JP2001308182A - Method for forming contact with chromium film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a contact having a low contact resistance when a contact is formed for a Cr film by making an opening in an insulation film formed on the Cr film. SOLUTION: An etching mask of photoresist film having an opening pattern of contact holes is formed on a pixel transistor part 12, a gate terminal part 14, a drain terminal part 16, and a D-G junction 18 of a protective transistor. By an RIE method using an SF6 based gas as an etching gas, contact holes 40, 42, 44, 46, 48 each having a wall tapered to decrease the opening dimensions downward are opened in the pixel transistor part 12, the gate terminal part 14, a first region of the D-G junction 18, the drain terminal part 16, and a second region of the D-G junction 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a contact with a Cr film, and more particularly, to a method for reducing the electric resistance between a Cr film and a conductive contact.
The present invention relates to a method for forming a contact with a Cr film.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices, particularly in the manufacture of liquid crystal display devices, contacts are often formed on Cr wirings covered with insulating films such as SiO ₂ films and SiN _X films. Conventionally, when forming a contact, a CF-based gas such as CF
_The insulating film covering the Cr wiring is etched by a dry etching method using a ₄ gas as an etching gas, for example, an RIE (reactive ion etching) method through an etching mask having a contact hole opening pattern, and penetrates the insulating film. Thus, a contact hole for exposing the Cr wiring is opened. For example, JP-A-6-202153 discloses that when a reverse staggered active matrix substrate used as a liquid crystal panel of a liquid crystal display device is manufactured, a passivation film, or a passivation film and a gate insulating film are opened and each electrode is formed. A method for forming a connecting contact is disclosed.

Here, with reference to FIGS. 5 to 7, a conventional method for forming a contact with each electrode when manufacturing an inverted staggered type active matrix substrate described in Japanese Patent Application Laid-Open No. 6-202153 will be described. explain. FIGS. 5A to 5D are cross-sectional views showing the configuration of the drain terminal portion, the TFT portion, the pixel portion, and the gate terminal portion of the inverted staggered active matrix substrate immediately before opening the contact hole, respectively. . FIGS. 6A to 6D are cross-sectional views showing the configurations of the drain terminal portion, the TFT portion, the pixel portion, and the gate terminal portion when the contact holes are opened. FIGS. 7A to 7D respectively show a drain terminal portion at the stage when a contact is formed,
It is sectional drawing which shows the structure of a TFT part, a pixel part, and a gate terminal part.

The drain terminal section 72, the TFT section 74, the pixel section 76, and the gate terminal section 78 shown in FIGS. 5 to 7, respectively, are main parts constituting an inverted staggered active matrix substrate. The drain terminal 72 is provided with each TFT functioning as a switching element between the drain bus line and the gate bus line of the active matrix substrate.
This is a terminal for connecting a drain bus line connected to the drain electrode of the (thin film transistor) to an external control circuit. The pixel unit 76 is a driving unit that drives liquid crystal, and includes an additional capacitance element and a pixel electrode. The gate terminal 78 is connected to each T
A terminal for connecting a gate bus line connected to the gate electrode of the FT to an external control circuit.

As shown in FIG. 5A, an n ⁺ formed on a transparent insulating substrate 80 as a lower electrode via an insulating film 82 and an i-type a-Si layer 84 is formed on a drain terminal portion 72.
A laminated film of the mold a-Si layer 86 and the Cr film 88 and a passivation film 90 formed on the laminated film are formed.

[0006] As shown in FIG.
A Cr film formed on the transparent insulating substrate 80
A gate electrode 92 and a gate insulating film 82a;
An a-Si active layer 84a sequentially formed on the electrode 92;
A channel protection film 94 is formed. Also, the TFT section 74
In the opposite positions on both sides of the channel protective film 94,
n ⁺Via the mold a-Si bonding layers 86a and 86b, respectively.
A saw made of a Cr film and connected to the a-Si active layer 84a
The source electrode 96a and the drain electrode 96b are formed. Saw
On the source electrode 96a and the drain electrode 96b and the source
Channel protection between electrode 96a and drain electrode 96b
On the film 94, a passivation film 90 is formed.
You.

