JP2921503B2 - Manufacturing method of electrical contact - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method of manufacturing an electrical contact, and more particularly to a method of manufacturing an electrical contact suitable for use in an aluminum wiring step in manufacturing a TFT array substrate of an active matrix color liquid crystal display. .

[0002]

2. Description of the Related Art Conventionally, for example, as shown in FIG. 5, a horizontal scanning line group and a vertical signal line group form a grid-like matrix, and transparent dot electrodes 101a, 101a,.
(Thin-film transisitor) switches 101b, 101b,.
An array substrate 101 and a color filter substrate 102 dyed in RGB primary colors are opposed to each other, a liquid crystal 103 is sealed between the two substrates, and a common electrode 104 is formed on the entire surface of the color filter substrate 102. In the manufacturing process of the TFT array substrate 101 when manufacturing the active matrix color liquid crystal display 107 in which the polarizing plates 106 and 106 are disposed on both sides of the liquid crystal panel 105 and the backlight is disposed behind the liquid crystal panel 105, the following process is performed. By such a method, an electrical contact is formed between the chromium film (lower conductor film) constituting the gate electrode of each TFT switch 101b of the TFT array substrate 101 and the aluminum film (upper conductor film) constituting the scanning line. doing. That is, as shown in FIG.
A chromium film 202 is formed on the substrate 1 by sputtering and then processed into a predetermined shape. Next, a silicon nitride film 203 is formed by plasma CVD (chemical vapor deposition).
A photoresist is applied on the substrate 03, and a predetermined pattern is transferred to the photoresist by a photolithography technique to form a photoresist mask 204. Next, the silicon nitride film 203 is etched by a dry etching method using a fluorine-based etching gas,
After forming the contact window, the photoresist mask 20
4 is peeled off, and an aluminum film 205 is formed by a sputtering method as shown in FIG.

However, the electrical contact manufactured by the above method has a high resistance and is not in a good condition. In order to analyze the composition of the components near the interface between the chromium film 102 and the aluminum film 105, the inventors of the present application conducted electron spectroscopy (ESCA) using X-ray irradiation.
al analysis)), the spectral intensity of each component with respect to the depth from the surface of the object was measured.
As shown in FIG. 6, it is confirmed that a large amount of fluorine exists in the vicinity of the interface, and the fluorine adheres to the surface of the chromium film 202 to form the altered layer 206 (see FIG. 6B). It has been found that the resistance of the electrical contact has been increased.

[0004] In order to avoid the occurrence of contact failure by forming an electrical contact while the surface of the chromium film is deteriorated, for example, a method as described in JP-A-1-101661 is used. Has been proposed. That is, as shown in FIG. 8, a chromium film 302 is formed on a transparent substrate 301 by vacuum evaporation and then patterned. Next, a tantalum oxide film 303 is formed by a sputtering method. Furthermore, for example, in order to form a switching element, amorphous silicon (a-S
i) Through a high temperature process to form a film. Next, a photoresist is applied on the tantalum oxide film 303, a predetermined pattern is transferred to the photoresist by a photolithography technique to form a photoresist mask, and thereafter, a dry etching method using CF ₄ gas is performed. Thereby, a contact window 304 is formed. Next, by immersing in a hydrofluoric acid-nitric acid etching solution for approximately 20 seconds,
The altered layer formed by the high-temperature process near the interface between the chromium film 302 and the tantalum oxide film 303 is removed. Thereafter, the photoresist mask is removed, and MoSi is removed.
/ Al film 305 and counter electrode 306 are formed.

According to the method described in Japanese Patent Application Laid-Open No. Hei 5-232491, first, a chromium film 402 having a predetermined pattern is formed on a glass substrate 401 as shown in FIG. Later, an ITO (indium tin oxide) film 403 is formed. Next, by the plasma CVD method,
A silicon nitride film 404 is formed.
A photoresist is coated on the substrate 04, and a predetermined pattern is transferred to the photoresist by using a photolithography technique to form a photoresist mask 405. Thereafter, as shown in FIG. 3B, the silicon nitride film 404 is wet-etched with buffered hydrofluoric acid to expose a surface of the ITO film 403 to form a contact window, and thereafter, an electrical contact is formed. .

