JPH0851220A - Semiconductor material and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a film-shaped semiconductor material high in mobility with excellent reproducibility by forming a specified protective film on an amorphous silicon film where each concentration of carbon, nitrogen, and oxygen is at a specified value or under, and applying a laser beam, etc., through the protective film, and performing annealing. CONSTITUTION:This semiconductor material consists of an amorphous silicon film 602 where any concentration of carbon, nitrogen, and oxygen is 5X 10<19>cm<-3> or over, and a protective film consisting of silicon oxides, silicon nitrides and /or silicon carbides made on the amorphous silicon film 602. This is such semiconductor material being obtained by the annealing which regularizes the amorphous silicon film 602 without fusing it by applying a laser beam or a strong beam equivalent to it through the protective film. For example, the thickness of the protective film is made 5-1000nm. And, after finishing the annealing, the protective film is removed, thus a thin film field-effect transistor, etc., are manufactured.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor material containing silicon as a main component and a method for manufacturing the same. In particular, the present invention aims to improve the characteristics of a thin film silicon semiconductor material, and by using the semiconductor material according to the present invention, it becomes possible to manufacture a thin film semiconductor device (thin film transistor or the like) having improved characteristics.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a thin film semiconductor device such as a thin film field effect transistor, an amorphous semiconductor material (so-called amorphous semiconductor) or a polycrystalline semiconductor material has been used. In the present specification, the term "amorphous" does not mean purely disorder at the atomic level, but is also used to include a substance in which short-range order of several nm exists. 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 the essential carrier mobility of the semiconductor material.

When an amorphous semiconductor (amorphous silicon, amorphous germanium, etc.) is used, its fabrication can be carried out at a relatively low temperature of 400 ° C. or lower, so that it is a promising method for liquid crystal displays and the like which cannot adopt a high temperature process. Attention has been paid.

However, since a carrier mobility (electron mobility or hole mobility) of a pure amorphous semiconductor is extremely small, it is rarely used as it is, for example, as a channel forming region of a thin film transistor (TFT). Irradiate these amorphous semiconductor materials with intense light such as laser light or xenon lamp light, melt and recrystallize them, and transform them into crystalline semiconductor materials to improve their carrier mobility. (In the following text, this method is called "laser annealing", but it does not necessarily have to use a laser. It also includes the case of irradiating a powerful flash lamp as well as laser light irradiation. However, the carrier mobility of semiconductor materials conventionally obtained by the laser annealing method was generally smaller than that obtained by single crystal semiconductor materials. For example, in the case of a silicon coating, the highest reported electron mobility is 200 cm ² / Vs, which is the electron mobility of single crystal silicon of 1350 cm ² / Vs for 7 minutes. 1
There is nothing. Further, the characteristics (mainly the mobility) of the semiconductor material obtained by the laser annealing method are poor in reproducibility, and the variability of the mobility in the same film is large, and when a large number of elements are formed in the same plane, Due to the large variation in the characteristics of the obtained semiconductor elements, the yield of the products was significantly reduced.

[0005]

In the conventional laser annealing method, the present invention cannot be put to practical use because its mobility is extremely smaller than that of a single crystal semiconductor material and its reproducibility is poor. It is intended 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 reproducibility and high mobility is provided.

[0006]

The semiconductor material according to the present invention has carbon, nitrogen and oxygen concentrations of 5 × 10 5.
^An amorphous silicon film having a size of ¹⁹ cm ⁻³ or less and a protective film formed on the amorphous silicon film and made of silicon oxide, silicon nitride and / or silicon carbide. It can be obtained by irradiating laser light or strong light equivalent thereto and annealing to make order without melting.

Furthermore, the semiconductor material according to the present invention has carbon, nitrogen, and oxygen concentrations of 5 × 10 ¹⁹ cm.
^-3 or less of an amorphous silicon coating and a protective coating formed on the amorphous silicon coating made of silicon oxide, silicon nitride and / or silicon carbide, and laser light is applied to the amorphous silicon coating through the protective coating. Alternatively, it can be obtained by irradiating strong light equivalent thereto and annealing for ordering without melting, and then performing heat treatment in an atmosphere containing hydrogen.

Further, in the method for producing a semiconductor material according to the present invention, the concentrations of carbon, nitrogen and oxygen are all 5 × 10 5.
Forming an amorphous silicon film having a thickness of ¹⁹ cm ^-3 or less; forming a protective film made of silicon oxide, silicon nitride and / or silicon carbide on the amorphous silicon film; and forming a protective film on the amorphous silicon film. Laser light or intense light equivalent thereto to irradiate the laser beam through the laser beam to perform ordering without melting.

