JP3435144B2 - Thin film transistor and active matrix display device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polycrystal (microcrystal).
The present invention relates to a method for manufacturing a silicon thin film transistor.

[0002]

2. Description of the Related Art One of methods for obtaining a polycrystalline (microcrystalline) silicon film is to form a film of amorphous silicon (hereinafter referred to as "a-
There is a method in which a-Si is crystallized by irradiating a laser on a film (referred to as “Si”), which is generally well known. Laser crystallized thin film transistors that utilize this technology have superior electrical characteristics such as field effect mobility compared to amorphous silicon thin film transistors (hereinafter referred to as “a-Si TFTs”), so they can be used in active liquid crystal displays (LCDs) and image sensors. It is used in peripheral drive circuits such as.

A typical method for manufacturing a laser crystallized thin film transistor is as follows: amorphous silicon as a starting film.
The (a-si) film is crystallized by irradiating it with a laser, and then the device structure is processed by a series of manufacturing processes. Performing the crystallization step at the beginning or in the middle of the manufacturing process is the most characteristic of the conventional manufacturing method.

[0004]

When a thin film transistor is manufactured by such a manufacturing method, the following problems occur. (1) Since the laser crystallization is performed as a part of the manufacturing process, the electrical characteristics of the TFT cannot be evaluated until the device is completed, and it is difficult to control it. (2) Since laser crystallization is performed at the beginning or in the middle of manufacturing the TFT, it is impossible to modify various electrical characteristics after the device structure is completed, resulting in a poor yield of the entire circuit system.

The present invention proposes a method for manufacturing a new polycrystalline (microcrystalline) thin film transistor for solving the above problems.

[0006]

According to the present invention, since the channel formation region and the source / drain ohmic contact regions can be activated by laser irradiation after completion of the device structure, the channel formation region and the source are formed. A structure in which a part of the drain region on the channel formation region side is exposed to incident laser light, or the source / drain regions are located on the laser light incident side with respect to the source / drain electrodes, and both regions A thin film transistor having a structure in which a part of it contacts the laser light incident side of the channel formation region is used.

The activation of the source / drain regions is defined as the process of adding P-type or N-type characteristics by adding impurity atoms of Group 3 or Group 5 to the intrinsic a-Si film by various methods. In order to obtain better P-type or N-type characteristics, energy is applied to the region to which the impurity is added to activate the impurity and improve the conductivity of the film.

FIG. 1 shows that after the device structure is completed, the impurity a-Si layer to be the source / drain regions and the intrinsic a-Si layer to be the channel forming region are effectively crystallized and activated by laser irradiation. T of the present invention that enables
1 shows the structure of FT.

In FIG. 1A, the distance between the source electrode 9 and the drain electrode 10 on the TFT island is made larger than the distance between the source region 11 and the drain region 12, so that the source irradiation by laser irradiation from above the substrate is performed. The drain regions 11 and 12 and the channel forming region 5 can be activated and crystallized.

At this time, by irradiating a laser beam having a sufficient energy value, an intrinsic region which becomes a channel forming region is formed.
The portions of the a-Si layer 5 below the source region and the drain region are also crystallized, and a channel having excellent characteristics can be obtained. Further, since the interface between the gate insulating film 4 and the channel formation region is below the channel formation region, the interface characteristics will not be deteriorated by the incidence of laser, so that the device characteristics will not be deteriorated.

UV light often used for laser light source is S
Since iO ₂ can be transmitted, if the passivation film 13 is silicon oxide (SiO ₂ ), laser irradiation can be performed from above the passivation film.

Further, it is possible to prevent the disturbance of the upper surface of the a-Si film due to the laser irradiation. That is, if the passivation film is silicon oxide, the passivation film is
The same as the silicon oxide film that is formed on the a-Si film to be laser-irradiated in order to prevent the upper surface of the film from being disturbed during laser irradiation, which is generally called a cap layer when laser-crystallizing the a-Si film. It plays a role and can obtain a high quality laser crystallized film.

Further, by selecting the wavelength of the laser or the material of the glass substrate so that the laser can pass through the glass substrate 1, the base film 2 and the gate insulation film formed on the glass substrate to prevent impurities from being mixed from the glass substrate. If the film is made of a material that transmits laser (for example, silicon oxide), the gate electrode 3 is made smaller than the width between the source and drain electrodes to irradiate the laser from the lower portion of the substrate to expose the impurity regions below the source and drain electrodes. Can be crystallized and activated, and greater improvements in various properties can be obtained. If the base film and the gate insulating film are silicon oxide films,
At the same time, they also act as a cap layer and can prevent the disorder of the surface under the membrane.

