JPH1187724A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for a semiconductor device of high performance and reliability, wherein the manufacturing process is simpler and throughput is improved. SOLUTION: A gate insulating film 5 is formed on an a-Si film 3 formed on a light-transmitting glass substrate 1. Then, impurity ions are implanted into a specified region on the gate insulating film 5 with a resist film 6 as a mask, and energy beam is emitted from the light-transmitting glass substrate 1 side to the a-Si film 3. Thus, the a-Si film 3 is crystallized to form a p-Si film 4, while the impurity ions implanted into a source region (a-Si) 3b and a drain region (a-Si) 3c are activated. As a result, a TFT of high performance and reliability is manufactured, while a method for manufacturing a TFT, wherein manufacturing process is simplified and throughput is significantly improved, is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display (L).
liquid Crystal Display: hereinafter referred to as “LCD”. The present invention relates to a method for manufacturing a semiconductor element such as a thin film transistor (hereinafter, referred to as “TFT”) used in the above method.

[0002]

2. Description of the Related Art In recent years, TFTs have been used as pixel switching elements and image sensors in active matrix type LCDs, and SRAMs (Static Rads).
nd Access Memory).

In particular, polycrystalline silicon (Polycrys)
talline Silicon: hereinafter referred to as “p-Si”. For example, when the TFT is manufactured by a low-temperature process in which the maximum temperature of the process is 450 ° C. or less, a large-area and inexpensive glass substrate can be used. Therefore, the development of the p-Si type TFT-LCD of the above-mentioned low-temperature process has been actively carried out, and some of them have been put into practical use.

Further, the p-Si type TFT as described above is
Since the source and drain regions are formed in a self-aligned manner by ion doping using the gate electrode as a mask, not only miniaturization and reduction of the parasitic capacitance between the gate and drain can be achieved, but also amorphous silicon (Amorphous Silo)
icon: Hereinafter, referred to as “a-Si”. It has a characteristic that the carrier mobility is larger than that of the TFT. Therefore, when the p-Si type TFT is applied to, for example, an active matrix type LCD, the p-Si type TFT is used.
Can be used not only for the switching elements of each pixel but also for a high-speed driver circuit for driving these switching elements. In this case, by forming the pixel and the driver circuit integrally and incorporating them on the same substrate, LC
D can be reduced in cost and higher in definition. For the above reasons, the development of LCDs has been proceeding in a direction in which a driver circuit for pixels is built on the same substrate.

Hereinafter, a conventional example of a method for manufacturing the p-Si type TFT will be described. FIG. 3 is a schematic sectional view illustrating a method for manufacturing a p-Si type TFT.

First, a base insulating film 111 is formed on a translucent glass substrate 1 having a strain point of about 600 ° C. Next, after forming an a-Si film on the base insulating film 111, it is crystallized by laser annealing or the like to form a p-Si film 113, which is patterned into an island shape. Furthermore, p-Si
A gate insulating film 114 is formed over the film 113. Further, a conductive metal thin film to be the gate electrode 116 is formed on the gate insulating film 114, and is patterned into a predetermined shape. Next, using the gate electrode 116 as a mask,
Impurity ions such as phosphorus or boron are implanted into the p-Si film 113 by an ion doping method.
Next, a channel region 113a, a source region 113b, and a drain region 113c are formed (see FIG. 3A).

Further, the impurity ions are activated by performing a thermal annealing process in an atmosphere of 300 ° C. to 600 ° C. for a few hours to several tens of hours in an apparatus such as an annealing furnace. That is, recovery of lattice defects caused by impurity ion implantation and substitution of the implanted impurity ions with lattice positions are performed (see FIG. 3B).

Subsequently, an interlayer insulating film 117 is formed.
Contact holes 118 are opened. further,
A conductive metal thin film is formed and patterned into a predetermined shape to form a source electrode 119 and a drain electrode 1.
20 is formed. Finally, for the p-Si film 113,
When plasma hydrogenation is performed in a hydrogen plasma atmosphere at a temperature of 350 ° C. and a processing time of 2 hours, a p-Si type TFT is completed (see FIG. 3C).

Here, the activation of the impurity ions is required for the following reasons. That is, if the implanted impurity ions are not replaced at the lattice positions, the impurity ions cannot be a source of electrons and holes, and therefore the number of carriers that can move around the crystal decreases, and T
FT characteristics are degraded. Therefore, it is necessary to replace the impurity ions implanted into the source region 113b and the drain region 113c with the lattice positions of the silicon crystal. Also,
In the p-Si film 113, the channel region 113a
Does not have impurity ions implanted, thereby maintaining the crystallinity, whereas the source region 113b and the drain region 11
In 3c, crystallinity is impaired by ion bombardment when impurity ions are implanted, and many lattice defects occur. Thereby, for example, the sheet resistance of the source region 113b and the drain region 113c increases, and the TFT characteristics deteriorate. Further, the source region 1 is formed by the ion bombardment.
In some cases, the upper layer portions of the drain region 13b and the drain region 113c become amorphous. In this case, the resistance of the contact portion between the source region 113b and the drain region 113c and the source electrode 119 and the drain electrode 120 may be increased.

