JP3442752B2 - Method for manufacturing crystalline silicon film - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor having crystallinity.

[0002]

2. Description of the Related Art A thin film transistor (hereinafter referred to as TFT) using a thin film semiconductor is known. This TFT is formed by forming a thin film semiconductor on a substrate and using this thin film semiconductor. This TFT is used in various integrated circuits, and is particularly attracting attention as a switching element provided in each pixel of an active matrix type liquid crystal display device and a driver element formed in a peripheral circuit portion.

As a thin film semiconductor used for TFT,
Although it is easy to use an amorphous silicon film, there is a problem in that its electrical characteristics are low. In order to improve the characteristics of the TFT, a crystalline silicon thin film may be used. A crystalline silicon film is referred to as polycrystalline silicon, polysilicon, microcrystalline silicon, or the like. In order to obtain this crystalline silicon film, an amorphous silicon film may first be formed and then crystallized by heating.

However, crystallization by heating requires heating at a temperature of 600 ° C. or higher for 10 hours or longer, which makes it difficult to use a glass substrate as a substrate. For example, Corning 7059 glass used in an active type liquid crystal display device has a glass strain point of 593 ° C., and there is a problem in heating at 600 ° C. or higher in consideration of increasing the area of a substrate.

BACKGROUND OF THE INVENTION According to the research conducted by the present inventors, a small amount of elements such as nickel, palladium, and lead are deposited on the surface of an amorphous silicon film, and then heated to 550. It has been found that crystallization can be performed in a treatment time of about 4 hours at ℃.

In order to introduce such a trace amount of elements (catalyst elements that promote crystallization), plasma treatment, vapor deposition, or ion implantation may be used. Plasma treatment is a parallel plate type or positive column type plasma CVD apparatus in which a material containing a catalytic element is used as an electrode, and plasma is generated in an atmosphere such as nitrogen or hydrogen to form a catalytic element on the amorphous silicon film. Is a method of adding.

However, the presence of a large amount of the above-mentioned elements in the semiconductor impairs the reliability and electrical stability of the device using these semiconductors and is not preferable.

That is, the above-mentioned element (catalyst element) that promotes crystallization, such as nickel, is necessary when crystallizing amorphous silicon, but the crystallized silicon should not be included as much as possible. Is desirable. To achieve this goal,
It is necessary to select a catalyst element that has a strong tendency to be inactive in crystalline silicon, at the same time reduce the amount of the catalyst element necessary for crystallization as much as possible, and perform crystallization with the minimum amount. For that purpose, it is necessary to precisely control the amount of the catalyst element added and to introduce it.

When nickel is used as a catalyst element, an amorphous silicon film is formed, nickel is added by a plasma treatment method to form a crystalline silicon film, and the crystallization process and the like are examined in detail. The following matters were found. (1) When nickel is introduced into the amorphous silicon film by the plasma treatment, nickel has already penetrated to a considerable depth in the amorphous silicon film before the heat treatment. (2) The initial nucleation of crystals occurs from the surface into which nickel is introduced. (3) Even when nickel is formed on the amorphous silicon film by the vapor deposition method, crystallization occurs as in the case of performing the plasma treatment.

From the above it is concluded that all the nickel introduced by the plasma treatment is not functioning effectively. Then, it is concluded that "what is necessary is to introduce an extremely small amount of nickel in the atomically dispersed manner near the surface of the amorphous silicon film."

As a method of introducing a very small amount of nickel only in the vicinity of the surface of the amorphous silicon film, in other words, a very small amount of a catalyst element that promotes crystallization only in the vicinity of the surface of the amorphous silicon film is introduced. , Vapor deposition method can be mentioned,
The vapor deposition method has poor controllability and has a problem that it is difficult to strictly control the introduction amount of the catalyst element.

[0012]

DISCLOSURE OF THE INVENTION According to the present invention, in the production of a thin film silicon semiconductor having crystallinity by heat treatment using a catalytic element at 600 ° C. or lower, (1) the catalytic element is introduced while controlling its amount. (2) Use a method with high productivity. The purpose is to meet such requirements.

[0013]

In order to satisfy the above object, the present invention uses the following means to obtain a crystalline silicon film. "A solution containing a catalytic element is applied to the surface of the amorphous silicon film, and thereby the catalytic element is introduced."

The crystalline silicon film is used to form an active region of a semiconductor device. Semiconductor devices include thin film transistors (TFTs), diodes,
An optical sensor can be used.

By adopting the configuration of the present invention, the following basic significance can be obtained. (A) The concentration of the catalyst element in the solution can be strictly controlled in advance to enhance the crystallinity and reduce the amount of the element. (B) If the solution is in contact with the surface of the amorphous silicon film,
The amount of the catalytic element introduced into the amorphous silicon depends on the concentration of the catalytic element in the solution. (C) Since the catalytic element adsorbed on the surface of the amorphous silicon film mainly contributes to crystallization, the catalytic element can be introduced at the required minimum concentration.

