JP4145963B2 - Semiconductor device manufacturing method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a semiconductor device using a crystalline semiconductor and a manufacturing method thereof.
[0002]
[Prior 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 with each pixel of an electro-optical device, particularly an active matrix liquid crystal display device, and a driver element formed in a peripheral circuit portion. .
[0003]
As a thin film semiconductor used for a TFT, it is easy to use an amorphous silicon film, but 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 crystalline silicon film is called polycrystalline silicon, polysilicon, microcrystalline silicon, or the like. In order to obtain this silicon film having crystallinity, an amorphous silicon film is first formed and then crystallized by heating.
[0004]
However, crystallization by heating requires a heating temperature of 600 ° C. or more and a time 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 with heating at 600 ° C. or higher in consideration of an increase in area of the substrate.
[0005]
BACKGROUND OF THE INVENTION
According to the study by the present inventors, a small amount of elements such as nickel, palladium, and lead are deposited on the surface of the amorphous silicon film, and then heated, so that the processing time is about 550 ° C. for about 4 hours. It has been found that crystallization can be performed.
[0006]
In order to introduce such a trace amount of element (catalytic element that promotes crystallization), plasma treatment, vapor deposition, or ion implantation may be used. The plasma treatment is a parallel plate type or positive column type plasma CVD apparatus using a material containing a catalytic element as an electrode, and generating a plasma in an atmosphere of nitrogen or hydrogen to form a catalytic element on the amorphous silicon film. It is a method of adding.
[0007]
However, the presence of a large amount of the elements as described above in the semiconductor is not preferable because it impedes the reliability and electrical stability of a device using these semiconductors.
[0008]
That is, the above-mentioned element (catalyst element) that promotes crystallization, such as nickel, is necessary when crystallizing amorphous silicon, but should not be included in crystallized silicon as much as possible. Is desirable. In order to achieve this purpose, a catalyst element that has a strong tendency to be inert in crystalline silicon is selected, and at the same time, the amount of catalyst element required for crystallization is minimized and crystallization is performed with a minimum amount. Need to do. For this purpose, it is necessary to precisely control the amount of the catalyst element added.
[0009]
In addition, when nickel is used as a catalyst element, an amorphous silicon film is formed, a nickel treatment is performed by plasma treatment to produce a crystalline silicon film, and the crystallization process and the like are examined in detail. There was found.
(1) When nickel is introduced onto the amorphous silicon film by plasma treatment, the nickel has already penetrated to a considerable depth in the amorphous silicon film before the heat treatment.
(2) The initial nucleation of the crystal is generated from the surface where nickel is introduced.
(3) Even when nickel is deposited on the amorphous silicon film by vapor deposition, crystallization occurs in the same manner as when plasma treatment is performed.
[0010]
From the above, it can be concluded that not all nickel introduced by plasma treatment is functioning effectively. That is, it is considered that there is nickel that does not function sufficiently even when a large amount of nickel is introduced. From this, it is considered that the point (plane) where nickel and silicon are in contact functions during low-temperature crystallization. It is concluded that nickel must be dispersed as finely as possible in the atomic form. That is, it is concluded that “what is necessary is that nickel as low as possible should be introduced in the form of atoms dispersed in the vicinity of the surface of the amorphous silicon film as long as low-temperature crystallization is possible”.
[0011]
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, as a method of introducing a very small amount of the catalytic element that promotes crystallization only in the vicinity of the surface of the amorphous silicon film, a vapor deposition method is used. However, the vapor deposition method has a problem of poor controllability, and it is difficult to strictly control the amount of catalyst element introduced.
[0012]
Further, it has been confirmed that crystal growth occurs from a region where the catalyst element for promoting crystallization as described above is introduced to a region where the catalyst element is not introduced. The region where the crystal is grown in this manner is extremely useful as an active layer of a semiconductor device because the concentration of the catalytic element is low. However, the method of selectively introducing the catalyst element is industrially problematic.
[0013]
[Problems to be solved by the invention]
In the production of a thin film silicon semiconductor having crystallinity by heat treatment at 600 ° C. or lower using a catalyst element,
(1) A controlled amount of catalyst element is introduced to minimize the amount.
