JP4397439B2 - Semiconductor device - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a semiconductor device using a semiconductor thin film having a crystal structure and a manufacturing method thereof. In particular, the present invention relates to a structure of an inverted staggered thin film transistor (hereinafter abbreviated as TFT). Further, the present invention relates to a structure of a semiconductor circuit, an electro-optical device, and an electronic device using the TFT.
[0002]
Note that in this specification, “semiconductor device” refers to all devices that can function using semiconductor characteristics, and TFTs, semiconductor circuits, electro-optical devices, and electronic devices described in this specification are all included. It is included in the category of semiconductor devices.
[0003]
[Prior art]
Conventionally, a TFT is used as a switching element of an active matrix liquid crystal display device (hereinafter abbreviated as AMLCD). At present, products having a circuit configuration with TFTs using an amorphous silicon film (amorphous silicon film) as an active layer occupy the market. In particular, as the TFT structure, an inverted stagger structure with a simple manufacturing process is often employed.
[0004]
However, as the performance of AMLCDs increases year by year, the operating performance (especially the operating speed) required for TFTs tends to be severe. Therefore, it has become difficult to obtain an element having sufficient performance at the operating speed of a TFT using an amorphous silicon film.
[0005]
Accordingly, TFTs using a polycrystalline silicon film (polysilicon film) instead of an amorphous silicon film have attracted attention, and development of TFTs using a polycrystalline silicon film as an active layer has been proceeding at a remarkable pace. At present, some of them are commercialized.
[0006]
Many presentations have already been made on the structure of an inverted staggered TFT using a polycrystalline silicon film as an active layer. For example, “Fabrication of Low-Temperature Bottom-Gate Poly-Si TFTs on Large-Area Substrate by Linear-Beam Excimer Laser Crystallization and Ion Doping Method: H. Hayashi et.al., IEDM95, PP829-832, 1995” There is a report.
[0007]
This report describes a typical example of an inverted stagger structure using a polycrystalline silicon film (Fig. 4), but there are various problems with such an inverted stagger structure (so-called channel stop type). I have it.
[0008]
First, since the entire active layer is as thin as about 50 nm, impact ionization occurs at the junction between the channel formation region and the drain region, and a deterioration phenomenon such as hot carrier injection appears remarkably. Therefore, it becomes necessary to form a large LDD region (Light Doped Drain region).
[0009]
The controllability of the LDD region becomes the most serious problem. In the LDD region, the control of the impurity concentration and the length of the region is very delicate, and the length control is particularly problematic. At present, a method of defining the length of the LDD region by a mask pattern is adopted. However, as the miniaturization proceeds, a slight patterning error causes a large difference in TFT characteristics.
[0010]
Variation in sheet resistance in the LDD region due to variation in the thickness of the active layer is also a serious problem. Further, variations such as the taper angle of the gate electrode can also cause variations in the effect of the LDD region.
[0011]
Further, in order to form the LDD region, a patterning process is necessary, which directly increases the manufacturing process and decreases the throughput. In the inverted stagger structure described in the above report, it is expected that at least six masks (up to source / drain electrode formation) are necessary.
[0012]
As described above, in the channel stop type inverted stagger structure, it is necessary to form LDD regions in a lateral plane on both sides of the channel formation region, and it is very difficult to form a reproducible LDD region. It is.
[0013]
[Problems to be solved by the present invention]
It is an object of the present invention to provide a technique for manufacturing a semiconductor device with high productivity and high reliability and reproducibility by a very simple manufacturing process.
[0014]
[Means for Solving the Problems]
A configuration of the present invention is a semiconductor device including a source region, a drain region, and a channel formation region configured by a semiconductor layer having a crystal structure,
The source region and the drain region are formed of at least a first conductive layer toward the gate insulating film, a second conductive layer having a higher resistance than the first conductive layer, and a semiconductor layer having the same conductivity type as the channel formation region. It has the laminated structure which becomes.
[0015]
In addition, the configuration of other inventions is as follows:
In the above structure, the semiconductor layer having the crystal structure and a grain boundary distribution peculiar to the melt crystallized film are characterized.
[0016]
In addition, the configuration of other inventions is as follows:
In the above structure, the concentration profile of impurities constituting the first and second conductive layers continuously changes from the first conductive layer to the second conductive layer.
[0017]
In addition, the configuration of other inventions is as follows:
In the above structure, the second conductive layer is 5 × 10 ¹⁷ ~ 1 × 10 ¹⁹ atoms / cm ^Three It is characterized by being formed by impurities that change continuously within the range of.
[0018]
In addition, the configuration of other inventions is as follows:
In the above structure, there are two offset regions having different thicknesses between the channel formation region and the second conductive layer.
[0019]
In addition, the configuration of other inventions is as follows:
In the above structure, an offset region having a thickness larger than that of the channel formation region exists between the channel formation region and the second conductive layer.
[0020]
According to another aspect of the present invention, there is provided a gate electrode formed over a substrate having an insulating surface, a source region, a drain region, and a channel formation region each including a semiconductor layer having a crystal structure, and the source region and the drain region. A semiconductor device including a source electrode and a drain electrode formed on each of the above,
The source region and the drain region include at least a first conductive layer toward the gate insulating film, a second conductive layer having a higher resistance than the first conductive layer, and a semiconductor layer having the same conductivity type as the channel formation region. Having a laminated structure
The source electrode and / or drain electrode overlaps the gate electrode on the channel formation region.
[0021]
According to another aspect of the invention, there is provided a semiconductor device including a source region, a drain region, and a channel formation region that are formed of a semiconductor layer having a crystal structure.
The source region and the drain region include at least a first conductive layer toward the gate insulating film, a second conductive layer having a higher resistance than the first conductive layer, and a semiconductor layer having the same conductivity type as the channel formation region. Having a laminated structure
An HRD structure including two offset regions having different thicknesses and the second conductive layer exists between the channel formation region and the first conductive layer.
[0022]
One of the two offset regions having different film thicknesses is an offset in the film surface direction made of a semiconductor layer having the same conductivity type and the same film thickness as the channel formation region, and the other is the same conductivity type as the channel and the It is an offset in the film thickness direction made of a semiconductor layer thicker than the channel formation region.
[0023]
In addition, the configuration of another invention related to the manufacturing method is
Forming a gate electrode, a gate insulating layer, and an amorphous semiconductor film over a substrate having an insulating surface;
Irradiating the amorphous semiconductor film with laser light or a strong light equivalent thereto to obtain a semiconductor film having a crystal structure;
Adding an impurity selected from only Group 15 or Group 13 and Group 15 to the semiconductor film having the crystal structure to form a conductive layer;
Forming a source electrode and a drain electrode on the conductive layer;
Forming a channel formation region by etching the semiconductor film having the crystal structure using the source electrode and the drain electrode as a mask;
Is included in the configuration.
[0024]
In addition, the configuration of other inventions is as follows:
Forming a gate electrode, a gate insulating layer, and an amorphous semiconductor film over a substrate having an insulating surface;
Irradiating the amorphous semiconductor film with laser light or a strong light equivalent thereto to obtain a semiconductor film having a crystal structure;
Adding an impurity selected from only Group 15 or Groups 13 and 15 to the semiconductor film having the crystal structure to form a conductive layer;
Forming a source electrode and a drain electrode on the conductive layer;
Forming a channel formation region by etching the semiconductor film having the crystal structure using the source electrode and the drain electrode as a mask;
Adding a threshold voltage control impurity only to the channel formation region using the source and drain electrodes as a mask;
Is included in the configuration.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
The embodiment of the present invention having the above-described configuration will be described in detail with the examples described below.
[0026]
【Example】
The embodiment of the present invention will be described in detail with reference to FIGS.
[0027]
[Example 1] A typical example of the present invention will be described with reference to FIGS. First, a method for manufacturing a semiconductor device of the present invention will be described with reference to FIGS. As a preparation for a substrate having an insulating surface, a base film 102 made of an insulating film containing silicon as a main component is formed over a glass substrate 101. A gate electrode (first wiring) 103 made of a conductive film is formed thereon.
[0028]
The line width of the gate electrode 103 is 1 to 10 μm (typically 3 to 5 μm). The film thickness is 200 to 500 nm (typically 250 to 300 nm). In this embodiment, a gate electrode having a line width of 3 μm is formed using an aluminum film having a thickness of 250 nm (containing 2 wt% scandium).
[0029]
In addition to aluminum, tantalum, tungsten, titanium, chromium, molybdenum, conductive silicon, metal silicide, or a stacked film thereof can be used as the gate electrode 103. Here, the first patterning step (gate electrode formation) is performed.
[0030]
Here, the gate electrode 103 is anodized to form an anodic oxide film 104 that protects the gate electrode 50 to 200 nm (typically 100 to 150 nm). In this embodiment, the film is formed in an ethylene glycol solution containing 3% tartaric acid (neutralized neutrally with ammonia) under conditions of an applied voltage of 80 V and a formation current of 5 to 6 mA. Thus, it can be formed to a thickness of about 100 nm.
[0031]
Next, a silicon nitride film 105 (film thickness is 0 to 200 nm, typically 25 to 100 nm, preferably 50 nm), a silicon oxynitride film or silicon oxide film (film thickness is 150 to 300) represented by SiOxNy nm, typically 200 nm) 106 is formed. In this embodiment, the gate insulating layer also includes the anodic oxide film 104.
[0032]
After forming the gate insulating layer, an amorphous semiconductor film 107 containing silicon as a main component is formed thereon. In this embodiment, an amorphous silicon film is taken as an example, but other compound semiconductor films (such as an amorphous silicon film containing germanium) may be used.
[0033]
Since the present invention has a channel etch type bottom gate structure, the amorphous silicon film 107 is formed thick. The film thickness range is 100 to 600 nm (typically 200 to 300 nm, preferably 250 nm). In this embodiment, it is 200 nm. As will be described later, the optimum film thickness needs to be appropriately determined depending on what offset region and LDD region are provided in the TFT of the present invention.
[0034]
In this embodiment, the amorphous silicon film 107 is formed by low pressure thermal CVD, but it is desirable to thoroughly control the concentration of impurities such as carbon, oxygen, and nitrogen during the film formation. If these impurities are large, the crystallinity uniformity of the crystalline semiconductor film may be lost later.
[0035]
In this example, the concentration of each impurity in the formed amorphous silicon film is 5 × 10 5 for carbon and nitrogen. ¹⁸ atoms / cm ^Three Less than (typically 5x10 ¹⁷ atoms / cm ^Three Less), oxygen is 1.5 × 10 ¹⁹ atoms / cm ^Three Less than (typically 1x10 ¹⁸ atoms / cm ^Three The following is controlled. If such management is performed, the impurity concentration finally contained in the channel formation region of the TFT falls within the above range.
[0036]
Thus, the state of FIG. 1A is obtained. When the state of FIG. 1A is obtained, the amorphous silicon film 107 is crystallized by laser light irradiation. (Fig. 1 (B))
[0037]
As the laser light, a pulsed excimer laser using KrF (248 nm), XeCl (308 nm), ArF (193 nm) or the like as an excitation gas may be used. Further, any other laser beam such as a harmonic of an Nd: YAG laser can be used.
[0038]
Note that when the amorphous semiconductor film to be crystallized is thick as in this embodiment, it is easier to crystallize the whole uniformly by using laser light having a long wavelength. In addition, a method of heating the substrate in a range of about 50 to 500 ° C. when irradiating the laser beam is also effective. It is also effective to adjust the film thickness so that the light absorption efficiency is increased in view of the wavelength period of the laser light.
