JP2004146823A - Apparatus for laser irradiation and semiconductor device manufacturing method using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solution to the problem that the transmittance of an fθ lens used as a laser condensing means is different at its center and edge, thus causing a difference in energy of a laser beam irradiating a semiconductor film when used for laser crystallization on an as-is basis, and making it impossible to uniformly irradiate the entire semiconductor film. <P>SOLUTION: An apparatus for laser irradiation using a galvanomirror, and an fθ lens optical system can offset an energy change caused by a change in fθ lens's transmittance, and can do laser scanning while controlling changes of energy given to an irradiated object. Further, a semiconductor device manufacturing method using the apparatus is provided. <P>COPYRIGHT: (C)2004,JPO

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. 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 nearly polycrystalline state with a laser and improves (promotes) the crystallinity of the semiconductor film. Furthermore, 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, the technology for forming a TFT on a substrate has been greatly advanced, and application development to an active matrix type semiconductor display device has been promoted. 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. Therefore, an attempt has been made to control a pixel, which has been conventionally performed by a drive circuit provided outside a substrate, by a drive circuit formed on the same substrate as the pixels.

As a substrate used for a semiconductor device represented by a TFT, a glass substrate is considered more promising than a single crystal silicon substrate in terms of cost. Since a glass substrate is inferior in heat resistance and easily deformed by heat, when a TFT having a polysilicon semiconductor film is formed on the glass substrate, laser annealing is performed during 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 significantly reduced compared to the annealing method using radiant heating or conduction heating, and that the semiconductor substrate or semiconductor film is selectively and locally heated to provide almost thermal It is said that no damage is caused.

Here, the laser annealing method refers to a technique for recrystallizing a damaged layer or an amorphous layer formed by adding impurities formed on a semiconductor substrate or a semiconductor film, or for crystallizing an amorphous semiconductor film formed on a substrate. Refers to the technology that causes Also, the present invention includes a technique applied to planarization and surface modification of a semiconductor substrate or a semiconductor film.

レ ー ザ 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 diameter of crystals formed in a semiconductor film is larger when a continuous wave laser is used than in a pulsed laser in 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 using the semiconductor film is reduced, so that the mobility is increased and the device can be used for developing a device with higher performance. For this reason, continuous wave lasers have begun to be spotlighted.

Also, when performing laser annealing of a semiconductor or a semiconductor film, a laser beam oscillated from a laser is processed by an optical system so as to be linear or elliptical on a surface to be irradiated, and a beam spot (a laser irradiation surface) There is known a method of scanning a surface to be illuminated. With the above method, the substrate can be efficiently irradiated with laser light, and mass productivity can be increased. Therefore, it is industrially favorably used (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. A scanning method is used.

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

(4) The beam deflected by the galvanometer mirror can be always focused on a plane by being condensed by the fθ lens. The beam deflected by the galvanomirror is scanned from the end to the center of the lens, so that the substrate, that is, the semiconductor film disposed on the plane is scanned.

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 entire surface cannot be uniformly irradiated. However, when irradiating a semiconductor film with a laser, it is necessary to uniformly irradiate the laser light to perform a uniform treatment of the semiconductor film.

Accordingly, it is an object of the present invention 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 above-described difference in transmittance of the lens and making the irradiation energy of the laser beam uniform on the irradiated surface.

In view of the above-described problem, the present invention is characterized in that a difference in energy distribution of laser light on the surface of an irradiation target is corrected by a scanning speed of laser light.

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 light shaped by the optical system is irradiated onto the object by the third means for deflecting the beam toward the substrate. Further, the apparatus of the present invention has fourth means for condensing the laser light on the substrate. In the configuration of the present invention, there is provided a fifth means for controlling an operation speed of the third means in order to cancel a beam energy difference generated by the fourth means.

The deflection is caused by giving the light beam a phase change having a linear gradient 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. This is applied to a rotating mirror type optical deflector and a rotating polygon mirror, and examples thereof include a galvano mirror and a polygon mirror.

That is, the present invention provides a laser irradiation apparatus using a galvanomirror and an fθ lens optical system, which cancels an energy change caused by a change in the transmittance of the fθ lens and suppresses a laser beam scanning while suppressing energy fluctuation given to an irradiation object. Is a laser irradiation device capable of performing the following. Further, a polygon mirror may be used instead of the galvanometer mirror.

