JPS62131578A - Manufacturing method of thin film transistor - Google Patents

Abstract

PURPOSE:To improve a contact characteristic, by forming a high resistance semiconductor film, a low resistance semiconductor film and a metal film on a gate electrode and on a part of a gate-electrode taking out part, forming a transparent conductor film after etching, and removing the metal film and the low resistance semiconductor film with the transparent conductor film as a mask. CONSTITUTION:On an insulating substrate 1, a gate electrode 2 and a gate-electrode taking out part 2' for external connection are selectively formed. Then, the gate- electrode taking out part 2' is masked except a part thereof. A gate insulating film 3, a high resistance semiconductor film 4, a low resistance semiconductor film 7 and a metal film 12 are successively deposited. Then, with resist 13 as a mask, selective etching is performed. An oxide film layer on the surface of the metal film 12 is removed. Thereafter, a transparent conductor film 14 is continuously deposited. With resist 15 as a mask, etching is performed. A source electrode 14-2 and a drain electrode 14-1, which serve the hole of picture element electrodes, and a transparent conductor film 14-3, are formed. With these parts as masks, the metal film 12 and the low resistance semiconductor film 7 are selectively removed. Then the resist 15 is peeled off. Thus an excellent contact characteristic for the source, the drain and the gate electrode taking out part can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing thin film transistors in active matrix liquid crystal display devices at low cost and with high yield.

[Summary of the invention]

A gate electrode is formed on an insulating substrate, a part of the gate electrically excavated lead-out part is masked, and a gate insulating film, an extremely thin high-resistance semiconductor film, an extremely thin low-resistance semiconductor film, and a metal film are successively formed. A high-resistance semiconductor film, a low-resistance semiconductor film, and a metal film are selectively formed in almost the same shape on the gate electrode and a part of the gate electrode extension part, and after sputter etching, a transparent conductive film is successively deposited. ,j3 By selectively forming a transparent conductive film on the lead-out portions of the source electrode, drain electrode, and gate electrode, and selectively removing the metal film and the low-resistance semiconductor film using the transparent conductive film as part of a mask, ,
It does not require light shielding, requires fewer manufacturing steps (3-mask process), and provides good contact between the source and drain electrodes, making it possible to produce thin film transistors that are low-cost active matrix liquid crystal display substrates. .

[Conventional technology]

For example, the sixth example shows an example of the manufacturing method of a thin film transistor, which is a display device substrate in a conventional active matrix liquid crystal display device using amorphous silicon (a-3L).
The figure (shown in 81-Tel, FIG. 6 ta) shows that Cr, A1. Gate electrode 2 made of Mo etc.
A cross-sectional view showing selectively formed after deposition using a sputtering device or the like is shown. A lead-out portion 2′ of the gate electrode 2 is also shown.

In the sixth step (6th opening), a gate insulating film 3 such as silicon dioxide or silicon nitride, and a high resistance semiconductor film 4 such as amorphous silicon are successively deposited, and the high resistance semiconductor film 4 is selectively etched.

Next, a glabellar insulating film 5 such as silicon dioxide and a pixel electrode 6 which is a transparent conductive film such as [TO] are deposited, and the pixel electrode 6 is selectively etched.
This shows the state in which the hole has been drilled. FIG. 6 (d+ indicates a metal film such as a low resistance semiconductor film 7 (for example, a N7 amorphous silicon film A/) is deposited and selectively etched to form a drain electrode 8.
Source electrode 9. Gate drawer': 4. The state in which ilo is formed is shown. Further, the source electrode 9 and the pixel electrode 6 are connected. FIG. 6(e) shows a cross-sectional view in which a surface protective film 11 made of silicon dioxide or the like is deposited, and part of the surface protective film 11 of the pixel electrode 6 and the gate extraction electrode 10 is exposed by etching. Although not shown, the surface protective film 11 of the drain electrode extension portion is also etched and notched to form contact with the outside. In many cases, the surface protection film 11 also serves as a light shield, or a light shielding film is formed on the surface protection film 11.