FIG. 1B is a further development of the structure of FIG. 1A to enable more effective laser activation for the source and drain regions.

In FIG. 1B, the source region 11 and the drain region 12, which are impurity regions, are located above the source electrode 9 and the drain electrode 10, respectively, and are in contact with the upper side of the channel forming region 5. Since the laser irradiation to the source / drain regions can be completely performed only by irradiation from above, a structure in which various characteristics can be improved and a controllable value range can be obtained as compared with FIG. 1A. Has become. Further, similarly to FIG. 1A, by irradiating a laser beam having a sufficient energy value, the lower part of the source region and the drain region of the intrinsic a-Si layer 5 which becomes the channel forming region is crystallized, A channel having good characteristics can be obtained. Further, since the interface between the gate insulating film 4 and the channel formation region is below the channel formation region, the interface characteristics are not deteriorated by the incidence of the laser, so that the device characteristics are not deteriorated. If the passivation film is silicon oxide, it acts as a cap layer during laser irradiation, and disturbs the laser irradiation of the upper surface of the impurity a-Si film that is the source / drain region and the intrinsic a-Si film that is the channel formation region. Can be prevented.

1 (c) and 1 (d) are shown in FIGS. 1 (a) and 1 (b).
The structure is completely upside down, and by selecting the wavelength of the laser or the material of the glass substrate so that the laser can pass through the glass substrate, mainly by irradiating the laser from the bottom of the substrate, the channel formation region and the source It enables crystallization and activation of the drain region.

FIG. 1C shows a structure in which FIG. 1A is turned upside down, and the source electrode 9 is the same as FIG. 1A.
By making the distance between the drain electrode 10 and the source region 11 larger than the distance between the source region 11 and the drain region 12, it is possible to activate and crystallize the source / drain region and the channel formation region 5 by laser irradiation from the lower portion of the substrate. .

At this time, by irradiating a laser beam having a sufficient energy value, an intrinsic region which becomes a channel formation region is formed.
The portions of the a-Si layer 5 below the source region and the drain region are also crystallized, and a channel having excellent characteristics can be obtained. Further, since the interface between the gate insulating film and the channel formation region is above the channel formation region, the interface characteristics are not deteriorated by the incidence of the laser from the lower side, so that the device characteristics are not deteriorated.

Further, if the underlying film 2 formed on the glass substrate 1 to prevent impurities from being mixed from the glass substrate is a silicon oxide film, it acts as a cap layer and serves as a source / drain region and a channel forming region. Disturbance of the lower surface of the a-Si film can be prevented. Also passivation film 1
3 and the gate insulating film 4 are materials that transmit laser, for example, silicon oxide, the gate electrode 3 is made smaller than the width between the source and drain electrodes to irradiate the laser from above the substrate and to the upper side of the source and drain electrodes. It is possible to crystallize and activate the impurity region of, and it is possible to obtain a great improvement in various characteristics. At that time, if the passivation film and the gate insulating film are silicon oxide, they simultaneously act as a cap layer, and a-
Disturbance of the upper surface of the Si film can be prevented.

FIG. 1D is a further development of the structure of FIG. 1C to enable more effective laser activation for the source region and the drain region.

In FIG. 1D, the source region 11 and the drain region 12, which are impurity regions, are located under the source electrode 9 and the drain electrode 10, respectively, and are in contact with both sides of the channel forming region 5. Since the laser irradiation to the source / drain region can be completely performed only by irradiating from the lower part, it is possible to obtain a larger improvement in various characteristics and a controllable value range as compared with FIG. 1 (c). It has a structure that allows Further, similarly to FIG. 1C, the upper side of the source region and the drain region of the intrinsic a-Si layer which becomes the channel forming region is crystallized by irradiating with a laser beam having a sufficient energy value, which is excellent. A channel with characteristics can be obtained.

Further, since the interface between the gate insulating film 4 and the channel formation region is above the channel formation region, the interface properties are not deteriorated by the incidence of the laser, so that the device properties are not deteriorated. If the underlying film is silicon oxide, it acts as a cap layer during laser irradiation, and the lower surface of the impurity a-Si film that is the source / drain region and the intrinsic a-Si film that is the channel formation region is disturbed by laser irradiation. Can be prevented.

