KR20070097442A - Systems and methods for creating crystallographic-orientation controlled poly-silicon films - Google Patents

Abstract

In accordance with one aspect, the present invention provides a method for providing polycrystalline films having a controlled microstructure as well as a crystallographic texture. The methods provide elongated grains or single-crystal islands of a specified crystallographic orientation. In particular, a method of processing a film on a substrate includes generating a textured film having crystal grains oriented predominantly in one preferred crystallographic orientation; and then generating a microstructure using sequential lateral solidification crystallization that provides a location-controlled growth of the grains orientated in the preferred crystallographic orientation.

Description

System and method for producing crystallographic orientation controlled polysilicon film {SYSTEMS AND METHODS FOR CREATING CRYSTALLOGRAPHIC-ORIENTATION CONTROLLED poly-SILICON FILMS}

The present invention relates to systems and methods for providing polycrystalline films with crystallographic textures as well as controlled microstructures.

In recent years, various techniques for crystallizing an amorphous or polycrystalline semiconductor film or improving the crystallinity thereof have been studied. This technique is used in the manufacture of various devices, such as image sensors and displays, for example AMLCD (active matrix liquid crystal display) devices. In the latter, a regular array of TFTs (thin film transistors) is fabricated on a suitable transparent substrate, each transistor serving as a pixel controller.

The semiconductor film is processed using ELA, also known as line beam ELA (excimer laser annealing), in which certain regions of the film are crystallized after being irradiated with an excimer laser that partially melts the film. 1A illustrates an LPTS (poly-si) microstructure that can be obtained by laser induced melting and solidification. Since this process typically uses a long narrow beam shape that continuously advances across the substrate surface, the beam may irradiate the entire semiconductor thin film in a single scan across the surface. ELA generates small grain polycrystalline films, but this method sometimes encounters microstructure non-uniformities that can be generated by pulses that convey energy density fluctuations and / or non-uniform beam intensity profiles. 2 is an image of a random microstructure obtained from ELA. The Si film is irradiated several times to produce a random polycrystalline film of uniform particle size.

One method that has been used to form high quality polycrystalline films with large and uniform particles is SLS (Sequential Lateral Solidification) using excimer lasers. SLS is a crystallization process that provides elongated particles of crystallized material to certain locations on the film. 1B-1D illustrate microstructures that can be obtained by SLS. Polycrystalline films of coarse particles may exhibit improved switching characteristics, because the reduction in the number of particle boundaries in the electron flow direction provides higher mobility. SLS processing controls the location of particle boundaries. The entire contents of which are incorporated herein by reference and assigned to the common assignee of the present application, US Patent No. 6,322,625 to James Im; 6,368,945; 6,368,945; 6,555,449; 6,555,449; And 6,573,531 describe such SLS systems and processes.

3A-3F schematically illustrate an SLS process. In the SLS process, the first amorphous or polycrystalline film (e.g., CW (continuous wave) -treated Si film, as-deposited film, or SPC (solid crystallization) film) is irradiated by a very narrow laser beamlet. . The beamlets are formed, for example, by passing a laser beam pulse through a slotted mask and are projected onto the surface of the silicon film. The beamlets melt amorphous silicon, and the amorphous silicon film is recrystallized upon cooling to form one or more crystals. This crystal mainly grows inward from the edge of the irradiated area toward the center. After the initial beamlet crystallizes a portion of the film, the second beamlet irradiates the film at a position less than the "lateral growth length" from the preceding beamlet. At the newly irradiated film position, crystal grains grow laterally from the crystal seed of the polycrystalline material formed in the preceding step. As a result of this lateral growth, the crystals are of high quality along the direction of the advancing beamlet. Extended crystal grains are generally separated by grain boundaries that are perpendicular to the length of the narrow beamlet and run approximately parallel to the particle long axis.

When polycrystalline materials are used to make electronic devices, the total resistance to carrier transport is affected by the combination of barriers that must cross when the carrier moves under the influence of a certain potential. When the carrier moves in a direction perpendicular to the particle long axis of the polycrystalline material or when the carrier moves across a number of small particles, the number of grain boundaries that are crossed is added, so that the carrier is compared with the carrier moving parallel to the particle long axis, There will be a higher resistance. Thus, the performance of devices fabricated on polycrystalline films formed using SLS, such as TFTs, will depend on the microstructure and crystal quality of the TFT channel relative to the particle long axis corresponding to the main growth direction.

In order to realize acceptable system performance for devices using polycrystalline thin films, there remains a need to optimize the manufacturing process to provide the prescribed crystallographic orientation of the crystal grains.

