JP4498716B2 - Laser irradiation apparatus and semiconductor device manufacturing method using the laser irradiation apparatus - Google Patents

Description

  The present invention relates to a laser irradiation apparatus that activates a semiconductor film or the like after crystallization or ion implantation using a laser beam. Further, the laser irradiation apparatus of the present invention includes, in its category, a laser irradiation apparatus that irradiates a semiconductor film in a polycrystalline or near-polycrystalline state with a laser and improves (facilitates) the crystallinity of the semiconductor film. Further, the present invention relates to a method for manufacturing a semiconductor device using a crystalline semiconductor film formed using the laser irradiation apparatus.

  In recent years, a technology for forming a TFT on a substrate has greatly advanced, and application development to an active matrix semiconductor display device has been advanced. In particular, a TFT using a polycrystalline semiconductor film has higher field effect mobility (also referred to as mobility) than a TFT using a conventional amorphous semiconductor film, and thus can operate at high speed. For this reason, attempts have been made to control a pixel, which is conventionally performed by a driving circuit provided outside the substrate, using a driving circuit formed on the same substrate as the pixel.

  By the way, as a substrate used for a semiconductor device typified by a TFT, a glass substrate is considered promising rather than a single crystal silicon substrate in terms of cost. Since glass substrates are inferior in heat resistance and easily deformed by heat, when forming TFTs with a polysilicon semiconductor film on a glass substrate, laser annealing is used for crystallization of the semiconductor film in order to avoid thermal deformation of the glass substrate. Is used.

  The characteristics of laser annealing are that the processing time can be greatly shortened compared to annealing methods using radiation heating or conduction heating, and the semiconductor substrate or semiconductor film is selectively and locally heated to make the substrate almost thermally It has been raised not to damage.

  In addition, the laser annealing method here means a technique for recrystallizing a damaged layer or an amorphous layer formed by addition of impurities formed on a semiconductor substrate or a semiconductor film, or a crystallizing an amorphous semiconductor film formed on a substrate. It points to the technology to make. Moreover, the technique applied to planarization and surface modification of a semiconductor substrate or a semiconductor film is also included.

  Lasers used for laser annealing are roughly classified into two types, pulse oscillation and continuous oscillation, depending on the oscillation method. In recent years, it has been found that the crystal grain size formed in a semiconductor film is larger when a continuous wave laser is used than when a pulsed laser is used for crystallization of a semiconductor film. When the crystal grain size in the semiconductor film is increased, the number of grain boundaries entering the TFT channel region formed by using the semiconductor film is reduced, so that the mobility is increased and it can be used for development of a higher performance device. For this reason, continuous wave lasers are starting to attract attention.

  Further, when laser annealing of a semiconductor or a semiconductor film is performed, a laser beam oscillated from the laser is processed by an optical system so as to be linear or elliptical on the irradiated surface, and a beam spot (laser irradiated surface) There is known a method of scanning the surface to be irradiated. Since the above method can efficiently irradiate the substrate with laser light and increase the mass productivity, it is preferably used industrially (for example, see Patent Document 1).

JP-A-8-195357

  In order to efficiently perform laser annealing of a semiconductor film formed on a substrate, the shape of a beam spot emitted from a continuous wave laser is processed using an optical system, and a linear or elliptical beam is applied to the substrate. In contrast, a scanning method is used.

  A galvanometer mirror is used as means for scanning the laser. That is, the laser incident on the galvanometer mirror is deflected in the direction of the substrate, the galvanometer mirror is vibrated, and the incident angle and reflection angle of the laser beam with respect to the galvanometer mirror are controlled to scan the deflected laser beam over the entire surface of the substrate. be able to. With the configuration in which the laser beam can be scanned only by the vibration of the galvanometer mirror, it is not necessary to reciprocate the substrate with a stage or the like, and laser irradiation can be performed in a short time.

  The beam deflected by the galvanometer mirror can be always focused on a plane by condensing with the fθ lens. The beam deflected by the galvanometer mirror is scanned from the end of the lens to the center, thereby scanning the substrate arranged on the plane, that is, the semiconductor film.

  However, since the transmittance of the fθ lens used for the laser condensing means is different between the center and the end of the lens, if it is used for laser crystallization as it is, a difference occurs in the energy distribution of the laser light irradiated on the semiconductor film, and the semiconductor film The entire surface cannot be irradiated uniformly. However, when performing laser irradiation on the semiconductor film, it is necessary to perform uniform processing on the semiconductor film by uniformly irradiating the laser beam.

  Accordingly, an object of the present invention is to provide a continuous wave laser irradiation apparatus capable of performing laser irradiation efficiently and uniformly. That is, the present invention provides means for canceling the energy distribution difference caused by the difference in transmittance of the lens and making the irradiation energy of the laser light uniform on the irradiated surface.

  In view of the above-described problems, the present invention is characterized in that the difference in energy distribution of the laser beam on the surface of the irradiated object is corrected by the scanning speed of the laser beam.

  The laser irradiation apparatus of the present invention has a laser oscillator (first means) and an optical system (second means) for shaping laser light emitted from the laser oscillator. The laser beam shaped by the optical system is irradiated onto the irradiated object by the third means for deflecting the beam toward the substrate. The apparatus of the present invention has a fourth means for condensing the laser beam on the substrate. The configuration of the present invention includes fifth means for controlling the operating speed of the third means for the purpose of canceling the beam energy difference generated by the fourth means.