By adopting the above structure, a-Si
After the device structure of the thin film transistor is completed, the source / drain regions and the channel formation region can be activated and crystallized by laser irradiation.

As described above, laser irradiation is not performed before or during processing of the device structure,
The device is processed by a complete a-Si TFT process to complete the device structure, that is, the formation of the impurity semiconductor layer, the intrinsic semiconductor layer, the gate insulating film, the formation of the source / drain regions, the source / drain / gate electrodes, and After the process including the formation of the protective film (passivation film) or the formation of circuit wiring is completed, the laser is applied to the source / drain region and the channel formation region of any one or more a-Si TFTs. By irradiating the crystallization of the channel formation region of the thin film transistor or the source
The drain region is activated and crystallized. If the electrodes and wiring are completed at this time, any a-Si TFT on the substrate
It is possible to irradiate the laser until the optimum value is reached while monitoring the electrical characteristics of the in real time. Alternatively, a thin film transistor having desired characteristics can be obtained by repeating the process of measuring electrical characteristics after laser irradiation.

As a result, after a number of a-SiTFTs are manufactured on the same substrate by the same manufacturing process and the device structure is completed, any one or a plurality of a-SiTFTs are made into TFTs having arbitrary electrical characteristics. It becomes possible. That is, it is possible to manufacture TFTs having different electric characteristics on the same substrate by performing laser irradiation after completion of the device structure.

Further, in this way, after a plurality of a-SiTFTs are manufactured on the same substrate by the same manufacturing process and the device structure thereof is completed, any one of the a-SiTFTs or a plurality of a-SiTFTs is laser crystallized. It is possible to make a polycrystalline silicon thin film transistor (hereinafter referred to as “poly-SiTFT”) according to, and to fabricate a system in which both a-SiTFT and poly-SiTFT coexist on the same substrate without dividing the device structure fabrication process. It becomes possible.

Further, since the laser irradiation is performed for an extremely short time, the substrate temperature is hardly raised,
It is possible to fabricate poly-Si TFTs at low temperatures (room temperature to 400 ° C), which makes it possible to fabricate large-area poly-Si TFT systems inexpensively without using expensive glass such as quartz glass. .

Examples using the present invention will be shown below.

[0029]

[Embodiment] [Embodiment 1] In this embodiment, an a-Si TFT and a poly-Si TFT in an integrated LCD (liquid crystal display) system are used.
A mixed system of SiTFT (polycrystalline silicon thin film transistor) will be described. The integrated LCD system shown in FIG. 2 has a pixel matrix driving TFT portion 3
0 and the peripheral circuit TFT portion 31 are required. The operation speed requirements for the two types of TFTs are completely different. For pixel driving, it is sufficient if the mobility is about 1 cm ² / Vs, but for peripheral circuit TFTs, high speed operation ( Number MHZ)
Is required. Therefore, the pixel TFT is a-Si material,
The peripheral circuit TFT is preferably composed of poly-Si material.

According to the present invention, a process for manufacturing a device structure of a system as shown in FIG. 2 is performed by using a-Si TFT and poly-Si.
The TFTs can be manufactured at once without being divided.

FIG. 3 is a schematic view for schematically explaining the manufacturing method of the TFT. In this embodiment, the TFT having the structure shown in FIG. 1A, that is, the inverted stagger structure is used. Of course, other structures may be used. In FIG. 3 (A), silicon oxide (SiO ₂ ) as a base film 2 is formed on a glass 1 such as quartz glass which can withstand a heat treatment at 700 ° C. or less, for example, about 600 ° C., which is not expensive, by using a magnetron RF (radio frequency) sputtering method. The film is formed to a thickness of 1000 to 3000 Å, 2000 Å in this embodiment. The film forming conditions were an atmosphere of 100% oxygen, a film forming temperature of 150 ° C., an output of 400 to 800 W, and a pressure of 0.5 Pa. Quartz or single crystal silicon was used as the target.
The film forming rate was 30 to 100Å / min.

A chromium (Cr) layer 3 to be a gate electrode is formed on this by a known sputtering method. The film thickness is 800
˜1000 Å, 1000 Å in this example. This was patterned with the first photomask P1 to obtain FIG. 3 (B). Also, tantalum (Ta) is used as the gate electrode material.
May be used.

