JP2015043388A - Semiconductor device, method of manufacturing semiconductor device, and electronic apparatus - Google Patents

Abstract

A semiconductor device including a thin film transistor having a structure that can be manufactured at low cost is provided.
A silicon layer which is an intrinsic semiconductor formed on a base material, a titanium layer electrically connected to both ends of the silicon layer, a gate electrode, and a gap between the silicon layer and the gate electrode. A semiconductor device having a formed gate insulating layer, in which a thin film transistor is configured by a silicon layer, a channel layer, a titanium layer as a source / drain, and a silicon layer, a titanium layer, a gate electrode, and a gate insulating layer. .
[Selection] Figure 1

Description

  The present invention relates to a semiconductor device having a thin film transistor, a method for manufacturing the semiconductor device, and an electronic apparatus including the semiconductor device.

LCD (liquid crystal display) panels and OLED (organic EL) panels are used in smartphones, small game machines, digital cameras, personal computers, and the like.
Conventionally, thin film transistors have been used to drive these panels.

A thin film transistor using LTPS (Low Temperature Poly Si) has high mobility, can drive an organic EL, and has high reliability (see, for example, Patent Document 1). For this reason, thin film transistors using LTPS are used in small and high-resolution active displays.
In addition, since thin film transistors using LTPS can be mounted on a substrate such as glass with a functional circuit, research on a system-on-panel in which a control circuit for controlling the screen of the panel is mounted on the panel. Is underway.

  However, thin film transistors using polysilicon such as LTPS are manufactured at a very high cost such as CVD (chemical vapor deposition), ion implantation, activation annealing of implanted ions, and excimer laser annealing. Therefore, the production cost increases for large-area panels.

Recently, a thin film transistor using an organic semiconductor or an oxide semiconductor is expected from the possibility of reducing the manufacturing cost.
However, it is difficult to obtain high mobility in a thin film transistor using a material that is not silicon, and reliability of characteristics such as deterioration due to light is a major issue.

JP 2010-243526 A

  In order to apply a thin film transistor to a large-area panel or the like, it is desired to improve the structure and manufacturing method of the thin film transistor to reduce the manufacturing cost.

In a general manufacturing method of a thin film transistor, ion implantation (or ion shower doping) of impurities is considered to be a factor of high manufacturing cost.
Ion implantation is an important process for forming an n-type or p-type source / drain of a transistor, but the cost of the apparatus and process is high.

  In order to solve the above problems, the present invention provides a semiconductor device having a thin film transistor having a structure that can be manufactured at low cost. In addition, the present invention provides a method for manufacturing a semiconductor device capable of manufacturing a thin film transistor at a low cost. Furthermore, an electronic device including a semiconductor device including a thin film transistor is provided.

  The semiconductor device of the present invention includes an intrinsic semiconductor silicon layer formed on a substrate, a titanium layer electrically connected to both ends of the silicon layer, a gate electrode, a silicon layer, and a gate electrode. A thin film transistor is composed of a silicon layer, a channel layer, a titanium layer as a source / drain, a silicon layer, a titanium layer, a gate electrode, and a gate insulating layer. is there.

  In the semiconductor device of the present invention, the silicon layer is preferably a polysilicon layer.

  In the method for manufacturing a semiconductor device of the present invention, a silicon layer that is an intrinsic semiconductor is formed on a base material, and a titanium layer is formed on the silicon layer so as to be electrically connected to the silicon layer. A semiconductor device in which a thin film transistor is formed by a silicon layer, which is an intrinsic semiconductor, a titanium layer, a gate electrode, and a gate insulating layer between the silicon layer and the gate electrode is manufactured.

In the method for manufacturing a semiconductor device of the present invention, preferably, the step of forming the silicon layer is a step of forming the polysilicon layer by crystallizing the amorphous silicon layer after forming the amorphous silicon layer.
More preferably, an amorphous silicon layer is formed by sputtering, and the amorphous silicon layer is crystallized by laser annealing using a blue semiconductor laser to form a polysilicon layer.