[0006]

However, according to the method described in JP-A-1-101661, a step of immersion in an etching solution is required to remove the altered layer on the surface of the chromium film 302. In addition, a dedicated etching solution and etching apparatus are required. Also, an ITO film 4 for preventing oxidation by buffered hydrofluoric acid can be produced by the method described in JP-A-5-232491.
A film forming step for forming the layer 03 and a photolithography step for patterning are required, which is complicated and increases the number of defective portions.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a method of manufacturing an electrical contact that can obtain a highly reliable contact only by adding a simple process. I have.

[0008]

In order to solve the above-mentioned problems, the present invention is directed to a chromium film formed as a lower conductive film on a substrate and an insulating film formed on the chromium film. And a method of manufacturing an electrical contact consisting of an upper conductive film electrically connected to the chromium film through a contact window opened in the insulating film, after forming the chromium film on the substrate. Oxidizing the surface of the chromium film to form a chromium oxide film having a thickness of 1 nm or more and 9 nm or less, then forming the insulating film on the chromium oxide film, and then using a fluorine-based etching gas. And opening the contact window in the insulating film such that the chromium oxide film remains at the bottom of the contact window.

According to a second aspect of the present invention, there is provided a method of manufacturing an electrical contact according to the first aspect, wherein the substrate comprises:
It is characterized by being a transparent substrate.

According to a third aspect of the present invention, there is provided the method for manufacturing an electrical contact according to the first aspect, wherein the upper conductive film is an aluminum film.

According to a fourth aspect of the present invention, there is provided the method for manufacturing an electrical contact according to the first aspect, wherein the insulating film is a silicon nitride film.

[0012]

[0013]

[0014]

[0015]

According to the structure of the present invention, the chromium oxide film formed on the surface of the chromium film as the lower conductor film prevents the surface of the chromium film from being deteriorated when the insulating film is etched. Since the formed chromium oxide film is an extremely thin film, a good electrical contact with low electric resistance can be manufactured.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. The description will be specifically made using an embodiment. First Embodiment FIGS. 1 and 2 are process diagrams for explaining a method of manufacturing an electrical contact according to a first embodiment of the present invention. FIG. 3 is a diagram showing the depth from the surface of the object to be processed. FIG. 4 is a characteristic diagram illustrating a relationship between a depth and a spectrum intensity of each component included in an object to be processed. The manufacturing method of the electrical contact of this example is as follows.
As described in the section of "Prior Art", for example, a chromium film (lower conductive film) constituting a gate electrode of a TFT switch of a TFT array substrate and an aluminum constituting a scanning line employed in an active matrix color liquid crystal display. It is used when forming an electrical contact with the film (upper conductor film).

First, as shown in FIG. 1A, a chromium film 2 is formed on a glass substrate 1 so as to have a thickness of several hundred nm by a sputtering method. Here, the sputtering conditions are as follows: a temperature of about 300 ° C. and a degree of vacuum of about 0.3.
Pa, the flow rate of argon (Ar) as a discharge gas is approximately 1
00sccm (standard cubic centimeter per minut
e). Next, a photoresist is applied on the chromium film 2 at a predetermined rotation speed using a resist coating spinner to a thickness of about 1.5 μm, and a predetermined mask pattern is applied to the photoresist in an exposure step. After the transfer, the photoresist is dissolved with an alkaline solution in a developing step, thereby forming a photoresist mask 3 as shown in FIG. Then, the photoresist mask 3 is formed by a dry etching method using a chlorine-based etching gas.
The chromium film 2 not covered with the chrome film 2 is removed. Thereafter, the photoresist mask 3 on the chromium film 2 is removed by using a stripping solution composed of DMSO (dimethyl sulfoxide) and monoethanolamine, as shown in FIG.

