JP3939383B2 - Method for manufacturing semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The invention disclosed in this specification relates to a structure of a thin film transistor. Further, the present invention relates to a manufacturing method thereof.
[0002]
[Prior art]
Conventionally, an active matrix type liquid crystal display device is known. This has a configuration in which a thin film transistor is arranged on each of the pixel electrodes arranged in a matrix.
[0003]
In such a configuration, unevenness of the displayed screen or a striped pattern becomes a problem. These problems can be attributed to variations in characteristics of thin film transistors arranged in the active matrix region.
[0004]
That is, there is a problem that the characteristics of thin film transistors formed in a matrix of several hundreds × several hundreds on a glass substrate or a quartz substrate vary from place to place.
[0005]
[Problems to be solved by the invention]
According to the studies by the present inventors, it is considered that the display unevenness and the striped pattern are generated by the following mechanism.
[0006]
In the thin film transistor disposed in the activity matrix region, a region called an LDD (lightly doped drain) region is disposed in order to improve the OFF current characteristics.
[0007]
This has a configuration in which a low concentration impurity region (generally referred to as an LDD region) to which an impurity imparting conductivity type is added at a lower concentration than the drain region is disposed between the channel formation region and the drain region. ing.
[0008]
This low concentration impurity region has a function of relaxing a high electric field formed between the channel formation region and the drain region.
[0009]
The LDD region is configured to have a weak conductivity type (must not be a drain region). Specifically, it is formed as a region containing an impurity imparting a conductivity type at a concentration of 1 × 10 ¹⁶ to 1 × 10 ¹⁹ cm ⁻³ . This impurity concentration is set so as to contain impurities at a concentration lower than that of the drain region.
[0010]
Generally, a crystalline silicon film (a general term for a polycrystalline silicon film or a microcrystalline silicon film) obtained by laser light irradiation is used as a silicon film constituting a thin film transistor.
[0011]
The crystalline silicon film utilizing this laser light irradiation has irregularities formed on its surface.
[0012]
The photograph which observed the state of this unevenness with the atomic force microscope is shown in FIG. FIG. 8 is a photograph showing the surface state of the silicon film irradiated with laser light.
[0013]
Further, as a method for performing irradiation of a laser beam on a large area with high efficiency, there is a technique of irradiating a laser beam processed on a line. Even when this technique is used, the above-described surface irregularities are formed.
[0014]
FIG. 3 schematically shows this phenomenon. FIG. 3 shows a pulse oscillation type excimer laser beam (having a longitudinal shape in the depth direction and the front side of the drawing) that is linearly beam processed with respect to the amorphous silicon film 303 by 300. This is a state when irradiation is performed while scanning in the direction.
[0015]
In FIG. 3, reference numeral 301 denotes a substrate. Usually, a glass substrate is used as the substrate. Reference numeral 302 denotes a base film. A silicon oxide film is used as the base film. Reference numeral 304 denotes a region after the laser beam irradiation, which is a region crystallized by the laser beam irradiation.
[0016]
In this situation, roughness (unevenness) as indicated by reference numeral 305 is formed on the mark irradiated with the laser beam. This rough state depends on the heating temperature, irradiation energy density, oscillation frequency, scan speed, and amorphous silicon film at the time of laser light irradiation.
[0017]
In the drawing, the roughness is shown as if it were formed at equal intervals, but in reality the intervals are random.
[0018]
This roughness is similarly formed when the amorphous silicon film is crystallized by heating and further annealed by laser light irradiation.
[0019]
Further, when an annealing method using a linear laser beam is used, a phenomenon that a striped pattern is displayed on a completed liquid crystal panel is observed.
[0020]
This stripe pattern reflects variations in characteristics of the thin film transistors arranged in the active matrix circuit. This is supported by the large variation in resistance in the LDD region.
[0021]
Also, the variation in the LDD region is much larger than the variation in the resistance of the source and drain regions.
[0022]
This is caused by using a plasma doping method known as a means for doping a large area and implanting impurity ions at a low dose.
[0023]
The plasma doping method is a method in which ions to be accelerated and implanted are extracted using plasma and are electrically accelerated to be implanted into a doped region.
[0024]
In this method, the crystallinity of the irradiated region tends to be non-uniform because various ions are included in the implanted ions. In other words, a component having microcrystalline properties tends to remain unspecified.