(2) A method of selectively introducing a catalytic element.
(2) Use a highly productive method.
The purpose is to satisfy such requirements.
[0014]
[Means for Solving the Problems]
In order to satisfy the above object, the present invention obtains a silicon film having crystallinity using the following means.
The amorphous silicon film is held in contact with an amorphous silicon film having a mask pattern formed by a resist on its surface, and holds a catalytic element alone or a compound containing the catalytic element that promotes crystallization of the amorphous silicon film. In a state where the catalyst element alone or the compound containing the catalyst element is in contact with the substrate, heat treatment is performed to crystallize the amorphous silicon film.
Specifically, the above-described configuration is realized by applying a solution containing a catalyst element to the surface of an amorphous silicon film on which a desired pattern is formed with a resist and introducing the catalyst element.
In particular, the present invention is characterized in that a catalytic element is introduced in contact with the surface of an amorphous silicon film having a pattern formed by a resist.
[0015]
Further, the present invention is characterized in that an active region having at least one PN, PI, NI or other electrical junction of a semiconductor device is formed using a crystalline silicon film crystallized by the action of a catalytic element. As the semiconductor device, a thin film transistor (TFT), a diode, and an optical sensor can be given.
[0016]
By adopting the configuration of the present invention, the following basic significance can be obtained.
(A) The concentration of the catalytic 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 and the surface of the amorphous silicon film are in contact with each other, the amount of the catalytic element introduced into the amorphous silicon is determined by 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 a necessary minimum concentration.
(D) By using the resist pattern, selective introduction of the catalyst element is selectively introduced, and it becomes easy to form a semiconductor device using a region in which crystal growth has occurred laterally from the introduction region of the catalyst element. .
[0017]
As a method of applying a solution containing an element that promotes crystallization on the amorphous silicon film, an aqueous solution, an organic solvent solution, or the like can be used as the solution. Here, the inclusion includes both the meaning of inclusion as a compound and the meaning of inclusion by simply dispersing. These solutions are desirably determined in consideration of the compatibility with the compound containing the catalytic element added therein and the contact angle with the thin film surface. In particular, when the pattern is fine, by using a material having a small contact angle, uniform processing can be performed even inside the pattern.
[0018]
As the solvent containing the catalyst element, a solvent selected from water, alcohol, acid and ammonia which are polar solvents can be used.
[0019]
When nickel is used as a catalyst and this nickel is included in a polar solvent, nickel is introduced as a nickel compound. Typical nickel compounds include nickel bromide, nickel acetate, nickel oxalate, nickel carbonate, nickel chloride, nickel iodide, nickel nitrate, nickel sulfate, nickel formate, nickel acetylacetonate, 4-cyclohexylbutyric acid. A material selected from nickel, nickel oxide and nickel hydroxide is used.
[0020]
As the solvent containing the catalyst element, a nonpolar solvent selected from benzene, toluene, xylene, carbon tetrachloride, chloroform, ether, trichloroethylene, and Freon can be used. Here, polar and nonpolar do not mean the presence or absence of a strict dipole moment, but are based on general chemical properties.
[0021]
In this case, nickel is introduced as a nickel compound. As this nickel compound, typically, one selected from nickel acetylacetonate and nickel 2-ethylhexanoate can be used.
[0022]
It is also useful to add a surfactant to the solution containing the catalyst element. This is for increasing the adhesion to the surface to be coated and controlling the adsorptivity. This surfactant may be applied on the surface to be coated in advance.
[0023]
When nickel simple substance is used as a catalyst element, it is necessary to dissolve in acid to form a solution.
[0024]
The above is an example using a solution in which nickel as a catalyst element is completely dissolved, but even if nickel is not completely dissolved, powder of nickel alone or a compound of nickel is uniformly distributed in the dispersion medium. Materials such as dispersed emulsions may be used.
[0025]
These are the same even when a material other than nickel is used as the catalyst element.
[0026]
When nickel is used as a catalytic element for promoting crystallization, and a polar solvent such as water is used as a solution solvent containing nickel, the solution is repelled when directly applied to the amorphous silicon film. Sometimes. In this case, a thin oxide film having a thickness of 100 mm or less is first formed, and a solution containing a catalytic element is applied thereon, whereby the solution can be uniformly applied. Also effective is a method of improving wetting by adding a material such as a surfactant to the solution.
