JP3386713B2 - Method for manufacturing active matrix display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having an integrated circuit in which a large number of insulating gate type semiconductors are formed on an insulating substrate with a high yield by laser light. More specifically, the present invention relates to a semiconductor device including an integrated circuit in which a semiconductor material of an active matrix circuit and a peripheral drive circuit is crystallized by laser light irradiation and a large number of insulating semiconductors are formed with high yield. The semiconductor device according to the present invention is a thin film transistor in an active matrix such as a liquid crystal display, a drive circuit such as an image sensor, an SOI integrated circuit, or a conventional semiconductor integrated circuit (microprocessor, microcontroller, microcomputer, semiconductor memory, or the like). Is used as.

[0002]

2. Description of the Related Art Recently, much research has been done on forming an insulating gate type semiconductor device (MOSFET) on an insulating substrate. Forming the semiconductor integrated circuit on the insulating substrate in this manner is advantageous for high-speed driving of the circuit. Because
This is because the speed of the conventional semiconductor integrated circuit is limited mainly by the capacitance (stray capacitance) between the wiring and the substrate, but such stray capacitance does not exist on the insulating substrate. A MOSFET having a thin film-like active layer formed on an insulating substrate in this manner is called a thin film transistor (TFT). Even in the conventional semiconductor integrated circuit, for example, SRA
A TFT is used as the M load transistor.

Further, recently, a product requiring the formation of a semiconductor integrated circuit on a transparent substrate has appeared. For example, it is a drive circuit for an optical device such as a liquid crystal display or an image sensor. A TFT is also used here. Since these circuits are required to be formed in a large area, it is required to lower the temperature of the TFT manufacturing process. Further, for example, in a device having a large number of terminals on an insulating substrate, even when it is necessary to connect the terminals to the semiconductor integrated circuit, in order to reduce the mounting density, the first stage of the semiconductor integrated circuit, Alternatively, it is considered that the semiconductor integrated circuit itself is monolithically formed on the same insulating substrate.

Conventionally, a TFT is provided with an amorphous, semi-amorphous, or microcrystalline semiconductor film 450.
It has been attempted to improve the crystallinity and improve the quality of the semiconductor film (that is, the mobility is sufficiently high) by annealing at a temperature of ℃ to 1200 ℃. Amorphous TFT using amorphous material for semiconductor film
However, mobility is 5 cm ² / Vs or less, usually 1 cm
Its use is greatly limited because it is as small as ² / Vs, the operating speed is low, and a P-channel TFT cannot be obtained. TFT with mobility of 5 cm ² / Vs or more
In order to obtain, it was necessary to anneal at the above temperature. Moreover, a P-channel TFT (PTFT) could be formed by such annealing.

[0005]

However, in such a thermal process, the substrate material and the like are significantly restricted. That is, in a so-called high temperature process (process having a maximum process temperature of 900 to 1200 ° C.), a high quality thermal oxide film can be used as a gate oxide film.
Only expensive materials such as quartz, sapphire, and spinel that are difficult to increase in area can be used for the substrate.

On the other hand, a low temperature annealing process (characterized by annealing a semiconductor in an amorphous state or a state of low crystallinity equivalent thereto at a temperature of this level in a process having a maximum process temperature of 450 to 650 ° C.)
So, although the range of choice of substrate material is wider than that of high temperature process, the characteristics of the obtained TFT (for example, ON current and OFF
Satisfactory results have not been obtained for the current ratio and mobility. For example, when the TFT is used in an active matrix type liquid crystal display device, the TFT obtained by such a low temperature annealing process has sufficient characteristics as an active matrix TFT, but is not suitable for use in peripheral circuits. Mobility was not satisfactory. For example, the advantage of using high-speed driving (mobility of 5 cm ² / Vs or more) for a device such as a liquid crystal display device is that even such peripheral circuits are manufactured by the same process. Up to now, no particular consideration has been given to the technique of separately manufacturing TFTs according to the characteristics.

The present invention has been made in consideration of such a current situation.
While making a TFT with high mobility, T with low OFF current
The inventors have developed an optimum method for manufacturing TFTs having different characteristics on the same substrate by the same process such as manufacturing FT. In the present invention, the method produced by this method can be obtained conventionally. The present invention provides a semiconductor device having excellent electric characteristics that has not been obtained.

