JP3237125B2 - Anodizing method for conductive film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for anodizing a conductive film.

[0002]

2. Description of the Related Art As a method of forming an insulating film, a metal film such as aluminum or tantalum, or a conductive film such as an n-type or p-type silicon semiconductor film is anodized to convert the conductive film into an insulating film. There is a way to do that.

[0003] Anodization of the conductive film is conventionally performed by using a method shown in FIG.
This is performed by the method shown in FIG.

In FIG. 10, reference numeral 1 denotes an electrolytic solution tank, and the inside thereof is filled with an electrolytic solution 2.

[0005] A reticulated cathode 3 made of platinum or the like is vertically immersed in the electrolytic solution 2, and the cathode 3 is connected to a negative electrode of a DC power supply 4. The cathode 3 is provided with its upper end protruding above the electrolyte surface, and is connected to the DC power supply 4 at the upper end protruding above the liquid surface.

[0006] On the other hand, reference numeral 10 denotes an insulating substrate having a conductive film 11 formed on one surface thereof. The substrate 10 is provided in the electrolyte 2 with the film surface of the conductive film 11 facing the cathode 3. Dipped vertically.

[0007] The substrate 10 has an electrolyte 2 with its upper end and the upper end of the conductive film 11 protruding above the electrolyte surface.
The clip type connecting member 5 which is immersed in the upper end of the substrate 10 and is in conductive contact with the upper end of the conductive film 11.
Are detachably fastened. This connection member 5 is connected to the positive pole of the DC power supply 4.

The anodic oxidation of the conductive film 11 is performed as follows.
This is performed by applying a voltage between the conductive film 11 and the cathode 3 in a state where the conductive film 11 faces the cathode 3 in the electrolytic solution 2.
When a voltage is applied between the electrode and the cathode, the conductive film 11 undergoes a chemical reaction in the electrolytic solution 2 to be anodized.

In the conductive film 11, only the region to be oxidized immersed in the electrolytic solution 2 is anodized, and the upper end protruding above the surface of the electrolytic solution is not oxidized. It remains a membrane. This conductive film portion is used as a conductive film as necessary, or is removed by etching in a later step.

[0010]

However, the above-described conventional anodic oxidation method cannot uniformly oxidize the conductive film 11 over the entire region to be oxidized. However, there is a problem that a portion that is not oxidized remains.

This is because there is a difference in the voltage of each part of the conductive film 11.

That is, the voltage applied from the DC power supply 4 to the conductive film 11 via the connecting member 5 is
Is applied to the entire conductive film from the voltage application point where it is in contact, but since this voltage drops due to the resistance of the conductive film itself, the voltage applied to the conductive film 11 increases with the distance from the voltage application point. Lower.

The depth of oxidation of the conductive film 11 in the thickness direction and the speed of its progress are mainly determined by the voltage applied between the conductive film 11 and the cathode 3.
The anodic oxidation of 1 progresses faster on the upper end side closer to the voltage application point, that is, on the side where a higher voltage is applied, of the part immersed in the electrolytic solution 2.

FIG. 11 shows the progress of oxidation of the conductive film 11 when the conductive film 11 is anodized by the above-mentioned conventional anodic oxidation method. FIG.
(B) shows a state where the oxidation has progressed to some extent, and (c) shows a state where the progress of the oxidation has stopped.

In FIG. 11, reference numeral 11a denotes a conductive film 11;
Indicates an anodized oxide layer. This oxide layer 11
a is a high-resistance insulating layer, and the thickness of the unoxidized layer (metal layer) of the conductive film 11 is the thickness of the oxide layer 11a (oxidation depth).
Becomes smaller, the resistance value of the conductive film 11 increases.

In the conventional anodic oxidation method, the oxidation of the conductive film 11 progresses more rapidly toward the upper end side closer to the voltage application point, and this portion is entirely covered with the conductive film 11 as shown in FIG. When oxidized over the thickness, the current path is cut off at this portion, and no voltage is applied to the portion of the conductive film below this portion. At this point, the anodic oxidation of the conductive film 11 stops and I will.