[0039]
In this embodiment, a pulse oscillation type XeCl excimer laser beam is processed into a linear shape by an optical system, and then laser annealing is performed on the entire surface of the amorphous silicon film by scanning from one end to the other end of the substrate.
[0040]
The oscillation frequency is 30 MHz, the scanning speed is 2.4 mm / s, and the laser energy is 300 to 400 mJ / cm. ² And the substrate is heated to 400 ° C. from the back side. Thus, a crystalline semiconductor film (crystalline silicon film in this embodiment) 108 is obtained.
[0041]
In addition, since the heat absorption coefficient is different between the amorphous silicon film and the glass substrate, the temperature of the amorphous silicon film can be intensively increased by irradiation from the upper surface side of the film. Therefore, it is possible to heat the amorphous silicon film at a temperature equal to or higher than the heat resistance temperature (around 650 ° C.) of the glass substrate.
[0042]
By the way, a semiconductor film crystallized by laser light irradiation as in this embodiment (referred to as a melt crystallized film in this specification) has a grain boundary distribution (existence distribution of crystal grain boundaries) peculiar to laser crystallization. Have. Observing the grain boundary with a well-known technique called Seco-etching, the crystal grain and the grain boundary can be clearly distinguished, and it can be seen that it is an aggregate of crystal grains having a grain size of several tens to several hundreds of nanometers. .
[0043]
On the other hand, the semiconductor film using other crystallization means shows a grain boundary distribution that is clearly different from that of the melt crystallized film. Because laser light (or strong light with the same intensity). This is because the semiconductor layer is once melted in crystallization using, but the other means is basically solid phase growth and the crystallization mechanism is different.
[0044]
Next, an element selected from Group 15 (typically phosphorus, arsenic or antimony) is added by ion implantation (with mass separation) or ion doping (without mass separation). In this embodiment, the phosphorus concentration is 1 × 10 × 10 within the range of 30 to 100 nm (typically 30 to 50 nm) from the surface of the crystalline silicon film 108. ¹⁹ ~ 3 x10 ^{twenty one} atoms / cm ^Three , Typically 1 × 10 ²⁰ ~ 1 × 10 ^{twenty one} atoms / cm ^Three Adjust so that
[0045]
In this embodiment, the region 109 containing the high concentration phosphorus formed in this way is formed into n. ⁺ This is called a layer (or first conductive layer). The thickness of this layer is determined in the range of 30 to 100 nm (typically 30 to 50 nm). In this case, n ⁺ Layer 109 will later function as part of the source / drain electrode. In this embodiment, n having a thickness of 30 nm is used. ⁺ Form a layer.
[0046]
N ⁺ A region 110 containing phosphorus at a low concentration formed under the layer 109 is n ^- This is called a layer (or a second conductive layer). In this case, n ^- Layer 110 is n ⁺ The resistance becomes higher than that of the layer 109 and functions later as an LDD region for electric field relaxation. In this embodiment, n having a thickness of 30 nm is used. ^- Form a layer. N ^- An intrinsic or substantially intrinsic region formed under layer 110 is referred to as i layer 120. A channel formation region is formed in the i layer 120. (Figure 1 (C))
[0047]
At this time, the concentration profile in the depth direction when phosphorus is added is very important. This will be described with reference to FIG. The concentration profile shown in FIG. 4 is phosphine (PH) by ion doping with an acceleration voltage of 80 keV and an RF power of 20 W. _Three ) Is added.
[0048]
In FIG. 4, 401 indicates a crystalline silicon film, and 402 indicates a concentration profile of added phosphorus. This concentration profile is determined by setting conditions such as RF power, added ion species, and acceleration voltage.
[0049]
At this time, the peak value of the concentration profile 402 is n ⁺ The phosphor concentration decreases with increasing depth in the crystalline silicon film 401 (or toward the gate insulating film) inside the layer 403 or in the vicinity of the interface. At this time, since the phosphorus concentration continuously changes over the entire area inside the film, n ⁺ Always n under layer 403 ^- Layer 404 is formed.
[0050]
And this n ^- Even within the layer 404, the phosphorus concentration continuously decreases. In this example, the phosphorus concentration is 1 × 10 ¹⁹ atoms / cm ^Three Over n ⁺ Think as layer 403, 5 × 10 ¹⁷ ~ 1 × 10 ¹⁹ atoms / cm ^Three The region in the concentration range is n ^- Considered as layer 404. However, since there is no clear boundary, it is only considered as a guide.
[0051]
Further, the region where the phosphorus concentration is extremely lowered and the lower layer thereof become an intrinsic or substantially intrinsic region (i layer) 405. Note that an intrinsic region is a region to which no impurity is intentionally added. In addition, a substantially intrinsic region is a region where the impurity concentration (here phosphorus concentration) is lower than the spin density of the silicon film or the impurity concentration is 1 × 10 ¹⁴ ~ 1 × 10 ¹⁷ atoms / cm ^Three A region showing one conductivity in the range of.
[0052]
Such intrinsic or substantially intrinsic regions are n ^- Formed below layer 404. However, the i layer 405 is basically composed of a semiconductor layer having the same conductivity type as the channel formation region. That is, when the channel formation region is weak n-type or p-type, the same conductivity type is exhibited.
[0053]
In this way, n ⁺ By using ion implantation or ion doping to form the layer, n ⁺ N under the layer ^- A layer can be formed. N as before ⁺ Such a configuration cannot be realized when the layers are provided by film formation. In addition, by properly setting the conditions at the time of ion addition, ⁺ Layer and n ^- The layer thickness can be easily controlled.
[0054]
In particular, n ^- Since the thickness of the layer 110 will be the thickness of the LDD region later, very precise control is required. In the ion doping method or the like, since the concentration profile in the depth direction can be precisely controlled by setting the addition conditions, the thickness of the LDD region can be easily controlled. In the present invention, n ^- The thickness of the layer 110 may be adjusted in the range of 30 to 200 nm (typically 50 to 150 nm).
[0055]
FIG. 4 shows a concentration profile when the doping process is performed once, but by dividing the doping process into a plurality of steps, n ⁺ Layer 403, n ^- The thickness of layer 402 can also be controlled. For example, n ⁺ Doping such that the peak of the concentration profile is located at the depth at which the layer 403 is to be formed, and a relatively deep portion with a low dose, n ^- Doping in which the peak of the concentration profile is located at a depth where the layer 402 is to be formed may be performed.
[0056]
N ⁺ Layer 109, n ^- After the layer 110 is formed, laser light irradiation is performed again to activate the added impurity (phosphorus). (Figure 1 (D))
[0057]
In addition to laser annealing, lamp annealing (irradiation with strong light) and furnace annealing (heating by an electric heating furnace) can also be performed. However, in the case of furnace annealing, it is necessary to perform processing in consideration of the heat resistance of the glass substrate.
[0058]
In this embodiment, laser annealing is performed using a XeCl excimer laser. The processing conditions may be basically the same as the above crystallization process, but the laser energy is 200-350mJ / cm. ² (Typically 250-300mJ / cm ² ) In addition, the substrate is heated to 300 ° C from the back side to improve the activation rate.
[0059]
Further, in this laser activation process, the damage that the crystalline silicon film 108 has received in the phosphorus addition process can be recovered. And the area | region which became amorphous by the ion collision at the time of addition can be recrystallized.
[0060]
When the phosphorus activation step is thus completed, the crystalline silicon film is patterned to form the island-shaped semiconductor layer 111. At this time, when the TFT is finally completed, the length (channel width (W)) in the direction perpendicular to the carrier moving direction is adjusted to 1 to 30 μm (typically 10 to 20 μm). . Here, the second patterning step is performed. (Fig. 2 (A))
[0061]
Here, although not shown in the drawing, a part of the exposed gate insulating layer is etched to make electrical connection between the gate electrode (first wiring) and the electrode (second wiring) to be formed next. A hole (a region indicated by 118 in FIG. 2C) is opened. Here, a third patterning step is performed.
[0062]
Next, a conductive metal film (not shown) is formed, and the source electrode 112 and the drain electrode 113 are formed by patterning. In this embodiment, a laminated film having a three-layer structure of Ti (50 nm) / Al (200 to 300 nm) / Ti (50 nm) is used. Further, as described above, wiring for electrically connecting to the gate electrode is also formed at the same time. Here, a fourth patterning step is performed. (Fig. 2 (B))
[0063]
As will be described later, the length (C) of a region (hereinafter referred to as a channel etch region) 114 immediately above the gate electrode 103, that is, a region sandwiched between the source electrode 112 and the drain electrode 113 (hereinafter referred to as a channel etch region). ₁ The lengths of the channel formation region and the offset region are determined later. C ₁ Can be selected from the range of 2 to 20 μm (typically 5 to 10 μm). ₁ = 4 μm.
[0064]
Next, dry etching is performed using the source electrode 112 and the drain electrode 113 as a mask, and the island-shaped semiconductor layer 111 is etched in a self-aligning manner. Therefore, etching proceeds only in the channel etch region 114. (Fig. 2 (C))
[0065]
At this time, n ⁺ Layer 109, n ^- Layer 110 is completely etched and stops etching leaving only intrinsic or substantially intrinsic regions (i-layer). In the present invention, finally, only the semiconductor layer of 10 to 100 nm (typically 10 to 75 nm, preferably 15 to 45 nm) is left. In this embodiment, a semiconductor layer having a thickness of 30 nm is left.
[0066]
When the etching of the island-like semiconductor layer 111 (channel etch process) is completed in this way, a silicon oxide film or a silicon nitride film is formed as the protective film 115, and an inverted staggered TFT having a structure as shown in FIG. 2C is obtained. .
[0067]
In this state, in the channel-etched island-like semiconductor layer 111, a region located directly above the gate electrode 112 becomes a channel formation region 116. In the configuration of this embodiment, the gate electrode width corresponds to the length of the channel formation region, and L ₁ The length indicated by is called the channel length. In addition, the region 117 located outside the end portion of the gate electrode 113 does not reach the electric field from the gate electrode 103 and becomes an offset region. This length is X ₁ Indicated by
[0068]
In this embodiment, the line width (L ₁ Is about 2.8 μm considering the reduction of the 100 nm thick anodic oxide film, and the length of the channel etch region 114 (C ₁ ) Is 4 μm, the length of the offset region (X ₁ ) Is about 0.6μm.
[0069]
Here, an enlarged view of the drain region (semiconductor layer in contact with the drain electrode 113) is shown in FIG. In FIG. 3, 103 is a gate electrode, 301 is a channel formation region, 302 is n ⁺ Layer (source or drain electrode), 303 and 304 are offset regions having different film thicknesses, and 305 is n ^- Layer (LDD region).
[0070]
Note that although not described here, the source region (semiconductor layer in contact with the source electrode 112) also has a similar structure.
[0071]
Further, although the structure shown in FIG. 3 is schematically shown, attention should be paid to the film thickness relationship in each region. The most preferable configuration for configuring the present invention is that the thickness of the film is n. ⁺ Layer 302 <n ^- This is a case where the relationship of layer 305 <offset region (i layer) 304 is satisfied.
[0072]
Because n ⁺ Since the layer 302 only functions as an electrode, it is sufficient to be thin. On the other hand, n ^- The layer 305 and the offset region 304 need to have appropriate thicknesses for effective electric field relaxation.
[0073]
In the configuration of this embodiment, the channel formation regions 301 to n ⁺ There are two offset regions 303 and 304 and LDD regions 305 having different film thicknesses up to the region 302. Reference numeral 303 denotes an offset region in the film surface direction formed by mask alignment, and is referred to as a mask offset region.
