JPH09293679A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a constitution which corrects irregularity in the characteristics of the transistors in the case where a multitude of thin film transistors are formed. SOLUTION: A low-concentration impurity region 115 deped with impurities giving a conductivity type higher than that of a drain region 112 at a low concentration is formed between a channel formation region 114 and the drain region 112. At this time, an impurity ion implantation is performed by a method of using mass separation. By performing such a way, an irregularity in the resistance values of the region 115, which are obtained as the result of activation of the region 115, can be inhibited and a constitution, comprising the characteristics of a multitude of thin film transistors, can be obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD [0001] The invention disclosed in the present specification is:
The present invention relates to a structure of a thin film transistor. Further, the present invention relates to a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, an active matrix type liquid crystal display device has been known. This has a configuration in which a thin film transistor is arranged on each of the pixel electrodes arranged in a matrix.

In such a structure, the unevenness of the displayed screen and the striped pattern become a problem. It is considered that these problems are caused by variations in characteristics of thin film transistors arranged in the active matrix region.

That is, there is a problem in that the characteristics of a thin film transistor, which is formed in a matrix of several hundreds × several hundreds on a glass substrate or a quartz substrate, varies from place to place.

[0005]

According to the research conducted by the present inventors, it is considered that display unevenness and striped patterns are caused by the following mechanism.

In the thin film transistor arranged in the active matrix region, a region called an LDD (lightly doped drain) region is arranged in order to improve the OFF current characteristic.

In this structure, a low-concentration impurity region (generally referred to as an LDD region) in which an impurity imparting a conductivity type is added at a concentration lower than that of the drain region is arranged between the channel forming region and the drain region. have.

The low-concentration impurity region has a function of relaxing a high electric field formed between the channel forming region and the drain region.

The LDD region is constructed to have a weak conductivity type (it must not become 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.

In general, a crystalline silicon film (generally referred to as a polycrystalline silicon film or a microcrystalline silicon film) obtained by irradiation with laser light is used as a silicon film forming a thin film transistor.

The crystalline silicon film utilizing the irradiation of this laser light has irregularities formed on its surface.

FIG. 8 shows a photograph of the unevenness observed by an atomic force microscope. FIG. 8 is a photograph showing the surface state of the silicon film irradiated with laser light.

As a method of irradiating a large area with a laser beam with high efficiency, there is a technique of irradiating a beam with a beam-processed laser beam. Even when this technique is used, the above-mentioned surface irregularities are formed.

FIG. 3 schematically shows this phenomenon. FIG. 3 shows that a pulse oscillation type excimer laser beam (having a long shape in the depth direction and the front side of the drawing) linearly beam-formed to the amorphous silicon film 303 is used.
This is the state when scanning is performed in the direction indicated by 00 and irradiation is performed.

In FIG. 3, reference numeral 301 is a substrate. Usually, a glass substrate is used as the substrate. 302 is a base film. A silicon oxide film is used as the base film.
304 is a region after laser light irradiation,
It is a region crystallized by the irradiation of laser light.

In this situation, roughness (unevenness) indicated by 305 is formed on the trace of the laser beam irradiation. This rough state depends on the heating temperature, the irradiation energy density, the oscillation frequency, the scan speed, and the amorphous silicon film when the laser beam is irradiated.

In the drawings, the roughness is shown as if it were formed at equal intervals, but in reality the intervals are random.

This roughness is also formed when the amorphous silicon film is crystallized by heating and further annealed by irradiation with laser light.

Further, when an annealing method using a linear laser beam is used, it is observed that a striped pattern is displayed on the completed liquid crystal panel.

The striped pattern reflects variations in characteristics of thin film transistors arranged in the active matrix circuit. This is supported by the large variation in resistance in the LDD region.

The variation in the LDD region is much larger than the variation in the resistance of the source and drain regions.

This is because the plasma doping method known as a means for doping a large area is used and the impurity ions are implanted at a low dose amount.

The plasma doping method is a method of extracting ions for accelerated implantation using plasma and electrically accelerating the ions to implant them in a doped region.

In this method, the crystallinity of the irradiated region is likely to be non-uniform because the implanted ions contain various types of ions. In other words, the component having microcrystalline properties tends to remain unspecified.

This tendency is particularly remarkable when the LDD region is doped with a low dose amount.