The additional capacitance element region of the pixel section 76 is shown in FIG.
As shown in (c), a lower electrode 98 made of a Cr film formed on a transparent insulating substrate 80 and a dielectric made of an insulating film 82 and an i-type a-Si layer 84 formed on the lower electrode 98 And a top electrode composed of an n ⁺ -type a-Si layer 86 and a Cr film 88. Similarly, as shown in FIG. 5C, the pixel electrode region of the pixel portion 76 has an a-Si active layer 84a formed on a transparent insulating substrate 80 via an insulating film 82, and an n ⁺ -type a- It has a laminated film composed of an Si layer 86 and a Cr film 88. A gate bus line 100 made of a Cr film is formed on the transparent insulating substrate 80 beside the pixel electrode region. Further, a passivation film 90 is formed over the entire surface of the pixel portion 76.

As shown in FIG. 5D, a lower electrode 102 made of a Cr film formed on a transparent insulating substrate 80 and a film formed on the lower electrode 102 are sequentially formed on the gate terminal portion 78. An insulating film 82 and a passivation film 90 are formed.

In this embodiment, the TFT 7 is used as a contact.
4 of the source electrode 96a and C of the pixel electrode region of the pixel portion 76.
r film 88 and Cr film 88 of the additional capacitance element of pixel portion 76
Is formed to connect to the pixel electrodes. At the same time, in order to prevent oxidation of the Cr terminal 88 composed of the Cr film 88 of the drain terminal portion 72 and the Cr film of the gate terminal portion 78, an oxide conductive film of the same material as the pixel electrode is formed on the Cr film. Form a film.

When forming a contact, first, a contact hole is opened. In this example, the passivation film 90 and the gate insulating film 82 are etched by a dry etching method using an etching gas containing CF ₄ gas as a main component, and as shown in FIGS. The film 90 and the gate insulating film 82 are opened in a tapered shape, and the source electrode 96a of the TFT portion 74,
Drain terminal part 72, pixel part 76, and gate terminal part 7
Contact holes 104 exposing the respective Cr films 88 of FIG.
a, 104b, 104c and 104d are formed.

Next, a transparent conductive film made of ITO or the like is formed, and as shown in FIGS.
The contact hole 10 is patterned into a predetermined shape.
4a and 104c, the source electrode 96a and the pixel portion 76
The pixel electrode 106 connected to the Cr film 88 in the pixel electrode region and the Cr film 88 of the additional capacitance element is formed. At the same time, an upper electrode 108 connected to the Cr film 88 of the drain terminal 72 via the contact hole 104b is formed, and an upper electrode 110 covering the Cr film 88 of the gate terminal 76 via the contact hole 104d.

[0012]

However, as described above, C
The conventional method of forming a contact by opening a contact hole exposing the Cr film by etching the insulating film on the r film with a CF-based gas includes the electrical resistance between the contact, that is, the transparent conductive film and the Cr film. Is extremely large. In this case, it is difficult to produce an active matrix substrate having good characteristics. For example, in a liquid crystal display device using an active matrix substrate manufactured in this way, the contact resistance between the Cr film of the source electrode and the pixel electrode made of ITO increases, and image display defects are likely to occur.

In the above-described example, taking an example of manufacturing an inverted staggered type active matrix substrate, an insulating film on the Cr film is opened to expose the Cr film, and then the transparent conductive film and the Cr film are exposed.
Although the problem of contact formation when making connection with the film has been described, this problem is not limited to the connection between the transparent conductive film and the Cr film, and the Cr film is formed by RIE using a CF-based gas as an etching gas. This is a universal problem that arises when a contact hole is opened by etching the upper insulating film and then forming a contact connected to the Cr film.

Therefore, an object of the present invention is to provide a method for forming a contact with a Cr film by opening an insulating film on the Cr film.
An object of the present invention is to provide a method for forming a contact having low electric resistance.

[0015]

Means for Solving the Problems The present inventor has proposed a method for forming a Cr film.
The process of studying the problems of conventional contact forming methods
Therefore, the resistance of the contact to the Cr film is increased because
When opening contact holes, use etching gas
Gas containing a CF-based gas as a main component, for example, CF _FourGas
Because of the use of gas as the main component, electrically insulating
Chromium nitride (CrF_X) But over-etched
On the surface of the Cr film, for example, on the surface of the Cr film in the opening in the above example,
It has been found through experiments that it is due to An example
For example, in the case of the active matrix substrate described above,
For example, at the gate terminal, passivation film and gate
Etch both insulating films to open contact holes
The source electrode has a passivation
When only the film is etched, the Cr film is exposed and
Exposed during the etching of the gate insulating film at the
The Cr film is exposed to the etching gas, and the CrF_X
Is generated. This phenomenon occurs when the gate terminal
This is for simultaneously opening the part and the source electrode. 5 seconds
20 seconds to open the gate terminal
CrFx is also generated in the mouth, but the amount is
Alternatively, it is smaller than that of the drain terminal portion. For example, secondary b
Analysis by on-mass spectroscopy (SIMS)
Opening Cr surface or contact between Cr and ITO
, Fluorine F is detected. Therefore, the present inventor
CrF on Cr film_XShould not be generated, and
And generated CrF_XInspired to remove
Was.

