Thin film transistor

[Detailed Description of the Invention]

[Summary of the Invention] It is improvement of a thin film transistor. About an active layer, they are hydrogenation amorphous carbonization silicon and hydrogenation amorphous nitriding silicon, It is considered as noncrystalline semiconductor thin film layered product 4 which laminates thin films 42, such as hydrogenation amorphous germanium-ized silicon and hydrogenation amorphous oxidization silicon, and thin film 41 of a hydrogenation amorphous silicon by turns. It is the thin film transistor which decreases dark current and enabled it to prevent generating of malfunction etc., without making this transparent to visible light and needing a gobo etc. [Industrial Application] The present invention relates to a thin film transistor. using a transparent active layer to visible light especially -- dark current -- sincerity a few -- it is related with improvement which prevents generating of malfunction etc. [Description of the Prior Art] Since being formed on amorphous boards, such as a glass substrate, is general as for a thin film transistor, its case where the hydrogenation amorphous silicon film which is a noncrystalline semiconductor is made into an active layer is general. [Problem(s) to be Solved by the Invention] However, a band gap is about 1.8 eV, and since a hydrogenation amorphous silicon absorbs visible light, even if it uses the light of long wavelength from infrared light as a signal light, it absorbs undesirable visible light, and produces dark current, and also has fear of malfunction. Although there are hydrogenation amorphous carbonization silicon, hydrogenation amorphous nitriding silicon, etc. as a noncrystalline semiconductor which should just make an active layer a noncrystalline semiconductor with a big band gap and which meets this request in order to cancel this fault, If it is desirable to introduce impurities in order to fall resistivity since a carrier's mobility is low and resistivity is large, if it is in these, but [ for this reason ] impurities are introduced. An electrical property is spoiled by a trap increasing. It is because the doping characteristics, such as hydrogenation amorphous carbonization silicon and hydrogenation amorphous nitriding silicon, are bad. Then, in conventional technology, it is general to use a hydrogenation amorphous silicon as an active layer, and to use a gobo together to this. Development of fa11 transistor which consists of a transparent active layer to visible light was desired. It is in the object of the present invention meeting this request, and it has a transparent active layer to visible light, and is in providing the taJ film transistor which dark current does not make malfunction etc. based on little undesirable visible optical absorption. [Means for Solving the Problem] A means which the present invention took in order to achieve the object of an account of L, Hydrogenation amorphous carbonization silicon, hydrogenation amorphous nitriding silicon, It is in forming an active layer with noncrystalline semiconductor thin film layered product 4 which laminates thin films 42, such as hydrogenation amorphous germanium-ized silicon and hydrogenation amorphous oxidization silicon, and thin film 41 of a hydrogenation amorphous silicon by turns. [Function] The present invention uses the character in which /Ground gap of an amorphous super lattice is determined as a function with effective Morality of the electron which is the depth, the width, and the carrier of a quantum well, or a hole, Hydrogenation amorphous carbonization silicon with the thin film of the small hydrogenation amorphous silicon of a band gap, and a large band gap, Let a layered product with thin films, such as hydrogenation amorphous nitriding silicon, water ll amorphous germanium-ized silicon, and hydrogenation amorphous oxidization silicon, be an active layer. If it puts in another way, a noncrystalline semiconductor with a bigger band gap than a hydrogenation amorphous silicon will be realized using the above-mentioned quantum effect, It is made for current to flow in a hydrogenation amorphous silicon using the locked-in effect of the carrier who eliminates visible optical absorption nature as an active layer, and produces this in an amorphous super lattice on the other hand. Since this noncrystalline semiconductor also has the advantage which is excellent in the doping characteristic in addition to control of a band gap being easy, when using as an active layer of a thin film transistor, it can introduce impurities and can make them low resistance. Hydrogenation amorphous carbonization silicon, hydrogenation amorphous nitriding silicon, Since it cannot dope since hydrogenation amorphous germanium-ized silicon, hydrogenation amorphous oxidization silicon, etc. have the bad doping characteristic, but