JP2770578B2 - Photo CVD 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 CVD method capable of performing patterning with good spatial selectivity by utilizing light without using processes such as resist coating, exposure, and resist stripping in CVD of various materials.

[0002]

2. Description of the Related Art Photo-inversion CVD, which irradiates light during thermal CVD and suppresses the growth of a CVD film in a light-irradiated portion to directly pattern the CVD film, is a conventional method for growing a film in a light-irradiated portion. Compared with the CVD method, the influence of the accumulation due to the gas phase decomposition can be removed, so that the resolution of pattern transfer can be improved. As a conventional example of this method, Japanese Patent Application Laid-Open No. Sho 62-116786 (Japanese Patent Application No. 60-254582), "Surface Selective Treatment Method", by Kishida's invention.
Sugita et al.'S 36th Joint Lecture on Applied Physics (Spring 1989), second volume, 592 pages, lecture number 2
There is an example of pL-5 "positive pattern transfer CVD using synchrotron radiation". These methods can be summarized as follows: desorption of an adsorbent by infrared light that resonates with the vibration energy of the bond between the substrate and the adsorbent, or adsorbent by breaking the bond between the substrate and the adsorbent by irradiation with vacuum ultraviolet light This is to utilize the desorption.

[0003]

SUMMARY OF THE INVENTION The above-mentioned conventional method C
In the patterning method of the VD film, patterning is performed by irradiating light only to a desired portion on the substrate and suppressing CVD at the light irradiation portion. The suppression of CVD
In the case of desorption of an adsorbent by irradiating infrared light that resonates with the vibration energy of the bond between the substrate and the adsorbent, the substrate is heated by the infrared light. And the suppression of CVD becomes insufficient. Also,
When CVD is suppressed by detachment of the adsorbent by breaking the bond between the substrate and the adsorbent by irradiation with vacuum ultraviolet light, photochemical CVD occurs not only by breaking the bond between the substrate and the adsorbent but also by breaking the bond within the adsorber. In addition, the suppression of CVD becomes insufficient.

In addition to the insufficiency caused by such a mechanism for suppressing CVD, there is a restriction on the type of light source. In the method of desorbing an adsorbent by irradiating infrared light that resonates with the vibration energy of the bond, it is necessary to resonate the energy of the irradiation light with the vibration energy. Also, since the type of adsorbent is usually not one type, in order to desorb all the adsorbents, it is necessary to use light that resonates with each other. Obstacles.

[0005] On the other hand, in the method in which the bond between the substrate and the adsorbent is broken by irradiation with ultraviolet light to desorb the adsorbent, electrons in the bond orbital are moved to the antibonding orbit by valence electron excitation of the adsorbent. By doing. Since this means that the starting state and the ending state of the photoexcitation are determined, the use of light having a wavelength corresponding to this energy is limited. Also, when vacuum ultraviolet light with a shorter wavelength is used,
Ionization of the adsorbent occurs, whereby the bond between the adsorbent and the substrate is broken, desorption of the adsorbent occurs, and CVD in the vacuum ultraviolet light irradiation region can be suppressed. In this case, the energy of the light to be used is only required to be larger than the threshold energy of ionization, so that the restriction on the wavelength is relaxed as compared with the above two methods. However, ionization by valence electron excitation is not practical because there is a problem that the suppression of CVD by desorption of an adsorbent is still insufficient.

There is also a problem in patterning a CVD film due to the light diffraction effect. The light irradiation region is determined by the shape of the opening of the mask, and the sharpness of the edge shape of the CVD film after patterning is reduced by suppressing the light from flowing into the non-irradiated portion due to diffraction of light at the opening of the mask. It depends. Since the magnitude of this wraparound is proportional to the wavelength of the light, wraparound of light due to diffraction can be suppressed by using vacuum ultraviolet light having a shorter wavelength than by using infrared light. However, at the wavelengths used so far,
The suppression of the diffraction effect is still insufficient.

SUMMARY OF THE INVENTION It is an object of the present invention to effectively suppress CVD by promoting desorption of an adsorbent in a light irradiation section, and to obtain a wide selection range of a light source emitting a desired wavelength. An object of the present invention is to provide a photoreversal patterning CVD method in which the diffraction effect is suppressed, the edge at the boundary between the light-irradiated portion and the non-irradiated portion is well cut, and the space selectivity is good.

