JP4651933B2 - Method for manufacturing semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device using a semiconductor having a crystal structure, and more specifically to a method for manufacturing a thin film transistor, a thin film diode, a field emission device, or the like using a crystalline semiconductor film.

  A semiconductor element using a crystalline semiconductor film over the same substrate, typically a semiconductor circuit having a driver circuit and a pixel portion formed using a thin film transistor, a thin film diode, a field emission element, an electro-optical device, Light emitting devices and electronic devices using them have been actively manufactured. A semiconductor film is used as an active layer of a semiconductor element, and high field effect mobility has been realized by using a crystalline silicon film as the active layer.

  In particular, the factors that determine the electrical characteristics of thin film transistors depend on the quality of the semiconductor film. In particular, the field effect mobility depends on the crystallinity of the semiconductor film, and the field effect mobility is directly related to the response characteristics of the thin film transistor and the display capability of a display device manufactured using the thin film transistor in a circuit.

  Currently, thermal annealing, laser annealing, or both thermal annealing and laser annealing are performed on amorphous semiconductor films formed on insulating substrates such as glass to form thin film transistors with high electrical characteristics. Thus, a technique for improving the crystallinity of an amorphous semiconductor film and a technique for forming a crystalline semiconductor film have been widely studied.

  However, when a crystalline semiconductor film is formed on an amorphous semiconductor film formed by a plasma CVD method or a sputtering method using a thermal annealing method or a laser annealing method, the crystal orientation tends to be oriented in an arbitrary direction. It is difficult to control. For this reason, the use of a crystalline semiconductor film crystallized by a thermal annealing method or a laser annealing method as an active layer of a thin film transistor is a factor that limits electric characteristics of the thin film transistor.

  One method for crystallizing an amorphous semiconductor film is the method described in Patent Document 1 (Japanese Patent Laid-Open No. 7-183540). This crystallization method will be briefly described below. First, a trace amount of a metal element, typically nickel, iron, cobalt, palladium, platinum, or the like is added to the amorphous semiconductor film. Note that as a method for adding the metal element, plasma treatment, vapor deposition, ion implantation, sputtering, or solution coating may be used. Thereafter, when the amorphous semiconductor film is heated in a nitrogen atmosphere at a low temperature, for example, 550 ° C., a compound of a metal element and an element of the semiconductor film (typically, nickel silicide, iron silicide, cobalt silicide, platinum silicide, A crystallization reaction centering on palladium silicide or the like occurs, and a crystalline semiconductor film is formed.

  It has been confirmed that a semiconductor film crystallized by this method can enhance the orientation of crystal orientation in a single direction and can form a semiconductor film composed of large crystal grains. Furthermore, it has been confirmed that there are few defects in the crystal grains. For this reason, if it arrange | positions so that the moving direction of a carrier may align with the direction where the formed crystal grain extends, the frequency | count that a carrier crosses a crystal grain boundary can be reduced extremely. Therefore, variations in on-current value (drain current value that flows when the thin film transistor is in an on state), off current value (drain current value that flows when the thin film transistor is in an off state), threshold voltage, S value, and field effect mobility Can be reduced, and the electrical characteristics are remarkably improved. Note that the heating temperature and heating time appropriate for crystallization of the amorphous semiconductor film depend on the amount of the metal element added and the state of the amorphous semiconductor film.

  However, since the metal element is added to the amorphous semiconductor film, the metal element (in the case where the semiconductor film is silicon, a silicide compound of the metal element, typically nickel silicide, Iron silicide, cobalt silicide, platinum silicide, palladium silicide, etc.) remain. This remaining metal element becomes a path of leakage current, and the off current of the thin film transistor is increased, which causes a variation in electric characteristics between the thin film transistor elements. Therefore, after the amorphous semiconductor film is crystallized, a process of removing the metal element in the semiconductor film or reducing the concentration of the metal element (hereinafter referred to as a gettering process) is necessary.

  Therefore, the present applicant has disclosed a method for removing a metal element in a crystalline semiconductor film in Patent Document 2, Patent Document 3, Patent Document 4, and Patent Document 5, respectively.

  In Patent Document 2, a solution containing a metal element that promotes crystallinity of a semiconductor is applied onto an amorphous semiconductor film, heated to form a crystalline semiconductor film, and then nickel silicide using a solution containing hydrochloric acid. A process for removing nickel (nickel silicide) in a semiconductor film by etching is disclosed.

  In Patent Document 3, a solution containing a metal element that promotes the crystallinity of a semiconductor is applied to an amorphous semiconductor film, heated to form a crystalline semiconductor film, and irradiated with a pulsed excimer laser to form a crystal. A process for etching a semiconductor film into an arbitrary shape after promoting the formation is disclosed.

  Patent Document 4 discloses a method of removing a metal element for promoting crystallization of a semiconductor film from a channel formation region of the thin film transistor by adding phosphorus to the source region and the drain region of the thin film transistor and heating at 450 to 700 degrees. Has been.