  The deflection occurs by giving a phase change having a linear gradient to the light beam in the light beam cross section. For example, when the plane mirror is rotated by θ with respect to the incident light, the reflected light is deflected by 2θ. Applications of this are rotating mirror type optical deflectors and rotating polygonal mirrors, and examples include galvanometer mirrors and polygon mirrors.

  That is, according to the present invention, in a laser irradiation apparatus using a galvano mirror and an fθ lens optical system, a laser beam scanning is performed while canceling out an energy change caused by a change in transmittance of an fθ lens and suppressing an energy fluctuation applied to an irradiated object. It is a laser irradiation apparatus that can perform. A polygon mirror may be used instead of the galvanometer mirror.

  The irradiated object is, for example, a semiconductor film formed on the substrate, but the film thickness of the semiconductor film is negligibly small with respect to the substrate. Therefore, the irradiated object will be described as a substrate.

  In the above configuration, the beam is scanned by a galvanometer mirror, but the energy is usually highest near the center of the substrate due to the difference in transmittance of the lens, and the energy decreases toward the substrate edge. Further, since the transmittance of the lens changes continuously depending on the location, the energy of the transmitted beam also changes continuously. And the energy of the laser beam irradiated to the to-be-irradiated surface of a board | substrate will increase / decrease with the scanning speed of a laser beam. Therefore, the present invention is characterized in that the operation speed of the galvano mirror (the speed at which the galvano mirror is shaken) is continuously changed according to the transmittance of the lens position where the laser light is incident.

  The specific operating speed of the galvanometer mirror is such that the beam scanning speed is increased at a location where the transmittance of the lens is high, and the beam scanning speed is decreased at a location where the transmittance is low. Can be controlled. That is, by controlling the beam scanning speed so as to cancel the transmittance change due to the lens, it is possible to prevent the occurrence of energy fluctuation of the laser light irradiated on the substrate.

  With the laser irradiation apparatus of the present invention as described above, the substrate can be irradiated with laser light at high speed, and the entire surface of the substrate can be crystallized uniformly.

  In the present invention, even a difference in energy distribution on the substrate that does not depend on an optical system such as an fθ lens or a galvanometer mirror can be corrected by the scanning speed of the laser beam. For example, even when the substrate cannot be arranged flat and is warped from the substrate center to the substrate edge, the energy distribution difference can be corrected by controlling the scanning speed of the laser light.

  A laser irradiation apparatus using a galvanometer mirror and an fθ lens optical system can process a substrate in a short time. The operating speed of the galvanometer mirror is controlled, and the scanning speed of the laser light is continuously changed in a manner that cancels out the change in transmittance of the lens. Irradiation can be performed while controlling the irradiation energy by the above configuration. Therefore, the configuration of the present invention can suppress the energy fluctuation of the laser beam applied on the substrate. Then, by performing laser annealing using the laser irradiation apparatus of the present invention, a semiconductor device with reduced variation in electrical characteristics can be obtained.

  Hereinafter, the structure of the laser irradiation apparatus of this invention is demonstrated.

  FIG. 1 shows an outline of the laser irradiation apparatus of the present invention. The laser irradiation apparatus 100 of the present invention has a laser oscillator 101 corresponding to a first means for oscillating laser light. Although FIG. 1 shows an example in which one laser oscillator 101 is provided, the number of laser oscillators 101 included in the laser irradiation apparatus 100 of the present invention is not limited to this number. The beam spots of the laser beams output from the laser oscillator may be overlapped with each other and used as one beam spot.

The laser can be appropriately changed depending on the purpose of processing. In the present invention, a known laser can be used. As the laser, a continuous wave gas laser or solid-state laser can be used. Examples of the gas laser include an Ar laser and a Kr laser, and examples of the solid laser include a YAG laser, a YVO ₄ laser, a YLF laser, a YAlO ₃ laser, a Y ₂ O ₃ laser, an alexandride laser, and a Ti: sapphire laser. The harmonic with respect to the fundamental wave can be obtained by using a nonlinear optical element.

  Furthermore, after converting infrared laser light emitted from a solid-state laser into green laser light using a nonlinear optical element, ultraviolet laser light obtained by another nonlinear optical element can also be used.

  In addition, the laser irradiation apparatus 100 of the present invention has an optical system 102 corresponding to a second means capable of processing a beam spot on an irradiated object of laser light oscillated from a laser oscillator 101.

  The shape of the beam spot on the irradiated object 106 of the laser light oscillated from the laser oscillator 101 is linear or elliptical. Note that the shape of laser light emitted from the laser differs depending on the type of laser. In the case of a YAG laser, the shape of the emitted laser light is circular if the rod shape is cylindrical, and is rectangular if it is a slab type. Note that the laser beam emitted from the slab type laser differs greatly in the beam divergence angle in the vertical and horizontal directions, so that the beam shape largely changes depending on the distance from the emission port. By shaping such laser light by the optical system 102, linear or elliptical laser light of a desired size can be produced.

  When a plurality of laser oscillators are used, one beam spot may be formed by superimposing the beam spots output from the laser oscillators using the optical system.

