KR960001165B1 - A method for manufacturing a semiconductor device and a method - Google Patents

Abstract

No content.

Description

Semiconductor device manufacturing method and semiconductor material forming method

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

2 shows the relationship between the center value (RAMAN SHIFT) of the Raman peak of the laser-annealed silicon film of various oxygen concentrations and the electron mobility (vertical axis).

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

A fourth intensity of turning the single crystal silicon component with respect to the intensity (peak of 480cm ^-1) of the amorphous component of the ramak peak for the laser annealing the silicon film in the various oxygen concentrations (peak of 521cm ^-1) ratio for (Ia / Ic, The relationship between the horizontal axis) and the electron mobility (vertical axis) is shown.

5 shows the positional dependence of the FWHM of the Raman peak in the channel formation region of a field effect transistor (vertical axis: FWHM, horizontal axis: X / L (L: channel length)).

6A to 6C show an example of a method of manufacturing a field effect transistor.

* Explanation of symbols for main parts of the drawings

601 substrate 602 semiconductor film

603: insulator coating 604: gate electrode

605: photo register 606: source region

607: drain region 608: source electrode

609: drain electrode

[Industrial use]

The present invention relates to a semiconductor material mainly containing silicon. In particular, the present invention aims at improving the characteristics of a thin silicon semiconductor material, and according to the present invention, a thin film semiconductor device (such as a thin film transistor) having improved characteristics can be manufactured.

[Prior art]

Conventionally, amorphous semiconductor materials (so-called amorphous semiconductors) or polycrystalline semiconductor materials have been used to fabricate thin film semiconductor devices such as thin film field effect transistors. Hereinafter, the language amorphous is not used to mean purely an atomic level disorder, but includes a substance which allows a near order order of several nm to exist. Specifically, a silicon material having an electron mobility of 10 cm ² / VS or less, or a carrier mobility of the material, means a material of 1% or less relative to the essential carrier mobility of the semiconductor material. Therefore, microcrystals (having a particle diameter of 50 to 50 microns calculated from the Raman shift Syrah formula) or semi-morphs (having lattice distortion, the Raman shift is off the lower wave side than 521 cm ^-1 , and amorphous and crystal are mixed Boundary has an ambiguous crystal structure). The material, which is an aggregate of fine crystals of about 10 nm, is also called amorphous.

By the way, when using an amorphous semiconductor (such as amorphous silicon, amorphous germanium, etc.), since it can manufacture at a comparatively low temperature of 400 degrees C or less, it is attracting attention as a promising method in the liquid crystal display etc. which cannot adopt a high temperature process.

However, since pure amorphous semiconductors have remarkably small carrier mobility (electron mobility and hole mobility), these amorphous semiconductors are rarely used as they are, for example, as channel formation regions of thin film transistors (TFTs). The material was irradiated with strong light such as laser light or xenon lamp light, melted and recrystallized into a crystalline semiconductor material, and this carrier mobility was improved and used (in the following sentence, this method is referred to as "laser annealing" It is not necessary to use a laser, including the case of irradiating a strong flash lamp light having an effect such as laser annealing light irradiation).

However, the carrier mobility of the semiconductor material conventionally obtained by the laser annealing method was generally smaller than that obtained as the single crystal semiconductor material. For example, in the case of the silicon film it is also largest electromigration that is reported is 200cm ² / VS, this is not only one-seventh of the electron mobility of the single crystal silicon is also 1350cm ² / VS. In addition, the characteristics (mobility mainly) of the semiconductor material obtained by the laser annealing method are insufficient in reproducibility, have a large imbalance in mobility in the same film, and are obtained when a large number of elements are formed in the same plane. Since the characteristic imbalance of a semiconductor element is large, the yield of a product fell remarkably.

[Problem to Solve Invention]

An object of the present invention is to improve the characteristics of a thin-film semiconductor material that cannot be put to practical use because the mobility in the conventional laser annealing method is very small compared to a single crystal semiconductor material and its reproducibility is poor. That is, the present invention provides a thin film semiconductor material having high mobility, and a method of manufacturing a semiconductor material having high mobility with high reproducibility.

[Means for solving the problem]

By the way, 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 the laser annealing method. The inventors of the present invention have found that, in the study of the laser annealing method, the center value of the Raman peak of the semiconductor film obtained, the width of the Raman peak, the height of the Raman peak, and the like are closely related to the characteristics of the semiconductor film.

For example, although the Raman peak exists in 521cm <^-1> in single crystal silicon, the Raman peak of the laser-annealed silicon film tended to move to the short wave length (long wavelength) rather than that. And it was found 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.

Although FIG. 1 is an example showing this relationship, the relationship of the center value (horizontal axis) of the Raman peak of a film obtained by laser annealing an amorphous silicon film and the electron mobility (vertical axis) of a film is shown. Electron mobility has shown the value obtained by manufacturing TFT by a silicon film, and measuring CV (capacitance-voltage) characteristic.