Further, in Patent Document 5, 1 × 10 ¹⁹ to 1 × 10 10 through a barrier layer formed of a silicon oxide film or the like on a crystalline semiconductor film (hereinafter referred to as a semiconductor film A in this paragraph). A semiconductor film containing a rare gas element such as argon at ²² / cm ³ (hereinafter, referred to as a semiconductor film B in this paragraph) is formed and subjected to heat treatment, whereby crystallization is promoted from the semiconductor film A to the semiconductor film B. A method for removing the metal element from the crystalline semiconductor film (semiconductor film A) of the thin film transistor by moving the metal element and then removing the semiconductor film B is disclosed.
JP-A-7-183540 (pages 7-8, FIG. 3) Japanese Patent No. 3107941 (pages 3 to 5, Fig. 3) JP-A-7-161634 (pages 7-8, FIG. 3) Japanese Patent Laid-Open No. 10-335672 (pages 4-7, FIGS. 1 and 2) JP 2002-324808 (pages 7 to 10, FIGS. 1 and 2)

  However, in the metal element gettering step disclosed in Patent Document 2, only the metal compound in the semiconductor film, typically nickel silicide, is removed. Irradiation etc.) is required. Further, the nickel silicide that can be removed here is only the one deposited on the surface of the semiconductor film, and there is a problem that the nickel silicide in the semiconductor film cannot be removed.

  In Patent Document 3, after heating an amorphous semiconductor film, a laser to be irradiated to promote crystallization is a pulsed laser such as an excimer laser. Since laser light emitted from a pulsed laser has low energy density, a region of the semiconductor film melted by laser light irradiation is an amorphous portion and a surface in the semiconductor film. For this reason, there is a problem that even when laser light is irradiated, the crystalline region in the semiconductor film is not melted, and a metal compound, typically nickel silicide, remains in that region.

  Furthermore, the metal element gettering methods disclosed in Patent Document 4 and Patent Document 5 have a problem in that the number of steps is large, resulting in a decrease in yield.

  The present invention is a means for solving such a problem, and an object of the present invention is to provide a method for effectively removing a metal element from a crystalline semiconductor film obtained using the metal element without increasing the number of steps. And

In the present invention, an amorphous semiconductor film is formed over an insulating surface, a metal element that promotes crystallization is added to the amorphous semiconductor film, and then crystallized by heating, and continuous oscillation is generated in the crystallized semiconductor film. It is characterized by irradiating a laser beam and removing an upper portion of the crystalline semiconductor film irradiated with the laser.
Note that the upper portion of the semiconductor film irradiated with the laser is a part of the semiconductor film including a region where a metal element is segregated.
In the present invention, an amorphous semiconductor film is formed over an insulating surface, a metal element that promotes crystallization is added to the amorphous semiconductor film, and then crystallized by heating, and continuous oscillation is generated in the crystallized semiconductor film. Irradiating a laser beam, and removing the upper part of the crystalline semiconductor film so that the metal element concentration of the crystalline semiconductor film irradiated with the laser becomes a detection lower limit of SIMS (secondary ion mass spectrometry) And
The detection limit concentration of the SIMS (secondary ion mass spectrometry) is 1 × 10 ¹⁷ / cm ³ .
Further, as a method of removing the upper portion of the semiconductor film irradiated with the laser light, wet etching, dry etching, polishing by CMP (Chemical Mechanical Polishing), or the like is used.
As the laser beam at this time, a continuous wave laser beam having a wavelength range absorbed by the semiconductor film, that is, a wavelength of 100 to 600 nm is applied. As the laser oscillator, a gas laser oscillator or a solid laser oscillator is applied. As a gas laser oscillator, a laser oscillator using He—Ne, Ar, Kr or the like, and as a solid-state laser oscillator, a crystal such as YAG, YVO ₄ , YLF, YAlO ₃ is formed on Cr, Nd, Er, Ho, Ce, Co, A laser oscillator using a crystal doped with Ti or Tm, or a glass laser, a ruby laser, an Alexandride laser, or a Ti: sapphire laser is applied. In the solid-state laser oscillator, it is preferable to apply the second to fourth harmonics of the fundamental wave.
When these lasers are used, the entire substrate can be irradiated with laser light in a short time by using a method in which a laser beam emitted from a laser oscillator is linearly collected by an optical system and irradiated onto a semiconductor film. It can be effective.