  The laser irradiation apparatus 100 of the present invention has a galvanometer mirror 103 corresponding to a third means for determining the irradiation position of the laser beam on the irradiated object. By operating the galvanometer mirror 103 and changing the incident angle and the reflection angle of the laser beam, the irradiation position of the laser beam on the irradiated object can be moved (scanned) and the scanning direction of the laser beam can be changed. . By operating the galvanometer mirror 103, the entire surface of the irradiated object can be scanned with the laser light.

  Further, the laser irradiation apparatus 100 of the present invention has an optical system 104 corresponding to the fourth means. The optical system 104 has a function of condensing the beam spot of the laser light on the irradiation object. The optical system 104 uses an fθ lens. By using the fθ lens, the beam spot can be always focused on the substrate. Note that the constant focus on the substrate here does not necessarily mean that the focus of the laser light irradiated through the fθ lens is on the substrate, but includes a state where the focus is deviated from the substrate. By shifting the focal point from the substrate in this way, the laser irradiation surface is increased, and the processing speed of laser irradiation is improved. Therefore, the fθ lens has a function of keeping the laser beam in a desired constant shape on the entire surface of the substrate.

  A telecentric fθ lens may be used instead of the fθ lens. By using the telecentric fθ lens, the incident angle of the laser light after passing through the lens with respect to the irradiated object can be made constant, and the reflectance of the irradiated object can be kept constant.

  Further, the laser irradiation apparatus 100 of the present invention has a control device 105 corresponding to the fifth means. The control device 105 can operate the galvanometer mirror 103 corresponding to the third means so that the entire surface of the irradiation object can be irradiated with a laser beam spot. Further, by continuously changing and controlling the operation speed, it is possible to cancel the beam energy difference due to the change in transmittance of the optical system 104.

  Then, by performing laser annealing using the laser irradiation apparatus of the present invention, a semiconductor device with reduced variation in electrical characteristics can be obtained.

  FIG. 2 shows an example of the laser irradiation apparatus of the present invention. The laser beam emitted from the laser oscillation device 201 is formed into a linear beam using the beam expander 202 and the cylindrical lens 203. A galvanometer mirror 204 and an fθ lens 205 are disposed above the substrate 210. The beam reflected by the galvanometer mirror 204 enters the fθ lens 205. The processed linear beam can always be focused on the substrate by the fθ lens 205. A telecentric lens may be used as the fθ lens. With the telecentric lens, the incident angle of the laser beam to the substrate can be made constant regardless of the lens incident position, and the reflectance of the irradiated object can be kept constant. Note that when laser irradiation is performed on a substrate that transmits laser light, such as a glass substrate, interference fringes may occur in the irradiated object on the substrate due to reflected light from the substrate surface and reflected light from the back surface of the substrate. On the other hand, a configuration in which laser light is incident from an oblique direction may be employed.

  Laser light scanning by the galvanometer mirror is performed along the X-axis direction in FIG. After scanning in the X-axis direction, the entire surface of the substrate can be irradiated by moving the substrate by the beam width in the Y-axis direction by the movable stage 206 and repeating scanning by the galvanometer mirror. With respect to the laser beam scanning, a linear beam may be scanned by reciprocating along the X axis as shown in FIG. 3A, or may be scanned in one direction as shown in FIG.

  Here, the speed of laser scanning by the galvanometer mirror 204 will be described. First, the operation speed of the galvanometer mirror 204 is controlled to make the laser scanning speed on the substrate constant. In this case, since the transmittance of the lens differs depending on the location, the energy of the laser beam scanned changes due to the change in transmittance. An example of a change in irradiation energy of laser light scanned on the substrate at this time is shown in FIG. FIG. 4 shows that the laser intensity is high near the center of the substrate and the laser intensity is low near the edge of the substrate. Therefore, the beam scanning speed is increased near the center of the substrate where the lens transmittance is high, and the beam scanning speed is decreased near the substrate edge where the transmittance is low, thereby changing the irradiation energy applied to the substrate. It becomes possible to suppress. FIG. 5 shows an example of the scanning speed distribution of the laser beam that can cancel the energy change of the beam shown in FIG. The apparatus of the present invention can perform laser scanning with the distribution shown in FIG.

Specifically, a case where there is a 5% difference in transmittance of the fθ lens between the lens position where the laser beam is incident when scanning the center of the substrate and the lens position where the laser beam is incident when scanning the substrate edge will be described. . For example, when a semiconductor film having a thickness of 540 nm is irradiated with a laser beam having an output of 6.5 W and a wavelength of 532 nm emitted from a YVO ₄ laser at a constant scanning speed, there is a difference in energy applied between the substrate center and the substrate edge. . Therefore, the width of the large grain size region (the crystal grain size is 10 μm or more) formed in the region (irradiation surface) irradiated with the laser of the semiconductor film differs between the substrate center and the substrate edge. Therefore, in order to make the width of the large grain size region constant at 180 μm between the substrate edge and the substrate center, the substrate edge is scanned at 40 cm / sec, and laser scanning is performed at a velocity distribution of 42 cm / sec at the substrate center. By giving the above-described change in scanning speed, the change in irradiation energy given on the substrate can be suppressed, and the width of the large particle size region can be made constant. In the apparatus of the present invention, the scanning speed of the laser beam is not limited to the above value. The scanning speed may be controlled in accordance with conditions such as a desired large grain width, semiconductor film material, and film thickness.

