JP3563809B2 - Pattern formation method - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a pattern forming method using a lift-off method, and more particularly to a method for forming a pattern of a photomask used for manufacturing a semiconductor device such as an IC, an LSI, and a super LSI.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a metal, a metal compound, and an organic compound have been used in the state of a patterned thin film when manufacturing a semiconductor element or a photomask used for manufacturing a semiconductor element.
For example, in a semiconductor element, a metal wiring, a resistor, a capacitor dielectric, an insulator, and in a photomask, patterning of a thin film of a metal or a metal compound used for a light-shielding film pattern or the like is usually performed on a substrate using the metal or metal compound. A thin film is formed on the entire surface by a sputtering method or a CVD method, a photoresist or the like is applied and formed on the thin film, ionizing radiation is selectively irradiated, a process such as development is performed, and a resist pattern is formed. As a mask, the metal or metal compound is selectively etched by a wet etching method or a dry etching method.
Patterning of organic compounds has been performed by a method of selective dry etching or a method of selective deposition.
The formation of a thin film pattern by a wet etching method or a dry etching method will be described with reference to FIG.
First, a photoresist (masking material) 33 is applied on a thin film 31 of a substrate 32 composed of a transparent substrate 30 and a thin film 31 (FIG. 3A), and then the photoresist 33 is selectively irradiated with ionizing radiation 34. (FIG. 3B), a desired resist pattern 33A is obtained through a development process and the like. (FIG. 3 (c))
Thereafter, using the resist pattern 33A as a mask, the exposed portions of the thin film 31 are removed by wet etching or dry etching (FIG. 3D), and then the resist pattern 33A is removed to obtain a desired thin film pattern. Obtain 31A. (FIG. 3 (e))
This method is generally used for producing a usual photomask.
However, depending on the type of metal, metal compound and organic compound, wet etching or dry etching cannot be performed, or even if wet etching or dry etching can be performed, wet etching with a resist (photosensitive polymer masking material) is chemically resistant. However, there is a problem in resistance to dry etching and the like, and some of them cannot be actually used.
[0003]
To cope with this, a method of patterning a thin film using a lift-off method has been proposed.
The lift-off method simply includes a masking material made of a resist or the like patterned on a base material, forms a thin film for performing desired patterning on the entire surface of the base material, and then applies the masking material to a solvent or the like. Dissolves and swells to remove the masking material and remove the thin film formed on the masking material, thereby obtaining a desired thin film pattern on the substrate.
Further, formation of a thin film pattern by a conventional lift-off process will be described with reference to FIG.
First, a photoresist (masking material) 23 is applied to the surface of a substrate (transparent substrate) 20 (FIG. 2A), and then the photoresist 23 is selectively irradiated with ionizing radiation 24 (FIG. 2B). And a developing process to obtain a desired resist pattern 23A. (Fig. 2 (c))
Thereafter, a metal thin film 25 is formed on the entire surface of the substrate 20 including the resist pattern 23A. (Fig. 2 (d))
Next, while dissolving or swelling the resist pattern (masking material) 23A portion with a solvent or the like to remove it, the metal thin film 25a formed on the resist pattern (masking material) 23A portion is simultaneously removed to remove another substrate. A pattern made of a desired metal thin film is formed while the metal thin film 25b directly formed thereon is left as it is. (FIG. 2 (e))
Here, the resist pattern 23A serves as a masking material when lifted off.
[0004]
However, even in the patterning of a thin film using the conventional lift-off process, depending on the composition of the film to be lifted off, the substrate needs to be heated during film formation or a high vacuum state is required.
If a photoresist is used as a masking material when lift-off is performed when heating or high vacuum of the substrate is required during film formation, problems may occur in terms of heat resistance and degassing properties.
Therefore, instead of the resist as a masking material in the conventional thin film patterning method using a lift-off method, a patterning method using a thin film made of a metal or a metal compound having excellent heat resistance and degassing properties has been proposed. I have.
[0005]
[Problems to be solved by the invention]
As described above, even in a conventional thin film patterning method using a lift-off method, use of a thin film made of a metal film or a metal compound having excellent heat resistance and degassing properties as a mask material for lift-off has been proposed. It is necessary to pattern a metal film or a metal compound thin film as a lift-off masking material. That is, a step of patterning a metal film or a thin film of a metal compound as a mask material for lift-off by transfer using a patterned photomask is required. For this reason, it is necessary to perform the buttering process twice as a whole process, the process becomes long and complicated, and there have been problems in terms of quality and workability in pattern production.