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

(4) In the above configuration, beam scanning is performed by a galvanometer mirror. Normally, the energy is highest near the center of the substrate due to the difference in transmittance of the lens, and decreases toward the edge of the substrate. Further, since the transmittance of the lens changes continuously depending on the place, the energy of the transmitted beam also changes continuously. The energy of the laser light applied to the irradiated surface of the substrate increases or decreases depending on the scanning speed of the laser light. Therefore, the present invention is characterized in that the operating speed of the galvanomirror (the speed at which the galvanomirror is shaken) is continuously changed in accordance with the transmittance of the lens position where the laser beam enters.

Specifically, the operating speed of the galvanomirror is such that the beam scanning speed is increased in a place where the transmittance of the lens is high, and the beam scanning speed is decreased in a place where the transmittance is low. Can be controlled. That is, by controlling the scanning speed of the beam so as to cancel the change in the transmittance caused by the lens, it is possible to prevent the energy fluctuation of the laser beam irradiated on the substrate from occurring.

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 uniformly crystallized.

According to the present invention, even a difference in energy distribution on a 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 a laser beam. For example, even when the substrate cannot be arranged flat and warps from the center of the substrate to the edge of the substrate, the energy distribution difference can be corrected by controlling the scanning speed of the laser beam.

(4) A laser irradiation apparatus using a galvanomirror and an fθ lens optical system can process a substrate in a short time. The operation speed of the galvanomirror is controlled, and the scanning speed of the laser beam is continuously changed so as to cancel the change in the transmittance of the lens. With the above configuration, irradiation can be performed while controlling irradiation energy. Therefore, according to the structure of the present invention, it is possible to suppress energy fluctuation of the laser light applied to the substrate. 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 configuration of the laser irradiation apparatus of the present invention will be described.

FIG. 1 schematically shows a laser irradiation apparatus according to 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 respective laser beams output from the laser oscillator may be superimposed on 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. As a gas laser, Ar laser, include a Kr laser, a solid state laser, YAG laser, YVO ₄ laser, YLF laser, YAlO ₃ laser, Y ₂ O ₃ laser, alexandrite laser, Ti: sapphire laser, and the like. Harmonics with respect to the fundamental wave can be obtained by using a nonlinear optical element.

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

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 object to be irradiated with laser light oscillated from a laser oscillator 101.

ビ ー ム The shape of the beam spot of the laser beam emitted from the laser oscillator 101 on the irradiation object 106 is linear or elliptical. Note that the shape of the 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 rectangular if the rod shape is a slab type. Note that the laser beam emitted from a slab-type laser has a greatly different beam spread angle in the vertical and horizontal directions, and thus the beam shape changes greatly depending on the distance from the exit. By shaping such laser light with the optical system 102, a linear or elliptical laser light having a desired size can be formed.

In the case where a plurality of laser oscillators are used, one beam spot may be formed by overlapping the beam spots output from each laser oscillator using the optical system.

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

The laser irradiation device 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. An fθ lens is used for the optical system 104. By using the fθ lens, the beam spot can always be focused on the substrate. Note that to always focus on the substrate here means that the focal point of the laser beam irradiated via the fθ lens is not always on the substrate, but includes a state where the focus is intentionally shifted from the substrate. By shifting the focal point from the substrate in this manner, the laser irradiation surface is enlarged, 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 over the entire surface on 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 beam after passing through the lens to the object can be made constant, and the reflectance of the object can be kept constant.

Furthermore, 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 galvano mirror 103 corresponding to the third means so that the beam spot of the laser beam can be irradiated on the entire surface of the object. In addition, by continuously changing and controlling the operation speed, it is possible to cancel the energy difference of the beam due to the change in the transmittance of the optical system 104.

{Circle over (2)} 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 by using a beam expander 202 and a cylindrical lens 203. A galvanometer mirror 204 and an fθ lens 205 are arranged above the substrate 210. The beam reflected by the galvanomirror 204 enters the fθ lens 205. The processed linear beam can always be focused on the substrate by the fθ lens 205. Note that a telecentric lens may be used for the fθ lens. The angle of incidence of the laser beam on the substrate can be made constant irrespective of the lens incidence position by the telecentric lens, and the reflectance of the irradiation object can be kept constant. Note that when laser irradiation is performed on a substrate such as a glass substrate that transmits laser light, reflected light from the substrate surface and light reflected from the back surface of the substrate may cause interference fringes on an irradiated object on the substrate. Alternatively, a configuration may be adopted in which laser light is incident from an oblique direction.