The abundance density of this microcrystalline component has a large in-plane variation. Therefore, in the annealing process by the irradiation of the laser beam performed after the implantation of the impurity ions, the variation of the crystal state is reflected as it is, and the resistance value becomes different in the partial portion.

In this way, the LD for each pixel is
The variation in resistance in the D region becomes large.

Further, the surface roughness caused by the irradiation of the laser beam in obtaining the above-mentioned crystalline silicon film causes the above LDD.
This promotes the variation in the resistance of the area. That is, the roughness of the surface state as shown in FIG. 3 greatly promotes the dispersion of the resistance value when forming the LDD region.

Further, there is known a method of obtaining a crystalline silicon film by utilizing a metal element such as nickel which promotes crystallization of silicon as described in JP-A 06-232059. By using this method, it is possible to obtain a crystalline silicon film having high crystallinity by a treatment at a heating temperature lower than that in the past. However, when this method is used, the presence of the metal element also contributes to the variation in the resistance value of the LDD region.

The above metal element has the property of becoming a nucleus during crystallization. This property naturally appears during laser annealing. Therefore, when the 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 the activation annealing by the laser light irradiation. Will be further promoted.

That is, the method of obtaining a crystalline silicon film by utilizing a metal element that promotes crystallization of silicon has the significance that high crystallinity can be obtained, while the resistance value varies in the LDD region. It has a function of promoting the variation of the resistance value in the region where the phenomenon is likely to occur.

[0032]

SUMMARY OF THE INVENTION An object of the invention disclosed in this specification is to provide a structure in which variations in characteristics do not occur when a large number of thin film transistors are manufactured over the same substrate.

[0033]

According to the findings of the present inventors, the largest contribution to the variation in the resistance value of the LDD region is the variation in the crystalline state due to the residual microcrystalline component in the doping process. It is in.

Therefore, the invention disclosed in this specification is based on LDD.
When forming the region, a method of mass-separating the implantation of impurity ions is used.

By doing so, when a process using laser light irradiation or a process using a metal element that promotes crystallization of silicon is used, the resistance value of the low-concentration impurity region represented by the LDD region is reduced. Variations can be corrected.

One of the inventions disclosed in this specification has a low-concentration impurity region in which an impurity imparting a conductivity type is added at a low concentration between the channel formation region and the drain region, Mass-separated impurity ions are implanted into the low-concentration impurity region, and the surface of the low-concentration impurity region has unevenness formed by laser light irradiation.

According to another aspect of the invention, a low concentration impurity region in which an impurity imparting a conductivity type is added at a lower concentration than the drain region is provided between the channel forming region and the drain region. Is characterized by being manufactured by implanting impurity ions separated by mass and then irradiating laser light.

Further, in the above-mentioned structure, the metal element for promoting the crystallization of silicon is 1 × 10 ¹⁶ cm in the low concentration impurity region.
It is characterized in that it is contained at a concentration of ^{−3 to} 5 × 10 ¹⁹ cm ⁻³ .

According to another aspect of the invention, there is provided a step of forming a low concentration impurity region in which an impurity imparting a conductivity type is added between the channel forming region and the drain region at a lower concentration than in the drain region. The low-concentration impurity region is characterized by being manufactured by implanting mass-separated impurity ions and then irradiating laser light.

According to another aspect of the present invention, there is provided a step of forming a crystalline silicon film using laser light irradiation and a step of forming an active layer using the crystalline silicon film. The formation of the active layer includes a step of doping an impurity imparting a conductivity type between the channel formation region and the drain region at a lower concentration than that of the drain region, and in the step, implantation of impurity ions subjected to mass separation is performed. Then, laser light irradiation is performed.

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION In a manufacturing process of a thin film transistor in which an LDD region is arranged, impurity ions are implanted by implanting impurity ions generated by mass separation. When the impurity ions formed by mass separation are acceleratedly implanted, the region where the impurity ions are implanted becomes substantially amorphous. Therefore, even if it is an LDD region in which impurities are implanted at a low concentration, the annealing effect by laser light irradiation can be made uniform. As a result, the resistance variation in the LDD region can be reduced.

This structure is particularly effective for manufacturing a thin film transistor using a crystalline silicon film obtained by irradiating 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 in the impurity ion implantation and the subsequent laser annealing process. This is because it is easy to realize.