Further, at the interface between the p-Si film 113 and the gate insulating film 114 and at the crystal grain boundaries of the p-Si film 113,
There are traps, levels, dangling bonds, and the like. In particular, at the boundary between the channel region 113a and the source region 113b and the drain region 113c, the order of the crystal structure is different depending on the presence or absence of impurity ions. Therefore, the crystal structure near these boundaries changes continuously. Therefore, many of the above defects are likely to occur. For this reason, the initial characteristics and reliability of the TFT tend to decrease. Therefore, the above-described activation is necessary in order to replace the impurity ions at the lattice positions and to restore the crystallinity of the lattice defect, the amorphous portion, and the like as described above.

The activation of the impurity ions is generally performed by
Although heat treatment at a high temperature close to 1,000 ° C. is preferable, when an inexpensive glass substrate is used, activation annealing cannot be performed at a temperature equal to or higher than the strain point temperature of the glass substrate. Therefore, as described above, a relatively low temperature (300 ° C. to 600 ° C.)
℃), and long-time thermal annealing is often performed. Also,
As another method for activating the impurity ions, a laser annealing method of locally irradiating a laser beam in a short time to impart energy to a p-Si film is also used.

[0012]

However, since the thermal annealing is performed at a low temperature, it takes a long time to activate the impurity ions. In addition, it is difficult to sufficiently activate the amorphous portion until the amorphous portion is recovered. Therefore, there is a problem that the throughput in the manufacture of the TFT is reduced, and it is difficult to improve the initial characteristics and reliability of the TFT.

On the other hand, when the activation annealing is performed by the laser annealing method, since the laser light is shielded by the gate electrode 116, the channel region 113a and the
The vicinity of the boundary between the source region 113b and the drain region 113c is hardly activated, and it is very difficult to continuously change the crystallinity over these regions. There is a problem that it causes a decrease.

Further, in the conventional method for manufacturing a TFT, p
Since the gate insulating film 114 is formed after the Si film 113 is patterned in a stripe shape, impurities are likely to be mixed or adsorbed at the interface between the p-Si film 113 and the gate insulating film 114. It is difficult to obtain a clean and low-defect interface like a transistor manufactured over a substrate. Therefore, there is also a problem that it is difficult to further improve the characteristics and the like of the TFT.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to simplify the manufacturing process and greatly improve the throughput, and to manufacture a high-performance and highly reliable semiconductor device. It is to provide a method.

[0016]

Means for Solving the Problems The present inventors diligently studied a method of manufacturing a semiconductor device in order to solve the above conventional problems. As a result, after previously implanting impurity ions into the amorphous semiconductor layer using the ion shielding film as a mask,
Irradiating an energy beam from the substrate side to crystallize the amorphous semiconductor layer to form a crystalline semiconductor layer,
The inventors have found that the method for manufacturing a semiconductor device that activates the impurity ions can simplify the manufacturing process and significantly improve the throughput, and can provide a semiconductor device with high performance and high reliability, thereby completing the present invention. Reached.

That is, according to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of: forming an amorphous semiconductor layer on a substrate; An ion shielding film forming step of forming an ion shielding film in a predetermined first region on the amorphous semiconductor layer; and forming an ion shielding film in the second region of the amorphous semiconductor layer which is not shielded by the ion shielding film. An impurity ion implanting step of implanting ions, and irradiating the first region and the second region in the amorphous semiconductor layer with an energy beam from the substrate side to crystallize the amorphous semiconductor layer. Forming a crystalline semiconductor layer and activating the impurity ions.

According to the above-described method, the amorphous semiconductor layer is melted and crystallized in the crystalline semiconductor layer forming step, and lattice defects caused by ion bombardment when impurity ions are implanted are recovered. Since the ions are replaced at the lattice positions and activated, the step of forming the crystalline semiconductor layer and the step of activating the impurity ions, which were conventionally required, can be performed at once, and the manufacturing process can be simplified. ,
It enables a significant improvement in throughput.

In addition, since the energy beam is irradiated from the substrate side, the energy beam is not blocked by the ion shielding film. Therefore, the boundary between the first region into which impurity ions are implanted and the second region into which impurity ions are not implanted. The vicinity of the part can also be activated.

Further, since the amorphous semiconductor layer is crystallized after the impurity ions are implanted into the amorphous semiconductor layer, the activation rate of the impurity ions can be further improved.
In addition, lattice defects and amorphous portions do not occur due to the implantation of the impurity ions, and even if damage or defects due to the implantation of the impurity ions occur in the amorphous semiconductor layer, the crystal semiconductor layer forming step is performed thereafter. Since the crystalline semiconductor layer is formed by the above, the damage and the defect can be eliminated.

