JP5598272B2 - Thin film transistor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a thin film transistor, and more particularly to a thin film transistor having a bottom gate structure (also referred to as an inverted stagger structure) used for a liquid crystal display or the like and a method for manufacturing the same.

  Thin film transistors (TFTs) used for liquid crystal displays are required to be low in cost, and therefore a thin film transistor having a back channel portion (hereinafter referred to as a back channel thin film transistor) that can simplify the process. ) Is generalized. In this case, since the protection of the surface of the back channel portion has a great influence on the characteristics, various methods have been devised. For example, in Patent Document 1, a Si—Al—O-based film is anodized on the surface of the back channel portion. A method of forming is described.

  However, even if a protective layer is provided on the surface of the back channel portion, by-products, resist mask residues, and the like generated by previous processes, such as etching processes, adhere or deposit. Further, the off-state current increases in many elements due to conduction through these elements, and as a result, the electrical characteristics between elements on the same substrate often vary.

  Therefore, as a method of eliminating the leakage current due to the contamination, after the etching for forming the back channel portion, the photoresist for patterning formed on the upper portion is removed, and the back channel is etched again. A method for removing contamination on the surface of the back channel portion has been proposed (for example, Patent Document 2).

JP 2000-36603 A JP 2009-81422 A

  However, in the case of an inverted staggered thin film transistor using an Al alloy material for the source electrode and the drain electrode, if etching is performed again after removing the photoresist, the residual gas component after etching absorbs moisture in the atmosphere, thereby causing hydrochloric acid. This leads to the elution of aluminum oxide used for the source / drain electrodes. The eluted aluminum ions contaminate the back channel surface. For this reason, current flows on the surface of the back channel portion due to contamination of the back channel portion, which causes an increase in leakage current when the transistor is off. Therefore, there is a possibility that problems such as deterioration of display quality such as a decrease in contrast and an increase in crosstalk may occur. In the case of the prior art as shown in the above-mentioned patent document, since plasma containing chlorine gas is irradiated onto the wiring from which the photoresist has been removed, when aluminum is used as the wiring material, it does not become a problem solving means. .

  The present invention has been made to solve the above-described problems, and can prevent suppression of leakage current caused by aluminum contamination on the surface of the back channel portion, realizing high reliability and high yield. An object of the present invention is to provide a thin film transistor having a structure.

  A thin film transistor according to the present invention is a bottom gate thin film transistor having a back channel portion including silicon as a semiconductor layer, and includes a source electrode or a drain electrode containing aluminum, and a part of the back channel portion, which is a surface layer of the semiconductor layer. And a sialon layer covering.

  The present invention also relates to a method of manufacturing a thin film transistor having a back channel etching type bottom gate structure using silicon as a semiconductor layer, the step of forming an electrode by forming a layer containing aluminum as a source electrode or a drain electrode, After the step of forming the substrate, the source / drain etching step or the back channel etching step is performed by dry etching using a gas containing chlorine, and in the resist stripping step after the dry etching step, an amine aqueous solution or ammonia water is used. A step of performing oxidation plasma treatment under reduced pressure after resist stripping, and a step of forming a protective film using silicon nitride after the oxidation plasma treatment step, wherein the film formation temperature of silicon nitride Alternatively, a protective film having an annealing temperature of 200 ° C. or more and 300 ° C. or less after film formation It is also a method of manufacturing a thin film transistor and a formation step.

  Since the thin film transistor according to the present invention is configured as described above, it is possible to prevent suppression of leakage current caused by aluminum contamination on the surface of the back channel portion, and to realize high reliability and high yield.

It is sectional drawing of the thin-film transistor concerning Embodiment 1 of this invention. It is sectional drawing in the manufacturing process of the thin-film transistor concerning Embodiment 1 of this invention. It is sectional drawing in the manufacturing process of the thin-film transistor concerning Embodiment 1 of this invention. It is sectional drawing in the manufacturing process of the thin-film transistor concerning Embodiment 1 of this invention. It is sectional drawing in the manufacturing process of the thin-film transistor concerning Embodiment 1 of this invention. It is sectional drawing in the manufacturing process of the thin-film transistor concerning Embodiment 1 of this invention. It is sectional drawing in the manufacturing process of the thin-film transistor concerning Embodiment 1 of this invention. It is sectional drawing in the manufacturing process of the thin-film transistor concerning Embodiment 1 of this invention. It is sectional drawing in the manufacturing process of the thin-film transistor concerning Embodiment 1 of this invention. It is a figure which shows the electrical property of the thin-film transistor concerning Embodiment 1 of this invention. It is sectional drawing of the thin-film transistor concerning Embodiment 2 of this invention. It is sectional drawing in the manufacturing process of the thin-film transistor concerning Embodiment 2 of this invention. It is sectional drawing in the manufacturing process of the thin-film transistor concerning Embodiment 2 of this invention. It is sectional drawing in the manufacturing process of the thin-film transistor concerning Embodiment 2 of this invention.