If a source region and a drain region other than the LDD region are formed, an impurity ion implantation method of directly extracting ions from plasma can be used. This is because in the source and drain regions where impurities are implanted at a high concentration, potential unevenness of crystallization does not easily appear as a variation in resistance value in the crystallization process by irradiation with laser light.

[0044]

【Example】

[Embodiment 1] FIG. 1 shows a manufacturing process of a thin film transistor having an LDD region. First, a silicon oxide film is formed as a base film 102 on a glass substrate 101 by a sputtering method at 3000
The film is formed to a thickness of Å. A quartz substrate may be used as the substrate. (Fig. 1 (A))

Next, an amorphous silicon film 103 is formed to a thickness of 500Å by a low pressure thermal CVD method. A plasma CVD method may be used as a method for forming the amorphous silicon film.

Next, heat treatment is performed to crystallize the amorphous silicon film to obtain a crystalline silicon film (not shown). Further, by scanning and irradiating a laser beam linearly processed into a beam, the crystallinity of a crystalline silicon film (not shown) is promoted.

Further, it is effective to further perform heat treatment after the irradiation of the laser beam. This heat treatment has the effect of relaxing the stress in the film generated at the time of laser light irradiation and reducing defects.

Next, patterning is performed to form the active layer 104 of the thin film transistor. Thus, FIG.
The state shown in (B) is obtained.

Next, as the gate insulating film 105, a silicon oxide film having a thickness of 1000 Å is formed by the plasma CVD method.

Further, an aluminum film (not shown) for forming a gate electrode is formed to a thickness of 4000Å by a sputtering method. (This aluminum film is the gate electrode 1
It becomes the starting film that constitutes 06)

Scandium is contained in this aluminum film.
Contains 0.12% by weight. This is to suppress the generation of hillocks and whiskers due to abnormal growth of aluminum in the subsequent process.

Hillocks and whiskers are angular or needle-like protrusions formed by abnormal growth of aluminum.

Next, by performing anodic oxidation, an anodic oxide film having a dense film quality (not shown) is formed. This step is performed by using a 3% oxalic acid aqueous solution as an electrolytic solution, and passing an electric current between the two electrodes in the solution using an aluminum film as an anode and platinum as a cathode. The film thickness can be controlled by the applied voltage. Here, the film thickness of the anodic oxide film having a dense film quality (not shown) is set to 10
0 °.

Next, the resist mask 109 is arranged and the aluminum film is patterned. Thus, a prototype of the gate electrode 106 shown by 106 in FIG. 1C is formed.

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)

Then, by performing anodic oxidation again,
A porous anodic oxide film 107 is formed. Here, an aqueous solution containing 3% oxalic acid is used as the electrolytic solution.
This porous anodic oxidation is also carried out by using an aluminum pattern as an anode and platinum as a cathode and applying a current between both electrodes.

In this step, the electrolytic solution does not come into contact with the upper surface of the aluminum pattern due to the existence of the resist mask 109. Therefore, as shown by 107 in FIG. 1C, an anodic oxide film is formed on the side surface of the gate electrode 106.

The thickness of the porous anodic oxide film 107 can be controlled by the anodic oxidation time. The thickness of the porous anodic oxide film 107 can be up to about 2 μm. Here, the film thickness is set to 5000 Å
And

Thus, the state shown in FIG. 1C is obtained. Next, the resist mask 109 is removed, and anodic oxidation is performed again under the condition that an anodic oxide film having a dense film quality is formed.

In this anodic oxidation step, the anodic oxide film 108 having a dense film quality is formed to a thickness of 1000Å. In this step, the gate electrode 106 is defined.
In this step, the electrolytic solution penetrates into the porous anodic oxide film 107. Therefore, the anodic oxide film 108 having a dense film quality is formed around the gate electrode 106.

Next, P ions are implanted by using the apparatus shown in FIG. 4 (the structure of which will be described later). The dose amount is 2 × 10 ¹⁵
/ Cm ² . In this step, P ions are implanted in the regions 110 and 112 in a self-aligned manner. Where 1
The area 10 is the source area. Further, the region 112 becomes the drain region. Impurity ions are not implanted into the region 111.

The apparatus shown in FIG. 4 uses non-mass separation to
It has a form of obtaining dopant ions. That is, the structure is such that the impurity ions obtained without mass separation are accelerated and injected.