As a method for applying a solution containing an element that promotes crystallization to the amorphous silicon film, an aqueous solution or an organic solvent solution can be used as the solution.

For example, when nickel is used as a catalyst element for promoting crystallization, nickel bromide, nickel acetate, nickel oxalate, nickel carbonate, nickel chloride, nickel iodide, nickel nitrate, nickel sulfate, formic acid is used as the nickel salt. Nickel, nickel 2-ethylhexanoate, nickel acetylacetonate, nickel 4-cyclohexylbutyrate and the like can be used.

Most of the above salts are water-soluble and can be used as an aqueous solution. However, some of them need to be dissolved in acid, aqueous ammonia, or alcohol, benzene, carbon tetrachloride, etc. before use.

Examples of compounds other than nickel salts include nickel oxide and nickel hydroxide, which must be dissolved in acid to form a solution. When nickel alone is used, it needs to be similarly dissolved in an acid to form a solution.

The above is an example of using a solution in which nickel, which is a catalytic element, is completely dissolved. However, even if nickel is not completely dissolved, a powder of a nickel compound is uniformly dispersed in the dispersion medium. Materials such as dispersed emulsions may be used. In this case, it is important to make the particle size of the dispersed powder as small as possible.

Further, the catalytic element may be contained in the coating liquid for forming a SiO ₂ film and introduced into the lower surface or the upper surface of the amorphous silicon film. In this case, as a coating liquid for forming a SiO ₂ film, OCD (Oh
ka Coat Diffusion-Source). That is, a catalytic element is contained in a coating liquid for forming an oxide film, and an oxide film using this coating liquid is provided in contact with the upper surface or the lower surface of the amorphous silicon film to form the amorphous silicon film. It is also possible to introduce a catalytic element on the surface.

The same applies to the case where a material other than nickel is used as the catalyst element.

Nickel is used as a catalyst element for promoting crystallization, and nitrate is used as a solution containing nickel.
When an aqueous solution of acetate or sulfate is used and the solution is applied to the amorphous silicon film, the solution is repelled. In this case, a thin oxide film having a thickness of 100 Å or less is first formed, and a solution containing a catalytic element is applied thereon, whereby the solution can be applied uniformly. A method of improving wetting by adding a material such as a surfactant to the solution is also effective.

Further, by using a non-polar solvent such as a toluene solution of nickel 2-ethylhexanoate as a solution, it is possible to apply directly to the surface of the amorphous silicon film. In this case, it is effective to pre-apply a material such as an adhesive used when applying the resist. However, if the coating amount is too large, the addition of the catalytic element into the amorphous silicon will be hindered, and therefore caution must be exercised.

The amount of the catalytic element contained in the solution depends on the type of the solution, but the general tendency is to set the amount of nickel to 200 ppm to 1 ppm, preferably 50 ppm to 1 ppm (weight conversion) based on the solution. Is desirable. This is a value determined in consideration of the nickel concentration in the film and the hydrofluoric acid resistance after completion of crystallization.

Further, by selectively applying a solution containing a catalytic element, crystal growth can be selectively performed. Particularly, in this case, crystal growth can be performed in the direction parallel to the surface of the silicon film from the area where the solution is applied, toward the area where the solution is not applied. In the present specification, a region in which crystal growth is performed in a direction parallel to the surface of the silicon film is referred to as a lateral crystal growth region.

It has been confirmed that the concentration of the catalytic element is low in the region where the crystal growth is performed in the lateral direction.
Although it is useful to use a crystalline silicon film as the active layer region of the semiconductor device, it is generally preferable that the concentration of impurities in the active layer region is low. Therefore, forming the active layer region of the semiconductor device by using the region in which the crystal growth is performed in the lateral direction is useful for device fabrication.

In the present invention, the most remarkable effect can be obtained when nickel is used as the catalyst element, but the other usable catalyst elements are preferably Ni, Pd, Pt, Cu and Ag. Au, In, S
n, Pd, Sn, Pd, P, As, and Sb can be used. Further, one or more kinds of elements selected from Group VIII elements, IIIb, IVb, and Vb elements can also be used.

The method of introducing the catalyst element is not limited to the use of an aqueous solution or a solution such as alcohol, but a wide range of substances containing the catalyst element can be used.
For example, a metal compound or oxide containing a catalytic element can be used.

[0030]

[Example] [Example 1]

This embodiment shows an example of forming a crystalline silicon film on a glass substrate. First, referring to FIG. 1, description will be made up to the point where a catalyst element (here, nickel is used) is introduced. In this embodiment, Corning 7059 glass is used as the substrate. The size is 10
The size is 0 mm × 100 mm.