[0074]
Reference numeral 304 denotes an offset region in the film thickness direction corresponding to the film thickness of the i layer, and is referred to as a thickness offset region. The thickness of the thickness offset region 304 may be determined in the range of 100 to 300 nm (typically 150 to 200 nm). However, it is necessary to make the film thickness larger than the film thickness of the channel formation region. If the film thickness is thinner than the channel formation region, a good offset effect cannot be expected.
[0075]
The present inventors call such a structure composed of offset + LDD as an HRD (High Resistance Drain) structure, and distinguish it from a normal LDD structure. In the case of the present embodiment, the HRD structure is constituted by a three-stage structure of mask offset + thickness offset + LDD.
[0076]
At this time, since the LDD region 303 is controlled by the film thickness and impurity concentration of the LDD region, it has the advantages of extremely high reproducibility and small characteristic variation. As described in the conventional example, the LDD region formed by patterning has a problem of variation in characteristics due to patterning errors.
[0077]
Note that the length of the mask offset region 303 (X ₁ ) Is controlled by patterning, and therefore is affected by errors due to patterning and shrinkage of glass. However, since the thickness offset region 304 and the LDD region 305 exist after that, the influence of the error is alleviated and the characteristic variation can be reduced.
[0078]
Note that the length of the mask offset (X ₁ ) Is the channel length (L ₁ ) And channel etch region length (C ₁ ) (C ₁ -L ₁ ) / 2. Therefore, a desired offset length (X ₁ ) Can be set. In the configuration of this embodiment, the offset length (X ₁ ) Can be 0.3 to 3 μm (typically 1 to 2 μm).
[0079]
Note that an inverted staggered TFT having a structure as shown in FIG. 2C cannot be realized by a conventional TFT using an amorphous silicon film as an active layer (island semiconductor layer). This is because, when an amorphous silicon film is used, the mobility of carriers (electrons or holes) becomes extremely slow unless the source / drain electrode and the gate electrode overlap each other.
[0080]
Even if the source / drain electrode and the gate electrode overlap each other, the mobility (field effect mobility) of the TFT using the amorphous silicon film is at most 1 to 10 cm. ² It is about / Vs. On the other hand, if the structure as in this embodiment is adopted, the mobility is too low to function as a switching element.
[0081]
However, since the crystalline silicon film is used as the active layer in the present invention, the carrier mobility is sufficiently fast. Therefore, sufficient mobility can be obtained even with the structure as in this embodiment. That is, the structure of this embodiment can be realized only by using a semiconductor film having a crystal structure as a semiconductor layer.
[0082]
In addition, since the inverted staggered TFT of this embodiment has an HRD structure, it is very strong against deterioration phenomena such as hot carrier injection due to impact ionization and has high reliability. Moreover, the effect of the LDD region is dominant, and the LDD region is formed with very good controllability, so that the variation in characteristics is very small.
[0083]
For this reason, the structure as in this embodiment is suitable for a TFT that constitutes a circuit that requires a high breakdown voltage and does not require a high operation speed.
[0084]
Further, as shown in the manufacturing process of this embodiment, only four masks are required to obtain an inverted staggered TFT having the structure shown in FIG. This means that the throughput and the yield are dramatically improved considering that the conventional channel stop type TFT requires six masks.
[0085]
As described above, according to the structure of this embodiment, a bottom gate type TFT having high reliability and reproducibility can be manufactured by a manufacturing process with high mass productivity.
[0086]
Note that the mobility of a bottom gate TFT (N-channel TFT) manufactured according to the manufacturing process of this example is 10 to 150 cm. ² / Vs (typically 60-120cm ² / Vs), the threshold voltage can be 1 to 4V.
[0087]
[Embodiment 2] In the present embodiment, a configuration example different from the first embodiment in the configuration of the present invention is shown. Since the TFT manufacturing process may basically follow the first embodiment, only necessary portions will be described in this embodiment.
[0088]
First, the state shown in FIG. 5A is obtained in accordance with the manufacturing process of Example 1. The difference from the first embodiment is that the length of the channel etch region 500 is set to C when the source electrode 501 and the drain electrode 502 are formed. ₂ It is in the point to. At this time, C ₂ Is narrower than the gate electrode width, and is selected in the range of 2 to 9 μm (typically 2 to 4 μm). That is, it is a feature of this embodiment that the gate electrode and the source / drain electrode are provided so as to overlap.
[0089]
In this state, when the channel etch process is performed as shown in the first embodiment and a protective film is provided, the state shown in FIG. 5B is obtained. At this time, a region indicated by 503 is a channel formation region, and the channel length is L ₂ (= C ₂ ). In addition, the length (Y) of the overlapped area (referred to as mask overlap area) 504 by mask design ₂ ) Where E is the gate electrode width, ₂ ) / 2.
[0090]
FIG. 5C is an enlarged view of the drain region. In the TFT operation, carriers are channel formation region 503 (thickness 50 nm), mask overlap region 504 (thickness 160 nm), and LDD region 505 (thickness). 50nm) through n ⁺ The layer 506 (thickness 40 nm) reaches the drain electrode 502.
[0091]
In this case, an electric field from the gate electrode is also formed in the mask overlap region 504. However, since the electric field is weakened as the LDD region 505 is approached, such a region has substantially the same function as the LDD region. . Of course, if it is further closer to the LDD region 505, the electric field is not completely formed, and it can function as an offset (thickness offset) region.
[0092]
As described above, in the structure of this embodiment, the HRD structure is constituted by substantial LDD due to overlap + LDD due to thickness offset + low concentration impurities. Further, when the thickness of the overlap region 504 is thin, an LDD structure consisting only of LDD due to overlap + LDD due to low concentration impurities can be taken.
[0093]
Even in the configuration of the present embodiment, the overlap region 504 and the LDD region 505 are controlled by the respective film thicknesses, so that the characteristic variation is very small. The length of the overlap area (Y ₂ ) Includes errors due to patterning, etc., but LDD due to overlap, offset in the thickness direction, and LDD due to low concentration impurities are not affected by such errors. ₂ The characteristic variation due to the error is reduced.
[0094]
Note that the structure as in this embodiment is suitable for a TFT constituting a circuit that has a small offset component and requires a high operating speed.
[0095]
In addition, the structure of this embodiment has an advantage that the substrate floating effect is unlikely to occur because minority carriers accumulated in the channel formation region due to impact ionization are quickly extracted to the source electrode. Therefore, it is possible to realize a TFT having a high operation speed and a very high breakdown voltage characteristic.
[0096]
[Embodiment 3] This embodiment shows a configuration example different from Embodiments 1 and 2 in the configuration of the present invention. Since the TFT manufacturing process may basically follow the first embodiment, only necessary portions will be described in this embodiment.
[0097]
First, the state shown in FIG. 6A is obtained in accordance with the manufacturing process of Example 1. Here, the difference from the first embodiment is that when the source electrode 601 and the drain electrode 602 are formed, the length of the channel etch region 600 is set to C. _Three It is in the point to. At this time, C _Three Is 1 to 10 μm (typically 3 to 5 μm) to match the gate electrode width.
[0098]
In this state, when the channel etch process is performed as shown in the first embodiment and a protective film is provided, the state shown in FIG. 6B is obtained. At this time, a region indicated by 603 becomes a channel formation region, and the channel length is L _Three (= C _Three ).
[0099]
FIG. 6C is an enlarged view of the drain region. In the TFT operation, carriers are channel formation region 603 (thickness 100 nm), thickness offset region 604 (thickness 150 nm), and LDD region 605 (thickness). 100 nm) through n ⁺ The layer 606 (thickness 50 nm) reaches the drain electrode 602. That is, in the structure of the present embodiment, the HRD structure is a two-stage structure of thickness offset + LDD.
[0100]
Also in the configuration of this embodiment, the thickness offset region 604 and the LDD region 605 are controlled by the respective film thicknesses, so that the characteristic variation is very small. In addition, sufficient breakdown voltage characteristics can be obtained.
[0101]
[Embodiment 4] This embodiment shows a configuration example different from Embodiments 1 to 3 in the configuration of the present invention. Since the TFT manufacturing process may basically follow the first embodiment, only necessary portions will be described in this embodiment.
[0102]
First, the state of FIG. 7A is obtained in accordance with the manufacturing process of Example 1. Here, the difference from the first embodiment is that when the source electrode 701 and the drain electrode 702 are formed, either the source electrode or the drain electrode is overlapped with the gate electrode, and the other is not overlapped. .
[0103]
In this embodiment, the length of the channel etch region 700 is set to C. _Four And At this time, C _Four Is selected in the range of 1 to 10 μm (typically 3 to 6 μm).
[0104]
In this state, a channel etch process is performed as shown in Embodiment 1 to provide a state shown in FIG. 7B when a protective film is provided. At this time, a region indicated by 703 becomes a channel formation region, and the channel length is L _Four (= C _Four -X _Four ).
[0105]
Where X _Four Is the length of the mask offset region 704. X _Four For the numerical range, reference may be made to Example 1. Further, the numerical range of the length of the mask overlap region 705 may be referred to the second embodiment.
[0106]
In this example, the HRD structure described in Example 1 and the HRD structure (or LDD structure) described in Example 2 are combined. Since the structural description has already been described in the first and second embodiments, the description thereof is omitted here.
[0107]
When the structure as in this embodiment is employed, it is particularly preferable to use the HRD structure (or LDD structure) shown in Embodiment 2 for the source region and the HRD structure described in Embodiment 1 for the drain region.
[0108]
For example, an electric field concentration is particularly intense at the channel end (junction) on the drain region side, and an HRD structure having a large resistance component as shown in the first embodiment is desirable. On the other hand, since there is no need for such a high withstand voltage countermeasure on the source side, an HRD (or LDD) structure with a small resistance component as shown in the second embodiment is suitable.
[0109]
In this embodiment, the configuration of Embodiment 2 can be combined with either one of the source / drain regions. As described above, the HRD structure or the LDD structure shown in the first to third embodiments may be appropriately selected by the practitioner and used in the source / drain region, and an optimum structure may be designed in view of circuit design. In this case, 3 ² = 9 possible combination patterns.
[0110]
[Embodiment 5] In this embodiment, an example in which a CMOS circuit (inverter circuit) is formed using bottom gate type TFTs having the configurations shown in Embodiments 1 to 4 will be described with reference to FIG. Note that the CMOS circuit is configured by complementarily combining an N-channel TFT and a P-channel TFT formed on the same substrate.
[0111]
FIG. 8 shows a CMOS circuit using the configuration shown in the fourth embodiment, in which 801 is a source electrode of a P-channel TFT, 802 is a source electrode of an N-channel TFT, and 803 is a drain electrode common to N / P.
[0112]
In addition, the N-channel TFT is formed by the manufacturing process described in Embodiment 1, and n ⁺ Layers 804, 805, n ^- Layers 806 and 807 are formed. On the other hand, p-channel TFTs have p ⁺⁺ Layers 808, 809, p ^- Layers 810 and 811 are formed.
[0113]
Note that it is very easy to manufacture a CMOS circuit on the same substrate. In the case of the present invention, first, the state of FIG.
[0114]
In this state, an element selected from the group 15 is added to the entire surface regardless of the N-type / P-type, but when a P-channel TFT is manufactured, the region to be the N-channel TFT is hidden by a resist mask or the like. An element selected from Group 13 (typically boron, indium, or gallium) may be added.
[0115]
In this embodiment, boron is taken as an example. At this time, boron must be added to a concentration higher than that of phosphorus to reverse the conductivity. N ⁺ Layers and n ^- Completely p all layers ⁺⁺ Layer and p ^- In order to invert the layer, it is important to adjust the concentration profile at the time of boron addition and add it deeper than the addition depth of phosphorus.
