JP2000114543A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity by applying a solution containing a catalyst element onto the surface of an amorphous silicon film and introducing the catalyst element thereto. SOLUTION: An amorphous silicon film 12 is formed. It is treated by hydrofluroric acid to form an oxide film 13. An acetate solution added with a nickel is prepared, and it is dripped on the surface of the oxide film 13 on the amorphous silicon film 12 and the entire body is subject to spin drying using a spinner. Further, it is heated in a nitrogen atmosphere in a heating furnace, forming a silicon thin film 12 with crystallinity on a substrate 11. Thus, a semiconductor device with high productivity and excellent characteristic can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor having crystallinity. Further, the present invention relates to a semiconductor device including a semiconductor having crystallinity.

[0002]

2. Description of the Related Art Thin film transistors (hereinafter referred to as TFTs) using thin film semiconductors are known. This TFT is formed by forming a thin-film semiconductor on a substrate and using the thin-film semiconductor. This TFT is used in various integrated circuits, and is particularly noted 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.

[0003] As a thin film semiconductor used for a TFT,
Although it is convenient to use an amorphous silicon film, there is a problem that its electrical characteristics are low. In order to obtain improved TFT characteristics, a silicon thin film having crystallinity may be used. The silicon film having crystallinity is called polycrystalline silicon, polysilicon, microcrystalline silicon, or the like. In order to obtain a silicon film having this crystallinity, an amorphous silicon film may be formed first, and then crystallized by heating.

[0004] However, crystallization by heating requires a heating temperature of 600 ° C. or more for a period of 10 hours or more, and there is a problem that it is difficult to use a glass substrate as a substrate. For example, Corning 7059 glass used for 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 more in consideration of an increase in substrate area.

BACKGROUND OF THE INVENTION According to the study of the present inventors, trace amounts of elements such as nickel, palladium, and lead are deposited on the surface of an amorphous silicon film and then heated to 550 mm. It has been found that crystallization can be performed at a temperature of about 4 hours.

[0006] In order to introduce the above trace elements (catalytic elements that promote crystallization), plasma treatment, vapor deposition, and ion implantation may be used. Plasma treatment refers to the use of a material containing a catalyst element as an electrode in a parallel plate type or positive column type plasma CVD apparatus, and generation of plasma in an atmosphere such as nitrogen or hydrogen to form a catalyst element on an amorphous silicon film. This is a method of adding.

However, the presence of a large amount of such elements in semiconductors impairs the reliability and electrical stability of devices using these semiconductors, and is not preferable.

That is, the above-mentioned elements (catalytic elements) which promote crystallization, such as nickel, are necessary when crystallizing amorphous silicon, but are not contained in crystallized silicon as much as possible. Is desirable. To achieve this goal,
It is necessary to select a catalyst element which has a strong tendency to be inactive in crystalline silicon as a catalyst element, and at the same time, minimize the amount of the catalyst element required for crystallization and perform crystallization with a minimum amount. For that purpose, it is necessary to precisely control the amount of the catalyst element to be introduced.

When nickel is used as a catalytic element, an amorphous silicon film is formed, nickel is added by a plasma treatment method to produce 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 onto an amorphous silicon film by plasma treatment, nickel has already penetrated to a considerable depth in the amorphous silicon film before heat treatment. (2) The initial nucleation of the crystal occurs from the surface into which nickel is introduced. (3) Even when nickel is formed on an amorphous silicon film by a vapor deposition method, crystallization occurs as in the case where plasma processing is performed.

[0010] From the above, it is concluded that all the nickel introduced by the plasma treatment is not functioning effectively. Then, it is concluded that "the only requirement is that a very small amount of nickel should be dispersed and introduced in the atomic state as much as possible near the surface of the amorphous silicon film".

A method for introducing a very small amount of nickel only near the surface of the amorphous silicon film, in other words, a method for introducing a very small amount of a catalytic element for promoting crystallization only near the surface of the amorphous silicon film is as follows. , Evaporation method can be mentioned,
The vapor deposition method has a problem that the controllability is poor and it is difficult to strictly control the introduction amount of the catalyst element.

[0012]

SUMMARY OF THE INVENTION The present invention provides a method for producing a crystalline silicon thin film semiconductor by heat treatment at 600 ° C. or lower using a catalytic element. (2) Use a method with high productivity. It is intended to satisfy such requirements.

[0013]

According to the present invention, a silicon film having crystallinity is obtained by using the following means in order to satisfy the above objects. "A solution containing a catalytic element is applied to the surface of the amorphous silicon film, thereby introducing the catalytic element."