The present inventor has found that a metal element is segregated in the vicinity of the surface of the crystalline semiconductor film by irradiating the crystalline semiconductor film formed by adding and heating the metal element with continuous oscillation laser light. . FIG. 4 shows the result of measuring the concentration of a metal element, specifically, nickel element, of a semiconductor film to which the present invention is applied using SIMS (secondary ion mass spectrometry).
The structure of the sample used for measurement is obtained by laminating each layer on a glass substrate as follows. The structure of the sample is shown below.
Sample structure “Glass // SiNO 50 nm / SiON 100 nm / poly Si 150 nm / cap a-Si 50 nm” (glass substrate / silicon oxynitride film 50 nm / silicon nitride oxide film 100 nm / crystalline silicon film (active layer, poly in FIG. 4) -Si region) 150 nm / amorphous silicon film (protective layer, cap a-Si region in FIG. 4) 50 nm)
Note that the silicon nitride oxide and the silicon oxynitride film are formed by a known technique. The crystalline silicon film is formed by applying a solution containing nickel (nickel concentration: 10 ppm) on an amorphous silicon film formed by a known method and heating it. Thereafter, an amorphous silicon film is formed as a protective layer.

  Also, in SIMS (secondary ion mass spectrometry) measurement, the initial measurement profile is uncertain due to the transient region (the region until the amount of sputtering from the primary irradiation ions and the sample surface reaches equilibrium) and the sample surface condition. Accompanied by. Therefore, an amorphous semiconductor film that is a protective layer is provided.

  Here, a solution containing 10 ppm of nickel is used. However, when a semiconductor film is crystallized using a solution containing more than 10 ppm of nickel, a region where nickel is segregated in the semiconductor film increases, and the etching process becomes longer. In addition, there is a high possibility that nickel element remains in the active layer. On the other hand, even when the semiconductor film is crystallized using a solution containing nickel element of less than 10 ppm, the entire semiconductor film is not sufficiently crystallized, and a semiconductor film with low crystallinity is formed. For this reason, in the present invention, a solution containing 10 ppm of nickel is used.

In FIG. 4, a sample 1 (broken line) is a sample using a crystalline semiconductor film formed by a conventional manufacturing method as an active layer, specifically, a semiconductor film without irradiating continuous oscillation laser light. The nickel element concentration of a sample on which an amorphous silicon film is formed is shown. On the other hand, Sample 2 (solid line) is a sample using a crystalline silicon film formed according to the present invention as an active layer, specifically, a semiconductor film is irradiated with continuous-wave laser light and then an amorphous film which is a protective film. This represents the nickel element concentration of the sample on which the porous silicon film was formed. The laser irradiation conditions are Nd: YVO ₄ laser second harmonic (532 nm), scan speed 50 cm / sec, and overlap rate 0%.

In the amorphous silicon film (cap a-Si region in FIG. 4) which is a protective layer, the nickel element concentrations of sample 1 and sample 2 are substantially the same. On the other hand, in the crystalline silicon film (poly-Si region in FIG. 4), the nickel element concentration in sample 1 is uniform (approximately 2 × 10 ¹⁸ / cm ³ ) in the depth direction, whereas in sample 2 The nickel element concentration is high in the nickel element in the region of 50 nm from the interface between the cap a-Si region and the poly-Si region, and in the region of 50 to 150 nm, the concentration is below the lower limit of detection (1 × 10 ¹⁷ / cm ³ ). It turns out that it is. Thus, when a metal element is added to an amorphous semiconductor film and heated to form a crystalline silicon film, the heated semiconductor film is irradiated with continuous-wave laser light, whereby the metal element is converted into a semiconductor film. It can be seen that it can be segregated on the surface. For this reason, by removing at least 50 nm from the surface of the semiconductor film, preferably 50 nm from the region where the metal element is segregated, and leaving the film thickness necessary for the semiconductor film by a known method, impurities are removed. A semiconductor film with a low concentration of certain metal elements and high crystallinity can be formed.

The reason for the segregation due to the continuous wave laser irradiation is as follows. Here, silicon is used as a representative semiconductor element.
The ratio of the solubility [C _M ] _S of the metal element in the solid phase to the solubility [C _M ] _L in the liquid phase, k ₀ (equilibrium segregation coefficient), is constant and is expressed by Equation 1.

k ₀ = [C _M ] _S / [C _M ] _L Formula 1

The metal element in the molten silicon diffuses in the melt and occupies the interstitial position of silicon. At high temperatures, metal elements occupying interstitial positions quickly diffuse through the bulk to reach an equilibrium concentration. However, when the equilibrium segregation coefficient k ₀ <1, the metal element occupying the interstitial position exceeds the solubility at a low temperature in the cooling process after the heat treatment, so that the metal element is precipitated in the solid phase as a metal silicide. In this case, when the semiconductor film is solidified at a rate higher than the diffusion rate of the metal element, the metal element in the metal silicide deposited on the solid phase is concentrated near the solid-liquid interface and diffuses toward the inside of the liquid phase. That is, the concentration of the metal element is increased in front of the solid-liquid interface. Since crystallization starts from the interface between the semiconductor film and the base film, the metal element is segregated at the upper part of the semiconductor film that exists as a melt, that is, near the surface.