As can be seen from the figure, the center of the Raman peak is bounded by 515 cm ^−1, which shows a large difference in the movement of the electron mobility. That is, below 515 cm ⁻¹ , the Raman peak of the electron mobility is small, but the 515 cm Above ^-1 , as the center value of the peak increases, electron mobility rapidly increases.

This phenomenon clearly shows that two phases exist. According to the research of the present inventors, the film does not melt even by laser annealing at 515 cm ^-1 or less, and the ordering of atoms remains as solid phase, and the film melts by laser annealing at 515 cm ^-1 or more, and solidifies through a liquid state. It is estimated that.

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 the obtained electron mobility was about 200 cm ² / VS.

Next, the inventors found that the amount of oxygen, nitrogen, and carbon contained in the coating has a great influence on the mobility during the study for improving the mobility. In FIG. 1, the number of nitrogen atoms and oxygen atoms present in the film was negligible, but the number of oxygen atoms was about 2 x 10 ²¹ cm ^-3 at the center of the film. Thus, by reducing the number of oxygen atoms contained in the film, it was investigated how the relationship between the center of the Raman peak and the electron mobility changes.

Hereinafter, in this specification, the density | concentration of these heterogeneous elements, such as oxygen, nitrogen, and carbon, means the density | concentration of the center part of a film. This is because the concentration of these dissimilar elements in the portion near the substrate of the coating or near the surface of the coating is very high, but the dissimilar elements present in these regions do not significantly affect the carrier mobility in question in the present invention. Because it becomes. This is because the portion of the film having the smallest concentration of these other elements is considered to be the central portion of the film in the ordinary coating, and the central portion of the film is considered to play an important role in semiconductor devices such as field effect transistors. For the above reasons, in the present specification, the concentration of the heterogeneous element refers to the concentration of the central portion of the film.

This is shown in FIG. As can be seen in Figure 2, by reducing the oxygen concentration in the film, it was possible to improve the remarkable electron mobility. This tendency was the same even when carbon and nitrogen were included in the film. For this reason, the present inventors believe that when the film is melt recrystallized by laser annealing when there are a large number of oxygen atoms in the film, the portion of the oxygen atoms becomes crystal nuclei and grows crystallized. Together with the surroundings, and when extracted through the grain boundary and viewed through the entire film, the mobility is reduced for the barrier generated in the grain boundary, and the region where the concentration of oxygen atoms or oxygen atoms is large by laser annealing ( Generally, melting point is thought to be larger than pure silicon), which becomes crystal nuclei and grows crystallized. However, when the number of oxygen atoms is large, crystal nuclei occur more frequently, so that the crystal size per one becomes smaller and the mobility is smaller. It is suggested that the crystallinity is impaired.

In any case, by making the oxygen concentration in the film small, very large electron mobility was obtained by laser annealing. For example, a large electron mobility of 1000 cm ² / VS was obtained by setting the oxygen concentration to 1 × 10 ¹⁹ cm ^-8 . In addition to the oxygen concentration, the same effect can be obtained by reducing the concentration of nitrogen and the concentration of carbon. The same effect was obtained for the hole mobility.

Even when the oxygen concentration is large or small, the curves of the Raman peak position and electron mobility show a curved shape as in the case of FIG. The inventors estimated that the region on the right side of the dotted line in FIG. 2 was recrystallized after the film melted once according to the laser annealing, and named this region the melt-recrystallization region. Large mobility was obtained in this melt-recrystallization region. The semiconductor material of the present invention preferably has a concentration of hetero atoms of oxygen, nitrogen, and carbon of 5 × 10 ¹⁹ cm ⁻³ or less and a Raman shift of 512 cm ⁻¹ or more (melt-recrystallization region).

The inventors have found that the same tendency is seen in the full width at half maximum (FWHM) of the Raman peak. This state is shown in FIG. The abscissa in Fig. 3 is the half width of the Raman peak of the laser annealed film divided by the half width of the long crystal silicon, which is referred to herein as the half width ratio (FWHM RATIO). It is thought that FWHM RATIO is small and has a structure close to single crystal silicon as close to one. As can be seen from the figure, when the oxygen concentrations are the same, the electron mobility is as large as the FWHM RATIO is close to one. As in the case of the center of the Raman peak, the electron mobility was as large as the oxygen concentration in the film was small, and the same tendency was observed in the concentration of nitrogen and carbon in addition to the oxygen concentration. That is, electron mobility as large as these concentrations were obtained was obtained. The same tendency was seen for the hole mobility. In this case as well as in the case of FIG. 2, the left side in the dotted line of FIG. 3 is considered to be the melt-recrystallized region.