First, an amorphous silicon film is formed into an amorphous silicon film by plasma CVD or LPCVD.
It forms from 00 to 1500Å. Here, plasma CVD
The amorphous silicon film 12 is formed to a thickness of 1000 Å by the method. (Fig. 1 (A))

Then, a hydrofluoric acid treatment is performed to remove the dirt and the natural oxide film, and then the oxide film 13 is removed by 10 to 50.
Deposit on Å. Needless to say, this step may be omitted if the stain can be ignored, and a natural oxide film may be used as it is instead of the oxide film 13. Since the oxide film 13 is extremely thin, the exact film thickness is unknown.
It is considered to be about 0Å. Here, the oxide film 13 is formed by irradiation with UV light in an oxygen atmosphere. The film formation was performed by irradiating UV for 5 minutes in an oxygen atmosphere. As a method of forming the oxide film 13,
A thermal oxidation method may be used. Alternatively, treatment with hydrogen peroxide may be used.

This oxide film 13 is provided to spread the acetate solution over the entire surface of the amorphous silicon film in the later step of applying the acetate solution containing nickel, that is, to improve the wettability. Is. For example, when the acetate solution is directly applied to the surface of the amorphous silicon film, the amorphous silicon repels the acetate solution, so that nickel cannot be introduced to the entire surface of the amorphous silicon film. That is, uniform crystallization cannot be performed.

Next, an acetate solution is prepared by adding nickel to the acetate solution. The concentration of nickel is 100 ppm. Then, 2 ml of this acetate solution is dropped on the surface of the oxide film 13 on the amorphous silicon film 12, and this state is maintained for 5 minutes. Then spin dry (2000
rpm, 60 seconds). (Fig. 1 (C), (D))

The concentration of nickel in the acetic acid solution is 1
Practical use is achieved when the content is at least ppm, preferably at least 10 ppm. When a nonpolar solvent such as a toluene solution of nickel 2-ethylhexanoate is used as the solution, the oxide film 1
3 is unnecessary, and the catalyst element can be directly introduced onto the amorphous silicon film.

A layer containing nickel having an average film thickness of several Å to several hundred Å is formed on the surface of the amorphous silicon film 12 after spin drying by performing this nickel solution coating step once to plural times. Can be formed. In this case, nickel in this layer diffuses into the amorphous silicon film in the subsequent heating step and acts as a catalyst for promoting crystallization. Note that this layer is not necessarily a perfect film.

After the application of the above solution, the state is maintained for 5 minutes. The concentration of nickel contained in the silicon film 12 can be finally controlled also by the holding time, but the largest control factor is the concentration of the solution.

Then, heat treatment is performed in a heating furnace in a nitrogen atmosphere at 550 ° C. for 4 hours. As a result,
It is possible to obtain the crystalline silicon thin film 12 formed on the substrate 11.

The above heat treatment can be performed at a temperature of 450 ° C. or higher, but if the temperature is low, the heating time must be lengthened and the production efficiency will be reduced. Further, if the temperature is 550 ° C. or more, the problem of heat resistance of the glass substrate used as the substrate is exposed.

Although the method of introducing the catalytic element onto the amorphous silicon film has been described in this embodiment, the method of introducing the catalytic element below the amorphous silicon film may be adopted. in this case,
The catalyst element may be introduced onto the base film using a solution containing the catalyst element before forming the amorphous silicon film.

[Embodiment 2] This embodiment is an example in which a 1200 Å silicon oxide film is selectively provided in the manufacturing method shown in Embodiment 1 and nickel is selectively introduced using this silicon oxide film as a mask. .

FIG. 2 shows an outline of the manufacturing process in this embodiment. First, the glass substrate (Corning 7059, 10c
A silicon oxide film 21 serving as a mask is formed on the (m square) to a thickness of 1000 Å or more, here 1200 Å. The film thickness of the silicon oxide film 21 is 5 according to experiments by the inventors.
It has been confirmed that there is no problem even with 00Å, and if the film quality is dense, it may be possible to make it thinner.

Then, the silicon oxide film 21 is patterned into a required pattern by a normal photolithographic patterning process. Then, a thin silicon oxide film 20 is formed by irradiation of ultraviolet rays in an oxygen atmosphere. This silicon oxide film 2
Production of 0 is performed by irradiating UV light for 5 minutes in an oxygen atmosphere. The thickness of the silicon oxide film 20 is considered to be about 20 to 50Å (FIG. 2 (A)). still,
The silicon oxide film for improving the wettability may be added just by the hydrophilicity of the silicon oxide film of the mask only when the size of the solution and the pattern match. However, such an example is special, and it is generally safer to use the silicon oxide film 20.

