JP2003249505A - Method for manufacturing thin-film semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a thin-film semiconductor layer, which is able to efficiently activate impurities injected to a source region and a drain region, without using complicated devices. <P>SOLUTION: The method for manufacturing TFT (thin-film semiconductor device) 1 comprises, a process for forming a polycrystalline semiconductor film 22 of a given pattern on a substrate 10, a process for forming a gate insulating film 31 on the polycrystalline semiconductor film 22, a process for forming a gate electrode 32 on the gate insulating film 31, a process for forming the source region 22b and the drain region 22c, by selectivity injecting impurities to given regions of the polycrystalline semiconductor film 22, and a process for activating the impurities that have been injected to the source region 22b and the drain region 22c of the polycrystalline semiconductor film 22 by irradiating flash lamp L to the polycrystalline semiconductor film 22 from the other side of the gate electrode 32. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin film semiconductor device, and more particularly, to implanting a source region and a drain region after selectively implanting an impurity into a predetermined region of a polycrystalline semiconductor film. The present invention relates to a technique for activating impurities.

[0002]

2. Description of the Related Art As a display device such as a liquid crystal device, an electroluminescence (EL) device, and a plasma display, a thin film semiconductor device is provided for each pixel in order to drive a large number of pixels arranged in a matrix. An active matrix type display device provided with a polycrystalline semiconductor TFT is known.

An example of a method for manufacturing a polycrystalline semiconductor TFT will be briefly described below. First, after forming a polycrystalline semiconductor film having a predetermined pattern on a substrate, a gate insulating film made of a silicon oxide film or the like is formed on the polycrystalline semiconductor film,
A gate electrode made of metal is sequentially formed. Next, by using the gate electrode as a mask, an impurity is implanted into the polycrystalline semiconductor film to selectively implant the impurity into a predetermined region of the polycrystalline semiconductor film to form a source region and a drain region. At this time, in the polycrystalline semiconductor film, a portion located immediately below the gate electrode and not implanted with impurities becomes a channel region. Next, after forming the interlayer insulating film, the impurities implanted into the source region and the drain region of the polycrystalline semiconductor film are activated. Finally, a contact hole is formed in a portion of the interlayer insulating film corresponding to the source region and the drain region, and a source electrode and a drain electrode are formed, whereby a polycrystalline semiconductor TFT can be manufactured.

[0004]

Conventionally, activation of impurities implanted in the source region and the drain region of the polycrystalline semiconductor film has been carried out by laser annealing, rapid thermal annealing, furnace annealing, or the like. Here, it is preferable to anneal the channel region when activating the impurities implanted in the source region and the drain region,
The laser annealing does not anneal the channel region directly below the gate electrode, and the rapid thermal annealing or furnace anneal anneals the channel region as well, but the annealing at 600 ° C. or lower does not damage the glass substrate. There was a fear that sufficient effects could not be obtained.

When the impurities are activated by laser annealing, the activation can be completed within a very short light irradiation time of the order of nsec. However,
Since the beam shape of laser light is a spot shape or a long shape having a very small area, the area that can be irradiated with laser light at one time is extremely small. Therefore, it is necessary to scan the beam over the entire surface of the substrate and shift the irradiation of the laser beam to irradiate the pulsed beam many times. Therefore, there is a problem that a complicated transport system for changing the irradiation position of the laser light and performing the irradiation sequentially is required, and the manufacturing apparatus becomes complicated. Further, when impurities are activated by rapid thermal annealing, it is necessary to scan the substrate with respect to a long lamp or the like. Therefore, as with laser annealing, a complicated transportation system is required, and the manufacturing apparatus However, there was a problem that it became complicated. In addition,
These problems in the case of activating impurities by laser annealing or rapid thermal annealing are particularly remarkable when a large number of TFTs are formed on a substrate.

Further, when the impurities are activated by furnace annealing, the entire surface of the substrate can be collectively processed even when a large number of TFTs are formed on the substrate.
Although a complicated transport system is not required, the time required for activation of impurities is significantly longer than that of laser annealing or rapid thermal annealing, and thus there is a problem that production efficiency is reduced.

Therefore, the present invention has been made in view of the above circumstances, and the activation of impurities implanted in the source region and the drain region and the annealing of the channel region are effectively performed by using a complicated apparatus. It is an object of the present invention to provide a method for manufacturing a thin film semiconductor device that can be efficiently performed.