The inventors have found that the Raman peak has a close correlation with the electron mobility also with respect to the intensity of the peak due to the amorphous component in the film. 4 will turn divided by a Raman peak Raman peak Ic (peak in the vicinity of 52cm ^-1) of (480cm ^-1 near the peak) single crystal silicon the intensity (Ia) of due to the amorphous component of the laser annealing the film, below, INTENSITY It is called RATIO. Regarding INTENSITY RATIO, if the oxygen concentration in the film is the same, INTENSITY RATIO is small. In other words, the less the amorphous component in the film, the greater the electron mobility, and the smaller the amount of oxygen contained in the film, the greater the electron mobility. The same trend was observed not only for the oxygen concentration but also for the nitrogen and carbon concentrations. That is, electron mobility as large as these concentrations was obtained was small. The same tendency was seen for the hole mobility. Also in this case, it is considered that the left side of the dotted line in FIG. 4 is a melt-recrystallized region as in the case of FIGS. 2 and 3.

Empirically, when the intensity of the Raman peak is large, a large carrier mobility is obtained, and the intensity of the Raman peak of the film having a small concentration of oxygen, nitrogen, and carbon becomes large.

As mentioned above, in order to improve carrier mobility, it was found that the amount of oxygen, nitrogen, and carbon in the film should be reduced. Particularly, the inventors of the present inventors have all of these elements to be 5 × 10 ¹⁹ cm ⁻³ or less, preferably 1 × 10 ¹⁹ cm ⁻³ or less, so that, for example, a 1000 cm ² / VS value is obtained as electron mobility in a silicon film. I found that. The present invention has found that by reducing the concentration of these elements, a value closer to the carrier mobility of a single crystal semiconductor can be obtained and the reproducibility can be improved. Moreover, by the same method, 300-500 cm <^2> / VS value was obtained stably as a hole mobility.

The laser annealing of the present invention may be performed at atmospheric pressure or under reduced pressure.

An amorphous semiconductor film having a concentration of carbon, nitrogen, and oxygen of 5 × 10 ¹⁹ cm ⁻³ or less, preferably 10 × 10 ¹⁹ cm ⁻³ or less, is irradiated with laser light or equivalent light beam.

However, for example, laser annealing the concentration of the above elements in the film of 1 × 10 ¹⁶ cm ^-3 or less in it a very high vacuum environment, so these elements have a small concentration (× 10 ¹⁶ cm ^-3 or less 1) of It can also be easily achieved. This is because oxygen gas, nitrogen gas, moisture, carbon dioxide, etc. contained in a small amount in the atmosphere are introduced into the film during the laser annealing, or these gases adsorbed on the surface of the film are introduced into the film during the laser annealing. I guess.

In order to avoid these difficulties, a special production method is required. One method has very small concentrations of oxygen, nitrogen and carbon. For example, the surface of an amorphous semiconductor film is covered by 10 ¹⁵ cm ^-3 or less to form a protective film such as silicon oxide, silicon nitride, silicon carbide, and then subjected to laser annealing in a vacuum atmosphere (10 ^-4 torr or less). Thus, the concentration of oxygen, nitrogen, and carbon is very small, and a high mobility semiconductor film can be formed. For example, a silicon film having a concentration of carbon, nitrogen, and oxygen of 1 × 10 ¹⁵ cm ⁻³ or less and an electron mobility of 1000 cm ² / VS was obtained.

When forming the protective film of silicon oxide, silicon nitride, silicon carbide, etc. by covering the surface of an amorphous semiconductor film, it is a chamber which has one vacuum apparatus, For example, an amorphous semiconductor film was formed by the CVD method or the sputtering method. Later, the film is continuously formed by changing the atmosphere in the same chamber or by setting it to a very high vacuum state and then setting it in an atmosphere suitable for film formation. However, in order to further improve the yield, reproducibility, and reliability of the product, it is better to prepare a dedicated chamber for forming the film, and to move each chamber while keeping the product in a very high vacuum. The selection of these deposition methods is made by the scale of facility investment. Either method is important, since oxygen, nitrogen, and carbon contained in the underlying amorphous semiconductor film are sufficiently small, and no gas is adsorbed at the amorphous semiconductor and the protective film interface thereon. For example, even when a very pure amorphous semiconductor film is formed, when the film is once exposed to the atmosphere and then a silicon nitride film is formed thereon, the carrier mobility of the film obtained by laser annealing the film is generally small, The probability of obtaining a large mobility is very small. This is considered to be because gas is adsorbed on the surface of the amorphous semiconductor film and this diffuses into the film during the subsequent laser annealing.

The material of the protective film at this time may be silicon oxide, silicon nitride or silicon carbide as long as the conditions for transmitting the laser light are satisfied, and the chemical formulas SiN _x O _y C _z (O≤x≤4 / 3, O≤y≤) are mixed. It may be a material containing a material represented by 2, O ≦ z ≦ 1, O ≦ 3x + 2y + 4z ≦ 4). 50-1000 nm was suitable for the thickness.

