JP4223470B2 - Method for determining pitch x and method for manufacturing semiconductor device - Google Patents

Description

  The invention disclosed in this specification relates to a technique capable of irradiating laser light with high homogeneity onto a large surface to be irradiated. The present invention is particularly suitable for annealing a semiconductor film.

  In recent years, laser annealing is performed on an amorphous semiconductor film or a crystalline semiconductor film (non-single crystal, polycrystalline, microcrystalline, etc. semiconductor film) formed on an insulating substrate such as glass, Techniques for crystallizing and improving crystallinity have been widely studied. A silicon film is often used as the semiconductor film.

  A glass substrate is cheaper and more workable than a quartz substrate that has been frequently used in the past, and has an advantage that a large-area substrate can be easily produced. This is the reason why the above research is conducted. In addition, the reason why laser is used for crystallization is that the melting point of the glass substrate is low. Laser can give high energy only to the non-single crystal film without changing the temperature of the substrate so much that it can be crystallized.

  Since the crystalline silicon film formed by laser annealing has high mobility, a thin film transistor (TFT) is formed using this crystalline silicon film, for example, on a single glass substrate for pixel driving. It is actively used in monolithic liquid crystal electro-optical devices and the like for producing TFTs for driving circuits. Since the crystalline silicon film has many crystal grains, it is called a polycrystalline silicon film or a polycrystalline semiconductor film.

  In addition, a laser beam is produced by processing a pulse laser beam such as an excimer laser having a high output with an optical system so that a square spot of several centimeters square or a line of several millimeters wide × several tens of centimeters is formed on the irradiated surface. The method of performing laser annealing by moving the laser beam (moving the irradiation position of the laser beam relative to the surface to be irradiated) is preferable because it is excellent in mass productivity and industrially excellent.

  In particular, when a linear laser beam is used, unlike the case of using a spot laser beam that requires front / rear / left / right scanning, the entire irradiated surface is scanned by scanning only in a direction perpendicular to the linear direction of the linear laser. Since irradiation can be performed, high mass productivity is obtained. The reason for scanning in the direction perpendicular to the line direction is that it is the most efficient scanning direction. Due to this high mass productivity, the use of linear laser beams for laser annealing is now becoming mainstream.

  Several problems have arisen when laser annealing is performed on a non-single-crystal semiconductor film by scanning the pulse laser beam processed into the linear shape.

  For example, in general, when a laser is irradiated on the surface of a semiconductor film formed on a substrate having a height difference due to the undulation of the substrate, there is a problem that the focal point of the laser beam is locally shifted.

  Due to the above problem, laser annealing is not uniformly performed on the entire film surface. For example, when a linear laser beam is used in laser annealing, a phenomenon that stripes are formed at the overlapping portions of the beams is conspicuous, and the semiconductor characteristics of the film are significantly different for each of these stripes.

  This problem is particularly serious when a large area substrate is irradiated with a laser. This is because a large area substrate has a relatively large difference in height between the substrates. For example, the waviness of a 600 × 720 mm substrate is about 100 μm. This value is very large depending on the characteristics of the laser beam used.

  Specifically, the state near the focal point of the laser beam is shown below. The energy distribution of the laser beam near the focal point of the laser beam behaves differently depending on the form of the optical system that forms the laser beam.

For example, if the laser beam is simply a linear beam, the focus shift affects the beam width and energy density. The optical system shown in FIG. 1A simply narrows the laser beam into a linear shape.
In FIG. 1, reference numeral 100 denotes a laser beam, reference numerals 101 and 102 denote cylindrical lenses constituting a system for expanding the laser beam 100 in the linear direction, and reference numeral 103 denotes a cylindrical lens that collects light in the width direction.

  Since such an optical system simply narrows the laser beam into a linear shape, the energy uniformity of the linear laser beam on the irradiated surface 104 is generally poor. When such an optical system is used, it is required that the laser beam has a very uniform energy before being processed into a linear shape. In addition, since the deviation of the focus changes the energy density on the irradiated surface, it is not preferable to form a laser beam with the optical system having such a configuration.

  The optical system in FIG. 1B is obtained by adding a concave cylindrical lens 105 to the optical system in FIG. If the laser beam is formed as shown in FIG. 1B, since the laser beam is a parallel light beam in the vicinity of the irradiated surface 106, the concept of the focal point of the laser beam is eliminated. Therefore, the problem of defocusing does not occur in the first place. However, the energy density of the laser beam passing through the lens placed immediately before forming the linear leather beam is high, and the durability of the lens cannot be caught up. Therefore, at present, such an optical system is not practical. Further, when such an optical system is used, the energy uniformity of the original laser beam (laser beam before being processed into a linear shape) needs to be very good.

  The above two examples require that the laser beam has a very high energy homogeneity before being processed into a linear shape. There are no existing laser generators with sufficient homogeneity to anneal the semiconductor film. Therefore, the above configuration waits for new technology development.

  The above two examples have poor uniformity of the energy distribution of the linear laser beam and are not suitable for annealing a semiconductor film at present. Next, an optical system that is actually used is taken as an example.