Therefore, a semiconductor device with improved initial characteristics and reliability can be obtained.

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to the first aspect, wherein the step of forming a crystalline semiconductor layer comprises the step of forming an amorphous semiconductor layer. Irradiating the first region and the second region with an energy beam having a first energy density capable of crystallizing the second region, thereby crystallizing the second region; The first region and the second region in the semiconductor layer can be crystallized in the first region and irradiated with an energy beam having a second energy density higher than at least the first energy density, so that the first region is crystallized. Crystallizing step.

According to the above method, the first region is crystallized after the second region in the amorphous semiconductor layer is crystallized using the difference in melting point between the first region and the second region. Therefore, crystal growth proceeds in the direction of the first region with the crystal grains formed in the second region as nuclei.

Thus, a crystalline semiconductor layer having large crystal grains can be formed, and a crystal structure that has continuously changed from the first region to the second region, in which the order of the crystal structure differs depending on the presence or absence of impurity ions, can be obtained. Can be formed. Therefore, in the vicinity of the boundary, the occurrence of crystal lattice mismatch, traps, levels, and the like can be reduced, and a semiconductor element having a favorable boundary can be obtained.

According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to the first aspect, wherein the crystalline semiconductor layer forming step is performed by irradiating the energy beam with the energy beam. Thus, the crystal is grown from the second region to the first region.

According to the above method, the crystal growth proceeds in the direction of the first region with the crystal grains formed in the second region as nuclei, so that a crystalline semiconductor layer having large crystal grains can be formed and impurities can be formed. A continuously changed crystal structure can be formed from the first region to the second region in which the order of the crystal structure differs depending on the presence or absence of ions. Therefore, in the vicinity of the boundary, the occurrence of crystal lattice mismatch, traps, levels, and the like can be reduced, and a semiconductor element having a favorable boundary can be obtained.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to the first or second aspect, wherein the step of forming a crystalline semiconductor layer comprises the steps of: When the ion shielding film is made of a material capable of reflecting an energy beam, the ion shielding film is performed in a state where the ion shielding film is present.

According to the above-described method, when at least a part of the energy beam irradiated from the substrate side passes through the amorphous semiconductor layer over at least the entire surface of the amorphous semiconductor layer, the ion shielding film causes the ion shielding film to close the crystalline semiconductor layer side. Is reflected to This allows
The amorphous semiconductor layer is further heated by the reflected energy beam, so that the energy density of the energy beam during irradiation can be reduced.

According to a fifth aspect of the invention, there is provided a method of manufacturing a semiconductor device according to the fourth aspect, wherein the ion shielding film is a gate electrode in order to solve the above problem. I do.

According to the above method, since the gate electrode is used as an ion shielding film, the second region is formed in a self-aligned manner when impurity ions are implanted using the gate electrode as a mask. As a result, the process of separately forming the ion shielding film and the gate electrode becomes unnecessary in addition to the reduction of the parasitic capacitance and miniaturization of the TFT, so that the manufacturing process can be further simplified.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to the first or second aspect of the present invention, wherein the method comprises the steps of: And a step of forming a reflection layer for reflecting the energy beam in a predetermined region on the amorphous semiconductor layer.

According to the above-described method, the energy density of the energy beam at the time of irradiation can be reduced as in the case where the ion shielding film is made of a material capable of reflecting the energy beam. Further, a thin film more suitable for shielding impurity ions can be formed as an ion shielding film, and a thin film more suitable for reflecting an energy beam can be formed as a reflection layer.

According to a seventh aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to the first or second aspect of the present invention, wherein the method comprises: A peeling step of peeling the ion shielding film, and a heat holding layer for holding heat generated when the amorphous semiconductor layer is heated by an energy beam in a predetermined region on the amorphous semiconductor layer. And a step of forming

According to the above-described method, the energy density of the energy beam at the time of irradiation can be reduced, similarly to the case where a material that holds the energy beam as heat is used as the ion shielding film. In addition, a thin film more suitable for shielding impurity ions can be formed as an ion shielding film, and a thin film more suitable for holding an energy beam as heat can be formed as a heat retaining layer.

According to a eighth aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to any one of the first to seventh aspects, wherein the amorphous semiconductor is provided to solve the above problem. A gate insulating film forming step of forming a gate insulating film on the amorphous semiconductor layer formed by the layer forming step, wherein the crystalline semiconductor layer forming step is performed after the gate insulating film forming step. I do.

According to the above method, the crystalline semiconductor layer is
Since the amorphous semiconductor layer is formed by crystallization after the formation of the gate insulating film, entry of impurities into the interface between the gate insulating film and the crystalline semiconductor layer and adsorption thereof are prevented. Thus, generation of defects can be suppressed, so that a semiconductor element having a favorable interface and high field-effect mobility can be obtained.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) An embodiment of the present invention will be described with reference to FIG.
This will be described below.