The laser beam scanning by the galvanometer mirror is performed along the X-axis direction in FIG. After the scanning in the X-axis direction is completed, the substrate can be moved by the beam width in the Y-axis direction on the movable stage 206 and the scanning by the galvanometer mirror is repeated, so that the entire surface of the substrate can be irradiated. Regarding the scanning of the laser beam, a method of scanning the linear beam reciprocatingly along the X axis as shown in FIG. 3A or a method of scanning in one direction as shown in FIG. 3B may be used.

Here, the speed of laser scanning by the galvanometer mirror 204 will be described. First, the operation speed of the galvanomirror 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, a change in the transmittance also causes a change in the energy of the scanned laser beam. FIG. 4 shows an example of a change in the irradiation energy of the laser beam scanned on the substrate at this time. FIG. 4 shows that the laser intensity is high near the center of the substrate and low near the edge of the substrate. Therefore, by increasing the beam scanning speed near the center of the substrate where the transmittance of the lens is high, and decreasing the beam scanning speed near the edge of the substrate where the transmittance is low, the change in irradiation energy given to the substrate can be reduced. It can be suppressed. FIG. 5 shows an example of a scanning speed distribution of laser light capable of canceling the change in beam energy shown in FIG. With the apparatus of the present invention, laser scanning can be performed with the distribution shown in FIG.

Specifically, a case will be described in which the difference between the transmittance of the fθ lens at the lens position where the laser beam enters when scanning the substrate center and the lens position where the laser beam enters when scanning the substrate edge is 5%. . 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 the energy applied between the substrate center and the substrate edge. . Therefore, the width of the large grain size region (the region having a crystal grain size of 10 μm or more) formed in the region of the semiconductor film irradiated with the laser (irradiation surface) is different between the substrate center and the substrate edge. Therefore, in order to keep the width of the large grain size region between the substrate edge and the substrate center at 180 μm, 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 scanning speed change, it is possible to suppress the change in the irradiation energy applied to the substrate and to keep the width of the large grain size region constant. In the device 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 particle size width, material and thickness of the semiconductor film, and the like.

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

Further, the change in the irradiation energy of the laser beam scanned on the substrate shown in FIG. 4 is only an example. The present invention can be applied to the case where the energy change is undulating as shown in FIG.

In this embodiment, a case will be described in which laser beam scanning is performed by controlling galvanomirrors in both the X axis and the Y axis in the first embodiment.

The speed of laser scanning by the galvanomirror will be described. First, the operation speed of the galvanomirror is controlled to make 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 scanned laser beam also changes due to the change in the transmittance. FIG. 6 shows an example of a change in the irradiation energy of the laser beam scanned on the substrate at this time. FIG. 6 shows that the laser intensity is high near the center of the substrate and decreases concentrically toward the edge of the substrate. Therefore, by increasing the beam scanning speed near the center of the substrate where the transmittance of the lens is high, and decreasing the beam scanning speed near the edge of the substrate where the transmittance is low, the change in irradiation energy given to the substrate can be reduced. It becomes possible to suppress.

FIG. 7 shows an example of a scanning speed distribution of laser light capable of canceling the energy change of the beam shown in FIG. In the apparatus of the present invention, laser scanning is performed according to the distribution shown in FIG. The laser scanning speed is controlled by controlling the operation speed of the galvanometer mirror. By performing irradiation with the above configuration, it is possible to suppress a change in the irradiation efficiency of the substrate and a change in the annealing effect of the substrate due to the change in the transmittance of the lens. The galvanomirror control device may store in advance a speed change pattern corresponding to various lenses so that the operation speed of the galvanomirror can be set according to the lens shape and the material. In order to uniformly irradiate the substrate, it is desirable that the energy variation of the beam applied to the substrate is within ± 5%.

(4) The change in the irradiation energy of the laser beam scanned on the substrate shown in FIG. 6 is only an example. The present invention can be applied to the case where the energy change is undulating as shown in FIG.

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 large particles formed on laser irradiation traces are suppressed. The width of the diameter region can be constant. Note that the scanning speed may be controlled in accordance with conditions such as a desired large grain size width, material and thickness of the semiconductor film, and the like.

In this embodiment, a process in which a crystalline semiconductor film is manufactured using the laser irradiation apparatus of the present invention and the semiconductor device is formed will be described with reference to FIGS.

