frequency higher than the frame rate of the ICD 406 or at a shorter time interval so that discrete portions of the annealing illumination line 272 can be imaged.

[0047] Figures 5A and 5B conceptually illustrate two alternative optical configurations 500 and 501 for scattering imaging. The configuration 500 includes an objective lens 502 and an image-forming lens 504 for forming a scattering image of a region of the wafer surface 12, including a molten pool 310, on the FPA of an ICD, such as an ICD 406. Configuration 500 corresponds to the example shown in Figures 4A and 4B, where light, such as a scanning laser beam 268 (the example in Figure 4A) or another probe light source (e.g., probe light 420 in the example in Figure 4B), is incident on an object, such as the molten pool 310. From a Fourier optics perspective, zero-order light 530 (non-scattered light) does not reach the objective lens 502 due to the spatial position and numerical aperture of lenses 502 and 504, and consequently, the image formed on the FPA is due to higher-order diffraction intensities 532 scattered by the molten pool 310 and / or other light scatterers or discontinuities on or below the wafer surface.

[0048] Figure 5B shows an alternative optical configuration 501 in which at least one opaque light-blocking element 520 is used to prevent zero-order light 530 (non-scattered light) from reaching the FPA of an ICD, such as the ICD406, and as a result the image formed on the FPA by the objective lens 510 and imaging lens 512 is due to higher-order diffraction intensities 532 scattered by the molten pool 310 and / or other light-scattering elements or discontinuities on or below the wafer surface. The scattering melt detector 280 in Figure 4A or the scattering melt detector in Figure 4B may be modified to have an optical configuration 501 that uses at least one opaque light-blocking element 520 to form a scattering image.

[0049] Figure 6A conceptually and graphically shows the data captured within the image frame by the ICD406 of the scattering melt detector 280 during the sweep of the annealing image 270 when the wafer surface 12 is in a non-melting state. Figure 6B conceptually shows the change in the data captured in the image as the optical output of the annealing laser system 250 increases and the temperature of the wafer surface 12 exceeds the melting threshold, causing the wafer material to begin melting.

[0050] In the non-molten state, the image captured by the melt detector 280 is the probe intensity I(x) scattered by the wafer roughness and, if applicable, by resonant scatterers embedded in the wafer surface 12. → ) is. In the thin film approximation, the height difference δ(x → The roughness caused by the random holographic phase grating φ(x → ) acts as e iφ(δ(x→)) =e iαδ(x→) It acts on the electric field as follows. The fluctuating output spectrum, i.e., δ(x → The square of the Fourier transform of |F(δ(x → ))| 2 =|δ(k → )| 2 In the process of manufacturing uniform wafers, typically k → =4π / λ is not zero even if it far exceeds this, and as a result, I(x → The light is scattered uniformly over the upper hemisphere of the wafer plane. Figure 6A conceptually illustrates this low-light, relatively flat response that can occur in a non-melted state.

[0051] In the case of a processed and highly patterned wafer 10, some material manufacturing processes may include rare light scatterers within the thin film, which can generate random images that may provide false melt signals. However, when image data from the melt detector 280 is averaged across edited image frames, false melt signals occurring in the non-melted state can be distinguished from true melt signals because high-intensity signals appear uniformly within edited image frames across the entire sweep across the annealing irradiation line 272 as the optical power density of the annealing laser 250 increases. An aspect of the present disclosure includes editing a set of high-resolution images of the non-melted wafer 10 to sample the shape of the irradiation probe beam, e.g., a scanning laser beam 268 or probe light 420 from a probe light source 410. The image data of the non-melted state is then edited across a radius r melt <r beamThis can be distinguished from molten state image data including high-intensity artifacts of the molten pool 310 and associated interface 312. The shorter absorption length of the probe beam in the liquid phase portion of the wafer material in the molten pool reduces scattering caused by subsurface optical discontinuities in the processed wafer, thereby simplifying the scattered light response when the melt threshold is exceeded and further facilitating the detection of the onset of melting.

[0052] Figure 6C shows image frames of test data from an exemplary embodiment of system 100, which uses the amplitude of captured light to identify melting. Figure 6C shows an example of a system that is not properly optimized, where the beginning (top of the image) and end (bottom) of the annealing image sweep are both in a melted state, and the dark area in the middle is just before the non-melted state. The optical power density of the annealing laser system 250 was not properly calibrated, resulting in undesirable fluctuations in optical power, which resulted in the beginning and end of the sweep being in a melted state and the middle of the sweep being in a non-melted state.