Then, CrF is formed on the Cr film._XDo not generate
In order to avoid this problem, use SF-based gas instead of CF-based gas.
E.g. SF₆Using gas, conductive chromium sulfide
(CrS _X) Is formed on the Cr film, but is electrically insulating
CrF_XIs hardly formed, and therefore,
Significantly reduce the electrical resistance between contact metals
Experiments to confirm that
It has arrived. When analyzed using SIMS, SF₆gas
RIE dry etching using Cr
Sulfur S was detected from the product. Also, slightly generated C
rF_XOxygen ashing, plasma etching with rare gas
By removing it by the etching process etc.,
The electric resistance between the contact metal can be further reduced
I found

In order to achieve the above object, a method for forming a contact with a Cr film according to the present invention (hereinafter, referred to as a first invention method) is based on a method of forming a chromium (C) layer formed under an insulating film.
r) A method of forming a contact to the film, wherein the insulating film on the Cr film is formed by an RIE dry etching method using an etching gas containing SF ₆ gas as a main component through an etching mask having an opening pattern of a contact hole. And a dry etching step of opening a contact hole exposing the Cr film, and filling the contact hole with a conductive film, or forming a conductive film on the side wall of the contact hole and on the exposed Cr film to form a Cr film. And a contact forming step of forming a conductive contact for electrical connection.

In the first invention method, the etching gas is:
There is no limitation as long as the gas contains SF ₆ gas as a main component, but preferably, a gas in which the ratio of SF ₆ gas is higher than that of CF gas, most preferably an SF ₆ gas-based etching gas containing no CF-based gas. Use In the first invention method,
Chromium fluoride (CrF _x ) having high insulation resistance is hardly formed on the Cr film, and instead, conductive chromium sulfide (C
Since rS _X) is produced, the contact resistance between the Cr film and the contact is reduced.

In applying the first and second methods of the present invention described below, the composition of the Cr film is not restricted, but the Cr film has high purity.
It can be suitably applied when forming a contact to a film, for example, a Cr film having a purity of 99.9% or more. It is not necessary that the electrode or the wiring under the insulating film is formed of a single layer of the Cr film, and the surface layer connected to the conductive film such as the oxide conductive film ITO is made of Cr.
Any film is acceptable. For example, if the surface layer is a Cr film, the electrodes or wirings may be formed as a laminated film of a Cr layer and an Al layer or a Cr layer and an Al alloy layer. Further, a laminated film in which an Al layer or an Al alloy layer is covered with a Cr film may be used.
The Al alloy layer is made of, for example, Al-Nd, Al-Si, Al
-An alloy layer of Si-Cu or the like.

Further, the first and second embodiments of the present invention described below are applicable.
For use, there is no restriction on the composition of the insulating film._Two
SiN_XA film may be used. As the gate insulating film,
Not only a single layer but also a combination of these, ie, a glass substrate
And SiO on the gate electrode_TwoFilm and SiN deposited on it
_XBilayer structure of film, glass substrate and SiN on gate electrode _X
Film and SiN deposited on it_XA two-layer structure of a film may be used.
Of course, it is disclosed in Japanese Patent Application Laid-Open No. 1-106470.
Cover the glass substrate and the gate electrode with an insulating film
After cleaning the substrate,_XCover the membrane
However, this is not the essence of the present invention. However, according to the present invention,
If the gate insulating film has a single-layer or two-layer structure,
It is clear that the effect is obtained. Also, remove the insulating film
The dry etching method for etching is plasma etching.
Method, especially reactive ion etching (RIE) method
It is. There is no restriction on the composition of the conductive film.
(Indium tin oxide) film, other metal film, polysilicon
Film may be used. There are no restrictions on the method of forming the conductive film.
Alternatively, a sputtering method or a CVD method may be used. First and second
In the method of the invention, the contact is not necessarily formed when forming the contact.
It is not necessary to completely fill the tact hole with a conductive film.
Contact while leaving a recess in the center of the contact hole
A conductive film is formed on the side wall of the through hole and the Cr film, and the conductive film is formed.
It may be electrically connected to the Cr film via the electric film.
No.