For this reason, in the conventional anodic oxidation method, of the region to be oxidized of the conductive film 11, the upper end near the voltage application point is oxidized over the entire thickness, but the lower end from this portion is oxidized. , Only the membrane surface is oxidized,
This portion remains conductive.

This is particularly remarkable for the conductive film 11 having a large area. If the area of the conductive film 11 is large, the voltage difference between the upper end and the lower end thereof becomes large. In the region to be oxidized, a portion where only the film surface is oxidized or a portion where the film surface is hardly oxidized remains widely.

An object of the present invention is to provide a method of anodizing a conductive film, which can oxidize a region to be oxidized of the conductive film almost uniformly over the entire region.

[0020]

[0021]

According to the anodic oxidation method of the present invention, the thickness of the outer peripheral portion surrounding the region to be oxidized of the conductive film is adjusted.
The voltage applied to at least one portion of the outer peripheral portion of the conductive film is applied to a region to be oxidized of the conductive film using the thick portion of the outer peripheral portion of the conductive film as a current path. It is characterized by the following.

[0022]

[0023]

[0024]

According to the present invention, the thickness of the outer peripheral portion surrounding the oxidized region of the conductive film is made larger than that of the oxidized region , and this portion is used as a current path.

This current path is anodic oxidized from the surface side together with the oxidized region. However, since the current path is thick, only the surface layer is oxidized and the lower layer side remains a metal. The current path is always conductive.

Therefore, in the present invention, it is possible to continue to apply a voltage from the periphery of the oxidized region of the conductive film to the region where the anodic oxidation proceeds with a delay. , It is almost evenly oxidized throughout.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a specific example of the anodic oxidation method will be described with reference to FIGS.

FIG. 1 shows an apparatus for performing anodic oxidation. This anodic oxidation apparatus comprises an electrolytic solution tank 1 filled with an electrolytic solution 2 and platinum or the like vertically immersed in the electrolytic solution 2. A reticulated cathode 3, a DC power supply 4, and an insulating substrate (for example, a glass substrate) 10 vertically immersed in the electrolytic solution 2 are detachably fastened to the upper end of the substrate 10 and formed on the surface of the substrate 10. A clip-type connecting member 5 for power supply connection, which is in conductive contact with the upper end of the conductive film 11. Note that this anodizing apparatus has the same configuration as that shown in FIG. 10, and a detailed description thereof will be omitted.

In this anodic oxidation method, the outer peripheral surface surrounding the oxidized region of the oxidized conductive film 11 formed on the substrate 10 is covered with an insulating film 12 such as a photoresist. The anodized region is anodically oxidized by the anodizing apparatus. The insulating film 12 is made of a conductive film except for a voltage application portion where the clip-type connecting member 5 contacts, as shown in FIGS. 11 is provided all around the outer peripheral portion.

The conductive film 11 to be oxidized is, for example, a metal film such as aluminum or tantalum, and the anodic oxidation of the conductive film 11 is performed on the substrate 10 on which the conductive film 11 is formed.
Is vertically immersed in the electrolyte solution 2 with its upper end and the upper end of the conductive film 11 protruding above the electrolyte surface, and a voltage is applied from the DC power supply 4 to the upper end of the conductive film 11 and the cathode 3. By applying a voltage between the conductive film 11 and the cathode 3.

When a voltage is applied between the conductive film 11 and the cathode 3 as described above, a portion of the conductive film 11 which is immersed in the electrolytic solution 2 undergoes a chemical reaction and is anodized from the surface side. Go.

In this case, the anodic oxidation of the conductive film 11 is performed in the portion immersed in the electrolytic solution 2 on the upper end side near the voltage application point (the contact point of the clip type connection member 5), that is, when the high voltage is applied. Since such a side proceeds faster, the conductive film 1
Of the one oxidized region, a portion near the above-mentioned voltage application portion becomes higher in resistance as anodic oxidation proceeds.