According to one aspect, the present invention provides a method for providing a polycrystalline film having a crystallographic texture as well as a controlled microstructure. This method provides extended particles or single crystal islands of specific crystallographic orientation. In particular, a method of treating a film on a substrate includes providing a textured film in which the crystal grains are primarily oriented in one preferred crystallographic orientation; And generating microstructures using SLS crystallization, which provides position-controlled growth of particles oriented in the desired crystallographic orientation. One preferred direction of crystallographic orientation is the direction perpendicular to the surface of the membrane.

The process of SLS generally includes generating a plurality of laser beam pulses; Directing the plurality of laser beam pulses through the mask to generate a plurality of patterned laser beams; And irradiating a portion of the selected area of the film with one of the plurality of patterned beams, the beam having an intensity sufficient to melt the irradiated portion of the film over the entire thickness of the film, The part crystallizes laterally upon cooling. This process includes repositioning the film to irradiate the subsequent portion of the selected region with the patterned beam such that the subsequent position overlaps the previously irradiated portion to allow for further lateral growth of the crystal grains. In one embodiment, successive portions of the selected areas are irradiated such that the patterned beam travels once across the selected areas of the film so that the film is virtually completely crystallized. The expression " fully crystallized " means that the selected area of the film possesses the desired microstructure and crystal orientation, so that additional laser scanning for this area is unnecessary. The mask comprises a dot-patterned mask and has an opaque array pattern comprising at least one of a dot region, a hexagon region, and a rectangular region.

According to one aspect of the invention, the textured film is one of ZMR (partially melt recrystallization), SPR (solid phase recrystallization), direct deposition method, surface-energy-driven secondary grain growth (SEDSGG) method, or pulse laser recrystallization (PLC) method. Is caused by. Direct deposition methods include one of CVD (chemical vapor deposition), sputtering, and vacuum deposition. PLC methods include SLS or multi-pulse ELA methods. The film may be a metal film or a semiconductor film.

According to another aspect of the invention, a system for processing a film on a substrate comprises: one or more lasers for generating a plurality of laser beam pulses; A film support for positioning the membrane that is movable in at least one direction; Mask support; Optics for directing a first set of laser beam pulses through a first mask to generate a textured film; Optics for directing a second set of laser beams into the textured film; And a controller for controlling the movement of the membrane support and the mask support in relation to the frequency of the laser beam pulses.

According to yet another aspect of the present invention, there is provided a device having a polycrystalline thin film in which particles are arranged periodically, wherein each particle mainly has one crystallographic orientation. The predominant crystallographic orientation is the <111> orientation, or in other embodiments the <100> orientation. Periodically placed particles form a column of elongated particles.

The above and other features and advantages of the present invention will become apparent from the following more detailed description of embodiments of the invention, which is illustrated in the accompanying drawings.

1A illustrates the LTPS (low temperature polycrystalline) microstructure obtained for laser induced melting and solidification.

1B-1D illustrate the microstructure obtained by SLS.

2 is an image of the random orientation of the microstructure obtained from ELA.

3A-3F schematically illustrate the process involved with SLS.

4 is a flowchart of a hybrid SLS method according to an embodiment of the present invention.

5A is a schematic diagram of a dual axis projection irradiation system used for SLS, in accordance with an embodiment of the present invention.

5B is an exemplary diagram illustrating a mask having a polka dot pattern.

5C illustrates mask translation using the mask of FIG. 5B.

6A and 6B illustrate EBSD (electron back) for mapping crystallographic orientations obtained from hybrid SLS processes for islands after generation of textured precursors and after SLS processes, respectively, according to embodiments of the present invention. Images of the crystallized film using diffraction) are respectively illustrated, and FIGS. 6A (a-1) and 6B (B-1) are IPFs (reverse pole viscosity) for each.

7A-7C illustrate a crystallized film in which a (111) textured precursor with ELA is multi-pulse particle amplified according to an embodiment of the present invention.

8A and 8B are respectively crystallized using EBSD to map the crystallographic orientation obtained from the hybrid SLS process for islands after the generation of the textured precursor and after the SLS process in accordance with an embodiment of the present invention. Images of the films are respectively illustrated, and FIGS. 8A (a-1) and 8B (B-1) are IPFs for each.

9 illustrates an image of a crystallized film of (100) textured precursor using high speed ZMR using a CW laser in accordance with an embodiment of the present invention.

10A-10C illustrate TEM (transmission electron microscopy) images of mainly <110>, <111>, and <100> azimuth islands, respectively.

11A-11C illustrate SEM (scanning electron microscope) images and EBSD data of islands of <110> orientation primarily corresponding to the image illustrated in FIG. 10A.

12A-12C illustrate SEM images and EBSD data of mainly <111> azimuth islands corresponding to the image illustrated in FIG. 10B.

13A-13C illustrate SEM images and EBSD data of mainly <100> azimuth islands corresponding to the image illustrated in FIG. 10C.