[0025]
This tendency becomes particularly noticeable when doping is performed at a low dose as in the LDD region.
[0026]
The existence density of the microcrystalline component has a large in-plane variation. Therefore, in the annealing process by laser beam irradiation performed after the impurity ion implantation, the variation in the crystal state is reflected as it is, and the resistance value differs in the portion.
[0027]
In this way, the resistance variation in the LDD region becomes large for each pixel.
[0028]
Further, the surface roughness caused by the laser light irradiation in obtaining the crystalline silicon film described above promotes the variation in resistance of the LDD region. That is, the roughness of the surface state as shown in FIG. 3 greatly promotes the variation in resistance value when forming the LDD region.
[0029]
In addition, a method for obtaining a crystalline silicon film using a metal element that promotes crystallization of silicon such as nickel described in JP-A-06-232059 is known. When this method is used, a crystalline silicon film having high crystallinity can be obtained by treatment at a lower heating temperature than in the prior art. However, the presence of the metal element when this method is used also contributes to the variation in the resistance value of the LDD region.
[0030]
The metal element has a property of becoming a nucleus during crystallization. This property naturally appears also during laser annealing. Therefore, when impurity ions are implanted by non-mass separation and the metal element is contained in the LDD region where the crystallinity is uneven, the resistance value varies during activation annealing by laser light irradiation. Will be further encouraged.
[0031]
That is, while a method of obtaining a crystalline silicon film using a metal element that promotes crystallization of silicon has the significance that high crystallinity can be obtained, resistance values such as those in the LDD region tend to vary. The region has a function of promoting variation in resistance value.
[0032]
[Problems to be solved by the invention]
An object of the invention disclosed in this specification is to provide a structure in which variation in characteristics does not occur when a large number of thin film transistors are formed over the same substrate.
[0033]
[Means for Solving the Problems]
According to the knowledge of the present inventors, the greatest contribution to the variation in resistance value of the LDD region lies in the variation in crystal state due to the remaining microcrystalline component in the doping process.
[0034]
Therefore, the invention disclosed in this specification uses a method of performing mass separation for impurity ion implantation when forming an LDD region.
[0035]
This corrects the variation in resistance values of low-concentration impurity regions typified by the LDD region when using a process that uses laser light irradiation or a process that uses a metal element that promotes crystallization of silicon. can do.
[0036]
One of the inventions disclosed in this specification is:
A low concentration impurity region to which an impurity imparting a conductivity type is added at a lower concentration than the drain region between the channel formation region and the drain region;
The low-concentration impurity region is implanted with impurity ions subjected to mass separation,
The surface of the low concentration impurity region has irregularities formed by laser light irradiation.
[0037]
Other aspects of the invention are:
A low concentration impurity region to which an impurity imparting a conductivity type is added at a lower concentration than the drain region between the channel formation region and the drain region;
The low-concentration impurity region is formed by implantation of impurity ions subjected to mass separation and then irradiation with laser light.
[0038]
In the above structure, the low-concentration impurity region includes a metal element that promotes crystallization of silicon at a concentration of 1 × 10 ¹⁶ cm ^{−3 to} 5 × 10 ¹⁹ cm ⁻³ .
[0039]
The configuration of another invention is as follows:
A step of forming a low concentration impurity region in which an impurity imparting a conductivity type is added at a lower concentration than the drain region between the channel formation region and the drain region,
The low-concentration impurity region is produced by implantation of impurity ions subjected to mass separation and then irradiation with laser light.
[0040]
Other aspects of the invention are:
A step of forming a crystalline silicon film using laser light irradiation;
Forming an active layer using the crystalline silicon film;
Have
The formation of the active layer includes a step of doping an impurity imparting a conductivity type at a lower concentration between the channel formation region and the drain region than the drain region,
In this step, the impurity ions which have been subjected to mass separation are implanted and then laser light irradiation is performed.
[0041]
DETAILED DESCRIPTION OF THE INVENTION
In the manufacturing process of the thin film transistor in which the LDD region is disposed, impurity ions are implanted by implanting impurity ions generated by mass separation. When impurity ions formed by mass separation are accelerated and implanted, the region into which the impurity ions are implanted becomes almost amorphous. Therefore, even if it is an LDD region into which impurities are implanted at a low concentration, the annealing effect by laser light irradiation can be made uniform. As a result, variations in resistance in the LDD region can be reduced.