[Problem that the invention seeks to solve]

In the conventional method for manufacturing thin film transistors for active matrix display device substrates, as shown in the example in Figure 6, there are many masking steps (six or more), which makes it impossible to provide low-cost thin film transistors for display devices, and interlayer insulation. Membrane 5. When forming an extremely thin high-resistance semiconductor film 4 (for example, an amorphous silicon film with a thickness of 500 Å or less) that does not require the formation of a light-shielding film in order to open the gate insulating film 3, the gate electrode extension portion 2° If etching is performed until the upper gate edge [3] is completely opened, the gate insulating film 3 of the transistor section will be etched due to pinholes in the amorphous silicon film 4, resulting in a drop in breakdown voltage or a short circuit. Pixel defects, line defects, etc. occur, resulting in poor yield.

Furthermore, it is difficult to judge whether the gate insulating film 3 of the gate electrode lead-out portion 2' has been completely etched, and if the etching proceeds to the next step without being completely etched, a defect will result. Furthermore, it is difficult to obtain good contact between the gate lead electrode and the gate electrode lead part 2'. Further, after depositing the high resistance semiconductor film 4, the low resistance semiconductor film 7 is formed after going through an etching process or the like.
(For example, when a N7 amorphous silicon film is deposited, a natural oxide film is formed on the surface of the high-resistance semiconductor film 40, making it impossible to obtain good contact with the low-resistance semiconductor film 7, resulting in poor transistor characteristics. Ta.

[Means for solving problems]

In order to solve the above problems, the present invention provides a gate insulating film,
A high-resistance semiconductor film, a low-resistance semiconductor film, and a metal film are sequentially deposited by masking a part of the gate electrode lead-out part with a metal mask, etc., and the high-resistance semiconductor film, the low-resistance semiconductor film, and the A resistive semiconductor film and a metal film are selectively formed in almost the same shape, a transparent conductive film is formed after sputter etching, a transparent conductive film is selectively formed on a source electrode, a drain electrode, and a gate electrode lead-out portion, and then a transparent conductive film is selectively formed. The above-mentioned problem was solved by selectively removing the metal film and the low-resistance semiconductor film using the mask as part of the mask.

[Effect]

The thin film transistor for an active matrix display device configured as described above can not only be produced in three mask steps, but also has good contact between the source electrode, drain electrode, and gate lead electrode, and is a thin film transistor that does not require a light shielding film. A thin film transistor for a cost-active matrix display device can be provided.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1(al~(fl) and FIG. 2(al~()) are a plan view and a cross-sectional view of a unit pixel portion and a gate electrode lead-out portion of a thin film transistor for an active matrix display device according to a first embodiment of the present invention. The manufacturing method shown in the figure is as follows.
A cross-sectional view taken along the line A-A' in Figure +Ill) shows that a gate electrode 2 and a gate electrode extension portion 2° for external extraction are selectively formed using Cr, Ni, NiCr, etc. on an insulating substrate l such as glass. Indicates the state of FIG. 1 (bl (in FIG. 2) is a cross-sectional view along line B-B' green in FIG. ．． High resistance semiconductor film 4, low resistance semiconductor film 7.
A state in which the metal film 12 is continuously deposited and the above film is not deposited on the gate electrode extension part 2' is shown. For example, SiH,
and N.H.

A nitride film (SiNX
), an amorphous silicon film (a-5t:H) as the high-resistance semiconductor film 4 using S+Ha, PHs and S
From the mixed gas of i Ha to the low-resistance semiconductor film 7, N゛a7morphous silicon film'a-5i:H) WorenVt
to form. Next, the metal film 12 is formed of Cr, Ni, NiCr, etc. by sputtering or vapor deposition. Note that if an in-line type device consisting of plasma CVD and sputtering is used, the gate insulating film 3. a-5t;)(
Film 4, N″a-5i: H film 7. The metal film 12 can be continuously deposited without exposing it to the atmosphere.
becomes a part of the drain electrode wiring, which will be described later, and is effective in reducing the wiring resistance. Also ITO and N'a-5i
Although it is difficult to obtain effective contact characteristics with the :H film 7, effective characteristics can be obtained since it is in contact with ITO via the metal film 12 (Cr, Ni, NiCr), etc.

