JP3986781B2 - Method for manufacturing thin film transistor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor material containing silicon as a main component. In particular, the present invention aims to improve the characteristics of a thin-film silicon semiconductor material. 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]
[Prior art]
Conventionally, in 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 this specification, the term “amorphous” does not mean purely disorder at the atomic level, but includes a substance in which a short-range order of several nanometers 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 intrinsic carrier mobility of the semiconductor material.
[0003]
When amorphous semiconductors (amorphous silicon, amorphous germanium, etc.) are used, they can be produced at a relatively low temperature of 400 ° C. or lower, and thus are attracting attention as a promising method for liquid crystal electro-optical devices that cannot employ high-temperature processes. Has been.
[0004]
However, pure amorphous semiconductors have remarkably low carrier mobility (electron mobility and hole mobility), and are rarely used as they are, for example, as a channel formation region of a thin film transistor (TFT). The semiconductor material was irradiated with intense light such as laser light or xenon lamp light, melted and recrystallized, and transformed into a crystalline semiconductor material to improve its carrier mobility. (In the text below, this method is called “laser annealing”, but it does not necessarily require the use of a laser. It includes the case of irradiating a powerful flash lamp as well as irradiating a laser beam. .)
[0005]
However, the carrier mobility of semiconductor materials conventionally obtained by laser annealing is generally smaller than that obtained with single crystal semiconductor materials. For example, in the case of a silicon film, the highest reported electron mobility is 200 cm ² / V · s, which is 7 minutes of the electron mobility of single-crystal silicon, 1350 cm ² / V · s. Only one. In addition, the characteristics (mainly mobility) of the semiconductor material obtained by the laser annealing method are poorly reproducible, and the variation in mobility within the same film is large. When a large number of elements are formed in the same plane, The yield of the product was significantly reduced due to the large variation in the characteristics of the obtained semiconductor elements.
[0006]
[Problems to be solved by the invention]
The present invention improves the characteristics of a thin-film semiconductor material that could not be put to practical use because the conventional laser annealing method has extremely low mobility compared to single crystal semiconductor material and its reproducibility is poor. The purpose is to do. 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.
[0007]
[Means for Solving the Problems]
Now, 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 present inventors obtained these numerical values by studying the center value of the Raman peak, the width of the Raman peak, the height of the Raman peak, etc. of the obtained semiconductor film in the study of the laser annealing method. It was found to have a very close relationship with the semiconductor thin film.
[0008]
For example, in single crystal silicon, there is a Raman peak at 521 cm ^−1, but the tendency of the Raman peak of the laser-annealed silicon film to move to the short wave number (long wavelength) side is observed. . And 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.
[0009]
FIG. 1 is an example showing this relationship. The relationship between the center value of the Raman peak of the film obtained by laser annealing the amorphous silicon film (horizontal axis) and the electron mobility (vertical axis) of the film is shown. Show. The electron mobility is a value obtained by fabricating a TFT with a silicon film and measuring its CV (capacitance-voltage) characteristics. As is clear from the figure, there is a large difference in the behavior of electron mobility with the central value of the Raman peak at 515 cm ⁻¹ . That is, in the 515 cm ^-1 or less Raman peak dependence of the electron mobility is small, the 515 cm ^-1 or more with an increase in the center of the peak, rapidly electron mobility is increased.
[0010]
This phenomenon clearly shows that there are two phases. According to the study by the present inventors, at 515 cm ⁻¹ or less, the film was not melted even by laser annealing, and the ordering of atoms proceeded in the solid phase. At 515 cm ⁻¹ or more, laser annealing was performed. It is estimated that the coating melts and solidifies through a liquid phase state.
[0011]
The central 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 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 high reproducibility, and even if laser annealing is performed under the same conditions, the crystal state seems to be slightly different, and the mobility is 100 cm ^2. The majority of cases were less than / V · 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.
[0012]
The fact that high mobility cannot be obtained with good reproducibility is, for example, that when 200 amorphous silicon films are laser-annealed under the same conditions, three of which are 200 cm ² / V · s or more, 100 cm ² 11 for 10 / V · s or more and less than 200 cm ² / V · s, 61 for 10 cm ² / V · s or more and less than 100 cm ² / V · s, 125 for less than 10 cm ² / V · s This is supported by the results.
[0013]
The reason is considered that the laser output varies considerably from pulse to pulse and that the optimum conditions for laser annealing are in a very narrow range. For example, it is observed that amorphous silicon does not melt if the laser output is too low, and if the laser output is too high, recrystallization does not occur well and becomes amorphous.
[0014]
Furthermore, in addition to those reasons, the present inventors thought that the presence of foreign elements such as oxygen, nitrogen, and carbon in the film may cause a decrease in reproducibility. The film used in the experiment shown in FIG. 1 contained oxygen atoms of 2 × 10 ²¹ cm ⁻³ as measured after laser annealing. This is considered to have entered through some route during the amorphous silicon film formation. Only traces of nitrogen and carbon were observed. Therefore, while keeping the raw material gas, chamber, exhaust system, etc. when producing 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 film was laser annealed, and the relationship between the center value of the Raman peak and the electron mobility was examined.
[0015]
However, in this specification, the concentration of these different elements refers to the concentration of the central portion of the film. This is because the concentration of these different elements is much higher than the substrate of the coating or in the vicinity of the surface of the coating, but the different elements existing in these regions have a large carrier mobility which is a problem in the present invention. It is because it was thought that it did not have the influence which I did. In the film, the portion with the lowest concentration of these different elements is the central part of the film in the normal film, and the central part of the film is considered to play an important role in a semiconductor device such as a field effect transistor. Because it is. For the reasons described above, in the present invention, when the concentration of a different element is simply referred to, it is defined as the concentration at the center of the coating.