When aluminum (Al) is used as the gate electrode material, this is used as the first photomask P1.
After patterning with, the surface may be anodized.

A silicon nitride film (SiN _x ) is formed as a gate insulating film 4 on this by the PCVD method. Film thickness is 10
It was set to 00 to 5000Å, and 3000Å in this embodiment. Silane (SiH ₄ ) and ammonia gas (NH
₃ ) was used in a ratio of 1: 3. The film forming condition is a film forming temperature of 250.
˜350 ° C., 260 ° C. in this embodiment, RF frequency 13.56 MHz, RF output 80 W, pressure 0.05
Torr and the film forming rate were 80Å / min.

An intrinsic a-Si layer 5 is formed on this by the PCVD method. The film thickness is 200 to 1000Å, 7 in this embodiment.
It was set to 00Å. Silane (SiH ₄ ) is used as the source gas, the film forming temperature is 150 to 300 ° C., in this embodiment 200 ° C., the RF frequency is 13.56 MHz, the RF output is 35 W, the pressure is 0.5 Torr, and the film forming rate. Was 60Å / min.

An impurity a-Si layer, here an n ⁺ -type
The a-Si layer 6 is formed by the PCVD method. The film thickness is 300 ~
500Å, 500Å in this embodiment. Silane is used as a source gas, and phosphine (PH ₃ ) is added in an amount corresponding to 1% of silane in order to add phosphorus as an N-type impurity. The film forming temperature is 150 to 300 ° C., 200 ° C. in the present embodiment, the RF frequency is 13.56 MHz, the RF output is 40 W, the pressure is 0.5 Torr, and the film forming rate is 60 Å /
Was a minute

As described above, the gate insulating film 4, the intrinsic a-Si layer 5, and the n ⁺ a-Si layer 6 were formed to obtain FIG. 3C. Since these are all formed by the PCVD method, it is effective to continuously form the films by using the multi-chamber method. Further, another film forming method such as a reduced pressure vapor phase method, a sputtering method, or a photo CVD method may be used. After that, dry etching is performed using the second photomask P2 to form a TFT island region as shown in FIG.

Next, a chromium (Cr) layer 7 to be source / drain electrodes is formed by using the sputtering method to obtain FIG. 3 (E). The film thickness is 500 to 1000Å, 800Å in this embodiment.
And This is patterned by the third photomask P3. At this time, the n ⁺ a-Si layer is patterned by dry etching without peeling off the resist 8 to form a channel forming region, a source electrode 9, a drain electrode 10, and a source region 11 and a drain 12 region. F) is obtained.

By wet etching without peeling the resist, overetching is performed to make the distance between the source / drain electrodes larger than the distance between the source / drain regions. This makes it possible to activate and crystallize the source / drain regions by laser irradiation from above. After that, the resist is peeled off to obtain FIG.

As shown in FIG. 3 (H), silicon oxide (SiO ₂ ) is used as a passivation film by the above RF sputtering method to a thickness of 1000 to 3000 Å, which is 2 in this embodiment.
A film was formed to a thickness of 000Å. A PCVD method or the like may be used. Thus, the device structure of the TFT is completed.

After that, wiring was performed, and a laser was irradiated from above while monitoring with connecting a measuring instrument. HP-4142B was used for the measuring instrument. The laser used was an excimer laser, here a KrF excimer laser with a wavelength of 248 nm. In this wavelength range, UV light can pass through the passivation film above the TFT. Energy E is 200 to 350 mJ / cm ² , irradiation number 1 to 5
0SHOTS, substrate temperature T _S during irradiation is room temperature to 400
It was ℃.

With this, crystallization and activation can be performed by irradiating the channel formation region or the source / drain region or both with laser while monitoring, and in the TFT for driving the pixel matrix of 30 in FIG. It was possible to obtain the various characteristics of the TFT.
It is very difficult to improve the yield because a huge number of TFTs for driving the pixel matrix, for example, 640 × 400 = 256,000 TFTs must all be made to have the same characteristics, but the method according to the present invention is very difficult. By using, it was possible to significantly reduce defective TFTs having greatly different characteristics, and it was possible to significantly improve the yield.

