JPH10144608A - Semiconductor thin film and semiconductor device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve carrier mobility of a semi-amorphous silicon thin film which is subjected to a solid phase ordering process by a method wherein the respective concentrations of oxygen, nitrogen and carbon in the amorphous silicon thin film are made not higher than specified. SOLUTION: An amorphous silicon film 602 which contains phosphorus and contains oxygen, nitrogen and carbon whose respective concentrations are at most 10<19> cm<-3> is formed on a substrate 601 by an RF sputtering method. A gate insulating film 603 and an aluminum film gate electrode 604 are formed on the film and then a source region 606 and a drain region 607 are formed by an ion-implantation method. Further, the whole substrate 601 is placed in a vacuum chamber and an excimer laser beam is applied to the rear of the substrate 601 to convert the amorphous silicon film 602 into a semi-amorphous silicon film by laser annealing. After heat annealing in a hydrogen atmosphere, aluminum electrodes 608 and 609 for the drain and source are formed. With this constitution, semiconductor material which has a high electron mobility and a low threshold voltage in a channel forming region can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor material containing silicon as a main component. In particular, the present invention aims at improving the characteristics of a silicon semiconductor material in the form of a thin film. By using the semiconductor material according to the present invention, a thin film semiconductor device (such as a thin film transistor) having improved characteristics can be manufactured.

[0002]

2. Description of the Related Art Conventionally, in manufacturing a thin film semiconductor device such as a thin film field effect transistor, an amorphous semiconductor material (a so-called amorphous semiconductor) or a polycrystalline semiconductor material has been used. In this specification, the term amorphous is used not only to refer to disorder at a purely atomic level but also to a substance having a short-range order of about several nm. More specifically, it means a silicon material having an electron mobility of 10 cm ² / V · s or less or a material having a carrier mobility of 1% or less of an intrinsic carrier mobility of the semiconductor material.

When an amorphous semiconductor (amorphous silicon, amorphous germanium, or the like) is used, its production can be performed at a relatively low temperature of 400 ° C. or less. Attention is being paid as a method.

However, since a pure amorphous semiconductor has extremely low carrier mobility (electron mobility or hole mobility), it is rarely used as it is, for example, as a channel forming region of a thin film transistor (TFT). Has been used by irradiating these amorphous semiconductor materials with intense light such as laser light or xenon lamp light and melting and recrystallizing them to transform them into crystalline semiconductor materials, thereby improving their carrier mobility. (In the following text, this method will be referred to as "laser annealing," but it is not necessary to use a laser. This includes the case of irradiating a powerful flash lamp as well as laser irradiation. .)

[0005] However, the carrier mobility of a semiconductor material conventionally obtained by the laser annealing method is generally lower than that of a single crystal semiconductor material. For example, in the case of silicon coating is greatest electron mobility that reported is 200cm ² / V · s, which is the electron mobility of the single crystal silicon, 1350 cm ² /
It is only one seventh of V · s. In addition, the characteristics (mainly, mobility) of the semiconductor material obtained by the laser annealing method are poor in reproducibility, and the mobility in the same film has a large variation, so that a large number of elements are formed on the same plane. Since the characteristics of the obtained semiconductor element vary greatly, the yield of the product is significantly reduced.

[0006]

SUMMARY OF THE INVENTION The present invention cannot be put to practical use by the conventional laser annealing method because the mobility is extremely small as compared with a single crystal semiconductor material and the reproducibility thereof is poor. It is an object of the present invention to improve the characteristics of a thin film semiconductor material. That is, a thin film semiconductor material with high mobility is provided, and a method for manufacturing a semiconductor material with high mobility with high reproducibility is provided.

[0007]

Means for Solving the Problems Raman spectroscopy is
This is an effective method for evaluating the crystallinity of a substance, and is also used for the purpose of quantifying the crystallinity of a semiconductor film formed by a laser annealing method. The present inventors obtained these numerical values by focusing on the center value of the Raman peak, the width of the Raman peak, the height of the Raman peak, and the like of the obtained semiconductor film in the study of the laser annealing method. Has a very close relationship with the semiconductor thin film to be obtained.

For example, in the case of single crystal silicon, a Raman peak exists at 521 cm ^-1, but the Raman peak of a silicon film subjected to laser annealing tends to move to a shorter wave number (longer wavelength) side. Was observed. Then, it was discovered that there is a strong correlation between the center value of the Raman peak at this time and the carrier mobility of the obtained semiconductor thin film.

FIG. 1 is an example showing this relationship. The center value of the Raman peak (horizontal axis) and the electron mobility of the film (vertical axis) of a film obtained by laser annealing an amorphous silicon film. Shows the relationship. The electron mobility indicates a value obtained by manufacturing a TFT using a silicon film and measuring its CV (capacitance-voltage) characteristic. As is apparent from the figure, the center value of the Raman peak is 515.
There is a large difference in the behavior of electron mobility from cm ^-1 as a boundary. That is, at 515 cm ^-1 or less, the dependence of the electron mobility on the Raman peak is small, but at 515 cm ^-1 or more, the electron mobility rapidly increases with an increase in the center value of the peak.

This phenomenon clearly indicates that there are two phases. According to our research, 515
At cm ^-1 or less, the film was not melted by laser annealing, and atoms were ordered in a solid phase. At 515 cm ^-1 or more, the film was melted by laser annealing and the liquid phase It is presumed to have solidified through the process.

The center value of the Raman peak did not exceed the Raman peak value of single crystal silicon of 521 cm ^−1, and the maximum value of the obtained electron mobility was about 200 cm ² / V · s. However, it is difficult to obtain a silicon film having such a high electron mobility with good reproducibility. Even if laser annealing is intended to be performed under the same conditions, the crystal state seems to be slightly different, and the mobility is 100 cm ^2. / V ・
The majority were less than s. Then, the center value of the thus indicates a low electron mobility Raman peak is much smaller than 521 cm ^-1, 515 cm ^-1 or less was etc. a photon.

The fact that high mobility cannot be obtained with good reproducibility means that, for example, when laser annealing is performed on 200 amorphous silicon films under the same conditions,
3 pieces of 0 cm ² / V · s or more, 100 cm ² / V
11 s or more and less than 200 cm ² / V · s, 1
This is supported by the results of 61 samples having a size of 0 cm ² / V · s or more and less than 100 cm ² / V · s and 125 samples having a size of 10 cm ² / V · s.

It is considered that the reason is that the output of the laser varies considerably from pulse to pulse and that the optimum conditions for laser annealing are in a very narrow range. For example, if the laser output is too low, the amorphous silicon will not melt, and if the laser output is too high,
It is observed that recrystallization does not take place well and becomes amorphous.

Further, in addition to those reasons, the present inventors have found that the presence of foreign elements such as oxygen, nitrogen and carbon in the film is
It was thought that the reproducibility was reduced.
The film used in the experiment shown in FIG. 1 contained oxygen atoms of 2 × 10 ²¹ cm ⁻³ as measured by laser annealing. This is considered to have been caused by some route during amorphous silicon film formation. Only traces of nitrogen and carbon were observed. Therefore, while keeping the source gas, chamber, exhaust system, etc. in the production of the amorphous silicon film sufficiently clean, intentionally adding a small amount of oxygen to the atmosphere to control the amount of oxygen atoms present in the film, The obtained coating was subjected to laser annealing, and the relationship between the center value of the Raman peak and the electron mobility was examined.

