JP2954442B2 - Wiring pattern forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for forming a wiring layer of a semiconductor device, for example, an LSI, and more particularly to a method of etching a metal film for wiring using an etching mask.

[0002]

2. Description of the Related Art Conventionally, aluminum (Al) is mainly used for wiring between elements of a semiconductor device such as an LSI.
The reason for using Al is that Al has characteristics such as low resistance, easy processing, easy contact with silicon and other metals, and low contact resistance. is there.

However, as the degree of integration of integrated circuits has been increased and the wiring width has been reduced to the submicron level, device failure due to disconnection of Al wiring has become a problem. It is becoming clear that the cause of the failure is Al electromigration and stress migration.

Therefore, in order to prevent such disconnection of the Al wiring, there has been proposed a contrivance such as forming a laminated wiring structure in which the Al wiring is lined with a refractory metal such as tungsten (W). On the other hand, a method of changing the wiring material itself has been proposed and studied. As a wiring material, a material having low resistance and high migration resistance, such as W or Cu, is being studied. For example, Reference 1: "Extended Abstracts of the 22
nd (International) Conference on Solid State Deveice
s and Materials, Sendai, 1990, pp, 215-218 ''
A method for forming a wiring is disclosed.

A method for forming a Cu wiring pattern disclosed in the above-mentioned reference 1 will be briefly described below with reference to the drawings. 3A to 3C are process diagrams for explaining a conventional method of forming a Cu wiring pattern.

First, a Cu film 1 formed on a thermal oxide film 10
A TiN film 14 is provided on the substrate 2 for improving adhesion, and a photoresist layer 16 is further formed thereon (FIG. 3A).

Next, the photoresist layer 16 is patterned by photolithography, and the obtained resist pattern 18 is UV-cured.
By performing the baking, the heat resistance of the resist pattern 18 is improved (FIG. 3B).

Next, the wiring pattern 20 is formed by etching the TiN film 14 and the Cu film 12 using the resist pattern 18 as an etching mask. This etching uses SiCl ₄ , N ₂ , Cl ₂ as an etching gas.
And a mixed gas of NH ₃ and NH ₃ at a high temperature of 280 ° C. By adding NH ₃ to the etching gas,
NH ₃ and SiCl ₄ react with each other to deposit a Si ₃ N ₄ film on the side wall of the wiring pattern 20 being etched. By acting as a protective film for the side wall, fine wiring processing with a width of 1 micron level can be formed on the side wall with a relatively high uprightness (FIG. 3C).

[0009]

However, as the degree of integration of integrated circuits further increases, it becomes necessary to process wiring having a width on the order of submicrons. In the above-mentioned embodiment, since a photoresist cured by UV curing is used as an etching mask, the etching selectivity with Cu can be set to only about 6. Further, if NH ₃ is added to improve the uprightness, the selectivity will be reduced to about 2. This selectivity also becomes smaller when tungsten (W) or the like is used as the wiring metal film, as in the case of Cu.

[0010] Therefore, it is difficult to form a finer wiring pattern having a submicron or sub-half micron level width by using a conventional photoresist as an etching mask because the etching selectivity cannot be increased. It is.

On the other hand, if an oxide film is used as an etching mask, a large etching selectivity can be obtained.
However, when an oxide film is used, a step of transferring the photoresist pattern to the oxide film by etching is added.
For this reason, not only the number of steps increases, but also the etching accuracy may decrease due to the superposition of dimensional conversion errors during transfer.

By the way, the inventor of the present application has disclosed in Patent Document 2: Japanese Patent Application No. 4-017588, which is composed of a silicone resin in which an alkoxy group is bonded to the side chain of Si of polysiloxane and an acid generator. A radiation-sensitive resin composition has been proposed. In this resin composition, t is added to Si.
-A functional group having a CO bond such as a butoxy group is bonded;
The CO bond is broken by the acid to remove the carbon component from the polymer. As a result, the polymer is converted to an oxide film. Therefore, the inventor of the present application has conducted tests and studies, and concluded that an oxide film pattern can be formed without transferring a photoresist pattern by using the radiation resin composition. did.

Accordingly, it is an object of the present invention to provide a method of forming a wiring pattern which enables fine wiring processing at a sub-half micron level.

[0014]

In order to achieve the above object, according to the pattern forming method of the present invention, a step of forming a metal wiring material film on a base, a step of forming a metal wiring material film on the metal wiring material film,
Radiation-sensitive comprising a linear or ladder-like silicone resin having a C—O—Si bond for each monomer unit and an acid generator that decomposes under the action of radiation to generate an acid Forming a resist film of a resin composition, selectively irradiating the resist film with radiation, heating the irradiated resist film, and developing the resist film to form an oxide film pattern; Forming a wiring pattern by etching the metal wiring film using the film pattern as an etching mask.