In this state, as in Example 1, 10
5 ml of an acetate solution containing 0 ppm of nickel is dropped (in the case of a 10 cm square substrate). At this time, spin coating is performed with a spinner at 50 rpm for 10 seconds to form a uniform water film on the entire surface of the substrate. In this state, 5
After holding for 2 minutes, using a spinner, 2000 rpm, 60
Perform a second spin dry. This holding may be performed while rotating the spinner at 0 to 100 rpm. (Fig. 2 (B))

Then, the amorphous silicon film 12 is crystallized by performing a heat treatment at 550 ° C. (nitrogen atmosphere) for 4 hours. At this time, crystal growth is performed in the lateral direction from the region of the portion 22 into which nickel has been introduced to the region into which nickel has not been introduced, as indicated by 23.

The following facts were observed as a result of examining the laterally grown crystal region 23 indicated by TEM (transmission electron microscope) and electron beam diffraction. (1) The crystal grown in the lateral direction is a needle-like or columnar single crystal having a uniform width. (2) The crystal growth direction is substantially parallel to the substrate, although it depends on the film thickness. (3) The crystal growth direction of this region is approximately the [111] axis direction.

From the above observation facts, the surface of the region 23 in which the crystal is grown in the lateral direction is { 110}, {1}.
12}, {123}, {134}, {235}, {14
5}, {156}, {257}, {167}, {hk
It is concluded that at least one or more plane orientations represented by l} (however, h + k = 1) or the plane orientations in the vicinity thereof are included.

It should be noted here that since crystalline silicon has a diamond type structure whose space group is represented by Fd3m, forbidden reflection occurs in the above-mentioned index hkl in the case of even-odd mixing and in electron beam diffraction. Not observed.

The relationship between the lateral crystal growth distance (μm) indicated by 23 and the nickel concentration (ppm) contained in the acetate solution is shown in FIG. In the data shown in FIG. 3, the holding time after applying the nickel-containing acetate was set to 5 minutes.

As can be seen from FIG. 3, a growth distance of 25 μm or more can be obtained by setting the nickel concentration to 100 ppm or more.

FIG. 3 shows the case where the holding time after applying the nickel-containing acetate was set to 5 minutes, and the lateral growth distance also changes depending on this holding time.

For example, when the nickel concentration is 100 ppm and the holding time is 1 minute or less, the longer the holding time, the longer the crystal growth in the lateral direction. However, if the holding time is set to 1 minute or more, the growth distance is gradually increased, and a remarkable difference cannot be obtained.

When the nickel concentration is 50 ppm, the holding time is up to 5 minutes, which time is proportional to the lateral crystal growth distance, but there is a tendency to saturate for 5 minutes or more.

Under the above conditions, if the holding time is further lengthened, the crystal growth distance in the lateral direction can be further increased, although it slightly increases. It should be added that these holding times need to be controlled because the time required to reach the equilibrium changes greatly when the temperature changes. Further, the crystal growth in the lateral direction can be increased as a whole by increasing the temperature of the heat treatment time or lengthening the heat treatment time.

FIG. 4 and FIG. 5 show that nickel was introduced using an acetate solution containing 100 ppm of nickel, and 550
In the case where crystallization is performed by heat treatment at 4 ° C. for 4 hours, the nickel concentration in the silicon film after crystallization is measured by SIMS (2
Representative data examined by secondary ion mass spectrometry).

FIG. 4 shows the concentration of nickel in the region 22 of FIG. 2, that is, the region where nickel was directly introduced.
Further, FIG. 5 shows the concentration of nickel in the region where the crystal is grown laterally from the region 22 as shown by 23 in FIG.

It can be seen from FIGS. 4 and 5 that the concentration of nickel in the laterally grown region is 1/2 or less as compared with the region in which nickel is directly introduced.

The results shown in FIGS. 4 and 5 are typical examples. By changing the solution concentration and the holding time, the concentration of nickel in the region where nickel was directly introduced was 5 × 10 ¹⁶ atoms cm ^−. It is possible to control in the range of ³ to 1 × 10 ¹⁹ atoms cm ⁻³ , and similarly, it is possible to control the concentration of the lateral growth region to be lower than that.

FIG. 6 shows 100 ppm nickel.
To the same extent as when using acetic acid solution containing
Nitrogen is treated by plasma treatment under the condition that crystal growth can be obtained.
And heat treatment at 550 ° C. for 4 hours.
The nickel concentration in the silicon film when crystallized
It For plasma treatment, use an electrode containing a large amount of nickel
Plasma discharge occurs, and the silicon film
Of introducing nickel into a silicon film by exposing
Is. As you can see in Figure 6, the plasma treatment
In the lateral growth region as well.
Axel concentration is 5 × 10 ¹⁸The above is the method shown in this embodiment.
The usefulness of is understood.