However, in this specification, the concentration of these different elements refers to the concentration at the center of the coating. because,
The concentration of these foreign elements is extremely high from the substrate of the coating or near the surface of the coating, but the foreign elements existing in these regions have a great effect on the carrier mobility which is a problem in the present invention. Because I thought it would not be given. In the coating, the portion where the concentration of these different elements is the lowest is the central portion of the film in a normal coating, and the central portion of the film is considered to play an important role in semiconductor devices such as field-effect transistors. Because it can be done. For the reasons described above, in the present invention, when simply referring to the concentration of a different element, it is defined as the concentration at the center of the coating.

This is shown in FIG. As is clear from FIG. 2, the electron mobility was significantly improved by reducing the oxygen concentration in the film. This tendency was the same even when the film contained carbon or nitrogen. The reason is that when the film has a large number of oxygen atoms, when the film is melted and recrystallized by laser annealing, a portion having a small number of oxygen atoms becomes a crystal nucleus and crystal grows. However, the oxygen atoms contained in the film are repelled to the periphery as the crystal grows, and are precipitated at the grain boundaries. Therefore, when viewed through the entire film, the mobility is small due to the barrier generated at the grain boundaries. The theory is that laser annealing causes oxygen atoms or regions with high oxygen atom concentrations (generally considered to have a higher melting point than pure silicon) as crystal nuclei for crystal growth, but the number of oxygen atoms is large. In this case, it has been proposed that crystal nuclei are often generated, so that the size of each crystal becomes small, the mobility becomes small, and the crystallinity is impaired.

In any case, by reducing the oxygen concentration in the coating, extremely large electron mobility could be obtained by laser annealing. For example, by setting the oxygen concentration to 1 × 10 ¹⁹ cm ⁻³ , 1000 c
A large electron mobility of m ² / V · s was obtained. Similar effects could be obtained by reducing the concentration of nitrogen and the concentration of carbon other than the oxygen concentration. further,
A similar tendency was obtained for the hole mobility.

Further, the curve of the position of the Raman peak and the electron mobility showed a bent state similarly to the case of FIG. 1 regardless of whether the oxygen concentration was high or low. The present inventors presumed that the film on the right side of the dotted line in FIG. 2 was recrystallized after the film was once melted by laser annealing, and named this region a melt-recrystallized region. Large mobility was obtained in this melt-recrystallization region.

However, obtaining such a high mobility with good reproducibility has not been particularly improved. For example, 100 amorphous silicon films in which the amount of oxygen atoms in the film is 1 × 10 ¹⁹ cm ⁻³ or less are manufactured, and 1000 cm
Even though laser annealing was intended under the same conditions as those at which ² / V · s was obtained, there were only 9 cases where the electron mobility exceeded 100 cm ² / V · s. Observation of the film after laser annealing revealed that the laser output was too large, crystallization was not successful, and the film was often re-amorphized.

In FIG. 2, the region on the right side of the dotted line is shown as a melt-recrystallization region. However, it is extremely unlikely that data of this region can be actually obtained as described above.
Rather, it proved undesirable because of the high probability of failure. On the other hand, the present inventors have found that high mobility can be obtained by reducing the concentration of oxygen, nitrogen, and carbon in the region existing on the left side of the melt-recrystallization region. This is shown in FIG.
For example, by setting the oxygen concentration to 1 × 10 ¹⁹ cm ⁻³ or less, a maximum electron mobility of 100 cm ² / V · s could be obtained. In addition, it is not difficult to obtain this degree of mobility;
When 00 amorphous silicon films were laser-annealed, 72 films were 80 cm ² / V · s or more.

The present inventors believe that in this region, the amorphous silicon film does not melt, and some lattice ordering occurs in the solid state or in the intermediate state between the solid phase and the liquid phase, and a certain long period is obtained. I believe it was. We named this region a solid-phase ordered region. The present inventors have not clarified the reason for the fact that high mobility can be obtained when the concentration of elements such as oxygen, nitrogen, and carbon is low in the solid-phase ordered region, but presumed as follows. ing.

That is, although there is no melting process in this solid-phase ordered region, atoms that have absorbed the light energy or heat energy of the laser beam move and attempt to shift to the state of lowest energy, that is, the crystalline state. . However, since it does not go through a melting process, it does not reach complete crystallization, and there are some ordered regions of several nm to several tens of nm in some places, and those regions are in a normal amorphous state. it is conceivable that. This state is significantly different from the polycrystalline state after the normal melting state. In other words, in the process of recrystallization after passing through the molten state, crystal nuclei are generated in the liquid phase, and they grow around and become large, so that a portion where the crystals collide with each other is generated. Becomes grain boundaries. In addition, in the grain boundary, lattice defects and impurities are precipitated, and the grain boundary is ionized and polarized. In many cases, a barrier to carriers is generated.

On the other hand, in the case of solid-phase ordering, crystals do not collide with each other, and impurities do not particularly precipitate at grain boundaries. Therefore, in the case of solid-phase ordering, the barrier between ordered regions such as crystals is considered to be extremely low. In a semiconductor with a solid-phase order, the presence of a different element that degrades semiconductor characteristics mainly affects its electrical characteristics.

As is apparent from FIG. 2, for example, when the oxygen concentration is 1 × 10 ¹⁹ cm ⁻³ or less, the electron mobility becomes 10 × 10 ¹⁹ cm ^−3.
0 cm ² / V · s about a but, the center value of the Raman peak at that time, and far removed from the single crystal silicon ones (521 cm ^-1), higher crystallinity not approached the single crystal It is obvious. This is supported by other data shown below.

The present inventors have further found that a similar tendency is observed in the half width of the Raman peak (hereinafter referred to as FWHM). This is shown in FIG. FIG.
The horizontal axis of the graph represents the half-width of the Raman peak of the laser-annealed film divided by the half-width of single-crystal silicon. Here, the half-width ratio of the Raman peak (hereinafter referred to as FWHM RA) is shown.
TIO). It is considered that the smaller the FWHM RATIO is, the closer to 1, the structure is closer to single crystal silicon. As is apparent from the figure, there are a melt-recrystallization region (on the left side of the dotted line in the figure) and a solid-phase ordered region (on the right side of the dotted line in the figure). As in the case of the peak center value, the electron mobility increases as the oxygen concentration in the film decreases, and the same tendency was observed not only for the oxygen concentration but also for the nitrogen and carbon concentrations. As is clear from FIG. 3, the oxygen concentration is 2 × 10 ²¹ cm.
^In the case of ^-3, the region where FWHM RATIO is larger than 2 corresponds to the solid-phase ordered region of the present invention, and the oxygen concentration is 1 × 1
In the case of 0 ¹⁹ cm ^-3, a region where FWHM RATIO is greater than 3 corresponds to the solid-phase ordered region of the present invention. That is, the smaller the concentration, the higher the electron mobility. Further, a similar tendency was observed for the hole mobility.

