JP3004821B2 - Electrode formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for application to, for example, a gate electrode of a miniaturized field effect transistor.
The present invention relates to a method for forming an electrode having an upper width dimension wider than a base width dimension (also referred to as a T-shaped electrode).

[0002]

2. Description of the Related Art It is effective to reduce the gate length to reduce the noise of microwave FETs such as MESFETs and HEMTs. However, since the gate resistance generally increases as the gate length is shortened, there is a fear that noise may be generated due to the increase in the gate resistance. Therefore, a technique is required that can shorten the gate length and prevent or reduce the increase in gate resistance. As an example of such a technique, as shown in FIG. 7, an attempt has been made to configure a gate electrode with an electrode 11 having a T-shaped cross section cut along the gate length direction. In FIG. 7, reference numeral 13 denotes a semiconductor substrate, an active layer, and the like.

[0003]

As a method of manufacturing the T-shaped gate electrode, the applicant of the present application has proposed the following method in Japanese Patent Application No. 3-31821. Was. FIGS. 8A to 8D are diagrams provided for explanation thereof. In each of the figures, a cross-sectional view of the sample in the main process taken along the gate length direction is shown.

In this method, first, a SiN film 23 is formed on a semiconductor substrate 21, a negative type resist layer is formed on the SiN film 23, and the resist layer is formed on Exposure is performed by the method disclosed in Japanese Patent Application Publication No. 76551 (hereinafter also referred to as Document I), and then the exposed resist is developed to obtain a resist pattern 25 (FIG. 8A). Here, the method disclosed in Document I is:
This is an exposure method using a phase shift method, which utilizes the fact that an unexposed portion corresponding to an edge line can be formed in a resist portion corresponding to an edge of a phase shifter. further,
The method disclosed in Document I can change the line width of the unexposed portion corresponding to the edge line by changing the exposure amount. In addition, the method of this document I was described in the document II (1990 IEDM Technical Dige) by the applicant of this application.
st p.33.3.1) and PEL method (Phase-Shifter Edge-Line)
The PEL method is also disclosed as PEL method for convenience of explanation.

Next, using the resist pattern 25 as a mask, the SiN film 23 is selectively etched to form an opening 23a in the SiN film 23, and then the resist pattern 25 is removed. The dimensions of the base of the T-shaped gate electrode are determined by the width W ₀ of the opening 23. Next, a negative resist layer is formed again on the sample, and thereafter, the resist layer is exposed by the above-described PEL method. This exposure is performed by aligning the photomask with the sample such that the edge line of the phase shifter faces the opening 23a of the SiN film 23, and using an exposure amount smaller than the exposure amount in the first exposure. Next, the exposed resist layer is developed to form a resist pattern 27 (this is referred to as a “second resist pattern 27”).
Also called. Get) Since the exposure amount for obtaining the second resist pattern 27 is smaller than that for obtaining the first resist pattern, the opening width W of the second resist pattern 27 is reduced.
Is wider than that of the first resist pattern (FIG. 8).
(B)).

Next, a gate electrode forming thin film 29 is formed on the entire surface of the sample (FIG. 8C).
The unnecessary portions 9 are removed (lift-off) together by removing the second resist pattern 27. Next, the SiN film 23 is removed. Thereby, a desired T-shaped electrode 29a is obtained (FIG. 8D). This method was also applicable to the formation of a field effect transistor having a recess structure.
In this case, after forming the second resist pattern 27 and before forming the gate electrode forming thin film 29, the substrate 2 is formed using the second resist pattern 27 and the SiN film 23 as a mask.
1 is recess etched.

However, as a result of a detailed study of the above-described method of forming the T-shaped electrode by the inventor of the present application, according to this method, an exposure light for exposing a resist and a reflection light of the exposure light from a semiconductor substrate are obtained. And a standing wave is generated due to the interference between the resist pattern and the side wall of the formed resist pattern. FIG. 4B is a diagram in which a scanning electron microscope photograph of the situation is copied (the details will be described in a comparative example described later). Such a problem hinders high-precision patterning. Therefore, improvement is desired.

[0008] In addition, etching for forming the opening 23a in the SiN film 23 is often over-etched in order to surely open the SiN film.
After this, the side etching of the SiN film 23 proceeds, and the width of the opening 23a becomes wide, so that the gate length cannot be reduced. As described above, in the conventional method, there is a problem that the etching margin when forming the opening in the thin film for forming the lower mask (the SiN film in the above example) is small.