First, the base insulating films 1101a and 1101b are formed over the substrate 1100. Examples of the substrate material include an insulating substrate such as a glass substrate, a quartz substrate, and a crystalline glass; a ceramic substrate, a stainless steel substrate; a metal substrate (such as tantalum, tungsten, and molybdenum); a semiconductor substrate; and a plastic substrate (polyimide, acrylic, and polyethylene). Terephthalate, polycarbonate, polyarylate, polyethersulfone, etc.) can be used, but at least a material capable of extinguishing the heat generated during the process is used. In this embodiment, a glass substrate is used.

(4) 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 a single layer or a plurality of layers. These are formed by a known method such as a sputtering method, a low pressure CVD method, and a plasma CVD method. In this embodiment, a two-layer structure is used. However, a single layer or three or more layers may be used. 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 oxynitride film and the silicon oxynitride film have different proportions of nitrogen and oxygen, and indicate that the former has a higher nitrogen content.

Next, an amorphous semiconductor film is formed. The amorphous semiconductor film may be formed to a thickness of 25~80nm a material mainly containing silicon or silicon (eg, Si _x Ge _1-x or the like). As a manufacturing method, a known method, for example, a sputtering method, a reduced pressure CVD method, a plasma CVD method, or the like can be used. In this embodiment, the film is formed to a thickness of 66 nm using amorphous silicon.

Subsequently, the amorphous silicon is crystallized. In this embodiment, a step of performing crystallization 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 type gas or solid laser oscillation device may be used. As the gas laser, Ar laser, there is a Kr laser and the like, as the solid-state laser, YAG laser, YVO ₄ laser, YLF laser, YAlO ₃ laser, alexandrite laser, Ti: sapphire laser, and the like. The crystal serving as the laser medium of the solid-state 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 of them are doped as impurities.

Laser annealing is performed using the laser irradiation apparatus of the present invention to crystallize amorphous silicon. More specifically, the method described in Embodiments 1 to 3 may be used. In the present embodiment, a YVO ₄ laser (wavelength: 532 nm) having a laser output of 10 W is used to process an ellipse having 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 applied to the substrate is controlled by changing the polarization splitting ratio of the laser light and using an optical system that depends on the polarization direction of the laser light. The polarization splitting ratio of the laser light is changed so as to cancel the change in irradiation energy caused by the change in the transmittance of the fθ lens. By providing the above change, it is possible to suppress a change in the irradiation energy applied to the substrate, and to make the width of the large particle size region constant.

In the case where the crystallized semiconductor film is used as an active layer of a TFT, it is desirable that the scanning direction of the laser beam be determined so as to be parallel to the direction in which carriers in the channel formation region move.
Therefore, as shown by an arrow in FIG. 9, the scanning direction of the laser beam is determined so as to be parallel to the direction in which carriers in the channel formation region move (channel length direction). Thereby, the crystal grows along the scanning direction of the laser light, and it is possible to prevent the crystal grain boundary from intersecting with the channel length direction.

Next, the crystalline semiconductor film is formed into desired shapes 1102a to 1102d by etching. Subsequently, a gate insulating film 1103 is formed. The thickness may be about 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. 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.

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

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

In this example, the first conductive layer was formed of TaN having a thickness of 30 nm, and the second conductive layer was formed of 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 may be formed. 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. Further, the combination may be appropriately selected. The thickness of the first conductive layer may be 20 to 100 nm, and the thickness of the second conductive layer may be 100 to 400 nm. In this embodiment, the laminated structure has two layers. However, the laminated structure may be one layer, or may be a laminated structure having three or more layers.

Next, in order to form an electrode and a 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 a gate electrode and a wiring. The etching conditions may be appropriately selected.

In this method, an ICP (Inductively Coupled Plasma) etching method is used. As first etching conditions, CF ₄ , Cl _2, and O ₂ are used as etching gases, the respective gas flow rates are 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) Power is supplied to generate plasma to perform etching. A 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 conditions to make the end of the first conductive layer 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. In addition, the taper angle of the W film is about 26 ° due to the first etching condition.

Subsequently, etching is performed under the second etching condition. Without removing the mask made of resist, while leaving the mask, CF ₄ and Cl ₂ were used as etching gases, the respective gas flow rates were 30/30 (sccm), the pressure was 1.0 Pa, and the coil type electrode was 500 W. RF (13.56 MHz) power is applied to generate plasma and perform etching for about 15 seconds. A 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.