Further, the characteristics are remarkably improved by sufficiently irradiating the peripheral circuit TFT portion 31 of FIG. 2 with the laser, and the field effect mobility μ ₁ is 0.5 to 0.8 cm before the laser irradiation. ² / vs, threshold voltage V
_{While th1} was 10 to 20 V, after laser irradiation, field-effect mobility μ ₂ was 10 to 100 cm ² / vs, and threshold voltage V _th2 was 5 to 7 V, which was a large improvement in characteristics. A sufficiently high speed operation was obtained as a TFT for the peripheral circuit of the device. The channel formation region formed by the a-Si film is crystallized and poly-Si with high carrier mobility is obtained.
It was a film and had sufficient characteristics as a poly-Si TFT.

After that, ITO (indium
Tin oxide) was formed to a thickness of 0.1 μm by a sputtering method, and a pixel electrode was formed using a photomask. This I
The TO film was formed at room temperature to 150 ° C. and was annealed at 200 to 400 ° C. in oxygen or air. If the pixel electrode is not deteriorated by laser, the TFT may be irradiated with laser after the pixel electrode is formed.

A polyimide precursor was printed on the substrate by the offset method, and baked at 350 ° C. for 1 hour in a non-oxidizing atmosphere such as nitrogen. Then, a known rubbing method was used to modify the surface of the polyimide, and a means for orienting liquid crystal molecules in a certain direction was provided at least in the initial stage. Thus, one substrate of the liquid crystal display device was obtained.

The other substrate is I over the entire one side of the glass substrate.
TO was formed in a thickness of 1 μm by a sputtering method, and a counter electrode was formed by using a photomask. This ITO is room temperature ~
A film was formed at 150 ° C., and the second substrate was obtained by annealing at 200 to 300 ° C. in oxygen or air.

A polyimide precursor was printed on the substrate by the offset method, and baked at 350 ° C. for 1 hour in a non-oxidizing atmosphere such as nitrogen. Then, a known rubbing method was used to modify the surface of the polyimide, and a means for orienting liquid crystal molecules in a certain direction was provided at least in the initial stage.

After that, the nematic liquid crystal composition was sandwiched between the two substrates, external wiring was performed, and a polarizing plate was attached to the outside,
A transmissive liquid crystal display device was obtained. The obtained liquid crystal display device was quite comparable with the one in which the pixel matrix driving TFT and the peripheral driving circuit were separately manufactured.

As described above, in order to crystallize and activate the channel formation region and the source / drain regions by laser irradiation after completion of the device structure, the passivation film on the laser light incident side, here the substrate, is UV light. Must be transparent. Also, since the channel forming region actually operates as a channel at the interface with the gate insulating film, the intrinsic a-Si layer serving as the channel forming region is preferably as thin as possible for sufficient crystallization.

In this way, a-Si after the device structure is completed
Control of various characteristics of TFT by laser irradiation and poly-
Si TFT has become possible. In addition, a-SiTFT and poly-SiT can be manufactured in the same device structure manufacturing process on the same substrate.
It has become possible to create FT and separate. Also many
Circuit system using poly-Si TFTs: room temperature to 400 ° C
Thus, it is possible to manufacture at low temperature without using expensive glass such as quartz glass.

[Embodiment 2] A poly-SiTFT type liquid crystal display device having a redundant circuit structure was manufactured as an application of the present invention. This will be described.

In a circuit system using a large number of poly-SiTFTs such as a poly-SiTFT type liquid crystal display device, it is very difficult to make all the TFTs fully operate, and in reality, the yield is improved. Therefore, some redundant configuration is often adopted. A plurality of, for example, two TFTs are connected in parallel as one of the redundant configurations of the pixel matrix driving a-SiTFT in the a-SiTFT type liquid crystal display device, and two T
By operating the FTs together, there is a method in which even if one of the TFTs does not operate for some reason, the other TFT operates to improve the yield. However
ON current of poly-Si TFT is about 0.1 per TFT
There is also mA, which is about 100 times that of 1 μA of a-Si TFT.
Operating twice the number of TFTs for the purpose of redundancy is a great waste of power and one TF per pixel.
It is desired to operate at T.

On the other hand, laser crystallization poly-Si TFT
In the circuit system, the exact same circuit is used for poly-SiTFT.
Make two circuits so that they can be connected in parallel, and initially operate one circuit, and when it does not operate normally or when it does not operate normally during operation check, the other circuit Both circuits were laser crystallized when the redundant configuration of connecting to
Since it must be composed of poly-Si TFTs, the laser irradiation time will be doubled, the energy consumption will be doubled, and the work time will be extended and the product cost will be increased.

