JP2684994B2 - Fine pattern forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In an LSI manufacturing process, a mask pattern is subjected to equal magnification or transfer reduction, and an inorganic resist is selectively grown on the pattern for direct patterning.

[0002]

2. Description of the Related Art A conventional fine pattern forming method is generally performed by the following lithography.
Apply a resist consisting of an organic substance on the substrate surface,
The mask pattern is transferred to the organic resist by development. After that, a pattern is formed on the substrate by etching, and finally the residual resist is removed. A general method of such lithography is described in, for example, G. (S.
M. Sze) and translated by Naminichi, Kawabe and Hasegawa (Semiconductor Devices) (Sangyo Tosho, 198).
7 years), pages 451 to 473.

As the miniaturization of LSI progresses, the wavelength of the light source for photolithography is becoming shorter, and 256
X-rays are about to be used in DRAMs of M to 1G level. In order to avoid difficulties in mask fabrication in X-ray lithography and to alleviate the limit of the minimum line width that allows Fresnel diffraction, reduction transfer X-ray lithography in the soft X-ray region has been studied. As an example of these studies, a journal of Vacuum Science and Technology (J. Vac. Sci. Techn) by AM Hawryuk et al.
ol. ) Volume B6 (1988) pages 2162-21
The paper described on page 66 and by Kinoshita et al., Journal of Vacuum Science and Technology (J. Vac. Sci. Techn.
ol. ) Volume B7 (1989) pp. 1648-16
The papers listed on page 51 can be cited. These papers report that it is possible to form a pattern of 0.25 μm to 0.5 μm by transferring a reduced pattern of a mask to PMMA, which is a kind of organic resist, using soft X-rays of 4 nm to 13 nm.

With respect to lithography using such an organic resist, a method has recently been proposed in which a metal pattern is formed on the surface of a substrate and used as a resist in order to further improve the pattern resolution. For example, J. Calvert et al., Journal of Vacuum Science and Technology (J. Vac. Sci.
A good example is the paper described in Volume 9 (1991), pages 3447-3450. This method comprises the following steps.

On the substrate, phenyltrichlorosilane, which is a kind of organic silicon compound, is used.
Lorosilane) is applied, and a KrF excimer laser or ArF excimer laser is used for exposure using a mask. As a result, it is considered that the Si—C bond in the irradiated portion is dissociated to form a Si—OH bond, which becomes hydrophilic. In this way, a single layer of lithography is performed, a Pd / Sn catalyst is formed on the hydrophobic surface by utilizing the difference in hydrophilicity / hydrophobicity, and then a metal pattern such as Ni is formed by plating. Plasma etching is performed using this metal pattern as a mask to transfer the pattern to the substrate.

[0006]

Lithography in which an organic resist is exposed by using light in the soft X-ray region from vacuum ultraviolet rays has the following problems.

Regardless of the type of organic resist used at present, carbon is the main component, so the wavelength range in which a resist having a desired thickness can be uniformly exposed in the depth direction is roughly: Limited to X-rays of 1 nm or less or 4.5 nm to 6 nm. On the other hand, in X-ray lithography, there is an attempt to shift the exposure wavelength to the long wavelength side in order to avoid difficulties in manufacturing an X-ray mask. Also, reduced X-ray lithography
However, light in the soft X-ray region is about to be used because of the problem of the reflectance of the optical element. In addition, studies have also been conducted using light in the vacuum ultraviolet region in order to further miniaturize patterns obtained by conventional photolithography for i-line and g-line. However, since the light in these regions is absorbed only by the surface of the organic resist, it is difficult to uniformly expose a resist having a desired thickness. Therefore, in order to solve this, a multi-layer resist method using a plurality of resists having different sensitivities is used. However, this method requires a number of steps because each step of development and etching is required for each resist.

On the other hand, when a metal is used as the inorganic resist, the existing methods include the steps of exposing and developing an organic resist for changing the chemical activity of the substrate surface, the step of forming a metal layer to have a catalytic action, and the subsequent steps. The number of plating processes for growing a metal is extremely large.

As described above, the existing method has a large number of steps, which makes it difficult to apply it to an actual process.