  An electronic apparatus of the present invention includes the semiconductor device of the present invention and is driven by a thin film transistor of the semiconductor device.

According to the above-described semiconductor device of the present invention, the thin film transistor is configured with the silicon layer which is an intrinsic semiconductor as the channel layer and the titanium layers electrically connected to both ends of the silicon layer as the source / drain. Since titanium has a relatively small work function, a Schottky barrier against electrons when titanium is connected to silicon can be lowered. As a result, electrons can be injected from the titanium layer to the silicon layer at a relatively low voltage, and the source / drain of the thin film transistor can be formed of the titanium layer without injecting impurities into the silicon layer. Note that the same effect can be expected if the metal has a low work function so that the barrier between metal and silicon against electrons is low, but titanium can also be easily deposited by thermal evaporation. In addition, it is relatively stable even in a subsequent heat treatment at a low temperature, is not difficult to process, and is preferable as a source (drain) electrode.
Further, since the source / drain of the thin film transistor can be formed without implanting impurities into the silicon layer, an impurity implantation process into the silicon layer and activation of the implanted impurities (thermal annealing or RTA) can be performed when manufacturing a semiconductor device. A (rapid heating) or laser annealing step is not required, and it is possible to manufacture at a low cost.

  In the semiconductor device of the present invention, when the silicon layer is a polysilicon layer, the thin film transistor has high mobility, stable characteristics, and high reliability.

According to the semiconductor device manufacturing method of the present invention described above, a titanium layer is formed on a silicon layer that is an intrinsic semiconductor so as to be electrically connected to the silicon layer. A semiconductor device in which a thin film transistor is formed is manufactured by the layer, the gate electrode, and the gate insulating layer between the silicon layer and the gate electrode.
As a result, the thin film transistor is formed as an intrinsic semiconductor without injecting impurities into the silicon layer, so that the process of injecting impurities into the silicon layer and the step of activating the implanted impurities are not required, and the manufacturing is performed at low cost. Is possible.
In addition, since titanium has a relatively low work function, as described above, the source / drain of the thin film transistor can be formed simply by electrically connecting the titanium layer to the silicon layer that is an intrinsic semiconductor. .

  In the method of manufacturing a semiconductor device according to the present invention, when the step of forming the silicon layer is a step of forming the polysilicon layer by crystallization of the amorphous silicon layer after forming the amorphous silicon layer, high mobility is obtained. Thus, a highly reliable thin film transistor can be formed.

Furthermore, when an amorphous silicon layer is formed by sputtering and the polysilicon layer is formed by crystallizing the amorphous silicon layer by laser annealing using a blue semiconductor laser, the amorphous silicon layer is formed at a low temperature by sputtering. Can do. This makes it possible to use a material having low heat resistance such as a resin for the base material.
In addition, since crystallization is performed by laser annealing using a blue semiconductor laser, the cost of the manufacturing apparatus can be reduced compared to laser annealing using an excimer laser, and flatness and crystallinity are good. A polysilicon layer can be formed.

  According to the configuration of the electronic device of the present invention described above, since the semiconductor device of the present invention is provided and driven by the thin film transistor of the semiconductor device, the manufacturing cost of the semiconductor device can be reduced. Thereby, the manufacturing cost of the electronic device provided with the semiconductor device can be reduced.

According to the present invention, a semiconductor device having a thin film transistor can be manufactured at a low cost, and the manufacturing cost of an electronic apparatus including the semiconductor device can also be reduced.
Accordingly, the thin film transistor can be applied to a panel of a display device having a large area.

In the present invention, in particular, when the silicon layer constituting the thin film transistor is a polysilicon layer, a thin film transistor having high mobility and high reliability can be realized by the polysilicon layer. In addition, the manufacturing cost can be reduced as compared with a conventional thin film transistor using polysilicon.
Therefore, for example, even in a large-screen display device, it is possible to realize high functions and high image quality.