[0008]

The present inventor has studied to solve the above problems and invented the following method for manufacturing a thin film semiconductor device. A first method for manufacturing a thin film semiconductor device according to the present invention is a thin film semiconductor device including a semiconductor film having a source region, a channel region, and a drain region, and a gate electrode facing the semiconductor film with a gate insulating film interposed therebetween. In the manufacturing method, a step of forming a polycrystalline semiconductor film having a predetermined pattern on a substrate, a step of forming a gate insulating film on the polycrystalline semiconductor film, and a step of forming a gate electrode on the gate insulating film. A step of selectively implanting an impurity into a predetermined region of the polycrystalline semiconductor film to form the source region and the drain region, and applying light to the polycrystalline semiconductor film from a side opposite to the gate electrode. The method includes activating the impurities implanted into the source region and the drain region of the polycrystalline semiconductor film by irradiation.

That is, according to the first method of manufacturing a thin film semiconductor device of the present invention, impurities are selectively implanted into a predetermined region of a polycrystalline semiconductor film to form a source region and a drain region, and then the polycrystalline semiconductor film is formed. On the other hand, by irradiating light, the impurity implanted in the source region and the drain region of the polycrystalline semiconductor film is activated.

It is preferable that the polycrystalline semiconductor film is irradiated with flash lamp light and the impurities are activated by flash lamp annealing. In the flash lamp annealing, the entire surface of the substrate can be irradiated with light at once, and thus unlike the laser annealing or the rapid thermal annealing, a complicated transport system is unnecessary. The present inventor has found that activation of impurities by flash lamp annealing requires a light irradiation time of 1 μsec to several msec.
Compared with the fact that impurities can be activated by light irradiation for a short time of the order of nsec, this light irradiation time is extremely long. However, in laser annealing, the area that can be irradiated with laser light at one time is extremely small. Therefore, in order to process the entire substrate, it is necessary to irradiate the laser light many times while shifting the position where the laser light is irradiated. In flash lamp annealing, the entire surface of the substrate can be irradiated with light at one time, so that the processing time of the entire substrate can be made equal to or less than that of laser annealing.

Thus, by adopting flash lamp annealing as a means for activating impurities, activation of the impurities implanted in the source region and the drain region is complicated by laser annealing or rapid thermal annealing. Can be efficiently performed in a processing time equal to or shorter than that of laser annealing without using.

Further, in the first method of manufacturing a thin film semiconductor device of the present invention, in the step of activating the impurities implanted in the source region and the drain region of the polycrystalline semiconductor film, the gate electrode is applied to the polycrystalline semiconductor film. It is characterized in that light such as flash lamp light is emitted from the opposite side (the back side of the substrate). The characteristics of flash lamp annealing are X
That is, high-energy light can be instantly irradiated by one emission using an e-lamp or the like. Also, for example, Xe
The flash lamp light emitted from the lamp is 300n
Wavelength of 4 including wavelengths from 1 m to 1 μm
It has a peak at about 00 nm to 500 nm. for that reason,
The flash lamp light is transmitted through the glass substrate and the underlying protective film made of a silicon oxide film, etc. formed on the glass substrate, and is almost selected only for the polycrystalline semiconductor film whose absorption coefficient increases from the wavelength of about 1 μm to the shorter wavelength. It has the property of being absorbed physically. Therefore, even if the flash lamp light is irradiated from the back surface side of the substrate, the polycrystalline semiconductor film can be annealed intensively and efficiently. Moreover, since only the polycrystalline semiconductor film can be annealed in a short time of 1 μsec to several msec, the glass substrate and the gate electrode are not damaged even if the polycrystalline semiconductor film is annealed at 600 ° C. or higher. As the light source, not only the Xe lamp but also other kinds of lamps can be applied.

By irradiating the polycrystalline semiconductor film with flash lamp light from the back surface side of the substrate, the entire polycrystalline semiconductor film can be annealed regardless of the material of the gate electrode. That is, not only the source region and the drain region of the polycrystalline semiconductor film but also the channel region located immediately below the gate electrode can be effectively annealed, so that the crystal defects in the channel region can be reduced. In addition, since the entire polycrystalline semiconductor film can be annealed, the heat generated in the entire polycrystalline semiconductor film can also anneal the gate insulating film.
The gate insulating film can be densified and the interface state between the polycrystalline semiconductor film and the gate insulating film can be reduced.

Further, as described above, the crystal defects in the channel region and the interface state between the polycrystalline semiconductor film and the gate insulating film can be reduced. As a result, the so-called S value (gate voltage Since the rising characteristics of the current flowing when applied and the threshold voltage can be reduced, this is preferable from the viewpoint of lowering the voltage. Moreover, since the gate insulating film can be densified, the reliability of the thin film semiconductor device can be improved.