Next, a processing body in which the patterned chromium film 2 is formed on the glass substrate 1 is moved to approximately 200 mm.
The surface of the chromium film 2 is oxidized by being left for about 30 minutes in an air atmosphere set to a range of not less than 250 ° C. and not more than 250 ° C., and as shown in FIG. The film 4 is formed. Note that the inventors of the present application control the thickness of the chromium oxide film 4 by changing the oxidation conditions of the surface of the chromium film 2 in various ways, form electrical contacts, and measure the electrical resistance and the like. However, when the thickness is less than about 1 nm, the effect of preventing fluorine from adhering to the surface of the chromium film 2 in the step of etching the silicon nitride film described later is not recognized, and therefore, a desired low resistance value is obtained. I couldn't. Conversely, when the film thickness was about 10 nm or more, the chromium oxide film 4 hindered electric conduction, and rather, a high resistance value was measured. Therefore, this chromium oxide film 4
It has been found that the film thickness needs to be in the range of about 1 nm to 9 nm. Next, using a mixed gas of silane gas and ammonia gas, by a plasma CVD method,
As shown in FIG. 2E, a silicon nitride film 5 having a thickness of about several hundred nm is formed on the chromium oxide film 4, and a photoresist is applied on the silicon nitride film 5 to form a photoresist. A predetermined pattern is transferred to a photoresist by a lithography technique to form a photoresist mask 6.
To form Here, the conditions for the film formation are as follows.
° C, the degree of vacuum is about 120 Pa, and the flow rates of the silane gas and the ammonia gas are about 100 sccm and about 200
sccm.

Next, the silicon nitride film 5 is etched by a dry etching method using a fluorine-based etching gas to form a contact window H as shown in FIG. The resist mask 6 is removed. Thereafter, as shown in FIG. 2G, an aluminum film 7 is formed on the silicon nitride film 5 and the like by sputtering to have a thickness of several 100 nm. here,
The sputtering conditions are as follows: the temperature is about 200 ° C., the degree of vacuum is about 0.4 Pa, and the flow rate of argon (Ar) as a discharge gas is about 200 sccm. Then, a photoresist is applied on the aluminum film 7, a predetermined pattern is transferred to the photoresist by a photolithography technique, a photoresist mask is formed, and a photoresist is formed from a mixed solution of phosphoric acid, nitric acid, and acetic acid. Immerse in etchant,
The aluminum film 7 that is not covered with the photoresist mask is removed, and the aluminum film 7 is further immersed in a stripping solution to remove the photoresist mask.

Thus, the contact windows H, H,.
An electrical contact having a size of approximately 12 μm square was formed, and the electrical resistance was measured using a wiring pattern for evaluation. As a result, a resistance value of approximately several tens of kΩ was obtained for approximately 2,000 electrical contacts. Abbreviation 1 by
The measurement result was significantly improved from the measurement result of 000 kΩ, and no poor conductivity was observed. Further, the spectral intensity of each component at an arbitrary depth from the surface of the object after the formation of the electrical contact was measured by ESCA, and the component composition was analyzed. As shown in FIG.
In the vicinity of the interface between the (chromium film 2) and the aluminum film 7,
It was confirmed that almost no fluorine was present, and it was found that the cause of the increase in the resistance of the electrical contact was eliminated.

According to the above configuration, after the chromium film 2 is formed on the glass substrate 1, the thin chromium oxide film 4 is formed by oxidizing the surface of the chromium film 2, and then the silicon nitride film 5 is formed. Since the etching is performed to provide the contact window H, even if the silicon nitride film 5 is etched using a fluorine-based etching gas, the chromium oxide film 4 prevents the fluorine from adhering to the chromium film 2. ,
The surface of the chromium film 2 does not deteriorate. Further, since the chromium oxide film 4 is an extremely thin film having a thickness of about several nm,
It does not affect conductivity. Therefore, even if the electrical contact is formed by forming the aluminum film 7 after the formation of the contact window H, the resistance of the electrical contact is not increased, so that the yield is improved and the reliability is further improved. High electrical contacts can be manufactured. Also,
The process of forming the chromium oxide film 4 is a simple process in which the object to be processed, in which the chromium film 2 is formed on the glass substrate 1, is left in a high-temperature air atmosphere for approximately 30 minutes, and is therefore complicated. Without the need for equipment and complicated processes,
Good electrical contacts can be manufactured while minimizing costs.