An active region of a semiconductor device is constituted by using the crystalline silicon film. Semiconductor devices include thin film transistors (TFTs), diodes,
An optical sensor can be used.

By employing 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 increase 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 catalyst element introduced into the amorphous silicon is determined by the concentration of the catalyst element in the solution. (C) Since the catalytic element adsorbed on the surface of the amorphous silicon film mainly contributes to the crystallization, the catalytic element can be introduced at a minimum necessary concentration.

As a method of applying a solution containing an element promoting crystallization on 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, nickel sulfate, nickel formate 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 dissolved in alcohol, benzene, carbon tetrachloride or the like.

Compounds other than nickel salts include nickel oxide and nickel hydroxide, which need to be dissolved in an acid to form a solution. When nickel alone is used, it is necessary to similarly dissolve it in an acid to form a solution.

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

Further, the catalyst element can be contained in a coating liquid for forming a SiO ₂ -based film and introduced into the lower or upper surface of the amorphous silicon film. In this case, as a film-forming coating liquid of the SiO ₂ system, the Tokyo Ohka Kogyo Co., Ltd. OCD (Oh
Ka Coat Diffusion-Source) may be used. That is, a catalyst element is contained in a coating solution for forming an oxide film, and an oxide film using this coating solution is provided in contact with the upper surface or the lower surface of the amorphous silicon film, whereby the amorphous silicon film is formed. A catalytic element can be introduced to 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.
In the case where an aqueous solution of an acetate or a sulfate is used, when these solutions are applied to an amorphous silicon film, the solution is repelled. In this case, a thin oxide film having a thickness of 100 ° or less is first formed, and a solution containing a catalyst element is applied thereon, whereby the solution can be applied uniformly. It is also effective to improve the wetting by adding a material such as a surfactant to the solution.

Further, by using a non-polar solvent such as a toluene solution of nickel 2-ethylhexanoate as a solution, it can be applied directly to the surface of the amorphous silicon film. In this case, it is effective to apply a material such as an adhesive used in applying the resist in advance. However, care must be taken when the amount of coating is too large, since this would hinder the addition of the catalytic element to the amorphous silicon.

The amount of the catalyst element contained in the solution depends on the type of the solution, but the general tendency is that the amount of nickel is 200 ppm to 1 ppm, preferably 50 ppm to 1 ppm (in terms of weight) based on the solution. It is desirable. This is a value determined in view of the nickel concentration in the film after crystallization and the resistance to hydrofluoric acid.

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

It has been confirmed that the region where the crystal growth has been performed in the lateral direction has a low concentration of the catalytic element.
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 impurity concentration in the active layer region is low. Therefore, it is useful in device fabrication to form an active layer region of a semiconductor device using the region where the crystal growth has been performed in the lateral direction.

In the present invention, the most remarkable effect can be obtained when nickel is used as a catalyst element. However, other usable types of catalyst elements are preferably Ni, Pd, Pt, Cu, Ag, and Ag. Au, In, S
n, P, As, and Sb can be used. Also VI
One or more elements selected from Group II elements, IIIb, IVb, and Vb elements can also be used.

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

[0030]

[Example] [Example 1]

In this embodiment, an example of forming a crystalline silicon film on a glass substrate will be described. First, the steps up to the introduction of a catalytic element (here, nickel is used) will be described with reference to FIG. In this embodiment, Corning 7059 glass is used as the substrate. The size is 10
It is set to 0 mm x 100 mm.

First, an amorphous silicon film is formed by plasma CVD or LPCVD.
It is formed at a temperature of 00 to 1500 °. Here, plasma CVD
An amorphous silicon film 12 is formed to a thickness of 1000.degree. (Fig. 1 (A))

Then, a hydrofluoric acid treatment is performed to remove dirt and a natural oxide film.
Å is formed. If the contamination can be neglected, it is needless to say that this step may be omitted, and a natural oxide film may be used as it is instead of the oxide film 13. The exact thickness of the oxide film 13 is unknown because it is extremely thin.
It is considered to be about 0 °. Here, the oxide film 13 is formed by irradiation with UV light in an oxygen atmosphere. The film was formed 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. Further, a treatment by hydrogen peroxide may be used.