[0008]

According to the present invention, in addition to the conventional thermal equilibrium process, the crystallinity of a semiconductor film is improved by irradiation with a pulsed laser beam to control the characteristics of the obtained TFT. It is characterized by doing. For example, the above object is achieved by combining a low-temperature annealing process and pulsed laser irradiation or changing the conditions of pulsed laser irradiation.

For example, a TFT using crystalline silicon obtained by irradiating a pulsed laser is extremely fast.
Despite its high mobility, pulse laser irradiation does not allow batch processing, and the current laser is 400 mm x 3
It takes about 1 minute to process one 00 mm substrate.
On the other hand, in the low temperature annealing process, batch processing is possible and, for example, the oxygen concentration in the silicon film is 10 ¹⁸ cm ² /
If it is Vs or lower, annealing at 550 ° C. for 1 hour can provide a TFT having characteristics sufficient for use as an active matrix used for normal display, and further, it is possible to shorten the time. . For example, if 60 substrates are processed at the same time, the same takt time as the laser irradiation process can be obtained. Considering the running cost, the low temperature annealing process is advantageous at all.

However, the low temperature annealing process is
As described above, the characteristics of the peripheral circuit are not so good. Therefore, it is not possible to configure the peripheral circuit by itself. This case can be solved by combining the laser irradiation process and the low temperature annealing process. That is, mainly the peripheral circuit portion is irradiated with laser, and the other regions are crystallized by low temperature annealing.

In this case, it should be noted that the characteristics of the amorphous semiconductor are almost determined by the first crystallization step. For example, even if the crystallized silicon is first subjected to low temperature annealing and further laser irradiation is performed, the characteristics are not significantly improved. That is, in order to obtain a high mobility TFT, laser irradiation must be performed first.

Another structure of the present invention is to control the characteristics of the obtained TFT by changing the irradiation conditions of the pulsed laser. Generally, the higher the energy density of the laser, the higher the mobility of the TFT that can be obtained. However, this depends on the semiconductor material and the wavelength of the laser. If the energy density is too high, TF
This will impair the characteristics of T. According to the findings of the present inventors,
As a laser, a KrF excimer laser (wavelength 24
8 nm, pulse width 10 nsec), 200 to 350 mJ / c in the range of 1 to 50 shots.
An energy density of m ² is suitable.

Also in this case, it should be noted that if the laser irradiation may overlap, the characteristics of the TFT in that portion are governed by the conditions of the laser initially irradiated. That is, when the laser irradiation is first performed under the condition of the low mobility TFT, it is almost impossible to manufacture the high mobility TFT even if the laser irradiation is performed thereafter under the condition of the high mobility.

In the present invention, the laser beam has a suitable shape. Therefore, the laser beam enables selective laser irradiation without using a mask. However, in microfabrication, even a slight leakage of laser light may have a great influence on the surroundings.
Therefore, it is also necessary to use an appropriate mask. Needless to say, patterning by a normal photolithography process is indispensable when manufacturing TFTs having different characteristics in a complicated circuit. Further, when the requirement for accuracy is looser, a mask used without being in close contact with the substrate, such as a metal mask, may be used. For example, when the blocks are clearly separated from each other like the active matrix and the peripheral circuit of the liquid crystal display device, a special mask may not be used, but the matrix and the peripheral circuit are 100 μm or more, It is preferable that the distance is 1 mm or more.

In the process of the present invention, a step of forming a semiconductor film on an insulating substrate, a step of forming an insulating film transparent to a laser beam thereon, and a pulsed laser beam are selectively applied to this laminated film. The step of irradiating to improve the crystallinity of the semiconductor film, and then irradiating the entire surface or a part of the substrate with laser light under low temperature annealing or under a condition different from the above laser irradiation; It is based on a step of crystallizing even a part, a step of removing the insulating film to form a gate insulating film on the surface of the semiconductor film, and a step of forming a gate electrode. After that, by using this gate electrode as a main mask, an impurity element is self-alignedly introduced into the semiconductor film by a method such as ion implantation or ion doping, and further pulse laser light is irradiated to destroy the impurity element in the process of introducing the impurity element. The crystallinity of the semiconductor film is improved, and metal wiring is formed in this impurity region to complete the TFT. Further, the impurity doping step may be replaced by laser doping (for example, Japanese Patent Application No. 4-100479) filed by the present inventors. In the present invention, a low resistance metal material such as aluminum is preferable as a material for the gate electrode / wiring. Further, as the pulse laser used in the present invention, Kr
Ultraviolet lasers such as F, ArF, XeCl, XeF excimer lasers are preferred.