[0042]
This configuration is particularly effective for manufacturing a thin film transistor using a crystalline silicon film obtained by irradiation with a linear laser beam. This is because, in crystallization using a linear laser beam, there is a potential linear crystallization unevenness, and this crystallization unevenness is caused by impurity ion implantation and the subsequent laser annealing process. It is because it is easy to manifest.
[0043]
Further, in the case of forming a source region or a drain region that is not an LDD region, an impurity ion implantation method in which ions are directly extracted from plasma can be used. This is because, in the source and drain regions into which impurities are implanted at a high concentration, in the crystallization process by laser light irradiation, potential uneven crystallization hardly appears as variations in resistance value.
[0044]
【Example】
[Example 1]
FIG. 1 shows a manufacturing process of a thin film transistor in which an LDD region is arranged. First, a silicon oxide film is formed as a base film 102 on the glass substrate 101 to a thickness of 3000 mm by sputtering. A quartz substrate may be used as the substrate. (Fig. 1 (A))
[0045]
Next, an amorphous silicon film 103 is formed to a thickness of 500 mm by a low pressure thermal CVD method. As a method for forming the amorphous silicon film, a plasma CVD method may be used.
[0046]
Next, heat treatment is performed to crystallize the amorphous silicon film to obtain a crystalline silicon film (not shown). Furthermore, the crystallinity of a crystalline silicon film (not shown) is promoted by scanning and irradiating a laser beam processed into a linear beam.
[0047]
Further, it is effective to perform heat treatment after the laser beam irradiation. This heat treatment has the effect of relaxing the stress in the film generated during laser light irradiation and reducing defects.
[0048]
Next, an active layer 104 of the thin film transistor is formed by patterning. In this way, the state shown in FIG.
[0049]
Next, as a gate insulating film 105, a silicon oxide film is formed to a thickness of 1000 mm by plasma CVD.
[0050]
Further, an aluminum film (not shown) for forming the gate electrode is formed by sputtering to a thickness of 4000 mm. (This aluminum film serves as a starting film constituting the gate electrode 106)
[0051]
This aluminum film contains scandium in an amount of 0.12% by weight. This is to suppress the generation of hillocks and whiskers due to the abnormal growth of aluminum in the subsequent process.
[0052]
Hillocks and whiskers are angular or needle-like protrusions formed by abnormal growth of aluminum.
[0053]
Next, anodic oxidation (not shown) having a dense film quality is formed by anodic oxidation. This step is performed by using a 3% oxalic acid aqueous solution as the electrolytic solution, and passing an electric current between the two electrodes using the aluminum film as the anode and platinum as the cathode. The film thickness can be controlled by the applied voltage. Here, the thickness of the anodic oxide film having a dense film quality (not shown) is 100 mm.
[0054]
Next, a resist mask 109 is disposed and the aluminum film is patterned. Thus, a prototype of the gate electrode 106 indicated by 106 in FIG. 1C is formed.
[0055]
Next, patterning is performed using the resist mask 109 to form an aluminum pattern. (This aluminum pattern becomes the prototype of the gate electrode 106)
[0056]
A porous anodic oxide film 107 is formed by performing anodic oxidation again. Here, an aqueous solution containing 3% oxalic acid is used as the electrolytic solution. This porous anodic oxidation is also performed by passing an electric current between both electrodes using an aluminum pattern as an anode and platinum as a cathode.
[0057]
In this step, the electrolytic solution does not contact the upper surface of the aluminum pattern due to the presence of the resist mask 109. Therefore, an anodic oxide film is formed on the side surface of the gate electrode 106 as indicated by 107 in FIG.
[0058]
The film thickness of the porous anodic oxide film 107 can be controlled by the anodic oxidation time. The film thickness of the porous anodic oxide film 107 can be up to about 2 μm. Here, the film thickness is 5000 mm.
[0059]
In this way, the state shown in FIG. Next, the resist mask 109 is removed, and anodic oxidation is performed again under the conditions for forming an anodic oxide film having a dense film quality.
[0060]
In this anodizing step, an anodized film 108 having a dense film quality is formed to a thickness of 1000 mm. In this step, the gate electrode 106 is defined. In this step, the electrolytic solution penetrates into the porous anodic oxide film 107. Therefore, an anodic oxide film 108 having a dense film quality is formed around the gate electrode 106.