When the gate electrode is made of metal, when the polycrystalline semiconductor film is irradiated with flash lamp light from the gate electrode side (the surface side of the substrate), the flash lamp light is shielded by the gate electrode and the gate electrode Since the channel region and the gate insulating film located directly below the electrode are not annealed, the above effect cannot be obtained.

A second method for manufacturing a thin film semiconductor device according to the present invention is a thin film including a semiconductor film having a source region, a channel region and a drain region, and a gate electrode facing the semiconductor film with a gate insulating film interposed therebetween. In a method of manufacturing a semiconductor device, a step of forming a polycrystalline semiconductor film having a predetermined pattern on a substrate, a step of forming a gate insulating film on the polycrystalline semiconductor film, and forming a gate electrode on the gate insulating film. And a step of selectively implanting an impurity into a predetermined region of the polycrystalline semiconductor film to form the source region and the drain region, and a light reflection plate on a side of the substrate opposite to the polycrystalline semiconductor film. And irradiating the polycrystalline semiconductor film with light from the side of the gate electrode so that the impurities injected into the source region and the drain region of the polycrystalline semiconductor film. Characterized by a step of activating.

Also in the second method for manufacturing a thin film semiconductor device of the present invention, it is preferable that the polycrystalline semiconductor film is irradiated with flash lamp light and the impurities are activated by flash lamp annealing. By adopting flash lamp annealing as a means for activating the impurities, the activation of the impurities implanted in the source region and the drain region can be performed by a complicated device, as in the first thin film semiconductor device manufacturing method of the present invention. It can be performed efficiently without using it.

Further, in the first method of manufacturing a thin film semiconductor device of the present invention, in the step of activating the impurities implanted in the source region and the drain region of the polycrystalline semiconductor film, While light such as flash lamp light is irradiated from the back surface side, in the second method for manufacturing a thin film semiconductor device of the present invention, the side opposite to the polycrystalline semiconductor film of the substrate (that is, the back surface side). A light reflecting plate is disposed on the substrate, and the polycrystalline semiconductor film is irradiated with light such as flash lamp light from the gate electrode side (the surface side of the substrate).

Flash lamp light is not as directional as laser light. Further, the flash lamp light is generated by an interlayer insulating film made of a silicon oxide film, a gate insulating film, a base protective film,
Since the glass substrate has a property of transmitting light, if a light reflecting plate is arranged on the back surface side of the substrate, the polycrystalline semiconductor film will be exposed even if flash lamp light is irradiated from the front surface side of the substrate. The light reflecting plate reflects the flash lamp light that has passed through the interlayer insulating film, the gate insulating film, the base protection film, and the glass substrate in the area where it is not formed, and the flash lamp light is reflected from the back surface side of the substrate to the polycrystalline semiconductor film. Can be irradiated.

As a result, the entire polycrystalline semiconductor film can be annealed regardless of the material of the gate electrode, as in the first method of manufacturing a thin film semiconductor device of the present invention. That is, not only the source region and the drain region of the polycrystalline semiconductor film but also the channel region located immediately below the gate electrode can be effectively annealed, so that the crystal defects in the channel region can be reduced. Further, since the entire polycrystalline semiconductor film can be annealed, the gate insulating film can be annealed by the heat generated in the entire polycrystalline semiconductor film, so that the gate insulating film can be densified and The interface state between the polycrystalline semiconductor film and the gate insulating film can be reduced.

Further, since the source region and the drain region of the polycrystalline semiconductor film are irradiated with flash lamp light from both the front surface side (gate electrode side) and the rear surface side (substrate side), the polycrystalline semiconductor film is formed. The impurity activation efficiency can be improved as compared with the first thin semiconductor device manufacturing method of the present invention in which the source region and the drain region of the film are irradiated with light only from the back surface side. As a result, the first aspect of the present invention
Compared with the method for manufacturing a thin film semiconductor device described above, it is preferable because the impurities can be efficiently activated with less energy.

Further, in the first method of manufacturing a thin film semiconductor device of the present invention, since the light is irradiated from the back surface side of the substrate, the structure of the annealing device is slightly complicated, but the second thin film semiconductor device of the present invention is used. In the manufacturing method of, since the flash lamp light may be irradiated from the front surface side (gate electrode side) of the substrate,
Flash lamp annealing can be performed without changing the structure of existing flash lamp annealing equipment.
It is suitable.