Further, in the present invention, the depth of the region having good crystallinity formed by laser irradiation may be adjusted as necessary as described in Japanese Patent Application No. 3-50793, which is the invention of the present inventors. The active layer may be set / changed freely, and as a result, the active layer may have a two-layer structure to reduce the leak current between the source and the drain.

[0017]

EXAMPLES Example 1 FIG. 1 shows this example. In this embodiment, T
A laser crystallized silicon TFT is used in the peripheral circuit of the FT type liquid crystal display device, and a crystalline TFT by low temperature annealing is used in the active matrix region. In this case, the active layers of both TFTs can be manufactured by the same process.

First, a base oxide film 102 having a thickness of 20 to 20 is formed on a Corning 7059 substrate 101 by a sputtering method.
200 nm was deposited. Further, an amorphous silicon film having a thickness of 5 is formed thereon by a plasma CVD method or a low pressure CVD method using monosilane or disilane as a raw material.
0 to 150 nm was deposited. At this time, if the oxygen concentration in the amorphous silicon film is 10 ¹⁸ cm ^-2 or less, preferably 10 ¹⁷ cm ^-2 or less, the temperature of the low temperature annealing step can be lowered and the annealing time can be shortened. The low pressure CVD method is suitable for this purpose. In this example, the oxygen concentration was set to 10 ¹⁷ cm ^-2 or less. Incidentally. When the amorphous silicon film is deposited by plasma CVD, a dehydrogenation step is required thereafter. On this amorphous silicon film, a protective silicon oxide film (thickness 10 to 50 nm) 105 was formed again by the sputtering method. Then, the active matrix region 103 was covered with a photoresist 106 or the like to expose only the peripheral circuit region.

Then, as shown in FIG. 1A, a KrF excimer laser (wavelength 248 nm, pulse width 20 ns) is used.
ec) was applied to improve the crystallinity of the region 104 in the silicon film. The configuration of the laser device is shown, for example, in Japanese Patent Application No. 4-193005 (filed on June 26, 1992). Laser energy density is 200 ~ 400mJ
/ Cm ² , preferably 250 to 300 mJ / cm ² . On the other hand, since the laser beam did not reach the portion 103 covered with the photoresist, it remained amorphous silicon. Then, the photoresist 106 is removed, and the substrate is left in a nitrogen atmosphere at 550 ° C. for 1 hour.
The entire amorphous silicon film was crystallized. As a result, the region 103 also became crystalline silicon.

The structure of the silicon film obtained by the above crystallization process was completely different. That is, in the laser-irradiated region 104, the crystal was relatively large even though it was subjected to the low temperature annealing thereafter. As a result, high mobility has become possible. On the other hand, although the region 103 was crystallized by low temperature annealing, it was composed of relatively small crystals. When the above steps are reversed and low temperature annealing is performed first, and then laser irradiation is performed, the region 104 is removed.
Will be composed of the same small crystals as the region 103.

After that, these Si films are patterned into islands, and, for example, as shown in FIG. 1B, the islands 107 of the peripheral circuit and the islands 10 of the active matrix region are formed.
8 was formed. Further, a silicon oxide film was formed by a sputtering method so as to cover these island regions, and this was used as a gate insulating film 109. After that, an aluminum film having a thickness of 200 nm to 5 μm is formed by an electron beam evaporation method,
This was patterned to form a gate electrode in each island region.

Further, the substrate was dipped in an electrolytic solution to pass a current through the gate electrode to form an anodic oxide layer around the gate electrode. In this case, Japanese Patent Application Nos. 4-30220, 4-38637, and 4-543, which are the inventions of the present inventors, should be considered.
As shown in FIG. 22, the structure may be adopted in which the anodic oxide film of the TFT in the peripheral circuit region is thinned to improve the mobility, and the anodic oxide film of the TFT in the active matrix portion is thickened to prevent the gate leak. Although desirable, in this embodiment, the thickness of the anodic oxide film is 200 to 250 in all cases.
nm. Through the above steps, the gate electrode portions 110 to 112 of each TFT were manufactured.