  The laser scanning speed is controlled by controlling the operating speed of the galvanometer mirror. By irradiating with the above configuration, it is possible to suppress the change in the irradiation efficiency of the substrate and the change in the annealing effect of the substrate due to the change in the transmittance of the lens. Note that the galvanometer mirror control device may store in advance speed change patterns corresponding to various lenses so that the operation speed of the galvanometer mirror can be set according to the lens shape and material.

Further, the change in the irradiation energy of the laser beam scanned on the substrate shown in FIG. 4 is only an example. As shown in FIG. 8, the present invention can be applied even when the energy change is undulating.

  In the present embodiment, a case where laser beam scanning is performed by controlling the galvanometer mirror in both the X axis and the Y axis in the first embodiment will be described.

  The speed of laser scanning with a galvanometer mirror will be described. First, the operation speed of the galvanometer mirror is controlled to keep the laser scanning speed on the substrate constant. In this case, since the transmittance of the lens varies depending on the location, the energy of the laser beam to be scanned changes due to the change in transmittance. An example of the irradiation energy change of the laser beam scanned on the substrate at this time is shown in FIG. FIG. 6 shows that the laser intensity is high near the center of the substrate, and the laser intensity decreases concentrically as it goes to the edge of the substrate. Therefore, the beam scanning speed is increased near the center of the substrate where the lens transmittance is high, and the beam scanning speed is decreased near the substrate edge where the transmittance is low, thereby changing the irradiation energy applied to the substrate. It becomes possible to suppress.

  FIG. 7 shows an example of the scanning speed distribution of the laser beam that can cancel the energy change of the beam shown in FIG. In the apparatus of the present invention, laser scanning is performed with the distribution shown in FIG. The laser scanning speed is controlled by controlling the operating speed of the galvanometer mirror. By irradiating with the above configuration, it is possible to suppress the change in the irradiation efficiency of the substrate and the change in the annealing effect of the substrate due to the change in the transmittance of the lens. Note that the galvanometer mirror control device may store in advance speed change patterns corresponding to various lenses so that the operation speed of the galvanometer mirror can be set according to the lens shape and material. In order to perform uniform irradiation of the substrate, the energy fluctuation of the beam given on the substrate is preferably within ± 5%.

  Further, the change in the irradiation energy of the laser light scanned on the substrate shown in FIG. 6 is only an example. As shown in FIG. 8, the present invention can be applied even when the energy change is undulating.

  As described above, in the present invention, when laser crystallization of a semiconductor film on a substrate is performed, a change in irradiation energy applied to the substrate is suppressed by giving a change in scanning speed, and a large grain formed on a laser irradiation trace. The width of the diameter region can be made constant. Note that the scanning speed may be controlled according to conditions such as a desired large grain width, a semiconductor film material, a film thickness, and the like.

  In this embodiment, a process for manufacturing a crystalline semiconductor film by using the laser irradiation apparatus of the present invention and forming a semiconductor device will be described with reference to FIGS.

  First, base insulating films 1101 a and 1101 b are formed over the substrate 1100. Substrate materials include glass substrates, quartz substrates, crystalline glass and other insulating substrates, ceramic substrates, stainless steel substrates, metal substrates (tantalum, tungsten, molybdenum, etc.), semiconductor substrates, plastic substrates (polyimide, acrylic, polyethylene) Terephthalate, polycarbonate, polyarylate, polyethersulfone, etc.) can be used, but at least a material that can withstand the heat generated during the process is used. In this embodiment, a glass substrate is used.

  As the base insulating films 1100a and 1100b, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or the like can be used. These insulating films are formed by forming a single layer or two or more layers. These are formed by using a known method such as a sputtering method, a low pressure CVD method, or a plasma CVD method. In this embodiment, a two-layer structure is used, but it is of course possible to use a single layer or a plurality of layers of three or more layers. In this embodiment, a silicon nitride oxide film is formed with a thickness of 50 nm as the first insulating film 1100a, and a silicon oxynitride film is formed with a thickness of 100 nm as the second insulating film 1100b. Note that the silicon nitride oxide film and the silicon oxynitride film have different ratios of nitrogen and oxygen, and the former indicates that the nitrogen content is higher.

Next, an amorphous semiconductor film is formed. The amorphous semiconductor film may be formed to a thickness of 25 to 80 nm using silicon or a material containing silicon as a main component (for example, Si _x Ge _{1 -x} ). As a manufacturing method, a known method such as a sputtering method, a low pressure CVD method, or a plasma CVD method can be used. In this embodiment, the film is formed with amorphous silicon to a film thickness of 66 nm.

  Subsequently, crystallization of amorphous silicon is performed. In this embodiment, a process of crystallizing by laser annealing will be described.

Laser annealing uses the laser irradiation apparatus of the present invention. As the laser oscillation device, a continuous oscillation gas or a solid-state laser oscillation device may be used. Examples of the gas laser include an Ar laser and a Kr laser, and examples of the solid laser include a YAG laser, a YVO ₄ laser, a YLF laser, a YAlO ₃ laser, an alexandride laser, and a Ti: sapphire laser. The crystal which is the laser medium of the solid laser is selected from Cr ³⁺ , Cr ⁴⁺ , Nd ³⁺ , Er ³⁺ , Ce ³⁺ , Co ²⁺ , Ti ³⁺ , Yb ³⁺ or V ³⁺ One or more species are doped as impurities.