[0010]

The fine pattern forming method of the present invention is a fine pattern forming method including a lithography step and an etching step, wherein a raw material molecule or a substrate is used during thermal CVD using a compound containing a metal element and carbon. performed by irradiating light energy of inner shell electrons can be excited in the constituent elements of said light irradiation region to form carbide of a metal element
Thermal CV of a metal on a surface on which a carbide of a metal element is formed
Suppresses D and does not form carbide of the metal element
It is characterized by including a lithography step of directly patterning the metal element by performing thermal CVD of the metal only on the surface .

Further, during thermal CVD using a compound containing a metal element and carbon on a Si substrate, light having energy for exciting core electrons of the metal or silicon is spatially selectively irradiated to perform light irradiation. Forming a carbide of a metal element on the area, and forming a metal on the surface on which the carbide of the metal element is formed.
Suppresses the thermal CVD of , and forms a metal layer only on the non-irradiated portion,
Using the formed metal layer as a mask for the inorganic resist, S
It is characterized in that the i substrate is patterned.

Further, in a fine pattern forming method including a lithography step and an etching step, light having an energy capable of exciting valence electrons of a raw material molecule or a constituent element of a substrate is used during thermal CVD using a compound containing a metal element and carbon. Selectively irradiate a chemically inert surface to form a metal layer in the light-irradiated area, and to form a metal element only on the metal layer.
It is characterized by including a lithography process of directly patterning the metal layer by exciting thermal CVD .

Further, during thermal CVD using a compound containing a metal element and carbon, the silicon oxide film is spatially selectively irradiated with light having energy for exciting valence electrons of metal or silicon, and the irradiation is performed. A metal layer is formed only on the portion, and the silicon oxide film is patterned by using the metal layer as a mask of the inorganic resist.

[0014]

The function of the present invention is based on the thermal CVD of Al as an inorganic resist and the synchronism during thermal CVD of Al using dimethyl aluminum hydride (DMAH; Al (CH ₃ ) ₂ H) as a raw material. This is due to the discovery of a phenomenon that can be controlled by irradiation of tron radiation (SR). S
A surface photochemical reaction due to R irradiation forms a modified layer, which changes the chemical properties of the original surface. As a result, spatial selective thermal CVD between the irradiation part and the non-irradiation part becomes possible.

Thermal CVD of Al is suppressed on the clean Si surface. In thermal CVD at 200 ° C., this phenomenon has a clear wavelength dependence as shown in FIG. If the 2p electron of the shallowest inner shell electron level of Al element or the inner shell electron deeper than this is excited, the thermal CVD reaction of Al is suppressed by 100%. This is because the modification layer formed on the irradiation part is Al
It was found that this is because it is composed of aluminum carbide of the atomic layer order that suppresses the thermal CVD .

On the other hand, it is difficult to grow Al by thermal CVD because the SiO ₂ surface is chemically inactive, but it is possible to induce Al growth by SR irradiation. 200 ° C heat C
In VD, it has been found that this phenomenon occurs due to the formation of a modification layer of aluminum in the metallic state in the atomic layer order that induces the CVD reaction. Further, it was found from FIG. 2 that this effect remarkably occurs due to valence electron excitation.
For details, see Applied Surface Science magazine (Appl. Surf. Sci.) No. 60.
Pp. 587-591 of Volume 61 (1992),
And Applied Surface Science (Ap
pl. Surf. Sci. ) Volume 79/80 (199
4) page 203 to page 207.

The patterning method on the Si surface can be performed as follows. A desired portion of the Si surface during thermal CVD is irradiated with light in an energy region capable of exciting core electrons to pattern aluminum carbide. Since Al grows only in the part without aluminum carbide, A
1 can be directly patterned. Next, the Al pattern can be transferred to Si by plasma etching with a fluorine-based gas using this Al as a mask.

Patterning on the SiO ₂ surface is performed as follows. Irradiation of light in an energy region capable of exciting valence electrons to a desired portion of the SiO ₂ surface during thermal CVD,
Pattern aluminum metal. Using this as a nucleus, a thick film of Al is grown by thermal CVD to directly grow patterned Al. Next, when plasma etching is performed using a fluorine-based gas, the Al film acts as a mask and SiO ₂
The Al pattern can be transferred to.

Finally, the patterning method according to the present invention is completed by removing the unnecessary Al film.