Further, in the method for producing a semiconductor material according to the present invention, the concentrations of carbon, nitrogen and oxygen are all 5 × 1.
A step of forming an amorphous silicon film having a thickness of 0 ¹⁹ cm ^-3 or less; a step of forming a protective film made of silicon oxide, silicon nitride and / or silicon carbide on the amorphous silicon film; An annealing step of irradiating laser light or strong light equivalent thereto through the coating to order without melting, and then,
And a heat treatment in an atmosphere containing hydrogen.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Raman spectroscopy 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 produced by a laser annealing method. . The inventors obtained these numerical values by paying attention to the Raman peak center value, Raman peak width, Raman peak height, etc. of the obtained semiconductor film in the study of the laser annealing method. It has been found to have a very close relationship with the semiconductor thin film used. For example, in single crystal silicon, a Raman peak exists at 521 cm ^−1, but the Raman peak of the laser-annealed silicon coating tends to move to a shorter wave number (long wavelength) side. . Then, it was discovered that there is a strong correlation between the central 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 (vertical axis) of the film obtained by laser annealing the amorphous silicon film. Shows the relationship. The electron mobility is a value obtained by forming a TFT with a silicon film and measuring its CV (capacitance-voltage) characteristic. As is clear from the figure, the center value of Raman peak is 515.
A large difference can be seen in the behavior of electron mobility from the cm ^-1 boundary. That is, at 515 cm ^-1 or less, the Raman peak dependency of electron mobility is small, but at 515 cm ^-1 or more, the electron mobility rapidly increases with the increase in the center value of the peak.

This phenomenon clearly indicates that there are two phases. According to the research conducted by the present inventors, 515
At cm ^-1 or less, the film is not melted even by laser annealing, and atomic ordering proceeds in the solid phase. At 515 cm ^-1 or more, the film is melted by laser annealing and is in a liquid phase state. It is presumed to have been solidified through.

The center value of the Raman peak did not exceed the Raman peak value of 521 cm ^-1 of single crystal silicon, and the maximum value of electron mobility obtained was about 200 cm ² / Vs. However, it is difficult to obtain a silicon film having such a high electron mobility with good reproducibility, and even if laser annealing is intended to be performed under the same conditions, the crystalline state seems to be slightly different and the mobility is 100 cm ^2. / V ・
The majority of cases 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 is due to the fact that, for example, when performing laser annealing of 200 amorphous silicon films under the same conditions,
0cm ² / V · s or more 3 pieces, 100cm ² / V
・ Seven or more and less than 200 cm ² / V ・ s 11
This is supported by the results of 61 pieces having a size of 0 cm ² / V · s or more and less than 100 cm ² / V · s and 125 pieces having a size of less than 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 an extremely 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 occur well and becomes amorphous.

Furthermore, in addition to these reasons, the present inventors have found that the presence of foreign elements such as oxygen, nitrogen and carbon in the film is
I suspected that this might have caused a decrease in reproducibility.
The film used in the experiment shown in FIG. 1 contained oxygen atoms as much as 2 × 10 ²¹ cm ⁻³ as measured by measurement after laser annealing. It is considered that this is due to some kind of intrusion when the amorphous silicon was formed. Only traces of nitrogen and carbon were observed. Therefore, while keeping the source gas, the chamber, the exhaust system, etc., sufficiently clean at the time of forming the amorphous silicon film, a small amount of oxygen is intentionally added to the atmosphere to control the amount of oxygen atoms present in the film, The obtained coating was laser-annealed, and the relationship between the center value of the Raman peak and electron mobility was investigated.

However, in this specification, the concentration of these different elements means the concentration of the central portion of the film. because,
The concentration of these foreign elements is extremely high in the coating substrate or in the vicinity of the coating surface, but the foreign elements present in these regions have a great influence on the carrier mobility which is a problem in the present invention. Because I thought it would not be given. The part of the film where the concentration of these dissimilar elements is the lowest is the central part of the film in a normal film, and the central part of the film is considered to play an important role in semiconductor devices such as field effect transistors. Because it will be done. For the above reasons, in the present invention, the term "concentration of a different element" is defined as the concentration of the central portion of the coating.

This is shown in FIG. As is clear from FIG. 2, it was possible to significantly improve the electron mobility by reducing the oxygen concentration in the film. This tendency was the same even when the film contained carbon or nitrogen. The reason for this is that, when the film contains many oxygen atoms, when the film is melted and recrystallized by laser annealing, the part with few oxygen atoms grows as a crystal nucleus to grow crystals. However, the oxygen atoms contained in the film are driven to the periphery as the crystal grows and precipitate at the grain boundaries.Therefore, when viewed throughout the film, the mobility is small due to the barrier that occurs at the grain boundaries. It is said that laser annealing causes oxygen atoms or a region having a high concentration of oxygen atoms (generally considered to have a melting point higher than that of pure silicon) to serve as crystal nuclei for crystal growth, but the number of oxygen atoms is large. In this case, it is proposed that many crystal nuclei are generated, so that the size of each crystal is reduced, the mobility is low, and the crystallinity is impaired.

In any case, an extremely large electron mobility could be obtained by laser annealing by reducing the oxygen concentration in the film. 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 in addition to the oxygen concentration. further,
A similar tendency was obtained for hole mobility.

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

However, obtaining such 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 formed, and 1000 cm
Even though the laser annealing was intended to be performed under the same conditions that ² / V · s was obtained, the electron mobility exceeded 100 cm ² / V · s in only 9 cases. Observation of the coating film after laser annealing showed that the laser output was too large and could not be crystallized well, resulting in re-amorphization in many cases.

In FIG. 2, the region on the right side of the dotted line is shown as a melting-recrystallizing region. Actually, however, it is extremely unlikely that data of this region can be obtained,
Rather, it became clear that it is not desirable because the probability of failure is high. On the other hand, the present inventors have found that a high mobility can be obtained by reducing the concentrations of oxygen, nitrogen, and carbon in the region existing on the left side of the melt-recrystallization region. This is shown in Figure 2,
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. If we add further, it is not difficult to obtain this degree of mobility, for example, 1
When 00 amorphous silicon films were laser-annealed, 72 films were 80 cm ² / V · s or more.