[0027]
Further, by using a nonpolar solvent such as a toluene solution of nickel 2-ethylhexanoate as the solution, it can be directly applied to the surface of the amorphous silicon film. In this case, it is effective to apply in advance a material such as an adhesive used in resist application. However, when the coating amount is too large, care must be taken because it interferes with the addition of the catalytic element into the amorphous silicon.
[0028]
The amount of the catalytic element contained in the solution depends on the type of the solution, but as a general tendency, the nickel amount is preferably 200 ppm to 1 ppm, preferably 50 ppm to 1 ppm (weight conversion) as a nickel amount. . This is a value determined in view of the nickel concentration in the film and the hydrofluoric acid resistance after crystallization is completed.
[0029]
Crystal growth can be selectively performed by selectively applying a solution containing a catalytic element using a resist mask formed on the surface of the amorphous silicon film. Particularly in this case, crystal growth can be performed in a direction substantially parallel to the surface of the silicon film from the region where the solution is applied toward the region where the solution is not applied. In this specification, a region where crystal growth is performed in a direction substantially parallel to the surface of the silicon film is referred to as a laterally crystallized region.
[0030]
Further, 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 impurity concentration in the active layer region is low. Therefore, it is useful for device fabrication to form the active layer region of the semiconductor device using the region where the crystal is grown in the lateral direction.
[0031]
In the present invention, the most prominent effect can be obtained when nickel is used as the catalyst element. Other types of catalyst elements that can be used include Fe, Co, Ru, Rh, Pd, Os, Ir, and Pt. Cu, Ag, Au, In, Sn, Pd, Sn, Pd, P, As, and Sb can be used. One or more kinds of elements selected from group VIII elements, IIIb, IVb, and Vb elements can also be used.
[0032]
When Fe (iron) is used as the catalyst element, a material known as an iron salt as the compound, for example, ferrous bromide (FeBr ₂ 6H ₂ O), ferric bromide (FeBr ₃ 6H ₂ O) ), Ferric acetate (Fe (C ₂ H ₃ O ₂ ) ₃ xH ₂ O), ferrous chloride (FeCl ₂ 4H ₂ O), ferric chloride (FeCl ₃ 6H ₂ O), ferric fluoride 2 Iron (FeF ₃ 3H ₂ O), ferric nitrate (Fe (NO ₃ ) ₃ 9H ₂ O), ferrous phosphate (Fe ₃ (PO ₄ ) ₂ 8H ₂ O), ferric phosphate (FePO) ₄ 2H ₂ O) can be used.
[0033]
When Co (cobalt) is used as the catalyst element, a material known as a cobalt salt as the compound, for example, cobalt bromide (CoBr6H ₂ O), cobalt acetate (Co (C ₂ H ₃ O ₂ ) ₂ 4H ₂ O), cobalt chloride (CoCl ₂ 6H ₂ O), cobalt fluoride (CoF ₂ xH ₂ O), and cobalt nitrate (Co (No ₃ ) ₂ 6H ₂ O) can be used.
[0034]
When Ru (ruthenium) is used as the catalyst element, a material known as a ruthenium salt, for example, ruthenium chloride (RuCl ₃ H ₂ O) can be used as the compound.
[0035]
When Rh (rhodium) is used as a catalyst element, a material known as a rhodium salt, for example, rhodium chloride (RhCl ₃ 3H ₂ O) can be used as the compound.
[0036]
When Pd (palladium) is used as the catalyst element, a material known as a palladium salt, for example, palladium chloride (PdCl ₂ 2H ₂ O) can be used as the compound.
[0037]
When Os (osnium) is used as the catalyst element, a material known as an osnium salt, for example, osmium chloride (OsCl ₃ ) can be used as the compound.
[0038]
When Ir (iridium) is used as the catalyst element, a material known as an iridium salt as the compound, for example, a material selected from iridium trichloride (IrCl ₃ 3H ₂ O) and iridium tetrachloride (IrCl ₄ ) is used. Can be used.