In the second method of manufacturing a thin film semiconductor device of the present invention, the substrate-side surface of the light reflecting plate is
It is preferable that a large number of fine irregularities are formed. With this configuration, the flash lamp light that has entered the light reflection plate can be reflected and scattered at the same time by the light reflection plate, so that the amount of light that enters the polycrystalline semiconductor film from the back surface side can be increased. You can As a result, the activation efficiency of impurities can be further improved, and the annealing efficiency of the channel region and the gate insulating film can be improved.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail. (First Embodiment) A method of manufacturing a thin film semiconductor device according to a first embodiment of the present invention will be described with reference to FIGS. In this embodiment, a case of manufacturing an n-channel type polycrystalline silicon TFT will be described as an example. Figure 1
3A to 3C are schematic cross-sectional views showing the method of manufacturing the thin film semiconductor device of this embodiment in the order of steps. In addition, in each drawing, in order to make each layer and each member recognizable in the drawing, the scale is different for each layer and each member.

First, as shown in FIG. 1A, after a glass substrate 10 cleaned by ultrasonic cleaning or the like is prepared, the entire surface of the glass substrate 10 is covered under the condition that the substrate temperature is 150 to 450 ° C. The base protective film 11 made of an insulating film such as a silicon oxide film is formed by a plasma CVD method or the like to
A film is formed to a thickness of 500 nm. As a raw material gas used in this step, a mixed gas of monosilane and dinitrogen monoxide, TEOS (tetraethoxysilane, Si (O 2
C ₂ H ₅ ) ₄ ) and oxygen, and disilane and ammonia are suitable.

Next, as shown in FIG. 1B, under the condition that the substrate temperature is 150 to 450 ° C., an amorphous silicon film (non-silicon film) is formed on the entire surface of the glass substrate 10 on which the base protective film 11 is formed. Amorphous semiconductor film) 21 is formed by plasma CVD method or the like.
A film is formed to a thickness of 0 to 100 nm. As the raw material gas used in this step, disilane or monosilane is suitable. Next, as shown in FIG. 1C, the amorphous silicon film 21 is irradiated with a laser beam and laser-annealed to polycrystallize the amorphous silicon film 21,
After forming a polycrystalline silicon film (polycrystalline semiconductor film), the polycrystalline silicon film is patterned by a photolithography method to form an island-shaped polycrystalline silicon film 22. That is, after applying a photoresist on the polycrystalline silicon film, by exposing, developing the photoresist, etching the polycrystalline silicon film, and removing the photoresist,
The polycrystalline silicon film is patterned.

Next, as shown in FIG. 1 (d), 350 ° C.
Under the following temperature conditions, a gate insulating film 31 made of a silicon oxide film, a silicon nitride film or the like is formed to a thickness of 50 to 150 nm on the entire surface of the glass substrate 10 on which the polycrystalline silicon film 22 is formed. As a raw material gas used in this step, a mixed gas of TEOS and oxygen gas or the like is suitable. Next, as shown in FIG. 2A, the gate insulating film 31
A metal film made of aluminum, tantalum, molybdenum, or an alloy containing any of these metals as a main component is formed over the entire surface of the glass substrate 10 on which the film has been formed, and then patterned by photolithography. Then, the gate electrode 32 having a thickness of 300 to 800 nm is formed. That is, after applying the photoresist on the glass substrate 10 on which the metal film is formed, the metal film is patterned by exposing and developing the photoresist, etching the metal film, and removing the photoresist. To form.

Next, as shown in FIG. 2B, with the gate electrode 32 as a mask, a high concentration of impurity ions (phosphorus ions) is applied at a dose of about 0.1 × 10 ¹⁵ to about 10 × 10 ¹⁵ / cm ² . The source region 22b and the drain region 22c are formed in self-alignment with the gate electrode 32 by implantation. Here, the portion directly below the gate electrode 32 and into which the impurity ions are not introduced becomes the channel region 22a. Next, as shown in FIG. 2C, an interlayer insulating film 33 made of a silicon oxide film or the like is formed to a thickness of 300 to 800 nm on the surface side of the gate electrode 32 by the CVD method or the like. The source gas used in this step is TEO.
A mixed gas of S and oxygen gas or the like is suitable.