FIG. 7 shows the result of Raman spectroscopic measurement of the region showing the nickel concentration in FIG. That is, it is the result of Raman spectroscopic measurement of the region where nickel was directly introduced by the solution. From FIG. 7, it is understood that the crystallinity of this region is extremely high. Further, FIG. 8 shows the result of Raman spectroscopic measurement of the region showing the nickel concentration in FIG. It is understood from FIG. 8 that the region having a crystal grown in the lateral direction has sufficient crystallinity.

Further, from FIGS. 7 and 8, even in the region where the crystal is grown in the lateral direction, the intensity in Raman spectroscopy is 1/3 or more as compared with that of single crystal silicon, and the crystallinity is extremely high. I understand.

The crystalline silicon film formed by the method as shown in this embodiment is characterized by good hydrofluoric acid resistance. According to the findings by the present inventors, a crystalline silicon film obtained by crystallizing nickel by plasma treatment is
Low hydrofluoric acid resistance.

For example, it is necessary to form a silicon oxide film functioning as a gate insulating film or an interlayer insulating film on a crystalline silicon film, and then perform a hole forming step to form an electrode and then form an electrode. It may be said that. In such a case, a process of removing the silicon oxide film with buffer hydrofluoric acid is usually adopted. However, when the hydrofluoric acid resistance of the crystalline silicon film is low, it is difficult to remove only the silicon oxide film, and there is a problem that the crystalline silicon film is also etched.

However, when the crystalline silicon film has hydrofluoric acid resistance, a large difference (selection ratio) between the etching rates of the silicon oxide film and the crystalline silicon film can be obtained, so that the silicon oxide film can be made larger. Only this can be selectively removed, which is extremely significant in the manufacturing process.

As described above, the region in which the crystal has grown in the lateral direction has a low concentration of the catalyst element and has good crystallinity, and therefore it is useful to use this region as the active region of the semiconductor device. For example, it is extremely useful to use it as a channel formation region of a thin film transistor.

[Embodiment 3] This embodiment is an example of manufacturing a TFT provided in each pixel portion of an active matrix type liquid crystal display device by using a crystalline silicon film manufactured by using the method of the present invention. Indicates. It is needless to say that the application range of the TFT is not limited to the liquid crystal display device but can be applied to a generally-known thin film integrated circuit.

FIG. 9 shows an outline of the manufacturing process of this embodiment.
First, an underlying silicon oxide film (not shown) is formed on the glass substrate by 2
Form a film with a thickness of 000Å. This silicon oxide film is provided to prevent the diffusion of impurities from the glass substrate.

Then, an amorphous silicon film is formed to a thickness of 1000 Å by the same method as in the first embodiment. After the hydrofluoric acid treatment for removing the natural oxide film, a thin oxide film 20 is formed to a thickness of about 20Å by UV light irradiation in an oxygen atmosphere.

Then, an acetate solution containing 10 ppm of nickel is applied, held for 5 minutes, and spin-dried using a spinner. After that, the silicon oxide films 20 and 21 are removed by buffer hydrofluoric acid, and the silicon film 100 is crystallized by heating at 550 ° C. for 4 hours. (Up to this point, it is the same as the manufacturing method shown in Example 1)

Next, the crystallized silicon film is patterned to form island-shaped regions 104. This island area 10
Reference numeral 4 constitutes an active layer of the TFT. And thickness 200 ~
The silicon oxide 105 of 1500 Å, here 1000 Å, is formed. This silicon oxide film also functions as a gate insulating film. (Fig. 9 (A))

Attention must be paid to the formation of the silicon oxide film 105. Here, TEOS is used as a raw material, and the substrate temperature is 150 to 600 ° C., preferably 300 to 45, together with oxygen.
It was decomposed and deposited at 0 ° C. by the RF plasma CVD method. TE
The pressure ratio of OS and oxygen is 1: 1 to 1: 3, the pressure is 0.05 to 0.5 torr, and the RF power is 100 to 25.
It was set to 0W. Alternatively, by using TEOS as a raw material together with ozone gas by a low pressure CVD method or a normal pressure CVD method,
The substrate temperature is 350 to 600 ° C., preferably 400 to 55
It was formed as 0 ° C. After the film formation, annealing was performed at 400 to 600 ° C. for 30 to 60 minutes in an atmosphere of oxygen or ozone.

In this state, the KrF excimer laser (wavelength 248 nm, pulse width 20 nsec) or intense light equivalent thereto may be irradiated to promote crystallization of the silicon region 104. In particular, RTA using infrared light
(Rapid thermal annealing) can selectively heat only silicon without heating the glass substrate, and can reduce the interface state at the interface between the silicon and the silicon oxide film. It is useful in the fabrication of a field effect semiconductor device.