[0009] The present invention has been made in view of such a point. Therefore, a first object of the present invention is disclosed in Japanese Patent Application No. Hei.
An object of the present invention is to provide a method capable of reducing the influence of a standing wave at the time of resist exposure in the method proposed in Japanese Patent No.
A second object of the present invention is to provide a method capable of improving the etching margin of a mask forming material when forming a mask for defining the width of the base of a T-shaped electrode.

[0010]

In order to achieve this object, according to the method of forming an electrode of the present invention, an electrode having an upper portion having a width larger than that of a base portion is formed on a substrate. Forming a thin film for forming a lower layer mask which is transparent to exposure light and having a thickness satisfying the following condition (a): A step of forming an intermediate film that satisfies the condition (b), a step of forming a first resist layer on the intermediate film,
Selectively exposing the first resist layer and then developing the first resist pattern to form a first resist pattern having a fine line-shaped opening; and using the first resist pattern as a mask to form the intermediate film and the lower layer. Selectively removing the mask forming thin film, obtaining a lower layer mask having a window exposing a part of the substrate surface, removing the first resist pattern,
Forming a second resist layer on the sample on which the lower mask has been formed, and selectively exposing the second resist layer;
Developing thereafter, forming a second resist pattern as an upper layer mask for forming the electrode, having a thin line-shaped opening wider than the window at a portion corresponding to the window of the lower layer mask; Forming the electrode forming thin film on the entire surface of the substrate on which the lower mask and the upper mask have been formed, and then removing the lower and upper masks. According to another aspect of the present invention, a thin film for forming a lower layer mask for forming an electrode having an upper width dimension wider than a base width dimension on a substrate, which is transparent to exposure light, A step of forming a lower mask forming thin film satisfying the following condition (a); and forming an intermediate film satisfying the following condition (b) on the lower mask forming thin film. Forming a negative first resist layer on the intermediate film, exposing the first resist layer via an exposure mask having a phase shifter, and applying the phase shifter to the first resist layer; Forming a first unexposed portion in the form of a thin line corresponding to an edge, developing the exposed first resist layer to form a first resist pattern, and masking the first resist pattern Select the above-mentioned intermediate film and thin film for forming lower layer mask as Removing, to obtain a lower layer mask having a window exposing a part of the base material surface, and removing the first resist pattern, and thereafter, a negative type second resist is formed on the lower layer mask-formed sample. Forming a second resist layer, and exposing the second resist layer with an exposure amount smaller than the exposure amount at the time of the first resist layer exposure through the exposure mask, thereby forming the second resist layer. Forming a second unexposed portion in the form of a thin line wider than the window in a portion of the resist layer corresponding to the window of the lower mask, and developing the exposed second resist layer to form Forming a second resist pattern as an upper layer mask for forming an electrode; forming the electrode forming thin film on the entire surface of the substrate on which the lower layer mask and the upper layer mask have been formed; And a step of removing And butterflies.

(A) between the light reflected by the intermediate film of the exposure light and the light passing through the intermediate film and the thin film for forming the lower mask and reflected by the base material; , 18
A film thickness that gives a phase difference of 0 degrees.

(B) A thin film having a refractive index different from that of the resist layer and partially reflecting and partially transmitting the exposure light. Of course, the intermediate film itself has a thickness that does not substantially cause a phase shift of light transmitted therethrough.

Here, as a specific material constituting the thin film for forming the lower layer mask, a silicon nitride film (SiN film), S
An organic insulating film such as an iO ₂ film, a SiON film, and a polyimide or other resist that is immiscible with the resist to be used can be given. Further, a conductive film such as polysilicon may be used as long as it can be selectively etched between the base material and the electrode forming thin film.

The term "film thickness giving a phase difference of 180 degrees" referred to in the present invention means not only a film thickness giving a phase difference of 180 degrees but also a film thickness in the vicinity of the film thickness. The film thickness in the obtainable range is also included.

Further, as a specific material constituting the intermediate film, a metal can be cited. This is because a metal thin film can be a thin film partially reflecting light and partially transmitting light depending on its thickness. Specifically, titanium (Ti), tungsten (W), and the like can be given.

In practicing the present invention, the above-mentioned intermediate film is made of a material which is anisotropically etched in the thickness direction of the intermediate film by etching with an etching means for selectively removing the above-mentioned thin film for forming a lower layer mask. It is preferred to configure. Examples of such a material include Ti and W.