Furthermore, the present inventors have found that, among the Raman peaks, the peak intensity attributable to the amorphous component in the film has a close correlation with the electron mobility. 4, of the Raman peak of the laser annealed film, the peak of the Raman peak Ic (521 cm around ^-1 intensity Ia single crystal silicon Raman peaks caused by the amorphous component (peak near 480 cm ^-1) ), And is hereinafter referred to as an intensity ratio of Raman peaks (INTENSITY RATIO). Regarding the intensity ratio of the Raman peak, the electron mobility was increased as the amount of oxygen contained in the film was smaller in the solid-phase ordered region (right side of the dotted line in the figure). A similar tendency was observed for nitrogen and carbon concentrations in addition to oxygen concentration.
As is clear from FIG. 4, when the oxygen concentration is 2 × 10 ²¹ cm ⁻³ , the region where the intensity ratio of the Raman peak is approximately 0.2 or more corresponds to the solid-phase ordered region of the present invention, and the oxygen concentration is 1%. × 10
^In the case of ¹⁹ cm ^-3 , the Raman peak intensity ratio is 0.4
The above region corresponds to the solid-phase ordered region of the present invention. That is, the smaller the concentration, the higher the electron mobility. Further, a similar tendency was observed for the hole mobility. In this case as well, as in FIGS. 2 and 3, the left side of the dotted line in FIG. 4 is considered to be a melt-recrystallization region.

As described above, it has been clarified that the carrier mobility can be improved by reducing the amounts of oxygen, nitrogen and carbon in the film. In particular, the present inventors set the amount of each of these elements to 5 × 10 ¹⁹ cm ⁻³ or less, preferably 1 × 10 ¹⁹ cm ⁻³ or less, so that a melting process with a higher probability of failure can be prevented. Then, by a solid-phase ordering process with a higher yield, the concentration of the different element is reduced to, for example, 5 × 10 ¹⁹ cm ⁻³ at a probability of up to 80%.
By setting the following, the electron mobility of the silicon film is 5
It has been found that a value of 100 cm ² / V · s can be obtained by setting the value to 0 cm ² / V · s or more and 1 × 10 ¹⁹ cm ² / V · s or less. Further, a value of 30 to 80 cm ² / V · s could be stably obtained as the hole mobility by the same method.

As described above, by reducing the concentration of the different elements in the film, the carrier transfer in a special state (the present inventors refer to this as a semi-amorphous state) through a solid-phase ordering process. It was found that the degree could be improved. In order to realize a semi-amorphous state, it is a necessary condition that the film is not in a molten state. Therefore, in a long time, the temperature of the portion irradiated with the laser is lower than the melting point of the semiconductor, that is,
In the case of silicon, the temperature must be 1400 ° C. under atmospheric pressure, and in the case of germanium, it must be 1000 ° C. or less under atmospheric pressure. However, in a very short time of 10 nanoseconds, for example, realized by an excimer laser, even if a temperature instantaneously exceeding 2000 ° C. is spectroscopically observed, the melting of the coating does not occur. Sometimes it is not observed, and this definition of temperature does not really make much sense.

As described above, it is effective to reduce the concentration of different elements in order to obtain high mobility. For example, the concentration of these elements is set to 1 × 10 ¹⁶ cm.
^{Setting to -3} or less means that the concentration of these elements is extremely low (1 × 10 ¹⁶⁾ in an environment with an extremely high degree of vacuum.
cm ^-3 or less) Even if laser annealing is performed on the amorphous semiconductor film, it cannot be easily achieved. this is,
Oxygen gas, nitrogen gas, moisture, carbon dioxide, etc. contained in the atmosphere in trace amounts are taken into the film during laser annealing, or these gases adsorbed on the surface of the film become It is presumed that it was taken in.

In order to avoid these difficulties, a special manufacturing method is required. One method is that the concentrations of oxygen, nitrogen and carbon are very low, for example, 10 ¹⁵ cm ^−3.
A protective film such as silicon oxide, silicon nitride, or silicon carbide is formed to cover the surface of the following amorphous semiconductor film, and then,
By performing laser annealing in a vacuum atmosphere (10 ^-4 torr or less), a semiconductor film with extremely low concentrations of oxygen, nitrogen, and carbon and high mobility can be formed. For example, the concentrations of carbon, nitrogen, and oxygen are all 1 × 10 ¹⁵ cm ⁻³ or less, and the electron mobility is 300 cm ² /
A V.s silicon coating was obtained.

When forming a protective film of silicon oxide, silicon nitride, silicon carbide or the like over the surface of the amorphous semiconductor film, the amorphous semiconductor film is formed by a CVD method or a sputtering method in a chamber having one vacuum device. A suitable method is to form a film continuously without changing the atmosphere in the same chamber after forming the film, or once in an extremely high vacuum state, and then setting the atmosphere suitable for film formation. However, more product yield,
In order to improve reproducibility and reliability, it is desirable to prepare a dedicated chamber for forming each film, and to adopt a method of moving each chamber while keeping the product extremely high vacuum . Selection of these film formation methods is made according to the scale of capital investment. Regardless of which method is adopted, it is important that oxygen, nitrogen, and carbon contained in the underlying amorphous semiconductor film are sufficiently small,
And that no gas is adsorbed at the interface between the amorphous semiconductor and the protective film thereon. For example, even if an extremely pure amorphous semiconductor film is formed, once the film is exposed to the atmosphere and then a silicon nitride film is formed thereon, the carrier of the film obtained by laser annealing the film is obtained. Mobility is generally small,
Also, the probability of obtaining a high mobility is extremely small. This is presumably because the gas is adsorbed on the surface of the amorphous semiconductor film and diffuses into the film during the subsequent laser annealing.

The material of the protective film at this time may be silicon oxide, silicon nitride or silicon carbide as long as the condition for transmitting laser light is satisfied, or a chemical formula of SiN _x O _y in which these are mixed. C _z (0 ≦ x ≦ 4/3, 0 ≦
A material including a material represented by y ≦ 2, 0 ≦ z ≦ 1, 0 ≦ 3x + 2y + 4z ≦ 4) may be used. Further, the thickness was suitably from 5 to 1000 nm.

The present invention provides high carrier mobility by reducing the concentration of oxygen, nitrogen and carbon in an amorphous semiconductor film and reducing the concentration of oxygen, nitrogen and carbon present during laser annealing. The electron mobility or the hole mobility obtained at this time is an average value of the channel formation region of the field-effect transistor formed for the measurement, and the channel formation region is obtained. The mobility in each fine part cannot be determined. However,
As apparent from FIGS. 1 to 4 of the present invention and the description related thereto, the carrier mobility is determined by the position of the Raman peak, the half width of the Raman peak, the intensity of the amorphous component in the Raman peak, and the Raman peak. It has been clarified that parameters can be uniquely determined from the parameters such as the strength of the sample. Therefore, the mobility of a minute area where the mobility cannot be measured directly can be calculated from these information by Raman spectroscopy.
Approximate mobility can be estimated.