[0061]
Next, P ions are implanted using the apparatus shown in FIG. 4 (configuration will be described later). The dose is 2 × 10 ¹⁵ / cm ² . In this step, P ions are implanted in the regions 110 and 112 in a self-aligning manner. Here, the region 110 becomes a source region. The region 112 becomes a drain region. Note that impurity ions are not implanted into the region 111.
[0062]
The apparatus shown in FIG. 4 has a form in which dopant ions are obtained by non-mass separation. That is, it has a configuration in which impurity ions obtained without mass separation are acceleratedly implanted.
[0063]
Here, since it is an implantation step into the source and drain regions where impurity ions are implanted at a high concentration, a non-mass separation method may be used. Of course, this step may be performed by means of mass separation.
[0064]
Next, the resist mask 107 having a porous shape is removed, and P ions are implanted again. This P ion implantation is performed with a dose amount of 0.5 to 1 × 10 ¹⁴ / cm ² .
[0065]
In the step of implanting impurity ions at a relatively low concentration, an apparatus of a type that selects dopant ions by mass separation shown in FIG. 5 is used.
[0066]
When this apparatus is used, only P ⁺ ions can be selected and implanted. Then, the implanted region of P ions can be made almost completely amorphous.
[0067]
That is, the regions 113 and 115 that are lightly doped (compared to the source / drain) can be made almost completely amorphous. Note that the regions 113 and 115 become low-concentration impurity regions. In particular, a region indicated by 115 on the drain side is an LDD (lightly doped drain) region. (Figure 1 (E))
[0068]
In the above process, a channel formation region 114 is defined.
[0069]
Thereafter, the region into which the impurity ions have been implanted is activated in the steps (D) and (E) by irradiating laser light. In this step, the crystallization of the region where the P ions are implanted and the activation of the implanted elements are performed simultaneously.
[0070]
In this step, the low-concentration impurity regions 113 and 115 formed by implantation of P ions obtained by mass separation are almost completely amorphized, so that the annealing effect of the laser beam is made uniform at various locations on the substrate. can do.
[0071]
In addition, since the regions 110 and 112 into which P ions are implanted at a high concentration have a large implantation amount, the resistance is sufficiently lowered, and annealing can be performed without any in-plane variation.
[0072]
Next, an interlayer insulating film 116 is formed as shown in FIG. The interlayer insulating film 116 is formed of a silicon oxide film or a silicon nitride film formed by a plasma CVD method.
[0073]
Then, contact holes are formed, and a source electrode 117 and a drain electrode 118 are formed. Finally, heat treatment is performed in a hydrogen atmosphere at 350 ° C. for 1 hour to complete the thin film transistor.
[0074]
[Device Description 1]
The structure of a device for obtaining impurity ions by performing the following mass separation and implanting the ions will be described.
[0075]
FIG. 5 shows a schematic configuration of the apparatus. First, impurity ions are generated from an ion generation source 905. The generated impurity ions are extracted to the acceleration chamber 916 by an extraction system 900 having an extraction electrode. The ions electrically accelerated in the acceleration chamber 916 pass through the magnetic field generated by the magnet 907. The mass is separated from the difference in the Lorentz force received at this time, and the trajectory differs depending on each ion (the generated ions include various types).
[0076]
Each ion having a predetermined trajectory is converged by an electromagnetic lens 909. The required ion trajectory is selected by the slit 910 in the separation chamber 908 and other ions are shielded.
[0077]
The ions selected by the slit 910 are irradiated to the sample placed on the substrate holder (or substrate stage) 912.
[0078]
In the figure, reference numeral 902 denotes a power source for supplying power for generating impurity ions. A power source 903 controls the voltage applied to the extraction electrode. Reference numeral 904 denotes a power source for applying an acceleration voltage.
[0079]
The apparatus as shown in FIG. 5 can select impurity ions to be doped by mass separation.
[0080]
When the crystalline silicon film is doped using the apparatus shown in FIG. 5, the crystallinity of the doped surface can be destroyed with good uniformity. This is the difference in doping effect from the case of using an apparatus as shown in FIG. 4 using ions that are directly extracted from plasma and not mass-separated.