Amorphous silicon is crystallized by laser annealing using the laser irradiation apparatus of the present invention. More specifically, the method described in Embodiments 1 to 3 may be performed. In this embodiment, a YVO ₄ laser (wavelength: 532 nm) with a laser output of 10 W is used and processed into an ellipse with a short axis of 20 μm and a long axis of 750 μm, and the laser incident angle on the irradiated surface is 30 °. The irradiation energy given to the substrate is controlled using an optical system that depends on the polarization direction of the laser light by changing the polarization split ratio of the laser light. The polarization split ratio of the laser light is changed so as to cancel the change in irradiation energy caused by the change in transmittance of the fθ lens. By giving the above change, it is possible to suppress the change in the irradiation energy given on the substrate and to make the width of the large particle size region constant.

In addition, when the crystallized semiconductor film is used as an active layer of a TFT, it is desirable to determine the scanning direction of the laser light so as to be parallel to the direction in which carriers in the channel formation region move.
Therefore, as shown by the arrow in FIG. 9, so that the flat line as direction (channel length direction) moving the carriers in the channel formation region, defining a scanning direction of the laser beam. As a result, the crystal grows along the scanning direction of the laser beam, and the crystal grain boundary can be prevented from crossing the channel length direction.

Next, the crystalline semiconductor film is etched into desired shapes 1102a to 1102d. Subsequently, a gate insulating film 1103 is formed. The thickness may be approximately 115 nm, and an insulating film containing silicon may be formed by a low pressure CVD method, a plasma CVD method, a sputtering method, or the like. In this embodiment, a silicon oxide film is formed. In this case, TEOS (Tetraethyl Ortho Silicate) and O ₂ are mixed by a plasma CVD method, and a high frequency (13.56 MHz) power density of 0.5 to 0.00 is obtained under a reaction pressure of 40 Pa and a substrate temperature of 300 to 400 ° C. It is formed by discharging at 8 W / cm ² . The silicon oxide film thus manufactured can obtain favorable characteristics as a gate insulating film by subsequent heat treatment at 400 to 500 ° C.

  By crystallizing the semiconductor film using the laser irradiation apparatus of the present invention, a crystalline semiconductor having good and uniform characteristics can be obtained.

  Next, tantalum nitride (TaN) with a thickness of 30 nm is formed as a first conductive layer over the gate insulating film, and tungsten (W) with a thickness of 370 nm is formed as a second conductive layer thereon. The TaN film and the W film may be formed by co-sputtering, the TaN film may be formed in a nitrogen atmosphere using a Ta target, and the W film may be formed using a W target.

  In this example, the first conductive layer is TaN having a thickness of 30 nm and the second conductive layer is W having a thickness of 370 nm. However, the present invention is not limited to this, and the first conductive layer and the second conductive layer are Both may be formed of an element selected from Ta, W, Ti, Mo, Al, Cu, Cr, and Nd, or an alloy material or a compound material containing the element as a main component. Alternatively, a semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus may be used. Further, an AgPdCu alloy may be used. Furthermore, the combination may be selected as appropriate. The film thickness may be in the range of 20 to 100 nm for the first conductive layer and 100 to 400 nm for the second conductive layer. In this embodiment, a two-layer structure is used, but a single layer may be used, or a three-layer or more structure may be used.

  Next, in order to form the electrode and the wiring by etching the conductive layer, a mask made of a resist is formed through an exposure process by photolithography. In the first etching process, etching is performed under the first etching condition and the second etching condition. Etching is performed using a resist mask to form gate electrodes and wirings. Etching conditions may be selected as appropriate.

In this method, an ICP (Inductively Coupled Plasma) etching method is used. As the first etching condition, CF ₄ , Cl ₂ and O ₂ are used as etching gases, the respective gas flow rates are set to 25/25/10 (sccm), and 500 W RF is applied to the coil-type electrode at a pressure of 1.0 Pa. (13.56 MHz) Electric power is applied to generate plasma and perform etching. 150 W RF (13.56 MHz) power is also applied to the substrate side (sample stage), and a substantially negative self-bias voltage is applied. The W film is etched under the first etching condition so that the end portion of the first conductive layer is tapered. Under the first etching conditions, the etching rate for the W film is about 200 nm / min, the etching rate for TaN is about 80 nm / min, and the selectivity ratio of W to TaN is about 2.5. Further, the taper angle of the W film is about 26 ° under this first etching condition.

Subsequently, the etching is performed under the second etching condition. Without removing the resist mask, CF ₄ and Cl ₂ are used as etching gases while leaving the mask, and each gas flow rate is 30/30 (sccm), the pressure is 1.0 Pa, and the coil type electrode is 500 W. RF (13.56 MHz) power is applied to generate plasma, and etching is performed for about 15 seconds. 20 W RF (13.56 MHz) power is also applied to the substrate side (sample stage), and a substantially negative self-bias voltage is applied. Under the second etching condition in which CF ₄ and Cl ₂ are mixed, the W film and the TaN film are etched to the same extent.

  The etching rate for W under the second etching condition is 59 nm / min, and the etching rate for TaN is 66 nm / min. Note that in order to perform etching without leaving a residue on the gate insulating film, it is preferable to increase the etching time at a rate of about 10 to 20%. In this first etching process, the gate insulating film not covered with the electrode is etched by about 20 nm to 50 nm.