The oxide film 13 is used to spread the acetate solution over the entire surface of the amorphous silicon film in the subsequent step of applying a nickel-containing acetate solution, that is, to improve the wettability. It is. For example, when an acetate solution is directly applied to the surface of an amorphous silicon film, nickel cannot be introduced into the entire surface of the amorphous silicon film because the amorphous silicon repels the acetate solution. 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. And spin dry using a spinner (2000
rpm, 60 seconds). (Fig. 1 (C), (D))

The concentration of nickel in the acetic acid solution is 1
If it is at least 10 ppm, preferably at least 10 ppm, it will be practical. 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 a catalytic element can be directly introduced on the amorphous silicon film.

This nickel solution coating step is performed once to a plurality of times to form a layer containing nickel having an average film thickness of several to several hundreds on the surface of the amorphous silicon film 12 after spin drying. 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 complete film.

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

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

The above-mentioned heat treatment can be performed at a temperature of 450 ° C. or higher. However, if the temperature is low, the heating time must be prolonged, and the production efficiency decreases. Further, if the temperature is 550 degrees or more, the problem of heat resistance of a glass substrate used as a substrate will surface.

In this embodiment, the method of introducing a catalytic element on the amorphous silicon film has been described, but a method of introducing a catalytic element below the amorphous silicon film may be employed. in this case,
Before forming the amorphous silicon film, the catalyst element may be introduced onto the base film using a solution containing the catalyst element.

[Embodiment 2] In this embodiment, in the manufacturing method shown in Embodiment 1, a silicon oxide film of 1200 ° is selectively provided, 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, a glass substrate (Corning 7059, 10c
On the (m square), a silicon oxide film 21 serving as a mask is formed to a thickness of 1000 ° or more, here 1200 °. According to experiments by the inventors, the thickness of the silicon oxide film 21 is 5
It has been confirmed that there is no problem even at 00 °, and it is considered that the film may be thinner if the film quality is dense.

Then, the silicon oxide film 21 is subjected to a necessary pattern by a usual photolithography patterning process. Then, a thin silicon oxide film 20 is formed by ultraviolet irradiation in an oxygen atmosphere. This silicon oxide film 2
The production of No. 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 50 ° (FIG. 2A). still,
When a silicon oxide film for improving the wettability matches the size of the solution and the pattern, the silicon oxide film may be added just by the hydrophilicity of the silicon oxide film of the mask. However, such an example is special, and it is generally safer to use the silicon oxide film 20.

In this state, 10 times as in the first embodiment.
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 at 50 rpm for 10 seconds using a spinner 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 at 2000 rpm, 60 rpm
Perform spin dry for 2 seconds. 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 where nickel has been introduced to the region where nickel has not been introduced as indicated by 23.

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

From the above observation facts, the surface of the region where the crystal was grown in the lateral direction indicated by 23 has a plane orientation perpendicular to the [111] axis direction, that is, {110},
{112}, {123}, {134}, {235},
{145}, {156}, {257}, {167},
It is concluded that at least one of the plane orientations indicated by {hkl} (where h + k = 1) or a plane orientation in the vicinity thereof is included.

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

FIG. 3 shows the relationship between the crystal growth distance (μm) in the lateral direction indicated by 23 and the nickel concentration (ppm) contained in the acetate solution. In the data shown in FIG. 3, the holding time after the application of the acetate containing nickel 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 a case where the holding time after the application of the acetate containing nickel is set to 5 minutes. The lateral growth distance also changes depending on the holding time.

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

When the nickel concentration is 50 ppm, the retention time is proportional to the crystal growth distance in the horizontal direction until the retention time is 5 minutes, but tends to be saturated when the retention time is 5 minutes or more.

Further, if the holding time is further lengthened under the above conditions, the crystal growth distance in the lateral direction can be further increased, although little by little. It should be noted that these holding times greatly change when the temperature changes, and the time required to reach the equilibrium greatly changes. Therefore, it is added that the temperature needs to be controlled. Also, by increasing the temperature of the heat treatment time or increasing the heat treatment time, the crystal growth in the lateral direction as a whole can be increased.

FIGS. 4 and 5 show that nickel was introduced using an acetate solution containing 100 ppm of nickel,
In a heat treatment at 4 ° C. for 4 hours, when the crystallization was performed, the nickel concentration in the silicon film after crystallization was determined by SIMS (2
Secondary ion mass spectrometry).

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

From FIGS. 4 and 5, it can be seen that the nickel concentration in the region grown in the lateral direction is １ ／ or less as compared with the region where nickel is directly introduced.