Embodiment 1 FIG.
First, the entire configuration of the thin film transistor of the present invention will be described in detail with reference to the drawings. 1 is a cross-sectional view showing a configuration of a thin film transistor for a liquid crystal display device according to Embodiment 1 of the present invention. Further, the thin film transistor of this embodiment is a bottom-channel back channel thin film transistor. The planar layout configuration is the same as that of a back channel thin film transistor having a general bottom gate structure.

  Hereinafter, the thin film transistor of this embodiment will be described in detail with reference to cross-sectional views illustrating the structure of the thin film transistor. Note that in a thin film transistor having a back channel structure with a bottom gate structure, a semiconductor layer far from the gate insulating layer in the channel formation region in which the off-current flows in the vicinity of the interface with the gate insulating layer in the channel formation region in which the on-current flows. The surface layer (that is, the surface of the back channel portion) is referred to as “back channel surface” and will be described below. Further, etching between the source / drain electrode wirings to dig into the semiconductor layer to form a back channel portion is referred to as “back channel etching”. Except as otherwise noted, the overall configuration of the thin film transistor is common to all the embodiments. Furthermore, what attached | subjected the same code | symbol is the same or it corresponds, This is common in the whole text of a specification.

In FIG. 1, a thin film transistor includes a gate electrode 1, a gate insulating film 2, a microcrystalline i-type silicon (Si (i)) thin film 3, an amorphous n-type on a transparent insulating substrate 100 such as glass from the substrate side. A silicon (Si (n)) thin film 4, an aluminum alloy single layer film (source electrode 5 and drain electrode 6), a silicon nitride SiN _x protective insulating film 9, and a pixel electrode 11 are laminated in this order. Further, in a region sandwiched between the source electrode 5 and the drain electrode 6, a back channel portion 7 of a thin film transistor in which a part of the surfaces of the Si (n) film 4 and the Si (i) film is dug is formed.

The surface of the back channel part 7 (back channel surface 70) is composed of a compound made of Si, Al, O, N having a thickness of 50 nm or less, and the composition of the compound is Si _(6-z) Al _z O _z N _{(8-z) The} Si—Al—O—N film 8 satisfying ( 0 <Z ≦ 4.2) is present.

The silicon nitride SiN _x protective insulating film 9 is formed on the entire substrate and protects the Si—Al—O—N film 8 and the back channel portion 7. The pixel electrode 11 is made of a transparent conductive film and is electrically connected to the lower drain electrode 6 through the pixel drain contact hole 10.

In summary, the thin film transistor of this embodiment is a back channel thin film transistor having a bottom gate structure in which silicon is used for a channel portion and an Al alloy material is used for at least a part of a source / drain electrode. Within 50 nm is composed of a compound consisting of Si, Al, O, N, and the composition of the compound is Si _(6-z) Al _z O _z N _(8-z) ( 0 <Z ≦ 4.2 ). It is characterized by this.

In addition, among the Al ₂ O ₃ —AlN—Si ₃ N ₄ -based solid solutions, the composition is represented by the composition of Si _(6-z) Al _z O _z N _(8-z) ( 0 <Z ≦ 4.2 ). The substance is commonly called sialon (Si—Al—O—N), and has the advantages of both silicon nitride (Si ₃ N ₄ ) with strong covalent bond and alumina (Al ₂ O ₃ ) with strong ionic bond. It is known to be a strong compound with excellent insulation and corrosion resistance.

  Therefore, since the thin film transistor of this embodiment forms a strong insulating film of sialon on the back channel surface, it is possible to suppress leakage current due to metal contamination such as aluminum on the back channel surface. Further, since the channel portion is made of microcrystalline silicon, high mobility can be achieved.