[0039]
When Pt (platinum) is used as the catalyst element, a material known as a platinum salt, for example, platinum chloride (PtCl ₄ 5H ₂ O) can be used as the compound.
[0040]
When Cu (copper) is used as a catalyst element, cupric acetate (Cu (CH ₃ COO) ₂ ), cupric chloride (CuCl ₂ 2H ₂ O), cupric nitrate (Cu (NO) ₃ ) Materials selected from ₂ 3H ₂ O) can be used.
[0041]
When gold was used as the catalyst element, the compound was selected from gold trichloride (AuCl ₃ xH ₂ O), gold chloride salt (AuHCl ₄ 4H ₂ O), and sodium tetrachlorogold (AuNaCl ₄ 2H ₂ O). Materials can be used.
[0042]
The method for introducing the catalyst element is not limited to using a solution such as an aqueous solution or alcohol, and a substance containing the catalyst element can be widely used. For example, a metal compound or oxide containing a catalyst element can be used.
[0043]
【Example】
[Example 1]
In this embodiment, a desired mask pattern is formed on the surface of the amorphous silicon film using a resist mask, and nickel is applied to the amorphous silicon film by applying a solution containing nickel on the mass pattern. It relates to an example of selective introduction.
[0044]
FIG. 1 shows an outline of a manufacturing process in this example. First, a resist pattern 21 serving as a mask is formed on a glass substrate (Corning 7059, 10 cm square). The resist may be positive or negative.
[0045]
Then, the resist mask 21 is panned into a required pattern by a normal photolithography patterning process. Then, a thin silicon oxide film 20 is formed by irradiation with ultraviolet rays in an oxygen atmosphere. The silicon oxide film 20 is produced 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 mm (FIG. 1A).
[0046]
The ultrathin silicon oxide film 20 is for improving the wettability of the amorphous silicon film 12 in a solution containing nickel to be applied in a later step.
[0047]
In this state, 5 ml of an acetate solution containing 100 ppm of nickel is dropped (in the case of a 10 cm square substrate). Further, a surfactant is added to the acetate solution so that the resist is not repelled by the resist. The solution is applied by spin coating with a spinner at 50 rpm for 10 seconds to form a uniform water film on the entire substrate surface. Furthermore, after maintaining for 5 minutes in this state, spin drying is performed at 2000 rpm for 60 seconds using a spinner. In addition, you may perform this holding | maintenance, rotating 0-150 rpm on a spinner. (Fig. 1 (B))
[0048]
Then, the resist mask 21 is removed by oxygen ashing, and a region where nickel element is selectively adsorbed is formed. Note that the resist mask may be removed by annealing in oxygen.
[0049]
Thereafter, 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 is introduced to the region where nickel is not introduced, as indicated by 23. In FIG. 1C, 24 is a region where nickel is directly introduced and crystallization is performed, and 25 is a region where crystallization is performed in the lateral direction. In addition, it has been confirmed that in the 25 region, crystal growth is performed substantially in the <111> axis direction.
[0050]
It is useful to perform annealing in the irradiation of laser light or strong light after the crystallization step by the heat treatment. This has the effect of increasing the crystallinity of the crystalline silicon film. As the laser light, a KrF excimer laser or XeCl laser may be used, and it is also useful to use infrared light as strong light. Infrared light is hardly absorbed by the glass substrate and is selectively absorbed by silicon, so that a great annealing effect can be obtained.
[0051]
In this embodiment, the concentration of nickel in the region where nickel is directly introduced can be controlled in the range of 1 × 10 ¹⁶ atoms cm ⁻³ to 1 × 10 ¹⁹ atoms cm ⁻³ by changing the solution concentration and holding time. Similarly, the concentration of the lateral growth region can be controlled to be lower than that.
[0052]
The crystalline silicon film formed by the method as shown in this embodiment is characterized by good hydrofluoric acid resistance. According to the knowledge of the present inventors, the crystalline silicon film obtained by introducing nickel by plasma treatment and crystallizing has low hydrofluoric acid resistance.
[0053]
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 drilling process for forming the electrode. There is a case. In such a case, a process of removing the silicon oxide film with buffer hydrofluoric acid is usually employed. 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.