However, 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 by reducing the concentration of oxygen, nitrogen and carbon present in the laser annealing. Although it is made clear, the electron mobility or hole mobility obtained at this time is an average value of the channel formation region of the field effect transistor formed for the measurement, and the mobility cannot be obtained at each minute portion of the channel formation region. However, as is clear from FIGS. 1 to 4 and related arts of the present invention, carrier mobility may include the position of the Raman peak, the half width of the Raman peak, the strength of the amorphous component with respect to the Raman peak, the intensity of the Raman peak, and the like. It is now clear that the parameters can be determined arbitrarily. Therefore, the mobility of the microscopic region in which the movement cannot be measured directly, and the mobility thereof can be estimated approximately from these information by Raman spectroscopy.

The fifth turning the electron mobility is ^{22cm 2 / VS, 201cm 2 /} VS and 980cm ² / VS and measuring the full width at half maximum of the Raman peak in each section of the channel forming region of a field effect transistor having a channel forming region formed by the laser annealing (FWHM) is shown. In the figure, the horizontal axis indicates the position of the channel formation region. L is the length of the channel formation region and is 100 m. X represents the coordinates of the channel formation region, X / L = 0 is the interface of the source region of the channel formation region, X / L = 1 is the interface of the drain region of the channel formation region, and X / L = 0.5 is of the channel formation region. It shows the center. As can be seen from the figure, an electron mobility of 22 cm ² / VS has a large FWHM, and its variation is not large. As the FWHM is smaller, the crystallinity of the film is closer to the single crystal, and the electron mobility is larger as described in FIG. 3 and the description related thereto, and this data itself does not contradict it. However, the small fluctuation (location dependence) due to the location of the FWHM means that the crystallinity of the film is almost the same regardless of the location. In addition, the oxygen concentration of this film is about 8 * 10 <^20> cm <^-3> , and it is estimated that it did not melt even by laser annealing.

On the other hand, the thing of 201cm <^2> / VS of electron mobility was 8 * 10 <^20> cm <^-3> with the same oxygen concentration. As can be seen from the figure, the overall FWHM is declining, but the location dependence of the FWHM is large. And depending on the place, the value of FWHM which is equivalent to or less than that of 980 cm <^2> / VS was shown. The small FWHM suggests that the electron mobility of the part is large, but this means that a part having the same crystallinity as that of single crystal silicon is localized in the same film. However, when mass-producing as a device, it is not preferable to use a material whose characteristics differ greatly by such a place, no matter how large the mobility is.

The electron mobility of 980 cm ² / VS was about 1 × 10 ¹⁹ cm ^{-3, which is} very small in oxygen concentration compared to the other two. As can be seen from the figure, the overall FWHM is small and the location dependence of the FWHM is small. This suggests that the electron mobility is large and is made of a material having crystallinity equivalent to that of single crystal silicon, and is very suitable for mass production for devices and the like.

In order to obtain high carrier mobility, it is necessary to reduce the concentration of heterogeneous elements in the film as described above and to optimize the laser annealing conditions. The conditions of the laser annealing vary depending on the laser oscillation conditions (continuous oscillation or pulse oscillation, repetition frequency, intensity, wavelength, film, etc.) and cannot be generally described.

As the laser, visible and infrared lasers can be used, such as ultraviolet lasers such as various excimer lasers and YAG lasers, and it is necessary to select them by the thickness of the film to be laser annealed. That is, in silicon or germanium materials in general, the absorption length to ultraviolet rays is short, so that the laser light does not reach the deep portion, and the laser annealing occurs only in a relatively shallow region of the surface. On the other hand, the absorption length is long for visible light and infrared light, and light penetrates into the inside relatively, so that laser annealing occurs at the deep portion. Therefore, by selecting the film thickness and the type of laser, it is possible to laser anneal only in the vicinity of the surface of the film.

In any case, high carrier mobility was obtained by selecting the wavelength, intensity, and the like of the laser so as to pass through the process of melt-recrystallization. In order to satisfy the condition of melting, the temperature of the part irradiated with the laser even in a long time is higher than the melting point of the semiconductor, that is, 1400 ° C or more under atmospheric pressure in case of silicon, and 1000 ° C or more under atmospheric pressure in case of germanium. . However, for example, in a very short time of 10 nanoseconds, which is realized as an excimer laser, even if a temperature exceeding 2000 ° C. is observed spectroscopically, melting of the film is also not observed, and the definition of this temperature is not very practical. It doesn't have meaning.