FIG. 1 is a schematic sectional view showing a manufacturing process of a TFT according to the present embodiment when used in an active matrix type liquid crystal display device or the like.

First, the structure of a TFT as a semiconductor element manufactured by the manufacturing method of the present embodiment will be described.

As shown in FIG. 1F, the TFT is
A base insulating film 2 is formed on a transparent glass substrate 1 as a substrate.
, P-Si film 4, gate insulating film 5, interlayer insulating film 8
And three electrodes of a gate electrode 7, a source electrode 10, and a drain electrode 11.

The translucent glass substrate 1 has, for example, a strain point of 670 ° C. and a thickness of 1.1 mm.

The p-Si film 4 is a crystalline semiconductor layer formed on the base insulating film 2 and patterned into a predetermined shape. Further, the p-Si film 4 includes a channel region (p-Si) 4a and a source region (p-Si)
4b and a drain region (p-Si) 4c. The source region (p-Si) 4b and the drain region (p-Si) 4c form a channel region (p-Si).
4a, both sides are doped with impurity ions such as phosphorus or boron.

The gate insulating film 5 is an insulating film made of, for example, SiO ₂ , and is formed above the p-Si film 4 and the underlying insulating film 2.

The gate electrode 7 is made of, for example, aluminum (Al) or the like.
It is located at a position corresponding to the channel region (p-Si) 4a of the p-Si film 4.

The interlayer insulating film 8 is made of, for example, SiO ₂ and is laminated above the gate electrode 7 and the gate insulating film 5.

The above-mentioned interlayer insulating film 8 and gate insulating film 5
Respectively, the source region (p-Si) of the p-Si film 4
A contact hole 9.9 reaching 4b or the drain region (p-Si) 4c is formed. The source electrode 10 and the drain electrode 11 are formed to be in contact with the source region (p-Si) 4b or the drain region (p-Si) 4c via the contact holes 9.9.

The gate electrode 7, the source electrode 10, and the drain electrode 11 form a wiring pattern by being patterned into a predetermined shape at a portion other than the illustrated cross section.

Next, a method of manufacturing the TFT according to the present embodiment will be described below.

First, as shown in FIG.
For example, SiO 2 _TwoBase insulation made of
The film 2 is formed by atmospheric pressure CVD (Chemical Vapor).
A film is formed at 450 ° C. by a Deposition method. Up
The thickness of the base insulating film 2 is, for example, 2,000 °.
Note that the base insulating film 2 is not necessarily provided.
Next, an amorphous semiconductor layer is formed by a plasma CVD method.
The a-Si film 3 is formed so that the film thickness becomes 500 °.
Then, it is patterned into a predetermined shape by etching. Continued
Then, the gate insulating film 5 is formed on the a-Si film 3 by the normal pressure C.
VD method so that the film thickness is 1,000 mm at 450 ° C.
Form a film. Further, a resist is formed on the entire surface of the gate insulating film 5.
A coating agent is applied and exposed and developed to form a predetermined shape.
Turn. As a result, the layer as an ion shielding film
A dist film 6 is formed. As the resist film 6,
What is particularly limited as long as it blocks pure ions
Rather, it is possible to adopt various conventionally known ones.
You. Specifically, for example, a positive resist (product name: OFP
R-5000, manufactured by Tokyo Ohka Co., Ltd.).
Also, limited to photosensitive materials such as resist agents
Can be patterned by photolithography
Or the like. Further, the resist film 6 has
Materials that generate less dust when implanting pure ions
It is more preferable if it consists of

Next, as shown in FIG. 1B, using the resist film 6 as a mask, an impurity ion such as phosphorus or boron is implanted into the a-Si film 3 by, for example, an ion doping method. That is, the first a-Si film 3
A channel region (a-Si) 3a as a region, and a source region (a-Si) 3b and a drain region (a-Si) 3c as second regions on both sides of the channel region 3a.
And are formed. Subsequently, after the resist film 6 is peeled off, the patterned a-Si film 3 is subjected to 450 ° C.
A dehydrogenation treatment is performed for 60 minutes. By this dehydrogenation treatment,
When the a-Si film 3 is crystallized (described later), generation of ablation of the silicon film due to desorption of hydrogen is prevented.