Under such circumstances, the present invention provides a method of patterning a thin film using a lift-off method, wherein a metal film is used as a masking material at the time of lift-off, and only one patterning is required. It is intended to provide. In particular, an object of the present invention is to provide a method of patterning a thin film made of a material that is difficult to pattern by a wet etching method or a dry etching method, such as a thin film containing gold, platinum, hafnium oxide, or the like.
[0006]
[Means for Solving the Problems]
The pattern forming method of the present invention is a method of forming a pattern such as a photomask by a lift-off method, and in order,
(A) a step of arranging a plating mask on a conductive layer on a transparent substrate and then performing plating, and selectively forming a plating film on the conductive layer;
(B) a step of removing a plating mask while leaving a plating film on the conductive layer formed selectively;
(C) using the plating film on the selectively formed conductive layer as a mask, selectively removing the conductive layer by etching or the like;
(D) forming a thin film for forming a lift-off layer on the entire surface of the plating film on the transparent substrate and on the selectively formed conductive layer;
(E) The plating film and the conductive layer on the conductive layer selectively formed are removed by etching or the like, the thin film on the plating film is removed, and a pattern is formed by the thin film formed directly on the transparent substrate. Lift-off process,
It is characterized by including.
The conductive layer is made of a metal or a metal compound such as chromium.
The pattern forming method of the present invention is a method of forming a pattern such as a photomask by a lift-off method.
(A) After performing a treatment such as immersion of a catalyst solution such as palladium on the surface of a transparent substrate, a plating mask is disposed on the surface of the transparent substrate, and then electroless plating is performed. A step of forming a plating film,
(B) removing the plating mask, leaving the plating film on the transparent substrate formed selectively;
(C) forming a thin film for forming a lift-off layer on the entire surface of the transparent substrate and the plating film;
(D) a lift-off step of removing the plating film on the transparent substrate formed selectively by etching or the like, removing the thin film on the plating film, and forming a pattern by the thin film directly formed on the transparent substrate;
It is characterized by including.
Then, the plating mask is, in order, a step of coating and forming a resist directly on the transparent substrate or on the conductive layer on the transparent substrate, a step of selectively irradiating the coated and formed resist with ionizing radiation, and developing. And a step of forming a plating mask made of a resist pattern by performing a process or the like. Further, the thin film for forming the lift-off layer is made of gold, platinum, hafnium oxide alone or a substance containing them.
[0007]
[Action]
According to the pattern formation method of the present invention, by adopting the above structure, in a thin film patterning method using a lift-off method, a metal film is used as a masking material at the time of lift-off, and only one patterning is required. This enables a patterning method by a lift-off method.
More specifically, since a metal film is used as a masking material at the time of lift-off, even when the substrate is heated or in a high vacuum state when forming a thin film for forming a desired thin film pattern, it is shown in FIG. This solves the problems of the heat resistance and degassing properties of the masking material (resist), which were found when the masking material at the time of lift-off was a photoresist.
In the case of the pattern forming method of the present invention, the patterning is performed only once, and the metal or metal compound is patterned on the substrate to form a mask material for lift-off. 23A greatly simplifies all the steps as compared to a step in which 23A is simply replaced with a metal or metal compound pattern formed by transfer.
As a result, a product excellent in quality is obtained, and the workability is also superior to the process in which the photoresist pattern 23A is replaced with a metal or metal compound pattern in the conventional process shown in FIG.
Further, since the thin film is patterned by the lift-off method, it is possible to pattern the thin film, which is incompatible with the conventional wet etching method or dry etching method shown in FIG.
Since the conductive layer is made of a metal or a metal compound such as chromium, a conventional photomask blank can be applied as it is.
Further, the step of forming the plating mask includes, in order, a step of applying and forming a resist on the conductive layer on the transparent substrate, and exposing and developing the resist on the conductive layer to form a plating comprising a resist pattern. Since the method includes a step of forming a mask for use, a conventional resist plate making step for producing a photomask can be applied as it is.