[0016]
This is shown in FIG. As apparent from FIG. 2, the electron mobility could be remarkably improved by reducing the oxygen concentration in the film. This tendency was the same when the film contained carbon or nitrogen. The reason for this is that, when there are many oxygen atoms in the film, when the film is melted and recrystallized by laser annealing, the portion with few oxygen atoms becomes crystal nuclei to grow crystals. However, oxygen atoms contained in the film are driven to the periphery as the crystal grows, and precipitate at the grain boundaries, so that when viewed throughout the coating, the mobility is low due to the barriers that occur at the grain boundaries. The theory is that, by laser annealing, oxygen atoms or regions with a high concentration of oxygen atoms (generally considered to have a melting point higher than that of pure silicon) grow as crystal nuclei, but there are many oxygen atoms. In some cases, the generation of crystal nuclei is large, so that the size of one crystal is reduced, the mobility is low, and the crystallinity is impaired.
[0017]
In any case, 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 , a large electron mobility of 1000 cm ² / V · s was obtained. In addition to the oxygen concentration, the same effect could be obtained by reducing the nitrogen concentration and the carbon concentration. Furthermore, the same tendency was obtained for the hole mobility.
[0018]
Further, the Raman peak position and the electron mobility curve were bent as in the case of FIG. 1 regardless of whether the oxygen concentration was large or small. The inventors presumed that the region on the right side of the dotted line in FIG. 2 was recrystallized after the film was once melted by laser annealing, and this region was named a melt-recrystallized region. A large mobility was obtained in this melt-recrystallization region.
[0019]
However, obtaining such high mobility with good reproducibility has not been particularly improved. For example, even if 100 amorphous silicon films in which the amount of oxygen atoms in the film is 1 × 10 ¹⁹ cm ⁻³ or less are produced and laser annealing is performed under the same conditions as 1000 cm ² / V · s, There were only 9 cases where the electron mobility exceeded 100 cm ² / V · s. When the film after laser annealing was observed, it was observed that the laser output was too large, the crystallization was not successful, and the film was re-amorphized.
[0020]
In FIG. 2, the region on the right side of the dotted line is shown as a melting-recrystallization region. Actually, it is very low probability that data in this region can be obtained, but rather, the probability of failure is large. It became clear that it was not desirable. 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 present on the left side of the melt-recrystallization region. This is shown in FIG. 2, and for example, by setting the oxygen concentration to 1 × 10 ¹⁹ cm ⁻³ or less, an electron mobility of 100 cm ² / V · s at the maximum could be obtained. In addition, it is not difficult to obtain this degree of mobility. For example, when 100 amorphous silicon films were laser annealed under the same conditions, 72 films were 80 cm ² / V · s or more.
[0021]
In this region, the inventors did not melt the amorphous silicon film, some sort of lattice ordering occurred in the solid phase state or in the intermediate state between the solid phase and the liquid phase, and some long periodicity was obtained. thinking. We 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 if the concentration of elements such as oxygen, nitrogen, and carbon is low in this solid-phase ordered region, but the estimation is as follows. ing.
[0022]
That is, although there is no melting process in this solid phase ordered region, the atoms that have absorbed the light energy or thermal energy of the laser light move and try to shift to the state with the lowest energy, that is, the crystalline state. However, since it does not go through the melting process, complete crystallization is not achieved, 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 passing through the normal molten state. In other words, in the process of recrystallization after passing through the molten state, crystal nuclei are generated in the liquid phase and grow around and become large. Becomes the grain boundary. In the grain boundary, lattice defects and impurities are deposited, and ionized and polarized. Therefore, in many cases, a barrier against carriers is generated.
[0023]
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 the electrical characteristics.
[0024]
As is clear from FIG. 2, for example, when the oxygen concentration is 1 × 10 ¹⁹ cm ⁻³ or less, the electron mobility is about 100 cm ² / V · s, but the central value of the Raman peak at that time is It is clear that the single crystal silicon (521 cm ⁻¹ ) is far from the single crystal silicon and the crystallinity is not close to that of the single crystal. This is supported by other data shown later.
[0025]
The present inventors have further found that a similar tendency can be seen in the half-width of the Raman peak (hereinafter referred to as FWHM). This is shown in FIG. The horizontal axis of FIG. 3 is obtained by dividing the half-value width of the Raman peak of the laser-annealed film by the half-value width of single crystal silicon, and is here called the half-value width ratio (hereinafter referred to as FWHM RATIO) of the Raman peak. The FWHM RATIO is smaller, and the closer to 1, the closer to the single crystal silicon. As is clear from the figure, there are 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 peak central value, the smaller the oxygen concentration in the film, the higher the electron mobility, and the same tendency was observed with respect to nitrogen and carbon concentrations in addition to the oxygen concentration. As apparent from FIG. 3, in the case of the oxygen concentration of 2 × 10 ²¹ cm ⁻³ , the region where FWHM RATIO is larger than 2 corresponds to the solid-phase ordering region of the present invention, and the oxygen concentration of 1 × 10 ¹⁹ cm ⁻³ . In some cases, the 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. Furthermore, the same tendency was observed for the hole mobility.
[0026]
Furthermore, the present inventors have revealed that, among the Raman peaks, the intensity of the peak due to the amorphous component in the film also 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 hereinafter referred to as the Raman peak intensity ratio (INTENSITY RATIO). Regarding the intensity ratio of Raman peaks, the electron mobility increased as the amount of oxygen contained in the film decreased in the solid-phase ordered region (right side of the dotted line in the figure). Similar trends were 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 Raman peak intensity ratio is approximately 0.2 or more corresponds to the solid-phase ordering region of the present invention. In the case of × 10 ¹⁹ cm ⁻³ , the region where the Raman peak intensity ratio is 0.4 or more corresponds to the solid phase ordered region of the present invention. That is, the smaller the concentration, the higher the electron mobility. Furthermore, the same tendency was observed for the hole mobility. In this case as well, as in the case of FIGS. 2 and 3, it is considered that the left side of the dotted line in FIG. 4 is the melt-recrystallization region.