[0054]
However, when the crystalline silicon film is resistant to hydrofluoric acid, the difference (selection ratio) between the etching rates of the silicon oxide film and the crystalline silicon film can be increased, so only the silicon oxide film is selected. This is extremely significant in the manufacturing process.
[0055]
As described above, the region where the crystal grows in the lateral direction has a low concentration of the catalytic element and 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 as a channel formation region of a thin film transistor.
[0056]
[Example 2]
In this embodiment, nickel, which is a catalyst element, is contained in alcohol, which is a non-aqueous solution, and applied onto an amorphous silicon film. In this example, nickel acetylacetonate is used as the nickel compound, and the alcohol is contained in the compound. The concentration of nickel may be set to a required concentration. The subsequent steps are the same as those shown in Example 1.
[0057]
Specific conditions will be described below. First, nickel acetylacetonate is prepared as a nickel compound. Since this substance is soluble in alcohol and has a low decomposition temperature, it can be easily decomposed during heating in the crystallization step.
[0058]
Further, ethanol is used as the alcohol. First, the above nickel acetylacetonate is adjusted to 100 ppm in terms of the amount of nickel in ethanol to prepare a solution containing nickel.
[0059]
And this solution is apply | coated on the amorphous silicon film in which the desired resist pattern was formed by the photonic. The reason for using photo nice is that photo nice baked at 300 ° C. does not dissolve in alcohol. The amorphous silicon film is formed by a plasma CVD method with a thickness of 1000 mm on a 100 mm square glass substrate on which a silicon oxide base film (thickness of 2000 mm) is formed.
[0060]
The application of the solution onto the amorphous silicon film is less than when the aqueous solution of Example 1 is used. This is due to the fact that the contact angle of alcohol is smaller than that of water. Here, it is set as 2 ml dripping with respect to an area of 100 square mm.
[0061]
And it hold | maintains for 5 minutes in this state. Thereafter, drying is performed using a spinner. At this time, the spinner is rotated at 1500 rpm for 1 minute. Thereafter, heating at 350 ° C. for 60 minutes is performed in a nitrogen atmosphere to decompose the nickel salt. In this process, nickel diffuses into the amorphous silicon film, and nickel as a catalytic element is introduced into the amorphous silicon film. Thereafter, the mask made of photonics is removed by wet etching or ashing with hydrazine. Then, crystallization is performed by heating at 550 ° C. for 4 hours. Thus, a crystalline silicon film is obtained.
[0062]
Of course, in this embodiment as well as in the first embodiment, crystal growth is performed from the region where the catalyst element is introduced to the region where the catalyst element is not introduced, and a crystalline silicon region where the crystal is grown laterally is obtained.
[0063]
Example 3
This embodiment is an example in which a nickel element as a catalytic element is selectively introduced by forming an oxide film containing nickel as a catalytic element on an amorphous silicon film on which a resist pattern is formed.
[0064]
In this embodiment, an oxide film containing the catalytic element is formed on an amorphous silicon film using an OCD solution containing a catalytic element that promotes crystallization, and then crystallized by heating. is there. The OCD solution is Ohka Diffusion Source of Tokyo Ohka Kogyo Co., Ltd., and is a solution in which a silicon compound and an additive are dissolved in an organic solvent. This solution has the utility that a silicon oxide film can be easily formed by applying and baking. In addition, the silicon oxide film to which impurities are added can be easily formed.
[0065]
In this embodiment, Corning 7059 glass is used as the substrate. Moreover, the magnitude | size shall be 100 mm x 100 mm.
[0066]
First, an amorphous silicon film is formed in a thickness of 100 to 1500 mm by plasma CVD or LPCVD. Here, the film is formed to a thickness of 1000 mm.
[0067]
Then, hydrofluoric acid treatment is performed to remove dirt and a natural oxide film, thereby forming a desired resist pattern. At this time, it is necessary to select a resist material having resistance to the organic solvent contained in the OCD solution.
[0068]
Thereafter, an oxide film containing nickel as a catalyst element is formed. This oxide film is produced using the following raw materials. This oxide film is formed on the portion of the applied solution 14 in the case of Example 1 shown in FIG.