Next, as shown in FIG. 3A, a flash lamp (not shown) such as a xenon flash lamp is arranged on the back side of the glass substrate 10, and the polycrystalline silicon is placed in a nitrogen atmosphere under a reduced pressure atmosphere. Gate electrode 3 for membrane 22
Flash lamp light L from the side opposite to 2 (the back side of the substrate)
Irradiate. The flash lamp light L is emitted from the glass substrate 10.
Alternatively, the underlying protective film 11 made of a silicon oxide film or the like is transmitted and is almost selectively absorbed only by the polycrystalline silicon film 22, so that the polycrystalline silicon film 22 can be annealed intensively and efficiently. As a result, the impurities implanted into the source region 22b and the drain region 22c of the polycrystalline silicon film 22 can be activated.

By appropriately designing the number, size, etc. of the flash lamps to be arranged, it is possible to irradiate the flash lamp light L on the entire surface of the substrate and to collectively process the entire surface of the substrate. As described above, in the flash lamp annealing, since the entire surface of the substrate can be collectively processed, unlike the laser annealing or the rapid thermal annealing, a complicated transport system is not necessary.

To activate the impurities, for example,
The light irradiation energy from the flash lamp to the glass substrate 10 is, for example, 15 to 50 J / cm ² , and the light irradiation time is 1 μm.
It may be set to sec to several msec, and irradiation may be performed once or multiple times. As described above, activation of impurities by flash lamp annealing requires a remarkably long light irradiation time of 1 μsec to several msec as compared with laser annealing, but in laser annealing, the area that can be irradiated with laser light at one time is large. Since it is extremely small, in order to process the entire substrate, it is necessary to irradiate the laser light multiple times while shifting the position to be irradiated with the laser light, but in flash lamp annealing, the entire surface of the substrate is irradiated with light at once. Therefore, the processing time of the entire substrate can be made equal to or less than that of laser annealing.

In this step, the glass substrate 10 is also used.
When the flash lamp light L is irradiated from the front surface side (gate electrode side) of the flash lamp light L, the flash lamp light L is shielded by the metal gate electrode 32, and the flash lamp is provided in the channel region 22a located immediately below the gate electrode 32. Although the light L is not emitted, in the present embodiment, the glass substrate 1
Since the flash lamp light L is irradiated from the back surface side (the side opposite to the gate electrode) of 0, the flash lamp light L is not shielded by the gate electrode 32 and the entire polycrystalline silicon film 22 can be annealed.

That is, not only the source region 22b and the drain region 22c of the polycrystalline silicon film 22 but also the channel region 22a located immediately below the gate electrode 32 can be effectively annealed, so that the crystal defects in the channel region 22a are affected. Can be reduced. Moreover, since the entire polycrystalline silicon film 22 can be annealed, the gate insulating film 31 can also be annealed by the heat generated in the entire polycrystalline silicon film 22, so that the gate insulating film 31 should be densified. In addition, the interface state between the polycrystalline silicon film 22 and the gate insulating film 31 can be reduced.

In this step, the glass substrate 10
When the glass substrate 10 is heated by absorbing a small amount of the flash lamp light L, the glass substrate 10 is passed through a filter having absorption characteristics similar to those of the glass substrate 10 in order to reduce heat damage to the glass substrate 10. Alternatively, the flash lamp light L may be emitted to the above.

Next, as shown in FIG. 3B, after forming a resist mask (not shown) having a predetermined pattern, the interlayer insulating film 33 is dry-etched through the resist mask to form the interlayer insulating film. In 33, contact holes 34 and 35 are formed in portions corresponding to the source region 22b and the drain region 22c, respectively. Next, as shown in FIG. 3C, aluminum is applied to the entire surface of the interlayer insulating film 33.
After a conductive material such as titanium, titanium nitride, tantalum, molybdenum, or an alloy containing any of these metals as a main component is formed by a sputtering method or the like, patterning is performed by a photolithography method.
A source electrode 36 and a drain electrode 37 having a thickness of m are formed. That is, the glass substrate 10 on which a conductive material is deposited
After applying a photoresist on the above, the conductive material is patterned by exposing and developing the photoresist, etching the conductive material, and removing the photoresist,
The source electrode 36 and the drain electrode 37 are formed. As described above, the n-channel type polycrystalline silicon TFT 1
Can be manufactured.

In the manufacturing method of this embodiment, since flash lamp annealing is employed as a means for activating the impurities implanted in the source region 22b and the drain region 22c of the polycrystalline silicon film 22, laser annealing or rapid thermal annealing is performed. It is possible to efficiently activate the impurities implanted into the source region 22b and the drain region 22c in a processing time equal to or shorter than that of laser annealing without using a complicated device such as annealing.