Defined as hybrid SLS (sequential lateral solidification), the processes and systems described herein provide for extended grain or single crystal islands of specific crystallographic orientation. Embodiments of the present invention are based on the recognition that the crystallographic orientation of lateral crystal growth during SLS depends on the material orientation at the boundary of the irradiated area. Lateral crystal growth of the material from the solidus boundary defined by the textured crystals promotes the growth of such crystallographic orientations.

As its most basic, hybrid SLS is a two-step process as illustrated in FIG. In a first step 42, a textured precursor is generated or provided. Textured films include particles with mainly the same crystallographic orientation in at least a single direction, but these particles are randomly placed on the surface and do not have prominent size (microstructure). More specifically, it is said that if a crystallographic axis of the majority of crystallites of a polycrystalline thin film preferentially points in a certain direction, the microstructure has a one-axis texture. For the embodiments described herein, the preferred direction of the one-axis texture is the direction perpendicular to the surface of the microcrystalline. As such, "texture" as used herein means a one-axial surface texture of a particle. The degree of texture may vary depending on the particular application. For example, in contrast to the TFT used in the switch circuit, the TFT used in the driver circuit is suitably high in texture.

In a second step 44 of the hybrid SLS process, SLS is performed. Lateral crystallization results in "position-controlled growth" of grain boundaries and elongation crystals of a given crystallographic orientation. Position-controlled growth referred to herein is defined as the location of particles and particle boundaries, controlled using a particular beam pattern and mask, such as, for example, a dot-patterned mask.

As briefly described herein above, SLS is a crystallization process that provides extended grains and single crystal islands of crystallized material at predetermined locations on the film. However, SLS cannot fully define the crystallographic orientation of such particles. In the SLS process, growth begins with existing particles, as in epitaxial growth, so the process cannot provide growth in the desired orientation. Since the growth of crystals of one material on the crystal plane of another material is called epitaxial growth, the crystal grains of both materials have the same structural orientation. SLS generates a coarse structure through small-scale translation of a thin film between sequential pulses emitted by a pulsed laser. As the film absorbs the energy of each of the pulses, the small areas of the film melt completely and recrystallize laterally from the solid / liquid interface to form crystal regions. The term "lateral crystal growth" or "lateral crystallization", as used herein, refers to a growth technique in which recrystallization occurs at the crystallization front where regions of the film melt to the film / surface interface and move laterally across the substrate surface. it means.

The thin film may be a metal or a semiconductor film. Exemplary metals include aluminum, copper, nickel, titanium, gold, and molybdenum. Exemplary semiconductor films include conventional semiconductor materials such as silicon, germanium, and silicon-germanium. It is anticipated that additional layers will be disposed below or above the metal or semiconductor film. Additional layers may be used as silicon oxide, silicon nitride, and / or oxide, nitrite, or, for example, as a thermal barrier to protect the substrate from overheating or as a diffusion barrier to prevent impurities from diffusing from the substrate into the film. It may consist of mixtures of other suitable materials as follows. PCT Publication No. WO 2003/084688 describes a method and system for providing controlled crystal orientation in an aluminum thin film using pulsed laser induced melting and nucleation-initiated crystallization, the full teachings of which are incorporated herein by reference. Is cited.

Thin films are processed into polycrystalline thin films of extended position controlled particles using SLS. An exemplary SLS process includes generating a plurality of excimer laser pulses of a predetermined energy density, controllably modulating the energy density of the excimer laser pulses, homogenizing the intensity profile of the laser pulse plane, patterning Masking each homogenized laser pulse to define a laser beam, irradiating the thin film with the laser beam to effect melting of portions of the thin film, and controlling to move the patterned beam across the substrate surface Translating the sample as possibly and continuously. The laser pulse frequency and movement (speed and direction) of the sample may be adjusted such that the sequential irradiation area of the sample overlaps from one irradiation / crystallization cycle to the next irradiation / crystallization cycle to provide lateral crystal growth that generates large particles. Can be. Pulse frequency and stage and mask position may be adjusted and controlled by a computer. Systems and methods for providing continuous movement to SLS are provided in US Pat. No. 6,368,945, which is incorporated herein by reference in its entirety. Exemplary SLS processes are described in US Pat. No. 6,555,449 and US Patent Application No. 10 / 944,350, the entire teachings of which are incorporated herein by reference.

5A illustrates an example dual axis projection SLS system. A light source, for example excimer laser 52, generates a laser beam, which includes a mirror 58, 62, 70, a telescope 60, a homogenizer 64, a beam splitter 66 and Pass through pulse width expander 54 and attenuator plate 56 before passing through an optical element, such as lens 72. The laser beam pulse then passes through mask 74 and projection optics 82. The projection optical system reduces the size of the laser beam and at the same time increases the intensity of the optical energy hitting the substrate 88 at a predetermined position. Substrate 88 can accurately position substrate 88 below the beam and assist in focusing or defocusing an image of mask 74 generated by the laser beam at a location on the substrate. Is provided on the precise xyz stage.