  The laser beam formed by the optical system having the configuration shown in FIG. 2A is a linear laser beam. In this optical system, the laser beam is divided vertically and horizontally, and each of the divided laser beams is combined into one on the irradiation surface while being processed into a linear shape. By doing so, the energy distribution in the linear laser beam can be homogenized.

  When the energy distribution is examined at the focal point (synthetic focal point) of the linear laser beam obtained through the lens group having the configuration shown in FIG. 2A and the cross section slightly separated from the focal point, the width direction of the linear laser beam is examined. The energy distribution is as shown in FIG. Since the divided laser beam cannot be one in the cross section away from the synthetic focus, the distribution is stepped.

  FIGS. 3A and 3B are those immediately before the focus, FIGS. 3B and 3B are those immediately after the focus, and FIGS. 3C and 3C correspond to the broken lines a 1, b 2, and c 2 in FIG. 2B, respectively. The focal point of the linear laser beam referred to here refers to a plane in which the divided laser beams are substantially one. In general, since a linear laser beam requires a high energy density, the width is often set to 1 mm or less. Therefore, the beam shapes in FIGS. 3a and 3c are substantially congruent.

  When the semiconductor film is irradiated with a laser having an energy distribution as shown in FIGS. 3, a, and c, the central portion with respect to the width direction of the linear laser beam and the end portion are irradiated. The effect of annealing is completely different. In order to perform laser annealing as uniformly as possible using such a laser beam, it is generally performed to irradiate a semiconductor film while overlapping the laser beam in the width direction.

  That is, it is preferable to irradiate the lasers so that the energy of the central part with respect to the width direction of the linear laser beam is irradiated from above the semiconductor film part irradiated with the end part. Since the laser generator to be used is an excimer laser which is a pulse laser, the laser beam is irradiated on the entire semiconductor film by superimposing a linear laser beam on the semiconductor film.

  In order to anneal the entire semiconductor film most uniformly using the laser beam, the semiconductor film is moved at a pitch x of 1/20 to 1/5 of the width W of the linear laser beam, It is important to overlap the irradiation positions of the linear laser beam. That is, it is necessary to irradiate the laser while satisfying the condition of W / 20 ≦ x ≦ W / 5.

  In that range, it was particularly good to superimpose at a pitch x of about 1/10 of the width W. However, even when laser irradiation is performed under such conditions, a phenomenon in which stripes are still formed in the overlapping portion of the beams is conspicuous.

  FIG. 4 shows this stripe state. The substrate shown in the figure is a 5 inch square. The unevenness (swell) of a 5-inch square substrate having a thickness of 0.7 mm was about 20 μm. These stripes appear due to light reflection when the surface of the silicon film after laser annealing is observed.

  FIG. 4 shows a case in which a Xe Cl excimer laser is used as a linear laser beam extending in the left-right direction on the paper surface, and is irradiated by scanning downward from above the paper surface.

  It is understood that the horizontal stripes in FIG. 4 are caused by the overlapping state of pulse laser shots.

  When a thin film transistor is formed using a silicon film in which a striped pattern as shown in FIG. 4 appears and an active matrix type liquid crystal display is manufactured, there is a disadvantage that the stripe appears as it is on the screen display. .

  This problem becomes more serious when the substrate has a large area such as 600 × 720 mm and a thickness of 0.7 mm, and the surface height difference becomes as large as about 100 μm.

  In general, when a linear laser beam is formed, a beam having a rectangular cross section is processed into a linear shape through an appropriate optical system. The rectangular beam has an aspect ratio of about 2 to 5. For example, the rectangular beam is transformed into a linear beam having an aspect ratio of 100 or more by the optical system shown in FIG. At this time, the optical system is designed so that the distribution of energy in the beam is also homogenized at the same time.

  The apparatus shown in FIG. 2 irradiates a laser beam from the oscillator 201 (in this state, having a substantially rectangular shape) as a linear beam via an optical system indicated by 202, 203, 204, 206, and 208. It has a function. Reference numeral 205 denotes a slit, and 207 denotes a mirror.

  Reference numeral 202 denotes a cylindrical lens group (also referred to as a multi-cylindrical lens), which has a function of dividing a beam into a large number. A large number of the divided beams are combined by a cylindrical lens 206 as a final lens.

  This configuration is required to improve the homogeneity of the intensity distribution within the beam. Further, the combination of the cylindrical lens group 203 and the cylindrical lens 204 has the same function as the combination of the cylindrical lens group 202 and the cylindrical lens 206 described above.

  That is, the combination of the cylindrical lens group 202 and the cylindrical lens 206 has a function of improving the homogeneity of the intensity distribution in the longitudinal direction of the linear laser beam, and the combination of the cylindrical lens group 203 and the cylindrical lens 204 is a linear laser beam. It has the function of improving the homogeneity of the intensity distribution in the beam width direction.

  An optical system that plays a role in homogenizing the energy distribution in the beam is called a beam homogenizer. The optical system shown in FIG. 2 is also one of the beam homogenizers. The method for uniformizing the energy distribution is to divide the original rectangular beam, and then to enlarge and superimpose them to homogenize them.

  The energy distribution in the cross section near the focal point of the linear laser beam formed through such an optical system is as shown in FIG. As can be seen from this figure, the energy distribution changes before and after the focal point of the laser beam. This change facilitates the formation of the striped pattern.