The inventors of the present invention did not melt the amorphous silicon film in this region, and some lattice ordering occurred in the solid state or in the intermediate state between the solid phase and the liquid phase, and a certain long periodicity was obtained. I believe that The present inventors have named this region the 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 this solid-phase ordered region, but it is estimated 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 to move to the lowest energy state, that is, the crystalline state. . However, since it does not go through the 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 a normal amorphous state is present between these regions. it is conceivable that. This state is very different from the polycrystalline state which has passed the usual molten state. That is, in the process of recrystallizing after passing through the molten state, crystal nuclei are generated in the liquid phase and grow to grow to the surroundings, which causes a part where the crystals collide with each other. Becomes the grain boundary. At the grain boundaries, lattice defects and impurities are deposited, and ionized and polarized. Therefore, in many cases, a barrier against 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 solid-phase ordered semiconductor, the presence of a different element that deteriorates the semiconductor characteristics mainly affects its electrical characteristics.

As is clear from FIG. 2, for example, when the oxygen concentration is 1 × 10 ¹⁹ cm ⁻³ or less, the electron mobility is 10
Although it is about 0 cm ² / V · s, the center value of Raman peak at that time is far from that of single crystal silicon (521 cm ⁻¹ ), and the crystallinity may not be close to that of single crystal. It's obvious. This is supported by other data shown later.

The inventors have further discovered that a similar trend is found in the Raman peak full width at half maximum (FWHM). This state is shown in FIG. The horizontal axis of FIG. 3 is
The full width at half maximum of the Raman peak of the laser annealed film is divided by the full width at half maximum of single crystal silicon, and here it is called the full width at half maximum (FWHM RATIO). FWHM RA
It is considered that the smaller TIO is, the closer it is to 1 and the closer the structure is to single crystal silicon. As is clear from the figure, there is a melt-recrystallization region (left side of the dotted line in the figure) and a solid phase ordered region (right side of the dotted line in the figure).・ As in the case of the center value of the peak, the smaller the oxygen concentration in the film, the higher the electron mobility, and a similar tendency was found in the concentrations of nitrogen and carbon in addition to the oxygen concentration. That is, the smaller the concentration of these, the higher the electron mobility obtained. further,
A similar tendency was observed in hole mobility.

Further, the inventors of the present invention have found that the Raman peak has a close correlation with the electron mobility with respect to the intensity of the peak caused by the amorphous component in the film. 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) ) Divided by
Call it RATIO. INTENSITY RATIO
Regarding, also in the solid-phase ordered region (right side of the dotted line in the figure), the smaller the amount of oxygen contained in the film, the higher the electron mobility. Similar tendency was observed not only in oxygen concentration but also in nitrogen and carbon concentrations. That is, the smaller the concentration of these, the higher the electron mobility obtained. Furthermore, the same tendency was observed in hole mobility.
In this case as well, as in the case of FIGS. 2 and 3, the left side of the dotted line in FIG. 4 is considered to be the melt-recrystallization region.

As described above, it has been clarified that in order to improve the carrier mobility, the amounts of oxygen, nitrogen and carbon in the film should be reduced. 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, thereby avoiding a melting process with a high probability of failure. Then, the solid-phase ordering process with a higher yield has a probability of 80% at maximum, for example, the concentration of the different element is 5 × 10 ¹⁹ cm ^−3.
By setting the following, the electron mobility of the silicon film is 5
It has been found that a value as high as 100 cm ² / V · s can be obtained by setting it to 0 cm ² / V · s or more and 1 × 10 ¹⁹ cm ² / V · s or less. Further, a hole mobility of 30 to 80 cm ² / V · s could be stably obtained by the same method.

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

As described above, in order to obtain a high mobility, it is effective to reduce the concentration of different elements. For example, the concentration of these elements is 1 × 10 ¹⁶ cm.
^Setting it to ^-3 or less means that the concentration of these elements is extremely low (1 × 10 ¹⁶ in an environment with a very high degree of vacuum).
cm ^-3 or less) be performed laser annealing to an amorphous semiconductor film, it is not 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 are removed during laser annealing. It is speculated that it was taken in.

A special manufacturing method is required to avoid these difficulties. One method is that the concentration of oxygen, nitrogen and carbon is extremely low, for example, 10 ¹⁵ cm ^-3.
A protective film of silicon oxide, silicon nitride, silicon carbide or the like is formed so as to cover the surface of the following amorphous semiconductor film, and thereafter,
By performing laser annealing in a vacuum atmosphere (10 ⁻⁴ torr or less), it is possible to form a semiconductor film having extremely low oxygen, nitrogen, and carbon concentrations and high mobility. 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 covering the surface of the amorphous semiconductor film, the amorphous semiconductor film is formed by, for example, a CVD method or a sputtering method in a chamber having one vacuum device. After forming the film, a method of continuously forming a film by changing the atmosphere in the same chamber or by once setting an extremely high vacuum state and then setting an atmosphere suitable for film formation is suitable. However, more product yield,
In order to improve reproducibility and reliability, it is desirable to prepare a dedicated chamber for forming each coating and move each chamber while keeping the product in an extremely high vacuum. . The selection of these film forming methods is made according to the scale of capital investment. Whichever 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 on it. For example, even if an extremely pure amorphous semiconductor film is formed, once the film is exposed to the air and then a silicon nitride film is formed thereon, the film carrier obtained by laser annealing is performed. Mobility is generally small,
In addition, the probability that a large mobility is obtained is extremely small. It is considered that this is because the gas is adsorbed on the surface of the amorphous semiconductor film and diffuses into the film during the subsequent laser annealing.