  Next, a method for manufacturing the thin film transistor of this embodiment will be described. 2 to 9 are schematic cross-sectional views sequentially showing the manufacturing process of the thin film transistor according to the present embodiment. Hereinafter, the manufacturing method will be described in the order of the drawings.

  First, in the step shown in FIG. 2, the transparent insulating substrate 100 such as a glass substrate is cleaned using a cleaning liquid or pure water to form a first metal film. As the first metal film, for example, Cr, Mo, Ti, Al, an alloy obtained by adding a small amount of other substances to these, or the like is used. Of these, Al is preferable for use in a thin film transistor substrate for a liquid crystal display device because it has a lower specific resistance value than other metals and can reduce wiring resistance. In the case of using an Al-based metal, in order to prevent projections called hillocks that cause pattern defects and yield reduction from occurring in the upper surface direction of the wiring, a group 8 transition element of Fe, Co, Ni, La, It is preferable to use an alloy to which a rare earth element such as Nd, Sm, or Gd is added. The composition range of these additive elements is preferably 0.2 to 6 at% (at%; atomic concentration). If it is less than 0.2 at%, the effect of preventing hillocks in the upper surface direction will be insufficient. On the other hand, if it exceeds 6 at%, the specific resistance value will increase and the superiority of low resistance to Cr, Mo, Ti will be reduced. . In this embodiment, an Al-3 at% Ni alloy film to which 3 at% Ni is added is formed as a first metal film with a thickness of 200 nm by a sputtering method using a known Ar gas. Thereafter, a photoresist pattern is formed in the first photoengraving step (also referred to as “photolithography”), and this is used as a mask to perform wet etching with a known solution containing phosphoric acid + nitric acid + acetic acid. The gate electrode 1 is formed by removing the pattern.

  Next, in the step shown in FIG. 3, the gate insulating film 2 and the i-type microcrystalline Si semiconductor film 3 to which no impurity is added are formed, and then the n-type amorphous Si to which the impurity is added. The ohmic low-resistance film 4 is sequentially formed, and a semiconductor pattern of a thin film transistor is formed through a photolithography process.

  Specifically, a chemical vapor deposition (CVD) method is used and the substrate insulating condition is about 300 ° C., and the SiN film is 400 nm as the gate insulating film 2 and the microcrystalline i-type Si film is the semiconductor film 3. As an ohmic low resistance film 4, an amorphous n-type Si film doped with phosphorus (P) as an impurity is sequentially formed to a thickness of 50 nm. Thereafter, a photoresist pattern is formed in the second photolithography process, and the microcrystalline i-type Si film 3 and amorphous ohmic low-resistance n-type Si film are formed by dry etching using a known fluorine-based gas using the photoresist pattern as a mask. 4 is etched. Finally, the photoresist pattern is removed to form a thin film semiconductor film.

  Subsequently, in the step shown in FIG. 4, after the second metal film is formed, the photoresist pattern 12 is formed in the third photoengraving step, and then the region serving as the back channel portion 7 of the thin film transistor is used as a mask. The second metal film is etched to separate the source electrode 5 and the drain electrode 6 into patterns. As the second metal film, for example, Cr, Mo, Ti, Al or an alloy obtained by adding a small amount of other substances to these can be used. Among them, the Al type has a specific resistance compared to other metals. Since the wiring resistance can be lowered because the value is low, it is preferable for use as a TFT substrate for a liquid crystal display device. When an Al-based metal is used as the second metal film, a common Al-based metal causes an eutectic reaction between Al and Si at the interface with the Si (n) film 4 that contacts the lower layer, resulting in poor contact characteristics. In addition, when an oxide conductive film such as ITO or IZO is used as the transparent conductive pixel electrode film in contact with the upper layer, an oxidation reaction of Al occurs at the interface, resulting in poor contact characteristics. . In order to solve these problems, it is preferable to use an Al alloy to which at least a group 8 transition element of Fe, Co, and Ni is added in a composition range of 0.2 to 6 at%.