In various embodiments, another SLS method, referred to herein as a dot-patterned SLS process, is used. 5B illustrates a mask 90 that includes a polka dot pattern 92. The polka dot mask 90 corresponds to the area where the polka dot pattern 92 is masked and the remainder 94 of the mask is a transparent inversion mask. To produce large silicon crystals, the polka dot pattern can be translated sequentially around the point on the sample where such crystals are desired. For example, as shown in FIG. 5C, the polka dot mask is negative after the second laser pulse by a short distance 96 in the positive Y direction after the first laser pulse to induce the formation of large crystals. It can be translated by a short distance 98 in the X direction and by a short distance 99 in the negative Y direction after the third laser pulse. If the spacing between the polka dots is greater than twice the lateral growth distance, a crystal structure is generated in which the crystals are separated by the polycrystalline silicon regions of the small particles. When the gap is less than twice the lateral growth distance to prevent nucleation, a crystal structure in which crystals are formed is generated. Further details regarding this SLS method are described in US Pat. No. 6,555,449, the entire teachings of which are incorporated herein by reference.

Embodiments of the present invention provide a uniformly oriented material in epitaxy by performing SLS on the textured precursor. Particles grown laterally adopt the seed's orientation. In the prior art, polycrystalline films vary greatly from particle to particle. By selecting seed crystals of similar crystallographic orientation (texture), it is possible to grow largely position-controlled (microstructured) particles of similar crystallographic orientation. Embodiments of the present invention relate to certain combinations of texture-development techniques and SLS processes.

In the first phase, ZMR (partial melt recrystallization), solid phase recrystallization, direct deposition techniques (CVD, stuttering, vapor deposition) surface-energy-driven secondary grain growth (SEDSGG), and pulsed laser crystallization (SLS) Conventional methods of obtaining a textured precursor film are used, including pulsed ELA) methods. It is contemplated that other texture derivation methods may be used in a similar manner to generate textured precursors. The method of obtaining a textured precursor film is applicable to a wide variety of metal and / or semiconductor films, but the following method is based on the level of understanding of silicon in the semiconductor industry and the semiconductor industry due to all the research done using silicon so far. Due to the importance of silicon, it is explained in connection with the silicon film.

The following method is used in various embodiments to provide a textured polycrystalline film that can be used to create micro structure controlled and crystallographic orientation controlled poly-Si films in a hybrid SLS process. This method illustrates the use of unpatterned planar samples. Methods using patterning, such as graphoepitaxy, are also often presented as a means for reaching certain control of the microstructure. However, not only does SLS not always tolerate non-planar or patterned films, but SLS will be better at controlling microstructures.

An as-deposited CVD polysilicon film can be used to provide a (110) or (100) texture to the crystalline film. As-deposited polysilicon films sometimes exhibit texture, depending on the details of the deposition process, such as pressure and temperature. Typically, the texture of this film develops throughout the deposition process, ie the initial growth at the SiO ₂ interface is randomly oriented. Since the lateral growth of the SLS starts at the very edge of the non-melting portion located at the SiO ₂ interface, the crystallographic orientation can still be random (as observed in the poly-Si film in the <110> orientation). However, a method can be developed that produces a texture or post-treatment throughout the film thickness to establish the same purpose through particle growth (ie, desirable particles growing at the expense of others).

Seed Selection through Ion Channeling (SSIC) may be used to provide a (110) texture in the crystal film. Untextured (or weakly (110) textured) as-deposited poly-silicon (Si) films are strongly (by themselves) injected by a silicon "self-injection" at a particular dose adjacent to a complete amorphous crystallization threshold involving solid phase crystallization. 110) can be translated into a textured film. Due to the ion channel ring effect along the <110> orientation in the Si particles, only particles whose directions are parallel to the implantation direction remain. If the implant is perpendicular to the Si film surface, this means that <110> surface orientation particles remain. During the subsequent recrystallization, the coarse <110> oriented poly-Si film is obtained.

SEDGG can be used to generate a (111) texture in the crystalline film. SEDGG is a special secondary particle growth mechanism, often referred to as SEDSGG. Primary or regular particle growth is observed upon heating of the material (> 1000 ° C.) and is driven by the reduction of particle boundary area. In the case of thin films, this process is stopped when the particle diameter reaches a value comparable to the film thickness. Beyond that point, secondary or abnormal particle growth may occur. This process is driven by free energy anisotropies at the interface of the surface and secondary particles. Since the magnitude of the surface free energy is almost certainly greater than the free energy of the Si—SiO ₂ interface, it is expected that minimization on it will govern the process. It is observed that the energy of the free surface of Si is minimized with the (111) texture, in fact the secondary particles are mainly <111>.