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

The present invention provides high carrier mobility by reducing the concentration of oxygen, nitrogen and carbon in the amorphous semiconductor film and by reducing the concentration of oxygen, nitrogen and carbon present during laser annealing. It was clarified that a semiconductor film having the above is obtained. The electron mobility or hole mobility obtained at this time is the average value of the channel formation region of the field effect transistor formed for the measurement, and It is not possible to obtain the mobility in each minute portion of the. However,
As is apparent from FIGS. 1 to 4 of the present invention and the description related thereto, the carrier mobility is 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 was clarified that it can be uniquely determined from the parameters such as the intensity of. Therefore, from the information obtained by Raman spectroscopy, the mobility of a minute area where the mobility cannot be directly measured is
Approximate mobility can be estimated.

FIG. 5 is a semi-amorphous silicon formed through a solid phase ordering process and having an electron mobility of 101.
cm ² / V · s, and half of the Raman peak in each part of the channel formation region of a field effect transistor having a channel formation region having an electron mobility of 201 cm ² / V · s formed through the melting process. Price range (FW
HM) is shown. In the figure, the horizontal axis represents the position of the channel formation region. L is the length of the channel formation region, which 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 the figure, the one having an electron mobility of 101 cm ² / V · s has a large FWHM, and its fluctuation is not large. The smaller the FWHM, the closer the crystallinity of the film is to that of a single crystal, and thus the higher the electron mobility, as described in FIG. 3 and the related description, and this data situation is not inconsistent therewith. However, the small variation (location dependency) of FWHM with location indicates that the crystallinity of the coating is almost the same regardless of 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.
The same had an oxygen concentration of 1 × 10 ¹⁹ cm ⁻³ . As is clear from the figure, the FWHM was generally reduced, but the FWHM was highly location-dependent. And depending on the location, the electron mobility may be FWHM even for single crystals.
FWH equal to or smaller than (4.5 cm ^-1 )
The value of M is shown and it is suggested that the electron mobility of that portion is as high as that of a single crystal. This means that a portion 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, no matter how large the mobility is. In particular, as the size of the device becomes smaller, non-uniformity, which has not been a problem because it has been averaged up to that point, becomes noticeable, which causes a significant decrease in device yield.

On the other hand, the electron mobility is 101 cm ² /
As is clear from the figure, Vs (semi-amorphous) generally has little FWHM location dependency. This leads to an improvement in yield in mass production of devices, and it is indicated that it is suitable as a material. To obtain high carrier mobility, reduce the concentration of different elements in the film as described above. At the same time, laser annealing conditions must be optimized. The conditions of the laser annealing differ depending on the laser oscillation conditions (continuous oscillation or pulse oscillation, repetition frequency, intensity, wavelength, film, etc.) and cannot be generally stated. As a laser, an ultraviolet laser such as an excimer laser, YA
Visible and infrared lasers such as G laser can be used, and it is necessary to select depending on the thickness of the film to be laser annealed. That is, generally in silicon or germanium materials, the absorption length for ultraviolet rays is short,
Laser light does not penetrate deeply, and laser annealing occurs only in a relatively shallow area of the surface. On the other hand, the absorption length for visible light and infrared light is long, and the light penetrates relatively to the inside, so that the laser annealing occurs even in the deep portion.

As an additional matter, after laser-annealing the semiconductor film, 200-600 in a hydrogen atmosphere is performed.
Annealing at C for 10 minutes to 6 hours was effective to obtain high carrier mobility with good reproducibility.
This is because solid-state ordering occurs in a specific region by laser annealing, and at the same time, dangling bonds (tangling bonds) remain in the remaining amorphous region, or laser annealing It is thought that this is newly caused by the fact that it functions as a barrier against carriers. When the semiconductor contains a large amount of oxygen, nitrogen, carbon, etc., these fill the dangling bond, but when the concentration of oxygen, nitrogen, carbon, etc. is extremely low as in the present invention, the dangling bond is reduced. The ring bond cannot be filled and therefore requires annealing in a hydrogen atmosphere after laser annealing.

[0040]

【Example】

Example 1 A TFT having a planar structure was produced and its electrical characteristics were evaluated. The manufacturing method is shown in FIG. 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). No hydrogen or other gases were intentionally added to the argon. The concentration of argon was 99.99% or more. Input power is 200
At W, the RF frequency was 13.56 MHz. After that, this amorphous silicon film is coated with 100 μm × 500
An amorphous silicon film 602 was obtained by etching into a rectangle of 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.

Then, 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 nanoseconds, irradiation energy 200 m
J, irradiation pulse number of 50 shots), and laser annealing was performed.

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

After that, 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 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, by ion implantation, boroso ions were implanted at 10 ¹⁴ cm ^-2 except for the gate electrode portion. Under the gate electrode, the gate electrode and the photoresist thereabove serve as a mask, and borosoions are not implanted. By this step, the impurity regions, that is, the source region 606 and the drain region 607 were formed in the silicon film. This is shown in FIG. 6 (B).