After that, impurities were self-alignedly implanted into the island-shaped silicon film of each TFT by ion doping using the gate electrode portion (that is, the gate electrode and the anodic oxide film around it) as a mask. At this time, first, phosphorus is implanted into the entire surface by using phosphine (PH ₃ ) as a doping gas, and then the left side of the island region 107 and the active matrix region in the figure are covered with a photoresist to remove diborane (B ₂ H ₆ ) As a doping gas, the island-shaped region 107
Boron was implanted only on the right side of the. The dose is 2-8 for phosphorus
× 10 ¹⁵ cm ^-2 , boron is 4 to 10 × 10 ¹⁵ cm ^-2 ,
The boron dose was set to exceed phosphorus.

After that, as shown in FIG. 1C, a KrF excimer laser (wavelength 248 nm, pulse width 20 ns) was used.
By irradiating ec) and introducing the impurity region, the crystallinity of the portion where the crystallinity is deteriorated is improved. The energy density of the laser was 200 to 400 mJ / cm ² , preferably 250 to 300 mJ / cm ² .

As a result, N type regions 113 and 115 and a P type region 114 were formed. The sheet resistance in these regions was 200 to 800 Ω / □. At the same time, active regions 116 to 118 were also formed.
The active regions 116 and 117 were crystallized by laser irradiation, and the active region 118 was crystallized by low temperature annealing. After that, an interlayer insulator 119 is formed on the entire surface,
A silicon oxide film having a thickness of 300 to 1000 is formed by the sputtering method.
nm formed. This may be a silicon oxide film formed by the plasma CVD method. In particular, a plasma CVD method using TEOS as a raw material can provide a silicon oxide film having good step coverage.

After that, an ITO film was formed as the pixel electrode 120 by a sputtering method and patterned. And source / drain of TFT (impurity region)
Contact holes are formed in the chrome wires 121 to 12
4 was formed. In FIG. 1 (D), NTFT and PTF on the left side are shown.
It is shown that the inverter circuit is formed by T. The wirings 121 to 124 may be multi-layered wiring with aluminum on which chrome or titanium nitride is used as a base to reduce the sheet resistance. Finally, it was annealed in hydrogen at 350 ° C. for 2 hours to reduce dangling bonds in the silicon film. Through the above steps, the peripheral circuit and the active matrix circuit could be integrally formed.

Second Embodiment FIG. 2 shows this embodiment. In this embodiment, laser crystallized silicon TFTs are used for both the peripheral circuit and active matrix of a TFT type liquid crystal display device. Naturally, the active layers of both TFTs can be manufactured in the same process. However, the conditions for laser crystallization are different.

First, a base oxide film 202 having a thickness of 20 to 20 is formed on a Corning 7059 substrate 201 by a sputtering method.
200 nm was deposited. Further, an amorphous silicon film having a thickness of 5 is formed thereon by a plasma CVD method or a low pressure CVD method using monosilane or disilane as a raw material.
0 to 150 nm was deposited. Incidentally. When the amorphous silicon film is deposited by plasma CVD, a dehydrogenation step is required thereafter. A protective silicon oxide film (thickness: 10 to 50 nm) 205 was formed again on the amorphous silicon film by the sputtering method. After that, the substrate was covered with a metal mask 206 made of quartz. In the metal mask, the upper part of the active matrix region 203 is covered with the metal coating 207, and the laser beam can be transmitted only in the peripheral circuit region.

Then, as shown in FIG. 2A, a KrF excimer laser (wavelength 248 nm, pulse width 20 ns) is used.
ec) was applied to improve the crystallinity of the region 204 in the silicon film. Laser energy density is 300
mJ / cm ² , 10 shots. On the other hand, since the laser light did not reach the portion 203 covered with the metal mask 206, it remained as amorphous silicon.
After that, the metal mask 206 is removed, and as shown in FIG. 2B, the KrF excimer laser (wavelength 2
48 nm, pulse width 20 nsec) to irradiate area 2
The crystallinity of all silicon films including 03 was improved. The energy density of the laser was 250 mJ / cm ² and 10 shots. As a result, the region 203 also became the crystalline silicon 208.