Figure 1 (C) (Figure 2 fcl is c-c' in Figure 1 (C)
In the cross-sectional view taken along the line), resist 13 is applied and exposed.

After development, the metal film 1 is formed using the resist 13 as a mask.
2. Low resistance semiconductor film7. A state in which the high-resistance semiconductor film 4 is continuously and selectively etched is shown.

At this time, it is important to leave the resist 13 on the gate electrode extension part 2'' so that the gate electrode extension part 2'' is not etched during the etching of the metal film 2. Figure 2 (fd) is a cross-sectional view taken along the line DD' in Figure 1 + di), which shows that after the oxide film layer on the surface of the metal film 12 is removed (for example, by sputter etching or plasma etching), a layer of ITO or the like is continuously etched. The transparent conductive film 14 is deposited on the transparent conductive film 14 without removing the oxide film layer on the surface of the gold G!4 film 12 and depositing the transparent conductive film 14 without exposing it to the atmosphere, so good contact can be obtained. 1(e) (FIG. 2 (el is a sectional view taken along line EE' in FIG. 1) shows that after coating the resist 15, exposing and developing, the transparent conductive film is removed. 14 is etched to form a source electrode 9 (14-2) which also serves as a pixel electrode, and a drain electrode 8 (14-2).
1) is shown. At this time, is there also a transparent conductor 2° above the gate electrode extension part? 1ill14-3 is formed. If the transparent conductive film 14-3 is not formed, when etching the transparent conductive film 14-3 (mainly etching with hydrochloric acid),
When the gate electrode extension part 2'' is etched, when the metal film 12 is etched in the next step, the gate electrode extension part 2'' is also etched, making it impossible to form a substrate for a display device. (f) (FIG. 2ffl is a cross-sectional view along the line FF' of fl). After forming the metal film 12 and the low resistance semiconductor film 7 selectively using the transparent conductive film 14-1.14-2.14-3 as part of a mask without peeling off the resist 15, The N''a-3i:H film 7 is generally etched by plasma etching using a CF1-based gas or etching using a mixed solution of fluoric acid and nitric acid.

In the method using CF, system gas, or a mixture of hydrofluoric acid and nitric acid,
a-5i: H$4 and Na-Si: H film 7
The etching rate is fast, and the etching rate hardly changes. ITJ is difficult. Therefore, when the thickness of the a-5i:H film 4 is extremely thin (for example, 500 Å or less), which is not easily affected by light, a-5i
: There are times when the H film 4 is completely etched and no transistor is formed. Therefore, when the thickness of the a-5i:H film 4 is 500 Å or less, the N'a-5i:H film 7
The film thickness is 200 Å or less, and an 'isJ film transistor is formed by oxygen plasma etching or sputter etching. With the above method, the a-5i:H film 4 can be extremely stably fabricated into a thin film transistor with little damage. In addition, since there is no process of opening holes in the insulating film, the source, drain,
Good contact characteristics of the gate electrode lead-out portion can be obtained. Although not shown, the drain electrode 8 extends to form a part where the drain electrode wiring and the drain 1 are pulled out, and the line resistance is reduced due to the two-layer structure of the metal film 12 and the transparent conductive film 14. preferable. Through the above three mask steps, a thin film transistor for an active matrix display device can be produced.