In addition, in the manufacturing method of the present invention, in particular, when an amorphous silicon layer is formed by sputtering and then the amorphous silicon layer is crystallized using a blue semiconductor laser to form a polysilicon layer, a resin or the like is used as the base material. It is possible to use a material having low heat resistance. Thereby, for example, it becomes possible to manufacture a semiconductor device having a thin film transistor on a flexible base made of resin.
Therefore, for example, a high-function or high-quality display device can be configured on the flexible panel.

1 is a schematic configuration diagram (cross-sectional view) of a semiconductor device according to an embodiment of the present invention. 2A to 2D are manufacturing process diagrams illustrating a manufacturing method of the semiconductor device of FIG. It is a figure which compares and shows the k- spectrum of the analysis result by a spectroscopic ellipsometry in the silicon layer before and behind BLDA. It is a TEM image of the silicon layer after crystallization by BLDA. It is an amplification characteristic curve of the thin film transistor of an Example. It is a figure which compares and shows the band structure of gold | metal | money, titanium, and intrinsic silicon.

Hereinafter, the best mode for carrying out the invention (hereinafter referred to as an embodiment) will be described.
The description will be given in the following order.
1. 1. Outline of the present invention Embodiment 3 FIG. Example

<1. Summary of the present invention>
First, prior to the description of the embodiments of the present invention, an outline of the present invention will be described.

In the present invention, a semiconductor device having a thin film transistor having a silicon layer as a channel layer is formed.
The silicon layer serving as the channel layer is an intrinsic semiconductor, and a titanium layer is electrically connected to both ends of the silicon layer.

  Note that the silicon layer and the titanium layer are directly connected or connected via a very thin silicon-titanium layer (reaction layer or mixed layer) near the bonding interface.

Polysilicon (polycrystalline silicon) or amorphous silicon can be used for the silicon layer. More preferably, polysilicon with high mobility is used.
Note that amorphous silicon may contain hydrogen.

  Since the silicon layer is an intrinsic semiconductor, it is not necessary to ion-implant impurities into the polysilicon or dope the impurities simultaneously with the formation of amorphous silicon.

The present invention utilizes the fact that the work function of titanium is relatively small.
Since the work function of titanium is relatively small and close to the electron affinity of silicon, the Schottky barrier for electrons when connected to silicon is small.

Here, the band structures of gold, titanium, and intrinsic silicon are compared and shown in FIG.
As shown in FIG. 6, the work function of gold is 5.1 eV, the work function of titanium is 4.33 eV, the electric affinity of silicon is 4.05 eV, and the band gap Eg of silicon is 1.17 eV.
Also, in the case of intrinsic silicon, Fermi level E _F is located in the center of the conductive level E _C and the valence electron level E _V, the difference between the vacuum level up to the Fermi level has a 4.635EV.

As shown in FIG. 6, since the difference between the work function of gold and the electric affinity of silicon is large, the Schottky barrier for electrons formed when gold and silicon are connected increases.
Therefore, when gold and silicon are connected, it is necessary to inject a high concentration n-type impurity into silicon.

On the other hand, as can be seen from FIG. 6, since the difference between the work function of titanium and the electric affinity of silicon is small, the Schottky barrier for electrons formed when titanium and silicon are connected is small. As a result, electrons can be injected from titanium into silicon with a relatively small voltage, and injection close to ohmic becomes possible.
Further, as shown in FIG. 6, since the difference between the vacuum level and the Fermi level of intrinsic silicon is larger than the work function of titanium, when titanium and intrinsic silicon are connected, the band of intrinsic silicon conduction level E _C is obtained. There are formed to bend to the Fermi level E _F side in the vicinity of the junction interface. This facilitates the movement of electrons from intrinsic silicon to titanium.

By utilizing the above properties, in the semiconductor device of the present invention, titanium layers are connected to both ends of the intrinsic silicon layer, respectively, and these titanium layers are used as a source and a drain, respectively, and a gate insulating layer with respect to the intrinsic silicon layer. A thin film transistor is formed by providing a gate electrode through the electrode.
The thin film transistor having this structure can be operated as an n-type transistor by applying a gate voltage to the gate electrode and applying a drain voltage between the source and the drain.
That is, it is possible to operate as an n-type transistor without injecting an n-type impurity into the silicon layer.