In the manufacturing method of this embodiment, the source region 22b and the drain region 22 of the polycrystalline silicon film 22 are also included.
In the step of activating the impurities implanted into c, the polycrystalline silicon film 22 is irradiated with the flash lamp light L from the side opposite to the gate electrode 32 (the back side of the substrate). , Polycrystalline silicon film 2
Not only the second source region 22b and the drain region 22c but also the channel region 22a and the gate insulating film 31 can be annealed. As a result, the crystal defects in the channel region 22a can be reduced, the gate insulating film 31 can be densified, and the interface state between the polycrystalline silicon film 22 and the gate insulating film 31 can be reduced. You can

Then, in this way, the channel region 22a
Crystal defects of polycrystalline silicon film 22 and gate insulating film 3
As a result of being able to reduce the interface state between 1 and
Since the S value of 1 and the threshold voltage can be reduced, it is preferable from the viewpoint of lowering the voltage. Moreover, since the gate insulating film 31 can be densified, the reliability of the TFT 1 can be improved.

(Second Embodiment) Next, based on FIG.
A method of manufacturing the thin film semiconductor device according to the second embodiment of the present invention will be described. Since the manufacturing method of the present embodiment is different from the first embodiment only in the step of activating impurities, only the step of activating impurities will be described. Further, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the step of activating the impurities implanted in the source region and the drain region of the polycrystalline silicon film, in the manufacturing method of the first embodiment, the side opposite to the gate electrode (the back surface of the substrate) with respect to the polycrystalline silicon film is used. In contrast to the configuration in which the flash lamp light is irradiated from the side), in the manufacturing method of the present embodiment, as shown in FIG. 4, aluminum on the back surface side (the side opposite to the polycrystalline silicon film) of the glass substrate 10
A light reflection plate 50 made of silver, a silver alloy, or the like is arranged, and the polycrystalline silicon film 22 is irradiated with the flash lamp light L from the gate electrode 32 side (the surface side of the substrate).

Thus, in the manufacturing method of this embodiment,
Since the flash lamp light L is applied to the polycrystalline silicon film 22 from the gate electrode 32 side (front surface side of the substrate), the flash lamp light L incident on the metal gate electrode 32 is reflected by the gate electrode 32. . Therefore, in the polycrystalline silicon film 22, the source region 22b and the drain region 22 which are not located immediately below the gate electrode 32 are formed.
The flash lamp light L is incident on the surface c of the channel region 22 located immediately below the gate electrode 32.
The flash lamp light L does not enter the surface a from its front side.

On the other hand, the flash lamp light L incident on the region where the polycrystalline silicon film 22 is not formed has an interlayer insulating film 33 made of a silicon oxide film or the like and a gate insulating film 31.
While passing through the base protective film 11 and the glass substrate 10, and reflected by the light reflecting plate 50 arranged on the back surface side of the glass substrate 10, the flash lamp light L has no directivity as much as the laser light, and therefore the light reflection. A part of the flash lamp light L reflected by the plate 50 is incident on the back surface side of the polycrystalline silicon film 22.

Thus, in the manufacturing method of this embodiment,
The source region 22b and the drain region 22c of the polycrystalline silicon film 22 are annealed by the flash lamp light L entering from both the front surface side and the back surface side, and the channel region 22a is
The flash lamp light L is incident only from the back surface side and is annealed.

Therefore, according to the manufacturing method of this embodiment as well, as in the first embodiment, not only the source region 22b and the drain region 22c of the polycrystalline silicon film 22 but also the channel region 22a located immediately below the gate electrode 32 are formed. Since it can be effectively annealed, the channel region 22
The crystal defects of a can be reduced. Further, since the entire polycrystalline silicon film 22 can be annealed, the gate insulating film 31 can also be annealed by the heat generated in the polycrystalline silicon film 22 as in the first embodiment. 31 can be densified, and the interface state between the polycrystalline silicon film 22 and the gate insulating film 31 can be reduced.

Furthermore, since the source region 22b and the drain region 22c of the polycrystalline silicon film 22 are irradiated with the flash lamp light L from both the front surface side (gate electrode side) and the rear surface side (substrate side), the polycrystalline silicon film 22 is formed. The impurity activation efficiency can be improved as compared with the first embodiment in which the source region and the drain region of the silicon film are irradiated with the flash lamp light only from the back surface side. As a result, the impurities can be activated efficiently with less energy as compared with the first embodiment, which is preferable.