However, in this anodic oxidation method, since the outer peripheral surface surrounding the oxidized region of the conductive film 11 is covered with the insulating film 12, this portion is not anodic oxidized. Is always in a conductive state.

For this reason, even if the upper end portion of the oxidized region of the conductive film 11 close to the above-mentioned voltage application portion becomes high in resistance with the progress of anodic oxidation, the voltage applied to the above-mentioned voltage application portion becomes high. Is applied to the region to be oxidized of the conductive film 11 from the periphery through the non-oxidized portion of the outer peripheral portion of the conductive film.

That is, in the anodic oxidation method, the outer peripheral surface surrounding the oxidized region of the conductive film 11 is covered with the insulating film 12, and the voltage applied to the upper end of the conductive film 11 is reduced by the insulating film 12. The outer peripheral portion of the conductive film covered with 12 is applied as a current path A to the oxidized region of the conductive film 11.

According to this anodic oxidation method, the conductive film 11
Of the region to be oxidized, even if the upper end portion near the voltage application point becomes higher in resistance with the progress of anodic oxidation, the voltage applied to the voltage application point passes through the current path A on the outer periphery of the conductive film. Is applied from the periphery to the region to be oxidized of the conductive film 11 through the region, so that a sufficiently high voltage is applied to the region of the oxidized region where anodic oxidation proceeds with a delay (a voltage that is merely a voltage drop in the current path A). Can be continuously applied,
Therefore, the region to be oxidized of the conductive film 11 is almost uniformly oxidized throughout.

FIGS. 4A and 4B show the progress of oxidation of the conductive film 11 when the conductive film 11 is anodized by the above-described anodic oxidation method, wherein FIG. 4A shows the initial oxidation state, and FIG. A state advanced to some extent, (c) shows an oxidation completed state.

In this anodic oxidation method as well, in the initial stage of oxidation, as shown in FIG. 4A, the anodic oxidation of the conductive film 11 progresses faster at the upper end portion closer to the voltage application point. As in the case of the conventional anodic oxidation method, the magnitude increases as the upper end portion is closer to the voltage application point.

However, even if the upper end portion becomes higher in resistance with the progress of anodic oxidation, the voltage applied to the above-mentioned voltage application portion is not applied to the conductive film 11 through the above-mentioned current path A.
Is applied to the region to be oxidized from the periphery thereof, the region to be oxidized is almost uniformly oxidized as shown in FIG. 4B, and finally the entire region to be oxidized is It is oxidized over its entire thickness as in FIG. 4 (c).

As described above, according to the anodic oxidation method,
Since the region to be oxidized of the conductive film 11 can be almost uniformly oxidized over the entire region, even if the area of the conductive film 11 is large, the entire region can be oxidized over the entire thickness.

In the conductive film 11, only a portion of the portion immersed in the electrolytic solution 2 which is not covered with the insulating film 12 is anodized, and a current path portion covered with the insulating film 12 is formed. And since the upper end projecting above the electrolyte surface is not oxidized, this non-oxidized portion remains a conductive film, but this conductive film portion is used as a conductive film if necessary, Alternatively, it may be removed by etching in a later step.

In the anodic oxidation method described above, the voltage is applied from one of the upper end portions of the outer peripheral portion of the conductive film 11, but the voltage is applied to the conductive film 11. The connection member 5 may be brought into contact with a plurality of locations on the outer periphery, and the voltage may be applied from a plurality of locations.

In the anodic oxidation method described above, the conductive film 11 is immersed in the electrolytic solution 2 except for the upper end, but the conductive film 11 is entirely immersed in the electrolytic solution 2. In such a case, the voltage application location may be coated with insulation from above the connection member 5.