FIG. 5 shows semi-amorphous silicon formed through a solid-phase ordering process and having an electron mobility of 101.
those of cm ² / V · s, and the electron mobility which is formed through the melting process of a field effect transistor having a channel forming region of one of 201cm ² / V · s, the Raman peak in each section of the channel formation region half Price range (FW
HM). In the drawing, the horizontal axis represents the position of the channel formation region. L is the length of the channel formation region and is 100 μm. X represents the coordinates of the channel formation region, X / L = 0 is the interface of the channel formation region with the source region, X / L = 1 is the interface of the channel formation region with the drain region, and X / L = 0.5 represents the center of the channel formation region. As is clear from FIG. 5, in the case of the electron mobility of 101 cm ² / V · s, the FWHM is larger than 10 cm ^−1, but the fluctuation (the variation depending on the place) is small, and the electron mobility of 201 cm ² / V · s is small. Although the FWHM is smaller than 10 cm ⁻¹ , the variation (variation depending on the place) is large. The fact that the smaller the FWHM is, the closer the crystallinity of the film is to that of a single crystal, and therefore the higher the electron mobility is, as described in FIG. 3 and the related description, and this data situation is not contradictory. However, the small variation (location dependence) of the FWHM depending on the location indicates that the crystallinity of the coating is almost the same regardless of the location.
The oxygen concentration of this coating was about 1 × 10 ¹⁹ cm ⁻³ .

On the other hand, the electron mobility is 201 cm ² / V · s
Had an oxygen concentration of 1 × 10 ¹⁹ cm ⁻³ as well. As is clear from the figure, the FWHM generally decreased, but the location dependency of the FWHM was large. And, depending on the location, the single crystal having electron mobility of FWHM
FWH equal to or less than (4.5 cm ^-1 )
It shows the value of M and suggests that the electron mobility of that part is as large as that of a single crystal. This means that a part having crystallinity equivalent to that of single crystal silicon is localized in the same film. Means However, when mass-produced as a device, it is not desirable to use a material whose characteristics greatly differ depending on the location, even if the mobility is large. In particular, as the size of the device becomes smaller, the non-uniformity which has not been a problem because it has been averaged up to that time becomes noticeable, and causes a significant reduction in the yield of the device.

On the other hand, the electron mobility is 101 cm ² /
In the case of V.s (semi-amorphous), the location dependence of FWHM is generally small as is clear from the figure. This leads to higher yields in mass-producing devices and demonstrates their suitability as materials.

In order to obtain high carrier mobility, it is necessary to reduce the concentration of different elements in the film and to optimize the laser annealing conditions as described above. The laser annealing conditions vary depending on the laser oscillation conditions (continuous oscillation or pulse oscillation, repetition frequency, intensity, wavelength, coating, etc.), and cannot be determined unconditionally. As a laser, an ultraviolet laser such as an excimer laser, a visible or infrared laser such as a YAG laser can be used, and it is necessary to select a laser depending on the thickness of a film to be laser annealed. That is, since silicon or germanium materials generally have a short absorption length with respect to ultraviolet light, laser light does not enter a deep portion, and laser annealing occurs only in a relatively shallow region of the surface. On the other hand, the absorption length of visible light and infrared light is long, and light penetrates relatively deeply, so that laser annealing occurs even in deep parts.

As an additional matter, after laser annealing of the semiconductor film, 200-600
Annealing at a temperature of C for 10 minutes to 6 hours was effective for obtaining high carrier mobility with good reproducibility.
This is because laser annealing causes solid-phase ordering in a specific region while leaving unpaired dangling bonds (tangling bonds) in the remaining amorphous region. It is considered that this newly occurs because it functions as a barrier to the carrier. When the semiconductor contains a large amount of oxygen, nitrogen, carbon, etc., these fill the dangling bonds. However, when the concentration of oxygen, nitrogen, carbon, etc. is extremely small as in the present invention, the dangling bond is filled. The ring bond cannot be filled, and therefore it is necessary to anneal in a hydrogen atmosphere after laser annealing.

[0039]

【Example】

Example 1 A TFT having a planar structure was manufactured, and its electrical characteristics were evaluated. FIG. 6 shows a manufacturing method. First, an amorphous silicon film having a thickness of about 100 nm was formed by a normal RF sputtering method. The substrate was quartz 601, the substrate temperature was 150 ° C., the atmosphere was substantially 100% argon, and the pressure was 0.5 Pascal (pa). Hydrogen and other gases were not intentionally added to argon. The concentration of argon was 99.99% or more. Input power is 200
At W, the RF frequency was 13.56 MHz. Then, this amorphous silicon film is formed into a 100 μm × 500
The amorphous silicon film 602 was obtained by etching in a rectangular shape of μm.

It was confirmed by secondary ion mass spectrometry (SIMS) that the concentrations of oxygen, nitrogen and carbon in this film were all 10 ¹⁹ cm ⁻³ or less.

Next, this film is placed in a vacuum vessel having a pressure of 10 ^-5 torr, and an excimer laser beam (KrF laser, wavelength 248) is passed through a quartz window provided in the vacuum vessel.
nm, pulse width 10 ns, irradiation energy 200 m
J, an irradiation pulse number of 50 shots) to perform laser annealing.

Further, a gate insulating film 603 having a thickness of about 100 nm was formed thereon by a sputtering method in an oxygen atmosphere. The substrate temperature at this time is 150 ° C., and RF (1
(3.56 MHz) input power was 400 W. The atmosphere was substantially oxygen and no other gas was intentionally added. The concentration of oxygen was 99.9% or more. The pressure is 0.
It was 5 pa.

Thereafter, an aluminum film (thickness: 200 n)
m) was formed by a known vacuum deposition method, and unnecessary portions were removed by a known dry etching method to form a gate electrode 604. The width of the gate electrode was 100 μm. At this time, the photoresist 605 used for the dry etching was left on the gate electrode.

Then, boron ions were implanted into the region other than the gate electrode at 10 ¹⁴ cm ^-2 by ion implantation. Under the gate electrode, the gate electrode and the photoresist on the gate electrode serve as a mask, so that boso ions are not implanted. By this step, impurity regions, that is, a source region 606 and a drain region 607 were formed in the silicon film. This is shown in FIG.

Further, the entire substrate is placed in a vacuum vessel, and
Excimer laser light (KrF laser, wavelength 248 nm, pulse width 10 nanoseconds, irradiation energy 100 mJ, irradiation pulse number 50 shots) was irradiated at a pressure of 0 ^-5 torr to perform laser annealing. By this step, the impurity region which was ion-implanted and became amorphous was semi-amorphized.

Next, thermal annealing was performed in a hydrogen atmosphere. Place the substrate in a chamber that can be evacuated,
Once exhausted by a turbo-molecular pump to 10 ^-6 torr and maintained in this state for 30 minutes, hydrogen gas with a purity of 99.99% or more is introduced into the chamber to 100 torr and the substrate is annealed at 300 ° C. for 60 minutes. did. Here, once evacuated, the gas adsorbed on the film
This is for removing water and the like. It has been empirically known that if thermal annealing is performed with these remaining, high mobility cannot be obtained with good reproducibility.

Finally, holes were made in the silicon oxide film (thickness: 100 nm) existing on the source region and the drain region, and aluminum electrodes 608 and 609 were formed in these regions. Through the above steps, a field effect transistor was formed.