  In the first etching process, the end portions of the first conductive layer and the second conductive layer are tapered due to the effect of the bias voltage applied to the substrate side.

Next, a second etching process is performed without removing the resist mask. In the second etching process, SF ₆ , Cl _2, and O ₂ are used as etching gases, the respective gas flow rates are set to 24/12/24 (sccm), and the power on the coil side is 700 W at a pressure of 1.3 Pa. The RF (13.56 MHz) power is applied to generate plasma, and etching is performed for about 25 seconds. 10 W RF (13.56 MHz) power was also applied to the substrate side (sample stage), and a substantially negative self-bias voltage was applied. Under this etching condition, the W film was selectively etched to form a second shape conductive layer. At this time, the first conductive layer is hardly etched. A gate electrode including the first conductive layers 1104a to 1104d and the second conductive layers 1105a to 1105d is formed by the first and second etching processes.

Then, the first doping process is performed without removing the resist mask. Thereby, an impurity imparting N-type is added to the crystalline semiconductor layer at a low concentration. The first doping process may be performed by an ion doping method or an ion implantation method. The ion doping method may be performed at a dose of 1 × 10 ^{13 to} 5 × 10 ¹⁴ ions / cm ² and an acceleration voltage of 40 to 80 kV. In this embodiment, the acceleration voltage is 50 kV. As the impurity element imparting N-type, an element belonging to Group 15 can be used, and typically phosphorus (P) or arsenic (As) is used. In this example, phosphorus (P) was used. At that time, the first conductive layer as a mask, a first impurity region self-aligned manner low concentration impurity is added ^- to form a (N region).

Subsequently, the resist mask is removed. Then, a new mask made of resist is formed, and the second doping process is performed at a higher acceleration voltage than the first doping process. In the second doping process, an impurity imparting N-type is added. The conditions for the ion doping method may be that the dose is 1 × 10 ^{13 to} 3 × 10 ¹⁵ ions / cm ² and the acceleration voltage is 60 to 120 kV. In this embodiment, the dose is set to 3.0 × 10 ¹⁵ ions / cm ² and the acceleration voltage is set to 65 kV. In the second doping treatment, the second conductive layer is used as a mask for the impurity element, and doping is performed so that the impurity element is also added to the semiconductor layer located below the first conductive layer.

When the second doping is performed, a portion of the crystalline semiconductor layer that overlaps with the first conductive layer does not overlap with the second conductive layer or a portion that is not covered with the mask. Regions (N ⁻ region, Lov region) are formed. An impurity imparting N-type is added to the second impurity region in a concentration range of 1 × 10 ^{18 to} 5 × 10 ¹⁹ atoms / cm ³ . Further, in the crystalline semiconductor film, the exposed portion (third impurity region: N ⁺ region) which is not covered with the first shape conductive layer or the mask and is exposed to 1 × 10 ^{19 to} 5 Impurities imparting N-type are added at a high concentration in the range of × 10 ²¹ atoms / cm ³ . In addition, the semiconductor layer has an N ⁺ region, but there is a portion that is partially covered only by the mask. The concentration of impurity imparting N-type in this portion, since the remains of the impurity concentration added in the first doping process, subsequently the first impurity regions ^- is referred to as (N region).

  In this embodiment, each impurity region is formed by two doping processes, but the present invention is not limited to this, and a desired impurity concentration is obtained by performing doping once or a plurality of times by appropriately setting conditions. An impurity region may be formed.

Next, after removing the resist mask, a new resist mask is formed, and a third doping process is performed. A fourth impurity region (impurity element imparting a conductivity type opposite to the first conductivity type and the second conductivity type is added to the semiconductor layer to be a P-channel TFT by the third doping treatment ( P ⁺ region) and a fifth impurity region (P ⁻ region) are formed.

In the third doping process, a fourth impurity region (P ⁺ region) is formed in a portion that is not covered with the resist mask and does not overlap with the first conductive layer. A fifth impurity region (P ⁻ region) is formed in a portion that is not covered and overlaps with the first conductive layer and does not overlap with the second conductive layer. As the impurity element imparting P-type, elements of Group 13 of the periodic table such as boron (B), aluminum (Al), and gallium (Ga) are known.

In this embodiment, boron (B) is selected as the P-type impurity element for forming the fourth impurity region and the fifth impurity region, and is formed by ion doping using diborane (B ₂ H ₆ ). . As conditions for the ion doping method, the dose was 1 × 10 ¹⁶ ions / cm ² and the acceleration voltage was 80 kV.

  In the third doping process, the semiconductor layers A and C forming the N-channel TFT are covered with a resist mask.

Here, phosphorus is added to the fourth impurity region (P ⁺ region) and the fifth impurity region (P ⁻ region) at different concentrations by the first and second doping processes. However, in any of the fourth impurity region (P ⁺ region) and the fifth impurity region (P ⁻ region), the concentration of the impurity element imparting P-type is 1 × 10 5 by the third doping treatment. Doping treatment is performed so as to be ^{19 to} 5 × 10 ²¹ atoms / cm ³ . Therefore, the fourth impurity region (P ⁺ region) and the fifth impurity region (P ⁻ region) function without problems as the source region and the drain region of the P-channel TFT.