[0027]
As described above, it has become clear that the amount of oxygen, nitrogen, and carbon in the film should be reduced in order to improve the carrier mobility. In particular, the inventors set the amount of these elements to 5 × 10 ¹⁹ cm ⁻³ or less, preferably 1 × 10 ¹⁹ cm ⁻³ or less, so that the melting process with a higher probability of failure does not occur. Then, by the solid-phase ordering process with a higher yield, the probability of the maximum of 80%, for example, by setting the concentration of the different elements to 5 × 10 ¹⁹ cm ⁻³ or less, the electron mobility in the silicon film is 50 cm. It has been found that a value as high as 100 cm ² / V · s can be obtained by setting it to ² / V · s or more and 1 × 10 ¹⁹ cm ⁻³ or less. Further, by the same method, a hole mobility of 30 to 80 cm ² / V · s could be stably obtained.
[0028]
As described above, by reducing the concentration of different elements in the film, the carrier mobility in a special state (this is called the semi-amorphous state) through the solid-phase ordering process is improved. I found out that it would be possible to dampen. In order to realize a semi-amorphous state, it is a necessary condition that the film does not become a molten state. Therefore, for a long time, the temperature of the portion irradiated with the laser is lower than the melting point of the semiconductor, that is, 1400 ° C. under atmospheric pressure in the case of silicon, and 1000 ° C. under atmospheric pressure in the case of germanium. It is necessary that: However, for example, in a very short time of 10 nanoseconds as realized by an excimer laser, even if a temperature exceeding 2000 ° C. is observed spectroscopically, the melting of the film does not occur. It can happen that it is not observed, and this definition of temperature is not really meaningful.
[0029]
As described above, it is effective to reduce the concentration of different elements in order to obtain high mobility. For example, it is possible to reduce the concentration of these elements to 1 × 10 ¹⁶ cm ⁻³ or less. In an environment with a very high degree of vacuum, even if laser annealing is performed on an amorphous semiconductor film having a very low concentration of these elements (1 × 10 ¹⁶ cm ⁻³ or less), it cannot be easily achieved. This is because oxygen gas, nitrogen gas, moisture, carbon dioxide, etc. contained in trace amounts in the atmosphere are taken into the film at the time of laser annealing, or these gases adsorbed on the film surface are subjected to laser annealing. It is presumed that it was taken into the film.
[0030]
In order to avoid these difficulties, a special manufacturing method is required. One method is to form a protective film of silicon oxide, silicon nitride, silicon carbide, etc., covering the surface of an amorphous semiconductor film having a very low concentration of oxygen, nitrogen, and carbon, for example, 10 ¹⁵ cm ⁻³ or less, Thereafter, laser annealing is performed in a vacuum atmosphere (10 ⁻⁴ torr or less), whereby a semiconductor film having a very low concentration of oxygen, nitrogen, and carbon and high mobility can be formed. For example, a silicon film having carbon, nitrogen and oxygen concentrations of 1 × 10 ¹⁵ cm ⁻³ or less and an electron mobility of 300 cm ² / V · s was obtained.
[0031]
When forming a protective film made of silicon oxide, silicon nitride, silicon carbide or the like covering the surface of the amorphous semiconductor film, after forming the amorphous semiconductor film by a CVD method or a sputtering method in a chamber having one vacuum device, for example. A continuous film formation method is suitable without changing the atmosphere in the same chamber, or by once making an extremely high vacuum state and then creating an atmosphere suitable for film formation. However, in order to improve the yield, reproducibility, and reliability of the product, a dedicated chamber is prepared for the formation of each film, and the product is moved in an extremely high vacuum state. It is desirable to adopt a method. These film formation methods are selected depending on the scale of capital investment. Whichever method is adopted, the important thing is that the underlying amorphous semiconductor film contains enough oxygen, nitrogen, and carbon, and gas is adsorbed at the interface between the amorphous semiconductor and the protective film on it. That is not. For example, even if an extremely pure amorphous semiconductor film is formed, if the silicon nitride film is formed on the film after being exposed to the atmosphere once, the carrier of the film obtained by laser annealing the film The mobility is generally small, and the probability of obtaining a high mobility is extremely small. This is presumably because gas is adsorbed on the surface of the amorphous semiconductor film and diffuses into the coating during the subsequent laser annealing.
[0032]
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. Also, the chemical formula SiN _x O _y C _z (mixture thereof) 0 ≦ x ≦ 4/3, 0 ≦ y ≦ 2, 0 ≦ z ≦ 1, 0 ≦ 3x + 2y + 4z ≦ 4). Moreover, the thickness of 5 to 1000 nm was suitable.
[0033]
Now, the present invention provides a semiconductor film having a high carrier mobility by reducing the concentration of oxygen, nitrogen and carbon in the amorphous semiconductor film and reducing the concentration of oxygen, nitrogen and carbon present during laser annealing. 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 measurement, and the fineness of the channel formation region is The mobility in each part cannot be obtained. However, as is clear from FIGS. 1 to 4 of the present invention and the related description, 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. -It became clear that it could be determined uniquely from parameters such as peak intensity. Therefore, the mobility of a minute region whose mobility cannot be measured directly can be estimated from this information by Raman spectroscopy.