  Specifically, an Al-3 at% Ni alloy film added with 3 at% Ni is formed as a second metal film with a thickness of 200 nm by a sputtering method using a known Ar gas. Thereafter, a photoresist pattern 12 is formed in the third photolithography process, and the pattern of the source electrode 5 and the drain electrode 6 is formed by wet etching with a known phosphoric acid + nitric acid + acetic acid solution using the photoresist pattern 12 as a mask. . In the case of a general etching process, even after the film to be etched is completely removed by etching (hereinafter referred to as “just etching”), etching is performed for a while to completely remove the minute etching residue remaining on the substrate. The process is extended (hereinafter referred to as “overetching”). Usually, the overetching time is set to about 0.5 to 2 times the time required for just etching. In the present embodiment, after the second metal film is just etched, it is appropriate to perform overetching in the same time (1 time) as the just etching time.

  Next, in the step shown in FIG. 5, the amorphous Si (n) film 4 is removed by dry etching using a gas containing chlorine using the photoresist pattern 12 as a mask to remove the back channel portion 7 of the thin film transistor. (Back channel etching).

At this time, chlorine adhering to the source / drain electrodes becomes hydrochloric acid by adsorbing moisture in the atmosphere, and the surface of the channel portion 7 is covered with aluminum chloride (AlCl ₃ ) 8A.

Subsequently, in the step shown in FIG. 6, the photoresist pattern 12 is completely removed using an aqueous solution containing an amine-based organic solvent, followed by washing with water, and the pattern of the source electrode 5, the drain electrode 6, and the channel portion 8. Form. For removal, an aqueous solution obtained by adding 2 wt% of pure water to a commercially available resist stripping solution containing known monoethanolamine (NH ₂ C ₂ H ₄ OH) may be used. Further, when a normal resist stripping solution is used instead of the amine-based aqueous solution, the same effect can be expected by performing treatment with ammonia water before stripping the resist.

When ammonia or an amine-based aqueous solution reacts with aluminum chloride, gel-like gibbsite Al ₂ O ₃ .nH ₂ O is formed. This gibbsite is insoluble in water. Therefore, the aluminum chloride layer 8A on the channel surface becomes a gibbsite layer 8B at the stage of resist stripping with a monoethanolamine aqueous solution, and the gibbsite layer 8B remains even after washing with water. In addition, since the gibbsite layer 8B formed in this process is a reaction at room temperature and in a short time, oxygen is easily lost and is in the form of (Al ₂ O _(3-x) · nH ₂ O). There are many. Moreover, since the gibbsite layer 8B in this state exists in a gel form, it is a mixture of water and gibbsite crystals.

Then, in the process shown in FIG. 7, the gel-like gibbsite layer 8B deficient in oxygen and containing water is irradiated with oxygen plasma under reduced pressure to fill the oxygen deficiency and evaporate the water. Solid gibbsite crystal layer 8C (Al ₂ O ₃ .nH ₂ O). In this embodiment, for example, in a parallel plate plasma generator, the substrate is placed on the anode electrode, and RF power of 13.56 MHz is appropriately applied at an oxygen pressure of 100 Pa.

  Next, in the step shown in FIG. 8, a silicon nitride SiN film is formed as the protective insulating film 9 at a film forming temperature of 200 ° C. or higher. In this embodiment, a chemical vapor deposition (CVD) method is used, and a silicon nitride SiNx film having a thickness of 300 nm is formed as the protective insulating film 9 under a substrate heating condition of about 250 ° C.

Here, when the protective insulating film 9 is formed, the crystal water contained in the gibbsite is released to form alumina (Al ₂ O ₃ ) and nitrogen is supplied from SiNx. Si—Al— which is an amorphous sialon layer Si _(6-z) Al _z O _z N _(8-z) ( 0 <Z ≦ 4.2 ) by causing a diffusion reaction with a part of Si at the interface. An O-N film 8 is generated.

When the film formation temperature of silicon nitride SiN _x is 200 ° C. or lower, or when the above reaction does not proceed sufficiently due to a short film formation time, annealing at 200 ° C. or higher after the formation of the protective insulating film 9 is performed. May be added.

  Thereafter, a photoresist pattern is formed in the fourth photoengraving process and etched using a dry etching method using a known fluorine-based gas, and then the photoresist pattern is removed to form a pixel drain contact hole 10. .

  Finally, in the step shown in FIG. 9, a transparent conductive film is formed to form a pixel electrode pattern 11 for liquid crystal display. Specifically, as the transparent conductive film, IZO (indium oxide In 2 O 3 + zinc oxide ZnO) is formed with a thickness of 100 nm by a sputtering method using a known Ar gas. Next, a photoresist pattern is formed in the fifth photoengraving step, and the photoresist pattern is removed after wet etching with a known oxalic acid solution using the photoresist pattern as a mask, whereby the transparent pixel electrode 11 can be formed.