Further, the above-described anodic oxidation method can be applied not only to the metal film but also to the anodic oxidation of a conductive film made of an n-type or p-type silicon semiconductor film or the like. The anodic oxidation of the silicon semiconductor film is performed by applying a voltage between the silicon semiconductor film immersed in the electrolytic solution and the cathode and irradiating the silicon semiconductor film with light.

Next, an embodiment of the present invention will be described with reference to FIGS.

The anodic oxidation method of the embodiments of the present invention, described above
Instead of covering the outer peripheral surface of the conductive film with the insulating film as in the anodic oxidation method shown in FIGS. 1 to 4, the thickness of the outer peripheral portion surrounding the oxidized region of the conductive film is changed to the oxidized region. more <br/> by thickening is obtained by the outer peripheral portion and electrode path a, anodic oxidation of the conductive film is performed by anodic oxidation apparatus shown in FIG.

FIGS. 5 and 6 show the conductive film 11 formed on the surface of the insulating substrate 10, and the conductive film 11 is a metal film such as aluminum or tantalum. The outer peripheral portion of the conductive film 11 is formed by a frame-shaped conductive film 13 formed thereover over the entire outer peripheral portion of the conductive film.
And a two-layer thick film consisting of

The frame-shaped conductive film 13 is formed of the same metal as the conductive film 11 to be anodized or another low-resistance metal. 11 is formed to a thickness approximately equal to or greater than the thickness of the film 11.

The anodic oxidation of the conductive film 11 is performed as follows.
The substrate 10 on which the conductive film 11 is formed is connected to the first
As in the embodiment of the present invention, the upper end portion and the conductive film 1
1 is vertically immersed in the electrolytic solution 2 with the upper end protruding above the electrolyte surface, and a voltage is applied between the upper end of the conductive film 11 and the cathode.

That is, the anodic oxidation method of this embodiment is as follows.
The thickness of the outer peripheral portion of the conductive film 11 surrounding the region to be oxidized is increased, and the voltage applied from the DC power supply to the upper end portion of the conductive film 11 via the clip-type connecting member 5 is reduced. The thick film portion is applied as a current path A to the oxidized region of the conductive film 11.

In this anodic oxidation method, similarly to the first invention, a sufficiently high voltage (current path) is also applied to the region of the conductive film 11 to be oxidized where the anodic oxidation proceeds with a delay. A can be continuously applied, so that the oxidized region of the conductive film 11 is almost uniformly oxidized throughout.

FIGS. 7A and 7B show the progress of oxidation of the conductive film 11 when the conductive film 11 is anodized by the above-described anodic oxidation method. FIG. 7A shows the initial oxidation state, and FIG. A state advanced to some extent, (c) shows an oxidation completed state.

Also in this anodic oxidation method, in the initial stage of oxidation, as shown in FIG. 7A, the anodic oxidation of the conductive film 11 proceeds more rapidly at the upper end portion closer to the voltage application point.

However, the current path A on the outer periphery of the conductive film is
Since the film thickness is large, the resistance is small and the voltage drop in the current path portion is small. Therefore, the voltage applied to the voltage application point is transferred to the oxidized region of the conductive film 11 through the current path A in the vicinity thereof. Is applied.

Therefore, the difference in the oxidation rate between the side near the voltage application point (upper end) and the side farther (lower end) of the conductive film 11 is smaller than that of the first embodiment.

In this case, the current path A on the outer peripheral portion of the conductive film 11 is also anodized from the front side together with the oxidized region of the conductive film 11, but since the current path A is thick, Since only the surface layer is oxidized and the lower layer remains a metal, the current path A is always in a conductive state.

For this reason, even if the upper end portion of the conductive film 11 close to the voltage application location becomes higher in resistance with the progress of anodic oxidation, the voltage applied to the voltage application location will not pass through the current path A. A voltage is applied to the region to be oxidized of the conductive film 11 from the periphery thereof.

Therefore, the oxidized region of the conductive film 11 is almost uniformly oxidized as shown in FIG. 7B, and finally, the entire oxidized region becomes
It is oxidized over its entire thickness as in (c).