In a preferred embodiment of the first invention method, after the dry etching step and before the contact forming step, an oxygen ashing process is performed on the Cr film exposed at the bottom of the contact hole and the etching mask. Having. As a result, chromium fluoride (CrF _x ) on the Cr film exposed at the bottom of the contact hole can be removed to further reduce the contact resistance and improve the removability of the etching mask.

In a further preferred embodiment of the method of the first invention, the dry etching step is followed by He gas or Ar gas.
And a sputter etching step of performing a sputter etching process using a gas as an etching gas. As a result, the chromium fluoride (CrF _x ) on the Cr film exposed at the bottom of the contact hole is removed by a rare gas / plasma etching process, and the remaining Cr is removed by an oxygen ashing process.
Since F _X can be removed, the contact resistance can be further reduced. In addition, Ar gas,
He gas and the like can be mentioned. Practically, RIE
Subsequent to the dry etching step, a sputter etching step is continuously performed in the same dry etching apparatus.

In a further preferred embodiment of the first invention method, before the dry etching step, there is provided a wet etching step of etching the insulating film by a wet etching method via an etching mask having a contact hole opening pattern. Then, in a dry etching step, a contact hole is opened through an etching mask by a dry etching method, or the contact hole opened in a wet etching step is shaped.
By using the wet etching method together, the time required for opening the contact hole can be reduced, and the productivity can be improved. The etchant used in the wet etching method of the first and second inventions may be a liquid containing at least hydrofluoric acid.

As another method for achieving the above object, a method of forming a contact with a Cr film according to the present invention (hereinafter referred to as a second invention method) is a method of forming a contact with a chromium (Cr) layer formed under an insulating film. A) a method of forming a contact with the film, wherein the RIE dry etching method using an etching gas mainly composed of a CF-based gas is used to form a Cr through an etching mask having an opening pattern of a contact hole;
A dry etching step of etching the insulating film on the film and opening a contact hole exposing the Cr film, a step of performing a sputter etching process using He gas or Ar gas as an etching gas, and forming the contact hole into a conductive film. And forming a conductive film on the side wall of the contact hole and on the exposed Cr to form a conductive contact electrically connected to the Cr film.

In the second invention method, the CF-based gas means a CF-based gas conventionally used in a dry etching method, for example, a gas such as a CF ₄ gas and a CHF ₃ gas.
A mixed gas containing O ₂ gas may be used. In a second inventive method, by removing the generated noble gas plasma etching treatment CrF _X and on the Cr film, it is possible to reduce the contact resistance between the Cr film and the contact.

[0026]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 This embodiment is an example of an embodiment in which the method for forming a contact with a Cr film according to the first invention method is applied to manufacture an inverted staggered active matrix substrate. FIG. 1 shows an insulating film to be etched to form a contact according to the method of the present embodiment, and Cr under the insulating film.
FIG. 2 is a circuit diagram of an inverted staggered type active matrix substrate, FIG. 3 is a sectional view showing a state where a contact hole is opened, and FIG. 4 is a sectional view showing a state where a contact is formed. By applying the method of forming a contact with a Cr film according to the present embodiment, the insulating film is etched, and the contact film is opened and exposed. As shown in FIG. This is present in the section 14, the drain terminal section 16, and the drain-gate (DG) connection section 18 of the protection transistor, respectively. The pixel transistor section 12, the gate terminal section 14, the drain terminal section 16, and the DG connection section 18
Are elements constituting a vertical electric field (twisted nematic: TN) type liquid crystal display active matrix substrate 10 (see FIG. 2), as shown in FIG.

As shown in FIG. 1, the pixel transistor portion 12 includes a gate electrode 22 made of Cr formed on a transparent insulating substrate 20 and a lower gate insulating film made of a 200 nm-thick SiN _X film or a SiO ₂ film. Film 24 and film thickness 3
I-type a-Si layer 2 formed on gate electrode 22 via upper gate insulating film 26 made of a 00 nm SiN _x film
8 is provided. After the lower gate insulating film is formed, the upper gate insulating film may be coated after cleaning. Further, the pixel transistor section 12 is provided at opposite positions on both sides of the i-type a-Si layer 28 with Cr films connected to the i-type a-Si layer 28 via n ⁺ -type a-Si layers 30a and 30b, respectively. A source electrode 32a and a drain electrode 32b.
I-type a- on the source electrode 32a and the drain electrode 32b and between the source electrode 32a and the drain electrode 32b;
On the Si layer 28, a passivation protection film 34 made of a 300 nm-thick SiN _x film is formed.