The analysis for SEDGG primarily discusses the results obtained as Si films doped with phosphorus (P) or arsenic (As). This dopant is known to improve the growth rate of secondary particles through an increase in particle boundary mobility. Intrinsic films still exhibit secondary particle growth; To achieve reasonable growth rates, drive forces and / or increases, particle boundary mobility is increased in other ways. Individual examples therefor include reducing the film thickness or increasing the annealing temperature.

Metal-Induced Lateral Crystallization (MIL) can be used to provide a crystalline film with a (110) texture. In metal-induced crystallization, nickel (Ni), the most prevalent metal, is contacted with a Si film and subsequent heating quickly crystallizes the film. If the Ni-Si contact is only made locally (eg by having a windowed buffer layer between the Si and the metal film), at lower Ni residues and at a higher texture degree of (110), Lateral crystallized poly-Si film is obtained.

In this process, NiSi ₂ precipitate is formed by Ni diffusion through the Si film. NiSi ₂ has a cubic lattice structure, and the lattice mismatch with c-Si is only 0.4%. Due to this small mismatch, several nm of c-Si will grow, after which Ni migrates / diffuses to its surface and the process is repeated. As the process continues, a high degree of crystallization can be reached if long needle shaped crystals are formed, and if some additional solid phase crystallization is allowed to occur laterally from these needle shaped crystals. Growth in the NiSi ₂ precipitate occurs only in one {111} plane, so it is one-dimensional. However, sometimes different {111} planes are selected and the needle shape crystal rotates 109 ° or 71 °. This process can be maintained until the needle remains in the plane of the membrane (ie, until the needle does not hit the surface of the interface), which can be realized when the surface orientation of the particles is <110>.

Partial melt ZMR can be used to provide a crystalline film with a (100) texture. ZMR of the Si film results in the formation of a coarse polycrystalline Si film with a preferential <100> surface orientation of the crystal. Embodiments of the invention use these oriented polycrystalline films as precursors for crystallization using SLS. Examples include using oriented seed particles to facilitate the formation of oriented largely grown orientation crystals. As such, ZMR of the polycrystalline film is used to obtain a poly-Si film of the (100) textured granulator. Growth of the (100) textured long particles begins with particles formed in the “transition region” between the unmelted and fully melted regions of the film. This is a situation of partial melting (i.e., coexistence of solid and liquid) which exists only in the radiantly heated Si film as a result of a significant increase in the reflectance of Si upon melting (semiconductor-metal transition). In this partial melting situation, it has been observed that the particles dominate the phenomena linked to crystallographic anisotropy in the SiO ₂ -Si interface energy.

The results were typically obtained at less than 1 mm / s at a scanning speed of several mm / s. At higher speeds (ie for "fast-ZMR"), the (100) textured growth is no longer stable and random orientation is obtained. It is observed that the crystallographic orientation of the lateral growth particles is "rolled off" in a random orientation. However, the "transition region" represents a strong (100) texture, although the degree decreases with increasing speed. One way to maximize the degree of texture in partial melt fast-ZMR is to create a precursor that maximizes the number of seeds for <100> growth. One method for doing so includes depositing a (lOO) -textured poly-Si film. If the orientation is random, it may also be effective to precrystallize the Si film with ultra-fine material that ensures the high density of the texture 100 particles, for example through complete-melting crystallization (CMC) to produce nucleated particles. .

ZMR using continuous lasers is described in "Zone-Melting recrystallization of Si films with a moveable-strip-heater oven", J. Electro-Chem. Soc. As described by 129, 2812 (1982), a silicon film having a <100> orientation is generated. 9 illustrates an image of a crystallized film of (100) textured precursor after partial melting using fast ZMR using CW-laser, as described previously herein. (100) Texturing is desirable for electronic devices because it results in the highest quality Si / SiO ₂ interface in terms of interface states.

Near-Complete-Melting (NCM) ELA can be used to generate a crystalline film with a (111) texture. Multi-pulse excimer laser crystallization in a partial melting situation is used to produce uniform poly-Si films with mainly <111> surface oriented particles. Uniformity of the maximum particle size can be obtained due to the interference effect on the assembly surface of the poly-Si film. This results in a poly-Si film having a particle size approximately equal to the wavelength, using, for example, XeCl laser of ˜300 nm. At slightly higher but still lower energy density than the complete melting threshold, the particle diameter is no longer stabilized by the interference effect, and much more predominantly <111> surface oriented particles are obtained.

Even if the energy density at which this process is performed is a partial melting situation, some complete melting must occur locally to allow for the gradual growth of particles larger than the film thickness. It is proposed that due to the locally improved absorption and / or reduced melting temperature, preferential melting may occur at the grain boundaries. During melting and regrowth of the particle-bound region, there is clearly a preference for <111> azimuthal particles in terms of resistance to melting or lateral growth rates. Thus, <111> orientation particles grow at the expense of differently oriented particles.