[0017]

According to the structure of the present invention, a predetermined intermediate film is interposed between the lower mask forming thin film and the resist layer.
A part of the exposure light is reflected by the intermediate film toward the resist layer (this reflected light is hereinafter referred to as “first reflected light”). On the other hand, the thin film for forming the lower mask is transparent to the exposure light, so that the light transmitted through the intermediate film reaches the base material, and the light reflected by the base material is returned to the resist layer. In addition, since the lower mask forming thin film is optically separated from the resist layer by the intermediate film, it effectively functions as the film having the above-mentioned thickness (a), and the light reflected by the substrate of the exposure light ( Hereinafter, "2nd
Reflected light. " ) Is shifted by 180 degrees with respect to the phase of the first reflected light. Therefore, when the first and second reflected lights return to the resist side, the two reflected lights interfere with each other, so that the light intensity is reduced and the influence of the reflected light from the base material side is reduced. Generation can be prevented, and even if a standing wave is generated, its intensity can be reduced. Here, if the intermediate film is not provided, the thin film for forming the lower mask is generally formed of an insulating film or a resin film, and the refractive index thereof is close to that of the resist layer. Even if a predetermined film thickness as shown in FIG.
Optically, the thickness of the resist layer is increased, and the above-mentioned effect (a) cannot be achieved. In this regard, the meaning of the present invention is significant.

When the intermediate layer is made of a material which is anisotropically etched during the etching of the thin film for forming the lower mask, the upper dimension of the etched portion of the thin film for forming the lower mask is defined by the etching trace of the intermediate film. Is done. That is, even if the thin film for forming the lower mask is slightly over-etched, the size of the opening is secured. Then, in a later step, a thin film for forming a T-shaped electrode is formed on the entire surface of the sample and then lift-off is performed, so that the base of the T-shaped electrode has a desired size.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a method for forming a T-shaped electrode according to the present invention. The following description will be made with an example in which the method of the present invention is applied to a case where a gate electrode of a field effect transistor (FET) having a recess structure is formed. Further, in the following embodiments, an example is shown in which the resist is exposed by i-line.

1. Example FIGS. 1A to 1E and FIGS. 2A to 2D are process diagrams for explaining an example. Each figure is shown by a cross-sectional view corresponding to a cross section of the FET cut along the gate length direction. However, the drawings used in the description merely schematically show the dimensions, shapes, and arrangements of the components so that the present invention can be understood.

First, a T-shaped substrate is formed on a GaAs substrate 31 as a base material on which an active layer (not shown) is formed and an element isolation region and an ohmic electrode (both not shown) are formed. A silicon nitride film (SiN film) 33 is formed as a thin film for forming a lower layer mask for forming an electrode to a thickness of 120 nm in this case, for example, by a plasma CVD method. Further, a 5 nm-thick Ti film 35 is formed as an intermediate film on the SiN film 33 by, for example, an electron beam evaporation method (FIG. 1A).

Here, the reason why the thickness of the Ti film 35 is set to 5 nm is that when this thickness is used, a part of the i-line which is the exposure light can be reflected and a part of the i-line can be transmitted in the subsequent resist exposure. Because you can. Of course, the thickness of the Ti film is not limited to this. However, if the thickness of the Ti film is too small, the exposure light is almost transmitted, so that almost no reflected light of the exposure light on the Ti film can be obtained.
Since it is difficult to allow the light to pass through the N film 33, the thickness of the Ti film needs to be within an appropriate range. According to experiments by the inventor, when the i-line is used, the above object is not achieved when the thickness of the Ti film is 3 nm, and the above object is achieved when the thickness is 10 nm.