As a result of measuring the CV characteristics of this field effect transistor, the electron mobility of the channel formation region was 98%.
cm ² / V · s. Further, the threshold voltage (threshold voltage) was 4.8V. Further, oxygen in the channel formation region of this field-effect transistor,
As a result of measuring the concentrations of nitrogen and carbon by SIMS, each was 1 × 10 ¹⁹ cm ⁻³ or less.

Example 2 A TFT having a planar structure was manufactured, and its electrical characteristics were evaluated. First, an amorphous silicon film having a thickness of about 100 nm and containing phosphorus at a concentration of 3 × 10 ¹⁷ cm ⁻³ was formed by a normal RF sputtering method. With this film thickness, the entire film is annealed by KrF laser light (248 nm) used for the subsequent laser annealing. The substrate was quartz, the substrate temperature was 150 ° C., the atmosphere was substantially 100% argon, and the pressure was 0.5 Pascal (pa). Hydrogen and other gases were not intentionally added to argon. Argon concentration is 99.99%
That was all. Input power is 200W, RF frequency is 1
It was 3.56 MHz. After that, this amorphous silicon film was etched into a rectangle of 100 μm × 500 μm.

It was confirmed by secondary ion mass spectrometry (SIMS) that the concentrations of oxygen, nitrogen and carbon in this coating were all 10 ¹⁹ cm ⁻³ or less.

Further, a gate insulating film having a thickness of about 100 nm was formed thereon by sputtering in an oxygen atmosphere. At this time, the substrate temperature was 150 ° C. and RF (13.5
6 MHz) input power was 400 W. The atmosphere was substantially oxygen and no other gas was intentionally added. The concentration of oxygen was 99.9% or more. The pressure was 0.5 pa.

Thereafter, an aluminum film (thickness: 200 n)
m) was formed by a known vacuum evaporation method, and unnecessary portions were removed by a known dry etching method to form a gate electrode. The width of the gate electrode was 100 μm.
At this time, the photoresist used for the dry etching was left on the gate electrode.

Then, boron ions were implanted into the region other than the gate electrode by 10 ¹⁴ cm ^-2 by ion implantation. Under the gate electrode, the gate electrode and the photoresist on the gate electrode serve as a mask, so that boso ions are not implanted. By this step, impurity regions, that is, a source region and a drain region, were formed in the silicon film.

Further, the entire substrate is placed in a vacuum vessel,
Excimer laser light (KrF laser, wavelength 248 nm, pulse width 10 nanoseconds, irradiation energy 100 mJ, irradiation pulse number 50 shots) was irradiated from the back surface of the substrate at a pressure of ^-5 torr to perform laser annealing. By this step, the amorphous silicon film was made semi-amorphous. This method is different from the first embodiment in that the source or drain region and the channel forming region are semi-amorphized simultaneously. Therefore, in the method of Example 1, while many defects occurred at the interface between the source or drain region and the channel formation region, an interface with few defects and continuous crystallinity was obtained.

Next, thermal annealing was performed in a hydrogen atmosphere. Place the substrate in a chamber that can be evacuated,
Once evacuated to 10 ⁻⁶ torr with a turbo-molecular pump, it was further heated to 100 ° C. Change this state to 30
And then supply hydrogen gas with a purity of 99.99% or more.
Until the substrate reaches 300 torr.
Annealed at a degree C for 60 minutes. Here, the reason why the evacuation is performed once is to remove gas, moisture, and the like adsorbed on the film. It has been empirically known that if thermal annealing is performed with these remaining, high mobility cannot be obtained with good reproducibility.

Finally, holes were made in the silicon oxide film (thickness: 100 nm) existing on the source and drain regions, and aluminum electrodes were formed in these regions. Through the above steps, a field effect transistor was formed.

As a result of measuring the CV characteristics of this field effect transistor, the electron mobility of the channel formation region was 11
It was 2 cm ² / V · s. Further, the threshold voltage (threshold voltage) was 3.9V. It is considered that the reason why the threshold voltage was improved (decreased) as compared with Example 1 is that the impurity region and the channel forming region were simultaneously and uniformly crystallized by performing laser annealing from the back surface. Also, turn on / off the gate voltage
Then, the ratio of the drain current was 5 × 10 ⁶ .

The concentration of oxygen, nitrogen and carbon in the channel forming region of this field-effect transistor was measured by SIMS and found to be 1 × 10 ¹⁹ cm ⁻³ or less. When the channel formation region was measured by Raman spectroscopy, the center value of the Raman peak was 515 c
m ⁻¹ , the half-width of the Raman peak was 13 cm ⁻¹ , and the presence of silicon that was once melted and then recrystallized was not observed, confirming that it was in a semi-amorphous state.

Example 3 A TFT having a planar structure was manufactured, and its electrical characteristics were evaluated. First, using a film forming apparatus having two chambers, an amorphous silicon film having a thickness of about 100 nm and a silicon nitride film having a thickness of 10 nm on the amorphous silicon film were formed on a quartz substrate coated with a silicon nitride film having a thickness of 10 nm. Formed continuously. The amorphous silicon film was formed by a normal sputtering method, and the silicon nitride film was formed by a glow discharge plasma CVD method.

First, the substrate was set in the first preparatory chamber, the preparatory chamber was heated to 200 ° C., evacuated, and held in the preparatory chamber at a pressure of 10 ⁻⁶ torr or less for one hour. Next, the first chamber, which is always kept at 10 ^-4 torr or less except for the time of film formation, is evacuated to 10 ^-6 torr so that no outside air enters, and the substrate is moved from the preliminary chamber to the first chamber. the substrate was set in a chamber, while maintaining the substrate and the target to 200 ° C, evacuated, the pressure in the chamber 1 in the following state 10 ^-6 torr
Hold for hours. Then, an argon gas was introduced into the chamber, RF plasma was generated, and a sputter film was formed. As a sputtering target, a silicon target having a purity of 99.9999% or more is used, and contains 1 ppm of phosphorus. The substrate temperature during film formation was 150 ° C., the atmosphere was substantially 100% argon, and the pressure was 5 × 10 ⁻² t.
orr. Hydrogen and other gases were not intentionally added to argon. The concentration of argon is 99.99999
% Or more. The input power was 200 W and the RF frequency was 13.56 MHz.

After the completion of the film formation, the RF discharge was stopped, and the first chamber was evacuated to 10 ^-6 torr. Next, the second spare chamber, which is always kept at 10 ^-5 torr or less and is provided between the first chamber and the second chamber, is set to 1
The substrate was evacuated to 0 ^-6 torr and the substrate was transferred from the first chamber to the second preliminary chamber. Further, except for the time of film formation, the second chamber which is kept at 10 ^-4 torr or less and is controlled so that no outside air enters, is evacuated to 10 ^-6 torr, and the substrate is moved from the second preliminary chamber. The substrate is set in the second chamber, and the substrate and the target are set to 200
While maintaining the temperature at C, the chamber was evacuated, and the chamber pressure was maintained at 10 ^-6 torr or less for 1 hour.