The results shown in FIGS. 4 and 5 are typical examples, and the nickel concentration in the region where nickel is directly introduced is changed by changing the solution concentration and the holding time to 5 × 10 ¹⁶ atoms cm ^{− It} can be controlled within the range of ³ to 1 × 10 ¹⁹ atoms cm ⁻³ , and similarly, the concentration of the lateral growth region can be controlled to be lower than that.

FIG. 6 shows 100 ppm nickel.
To the same extent as when using an acetic acid solution containing
Plasma treatment under conditions that allow crystal growth
Kelvin and bonded by thermal annealing at 550 ° C for 4 hours.
The nickel concentration in the silicon film when crystallized
You. Plasma treatment uses an electrode containing a large amount of nickel
Causes a plasma discharge, and the plasma at this time
To introduce nickel into silicon film by exposing
It is. As can be seen from FIG.
In the lateral growth area
Axle density is 5 × 10 ¹⁸As described above, the method shown in this embodiment
The usefulness of is understood.

FIG. 7 shows the result of Raman spectroscopy measurement of the region whose nickel concentration is shown in FIG. That is, it is the result of Raman spectroscopy 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. FIG. 8 shows the result of Raman spectroscopy measurement of the region whose nickel concentration is shown in FIG. From FIG. 8, it is understood that the region where the crystal has grown in the lateral direction has sufficient crystallinity.

7 and 8, it can be seen from FIG. 7 and FIG. 8 that the intensity in Raman spectroscopy is at least 1/3 or more of that of single crystal silicon even in the region where the crystal is grown in the lateral direction, and that the crystallinity is extremely high. I understand.

The crystalline silicon film formed by the method shown in this embodiment is characterized by having good hydrofluoric acid resistance. According to the findings of the present inventors, a crystalline silicon film obtained by introducing nickel by plasma treatment and crystallizing
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 form an electrode through a hole forming process for forming the electrode. And may be. In such a case, a step of removing the silicon oxide film with buffered 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, the difference (selectivity) between the etching rates of the silicon oxide film and the crystalline silicon film can be made large, so that the silicon oxide film Can be selectively removed, which is extremely significant in the production process.

As described above, the region where the crystal has grown in the lateral direction has a low concentration of the catalytic element and has good crystallinity. 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 using a crystalline silicon film manufactured by using the method of the present invention. Is shown. It is needless to say that TFTs can be applied not only to liquid crystal display devices but also to thin film integrated circuits generally referred to.

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

Then, an amorphous silicon film is formed to a thickness of 1000 ° in the same manner 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 20 ° by irradiation with UV light 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. Thereafter, silicon oxide films 20 and 21 are removed with buffered hydrofluoric acid, and silicon film 100 is crystallized by heating at 550 ° C. for 4 hours. (Up to this point, the same as the manufacturing method shown in Example 1)

Next, island regions 104 are formed by patterning the crystallized silicon film. This island-shaped area 10
4 constitutes an active layer of the TFT. And the thickness 200 ~
The silicon oxide 105 is formed at 1500 °, here 1000 °. This silicon oxide film also functions as a gate insulating film. (FIG. 9A)

Attention should be paid to the production of the silicon oxide film 105. Here, TEOS is used as a raw material, and a substrate temperature is 150 to 600 ° C., preferably 300 to 45 ° C. together with oxygen.
Decomposition and deposition were performed at 0 ° C. by an RF plasma CVD method. TE
The pressure ratio between 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.
0 W. Alternatively, TEOS is used as a raw material together with ozone gas by a low pressure CVD method or a normal pressure CVD method.
The substrate temperature is set to 350 to 600 ° C, preferably 400 to 55.
Formed at 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, crystallization of the silicon region 104 may be promoted by irradiating a KrF excimer laser (wavelength: 248 nm, pulse width: 20 nsec) or strong light equivalent thereto. 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 silicon and the silicon oxide film. It is useful in manufacturing a field-effect semiconductor device.

Thereafter, an aluminum film having a thickness of 2000 to 1 μm is formed by an electron beam evaporation method, and is patterned to form a gate electrode 106. Aluminum may be doped with scandium (Sc) by 0.15 to 0.2% by weight. Next, the substrate is adjusted to pH ≒.
7, immersed in an ethylene glycol solution of 1 to 3% tartaric acid, and anodized using platinum as a cathode and the aluminum gate electrode as an anode. The anodic oxidation is performed by first increasing the voltage to 220 V with a constant current and maintaining the state for one hour to complete the process. In this embodiment, in the constant current state, the voltage rising speed is suitably 2 to 5 V / min. Thus, anodic oxide 109 having a thickness of 1500 to 3500 °, for example, 2000 ° is formed. (FIG. 9 (B))

Thereafter, an impurity (phosphorus) was implanted into the island-like silicon film of each TFT in a self-aligned manner 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 a doping gas. Dose amount is 1-4 × 10
¹⁵ cm ^-2 .