As described above, according to the anodic oxidation method,
Since the region to be oxidized of the conductive film 11 can be oxidized almost uniformly over the entire area, even if the area of the conductive film 11 is large, the entire area is oxidized over the entire thickness to obtain a uniform insulating film. Can be.

In the conductive film 11, only the portion immersed in the electrolyte 2 is anodized, the upper end protruding above the surface of the electrolyte is not oxidized, and the current on the outer periphery of the conductive film 11 is not oxidized. The path portions are oxidized only on the surface layer, and the lower layer remains metal, but these portions may be used if necessary.
It may be used as a conductive film or may be removed by etching in a later step.

In this anodic oxidation method, the conductive film 1
1 may be applied from a plurality of locations by bringing the clip-type connecting member 5 or the like into contact with a plurality of locations on the outer peripheral portion of the conductive film 11, respectively. Anodization may be performed by dipping in the liquid 2.

In the above embodiment, the frame-shaped conductive film 13 for forming the outer peripheral portion of the conductive film as the thick current path A is formed below the outer peripheral portion of the conductive film 11 to be oxidized. As shown in FIG. 8, the frame-shaped conductive film 13 is a conductive film 11 to be oxidized.
May be formed on the outer periphery.

Further, the current path A may be a single-layer film as shown in FIG. 9. In this case, the conductive film 11 is formed thick, and the oxidized region except the outer peripheral portion is formed to a predetermined thickness. After etching, the thick film portion left on the outer peripheral portion is
And it is sufficient.

The above-described anodic oxidation method is of course applicable to not only the metal film but also the anodic oxidation of a conductive film made of an n-type or p-type silicon semiconductor film or the like.

[0065]

According to the anodic oxidation method of the present invention, the outer peripheral portion of the conductive film surrounding the oxidized region is made thicker than the oxidized region.
The voltage applied to at least one portion of the outer peripheral portion of the conductive film is applied to the oxidized region of the conductive film using the thick film portion of the outer peripheral portion of the conductive film as a current path. In addition, the oxidized region of the conductive film can be oxidized almost uniformly over the entire region.

[Brief description of the drawings]

FIG. 1 is a perspective view of an anodizing apparatus according to an embodiment of the first invention.

FIG. 2 is a front view of a conductive film to be oxidized.

FIG. 3 is a sectional view of FIG. 2;

FIG. 4 is a diagram showing the progress of oxidation of a conductive film according to the first invention.

FIG. 5 is a front view of an oxidizable conductive film showing one embodiment of the second invention.

FIG. 6 is a sectional view of FIG. 5;

FIG. 7 is a diagram showing the progress of oxidation of a conductive film according to the second invention.

FIG. 8 is a cross-sectional view of an oxidized conductive film showing another embodiment of the second invention.

FIG. 9 is a cross-sectional view of an oxidizable conductive film showing another embodiment of the second invention.

FIG. 10 is a perspective view of an anodizing apparatus showing a conventional anodizing method.

FIG. 11 is a diagram showing the progress of oxidation of a conductive film by a conventional anodic oxidation method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electrolyte tank, 2 ... Electrolyte, 3 ... Cathode, 4 ... Power supply, 5 ...
Connection member, 10: substrate, 11: conductive film to be oxidized, 11a
... oxide layer, 12 ... insulating film, 13 ... frame-shaped conductive film, A ... current path.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/316 C25D 11/00 308

Claims (1)

(57) [Claims] 1. A method of immersing a conductive film in an electrolytic solution and applying a voltage between the conductive film and a cathode immersed in the electrolytic solution to anodize the conductive film. , the thickness of the outer peripheral portion surrounding the oxidized region of the conductive layer the object
The voltage applied to at least one portion of the outer peripheral portion of the conductive film is applied to a region to be oxidized of the conductive film using the thick portion of the outer peripheral portion of the conductive film as a current path. An anodic oxidation method for a conductive film.