  The configuration of the lens group shown in FIG. 2 is basic, and another optical system may be arranged. A part of the lens may be replaced with another lens having the same function. Moreover, you may utilize the said structure as a part of whole. For example, although the cylindrical lens group 202 and the cylindrical lens group 203 shown in FIG. 2 are convex lens groups, a concave lens group or a concave / convex mixed lens group may be used.

  However, when using lens groups that are not congruent as represented by the concave-convex mixed lens group, the parallel light beams processed by these lenses are composed of lens groups having the same spread angle after processing. There must be.

  Otherwise, when the split beams are recombined, the individual beams overlap in different sizes and shapes and the beam contours are unclear.

  Further, the laser beam may be divided by another method instead of the cylindrical lens. For example, as shown in FIG. 10, the cylindrical lens group 203 and the cylindrical lens 204 shown in FIG. 2 may be replaced with a multi-phase prism having substantially the same action. Since this optical system can reduce the number of lens groups, there are advantages such as a reduction in light amount loss and easy adjustment of the arrangement of the optical system.

  An object of the invention disclosed in this specification is to improve the irradiation unevenness of laser light as shown in FIG.

  The present invention provides an optical system configuration that can suppress changes in energy distribution in the cross section near the focal point of the laser beam shown in FIG.

  The optical path of the laser beam from the cylindrical lens for condensing (hereinafter referred to as the final lens) to the irradiation surface placed at the end of the optical system based on the configuration of the optical system shown in FIG. The figure is shown in FIG. As apparent from FIG. 2B, it can be seen that a plurality of beams are combined into one on the irradiated surface to form a linear beam. When the irradiated surface deviates before and after the synthetic focus (the focus of the entire optical system), that is, when the distance from the final lens changes, the energy distribution changes because the plurality of laser beams do not become one completely. The cross sections a 1, b 2, and c in FIG. 2A correspond to the energy distributions a 1, b 2, and c 3 in FIG.

  The height difference r of the semiconductor film to be irradiated is often about 100 μm when a substrate of 600 × 720 mm is used. This is a numerical value when the substrate is placed on a flat stage. In this case, it is necessary to design an optical system in which the focus shift is not reflected in the crystallization state of the semiconductor film in the range of 100/2 μm = 50 μm before and after the synthetic focus of the laser beam.

  For the convenience of transporting the substrate, it is preferable that the stage on which the substrate is placed has a three-point support (in some cases, four or more are preferable depending on the rigidity of the substrate). The substrate is warped, and the substrate surface is warped more than the undulation inherent to the substrate. In this case, naturally, it is necessary to perform laser annealing with a laser beam that allows good crystallization even if there is warping. When a substrate of 600 × 720 mm and a thickness of 0.7 mm was placed on a three-point support stage, the apparent height difference of the surface of the substrate was about 1000 μm.

  FIG. 5 shows two final lenses having different focal lengths. From the optical path of the laser beam passing through the two final lenses, the size D of the light incident range of the laser beam incident on the final lens in the direction perpendicular to the generatrix of the final lens, the generatrix of the final lens, and the semiconductor film It can be seen that the larger the ratio of F to D, the smaller the change in the energy distribution of the laser beam near the irradiated surface.

  This point will be described below with reference to FIG. In FIGS. 5 (a) and 5 (b), z is a cross section of the beam in the vicinity of the synthetic focus, from a cross section where the beam width is w *, to a cross section where the beam width is W *, through the cross section where the beam width is W. Represents the distance.

  When F1 / D1 ≦ F2 / D2, z1 ≦ z2, and the amount of change in the beam width with respect to the shift of the composite focus is smaller in (b).

  The width W of the linear laser beam at the synthetic focal point decreases by Δ = W−w * when it deviates from the synthetic focal point to about z / 2. Here, since D >> W, it can be approximated as Δ (z) ≈ (z / 2) × D / F.

As shown in FIG. 3, the definition of the beam width w * in the region shifted from the synthetic focal point to around z / 2 is the width of the region having an energy density substantially equal to the energy density at the synthetic focal point. In the present specification, Δ is referred to as a beam width change amount.
Further, when Δ is written as Δ (r) in particular, it represents the amount of change in beam width when a semiconductor film having a height difference r is irradiated with a beam.

  As described above, the beam width W changes by Δ depending on the distance from the synthetic focus. Conventionally, when a linear laser beam is superimposed and irradiated at a pitch x of about 1/10 of the width of the laser beam, the linear irradiation unevenness of the laser beam is least noticeable.

  However, the present applicant has empirically found that the homogeneity is significantly impaired when laser irradiation is performed under such conditions that Δ is larger than the pitch x.

  Therefore, the present applicant has found that homogeneous laser annealing can be performed when laser irradiation is performed under the condition of x ≧ Δ satisfying the condition of W / 20 ≦ x ≦ W / 5.

  In the invention disclosed in this specification, the beam width W, the pitch (distance) x at which the irradiated surface moves during the oscillation period of the pulse laser beam light source, and the final lens of the laser beam incident on the final lens of the optical system. Providing optimum combinations of parameters with respect to the size of the light incident range in the direction perpendicular to the bus bar, D, the distance F between the bus bar of the final lens and the semiconductor film, and the height difference r of the semiconductor film to be irradiated. It is possible to perform homogeneous laser annealing on the substrate.