[0116]
Therefore, the concentration profile of boron in the film is as shown in FIG. In FIG. 9, 900 is a semiconductor layer, 901 is a phosphorus concentration profile before boron addition, 902 is a boron concentration profile after boron addition, and 903 is p ⁺⁺ Layer, 904 is p ^- Layer 905 is the i layer.
[0117]
At this time, p ⁺⁺ The thickness of the layer 903 is 10 to 150 nm (typically 50 to 100 nm), and p ⁺⁺ The boron concentration in the layer is 3 × 10 ¹⁹ ~ 1x10 ^{twenty two} atoms / cm ^Three , Typically 3 × 10 ¹⁹ ~ 3x10 ^{twenty one} atoms / cm ^Three Adjust so that
[0118]
On the other hand, p ^- The thickness of the layer 904 is 30 to 300 nm (typically 100 to 200 nm), and the boron concentration is 5 × 10 5. ¹⁷ ~ 3x10 ¹⁹ atoms / cm ^Three Adjust so that To do. However, since p-channel TFTs are inherently resistant to deterioration, p ^- It is not always necessary to use the layer as an LDD region. Bother p ^- The thickness of the layer 904 is referred to by the concentration gradient that changes continuously as long as an addition means such as an ion implantation method is used. ^- This is because a layer is formed.
[0119]
By the way, in this embodiment, both the N-channel TFT and the P-channel TFT use the HRD structure (type using an overlap region) having the structure shown in Embodiment 2 on the source region side, and on the drain region side. The HRD structure (type using mask offset) having the configuration shown in the first embodiment is provided.
[0120]
Therefore, as apparent from the top view, the source region side of the P-channel TFT has an overlap region having a length of Yi, and the drain region side has a mask offset region having a length of Xi. Yes. In addition, an overlap region having a length of Yj is provided on the source region side of the N-channel TFT, and a mask offset region having a length of Xj is provided on the drain region side.
[0121]
At this time, the lengths of Xi and Xj and Yi and Yj can be freely adjusted by mask design. Therefore, each length may be determined as appropriate according to the circuit configuration, and it is not necessary to arrange the lengths of the N-channel type and the P-channel type.
[0122]
In addition, with such a structure, the breakdown voltage characteristics of the region serving as the common drain of the CMOS circuit can be increased, which is a very effective configuration when configuring a circuit with a high operating voltage.
[0123]
Although the configuration of the CMOS circuit using the TFT having the configuration shown in Examples 1 to 4 is shown in FIG. 8, it goes without saying that all other combinations are possible. Since there are nine possible configuration patterns for one TFT, it is 9 in the CMOS circuit. ² There are 81 ways. Among these combinations, an optimal combination may be adopted according to the performance required by the circuit.
[0124]
Further, as shown in this embodiment, the present invention can be easily applied to a P-channel TFT. In that case, the mobility of the bottom gate type TFT (P channel type TFT) of the present invention is 10 to 100 cm. ² / Vs (typically 50-100cm ² / Vs), the threshold voltage can be -1.5 to -5V.
[0125]
[Embodiment 6] In this embodiment, an example will be described in which a device for controlling the threshold voltage is applied to the TFT of the present invention.
[0126]
In order to control the threshold voltage, an element selected from group 13 (typically boron, indium, gallium) or group 15 (typically phosphorus, arsenic, antimony) is added to the channel formation region. The technique is called channel doping.
[0127]
Channel doping is effective for the present invention, and the following two methods may be simple.
[0128]
First, at the time of forming an amorphous silicon film, a gas containing impurities for controlling a threshold voltage (for example, diborane, phosphine, etc.) is mixed in a film forming gas, and a predetermined amount is included simultaneously with film formation. There is. In this case, it is not necessary to increase the number of processes at all, but since the same concentration is added to both the N-type and P-type TFTs, it is not possible to meet the demand for different concentrations between the two.
[0129]
Next, after the channel etching step (channel forming region forming step) as described in FIG. 2C is completed, the channel forming region (or the channel forming region and the mask offset region) is formed using the source / drain electrodes as a mask. There is a method of selectively adding impurities.
[0130]
As an addition method, various methods such as an ion implantation method, an ion doping method, a plasma treatment method, a gas phase method (diffusion from an atmosphere), and a solid phase method (diffusion from the film) can be used. Since it is thin, a method that does not give damage, such as a gas phase method or a solid phase method, is preferable.
[0131]
Note that when an ion implantation method or the like is used, damage to the channel formation region can be reduced if a protective film that covers the entire TFT is provided.
[0132]
Further, after the impurity is added, an impurity activation step is performed by laser annealing, lamp annealing, furnace annealing, or a combination thereof. At this time, the damage received by the channel formation region is almost recovered.
[0133]
When implementing this example, the channel formation region is 1 × 10 ¹⁵ ~ 5 × 10 ¹⁸ atoms / cm ^Three (Typically 1 × 10 ¹⁵ ~ 5 × 10 ¹⁷ atoms / cm ^Three ) To add an impurity for controlling the threshold voltage.
[0134]
When this embodiment is applied to the TFT of the present invention, the threshold voltage of the N-channel TFT can be kept in the range of 1.5 to 3.5V. When applied to a P-channel TFT, the threshold voltage can be kept within the range of -1.5 to -3.5V.
[0135]
In addition, the structure of a present Example can be combined with any structure of Examples 1-5. Further, when applied to the CMOS circuit of Example 5, the N-type TFT and the P-type TFT can have different addition concentrations and different types of impurities to be added.
[0136]
Example 7 In the structure shown in FIG. 2C, the source electrode 112 and the drain electrode 113 are formed so as to completely surround the island-like semiconductor layer. In this embodiment, a configuration different from this will be described.
[0137]
The structure shown in FIG. 10A is basically similar to FIG. 2C, but is characterized in that the shapes of the source electrode 11 and the drain electrode 12 are different. That is, in part, the source electrode 11 and the drain electrode 12 are formed inside the island-shaped semiconductor layer (strictly, the source / drain region) by a distance indicated by a.
[0138]
A region indicated by 13 is a region having the same film thickness as the channel formation region 14 and has a width of a distance a. Although schematically shown in the drawing, the distance a is 1 to 300 μm (typically 10 to 200 μm).
[0139]
Here, the characteristics of this embodiment will be described in the light of the manufacturing process. In this embodiment, the source electrode 11 and the drain electrode 12 are formed as shown in FIG. Here, 15 is an island-like semiconductor layer, and the end 16 is exposed.
[0140]
When the channel etch process is performed in this state, the island-like semiconductor layer 15 is etched in a self-aligning manner using the source electrode 11 and the drain electrode 12 as a mask. In this case, the end portion 16 is also etched at the same time.
[0141]
In this way, a structure as shown in FIG. Therefore, it is clear that the end portion 16 has the same film thickness as the channel formation region 14.
[0142]
There are the following two reasons for forming the protruding portion 13 of the island-like semiconductor layer.
(1) Used as an etching monitor in a channel etch process.
(2) When a protective film or an interlayer insulating film is formed in a later process, coverage defects due to steps in the island-shaped semiconductor layer are reduced.
[0143]
The etching monitor is used when inspecting whether or not the channel formation region has an appropriate film thickness by sampling inspection in the manufacturing process.
[0144]
In addition, the structure of a present Example can be combined with any structure of Examples 1-6.
[0145]
[Embodiment 8] In this embodiment, an example of a circuit configuration of the CMOS circuit (inverter circuit) shown in Embodiment 5 will be described with reference to FIG.
[0146]
FIG. 11A shows a CMOS circuit having the same structure as that shown in FIG. In this case, the circuit configuration includes a gate electrode 20 made of a chromium film, an N-type TFT semiconductor layer 21, a P-type TFT semiconductor layer 22, an N-type TFT source electrode 23, a P-type TFT source electrode 24, and a common drain electrode 25. Consists of
[0147]
Note that the terminal portions a, b, c, and d correspond to the terminal portions a, b, c, and d of the inverter circuit shown in FIG.
[0148]
Next, FIG. 11B shows an example in which a semiconductor layer serving as a drain region is shared between an N-type TFT and a P-type TFT. Each code corresponds to the code described in FIG.
[0149]
In the structure shown in FIG. 11B, TFTs can be formed at a very high density, which is very effective when a circuit is highly integrated. The common semiconductor layer forms a PN junction, but this is not a problem.
[0150]
[Example 9] In Example 1, in the crystallization process of an amorphous semiconductor film, laser crystallization, in particular, pulse oscillation type excimer laser is used for melt crystallization. It is also possible to crystallize by solid phase growth using laser light or strong light having the same intensity without distorting the glass substrate.
[0151]
As a light source that emits such intense light or laser light, an infrared lamp such as a halogen lamp or a continuous wave laser such as an Ar laser can be used. Since RTA (Rapid Thermal Anneal) technology using an infrared lamp or a continuous wave laser can be crystallized by heat treatment for several seconds to several tens of seconds, throughput can be significantly improved.
[0152]
When irradiated with infrared lamp light or continuous wave laser light, the lamp light absorbed by the amorphous silicon film changes into heat, which generates crystal nuclei in the amorphous semiconductor film and causes crystal growth by solid phase growth. As a result, the crystalline semiconductor film can be obtained.
[0153]
When a halogen lamp (peak wavelength: 1.15 μm, wavelength: 0.4 to 4 μm) is used, the heating time is 10 to 60 seconds, typically 15 to 30 seconds. The amorphous semiconductor film is heated to 700 to 1000 ° C. Although the amorphous semiconductor film is heated to 700 to 1000 ° C., the glass substrate is difficult to absorb infrared light, and the irradiation time of the lamp light is short. (About ℃) does not heat more.
[0154]
After crystallizing the semiconductor film with infrared lamp light or continuous wave laser light, the semiconductor film may be annealed with laser light irradiation to improve crystallinity. In this case, annealing with laser light can be performed as an impurity activation step.
[0155]
The semiconductor film crystallization method according to the RTA technique of this embodiment can be combined with the structures of all other embodiments.
[0156]
[Embodiment 10] In this embodiment, an active matrix display device in which a driver circuit (peripheral drive circuit) and a pixel matrix circuit are integrally formed on the same substrate in accordance with the basic manufacturing process described in Embodiment 1 is manufactured. An example is shown.
[0157]
In this embodiment, a CMOS circuit (type shown in FIG. 11B) which is a basic configuration is shown as a driver circuit. In addition to the driver circuit, a signal processing circuit such as a D / A converter circuit, a memory circuit, and a γ correction circuit (referred to as a logic circuit in order to distinguish them from the driver circuit) can be configured with the TFT of the present invention. It is. Even in this case, a CMOS circuit is used as a basic circuit.
[0158]
An example in which a multigate TFT is used as the pixel matrix circuit is shown. In this embodiment, an example of a double gate structure is shown, but a single gate structure or a triple gate structure may be used.
[0159]
First, the process up to the step shown in FIG. 1B (laser crystallization step) is completed using the manufacturing step of Example 1. This state is shown in FIG.
[0160]
In FIG. 12A, 30 is a glass substrate, 31 is a base film, 32 is a gate electrode of PTFT which becomes a CMOS circuit, and 33 is a gate electrode of NTFT. Reference numerals 34 and 35 denote gate electrodes of the pixel TFT, and both electrodes are connected at a portion not shown. As a material for the gate electrodes 31 to 35, an aluminum film (containing 2 wt% Sc) is used. In order to protect the gate electrode from thermal and physical damage, anodized films 3000 and 3001 made of aluminum oxide are formed around the gate electrodes 31 and 31 of the CMOS circuit, and the gate electrode 34 and the pixel TFT 34, An anodic oxide film 3002 made of aluminum oxide is also formed around 35. The method for forming the anodic oxide films 3001 to 3002 is the same as that in the first embodiment.