The structure of the silicon film obtained by the above crystallization process was completely different. That is, although the region 204 which was initially irradiated with laser was irradiated with laser under another condition after that, the crystal was relatively large. As a result, high mobility has become possible. On the other hand, the region 203 was composed of relatively small crystals. By reversing the above steps, the previously performed laser irradiation 250 mJ / cm ^2, followed by performing the laser irradiation 300 mJ / cm ^2, region 204 is a high mobility is composed of the same small crystals as region 203 can be accomplished There wasn't.

Thereafter, these Si films are patterned into islands, and, for example, as shown in FIG. 2C, the islands 209 of the peripheral circuit and the islands 21 of the active matrix region are formed.
Formed 0. Further, a silicon oxide film is formed by a sputtering method so as to cover these island regions, and this is used as a gate insulating film 211. After that, an aluminum film having a thickness of 200 nm to 5 μm is formed by an electron beam evaporation method,
This was patterned, a gate electrode was formed in each island region, and anodization was performed in the same manner as in Example 1 to form gate electrode portions 212 to 214.

After that, by ion doping, impurities were self-alignedly implanted into the island-shaped silicon film of each TFT by using the gate electrode portion (that is, the gate electrode and the anodic oxide film around it) as a mask. At this time, phosphorus is first injected into the entire surface using phosphine (PH ₃ ) as a doping gas, and then the left side of the island region 209 in the figure and the active matrix region are covered with a photoresist to remove diborane (B ₂ H ₆ ) As a doping gas, the island region 209
Boron was implanted only on the right side of the. The dose is 2-8 for phosphorus
× 10 ¹⁵ cm ^-2 , boron is 4 to 10 × 10 ¹⁵ cm ^-2 ,
The boron dose was set to exceed phosphorus.

After that, as shown in FIG. 2D, a KrF excimer laser (wavelength 248 nm, pulse width 20 ns) was used.
By irradiating ec) and introducing the impurity region, the crystallinity of the portion where the crystallinity is deteriorated is improved. The energy density of the laser was 200 to 400 mJ / cm ² , preferably 250 to 300 mJ / cm ² .

As a result, N-type regions 215 and 217 and a P-type region 216 were formed. The sheet resistance in these regions was 200 to 800 Ω / □. At the same time, active regions 218 to 220 were also formed. After that, a silicon oxide film having a thickness of 300 to 1000 nm was formed as an interlayer insulator 221 on the entire surface by a sputtering method. This may be a silicon oxide film formed by the plasma CVD method. In particular, a plasma CVD method using TEOS as a raw material can provide a silicon oxide film having good step coverage.

After that, an ITO film was formed as the pixel electrode 222 by the sputtering method and patterned. And source / drain of TFT (impurity region)
Forming a contact hole in the chrome wiring 223-22
6 was formed. In Fig. 2 (E), NTFT and PTF on the left side
It is shown that the inverter circuit is formed by T. The wirings 223 to 226 may be multi-layered wiring with chromium or aluminum based on titanium nitride in order to reduce the sheet resistance. Finally, it was annealed in hydrogen at 350 ° C. for 2 hours to reduce dangling bonds in the silicon film. Through the above steps, the peripheral circuit and the active matrix circuit could be integrally formed.

[Third Embodiment] FIG. 3 shows the present embodiment. In this embodiment, laser crystallized silicon TFTs are used for both the peripheral circuit and active matrix of a TFT type liquid crystal display device. Naturally, the active layers of both TFTs can be manufactured in the same process. However, the conditions for laser crystallization are different.

First, a base oxide film 302 having a thickness of 20 to 20 is formed on a Corning 7059 substrate 301 by a sputtering method.
200 nm was deposited. Further, an amorphous silicon film having a thickness of 5 is formed thereon by a plasma CVD method or a low pressure CVD method using monosilane or disilane as a raw material.
0 to 150 nm was deposited. Incidentally. When the amorphous silicon film is deposited by plasma CVD, a dehydrogenation step is required thereafter. On this amorphous silicon film, a protective silicon oxide film (thickness 10 to 50 nm) 305 was formed again by the sputtering method. Then, as shown in FIG. 3 (A), a KrF excimer laser (wavelength 248 nm, pulse width 20 nsec) is applied to the peripheral circuit region 3.
Only 04 was irradiated to improve the crystallinity of the region. The energy density of the laser was 300 mJ / cm ² and 10 shots. On the other hand, the portion 303 which was not irradiated with laser remained amorphous silicon. Then, as shown in FIG. 3 (B), a KrF excimer laser (wavelength 248 nm, pulse width 20 nse is formed on the entire surface of the substrate.
C) was irradiated to improve the crystallinity of all silicon films including the region 303. Laser energy density is 25
It was 0 mJ / cm ² and 10 shots. As a result, the region 303 also became the crystalline silicon 306.