[0034]
FIG. 5 shows semi-amorphous silicon formed through a solid-phase ordering process, having an electron mobility of 101 cm ² / V · s, and an electron mobility formed through a melting process of 201 cm ² / V · s. The half-value width (FWHM) of the Raman peak in each part of the channel formation region of the field effect transistor having the channel formation region of s 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 and is 100 μm. X represents the coordinates of the channel formation region, X / L = 0 is an interface with the source region of the channel formation region, X / L = 1 is an interface with the drain region of the channel formation region, and X / L = 0.5 represents the center of the channel formation region. As is clear from FIG. 5, the electron mobility of 101 cm ² / V · s has a FWHM larger than 10 cm ^−1, but its fluctuation (variation by location) is small, and the electron mobility is 201 cm ² / V · s. Although the FWHM is smaller than 10 cm ⁻¹ , the fluctuation (variation by location) 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 hence the higher the electron mobility, as described in FIG. 3 and the related description, this data situation is not inconsistent with that. However, the small variation (location dependence) depending on the location of FWHM indicates that the crystallinity of the coating is almost the same regardless of the location. The oxygen concentration of this film was about 1 × 10 ¹⁹ cm ⁻³ .
[0035]
On the other hand, when the electron mobility was 201 cm ² / V · s, the oxygen concentration was also 1 × 10 ¹⁹ cm ⁻³ . As is clear from the figure, the FWHM generally decreased, but the location dependence of the FWHM was large. Depending on the location, the single crystal has a FWHM value equal to or smaller than that of FWHM (4.5 cm ⁻¹ ), suggesting that the electron mobility of the portion is as large as that of the single crystal. This means that a portion having crystallinity equivalent to single crystal silicon is localized in the same film. However, in the case of mass production as a device, it is not desirable to use a material whose characteristics vary greatly depending on the location, even if the mobility is large. In particular, as the size of the device becomes smaller, non-uniformity that has not been a problem since it has been averaged until then becomes conspicuous, which causes a significant decrease in device yield.
[0036]
On the other hand, when the electron mobility is 101 cm ² / V · s (semi-amorphous), the location dependence of FWHM is generally small as is apparent from the figure. This has led to an improvement in yield in mass production of devices, which indicates that it is suitable as a material. [0037]
In order to obtain high carrier mobility, it is necessary to reduce the concentration of different elements in the film and 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, film, etc.), and cannot be generally specified. As the laser, an ultraviolet laser such as an excimer laser or a visible or infrared laser such as a YAG laser can be used, and it is necessary to select it according to the thickness of the film to be laser annealed. That is, in general, silicon or germanium materials have a short absorption length for ultraviolet rays, so that laser light does not enter deeper portions, and laser annealing occurs only in a relatively shallow surface area. On the other hand, the absorption length is long for visible light and infrared rays, and the light penetrates relatively into the inside, so that laser annealing occurs even in a deep part.
[0038]
As an additional matter, after laser annealing the semiconductor film, annealing in a hydrogen atmosphere at 200 to 600 ° C. for 10 minutes to 6 hours is effective for obtaining high carrier mobility with good reproducibility. Met. This is because laser annealing causes solid-phase ordering in a specific region, and at the same time, unpaired bonds (tangling bonds) remain in the remaining amorphous region, or laser annealing. This is considered to be caused by the fact that it acts as a barrier against carriers. If the semiconductor contains a large amount of oxygen, nitrogen, carbon, etc., these fill dangling bonds. However, if the concentration of oxygen, nitrogen, carbon, etc. is extremely low as in the present invention, Ring bonds cannot be filled, and thus it is necessary to anneal in a hydrogen atmosphere after laser annealing.
[0039]
【Example】
[Example 1]
A planar TFT was fabricated 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). Hydrogen and other gases were not intentionally added to argon. The concentration of argon was 99.99% or more. The input power was 200 W and the RF frequency was 13.56 MHz. Thereafter, this amorphous silicon film was etched into a 100 μm × 500 μm rectangle to obtain an amorphous silicon film 602.
[0040]
It was confirmed by secondary ion mass spectrometry (SIMS) that the oxygen, nitrogen, and carbon concentrations in the coating were all 10 ¹⁹ cm ⁻³ or less.
[0041]
Next, this film is placed in a vacuum vessel having a pressure of 10 ⁻⁵ torr, and excimer laser light (KrF laser, wavelength 248 nm, pulse width 10 nanoseconds, irradiation energy 200 mJ, irradiation pulse number through a quartz window provided in the vacuum vessel. Laser annealing was performed.
[0042]
Further, a gate insulating film 603 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 (13.56 MHz) input power was 400 W. The atmosphere was substantially oxygen and no other gases were intentionally added. The concentration of oxygen was 99.9% or higher. The pressure was 0.5 pa.
[0043]
Thereafter, an aluminum film (thickness: 200 nm) 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.
[0044]
Subsequently, boron ions were implanted at 10 ¹⁴ cm ⁻² other than the gate electrode portion by ion implantation. Under the gate electrode, boron ions are not implanted by using the gate electrode and photoresist as a mask. 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.
[0045]
Further, the entire substrate is placed in a vacuum vessel and irradiated 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 10 ⁻⁵ torr. Annealed. By this process, the ion-implanted impurity region was semi-amorphized.
[0046]
Next, thermal annealing was performed in a hydrogen atmosphere. The substrate is placed in a chamber that can be evacuated and exhausted to 10 ^-6 torr by a turbo molecular pump. After 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. The substrate was annealed at 300 ° C. for 60 minutes. Here, the vacuum evacuation is performed in order to remove gas, moisture and the like adsorbed on the coating. It has been empirically known that high thermal mobility cannot be obtained with good reproducibility if thermal annealing is performed in a state where these remain.
[0047]
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 process.