Second Embodiment FIG. 4 is a process chart for explaining a method of manufacturing an electrical contact according to a second embodiment of the present invention. The difference between the second embodiment and the first embodiment is that the first embodiment is different from the first embodiment.
In the embodiment, as shown in FIG. 1, the chromium film 2 is processed into a predetermined pattern, and then the surface of the chromium film 2 is oxidized to form the chromium oxide layer 4. As shown in FIG. 3C, the chromium film 2 and the chromium oxide layer 4 are processed into a predetermined pattern after the surface of the chromium film 2 is oxidized to form a chromium oxide layer 4. Accordingly, the chromium oxide layer 4 is not formed on the side surface of the chromium film 2 as shown in FIGS. Other than this, the steps are almost the same as those described in the first embodiment.
The description is omitted.

According to the above configuration, the same effects as described in the first embodiment can be obtained.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like that do not depart from the gist of the present invention. Is also included in the present invention. For example, in the above-described embodiment, a case has been described in which an electrical contact is formed between a chrome film constituting a gate electrode of a TFT switch and an aluminum film constituting a scanning line employed in an active matrix color liquid crystal display. The use is, of course, not limited to this. In the above-described embodiment, when the chromium film 2 is etched, the dry etching method is used. For example, a wet etching method using an etchant containing ceric ammonium sulfate and perchloric acid as main components is used. May be.

[0025]

As described above, according to the structure of the present invention, the chromium oxide film formed on the surface of the chromium film as the lower conductor film is deteriorated when the insulating film is etched. In addition, since the formed chromium oxide film is an extremely thin film, a good electric contact with low electric resistance can be manufactured.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining a method of manufacturing an electrical contact according to a first embodiment of the present invention.

FIG. 2 is a process chart for explaining a method of manufacturing the electrical contact.

FIG. 3 is a characteristic diagram showing a relationship between a depth from a surface of a target object and spectral intensities of components constituting the target object at the depth.

FIG. 4 is a process chart illustrating a method for manufacturing an electrical contact according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram for explaining a conventional technique.

FIG. 6 is a process chart for explaining a conventional technique.

FIG. 7 is a characteristic diagram for explaining a conventional technique.

FIG. 8 is an explanatory diagram for explaining a conventional technique.

FIG. 9 is a process chart for explaining a conventional technique.

[Explanation of symbols]

 Reference Signs List 1 glass substrate (substrate) 2 chromium film (lower conductor film) 4 chromium oxide film 5 silicon nitride film 7 aluminum film (upper conductor film) H contact window

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/28-21/288 H01L 21/3205-21/3213 H01L 21/768 H01L 29/786

Claims (4)

(57) [Claims] 1. A chromium film formed as a lower conductor film on a substrate, an insulating film formed on the chromium film, and electrically connected to the chromium film through a contact window opened in the insulating film. A method for manufacturing an electrical contact comprising an upper conductive film, wherein the chromium film is formed on the substrate, and then the chromium film surface is oxidized to form a chromium oxide film having a thickness of 1 nm or more and 9 nm or less. Next, the insulating film is formed on the chromium oxide film, and thereafter, the contact window is formed on the insulating film using a fluorine-based etching gas, and the chromium oxide film is formed on the bottom of the contact window. A method for manufacturing an electrical contact, characterized in that an opening is formed in a remaining mode. 2. The method according to claim 1, wherein the substrate is a transparent substrate. 3. The method according to claim 1, wherein the upper conductor film is an aluminum film. 4. The method according to claim 1, wherein the insulating film is a silicon nitride film.