Further, the whole substrate is placed in a vacuum container, and 1
Laser annealing was performed by irradiation with excimer laser light (KrF laser, wavelength 248 nm, pulse width 10 nanoseconds, irradiation energy 100 mJ, irradiation pulse number 50 shots) at a pressure of 0 ⁻⁵ torr. By this step, the impurity regions which were ion-implanted and made amorphous were made semi-amorphous.

Then, thermal annealing was performed in a hydrogen atmosphere. Place the substrate in a chamber that can be evacuated,
After exhausting to 10 ^-6 torr with a turbo molecular pump and maintaining this state for 30 minutes, hydrogen gas with a purity of 99.99% or more is introduced into the chamber up to 100 torr, and the substrate is annealed at 300 ° C for 60 minutes. did. Here, what was evacuated once was the gas adsorbed on the film.
This is to remove 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 formed 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. A field effect transistor was formed by the above steps.

As a result of measuring the CV characteristics of this field effect transistor, the electron mobility in the channel formation region is 98.
It was cm ² / V · s. Furthermore, the threshold voltage (threshold voltage) was 4.8V. In addition, oxygen in the channel formation region of this field effect transistor,
As a result of measuring the concentrations of nitrogen and carbon by SIMS, both were 1 × 10 ¹⁹ cm ⁻³ or less. Example 2 A TFT having a planar structure was produced and its electrical characteristics were evaluated. First, a thickness of about 100 including phosphorus with a concentration of 3 × 10 ¹⁷ cm ⁻³ was formed by a normal RF sputtering method.
nm amorphous silicon film was formed. With this film thickness, the entire film is annealed by the KrF laser beam (248 nm) used for the later 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). No hydrogen or other gases were intentionally added to the argon. The concentration of argon was 99.99% or more. Input power is 200W, RF frequency is 13.56M
It was Hz. Then, 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 on this by a sputtering method in an oxygen atmosphere. At this time, the substrate temperature is 150 ° C., RF (13.5
Input power was 400W. The atmosphere was essentially oxygen and no other gases were intentionally added. The oxygen concentration was 99.9% or more. The pressure was 0.5 pa.

After that, 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 dry etching was left on the gate electrode.

Then, by ion implantation, boroso ions were implanted at 10 ¹⁴ cm ^-2 except for the gate electrode portion. Under the gate electrode, the gate electrode and the photoresist thereabove serve as a mask, and borosoions are not implanted. By this step, the impurity regions, that is, the source region and the drain region were formed in the silicon coating.

Further, the whole substrate is placed in a vacuum container, and 10
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. In this method, unlike the case of the first embodiment, the source or drain region and the channel formation region are semi-amorphized at the same time. Therefore, according to the method of Example 1, many defects were generated at the interface between the source region or the drain region and the channel formation region, but an interface with few defects and continuous crystallinity was obtained.

Then, thermal annealing was performed in a hydrogen atmosphere. Place the substrate in a chamber that can be evacuated,
The gas was once evacuated to 10 ⁻⁶ torr by a turbo molecular pump and further heated to 100 ° C. This state is 30
After keeping for 1 minute, hydrogen gas with a purity of 99.99% or more is
Introduced into the chamber up to 00 torr, 300 substrate
Annealed at C for 60 minutes. Here, the vacuum evacuation is performed once in order to remove gas, moisture, etc. adsorbed on the coating. 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 were formed in these regions. A field effect transistor was formed by the above steps.

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

The concentrations of oxygen, nitrogen, and carbon in the channel formation region of this field effect transistor were measured by SIMS, and as a result, all were 1 × 10 ¹⁹ cm ^-3 or less. Further, when the channel formation region was measured by Raman spectroscopy, the center value of Raman peak was 515c.
m- ¹ and a half-value width of Raman peak were 13 cm- ¹ , and the presence of silicon that was once melted and then recrystallized was not particularly observed, and it was confirmed to be in a semi-amorphous state.

Example 3 A TFT having a planar structure was produced 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 thereon are formed on a quartz substrate coated with a silicon nitride film having a thickness of 10 nm. It was 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 preliminary chamber, the preliminary chamber was heated to 200 ° C., the chamber was evacuated, and the pressure in the preliminary chamber was kept at 10 ⁻⁶ torr or less for 1 hour. Then, except during film formation, the first chamber, which is kept at 10 ^-4 torr or less at all times and is controlled so that the outside air does not enter, is evacuated to 10 ^-6 torr and the substrate is moved from the preliminary chamber to the first chamber. Place the substrate in the chamber, evacuate the substrate and the target at 200 ° C, and keep the chamber pressure at 10 ^-6 torr or less.
Held for hours. Then, argon gas was introduced into the chamber, RF plasma was generated, and sputtering film formation was performed. As a target for sputtering, a silicon target having a purity of 99.9999% or higher is used and 1 ppm of phosphorus is contained. The substrate temperature during film formation was 150 ° C., the atmosphere was substantially 100% argon, and the pressure was 5 × 10 ^-2 t.
It was orr. No hydrogen or other gases were intentionally added to the argon. Argon concentration is 99.9999
% Or more. The input power was 200 W and the RF frequency was 13.56 MHz.

After the film formation was completed, the RF discharge was stopped and the first chamber was evacuated to 10 ^-6 torr. Then, the second auxiliary chamber, which is kept between 10 ^-5 torr and below, is installed between the first chamber and the second chamber.
The chamber was evacuated to 0 ^-6 torr and the substrate was transferred from the first chamber to the second preliminary chamber. Furthermore, except during film formation, the second chamber, which is always kept at 10 ^-4 torr or less and is controlled so that outside air does not enter, 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 pressure in the chamber was kept at 10 ^-6 torr or less for 1 hour.