By using the method according to the present invention, the above problems can be solved.

FIG. 4 shows a redundant configuration p according to the present invention.
1 shows an oly-Si TFT type liquid crystal display device. As shown in FIGS. 4 and 5, in this liquid crystal display device, all the TFTs in the pixel matrix driving TFT portion 20 and the shift register circuit 21 in the peripheral circuit have a redundant configuration.
The pixel matrix driving TFT has two TFTs, and the shift register circuit has two redundant circuits having the same circuit.

First, all the TFTs to be subjected to redundancy were manufactured by the structure according to the present invention as shown in FIG. 1 and irradiated with laser after completion of the device structure so that they could operate as poly-Si TFTs. . The fabrication of the TFT was performed in the process shown in FIG. 3 as described in the first embodiment. The passivation film is formed, and the process is advanced to the state before the pixel electrode is formed, that is, FIG.

FIG. 5 shows a layout of the pixel matrix driving TFTs. As shown here, the TFT is an a-Si TFT, and the two TFTs are connected in parallel. First, of the two TFTs connected to all the pixel electrodes, one of them, that is, 23 TFTs in this case, is irradiated with laser to form a poly-Si TFT. Here, the measuring instrument was connected and the operation was checked. If there is no abnormality here, proceed to the next step. Since the TFT 24 on the redundant side is an a-Si TFT, the operating current is about two orders of magnitude smaller than that of the poly-Si TFT, so its effect can be ignored. Also, the threshold voltage is pol
Since y-SiTFT is 0 to about 10V, a-SiTFT is about 10 to about 20V, so that only laser-crystallized poly-SiTFT operates without parallel operation.

When there is a TFT that does not operate normally, the a-Si TFT on the redundant side of the TFT, that is, 24 TFTs in this case.
It was possible to easily switch to the redundant side by irradiating a laser beam to a poly-Si TFT and wiring to the TFT on the non-redundant side, if necessary, by burning off point A with a laser.

By doing so, when there is no need to switch to the redundant side, there is substantially one poly-Si TFT that drives one pixel while having a redundant configuration with two TFTs, and there are two poly-Si TFTs. It was possible to reduce the power consumption to about half that of the method in which Si TFTs were connected in parallel to realize a redundant configuration. Also, switching to the TFT on the redundant side can be performed by laser irradiation once to several times, and a very simple and efficient method can be realized.

Next, the redundancy circuit of the shift register is also 2
Three identical circuits were made in parallel, and the TFT was made as an a-Si TFT up to the state where the electrodes were connected after the state of FIG. 3 (H). It may be possible to connect and switch later using a connector or the like. Laser crystallization is first performed on all TFTs in one circuit, here 21 circuits, and a measuring instrument is connected to check the operation. If the operation is normal, proceed to the next step.

If both circuits are connected in parallel,
Since the TFT in the redundant circuit is an a-Si TFT, the operating current is
It is about two orders of magnitude smaller than that of poly-Si TFTs, so its effect is virtually negligible. In addition, the threshold voltage of poly-SiTFT is 0 to about 10V, whereas that of a-SiTFT is about 10 to 20V, so only the laser-crystallized poly-SiTFT operates without parallel operation. Become.

When the circuit does not operate normally, the a-SiTFT in the redundant circuit 22 is irradiated with laser to perform poly-SiT.
It was possible to easily switch to the redundant side by setting FT, and if necessary, wiring to the circuit on the non-redundant side, here point B was burnt off with a laser. Of course, you may connect and switch by a connector etc.

As a result, the laser crystallization may be performed only when it becomes necessary to switch to the redundant side.
Compared with the manufacturing process in which all TFTs are irradiated with laser at the beginning or in the middle of the manufacturing process, the laser irradiation time is halved and unnecessary energy is not used, so work time is shortened, costs are reduced, energy saving, etc. Could be realized. In addition, the switching operation to the redundant side could be made very simple without complicated wiring work.

This method is not limited to the manufacturing stage,
It can be used even for those that have failed during use, and the performance can be restored in a similar manner.

As described above, by using the structure according to the present invention, in a circuit composed of poly-Si TFTs,
It has become possible to realize effective redundancy methods such as lower power consumption, shorter work time, lower costs, and energy savings.