[0048]
As a result of measuring the CV characteristics of this field effect transistor, the electron mobility in the channel formation region was 98 cm ² / V · s. Further, the threshold voltage (threshold voltage) was 4.8V. Moreover, as a result of measuring the concentration of oxygen, nitrogen, and carbon in the channel formation region of this field effect transistor by SIMS, all were 1 × 10 ¹⁹ cm ⁻³ or less.
[0049]
[Example 2] A TFT having a planar structure was fabricated and its electrical characteristics were evaluated. First, an amorphous silicon film having a thickness of about 100 nm 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 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. The concentration of argon was 99.99% or more. The input power was 200 W and the RF frequency was 13.56 MHz. Thereafter, this amorphous silicon film was etched into a rectangle of 100 μm × 500 μm.
[0050]
It was confirmed by secondary ion mass spectrometry (SIMS) that the oxygen, nitrogen, and carbon concentrations in the coating were all 10 ¹⁹ cm ⁻³ or less.
[0051]
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 (13.56 MHz) input power was 400 W. The atmosphere was substantially oxygen and no other gases were intentionally added. The concentration of oxygen was 99.9% or higher. The pressure was 0.5 pa.
[0052]
Thereafter, an aluminum film (thickness: 200 nm) was formed by a known vacuum deposition 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.
[0053]
Subsequently, boron ions were implanted at 10 ¹⁴ cm ⁻² other than the gate electrode portion by ion implantation. Under the gate electrode, boron ions are not implanted by using the gate electrode and photoresist as a mask. By this step, impurity regions, that is, a source region and a drain region were formed in the silicon film.
[0054]
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) is irradiated from the back surface of the substrate at a pressure of 10 ⁻⁵ torr. Then, laser annealing was performed. By this process, the amorphous silicon film was semi-amorphized. In this method, unlike the case of the first embodiment, the semi-amorphization of the source region or the drain region and the channel formation region is performed at the same time. Therefore, in the method of Example 1, many defects occurred at the interface between the source region or the drain region and the channel formation region, whereas an interface having few defects and continuous crystallinity was obtained.
[0055]
Next, thermal annealing was performed in a hydrogen atmosphere. The substrate was placed in a chamber that can be evacuated, and once evacuated to 10 ⁻⁶ torr with a turbo molecular pump, and further heated to 100 ° C. After maintaining this state for 30 minutes, hydrogen gas having a purity of 99.99% or more was introduced into the chamber up to 100 torr, and the substrate was annealed at 300 ° C. for 60 minutes. Here, the vacuum evacuation is performed in order to remove gas, moisture and the like adsorbed on the coating. It has been empirically known that high thermal mobility cannot be obtained with good reproducibility if thermal annealing is performed in a state where these remain.
[0056]
Finally, a hole was made in the silicon oxide film (thickness 100 nm) existing on the source region and the drain region, and an aluminum electrode was formed in these regions. A field effect transistor was formed by the above process.
[0057]
As a result of measuring the CV characteristics of this field effect transistor, the electron mobility in the channel formation region was 112 cm ² / V · s. Further, the threshold voltage (threshold voltage) was 3.9V. It is considered that the threshold voltage was improved (decreased) compared to Example 1 because the impurity region and the channel formation region were uniformly crystallized simultaneously by laser annealing from the back surface. The ratio of the drain current when the gate voltage was turned on / off was 5 × 10 ⁶ .
[0058]
The concentration of oxygen, nitrogen, and carbon in the channel formation region of this field effect transistor was measured by SIMS, and all were 1 × 10 ¹⁹ cm ⁻³ or less. The measured channel formation region by Raman spectroscopy, the center value of the Raman peak 515 cm ^-1, a half value width 13cm ^-1 Raman peak, once the presence of the recrystallized silicon After melted In particular, it was not observed and it was confirmed that it was in a semi-amorphous state.
[0059]
[Example 3] A TFT having a planar structure was fabricated 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 coated on a quartz substrate coated with a silicon nitride film having a thickness of 10 nm. Formed continuously. The amorphous silicon film was produced by a normal sputtering method, and the silicon nitride film was produced by a glow discharge plasma CVD method.
[0060]
First, the substrate was set in the first preliminary chamber, and the preliminary chamber was heated to 200 ° C. and evacuated, and the pressure in the preliminary chamber was maintained at 10 ⁻⁶ torr or less for 1 hour. Next, except for the time of film formation, the first chamber, which is always kept at 10 ⁻⁴ torr or less so that no outside air enters, is exhausted to 10 ⁻⁶ torr, the substrate is moved from the preliminary chamber, and the first chamber is moved. The substrate was set in the chamber, and the substrate and the target were held at 200 ° C., evacuated, and held for 1 hour while the pressure in the chamber was 10 ⁻⁶ torr or less. Then, argon gas was introduced into the chamber, RF plasma was generated, and sputtering film formation was performed. The sputtering target uses a silicon target with a purity of 99.9999% or more 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 torr. Hydrogen and other gases were not intentionally added to argon. The concentration of argon was 99.9999% or more. The input power was 200 W and the RF frequency was 13.56 MHz.
[0061]
After completion of the film formation, the RF discharge was stopped, and the first chamber was evacuated to 10 ⁻⁶ torr. Next, the second preliminary chamber, which is always maintained at 10 ⁻⁵ torr or less and is provided between the first chamber and the second chamber, is evacuated to 10 ⁻⁶ torr, and then the second chamber is discharged from the first chamber to the second chamber. The substrate was transferred to the preliminary chamber. Further, the second chamber, which is always kept at 10 ⁻⁴ torr or less except during film formation and is controlled so that no outside air enters, is exhausted to 10 ⁻⁶ torr, and the substrate is moved from the second preliminary chamber. The substrate was set in the second chamber, and the substrate and the target were held at 200 ° C., and evacuated. The chamber was held at a pressure of 10 ⁻⁶ torr or less for 1 hour.