Regarding the Si precursor film, multi-pulse irradiation from an excimer laser of a near-melting regime (NMR) is described in Mat. Res. Soc. Sym. As described in Proc, 321, 665-670 (1994), a Si film with a <111> orientation is provided. 7A-7C illustrate a film that has been processed and crystallized with multi-pulse particle magnification of a (111) textured precursor with ELA.

SLS can be used to generate a crystalline film with a (110) texture. The hybrid SLS process of certain embodiments may use the SLS process in a first step of generating a textured precursor. The SLS process used in the first step is a texture derived SLS process. Analysis of the directional poly-Si (see FIG. 5A) obtained via excimer-laser based SLS is based on (100) or (110) texture in the scan direction, depending on the details of the process (film thickness, step size, pulse width). Indicates that is obtained. For the surface orientation of the particles, this results in a limit to a range of orientations that are comparable to these in-plane orientations (e.g., where (100) in-plane textures exist, the (111) surface texture is physical Is impossible). In-plane textures have developed rather rapidly, as observed from weak textures for two-shot SLS. However, due to the "roll off" of the orientation, even for long scan direction SLS, it may not be very effective when the particles are extended.

One method for obtaining a particular (100) texture includes a special SLS process for doubling a predetermined in-plane texture that is perpendicular to each other. Details of this process are described in J.S., entitled "Method and system for producing crystalline thin films with a uniform crystalline orientation," the entire teachings of which are incorporated herein by reference. It is described in US patent application 60 / 503,419 to Im. This can lead to the formation of surface oriented material, if the orientation is controlled in both the x and y directions, the definition in the z direction is also controlled by definition.

SLS can be used to generate a crystalline film with a (111) texture. Analysis of SLS using pulsed solid state lasers (frequency doubled Nd: YVO ₄ ) is described in M. Nerding's "Tailoring texture in laser crystallization of silicon thin-films on", which is hereby incorporated by reference in its entirety. glass ", Solid State Phenom. 93, 173 (2003). Although basically the same process as with an excimer laser, there are some differences that can affect the orientation of the particles. The most prominent of these is the wavelength (532 nm), but the spatial profile (Gaussian) and pulse width (20 ns) can also play an important role in the process. However, when a SiN _x buffer layer is used, a strong (111) surface orientation is obtained for film thicknesses above about 150 nm.

In an embodiment, the epitaxial growth of a III-V semiconductor, such as GaAs, on a silicon (Si) carrier is a combination of the advantages of both materials, for example an LED made of GaAs combined with an electrical circuit made of Si (light emitting) Diodes). In addition, if Si is a film deposited on top of a non-semiconductor substrate such as glass, this advantage for a large area and / or transparent substrate can be taken at low cost.

However, proper epitaxy requires both high quality (ie, flawless) as well as uniformly oriented materials. High quality can be realized with the SLS (Sequential Lateral Solidification) method, most importantly with a process that can be used to create a position controlled single crystal island. Embodiments described herein of a hybrid SLS process are particularly useful in the TFT industry, which enhances epitaxial growth and improves TFT uniformity and material quality through performance levels of anisotropy through both mobility and interface defect density. This is because the TFT uniformity is provided through. Details of the effects of uniformity of TFTs as field effect devices are described in T. Sato, Y. Takeishi, H. Hara, and Y. Okamoto, "Mobility anisotropy of," the entire teaching of which is incorporated herein by reference. electrons in inversion layers on oxidized silicon surfaces "(Physical Review B (Solid State) 4, 1950 (1971)) and MH White and J.R. Cricchi's "Characterization of thin-oxide MNOS memory transistors" (IEEE Trans. Electron Devices ED-19, 1280 (1972)).

In one embodiment, the higher energy-density ELA process described herein above is used, where a film of larger average particle size is obtained. This film may have a strong (111) or (100) texture depending on the conditions of the ELA process selected: process likely to be related to anisotropy in melting and solidification of differently oriented particles. By the commercialized line beam ELA system, very high texture degree is obtained. These textured precursor films are not used in the production of TFTs or epitaxial processes due to the randomness of the microstructures.