As described above, according to the semiconductor device of the present invention, since it can be operated as a thin film transistor without injecting impurities into the silicon layer, the number of manufacturing steps when manufacturing the semiconductor device can be reduced and low. It becomes possible to manufacture at a cost.
For example, in a thin film transistor using polysilicon, usually, an implantation process (an ion implantation process) for injecting an n-type impurity or a p-type impurity into the polysilicon layer and an annealing process for activating the implanted impurity are performed. .
According to the configuration of the semiconductor device of the present invention, the implantation step and the annealing step are not required when manufacturing the semiconductor device.
For example, in a thin film transistor using amorphous silicon, impurities are usually doped simultaneously with the formation of amorphous silicon.
According to the configuration of the semiconductor device of the present invention, it is not necessary to dope impurities when forming the amorphous silicon when manufacturing the semiconductor device. Even when used as a CMOS circuit, the steps of ion implantation and doping film formation can be reduced. In order to drive an organic EL pixel expected in place of liquid crystal, the mobility of the thin film transistor is required to be 5 cm ² / V · s or more (or 10 cm ² / V · s or more). This is advantageous in reducing the cost of the process.

  In the method for manufacturing a semiconductor device of the present invention, in manufacturing the semiconductor device of the present invention, a silicon layer which is an intrinsic semiconductor is formed, and a titanium layer is formed so as to be electrically connected to both ends of the silicon layer. . As a result, the impurity implantation step and the annealing step described above and impurity doping during the formation of amorphous silicon are not required for the source / drain.

The titanium layer can be formed at a relatively low temperature around room temperature by vapor deposition or sputtering.
Thus, by forming the titanium layer at a low temperature, titanium silicide is hardly generated by the reaction between titanium and the underlying silicon.
Therefore, it is desirable to form the titanium layer at a low temperature using a vapor deposition method or a sputtering method.

  In the semiconductor device of the present invention, the thin film transistor is either a top gate type in which the gate electrode is formed above the silicon layer of the channel layer or a bottom gate type in which the gate electrode is formed below the silicon layer of the channel layer. A mold may be adopted.

In the semiconductor device and the manufacturing method thereof according to the present invention, as described above, the silicon layer is more preferably a polysilicon layer (polycrystalline silicon layer).
In the semiconductor device of the present invention, when the silicon layer of the thin film transistor is a polysilicon layer, high mobility and high reliability can be obtained as compared with a thin film transistor using amorphous silicon, an oxide semiconductor, or an organic semiconductor.
Further, in the semiconductor device of the present invention, when the silicon layer of the thin film transistor is a polysilicon layer, compared to a thin film transistor using normal polysilicon, the impurity implantation process and the impurity activation for manufacturing are performed. An annealing process becomes unnecessary. As a result, the number of manufacturing steps can be reduced, and the manufacturing cost and time required for manufacturing can be greatly reduced. For example, a thin film transistor using polysilicon can be applied to a large panel of liquid crystal or organic EL. It becomes possible.

  In the method of manufacturing a semiconductor device according to the present invention, when the silicon layer is a polysilicon layer (polycrystalline silicon layer), the amorphous silicon layer is formed and then the amorphous silicon layer is crystallized to form the polysilicon layer. .

More preferably, the amorphous silicon layer is formed by a sputtering method.
By adopting the sputtering method, an amorphous silicon layer can be formed at a lower temperature and at a lower cost as compared with the CVD (chemical vapor deposition) method. Then, an amorphous silicon layer can be formed at a low temperature.
Note that the CVD method has better film quality as the amorphous silicon layer than the sputtering method, and crystallization after forming the amorphous silicon layer is easy. In the case where a TFT is manufactured as it is, a plasma CVD method including hydrogen can provide the most stable and good TFT characteristics. However, even if the amorphous silicon layer is formed by sputtering, the film quality can be improved when the amorphous silicon layer is crystallized to form the polysilicon layer.