After that, an aluminum film having a thickness of 2000Å to 1 μm is formed by electron beam evaporation, and this is patterned to form a gate electrode 106. The aluminum may be doped with scandium (Sc) in an amount of 0.15 to 0.2% by weight. Next, set the substrate pH
It is immersed in an ethylene glycol solution of 7 to 1 to 3% tartaric acid, and anodization is performed using platinum as a cathode and this aluminum gate electrode as an anode. The anodization is completed by first raising the voltage to 220 V with a constant current and then maintaining that state for 1 hour. In the present embodiment, in the constant current state, it is appropriate that the voltage rising rate is 2 to 5 V / min. In this way, the anodic oxide 109 having a thickness of 1500 to 3500Å, for example 2000Å, is formed. (Fig. 9 (B))

After that, an impurity (phosphorus) was self-alignedly injected into the island-shaped silicon film of each TFT by an ion doping method (also referred to as a plasma doping method) using the gate electrode portion as a mask. Phosphine (PH ₃ ) was used as the doping gas. The dose amount is 1 to 4 × 10
¹⁵ cm ^-2 .

Further, as shown in FIG. 9C, a KrF excimer laser (wavelength 248 nm, pulse width 20 ns) is used.
ec) is applied to improve the crystallinity of the portion where the crystallinity is deteriorated by the introduction of the impurity region. The energy density of the laser is 150 to 400 mJ / cm ² , preferably 200 to 250 mJ / cm ² . Thus, the N-type impurity (phosphorus) regions 108 and 109 are formed. The sheet resistance in these regions was 200 to 800 Ω / □.

In this process, instead of using a laser, a flash lamp is used, and 1000 to
Raise it to 1200 ° C (silicon monitor temperature),
So-called RTA (Rapid Thermal Annealing) (RTP, also called rapid thermal process) for heating the sample may be used.

After that, an interlayer insulator 110 is formed on the entire surface.
Plasma CVD with TEOS as raw material and oxygen
Method, low pressure CVD method with ozone, or atmospheric pressure CV
A silicon oxide film having a thickness of 3000 Å is formed by the D method. The substrate temperature is 250 to 450 ° C., for example 350 ° C.
After the film formation, this silicon oxide film is mechanically polished to obtain the flatness of the surface. Further, an ITO film is deposited by the sputtering method and patterned to form the pixel electrode 111. (Fig. 9 (D))

Then, the inter-layer insulator 110 is etched to form contact holes in the source / drain of the TFT as shown in FIG. 1E, wirings 112 and 113 of chromium or titanium nitride are formed, and wiring 113 is formed. Is connected to the pixel electrode 111.

Since the crystalline silicon film into which nickel is introduced by the plasma treatment has lower selectivity to buffer hydrofluoric acid than the silicon oxide film, it is often etched in the contact hole forming step. It was

However, when nickel is introduced by using an aqueous solution at a low concentration of 10 ppm as in this embodiment, since the hydrofluoric acid resistance is high, the formation of the contact hole can be stably performed with good reproducibility. it can.

Finally, in hydrogen at 300 to 400 ° C.
Anneal for 1-2 hours to complete hydrogenation of silicon. In this way, the TFT is completed. Then, a large number of TFTs manufactured at the same time are arranged in a matrix to complete an active matrix liquid crystal display device.

When the structure of this embodiment is adopted, the concentration of nickel existing in the active layer is about 3 × 10 ¹⁸ cm ⁻³ or less, 5 × 10 ¹⁶ atoms cm ^{−3 to} 3 × 10 5.
It is considered to be ¹⁸ atoms cm ^-3 .

[Embodiment 4] In this embodiment, as shown in Embodiment 2, nickel is selectively introduced, and electrons are emitted from the portion where crystals are grown laterally (direction parallel to the substrate). An example of forming a device is shown. When such a structure is adopted, the nickel concentration in the active layer region of the device can be further lowered, and the structure can be made extremely preferable in terms of electrical stability and reliability of the device.

This example relates to a process of manufacturing a TFT used for controlling pixels of an active matrix. FIG. 10 shows a manufacturing process of this embodiment. First, the substrate 2
01 washed, TEOS (Tetra ethoxy silane)
A base film 202 of silicon oxide having a thickness of 2000 Å is formed by plasma CVD using oxygen and oxygen as source gases. Then, the thickness is 500 to 1500 by the plasma CVD method.
Å, for example, 1000 Å intrinsic (I-type) amorphous silicon film 2
03 is deposited. Next, continuously thickness 500-2000
Å, for example, 1000 Å of silicon oxide film 205 with plasma
The film is formed by the VD method. Then, the silicon oxide film 205 is selectively etched to expose the region 2 where the amorphous silicon is exposed.
06 is formed. Then, by the method described in Example 2, a solution containing nickel element (here, an acetate solution)
Apply. The concentration of nickel in acetic acid solution is 100
It is ppm. In addition, the detailed process order and conditions are the same as those shown in the second embodiment.