  As described above, a TFT substrate for a liquid crystal display device can be completed by sequentially performing the manufacturing steps shown in FIGS.

  In the method for manufacturing the thin film transistor according to the present embodiment, the AlNi alloy film in which at least Ni is added to Al is used as the second metal film, thereby preventing eutectic reaction with the lower Si (n) film and the upper layer. Since it is possible to obtain good contact characteristics with a pixel electrode made of an oxide transparent conductive film, a low resistance Al-based alloy, which has been impossible in the past, is formed as a single layer film source / drain of a TFT for a liquid crystal display device It becomes possible to apply to an electrode.

  In a conventional staggered thin film transistor manufacturing process using AlNi alloy films as source and drain electrodes, aluminum chloride is eluted during back channel etching using a chlorine-based gas and contaminates the back channel surface, which causes leakage of the thin film transistor. Electrical current is adversely affected as electrical current.

However, according to the method of manufacturing a thin film transistor according to the present embodiment, aluminum chloride eluted on the back channel surface is changed to gel-like gibbsite (Al ₂ O _(3-x) · nH ₂ O) by an amine-based aqueous solution or aqueous ammonia. Then, the gibbsite that has been solidified and adjusted in stoichiometry by the oxygen plasma treatment under reduced pressure and the silicon nitride film forming process accompanied by annealing at 200 ° C. or higher is subjected to silicon and nitridation on the channel surface via alumina. Combined with nitrogen supplied from the silicon film, a sialon film Si _(6-z) Al _z O _z N _(8-z) ( 0 <Z ≦ 4.2 ) is formed on the back channel surface. The sialon film 8 is excellent in insulation and can prevent a leakage current of the thin film transistor due to the metal element contamination of the channel portion.

In addition, since the sialon film is stronger in both mechanical strength and interatomic bond than the normal SiN _x film, it prevents the entry of impurities from the outside and prevents the hydrogen from leaving the amorphous silicon inside the channel, thereby reducing the thin film transistor. Can contribute to the improvement of long-term reliability.

FIG. 10 shows a comparison of electrical characteristics between a thin film transistor manufactured in this embodiment mode and a thin film transistor manufactured by a conventional manufacturing method. The solid line represents the electrical characteristics of the thin film transistor prepared according to this embodiment, and the dotted line represents the electrical characteristics of the thin film transistor that was not subjected to the amine aqueous solution treatment and the subsequent oxygen plasma treatment as a conventional example. As shown in this figure, the thin film transistor according to the present embodiment has a significantly reduced leakage current in the off region and realizes good electrical characteristics. As a result of observation with an analytical electron microscope, in the thin film transistor of this embodiment, Si _4.1 Al _1.9 O _1.9 N _6.1 having a thickness of about 8 nm is formed at the interface between the back channel portion and the SiN _x protective film. Of amorphous sialon was observed. Further, the channel dimensions and the gate insulating film thickness of both thin film transistors are the same.

As described above, according to this embodiment, even if aluminum elution occurs due to back channel etching or subsequent resist stripping, it becomes a Si—Al—O—N compound. There is no contamination. Also, the back channel surface can be kept clean with respect to by-products, resist mask residues, and the like generated by the etching process. In addition, since the sialon film is strong in both mechanical strength and interatomic bond, it is possible to prevent the intrusion of impurities from the outside and to prevent hydrogen detachment from the amorphous silicon inside the channel.
Accordingly, a TFT for a liquid crystal display having a low resistance Al alloy in the source / drain electrodes and excellent in low leakage current and long-term reliability can be manufactured with high yield.

  In the above-described embodiment, the wet etching process is used to pattern the Al alloy in the step shown in FIG. 4, but a dry etching step using a chlorine-based gas may be employed here. In this case, a large amount of aluminum chloride adheres to the surface of the source / drain electrode after the Al alloy etching and contaminates the silicon surface after the back channel etching, but the subsequent amine-based aqueous solution turns the aluminum chloride into gibbsite, and the subsequent oxygen The characteristics that a sialon layer is formed on the surface of the back channel by plasma irradiation and subsequent silicon nitride film formation with annealing are the same. Further, when dry etching using a chlorine-based gas of an Al alloy is used, the same effect can be expected even if a process using no chlorine-based gas is used for back channel etching.