エ ッ チ ン グ 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, the etching time may be increased by about 10 to 20%. In the first etching process, the gate insulating film not covered with the electrode is etched by about 20 nm to 50 nm.

(4) In the above-described first etching process, the ends 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 increased to 700 W at a pressure of 1.3 Pa. RF (13.56 MHz) power is supplied to generate plasma, and etching is performed for about 25 seconds. A 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 these etching conditions, the W film was selectively etched to form a second shape conductive layer. At this time, the first conductive layer is hardly etched. By the first and second etching processes, a gate electrode including the first conductive layers 1104a to 1104d and the second conductive layers 1105a to 1105d is formed.

Then, a first doping process is performed without removing the resist mask. Thus, an impurity imparting N-type is added to the crystalline semiconductor layer at a low concentration. The first doping treatment may be performed by an ion doping method or an ion implantation method. The conditions of the ion doping method may be such that the dose is 1 × 10 ^{13 to} 5 × 10 ¹⁴ ions / cm ² and the acceleration voltage is 40 to 80 kV. In this embodiment, the acceleration voltage was set to 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 embodiment, phosphorus (P) is used. At that time, using the first conductive layer as a mask, a first impurity region (N ⁻ region) to which a low-concentration impurity was added in a self-aligned manner was formed.

Subsequently, the mask made of the resist is removed. Then, a mask made of a resist is newly formed, and the second doping process is performed at an acceleration voltage higher than that of the first doping process. The second doping process also adds an impurity imparting N-type. The conditions of the ion doping method may be such 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 such 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 overlapping with the first conductive layer, which does not overlap with the second conductive layer or is not covered with the mask, A region (N ^- region, Lov region) is formed. The second impurity region is doped with an impurity imparting N-type in a concentration range of 1 × 10 ^{18 to} 5 × 10 ¹⁹ atoms / cm ³ . In the crystalline semiconductor film, a portion which is not covered by the first shape conductive layer nor the mask and is exposed (third impurity region: N ⁺ region) is 1 × 10 ^{19 to} 5 × 10 ^19. An impurity that imparts N-type is added at a high concentration in the range of × 10 ²¹ atoms / cm ³ . Although the semiconductor layer has an N ⁺ region, there is a portion that is partially covered with only the mask. Since the concentration of the impurity imparting N-type in this portion remains the same as the impurity concentration added in the first doping process, it is referred to as a first impurity region (N ⁻ region).

In this embodiment, each impurity region is formed by two doping processes. However, the present invention is not limited to this, and a desired impurity concentration can be obtained by performing appropriate doping once or a plurality of times. 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. By the third doping treatment, a fourth impurity region in which an 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 ( P ⁺ region) and a fifth impurity region (P ⁻ region) are formed.

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

In this embodiment, boron (B) is selected as a P-type impurity element for forming the fourth impurity region and the fifth impurity region, and is formed by an ion doping method using diborane (B ₂ H ₆ ). . The conditions of the ion doping method were a dose of 1 × 10 ¹⁶ ions / cm ² and an acceleration voltage of 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 at different concentrations to the fourth impurity region (P ⁺ region) and the fifth impurity region (P ⁻ region) 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 process. 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 as a source region and a drain region of the P-channel TFT without any problem.

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

Next, the first passivation film 1120 is formed by removing the resist mask. As the first passivation film, an insulating film containing silicon is formed to a thickness of 100 to 200 nm. As a film formation method, a plasma CVD method or a sputtering method may be used. In this embodiment, a 100-nm-thick silicon oxynitride film is formed by a plasma CVD method. In the case of using a silicon oxynitride film, a silicon oxynitride film formed from SiH ₄ , N ₂ O, and NH ₃ or a silicon oxynitride film formed from SiH ₄ and N ₂ O is formed by a plasma CVD method. Good. The manufacturing 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 hydride 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 a single-layer structure of a silicon oxynitride film as in this embodiment, but may be formed by using another insulating film containing silicon as a single-layer structure or a stacked structure. Is 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 the present embodiment, a YVO ₄ laser (wavelength: 532 nm) having a laser output of 1.8 W is used, processed into an elliptical shape with a short axis of 20 μm and a long axis of 250 μm, scanned 800 times at a pitch of 125 μm, and a laser scan speed of 25 cm / sec. And Note that, in addition to the laser annealing method, a heat treatment method or a rapid thermal annealing method (RTA method) can be applied.