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

After the film formation was completed, the RF discharge was stopped and the second chamber was evacuated to 10 ^-6 torr. Then, the second
Third chamber with quartz window on one side of the chamber
Was evacuated to 10 ⁻⁶ torr and the substrate was transferred from the second chamber to the third preliminary chamber. Then, the excimer laser light (KrF) is passed through the window of the third auxiliary chamber.
Laser annealing was performed by irradiating a laser with 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 semi-amorphized.

As described in this embodiment, the method of continuously performing the laser annealing without breaking the vacuum state from the film-forming state as described above has a protective film on the amorphous semiconductor film. Even when it was formed, or when the protective film was not formed as in Examples 1 and 2, it was extremely effective. The reason for this is, of course, when the material that becomes the nucleus of crystal growth such as dust adheres or is scratched on the film, but it is only adsorbed by water or gas, and the laser This is because the film is easily polycrystallized by annealing. In addition, the film may be subjected to non-uniform stress during the transition from the vacuum state to the atmospheric pressure state, and small changes in the film surface, protrusions, etc. that occur at that time easily become nuclei for polycrystallization. I think this is because it ends up.

When the film formation and the laser annealing are continuously performed in this way, the film formation chamber and the auxiliary chamber are provided as in the present embodiment, and the window is provided in the auxiliary chamber to perform the laser annealing. A method or a method in which a window is provided in the film formation chamber and laser annealing is performed after the film formation in the film formation chamber is completed, but in the latter case, since the window becomes cloudy due to film formation, the film that always adheres to the window is etched. The former does not have to, whereas the former has to. Therefore, it can be said that the former method is superior in consideration of mass productivity and maintainability.

After the laser annealing was completed in the third preliminary chamber, dry nitrogen gas was introduced into the third preliminary chamber to bring it to atmospheric pressure, 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 are all 10 ¹⁶ cm ^-3 or less, which means that another coating prepared in the same step was subjected to secondary ion mass spectrometry (SIMS).
Confirmed by analyzing by.

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

After that, 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 dry etching was left on the gate electrode.

Then, by ion implantation, boroso ions were implanted at 10 ¹⁴ cm ^-2 except for the gate electrode portion. Under the gate electrode, the gate electrode and the photoresist thereabove serve as a mask, and borosoions are not implanted. By this step, the impurity regions, that is, the source region and the drain region were formed in the silicon coating.

Further, the whole substrate is placed in a vacuum container and 10
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 steps, but the second laser annealing is performed from the back surface of the substrate, so that the impurity region and the channel forming region are continuously formed. For connection purposes. However, unlike the method of Example 2, the reason for purposely performing the first laser annealing for forming 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 There is a high possibility that it will not happen or that a high mobility state will not 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 rear surface of the substrate so that the channel formation region and the impurity region are continuously irradiated. The method of obtaining a joint was adopted.

Then, thermal annealing was performed in a hydrogen atmosphere. Place the substrate in a chamber that can be evacuated,
The gas was once evacuated to 10 ⁻⁶ torr by a turbo molecular pump and further heated to 100 ° C. This state is 30
After keeping for 1 minute, hydrogen gas with a purity of 99.99% or more is
Introduced into the chamber up to 00 torr, 300 substrate
Annealed at C for 60 minutes. Here, the vacuum evacuation is performed once in order to remove gas, moisture, etc. adsorbed on the coating. 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 were formed in these regions. A field effect transistor was formed by the above steps.

As a result of producing 100 field effect transistors and measuring their CV characteristics, the electron mobility in the channel formation region was 275 cm ² / V · s on average. Furthermore, the average threshold voltage (threshold voltage) was 4.2V. The average drain current ratio was 8 × 10 ⁶ . The standard value of electron mobility is 10
When 0 cm ² / V · s, the threshold voltage reference value is 5.0 V, and the drain current ratio reference value is 1 × 10 ⁶ , the pass / fail of 100 field effect transistors was examined, and 81 were found. passed it.

In addition, the concentrations of oxygen, nitrogen and carbon in the channel formation region of these field effect transistors are measured by SI.
As a result of measurement by MS, all of the field effect transistors that passed the test were 1 × 10 ¹⁶ cm ⁻³ or less.

Example 4 A TFT having a planar structure was produced 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 thereon are formed on a quartz substrate coated with a silicon nitride film having a thickness of 10 nm. It was 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 preliminary chamber, the preliminary chamber was heated to 200 ° C., the chamber was evacuated, and the pressure in the preliminary chamber was maintained at 10 ⁻⁶ torr or less for 1 hour. Then, except during film formation, the first chamber, which is kept at 10 ^-4 torr or less at all times and is controlled so that the outside air does not enter, is evacuated to 10 ^-6 torr and the substrate is moved from the preliminary chamber to the first chamber. Place the substrate in the chamber, evacuate the substrate and the target at 200 ° C, and keep the chamber pressure at 10 ^-6 torr or less.
Held for hours. Then, argon gas was introduced into the chamber, RF plasma was generated, and sputtering film formation was performed. As a target for sputtering, a silicon target having a purity of 99.9999% or higher is used and 1 ppm of phosphorus is contained. The substrate temperature during film formation was 150 ° C., the atmosphere was substantially 100% argon, and the pressure was 5 × 10 ^-2 t.
It was orr. No hydrogen or other gases were intentionally added to the argon. Argon concentration is 99.9999
% Or more. The input power was 200 W and the RF frequency was 13.56 MHz.