3(a-1f) are cross-sectional views of a thin film transistor for an active matrix display device according to a second embodiment of the present invention.
(Figure 3+al shows an example for stably manufacturing the thin film transistor of the present invention shown in rl at a higher yield.
is the same as the manufacturing process shown in Fig. 2('b).
After forming the rod 2, the gate electrode extension portion 2° is masked with a metal mask or the like, and the gate insulation 193. High resistance semiconductor film 4. Low resistance semiconductor film7. A state in which the metal film 12 is continuously formed is shown. FIG. 3 (bl shows that after applying the resist 13, exposing and developing the resist pattern so that a resist pattern is formed on the gate electrode 2 and 2 degrees above the gate electrode extension part, the metal film 12
Figure 3 (for example, a Cr film) showing an etched view
In C1, after etching the metal film 12, the low resistance semiconductor film 7 (e.g. N''a-5i:l (film)) and the high resistance semiconductor film 4 (e.g. a-5i:H film) are etched with hydrofluoric acid. An example of etching with a mixed solution of nitric acid and nitric acid is shown below.
As in l, N''a-5i:H film 7 and a-3i:
The H film 4 is formed in a smaller pattern than the metal film 12 (for example, a Cr film). A similar problem is also likely to occur in plasma etching using CF or other gases. Figure 3 +d+ shows the state in which the metal film 12 is etched again so that the gold 8 film 12 (for example, Cr film) has a smaller pattern than the N''a-3i:)I film 7 and the a-3i:H film 4. 3 shows the state in which the resist 13 has been peeled off.The subsequent steps are performed in the same manner as in FIG.
A thin film transistor as shown in Figure (fl) is obtained. As can be seen from Figure 3 ffl, the ITO
The source electrode 14-2 is connected to the metal film 12 without disconnection at the end of the transistor.

Fig. 4 Fa1-(fl is a cross-sectional view of a thin film transistor according to the third embodiment of the present invention. Fig. 4 ta) and Fig. 4 (b) are exactly the same as Fig. 3 + al and ibl. The explanation will be omitted from here. FIG. 4(C) shows a state in which, after etching the metal film 12, the resist 13 is deformed and heat-treated at a temperature (for example, 150° C. or higher) to form a pattern larger than the metal film 12. Figure 4 +dl shows the low resistance semiconductor film 7 (N″a-9i:)I film) and the high resistance semiconductor film 4 (a
-Si:) (film) is shown in an etched state.

N'' a-5i: H film 7 and a-5i: A resist 13 is formed to a degree that allows some side etching (approximately 2 μm) to occur on HRQ4. The subsequent steps are carried out in the same manner as shown in FIGS. 2 fdl to (fl) to obtain a thin film transistor as shown in FIG. Figures ta+ to te+ show the fourth aspect of the present invention.
1 is a cross-sectional view showing an example of a thin film transistor for an active matrix display device according to an example.

Figures 5(al to 5e) show examples for producing the A-film transistors of the present invention shown in Figures 2(al to (fl) with a higher production yield. Figure (al~
(It is exactly the same as the process up to C1, and the metal film 12 (for example, C
"film).

After selectively forming a low resistance semiconductor film 7 (N'a-Si:+1 film) and a high resistance semiconductor [4<a-3r:H film], the resist is separated by 211 points. Figure 5 (bl is transparent conductive film 14-1.14-2.14-3 (for example, ITO film)
After depositing ITO, apply resist 15, expose and develop it.
ITo film 14-1.1 showing a state where films 14 to 1.11-2.14-3 have been etched with a solution containing hydrochloric acid as a main component.
4-2.14-3 is often formed as shown in the figure because it is easy to side-etch.The tel in FIG. 5 shows that the resist I5 is formed after the ITO film 14-1. FIG. 5fd+ shows a state in which the metal film 12 and the low resistance semiconductor are heat-treated at a temperature (for example, 150° C. or higher) that deforms and completely covers the ITO film 14-1.14-2.14-3. A state in which the film 7 is etched is shown. Figure 5 (el
1 shows a state in which the resist 15 has been peeled off. Figure 5 ft1
As can be seen from l, ITOIIJ14-1.14-2
．． Even if side etching occurs in 14-3 and the pattern becomes smaller, the source electrode 17 (7,
12, 14-2), drain electrode 16 (7, 12
, 14-1) is determined by the metal film 12, so the transistor does not become an offset gate, which is preferable. Furthermore, a stable thin film transistor can be obtained without an increase in wiring resistance of the drain electrode 8 or disconnection due to thinning of the pattern.