(4) By performing heat treatment after the formation of the first passivation film 1120, hydrogenation of the semiconductor layer can be performed simultaneously with the activation treatment. Hydrogenation terminates dangling bonds in the semiconductor layer with hydrogen contained in the first passivation film.

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

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

Next, a first interlayer insulating film 1121 is formed over the first passivation film 1120. As the first interlayer insulating film, an inorganic insulating film or an organic insulating film can be used. 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 the organic insulating film, polyimide, polyamide, or BCB (benzo) is used. A film of cyclobutene), acrylic or positive photosensitive organic resin, negative photosensitive organic resin, or the like can be used. Alternatively, a stacked structure of an acrylic film and a silicon oxynitride film may be used.

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

Siloxane polymers can be classified into silica glass, alkylsiloxane polymers, alkylsilsesquioxane polymers, silsesquioxane hydride polymers, alkylsilsesquioxane hydride polymers, and the like, depending on their structures.

層 間 Alternatively, the interlayer insulating film may be formed of a material containing a polymer having an Si-N bond (polysilazane).

こ と By using the above materials, an interlayer insulating film having sufficient insulating properties and flatness can be obtained even when the film thickness is reduced. Further, since the above materials have high heat resistance, an interlayer insulating film that can withstand reflow processing in multilayer wiring can be obtained. Further, since the film has low hygroscopicity, an interlayer insulating film with a small amount of dehydration can be formed.

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

(4) After that, 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 second passivation film can suppress entry and exit of moisture into and from the first interlayer insulating film. As the second passivation film, a silicon nitride film, an aluminum nitride film, an aluminum oxynitride film, a diamond-like carbon (DLC) film, or a carbon nitride (CN) film can be similarly used.

Further, a film formed by an RF sputtering method has high density and excellent barrier properties. RF sputtering conditions include, for example, when a silicon oxynitride film is formed, N ₂ , Ar, and N ₂ O are flowed at a flow rate of 31: 5: 4 with a Si target at a pressure of 0.4 Pa. And a power of 3000 W. Further, for example, when a silicon nitride film is formed, N ₂ and Ar in the chamber are flowed with a Si target so that the gas flow ratio is 20/20 (sccm), and the pressure is 0.8 Pa, the power is 3000 W, and the Si target is formed. 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 an RF sputtering method.

(4) Next, the second passivation film, the first interlayer insulating film, and the first passivation film are etched by etching to form contact holes reaching the third impurity region and the fourth impurity region.

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

The semiconductor device manufactured using the laser irradiation apparatus of the present invention has good and uniform characteristics, and thus can be suitably used for various electronic devices and particularly for display devices. Also, the reliability of the product is improved.

FIG. 1 is a diagram illustrating a configuration of a laser irradiation apparatus according to the present invention. FIG. 2 is a diagram illustrating an example of a laser irradiation apparatus disclosed by the present invention. FIG. 4 is a diagram showing a scanning method of laser light. FIG. 5 is a diagram illustrating an example of a change in beam energy due to a change in the transmittance of a lens. FIG. 4 is a diagram illustrating an example of a laser scanning speed disclosed by the present invention. FIG. 5 is a diagram illustrating an example of a change in beam energy due to a change in the transmittance of a lens. FIG. 4 is a diagram illustrating an example of a laser scanning speed disclosed by the present invention. FIG. 5 is a diagram illustrating an example of a change in beam energy due to a change in the transmittance of a lens. FIG. 4 is a diagram illustrating a laser scanning method. 4A to 4C illustrate a method for manufacturing a semiconductor device disclosed in the present invention. 4A to 4C illustrate a method for manufacturing a semiconductor device disclosed in the present invention.

Claims (23)