[0053] Figures 7A to 7C show test data from melt threshold calibration at a specific chuck temperature for a specific processed wafer type having a specific material laminate. Figures 7A to 7C show one or more sweeps from three different stripes of scanning laser beam 268, where the stripes are a series of consecutive sweeps. In Figure 7A, the output of the annealing laser system 250 is set to 132W, in the next stripe in Figure 7B the output level is increased to 135W, and in the third stripe in Figure 7C the output is increased to 138W. Arrows indicate locations in the image where the signal is saturated, indicating high light intensity in these areas of the image due to a sharp increase in scattered light as the wafer material melts. The images in Figures 7A to 7C also show low-intensity artifacts caused by the inherent roughness and non-uniformity of the processed wafer (low-intensity artifacts are enclosed by dotted lines in each figure). However, the high-intensity locations corresponding to the melted regions of the wafer have a greater spatial density and are orders of magnitude larger than the background light of the non-melted state in the scattered image, and stand out strongly from the background scattering. Figures 7A to 7C show an example in which the melt threshold can be calibrated for a specific processed wafer type with a particular material laminate by increasing the laser power and studying the melt measurement.

[0054] Figure 8 shows additional data from the same calibration process as shown in Figures 7A to 7C. The Y-axis is the cumulative intensity of light captured by the FPA of the ICD406. More specifically, the Y-axis is the sum of all gray values ​​for all pixels in the image, where each pixel of the FPA records the level of incident light intensity on a gray level scale between 0 (black) and 1 (white), as is known in the art. The X-axis is the sweep argument of the annealed image. Figure 8 shows the first several sweeps of the annealed image at 132W, where the sum of gray values ​​is the low first value, indicating the non-melted state and background light scattering captured by the FPA of the ICD406. Figure 8 shows the increase in gray values ​​as the output is increased to 135W, which is determined to be the melting threshold, and then as the laser output is increased to 138W, which is determined to be above the melting threshold, showing a sharp increase in the intensity of light captured by the ICD406 as the liquid volume of the wafer material is consistently formed over most of the annealed image sweeps.

[0055] Figures 9A and 9B show test data for a well-optimized system with the output of the annealing laser system 250 set to what was determined to be the semiconductor wafer melting threshold. Figures 9A and 9B show the same data in two different formats, each being a collection of profile analyses from many image frames in a high-speed spot sweep direction. In Figure 9A, the Y-axis is intensity and the X-axis is position along the annealing image sweep, with multiple consecutive sweep light intensity profiles superimposed. In Figure 9B, the same sweep intensity profiles are shown on a three-dimensional color map where the Y-axis is the position in the sweep direction of the annealing image, the X-axis is the position in the image frame and stage scanning direction, and the color indicates the intensity of the optical signal. Figure 9B is a mosaic of multiple image frames captured by the scattering melt detector 280.

[0056] The position within the image frame can be transformed into a specific position along the sweep of the annealed image and a point in time, using knowledge of the annealed image speed and the spatial resolution of the ICD. For example, if the sweep speed of the annealed image is 500 m / s and the spatial resolution of the ICD is 30 μm / pixel, then each pixel represents a time of 60 ns, and the swept image of the annealed image with a 50 ns exposure can be resolved into 60 ns time units. More generally, a scattering melt detector 280, for example, the example shown in Figure 4A, can resolve all points x = v·(t ± t) within a single frame. d By spatially decomposing ), the frequency f ≤ 1 / t d It can be used to measure melting behavior and uniformity, which is practical and useful for optimizing the annealing laser 250. In an example where a pulse probe separate from the process laser beam is used, as shown in Figure 4B, data can be obtained at higher frequencies.

[0057] In some cases, slight variations in the optical power density of the scanning laser beam 268 may occur across sweeps of the annealing image 270. Therefore, a method for calibrating the annealing laser system 250 may include analyzing the melting signal from the scattered melting detector 280 at specific points in the sweeps across multiple sweeps, thereby eliminating the influence of variability in optical power along the sweeps from the calibration process. For example, position 902 in Figure 9B indicates a specific sweep position where melting signals from multiple sweeps at position 902 can be analyzed. For example, by adjusting the output level of the annealing laser system 250 in steps, such as in units of less than 1% of the total output, the percentage of the annealing image sweeps in which melting is detected can be identified. For example, given a chuck temperature T ch and dwell time t dwell For this, the melting threshold energy density Em(T ch ,t d ) exists, and the actual energy density supplied is E m ±δ E This is the setting output E. m -δ ETherefore, melting is rarely detected because the output occasionally reaches the melting threshold. Melting occurs when E exceeds the process range. m +δ E It is always detected. The output of the scanning laser beam 268 is E m -δ E Less than E m +δ E By varying the range across multiple stripes to a range exceeding E, and analyzing the proportion of times melting is detected at a specific sweep position (e.g., position 902), we can determine the range from below the energy at which melting is never detected to above the energy at which melting is detected in all or nearly all sweeps. m and δ E Both can be identified independently. In one example, during the annealing process, the output level of the scanning laser beam 268 is changed stepwise throughout the sweep of the annealed image. Therefore, by repeating the calibration process described above at multiple sweep positions, the melt threshold output level setpoint can be identified throughout the sweep of the annealed image.