[0081]
[Device Description 2]
The structure of an apparatus for obtaining impurity ions by non-mass separation and implanting the ions will be described below. FIG. 4 shows an outline of the apparatus. This apparatus has a type called a plasma doping apparatus.
[0082]
The plasma doping apparatus shown in FIG. 4 includes an airtight casing 215. The apparatus is provided with an exhaust system 218 for obtaining a required reduced pressure state.
[0083]
Doping is performed by ionizing (plasmaizing) a doping gas with high-frequency energy, electrically extracting ionized ions therefrom, further accelerating them, and injecting them into a sample.
[0084]
The doping gas introduced from the gas introduction system 200 is discharged with good uniformity into the region of the gas discharge ports 206 to 207 and is ionized there.
[0085]
In the region 207, high frequency discharge is performed between the pair of electrodes 206 and 202, and the doping gas is decomposed and ionized. This high frequency discharge is performed by high frequency power supplied from the high frequency power supply 211 via the impedance matching device 210.
[0086]
The ionized dopant ions are extracted to the acceleration region 220 by the extraction electrode 202. The dopant ions extracted to the acceleration region 220 by the extraction electrode 202 are accelerated by the acceleration electrode 203. Further, the injection energy (acceleration voltage) required for the deceleration electrode 208 is adjusted.
[0087]
Each electrode is set to have a potential with reference to the electrode indicated by 209.
[0088]
The dopant ions accelerated in the acceleration region 220 are implanted into the sample 216 with a predetermined acceleration voltage. Note that the stage 217 on which the sample 216 is placed has a mechanism for rotating in order to improve the uniformity of injection.
[0089]
Reference numeral 219 denotes an ammeter for measuring the ion current. The amount of ions injected into the sample 216 can be measured based on the ion current measured by the ammeter 219.
[0090]
In the apparatus shown in FIG. 4, what is indicated by 212 is a power supply for applying an extraction voltage. Reference numeral 213 denotes a power source for applying a deceleration voltage. Reference numeral 214 denotes a power source for applying an acceleration voltage.
[0091]
In order to implement the invention disclosed in this specification using the apparatus illustrated in FIG. 4, first, hydrogen is introduced from the gas introduction system 200 as a doping gas, and hydrogen ions are implanted into the sample 216.
[0092]
The sample is preheated to a predetermined temperature by the implantation of hydrogen ions. Next, the doping gas is switched to a gas containing a predetermined dopant (phosphorus or boron), and the predetermined dopant is doped.
[0093]
The gas containing a predetermined dopant is usually diluted with hydrogen gas to a required concentration.
[0094]
Note that a heating unit may be provided in the stage 217 so that heating by implantation of hydrogen ions is promoted. That is, the heating uniformity may be maintained by implanting hydrogen ions, and the heating means in the stage 217 may be used as an auxiliary.
[0095]
This type of apparatus has a feature that impurity ions can be implanted at once over a large area. In addition, the overall configuration of the apparatus is simple and can be miniaturized.
[0096]
However, since the source gas is turned into plasma and ions are extracted and accelerated by an electric field, it has the following drawbacks.
[0097]
For example, when doping P (phosphorus), PH ₃ (phosphine) and hydrogen gas for dilution are used as source gases. At this time, dopant ions extracted from the source plasma to the acceleration region 220 include many types such as P ⁺ , PH ⁺ , H ⁺ , and H ₂ ⁺ . Then, they are accelerated and implanted into the sample to be doped.
[0098]
When impurity ions are implanted into a crystalline silicon film in such a state, the silicon film is damaged by the implanted ions, but the damage is not uniform and locally. A crystalline component remains. This tendency is particularly strong when light doping is performed as in the formation of an LDD region.
[0099]
In addition, when the surface is rough like a silicon film that has been crystallized or promoted by laser light irradiation, the above tendency becomes even stronger.
[0100]
This state is a main factor of variation in the effect upon activation after impurity ion implantation. Therefore, it is not preferable to use the method of generating implanted ions by non-mass separation as shown in FIG. 4 for forming the LDD region.
[0101]
[Explanation 3 of device]
The outline of an apparatus for irradiating linear laser light is shown below. FIG. 6 is a schematic diagram showing a state in which the amorphous silicon film 1204 is irradiated with laser light 1200 processed into a linear shape by an optical system to be transformed into a crystalline silicon film 1205.