[0020]

【Example】

(Embodiment 1) In this embodiment, an example of forming a trench in a Si substrate will be described with reference to FIG.

As shown in FIG. 3A, the Si substrate 11 is replaced with 20
While being heated to 0 ° C. and supplying the Al source gas DMAH, the mask 12 is used to irradiate the light 13 in a wavelength region capable of exciting 2p electrons of the Al element. The opening 14 of the mask 12 corresponds to a region where a trench is desired to be formed, and B
e It is a window. Therefore, only the light 13 in the wavelength region capable of exciting 2p electrons of Al element is transmitted. Si substrate 1
The aluminum carbide (AlC) layer 15 is formed by the surface photochemical reaction of the DMAH molecules on the irradiated portion of the light 13 on 1 and therefore, the growth of Al by the thermal CVD does not occur. On the other hand, in the non-irradiated portion of the light 13, the Al film 16 is formed by thermal CVD.
Is formed.

Next, when reactive ion etching (RIE) using XeF ₂ is performed, since the Al film 16 acts as a mask, the AlC layer 15 formed in the irradiated portion of the light 13 and the Si below it. Only the substrate 11 is etched.
As a result, the trench 17 can be formed as shown in FIG. After that, the unnecessary Al film 16 is removed by etching with hot phosphoric acid.

(Embodiment 2) In this embodiment, a method of patterning SiO ₂ will be described with reference to FIG.

[0024] As shown in FIG. 4 (a), heating the SiO ₂ film 18 formed on the Si substrate 11 to 200 ° C., Al
While supplying the source gas DMAH of
Is used to irradiate the light 13 in a wavelength region in which only valence electrons can be excited. The opening 14 of the mask 12 corresponds to the non-etched region of the SiO ₂ film 18, and is made of quartz. Therefore, the light 13 is composed only of light in the wavelength region in which only valence electrons can be excited. In the light irradiation portion, a thermal CVD inducing layer 19 made of aluminum in a metal state is formed by a surface photochemical reaction caused by valence electron excitation of DMAH molecules. Once this layer is formed, thermal CVD is performed only on this layer.
Occurs, and the Al film 16 grows. Once the thermal CVD has occurred, the irradiation of the light 13 may be stopped or continued.

Next, using CHF ₃ as an etching gas, E
When CR plasma etching is performed, the Al film 16 acts as a mask, and only the portion without this is etched. When the underlying Si substrate 11 is exposed, as shown in FIG.
The etching stops as shown in. After that, the unnecessary Al film 16 is removed by etching with hot phosphoric acid.

(Embodiment 3) In Embodiment 1 and Embodiment 2 described above, the mask pattern is formed by one pattern formation.
The case of transfer to pair 1 has been described. As described in the section of the operation of the present invention, the essence of the present invention controls the thermal CVD reaction of Al by selecting the wavelength region of light, thereby
The purpose is to directly pattern the l film and use this as an inorganic resist. Therefore, the transfer of the mask pattern is not limited to one-to-one, and it is clear that the same applies to the reduction transfer.

In this embodiment, a case where a reduction transfer optical system called a Schwarzschild optical system using a transmission type mask is used will be described with reference to FIG.

The mask 12 is made of Si ₃ N ₄ having a thickness of 100 nm as a membrane, and Au (220 nm) / Ti is used as an absorber.
(10 nm) is patterned. When a soft X-ray having a wavelength of 13 nm is used as the light 13, the light 13 is transmitted only in the portion where there is no Au / Ti absorber. After passing through the aperture 20, the light 13 after passing through the Mo / Si multilayer convex mirror 21 and the M
It is reflected and condensed by the o / Si multilayer concave mirror 22 and the pattern of the mask 12 is transferred onto the Si substrate 11. Substrate 1
When the temperature of 1 is set to the thermal CVD temperature or lower and the DMAH of Al raw material used as the inorganic resist is supplied,
The AlC film 15 is formed only on the irradiated portion. When the temperature of the substrate 11 is set to 200 ° C. after the patterning of the AlC film 15, the Al film is heated to the thermal CV only in the portion where the AlC film 15 is not present.
Grow by D. By using this as a resist and performing etching with a fluorine-based gas such as XeF ₂ , a trench can be formed in the Si substrate 11 as described in the first embodiment.