[0058] controller

[0059] Figure 10 is a block diagram illustrating the physical components of one exemplary implementation of one or more computing devices 1000 that may be used with the annealing system of the present disclosure, including providing functionality for a controller 300, a stage controller 124, and a melt detector 280. At least one processor 1002 connected to a chipset 1004 is shown. Also connected to the chipset 1004 are memory 1006, a network adapter 1008, and a communications module 1010. Peripherals 1012 and a display 1014 are connected to the computing device 1000. In another embodiment, the memory 1006 is directly connected to the processor 1002. A storage device 1016 is also connected to the chipset 1004.

[0060] The storage device 1016 may be any non-temporary computer-readable storage medium such as a hard drive, compact disk read-only memory (CD-ROM), DVD, or solid-state memory device. The storage device 1016 may contain any software or data that can be stored in a computer storage device that communicates with an annealing system known in the art of laser annealing systems. Figure 10 shows a non-limiting illustrative list of applications 1020 that may be stored in the storage device 1016, as well as the melt threshold 1022 and the annealing laser melt calibration setpoint 1024.

[0061] In the illustrated example, application 1020 includes an ICD control application 1030 and an image processing application 1032, which include commands for controlling the ICD of the scattering melt detector, for example, the ICD 406 of the scattering melt detector 280. The ICD control application 1030 may include commands for controlling functions such as frame rate and shutter speed, and commands for processing signals generated by the FPA(F) of the ICD. The image processing application 1032 may be configured to execute one or more image processing algorithms to analyze light collected from a scattering detector path having an FOV including an annealed image.

[0062] As described herein, when an annealed image, e.g., annealed image 270, begins to melt the material on or beneath the wafer surface 12, a substantial change occurs in the optical properties of the material, resulting in a significant increase in the intensity of light collected by the scattering melt detector. The image processing application 1032 may be configured to identify the increase in the intensity of light collected by the ICD using any of a variety of image processing algorithms. For example, a fitting algorithm, an edge detection algorithm, intrinsic basis resolution, feedforward classification, or detection of any intensity in the captured image frame that exceeds the melt threshold, or one or more intensity values ​​corresponding to the light scattering effect caused by the interface between the liquid and solid phases of the wafer material. In one example, the image processing application 1032 may be configured to identify the increase in the intensity of light collected by the ICD in a region smaller than the annealed image 270 formed by a process beam, e.g., a laser beam 268. In one example, the image processing application 1032 may compare the light intensity to a melting threshold 1022, which may include thresholds corresponding to the light intensity captured by the scattering melt detector 280 for melt pools of different sizes, or thresholds relating the light intensity to the intensity of the non-melted state and the laser power level. Referring to Figure 3C as an example, the image processing application 1032 may be configured to detect the onset of melting and the formation of the melt pool 310 and the corresponding interface 312 by detecting the light intensity captured along the scattering detector path 402 or 416 that exceeds a relative scattering intensity that exceeds the intensity of the surrounding probe beam. In one example, the threshold may be normalized to the intensity profile of the pre-melting scattered beam light. The image processing application 1032 may be configured to analyze the spatial density or spatial range of image frames containing light intensities exceeding the melting threshold in order to distinguish between true melting signals and discrete false signals caused by non-melting scatterers.The image processing application 1032 may be configured to compare the spatial position of a high-intensity signal within an image frame with a known position in the moving annealed image 270 and / or the position of the annealing illumination line 272 to verify whether the high-intensity signal overlaps with or is immediately adjacent to the annealed image or the annealing illumination line.

[0063] Figure 11 conceptually shows a portion of an exemplary image frame 1100 captured by ICD406 during the annealing process. Figure 11 shows a grid of pixels 1102 and a portion of illumination lines 272. The image frame 1100 consists of several columns 1104 (two columns 1104a and 1104b are labeled) aligned in the stage scanning direction and labeled y in Figure 11, and several rows 1106 (one row 1106a is labeled) aligned in the sweep direction of the annealed image and labeled x in Figure 11. To illustrate an example of varying the gray level of pixels along a given column 1104, one column of pixels includes cross-hatch shading.