The structure of the silicon film obtained by the above crystallization process was completely different. That is, although the region 304 initially irradiated with laser was subsequently irradiated with laser under another condition, the crystal was relatively large. As a result, high mobility has become possible. On the other hand, the region 303 was composed of relatively small crystals. If, in the reverse of the above steps, the previously performed laser irradiation 250 mJ / cm ^2, then, by performing laser irradiation 300 mJ / cm ^2, the area 304 is composed of the same small crystals as region 303, high mobility The degree could not be achieved.

Thereafter, these Si films are patterned into islands, and, for example, as shown in FIG. 3C, the islands 307 of the peripheral circuit and the islands 30 of the active matrix region are formed.
8 was formed. Further, a silicon oxide film was formed by a sputtering method so as to cover these island regions, and this was used as a gate insulating film 309. After that, an aluminum film having a thickness of 200 nm to 5 μm is formed by an electron beam evaporation method,
This was patterned, a gate electrode was formed in each island region, and anodization was performed in the same manner as in Example 1 to form gate electrode portions 310 to 312.

After that, by ion doping, impurities were self-alignedly implanted into the island-shaped silicon film of each TFT by using the gate electrode portion (that is, the gate electrode and the anodic oxide film around it) as a mask. At this time, first, phosphorus is implanted into the entire surface by using phosphine (PH ₃ ) as a doping gas, and then the left side of the island region 307 and the active matrix region are covered with a photoresist to remove diborane (B ₂ H ₆ ) As a doping gas, the island region 307
Boron was implanted only on the right side of the. The dose is 2-8 for phosphorus
× 10 ¹⁵ cm ^-2 , boron is 4 to 10 × 10 ¹⁵ cm ^-2 ,
The boron dose was set to exceed phosphorus.

After that, as shown in FIG. 3D, a KrF excimer laser (wavelength 248 nm, pulse width 20 ns) was used.
By irradiating ec) and introducing the impurity region, the crystallinity of the portion where the crystallinity is deteriorated is improved. The energy density of the laser was 200 to 400 mJ / cm ² , preferably 250 to 300 mJ / cm ² .

As a result, N-type regions 313 and 315 and a P-type region 314 were formed. The sheet resistance in these regions was 200 to 800 Ω / □. At the same time, active regions 316 to 318 were also formed. After that, a silicon oxide film having a thickness of 300 to 1000 nm was formed as an interlayer insulator 319 on the entire surface by a sputtering method. This may be a silicon oxide film formed by the plasma CVD method. In particular, a plasma CVD method using TEOS as a raw material can provide a silicon oxide film having good step coverage.

After that, an ITO film was formed as the pixel electrode 320 by a sputtering method and patterned. And source / drain of TFT (impurity region)
Contact holes are formed in the chrome wires 321 to 32
4 was formed. In FIG. 3 (E), the NTFT and PTF on the left side are shown.
It is shown that the inverter circuit is formed by T. The wirings 321 to 324 may be multi-layered wirings with aluminum on which chromium or titanium nitride is used as a base to reduce the sheet resistance. Finally, 3 in hydrogen at atmospheric pressure
Annealing was performed at 00 ° C. for 2 hours to reduce dangling bonds in the silicon film. Through the above steps, the peripheral circuit and the active matrix circuit could be integrally formed.

[Fourth Embodiment] FIG. 4 shows the present embodiment. In this embodiment, laser crystallized silicon TFTs are used for both the peripheral circuit and active matrix of a TFT type liquid crystal display device. Naturally, the active layers of both TFTs can be manufactured in the same process. However, the conditions for laser crystallization are different.