Then, ammonia gas and disilane gas (Si ₂ H ₆ ) diluted with hydrogen and having a purity of 99.9999% or more diluted with hydrogen are introduced into the second chamber at a ratio of 3: 2.
The total pressure was set to 10 ^-1 torr. Then, an RF current was introduced into the chamber, plasma was generated, and a silicon nitride film was formed. The input power (13.56 MHz) is 2
00W.

After completion of the film formation, the RF discharge was stopped, and the second chamber was evacuated to 10 ^-6 torr. Then the second
A third side of the chamber with a quartz window
Was evacuated to 10 ⁻⁶ torr, and the substrate was transferred from the second chamber to the third preliminary chamber. Then, an excimer laser beam (KrF) is passed through the window of the third preliminary room.
Laser irradiation was performed at a wavelength of 248 nm, a pulse width of 10 nanoseconds, an irradiation energy of 100 mJ, and an irradiation pulse number of 50 shots. Thus, the amorphous silicon film was made semi-amorphous.

As described above, the method of continuously performing laser annealing without substantially breaking the vacuum state from the film-forming state involves a method of forming a protective film on an amorphous semiconductor film as shown in this embodiment. It was extremely effective even when it was formed, and also when no protective film was formed as in Examples 1 and 2. The reason for this is that, if a material such as dust, which is a nucleus for crystal growth, adheres or is scratched on the coating film, the laser or This is because the film is easily polycrystallized by annealing. In addition, when shifting from a vacuum state to an atmospheric pressure state, the coating film may be subjected to non-uniform stress, and small changes in the film surface, projections, etc. generated at that time easily become nuclei for polycrystallization. We think that it is to be.

When film formation and laser annealing are performed continuously as described above, a film formation chamber and a preparatory chamber are provided as in this embodiment, and a window is provided in the preparatory chamber to perform laser annealing. There is a method and a method in which a window is provided in the film formation chamber and laser annealing is performed after the film formation is completed in the film formation chamber. However, the latter method always etches the film adhered to the window because the film becomes cloudy due to film formation. The former is not necessary. Therefore, the former method can be said to be superior in consideration of mass productivity and maintainability.

After the laser annealing in the third preparatory chamber was completed, dry nitrogen gas was introduced into the third preparatory chamber, the atmospheric pressure was reached, and the substrate was taken out. Then, after removing the silicon nitride film by a known dry etching method, the silicon film was etched into a rectangle of 100 μm × 500 μm.

The oxygen, nitrogen and carbon concentrations of this coating were all 10 ¹⁶ cm ^-3 or less, which means that another coating made in the same process was subjected to secondary ion mass spectrometry (SIMS).
Was confirmed by analysis.

Further, a gate insulating film having a thickness of about 100 nm was formed thereon by a sputtering method in an oxygen atmosphere. At this time, the substrate temperature was 150 ° C. and RF (13.5
6 MHz) input power was 400 W. The sputtering target was silicon oxide having a purity of 99.9999% or more. The atmosphere was substantially oxygen and no other gas was intentionally added. The concentration of oxygen was 99.999% or more. The pressure was 5 × 10 ^-2 torr.

Thereafter, an aluminum film (thickness: 200 n)
m) was formed by a known vacuum evaporation method, and unnecessary portions were removed by a known dry etching method to form a gate electrode. The width of the gate electrode was 100 μm.
At this time, the photoresist used for the dry etching was left on the gate electrode.

Then, boron ions were implanted at a dose of 10 ¹⁴ cm ^-2 into portions other than the gate electrode by ion implantation. Under the gate electrode, the gate electrode and the photoresist on the gate electrode serve as a mask, so that boso ions are not implanted. By this step, impurity regions, that is, a source region and a drain region, were formed in the silicon film.

Further, the entire substrate is placed in a vacuum vessel,
Excimer laser light (KrF laser, wavelength 248 nm, pulse width 10 nanoseconds, irradiation energy 50 mJ, irradiation pulse number 50 shots) was irradiated from the back surface of the substrate at a pressure of ^-5 torr to perform laser annealing.
By this step, the amorphous silicon film in the impurity region which was made amorphous by the ion implantation step was made semi-amorphous.

This method is the same as that of the first embodiment in that the laser annealing is performed in two stages. However, by performing the second laser annealing from the back surface of the substrate, the continuous formation of the impurity region and the channel forming region is performed. For connection purposes. However, unlike the method of the second embodiment, the reason for performing the first laser annealing for preparing the channel formation region is that when the laser annealing is performed by the ultraviolet laser, the laser irradiation surface is annealed, but the deep portion is formed. It is highly likely that this does not happen, or that a high mobility state cannot be obtained,
This is because the product yield may be reduced. Therefore, in order to improve the yield of the product, in this embodiment, the laser is first irradiated from the front surface of the amorphous silicon film, and then the laser is also irradiated from the back surface of the substrate, so that the continuous formation of the channel forming region and the impurity region is performed. The method of obtaining a joint was adopted.

Next, thermal annealing was performed in a hydrogen atmosphere. Place the substrate in a chamber that can be evacuated,
Once evacuated to 10 ⁻⁶ torr with a turbo-molecular pump, it was further heated to 100 ° C. Change this state to 30
And then supply hydrogen gas with a purity of 99.99% or more.
Until the substrate reaches 300 torr.
Annealed at a degree C for 60 minutes. Here, the reason why the evacuation is performed once is to remove gas, moisture, and the like adsorbed on the film. It has been empirically known that if thermal annealing is performed with these remaining, high mobility cannot be obtained with good reproducibility. Finally, holes were made in the silicon oxide film (thickness: 100 nm) existing over the source region and the drain region, and aluminum electrodes were formed in these regions. Through the above steps, a field effect transistor was formed.

As a result of producing 100 field effect transistors and measuring their CV characteristics, the electron mobility of the channel forming region was 275 cm ² / V · s on average. Further, the average of the threshold voltage (threshold voltage) was 4.2V. The average of the ratio of the drain current was 8 × 10 ⁶ . The electron mobility reference value is 10
When 0 cm ² / V · s, the reference value of the threshold voltage was 5.0 V, and the reference value of the drain current ratio was 1 × 10 ⁶ , the pass / fail of 100 field effect transistors was examined. passed it.

Further, the concentration of oxygen, nitrogen and carbon in the channel formation region of these field-effect transistors is
As a result of measurement by MS, all of the passed field-effect transistors were 1 × 10 ¹⁶ cm ⁻³ or less.

Example 4 A TFT having a planar structure was manufactured, and its electrical characteristics were evaluated. First, using a film forming apparatus having two chambers, an amorphous silicon film having a thickness of about 100 nm and a silicon nitride film having a thickness of 10 nm on the amorphous silicon film were formed on a quartz substrate coated with a silicon nitride film having a thickness of 10 nm. Formed continuously. The amorphous silicon film was formed by a normal sputtering method, and the silicon nitride film was formed by a glow discharge plasma CVD method.