Since this is the step of implanting the source and drain regions in which the impurity ions are implanted at a high concentration,
Non-mass separation methods may be used. Of course, this step may be carried out by means of mass separation.

Next, the resist mask 10 having a porous shape is formed.
7 is removed, and P ions are implanted again. This P ion implantation has a dose amount of 0.5 to 1 × 10 ¹⁴ / cm ^2.
Do as.

The step of implanting impurity ions at a relatively low concentration uses an apparatus of the type shown in FIG. 5 in which dopant ions are selected by mass separation.

When this device is used, only P ⁺ ions can be selected and implanted. Then, the P ion-implanted region can be almost completely made amorphous.

That is, the regions 113 and 115 which are lightly doped (compared to the source / drain) can be made almost completely amorphous. The regions 113 and 115 are low-concentration impurity regions. In particular, a region denoted by 115 on the drain side is an LDD (lightly doped drain) region. (FIG. 1 (E))

In the above process, the channel forming region 114 is defined.

Thereafter, laser light irradiation is performed to activate the regions into which the impurity ions have been implanted in the steps (D) and (E). In this step, crystallization of the region where P ions are implanted and activation of the implanted element are performed simultaneously.

In this step, the low-concentration impurity region 1 formed by implanting P ions obtained by mass separation
Since 13 and 115 are almost completely amorphized, the annealing effect of the laser light can be made uniform in various parts of the substrate.

Further, P ions were implanted at a high concentration 11
Since the regions 0 and 112 have a large implantation amount, the resistance is sufficiently low, and annealing can be performed without causing in-plane variations.

Then, as shown in FIG. 2, the interlayer insulating film 116 is formed.
To form The interlayer insulating film 116 is formed of a silicon oxide film or a silicon nitride film formed by a plasma CVD method.

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.

[Explanation 1 of Apparatus] The configuration of an apparatus for obtaining ions of impurities by performing the following mass separation and implanting the ions will be described.

FIG. 5 shows a schematic structure of the apparatus. First, the impurity ions are generated from the ion generation source 905. The generated impurity ions are extracted into the acceleration chamber 916 by the extraction system 900 equipped with extraction electrodes. And acceleration room 9
The ions electrically accelerated by 16 pass through the magnetic field generated by the magnet 907. Due to the difference in Lorentz force received at this time, they are mass-separated, and their trajectories are different for each ion (the generated ions include various kinds).

Each ion having a predetermined orbit is converged by the electromagnetic lens 909. Then, a slit 910 in the separation chamber 908 selects a required ion trajectory, and shields other ions.

The ions selected by the slit 910 are applied to the sample placed on the substrate holder (or substrate stage) 912.

In the figure, 902 is a power supply for supplying electric power for generating impurity ions. A power source 903 controls the voltage applied to the extraction electrode. 904
Is a power supply for giving an accelerating voltage.

The device as shown in FIG. 5 can select impurity ions to be doped by mass separation.

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 point is the difference in the doping effect from the case of using the apparatus as shown in FIG. 4 which uses the mass-separated ions directly extracted from the plasma.

[Description of Apparatus 2] The configuration 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 device. This device is
It has a type called a plasma doping apparatus.

The plasma doping apparatus shown in FIG. 4 comprises a housing 215 having airtightness. The equipment includes
An exhaust system 218 for arranging the required reduced pressure state is arranged.

The doping is performed by ionizing (plasmaizing) the doping gas by high frequency energy, electrically extracting the ionized ions from the ionization gas, further accelerating the ionized ion, and injecting it into the sample.

The doping gas introduced from the gas introduction system 200 is uniformly emitted to the regions of the gas emission ports 206 to 207 and ionized there.

In the region 207, a pair of electrodes 206 and 2
A high-frequency discharge is performed between the two and the doping gas is decomposed and ionized. This high-frequency discharge is generated by the high-frequency power source 211 from the impedance matching device 21.
It is performed by the high frequency power supplied via 0.

The ionized dopant ions are extracted to the acceleration region 220 by the extraction electrode 202.
Then, 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.

The potential of each electrode is set with reference to the electrode indicated by 209.

The dopant ions accelerated in the acceleration region 220 are implanted into the sample 216 with a predetermined acceleration voltage. The stage 217 on which the sample 216 is placed has a rotating mechanism in order to improve the uniformity of injection.