First, a base oxide film 402 having a thickness of 20 to 20 is formed on a Corning 7059 substrate 401 by a sputtering method.
200 nm was deposited. Further, an amorphous silicon film having a thickness of 5 is formed thereon by a plasma CVD method or a low pressure CVD method using monosilane or disilane as a raw material.
0 to 150 nm was deposited. Incidentally. When the amorphous silicon film is deposited by plasma CVD, a dehydrogenation step is required thereafter. A protective silicon oxide film (thickness: 10 to 50 nm) 405 was formed again on the amorphous silicon film by the sputtering method. After that, the substrate was covered with a metal mask 406 made of quartz. In the metal mask, the upper part of the active matrix region 403 is covered with the metal coating 407, and the laser beam can be transmitted only in the peripheral circuit region.

Then, as shown in FIG. 4A, a KrF excimer laser (wavelength 248 nm, pulse width 20 ns) is used.
ec) was applied to improve the crystallinity of the region 404 in the silicon film. Laser energy density is 300
mJ / cm ² , 10 shots. On the other hand, since the laser light does not reach the portion 403 covered with the metal mask 406, it remains amorphous silicon.
After that, the metal mask 406 was removed, and another metal mask 408 was newly placed on the substrate. The metal mask 408 is covered with the metal film 409 only in the peripheral circuit region 404. Then, as shown in FIG. 4B, the entire surface of the substrate was irradiated with a KrF excimer laser (wavelength 248 nm, pulse width 20 nsec) to improve the crystallinity of the region 403. Laser energy density is 250 mJ / cm
² , 10 shots.

The structure of the silicon film obtained by the above crystallization process was completely different. That is, the crystal was relatively large in the region 404 that was initially irradiated with laser. As a result, high mobility has become possible. On the other hand, area 4
03 consisted of relatively small crystals. In this embodiment, the above steps may be reversed.

After that, these Si films are patterned into islands, and, for example, as shown in FIG. 4C, the island-shaped region 410 of the peripheral circuit and the island-shaped region 41 of the active matrix region are formed.
1 was formed. Further, a silicon oxide film was formed by a sputtering method so as to cover these island regions, and this was used as a gate insulating film 412. After that, an aluminum film having a thickness of 200 nm to 5 μm is formed by an electron beam evaporation method,
This was patterned, a gate electrode was formed in each island region, and anodization was performed in the same manner as in Example 1 to form gate electrode portions 413 to 415.

After that, impurities were implanted into the island-shaped silicon film of each TFT by ion doping in a self-aligned manner using the gate electrode portion (that is, the gate electrode and the surrounding anodic oxide film) as a mask. At this time, phosphorus is first injected into the entire surface by using phosphine (PH ₃ ) as a doping gas, and then the left side of the island region 410 and the active matrix region in the figure are covered with a photoresist to remove diborane (B ₂ H ₆ ) As a doping gas, the island region 410
Boron was implanted only on the right side of the. The dose is 2-8 for phosphorus
× 10 ¹⁵ cm ^-2 , boron is 4 to 10 × 10 ¹⁵ cm ^-2 ,
The boron dose was set to exceed phosphorus.

After that, as shown in FIG. 4D, a KrF excimer laser (wavelength 248 nm, pulse width 20 ns) was used.
By irradiating ec) and introducing the impurity region, the crystallinity of the portion where the crystallinity is deteriorated is improved. The energy density of the laser was 200 to 400 mJ / cm ² , preferably 250 to 300 mJ / cm ² .

As a result, N-type regions 416 and 418 and P-type region 417 were formed. The sheet resistance in these regions was 200 to 800 Ω / □. At the same time, active regions 419 to 421 were also formed. After that, a silicon oxide film having a thickness of 300 to 1000 nm was formed as an interlayer insulator 422 on the entire surface by a sputtering method. This may be a silicon oxide film formed by the plasma CVD method. In particular, a plasma CVD method using TEOS as a raw material can provide a silicon oxide film having good step coverage.

After that, an ITO film was formed as the pixel electrode 423 by a sputtering method and patterned. And source / drain of TFT (impurity region)
A contact hole is formed in the chrome wiring 424-42.
Formed 7. In FIG. 4 (E), the NTFT and PTF on the left side are shown.
It is shown that the inverter circuit is formed by T. The wirings 424 to 427 may be multi-layer wirings with aluminum on which chromium or titanium nitride is used as a base to reduce the sheet resistance. Finally, it was annealed in hydrogen at 350 ° C. for 2 hours to reduce dangling bonds in the silicon film. Through the above steps, the peripheral circuit and the active matrix circuit could be integrally formed.