According to W. Zulehner and D. Huber: "Czochralski-grown silicon, Crystals 8: Silicon, chemical Ething, pp. 1-143, Springer-Verlag (1982)", the equilibrium segregation coefficient of nickel in silicon is k ₀ = 3 × 10 ⁻⁵ . In addition, k _{0 of} iron and cobalt is 8 × 10 ⁻⁶ and 8 × 10 ⁻⁶ , respectively. Since the time from silicon melting to solidification is as short as μsec order, metal elements in silicon melt, typically nickel element, cobalt element, iron element, etc. are finally melted. Metal elements are segregated in the upper part of the semiconductor film existing as a liquid, that is, near the surface.

  By the way, the continuous wave laser beam continuously emits the laser beam, and therefore the energy density of the laser beam irradiated onto the irradiated surface is higher than that of the conventionally used pulsed laser beam. Conventionally, even when a pulsed laser beam is irradiated onto a crystalline semiconductor film, only a part of the amorphous semiconductor film or a surface part is typically melted. For this reason, the metal element contained in the crystalline semiconductor film cannot be diffused and segregated and is dispersed throughout the semiconductor film. On the other hand, when a semiconductor film is irradiated with continuous wave laser light, the semiconductor film is melted in a wide area including the crystalline semiconductor film. For this reason, in the recrystallization of the semiconductor film by cooling, the metal element contained in the melt is segregated to the upper part of the recrystallized semiconductor film by the above-described segregation reaction mechanism. Further, since the semiconductor film is melted by irradiation with continuous wave laser light, the recrystallized semiconductor film becomes a film with few defects.

  In the process of crystallizing a semiconductor film using a metal element, the crystalline semiconductor film is irradiated with continuous-wave laser light, thereby making the semiconductor film having crystallinity simpler and fewer than conventional processes. A thin film transistor having a structure can be manufactured. That is, by using the present invention, a thin film transistor including a semiconductor film including crystal grains having a large grain size can be manufactured with high yield. In addition, by using the present invention, the yield can be similarly improved in a method for manufacturing a semiconductor device using a semiconductor film having a crystal structure.

  1A and 1B, a catalytic metal element is added to the entire surface of an amorphous semiconductor film, heated to crystallize the amorphous semiconductor film, and then irradiated with continuous-wave laser light for gettering. The method to perform is demonstrated.

  FIG. 1A will be described. The material of the substrate 11 is not particularly limited, but barium borosilicate glass, alumino borosilicate glass, or quartz is preferably used. An inorganic insulating film having a thickness of 10 to 200 nm is formed on the surface of the substrate 11 as the base film 12. In FIG. 1, the base film is a single layer, but it may be two or more layers. Examples of a suitable base insulating film include a silicon oxide film, a silicon oxynitride film, and a silicon nitride film.

  Next, the semiconductor film 13 is formed over the base insulating film. After a semiconductor film is formed to a thickness of 80 to 200 nm (preferably 100 to 150 nm) by a known means (sputtering method, LPCVD method, plasma CVD method, etc.), nickel, iron, cobalt, platinum Alternatively, a solution 14 containing a metal element such as palladium is applied on the semiconductor film. Note that a known method such as a plasma CVD method or a sputtering method may be used as a method for adding a metal element to the semiconductor film. In the present invention, since the region containing the metal element is removed after the amorphous semiconductor film is thermally crystallized, an amorphous semiconductor film having a thickness in consideration of a portion to be an active layer and a layer to be removed is formed.

  Next, the semiconductor film to which the metal element is added is heated at 400 to 600 degrees for 1 to 12 hours, so that the crystalline semiconductor film 15 is formed (FIG. 1B).

Next, as shown in FIG. 1C, the crystalline semiconductor film 15 is irradiated with continuous-wave laser light, and the metal element 16 in the crystalline semiconductor film, for example, nickel, iron, cobalt, platinum, palladium, or the like. Is segregated on the surface of the semiconductor film.
Thereafter, as shown in FIG. 1D, the upper portion of the crystalline semiconductor film, that is, the region of the semiconductor film containing a metal element is removed by a known method.
Thereafter, the crystalline semiconductor film 17 is patterned using a photolithography technique and formed into a desired shape, and then a first insulating film 19 is formed as a gate insulating film. The first insulating film 19 is formed by a known means (plasma CVD method, sputtering method, etc.) with a thickness of 40 to 150 nm and a single layer or a laminated structure of insulating films.

Subsequently, a conductive film, for example, a film made of a metal element is formed on the gate insulating film 19, and this is patterned using a photolithography technique to form the gate electrode 20. Here, the conductive film has a single-layer structure; however, two or more layers may be stacked. Further, as a material for the conductive film, a metal element selected from Ta, W, Ti, Mo, Al, and Cu, or an alloy material or a compound material containing them as a main component may be used. Alternatively, a semiconductor film typified by a crystalline silicon film doped with an impurity element such as phosphorus may be used.
Next, a second insulating film 21 is formed so as to cover the surfaces of the gate electrode 20 and the gate insulating film 19. The second insulating film 21 is formed by a known means (plasma CVD method, sputtering method, or the like) with a thickness of 40 to 150 nm and a single layer or a stacked structure of insulating films (FIG. 1F).