6A and 6B illustrate islands after generation of precursors textured (FIG. 6A) using the aforementioned high energy ELA process, each involving an SLS process (FIG. 6B) in accordance with an embodiment of the present invention. Illustrates an image of a crystallized film obtained from a hybrid SLS process. Data for FIGS. 6A and 6B were collected using electron back scatter diffraction (EBSD), SEM-based methods for mapping crystallographic orientations. FIG. 6A is a map of the film after step 1 of the process and its use, using multi-pulse ELA at a slightly higher energy density than commonly used in the manufacture of TFTs (ie, as shown in FIG. 6B). The corresponding IPF (FIGS. 6A-1) is shown. The map 100 illustrates random high angle particle boundaries, while the IPF exhibits a strong texture in these (111) particles. 6B and its corresponding IPF (FIG. 6B-1) are the dot-patterns (also referred to herein as dot-SLS) described in US Patent Application No. 10 / 944,350, the entire teaching of which is incorporated herein by reference. The image of the film after performing the SLS process with the type mask is illustrated. The microstructure is well controlled (ie, position-controlled single grain area) and the texture is maintained.

Experimental conditions for the example [(111) texture, SLS (150 nm Si)] are 500 × as a 4 μm inter pulse translation that generates 125 pulses per unit area, performed with the SLS system described in connection with FIG. 5A. Scanning 500 μm ² . A commercialized ELA system may be used in other embodiments and fewer pulses per unit area may be sufficient to reach a predetermined texture degree. For the second stage of the SLS processing, a four-shot dot-SLS system using a large shadow area of ˜1.8 μm disposed in an 8 μm square grid is used.

As described in US patent application Ser. No. 10 / 944,350, which is hereby incorporated by reference in its entirety, combining an SLS process with ELA pretreatment may be useful for epitaxial growth of III-V semiconductors or of large area. This results in a position-controlled single crystal island of <111> orientation that may also be useful for uniform TFTs on low cost transparent substrates.

8A and 8B illustrate hybrid SLS processes for islands after the generation of textured precursor using the ELA process described above (FIG. 8A) and after the SLS process (FIG. 8B), respectively, according to an embodiment of the present invention. It illustrates an image of a crystallized film for the mapping of crystallographic orientations resulting from. Data for the images of FIGS. 8A and 8B are collected using an electron back scatter diffraction (EBSD) method for the mapping of crystallographic orientations. 8A shows a map of the film after step 1 of the process performed using multi-pulse ELA and its corresponding IPF (FIGS. 8A-1) at a slightly higher energy density than commonly used in the manufacture of TFTs. 8B and its corresponding IPF (FIG. 8B-1) show the image after performing the dot-SLS process. Experimental conditions for this example include the use of a frequency doubled (532 nm) Nd: YV0 ₄ continuous wave laser in the form of a thin beam (hundreds of μm long, ˜10 or tens of μm wide) scanned at 1 cm / s. FIG. 8B uses a 3.3 cm / s scan involving a four-shot dot-SLS process using the system described in FIG. 5A.

10A-10C illustrate TEM images of <110>, <111>, and <100> orientation islands, respectively. 11A-11C illustrate SEM images and EBSD data of mainly <110> azimuth islands corresponding to the image illustrated in FIG. 10A. 12A-12C illustrate SEM images and EBSD data of mainly <111> azimuth islands corresponding to the image illustrated in FIG. 10B. 13A-13C illustrate SEM images and EBSD data of mainly <100> azimuth islands corresponding to the image illustrated in FIG. 10C.

In FIGS. 10A-10C it is observed that the predominant plane defect is the Sigma3 boundary. Sigma3 boundaries are a series described by coincident-site lattice (CSL), in contrast to the random high-angle particle boundaries in the EBSD results shown earlier in connection with FIGS. 6A, 6B, 8A, and 8B. Is one of the special high-angle particle boundaries. In its most special form, these boundaries are twin boundaries, meaning that they may not have electrical activity. In general, CSL boundaries tend to have lower defect densities and therefore less harmful to electrical properties. This boundary was observed not to be present in the precursor but to form during crystallization. 10A illustrates that the surface orientation varies upon formation of Sigma3 planar defects and that the islands contain multiple defects. In FIG. 10B, the <111> surface orientation (important for applications where surface orientation is critical, such as epitaxy and TFT) has fewer defects and no change in surface orientation. In FIG. 1OC, the <100> surface orientation has little planar defects.

In an embodiment using dot-SLS (process using a dot-patterned mask), <111> and <100> islands can be obtained, and islands with an <100> orientation have the lowest density of defects, <111> is next. These two observations in particular indicate a preference for <100> and a lower degree of <111> orientation. These observations are effective when working under normal conditions (ie, 50-250 nm Si film, 30-300 ns pulse width, room temperature, etc.). Other embodiments, including working in different conditions, can inhibit the formation of Sigma3 boundaries, meaning that flawless islands of any orientation can be obtained.

In view of the broad embodiments to which the principles of the invention may be applied, it should be understood that the illustrated embodiments are merely examples and that they should not be regarded as limiting the scope of the invention. For example, the steps of the figures may be taken in a sequence other than the described sequence, and more or fewer elements may be used in the figure. Although various elements of the embodiments have been described as being implemented in software, in other ways, other embodiments of hardware or firmware implementations may be used, and vice versa.