Next, as shown in FIG. 1C, after the dehydrogenation treatment, the entire surface of the a-Si film 3 is irradiated with laser light from the side of the translucent glass substrate 1 by, for example, a pulse laser annealing method. Then, a p-Si film 4 as a crystalline semiconductor layer is formed. More specifically, for example, XeCl (wavelength 308 nm)
Using an excimer laser such as that described above, 16 pulses of a 30 ns laser light pulse whose cross-sectional shape is a square having several millimeters on one side are applied. Here, the energy density of laser light (irradiation energy per unit area: mJ / c
m ² ) may be appropriately set so that the a-Si film 3 can be heated to a temperature suitable for crystallization. Further, it is necessary to use the wavelength of the laser light that has a large absorption in the silicon thin film and that transmits the light transmitting glass substrate 1. Specifically, the laser light having a wavelength of 308 nm is easily absorbed by a silicon thin film, and the translucent glass substrate 1 is a 1.1 mm thick # 7 manufactured by Corning Incorporated.
It has been confirmed that when using 059 (trade name) and irradiating a laser beam having a wavelength of 300 nm or more, a transmittance of 50% or more can be obtained. Further, the translucent glass substrate 1
If a quartz substrate is used, laser light having a shorter wavelength can be used.

By the irradiation of the laser beam as described above,
By heating and completely melting the a-Si film 3, crystal grains are formed and crystallized. Thereby, the p-type having a good regularity of the crystal lattice, in which impurity ions such as phosphorus or boron are substituted at the lattice position of the silicon crystal.
The Si film 4 is formed, and disorder of crystallinity and amorphization due to ion bombardment are eliminated. Therefore, in a short time, it is possible to perform sufficient activation with an improved activation rate,
While the sheet resistance of the p-Si film 4 is low, a TFT having high field-effect mobility, good characteristics, and high reliability can be formed.

Further, a-Si from the transparent glass substrate 1 side.
Since the film 3 is irradiated with laser light, the channel region (a-Si) 3a of the a-Si film 3 is not shielded by the gate electrode 7 as in the conventional laser annealing, and the channel region (a-Si) 3a Thus, the vicinity of the boundary between the source region (a-Si) 3b and the drain region (a-Si) 3c can be reliably activated. Therefore, the crystal grains are large and
In the vicinity of the boundary, a p-Si film 4 in which the mismatch of crystal lattice, traps, levels, and the like are suppressed is obtained.

Further, the a-Si film 3 is crystallized in a state where the a-Si film 3 is covered with the gate insulating film 5, and p-S
Since the i film 4 is formed, the p-Si film 4 and the gate insulating film 5
It is possible to prevent the occurrence of defects due to mixing of impurities and adsorption at the interface with the substrate. Therefore, a TFT having better field effect mobility can be obtained.

Subsequently, as shown in FIG. 1D, an Al film is sputtered on the gate insulating film 5 so as to have a thickness of 3,000 °, and wet etching is performed for about 1 minute using an Al etchant. Do. Thus, the gate electrode 7 and the wiring pattern are formed by patterning into a predetermined shape. Further, an interlayer insulating film 8 made of, for example, SiO _{2 is} formed at 450 ° C. by a normal pressure CVD method at a thickness of 4,000 °
And covers the gate electrode 7.

Next, as shown in FIG. 1E, the source region (p-Si) 4b or the drain region (p-Si) of the p-Si film 4 is formed in the interlayer insulating film 8 and the gate insulating film 5, respectively.
Si) Contact holes 9.9 reaching 4c are opened. Further, the Ti film and the Al film are each formed to have a thickness of 1,0.
After sputtering to 00 ° and 7,000 °, patterning is performed into a predetermined shape by dry etching using a BCl 3 / Cl 2 gas. This allows
The source electrode 10 and the drain electrode 11 and their wiring patterns are formed.

Subsequently, as shown in FIG.
Exposed to a hydrogen (H) plasma atmosphere at
A plasma hydrogenation process is performed on the Si film 4. Hydrogen introduced by the above-described processing is converted into p-Si film 4
-Si is diffused to the crystal grain boundary, and the silicon dangling hand at the interface between the p-Si film 4 and the gate insulating film 5 (interface level) and Si-H Bonds are formed to inactivate defects at grain boundaries and interfaces. Thereby, the TFT according to the present embodiment can be obtained.

In the present embodiment, the mode in which laser annealing is performed after the resist film 6 is peeled off has been described. However, a material in which the resist film 6 has sufficient heat resistance to heating by laser annealing, particularly, In the case of a metal or the like, laser annealing may be performed in a state where the resist film 6 is present on the gate insulating film 5.

In this case, the resist film 6 plays a role as a reflection layer for reflecting a laser beam in addition to a function for shielding impurity ions. That is, the translucent glass substrate 1
The laser light emitted from the side and transmitted through the a-Si film 3 is almost reflected by the resist film 6. And
The a-Si film 3 is further heated by the reflected laser light. That is, the a-Si film 3 can be efficiently heated by the laser light irradiated from the translucent glass substrate 1 side and the laser light reflected on the back surface of the resist film 6. Generally, when a laser annealing apparatus (not shown) irradiates a laser beam having a high energy density, it may be difficult to stably irradiate the laser beam at a high energy density. However, in this embodiment, since the energy density at the time of irradiation can be reduced, it is easy to obtain a stable and uniform laser beam from the laser annealing apparatus.