The reason why the thickness of the SiN film 33 is set to 120 nm is that the light (first reflected light) reflected by the i-line intermediate film 35, which is the exposure light, has this thickness. GaAs substrate 31 passing through light intermediate film 35 and SiN film 33
This is because it is considered that a phase difference of 180 degrees can be given to the light reflected by the light source (the second reflected light).
However, for the film thickness of 120 nm, a value obtained by calculation as follows is actually applied to the present production. That is, assuming a structure having a SiN film on a GaAs substrate, the reflectance of the SiN film when an i-line is made incident perpendicularly to the surface of the SiN film and through air, and the film thickness of the SiN film as a parameter , Respectively. However,
The refractive index of the SiN film is considered to be 2.1. The reflectivity shows a minimum at several different film thicknesses. FIG. 3 is a characteristic diagram showing the results in which the vertical axis indicates the reflectance and the horizontal axis indicates the thickness of the SiN film. As is apparent from FIG.
The reflectance of the i-line on the iN film is 40 n
m and a minimum value at 120 nm (of course, there is a film thickness at which the reflectance has a minimum value even in a thicker film thickness region). When such a minimum value is obtained, when the thickness of the SiN film is 40 nm or 120 nm, the light reflected by the interface between the air and the SiN film of the i-line and the GaAs after passing through the SiN film. This is because the phase difference between the light reflected on the substrate surface and returned to the air side is 180 degrees, and the light interferes so as to weaken each other. However, if a resist layer is provided directly on the SiN film, the refractive index of the resist is 1.65, which is relatively close to that of the SiN film, so that the interface between the SiN film and the resist layer functions as an i-line reflecting surface. No longer
The effect of minimizing the reflectance as shown in FIG. 3 cannot be obtained. However, in the present invention, since the reflection surface is provided by providing the Ti film on the SiN film, the effect of minimizing the reflectance as shown in FIG. 3 can be obtained. The thickness of the SiN film for minimizing the reflectance is 40 nm or 120 nm as described above.
Further, there is another specific film thickness which is larger than this. However, if the film thickness is too thin, it is difficult to control the film thickness at the time of film formation. In this case, it is 120 nm.

Next, on this Ti film 35, a first negative type
FSMR (resist manufactured by Fuji Pharmaceutical Co., Ltd.) is coated to a thickness of 0.7 μm in this case. Next, this dying layer is formed by the PEL disclosed in the above-mentioned Document II.
Exposure by the method. The exposure amount at this time is 250 mJ / cm
^{And 2} . On the exposed first resist layer, a first thin unexposed portion (not shown) corresponding to the edge of the phase shifter is formed. The exposed sample is developed. Thus, the opening width (the dimension indicated by W in FIG.
A first resist pattern 37 having an opening 37a of 15 μm is obtained (FIG. 1B). FIG. 4A is a view simulating a scanning electron micrograph of a cross section of the first resist pattern 37 thus obtained. As is clear from this figure, according to the method of Example, the comparative example (FIG.
(B). It can be seen that a resist pattern in which the unevenness of the resist side wall is smaller than that of the resist pattern described later can be obtained. This is because the Ti film 35 and the SiN film 33 having a predetermined thickness are formed.
This is because the intensity of light returning from the lower side of the resist to the resist side is reduced, and the standing wave is accordingly reduced.

In the PEL method, as described above, the resist pattern size can be controlled by the exposure amount. The width of the opening (the dimension indicated by W in FIG. 1B) of the resist pattern obtained by exposing the FSMR (resist) used in this embodiment by the PEL method and then developing it is different in the exposure amount. FIG. 5 shows how the above changes occur.

Next, using the resist pattern 37 as a mask, the Ti film 35 and the SiN film 33 are selectively removed by reactive ion etching (RIE) using SF ₆ , respectively, and a part of the surface of the GaAs substrate 31 is removed. Window 3 exposed
A lower mask 39 having 9a is obtained (FIG. 1C). When the formed lower layer mask 39 was observed, FIG.
As shown in (1), the side etching of the SiN film 33 is extremely smaller than that of the comparative example (described later). Therefore, a window 39a having an opening width substantially equal to the opening width W of the resist pattern 37 is formed. I knew it was there.
This is because the Ti film 35 is anisotropically etched in the film thickness direction by RIE using SF ₆ , so that the opening width of the Ti film 35 is not widened and becomes a desired width (a small opening). This is because the effect of the radical on the SiN film is reduced.

Next, the first resist pattern 37 is removed, and then the above-described F
SMR is applied to a thickness of 0.7 μm to form a second resist layer 4
1 (FIG. 1D).

Next, the second resist layer 41 is passed through an exposure mask used at the time of exposure for forming the first resist pattern 37, corresponding to 1 / 2.5 of the previous exposure amount.
Exposure is performed at an exposure amount of 0 mJ / cm ² . Thereby, the second
In a portion of the resist layer 41 corresponding to the window 39a of the lower layer mask 39, a thin line-shaped second unexposed portion (not shown) wider than the window 39a is formed. Next, the exposed second
Is developed to obtain a second resist pattern 41a as an upper layer mask for forming the T-shaped electrode (FIG. 1E). The second resist pattern (lower mask) 41a of the opening width (dimension shown in FIG. 1 (E) medium W _1.) Will be 0.35 .mu.m (the exposure amount and the resist opening length shown in FIG. 5 It is clear from the relationship diagram.).