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.

In the apparatus shown in FIG. 4, reference numeral 212 is a power source for applying the extraction voltage. Also, 2
Reference numeral 13 is a power source for applying a deceleration voltage. Reference numeral 214 is a power supply for applying an acceleration voltage.

In order to carry out the invention disclosed in this specification using the apparatus shown in FIG. 4, hydrogen is first introduced as a doping gas from the gas introduction system 200, and hydrogen ions are implanted into the sample 216. .

By this hydrogen ion implantation, the sample is preheated to a predetermined temperature. Next, switch the doping gas to a gas containing the specified dopant (phosphorus or boron),
Doping with a predetermined dopant is performed.

The gas containing the predetermined dopant is
It is usually diluted with hydrogen gas to the required concentration.

A heating means may be arranged in the stage 217 to promote heating by implantation of hydrogen ions. That is, the uniformity of heating may be maintained by implanting hydrogen ions, and the heating means in the stage 217 may be used supplementarily.

The device of this type has a feature that it is possible to implant impurity ions collectively over a large area. Further, it has a feature that the whole structure of the device is simple and can be downsized.

However, the source gas is turned into plasma,
Due to the method of extracting and accelerating ions by an electric field, it has the following drawbacks.

For example, when doping P (phosphorus), PH ₃ (phosphine) and hydrogen gas for dilution are used as source gases. At this time, the dopant ions extracted from the source plasma to the acceleration region 220 include a large number of types such as P ⁺ , PH ⁺ , H ⁺ , and H ₂ ⁺ . Then, they are acceleratedly injected into the sample to be doped.

When the impurity ions are implanted into the crystalline silicon film in such a state, the silicon film is damaged by the implanted ions, but the damage is not uniform. The crystal component remains locally. This tendency is particularly strong when light doping is performed as in the formation of LDD regions.

If the surface is roughened like a silicon film crystallized by laser light irradiation, or promoted for crystallization, the above tendency becomes stronger.

This state is the main cause of variations in the effect upon activation after the impurity ion implantation. Therefore, LD
It is not preferable to use the method of generating implanted ions by non-mass separation as shown in FIG. 4 for forming the D region.

[Explanation 3 of Apparatus] An outline of an apparatus for irradiating a linear laser beam is shown below. FIG. 6 is a schematic drawing showing a state in which the amorphous silicon film 1204 is irradiated with a laser beam 1200 linearly processed by an optical system to be transformed into a crystalline silicon film 1205.

In the figure, the amorphous silicon film 1204 is formed on the glass substrate 1203, and the stage 1202 on which the substrate 1203 is placed moves in the direction of arrow 1206, whereby the laser light reflected by the mirror 1201 is reflected. Is scanned and irradiated.

Such a structure has an advantage that a large area can be irradiated with laser light. However, there are drawbacks in that the optical system becomes complicated and the adjustment is time-consuming.

The laser light used in such an apparatus is a KrF excimer laser (wavelength 248 nm) or X-ray.
An eCl excimer laser (wavelength 308 nm) can be used.

The form of annealing includes a step of transforming the 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. .

[Explanation 4 of Apparatus] FIG. 7 shows an apparatus for performing annealing by irradiating a spot-shaped laser beam.

The figure schematically shows a state in which a rectangular laser beam 700 is reflected by a mirror 701 to irradiate the amorphous silicon film 704.

The figure shows a state in which the amorphous silicon film 704 is transformed into a crystalline silicon film 705 by irradiating the laser beam with a locus shown by 707.

The silicon film is formed on the glass substrate 703, and the stage 702 is two-dimensional XY as shown by 706.
By moving in the direction, the laser light is emitted along the locus shown by 707.

The structure as shown in FIG. 7 is disadvantageous in irradiating a large area, but is characterized by a simple optical system and easy maintenance and adjustment.

[Embodiment 2] This embodiment is an example in which a metal element that promotes crystallization of silicon is used as a means for obtaining a crystalline silicon film in the structure shown in Embodiment 1.

Here, Ni (nickel) is used as a metal element that promotes crystallization of silicon. Fe, Co, Ni, R are metal elements having such an action.
One or a plurality of elements selected from u, Rh, Pd, Os, Ir, Pt, Cu, and Au can be used.