In the present embodiment, the case where the reduction transfer optical system by the Schwarzschild optical system using the transmission type mask is used has been described. However, in addition to this, the Schwarzschild optical system using the reflection type mask similarly has the same inorganic resist. The Al film can be directly patterned, and a fine pattern can be formed by etching using the Al film as a mask. Further, the same thing can be done by using a reduction transfer optical system called an Inverse Cassegrain optical system using a reflective mask or a reduction transfer optical system called a telecentric optical system using a reflective mask.

In the embodiments described above, Al is used as the inorganic resist and Al (CH ₃ ) is used as the source gas.
_{Although 2} H is used, the same phenomenon occurs even when Al (C ₂ H ₅ ) ₂ H is used. Therefore, the use of this gas can realize what has been described in this embodiment.

In addition to Al, it is also possible to use Mo or W. In the case of Mo, Mo (CO) ₆ is used as a raw material and MoC is patterned by light irradiation. Next, when the substrate temperature is set to 150 ° C. or higher, Mo grows only in the MoC non-formation region by thermal CVD, so that this can be used as a resist. The same applies to the case of W. W (CO) ₆ is used as a raw material, and WC is patterned by light irradiation. Next, when the substrate temperature is set to 200 ° C. or higher, W grows by thermal CVD only in the WC non-formed region, and this can be used as a resist.

[0032]

In the LSI manufacturing process, the mask pattern is transferred in the same size or reduced, and the inorganic resist is selectively grown on the pattern for direct patterning.

[Brief description of the drawings]

FIG. 1 is a diagram showing an experimental result which serves as a basis for an operation of the present invention.

FIG. 2 is a diagram showing another experimental result which is the basis of the operation of the present invention.

FIG. 3 is a diagram showing an embodiment based on the operation of the present invention.

FIG. 4 is a diagram showing another embodiment based on the operation of the present invention.

FIG. 5 is a diagram showing another embodiment based on the operation of the present invention.

[Explanation of symbols]

11 Si Substrate 12 Mask 13 Light 14 Opening 15 AlC Layer 16 Al Film 17 Trench 18 SiO ₂ Film 19 Thermal CVD Inducing Layer 20 Aperture 21 Convex Mirror 22 Concave Mirror

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 21/027 H01L 21/30 569H

Claims (4)

(57) [Claims] 1. A method for forming a fine pattern including a lithography process and an etching process, wherein chemical vapor deposition (thermal CV) using a compound containing a metal element and carbon is performed by heat.
During D), performs inner-shell electron of the constituent elements of the source molecules or substrate is irradiated with light of energy that can be excited, to form a carbide of a metal element in the light irradiation region, a carbide of the metal element
Suppresses the thermal CVD of the metal on the surface where the
Metals only on surfaces where no carbides of metallic elements are formed
The method for forming a fine pattern, which comprises the step of directly patterning the metal element by performing the thermal CVD of . 2. A Si substrate is subjected to thermal CVD using a compound containing a metal element and carbon by spatially irradiating light having energy for exciting core electrons of the metal or silicon, By forming carbides of metal elements in the irradiated area,
Heat of the metal on the surface where the carbide of the metal element is formed
A method for forming a fine pattern , which suppresses CVD, forms a metal layer only on a non-irradiated portion, and patterns the Si substrate using the formed metal layer as a mask of an inorganic resist. 3. A method for forming a fine pattern including a lithography step and an etching step, wherein light having energy capable of exciting valence electrons of a raw material molecule or a constituent element of a substrate is used during thermal CVD using a compound containing a metal element and carbon. The chemically inert surface is irradiated by spatially selective irradiation to form a metal layer in the light irradiation area, and the metal element is formed only on the metal layer.
A method for forming a fine pattern, which comprises a lithography step of directly patterning the metal layer by exciting the thermal CVD . 4. The silicon oxide film is spatially selectively irradiated with light having energy for exciting valence electrons of metal or silicon during thermal CVD using a compound containing a metal element and carbon, and the irradiation is performed. A method for forming a fine pattern, comprising forming a metal layer only on a portion and using the metal layer as a mask of an inorganic resist to pattern a silicon oxide film.