[0064] Figures 12 to 14 show examples of melt detection algorithms that may be configured to be executed by an image processing application, such as image processing application 1032 (Figure 10). Figure 12 shows an exemplary method 1200 that generates a reference image of the non-melted state and associated parameters. In block 1203, method 1200 may include annealing the wafer in the non-melted state, capturing the image frame with a scattering melt detector, and recording the annealing laser power level. In one example, the laser power is a voltage V corresponding to the optical power density of the annealing laser beam, such as the annealing laser beam 268. refMeasurements can be taken using an onboard detector (OBD) that generates the output. In other examples, any other sensor technology or technique may be used to monitor the laser output. Block 1203 may also include receiving wafer type information, such as a unique identification number corresponding to a particular wafer design. In Block 1203, an image frame, such as image frame 1100 (Figure 11), is captured. Thus, Block 1203 includes performing the annealing process at an annealing laser output level lower than the output level that melts the wafer material, and collecting image data of the non-melted state using a scattering melt detector, such as a scattering melt detector 280, which can be used as a reference to the data during the melting process to detect melting.

[0065] In block 1205, method 1200 obtains a control image I of the non-melted state from the captured image frame. ref This may include creating a , which may include averaging the pixel values ​​of multiple image frames and excluding any images that contain wafer edges in the image. Block 1207 processes a non-melted control image to generate multiple non-melted one-dimensional stage scanning direction intensity profiles. Block 1207 runs a one-dimensional peak detection algorithm or fitting algorithm on one or more columns 1104 of pixels in the stage scanning direction and for each one-dimensional intensity profile, amplitude A ref (x), width w ref (x), and the centroid or maximum position y 0,ref This may include generating parameters such as (x), for example, width w ref (x) is y 0,ref (x) is the distance ±y from (x), and the total width is 2·w ref (x) is given by (x), where y refers to the stage scanning direction and x refers to the sweep direction (see Figure 11). Thus, block 1207 returns the intensity profile of each column 1104 or group of columns along the y direction. Block 1207 may also include saving multiple profiles as sweep profiles.

[0066] In Block 1209, ROI is used in this specification. ref A region of interest (ROI) may be identified in the non-melted control image, which corresponds to the spatial location of the irradiation line 272 in the image. ref This may be determined by identifying pixels with an intensity exceeding the minimum value located within the sweep profile. For example, ROI ref This is determined from the sweep profile parameters determined in block 1207, and has an amplitude greater than, for example, the sum of the black level and the number of gray levels corresponding to the background outside the annealed image, such as 2 gray levels on the FPA's 255 gray level scale, where y=y 0,ref (x) ± 2·w ref This is a pixel of the reference image having a y position located within the range (x). In block 1211, method 1200 is, for example, ROI for each row 1106 ref This may include creating an average one-dimensional stage scanning direction intensity profile by summing the gray values ​​of the pixels within and dividing by the number in column 1104 (see Figure 11).

[0067] Figure 13 shows one exemplary method 1300 of the melt detection algorithm, in which melt is detected from the nonlinearity of the amplitude in the image frame. In block 1303, method 1300 involves annealing the wafer below the melt threshold, at the melt threshold, or above the melt threshold, capturing an image frame using a scattering melt detector, and indicating the output level of the annealing laser beam when the image is captured, as specified herein. meltBlock 1303 may also include recording the corresponding OBD voltage, which is called the . Block 1303 may also include receiving wafer information, such as a specific ID, so that appropriate non-melted reference data obtained in method 1200 can be referenced. In block 1305, method 1300 may include creating an averaged image from the captured image frames by averaging all the image frames of sweeps performed at the same laser power level, excluding any frames that include the wafer edge, and saving the averaged image. In block 1307, a melted detection image I is created to associate the averaged image created in block 1305 with a non-melted reference image corresponding to the same wafer type. data This is generated. In one example, the pixel values ​​and corresponding laser power values ​​of the averaged image from block 1305 are related to the pixel values ​​and corresponding laser power of the unmelted control image generated in block 1205 in Figure 12 as follows: where I data I is the pixel value of the averaged image generated in block 1307. ref V is the pixel value of the non-melted control image. ref and V melt This is the corresponding OBD signal value. In block 1309, the melted image value can be compared with a threshold such as 1.1 to determine whether melting has occurred in the image. For example, ROI in the melted image. ref The pixel values ​​within can be averaged and compared to a threshold.