As an additional matter, after laser annealing the semiconductor film, annealing for 10 minutes to 6 hours at 200 to 600 ° C. in a hydrogen atmosphere was effective in order to obtain high carrier mobility with good reproducibility. This is thought to be because recrystallization takes place by laser annealing, and an ancillary number of bonds (turngling bonds) occurs in the bond between semiconductor atoms, which is possible as a barrier to the carrier. When oxygen, nitrogen, carbon, etc. are contained in a semiconductor in many cases, it is considered that they take a turnling bond, but when the concentration of oxygen, nitrogen, carbon, etc. is remarkably small like this invention, a turnling bond is removed. Therefore, it is considered that it is necessary to anneal in a hydrogen atmosphere after laser annealing.

EXAMPLE

Example 1

The planar structure TFT was produced and its electrical characteristics were evaluated. The fabrication method is shown in FIGS. 6A to 6C. First, an amorphous silicon film having a thickness of about 100 nm was formed by a conventional 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 Pascals (Pa). Argon was not intentionally added to the gas other than hydrogen. The concentration of argon was at least 99.99%. The input power was 200 W and the RF frequency was 13.56 MHz. Thereafter, the amorphous silicon film was etched in a rectangle of 100 µm x 500 µm to obtain an amorphous silicon film 602.

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

Next, the membrane was placed in a vacuum vessel at a pressure of 10 ^-5 torr, and excimer laser light (KrF laser, wavelength 248 nm, pulse width 10 nanoseconds, irradiation energy 200mJ, irradiation number of 50 shots) was passed through a quartz window installed in the vacuum vessel. It irradiated and laser annealed.

The gate insulating film 603 of thickness about 100 nm was formed in this by the sputtering method in oxygen atmosphere. At this time, the board | substrate temperature was 150 degreeC and RF (13.56 MHz) input power was 400W. The atmosphere was substantially oxygen and no other gas was intentionally added. The concentration of oxygen was at least 99.9%. The pressure was 0.5 Pa.

Thereafter, an aluminum film (thickness of 200 nm) was formed by a well-known vacuum vapor deposition method, unnecessary portions were removed by a well-known dry etching method, and the gate electrode 604 was formed. The width of the gate electrode was 100 µm. At this time, the photoresist 605 used for the dry etching remained on the gate electrode.

Next, by the ion type method, 10 ¹⁴ cm ^-2 were implanted with hoso ions other than the part of the gate electrode. Under the gate electrode, the gate electrode and the photoresist thereon were masked and no homeo ions were implanted. By this process, an impurity region, that is, a source region 606 and a drain region 607 was formed in the silicon film. This is shown in Fig. 6B.

The entire substrate was placed in a vacuum vessel, and irradiated with excimer laser light (KrF laser, wavelength 248 nm, pulse width 10 nanoseconds, irradiation energy 100mJ, irradiation number of 50 shots) at a pressure of 10 ^-5 torr to perform laser annealing. By this process, the ionized and amorphous regions were recrystallized.

Next, thermal annealing in a hydrogen atmosphere was performed. The substrate is placed in a chamber that can be evacuated, and once exhausted by a turbomolecular pump to 10 ^-6 torr, and after 30 minutes of induction, hydrogen gas having a purity of 99.9a% or more is introduced into the chamber up to 100torr, The substrate was annealed at 300 ° C. for 60 minutes.

Here, the vacuum evacuation is for removing gas, moisture, and the like adsorbed on the film. It has been empirically found that when the thermal annealing is carried out in the remaining state, high mobility cannot be obtained with good reproducibility.

Finally, a hole was opened 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. The field effect transistor was formed by the above process.

As a result of measuring the CV characteristic of this field effect transistor, the electron mobility of the channel formation area was 980 cm <^2> / VS. Threshold voltage (threshold voltage) was 4.9V. As a result of measuring the concentrations of oxygen, nitrogen and carbon in the channel formation region of the field effect transistor by SIMS, all were 1 × 10 ¹⁹ cm ⁻³ or less.

Example 2

The planar structure TFT was produced 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 conventional RF sputtering method. At 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 Pascals (Pa). Argon was not intentionally added to the gas other than hydrogen. The concentration of argon was at least 99.99%. The input power was 200 W and the RF frequency was 13.56 MHz. Thereafter, the amorphous silicon film was etched in a rectangle of 100 µm x 500 µm.

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

The gate insulating film of thickness about 100 nm was formed in this by the sputtering method in oxygen atmosphere. At this time, the board | substrate temperature was 150 degreeC and RF (13.56 MHz) input power was 400W. The atmosphere was substantially oxygen and no other gas was intentionally added. The concentration of oxygen was at least 99.9%. The pressure was 0.5 Pa.

Then, an aluminum film (thickness 200 nm) was formed by a well-known vacuum vapor deposition method, the unnecessary part was removed by the well-known dry etching method, and the gate electrode was formed. The width of the gate electrode was 100 µm. At this time, the photoresist 605 used for the dry etching remained on the gate electrode.

Next, by the ion type method, 10 ¹⁴ cm ^-2 were implanted with hoso ions other than the part of the gate electrode. Under the gate electrode, the gate electrode and the photoresist thereon were masked and no homeo ions were implanted. By this step, an impurity region, that is, a source region and a drain region, was formed in the silicon film.