It should be noted that the present invention can achieve more effective effects by combining the embodiments shown in FIGS. 3 and 5 or by combining the embodiments shown in FIGS. 4 and 5. [Effects of the Invention] As described above, With three mask steps (5 n-light development steps), it is possible to provide a thin film transistor for an active matrix display device with good contact characteristics and low cost yield. In addition, a-
Although the embodiment has been described using a 5-inch film transistor as an example, the optical C
Semiconductor thin films and p-Si by VD and ion beam deposition methods
It is also applicable and effective to thin films and semiconductor thin films other than S1.

[Brief explanation of drawings]

Figure 1 (al~(fl) is a plan view along the manufacturing process of the thin film transistor according to the first embodiment of the present invention, Figure 2 +8
) to () are cross-sectional views corresponding to FIG. 1+al to ifl, respectively, and FIG.
4(a) to 4(r) are cross-sectional views along the manufacturing process of a thin film transistor according to a third embodiment of the present invention, and FIG. 5(a)
+ to te+ are cross-sectional views along the manufacturing process of a thin film transistor according to the fourth embodiment of the present invention, and FIGS. 6(5) to (cl
These are cross-sectional views along the manufacturing process of a conventional 7i film transistor. 1 - Insulating substrate 2 - Gate electrode 2° - 11 - Gate electrode extension part 3 - Gate insulating film 4 - High resistance semiconductor film 7 - Low resistance semiconductor film 8 - -・-Drain electrode 9--1-・Source electrode 12-11-1・Metal film 14-・Transparent conductive film Applicant Seiko Electronics Co., Ltd. 2' (a) No. 10 Fig. 1 Base No. 3 Figure 3 - No.
ζ-no
-ノ 、ノ 張5
figure

Claims (5)

[Claims] (1) a) First step of selectively forming a gate electrode on an insulating substrate b) At least a part of the gate electrode extension part is masked to form a gate insulating film, a high-resistance semiconductor film, a low-resistance semiconductor film, a second step of continuously depositing metal films; c) a third step of leaving the high-resistance semiconductor film, low-resistance semiconductor film, and metal film in substantially the same shape on at least the gate electrode and a part of the gate electrode extension part; d) ) A fourth step of successively depositing a transparent conductive film after removing the oxide film layer on the surface of the metal film e) Selectively depositing the transparent conductive film on the source electrode, the drain electrode wiring, and the gate electrode extension part that also serves as the pixel electrode f) a sixth step of selectively removing the metal film and the low-resistance semiconductor film, using the transparent conductive film as at least a part of a mask. (2) In the third step, after etching the metal film using the same mask, the low-resistance semiconductor film and the high-resistance semiconductor film are etched so that the metal film has a smaller pattern than the high-resistance semiconductor film and the low-resistance semiconductor film. 2. The method of manufacturing a thin film transistor according to claim 1, further comprising etching the metal film again. (3) In the third step, after etching the metal film using the same mask, heat treatment is performed at a temperature that deforms the resist and causes the edges of the resist to expand beyond the edges of the metal film, forming a low-resistance semiconductor film and a high-resistance semiconductor film. A method for manufacturing a thin film transistor according to claim 1, characterized in that a resistive semiconductor film is etched. (4) In the sixth step, the metal film and the low-resistance semiconductor film are selectively removed after heat treatment at a temperature at which the resist is deformed after the end of the fifth step. manufacturing method. (5) The method for manufacturing a thin film transistor according to claim 1, wherein the high-resistance semiconductor film has a thickness of 500 Å or less, and the low-resistance semiconductor film has a thickness of 200 Å or less.