Further, by forming the thin film for forming the lift-off layer from gold, platinum, hafnium oxide or a substance containing them, particularly, patterning of a thin film made of a material that is difficult to pattern by a wet etching method or a dry etching method. The method allows the process to be accomplished with relatively simple steps.
[0008]
【Example】
An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a process chart showing a pattern forming method of the present embodiment.
In FIG. 1, 10 is a transparent substrate, 11 is a light shielding film, 12 is a photomask blank, 13 is a resist, 13A is a resist pattern, 14 is ionizing radiation, 15 is a plating layer, 16 is a thin film, 16a is a lift-off layer, and 16b thin film. This is the pattern section.
[0009]
Hereinafter, the pattern forming method of this embodiment will be described along each step with reference to FIG. First, a resist 13 is formed on a conductive film (light-shielding film) 11 of a photomask blank 12 in which a conductive film (light-shielding film) 11 of a 0.1 μm- thick metallic chromium thin film is provided on a transparent substrate 10 made of a quartz glass plate. It was applied (FIG. 1A). As the resist 13, an electron beam positive type resist AZ-5200 (manufactured by Hoechst) was used, and was subjected to a heat drying treatment by a spin coating method to have a thickness of about 1.0 μm. The heat treatment was performed at 150 ° C. for 20 minutes using a hot plate. Next, the resist 13 was selectively irradiated with ionizing radiation 14 (FIG. 1B), developed and dried to form a resist pattern 13A. (Fig. 1 (c))
Irradiation with ionizing radiation 14 is carried out using a normal electron beam apparatus at an acceleration voltage of 10 KeV and an exposure amount of 10 μC / cm 2, and developed with a water-soluble alkali developer containing tetramethylammonium oxide as a main component at room temperature for 1 minute. After rinsing with pure running water and spin drying, heat treatment was performed in an oven at 120 ° C. for 30 minutes to increase the adhesion between the resist pattern 13A and the conductive film (light-shielding film) 11. Next, copper sulfate electrolytic plating is performed using the resist pattern 13A as a plating mask, and a plating layer 15 is formed on the exposed region of the conductive film (light shielding film) 11 to a thickness of about 0.8 μm, which is slightly thinner than the plating mask. Filmed. (Fig. 1 (d))
The copper sulfate plating used here was prepared by mixing a suitable amount of 220 g / l of copper sulfate hydrate, 60 g / l of sulfuric acid, 50 mg / l of chloride ion, and an appropriate amount of a commercially available brightener for copper plating. The plating was performed at 23 to 28 ° C., a cathode current density of 1 to 4 Ad / mm 2, and an anode current density of 1 to 24 Ad / mm 2. The plating layer 15 is formed only on the conductive film (light-shielding film 11) exposed due to the electrolytic plating. Further, since it is used as a masking material for lift-off, it is necessary that the thickness is not larger than the size of the opening of the resist, and the plating time is adjusted so that the thickness of the plating layer 15 is smaller than the thickness of the resist pattern 13A. Thereafter, the resist pattern 13A was removed by solvent stripping. (Fig. 1 (e))
Stripping of the resist pattern 13A was performed with a stripping solution containing ethanolamine as a main component at 60 ° C. for 3 minutes under ultrasonic waves, and rinsed with pure water. Next, the exposed conductive film (light shielding layer) 11 was wet-etched using the plating layer 15 as a mask. (Fig. 1 (f))
The wet etching was performed by spray etching with an aqueous solution containing ceric ammonium nitrate as a main component at room temperature for 1 minute, and pure and rinsed. Next, a thin film 16 made of hafnium oxide (HfO2) was formed to a thickness of about 300 nm on the entire surface of the transparent substrate 10 including the plating layer 15 by sputtering. (Fig. 1 (g))
Thereafter, the plating layer 15 made of metallic copper and the conductive film (light shielding film) 11 made of metallic chromium are removed by etching with an aqueous solution containing ceric ammonium nitrate as a main component, and are formed on the plating layer 15. The lift-off layer 16a was removed to obtain a desired thin film pattern 16b made of hafnium oxide (HfO2). (Fig. 1 (h))

[0010]
Although the embodiments of the present invention have been described above, the materials, devices, conditions, and the like used in the embodiments are not limited thereto. In particular, the plating conditions are not limited to these conditions because they are strongly affected by the plating apparatus, the area of the plating surface, the type of plating film, and the like.