Here, the light reflecting plate 50 arranged on the back surface side of the glass substrate 10 may be flat, but a large number of fine irregularities (not shown) are formed on the surface of the glass substrate 10 side. Is more preferable. With such a configuration, the flash lamp light L that has entered the light reflection plate 50 can be reflected and scattered at the same time by the light reflection plate 50, so that the flash light that enters the polycrystalline silicon film 22 from the back surface side. The light amount of the lamp light L can be increased. As a result, the activation efficiency of the impurities implanted in the source region 22b and the drain region 22c can be further improved, and the annealing efficiency of the channel region 22a and the gate insulating film 31 can be improved, which is preferable.

Also, in the manufacturing method of the present embodiment,
As in the first embodiment, since flash lamp annealing is adopted as a means for activating the impurities, the activation of the impurities implanted in the source region 22b and the drain region 22c can be efficiently performed without using a complicated device. Although it can be performed well, in the manufacturing method of the first embodiment, since the flash lamp light is irradiated from the back surface side of the substrate, the structure of the flash lamp annealing apparatus is somewhat complicated, whereas the manufacturing method of the present embodiment is different. In the method, since the flash lamp light L may be irradiated from the surface side (gate electrode side) of the glass substrate 10, flash lamp annealing can be performed without changing the structure of the existing flash lamp annealing apparatus, which is preferable. is there.

In the first and second embodiments, the TFT provided with the polycrystalline silicon film has been described as an example, but the present invention is a TFT provided with a polycrystalline semiconductor film other than the polycrystalline silicon film.
The same applies to the FT. Further, although the TFT provided with the gate electrode made of metal has been described as an example, the present invention is similarly applicable to the case where the gate electrode is made of nonmetal. Although the n-channel TFT has been described as an example, the present invention can be applied to a p-channel TFT. Further, the TFT including the source region and the drain region having the self-aligned structure has been described as an example, but the present invention is a TFT including the source region and the drain region having the LDD (Lightly Doped Drain) structure or the offset structure.
Can be similarly applied to. In addition, the manufacturing method of the present invention can be suitably applied particularly when manufacturing a display device such as an active matrix type liquid crystal device or an EL device in which a large number of TFTs are formed on a substrate.

[0049]

EXAMPLES Next, examples and comparative examples according to the present invention will be described. (Example) First, a base protective film made of a silicon oxide film was formed to a thickness of about 500 nm on a glass substrate, and then an amorphous silicon film was formed to a thickness of about 40 nm on the base protective film. Filmed Then, laser annealing is performed to polycrystallize the amorphous silicon film to form a polycrystalline silicon film, and the polycrystalline silicon film is patterned by a photolithography method to form an island-shaped polycrystalline silicon film. . Next, after forming a gate insulating film made of a silicon oxide film to a thickness of about 75 nm, a gate electrode having a predetermined pattern made of aluminum and having a thickness of about 500 nm was formed. Next, using the gate electrode as a mask,
After implanting phosphorus ions at a dose of about 1 × 10 ¹⁵ / cm ² to form a source region, a drain region and a channel region in a self-aligned manner in the polycrystalline silicon film, an interlayer insulating film made of a silicon oxide film with a thickness of about 800 nm is formed. The film was formed to a thickness. Next, a flat silver light reflector is placed on the back side of the substrate, and flash lamp light is irradiated from the gate electrode side to activate the impurities implanted in the source region and the drain region of the polycrystalline silicon film. I went.

(Comparative Example) Similar to the example, a base protective film, a polycrystalline silicon film, a gate insulating film and a gate electrode were sequentially formed on a glass substrate, and then phosphorus ions were implanted to self-align with the polycrystalline silicon film. Source region, drain region,
A channel region was formed, and an interlayer insulating film was further formed.
Next, the impurities implanted into the source region and the drain region of the polycrystalline silicon film were activated in the same manner as in the example except that the light reflecting plate was not arranged on the back surface side of the substrate.

(Evaluation and Results) In the step of activating the impurities, the sheet resistance of the source region and the drain region is set to 2
Comparing the total irradiation energy of the flash lamp light required to obtain kΩ / □, in the example, about 25 J /
While it was cm ² , it was about 20 J / cm ² in the comparative example. This is because in the comparative example in which the light reflection plate is not arranged on the back surface side of the substrate in the step of activating the impurities, only from the front surface side (gate electrode side) with respect to the source region and the drain region of the polycrystalline silicon film. In the embodiment (corresponding to the second method for manufacturing a thin film semiconductor device of the present invention) in which the light reflecting plate is arranged on the back surface side of the substrate while the light from the flash lamp is irradiated, the polycrystalline silicon film is removed from the flash lamp. Light directly incident on the surface of the source and drain regions of
There is light that is emitted from the flash lamp and reflected by the light reflection plate, and then is incident on the back surface of the source region and drain region of the polycrystalline silicon film, and the front surface side of the source region and drain region of the polycrystalline silicon film is present. This is because the flash lamp light is emitted from both the back surface side and the back surface side, and the activation efficiency of impurities is improved.