In order to solve the above problems, the invention disclosed in this specification is
An optical system for obtaining a linear beam having a beam width W by dividing a pulse laser beam light source and a plurality of pulse laser beams irradiated from the light source vertically and horizontally, and then combining the divided beams into a linear shape And means for moving the substrate provided with the semiconductor film irradiated with the linear beam,
A laser irradiation apparatus for irradiating the semiconductor film while scanning a linear laser beam,
The height difference on the surface of the semiconductor film is r, the amount of change of the beam width W with respect to the height difference r is Δ (r), and the pitch at which the substrate moves during the pulse laser oscillation period of the pulse laser beam light source is x. And when
A laser irradiation apparatus for a semiconductor film, which satisfies the condition of W / 20 ≦ Δ (r) ≦ x ≦ W / 5.

Other inventions disclosed in this specification are:
An optical system for obtaining a linear beam having a beam width W by dividing a pulse laser beam light source and a plurality of pulse laser beams irradiated from the light source vertically and horizontally, and then combining the divided beams into a linear shape And means for moving the substrate provided with the semiconductor film irradiated with the linear beam,
A laser irradiation apparatus for irradiating the semiconductor film while scanning a linear laser beam,
The height difference on the surface of the semiconductor film is r, the amount of change of the beam width W with respect to the height difference r is Δ (r), and the pitch at which the substrate moves during the pulse laser oscillation period of the pulse laser beam light source is x. And when
A laser irradiation apparatus characterized by satisfying the condition of Δ (r) ≦ W / 20 ≦ x ≦ W / 5.

Other inventions disclosed in this specification are:
An optical system for obtaining a linear beam having a beam width W by dividing a pulse laser beam light source and a plurality of pulse laser beams irradiated from the light source vertically and horizontally, and then combining the divided beams into a linear shape And means for moving the substrate provided with the semiconductor film irradiated with the linear beam,
A laser irradiation apparatus for irradiating the semiconductor film while scanning a linear laser beam,
The height difference of the surface of the semiconductor film is r, the beam width is W, the size of the incident range of the laser beam incident on the final lens of the optical system in the direction perpendicular to the generatrix of the final lens is D, and the final lens When the distance between the bus and the semiconductor film is F, and the pitch at which the substrate moves during the pulse laser oscillation period of the pulse laser beam light source is x,
A laser irradiation apparatus for a semiconductor film, which satisfies the condition of W / 20 ≦ rD / 2F ≦ x ≦ W / 5.

Other inventions disclosed in this specification are:
An optical system for obtaining a linear beam having a beam width W by dividing a pulse laser beam light source and a plurality of pulse laser beams irradiated from the light source vertically and horizontally, and then combining the divided beams into a linear shape And means for moving the substrate provided with the semiconductor film irradiated with the linear beam,
A laser irradiation apparatus for irradiating the semiconductor film while scanning a linear laser beam,
The height difference of the surface of the semiconductor film is r, the beam width is W, the size of the incident range of the laser beam incident on the final lens of the optical system in the direction perpendicular to the generatrix of the final lens is D, and the final lens When the distance between the bus and the semiconductor film is F, and the pitch at which the substrate moves during the pulse laser oscillation period of the pulse laser beam light source is x,
A laser irradiation apparatus for a semiconductor film characterized by satisfying a condition of rD / 2F ≦ W / 20 ≦ x ≦ W / 5.

  The above configuration is particularly effective when the height difference r ≦ 1000 μm, and the effect is particularly remarkable when r ≦ 100 μm.

  Moreover, in said structure, the in-plane homogeneity of a laser annealing improves effectively that the magnitude | size of a board | substrate is 100 mm x 100 mm-1000 mm x 1000 mm. In particular, when the thickness is in the range of 300 mm × 300 mm to 800 mm × 800 mm, the effect of improving the homogeneity is remarkably obtained. In such a size, the effect is remarkable when the thickness of the substrate is particularly 1.5 mm or less.

  The optimum condition in the range of W / 20 ≦ x ≦ W / 5 varies depending on the state of the semiconductor film to be irradiated (for example, the hydrogen concentration in the film). Therefore, when W / 20 ≦ Δ ≦ x ≦ W / 5, the selection range of x becomes narrow and sufficient homogeneity may not be obtained.

  On the other hand, when Δ ≦ W / 20 ≦ x ≦ W / 5, since the pitch x can be freely selected within the range of W / 20 ≦ x ≦ W / 5, laser annealing is performed on all semiconductor films under optimum conditions. be able to.

  For example, when an active matrix liquid crystal display having a thin film transistor formed using a semiconductor film crystallized with a laser satisfying Δ ≦ W / 20 ≦ x ≦ W / 5 as a pixel switching element is manufactured, There was no noticeable stripe pattern.

  Taking into account the height difference r of the irradiated surface, as shown in FIG. 6, it can be understood from the equation, W / 20 ≦ Δ ≦ x ≦ W / 5, that Δ ≦ W / 5 is satisfied. .