In this example, as a method of introducing Ni, a method using a nickel acetate salt solution is used. 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, there is a feature that the structure of the device is simple and the process is simple.

Other than the method using a solution, a CVD method, a sputtering method, an ion implantation method, a vapor deposition method, an adsorption method, or a plasma treatment can be used.

The nickel element is introduced as follows. First, a nickel acetate salt 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 by using a spin coater, so that the nickel element is held in contact with the surface of the amorphous silicon film.

Regarding the concentration of nickel element in the solution, the concentration of the nickel element remaining finally is 1 × 10 ¹⁶ cm ^-3.
The concentration is set to 5 × 10 ¹⁹ cm ^-3 . It is necessary to be careful because if the nickel element in the concentration range or higher remains, the properties as a semiconductor will be impaired. Further, when the residual concentration is less than this concentration range, the effect of promoting crystallization cannot be obtained in the first place.

Next, heat treatment is performed to crystallize the amorphous silicon film to obtain a crystalline silicon film. This heat treatment is 640
It is carried out under conditions of 4 ° C. and 4 hours.

The crystalline silicon film thus obtained is
It is obtained as having higher crystallinity as compared with the case where nickel element is not used.

The crystalline silicon film thus obtained is further irradiated with laser light to promote its crystallinity.

Thus, a crystalline silicon film is obtained. Subsequent steps may be performed according to the process shown in FIG.

When a metal element that promotes crystallization of silicon as shown in this embodiment is used, the resistance of the low-concentration impurity regions 113 and 115 in FIG. 1 tends to vary. However, by implanting impurity ions into these low-concentration impurity regions by using a method based on mass separation, 113 or 11
It is possible to suppress variations in resistance in the low concentration impurity region 5 of FIG.

This is because the implantation of impurity ions by the method using mass separation almost completely amorphizes the ion implantation region, so that the reproducibility of the crystallization process by laser light irradiation is high. Because you can.

[0123]

By utilizing the invention disclosed in this specification, it is possible to provide a structure in which variations in characteristics do not occur when a large number of thin film transistors are formed on the same substrate. Then, when an active matrix type liquid crystal display device is configured, it is possible to suppress the display unevenness and the appearance of stripe patterns.

[Brief description of drawings]

FIG. 1 illustrates a manufacturing process of a thin film transistor.

FIG. 2 illustrates a manufacturing process of a thin film transistor.

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 condition 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 Anodizing with Dense Film Quality Film 109 Resist mask 110 Source region 111 Region where 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 (6)

[Claims] 1. A low-concentration impurity region in which an impurity imparting a conductivity type is added at a lower concentration than a drain region is provided between a channel forming region and a drain region, and the low-concentration impurity region is subjected to mass separation. A semiconductor device, in which impurity ions are implanted, and the surface of the low-concentration impurity region has irregularities formed by laser light irradiation. 2. A low concentration impurity region in which an impurity imparting a conductivity type is added at a lower concentration than the drain region is provided between the channel forming region and the drain region, and the low concentration impurity region is mass-separated. A semiconductor device manufactured by implanting impurity ions and then irradiating laser light. 3. The low concentration impurity region according to claim 1 or 2, wherein a metal element which promotes crystallization of silicon is 1 ×.
A semiconductor device, which is contained at a concentration of 10 ¹⁶ cm ^{−3 to} 5 × 10 ¹⁹ cm ⁻³ . 4. A process for producing a low-concentration impurity region in which an impurity imparting a conductivity type is added at a low concentration between a channel forming region and a drain region, the low-concentration impurity region comprising: A method for manufacturing a semiconductor device, which is manufactured by implanting impurity ions that have been subjected to mass separation and then irradiating laser light. 5. A step of forming a crystalline silicon film using laser light irradiation, and a step of forming an active layer using the crystalline silicon film, wherein the formation of the active layer is performed. A step of doping an impurity imparting a conductivity type between the channel formation region and the drain region at a lower concentration than that of the drain region, and in the step, the ion implantation of the impurity ions subjected to the mass separation and the subsequent laser light irradiation are performed. A method for manufacturing a semiconductor device, wherein irradiation is performed. 6. The method for manufacturing a semiconductor device according to claim 5, wherein the irradiation of the laser light is performed by using a linearly processed beam.