JP2782829B2 - Method for manufacturing thin film transistor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a thin film transistor provided with a light shielding film.

[Conventional technology]

For example, in a thin film transistor used under conditions of exposure to light, such as a thin film transistor for selecting a pixel electrode of a TFT active matrix type liquid crystal display device, the semiconductor is used to prevent a semiconductor layer from being exposed to light and causing a leak current in the transistor. A light-shielding film is provided on the side of the layer not facing the gate electrode.

A thin film transistor provided with such a light-shielding film is conventionally manufactured by the following method.

Fig. 2 shows a TFT active matrix liquid crystal display element T
1 shows a conventional manufacturing process for manufacturing a pixel electrode selecting thin film transistor formed on an FT panel. Note that this thin film transistor is of an inverted stagger type.

The method of manufacturing this thin film transistor will be described. First, as shown in FIG. 2 (a), a metal film made of chromium or the like is deposited on a transparent substrate 1 made of glass or the like, and this is patterned by photolithography. After the gate electrode 2 is formed, the entire surface of the substrate 1 is formed thereon.
Transparent gate insulating film 3 made of silicon nitride (SiN)
A semiconductor layer 4 made of i-type amorphous silicon (ia-Si), an n-type semiconductor layer 5 made of amorphous silicon (n ⁺ -a-Si) doped with n-type impurities,
A metal film 6, such as chromium, serving as source and drain electrodes is sequentially deposited.

Next, as shown in FIG. 2B, the metal film 6 is patterned by photolithography to form a source electrode 6a.
And the drain electrode 6b are formed, and then the n-type semiconductor layer 5 thereunder is patterned into the shapes of the source and drain electrodes 6a and 6b.

Next, as shown in FIG. 2C, the semiconductor layer 4 is patterned into a transistor element shape by a photolithography method to complete an element portion of the thin film transistor.

Next, as shown in FIG.
On this, a transparent pixel electrode 10 made of ITO or the like is formed so that one end thereof is overlapped with the source electrode 6a.

Next, as shown in FIG. 2E, a transparent upper insulating film 7 made of silicon nitride and a light shielding film 8 made of a metal such as chromium are sequentially deposited over the entire surface of the substrate 1, and thereafter, the light shielding film 8 is formed. Is patterned by photolithography into a predetermined shape covering a channel region (a portion between the source and drain electrodes 6a and 6b) of the semiconductor layer 4 to complete a thin film transistor provided with a light shielding film 8.

The thin film transistor includes a semiconductor layer 4 and a source,
In some cases, the n-type semiconductor layer 5 is not provided between the drain electrodes 6a and 6b.
The step of forming the n-type semiconductor layer 5 becomes unnecessary.

[Problems to be solved by the invention]

However, in the above-described conventional manufacturing method, the light-shielding film 8 is formed after the element portion of the thin-film transistor is completed, and then the upper insulating film 7 and the light-shielding film 8 are formed thereon. Four patterning operations of patterning the electrode 2, patterning the source and drain electrodes 6a and 6b, patterning the semiconductor layer 4, and patterning the light shielding film 8 must be performed.
Therefore, the number of patterning steps is large and the cost is high, and the fact that the number of patterning steps is large means that
Since this leads to an increase in the occurrence rate of a mask alignment error or the like in the patterning process, it also causes a reduction in manufacturing yield.

The present invention has been made in view of the above circumstances, and an object of the present invention is to manufacture a thin film transistor having a light-shielding film at a low cost and with a high yield with a small number of patterning steps. An object of the present invention is to provide a method for manufacturing a thin film transistor.

[Means for Solving the Problems] The method for manufacturing a thin film transistor according to the present invention comprises, after forming a gate electrode on a substrate, sequentially depositing a gate insulating film, a semiconductor layer, and a metal film thereon, After patterning to form source and drain electrodes, an upper insulating film and a light-shielding film are sequentially deposited thereon, and the light-shielding film and the upper insulating film are patterned in the same manner. It is characterized by patterning into a transistor element shape using the drain electrode as a mask.

(Operation)

That is, according to the present invention, an upper insulating film and a light-shielding film are deposited before patterning a semiconductor layer, and the light-shielding film and an upper insulating film thereunder are patterned into the same shape. The layer is patterned into a transistor element shape using the source and drain electrodes as masks. According to this manufacturing method, the semiconductor layer can be patterned when the light shielding film is patterned. Can be manufactured with low number of patterning steps at low cost and with good yield.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 for manufacturing a thin film transistor for selecting a pixel electrode formed in a TFT panel for a TFT active matrix type liquid crystal display device.

First, as shown in FIG. 1 (a), a metal film made of chromium or the like is deposited on a transparent substrate 11 made of glass or the like to a thickness of 1000 ° by sputtering or the like, and is patterned by photolithography. With gate electrode 12
After that, a transparent gate insulating film 13 made of silicon nitride (SiN), a semiconductor layer 14 made of I-type amorphous silicon (ia-Si), and an n-type impurity An n-type semiconductor layer 15 made of amorphous silicon (n ⁺ -a-Si) doped with
The metal film 16 such as chromium serving as the drain electrode is plasma-CV
Continuous deposition is performed by the method D. Note that the gate insulating film 13 is 3000 °, the semiconductor layer 14 is 1500 °, and the n-type semiconductor layer 15 is
250 mm, the metal film 16 is deposited to a thickness of 1000 mm.