First, the substrate was set in the first preparatory chamber, the preparatory chamber was heated to 200 ° C., evacuated, and maintained at a pressure of 10 ⁻⁶ torr or less for one hour. Next, the first chamber, which is always kept at 10 ^-4 torr or less except for the time of film formation, is evacuated to 10 ^-6 torr so that no outside air enters, and the substrate is moved from the preliminary chamber to the first chamber. the substrate was set in a chamber, while maintaining the substrate and the target to 200 ° C, evacuated, the pressure in the chamber 1 in the following state 10 ^-6 torr
Hold for hours. Then, an argon gas was introduced into the chamber, RF plasma was generated, and a sputter film was formed. As a sputtering target, a silicon target having a purity of 99.9999% or more is used, and contains 1 ppm of phosphorus. The substrate temperature during film formation was 150 ° C., the atmosphere was substantially 100% argon, and the pressure was 5 × 10 ⁻² t.
orr. Hydrogen and other gases were not intentionally added to argon. The concentration of argon is 99.99999
% Or more. The input power was 200 W and the RF frequency was 13.56 MHz.

After the completion of the film formation, the RF discharge was stopped, and the first chamber was evacuated to 10 ^-6 torr. Next, the second spare chamber, which is always kept at 10 ^-5 torr or less and is provided between the first chamber and the second chamber, is set to 1
The substrate was evacuated to 0 ^-6 torr and the substrate was transferred from the first chamber to the second preliminary chamber. Further, except for the time of film formation, the second chamber which is kept at 10 ^-4 torr or less and is controlled so that no outside air enters, is evacuated to 10 ^-6 torr, and the substrate is moved from the second preliminary chamber. The substrate is set in the second chamber, and the substrate and the target are set to 200
While maintaining the temperature at C, the chamber was evacuated, and the chamber pressure was maintained at 10 ^-6 torr or less for 1 hour.

Then, ammonia gas and disilane gas (Si ₂ H ₆ ) diluted with hydrogen and having a purity of 99.9999% or more were introduced into the second chamber at a ratio of 3: 2.
The total pressure was set to 10 ^-1 torr. Then, an RF current was introduced into the chamber, plasma was generated, and a silicon nitride film was formed. The input power (13.56 MHz) is 2
00W.

After the completion of the film formation, the RF discharge was stopped, and the second chamber was evacuated to 10 ^-6 torr. Then the second
A third side of the chamber with a quartz window
Was evacuated to 10 ⁻⁶ torr, and the substrate was transferred from the second chamber to the third preliminary chamber. Then, an argon gas having a purity of 99.9999% or more was introduced into the third preliminary chamber, and the internal pressure was adjusted to 5 atm. Excimer laser light (KrF laser, wavelength: 248 nm, pulse width: 10 nanoseconds, irradiation energy: 100 mJ, irradiation pulse number: 50 shots) was irradiated through the window of the third preliminary chamber, and laser annealing was performed. Thus, the amorphous silicon film was made semi-amorphous.

As described above, the method of continuously performing laser annealing without contacting outside air from the film formation state is as follows.
As shown in this embodiment, even when a protective film is formed on an amorphous semiconductor film,
It was extremely effective even when the protective film was not formed as in Examples 1 and 2. The reason is that
It is considered that this is because a material such as dust, which is a nucleus for crystal growth, does not adhere to the film or is not scratched. Furthermore, as in the case of the present embodiment, laser annealing in a pressurized atmosphere suppresses generation of microbubble lines in the coating due to laser irradiation,
Therefore, there is an effect of preventing the film from becoming a nucleus and the film being polycrystallized.

When film formation and laser annealing are performed continuously in this way, a film formation chamber and a preparatory chamber are provided as in this embodiment, and a window is provided in the preparatory chamber to perform laser annealing. There is a method and a method in which a window is provided in the film formation chamber and laser annealing is performed after the film formation is completed in the film formation chamber. However, the latter method always etches the film adhered to the window because the film becomes cloudy due to film formation. The former is not necessary. Therefore, the former method can be said to be superior in consideration of mass productivity and maintainability.

After the laser annealing in the third preparatory chamber was completed, dry nitrogen gas was introduced into the third preparatory chamber, the atmospheric pressure was reached, and the substrate was taken out. Then, after removing the silicon nitride film by a known dry etching method, the silicon film was etched into a rectangular shape of 10 μm × 1 μm.

The oxygen, nitrogen and carbon concentrations of this film were all 10 ¹⁶ cm ^-3 or less, which means that another film produced in the same process was subjected to secondary ion mass spectrometry (SIMS).
Was confirmed by analysis.

Further, a gate insulating film having a thickness of about 100 nm was formed thereon by sputtering in an oxygen atmosphere. At this time, the substrate temperature was 150 ° C. and RF (13.5
6 MHz) input power was 400 W. The sputtering target was silicon oxide having a purity of 99.9999% or more. The atmosphere was substantially oxygen and no other gas was intentionally added. The concentration of oxygen was 99.999% or more. The pressure was 5 × 10 ^-2 torr.

Thereafter, an aluminum film (thickness: 200 n)
m) was formed by a known vacuum evaporation method, and unnecessary portions were removed by a known dry etching method to form a gate electrode. Gate electrode width (channel length) is 0.5
μm, and the channel width was 1 μm. At this time, the photoresist used for the dry etching was left on the gate electrode.

Then, boron ions were implanted into the region other than the gate electrode at 10 ¹⁴ cm ^-2 by ion implantation. Under the gate electrode, the gate electrode and the photoresist on the gate electrode serve as a mask, so that boso ions are not implanted. By this step, impurity regions, that is, a source region and a drain region, were formed in the silicon film. Further, the whole substrate is placed in a vacuum vessel and excimer laser light (KrF laser, wavelength 248) is applied at a pressure of 10 ^-5 torr.
nm, pulse width 10 ns, irradiation energy 50 mJ,
(Irradiation pulse number: 50 shots) was applied from the back surface of the substrate to perform laser annealing. By this step, the amorphous silicon film in the impurity region which was made amorphous by the ion implantation step was made semi-amorphous.

This method is the same as that of the first embodiment in that two-stage laser annealing is performed. However, by performing the second laser annealing from the back surface of the substrate, the continuous formation of the impurity region and the channel formation region is performed. For connection purposes. However, unlike the method of the second embodiment, the reason for performing the first laser annealing for preparing the channel formation region is that when the laser annealing is performed by the ultraviolet laser, the laser irradiation surface is annealed, but the deep portion is formed. It is highly likely that this does not happen, or that a high mobility state cannot be obtained,
This is because the product yield may be reduced. Therefore, in order to improve the yield of the product, in this embodiment, the laser is first irradiated from the front surface of the amorphous silicon film, and then the laser is also irradiated from the back surface of the substrate, so that the continuous formation of the channel forming region and the impurity region is performed. The method of obtaining a joint was adopted.

Next, thermal annealing was performed in a hydrogen atmosphere. Place the substrate in a chamber that can be evacuated,
Once evacuated to 10 ⁻⁶ torr with a turbo-molecular pump, it was further heated to 100 ° C. Change this state to 30
And then supply hydrogen gas with a purity of 99.99% or more.
Until the substrate reaches 300 torr.
Annealed at a degree C for 60 minutes. Here, the reason why the evacuation is performed once is to remove gas, moisture, and the like adsorbed on the film. It has been empirically known that if thermal annealing is performed with these remaining, high mobility cannot be obtained with good reproducibility. Finally, holes were made in the silicon oxide film (thickness: 100 nm) existing over the source region and the drain region, and aluminum electrodes were formed in these regions. Through the above steps, a field effect transistor was formed.