[0069]
First, as a base, OCD Type 2 Si 59000 made by Tokyo Ohka was used, and this OCD solution and nickel (II) acetylacetonate dissolved in methyl acetate were mixed, and SiO ₂ was 2.0 wt% and nickel was 200%. A solution adjusted to ˜2000 ppm is prepared.
[0070]
10 ml of this solution is dropped on the surface of the amorphous silicon film, and spin coating is performed at 2000 rpm for 15 seconds using a spinner. Then, by pre-baking at 150 ° C. for 30 minutes, a silicon oxide film containing nickel is formed to a thickness of about 1300 mm. What is necessary is just to determine the temperature of this prebaking in view of the decomposition temperature of a nickel compound.
[0071]
Then, the resist is removed with a stripping solution. Thereafter, heat treatment is performed at 550 ° C. for 4 hours in a nitrogen atmosphere in a heating furnace. As a result, a silicon thin film having crystallinity formed on the substrate can be obtained. At the same time, crystal growth in the lateral direction is performed from the region where nickel is introduced to the region where nickel is not introduced.
[0072]
The above heat treatment can be performed at a temperature of 450 ° C. or higher. However, if the temperature is low, the heating time must be lengthened and the production efficiency is lowered. On the other hand, if it is 550 ° or more, the problem of heat resistance of the glass substrate used as the substrate will surface.
[0073]
The concentration of nickel element in the OCD solution is determined by the correlation with the concentration of SiO _{2 in} the OCD solution, and is not uniquely determined. Also, since the amount of diffusion from the silicon oxide film formed from OCD into the crystalline silicon film differs depending on the heating temperature and heating time during crystallization, the concentration of nickel element should be determined in consideration of these factors. It is necessary to decide.
[0074]
Example 4
In this embodiment, an example is shown in which an electronic device is formed using a region in which nickel is selectively introduced and crystal is grown from the portion in the lateral direction (direction parallel to the substrate). When such a configuration is adopted, the nickel concentration in the active layer region of the device can be further reduced, and a very preferable configuration can be obtained from the viewpoint of electrical stability and reliability of the device.
[0075]
As a method for introducing nickel element in the present embodiment, any of the methods of Embodiments 1 to 3 may be used.
[0076]
This embodiment relates to a manufacturing process of a TFT used for controlling an active matrix pixel. FIG. 2 shows a manufacturing process of this embodiment. First, the substrate 201 is cleaned, and a silicon oxide base film 202 having a thickness of 2000 mm is formed by plasma CVD using TEOS (tetraethoxysilane) and oxygen as source gases. Then, an intrinsic (I-type) amorphous silicon film 203 having a thickness of 500 to 1500 mm, for example, 1000 mm is formed by plasma CVD. Next, a resist mask 205 is formed. Thus, the exposed region 206 of amorphous silicon is formed.
[0077]
Then, a solution (here, an acetate solution) containing nickel element as a catalytic element for promoting crystallization is applied by the method shown in Example 1. The concentration of nickel in the acetic acid solution is 100 ppm. In addition, the detailed process sequence and conditions are the same as those shown in the first embodiment. This step may be performed by the method shown in Example 2 or Example 3.
[0078]
Thereafter, heat annealing is performed in a nitrogen atmosphere at 500 to 620 ° C., for example, 550 ° C. for 4 hours to crystallize the silicon film 303. In crystallization, crystal growth proceeds in a direction parallel to the substrate as indicated by an arrow starting from a region 206 where nickel and a silicon film are in contact with each other. In the figure, a region 204 indicates a portion crystallized by direct introduction of nickel, and a region 203 indicates a portion crystallized in the lateral direction. The crystal in the horizontal direction indicated by 203 is about 25 μm. Further, it has been confirmed that the crystal growth direction is approximately the <111> axis direction. (Fig. 2 (A))
[0079]
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, the island-shaped active layer region 208 is formed by dry etching. At this time, a region indicated by 206 in FIG. 2A 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 is also present at a high concentration at the tip of crystal growth. In these regions, it has been found that the nickel concentration is higher than in the middle region. Therefore, in this example, in the active layer 208, these high nickel concentration regions were not overlapped with the channel formation region.