In this embodiment, the fourth impurity region (P ⁺ region) and the fifth impurity region (P ⁻ region) are formed by one third doping, but the present invention is not limited to this. The fourth impurity region (P ⁺ region) and the fifth impurity region (P ⁻ region) may be formed by a plurality of doping processes as appropriate depending on the conditions of the doping process.

By these doping treatments, the first impurity region (N ⁻ region) 1112b, the second impurity region (N ⁻ region, Lov region) 1111b, the third impurity region (N ⁺ region) 1111a, 1112a, the fourth Impurity regions (P ⁺ regions) 1113a and 1114a and fifth impurity regions (P ⁻ regions) 1113b and 1114b are formed.

Next, the resist mask is removed to form a first passivation film 1120. As this first passivation film, an insulating film containing silicon is formed to a thickness of 100 to 200 nm. As a film forming method, a plasma CVD method or a sputtering method may be used. In this embodiment, a silicon oxynitride film having a thickness of 100 nm is formed by plasma CVD. In the case of using a silicon oxynitride film, SiH _4, N ₂ O, a silicon oxynitride film formed from NH _3, or by SiH _4, N form a silicon oxynitride film formed from the ₂ O by plasma CVD It ’s fine. The production conditions in this case are a reaction pressure of 20 to 200 Pa, a substrate temperature of 300 to 400 ° C., and a high frequency (60 MHz) power density of 0.1 to 1.0 W / cm ² . Alternatively, a silicon oxynitride silicon film formed from SiH ₄ , N ₂ O, and H ₂ may be used as the first passivation film. Needless to say, the first passivation film 1120 is not limited to the single layer structure of the silicon oxynitride film as in this embodiment, and other insulating films containing silicon are used as a single layer structure or a stacked structure. Also good.

After that, laser annealing is performed using the laser irradiation apparatus of the present invention to recover the crystallinity of the semiconductor layer and activate the impurity element added to the semiconductor layer. In this embodiment, a YVO ₄ laser (wavelength of 532 nm) with a laser output of 1.8 W is used, processed into an ellipse with a minor axis of 20 μm and a major axis of 250 μm, scanned 800 times at a 125 μm pitch, and a laser scanning speed of 25 cm / sec. And In addition to the laser annealing method, a heat treatment method or a rapid thermal annealing method (RTA method) can be applied.

  Further, by performing heat treatment after the first passivation film 1120 is formed, the semiconductor layer can be hydrogenated simultaneously with the activation treatment. In hydrogenation, dangling bonds in a semiconductor layer are terminated by hydrogen contained in the first passivation film.

  In addition, heat treatment may be performed before the first passivation film 1120 is formed. However, when the materials constituting the first conductive layers 1104a to 1104d and the second conductive layers 1105a to 1105d are weak against heat, the first passivation film 1120 is used to protect the wiring and the like as in this embodiment. It is desirable to perform heat treatment after forming the film. Further, in this case, since there is no first passivation film, naturally hydrogenation using hydrogen contained in the passivation film cannot be performed.

  In this case, hydrogenation using means (plasma hydrogenation) using hydrogen excited by plasma, or heat treatment at 300 to 450 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% hydrogen. Hydrogenation by means of the above may be used.

  Next, a first interlayer insulating film 1121 is formed over the first passivation film 1120. An inorganic insulating film or an organic insulating film can be used as the first interlayer insulating film. As the inorganic insulating film, a silicon oxide film formed by a CVD method, a silicon oxide film applied by an SOG (Spin On Glass) method, or the like can be used. As an organic insulating film, polyimide, polyamide, BCB (benzoic acid) is used. A film such as cyclobutene), acrylic or positive photosensitive organic resin, or negative photosensitive organic resin can be used. Alternatively, a stacked structure of an acrylic film and a silicon oxynitride film may be used.

  The interlayer insulating film can be formed using a material having a skeleton structure of a bond of silicon (Si) and oxygen (O) and containing at least hydrogen as a substituent. Furthermore, it can be formed of a material having at least one of fluorine, alkyl group, and aromatic hydrocarbon as a substituent. Representative examples of these materials include siloxane polymers.

  Siloxane polymers can be classified according to their structures into, for example, silica glass, alkylsiloxane polymers, alkylsilsesquioxane polymers, hydrogenated silsesquioxane polymers, hydrogenated alkylsilsesquioxane polymers, and the like.

  Alternatively, the interlayer insulating film may be formed using a material containing a polymer (polysilazane) having a Si—N bond.

  By using the above material, an interlayer insulating film having sufficient insulation and flatness can be obtained even when the film thickness is reduced. In addition, since the above material has high heat resistance, an interlayer insulating film that can withstand reflow processing in a multilayer wiring can be obtained. Further, since the hygroscopic property is low, an interlayer insulating film with a small amount of dehydration can be formed.

  In this embodiment, a non-photosensitive acrylic film having a thickness of 1.6 μm is formed. With the first interlayer insulating film, unevenness due to the TFT formed on the substrate can be relaxed and planarized. In particular, since the first interlayer insulating film has a strong meaning of flattening, it is preferable to use an insulating film made of a material that is easily flattened.