[0062]
Then, ammonia gas having a purity of 99.9999% or more and disilane gas (Si ₂ H ₆ ) diluted with hydrogen was introduced into the second chamber at a ratio of 3: 2, and the total pressure was set to 10 ⁻¹ torr. Then, RF current was introduced into the chamber, plasma was generated, and silicon nitride was formed. The input power (13.56 MHz) was 200 W.
[0063]
After the film formation was completed, the RF discharge was stopped, and the second chamber was evacuated to 10 ⁻⁶ torr. Next, the third auxiliary chamber provided on one side of the second chamber and having a quartz window was evacuated to 10 ⁻⁶ torr, and the substrate was transferred from the second chamber to the third auxiliary chamber. 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 preliminary chamber, and laser annealing was performed. In this way, the amorphous silicon film was semi-amorphized.
[0064]
In this way, the method of performing laser annealing continuously without substantially breaking the vacuum state from the film formation state is that a protective film is formed on the amorphous semiconductor film as shown in this embodiment. Even when the protective film is not formed as in Examples 1 and 2, it was extremely effective. The reason for this is, of course, that the material that becomes the core of crystal growth such as dust adheres to the film or is scratched. This is because the film is easily polycrystallized by annealing. In addition, when changing from a vacuum state to an atmospheric pressure state, the film may be subjected to non-uniform stress, and small changes in the film surface, protrusions, etc. that occur at that time can easily become the nucleus of polycrystallization. I think that is because it ends.
[0065]
Further, in the case where film formation and laser annealing are continuously performed in this way, a film forming chamber and a spare chamber are provided as in this embodiment, a window is provided in the spare chamber, and laser annealing is performed, A method of providing a window in the film formation chamber and performing laser annealing after film formation in the film formation chamber is conceivable. However, since the latter becomes cloudy due to film formation, the film attached to the window must always be etched. This is not necessary for the former, whereas Therefore, it can be said that the former method is superior in consideration of mass productivity and maintainability.
[0066]
Now, 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.
[0067]
It was confirmed that the oxygen, nitrogen, and carbon concentrations of this coating were all 10 ¹⁶ cm ⁻³ or less by analyzing another coating prepared in the same step by secondary ion mass spectrometry (SIMS). .
[0068]
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 (13.56 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 gases were intentionally added. The oxygen concentration was 99.999% or higher. The pressure was 5 × 10 ⁻² torr.
[0069]
Thereafter, an aluminum film (thickness: 200 nm) was formed by a known vacuum deposition 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.
[0070]
Subsequently, boron ions were implanted at 10 ¹⁴ cm ⁻² other than the gate electrode portion by ion implantation. Under the gate electrode, boron ions are not implanted by using the gate electrode and photoresist as a mask. By this step, impurity regions, that is, a source region and a drain region were formed in the silicon film.
[0071]
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 50 mJ, irradiation pulse number 50 shots) is irradiated from the back surface of the substrate at a pressure of 10 ⁻⁵ torr. Then, laser annealing was performed. By this process, the amorphous silicon film in the impurity region that has been made amorphous by the ion implantation process has been made semi-amorphous.
[0072]
This method is the same as that of Example 1 in that two-stage laser annealing is performed, but the second laser annealing is performed from the back surface of the substrate, so that the impurity region and the channel formation region are connected continuously. And However, unlike the method of the second embodiment, the reason for performing the first laser annealing for preparing the channel formation region is that the laser irradiation surface is annealed by the ultraviolet laser, but the deep part This is because there is a high possibility that it will not occur or a state with high mobility cannot be obtained, and the yield of the product may be lowered. Therefore, in this embodiment, in order to improve the yield of the product, the laser is first irradiated from the surface of the amorphous silicon film, and the laser is also irradiated from the back surface of the substrate later, so that the channel formation region and the impurity region are continuously formed. The method of obtaining a joint was adopted.
[0073]
Next, thermal annealing was performed in a hydrogen atmosphere. The substrate was placed in a chamber that can be evacuated, and once evacuated to 10 ⁻⁶ torr with a turbo molecular pump, and further heated to 100 ° C. After maintaining this state for 30 minutes, hydrogen gas having a purity of 99.99% or more was introduced into the chamber up to 100 torr, and the substrate was annealed at 300 ° C. for 60 minutes. Here, the vacuum evacuation is performed in order to remove gas, moisture and the like adsorbed on the coating. It has been empirically known that high thermal mobility cannot be obtained with good reproducibility if thermal annealing is performed in a state where these remain.
Finally, a hole was made in the silicon oxide film (thickness 100 nm) existing on the source region and the drain region, and an aluminum electrode was formed in these regions. A field effect transistor was formed by the above process.
[0074]
As a result of fabricating 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. Further, 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 100 cm ² / V · s, the standard value of threshold voltage is 5.0 V, the standard value of drain current ratio is 1 × 10 ⁶ , and pass / fail of 100 field effect transistors When examined, 81 passed.
[0075]
In addition, the concentration of oxygen, nitrogen, and carbon in the channel formation region of these field effect transistors was measured by SIMS, and as a result, all passed field effect transistors were 1 × 10 ¹⁶ cm ⁻³ or less.
[0076]
[Example 4] A TFT having a planar structure was fabricated 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 coated on a quartz substrate coated with a silicon nitride film having a thickness of 10 nm. Formed continuously. The amorphous silicon film was produced by a normal sputtering method, and the silicon nitride film was produced by a glow discharge plasma CVD method.