Next, using the lower layer mask 39 as a mask, the GaAs substrate 31 is moved 100 nm from the surface by an etching solution.
2 to form a recess 31a (FIG. 2)
(A)).

Next, a T-shaped electrode forming thin film 43 is formed on the sample. In this case, as the thin film 43, Ti
(Titanium) with a thickness of 20 nm, Al (aluminum)
Are sequentially formed to a thickness of 500 nm by an electron beam evaporation method. However, both films are not separately shown in the figure.

Next, the upper layer pattern (second resist pattern) 41a is removed using an organic solvent. At this time, the portion of the thin film 43 for forming the T-shaped electrode on the upper layer pattern 41a is also removed (lifted off). Then, the lower layer mask 3
9 (Ti film 35 and SiN film 33) are removed by plasma etching. Thereby, the T-shaped electrode 43a can be formed on the recess 31a.

2. Comparative Example A T-shaped electrode was formed in exactly the same procedure as in the example except that the Ti film was not used in the configuration of the example. At this time, the cross-sectional shape of the side wall of the first resist pattern and the state of the opening after forming the opening in the SiN film are observed with a scanning electron microscope (SEM). FIG.
(B) shows a simulated SEM photograph of the first resist pattern of the comparative example. It can be seen that the side walls have significantly more irregularities than those of the example (FIG. 4A). FIG. 6 (B) is a simulated SEM photograph of the opening of the SiN film of the comparative example. It can be seen that the side etching is larger than that of the example (FIG. 6A).

Although the embodiment of the method for forming a T-shaped electrode according to the present invention has been described above, the present invention is not limited to the above embodiment.

For example, in the above description, the etching of the intermediate film and the thin film for forming the lower mask is performed in the same step. However, in order to increase the etching accuracy, the etching is performed under different etching conditions or different etching means. May be.

In the above description, the recess etching is performed by wet etching, but may be performed by dry etching. At this time, if Cl ₂ is used as an etching gas when the intermediate film is a Ti film, the Ti film functions as a suitable etching mask and recess etching can be performed without increasing the opening width of the SiN film.
A finer recess gate structure can be obtained. In other words, by appropriately selecting the material of the intermediate film and / or by appropriately selecting the means for etching the thin film for forming the lower layer mask and the base material, the intermediate film is provided with a function as an etching mask in addition to the function of the antireflection film. it can.

In the above description, the present invention is applied to the formation of the gate electrode of the FET having the recess gate.
The present invention relates to a MOSFET, a bipolar transistor,
Obviously, the present invention can be applied not only to the manufacture of various semiconductor elements such as diodes, but also to various fields requiring fine electrodes.

In the above description, an example was described in which the exposure light was i-line. However, the present invention can be applied to the case where light of another wavelength is used for exposure.

[0038]

As is apparent from the above description, according to the electrode forming method of the present invention, the thickness of the thin film for forming the lower mask is set to a predetermined value and a predetermined intermediate film is used.
The intensity of the reflected light returning from below the resist layer to the resist layer side can be reduced as compared with the related art. For this reason, the degree of interference between the exposure light and the reflected light is reduced, so that generation of a standing wave can be prevented or the intensity of the standing wave can be reduced as compared with the related art. Therefore, a fine T
A shaped electrode (for example, one having a base width of 0.2 μm or less) can be formed.

When the intermediate layer is made of a material which is anisotropically etched when etching the thin film for forming the lower mask, the intermediate film can define the base dimension of the T-shaped electrode. The etching allowance of the mask forming thin film can be increased as compared with the related art.

[Brief description of the drawings]

FIGS. 1A to 1E are process diagrams for explaining a method of an embodiment.

2 (A) to 2 (D) are process diagrams following FIG. 1 for explaining a method of an embodiment.

FIG. 3 is a diagram showing grounds for determining the thickness of a thin film for forming a lower mask.

FIGS. 4A and 4B are diagrams showing a state of a resist pattern side wall of an example and a comparative example.

FIG. 5 is a diagram showing a relationship between a resist exposure amount and a resist opening length in an exposure method (PEL method) used in Examples.

FIGS. 6A and 6B are diagrams showing a difference in a side etching amount between an example and a comparative example.