[0161]
In addition to aluminum, a metal such as metal silicide, titanium, or chromium can be used as a material for the gate electrode. For example, a laminated film made of tantalum (Ta) and tantalum nitride (TaN) or a single tantalum film can be used as the anodizable conductive film. Ta on this electrode surface ₂ O _Five You may provide the anodic oxide film shown by these. Tantalum (Ta) and tantalum nitride (TaN) have higher heat resistance than an aluminum film, and can withstand the process temperature of the present invention without forming an anodic oxide film.
[0162]
On the anodic oxide films 3000 to 3002, a silicon nitride film 36 and a silicon oxynitride film 37 are provided. Instead of the silicon oxynitride film 37, a silicon oxide film may be formed. In the pixel TFT and CMOS circuit, a laminated film of a silicon nitride film 36 and a silicon oxynitride film 37 functions as a gate insulating layer over the anodic oxide films 3000 to 3002.
[0163]
A crystalline silicon film 3003 is formed on the silicon oxynitride film 37 by the laser crystallization process described in Embodiment 1.
[0164]
The phosphorus addition step shown in FIG. 12B is performed, and the crystalline silicon film 3003 is formed with n. ⁺ Layer 38, n ^- Layer 39 and i layer 40 are formed. Detailed conditions for each of these layers are given in Example 1.
[0165]
Next, the region other than the region to be the PTFT of the CMOS circuit is hidden with a resist mask (not shown), and boron which is an element selected from the group 13 is added by an ion implantation method or an ion doping method. In this embodiment, boron having a concentration three times the phosphorus concentration added earlier is added, and p. ⁺⁺ Layer 41, p ^- Layer 42 is formed. P ^- It is necessary to set conditions such as the added ion species and the acceleration voltage so that the intrinsic or substantially intrinsic i-layer 40 remains below the layer 42. p ⁺⁺ Layer 41, p ^- Detailed conditions for layer 42 are given in Example 5. (Figure 12 (C))
[0166]
Next, a laser annealing step is performed to improve the crystallinity of the amorphous silicon film 3003 that has been amorphized by a phosphorus and boron addition step. In addition, the impurities (phosphorus and boron) added at the same time are activated. If dehydrogenation by RTA treatment is performed before this laser annealing step, a hydrogen bumping phenomenon can be prevented during laser annealing. (Fig. 12D)
[0167]
Next, the crystalline silicon film 3003 is etched to form island-like semiconductor layers 43 and 44. At this time, a contact hole is formed in order to connect a part of the electrode (second wiring) to be formed next and the gate wiring.
[0168]
The laser annealing step described above can also be performed after the crystalline silicon film is processed into the island-shaped semiconductor layers 43 and 44.
[0169]
Then, a conductive thin film is formed and patterned to form source electrodes 45 (NTFT) and 46 (PTFT) and a common drain electrode 47 of the CMOS circuit. Further, a source electrode 48 and a drain electrode 49 of the pixel TFT are formed. Note that the electrode indicated by 50 functions only as a mask, and is therefore referred to as a mask electrode in this specification. (FIG. 13 (A))
[0170]
When the state of FIG. 13A is obtained, a channel etching step is performed to form channel formation regions 51 to 54. At this time, the driver circuit has a configuration in which both TFTs are provided with a mask offset region only on the drain side and an overlap region is provided on both source sides.
[0171]
Further, as shown in FIG. 13B, the pixel TFT has a configuration in which a mask offset region is provided on the side connected to the source electrode 48 and the drain electrode 49 and an overlap region is provided below the mask electrode 50.
[0172]
Since the source / drain regions of the pixel TFT are switched during charging / discharging of the video signal, it is necessary to increase the breakdown voltage at both ends of the TFT. Also, if the resistance component below the mask electrode 50 is high, the switching operation slows down. Therefore, it is desirable to provide an overlap region so that carriers can easily move.
[0173]
In addition, this Example is an example considered to be the most preferable, and this Example is not limited to this structure. The practitioner may select an optimum structure by taking advantage of each structure described in the first to fourth embodiments.
[0174]
Next, a protective film 55 made of a silicon oxynitride film is formed to a thickness of 200 nm, and an interlayer insulating film 56 made of an organic resin film is formed thereon. As the organic resin film 56, polyimide, polyamide, polyimide amide, or acrylic can be used.
[0175]
Next, contact holes are formed in the interlayer insulating film 56 to form pixel electrodes 57 made of a transparent conductive film (typically ITO). Finally, hydrogenation is performed to complete an active matrix substrate as shown in FIG.
[0176]
Thereafter, an active matrix type liquid crystal display device can be manufactured by sandwiching a liquid crystal layer between a counter substrate and an active matrix substrate using a known cell assembling process.
[0177]
Note that the number of times of patterning necessary for manufacturing the active matrix substrate shown in this embodiment is seven. The process is shown below.
(1) Gate electrode patterning
(2) Boron added region patterning
(3) Island-like semiconductor layer patterning
(4) Gate contact patterning
(5) Source / drain electrode patterning
(6) ITO contact patterning
(7) ITO patterning
[0178]
As described above, since the active matrix substrate can be manufactured with a very small number of masks, the throughput is significantly improved. At the same time, since the circuit can be freely designed using the TFTs having the configurations shown in Embodiments 1 to 5, a display device with high reliability and reproducibility can be easily realized.
[0179]
Note that FIG. 14A illustrates a part of the pixel matrix circuit described in this embodiment as viewed from above. In FIG. 14A, the reference numerals used in the present embodiment are basically attached. Therefore, only necessary parts will be described.
[0180]
FIG. 14B is a cross-sectional view taken along the line AA ′ in FIG. 14A. Although not shown in FIG. 13C, a capacitor wiring 58 made of the same aluminum film as the gate wiring is formed in parallel with the gate wiring as shown in FIG. 14B, and its surface is anodized. An anodized film 3005 is formed.
[0181]
The capacitor wiring 58 forms an auxiliary capacitor (Cs) in a region overlapping with the drain electrode 50 (a region surrounded by a dotted line). At this time, the gate insulating layers 3005, 36, and 37 serve as the dielectric of the auxiliary capacitance. The structure of the auxiliary capacitor is not limited to this embodiment.
[0182]
[Embodiment 11] Embodiment 10 shows an example in which a driver circuit (peripheral drive circuit) and a pixel matrix circuit are integrally formed on the same substrate using a semiconductor film crystallized by laser irradiation. In this embodiment, a case where a semiconductor film is crystallized using a semiconductor film crystallized by RTA is shown.
[0183]
FIG. 15 shows a manufacturing process of this example. The reference numerals in FIG. 15 apply mutatis mutandis to the reference numerals in FIG. An amorphous silicon film having a thickness of 100 to 600 nm is formed on the silicon oxynitride film 37. Here, the film thickness is 200 nm. Next, the amorphous silicon film is crystallized by solid phase growth by RTA as shown in Example 9 to obtain a crystalline silicon film 3004.
[0184]
In the crystallization process of this example, a halogen lamp (peak wavelength: 1.15 μm, wavelength: 0.4 to 4 μm) is used. The lamp light is linearly condensed with a width of 10 mm, the substrate is scanned, and the irradiation time is adjusted to be 10 to 60 seconds, typically 15 to 30 seconds, depending on the scanning speed. In addition, the amorphous semiconductor film is heated to 700 to 1000 ° C. by adjusting the output of the halogen lamp. Here, the scanning speed is 0.5 mm / sec (corresponding to an irradiation time of 20 seconds), the output of the halogen lamp is 7.7 W, the amorphous silicon film is heated to about 920 ° C., and is crystallized. Conductive silicon film 3004 is obtained.
[0185]
After the RTA crystallization step, the crystalline silicon film 3004 may be annealed by irradiating laser light such as excimer laser or YAG laser or strong light equivalent thereto. By this annealing, the amorphous component remaining in the crystalline silicon film 3004 is crystallized and crystallinity is promoted.
[0186]
Crystallization by solid-phase growth in an electric furnace takes several tens of hours, but the crystallization process by RTA takes about several tens of seconds, so that throughput can be improved and thermal damage to the glass substrate is further reduced. There is an advantage of being small.
[0187]
The steps after the RTA crystallization step may be performed in the same manner as in Example 10. The phosphorus addition step shown in FIG. 15B is performed, and the crystalline semiconductor film 3003 is formed with n. ⁺ Layer 38, n ^- Layer 39 and i layer 40 are formed. Next, p shown in FIG. ⁺⁺ Layer 41, p ^- Layer 42 is formed.
[0188]
Next, a laser annealing step shown in FIG. 15D is performed, and the crystallinity of the amorphous semiconductor film 3004 is improved by adding phosphorus and boron, and at the same time, impurities (phosphorus and boron) added. Activation is also performed. If dehydrogenation by RTA treatment is performed before this laser annealing step, a hydrogen bumping phenomenon can be prevented during laser annealing.
[0189]
When the state shown in FIG. 15D is obtained, an active matrix display device in which a driver circuit and a pixel matrix circuit are integrally formed is manufactured according to the manufacturing process of Example 10 shown in FIGS.
[0190]
[Embodiment 12] In this embodiment, an example in which an active matrix display device is manufactured with a structure different from the steps shown in Embodiments 10 and 11 will be described.
[0191]
The feature of this embodiment is that the crystallinity improvement step by laser annealing is not performed after the melt crystallization step by laser light or the crystallization step by solid phase growth by RTA. That is, after crystallization, the phosphorus addition step, the catalytic element gettering step, and the like are performed in the same manner as in Example 10.
[0192]
The feature of this embodiment is that the step of improving the crystallinity of the channel formation region (impurity activation, recrystallization, etc.) is performed after the protective film 55 is provided as shown in FIG. In other words, the laser light is irradiated through the protective film 55 made of a silicon oxynitride film and is applied to the channel formation regions 51 to 54 in a self-aligning manner.
[0193]
In this way, when laser annealing is performed in the state of FIG. 16, reverse diffusion (out diffusion) of impurities such as phosphorus and boron from the source / drain regions can be suppressed. Further, it is possible to obtain an advantage that the power (laser energy) of the laser light is about half.
[0194]
In addition, a present Example is not limited to the structure shown by drawing. The practitioner may perform circuit design by selecting an optimum structure by taking advantage of each TFT structure described in the first to fourth embodiments. In addition, this embodiment can be combined with the configuration shown in all other embodiments.
[0195]
Example 13 In this example, as in Example 12, an example in which the laser annealing step immediately after crystallization in Examples 10 and 11 is omitted is shown. First, after the crystallization step, phosphorus is added using an ion doping method. ⁺ Layers 38 and n ^- Layer 39 is formed. (See FIGS. 12B and 15B). Next, boron is added by ion doping to form a pTFT on the semiconductor layer to be a PTFT. ⁺⁺ Layer 41, p ^- The layer 42 is formed (see FIGS. 12B and 15B).
[0196]
In this state, an annealing process using RTA is performed. In this embodiment, activation of impurities (phosphorus and boron) added by annealing with RTA and dehydrogenation of the semiconductor layer (since ion doping without mass separation causes hydrogen to be implanted together with phosphorus and boron). It is carried out. (Fig. 17 (A))
[0197]
Next, a laser annealing process is performed to recrystallize the semiconductor layer that has been amorphized in the impurity addition process, thereby improving crystallinity. This laser annealing step may be performed after the semiconductor layer is etched and processed into an island-shaped semiconductor layer.