The entire substrate is placed in a vacuum vessel, and excimer laser light (KrF laser, wavelength 248 nm, pulse width 10 nanoseconds, irradiation energy 100mJ, irradiation pulse number of 50 shots) is irradiated on the back surface of the substrate at a pressure of 10 ^-5 torr. It was done. By this process, the amorphous silicon film was crystallized. This method is different from that of the first embodiment, and crystallization of the source region or the drain region and the channel formation region is performed simultaneously. Therefore, in 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. Thus, the interface with fewer defects and crystallinity was obtained.

Next, thermal annealing in a hydrogen atmosphere was performed. The substrate was placed in a chamber capable of evacuating, and once exhausted by a turbo molecular pump to 10 ⁻⁶ torr, and 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 for removing gas moisture and the like adsorbed on the film. It has been empirically found that when the thermal annealing is carried out in the remaining state, high mobility cannot be obtained with good reproducibility.

Finally, a hole was opened 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. The field effect transistor was formed by the above process.

As a result of measuring the CV characteristic of this field effect transistor, the electron mobility of the channel formation area was 990cm <^2> / VS. The threshold voltage was 3.9V.

The reason why the threshold voltage is improved (decreased) in comparison with the above Example 1 is considered to be that the impurity region and the channel region are simultaneously crystallized simultaneously by performing laser annealing on the back surface. The ratio of the drain current at the time of turning on / off the gate voltage was 5x10 <^6> .

As a result of measuring the concentrations of oxygen, nitrogen, and carbon in the channel formation region of the field effect transistor by SIMS, all were 1 × 10 ¹⁹ cm ⁻³ or less. Hanba a channel formation region measured by the Raman spectroscopy, the half-width of the Raman peak 520cm ^-1, the center value of the Raman peak has been confirmed the presence of the then 4.5cm ^-1 and, once melted, the re-crystallization of silicon.

Example 3

The planar structure TFT 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 were successively formed on a quartz substrate coated with a silicon nitride film having a thickness of 10 nm. The amorphous silicon film was produced by the usual sputtering method, and the silicon nitride film was produced by the glow discharge plasma CVD method.

First, a substrate was set in the first preliminary chamber, the preliminary chamber was heated to 200 ° C, and vacuum evacuated, and the preliminary chamber pressure was maintained for 1 hour in a state of 10 ⁻⁶ torr or less.

Next, except for the film formation, the first chamber maintained at 10 ⁻⁴ torr or less at all times and managed to prevent outside air from entering is exhausted to 10 ⁻⁶ torr, and the substrate is moved to the first chamber by moving the substrate from the preliminary chamber. It set, the board | substrate and the target were maintained at 200 degreeC, vacuum evacuation, and hold | maintained for 1 hour in the state of the pressure of ^10-6 torr or less. Then, argon gas was introduced into the chamber, and RF plasma was generated to sputter film formation. The target of the sputter uses a silicon target of 99.9999% or more purity and contains 1 ppm of phosphorus. At the time of film formation, the substrate temperature was 150 ° C., the atmosphere was substantially 100% argon, and the pressure was 5 × 10 ⁻² torr. Argon was not intentionally added to the gas other than hydrogen. Argon concentration was over 99.9999%. The input power was 200 W and the RF frequency was 13.56 MHz.

After the film formation was completed, 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 the substrate is transferred from the first chamber to the second preliminary chamber. Transferred. Except during film formation, the second chamber, which is kept below 10 ^-4 torr at all times and managed to prevent outside air, is evacuated to 10 ^-6 torr, and the substrate is set in the second chamber by moving the substrate in the second preliminary chamber. Then, the substrate and the target were kept at 200 ° C., evacuated, and kept in a state in which the pressure of the chamber was 10 ⁻⁶ torr or less for 1 hour.

Then, 99.9999% or more of ammonia gas and indicator egg gas (Si ₂ H ₆ ) diluted as hydrogen in the second chamber were introduced at a ratio of 3: 2, and the total pressure was set to 10 ⁻¹ torr. Then, an RF current was introduced into the chamber, and plasma was generated to form silicon nitride. Input power (13.56 MHz) was 200W.

After the film formation was completed, RF discharge was stopped and the second chamber was evacuated to 10 ⁻⁶ torr. Next, the third preliminary chamber provided on one side of the second chamber and having a window of quartz was evacuated to 10 ⁻⁶ torr, and the substrate was transferred from the second chamber to the third preliminary chamber. The excimer laser light (KrF laser, wavelength 248 nm), pulse width of 10 nanoseconds, irradiation energy of 100 mJ, and the number of irradiation pulses of 50 shots were irradiated through a third reserve chamber window, and laser annealing was performed. In this way, the amorphous silicon film was crystallized.