Preferably, the linear poly (siloxane) is represented by the following formula (1), and the ladder poly (siloxane) is represented by the following formula (2): (2) The functional group R in the formula is at least selected from a functional group of hydrogen, tert-butyl, 1-phenethyl, 1-methyl-1-phenethyl, cyclohexen-2-yl and t-butoxycarbonyl. One or more functional groups are preferred.

[0016]

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Preferably, the acid generator comprises an aromatic compound having at least one trichloroethyl group,
It is preferable to use one kind of acid generator selected from the group consisting of sulfonium salts, iodonium salts and p-toluenesulfonic acid esters.

The heating temperature is desirably 60 ° C. or higher. This is because the heating time can be shortened.

[0019]

It is obvious that the oxide film itself does not have photosensitivity. However, if a radiation-sensitive composition that can be converted to an oxide film by photolithography is used, etching by transfer can be performed by only one photolithography. An etching pattern of an oxide film having a large etching selectivity with respect to a wiring metal material can be easily formed without fear of a decrease in accuracy. As a result, fine wiring processing at the sub-half micron level becomes possible. Here, the photolithography is
It includes steps from exposing the resist film to developing and forming an oxide film pattern.

As such a radiation-sensitive composition, the inventor of the present application describes in the literature: "Japanese Patent Application No. 4-01758.
No. 8 "and a trace amount of an acid generator which decomposes under the action of radiation such as light, electron beam, X-ray or ion beam to generate an acid, with the silicone resin shown in the following formulas (1) and (2). Have been proposed (hereinafter also referred to as compositions). After irradiating the composition with radiation, heat treatment is performed to obtain C as shown in the following formula (3).
Causes an elimination reaction to break the -O bond. In the film thus formed, a trace amount of a decomposition product of the acid generator remains as an organic component. However, the film used for etching may be substantially considered as an oxide film.

[0021]

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[0022]

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[0023]

Embodiments of the pattern forming method according to the present invention will be described below with reference to the drawings. The materials used and the numerical conditions such as the amount thereof, the processing time, the processing temperature, and the film thickness in the following examples are only preferred examples within the scope of the present invention. The drawings referred to below merely schematically show the sizes, shapes, and arrangements of the components so that the present invention can be understood. Therefore, it is clear that the present invention is not limited only to this embodiment.

First Embodiment FIGS. 1A to 1D are process diagrams for explaining a first embodiment of a method for forming a wiring pattern according to the present invention. still,
In the drawing, hatching or the like representing a cross section is partially omitted.

First, a linear poly (siloxane) silicone resin having a C—O—Si bond for each monomer unit and an acid generator that decomposes under the action of radiation to generate an acid are included. As a radiation-sensitive resin composition, 1.0 g of poly (siloxane) represented by the following formula (4) and 10 mg of triphenyltrifluoromethanesulfonate were dissolved in 9.0 ml of methyl isobutyl ketone, and this was dissolved in 0.2 ml.
A resist solution was prepared by filtration through a μm filter.

[0026]

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On the other hand, a 6-inch Si substrate 30 having a thermal oxide film 32 formed on its surface is used as a base 34, and a metal wiring material film 36 is formed on the thermal oxide film 32 by DC sputtering.
Then, a Cu film 36 is formed to a thickness of 0.5 μm (FIG. 1A).

Next, the above-mentioned resist solution is spin-coated at 2500 rpm on the Cu film 36, and baked at a temperature of 80 ° C. for 1 minute to form a resist film 38 having a thickness of 0.2 μm. Form.

Next, the resist film 38 is selectively irradiated with radiation. In this embodiment, a test pattern is selectively exposed on the resist film 38 with light having a wavelength of 249 nm using a KrF excimer laser stepper (NA = 0.42, reduced to 1/5). Exposure is 15mJ /
cm ² (FIG. 1B).

Next, the exposed sample was baked on a hot plate at a temperature of 120 ° C. for 2 minutes to form a resist film 38.
Is converted into an oxide film (not shown).

Next, the sample is developed in isoamyl acetate for 30 seconds and rinsed with cyclohexane for 30 seconds to form an oxide film pattern 40 (FIG. 1C). When the pattern of the sample on which the oxide film pattern 40 was formed was measured with a SEM length measuring machine, the minimum design dimension of the reticle was 0.4.
It was confirmed that micron lines and spaces were resolved. According to a characteristic curve obtained by examining the characteristics of the exposure amount and the residual film ratio prior to the formation of the oxide film pattern 40 of the first embodiment, the residual film ratio when the exposure amount is 15 mJ / cm ² is 60%. It is. Therefore, the thickness of the oxide film pattern 40 formed in this embodiment is 0.12 μm, which is 60% of the 0.2 μm thickness of the resist film.

Next, the sample on which the oxide film pattern 40 was formed was mounted on a parallel plate type dry etcher equipped with a 13.56 MHz rf oscillator, and SiCl ₄ , N ₂ , and Cl _{2 were used} as etching gases. , NH ₃ were introduced at 20, 80, 20, and ₃₀ SCCM, respectively, at a pressure of 2P.
a, the oxide film pattern 40 under the condition of the substrate temperature of 280 ° C.
Is used as an etching mask to etch the Cu film 36 to form a wiring pattern 38 (FIG. 1D).