  Further, when taking into account the height difference r of the irradiated surface, it can be seen from the equation, Δ ≦ W / 20 ≦ x ≦ W / 5 that it is better if at least Δ ≦ W / 20 is satisfied.

  The beam width change amount Δ (r) is defined by Δ (r) = (r / 2) × (D / F) as described above.

  Note that the above-described conditions are limitations when the center of the height difference of the semiconductor film surface is at the focal point of the linear laser beam. Restrictions in other situations can be even more severe. For this alignment, it is preferable that the position of the stage can be finely adjusted up and down.

  According to the present invention, when a semiconductor film is crystallized or crystallinity is improved by irradiating a laser beam, even if the surface of the semiconductor film has a height difference due to unevenness or waviness of the substrate, the laser is uniformly distributed in the substrate surface. Annealing can be performed.

  For example, the energy distribution in the linear laser beam formed by the optical system shown in FIG. 2 changes before and after the focal point (synthetic focal point) of the linear laser beam, as shown in FIG.

  Therefore, when such a linear laser beam is irradiated onto a semiconductor film having a difference in height, a change in energy distribution in the linear laser beam is reflected as it is, and laser annealing cannot be performed uniformly.

  In the present invention, the condition of the linear laser beam can be obtained in accordance with the undulation state of the surface of the semiconductor film to be irradiated with laser, and laser annealing can be performed more uniformly.

  The above-described configuration is obtained by an optical system that obtains a linear beam having a beam width W by dividing a laser beam whose aspect ratio is not so large into a plurality of lengths and widths and then combining the divided beams into a linear shape. This is particularly effective when the beam is processed into a linear laser beam having an aspect ratio of 100 or more.

  Laser annealing of a semiconductor film is performed using the laser irradiation apparatus described in this specification to form a polycrystalline semiconductor film, and a device such as a TFT liquid crystal display is manufactured using the semiconductor film. Variations are suppressed, and high quality images can be obtained.

  Further, when a semiconductor integrated circuit is manufactured using the apparatus of the present invention, the characteristics of elements formed on the same substrate can be aligned, and a circuit having high performance can be obtained.

  According to the present invention, it is possible to greatly improve the in-plane homogeneity of laser annealing on a semiconductor film by scanning a laser beam obtained by homogenizing a laser beam by split recombination.

  In the manufacturing process of the example, first, a manufacturing method of a film irradiated with a laser will be described. There are three types of films irradiated with laser in this specification. The present invention is effective for any film.

  First, each of the three types of films has a substrate of 600 × 720 mm and a thickness of 0.7 mm on a Corning 1737 glass substrate, a silicon oxide film as a base film having a thickness of 200 nm, and an amorphous silicon film thereon. Both films are formed to a thickness of 50 nm by plasma CVD. This membrane is hereinafter referred to as the starting membrane.

(Procedure for Membrane A)
The starting membrane is exposed to a 500 ° C. heat bath for 1 hour. This step is a step for reducing the hydrogen concentration in the amorphous silicon film. This process is necessary because the film cannot withstand the laser energy if there is too much hydrogen in the film.

The density of hydrogen in the film is suitably on the order of 10 ²⁰ atoms / cm ³ . This film is called a non-single crystal silicon film A.

(Producing procedure of membrane B)
A 10 ppm nickel acetate aqueous solution is applied onto the starting film by a spin coating method to form a nickel acetate layer. It is more preferable to add a surfactant to the nickel acetate aqueous solution. Since the nickel acetate layer is extremely thin, it is not always a film, but there is no problem in the subsequent steps.

  Next, the substrate on which the films are laminated as described above is subjected to thermal annealing at 550 ° C. for 4 hours. Then, the amorphous silicon film is crystallized, and a crystalline silicon film B which is a non-single crystal silicon film is formed.

  At this time, the catalyst element nickel plays a role of crystal growth nucleus, and crystallization is promoted. The reason why crystallization can be performed at a low temperature of 550 ° C. for 4 hours and in a short time is due to the function of nickel. Details are described in JP-A-6-244104.

The concentration of the catalyst element is preferably 1 × 10 ¹⁵ to 10 ¹⁹ atoms / cm ³ . At a high concentration of 1 × 10 ¹⁹ atoms / cm ³ or more, metallic properties appear in the crystalline silicon film and the characteristics as a semiconductor disappear. In this embodiment, the concentration of the catalytic element in the crystalline silicon film is 1 × 10 ^{17 to} 5 × 10 ¹⁸ atoms / cm ^3, which is the minimum value in the film. These values are analyzed and measured by secondary ion mass spectrometry (SIMS).

(Producing procedure of membrane C)
A silicon oxide film is further formed on the starting film to a thickness of 700 mm. A plasma CVD method is used as a film forming method.

  Next, a part of the silicon oxide film is completely opened by a photolithography patterning process.

  Further, UV light is irradiated for 5 minutes in an oxygen atmosphere in order to form a thin oxide film in the opening. This thin oxide film is formed in order to improve the wettability of the opening portion with respect to the nickel aqueous solution to be introduced later.

  Next, 100 ppm of nickel acetate aqueous solution is applied onto the film by spin coating, and nickel acetate enters the aperture. It is more preferable to add a surfactant to the nickel acetate aqueous solution.