After the film formation was completed, the RF discharge was stopped and the first chamber was evacuated to 10 ^-6 torr. Then, the second auxiliary chamber, which is kept between 10 ^-5 torr and below, is installed between the first chamber and the second chamber.
The chamber was evacuated to 0 ^-6 torr and the substrate was transferred from the first chamber to the second preliminary chamber. Furthermore, except during film formation, the second chamber, which is always kept at 10 ^-4 torr or less and is controlled so that outside air does not enter, 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 pressure in the chamber was kept at 10 ^-6 torr or less for 1 hour.

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

After the film formation, the RF discharge was stopped and the second chamber was evacuated to 10 ^-6 torr. Then, the second
Third chamber with quartz window on one side of the chamber
Was evacuated to 10 ⁻⁶ torr and the substrate was transferred from the second chamber to the third preliminary chamber. Then, argon gas having a purity of 99.9999% or more was introduced into the third preliminary chamber, and the internal pressure was set to 5 atm. Then, 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 auxiliary chamber to perform laser annealing. Thus, the amorphous silicon film was semi-amorphized.

As described above, the method of continuously performing laser annealing without exposing the film forming state to the outside air is as follows.
As shown in this embodiment, even when the protective film is formed on the amorphous semiconductor film,
Even when the protective film was not formed as in Examples 1 and 2, it was extremely effective. The reason is
It is considered that this is because a material such as dust that serves as a nucleus for crystal growth does not adhere to or scratch the film. Further, as in the case of this example, the laser annealing in a pressurized atmosphere suppresses the generation of microscopic bubble rows in the coating due to laser irradiation,
Therefore, these bubbles serve as nuclei to prevent the film from being polycrystallized.

Further, when the film formation and the laser annealing are continuously performed in this way, the film formation chamber and the preliminary chamber are provided as in the present embodiment, and the window is provided in the preliminary chamber to perform the laser annealing. A method or a method in which a window is provided in the film formation chamber and laser annealing is performed after the film formation in the film formation chamber is completed, but in the latter case, since the window becomes cloudy due to film formation, the film that always adheres to the window is etched The former does not have to, whereas the former has to. Therefore, it can be said that the former method is superior in consideration of mass productivity and maintainability.

After the laser annealing was completed in the third preliminary chamber, dry nitrogen gas was introduced into the third preliminary chamber to bring it to atmospheric pressure, 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 10 μm × 1 μm.

The oxygen, nitrogen and carbon concentrations of this coating were all 10 ¹⁶ cm ^-3 or less, which means that another coating prepared in the same step was treated by secondary ion mass spectrometry (SIMS).
Confirmed by analyzing by.

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

After that, 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
The channel width was 1 μm. At this time, the photoresist used for dry etching was left on the gate electrode.

Then, boron ions were implanted at 10 ¹⁴ cm ^-2 except for the gate electrode by the ion implantation method. Under the gate electrode, the gate electrode and the photoresist thereabove serve as a mask, and borosoions are not implanted. By this step, the impurity regions, that is, the source region and the drain region were formed in the silicon coating.

Further, the entire substrate is placed in a vacuum container and placed at 10
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 Example 1 in that the laser annealing is performed in two steps, but the second laser annealing is performed from the back surface of the substrate, so that the impurity region and the channel forming region are continuously formed. For connection purposes. However, unlike the method of Example 2, the reason for purposely performing the first laser annealing for forming 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 There is a high possibility that it will not happen or that a high mobility state will not 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 rear surface of the substrate so that the channel formation region and the impurity region are continuously irradiated. The method of obtaining a joint was adopted.

Then, thermal annealing was performed in a hydrogen atmosphere. Place the substrate in a chamber that can be evacuated,
The gas was once evacuated to 10 ⁻⁶ torr by a turbo molecular pump and further heated to 100 ° C. This state is 30
After keeping for 1 minute, hydrogen gas with a purity of 99.99% or more is
Introduced into the chamber up to 00 torr, 300 substrate
Annealed at C for 60 minutes. Here, the vacuum evacuation is performed once in order to remove gas, moisture, etc. adsorbed on the coating. 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 were formed in these regions. A field effect transistor was formed by the above steps.

100 field-effect transistors were produced and their CV characteristics were measured. As a result, the electron mobility in the channel formation region was 259 cm ² / Vs on average. Furthermore, the average threshold voltage (threshold voltage) was 4.2V. The average drain current ratio was 8 × 10 ⁶ . The standard value of electron mobility is 10
When 0 cm ² / V · s, the threshold voltage reference value is 5.0 V, and the drain current ratio reference value is 1 × 10 ⁶ , the pass / fail of 100 field effect transistors was examined, and 71 were found. passed it. This example shows that the present invention is extremely effective for device miniaturization.

In addition, the concentrations of oxygen, nitrogen and carbon in the channel formation region of these field effect transistors are measured by SI.
As a result of measurement by MS, all of the field effect transistors that passed the test were 1 × 10 ¹⁶ cm ⁻³ or less.