FIG. 7 is a diagram provided for explanation of a conventional device and the present invention;
It is a figure showing the outline of a character-shaped electrode.

FIG. 8 is a process chart for explaining a conventional method.

[Explanation of symbols]

 31: base material (for example, GaAs substrate) 33: thin film for forming lower layer mask (for example, SiN film) 35: intermediate film (for example, Ti film) 37: first resist pattern 39: lower layer mask 41: second resist layer 41a: Second resist pattern (upper layer mask) 31a: Recess 43: Thin film for forming T-shaped electrode 43a: T-shaped electrode

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/338 H01L 21/28 H01L 29/778 H01L 29/812 H01L 21/306 H01L 21/30 576 G03F 7 / 26 511 G03F 7/26 513

Claims (4)

(57) [Claims] 1. A thin film for forming a lower layer mask for forming an electrode having an upper portion having a width larger than that of a base portion on a substrate, wherein the thin film is transparent to exposure light and has the following (a): Forming a lower-layer mask-forming thin film having a thickness satisfying the following conditions; and forming an intermediate film satisfying the following condition (b) on the lower-layer mask-forming thin film; Forming a resist layer, selectively exposing the first resist layer, and then developing the first resist layer to form a first resist pattern having a fine line opening; and forming the first resist pattern. A step of selectively removing the intermediate film and the lower layer mask forming thin film using a mask as a mask to obtain a lower layer mask having a window exposing a part of the base material surface; and removing the first resist pattern, Second resist on sample with lower mask formed Forming a layer, selectively exposing the second resist layer, and then developing the second resist layer to have a fine line-shaped opening wider than the window at a portion corresponding to the window of the lower layer mask; Forming a second resist pattern as an upper layer mask for forming an electrode; forming the electrode forming thin film over the entire surface of the substrate on which the lower layer mask and the upper layer mask have been formed; Removing the electrode. (A) between the light of the exposure light reflected by the intermediate film and the light of the exposure light passing through the intermediate film and the thin film for forming a lower mask and reflected by the substrate, at an angle of about 180 degrees; A film thickness that gives a phase difference. (B) A thin film having a refractive index different from that of the resist layer and partially reflecting and partially transmitting the exposure light. 2. The method according to claim 1 , wherein the width of the upper portion is equal to the width of the base portion.
Forming a lower-layer mask-forming thin film for forming a wider electrode, wherein the lower-layer mask-forming thin film is transparent to exposure light and has a thickness satisfying the following condition (a): Forming an intermediate film that satisfies the following condition (b) on the lower mask forming thin film; forming a negative first resist layer on the intermediate film; Exposing through a mask for exposure including a shifter to form a first thin line-shaped unexposed portion corresponding to an edge of the phase shifter in the first resist layer; Developing a first resist pattern, and selectively removing the intermediate film and the lower mask forming thin film using the first resist pattern as a mask, thereby exposing a part of the substrate surface. Obtaining a lower layer mask having a window; Removing the first resist pattern and forming a negative-type second resist layer on the sample on which the lower-layer mask has been formed; and applying the second resist layer to the first mask through the exposure mask. Exposure is performed with an exposure amount smaller than the exposure amount at the time of exposure of the resist layer, and a thin line-shaped second unexposed portion wider than the window is formed on a portion of the second resist layer corresponding to the window of the lower layer mask. Forming, developing the exposed second resist layer to form a second resist pattern as an upper mask for forming the electrode, and forming the base material on which the lower mask and the upper mask are formed after forming the <br/> those electric electrode-forming film on the entire surface, forming method that electrodes be characterized in that it comprises a step of removing these lower and upper mask. (A) between the light of the exposure light reflected by the intermediate film and the light of the exposure light passing through the intermediate film and the thin film for forming a lower mask and reflected by the substrate, at an angle of about 180 degrees; A film thickness that gives a phase difference. (B) A thin film having a refractive index different from that of the resist layer and partially reflecting and partially transmitting the exposure light. 3. A method of forming electrodes according to claim 1 or 2, the intermediate layer, a material that is anisotropically etched by etching with etching means for selectively removing said thin film for lower layer mask forming configuration formed method that electrodes be characterized by the. 4. A method for forming a conductive <br/> pole according to any one of claims 1 to 3, constitutes the thin film underlayer mask formed of a silicon nitride film,
The intermediate layer of titanium (Ti) forming method that electrodes be <br/> characterized by being configured with a membrane.