[0198]
Subsequent steps may follow Example 10. In addition, a present Example is not limited to the structure shown by drawing. The practitioner may perform circuit design by selecting an optimum structure by taking advantage of each TFT structure described in the first to fourth embodiments. In addition, this embodiment can be combined with the configuration shown in all other embodiments.
[0199]
[Embodiment 14] In this embodiment, an example of manufacturing a reflective liquid crystal display device based on the manufacturing process shown in Embodiment 10 will be described. Here, a top view of an arbitrary pixel of the pixel matrix circuit of the reflective liquid crystal display device is shown in FIG.
[0200]
In addition, the same part as the part demonstrated in Example 10 is attached | subjected and shown with the same code | symbol, and detailed description is abbreviate | omitted. 18B is a cross-sectional view taken along the line BB ′ of FIG.
[0201]
First, the difference from the tenth embodiment is that the capacitor wiring 59 extends over the entire surface of the pixel. Unlike the transmissive type as shown in the tenth embodiment, the reflective type does not require a high aperture ratio, and therefore the back side of the pixel electrode 61 can be used freely.
[0202]
In the case of this embodiment, the drain electrode 60 is also spread over the entire surface of the pixel, and is arranged so as to overlap with the capacitor wiring 59 in the widest possible range. In this way, most of the pixels can be used as auxiliary capacitors, and a large capacity can be secured. The auxiliary capacitor dielectric is an anodic oxide film 3004, a silicon nitride film 36, and a silicon oxynitride film 37.
[0203]
The pixel electrode 61 is a reflective electrode, and it is preferable to use aluminum having high reflectivity or a material mainly composed of aluminum. If the liquid crystal display device of this embodiment is used for a projection display device, the surface of the pixel electrode is preferably flat. On the other hand, if it is used for a direct-view display device, it is necessary to devise a method for widening the viewing angle by increasing the irregular reflectance by providing irregularities on the surface.
[0204]
In addition, a present Example is not limited to the structure shown by drawing. The practitioner may perform circuit design by selecting an optimum structure by taking advantage of each TFT structure described in the first to fourth embodiments. In addition, this embodiment can be combined with the configuration shown in all other embodiments.
[0205]
[Embodiment 15] In this embodiment, description will be made regarding the configuration of a BM (black matrix) in the liquid crystal display device shown in Embodiment 10.
[0206]
First, the formation of the interlayer insulating film 56 is performed according to the manufacturing steps of Example 10. In this embodiment, a photosensitive acrylic resin is used as the interlayer insulating film 56. Then, after patterning the interlayer insulating film 56, the recesses 65 and 66 are formed by half etching. (FIG. 19 (A))
[0207]
After obtaining the state of FIG. 19A, a black resin (not shown) is formed on the entire surface. As the black resin, an organic resin film containing graphite, carbon, pigment, or the like can be used. For the organic resin film, polyimide, acrylic, or the like is used. In this embodiment, a photosensitive acrylic resin in which graphite is dispersed is used.
[0208]
When the black resin is formed in this way, it is possible to selectively expose only the region where the recesses 65 and 66 are formed, and leave the black resin only in that portion. Thereafter, it is also effective to perform ashing in an oxygen plasma atmosphere to improve flatness.
[0209]
After the black matrices 67 and 68 made of black resin are formed in this way, a pixel electrode 69 composed of an ITO film is formed next. In the present embodiment, the pixel electrode 69 is patterned so that the end of the pixel electrode 69 and the end of the black matrix 68 overlap (the end face of the pixel electrode is inside the BM).
[0210]
As described above, an active matrix substrate having a structure as shown in FIG. 19B is completed. After that, if a known cell assembling process is performed, a liquid crystal display device can be manufactured. The black matrix as in this embodiment has an advantage that no parasitic capacitance is formed with other wirings.
[0211]
In addition, a present Example is not limited to the structure shown by drawing. The practitioner may perform circuit design by selecting an optimum structure by taking advantage of each TFT structure described in the first to fourth embodiments. In addition, this embodiment can be combined with the configuration shown in all other embodiments.
[0212]
[Embodiment 16] In this embodiment, an example in which a black matrix different from that in Embodiment 15 is used will be described. Specifically, an example in which a conductive film is used as the black matrix is shown.
[0213]
In FIG. 20, reference numeral 56 denotes an interlayer insulating film made of an organic resin film, and reference numerals 71 to 74 denote a black matrix made of a conductive film or a wiring pattern also serving as a black matrix. As the conductive film, a titanium film, a chromium film, a laminated film of titanium and aluminum, or the like can be used.
[0214]
In addition, since the black matrix of this embodiment is conductive, there are various utilization methods other than the role as the black matrix. First, a pattern indicated by 71 is a black matrix fixed at a common potential (ground potential). A pattern indicated by 72 is connected to the drain electrode of the CMOS circuit and used as a lead-out wiring. In this way, a multilayer wiring structure can be easily realized by using this embodiment.
[0215]
A pattern 73 is connected to the source electrode of the CNMOS circuit, and has a function as a connection wiring and a function as a black matrix. A pattern indicated by 74 is a black matrix arranged in the pixel matrix circuit, and is basically provided on the wiring or TFT.
[0216]
Then, an interlayer insulating film 75 is again provided on the black matrix (or wiring also serving as the black matrix) 71 to 74. This interlayer insulating film 75 is composed of a silicon oxide film, a silicon nitride film, a silicon oxynitride film, an organic resin film, or a laminated film thereof. This interlayer insulating film 75 will later function as a dielectric for the auxiliary capacitor.
[0217]
After the interlayer insulating film 75 is thus formed, contact holes are formed to form pixel electrodes 76 made of ITO. In the pixel matrix circuit, an auxiliary capacitor 77 is formed between the black matrix 74 and the pixel electrode 76.
[0218]
Here, an arrangement example of the black matrix of the pixel matrix circuit is shown in FIG. FIG. 21 shows an arrangement example when the black matrix 78 is superimposed on the structure shown in FIG. In addition, a thick line indicated by 79 is a pixel electrode, and 80 is a contact portion between the pixel electrode 79 and a lower drain electrode.
[0219]
The black matrix 78 basically covers the wiring and TFT, and has an opening window only in the video display area 81 and the contact portion 80. In the transmissive liquid crystal display device as in this embodiment, the most important issue is to reduce the area occupied by the black matrix and widen the area of the video display area 81 (improve the aperture ratio).
[0220]
In addition, a present Example is not limited to the structure shown by drawing. The practitioner may perform circuit design by selecting an optimum structure by taking advantage of each TFT structure described in the first to fourth embodiments. In addition, this embodiment can be combined with the configuration shown in all other embodiments.
[0221]
[Embodiment 17] In this embodiment, an example in which an active matrix substrate is manufactured with a TFT structure different from the structure shown in Embodiment 10 will be described.
[0222]
The most important point in the structure shown in FIG. 22 is that the uppermost portion of each semiconductor layer (source / drain region) is the first conductive layer (n ⁺ Region or p ⁺⁺ Each conductive layer is once covered with the protective film 55 and the interlayer insulating film 56, and the extraction electrodes 81 to 85 are electrically connected thereon.
[0223]
In the case of such a structure, a channel etching process for forming a channel formation region is performed using a resist mask. Then, a protective film 55 and an interlayer insulating film 56 are formed, and take-out electrodes 87 to 91 are formed.
[0224]
As in the structure of the present embodiment, each of the extraction electrodes (functioning as source / drain electrodes or routing wirings) 87 to 91 is separated from the gate electrode by the interlayer insulating film 56, thereby providing a gap between the source / drain electrode and the gate electrode. It is possible to further reduce the parasitic capacitance. It is more effective if an organic resin material having a small relative dielectric constant is used as the interlayer insulating film 56.
[0225]
Note that the structure of this embodiment can also be applied to the TFTs shown in Embodiments 1 to 4, and can be combined with all other embodiments. Further, the present embodiment is not limited to the structure shown in the drawings. The practitioner may perform circuit design by selecting an optimum structure by taking advantage of each TFT structure described in the first to fourth embodiments.
[0226]
[Embodiment 18] In this embodiment, a connection structure with an external terminal in the active matrix substrate having the configuration shown in Embodiments 10 to 18 will be described. FIG. 23 is an enlarged view of a terminal portion (hereinafter referred to as an FPC mounting portion) connected to an external terminal (typically a flexible printed circuit (FPC)), and is located at an end portion of the active matrix substrate.
[0227]
In FIG. 23, reference numeral 101 denotes a glass substrate, and 86 denotes an insulating layer, which actually has a laminated structure of the base film 102, the silicon nitride film 104, and the silicon oxynitride film 105 shown in FIG. Is done. A second wiring layer 87 is formed thereon. The second wiring layer 87 is a connection wiring layer for transmitting a signal from an external terminal to a source / drain electrode, a gate electrode or the like.
[0228]
The feature of this embodiment is that the second wiring layer 87 is in direct contact with the glass substrate 101. In order to realize this structure, it is necessary to completely remove the insulating layer 86 present in the FPC attachment portion shown in FIG. 23 in the third patterning step described in the first embodiment. If the base of the second wiring layer 87 is a hard glass substrate, the FPC can be firmly bonded.
[0229]
Further, in the FPC attachment portion, the interlayer insulating film 56 is also partially removed in the subsequent process, and the ITO film 57 thereon is in contact with the second wiring layer 86. The ITO film 57 is only required to be laminated on the second wiring layer 86 at least at the FPC attachment portion. In some cases, the ITO film 57 may be formed as an electrode pad as an independent pattern only on the FPC attachment portion.
[0230]
When the anisotropic conductive film 88 is formed later, the ITO film 57 is filled with the conductive particles (such as silica glass coated with gold) contained in the anisotropic conductive film to make the ohmic contact good. Function as a buffer layer.
[0231]
Then, when the FPC attachment portion has a structure as shown in FIG. 23, the FPC terminal 89 is pressure-bonded using the anisotropic conductive film 88. In this way, a connection structure as shown in FIG. 23 can be realized. When such a connection structure is applied to the active matrix substrate shown in Embodiments 10 to 20, good electrical connection with external terminals becomes possible.
[0232]
[Embodiment 19] In this embodiment, a device for improving the patterning efficiency in forming the TFT of the present invention on a large glass substrate will be described.
[0233]
When a fine semiconductor circuit is manufactured over a large glass substrate, patterning errors due to warpage or shrinkage of the glass substrate become a problem. Therefore, an exposure method using an exposure apparatus called a stepper has attracted attention. In stepper exposure, only a part of one reticle can be partially exposed.
[0234]
In the case of this embodiment, necessary circuit patterns such as a driver circuit and a pixel matrix circuit are formed for each part on one reticle. Further, at this time, a region where the same structure is repeated is formed by repeated exposure of the same circuit pattern.
[0235]
In FIG. 24, A, C, G, and I patterns are circuit patterns for producing end portions of the driver circuit. B and H patterns are horizontal circuit patterns of the horizontal scanning driver circuit, and D and F patterns are vertical circuit patterns of the vertical scanning driver circuit. The E pattern is a repeated circuit pattern of the pixel matrix circuit.
[0236]
In this way, driver circuits and pixel matrix circuits that are configured by continuously connecting circuits with the same structure are formed with dedicated circuit patterns only at the ends, and the same circuit pattern is completely repeated inside. The entire pattern is formed using this.