[0008]

[0009]

According to the present invention, there is provided a photo-assisted CVD method.
According If, in the CVD method of irradiating light into thermal CVD, changing a non-irradiated portion of the surface composition of the irradiated portion by the light irradiation, by suppressing the CVD reaction at the irradiated portion, the non
The method is characterized in that a CVD film is selectively formed only on an irradiated portion .

Further, the above-mentioned optical CVD method is characterized in that a step of exposing a clean surface of the substrate is included prior to the above-mentioned step of light irradiation during CVD. The surface can be cleaned by irradiation with a beam of electrons or particles or high-energy light.

[0011]

The operational features of the present invention are as follows: (1) Acceleration or desorption of an adsorbent by inner-shell excitation of at least one of the atoms constituting the substrate or the adsorbent; Adsorption inhibition by surface composition modification using such short-wavelength light and (2) suppression of the diffraction effect due to the fact that the wavelength of light capable of core excitation is shorter than that of conventionally used light. This results in two factors.

One of the methods of suppressing CVD by the method of the present invention is as follows.
The first is the decomposition and elimination of unstable multiply-charged ions of the adsorbent formed by the cascaded Auger transition of inner-shell holes formed by inner-shell excitation. Until now,
It is known that in a decomposition reaction of an organometallic compound or SiH ₄ in a gas phase, a decomposition product having a higher degree of dissociation can be formed by exciting the inner shell of the atoms constituting the compound than by exciting a valence electron. Have been. These are described, for example, by Nagaoka et al. In Chemical Physics.
Letters Magazine (Chem. Phy. Lett.) 154
Vol. (1988), pages 363 to 368, and a paper published by Yagita et al. In Chemical Physics Letters (Chem. Ph.
y. Lett. This can be seen in the paper published on pages 437 to 440 of Volume 132 (1986).

[0013] Exciting the inner shell of not only the gas phase reaction reported so far but also the adsorbed molecules on the substrate not only increases the degree of dissociation but also desorbs dissociation products. It was found from the inventor's experimental results that it was accelerated. Therefore, the use of light having a short wavelength enough to excite the inner shell has a more effective effect of suppressing CVD than the conventional method of suppressing CVD using infrared light or vacuum ultraviolet light. For this reason, the decrease in spatial selectivity due to the diffusion of the active species generated in the gaseous phase to a region other than the light irradiation region, which is a problem when performing CVD on the light irradiation unit, is due to the desorption of the active species diffused in the light irradiation unit. In addition, by performing patterning by suppressing CVD due to desorption of adsorbed molecules, spatial selectivity can be significantly improved as compared with the related art.

In the second method for suppressing CVD according to the method of the present invention, adsorption of a raw material gas is inhibited by modifying the surface composition by photolysis of an adsorbent. From the experimental results of the inventor, it has been found that the effect of the modification occurs even with light having a wavelength that cannot excite the inner shell, but is more remarkable when light having a wavelength that can excite the inner shell is used. Therefore, when light having such a wavelength is used, the difference in composition between the irradiated portion and the non-irradiated portion can be increased, and as a result, the effect of suppressing CVD in the irradiated portion increases. The suppression of CVD by the surface modification utilizes the difference in the speed of the adsorption reaction between the light-irradiated portion and the non-irradiated portion.

If the surface of the substrate is a clean surface, this surface is active, and the decomposition reaction of the adsorbed molecules starts at a low temperature. Therefore, by performing a step of cleaning the surface prior to the surface modification step by light irradiation, the effect of suppressing CVD can be realized over a wide temperature range. Regarding spatial selectivity, even if the active species generated in the gas phase diffuses to a region other than the light irradiation region, the degree of modification is lower than that of the dense surface composition modification in the irradiation part, so that the CVD cannot be suppressed. In addition, spatial selectivity can be greatly improved as compared with the prior art.

In the case where the film is patterned by suppressing the CVD in the light irradiation part, the diffracted light diffracted at the end of the opening of the mask which determines the light irradiation area on the substrate is also irradiated to the non-irradiation part. . As a result, not only the irradiated part by the light that goes straight without being diffracted, but also the non-irradiated part,
VD is partially suppressed, and the CVD
The film cannot be patterned. However, when the wavelength of the light used is short enough to be able to excite the inner shell, compared to the infrared light and vacuum ultraviolet light that can be used to excite valence electrons, which have been used so far,
Since the intensity of the diffracted light and the wraparound are reduced by two to three orders of magnitude, it is possible to suppress the CVD only by the irradiation part by the light traveling straight,
The CVD film can be patterned into a desired shape.