As shown in FIG. 2, the pixel transistor section 12 is formed near the intersection of a gate line 36 connected to the gate terminal section 14 and a drain line 38 connected to the drain terminal section 16, and the gate electrode 22 is The drain electrode 32b is connected to the gate line 36 and the drain line 38.

As shown in FIG. 1, the gate terminal 14 is
A gate line 36 made of Cr formed on the transparent insulating substrate 20 in the same step as the gate electrode 22, and a lower gate insulating film 24, an upper gate insulating film 26, which are sequentially formed on the gate line 36, and And a passivation protection film 34.

The drain terminal portion 16 is formed on the transparent insulating substrate 2
Lower gate insulating film 24 and upper gate insulating film 26
A drain line 38 made of a Cr film formed through
And a passivation protection film 34 formed on the drain line 38.

The DG connecting portion 18 is formed on the gate line 36 made of a Cr film formed on the transparent insulating substrate 20 in the same process as the gate electrode 22, and on the gate line 36 in sequence.
Lower gate insulating film 24, upper gate insulating film 2 formed
6, a drain region 38 made of a Cr film formed on the transparent insulating substrate 20 via the lower gate insulating film 24 and the upper gate insulating film 26, and a first region having the passivation protection film 34, and a drain line. And a second region having a passivation protective film 34 formed on the surface 38.

In forming a contact, first, an opening pattern of a contact hole is provided on the pixel transistor section 12, the gate terminal section 14, the drain terminal section 16, and the DG connection section 18 of the protection transistor.
An etching mask (not shown) made of a photoresist film is formed.

In this embodiment, as shown in FIG. 3, the pixel transistor portion 12 is formed by an RIE method using an SF ₆ -based gas as an etching gas under the following conditions.
The passivation protection film 34 in the second region of the drain terminal portion 16 and the DG connection portion 18 is etched to 5 μm.
Contact holes 40, 42, 4 of a tapered wall having an opening size of m × 10 μm, and the opening size is reduced downward.
4 is opened. At the same time, the passivation protection film 34, the upper insulating film 26, and the lower insulating film 24 in the first region of the gate terminal portion 14 and the DG connecting portion 18 are etched to
The contact holes 46 and 48 having a tapered wall having an opening size of μm × 10 μm and having the opening size reduced downward are opened. Etching gas: SF ₆ gas / 50 sccm + He gas / 1
50 sccm pressure: 5 Pa temperature: room temperature Discharge power: 0.01 W / cm ² etching time: 260 seconds

According to the above-described RIE, the contact hole 40 provided in the pixel transistor section 12 is
Expose a. Gate terminal part 14 and DG connection part 18
The contact holes 46 and 48 provided in the first region expose the gate line 36, respectively. In addition, the contact holes 42 and 44 provided in the drain terminal portion 16 and the second region of the DG connection portion 18 expose the drain line 38.

In this embodiment, the contact holes 4
Openings 0, 42 and 44 are formed only by etching the passivation protection film 34. On the other hand, the contact hole 46,
48 denotes a passivation protection film 34 and an upper insulating film 2
6, and since the lower insulating film 24 is opened only after etching, the time required for the opening is long. Accordingly, during this time, the source electrode 32a and the drain line 3 made of a Cr film exposed at the bottoms of the contact holes 40, 42, and 44 opened.
8 is exposed to the etching gas, in the present embodiment, because it uses mainly composed of SF ₆ gas as an etching gas gas, high CrF _X electric resistance does not generate almost behalf , Conductive CrS _X is produced.