More preferably, when crystallizing the amorphous silicon layer, BLDA (Blue Laser Diode Annealing), that is, laser annealing using a blue semiconductor laser is employed.
By adopting BLDA, compared with other crystallization methods such as ELA (Excimer Laser Annealing), it becomes a small manufacturing device, and can reduce the manufacturing cost and the maintenance cost of the manufacturing device, and it has high quality. It becomes possible to realize a simple polysilicon thin film. Further, by adopting BLDA, it becomes possible to control the crystal grain size of polysilicon by the output of the laser. In particular, in pulse ELA, it is difficult to control a minute and uniform particle size. According to BLDA, the silicon film can be flattened after crystallization, and higher performance can be expected in a top gate type thin film transistor.
In addition, by adopting BLDA, it is possible to almost eliminate the thermal influence on the base material and the like at the time of crystallization similarly to ELA. By forming an amorphous silicon layer at a low temperature by a sputtering method and crystallizing the amorphous silicon layer by BLDA, it becomes possible to use a material having low heat resistance such as a resin for the base material. Thereby, for example, it becomes possible to manufacture a semiconductor device having a thin film transistor on a flexible base made of resin.
Therefore, for example, a high-function or high-quality display device can be configured on the flexible panel.

Furthermore, other layers constituting the semiconductor device, such as an insulating layer and a wiring layer, can be formed at a low temperature by being formed by a sputtering method or a vapor deposition method. A TFT manufacturing method that does not use the CVD method is also possible, and safer and lower cost can be achieved.
In this manner, by forming each layer constituting the semiconductor device at a low temperature, the influence of heat on the base material can be further reduced, and a low heat-resistant material such as a resin can be easily used for the base material. .

In the present invention, when the silicon layer of the thin film transistor is a polysilicon layer, the amorphous silicon layer is preferably flat in order to easily crystallize the amorphous silicon layer.
Therefore, it is desirable to adopt a top gate type or form an amorphous silicon layer after planarizing the surface after forming a gate electrode with a bottom gate type.

An electronic apparatus of the present invention includes the above-described semiconductor device of the present invention and is configured to be driven by a thin film transistor of the semiconductor device.
Since the manufacturing cost of a semiconductor device having a thin film transistor can be reduced, the manufacturing cost of an electronic device including the semiconductor device can also be reduced.

  Specific examples of the electronic device include a display device (display) using a liquid crystal or organic EL panel, and an electronic device (smart phone, game machine, and other home appliances) including a display unit.

<2. Embodiment>
Next, an embodiment of the present invention will be described.
FIG. 1 shows a schematic configuration diagram (cross-sectional view) of a semiconductor device according to an embodiment of the present invention.

In the semiconductor device shown in FIG. 1, a thin film transistor Tr is configured by using a silicon layer 13 formed on a base material 11 as a channel layer.
A buffer layer 12 is formed between the base material 11 and the silicon layer 13.
The silicon layer 13 is an intrinsic semiconductor (i-type semiconductor) in which no impurity is introduced.
Titanium layers 14 are respectively formed on the left and right ends of the silicon layer 13.
An insulating layer 15 is formed around the silicon layer 13 and the titanium layer 14.
A gate electrode 16 of the thin film transistor Tr is formed on the insulating layer 15 above the central portion of the silicon layer 13.
On the titanium layer 14, a wiring layer 17 is connected through a contact hole formed in the insulating layer 15.

As the material of the base material 11, for example, glass or resin can be used.
As a material of the buffer layer 12, for example, SiO ₂ (or / SiN) can be used.
In addition, as a material of the base material 11, a conductive material such as a metal foil can be used. In this case, the buffer layer 12 made of an insulating material may be formed on the entire surface of the base material 11 to insulate the base material 11 from the silicon layer 13.

Polysilicon (polycrystalline silicon) or amorphous silicon can be used for the silicon layer 13. Note that amorphous silicon may contain hydrogen.
More preferably, polysilicon having high mobility is used for the silicon layer 13.