  Next, an impurity is added to the semiconductor film 18 by a known method to form a source region and a drain region. Thereafter, a second interlayer insulating film is formed, contact holes reaching the source region and the drain region are formed, and wiring reaching the source region drain region is formed. (Not shown)

  Through the above steps, when a semiconductor film is crystallized using a metal element, the semiconductor film can be crystallized and the metal element can be gettered by a simple and short-time method. Thus, the orientation of the crystal orientation can be improved in a single direction, and a semiconductor film including large crystal grains can be formed with a high yield.

  In this embodiment, a method for manufacturing a thin film transistor using the present invention will be described with reference to FIGS.

First, FIG. 2A will be described. A base film 102 made of an insulating film such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film is formed over the substrate 101 using a known technique. The base film may be a single layer or a stacked structure of two or more layers. In this embodiment, a two-layer base film is formed, a silicon nitride oxide film having a thickness of 10 to 100 nm is formed on the first base film 102b by a plasma CVD method, and a plasma CVD method is formed on the second base film 102a. A silicon oxynitride film with a thickness of 50 to 150 nm is formed.
In this embodiment, barium borosilicate glass is used for the substrate.

  Next, the semiconductor film 104 is formed over the base films 102a and 102b. As the semiconductor film 104, an amorphous semiconductor film is formed with a thickness of 80 to 200 nm (preferably 100 to 150 nm) by a known means (such as sputtering, LPCVD, or plasma CVD). There is no limitation on the material of the semiconductor film, but it is preferably formed of silicon or a silicon germanium (SiGe) alloy. In this embodiment, an amorphous silicon film with a thickness of 150 nm is formed.

  Next, a metal element that promotes crystallinity of the semiconductor film, for example, nickel, iron, cobalt, platinum, palladium, or the like is added to the semiconductor film 104 using a known technique, and the semiconductor film 104 is then subjected to a known crystallization treatment ( Crystallization is performed by laser crystallization or thermal crystallization. In this embodiment, a nickel acetate solution 105 (weight conversion concentration 10 ppm) is applied over the entire surface by spin coating, and exposed to a nitrogen atmosphere at a temperature of 550 ° C. for 12 hours to form the crystalline semiconductor film 106.

Next, FIG. 2B will be described. The crystalline semiconductor film 106 is irradiated with continuous-wave laser light to melt the crystalline semiconductor film 106, and then cooled, so that a metal element contained in the crystalline semiconductor film 106, which is a nickel element in this embodiment, is used. Is segregated on the semiconductor film 106.
Note that a continuous wave laser beam having a wavelength region absorbed by the semiconductor film, that is, a wavelength of 100 to 600 nm, is applied to a laser capable of continuous wave. As the laser oscillator, a gas laser oscillator or a solid laser oscillator is applied. As a gas laser oscillator, a laser oscillator using He—Ne, Ar, Kr or the like, and as a solid-state laser oscillator, a crystal such as YAG, YVO ₄ , YLF, YAlO ₃ is formed on Cr, Nd, Er, Ho, Ce, Co, A laser oscillator using a crystal doped with Ti or Tm, or a glass laser oscillator, a ruby laser oscillator, an alexandrite laser oscillator, or a Ti: sapphire laser oscillator is applied. In the solid-state laser oscillator, it is preferable to apply the second to fourth harmonics of the fundamental wave.
When these lasers are used, the entire substrate can be irradiated with laser light in a short time by using a method in which a laser beam emitted from a laser oscillator is linearly collected by an optical system and irradiated onto a semiconductor film. It can be effective.

Next, FIG. 2C will be described. A region where the metal element is segregated is removed from the crystalline semiconductor film 106 by wet etching to form the semiconductor film 107. As the etchant, hydrazine, ethylenediamine, pyrocatechol aqueous solution (EPW), potassium hydroxide, tetramethylammonium hydroxide solution (TMAH), or the like can be used. In this embodiment, the silicon semiconductor film is immersed in a 50-degree tetramethylammonium hydroxide solution (TMAH) for 500 seconds, and the region of the crystalline semiconductor film having a metal element is 50 nm in the depth direction from the upper part (surface) of the silicon film. Etch. By this step, the metal element can be removed from the crystalline semiconductor film 106 that can be an active region or reduced to the extent that the semiconductor characteristics are not affected. The thin film transistor having an active region manufactured in this manner has good characteristics in which the off-state current value is suppressed while obtaining high field-effect mobility because the concentration of the metal element serving as a path for leakage current is reduced. become.
Next, FIG. 2D will be described. After a mask (not shown) is formed using a photolithography technique, unnecessary portions are removed by a known etching method to form semiconductor films 108a and 108b having desired shapes. Note that after the semiconductor films 108a and 108b are formed, a small amount of impurity element (boron or phosphorus) may be doped in order to control the threshold value of the thin film transistor. (Not shown).