[0237]
When this method is used, the circuit pattern can be shared, so that the number of circuit patterns written on one reticle is reduced, and the reticle can be reduced. In addition, since a single reticle can be used for any large substrate, the time for mask change is saved and the throughput is improved.
[0238]
For example, when the pixel matrix circuit is SXGA, 1280 pixels are arranged in the row direction and 1024 pixels are arranged in the column direction. Therefore, if a pattern circuit corresponding to 256 pixels is written in the row direction of the above-mentioned E pattern, the row direction is completed by repeated exposure five times. In addition, if a pattern circuit corresponding to 256 pixels is written in the column direction, the column direction ends with four repeated exposures.
[0239]
As described above, when the number of repeated exposures in the row direction and the column direction is n and m, respectively, and the numbers of pixels in the row direction and the column direction are X and Y, respectively, the circuit pattern for forming the pixel matrix circuit includes a row. It is necessary to write a pixel pattern of X / n in the direction and Y / m in the column direction. By utilizing this regularity, a high-definition display such as 1920 × 1080 pixels such as ATV (Advanced TV) can be easily realized.
[0240]
[Embodiment 20] In this embodiment, an example in which an AMLCD (active matrix liquid crystal display device) is configured using the active matrix substrate having the configuration shown in Embodiments 10 to 17 will be described. In the AMLCD of this embodiment, the drive circuit and the pixel matrix circuit are composed of inverted staggered TFTs manufactured on the same substrate. In addition, since the drive circuit has a circuit configuration based on a CMOS circuit, power consumption is low.
[0241]
Here, the appearance of the AMLCD of this embodiment is shown in FIG. In FIG. 25A, reference numeral 1101 denotes an active matrix substrate, on which a pixel matrix circuit 1102, a source side driver circuit 1103, and a gate side driver circuit 1104 are constituted by TFTs of the present invention. Reference numeral 1105 denotes a counter substrate.
[0242]
In the AMLCD of this embodiment, an active matrix substrate 1101 and a counter substrate 1105 are bonded with their end faces aligned. However, a part of the counter substrate 1105 is removed, and an FPC (flexible printed circuit) 1106 is connected to the exposed active matrix substrate. The FPC 1106 transmits an external signal into the circuit.
[0243]
Further, IC chips 1107 and 1108 are attached using a surface to which the FPC 1106 is attached. These IC chips are configured by forming various circuits on a silicon substrate, such as a video signal processing circuit, a timing pulse generation circuit, a γ correction circuit, a memory circuit, and an arithmetic circuit. Although two are attached in FIG. 8, one or more may be used.
[0244]
Further, a configuration as shown in FIG. In FIG. 25B, the same portions as those in FIG. 25A are denoted by the same reference numerals. Here, an example is shown in which the signal processing performed by the IC chip in FIG. 25A is performed by a logic circuit 1109 formed with TFTs over the same substrate.
[0245]
In this case, the logic circuit 1109 is also configured on the basis of a CMOS circuit like the drive circuits 1103 and 1104, and can be manufactured with an inverted staggered TFT using the present invention.
[0246]
In addition to the switching element of AMLCD, the TFT using the present invention can be used as a switching element of an EL (electroluminescence) display device. Further, a circuit such as an image sensor can be constituted by the bottom gate type TFT of the present invention.
[0247]
As described above, various electro-optical devices can be manufactured with TFTs using the present invention. In this specification, an electro-optical device is defined as a device that converts an electrical signal into an optical signal and vice versa.
[0248]
In manufacturing the AMLCD of this embodiment, the black matrix may be provided on the counter substrate side, or may be provided on the active matrix substrate (BM on TFT).
[0249]
Further, color display may be performed using a color filter, or the liquid crystal may be driven in an ECB (electric field control birefringence) mode, a GH (guest host) mode, or the like, and the color filter may not be used.
[0250]
Also, JP flat A configuration using a microlens array may be used as in the technique described in Japanese Patent No. 8-15686.
[0251]
[Example 21] The AMLCD shown in Example 20 is used as a display of various electronic devices. Note that the electronic device described in this embodiment is defined as a product on which an electro-optical device typified by AMLCD is mounted.
[0252]
Examples of such electronic devices include a video camera, a still camera, a projector, a projection TV, a head mounted display, a car navigation, a personal computer (including a notebook type), a portable information terminal (a mobile computer, a mobile phone, etc.). . An example of them is shown in FIG.
[0253]
FIG. 26A illustrates a mobile phone, which includes a main body 2001, an audio output portion 2002, an audio input portion 2003, a display device 2004, operation switches 2005, and an antenna 2006. The present invention can be applied to the display device 2004 and the like.
[0254]
FIG. 26B illustrates a video camera, which includes a main body 2101, a display device 2102, an audio input portion 2103, operation switches 2104, a battery 2105, and an image receiving portion 2106. The present invention can be applied to the display device 2102.
[0255]
FIG. 26C illustrates a mobile computer, which includes a main body 2201, a camera unit 2202, an image receiving unit 2203, operation switches 2204, and a display device 2205. The present invention can be applied to the display device 2205 and the like.
[0256]
FIG. 26D illustrates a head mounted display which includes a main body 2301, a display device 2302, and a band portion 2303. The present invention can be applied to the display device 2302.
[0257]
FIG. 26E shows a rear projector, which includes a main body 2401, a light source 2402, a display device 2403, a polarizing beam splitter 2404, reflectors 2405 and 2406, and a screen 2407. The present invention can be applied to the display device 2403.
[0258]
FIG. 26F illustrates a front projector, which includes a main body 2501, a light source 2502, a display device 2503, an optical system 2504, and a screen 2505. The present invention can be applied to the display device 2503.
[0259]
As described above, the application range of the present invention is extremely wide and can be applied to electronic devices in various fields. In addition, it can also be used for electric billboards, advertising announcement displays, and the like.
[0260]
[Embodiment 22] In this embodiment, a configuration example of a circuit configured using the inverted staggered TFT of the present invention will be described. Here, an example in which a shift register circuit is configured will be described with reference to FIG. In this example, the layer structure having the structure shown in Example 10 is adopted.
[0261]
FIG. 27A is a circuit pattern in which only one arbitrary stage of the shift register circuit is taken out, and FIG. 27B is an equivalent circuit diagram thereof. In this embodiment, since the positional relationship between FIG. 27A and FIG. 27B generally corresponds, in the description of FIG. 27A, reference numerals in FIG. 27B are referred to as necessary. .
[0262]
In FIG. 27A, a circuit composed of TFT (a) to TFT (d) and TFT (g) to TFT (j) is composed of a clocked inverter circuit, TFT (e), and TFT (g). The circuit is an inverter circuit. The TFT (e) is a double gate structure TFT.
[0263]
Reference numeral 1201 denotes a CLK line (clock signal line), 1202 denotes an inverted CLK line (inverted clock signal line), 1203 denotes a GND wiring (ground line), and 1204 denotes a Vdd line (power supply line). All of the wirings indicated by the diagonally upward slanting pattern are the second wiring layers (indicated by 45 to 50 in FIG. 13A).
[0264]
For example, the wiring indicated by 1205 functions as a gate electrode of the TFT (a). As described above, all the wiring layers indicated by the oblique line pattern rising to the right are the first wiring layers (indicated by 32 to 35 in FIG. 12A), and the first wiring layer and the semiconductor layer overlap. This part is particularly called a gate electrode.
[0265]
In this embodiment, an overlap region (shown as ov in the figure) is provided on the source side of the TFT, and a mask offset region (shown as in the figure) is provided on the drain side. Therefore, taking the clocked inverter circuit composed of TFTs (a) to (d) in FIG. 27B as an example, ov / of / ov / of / of / ov / of / ov is obtained in order from the top. .
[0266]
That is, since the TFTs (a) and (b) have almost the same structure as the double gate structure of the pixel TFT described in the tenth embodiment, the process is repeated as ov / of / ov / of. In addition, since the TFTs (b) and (c) have a CMOS structure in which the drain electrode is shared by NTFT and PTFT, as described in the fifth embodiment, ov / of / of / ov It becomes the composition.
[0267]
The other circuits are basically the same, and since the TFT (e) has a double gate structure, each TFT has a configuration like ov / of / ov / of in order from the side connected to the GND line 1203. The structure has been determined.
[0268]
With the above-described configuration, a highly reliable semiconductor circuit with improved withstand voltage characteristics can be configured without reducing the operation speed. Further, the reliability of the electro-optical device can be improved by using such a semiconductor circuit.
[0269]
[Embodiment 23] In this embodiment, a configuration example of a circuit configured using the inverted staggered TFT of the present invention will be described. First, an example in which a buffer circuit (left of the drawing) and an analog switch circuit (right of the drawing) are configured will be described with reference to FIG. In this example, the layer structure having the structure shown in Example 20 is adopted. FIG. 28A is a circuit pattern, and FIG. 28B is an equivalent circuit diagram thereof.
[0270]
In the circuit pattern of FIG. 28A, TFTs (a ′) to (h ′) are TFTs using the present invention, and TFTs (a ′), (b ′) and TFTs (c ′), (d ′) ) Constitute one buffer circuit. Further, since the buffer circuit operates at the maximum operating voltage in the liquid crystal display device as in the pixel matrix circuit, high withstand voltage characteristics are required.
[0271]
Each pair of TFTs (e ′) and (f ′) and TFTs (g ′) and (h ′) PTFT) constitutes one analog switch circuit. Since the analog switch circuit also operates at the same operating voltage as the pixel matrix circuit, high withstand voltage characteristics are required.
[0272]
Here, a description will be given focusing on a buffer circuit composed of TFTs (a ′) and (b ′). 1301 is a source electrode (Vdd line) of TFT (a ′), 1302 is a source electrode (GND line) of TFT (b ′), 1303 is a common drain electrode (output signal) of TFT (a ′) and TFT (b ′) Line) 1304 is a common gate electrode (input signal line).
[0273]
Reference numeral 1305 denotes a first conductive layer (n ⁺ Layer) 1306 is a first conductive layer (n on the source side) ⁺ Layer) 1307 is a thinned i layer. The TFT (b ′) has the same structure, and n ⁺ P instead of layer ⁺⁺ A layer is provided.
[0274]
This buffer circuit employs the configuration shown in the fifth embodiment in order to obtain high breakdown voltage characteristics. That is, an overlap region (ov) is formed on the source side, and a mask offset region (of) is formed on the drain side. In this way, the breakdown voltage can be increased only on the drain region side, and the resistance component can be reduced on the source region side.
[0275]
This configuration is the same in a buffer circuit including TFT (c ′) and TFT (d ′).
[0276]
Next, an explanation will be given focusing on an analog switch circuit composed of TFT (e ′) and TFT (f ′). The gate electrode 1204 of the above-described buffer circuit is connected to the gate electrode of the TFT (e ′), and the common drain electrode 1203 of the TFT (a ′) and the TFT (b ′) is connected to the gate electrode of the TFT (f ′).
[0277]
1208 and 1209 are common source electrodes (input data signal lines) of the analog switch circuit, and 1209 is a common drain electrode (output data signal line). However, 1208 corresponds to TFT (e ′) and TFT (f ′), and 1209 corresponds to TFT (g ′) and TFT (h ′). These 1208 and 1209 transmit different video signals.
[0278]
At this time, if either TFT (e ′) or TFT (f ′) is in the on state, the data signal (video signal) sent from the input data signal line 1208 passes through the output data signal line 1209 and passes through the pixel. Sent to the matrix circuit. Therefore, in the case of TFT (e ′) and TFT (f ′) constituting the analog switch circuit, a mask offset region is provided on the drain side and an overlap region is provided on the source side.