[0066]

By adopting the manufacturing method proposed by the present invention, the following excellent effects can be obtained.

According to the present invention, after the device structure is completed, it is possible to easily control the optimum parameter of the thin film transistor for constructing the circuit system by irradiating the laser while monitoring the electrical characteristics. As a result, when a large number of TFTs, such as a TFT type liquid crystal display device, need to have uniform characteristics, variations in the characteristics of the TFTs occur, they can be eliminated by using the method according to the present invention. Can be modified,
The quality and yield have improved remarkably.

Moreover, the quality and the yield could be improved at the same time without adding any difficult steps to the device structure.

Further, according to the present invention, various electric characteristics such as mobility of thin film transistors on the same substrate can be freely controlled, and only necessary TFTs are crystallized.
It became possible to realize a mixed system of SiTFT and poly-SiTFT

Further, since the laser irradiation is performed in a very short time, the substrate temperature is hardly raised, and pol
It is possible to fabricate y-Si TFTs at low temperatures (room temperature to 400 ° C), which makes it possible to fabricate large-area poly-Si TFT systems inexpensively without using expensive glass such as quartz glass. It was

The TFT structure according to the present invention and a general TFT structure are made of a-Si on the same substrate, and the TFT having the structure of the present invention is irradiated with laser light to obtain a-SiTF.
It goes without saying that it is possible to realize a mixed system of T and poly-Si TFTs.

As described above, the present invention can bring many merits in the method of manufacturing a thin film transistor, and its industrial effect is great.

[Brief description of drawings]

FIG. 1 ... Example of structure of thin film transistor of the present invention

[Fig. 2] ... Structure of liquid crystal display device

[Fig. 3] --- Thin film transistor manufacturing process

[Fig. 4] ··· Poly-Si TFT drive type liquid crystal display device having a redundant configuration

5 ... TF for driving pixels of the liquid crystal display device of FIG.
Redundant configuration of T

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate 2 ... Base film 3 ... Gate electrode 4 ... Gate insulating film 5 ... Channel formation region 9 ... Source electrode 10 ... Drain electrode 11 ... Source region 12 ... Drain region 13 ... Passivation film 20 ... Poly-SiTFT drive type liquid crystal display device pixel matrix driving poly-SiTFT portion 21 ... Shift register circuit 22 in peripheral circuit of liquid crystal display device ..Redundant shift register circuit 23 in peripheral circuits of liquid crystal display device ... Poly-for driving pixel matrix of liquid crystal display device
SiTFT 24: Redundant pixel matrix drive for liquid crystal display p
oly-SiTFT 30 ・ ・ ・ Pixel matrix driving TFT of liquid crystal display device
Part 31: TFT part for peripheral circuit of liquid crystal display device

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI H01L 29/78 616V 617J 617M 618Z (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 29/786 H01L 21/336

Claims (2)

(57) [Claims] 1. A gate electrode, a gate insulating film on the gate electrode, a semiconductor layer on the gate insulating film, a pair of N-type semiconductor layers formed on the semiconductor layer and in contact with the semiconductor, A thin film transistor, comprising: a source electrode and a drain electrode formed on each of the pair of N-type semiconductor layers and in contact with a part of each of the pair of N-type semiconductor layers; in contact with the source electrode of the layers
Portion not in contact with the drain electrode
Is crystallized and activated, the other part is amorphous
And a pair of the N-type semiconductors of the semiconductor layer.
The part not in contact with the body layer is crystallized, and the other part is crystallized.
Thin film transistor, wherein Amorphous der Rukoto. 2. A gate electrode, a gate insulating film on the gate electrode, a semiconductor layer on the gate insulating film, and a pair of N-type semiconductor layers formed on the semiconductor layer and in contact with the semiconductor layer. An active matrix display having a thin film transistor and a pixel electrode having a source electrode and a drain electrode formed on each of the pair of N-type semiconductor layers and in contact with a part of each of the pair of N-type semiconductor layers. A device in contact with the source electrode of the pair of N-type semiconductor layers,
Portion not in contact with the drain electrode
Is crystallized and activated, the other part is amorphous
And a pair of the N-type semiconductors of the semiconductor layer.
The part not in contact with the body layer is crystallized, and the other part is crystallized.
An active matrix display device according to claim Amorphous der Rukoto.