In the present embodiment, the mode in which the resist film 6 is formed on the gate insulating film 5 has been described, but the resist film 6 is provided before the gate insulating film 5 is formed, and a-S
Impurity ions may be implanted into the i film 3. In the above case, the same effect as in the present embodiment can be obtained.

Further, even if a reflection layer or a heat retaining layer is provided separately from the ion shielding film, a TFT with high performance and high reliability can be manufactured. Specifically, first, impurity ions are implanted into the a-Si film 3 using the ion shielding film as a mask, and then the ion shielding film is removed. Then, a reflective layer or a heat retaining layer is formed at least in a region above the a-Si film 3 on the gate insulating film 5. Subsequently, the a-Si film 3 is irradiated with laser light from the translucent glass substrate 1 side to form the p-Si film 4. Thereby, when the reflective layer is formed, the energy density at the time of irradiation can be reduced as in the case where the resist film 6 is made of metal or the like, so that it is easy to obtain a stable and uniform laser beam from the laser annealing apparatus. The effect is obtained. On the other hand, when the heat retaining layer is formed, the following effects can be obtained. That is, the a-Si film 3 is irradiated with the laser light irradiated from the light transmitting glass substrate 1 side.
Is heated, the heat retaining layer prevents the diffusion of heat by its heat retaining effect. Therefore, when the a-Si film 3 is melted and crystallized by the irradiation of the laser beam, the crystal grains can be formed while being gradually cooled. As a result, a p-Si film 4 having very large crystal grains can be obtained, and the field effect mobility of the TFT can be improved. Further, the a-Si film 3 can be sufficiently heated by the heat holding effect of the heat holding layer, so that crystallization of the a-Si film 3 is promoted,
Therefore, the energy density at the time of irradiation can be reduced. As a result, the energy density of the laser beam can be reduced, so that a stable and uniform laser beam can be easily obtained, and the p-Si film 4 having large crystal grains can be formed.

As described above, the TFT according to the present embodiment
Is manufactured by implanting impurity ions into the a-Si film 3 using the resist film 6 as a mask, and then irradiating the a-Si film 3 with a laser beam from the translucent glass substrate 1 side. The film 3 is crystallized to form the p-Si film 4, and the impurity ions are activated.

According to the above-mentioned method, p which is conventionally required
-The step of forming the Si film 4 and the step of activating the impurity ions can be performed at once. Therefore, the manufacturing process can be simplified and the throughput can be improved. Further, it is possible to manufacture a TFT with high reliability and further improved initial characteristics.

(Embodiment 2) Another embodiment of the present invention is described below with reference to FIG. Note that components having the same functions as those of the semiconductor element of the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

FIG. 2 shows a TFT used in a liquid crystal display device.
It is a cross-sectional schematic diagram which shows the manufacturing process.

The structure of the TFT manufactured according to the second embodiment is the same as that of the TFT manufactured according to the first embodiment. The main difference is that it is used as a shielding film. Hereinafter, the manufacturing method will be described.

First, as shown in FIG. 2A, a base insulating film 2, an a-Si film 3, and a gate insulating film are formed on a transparent glass substrate 1 by the same steps as in the first embodiment. 5 are sequentially formed. Further, instead of the resist film 6, a gate electrode 7 is formed as an ion shielding film.

Next, as shown in FIG. 2B, the gate electrode 7 is used as an ion shielding film and impurity ions are
The i film 3 is ion-doped. As a result, the channel region (a-Si) 3a can be formed in a self-aligned manner.
The parasitic capacitance between the gate electrode 7 and the channel region (p-Si) 4a can be suppressed. Subsequently, a dehydrogenation process is performed on the a-Si film 3.

Next, as shown in FIG. 2 (c), in the same manner as in the first embodiment, a-
The p-Si film 4 is formed by irradiating the Si film 3 with laser light. Thus, even if the gate electrode 7 is formed on the a-Si film 3 as described above, the channel region (a-S
i) 3a can be crystallized and the source region (a-Si)
3b and the vicinity of the boundary between the drain region (a-Si) 3c and the channel region (a-Si) 3a can be sufficiently activated.

Further, the resist film 6 of the first embodiment is used.
As in the case of the (ion shielding film), by selecting the material of the gate electrode 7, the gate electrode 7 can function as a heat holding layer or a reflection layer.

That is, as a material of the gate electrode 7, a material having a high heat retention effect, specifically, for example, Ta,
When Cr or Ti or the like is employed, when the a-Si film 3 is heated by irradiating a laser beam from the back surface of the translucent glass substrate 1, heat diffusion is suppressed by the heat retention effect of the gate electrode 7. be able to. Therefore, when the a-Si film 3 is melted to form crystal grains, it can be gradually cooled. Thereby, p-Si having very large crystal grains is obtained.
The film 4 is obtained, and the field effect mobility of the TFT can be greatly improved. Further, since the efficiency of heating can be increased and the energy density of the laser light to be irradiated can be reduced, it is easy to obtain a stable and uniform laser light.