[0077]
First, the substrate was set in the first preliminary chamber, and the preliminary chamber was heated to 200 ° C. and evacuated, and the pressure in the preliminary chamber was maintained at 10 ⁻⁶ torr or less for 1 hour. Next, except for the time of film formation, the first chamber, which is always kept at 10 ⁻⁴ torr or less so that no outside air enters, is exhausted to 10 ⁻⁶ torr, the substrate is moved from the preliminary chamber, and the first chamber is moved. The substrate was set in the chamber, and the substrate and the target were held at 200 ° C., evacuated, and held for 1 hour while the pressure in the chamber was 10 ⁻⁶ torr or less. Then, argon gas was introduced into the chamber, RF plasma was generated, and sputtering film formation was performed. The sputtering target uses a silicon target with a purity of 99.9999% or more 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 torr. Hydrogen and other gases were not intentionally added to argon. The concentration of argon was 99.9999% or more. The input power was 200 W and the RF frequency was 13.56 MHz.
[0078]
After completion of the film formation, the RF discharge was stopped, and the first chamber was evacuated to 10 ⁻⁶ torr. Next, the second preliminary chamber, which is always maintained at 10 ⁻⁵ torr or less and is provided between the first chamber and the second chamber, is evacuated to 10 ⁻⁶ torr, and then the second chamber is discharged from the first chamber to the second chamber. The substrate was transferred to the preliminary chamber. Further, the second chamber, which is always kept at 10 ⁻⁴ torr or less except during film formation and is controlled so that no outside air enters, is exhausted to 10 ⁻⁶ torr, and the substrate is moved from the second preliminary chamber. The substrate was set in the second chamber, and the substrate and the target were held at 200 ° C., and evacuated. The chamber was held at a pressure of 10 ⁻⁶ torr or less for 1 hour.
[0079]
Then, ammonia gas having a purity of 99.9999% or more and disilane gas (Si ₂ H ₆ ) diluted with hydrogen was introduced into the second chamber at a ratio of 3: 2, and the total pressure was set to 10 ⁻¹ torr. Then, RF current was introduced into the chamber, plasma was generated, and silicon nitride was formed. The input power (13.56 MHz) was 200 W.
[0080]
After the film formation was completed, the RF discharge was stopped, and the second chamber was evacuated to 10 ⁻⁶ torr. Next, the third auxiliary chamber provided on one side of the second chamber and having a quartz window was evacuated to 10 ⁻⁶ torr, and the substrate was transferred from the second chamber to the third auxiliary 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 preliminary chamber, and laser annealing was performed. In this way, the amorphous silicon film was semi-amorphized.
[0081]
Thus, the method of continuously performing laser annealing without touching the outside air from the film formation state is a case where a protective film is formed on the amorphous semiconductor film as shown in this embodiment. However, it was extremely effective even when the protective film was not formed as in Examples 1 and 2. The reason is considered to be that a material that becomes a nucleus of crystal growth such as dust does not adhere to or become scratched on the coating. Further, as in this example, laser annealing in a pressurized atmosphere suppresses the generation of microbubbles in the coating due to laser irradiation, and therefore these bubbles serve as nuclei. There is an effect of preventing the coating from being polycrystallized.
[0082]
Further, in the case where film formation and laser annealing are continuously performed in this way, a film forming chamber and a spare chamber are provided as in this embodiment, a window is provided in the spare chamber, and laser annealing is performed, A method of providing a window in the film formation chamber and performing laser annealing after film formation in the film formation chamber is conceivable. However, since the latter becomes cloudy due to film formation, the film attached to the window must always be etched. This is not necessary for the former, whereas Therefore, it can be said that the former method is superior in consideration of mass productivity and maintainability.
[0083]
Now, 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 10 μm × 1 μm rectangle.
[0084]
It was confirmed that the oxygen, nitrogen, and carbon concentrations of this coating were all 10 ¹⁶ cm ⁻³ or less by analyzing another coating prepared in the same step by secondary ion mass spectrometry (SIMS). .
[0085]
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 (13.56 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 gases were intentionally added. The oxygen concentration was 99.999% or higher. The pressure was 5 × 10 ⁻² torr.
[0086]
Thereafter, an aluminum film (thickness: 200 nm) was formed by a known vacuum deposition method, and unnecessary portions were removed by a known dry etching method to form a gate electrode. The gate electrode had a width (channel length) of 0.5 μm and a channel width of 1 μm. At this time, the photoresist used for the dry etching was left on the gate electrode.
[0087]
Subsequently, boron ions were implanted at 10 ¹⁴ cm ⁻² other than the gate electrode portion by ion implantation. Under the gate electrode, boron ions are not implanted by using the gate electrode and photoresist as a mask. 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, and excimer laser light (KrF laser, wavelength 248 nm, pulse width 10 nanoseconds, irradiation energy 50 mJ, irradiation pulse number 50 shots) is irradiated from the back surface of the substrate at a pressure of 10 ⁻⁵ torr. Then, laser annealing was performed. By this process, the amorphous silicon film in the impurity region that has been made amorphous by the ion implantation process has been made semi-amorphous.
[0088]
This method is the same as that of Example 1 in that two-stage laser annealing is performed, but the second laser annealing is performed from the back surface of the substrate, so that the impurity region and the channel formation region are connected continuously. And However, unlike the method of the second embodiment, the reason for performing the first laser annealing for preparing the channel formation region is that the laser irradiation surface is annealed by the ultraviolet laser, but the deep part This is because there is a high possibility that it will not occur or a state with high mobility cannot be obtained, and the yield of the product may be lowered. Therefore, in this embodiment, in order to improve the yield of the product, the laser is first irradiated from the surface of the amorphous silicon film, and the laser is also irradiated from the back surface of the substrate later, so that the channel formation region and the impurity region are continuously formed. The method of obtaining a joint was adopted.