  Further, although an example in which the i-type microcrystalline Si semiconductor film 3 is used as a semiconductor has been described, the semiconductor film may be amorphous silicon or polysilicon.

Embodiment 2. FIG.
FIG. 11 is a cross-sectional view showing a configuration of a thin film transistor for a liquid crystal display device according to Embodiment 2 of the present invention. Similarly to the first embodiment, the back channel TFT has a bottom gate structure.

  In the first embodiment, the i-type microcrystalline Si semiconductor film 3 is used as a semiconductor. However, in the second embodiment, an amorphous state is once formed as a semiconductor film, and is subsequently microcrystalline. To do. Since the entire configuration other than the microcrystalline Si semiconductor film 3 is the same as that of the first embodiment, the following description will be focused on the configuration unique to this embodiment.

In FIG. 11, a thin film transistor includes a gate electrode 1, a gate insulating film 2, an amorphous i-type silicon (Si (i)) thin film 3, an amorphous n-type silicon on a transparent insulating substrate 100 such as glass from the substrate side. A (Si (n)) thin film 4, an aluminum alloy single layer film (source electrode 5, drain electrode 6), a silicon nitride SiN _x protective insulating film 9, and a pixel electrode 11 are laminated in this order. Further, in a region sandwiched between the source electrode 5 and the drain electrode 6, a back channel portion 7 of a thin film transistor in which a part of the surfaces of the Si (n) film 4 and the Si (i) film is dug is formed.

The surface of the back channel portion 7 (corresponding to the back channel surface 70) is composed of a compound made of Si, Al, O, N having a thickness of 10 nm or less, and the composition of the compound is Si _(6-z) Al _z. There is a Si—Al—O—N film 8E which is O _z N _(8-z) ( 0 <Z ≦ 4.2 )). Further, there is a microcrystalline i-type silicon thin film 30 immediately below.

The silicon nitride SiN _x protective insulating film 9 is formed on the entire substrate and protects the Si—Al—O—N film 8 and the back channel portion 7. The pixel electrode 11 is made of a transparent conductive film and is electrically connected to the lower drain electrode 6 through the pixel drain contact hole 10.

Next, a method for manufacturing the thin film transistor of this embodiment will be described. In the present embodiment, the steps up to the step of peeling and washing the resist in the third photoengraving step are the same as those in the first embodiment, and thus description thereof is omitted. Note that the gate insulating film 2 of the first embodiment is silicon nitride, whereas the gate insulating film 2 shown in the second embodiment is formed at 350 ° C. using a chemical vapor deposition (CVD) method. A silicon oxide SiO _x film may be formed.

FIG. 12 to FIG. 14 are schematic cross-sectional views of the manufacturing process of the thin film transistor according to the present embodiment. The steps after the resist stripping / water washing step in the third photolithography process in the second embodiment will be described below. In contrast to the gel-like gibbsite 8B (Al ₂ O _(3-x) · nH ₂ O) in which the stoichiometry existing on the surface of the back channel portion 7 is incomplete in the step shown in FIG. Nitrogen-containing gibbsite Al ₂ O _(3-x) N by performing nitrogen plasma irradiation under reduced pressure in the process shown in FIG. 8D which is _(1.5x) .nH ₂ O is formed.

Then, in the step shown in FIG. 14, laser annealing is performed on the region including the back channel portion 7 of the thin film transistor. In this example, a YAG2ω laser with a wavelength of 550 nm was used, and annealing was performed in the atmosphere. By this laser annealing, the amorphous silicon in the back channel portion 7 becomes microcrystalline silicon 30, and the nitrogen-containing gibbsite 8D is crystalline by combining with the silicon on the channel surface, and belongs to the space group of (P6 ₃ / m). β sialon _{Si (6-z) Al z} O z N (8-z) becomes (0 <Z ≦ 4.2) 8E .

Further, the sialon film formed at this time may be an α sialon belonging to the space group (P31 _C ) depending on conditions, but the same effect can be expected even in this case.

  After the steps described above, the protective insulating film 9, the pixel drain contact hole 10, and the pixel electrode 11 are formed through the same steps as in the first embodiment, and the liquid crystal according to the second embodiment of the present invention is formed. A TFT substrate for a display device is completed.