  Thereafter, a second passivation film (not shown) made of a silicon nitride oxide film or the like is formed on the first interlayer insulating film. The film thickness may be about 10 to 200 nm, and the second passivation film can prevent moisture from entering and exiting the first interlayer insulating film. In addition, a silicon nitride film, an aluminum nitride film, an aluminum oxynitride film, a diamond-like carbon (DLC) film, and a carbon nitride (CN) film can be used as the second passivation film.

A film formed using an RF sputtering method has high density and excellent barrier properties. For example, when a silicon oxynitride film is formed, RF sputtering is performed by flowing N ₂ , Ar, and N ₂ O at a gas flow ratio of 31: 5: 4 using a Si target and a pressure of 0.4 Pa. The film is formed with an electric power of 3000 W. For example, when a silicon nitride film is formed, N ₂ and Ar in the chamber are flowed so that the gas flow ratio is 20/20 (sccm) with a Si target, pressure 0.8 Pa, power 3000 W, and composition. The film is formed at a film temperature of 215 ° C. In this embodiment, a silicon oxynitride film is formed with a thickness of 70 nm by RF sputtering.

  Next, the second passivation film, the first interlayer insulating film, and the first passivation film are etched by etching to form contact holes that reach the third impurity region and the fourth impurity region.

  Subsequently, wirings and electrodes that are electrically connected to the respective impurity regions are formed. Note that these wirings are formed by patterning a laminated film of a Ti film having a thickness of 50 nm and an alloy film (Al and Ti) having a thickness of 500 nm. Of course, it is not limited to a two-layer structure, and may be a single-layer structure or a laminated structure of three or more layers. Further, the wiring material is not limited to Al and Ti. For example, the wiring may be formed by forming an Al film or a Cu film on the TaN film and then patterning a laminated film formed with a Ti film.

  As described above, a semiconductor device manufactured using the laser irradiation apparatus of the present invention exhibits favorable and uniform characteristics, and thus can be suitably used for various electronic devices and particularly display devices. In addition, the reliability of the product is increased.

The figure which shows the structure of the laser irradiation apparatus of this invention. The figure which shows the example of the laser irradiation apparatus which this invention discloses. The figure which shows the scanning method of a laser beam. The figure which shows the example of the energy change of the beam by the transmittance | permeability change of a lens. The figure which shows the example of the laser scanning speed which this invention discloses. The figure which shows the example of the energy change of the beam by the transmittance | permeability change of a lens. The figure which shows the example of the laser scanning speed which this invention discloses. The figure which shows the example of the energy change of the beam by the transmittance | permeability change of a lens. The figure which shows the laser scanning method. 4A and 4B illustrate a method for manufacturing a semiconductor device disclosed in the present invention. 4A and 4B illustrate a method for manufacturing a semiconductor device disclosed in the present invention.

Claims (11)

A laser oscillator;
An optical system for processing the laser beam output from the laser oscillator so that the beam spot on the irradiated surface is linear or elliptical;
Means for deflecting the processed laser beam and scanning the laser beam;
An fθ lens having a function of condensing the laser beam and keeping the shape of the laser beam constant ;
The operation speed of the scanning means is large in the region where the transmittance of the fθ lens is high so that the energy that cancels the energy change of the laser light caused by the transmittance change of the fθ lens is large. And a means for controlling the scanning speed of the processed laser beam by controlling it so as to be small in a region where the rate is low. In claim 1,
The laser irradiation apparatus, wherein the scanning means is a galvanometer mirror or a polygon mirror. In claim 1 or 2,
The laser irradiation apparatus, wherein the fθ lens is a telecentric fθ lens. In any one of Claims 1 thru | or 3,
A laser irradiation apparatus, wherein a focal point of the laser beam is shifted from the irradiated surface. In any one of Claims 1 thru | or 4,
A laser irradiation apparatus characterized by controlling a scanning speed of the laser beam to uniformize irradiation energy applied to the irradiated surface. Forming an amorphous semiconductor film;
The laser beam output from the laser oscillator is processed so that the amorphous semiconductor film is the irradiated surface, and the beam spot on the irradiated surface is linear or elliptical,
And deflecting the working laser beam is scanned by means for scanning the record laser light,
The processed laser beam is condensed by an fθ lens having a function of keeping the shape of the laser beam constant ,
The operating speed of the scanning means is large in the region where the transmittance of the fθ lens is high so that the energy that cancels the energy change of the laser light caused by the transmittance change of the fθ lens is large. A method for manufacturing a semiconductor device, characterized in that the scanning speed of the processed laser beam is changed by controlling to be small in a region where the rate is low. In claim 6,
A method for manufacturing a semiconductor device, wherein a scanning direction of the laser beam is parallel to a carrier moving direction of a channel formation region of the amorphous semiconductor film. In claim 6 or 7,
A method for manufacturing a semiconductor device, wherein the processed laser beam is deflected using a galvanometer mirror or a polygon mirror. In any one of Claims 6 thru | or 8,
The method of manufacturing a semiconductor device, wherein the fθ lens is a telecentric fθ lens. In any one of Claims 6 thru | or 9,
A method for manufacturing a semiconductor device, wherein the focal point of the laser beam is shifted from the surface to be irradiated. In any one of Claims 6 thru | or 10,
A method for manufacturing a semiconductor device, wherein the scanning speed of the laser light is changed so that irradiation energy applied to the irradiated surface is made uniform.

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