[0068]

number

[0069] In addition to performing block 1309, or instead, in block 1311, the method may include applying a one-dimensional profile analysis of the melt detection image generated in block 1307 to identify narrow peaks in the stage scanning direction having a width smaller than the width of the laser beam. In block 1313, the width w(x) of the identified peaks is determined and compared with the width w(x) of the non-melted control image. If the width of the identified peaks is smaller, for example, the width w of the non-melted control image ref If the width is less than 50% of (x), melting is determined to have occurred. The above is based on the energy profile of the laser beam and assumes a Gaussian profile in the stage scanning direction y, and as a result, melting occurs only in a narrow area of ​​the larger annealing image 270. Therefore, a detection peak with an intensity smaller than the width of the annealing image in the stage scanning direction (orthogonal to the sweep direction) indicates a localized melting region or melt pool in the annealing image. Referring to Figure 11 as an example, pixels 1102a to 1102e along column 1104 include cross-hatching that shows different amplitudes of the melt detection image created in block 1307. For example, method 1300 determines if pixels 1102c or 1102b to 1102d have an amplitude greater than that of the surrounding pixels, for example, an amplitude exceeding a threshold, and the width of pixels 1102b to 1102c in the stage scanning direction y is greater than that of the annealing illumination line 272 or the corresponding ROI ref Melting may be determined to have occurred if the width is sufficiently narrow compared to the width of the pixel. Steps 1311 and 1313 are most useful for processed wafers with high scattering and can be achieved using a scattering melt detector with a high-resolution optical element.

[0070] Figure 14 shows Method 1400, which is another exemplary algorithm for detecting melting according to melting statistics. In block 1403, Method 1400 involves annealing the wafer below the melting threshold, at the melting threshold, or above the melting threshold, capturing an image frame using a scattering melting detector, and detecting the OBD voltage signal V meltIt may also include recording. In block 1405, the standard deviation of pixel values within the ROI of the image frame ref (determined in step 1209) is calculated. In one example, block 1405 may include calculating a fractional standard deviation that is the standard deviation of the ratio of pixel values within the ROI ref to the average of pixel values within the ROI ref . A large standard deviation indicates that there is a large variation in the intensity values within the ROI ref , and as shown in the example of FIG. 9B, it indicates that the laser output is set to a melting threshold with a large variation in pixels in the molten state and non-molten state. In block 1407, the calculated standard deviation is compared with a threshold to determine the presence of melting. Method 1400 may be most useful for wafers with minimal scattering, such as an untreated Si wafer.

[0071] Methods 1200, 1300, and 1400 may be selectively used according to a specific wafer type and application as a melting detection subroutine for calibrating a laser system, for a laser annealing process, and for determining a laser power calibration table or curve for a specific combination of process conditions including wafer type, chuck temperature, and dwell time. V ref , ROI ref , V melt , parameters and reference data such as the one-dimensional stage scan direction intensity profile in the non-molten state may be stored in a memory such as storage device 1016 and be accessible by image processing application 1032 to execute any image processing algorithm disclosed herein.

[0072] A computing device 1000 having an annealing laser control application 1034 may be configured to control one or more parameters of the preheating and / or annealing laser systems 150, 250 to achieve desired process conditions above a melting threshold. The annealing laser control application 1034 may be configured to control the output level of the annealing laser system 250 according to an annealing laser melt calibration setpoint 1024. The annealing laser melt calibration setpoint 1024 may specify a laser output level setpoint to achieve sub-melting, melting threshold, or above-melting threshold annealing conditions for setting specific process conditions such as a particular chuck heater temperature, residence time of the annealed image, and type of wafer 10. As described herein, a scattering melt detector 280 may be used to perform melt calibration of the annealing laser system 250 in order to determine the annealing laser melt calibration setpoint 1024.

[0073] For example, the ICD406 has a sweep frequency f of the annealed image. sweep It may have a maximum exposure frequency lower than that. The FOV of the scattering melt detector 280 may include at least one annealing irradiation line 272 (i.e., at least one sweep of the annealing image), and optionally may include multiple annealing irradiation lines (multiple consecutive sweeps of the annealing image). Thus, a single image captured by a single exposure of the ICD406 may include at least one sweep of the annealing image 270, and in some examples, multiple sweeps. The image processing application 1032 may use predetermined information regarding a known intensity profile of the material phase transition to extract one or more statistical correlation functions from the captured intensities of multiple sweeps from one or more image frames to characterize the consistency of the melting process, or act as a multisampler on the device wafer, or act as a spatial lock-in frequency, and simplify melt detection using the Fast Fourier Transform.