The cross section of the formed wiring pattern 42 is SEM
As a result, it was found that a 0.4 μm line and space pattern was formed at a taper angle of 80 °.

Second Embodiment FIGS. 2A to 2D are process diagrams for explaining a first embodiment of a method for forming a wiring pattern according to the present invention. still,
In the drawing, hatching or the like representing a cross section is partially omitted.

First, using the same method and material as in the first embodiment, a Cu film 36 and a resist film 38 having the same film thickness as in the first embodiment are formed on the thermally oxidized 32 film (see FIG. A)).

Next, the resist film is selectively irradiated with an electron beam as radiation. In this embodiment, a test pattern is selectively exposed on the resist film 38 under the condition of an acceleration voltage of 20 kV using an electron beam lithography apparatus. The exposure amount is 5.0 μC / cm ² ((B) of FIG. 2).

Next, an oxide film pattern 46 is formed through the same steps as the formation of the oxide film pattern 40 of the first embodiment (FIG. 2C). When the pattern of the sample on which the oxide film pattern 46 was formed was measured with a SEM length measuring device, it was confirmed that a 0.25 micron line and space, which is the minimum design size of the reticle, was resolved. According to a characteristic curve obtained by examining the characteristics of the exposure amount and the residual film ratio before the formation of the oxide film pattern 46 of the second embodiment, the residual film ratio when the exposure amount is 5.0 μC / cm ² is obtained. 60%. Therefore, the thickness of the oxide film pattern 46 formed in this embodiment is 0.1%, which is 60% of the thickness of the resist film 38 of 0.2 μm.
Next, the Cu film is etched using the oxide film pattern 46 as an etching mask to form a wiring pattern 48 under the same conditions as in the first embodiment (FIG. 2D). Cross-section SEM of the formed wiring pattern
As a result, it was found that a 0.25 μm line and space pattern was formed at a taper angle of 75 °.

The etching of the Cu film is performed under the same conditions as in the second embodiment, and the etching is stopped when the wide portion of the Cu film has just disappeared. It was measured using SEM. As a result, it was found that the oxide film pattern was etched by about 50 nm. Therefore, the etching selectivity between the oxide film and Cu was about 0.5 μm / 50 nm = 10, which was larger than the conventional etching selectivity between cured photoresist and Cu.

In each of the embodiments described above, the present invention has been described with respect to an example in which a specific material is used and formed under specific conditions. However, the present invention can be subjected to many changes and modifications. For example, although Cu is used as the wiring metal material in the above-described embodiment, for example, tungsten W may be used in the present invention.

[0040]

According to the method for forming a wiring pattern of the present invention, since a radiation-sensitive composition that can be converted to an oxide film by photolithography is used, the pattern can be transferred by etching only once in photolithography. The etching pattern of the oxide film can be formed without performing this step. As a result, fine wiring processing at the sub-half micron level becomes possible.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining a first embodiment of a method for forming a wiring pattern according to the present invention;

FIG. 2 is a process chart for explaining a second embodiment of the method for forming a wiring pattern according to the present invention;

FIG. 3 is a process chart for explaining a conventional method for forming a wiring pattern;

[Explanation of symbols]

 10: Thermal oxide film 12: Cu film 14: TiN film 14a: TiN film pattern 16: Resist 18: Resist pattern 20: Wiring pattern 30: Si substrate 32: Thermal oxide film 34: Underlayer 36: Cu film 38: Resist film 40 : Oxide film pattern 42: Wiring pattern 44: Exposure area 46: Oxide film pattern 48: Wiring pattern

Claims (3)

(57) [Claims] A step of forming a metal wiring material film on an underlayer; and forming a linear or ladder-like poly (siloxane) having a C—O—Si bond for each monomer unit on the metal wiring material film. )
Forming a resist film of a radiation-sensitive resin composition containing a silicone resin consisting of and an acid generator that decomposes by the action of radiation to generate an acid; and selectively irradiating the resist film with radiation. Heating the resist film irradiated with the radiation and developing the resist film to form an oxide film pattern; and etching the metal wiring film using the oxide film pattern as an etching mask to form a wiring pattern. A pattern forming method. 2. The pattern forming method according to claim 1, wherein the linear poly (siloxane) is represented by the following formula (1), and the ladder poly (siloxane) is represented by the following formula (2). Wherein R is a hydrogen atom, tert-butyl, 1-phenethyl, 1-methyl-1-phenethyl, cyclohexen-2-yl and t-butoxycarbonyl. A pattern forming method, comprising at least one or more functional groups selected from a functional group. Embedded image 3. The pattern forming method according to claim 1, wherein the acid generator is an aromatic compound having at least one trichloroethyl group, a sulfonium salt, an iodonium salt or a p-toluenesulfonic acid ester. A pattern forming method comprising using one kind of an acid generator selected from a group.