Next, as shown in FIG. 1B, the metal film 16 is patterned by photolithography to form a source electrode 16.
a and a drain electrode 16b are formed, and the n-type semiconductor layer 5 thereunder is subsequently formed on the source and drain electrodes 16a and 16b.
Is patterned.

Next, as shown in FIG. 1C, an upper insulating film 17 made of silicon nitride is formed on the entire surface of the substrate 1 by plasma CVD.
Then, a light-shielding film 18 made of a metal such as chromium is deposited thereon to a thickness of 6000 mm by a sputtering method or the like.

Next, as shown in FIG. 1 (d), the light shielding film 18 and the upper insulating film 17 thereunder are formed by photolithography on the channel regions (source / drain electrodes 16a, 16b) of the semiconductor layer 14.
The semiconductor layer 14 exposed by the patterning of the light-shielding film 18 and the upper insulating film 17 is patterned while leaving a resist mask (not shown) on the light-shielding film 18 while patterning it into a predetermined shape covering the portion between them. The resist mask and the portions of the source and drain electrodes 16a and 16b protruding from the upper insulating film 17 are etched as an etching mask, and the semiconductor layer 14 is patterned into a transistor element shape. To complete. In this case, the light shielding film 18, the upper insulating film 17, and the semiconductor layer
The patterning of 14 is performed continuously while changing the etching conditions.

Thereafter, as shown in FIG. 1 (e), a transparent pixel electrode 20 made of ITO or the like is formed on the gate insulating film 13 so that one end of the transparent pixel electrode 20 overlaps the source electrode 16a. To complete. In this manufacturing method, the semiconductor layer 14
Before performing patterning, the upper insulating film 17 and the light shielding upper 18
The light-shielding film 18 and the upper insulating film 17 thereunder are patterned into the same shape, and the semiconductor layer 14 exposed by this patterning is removed from the source and drain electrodes.
According to this manufacturing method, the light shielding film 18 is patterned because the transistor elements are patterned using the masks 16a and 16b as masks.
The semiconductor layer 14 can be simultaneously patterned at the time of patterning. According to this manufacturing method, the number of patterning steps required to manufacture a thin film transistor includes the patterning of the gate electrode 12, the patterning of the source and drain electrodes 16a and 16b, the light shielding film 18, the upper insulating film 17, and the semiconductor. Only three times of simultaneous patterning of the layer 14 are required. Therefore, a thin film transistor provided with the light-shielding film 18 can be manufactured at a low cost with a small number of patterning steps. Since the occurrence rate of a mask alignment error or the like becomes low, the manufacturing yield can be improved.

In the above embodiment, the source and drain electrodes 16a and 16b are formed on the semiconductor layer 4 via the n-type semiconductor layer 15, but the n-type semiconductor layer 15 is not always necessary.
When eliminating the n-type semiconductor layer 15, the above-mentioned n-type semiconductor layer
The step 15 is unnecessary. In the above embodiment, the TFT
Although the manufacture of a thin film transistor for selecting a pixel electrode formed in a TFT panel for an active matrix type liquid crystal display element has been described, the present invention is applied to all thin film transistors in which a light shielding film is provided on a semiconductor layer via an upper insulating film. You can do it.

〔The invention's effect〕

In the method of manufacturing a thin film transistor according to the present invention, after forming a gate electrode on a substrate, a gate insulating film, a semiconductor layer, and a metal film are sequentially deposited thereon, and the metal film is patterned to form source and drain electrodes. After that, an upper insulating film and a light shielding film are sequentially deposited thereon, and the light shielding film and the upper insulating film are patterned into the same shape, and the semiconductor layer is formed into a transistor element shape using the source and drain electrodes as a mask. Since patterning is performed, a thin film transistor having a light-shielding film can be manufactured with low number of patterning steps at low cost and with high yield.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a thin film transistor showing an embodiment of the present invention, and FIG. 2 is a manufacturing process diagram of a conventional thin film transistor. 11 ... substrate, 12 ... gate electrode, 13 ... gate insulating film,
14 ... semiconductor layer, 15 ... n-type semiconductor layer, 16 ... metal film,
16a: Source electrode, 16b: Drain electrode, 17: Upper insulating film, 18: Light shielding film, 20: Pixel electrode.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/336 H01L 29/786 G02F 1/136 500 G02F 1/1343

Claims (1)

(57) [Claims] 1. A method of manufacturing a thin film transistor provided with a light-shielding film, comprising: forming a gate electrode on a substrate, sequentially depositing a gate insulating film, a semiconductor layer, and a metal layer thereon;
After forming the source and drain electrodes by patterning the metal film, an upper insulating film and a light-shielding film are sequentially deposited thereon, and the light-shielding film and the upper insulating film are patterned into the same shape and the semiconductor layer is formed. Is patterned into a transistor element shape using the source and drain electrodes as masks.