[0102]
In the figure, an amorphous silicon film 1204 is formed on a glass substrate 1203, and the stage 1202 on which the substrate 1203 is placed moves in the direction of an arrow 1206, whereby the laser beam reflected by the mirror 1201 is scanned. It has the composition irradiated.
[0103]
Such a configuration has an advantage that laser light can be irradiated to a large area. However, there are drawbacks that the optical system becomes complicated and that adjustment takes time.
[0104]
As a laser beam used in such an apparatus, a KrF excimer laser (wavelength 248 nm) or a XeCl excimer laser (wavelength 308 nm) can be used.
[0105]
As a form of annealing, there are a step of transforming an amorphous silicon film into a crystalline silicon film, a step of further promoting the crystallinity of the crystalline silicon film, an activation step after implantation of impurity ions, and the like.
[0106]
[Device Description 4]
FIG. 7 shows an apparatus that performs annealing by irradiating spot-like laser light.
[0107]
In the figure, a state in which a rectangular laser beam 700 is reflected by a mirror 701 and is irradiated onto an amorphous silicon film 704 is schematically shown.
[0108]
In the figure, a state in which the amorphous silicon film 704 is transformed into a crystalline silicon film 705 is shown by irradiating a laser beam with a locus as indicated by 707.
[0109]
The silicon film is formed on the glass substrate 703. By moving the stage 702 in the two-dimensional XY direction as indicated by 706, laser light is irradiated along a locus as indicated by 707.
[0110]
The configuration as shown in FIG. 7 is disadvantageous for irradiation to a large area, but has a feature that the optical system is simple and maintenance and adjustment are easy.
[0111]
[Example 2]
The present embodiment is an example in the case where a metal element that promotes crystallization of silicon is used as a means for obtaining a crystalline silicon film in the configuration shown in the first embodiment.
[0112]
Here, Ni (nickel) is used as a metal element that promotes crystallization of silicon. As the metal element having such an action, one or more kinds of elements selected from Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au can be used.
[0113]
In this embodiment, a method using a nickel acetate salt solution is used as a method for introducing Ni. This method has an advantage that the concentration of the nickel element introduced into the silicon film can be adjusted by controlling the concentration of the nickel element in the solution. Further, the apparatus has a simple structure and a simple process.
[0114]
Besides the method using a solution, a CVD method, a sputtering method, an ion implantation method, a vapor deposition method, an adsorption method, and a plasma treatment can be used.
[0115]
The introduction of nickel element is performed as follows. First, a nickel acetate solution adjusted to a predetermined concentration is applied onto an amorphous silicon film (103 in FIG. 1) to form a water film. Then, the excess solution is blown off using a spin coater, and the nickel element is brought into contact with the surface of the amorphous silicon film.
[0116]
The concentration of the nickel element in the solution is such that the concentration of the finally remaining nickel element is 1 × 10 ¹⁶ cm ^{−3 to} 5 × 10 ¹⁹ cm ⁻³ . Care must be taken because the properties as a semiconductor are impaired if nickel elements exceeding this concentration range remain. Further, when the residual concentration is lower than this concentration range, the effect of promoting crystallization cannot be obtained in the first place.
[0117]
Next, heat treatment is performed to crystallize the amorphous silicon film to obtain a crystalline silicon film. This heat treatment is performed at 640 ° C. for 4 hours.
[0118]
The crystalline silicon film obtained in this way is obtained as having higher crystallinity than when no nickel element is used.
[0119]
The crystalline silicon film thus obtained is further irradiated with laser light to promote its crystallinity.
[0120]
A crystalline silicon film is thus obtained. The subsequent steps may be performed according to the process shown in FIG.
[0121]
When a metal element that promotes crystallization of silicon as shown in this embodiment is used, variations in resistance of the low-concentration impurity regions 113 and 115 in FIG. 1 are likely to occur. However, by implanting impurity ions into these low-concentration impurity regions using a method based on mass separation, it is possible to suppress variations in resistance of the 113 and 115 low-concentration impurity regions.
[0122]
This is because impurity ion implantation by a method using mass separation almost completely amorphizes the ion implantation region, so that the reproducibility of the crystallization process by laser light irradiation can be improved. is there.