A laser oscillator,
An optical system that processes the laser light output from the laser oscillator so that the beam spot on the irradiated surface becomes linear or elliptical,
Means for controlling the scanning speed of the processed laser light,
A laser irradiation device, comprising: A laser oscillator,
An optical system that processes the laser light output from the laser oscillator so that the beam spot on the irradiated surface becomes linear or elliptical,
Means for scanning while keeping the shape of the processed laser light constant on the irradiated surface,
Means for controlling the scanning speed of the means for scanning,
A laser irradiation device, comprising: A laser oscillator,
An optical system that processes the laser light output from the laser oscillator so that the beam spot on the irradiated surface becomes linear or elliptical,
Means for deflecting the processed laser light and scanning while maintaining the shape of the deflected laser light on the irradiated surface constant.
Means for controlling the scanning speed of the processed laser light by controlling the operation speed of the deflecting means,
A laser irradiation device, comprising: 4. The device according to claim 3, wherein the means for deflecting the processed laser light and scanning the irradiated surface while keeping the shape of the deflected laser light constant is a galvano mirror or a polygon mirror, an fθ lens or a telecentric fθ lens. And a laser irradiation device comprising: (5) The laser irradiation apparatus according to any one of (2) to (4), wherein a shape of the laser light is kept constant by adjusting a focus of the laser light on a surface to be irradiated. The laser irradiation apparatus according to any one of claims 1 to 5, wherein the scanning speed of the laser light is determined based on an energy distribution by means for condensing the laser light. The laser irradiation apparatus according to any one of claims 1 to 6, wherein a scanning speed of the laser light is controlled to make irradiation energy applied to the irradiation surface uniform. 8. The laser irradiation apparatus according to claim 1, wherein an irradiation position of the beam spot is controlled to scan a specific position on the irradiation surface. A laser irradiation apparatus according to any one of claims 1 to 8, wherein the laser oscillator is a continuous wave solid-state laser. In any one of claims 1 to 9, wherein the laser oscillator is a YAG laser of a continuous oscillation, YVO ₄ laser, YLF laser, YAlO ₃ laser, Y ₂ O ₃ laser, alexandrite laser, Ti: selected from sapphire laser A laser irradiation apparatus characterized in that it is a kind of laser irradiation. The laser irradiation apparatus according to any one of claims 1 to 8, wherein the laser oscillator is one kind selected from a continuous wave Ar laser or a Kr laser. The laser irradiation device according to any one of claims 1 to 11, wherein the laser oscillator outputs a harmonic. Forming an amorphous semiconductor film on the substrate;
Laser annealing the amorphous semiconductor film by scanning a laser beam processed so that a beam spot on the irradiated surface becomes linear or elliptical with the amorphous semiconductor film as a surface to be irradiated; and Has,
A method for manufacturing a semiconductor device, wherein a scanning speed of the laser light is changed. Forming an amorphous semiconductor film on the substrate;
Using the amorphous semiconductor film as a surface to be irradiated, laser light is processed so that a beam spot on the surface to be irradiated becomes linear or elliptical, and the shape of the processed laser light on the surface to be irradiated is kept constant. Laser annealing the amorphous semiconductor film by scanning while keeping the amorphous semiconductor film,
A method for manufacturing a semiconductor device, wherein a scanning speed of the laser light is changed. Forming an amorphous semiconductor film on the substrate;
The laser light output from the laser oscillator, the amorphous semiconductor film as a surface to be irradiated, processing such that the beam spot on the surface to be irradiated is linear or elliptical,
Deflecting the processed laser light, and scanning while maintaining a constant shape of the deflected laser light on the irradiated surface,
A method for manufacturing a semiconductor device, wherein a scanning speed of the processed laser light is changed by controlling an operation speed of the deflecting unit. In claim 15, the means for deflecting the processed laser light and performing scanning while keeping the shape of the deflected laser light constant on the irradiated surface includes a galvano mirror or a polygon mirror, an fθ lens or a telecentric fθ lens. A method for manufacturing a semiconductor device, comprising: 17. The method for manufacturing a semiconductor device according to claim 14, wherein a shape of the laser light is kept constant by adjusting a focus of the laser light on a surface to be irradiated. 18. The method for manufacturing a semiconductor device according to claim 13, wherein the scanning speed of the laser light is determined based on an energy distribution by means for condensing the laser light. 19. The method for manufacturing a semiconductor device according to claim 13, wherein a scanning speed of the laser light is changed so as to make irradiation energy applied to the irradiation surface uniform. 20. The method for manufacturing a semiconductor device according to claim 13, wherein the laser light is a continuous wave solid-state laser. In any one of claims 13 to claim 20, wherein the laser beam is a YAG laser of a continuous oscillation, YVO ₄ laser, YLF laser, YAlO ₃ laser, Y ₂ O ₃ laser, alexandrite laser, Ti: selected from sapphire laser A method for manufacturing a semiconductor device, which is a kind of semiconductor device. 20. The method for manufacturing a semiconductor device according to claim 13, wherein the laser light is one kind selected from a continuous wave Ar laser and a Kr laser. 23. The method for manufacturing a semiconductor device according to claim 13, wherein the laser light is a harmonic.

Images