After that, 500 to 620 under a nitrogen atmosphere.
The silicon film 303 is crystallized by performing heat anneal at 4 ° C., for example, 550 ° C. for 4 hours. Crystallization proceeds from a region 206 where the nickel film and the silicon film are in contact with each other as a starting point, and crystal growth proceeds in a direction parallel to the substrate as indicated by an arrow. In the figure, region 204 is a crystallized portion, region 2
Reference numeral 03 indicates an uncrystallized (amorphous) portion. The crystal in the horizontal direction indicated by 202 has a size of about 25 μm. (Fig. 2 (A))

Next, the silicon oxide film 205 is removed. At this time, the oxide film formed on the surface of the region 206 is also removed at the same time. Then, after patterning the silicon film 204, dry etching is performed to form an island-shaped active layer region 208.
At this time, a region 206 shown in FIG. 10A is a region into which nickel is directly introduced, and is a region in which nickel is present at a high concentration. It has also been confirmed that nickel also exists at a high concentration at the tip of crystal growth.
It has been found that the nickel concentration in these regions is higher than that in the intermediate region. Therefore, in this embodiment, in the active layer 208, these regions having a high nickel concentration are prevented from overlapping the channel formation region.

Thereafter, 10% by volume containing 100% steam
The surface of the active layer (silicon film) 208 is oxidized by leaving it in the atmosphere of 500 to 600 ° C., typically 550 ° C. for 1 hour to oxidize the surface of the silicon oxide film 209.
To form. The thickness of the silicon oxide film is 1000Å. After forming the silicon oxide film 209 by thermal oxidation, the substrate is placed in an ammonia atmosphere (1 atm, 100%) at 400 ° C.
To hold. Then, in this state, the substrate is irradiated with infrared light having a peak at a wavelength of 0.6 to 4 μm, for example, 0.8 to 1.4 μm for 30 to 180 seconds, and the silicon oxide film 20 is irradiated.
A nitriding process is performed on 9. At this time, the atmosphere was 0.
1-10% HCl may be mixed.

A halogen lamp is used as the infrared light source. The intensity of infrared light is adjusted so that the temperature on the monitor's single crystal silicon wafer is between 900 and 1200 ° C. Specifically, the temperature of the thermocouple embedded in the silicon wafer is monitored, and this is fed back to the infrared light source. In this embodiment, the temperature rise is constant, the speed is 50 to 200 ° C./sec, and the temperature fall is 20 to 100 by natural cooling.
℃. Since this infrared light irradiation selectively heats the silicon film, the heating of the glass substrate can be minimized. (Fig. 2 (B))

Subsequently, by the sputtering method,
A film of aluminum (containing 0.01 to 0.2% scandium) having a thickness of 3000 to 8000Å, for example, 6000Å is formed. Then, the aluminum film is patterned to form the gate electrode 210. (Fig. 2 (C))

Further, the surface of the aluminum electrode is anodized to form an oxide layer 211 on the surface. This anodic oxidation is performed in an ethylene glycol solution containing 1-5% tartaric acid. The resulting oxide layer 211 has a thickness of 2
It is 000Å. Since the oxide 211 has a thickness to form the offset gate region in the subsequent ion doping process, the length of the offset gate region can be determined by the anodic oxidation process. (Fig. 2
(D))

Next, the gate electrode portion, that is, the gate electrode 210 and the oxide layer 211 around it is used as a mask in the active layer region (which constitutes the source / drain and the channel) by the ion doping method (also called plasma doping method). An impurity (here, phosphorus) that imparts the N conductivity type is added in a self-aligning manner. Phosphine (PH ₃ ) is used as the doping gas, and the acceleration voltage is set to 60 to 90 kV, for example, 80 kV. Dose amount is 1 × 10 ¹⁵ to 8 × 10
^{It is set to 15} cm ^-2 , for example, 4 × 10 ¹⁵ cm ^-2 . As a result, N-type impurity regions 212 and 213 can be formed. As is clear from the figure, the impurity region and the gate electrode are in an offset state separated by a distance x. Such an offset state is particularly effective in reducing a leak current (also referred to as an off current) when a reverse voltage (negative in the case of an N-channel TFT) is applied to the gate electrode.
In particular, in the TFT for controlling the pixels of the active matrix as in the present embodiment, it is desired that the leak current is low so that the charges accumulated in the pixel electrode do not escape in order to obtain a good image, and therefore an offset is provided. That is valid.