Although two kinds of masks are used in this embodiment, three or more kinds of masks may be used if necessary. Further, even if the first embodiment and the second embodiment are used together, a further effect is obtained. Can be obtained.

[0054]

According to the present invention, a TFT can be manufactured at a low temperature with a very high yield. Then, as shown in the examples, various TFTs could be formed on one substrate by utilizing the present invention. This is because the characteristics required by the TFT can be freely set by crystallization by laser irradiation. Therefore, for example, even in the production of an active matrix type liquid crystal display device, the characteristics of the TFT in the matrix region and the TFT in the peripheral circuit region can be optimized, and as a result, in the semiconductor device of the present invention, It was possible to obtain one having excellent electrical characteristics that could not be obtained by the method. Moreover, it could be manufactured by substantially the same process. Conventionally, for example, the peripheral circuit is TAB of IC
Although it had to be manufactured by a method such as connection, which resulted in an increase in cost, the present invention solved most of such problems. Although not shown in the embodiments, the present invention may be used for forming a so-called three-dimensional IC in which semiconductor circuits are further stacked on a single crystal IC or other IC.

[Brief description of drawings]

FIG. 1 shows a method for manufacturing a TFT according to the present invention.

FIG. 2 shows a method for manufacturing a TFT according to the present invention.

FIG. 3 shows a method for manufacturing a TFT according to the present invention.

FIG. 4 shows a method for manufacturing a TFT according to the present invention.

[Explanation of symbols]

Reference Signs List 101 insulating substrate 102 underlying oxide film 103 semiconductor region (matrix region) 104 semiconductor region (peripheral circuit region) 105 protective insulating film 106 mask (photoresist) 107 island semiconductor region (for peripheral circuit) 108 island semiconductor region (for matrix) ) 109 gate insulating film 110 gate electrode (for NTFT) 111 gate electrode (for PTFT) 112 gate electrode (active matrix T
FT) 113, 115 N-type impurity region 114 P-type impurity region 116-118 Active region 119 Interlayer insulator 120 Pixel electrode (ITO) 121-124 Metal wiring

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A 64-45162 (JP, A) JP-A 4-124813 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 29/786 H01L 21/336

Claims (2)

(57) [Claims] 1. An amorphous semiconductor film is formed on a substrate, a part of the amorphous semiconductor film is masked, and a first pulsed laser beam is irradiated to form a first crystalline semiconductor film, The mask is removed, and the second pulsed laser light is irradiated at an energy density lower than that of the first pulsed laser light,
The first crystalline semiconductor film is a second crystalline semiconductor film, and the amorphous semiconductor film is a third crystalline semiconductor film made of a crystal smaller than the second crystalline semiconductor film; Patterning the crystalline semiconductor film and the third crystalline semiconductor film, the second crystalline semiconductor film is used as the first island-shaped crystalline semiconductor film, and the third crystalline semiconductor film is used as the third crystalline semiconductor film. Two
Of the island-shaped crystalline semiconductor film, a gate insulating film is formed on the first island-shaped crystalline semiconductor film and the second island-shaped crystalline semiconductor film, and the gate insulating film is interposed therebetween. A first gate electrode is formed on the first island-shaped crystalline semiconductor film, and a second gate electrode is formed on the second island-shaped crystalline semiconductor film, and the first gate electrode and the second gate electrode are formed. Using the gate electrode as a mask, an N-type impurity or a P-type impurity is added to the first island-shaped crystalline semiconductor film and the second island-shaped crystalline semiconductor film, and the N-type impurity or the P-type impurity is added. A method of manufacturing an active matrix display device, which comprises recovering the crystallinity of an impurity-doped region of a type to form a thin film transistor in a peripheral circuit region and a thin film transistor in a pixel region. An island-shaped crystalline semiconductor film, the gate insulating film, An active matrix display device having a first gate electrode, wherein the thin film transistor in the pixel region has the second island-shaped crystalline semiconductor film, the gate insulating film, and the second gate electrode. Of manufacturing. 2. The method for manufacturing an active matrix display device according to claim 1, wherein the first pulsed laser light and the second pulsed laser light are excimer laser light.