In this way, the laser annealing is performed continuously in the film forming state without substantially damaging the vacuum state. As shown in the present embodiment, even when the protective film is formed on the amorphous semiconductor film, the protective film is formed as in the above embodiment. Even if not, it was very effective in improving the yield. As a reason, it can avoid that a hickory etc. adhere to a film, and adsorption | suction of water or gas arises or damages.

As described above, in the case where film formation and laser annealing are performed in this way, a film formation chamber and a preliminary chamber are provided as in this embodiment, a window is provided in the preliminary chamber, and a laser annealing method is provided. Although the method of performing laser annealing after film-forming is considered, the latter will blur the window by film-forming, and the former does not need to etch the film which always adheres to a window. Therefore, in consideration of mass productivity and maintenance, it can be said that the former method is excellent.

By the way, after laser annealing was finished in the 3rd preliminary chamber, dry nitrogen gas was introduce | transduced into the 3rd preliminary chamber, and the board | substrate was taken out at atmospheric pressure. Then, the silicon film was removed by a known dry etching method, and then the silicon film was etched in a rectangle of 100 µm x 500 µm.

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

The gate insulating film of thickness about 100 nm was formed in this by the sputtering method in oxygen atmosphere. At this time, the board | substrate temperature was 150 degreeC and RF (13.56 MHz) input power was 400W. The target of sputter was silicon oxide of purity 99.9999% or more. The atmosphere was substantially oxygen and no other gas was intentionally added. The concentration of oxygen was at least 99.9999%. The pressure was 5 × 10 ⁻² torr.

Thereafter, an aluminum film (thickness of 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 dry etching remained on the gate electrode.

Next, by the ion type method, 10 ¹⁴ cm <^{-2> was} implanted in the hoso ion other than the part of a gate electrode. Under the gate electrode, the gate electrode and the photoresist on it serve as masks, and no homeo ions are implanted. By this process, impurity regions, i.e., source regions and drain regions, were formed in the silicon film.

To leave the entire substrate in a vacuum vessel, 10 ²⁵ torr pressure excimer laser light in the (KrF laser, wavelength 248nm, 10 ns pulse width, the irradiation energy 50mJ, to investigate pulse 50 shot), is irradiated from the back surface of the substrate, laser annealing Was performed. By this step, the amorphous silicon film of the impurity region that has been amorphous by the ion type step is crystallized.

This method is the same as in Example (1) in that the laser annealing is performed in two stages, but the second laser annealing is performed on the back surface of the substrate, whereby the impurity region and the channel formation region are continuously connected. In particular, the first laser annealing melt-recrystallization process aims to obtain a film having a high carrier mobility, while the second laser annealing suppresses the output of the laser and does not melt the microscopic crystals. It aims at promoting phosphorylation and lowering the resistance of the impurity region. As the output of the laser is controlled, the crystalline region (mainly the channel forming region) with high mobility formed by the first laser annealing hardly changes. As can be seen from the above embodiment, at the interface between the source region or the drain region and the channel formation region, defects can be reduced and an interface with continuous crystallinity can be obtained.

The method of the first embodiment is different from that of the second embodiment, and in particular, in order to fabricate the channel type region, the reason for performing the first laser annealing is that when the laser annealing is performed by an ultraviolet laser, the laser irradiation surface is annealed, but not deep. This is because there is a high possibility that a state of high mobility cannot be obtained, and the yield of the product is lowered. The fact that the mobility of the region close to the gate electrode is not high by irradiation of the laser light on the back surface is fatal to the field effect transistor, and therefore irradiation on the film surface is desired. Therefore, in order to improve the yield of the product, in the present embodiment, a method of firstly irradiating a laser on the surface of an amorphous silicon film and then irradiating a laser on the back surface of the substrate to obtain a continuous junction between the channel formation region and the impurity region Adopted.

Next, thermal annealing in a hydrogen atmosphere was performed. The substrate was placed in a chamber that could be evacuated, and once exhausted by a turbo molecular pump to 10 ⁻⁶ torr, and 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. The vacuum evacuation is because the gas moisture and the like adsorbed on the film are removed. When the thermal annealing is performed in the remaining state, it can be seen experimentally that high mobility cannot be obtained with good reproducibility.

Finally, a hole was opened 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.

The field effect transistor was formed by the above process.

As a result of manufacturing 100 field-effect transistors and measuring their CV characteristics, the average electron mobility of the channel formation region was 995 cm ² / VS.

The average of the threshold voltages (the threshold voltages) was 4.2V. The average drain current ratio was 8x10 ⁶ . The pass / fail of 100 field effect transistors was examined as 91 reference | standards as the reference value of electron mobility was 800 cm <^2> / VS, the threshold voltage was 5.0V, and the reference value of the drain current ratio was 1x10 <^6> .