The TFT substrate for a liquid crystal display device according to the second embodiment of the present invention thus completed can obtain the same effects as those of the first embodiment. That is, even if elution of aluminum occurs due to back channel etching or subsequent resist peeling, it becomes a Si—Al—O—N compound, and thus the eluted aluminum does not contaminate the back channel surface. Also, the back channel surface can be kept clean with respect to by-products, resist mask residues, and the like generated by the etching process. In addition, since the sialon film is strong in both mechanical strength and interatomic bond, it is possible to prevent the intrusion of impurities from the outside and to prevent hydrogen detachment from the amorphous silicon inside the channel.
Accordingly, a TFT for a liquid crystal display having a low resistance Al alloy in the source / drain electrodes and excellent in low leakage current and long-term reliability can be manufactured with high yield.

  Furthermore, as compared with Embodiment Mode 1, the channel portion is made of microcrystalline silicon formed by laser annealing, so that it can have high mobility and can be used for purposes other than pixels such as a gate driver. Become.

  In the above-described embodiment of the present invention, the use of the liquid crystal display device has been described. However, the present invention is not limited to this, and includes a TFT substrate of a self-luminous display device using an electroluminescence (EL) element and a TFT having the same structure. The present invention can also be applied to other semiconductor devices.

  Further, it should be understood that the above-described embodiment is illustrative in all points and not restrictive. It is to be understood that the scope of the present invention includes all modifications within the scope equivalent to the scope of the claims, not to mention the scope of the claims.

1 gate electrode, 2 gate insulating film, 3 i-type silicon, 4 n-type amorphous silicon, 5 Al-based alloy source electrode, 6 Al-based alloy drain electrode, 7 back channel portion,
8 Si-Al-O-N film, 9 protective insulating film, 10 pixel drain contact hole,
11 pixel electrode, 12 photoresist pattern, 13 second metal film,
14 photoresist pattern, 30 microcrystalline silicon 70 back channel surface 100 substrate.

Claims (6)

A bottom-gate thin film transistor having a back channel portion using silicon as a semiconductor layer,
A source or drain electrode comprising aluminum;
A thin film transistor having a sialon layer that is a part of the back channel portion and covers a surface layer of a semiconductor layer. The composition of the sialon is represented by the general formula Si _(6-z) Al _z O _z N _(8-z) , the z is greater than 0 and 4.2 or less, and impurities of metal elements other than Si and Al Content is 6 at% or less, The thin-film transistor of Claim 1 characterized by the above-mentioned. 3. The thin film transistor according to claim 1, wherein the semiconductor layer is microcrystalline silicon. _3. The thin film transistor according to claim 2, wherein the crystal system of sialon is hexagonal and the space group is P6 ₃ / m, or the space group is P31 _C and the space group is P31 _C. A method of manufacturing a thin film transistor having a back channel etching type bottom gate structure using silicon as a semiconductor layer,
Forming a layer containing aluminum as a source or drain electrode to form an electrode;
A step of performing dry etching using a gas containing chlorine in a source / drain etching step or a back channel etching step after the electrode forming step;
A step of using an aqueous amine solution or aqueous ammonia in the resist stripping step after the dry etching step;
A step of performing an oxidative plasma treatment under reduced pressure after resist stripping;
A step of forming a protective film using silicon nitride after the oxidation plasma treatment step,
A protective film forming step in which the film formation temperature of silicon nitride or the annealing temperature after film formation is 200 ° C. or higher and 300 ° C. or lower;
The manufacturing method of the thin-film transistor which has this. A method of manufacturing a thin film transistor having a back channel etching type bottom gate structure using silicon as a semiconductor layer,
Forming a layer containing aluminum as a source or drain electrode to form an electrode;
A step of performing dry etching using a gas containing chlorine in a source / drain etching step or a back channel etching step after the electrode forming step;
A step of using an aqueous amine solution or aqueous ammonia in the resist stripping step after the dry etching step;
Performing a nitrogen plasma treatment under reduced pressure after resist stripping;
After the nitrogen plasma treatment, annealing the semiconductor layer by irradiating the back channel portion of the thin film transistor with a laser;
A step of forming a protective film after the annealing step;
The manufacturing method of the thin-film transistor which has this.

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