[0095]

According to the present invention, it has been clarified that a film semiconductor having good 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 was mainly described. However, the substrate material is a single crystal semiconductor such as a single crystal silicon substrate used in a monolithic IC or the like. May be. However, when a relatively thin amorphous film, which can be laser-annealed, is directly formed on a single crystal or polycrystal substrate, the laser irradiation causes the crystal to grow with these substrates as nuclei and become polycrystal. Not desirable. However, when a sufficiently thick amorphous film is formed on a single crystal or polycrystal substrate, the laser annealing does not reach the deep part of the amorphous film, so that a good semi-amorphous state can be obtained. 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 silicon film is described in the embodiments, the present invention can be applied to a germanium film, a silicon-germanium alloy film, other intrinsic semiconductor material or compound semiconductor material. Can be applied. As mentioned earlier, in the present specification, it is described that a method called laser annealing is used as a method for improving the mobility of an amorphous film. However, this expression includes a method in which a laser is not used, such as flash lamp annealing. is there. That is, the present invention relates to a method of improving crystallinity of a semiconductor material by utilizing strong optical energy.

[Brief description of drawings]

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

FIG. 2 is a center value of Raman peaks of a laser-annealed silicon film having various oxygen concentrations (RAMAN SHIF).
The relationship between T and the horizontal axis and the electron mobility (vertical axis) is shown.

FIG. 3 shows the ratio of the half width of the Raman peak to the half width of the Raman peak of single crystal silicon (FWHM RATIO, horizontal axis) and the electron mobility (vertical axis) of the silicon coatings annealed by laser with various oxygen concentrations. Shows the relationship.

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

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

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

[Explanation of symbols]

 601 ... Substrate 602 ... Semiconductor coating 603 ... Insulator coating 604 ... Gate electrode 605 ... Photoresist 606 ... Source region 607 ... Drain region 608 ... Source electrode 609. ..Drain electrodes

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[Procedure amendment]

[Submission date] September 11, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[Figure 6]

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H01L 21/203 S 9545-4M 21/268 Z 21/324 Z 27/12 R (72) Inventor Yasuhiko Takemura Kanagawa 398 Hase, Atsugi-shi, Japan Inside Semiconductor Energy Laboratory Co., Ltd.

Claims (11)

[Claims] 1. An amorphous silicon coating film having carbon, nitrogen, and oxygen concentrations of 5 × 10 ¹⁹ cm ⁻³ or less, and silicon oxide formed on the amorphous silicon coating film.
A semiconductor material comprising a protective film made of silicon nitride and / or silicon carbide, which is irradiated with laser light or strong light equivalent thereto through the amorphous silicon film to form order without melting. A semiconductor material characterized by being obtained by annealing. 2. An amorphous silicon coating having a carbon, nitrogen, and oxygen concentration of 5 × 10 ¹⁹ cm ⁻³ or less, and silicon oxide formed on the amorphous silicon coating.
A semiconductor material comprising a protective film made of silicon nitride and / or silicon carbide, which is irradiated with laser light or strong light equivalent thereto through the amorphous silicon film to form order without melting. The semiconductor material is obtained by performing an annealing process, and then performing a heat treatment in an atmosphere containing hydrogen. 3. The semiconductor material according to claim 1, wherein the laser light is pulse oscillation excimer laser light. 4. The protective film according to claim 1, wherein the chemical formula of the protective film is SiN _x O _y C _z (0 ≦ x ≦ 4 / 3,0).
≦ y, 0 ≦ z ≦ 1, 0 ≦ 3x + 2y + 4z ≦ 4), and transmits the laser light or strong light equivalent thereto, a semiconductor material. 5. The semiconductor material according to claim 1, wherein the protective coating has a thickness of 5 to 1000 nm. 6. A step of forming an amorphous silicon coating film in which the concentrations of carbon, nitrogen, and oxygen are all 5 × 10 ¹⁹ cm ⁻³ or less, and silicon oxide, silicon nitride and / or carbonization on the amorphous silicon coating film. It has a step of forming a protective film made of silicon, and an annealing step of irradiating the amorphous silicon film with a laser beam or strong light equivalent thereto through the protective film so as to be ordered without melting. And a method for manufacturing a semiconductor material. 7. A step of forming an amorphous silicon coating film in which the concentrations of carbon, nitrogen, and oxygen are all 5 × 10 ¹⁹ cm ⁻³ or less, and silicon oxide, silicon nitride and / or carbonization on the amorphous silicon coating film. A step of forming a protective coating made of silicon, an annealing step of irradiating the amorphous silicon coating with a laser beam or strong light equivalent thereto through the protective coating to order without melting, and then hydrogen And a step of performing heat treatment in an atmosphere containing the semiconductor material. 8. The method for manufacturing a semiconductor material according to claim 6, wherein the laser light is pulsed excimer laser light. 9. The protective film according to claim 6, wherein the chemical formula of the protective film is SiN _x O _y C _z (0 ≦ x ≦ 4 / 3,0).
≦ y, 0 ≦ z ≦ 1, 0 ≦ 3x + 2y + 4z ≦ 4), and transmitting the laser beam or strong light equivalent thereto, a method for producing a semiconductor material. 10. The method for manufacturing a semiconductor material according to claim 6 or 7, wherein the protective coating has a thickness of 5 to 1000 nm. 11. The heat treatment according to claim 7,
A method for manufacturing a semiconductor material, which is performed at 0 to 600 ° C.