When the gate electrode 7 is made of a material having a high reflectivity such as Al, for example, the material is irradiated from the translucent glass substrate 1 side to form the a-Si film 3.
Is almost reflected by the gate electrode 7. And by the reflected laser light,
The a-Si film 3 is further heated. That is, a-Si
The film 3 can be efficiently heated by the laser light irradiated from the translucent glass substrate 1 side and the laser light reflected on the back surface of the gate electrode 7. As a result, the energy density of the laser beam can also be reduced, so that a stable and uniform laser beam can be easily obtained.

Hereinafter, as shown in FIGS. 2D to 2F,
Through the same steps as in the first embodiment, the TFT according to the present embodiment can be obtained.

Although the gate electrode 7 is used as the ion shielding film in the second embodiment, an ion shielding film is provided and impurity ions are implanted into the a-Si film 3 as in the first embodiment. After that, a gate electrode 7 is formed and p-
An Si film 4 may be formed. In this case, the same effect as in the second embodiment can be obtained.

As described above, the TFT according to the present embodiment
First, impurity ions are implanted into the a-Si film 3 using the gate electrode 7 as a mask, and the a-Si film 3 is irradiated with laser light from the light transmitting glass substrate 1 side. Thus, the a-Si film 3 is crystallized to form the p-Si film 4, and the impurity ions are activated.

According to the above-described method, in addition to the same effects as in the first embodiment, since the gate electrode 7 is used as an ion shielding film, the manufacturing process can be further simplified, and
Throughput can be further improved.

(Embodiment 3) The following will describe still another embodiment of the present invention. Note that components having the same functions as those of the semiconductor element of the above embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the third embodiment, the difference in melting point between the channel region (a-Si) 3a and the source region (a-Si) 3b and the drain region (a-Si) 3c, -Si) By utilizing the fact that 3a has a higher melting point, a-Si is divided into two stages as follows.
The film 3 is crystallized. The steps other than the crystallization may be either of the first embodiment or the second embodiment.

First, as a first stage, the channel region (a
-Si) 3a without crystallizing the source region (a-S
i) Crystallize 3b and drain region (a-Si) 3c. That is, the energy density of the laser beam is not crystallized in the channel region (a-Si) 3a, but the source region (a-Si) 3b and the drain region (a-S
i) 3c is a degree of melting or crystallization, for example, 160 m
J / cm ² and aS from the translucent glass substrate 1 side.
The entire surface of the i-film 3 is irradiated. Thereby, the source region (a-Si) 3b and the drain region (a-Si) 3
Crystallize c. Here, the irradiation time of the laser light is
There is no particular limitation. For example, 16 laser light pulses of 30 ns are applied.

Next, as a second stage, a predetermined energy density higher than that of the first stage, that is, the channel region (a−
Si) 3a is crystallized and the source region (p-Si) 4
b and the drain region (p-Si) 4c have improved crystallinity and an energy density at which a more uniform film can be obtained, for example, 3
Irradiate with laser light at 00 to 400 mJ / cm ² .

As a result, the channel region (a-Si) is formed by using the crystal grains formed in the source region (p-Si) 4b and the drain region (p-Si) 4c as nuclei by the first-stage laser light irradiation. 3) Crystal growth proceeds in the direction 3a, and the channel region (a-Si) 3a is crystallized to form a channel region (p-Si) 4a. Here, the irradiation time of the laser light is not particularly limited. For example, 16 laser light pulses of 30 ns are irradiated.

As described above, a-S is determined by utilizing the difference in melting point.
By crystallizing the i film 3, the p-Si film 4 having large crystal grains can be formed as in the first and second embodiments, and the channel region (p-Si) 4a and
The source region (p-Si) 4b and the drain region (p-Si)
The crystallinity at the boundary with Si) 4c can be further improved. That is, the channel region (p-Si) 4
a and a source region (p-S
i) Although the order of the crystal structure is different from 4b and the drain region (p-Si) 4c, the source region (p-Si) 4c
Since the crystal nuclei of b and the drain region (p-Si) 4c grow in the direction of the channel region (p-Si) 4a, the p-Si film 4 whose crystallinity continuously changes at the boundary can be formed. . Therefore, the p-Si film 4 can significantly suppress the occurrence of crystal lattice mismatch, traps, levels, and the like in the vicinity of the boundary, so that a much better boundary than before can be obtained.

Therefore, the initial characteristics of the TFT can be further improved, and the reliability of the TFT can be greatly improved. According to the life test by the present inventors, the time required for the carrier mobility of the TFT to be reduced by, for example, 50% of the initial value is about two orders of magnitude compared with the TFT activated by the conventional thermal annealing method. Improved.

In the first to third embodiments, the p-Si film 4 is formed after the impurity ions are doped.
Has been described above, but may be performed after formation of the interlayer insulating film 8 or after formation of the source electrode 10 and the drain electrode 11. In the above case, the energy density of laser light can be further reduced by using a material having a large heat retention effect as the interlayer insulating film 8.