[0074] In an example where the scatter melt detector of the present disclosure includes a probe separate from the process laser, such as probe light source 410 (FIG. 4B), application 1020 may also include a probe control application 1036 for controlling the intensity, phase, and / or frequency of the pulsed radiation emitted by probe light source 410 and / or the pulse timing of the radiation emitted by the probe, and / or the sensor exposure timing such as the exposure timing of ICD 406 for various lengths or periods. Probe control application 1036 synchronizes the probe and the ICD via a common clock to a sweep frequency f sweep and includes instructions for determining the pulse frequency f Probe and pulse phase φ Probe of the exposures of probe 410 and the ICD as a function of the sweep frequency, sweep phase, and aspects of the phase transition process of the measured wafer material. In one example, since f exposure is sufficiently smaller than f Probe , the number n exposure per ICD exposure becomes 1. In one example, the frequency ratio R = f sweep / f probes may be any integer, and as a result, statistics regarding the stability of the phase transition process may be extracted. In one example, f sweep may not be present, rather, a random distribution of pulses at known times may be collected for the extraction of broadband statistics. In some examples, f Probe may be a rational beat frequency having f Probe for determining and optimizing the uniformity of the sweep. In one example, the probe pulse frequency f Probe is f sweep Probe is f ProbeThe probe 410 is selected to be synchronized with the sweep of the annealed image 270 in the x-direction, and a subset of synchronized moments in the set of annealed image sweeps is probed with individual pulses, and multiple pulses are collected into a single image frame by the ICD406, thereby allowing high bandwidth consistency of the phase transition to be extracted from the contrast of the molten region. In some examples, the probe 410 is configured to emit pulses of light having durations of 3 ns to 20 ns, in some examples 5 ns to 15 ns, in some examples 5 ns to 10 ns, and in some examples 5 ns to 7 ns.

[0075] Memory 1006 may hold instructions and data used by processor 1002. Network adapter 1008 connects computing device 1000 to a local area network or wide area network, and communication module 1010 provides additional channels for wired or wireless communication. As is known in the art, computing device 1000 may have different and / or other components than those shown in Figure 10. In addition, computing device 1000 may lack certain illustrated components. In some examples, storage device 1016 may be local to and / or remote from computing device 1000, such as another storage device, cold storage device, storage area network (SAN), or cloud-based storage architecture.

[0076] As is known in the art, the computing device 1000 is adapted to run a computer program module for providing the functions described herein. As used herein, the term module refers to the computer program logic used to provide the specified functions. Thus, a module may be implemented in hardware, firmware, and / or software. In one embodiment, the program module is stored in storage device 1016, loaded into memory 1006, and executed by processor 1002.

[0077] Several parts of this disclosure illustrate examples in terms of algorithmic processes or operations. These algorithmic descriptions and expressions are commonly used by those skilled in the field of data processing technology to effectively communicate the nature of their work to others skilled in the field. These operations are described functionally, computationally, or logically, but are understood to be implemented by computer programs, which include instructions for execution by a processor or equivalent electrical circuit, microcode, etc. Furthermore, without loss of generality, these configurations of functional operations may also be called modules, which has proven convenient at times.

[0078] Figure 10 shows a single computing device 1000 and storage device 1016, but it will be understood that the functions and storage provided by the computing device 1000 and storage device 1016 can be implemented in any number of computing devices and storage devices. For example, the first computing device 1000 may be used to implement the controller 300, and one or more other computing devices 1000 may be used to perform other functions disclosed herein, such as the stage controller 124, chuck heater, and melt detector 280.

[0079] The computing device 1000 may be configured to communicate with other computing devices of System 100 over one or more networks, which may include any combination of local area networks and / or wide area networks, using both wired and / or wireless communication systems. In one embodiment, the network uses standard communication technologies and / or protocols. For example, the network includes communication links using technologies such as Ethernet, 802.11, worldwide interoperability for microwave access (WiMAX), 3G, 4G, code division multiple access (CDMA), and digital subscriber line (DSL), and examples of networking protocols used for communication over the network include MPLS (multiprotocol label switching), TCP / IP (transmission control protocol / internet protocol), HTTP (hypertext transport protocol), SMTP (simple mail transfer protocol), and FTP (file transfer protocol). Data exchanged over the network may be represented using any suitable format, such as hypertext markup language (HTML) or extended markup language (XML). Those skilled in the art will recognize that encryption using other suitable techniques is appropriate for various applications based on the nature of the network.

[0080] Examples of the present disclosure include a method for analyzing scattered image data. This method includes receiving scattered images of a region of a semiconductor surface captured during a laser annealing process of a semiconductor, and identifying a solid-to-liquid material phase transition of the semiconductor material from the images, wherein identification includes identifying statistical, time-series, or geometric nonlinear fluctuations of the image intensity as a function of one or more annealing process control parameters. In some examples, one or more annealing process control parameters include laser power or optical power density.

[0081] Examples of the present disclosure also include a method for performing melt calibration for a laser annealing process of a semiconductor material. The method includes annealing a region of the semiconductor material with an annealing laser beam from an annealing laser, which includes stepwise varying the power level of the annealing laser above and below a melt threshold power level at which a transition from the solid phase to the liquid phase of the semiconductor material occurs; capturing a scattering image of the region of the semiconductor material during annealing; and determining at least one melt threshold setpoint power level of the annealing laser from the captured scattering image.