  Next, thermal annealing is performed at 600 ° C. for 8 hours, and crystals grow laterally from the nickel-introduced portion. At this time, the role played by nickel is the same as that of the film B. Under this condition, a lateral growth amount of about 40 μm is obtained.

  In this way, the amorphous silicon film is crystallized to form a crystalline silicon film C which is a non-single crystal silicon film. Thereafter, the silicon oxide film on the crystalline silicon film is peeled and removed using buffer hydrofluoric acid.

  The non-single crystal silicon films A, B, and C thus obtained are crystallized.

  Each of the substrates having the non-single-crystal silicon films A, B, and C had minute waviness, and the height difference on the non-single-crystal semiconductor film surface was about 100 μm.

  Next, in order to further enhance the crystallinity, laser annealing is performed using an excimer laser.

  FIG. 7 shows a laser irradiation system in the embodiment. FIG. 7 is an overview of the laser irradiation system.

  In FIG. 7, the laser irradiation system is irradiated with a pulse laser beam irradiated from a laser oscillation device 201, adjusted in laser traveling direction by two pairs of reflecting mirrors 701, and then processed into a linear cross section by an optical system 702. The substrate 704 has a function of irradiating a substrate 704 having an irradiated surface while being reflected by a mirror 207 and condensed by a cylindrical lens 208 as a final lens. A beam expander that can suppress the spread angle of the laser beam and adjust the beam size may be inserted between the two pairs of reflecting mirrors 701.

  The optical system 702, the mirror 207, and the cylindrical lens 208 as the final lens conform to the structure shown in FIG.

  The optical system used in this embodiment has the configuration shown in FIG. The reason for using this optical system is that the beam shape can be processed into a linear shape while homogenizing the energy inhomogeneity of the beam before entering the optical system by superimposing the beams after the division.

  Here, as the laser oscillation device 201 that is a pulse laser light source, a device that oscillates a XeCl excimer laser (wavelength 308 nm) is used. In addition, a KrF excimer laser (wavelength 248 nm) or the like may be used.

  The substrate to be processed 704 is arranged on a stage (stage) 705 having a flat upper surface. The stage 705 is moved straight in a direction perpendicular to the linear direction of the linear laser beam by the moving mechanism 703, and can irradiate the upper surface of the substrate 704 while scanning the laser beam.

  Since the length of the linear laser beam is 150 mm, a 600 × 720 mm substrate cannot be processed at one time. Therefore, laser annealing is performed on the entire surface of the substrate by repeating four scans. For each scan, the stage 705 slides in the linear direction of the linear laser beam by a beam length (in this case, 150 mm). The slide is performed by the scanning area changing device 706.

  By repeating this operation four times while sandwiching the step of sliding the substrate, the entire surface of the 600 × 720 mm substrate is irradiated with laser.

  Further, if the height of the stage 705 can be finely adjusted so that the focal point of the linear laser beam is at an appropriate position with respect to the semiconductor film, the adjustment of the optical system becomes easier.

  When the fine adjustment is performed, it is preferable to make an adjustment while confirming the energy distribution by actually hitting the semiconductor film with one shot. An energy distribution measuring device may be attached to the base 705.

  In FIG. 7, the linear laser beam irradiated onto the substrate 704 to be processed has a width of 0.5 mm × a length of 150 mm. This beam is formed by the lens arrangement shown in FIG.

The energy density of the laser beam on the irradiated surface is in the range of ^{100mJ / cm 2 ~500mJ / cm 2} , for example, 300 mJ / cm ^2. A linear laser beam is scanned by moving the stage 705 while moving it in one direction at 1.5 mm / s. In this embodiment, the oscillation frequency of the pulse laser in the laser light source is 30 Hz.

  In the laser irradiation apparatus used in this example, D is 90 mm, F is 275 mm, and the beam width W of the linear laser beam is 500 μm.

  Further, as described above, the non-single-crystal semiconductor film which is the irradiated surface has a height difference r of 100 μm.

Then, Δ (r) = rD / 2F = (100 × 90 × 10 ³ ) / (2 × 275 × 10 ³ ) ≈16 μm, and W / 5 = 100 μm and W / 20 = 25 μm. r) When ≦ W / 20 ≦ x ≦ W / 5.

  Therefore, the pitch x, which is the distance that the irradiated surface (stage) moves during the oscillation period of the oscillation frequency, can be freely selected and determined from the range of 25 μm ≦ x ≦ 100 μm, and if this condition is satisfied, Uniform laser annealing can be performed in the substrate surface.

  Here, Δ (r) is obtained by calculation from the optical system, but it goes without saying that actually measured Δ (r) may be used.

  In some circumstances, Δ (r) may satisfy W / 20 ≦ Δ (r) ≦ x ≦ W / 5. Even under such conditions, uniform laser annealing is possible within the substrate surface. However, the range of the pitch x is narrowed.

  The apparatus shown in FIG. 8 will be described. The apparatus shown in FIG. 8 is a continuous processing apparatus having a laser irradiation apparatus having the configuration shown in FIG.

  In the load / unload chamber 805, a cassette 803 that accommodates a large number of substrates to be processed 704, for example, 20 sheets, is disposed. One substrate is moved from the cassette 803 to the alignment chamber by the robot arm 805.