In the first to third embodiments, the XeCl excimer laser is used as the energy beam. However, the energy beam is not particularly limited. Specifically, for example, even if various lasers such as an argon laser, strong light such as infrared light, an electron beam, or the like is employed, the same effect as that of each embodiment can be obtained.

Further, in the first to third embodiments, a method of manufacturing a TFT used for a liquid crystal display device has been described as an application example of a semiconductor element, but the present invention is not limited to this. That is, the semiconductor device according to the present invention can be used as an image sensor or a semiconductor memory (SRAM).
It can also be used for various thin film integrated circuits.

Further, since the TFT obtained by the method of manufacturing the TFT according to each of the above embodiments has high performance and high reliability, a driver such as a liquid crystal display device or an image sensor which requires high reliability is required. Can be used for circuits. Thus, the driver circuit can be formed on the same substrate and incorporated.

[0088]

The present invention is embodied in the form described above and has the following effects.

That is, according to the method of manufacturing a semiconductor device of the present invention, the generation of defects at the interface between the gate insulating film and the crystalline semiconductor layer is suppressed, and the crystalline semiconductor layer having good film quality and large crystal grains is formed. Can be obtained. Further, it is possible to suppress the occurrence of crystal lattice mismatch, trapping, levels, and the like in the vicinity of the boundary between the channel region and the source and drain regions, and to obtain a semiconductor element having a favorable boundary. Thereby, the semiconductor device obtained by the above-described manufacturing method has the effects of improving its initial characteristics, and having high performance and high reliability.

According to the method of manufacturing a semiconductor device according to the present invention, it is possible to crystallize the amorphous semiconductor layer and activate the implanted impurity ions in a very short time. This has the effect of simplifying the manufacturing process and significantly improving the throughput.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a manufacturing process of a TFT according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a manufacturing process of a TFT according to another embodiment of the present invention.

FIG. 3 is a schematic sectional view showing a manufacturing process of a conventional TFT.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 translucent glass substrate 2 base insulating film 3 a-Si film 3 a channel region (a-Si) 3 b source region (a-Si) 3 c drain region (a-Si) 4 p-Si film 4 a channel region (p- Si) 4b Source region (p-Si) 4c Drain region (p-Si) 5 Gate insulating film 6 Resin layer 7 Gate electrode 8 Interlayer insulating film 9 Contact hole 10 Source electrode 11 Drain electrode

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 29/78 627F

Claims (8)

[Claims] An amorphous semiconductor layer forming step of forming an amorphous semiconductor layer on a substrate; and forming an ion shielding film in a predetermined first region on the amorphous semiconductor layer. A step of implanting impurity ions into a second region of the amorphous semiconductor layer that is not shielded by the ion shielding film; and a first region and a second region of the amorphous semiconductor layer. A crystalline semiconductor layer forming step of irradiating an energy beam from the substrate side to crystallize the amorphous semiconductor layer to form a crystalline semiconductor layer and activate the impurity ions. A method for manufacturing a semiconductor device, comprising: 2. The step of forming a crystalline semiconductor layer includes irradiating a first region and a second region in the amorphous semiconductor layer with an energy beam having a first energy density capable of crystallizing the second region. Crystallizing the second region; and after the step, the first region can be crystallized in the first region and the second region in the amorphous semiconductor layer, and at least the first energy density is higher than the first energy density. Irradiating an energy beam having a high second energy density to crystallize the first region, the method comprising the steps of: 3. The method according to claim 1, wherein the step of forming the crystalline semiconductor layer includes the step of:
2. The method according to claim 1, wherein a crystal is grown in the region. 4. The method according to claim 1, wherein the step of forming the crystalline semiconductor layer is performed in a state where the ion shielding film is present when the ion shielding film is made of a material capable of reflecting an energy beam. A method for manufacturing a semiconductor device according to claim 2. 5. The method according to claim 4, wherein the ion shielding film is a gate electrode. 6. An exfoliating step of exfoliating the ion shielding film before forming the crystalline semiconductor layer, and forming a reflection layer for reflecting the energy beam in a predetermined region on the amorphous semiconductor layer. 3. The method of manufacturing a semiconductor device according to claim 1, further comprising the step of: 7. An exfoliating step of exfoliating the ion shielding film before the crystalline semiconductor layer forming step, and applying an energy beam to the amorphous semiconductor layer in a predetermined region on the amorphous semiconductor layer. 3. A method for manufacturing a semiconductor device according to claim 1, further comprising the step of forming a heat retaining layer that retains heat generated during heating. 8. A gate insulating film forming step of forming a gate insulating film on the amorphous semiconductor layer formed by the amorphous semiconductor layer forming step. The method for manufacturing a semiconductor device according to claim 1, wherein a semiconductor layer forming step is performed.