Next, in the same etching chamber,
An oxygen ashing process is performed under the following conditions to make the source electrode 3
2a, Cr forming gate line 36 and drain line 38
Enhancing the releasability of the etch mask (not shown) to remove the CrF _X generated slightly above the membrane. Ashing gas: Oxygen (O ₂ ) Pressure: 30 Pa Temperature: Room temperature Output: 0.02 W / cm ² Ashing time: 120 seconds

Next, a 70 nm-thick conductive film made of ITO (indium tin oxide) is formed by sputtering and patterned to form a contact as shown in FIG. That is, in the pixel transistor section 12, the pixel electrode 50 formed on the passivation film 34 and electrically connected to the source electrode 32a via the contact 49 provided on the side wall of the contact hole 40 is formed. In the gate terminal section 14, a contact 52 electrically connected to the gate line 36 via the contact hole 46, and in the drain terminal section 16, a contact 54 electrically connected to the drain line 38 via the contact hole 42 are formed. In the DG connection section 18, a contact 56 is formed at one end to be connected to the gate line 36 via the contact hole 48 and to be connected at the other end to the drain line 38 via the contact hole 44.

Each of the layers formed by the method of this embodiment is
The electric resistance between the pixel electrode 50 and the source electrode 32a via the contact 49 of the pixel transistor section 12, the electric resistance between the contact 54 of the drain terminal section 16 and the drain line 38, and the contact of the DG connection section 18 When the electric resistance between 56 and the drain line 38 was measured, each was in the range of 0.2 kΩ or more and 5 kΩ. The electrical resistance between the contact 52 of the gate terminal portion 14 and the gate line 36 and the electrical resistance between the contact 56 of the DG connection portion 18 and the gate line 36 were measured.
It was 2 kΩ or less.

Conventional Examples In order to evaluate this embodiment using SF ₆ gas as an etching gas, the following conventional examples 1 to 3 were used as conventional examples.
RIE using CF-based gas under the conditions shown in FIG.
As shown in FIG. 7, contact holes 40 to 48 were opened. Then, a conductive film made of ITO is formed and patterned, and as shown in FIG. 4, a pixel electrode 50 electrically connected to the source electrode 32a, a contact 52 electrically connected to the gate line 36, and a drain line 38. A contact 54 that is electrically connected to the gate line 36 at one end;
At the other end, a contact 56 connected to the drain line 38 was formed.

[0040] Conventional Example 1 etching _{gas: CF 4 / 40sccm + CHF 3} / 120sccm + O 2 / 60sccm Pressure: 10 Pa Temperature: room temperature discharge power: 0.007 W / cm ³ Etching time: 200 seconds

[0041] Conventional Example 2 etching _{gas: CF 4 / 160sccm + O 2} / 60sccm Pressure: 15 Pa Temperature: room temperature discharge power: 0.007 W / cm ³ Etching time: 180 seconds

[0042] Conventional Example 3 etching gas: CF _4/200 sccm Pressure: 10 Pa Temperature: room temperature discharge power: 0.007 W / cm ³ Etching time: 320 seconds

When the electrical resistance between the contact formed in the contact hole opened according to Conventional Examples 1 to 3 and the Cr film was measured in the same manner as in Embodiment 1, the contact resistance was 1 MΩ or more. From the above, it was confirmed that the contact formed according to the method of Embodiment 1 had a significantly lower contact resistance than the contacts formed in the contact holes opened according to Conventional Examples 1 to 3.

Embodiment 2 This embodiment is another example of the embodiment in which the method of forming a contact with a Cr film according to the first invention method is applied in a process of manufacturing an inverted staggered type active matrix substrate. . In the present embodiment, before the dry etching process using SF ₆ gas of the first embodiment, the passivation film is formed by a wet etching method using buffered hydrofluoric acid (a hydrofluoric acid buffer) as an etchant under the following conditions. 34 and the like are etched to form contact holes 40-48.
To form Composition of buffered hydrofluoric acid: 0.5% hydrofluoric acid aqueous solution Temperature: room temperature Etching time: 180 seconds

Next, under the same conditions as in the first embodiment, the SF
Dry etching by RIE using an etching gas containing ₆ as a main component is performed to form contact holes 40 to 4.
8. Open and shape 8 completely. Hereinafter, Embodiment 1
Similarly, the pixel electrode 50, the contacts 49, 52,
54 and 56 are formed. In this embodiment, since the wet etching method is also used, the contact hole 40 is formed.
To 48 can be shortened, and productivity can be improved.