Those skilled in the art will appreciate that a method related to producing a crystallographic orientation controlled polysilicon film may be implemented in a computer program product comprising a computer usable medium. For example, such computer readable media include readable memory devices, such as hard drive devices, CD-ROMs, DVD-ROMs, or computer diskettes, in which computer readable program code segments are stored. Computer-readable media may include communication or transmission media, such as an optical, wired, or wireless, bus or communication link, on which program code segments are conveyed as digital or analog data signals.

Other aspects, modifications and embodiments are within the scope of the following claims.

Claims (26)

As a method of treating a film on a substrate, Providing a textured film having crystal grains whose crystallographic orientation is predominantly in one direction; And Generating a microstructure using SLS (Sequential Lateral Solidification) crystallization to provide position-controlled growth of the crystal grains oriented in the crystallographic orientation. Membrane treatment method comprising a. The method of claim 1, wherein the SLS crystallization, Generating a plurality of laser beam pulses; Passing the plurality of laser beam pulses through a mask to generate a plurality of patterned laser beams; Irradiating a portion of the film with one of the plurality of patterned beams, the beam having a strength sufficient to melt the irradiated portion of the film over its entire thickness, wherein the irradiated portion of the film Beam irradiation step of crystallizing laterally upon cooling; And And repositioning the film to irradiate the subsequent portion with a patterned beam such that a subsequent portion of the film overlaps the previously irradiated portion to allow for further lateral growth of the crystal grains. The method of claim 1, wherein the SLS crystallization, Generating a plurality of laser beam pulses; Passing the plurality of laser beam pulses through a mask to generate a plurality of patterned laser beams; Irradiating a portion of a selected area of the film with one of the plurality of patterned beams, the beam having a strength sufficient to melt the irradiated portion of the film, wherein the irradiated portion of the film crystallizes upon cooling A beam irradiation step; And Along the first translational path, while a continuous portion of the selected area is irradiated with the patterned beam such that the patterned beam moves once across the selected area of the film so that the selected area of the film is substantially fully crystallized. Moving the film and moving the mask along a second translational path. 3. The film processing method according to claim 2, wherein the mask comprises a dot-patterned mask. The method of claim 4, wherein the mask comprises an opaque array pattern comprising at least one of a dot region, a hexagon region, and a rectangular region. The method of claim 1, wherein the textured film is subjected to one of ZMR (partial melt recrystallization), SPR (solid phase recrystallization), direct deposition method, surface-energy-driven secondary grain growth (SEDSGG) method, and pulsed laser crystallization method. Membrane treatment method. The method of claim 6, wherein the direct deposition method comprises one of CVD (chemical vapor deposition), sputtering, and vapor deposition. The method of claim 6, wherein the pulsed laser crystallization method comprises one of an SLS and a multi-pulse ELA process. The film processing method according to claim 1, wherein the film is a semiconductor film. The method of claim 1, wherein the film is a metal film. The method of claim 1, wherein the one direction is a direction perpendicular to the film surface. The method of claim 1, wherein the predominant crystallographic orientation is a <111> orientation. The method of claim 1, wherein the predominant crystallographic orientation is a <100> orientation. A system for processing a film on a substrate, One or more lasers for generating a plurality of laser beam pulses; A membrane support for positioning the membrane that can move in at least one direction; Mask support; Optics for passing a first set of laser beam pulses through a first mask to generate a textured film; Optics for directing a second set of laser beam pulses through the second mask to the textured film; And A controller for controlling movement of the membrane support and the mask support in relation to the frequencies of the first and second set laser beam pulses Membrane treatment system having a. The film processing system of claim 14, wherein the textured film is generated by one of a ZMR, SPR, direct deposition method, SEDSGG method, and pulsed laser crystallization method. 15. The film processing system of claim 14, wherein the direct deposition method comprises one of CVD, sputtering, and vapor deposition. 15. The film processing system of claim 14, wherein the pulsed laser crystallization method comprises one of an SLS and a multi-pulse ELA process. The film processing system according to claim 14, wherein the film is a semiconductor film. The film processing system of claim 14, wherein the film is a metal film. A device having a polycrystalline thin film, Wherein said polycrystalline thin film has particles in which each of particles in a state in which one crystallographic orientation is predominant is arranged periodically. The device of claim 20, wherein the film is a semiconductor film. The device of claim 20, wherein the film is a metal film. The device of claim 20, wherein the predominant crystallographic orientation is a <111> orientation. The device of claim 20, wherein the predominant crystallographic orientation is a <100> orientation. The device of claim 20, wherein the microstructure of the periodically disposed particles is a hexagonal pattern, a circular pattern, a rectangular pattern, or a square pattern. The device of claim 20, wherein the periodically disposed particles form a column of elongated particles.

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