Further, as shown in FIG. 9C, a KrF excimer laser (wavelength: 248 nm, pulse width: 20 ns)
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, N-type impurity (phosphorus) regions 108 and 109 are formed. The sheet resistance in these regions was 200 to 800 Ω / □.

In this step, instead of using a laser, a flash lamp is used for 1000 to 1000
Raise to 1200 ° C (temperature of silicon monitor)
A so-called RTA (rapid thermal annealing) (RTP, also called a rapid thermal process) for heating a sample may be used.

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

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

The crystalline silicon film into which nickel has been introduced by the plasma treatment has a lower selectivity to buffered hydrofluoric acid than the silicon oxide film, and thus is often etched in the contact hole forming step. Was.

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

Finally, at 300 to 400 ° C. in hydrogen at 0.
Anneal for 1-2 hours to complete silicon hydrogenation. Thus, 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 present in the active layer is about 3 × 10 ¹⁸ cm ⁻³ or less, that is, 5 × 10 ¹⁶ atoms cm ^{−3 to} 3 × 10 3.
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 grown by using a region where crystal growth is performed in a lateral direction (a direction parallel to the substrate) from that portion. 4 shows an example of forming a device. When such a configuration is employed, the nickel concentration in the active layer region of the device can be further reduced, and a highly preferable configuration can be obtained from the viewpoint of electrical stability and reliability of the device.

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

Thereafter, under a nitrogen atmosphere, 500 to 620
C., for example, at 550.degree. C., for 4 hours, to crystallize the silicon film 303. FIG. In the crystallization, the crystal growth proceeds in a direction parallel to the substrate as indicated by an arrow, starting from a region 206 where the nickel and silicon films are in contact. In the figure, region 204 is a crystallized portion, region 2
03 indicates an uncrystallized (amorphous) portion. The crystal in the horizontal direction indicated by 202 is 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 indicated by 206 in FIG. 10A is a region where nickel is directly introduced, and is a region where 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 in these regions, the nickel concentration is higher than in the intermediate region. Therefore, in the present embodiment, in the active layer 208, these regions where the nickel concentration is high do not overlap with the channel formation region.

Thereafter, 10% by volume containing water vapor of 100%
The surface of the active layer (silicon film) 208 is oxidized by leaving it for 1 hour in an atmosphere of atmospheric pressure at 500 to 600 ° C., typically 550 ° C.
To form The thickness of the silicon oxide film is 1000 °. After the silicon oxide film 209 is formed by thermal oxidation, the substrate is placed in an ammonia atmosphere (1 atm, 100%) at 400 ° C.
To be held. 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.
9 is subjected to a nitriding treatment. At this time, 0.
HCl of 1 to 10% may be mixed.

A halogen lamp is used as the infrared light source. The intensity of the infrared light is adjusted so that the temperature on the single crystal silicon wafer of the monitor 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 decrease is 20 to 100 by natural cooling.
° C. This infrared light irradiation selectively heats the silicon film, so that heating of the glass substrate can be minimized. (FIG. 2 (B))

Subsequently, by a sputtering method,
Aluminum (including 0.01 to 0.2% scandium) having a thickness of 3000 to 8000 °, for example, 6000 ° is formed. Then, the gate electrode 210 is formed by patterning the aluminum film. (Fig. 2 (C))

Further, the surface of the aluminum electrode is anodized to form an oxide layer 211 on the surface. This anodization is performed in an ethylene glycol solution containing tartaric acid at 1 to 5%. The thickness of the obtained oxide layer 211 is 2
000. Note that the oxide 211 has a thickness for forming an offset gate region in a later ion doping process, so that the length of the offset gate region can be determined in the anodic oxidation process. (Figure 2
(D))

Next, a gate electrode portion, that is, the gate electrode 210 and its surrounding oxide layer 211 are used as masks in an active layer region (which constitutes a source / drain and a channel) by an ion doping method (also called a plasma doping method). In addition, an impurity (here, phosphorus) which imparts the N conductivity type in a self-aligned manner is added. 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
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 offset from each other by a distance x. Such an offset state is particularly effective in reducing a leakage current (also referred to as an off-state current) when a reverse voltage (minus 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 this embodiment, it is desired that the leakage current is low so that the charge accumulated in the pixel electrode does not escape in order to obtain a good image. That is valid.