Embodiment 3 This embodiment is still another example of the embodiment in which the method for forming a contact with a Cr film according to the first invention method is applied in the step of manufacturing an inverted staggered type active matrix substrate. is there. In this embodiment, a sputter etching process using Ar gas or He gas as an etching gas under the following conditions as a pretreatment for ITO sputtering before forming an ITO film in the first and second embodiments. the (cathode coupling) conducted under the following conditions to remove the CrF _X are produced on Cr film exposed at the bottom of the contact hole 40 to 48. Conditions for sputter etching Etching gas: Ar pressure: 5 Pa Temperature: Room temperature Output: 0.02 W / cm ² Etching time: 120 seconds

In this embodiment, since the residual CrF _X can be completely removed, the contact resistance can be further reduced. The RIE dry etching, sputter etching, and oxygen ashing can be performed continuously in a dry etching apparatus.

Fourth Embodiment This embodiment is an example of an embodiment in which the method for forming a contact with a Cr film according to the third embodiment is applied to manufacture an inverted staggered active matrix substrate. In the present embodiment, the contact holes 40 to 48 are opened in the state shown in FIG. 1 described in the method of the second embodiment or by any one of the conventional examples 1 to 3. Next, after removing the etching mask of the photoresist film,
Ar gas or He gas by performing sputter etching process to an etching gas under the following conditions to remove the CrF _X are produced on Cr film exposed at the bottom of the contact hole 40 to 48. Conditions for sputter etching Etching gas: Ar pressure: 5 Pa Temperature: Room temperature Output: 0.02 W / cm ² Etching time: 120 seconds

Next, an ITO film is formed and the contact 50 is formed.
To 56 are formed. Sputter etching and ITO film formation can be processed continuously in a sputtering apparatus. When the electrical resistance between the contact formed in the fourth embodiment and the Cr film was measured in the same manner as in the first embodiment, the contact resistance was 5 kΩ or less, as in the first embodiment. Also in the present embodiment, the productivity can be improved by performing the wet etching process and shortening the etching time before the dry etching process as in the second embodiment.

In the first to fourth embodiments, the gate electrode 22 and the gate line 36 are formed of a single Cr film. However, the present invention is not limited to this. For example, an Al layer and a Cr film or A
It may be formed of a laminated film of an alloy layer and a Cr layer. Further, a laminated film in which an Al layer or an Al alloy layer is covered with a Cr film may be used. The Al alloy layer is made of, for example, Al-Nd, A
It is an alloy layer of l-Si, Al-Si-Cu, or the like.

[0051]

According to the first invention, the insulating film on the Cr film is etched by a dry etching method using an etching gas containing SF ₆ gas as a main component, and a contact hole for exposing the Cr film is formed. By opening
Since high CrF _X electrical resistance does not generate almost on the Cr film, it is possible to form a small contact of the contact resistance to the Cr film. After opening the contact hole with an etching gas mainly composed of a CF-based gas,
The Cr film exposed at the bottom of the contact hole is subjected to plasma etching using an Ar or He gas as an etching gas, and is formed on the Cr film and has a high electric resistance.
By removing F _X , a contact having a low contact resistance with the Cr film can be formed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an insulating film to be etched to form a contact according to the method of Embodiment 1, and a Cr film below the insulating film.

FIG. 2 is a circuit diagram of an inverted staggered type active matrix substrate.

FIG. 3 is a cross-sectional view showing a state where a contact hole is opened.

FIG. 4 is a sectional view showing a formed contact.

FIGS. 5 (a) to 5 (d) respectively show a drain terminal section, a TFT section, a pixel section, and a drain section of an inverted staggered type active matrix substrate before opening contact holes.
FIG. 3 is a cross-sectional view illustrating a configuration of a gate terminal unit.

FIGS. 6A to 6D show configurations of a drain terminal portion, a TFT portion, a pixel portion, and a gate terminal portion of an inverted staggered active matrix substrate at the stage when a contact hole is opened, respectively. FIG.

FIGS. 7A to 7D respectively show the configuration of a drain terminal portion, a TFT portion, a pixel portion, and a gate terminal portion of an inverted staggered active matrix substrate at the stage when a contact is formed. It is sectional drawing.