Next, a gate insulating film 109 having a thickness of 20 to 150 nm is formed using a known technique. In this embodiment, a silicon oxynitride film having a thickness of 115 nm is formed by a plasma CVD method with a flow rate of the source gas of SiH ₄ / N ₂ O = 4/800 (sccm) and a deposition temperature of 400 degrees. Needless to say, the gate insulating film is not limited to the silicon oxynitride film, and other insulating films (such as a silicon oxide film, a silicon nitride oxide film, and a silicon nitride film) may be used.

  Next, a conductive film is formed by a known film formation method. In this embodiment, a first conductive film 110a made of a tantalum nitride film with a thickness of 30 nm and a second conductive film 110b made of a tungsten film with a thickness of 370 nm are stacked. The tantalum nitride film and the tungsten film are formed by a sputtering method.

  In this embodiment, the first conductive film 110a is a tantalum nitride film, and the second conductive film 110b is a tungsten film. However, the present invention is not particularly limited, and any of them is tantalum (Ta), tungsten (W), titanium ( Formed of an element selected from Ti), molybdenum (Mo), aluminum (Al), copper (Cu), chromium (Cr), neodymium (Nd), or an alloy material or a compound material containing these elements as main components. May be. Alternatively, a silver-copper-palladium alloy (AgPdCu alloy) may be used.

  Next, FIG. 3A will be described. After forming a mask (not shown) using a photolithography technique, unnecessary portions of the first conductive film 110a and the second conductive film 110b are removed by a known etching method (RIE method, ECR method, etc.). Thus, gate electrodes 111a and 111b are formed.

Next, FIG. 3B will be described. An impurity element is introduced into the semiconductor film (112a and 112b in FIG. 3A) by a known technique (ion doping method, ion implantation method, or the like) using the gate electrodes 111a and 111b as a mask, and the source and drain regions 113a, 113b is formed. The above-described steps are performed with the ion doping conditions set to a dose of 1 × 10 ^{13 to} 5 × 10 ¹⁴ / cm ² and an acceleration voltage of 30 to 120 keV.
In this embodiment, when doping an n-type impurity, the impurity dose is set to 2 × 10 ¹³ / cm ² and the acceleration voltage is set to 90 keV. Note that an element belonging to Group 15, typically phosphorus (P) or arsenic (As), is used as an impurity element imparting n-type conductivity. In this embodiment, a compound containing phosphorus (P) is used as an impurity.
Further, when doping the p-type impurity, the impurity dose is set to 3 × 10 ¹³ / cm ² and the acceleration voltage is set to 60 keV. Note that as the impurity element imparting p-type conductivity, an element belonging to Group 13, typically boron (B), can be used.

  Next, heat treatment is performed to recover the crystallinity of the semiconductor film and to activate the impurity element introduced into each semiconductor film. As a heat treatment method, a thermal annealing method using a furnace annealing furnace, a laser annealing method, or a rapid thermal annealing method (RTA method) can be applied. In this embodiment, a thermal annealing method is used, and heating is performed at 550 ° C. in a nitrogen atmosphere for 4 hours.

  Next, FIG. 3C will be described. After the first interlayer insulating film 114 and the second interlayer insulating film 115 are formed, the surface of the insulating film may be planarized by a chemical and mechanical polishing process (typically, CMP technique) or the like. The first interlayer insulating film 114 may be used as a single layer or a stacked structure. In this embodiment, a silicon nitride film 114 having a thickness of 50 nm is formed as a first interlayer insulating film by a plasma CVD method, and a silicon oxide film 115 having a thickness of 400 nm is formed as a second interlayer insulating film by a similar method. To do. Note that a film made of an inorganic insulating film material or an organic insulating material can be formed as the second interlayer insulating film.

  Note that hydrogenation may be performed by heat treatment (300 to 550 ° C. for 1 to 12 hours) before forming the second interlayer insulating film over the first interlayer insulating film. This step is a step of terminating dangling bonds in the semiconductor film with hydrogen contained in the first interlayer insulating film 114. As other means for hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) or heat treatment at 300 to 450 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% hydrogen is performed. May be. In this embodiment, heating is performed at 410 ° C. for 1 hour in a nitrogen atmosphere.

  Then, contact holes reaching the source and drain regions 113a and 113b are formed, and wirings 116 to 119 electrically connected to the source and drain regions 113a and 113b are formed.

  In this manner, contact holes reaching the semiconductor film are formed, and wirings 116 to 119 are formed. Note that these wirings are formed by etching a laminated film of a titanium film with a thickness of 100 nm, an alloy film with a thickness of 350 nm (typically an alloy film of aluminum and silicon), and a titanium film with a thickness of 100 nm. To do. The wiring material is not limited to Ti, an alloy of Al and Si, and other low-resistance materials may be used.