[0082] An example of the present disclosure includes a method for controlling the operating parameters of an annealing laser during a laser annealing process. This method includes controlling the operating parameters of an annealing laser during an annealing process of a semiconductor material in accordance with a laser annealing temperature calibration created by performing the method described in the preceding paragraph.

[0083] Examples of the present disclosure also include machine-readable instructions configured to cause a processor in a laser annealing system controller to control an annealing laser according to annealing process parameters and at least one annealing laser melting threshold calibration setpoint determined according to the methods disclosed herein.

[0084] An example of the present disclosure includes a method for forming non-melted reference images and parameters for use with a melt detection algorithm. The method includes annealing a non-melted wafer, capturing an image frame using a scattering melt detector, recording the annealing laser power level, creating a non-melted reference image from the captured image frame, processing the non-melted reference image to generate multiple non-melted one-dimensional stage scanning intensity profiles, identifying a region of interest (ROIref) in the non-melted reference image, and creating an averaged one-dimensional stage scanning intensity profile.

[0085] An example of the present disclosure includes a method for detecting whether wafer material has melted during an annealing process. The method includes annealing the wafer below a melt threshold, at a melt threshold, or above a melt threshold; capturing image frames using a scattering melt detector during annealing; recording the laser power level; creating an averaged image from the captured image frames; and creating a melt detection image relating the averaged image to a corresponding non-melted control image of the same wafer type.

[0086] Paragraph [ further includes comparing the values ​​of the melt detection image with a threshold to determine whether melting has occurred in one or more regions of the image.] 0085 The method used in [ ].

[0087] The paragraph further includes applying one-dimensional profile analysis of the melt detection image to identify narrow peaks in the stage scanning direction that have a width smaller than the width of the process laser beam. 0085 The method used in [ ].

[0088] The non-molten control image was obtained by performing any method using any of the systems disclosed herein, paragraph [ 0085 The method used in [ ].

[0089] Examples of the present disclosure include a method for detecting whether wafer material has melted during an annealing process. This method includes annealing the wafer below a melting threshold, at a melting threshold, or above a melting threshold; capturing an image frame during annealing using a scattering melt detector; calculating a statistical variation in pixel values ​​within a region of interest (ROIref) of the image frame, which is the region of the image where an annealing laser image has been formed on the wafer; and comparing the calculated statistical variation to identify the onset of melting.

[0090] The above is a detailed description of exemplary embodiments of the present disclosure. It should be noted that, in this specification and the appended claims, any conjunction language used in the phrases “at least one of X, Y, and Z” and “one or more of X, Y, and Z” shall be interpreted, unless otherwise specified or indicated, as meaning that each item of the conjunction list may exist in any number other than all other items in the list, or in any number combined with any or all other items of the conjunction list, and each of these may also exist in any number. Applying this general rule, the conjunction phrases in the above example, where the conjunction list consists of X, Y, and Z, shall each encompass one or more X, one or more Y, one or more Z, one or more X and one or more Y and one or more Z, and one or more X, one or more Y and one or more Z.

[0091] Various modifications and additions can be made without departing from the spirit and scope of this disclosure. Each feature of the various embodiments described above may be combined with features of other described embodiments as needed to provide a number of feature combinations in the new embodiments relating to the disclosure. Furthermore, although several other embodiments are described above, those described herein are merely illustrative of the application of the principles of this disclosure. Moreover, certain methods described herein may be exemplified and / or described as being performed in a particular order, but the ordering is highly variable within the scope of the art to achieve the aspects of this disclosure. Therefore, this description is intended to be conspicuously illustrative and not intended to limit the scope of this disclosure.

Claims

1. A method for determining whether a material phase transition from solid to liquid has occurred in a semiconductor material during a laser annealing process, To form an annealed image on the surface of the semiconductor material using an annealing laser beam from an annealing laser, To form a scattering image of the surface region of the semiconductor material, including the annealed image, and The material phase transition from solid to liquid of the semiconductor material is identified according to the intensity of the light collected in the aforementioned scattering image. Methods that include...

2. The method according to claim 1, wherein the identification includes detecting an intensity in the scattering image that reaches or exceeds a threshold, the threshold corresponding to the onset of the solid-to-liquid phase transition of the semiconductor material.

3. The method according to claim 2, wherein the identification includes detecting the intensity of the scattering image in a region of the scattering image that is within the annealed image and smaller than the region of the annealed image.

4. The method according to claim 1, wherein the identification includes identifying discontinuities in the intensity of light collected in the scattering image compared to a control image of a non-melted state.