[Explanation of symbols]

Reference Signs List 10 Active matrix substrate for TN mode liquid crystal display device 12 Pixel transistor section 14 Gate terminal section 16 Drain terminal section 18 Drain-gate connection section of protection transistor 20 Transparent insulating substrate 22 Gate electrode 24 Lower gate insulating film 26 Upper gate insulating film 28 i-type a-Si layer 30a, 30b n ⁺ type a-Si layer 32a source electrode 32b drain electrode 34 passivation protective film 36 gate line 38 drain line 40, 42, 44, 46, 48 contact hole 49 contact 50 pixel electrode 52, 54, 56 contact 72 drain terminal part 74 TFT part 76 pixel part 78 gate terminal part 80 transparent insulating substrate 82 insulating film 84 i-type a-Si layer 86 n ⁺ type a-Si layer 88 Cr film 90 passivation film 92 gate electrode 94 Channel protective film 96a Source electrode 96b Drain electrode 98 Lower electrode of drain terminal 100 Gate bus line 102 Lower electrode of gate terminal 104 Contact hole 106 Pixel electrode 108 Upper electrode of drain terminal 110 Upper electrode of gate terminal

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Satoshi Kimura 3-1-1, Goshonoshita, Akita City, Akita Prefecture Inside Akita NEC Corporation (72) Inventor Atsushi Yamamoto 3-1-1, Goshonoshita, Akita City, Akita Prefecture No.1 Akita NEC F-term (reference) 4M104 AA10 BB01 BB02 BB04 BB36 CC01 DD08 DD09 DD12 DD16 DD17 DD22 DD37 HH15 5F004 AA12 AA14 BD01 DA01 DA16 DA18 DA22 DA23 DA26 DB03 DB07 DB26 EA10 EA28 EB01 EB02 EB03 EB02 HH08 HH09 HH38 JJ08 JJ09 JJ38 KK07 NN32 PP15 QQ09 QQ13 QQ14 QQ15 QQ19 QQ34 QQ37 QQ95 RR04 RR06 XX09 XX21 5F110 AA03 BB01 CC07 DD02 EE03 EE04 EE05 EE06 EE21 EE36 FF02 FF03 FF23 NN04 NN24 NN72 QQ04 QQ05

Claims (10)

[Claims] A chromium (C) formed under an insulating film.
r) A method of forming a contact with the film, wherein the C is formed by an RIE dry etching method using an etching gas containing SF ₆ gas as a main component through an etching mask having a contact hole opening pattern.
a dry etching step of etching the insulating film on the r film and opening a contact hole exposing the Cr film; filling the contact hole with a conductive film, or forming a conductive film on the side wall of the contact hole and on the exposed Cr film. A step of forming a film and forming a conductive contact electrically connected to the Cr film. 2. A step of performing an oxygen ashing process on the Cr film exposed at the bottom of the contact hole and the etching mask after the dry etching step and before the contact forming step. The method for forming a contact with a Cr film according to claim 1. 3. Following the dry etching step, H
3. The method for forming a contact with a Cr film according to claim 1, further comprising a sputter etching step of performing a sputter etching process using e gas or Ar gas as an etching gas. 4. The method according to claim 3, wherein the sputter etching step is continuously performed in the same dry etching apparatus after the RIE dry etching step.
A method for forming a contact with an r film. 5. A wet etching step of etching the insulating film by a wet etching method via an etching mask having a contact hole opening pattern before the dry etching step. 5. The Cr according to claim 1, wherein a contact hole is opened through the etching mask by the dry etching method, or the contact hole opened in the wet etching step is shaped. 6. A method for forming a contact with a film. 6. After removing the etching mask, A
The method for forming a contact with a Cr film according to any one of claims 1 to 5, wherein sputter etching is performed using r gas or He gas as an etching gas. 7. The etching gas containing SF ₆ as a main component does not contain a CF-based gas.
7. The method for forming a contact with a Cr film according to any one of items 1 to 6. 8. A chromium (C) formed under an insulating film.
r) A method of forming a contact to a film, wherein a RI using an etching gas mainly containing a CF-based gas is used.
E By dry etching, the Cr is etched through an etching mask having an opening pattern of a contact hole.
A dry etching step of etching the insulating film on the film to open a contact hole exposing the Cr film; a sputter etching process using He gas or Ar gas as an etching gas; Forming a conductive contact on the side wall of the contact hole and on the exposed Cr to form a conductive contact electrically connected to the Cr film. Forming a contact with the Cr film. 9. A step of performing an oxygen ashing process on the Cr film exposed at the bottom of the contact hole and the etching mask before the contact forming step following the sputter etching step. A method for forming a contact with a Cr film according to claim 8. 10. A wet etching step of etching the insulating film by a wet etching method via an etching mask having a contact hole opening pattern before the dry etching step. 10. A contact hole with a Cr film according to claim 8 or 9, wherein a contact hole is opened by a dry etching method through the etching mask, or the contact hole opened in the wet etching step is shaped. Forming method.