As a material of the insulating layer 15, for example, SiN can be used.
As a material of the gate electrode 16, a metal or an alloy can be used.
As a material of the wiring layer 17, a metal or an alloy which is usually used for the wiring layer can be used. For example, Al can be used for the wiring layer 17.

It is also possible to use the same material (metal or alloy) for the gate electrode 16 and the wiring layer 17.
When the same material is used for the gate electrode 16 and the wiring layer 17, the gate electrode 16 and the wiring layer 17 are simultaneously formed by patterning after the layer of this material is connected to the titanium layer 14. Can do.

The silicon layer 13 and the titanium layer 14 are electrically connected directly or via a very thin silicon-titanium layer (reaction layer or mixed layer) (not shown).
As a result, since titanium has a relatively small work function, as described above, the Schottky barrier for electrons formed when titanium and silicon are connected is reduced, so that electrons can be transferred from titanium to silicon at a relatively low voltage. It is possible to inject into the vicinity of ohmic.
The thin film transistor Tr can be operated as an n-type transistor by applying a gate voltage to the gate electrode 16 and applying a drain voltage between the two titanium layers 14 through the wiring layer 17.

The thin film transistor Tr shown in FIG. 1 can be manufactured, for example, as described below.
The manufacturing method described below is a manufacturing method in the case where the silicon layer 13 is a polysilicon layer.

First, the buffer layer 12 is formed over the entire surface of the substrate 11.
Next, an amorphous silicon layer is formed on the buffer layer 12 by an RF sputtering method or the like at an extremely low temperature (less than 120 ° C.) such as room temperature.
Next, the amorphous silicon layer is crystallized by BLDA to form a silicon layer 13 made of a polysilicon layer.
Thereafter, the silicon layer 13 is patterned to form a silicon layer 13 that becomes a channel layer of the thin film transistor Tr as shown in FIG. 2A.

Next, a titanium layer 14 is formed on the silicon layer 13 by vapor deposition.
Further, the titanium layer 14 is patterned so as to remain on both ends of the silicon layer 13 as shown in FIG. 2B.

Next, the insulating layer 15 is formed by an RF sputtering method or the like at a very low temperature (less than 120 ° C.) such as room temperature, covering the silicon layer 13 and the titanium layer 14.
Next, as shown in FIG. 2C, a contact hole reaching the titanium layer 14 is formed in the insulating layer 15.

Thereafter, the contact hole is filled to form a metal or alloy layer.
Further, as shown in FIG. 2D, this metal or alloy layer is patterned to form a gate electrode 16 of the transistor Tr and a wiring layer 17 connected to the titanium layer 14.
In this way, the thin film transistor Tr shown in FIG. 1 can be manufactured.

  In the case where different materials are used for the gate electrode 16 and the wiring layer 17, the gate electrode 16 and the wiring layer 17 are formed in separate steps.

  When the silicon layer 13 is an amorphous silicon layer, the step of crystallizing amorphous silicon to form a polysilicon layer is not required in the above-described manufacturing method, and other steps can be performed in the same manner.

  In the manufacturing method described above, an amorphous silicon layer is formed and crystallized by BLDA at an extremely low temperature (less than 120 ° C.) such as room temperature. Therefore, a material having low heat resistance such as a resin should be used for the substrate 11. Is possible. By adopting BLDA, it is possible to reduce the manufacturing cost and the maintenance cost of the manufacturing apparatus, and to realize a high-quality polysilicon thin film. Further, the crystal grain size of polysilicon can be controlled by the output of the laser.

Further, in the manufacturing method described above, since the titanium layer 14 is formed by the vapor deposition method, it is possible to form the film at a relatively low temperature around room temperature.
Thus, by forming the titanium layer 14 at a low temperature, titanium silicide is hardly generated by the reaction between the titanium layer 14 and the lower silicon layer 13.
Furthermore, since the insulating layer 15 is formed at a very low temperature (less than 120 ° C.) such as room temperature, the influence of heat on the base material 11 is further reduced, and a material having low heat resistance such as a resin is applied to the base material 11. Easy to use.