[0123]
【The invention's effect】
By utilizing the invention disclosed in this specification, a structure in which variation in characteristics does not occur when a large number of thin film transistors are formed over the same substrate can be provided. In the case where an active matrix type liquid crystal display device is configured, it is possible to suppress display unevenness and stripes from being seen.
[Brief description of the drawings]
FIGS. 1A to 1C illustrate a manufacturing process of a thin film transistor. FIGS.
FIGS. 2A and 2B illustrate a manufacturing process of a thin film transistor. FIGS.
FIG. 3 is a diagram showing a state in which a silicon film is irradiated with laser light.
FIG. 4 is a diagram showing an outline of an apparatus for implanting impurity ions.
FIG. 5 is a diagram showing an outline of an apparatus for implanting impurity ions.
FIG. 6 is a diagram showing a state in which laser light irradiation is performed.
FIG. 7 is a diagram showing a state in which laser light irradiation is performed.
FIG. 8 is a photograph showing the surface state of a silicon thin film.
[Explanation of symbols]
101 glass substrate 102 base film (silicon oxide film)
103 Amorphous silicon film 104 Active layer pattern 105 Gate insulating film (silicon oxide film)
106 Gate electrode 107 Porous anodic oxide film 108 Anodized film 109 having a dense film quality Resist mask 110 Source region 111 Region in which impurity ions are not implanted 112 Drain region 113 Low concentration impurity region 114 Channel formation region 115 Low concentration impurity region (LDD region)
116 Interlayer insulating film 117 Source electrode 118 Drain electrode

Claims (5)

In a method for manufacturing a semiconductor device having a source region and a drain region, a channel formation region, and a low concentration impurity region between the source region and the drain region and the channel formation region,
Forming an amorphous silicon film on an insulating substrate;
Irradiating the amorphous silicon film with a first laser beam to form a crystalline silicon film;
Forming a gate insulating film on the crystalline silicon film;
Forming a gate electrode on the gate insulating film;
Impurity ions obtained without mass separation are implanted into the crystalline silicon film in the portions to be the source region and the drain region to form the source region and the drain region,
Impurity ions subjected to mass separation are implanted into the crystalline silicon film in a portion to be the low-concentration impurity region to form the low-concentration impurity region,
A method for manufacturing a semiconductor device , wherein the source region, the drain region, and the low-concentration impurity region are activated and crystallized by irradiation with a second laser beam . In a method for manufacturing a semiconductor device having a source region and a drain region, a channel formation region, and a low concentration impurity region between the source region and the drain region and the channel formation region,
Forming an amorphous silicon film on an insulating substrate;
A heat treatment of the amorphous silicon film to form a crystalline silicon film;
Irradiating the crystalline silicon film with a first laser beam;
Forming a gate insulating film on the crystalline silicon film;
Forming a gate electrode on the gate insulating film;
Impurity ions obtained without mass separation are implanted into the crystalline silicon film in the portions to be the source region and the drain region to form the source region and the drain region,
Impurity ions subjected to mass separation are implanted into the crystalline silicon film in a portion to be the low-concentration impurity region to form the low-concentration impurity region,
A method for manufacturing a semiconductor device , wherein the source region, the drain region, and the low-concentration impurity region are activated and crystallized by irradiation with a second laser beam . In a method for manufacturing a semiconductor device having a source region and a drain region, a channel formation region, and a low concentration impurity region between the source region and the drain region and the channel formation region,
Forming an amorphous silicon film on an insulating substrate;
Forming a film containing a metal element for promoting crystallization of silicon on the amorphous silicon film;
A heat treatment of the amorphous silicon film to form a crystalline silicon film;
Irradiating the crystalline silicon film with a first laser beam;
Forming a gate insulating film on the crystalline silicon film;
Forming a gate electrode on the gate insulating film;
Impurity ions obtained without mass separation are implanted into the crystalline silicon film in the portions to be the source region and the drain region to form the source region and the drain region,
Impurity ions subjected to mass separation are implanted into the crystalline silicon film in a portion to be the low-concentration impurity region to form the low-concentration impurity region,
A method for manufacturing a semiconductor device , wherein the source region, the drain region, and the low-concentration impurity region are activated and crystallized by irradiation with a second laser beam . 4. The method for manufacturing a semiconductor device according to claim 3, wherein the metal element is Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, or Au. 5. The method for manufacturing a semiconductor device according to claim 1, wherein the first laser beam is a linear laser beam. 6.

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