[0080]
Then, the surface of the active layer (silicon film) 208 is oxidized by leaving it in an atmosphere of 10 atm and 500 to 600 ° C., typically 550 ° C. containing 100% by volume of water vapor, to oxidize the surface of the active layer (silicon film) 208. A silicon film 209 is formed. The thickness of the silicon oxide film is 1000 mm. After the silicon oxide film 209 is formed by thermal oxidation, the substrate is held at 400 ° C. in an ammonia atmosphere (1 atm, 100%). 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 209 is nitrided. Apply. At this time, 0.1 to 10% HCl may be mixed in the atmosphere.
[0081]
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 900-1200 ° 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./second, and the temperature drop is natural cooling to 20 to 100 ° C. Since this infrared light irradiation selectively heats the silicon film, heating of the glass substrate can be minimized. (Fig. 2 (B))
[0082]
Subsequently, an aluminum film (including 0.01 to 0.2% scandium) having a thickness of 3000 to 8000 mm, for example, 6000 mm is formed by a sputtering method. Then, the gate electrode 210 is formed by patterning the aluminum film. (Fig. 2 (C))
[0083]
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 1 to 5% tartaric acid. The thickness of the resulting oxide layer 211 is 2000 mm. Note that the oxide 211 has a thickness for forming an offset gate region in a subsequent ion doping step, and thus the length of the offset gate region can be determined by the anodic oxidation step. (Fig. 2 (D))
[0084]
Next, by an ion doping method (also called plasma doping method), self-alignment is performed in the active layer region (which constitutes the source / drain and channel) using the gate electrode portion, that is, the gate electrode 210 and the surrounding oxide layer 211 as a mask In particular, an impurity imparting N conductivity type (here, phosphorus) is added. As the doping gas, phosphine (PH ₃ ) is used, and the acceleration voltage is set to 60 to 90 kV, for example, 80 kV. The 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 apparent 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 leakage current (also referred to as off-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. It is effective.
[0085]
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 other lasers may be used. The laser light was irradiated at an energy density of 200 to 400 mJ / cm ² , for example, 250 mJ / cm ^2, and ² to 10 shots, for example, 2 shots were irradiated at one place. The effect may be increased by heating the substrate to about 200 to 450 ° C. during the laser light irradiation. (Figure 2 (E))
[0086]
Subsequently, a silicon oxide film 214 having a thickness of 6000 mm is formed as an interlayer insulator by a plasma CVD method. Further, a transparent polyimide film 215 is formed by spin coating to flatten the surface. A transparent conductive film (ITO film) having a thickness of 800 mm is formed on the plane formed in this manner by sputtering, and this is patterned to form a pixel electrode 216.
[0087]
Then, contact holes are formed in the interlayer insulators 214 and 215, and TFT electrodes and wirings 217 and 218 are formed of a multilayer film of a metal material, for example, 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))
[0088]
【effect】
By producing a semiconductor device using a crystalline silicon film that has been selectively introduced with a resist and crystallized at a low temperature in a short time, a device with high productivity and good characteristics can be obtained. Can do.
[Brief description of the drawings]
FIG. 1 shows a manufacturing process of an example. FIG. 2 shows a manufacturing process of the example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Glass substrate 12 ... Amorphous silicon film 13 ... Silicon oxide film 14 ... Acetic acid solution film 15 containing nickel ... Spinner

Claims (3)

A resist mask is selectively formed on the surface of the amorphous silicon film,
Forming an oxide film having a thickness of 10 nm or less on the surface of the amorphous silicon film where the resist mask is not formed;
By applying a nickel acetate containing nickel for promoting crystallization of the amorphous silicon in the resist mask and the oxide film surface, the nickel is introduced into the amorphous silicon film through the oxide film ,
Removing the resist mask;
Wherein by heating the amorphous silicon film, a semiconductor device manufacturing method characterized by performing the crystal growth in the lateral direction to the nickel from the introduction of the nickel region is not introduced region. Oite to claim 1, wherein the crystalline silicon film formed by heating the amorphous silicon film semiconductor device manufacturing method characterized by being grown in the <111> axial direction. 3. The method for manufacturing a semiconductor device according to claim 1 , wherein the oxide film has a thickness of 2 nm to 5 nm.

Images