As a result of measuring the concentrations of oxygen, nitrogen, and carbon in the channel formation regions of these field effect transistors by SIMS, all of the passed field effect transistors were 1 × 10 ¹⁶ cm ⁻³ or less.

[Effects of the Invention]

According to the present invention, it has become clear that a film-like semiconductor having high mobility can be obtained with good reproducibility. In the present invention, the laser annealing of the semiconductor film formed mainly on an insulating substrate such as quartz has been described. However, the material of the substrate may be a single crystal semiconductor such as a single crystal silicon substrate to be used in a monolithic IC or the like. Although the silicon film was demonstrated in the Example, even if it is a germanium film, a silicon germanium alloy film, or another intrinsic semiconductor material or a compound semiconductor material, this invention can function. As described earlier, a method of laser annealing was used as a method for improving the mobility of the amorphous coating, but the surface also includes a method in which a laser such as a flash lamp annealing is not used. That is, the present invention relates to a method of improving the crystallinity of a semiconductor material by using strong optical energy.

Claims (16)

A method of manufacturing a semiconductor device, comprising: forming a non-single crystal semiconductor film on an insulating surface, irradiating the semiconductor film with first light to melt and crystallize the semiconductor film, and doping a portion of the semiconductor film with impurities And irradiating the semiconductor film with a second light after the doping to increase crystallinity without melting the semiconductor film. The method of claim 1, wherein the first light is laser light. The method of claim 1, wherein the first light is emitted from a flash lamp. The method of claim 1, wherein the second light is laser light. The method of claim 1, wherein the second light is emitted from a flash lamp. 2. The method of claim 1, further comprising annealing the semiconductor film in hydrogen gas after irradiating the second light. A method of manufacturing a semiconductor device, comprising: forming an amorphous semiconductor film on a transparent surface, and irradiating the semiconductor film with first light to melt and crystallize the semiconductor film, wherein the first light is opposed to the substrate. The melting and crystallization steps emitted from the upper surface of the semiconductor film and increasing the crystallinity without irradiating and melting the semiconductor light with a second light after irradiating the first light, wherein the second light is the A semiconductor device manufacturing method, characterized in that emitted from an opposite side of the substrate in relation to a semiconductor film. 8. The method of claim 7, wherein the first light is laser light. 8. The method of claim 7, wherein the first light is emitted from a flash lamp. 8. The method of claim 7, wherein said second is laser light. 8. The method of claim 7, wherein the second light is emitted from a flash lamp. 8. The method of claim 7, further comprising annealing the semiconductor film in hydrogen gas after irradiating the second light. A method of manufacturing a semiconductor device, comprising: forming an amorphous semiconductor film on an insulating surface, irradiating the semiconductor film with first light to melt and crystallize the semiconductor film, and forming a gate insulating film on the semiconductor film; Forming a gate electrode on the insulating film, doping ions on the gate insulating film to form a source and a drain in the semiconductor film, and forming the source and drain region and then forming the semiconductor film with a second light. Increasing the crystallinity without irradiating and melting. A method of manufacturing a semiconductor device, comprising: forming an amorphous semiconductor film on a transparent surface, and irradiating the semiconductor film with first light to melt and crystallize the semiconductor film, wherein the first light is opposed to the substrate. The melting and crystallization steps emitted from the upper surface of the semiconductor film, forming a gate insulating film on the semiconductor film, forming a gate electrode on the insulating film, and doping ions on the gate insulating film to do the semiconductor Forming a source and a drain region in the film, and increasing the crystallinity without irradiating and melting the semiconductor film with a second light after forming the source and drain region, wherein the second light is the semiconductor. Manufacture of semiconductor device characterized in that it is emitted from the opposite side of the substrate in relation to the film Way. A method of forming a semiconductor material, comprising: forming a film on the surface of an amorphous semiconductor containing carbon, nitrogen, and oxygen, each having a concentration of 5 x 10 ¹⁹ atoms · cm ^-3 or less, and irradiating the film with first light; Crystallizing an amorphous semiconductor with a crystallized semiconductor having a peak of light intensity dispersed at a Raman shift of 512 cm −1 or more in Raman spectroscopy, and irradiating the film with second light to increase crystallinity And a step of making the semiconductor device. A method of forming a semiconductor material, comprising: forming a film on the surface of an amorphous semiconductor containing carbon, nitrogen, and oxygen at a concentration of 5 x 10 ¹⁹ atoms · cm ^-3 or less, and silicon oxide, silicon nitride, and silicon carbide Forming a protective film comprising a material selected from the group comprising: on the film comprising an amorphous semiconductor, and irradiating the film with first light to produce a light intensity dispersed at a Raman shift of 512 cm ⁻¹ or more in Raman spectroscopy. Crystallizing the amorphous semiconductor with a crystallized semiconductor having a peak, and irradiating the film with a second light after irradiating the first light to increase crystallinity.