After that, annealing was performed by irradiation with laser light. As the laser light, a KrF excimer laser (wavelength 248 nm, pulse width 20 nsec) is used, but other laser may be used. The laser beam irradiation condition is such that the energy density is 200 to 400 mJ / c.
m ² , for example, 250 mJ / cm ^2, and 2 per place
Irradiation was performed for 10 shots, for example, 2 shots. The effect may be increased by heating the substrate to about 200 to 450 ° C. during the irradiation of the laser light. (Fig. 2
(E))

Then, a silicon oxide film 21 having a thickness of 6000Å is formed.
4 as an interlayer insulator is formed by the plasma CVD method. Further, a transparent polyimide film 215 is formed by spin coating to flatten the surface. A thickness of 80 is formed on the flat surface thus formed by the sputtering method.
A 0 Å transparent conductive film (ITO film) is formed and patterned to form a pixel electrode 216.

Then, contact holes are formed in the interlayer insulators 214 and 215, and the electrodes / wirings 217 and 218 of the TFT are formed from a metal material, for example, a multilayer film of titanium nitride and aluminum. Finally, annealing is performed at 350 ° C. for 30 minutes in a hydrogen atmosphere of 1 atm to complete an active matrix pixel circuit having TFTs. (Fig. 2
(F))

[0096]

[Effect] By manufacturing a semiconductor device using a crystalline silicon film in which a catalytic element is introduced and crystallized at low temperature in a short time, a device with high productivity and excellent characteristics can be obtained.

[Brief description of drawings]

FIG. 1 shows a process of an example.

FIG. 2 shows a process of an example.

FIG. 3 shows the relationship between the nickel concentration in the solution and the crystal growth distance in the lateral direction.

FIG. 4 shows nickel concentration in a region where nickel is introduced.

FIG. 5 shows a nickel concentration in a region crystallized in a lateral direction from a region into which nickel is introduced.

FIG. 6 shows nickel concentration in a region where nickel is introduced by plasma treatment.

FIG. 7 shows a Raman spectroscopic measurement of a region in which nickel is introduced.

FIG. 8 shows Raman spectroscopy measurements in the laterally crystallized region from the nickel-introduced region.

FIG. 9 shows a manufacturing process of an example.

FIG. 10 shows a manufacturing process of an example.

[Explanation of symbols]

11 ... Glass substrate 12 ... Amorphous silicon film 13 ··· Silicon oxide film 14 ... Acetic acid solution film containing nickel 15 ... Zpiner 21..Silicon oxide film for mask 20 ... Silicon oxide film 11 ... Glass substrate 104 ... Active layer 105 ... Silicon oxide film 106 ... Gate electrode 109 ... Oxide layer 108 ... Source / drain region 109 ... Drain / source region 110 ... Interlayer insulating film (silicon oxide film) 111 ... Pixel electrode (ITO) 112 ... Electrode 113 ... Electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 29/786 H01L 21/336 H01L 21/20

Claims (6)

(57) [Claims] 1. An element which promotes crystallization of an amorphous silicon film is included.
The applied solution was selectively coated on the amorphous silicon film.
Then, by heat-treating at 600 ° C. or less, the amorphous
A method for producing a crystalline silicon film, characterized in that a silicon film is crystal-grown , and the direction of the crystal growth coincides with a [111] axis direction of a silicon crystal.
Law . 2. An element which promotes crystallization of an amorphous silicon film is included.
The applied solution was selectively coated on the amorphous silicon film.
Then, by heat-treating at 600 ° C. or less, the amorphous
The solution is applied from the area of the silicon film to which the solution is applied.
By crystal growth did not the amorphous silicon film to a region is, the direction of the crystal growth, making side of the crystalline silicon film, which coincides with the [111] axial direction of the crystal of silicon
Law . 3. An element which promotes crystallization of an amorphous silicon film is included.
The applied solution was selectively coated on the amorphous silicon film.
Then, by heat-treating at 600 ° C. or less, the amorphous
The silicon film is crystal-grown, the surface orientation of the surface of the crystal grown-obtained crystalline silicon film are shorted with a electron diffraction {110}, {112}, {12
3}, {134}, {235}, {145}, {15
6}, {257}, {167} or {hkl} (h +
production of crystalline silicon film characterized in that k = 1)
Manufacturing method . 4. An element which promotes crystallization of an amorphous silicon film is contained.
The applied solution was selectively coated on the amorphous silicon film.
Then, by heat-treating at 600 ° C. or less, the amorphous
The solution is applied from the area of the silicon film to which the solution is applied.
Were were not the amorphous silicon film into a region to crystal growth is, the plane orientation of the surface of the crystal grown-obtained crystalline silicon film are shorted with a electron diffraction {110}, {112}, {12
3}, {134}, {235}, {145}, {15
6}, {257}, {167} or {hkl} (h +
production of crystalline silicon film characterized in that k = 1)
Manufacturing method . Crystal wherein said silicon, crystalline silicon film according to claim 1 or 2, characterized in that a columnar or needle-like
Of manufacturing . 6. The method for manufacturing a crystalline silicon film according to any one of claims 1 to 5, wherein the element for promoting the crystallization is nickel.