In the case where the light reflecting plate is not arranged on the back surface side of the substrate and the polycrystalline silicon film is irradiated with the flash lamp light only from the back surface side of the substrate (the first embodiment of the present invention).
(Corresponding to the method for manufacturing a thin film semiconductor device), the efficiency of activating impurities is about the same as that of the comparative example in which the source region and the drain region of the polycrystalline silicon film are irradiated with flash lamp light only from the surface side.

[0053]

As described above in detail, the first aspect of the present invention,
According to the second method of manufacturing the thin film semiconductor device, the impurities implanted into the source region and the drain region can be efficiently activated without using a complicated device. Further, in the step of activating the impurities implanted in the source region and the drain region of the polycrystalline semiconductor film, the entire polycrystalline semiconductor film can be annealed regardless of the material of the gate electrode, so that the channel region can be effectively removed. Can be annealed, and crystal defects in the channel region can be reduced. In addition, since the entire polycrystalline semiconductor film can be annealed, the heat generated in the entire polycrystalline semiconductor film can also anneal the gate insulating film.
The gate insulating film can be densified and the interface state between the polycrystalline semiconductor film and the gate insulating film can be reduced.

[Brief description of drawings]

1A to 1D are process diagrams showing a method of manufacturing a thin film semiconductor device according to a first embodiment of the present invention.

2A to 2C are process diagrams showing a method of manufacturing the thin film semiconductor device according to the first embodiment of the present invention.

3A to 3C are process diagrams showing a method of manufacturing the thin film semiconductor device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a method of manufacturing a thin film semiconductor device according to a second embodiment of the present invention.

[Explanation of symbols]

1 Polycrystalline silicon TFT (thin film semiconductor device) 10 glass substrates 11 Base protection film 21 Amorphous silicon film 22 Polycrystalline silicon film (polycrystalline semiconductor film) 22a channel region 22b Source area 22c drain region 31 Gate insulating film 32 gate electrode 33 Interlayer insulation film 36 source electrode 37 Drain electrode 50 light reflector L flash lamp light

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5F052 AA02 DA02 DB03 JA01                 5F110 AA27 AA30 BB01 CC02 DD02                       DD13 EE03 EE04 EE44 FF02                       FF03 GG02 GG13 GG45 HJ01                       HJ13 HJ23 HL01 HL03 HL04                       HL23 NN02 NN23 NN35 PP03

Claims (4)

[Claims] 1. A method of manufacturing a thin film semiconductor device comprising a semiconductor film having a source region, a channel region, and a drain region, and a gate electrode facing the semiconductor film with a gate insulating film interposed therebetween. A step of forming a polycrystalline semiconductor film having a pattern; a step of forming a gate insulating film on the polycrystalline semiconductor film; a step of forming a gate electrode on the gate insulating film; A step of selectively implanting an impurity into a region to form the source region and the drain region; and irradiating the polycrystalline semiconductor film with light from a side opposite to the gate electrode, thereby forming the polycrystalline semiconductor A method of manufacturing a thin film semiconductor device, comprising the step of activating impurities implanted in the source region and the drain region of the film. 2. A method of manufacturing a thin film semiconductor device, comprising: a semiconductor film having a source region, a channel region, and a drain region; and a gate electrode facing the semiconductor film with a gate insulating film interposed therebetween. A step of forming a polycrystalline semiconductor film having a pattern; a step of forming a gate insulating film on the polycrystalline semiconductor film; a step of forming a gate electrode on the gate insulating film; A step of selectively implanting an impurity into the region to form the source region and the drain region; and disposing a light reflection plate on the opposite side of the substrate from the polycrystalline semiconductor film, Activating the impurities implanted into the source region and the drain region of the polycrystalline semiconductor film by irradiating light from the gate electrode side. Method of manufacturing a thin film semiconductor device that. 3. The method of manufacturing a thin film semiconductor device according to claim 2, wherein a large number of fine irregularities are formed on the substrate-side surface of the light reflection plate. 4. In the step of activating the impurities,
The method of manufacturing a thin film semiconductor device according to claim 1, wherein the polycrystalline semiconductor film is irradiated with flash lamp light.