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

Subsequently, a silicon oxide film 21 having a thickness of 6000.degree.
4 is formed as an interlayer insulator by a plasma CVD method. Further, a transparent polyimide film 215 is formed by spin coating, and the surface is flattened. On the plane thus formed, a thickness of 80
A 0 ° transparent conductive film (ITO film) is formed, and is 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 of 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 at 1 atm to complete an active matrix pixel circuit having a TFT. (Figure 2
(F))

[0096]

According to the present invention, a semiconductor device is manufactured using a crystalline silicon film crystallized at a low temperature in a short time by introducing a catalytic element, whereby a device having high productivity and excellent characteristics can be obtained. .

[Brief description of the drawings]

FIG. 1 shows the steps of an example.

FIG. 2 shows a process of an example.

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

FIG. 4 shows a 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 a nickel concentration in a region into which nickel has been introduced by plasma processing.

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

FIG. 8 shows a Raman spectroscopic measurement in a region crystallized laterally from a region into which nickel has been introduced.

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 ··· spinner 21 ··· for mask Silicon oxide film 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

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01L 31/10 A

Claims (12)

[Claims] 1. A semiconductor device selected from a thin film transistor, a diode, and an optical sensor having an active region using a crystalline silicon film formed on a substrate, wherein a surface of the silicon film is {111} plane or {hkl} (h
+ K = 1), and the silicon film contains 1 × 10 ¹⁹ atoms / cm ³ or less of a catalytic element for promoting crystallization of the amorphous silicon film. Semiconductor device. 2. The active region has a thickness of 100-1500.
The semiconductor device according to claim 1, wherein? 3. The catalyst element is Ni, Pd, Pt, C
3. The semiconductor device according to claim 1, wherein the semiconductor device is one or more elements selected from u, Ag, Au, In, Sn, P, As, and Sb. 4. 4. An active matrix type liquid crystal display device having a plurality of thin film transistors on an insulating surface, wherein the thin film transistor comprises a semiconductor active region using a crystalline silicon film formed on the insulating surface. A channel region formed in the semiconductor active region; and a gate electrode formed on the channel region via a gate insulating film, wherein the silicon film is a crystal of an amorphous silicon film. A liquid crystal display device comprising a catalyst element that promotes the formation of a liquid crystal element at 1 × 10 ¹⁹ atoms / cm ³ or less. 5. The semiconductor active region has a thickness of 100 to 1
The liquid crystal display device according to claim 4, wherein the angle is 500 °. 6. The catalyst element is Ni, Pd, Pt, C
The liquid crystal display device according to claim 4, wherein the liquid crystal display device is one or more elements selected from u, Ag, Au, In, Sn, P, As, and Sb. 7. An active region using a crystalline silicon film formed on a substrate, a channel region formed in the active region, and a gate insulating film formed on the channel region. And a gate electrode, wherein the surface of the silicon film has a {111} plane or {hkl}
(H + k = 1), wherein the silicon film contains 1 × 10 ¹⁹ atoms / cm ³ or less of a catalytic element for promoting crystallization of the amorphous silicon film. Semiconductor device. 8. The semiconductor active region has a thickness of 100-1.
The semiconductor device according to claim 7, wherein the angle is 500 °. 9. The catalyst element is Ni, Pd, Pt, C
9. The semiconductor device according to claim 7, wherein the semiconductor device is one or more elements selected from u, Ag, Au, In, Sn, P, As, and Sb. 10. A semiconductor device having a plurality of thin film transistors on an insulating surface, wherein the thin film transistor is formed in a crystalline semiconductor layer containing silicon formed on the insulating surface, and in the crystalline semiconductor layer. And a gate electrode formed on the channel region with a gate insulating film interposed therebetween. The silicon film contains 1 × a catalytic element for promoting crystallization of the amorphous silicon film. A semiconductor device containing 10 ¹⁹ atoms / cm ³ or less, wherein the crystalline semiconductor layer has crystalline silicon grown in a direction parallel to the insulating surface. 11. The semiconductor active region has a thickness of 100 to 100.
The semiconductor device according to claim 10, wherein the angle is 1500 °. 12. The catalyst element is Ni, Pd, Pt, C
12. The semiconductor device according to claim 10, wherein the semiconductor device is at least one element selected from u, Ag, Au, In, Sn, P, As, and Sb.