According to the semiconductor device of the present embodiment described above, the titanium layer 14 is connected to both ends of the silicon layer 13 which is an intrinsic semiconductor, the silicon layer 13 is used as a channel layer, and the titanium layer 14 is used as a source / drain. A thin film transistor Tr is formed.
Thereby, since the work function of titanium is relatively small, as described above, it becomes possible to inject electrons from the titanium layer 14 to the silicon layer 13 with a relatively small voltage, and it is possible to inject near ohmic, The thin film transistor Tr can be operated as an n-type transistor.
Even if the silicon layer 13 is an intrinsic semiconductor into which impurities are not implanted, it can be operated as the thin film transistor Tr. Therefore, the number of steps for manufacturing a semiconductor device can be reduced and manufacturing can be performed at low cost. It becomes possible.

  In particular, when the silicon layer 13 is a polysilicon layer, an impurity implantation step and an annealing step for activating the impurities are not necessary as compared with a thin film transistor using normal polysilicon. . As a result, the number of manufacturing steps can be reduced, and the manufacturing cost and time required for manufacturing can be greatly reduced. For example, a thin film transistor using polysilicon can be applied to a large panel of liquid crystal or organic EL. It becomes possible.

In the above-described embodiment, the gate electrode 16 is formed above the titanium layer 14, and the insulating layer 15 covering the titanium layer 14 is the gate insulating layer.
In the semiconductor device of the present invention, a gate electrode is formed on the center of the silicon layer via a relatively thin gate insulating layer, a titanium layer is formed on both ends of the silicon layer, and a gate is formed between the two titanium layers. A configuration in which electrodes are arranged is also possible.
In the case of manufacturing this configuration, for example, after forming a gate electrode on a silicon layer via a gate insulating layer, an insulating layer is formed to cover the gate electrode, and then a titanium layer is formed.

In the above-described embodiment, the gate electrode 16 is a top gate type formed above the silicon layer 13.
The semiconductor device of the present invention may be a bottom gate type in which the gate electrode is formed below the silicon layer.
When the silicon layer is a polysilicon layer, it is easier to crystallize if the silicon layer is flat. Therefore, the top gate type is adopted, or the surface is flat after the bottom gate type gate electrode is formed. It is desirable to form a silicon layer after conversion.

<3. Example>
Actually, a semiconductor device having the thin film transistor of the present invention was manufactured and the characteristics were examined.

As described below, a semiconductor device having the thin film transistor Tr having the configuration shown in FIG. 1 was manufactured.
Glass was prepared as the substrate 11.
Then, a SiO ₂ layer having a thickness of 50 nm was formed as the buffer layer 12 on the substrate 11.
Next, an amorphous silicon layer having a thickness of 50 nm was formed at room temperature by RF sputtering using neon gas.
Further, the amorphous silicon layer was crystallized by BLDA to form a silicon layer 13 made of polysilicon. The size of the BLDA beam was 600 × 2.4 μm ² .
Next, the silicon layer 13 was patterned to form a channel layer made of the silicon layer 13.
Next, a titanium layer 14 was formed on the silicon layer 13 by vacuum deposition.
Next, the titanium layer 14 was patterned.
Subsequently, a SiN layer having a thickness of 105 nm was formed as the insulating layer 15 by RF sputtering at room temperature.
Further, after forming a contact hole in the insulating layer 15 on the titanium layer 14, the contact hole was filled by a vacuum deposition method, and an Al layer was formed as the wiring layer 17.
In this way, the thin film transistor Tr shown in FIG. 1 was produced. As an example, the thin film transistor Tr has a channel length of 10 μm and a channel width of 5 μm.
In addition, the sample which made the output of the laser 4BL into BLDA with the above-mentioned manufacturing method was produced.