the hydrogenation amorphous silicon is excellent in the doping characteristic, Impurities are introduced only into a hydrogenation amorphous silicon, the impurity density of a layered product is controlled, and they are salted entrails and roe of the ayu, or sweetfish. [Example] The thin film transistor which starts one example of the One 11 present invention with reference to one drawing below is further explained. Refer to the 2nd figure. After forming electric conduction body membranes, such as nickel chromium, on l, such as a glass substrate, at about 1,000 thickness, butter Ning of this is carried out at about 20% of Radiation fat, and gate electrode 2 is formed. Refer to the 3rd figure. A high frequency glow discharge part solution is used, and it is with film (gate dielectric film) 3 of the nitriding silicon of about 3.000 thickness, " - Thin film 41 and hydrogenation amorphous carbonization silicon of a hydrogenation amorphous silicon which can be described, Layered product 4 of thin W142, such as hydrogenation amorphous nitriding silicon, hydrogenation amorphous germanium-ized silicon, and hydrogenation amorphous oxidization silicon, and thin film 5 of the hydrogenation amorphous silicon by which Lynn was doped are continued and formed. Although the thickness of each thin film which constitutes layered product 4 is 5~50^, thickness of the layered product 4 whole is made into about 1,000 persons. At least 10 sets of layered products 4 will be formed. Usu of the hydrogenation amorphous silicon by which Lynn was doped! The thickness of 15 is 100 abbreviation. This process is possible if the high frequency glow discharge part solution which switches the mixed gas of mono-Silane diluted by having hydrogen, and methane and mono-Silane one by one, and makes it is used. Refer to the 4th figure. Thickness abbreviation 1, and titanium s6 of 000 and aluminum film 7 of about 2,000 thickness are formed. This process is possible using the usual vacuum evaporation method, the sputtering method, etc. Film 5.6.7 is removed from the field which counters gate electrode 2 in width of about 15~20 micrometers, and sauce electrode 8 and the Dorain electrode 9 are formed. Since the band gap of the active layer of the thin film transistor manufactured with the process of With is larger than the band gap of a hydrogenation amorphous silicon, visible light is not absorbed, and dark current does not flow, or undesirable visible light is absorbed, and it does not malfunction. [Effect of the Invention] The active layer of the thin film transistor concerning the present invention is hydrogenation amorphous carbonization silicon above as explanation To, Hydrogenation amorphous nitriding silicon, hydrogenation amorphous germanium-ized silicon, The Quality semiconductor which makes mixture thin films, such as hydrogenation amorphous oxidization silicon, and 81 layers of thin films of a hydrogenation amorphous silicon, It is constituted with the thin film layered product, and the band gap is freely controlled by a quantum effect, and is made larger than the band gap of a hydrogenation amorphous silicon, And in a hydrogenation amorphous silicon, the power traps etc. in which a dope is possible are not afraid, and it can do doping freely. Therefore, it is since absorb unexpected visible light and dark current is generated, or undesirable visible light is absorbed, it does not malfunction and current flows by the carrier locked-in effect of an amorphous super lattice in a hydrogenation amorphous silicon. Mobility is also high, its working speed is also quick, and the characteristic of this thin film transistor is excellent in it. When it is especially used as a thin film transistor for a drive of a plane display, effective pixel area increases and there are effects -- a bright plane display is obtained.

[Brief Description of the Drawings]

Drawing 1 is a sectional view of the thin film transistor concerning one example of the present invention. The 2~4th figure is a manufacturing process figure of the thin film transistor concerning one example of the 1 present invention. l ... Glass repellent 2 --- Gate electrode. The film of 3 and phi-M-ized silicon (gate Aarga>, 4 and fist -, tf object) pJS(s), such as a thin film of 41, watch, and a hydrogenation amorphous silicon, 420 3 and hydrogenation amorphous carbonization silicon 1. hydrogenation amorphous nitriding silicon, hydrogenation amorphous germanium-ized silicon, and hydrogenation amorphous oxidization silicon. 5 Conflict .. The thin film of the hydrogenation amorphous silicon by which Lynn was doped, 6 -.. Titanium membrane, 7 ee e aluminum film, 8, phi and a sauce electrode, 9 Fist meeting Dorain electrode. representative Patent attorney Tadashi Inoda - + and '-\1.-Yu -A- - Engineering yrt day The 4th Prisoner Non-Swamp ': LAt A Drawing 2 The account of Flutter Drawing 3