As a result of producing 100 field effect transistors and measuring their CV characteristics, the electron mobility of the channel formation region was 259 cm ² / V · s on average. Further, the average of the threshold voltage (threshold voltage) was 4.2V. The average of the ratio of the drain current was 8 × 10 ⁶ . The electron mobility reference value is 10
When 0 cm ² / V · s, the reference value of the threshold voltage was 5.0 V, and the reference value of the drain current ratio was 1 × 10 ⁶ , the pass / fail of 100 field effect transistors was examined. passed it. This example shows that the present invention is extremely effective for miniaturization of a device.

The concentration of oxygen, nitrogen, and carbon in the channel formation region of these field-effect transistors
As a result of measurement by MS, all of the passed field-effect transistors were 1 × 10 ¹⁶ cm ⁻³ or less.

[0092]

According to the present invention, it has been clarified that a film semiconductor having high reproducibility and high mobility can be obtained. In the present invention, laser annealing of a semiconductor film formed on an insulating substrate such as quartz is mainly described. However, the substrate is made of a single crystal semiconductor such as a single crystal silicon substrate used in a monolithic IC or the like. You may. However, when a relatively thin amorphous film that causes laser annealing is formed directly on a single-crystal or polycrystalline substrate, the laser irradiation causes the crystal to grow from these substrates as nuclei and become polycrystalline. Undesirable. However, when a sufficiently thick amorphous film is formed on a single-crystal or polycrystalline substrate, a good semi-amorphous state can be obtained because laser annealing does not reach the deep portion of the amorphous film. Of course, there is no problem when an amorphous material such as silicon oxide or silicon nitride is formed on a single crystal or polycrystalline substrate.

Although the embodiment has been described with reference to the silicon film, the present invention may be applied to a germanium film, a silicon-germanium alloy film, other intrinsic semiconductor materials or compound semiconductor materials. Can be applied. As mentioned earlier, in this specification, the method of using laser annealing was described as a method of improving the mobility of an amorphous film, but this expression includes a method in which laser is not used, such as flash lamp annealing. is there. That is, the present invention relates to a method for improving the crystallinity of a semiconductor material using strong optical energy.

[Brief description of the drawings]

FIG. 1 shows the relationship between the center value of the Raman peak (RAMAN SHIFT, horizontal axis) and the electron mobility (vertical axis) of a silicon film annealed by laser. The concentration of oxygen in the coating is 2
× 10 ²¹ cm ^-3 .

FIG. 2: Raman peak median (RAMAN SHIF) of laser annealed silicon coatings with various oxygen concentrations
T, horizontal axis) and electron mobility (vertical axis).

FIG. 3 shows Raman peaks of single crystal silicon having a half width of the Raman peak of a laser-annealed silicon film having various oxygen concentrations.
Ratio of peak to half width (FWHM RATIO,
The relationship between the horizontal axis) and the electron mobility (vertical axis) is shown.

FIG. 4 shows the intensity of the amorphous component of the Raman peak of the laser-annealed silicon coating with various oxygen concentrations (48
0 cm ^-1 peak) single crystal silicon component intensity (521c
The relationship between the ratio (Ia / Ic, horizontal axis) to the electron mobility (vertical axis) with respect to the peak at m- ¹ ) is shown.

FIG. 5 shows the location dependence of the FWHM of the Raman peak in the channel formation region of two field effect transistors. Vertical axis: FWHM, horizontal axis: X / L (L: channel length)

FIG. 6 illustrates an example of a method for manufacturing a field-effect transistor.

[Explanation of symbols]

 601: substrate 602: semiconductor film 603: insulator film 604: gate electrode 605: photoresist 606: source region 607: drain region 608: source electrode 609 ..Drain electrodes

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/336 (72) Inventor Yasuhiko Takemura 398 Hase, Atsugi-shi, Kanagawa Inside Semiconductor Energy Laboratory Co., Ltd.

Claims (12)

[Claims] 1. The method according to claim 1, wherein the concentrations of carbon, nitrogen and oxygen are all 1
A semiconductor thin film obtained by irradiating an amorphous silicon thin film of × 10 ¹⁹ cm ^-3 or less with an ultraviolet laser beam so as to reduce the Raman peak Raman shift to a wave number of 515 cm ^-1 or less. 2. The concentration of each of carbon, nitrogen and oxygen is 1
× 10 ¹⁹ cm ^-3 or less and electron mobility of 10 cm ²
A semiconductor thin film obtained by irradiating a silicon thin film having a V / s or less with an ultraviolet laser beam to reduce the Raman peak Raman shift to a wave number of 515 cm ^-1 or less. 3. The concentration of each of carbon, nitrogen and oxygen is 1
An amorphous silicon thin film of × 10 ¹⁹ cm ^-3 or less is irradiated with an ultraviolet laser beam, and the half width of the Raman peak is 10
A semiconductor thin film obtained by making the wave number larger than cm ^-1 . 4. The method according to claim 1, wherein the concentrations of carbon, nitrogen and oxygen are all 1
× 10 ¹⁹ cm ^-3 or less and electron mobility of 10 cm ²
A semiconductor thin film obtained by irradiating a silicon thin film having a V / s or less with an ultraviolet laser beam so that the half-width of the Raman peak is increased to a wave number larger than 10 cm ^-1 . 5. The method according to claim 1, wherein the concentrations of carbon, nitrogen and oxygen are all 1
An amorphous silicon thin film of × 10 ¹⁹ cm ^-3 or less is irradiated with an ultraviolet laser beam to reduce the half-width ratio of the Raman peak to 3
A semiconductor thin film obtained by making it larger. 6. The carbon, nitrogen and oxygen concentrations are all 1
× 10 ¹⁹ cm ^-3 or less and electron mobility of 10 cm ²
A semiconductor thin film obtained by irradiating an ultraviolet laser beam to a silicon thin film of not more than / V · s to increase the half-width ratio of the Raman peak to more than 3. 7. The method according to claim 1, wherein the concentrations of carbon, nitrogen and oxygen are all 1
An amorphous silicon thin film is × 10 ¹⁹ cm ^-3 or less by irradiating the ultraviolet laser beam, the intensity ratio of the Raman peak 0.
A semiconductor thin film obtained by reducing the number to four or more. 8. The method according to claim 1, wherein the concentrations of carbon, nitrogen and oxygen are all 1
× 10 ¹⁹ cm ^-3 or less and electron mobility of 10 cm ²
A semiconductor thin film obtained by irradiating a silicon thin film having a V / s or less with an ultraviolet laser beam to increase the intensity ratio of the Raman peak to 0.4 or more. 9. The semiconductor thin film according to claim 1, wherein the output of the ultraviolet laser beam is an output that does not reach the melting-recrystallization region. 10. The semiconductor thin film according to claim 1, wherein the ultraviolet laser beam is an excimer laser. 11. A thin film semiconductor device using the semiconductor thin film according to claim 1 for a semiconductor region. 12. A liquid crystal electro-optical device comprising a plurality of the thin film semiconductor devices according to claim 11.