  In this embodiment, another step is shown in the step of removing the region where the metal element is segregated on the upper portion of the semiconductor film in the thin film transistor formed by the manufacturing method described in Embodiment 1.

  In accordance with Embodiment 1, the crystalline semiconductor film is irradiated with continuous-wave laser light to segregate a metal element, typically nickel element, on the semiconductor film. After that, the surface of the semiconductor film is polished by CMP (Chemical Mechanical Polishing) to remove the region containing the metal element of the semiconductor film. In this embodiment, the surface of the semiconductor film is polished using a polishing liquid containing silicon oxide in the slurry. The polishing conditions at this time may be set as appropriate in accordance with the film quality and film thickness of the semiconductor film. By the polishing step, the surface of the thin film transistor can be planarized and the metal element of the semiconductor film including the active layer can be removed. In other words, a thin film transistor manufactured using this process has good characteristics in which the off-state current value is suppressed while having high field-effect mobility because the concentration of the metal element serving as a leakage current path is reduced. become.

  In this embodiment, as in Embodiment 2, in the thin film transistor formed by the manufacturing method described in Embodiment 1, another step is shown in the step of removing the region where the metal element is segregated on the upper portion of the semiconductor film.

In accordance with Embodiment 1, the crystalline semiconductor film is irradiated with continuous-wave laser light to segregate a metal element, typically nickel element, on the semiconductor film. After that, the region containing the metal element of the semiconductor film is removed by dry etching. The dry etching conditions may be set as appropriate depending on the film quality and film thickness of the semiconductor film. In this embodiment, the etching condition is CF ₄ / O ₂ = 50/45 (sccm), and the upper 50 nm of the semiconductor film is etched.
As a result, the metal element in the semiconductor film including the active layer can be removed, and the concentration of the remaining metal element can be reduced. In other words, a thin film transistor manufactured using this process has favorable characteristics in which the off-state current value is suppressed while obtaining high field-effect mobility because the concentration of the metal element serving as a leakage current path is reduced. Become.

  In Embodiments 1 to 3, an example in which the present invention is applied to a thin film transistor manufacturing process has been described, but the present invention is not limited to this. The present invention can be applied to a semiconductor device using a semiconductor film, such as a thin film diode and a field emission device.

  By applying the present invention, various electronic devices (electro-optical devices, light-emitting devices, semiconductor circuits, and the like) can be manufactured. That is, the present invention can be applied to various electronic devices in which these electronic devices are incorporated.

  Such electronic devices include video cameras, digital cameras, projectors, head-mounted displays (goggles type displays), car navigation systems, car stereos, personal computers, personal digital assistants (mobile computers, mobile phones, electronic books, etc.), etc. Can be mentioned. Examples thereof are shown in FIGS. 5, 6 and 7.

  FIG. 5A illustrates a personal computer, which includes a main body 3001, an image input portion 3002, a display portion 3003, a keyboard 3004, and the like. By applying the present invention, a personal computer with low power consumption capable of high-definition display with high yield can be manufactured.

  FIG. 5B illustrates a video camera, which includes a main body 3101, a display portion 3102, an audio input portion 3103, operation switches 3104, a battery 3105, an image receiving portion 3106, and the like. By applying the present invention, a video camera capable of high-definition display with high yield can be manufactured.

  FIG. 5C illustrates a mobile computer, which includes a main body 3201, a camera unit 3202, an image receiving unit 3203, an operation switch 3204, a display unit 3205, and the like. By applying the present invention, a low-power consumption mobile computer (mobile computer) capable of high-definition display with high yield can be manufactured.

  FIG. 5D illustrates a goggle type display, which includes a main body 3301, a display portion 3302, an arm portion 3303, and the like. By applying the present invention, a goggle type display capable of high-definition display with high yield can be manufactured.

  FIG. 5E shows a player using a recording medium (hereinafter referred to as a recording medium) on which a program is recorded, and includes a main body 3401, a display portion 3402, a speaker portion 3403, a recording medium 3404, an operation switch 3405, and the like. This player uses a DVD (Digital Versatile Disc), CD, or the like as a recording medium, and can perform music appreciation, movie appreciation, games, and the Internet. By applying the present invention, a player capable of high-definition display with high yield can be manufactured.

  FIG. 5F illustrates a digital camera, which includes a main body 3501, a display portion 3502, an eyepiece portion 3503, an operation switch 3504, an image receiving portion (not shown), and the like. By applying the present invention, a low power consumption digital camera capable of high-definition display with high yield can be manufactured.

  FIG. 6A illustrates a front type projector, which includes a projection device 3601, a screen 3602, and the like. By applying the present invention, a high-luminance front projector can be manufactured with high yield.

  FIG. 6B illustrates a rear projector, which includes a main body 3701, a projection device 3702, a mirror 3703, a screen 3704, and the like. By applying the present invention, a high-luminance rear projector can be manufactured with high yield.