  An alignment mechanism for correcting the positional relationship between the substrate to be processed 704 and the robot arm 804 is disposed in the alignment chamber 802. The alignment chamber 802 is connected to the load / unload chamber 805.

  The substrate is transferred to the substrate transfer chamber 801 by the robot arm 804 and further transferred to the laser irradiation chamber 806 by the robot arm 804.

In the laser irradiation chamber 806, a laser irradiation apparatus having the configuration shown in FIG. In FIG. 8, the description of the optical system is omitted because it is complicated.
After the laser irradiation, the substrate 704 to be processed is pulled back to the substrate transfer chamber 802 by the robot arm 804.

  The substrate 704 to be processed is transferred to the load / unload chamber 805 by the robot arm 804 and stored in the cassette 803.

  Thus, the laser annealing process is completed. In this way, by repeating the above steps, a large number of substrates can be successively processed one by one.

  The semiconductor film laser-annealed according to this example was uniformly crystallized in the substrate surface without causing unevenness.

  When a TFT using the semiconductor film subjected to laser annealing as an active layer is manufactured, both an N channel type and a P channel type can be manufactured.

  It is also possible to obtain a structure in which an N channel type and a P channel type are combined. In addition, an electronic circuit can be configured by integrating a large number of TFTs.

  The above is also true for a semiconductor film that has been laser-annealed through the optical system shown in the other embodiments. When a 5-inch liquid crystal display composed of TFTs is manufactured by using a semiconductor film that has been laser-annealed via the optical system of the present invention, a high-quality image with little variation in individual TFT characteristics can be obtained.

  In this example, the substrate having the semiconductor films A 1, B 2, and C 2 prepared in Example 1 is placed on a four-point supported stage instead of a flat stage, and homogeneous laser annealing is performed as in Example 1. The apparatus and the method for this are described.

When a substrate of 600 × 720 mm and a thickness of 0.7 mm is placed on a four-point support stage, the surface height difference r becomes about 1000 μm due to the undulation of the substrate.
. Even with such a large height difference, if the above-described conditions are satisfied, homogeneous annealing that is hardly affected by the height difference can be performed.

  When placing the substrate on the four-point support stage, the robot arm 804 moves up and down. Thereby, the substrate can be left on the stage.

  In this embodiment, the laser optical system shown in FIG. 9 is used. The laser beam produced by the laser optical system shown in FIG. 9 has a beam width of 0.5 mm and a beam length of 150 mm, as in Example 1. Therefore, W = 500 μm. D is 60 mm and F is 320 mm.

Then, Δ (r) = rD / 2F = (1000 × 60 × 10 ³ ) / (2 × 320 × 10 ³ ) ≈94 μm, and W / 5 = 100 μm and W / 20 = 25 μm. 20 ≦ Δ (r) ≦ x ≦ W / 5.

  Therefore, the movement pitch x of the irradiated surface (stage) is limited to a range of 94 μm ≦ x ≦ 100 μm, and if this condition is satisfied, homogeneous laser annealing can be performed in the substrate surface.

  Here, Δ (r) is obtained by calculation from the optical system, but it goes without saying that actually measured Δ (r) may be used.

  Although this semiconductor film did not have the homogeneity as shown in Example 1, for example, when a liquid crystal display was produced based on the semiconductor film, there was no problem at all.

In this embodiment, an optical system having a different shape and having the same properties as those of the laser optical systems shown in Embodiments 1 and 2 is shown. In this embodiment, a multi-phase prism is used for processing in the laser beam width direction.

  A multi-phase prism 1001 is shown in FIG. The advantage of using this optical prism is that the number of lens groups can be reduced. By reducing the number of lenses, the arrangement of the optical system can be easily adjusted. In addition, light loss can be suppressed.

  The optical path of the laser ahead of the final lens of the optical system shown in this embodiment is exactly the same as that of the optical system shown in Embodiments 1 and 2. Therefore, the properties of the semiconductor film obtained by this example were also the same as those shown in Examples 1 and 2.

  In this embodiment, an example of manufacturing a TFT (thin film transistor) using the crystallized non-single-crystal silicon film obtained in Embodiments 1 to 3 will be described. The steps of this example are shown in FIG.

  In FIG. 11, a silicon oxide film 1102 is provided as a base film on a substrate 1101 such as glass, and the non-single-crystal silicon film 1103 obtained in Embodiments 1 to 3 is formed on the substrate. (Fig. 11 (A))

  By patterning the non-single crystal silicon film 1103, an island-shaped active layer pattern 1104 of the TFT is formed. In this active layer pattern, a channel forming region and a high resistance region are formed. (FIG. 11 (A)).

  After forming the active layer, a silicon oxide film is formed as a gate insulating film 1105 to a thickness of 100 nm by plasma CVD.

  Next, a titanium film is formed to a thickness of 400 nm by sputtering. Then, this titanium film is patterned. Further, an anodized film 1117 is formed with a thickness of 200 nm on the exposed surface of the titanium film pattern by anodizing to obtain a gate electrode 1116.