Incidentally, hafnium oxide (HfO ₂ ), which is a masking material at the time of lift-off, is used for an etching stopper layer of a phase shift photomask and the like, and it is said that dry etching and wet etching are difficult.
[0011]
In the above embodiment, a photomask blank in which a conductive film (light shielding layer) 11 is provided on the transparent substrate 10 is used. However, after forming a resist pattern directly on the transparent substrate 10, only the exposed substrate surface is used. May be formed by electroless plating to form a plating layer 15 shown in FIG.
In this case, immersion is performed in advance with a catalyst solution such as palladium before applying a resist on the transparent substrate 10.
[0012]
【The invention's effect】
The pattern forming method of the present invention is, as described above, a method of patterning a thin film using a lift-off method, wherein a metal film is used as a masking material at the time of lift-off, and only one patterning is required. Is possible.
For this reason, in the conventional lift-off method shown in FIG. 2, since the process is simplified as compared with a case where a metal or a metal compound is used as a masking material for lift-off by transfer, patterning excellent in quality is achieved. It is possible.
Of course, since the thin film is patterned by the lift-off method, it is possible to pattern the thin film, which is incompatible with the conventional wet etching method or dry etching method, as shown in FIG.
As a result, it is possible to pattern and produce thin films made of gold, platinum, hafnium oxide alone or a substance containing them, which were considered to be difficult to produce by conventional wet etching or dry etching, with relatively simple steps. I have.
[Brief description of the drawings]
FIG. 1 is a process diagram of a pattern forming method of an embodiment. FIG. 2 is a process diagram of a conventional lift-off method. FIG. 3 is a process diagram for explaining a conventional wet etching method and a dry etching method.
10 transparent substrate 11 conductive film (light shielding film)
12 Photomask blanks 13 Resist 13A Resist pattern 14 Ionizing radiation 15 Plating layer 16 Thin film 16a Lift-off layer 16b Thin film pattern section 20 Substrate (transparent substrate)
23 Photoresist (masking material)
23A resist pattern 24 ionizing radiation 25, 25a, 25b metal thin film 30 transparent substrate 31 thin film 31A thin film pattern 32 substrate 33 photoresist (masking material)
33A resist pattern 34 ionizing radiation

Claims (5)

In this method, a pattern such as a photomask is formed by a lift-off method. (A) A plating mask is disposed on a conductive layer on a transparent substrate, plating is performed, and plating is selectively performed on the conductive layer. Forming a film, (B) removing a plating mask while leaving a plating film on the selectively formed conductive layer, and (C) using a plating film on the selectively formed conductive layer as a mask. Selectively removing the conductive layer by etching or the like; (D) forming a thin film for forming a lift-off layer on the entire surface of the plating film on the transparent substrate and the selectively formed conductive layer. (E) removing the plated film and the conductive layer on the selectively formed conductive layer by etching or the like, removing the thin film on the plated film, and forming a pattern by the thin film directly formed on the transparent substrate. Form Pattern forming method, which comprises the lift-off step. 2. A pattern forming method according to claim 1, wherein the conductive layer is made of a metal or a metal compound such as chromium. This is a method of forming a pattern such as a photomask by a lift-off method. (A) After immersing a transparent substrate surface in a catalyst solution such as palladium, a plating mask is disposed on the transparent substrate surface. After that, a step of performing electroless plating to selectively form a plating film on a transparent substrate, (b) a step of removing a plating mask while leaving the selectively formed plating film on the transparent substrate, ( c) a step of forming a thin film for forming a lift-off layer over the entire surface of the transparent substrate and the plating film, and (d) removing the selectively formed plating film on the transparent substrate by etching or the like, A lift-off step of removing the thin film on the plating film and forming a pattern with the thin film formed directly on the transparent substrate. The plating mask according to any one of claims 1 to 3, is a step of coating and forming a resist directly on a transparent substrate or on a conductive layer on the transparent substrate, and selectively irradiating the coated resist with ionizing radiation. A pattern forming method, wherein the pattern forming method is performed through a step of performing, a step of performing a developing process, and a step of forming a plating mask made of a resist pattern. 5. A pattern forming method according to claim 1, wherein the thin film for forming the lift-off layer is made of gold, platinum, hafnium oxide alone or a substance containing them.

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