[0279]
This configuration is the same in a buffer circuit including TFT (g ′) and TFT (h ′).
[0280]
As described above, a highly reliable semiconductor circuit can be realized by using the configuration of the present invention for a semiconductor circuit that requires a withstand voltage characteristic. This is also important for producing a highly reliable electro-optical device.
[0281]
【The invention's effect】
By implementing the present invention, a TFT with high productivity can be manufactured with a very small number of masks (typically four).
[0282]
In addition, since an electric field relaxation layer (LDD region, mask offset region, thickness offset region, etc.) with small variation in characteristics can be formed between the channel formation region and the source / drain electrodes, a highly reliable and reproducible TFT can be obtained. It is possible to realize.
[0283]
In addition, from a semiconductor circuit formed on a substrate with such a TFT, an electro-optical device combining such a semiconductor circuit and a liquid crystal layer, and further to an electronic device equipped with the electro-optical device as a display, The present invention can be applied to all types of semiconductor devices.
[Brief description of the drawings]
FIGS. 1A to 1C illustrate a manufacturing process of a thin film transistor. FIGS.
FIGS. 2A and 2B illustrate a manufacturing process of a thin film transistor. FIGS.
FIG. 3 is an enlarged view showing a structure of a thin film transistor.
FIG. 4 is a diagram showing a concentration profile in a film.
FIG. 5 illustrates a structure of a thin film transistor.
FIG. 6 illustrates a structure of a thin film transistor.
FIG 7 illustrates a structure of a thin film transistor.
FIG. 8 is a diagram showing a configuration of a CMOS circuit.
FIG. 9 is a diagram showing a concentration profile in a film.
FIG. 10 illustrates a structure of a thin film transistor.
FIG. 11 shows a structure of a CMOS circuit.
FIGS. 12A to 12C illustrate a manufacturing process of a semiconductor circuit. FIGS.
FIGS. 13A to 13C are diagrams illustrating a manufacturing process of a semiconductor circuit. FIGS.
FIG. 14 is a diagram showing a configuration of a pixel matrix circuit.
FIGS. 15A to 15C are diagrams illustrating a manufacturing process of a semiconductor circuit. FIGS.
FIGS. 16A and 16B illustrate a manufacturing process of a semiconductor circuit. FIGS.
FIGS. 17A to 17C are diagrams illustrating a manufacturing process of a semiconductor circuit. FIGS.
FIG. 18 is a diagram showing a configuration of a pixel matrix circuit.
FIG. 19 shows a structure of a pixel TFT.
FIG. 20 is a diagram showing a configuration of a pixel TFT.
FIG. 21 is a diagram showing a configuration of a pixel matrix circuit.
FIG. 22 shows a structure of a pixel TFT.
FIG. 23 is a diagram showing a configuration of an external terminal mounting portion.
FIG. 24 is a diagram showing a configuration relating to a semiconductor circuit exposure processing method;
FIG. 25 is a diagram illustrating a configuration of an electro-optical device.
FIG 26 illustrates a structure of an electronic device.
FIG. 27 is a diagram showing a pattern configuration of a semiconductor circuit.
FIG. 28 is a diagram showing a pattern configuration of a semiconductor circuit.
[Explanation of symbols]
101 substrate
102 Base film
103 Gate electrode
104 Anodized film
105 Silicon nitride film
106 Silicon oxynitride film
107 Amorphous semiconductor film
108 crystalline semiconductor film
109 n ⁺ Layer (first conductive layer)
110 n ^- Layer (second conductive layer)
111 Island-like semiconductor layer
112 Source electrode
113 Drain electrode
114 channel etching region
115 Protective film
116 Channel formation region
117 Mask offset area
118 Contact hole

Claims (3)

A first gate electrode formed on the insulating surface; a gate insulating film formed to cover the first gate electrode; and a first gate electrode formed to cover the first gate electrode on the gate insulating film. 1 crystalline semiconductor layer, a first conductive layer formed on the first crystalline semiconductor layer, a fifth conductive layer, and a first source electrode composed of a metal film are sequentially stacked. An N-channel thin film transistor having a stacked structure and a second stacked structure in which a second conductive layer, a sixth conductive layer, and a first drain electrode made of a metal film are stacked in this order;
A second gate electrode formed on the insulating surface; the gate insulating film formed over the second gate electrode; and the second gate electrode formed over the gate insulating film. The second crystalline semiconductor layer, the third conductive layer formed on the second crystalline semiconductor layer, the seventh conductive layer, and the second drain electrode made of a metal film are sequentially stacked. And a P channel thin film transistor having a fourth stacked structure in which a second source electrode made of a metal film and a fourth conductive layer are stacked in this order. Because
At least one of the first stacked structure and the second stacked structure does not overlap with the first gate electrode, and the first stacked structure and the second stacked structure include the first stacked structure and the second stacked structure. By being formed inside one crystalline semiconductor layer, the first crystalline semiconductor layer has a protrusion,
At least one of the third stacked structure and the fourth stacked structure does not overlap with the second gate electrode, and the third stacked structure and the fourth stacked structure include the first stacked structure and the fourth stacked structure. The second crystalline semiconductor layer has a protrusion by being formed inside the crystalline semiconductor layer of
The first crystalline semiconductor layer includes: a first region overlapping with the first stacked structure; a second region overlapping with the second stacked structure; the first stacked structure; A third region that does not overlap the second stacked structure,
The second crystalline semiconductor layer includes a fourth region overlapping the third stacked structure, a fifth region overlapping the fourth stacked structure, the third stacked structure, and the A sixth region that does not overlap the fourth stacked structure,
The film thickness of the first region and the second region is thicker than the film thickness of the third region,
The film thickness of the fourth region and the fifth region is thicker than the film thickness of the sixth region,
The concentration of the impurity element imparting conductivity contained in the first conductive layer is lower than the concentration of the impurity element imparting conductivity contained in the fifth conductive layer ,
The concentration of the impurity element imparting conductivity contained in the second conductive layer is lower than the concentration of the impurity element imparting conductivity contained in the sixth conductive layer ,
The concentration of the impurity element imparting conductivity contained in the third conductive layer is lower than the concentration of the impurity element imparting conductivity contained in the seventh conductive layer ,
The semiconductor device is characterized in that the concentration of the impurity element imparting conductivity contained in the fourth conductive layer is lower than the concentration of the impurity element imparting conductivity contained in the eighth conductive layer . A first gate electrode formed on the insulating surface; a gate insulating film formed to cover the first gate electrode; and a first gate electrode formed to cover the first gate electrode on the gate insulating film. 1 crystalline semiconductor layer, a first conductive layer formed on the first crystalline semiconductor layer, a fifth conductive layer, and a first source electrode composed of a metal film are sequentially stacked. An N-channel thin film transistor having a stacked structure and a second stacked structure in which a second conductive layer, a sixth conductive layer, and a first drain electrode made of a metal film are stacked in this order;
A second gate electrode formed on the insulating surface; the gate insulating film formed over the second gate electrode; and the second gate electrode formed over the gate insulating film. The second crystalline semiconductor layer, the third conductive layer formed on the second crystalline semiconductor layer, the seventh conductive layer, and the second drain electrode made of a metal film are sequentially stacked. And a P channel thin film transistor having a fourth stacked structure in which a second source electrode made of a metal film and a fourth conductive layer are stacked in this order. Because
The first stacked structure and the second stacked structure overlap with the first gate electrode, and the first stacked structure and the second stacked structure are formed of the first crystalline semiconductor layer. By being formed inside, the first crystalline semiconductor layer has a protrusion,
At least one of the third stacked structure and the fourth stacked structure does not overlap the second gate electrode, and the third stacked structure and the fourth stacked structure are the second stacked structure. The second crystalline semiconductor layer has a protrusion by being formed inside the crystalline semiconductor layer of
The first crystalline semiconductor layer includes: a first region overlapping with the first stacked structure; a second region overlapping with the second stacked structure; the first stacked structure; A third region that does not overlap the second stacked structure,
The second crystalline semiconductor layer includes a fourth region overlapping the third stacked structure, a fifth region overlapping the fourth stacked structure, the third stacked structure, and the A sixth region that does not overlap the fourth stacked structure,
The film thickness of the first region and the second region is thicker than the film thickness of the third region,
The film thickness of the fourth region and the fifth region is thicker than the film thickness of the sixth region,
The concentration of the impurity element imparting conductivity contained in the first conductive layer is lower than the concentration of the impurity element imparting conductivity contained in the fifth conductive layer ,
The concentration of the impurity element imparting conductivity contained in the second conductive layer is lower than the concentration of the impurity element imparting conductivity contained in the sixth conductive layer ,
The concentration of the impurity element imparting conductivity contained in the third conductive layer is lower than the concentration of the impurity element imparting conductivity contained in the seventh conductive layer ,
The semiconductor device is characterized in that the concentration of the impurity element imparting conductivity contained in the fourth conductive layer is lower than the concentration of the impurity element imparting conductivity contained in the eighth conductive layer . A first gate electrode formed on the insulating surface; a gate insulating film formed to cover the first gate electrode; and a first gate electrode formed to cover the first gate electrode on the gate insulating film. 1 crystalline semiconductor layer, a first conductive layer formed on the first crystalline semiconductor layer, a fifth conductive layer, and a first source electrode composed of a metal film are sequentially stacked. An N-channel thin film transistor having a stacked structure and a second stacked structure in which a second conductive layer, a sixth conductive layer, and a first drain electrode made of a metal film are stacked in this order;
A second gate electrode formed on the insulating surface; the gate insulating film formed over the second gate electrode; and the second gate electrode formed over the gate insulating film. The second crystalline semiconductor layer, the third conductive layer formed on the second crystalline semiconductor layer, the seventh conductive layer, and the second drain electrode made of a metal film are sequentially stacked. And a P channel thin film transistor having a fourth stacked structure in which a second source electrode made of a metal film and a fourth conductive layer are stacked in this order. Because
At least one of the first stacked structure and the second stacked structure does not overlap the first gate electrode, and the first stacked structure and the second stacked structure are the first stacked structure. The first crystalline semiconductor layer has a protrusion by being formed inside the crystalline semiconductor layer of
The third stacked structure and the fourth stacked structure overlap with the second gate electrode, and the third stacked structure and the fourth stacked structure are formed of the second crystalline semiconductor layer. By being formed inside, the second crystalline semiconductor layer has a protrusion,
The first crystalline semiconductor layer includes: a first region overlapping with the first stacked structure; a second region overlapping with the second stacked structure; the first stacked structure; A third region that does not overlap the second stacked structure,
The second crystalline semiconductor layer includes a fourth region overlapping the third stacked structure, a fifth region overlapping the fourth stacked structure, the third stacked structure, and the A sixth region that does not overlap the fourth stacked structure,
The film thickness of the first region and the second region is thicker than the film thickness of the third region,
The film thickness of the fourth region and the fifth region is thicker than the film thickness of the sixth region,
The concentration of the impurity element imparting conductivity contained in the first conductive layer is lower than the concentration of the impurity element imparting conductivity contained in the fifth conductive layer ,
The concentration of the impurity element imparting conductivity contained in the second conductive layer is lower than the concentration of the impurity element imparting conductivity contained in the sixth conductive layer ,
The concentration of the impurity element imparting conductivity contained in the third conductive layer is lower than the concentration of the impurity element imparting conductivity contained in the seventh conductive layer ,
The semiconductor device is characterized in that the concentration of the impurity element imparting conductivity contained in the fourth conductive layer is lower than the concentration of the impurity element imparting conductivity contained in the eighth conductive layer .

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