5. The method according to claim 1, wherein the identification includes identifying a nonlinear scaling relationship between the light intensity and process parameters.

6. The method according to claim 5, wherein the process parameter is the output level of the annealing laser or the local output density of the annealing laser.

7. The method according to claim 1, wherein the annealing laser process comprises performing a sequential sweep of the annealing image over the surface of the semiconductor material, each sweep comprising forming an annealing irradiation line and a scattering image, or forming an image of at least one annealing irradiation line.

8. The method according to claim 7, wherein the identifying step includes analyzing the intensity of light along the annealing irradiation line to determine the degree of material phase transition of the semiconductor material along the annealing irradiation line.

9. The method according to claim 7, wherein the identifying step includes analyzing the intensity of light along the annealing irradiation line to determine the proportion of the annealing irradiation line in which the initiation of the solid-to-liquid phase transition occurred.

10. The method according to claim 7, wherein the identifying step includes analyzing the intensity of light at a first position along the annealing irradiation line in a plurality of sequential sweeps of the annealing image to determine at least one of the melting threshold power level or statistical power variation of the annealing laser.

11. The laser annealing process has a sweep frequency f ｓｗｅｅｐ The method includes sequentially sweeping across the surface of the semiconductor material, wherein the pulse frequency f Ｐｒｏｂｅ The method further includes irradiating the surface of the semiconductor material with a probe light source having a radiation pulse at f Ｐｒｏｂｅ <f ｓｗｅｅｐ The method according to claim 1.

12. The method according to claim 1, wherein the identification includes applying one or more of the following: a fitting algorithm, an edge detection algorithm, an intrinsic basis decomposition, a feedforward classification, or the detection of any intensity in an image frame that exceeds a captured threshold.

13. The aforementioned identification means To create a melt detection image by associating the aforementioned scattering image with a corresponding non-melted state control image. The method according to claim 1, including the method described in claim 1.

14. The method according to claim 13, further comprising comparing the values ​​of the melting detection image with a threshold to determine whether melting has occurred in one or more regions of the melting detection image.

15. The method according to claim 13, further comprising applying one-dimensional profile analysis of the melt detection image to identify a narrow peak in the stage scanning direction having a width smaller than the width of the process laser beam.

16. The aforementioned non-molten state control image is Annealing a wafer in a non-molten state, To capture an image frame using a scattering melt detector, Record the annealing laser output level. Creating a non-melted control image from the captured image frame, The process involves processing the aforementioned non-melted control image to generate multiple one-dimensional stage scanning direction intensity profiles for non-melted states. Identifying the region of interest (ROIref) of the non-melted control image, and Create an average one-dimensional stage scanning direction intensity profile. The method according to claim 13, obtained by performing the steps of:

17. The aforementioned identification means The calculation of statistical variation in pixel values ​​within a region of interest (ROIref) of a captured image frame, where the annealed laser image is a region of the image formed on the surface of the semiconductor material, and The onset of melting is identified by comparing the calculated statistical variations. The method according to claim 1, including the method described in claim 1.

18. A stage configured to support a semiconductor wafer, An annealing laser configured to anneal the aforementioned semiconductor wafer, A scattering melt detector including an image acquisition device including a focal plane array (FPA), and a scattering optical arrangement configured to block or avoid specular reflection of the beam formed by the annealing laser and to form a scattering image of the surface of the semiconductor wafer on the FPA. A scattering melt detection system, including the above.

19. The system further includes a processor and a machine-readable recording medium containing program instructions executed by the processor, The aforementioned program instruction is, To form an annealed image on the surface of the semiconductor wafer using an annealing laser beam from an annealing laser, To form a scattering image of the surface region of the semiconductor wafer, including the annealed image, and The material phase transition from solid to liquid of the semiconductor wafer is identified according to the intensity of the light collected in the aforementioned scattering image. This is for the purpose of executing The system according to claim 18.

20. Annealing laser and A recording device comprising: a storage device including at least one annealing laser melt threshold calibration setting value that specifies the operating parameters of the annealing laser in order to raise the temperature of a local region of a semiconductor material to a melt threshold under a set of predetermined annealing process conditions, wherein the setting value is derived from a scattering image of the semiconductor material acquired during the laser annealing process of the semiconductor material; A controller configured to control the annealing laser according to the annealing laser melting threshold calibration setting value. A laser annealing system, including...

21. The annealing laser melting threshold calibration setting value is, An annealing image is formed on the surface of the semiconductor material by the annealing laser beam from the annealing laser. To form a scattering image of the surface region of the semiconductor material, including the annealed image, and The material phase transition from solid to liquid of the semiconductor material is identified according to the intensity of the light collected in the aforementioned scattering image. The system according to claim 20, determined by a process including the following:

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