  Note that FIG. 6C is a diagram illustrating an example of the structure of the projection devices 3601 and 3702 in FIGS. 6A and 6B. The projection devices 3601 and 3702 include a light source optical system 3801, mirrors 3802 and 3804 to 3806, a dichroic mirror 3803, a prism 3807, a liquid crystal display device 3808, a phase difference plate 3809, and a projection optical system 3810. The projection optical system 3810 is composed of an optical system including a projection lens. Although the present embodiment shows an example of a three-plate type, it is not particularly limited, and for example, a single-plate type may be used. In addition, the practitioner may appropriately provide an optical system such as an optical lens, a film having a polarization function, a film for adjusting a phase difference, an IR film, or the like in the optical path indicated by an arrow in FIG. Good.

  FIG. 6D illustrates an example of the structure of the light source optical system 3801 in FIG. In this embodiment, the light source optical system 3801 includes a reflector 3811, a light source 3812, lens arrays 3813 and 3814, a polarization conversion element 3815, and a condenser lens 3816. Note that the light source optical system illustrated in FIG. 6D is an example and is not particularly limited. For example, the practitioner may appropriately provide an optical system such as an optical lens, a film having a polarization function, a film for adjusting a phase difference, or an IR film in the light source optical system.

  However, the projector shown in FIG. 6 shows a case where a transmissive electro-optical device is used, and an application example in a reflective electro-optical device and a light-emitting device is not shown.

  FIG. 7A illustrates a mobile phone, which includes a main body 3901, an audio output portion 3902, an audio input portion 3903, a display portion 3904, operation switches 3905, an antenna 3906, and the like. By applying the present invention, a mobile phone with low power consumption that can display with high yield and high definition can be manufactured.

  FIG. 7B illustrates a portable book (electronic book), which includes a main body 4001, display portions 4002 and 4003, a storage medium 4004, operation switches 4005, an antenna 4006, and the like. By applying the present invention, a portable book with low power consumption and high-definition display with high yield can be manufactured.

  FIG. 7C illustrates a display, which includes a main body 4101, a support base 4102, a display portion 4103, and the like. A display to which the present invention is applied is particularly advantageous when the screen is enlarged, and is advantageous for a display having a diagonal of 10 inches or more (particularly 30 inches or more).

  As described above, the applicable range of the present invention is so wide that the present invention can be applied to electronic devices in various fields. Moreover, the electronic device of a present Example is realizable even if it uses the structure which consists of what combination of Examples 1-4.

The figure which shows an example of the concept of this invention. 10 is a cross-sectional view illustrating a manufacturing process of a thin film transistor. 10 is a cross-sectional view illustrating a manufacturing process of a thin film transistor. The figure which shows the density | concentration of nickel in a semiconductor film. FIG. 14 illustrates an example of an electronic device. FIG. 14 illustrates an example of an electronic device. FIG. 14 illustrates an example of an electronic device.

Claims (8)

Forming an amorphous semiconductor film on the insulating surface;
Crystallization by heating after adding a metal element that promotes crystallization to the amorphous semiconductor film,
Irradiating the crystallized semiconductor film with continuous wave laser light,
A method for manufacturing a semiconductor device, wherein an upper portion of the crystalline semiconductor film irradiated with the continuous wave laser light is removed by a wet etching method.   2. The method for manufacturing a semiconductor device according to claim 1, wherein an upper portion of the crystalline semiconductor film irradiated with the continuous wave laser light is a region of a semiconductor film containing a metal element. Forming an amorphous semiconductor film on the insulating surface;
Crystallization by heating after adding a metal element that promotes crystallization to the amorphous semiconductor film,
Irradiating the crystallized semiconductor film with continuous wave laser light,
Wet etching is performed on the upper part of the crystalline semiconductor film irradiated with the continuous wave laser light so that the metal element concentration of the crystalline semiconductor film irradiated with the laser light becomes a detection limit of SIMS (secondary ion mass spectrometry). A method for manufacturing a semiconductor device, characterized by being removed by a method. 4. The method for manufacturing a semiconductor device according to claim 3, wherein the detection limit concentration of the SIMS (secondary ion mass spectrometry) is 1 × 10 ¹⁷ / cm ³ .   5. The method for manufacturing a semiconductor device according to claim 1, wherein an upper portion of the crystalline semiconductor film is removed by at least 50 nm. In any one of claims 1 to 5, the laser beam of the continuous wave, a continuous wave Nd: YAG laser, Nd: YVO ⁴ laser, Nd: YLF laser, Nd: YAlO ³ laser, a glass laser, A method for manufacturing a semiconductor device, wherein the semiconductor device is oscillated from a ruby laser, an alexandride laser, or a Ti: sapphire laser. The method for manufacturing a semiconductor device according to claim 6 , wherein the laser light has a second harmonic to a fourth harmonic. In any one of claims 1 to 5, the laser beam of the continuous wave method for manufacturing a semiconductor device, characterized in that He-Ne laser, a Ar laser or Kr laser in which oscillated.

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