  This anodic oxide film has a function of electrically and physically protecting the surface of the gate electrode. Further, in a later process, it functions to form a high resistance region called an offset region adjacent to the channel region.

  Next, phosphorus is doped using the gate electrode and the surrounding anodic oxide film as a mask. This phosphorus serves as a dopant for determining the source and drain regions.

By performing phosphorus doping, a source region 1118, a channel formation region 1119, a drain region 1110, and offset regions 1111 and 1112 are formed in a self-aligned manner. In this embodiment, a phosphorus dose of 5 × 10 ¹⁴ ions / cm ² was introduced using an ion doping apparatus. Next, phosphorus is activated by a laser. The laser was irradiated by the method shown in Example 1. Thereby, uniform activation could be performed in the substrate surface.

The energy density of the laser beam was about 200 mJ / cm ² . Note that the appropriate energy density in this step varies depending on the type of laser, the irradiation method, and the state of the semiconductor film, and is adjusted accordingly. The sheet resistance in the source / drain region was lowered to 1 KΩ / □ by laser irradiation. (Fig. 11 (C))

  Next, as an interlayer insulating film, a silicon nitride film 1113 is formed to a thickness of 150 nm by plasma CVD, and an acrylic resin film 1114 is further formed. The thickness of the acrylic resin film is set to 700 nm at the minimum portion. Here, the resin film is used to flatten the surface.

  In addition to acrylic, materials such as polyimide, polyamide, polyimide amide, and epoxy can be used. This resin film may be configured as a multilayer film.

  Next, contact holes are formed, and a source electrode 1115 and a drain electrode 1116 are formed. (Fig. 11 (D))

  Thus, an N-channel TFT is completed. In this embodiment, phosphorus is introduced into the source / drain region, so that an N-channel TFT is manufactured. However, if a P-channel type is manufactured, boron may be doped instead of phosphorus.

  For example, when a liquid crystal display is manufactured using the TFT manufactured using the semiconductor film formed according to Examples 1 to 3, a laser processing after the laser processing is not conspicuous as compared with the conventional case.

The figure which shows the example of the optical system for forming a linear laser beam. The optical system and optical path diagram which form the linear laser in a prior art example. The figure which shows the energy distribution in the width direction of the linear laser beam formed in the focus vicinity of the optical system of FIG. Photo of a silicon thin film crystallized by a linear laser. The figure which shows the difference in the laser optical path by the shape of the last lens. The figure which shows the relationship between the width W of a linear laser beam, beam width variation | change_quantity (DELTA), and the pitch x. The figure which shows the laser irradiation apparatus in an Example. The figure of the continuous processing apparatus in an Example. The optical system and optical path diagram which form the linear laser in an Example. The optical system and optical path diagram which form the linear laser in an Example. The figure which shows the process of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 201 Laser oscillation apparatus 202 Cylindrical lens group 203 for laser beam splitting Cylindrical lens group 204 for laser beam splitting Laser beam, Cylindrical lens 205 for recombination Slit 206 Laser beam, Cylindrical lens 207 for recombination Mirror 208 Cylindrical lens 701 for condensing a linear beam Mirror 702 for adjusting the direction of laser light incident on the optical system 702 Optical system 703 Moving mechanism 704 Substrate 705 Stand 706 Scanning region changing device 801 Substrate transport chamber 802 Alignment chamber 803 Cassette 804 Robot arm 805 Load / unload chamber 806 Laser irradiation chamber 1001 Multi-phase prism

Claims (2)

A method of determining a pitch x when a semiconductor film formed on a substrate and having a surface height difference r is irradiated with a linear laser beam having a beam width W,
(A) The linear laser beam is synthesized by dividing the pulse laser beam into a plurality of lengths and widths and then condensing each of the divided beams with a final lens,
(B) When the size of the laser beam incident on the final lens in the direction perpendicular to the bus of the final lens is D and the distance between the bus of the final lens and the semiconductor film is F, Δ (r ) = RD / 2F, and the value of Δ (r) is calculated.
(C) When the Δ (r) is smaller than W / 20, the pitch x is selected from the range of W / 20 ≦ x ≦ W / 5,
(D) A method for determining the pitch x, wherein the pitch x is selected from a range of Δ (r) ≦ x ≦ W / 5 when Δ (r) is greater than W / 20. A method of manufacturing a semiconductor device, wherein a semiconductor film formed on a substrate and having a surface height difference r is irradiated with a linear laser beam having a beam width W at a pitch x,
(A) The linear laser beam is synthesized by dividing the pulse laser beam into a plurality of lengths and widths and then condensing each of the divided beams with a final lens,
(B) When the size of the laser beam incident on the final lens in the direction perpendicular to the bus of the final lens is D and the distance between the bus of the final lens and the semiconductor film is F, Δ (r ) = RD / 2F, and the value of Δ (r) is calculated.
(C) When the Δ (r) is smaller than W / 20, the pitch x is selected from the range of W / 20 ≦ x ≦ W / 5, and the selected x pitch is applied to the semiconductor film. Irradiate the linear laser beam,
(D) When Δ (r) is larger than W / 20, the pitch x is selected from the range of Δ (r) ≦ x ≦ W / 5, and the semiconductor film is selected at the selected pitch x. And irradiating the linear laser beam.