[0089]
Next, thermal annealing was performed in a hydrogen atmosphere. The substrate was placed in a chamber that can be evacuated, and once evacuated to 10 ⁻⁶ torr with a turbo molecular pump, and further heated to 100 ° C. After maintaining this state for 30 minutes, hydrogen gas having a purity of 99.99% or more was introduced into the chamber up to 100 torr, and the substrate was annealed at 300 ° C. for 60 minutes. Here, the vacuum evacuation is performed in order to remove gas, moisture and the like adsorbed on the coating. It has been empirically known that high thermal mobility cannot be obtained with good reproducibility if thermal annealing is performed in a state where these remain.
Finally, a hole was made in the silicon oxide film (thickness 100 nm) existing on the source region and the drain region, and an aluminum electrode was formed in these regions. A field effect transistor was formed by the above process.
[0090]
As a result of fabricating 100 field effect transistors and measuring their CV characteristics, the electron mobility in the channel formation region was 259 cm ² / V · s on average. Further, 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 100 cm ² / V · s, the standard value of threshold voltage is 5.0 V, the standard value of drain current ratio is 1 × 10 ⁶ , and pass / fail of 100 field effect transistors When examined, 71 passed. This example shows that the present invention is extremely effective for device miniaturization.
[0091]
In addition, the concentration of oxygen, nitrogen, and carbon in the channel formation region of these field effect transistors was measured by SIMS, and as a result, all passed field effect transistors were 1 × 10 ¹⁶ cm ⁻³ or less.
[0092]
【The invention's effect】
According to the present invention, it has become clear that a film-like semiconductor with high reproducibility and high mobility can be obtained. In the present invention, laser annealing of a semiconductor film formed mainly on an insulating substrate such as quartz has been described. However, the material of the substrate 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 to the extent that laser annealing occurs is formed directly on a single crystal or polycrystal substrate, the crystal grows using these substrates as nuclei and becomes polycrystal by laser irradiation. Therefore, it is not desirable. However, when a sufficiently thick amorphous film is formed on a single crystal or polycrystalline substrate, since laser annealing does not reach the deep part of the amorphous film, 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.
[0093]
In the embodiments, the silicon film is described. However, the present invention is applied to a germanium film, a silicon-germanium alloy film, and any other intrinsic semiconductor material or compound semiconductor material. be able to. As mentioned at the beginning, in this specification, it has been 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, for example, flash lamp annealing. is there. That is, the present invention relates to a method for improving the crystallinity of a semiconductor material by using strong optical energy.
[Brief description of the drawings]
FIG. 1 shows the relationship between the center value of a Raman peak (RAMAN SHIFT, horizontal axis) and electron mobility (vertical axis) of a laser-annealed silicon film. The concentration of oxygen in the coating is 2 × 10 ²¹ cm ⁻³ .
FIG. 2 shows the relationship between the Raman peak center value (RAMAN SHIFT, horizontal axis) and electron mobility (vertical axis) of laser-annealed silicon films with various oxygen concentrations.
FIG. 3 shows the ratio of the half-width of the Raman peak of the laser-annealed silicon film with various oxygen concentrations to the half-width of the Raman peak of single crystal silicon (FWHM RATIO, horizontal axis) and the electron mobility (vertical axis). The relationship is shown.
[4] the ratio to the intensity of the single crystal silicon component varying oxygen concentration of the laser annealed strength of the amorphous component of the Raman peak of silicon film (peak of 480 cm ^-1) (peak of 521 cm ^-1) (Ia / (Ic, horizontal axis) and electron mobility (vertical axis).
FIG. 5 shows the FWHM location dependence 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 coating 603 ... Insulator coating 604 ... Gate electrode 605 ... Photoresist 606 ... Source region 607 ... Drain region 608 ... Source electrode 609 ..Drain electrode

Claims (7)

In the first chamber, an amorphous silicon film having carbon, nitrogen, and oxygen concentrations of 5 × 10 ¹⁹ cm ⁻³ or less is formed by sputtering using silicon as a target .
Without moving the surface of the amorphous silicon film to the atmosphere, the first chamber is moved to the second chamber to form a protective film on the amorphous silicon film,
The amorphous silicon film is irradiated with a continuous wave laser beam through the protective film by moving from the second chamber to a preliminary chamber connected to the second chamber. Crystal growth of the silicon film in the solid phase,
The value obtained by dividing the first Raman peak attributed to the amorphous component of the silicon film by the second Raman peak attributed to the component of single crystal silicon is 0.4 or more. Manufacturing method. In the first chamber, an amorphous silicon film having carbon, nitrogen, and oxygen concentrations of 5 × 10 ¹⁹ cm ⁻³ or less is formed by sputtering using silicon as a target .
Without moving the surface of the amorphous silicon film to the atmosphere, the first chamber is moved to the second chamber to form a protective film on the amorphous silicon film,
The amorphous silicon film is irradiated with a continuous wave laser beam through the protective film by moving from the second chamber to a preliminary chamber connected to the second chamber. Crystal growth of the silicon film in the solid phase,
Forming the silicon film in which dangling bonds are filled with hydrogen;
The value obtained by dividing the first Raman peak attributed to the amorphous component of the silicon film by the second Raman peak attributed to the component of single crystal silicon is 0.4 or more. Manufacturing method. According to claim 1 or claim 2,
A method for manufacturing a thin film transistor, wherein an excimer laser is used as the laser light. According to claim 1 or claim 2,
A method for manufacturing a thin film transistor, wherein a YAG laser is used as the laser light. According to claim 1 or claim 2,
A method for manufacturing a thin film transistor, wherein an ultraviolet laser is used as the laser light. According to claim 1 or claim 2,
A method for manufacturing a thin film transistor, wherein a visible laser is used as the laser light. According to claim 1 or claim 2,
A method for manufacturing a thin film transistor, wherein an infrared laser is used as the laser light.

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