The silicon layer 13 before and after BLDA was analyzed by spectroscopic ellipsometry. As an analysis result, k-spectrum which is an absorptance is shown in FIG. In FIG. 3, the broken line shows the k-spectrum of the amorphous silicon layer before BLDA.
Further, the silicon layer 13 of the sample crystallized by BLDA with a laser output of 4 W was observed with a TEM (transmission electron microscope). The obtained TEM image is shown in FIG.

From FIG. 3, it can be seen that in the spectrum after BLDA, the peak at 280 nm becomes sharp and the crystallinity of the silicon layer 13 is improved.
Further, it can be seen from the TEM image in FIG. 4 that relatively small crystal grains of polysilicon are formed.

Further, the amplification characteristics of the manufactured thin film transistor Tr were measured for a sample in which the laser output during BLDA was 4 W. The drain potential Vd was 1 V and 0.1 V, and the drain current Id was measured by changing the gate voltage Vg.
As a measurement result, an amplification characteristic curve of the manufactured thin film transistor Tr is shown in FIG.

From FIG. 5, it was confirmed that the manufactured thin film transistor Tr operates correctly as a transistor.
From the results of FIG. 5, the estimated electron mobility was 12.9 cm ² / Vs, and the threshold voltage when the drain potential Vd was 1 V was 7.0 V. Although the threshold is relatively high, it can be lowered to a low value by optimizing the hydrogenation before and after the last electrode formation.

  The present invention is not limited to the above-described embodiments and examples, and various other configurations can be taken without departing from the gist of the present invention.

11 Base material, 12 Buffer layer, 13 Silicon layer, 14 Titanium layer, 15 Insulating layer, 16 Gate electrode, 17 Wiring layer, Tr Thin film transistor

Claims (10)

A silicon layer that is an intrinsic semiconductor formed on a substrate;
A titanium layer electrically connected to both ends of the silicon layer, and
A gate electrode;
A gate insulating layer formed between the silicon layer and the gate electrode;
A semiconductor device, wherein the silicon layer is used as a channel layer, the titanium layer is used as a source / drain, and the silicon layer, the titanium layer, the gate electrode, and the gate insulating layer constitute a thin film transistor.   The semiconductor device according to claim 1, wherein the silicon layer is a polysilicon layer.   2. The semiconductor device according to claim 1, wherein the thin film transistor is a top gate type in which the gate electrode is formed above the silicon layer or a bottom gate type formed in a layer below the silicon layer.   The semiconductor device according to claim 1, wherein the base material is glass.   The semiconductor device according to claim 1, wherein the base material is a resin. Forming a silicon layer that is an intrinsic semiconductor on a substrate;
At least a step of forming a titanium layer on the silicon layer so as to be electrically connected to the silicon layer;
A method for manufacturing a semiconductor device, comprising: manufacturing a semiconductor device in which a thin film transistor is configured by the silicon layer, the titanium layer, the gate electrode, and the gate insulating layer between the silicon layer and the gate electrode, which are intrinsic semiconductors.   The method of manufacturing a semiconductor device according to claim 6, wherein in the step of forming the silicon layer, after the amorphous silicon layer is formed, the amorphous silicon layer is crystallized to form a polysilicon layer.   8. The method of manufacturing a semiconductor device according to claim 7, wherein the amorphous silicon layer is formed by a sputtering method, and the amorphous silicon layer is crystallized by laser annealing using a blue semiconductor laser to form the polysilicon layer.   9. The method of manufacturing a semiconductor device according to claim 8, wherein a maximum temperature of all the processes is 500 ° C. or less except for the step of crystallizing the amorphous silicon by the laser annealing. A silicon layer formed on a base material, which is an intrinsic semiconductor, a titanium layer electrically connected to both ends of the silicon layer, a gate electrode, and formed between the silicon layer and the gate electrode. A thin film transistor comprising a gate insulating layer, the silicon layer as a channel layer, the titanium layer as a source / drain, and the silicon layer, the titanium layer, the gate electrode, and the gate insulating layer. Equipped with equipment,
Electronic equipment driven by the thin film transistor of the semiconductor device.