As described above, according to the photo-CVD method of the present invention, a high-quality CVD film having an inverted mask pattern and good spatial selectivity can be formed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the photo-CVD method according to the present invention will be described below with reference to FIG. In this embodiment, S
A case in which an Al wiring is selectively formed in forming an i-device will be described.

FIG. 1A shows that a thermal oxide film 12 is patterned on a Si substrate 11 and a pol
A y-Si film 13 is formed.

FIG. 1 (b) shows that the substrate shown in FIG.
A method is shown in which an Al wiring 14 is deposited while being directly patterned using light 15, and an electrical contact is formed between the Al wiring 14 and the Si substrate 11 via the poly-Si film 13. A specific film forming method will be described below.

A substrate having the structure shown in FIG. 1A is set in a CVD chamber, dimethyl aluminum hydride and Al (CH ₃ ) ₂ H as an Al material are introduced into the chamber, and the substrate is heated to 300 ° C. Perform CVD. Light 15
Using synchrotron radiation having a higher energy than 100 eV, which can excite the inner shells of Al, C and Si atoms. Al CV only
D is performed to form the Al wiring 14. That is, the wiring is obtained by inverting the mask pattern. Thus, the Al wiring 14
Is deposited while directly patterning using light 15,
Electrical contacts can be formed.

Thereafter, using the deposited Al as a mask,
Poly-Si is removed by plasma etching to remove Al
The wiring forming process ends. After forming the Al wiring by this method, the resistance between this wiring and the wiring having no contact was measured. As a result, there was no electric leak and the green color was good.

A second embodiment of the present invention will be described.
The formation of Al wiring in the same Si device formation process as in the first embodiment will be described with reference to FIG. FIG. 2 is a schematic sectional view illustrating the CVD process. A substrate having the same structure as that of the previous embodiment was placed in an ultra-high vacuum chamber, and FIG.
As shown in (a), the electron beam shower 17 is irradiated,
The hydrogen atoms terminating the surface of the ly-Si film 13 are removed to obtain a clean surface.

Next, Al (CH ₃ ) ₂ as an Al raw material
H is introduced into the chamber, the substrate temperature is set to 200 ° C., and thermal CVD is performed. 250 ° C if no clean surface
In the following, CVD does not occur, but by producing a clean surface, CVD occurs even at 200 ° C. Al as light 15
Using radiation light having a wavelength of about 4 nm capable of exciting the inner shell of atoms, C atoms, and Si atoms, the mask 16 is used to prevent the light 15 from being applied to the wiring formation region. In the portion where the opening shape of
VD is performed to form an Al wiring 14 as shown in FIG. In this way, the Al wiring 14 can be deposited while being directly patterned using the light 15 to form an electrical contact.

Then, using the deposited Al as a mask,
Poly-Si is removed by plasma etching to remove Al
The wiring forming process ends. The effect of suppressing the CVD in the light irradiation part is larger than that in the first embodiment in which the poly-Si film 13 is not cleaned. In this embodiment, since the wraparound of the diffracted light is sufficiently small, the inverted pattern of the mask is accurately reflected, and a pattern with sharp edges can be formed.

In this example, an electron beam shower was used to expose the clean surface. Alternatively, an ion beam or high-energy light may be applied. In addition, this method may be used as long as cleaning by heating can be performed due to the structure of the device.

In the above embodiment, the inverse CVD of Al using Al (CH ₃ ) ₂ H as a raw material has been described. However, the raw material is not limited to this, and triisobutylaluminum and Al-iso (C ₄ H ₉ ) Other organic metals, such as ₃ , may be used, or may contain chlorine atoms. Also, the substrate is not limited to the embodiment, and other semiconductor substrates are also effective.

Further, even those to invert CVD, not limited to Al, initially a metal such as Cu or Au, may be a semiconductor or a mixed crystal thereof, such as Si or GaAs, absolute including the SiO ₂ It may be a green film. The growth conditions such as the substrate, source gas, light energy, and substrate temperature may be changed in accordance with the principles described in the section of the operation in accordance with the type of growth.

[0029]

According to the present invention, in the CVD of various materials, the mask pattern is inverted even in a desired fine pattern shape by utilizing high energy light without processes such as resist coating, exposure, and resist peeling. ,
An optical CVD method capable of patterning with good spatial selectivity can be obtained.

[Brief description of the drawings]

FIG. 1 is a view for explaining an optical CVD method of the present invention by taking wiring formation as an example.

FIG. 2 is a diagram for explaining a photo CVD method of the present invention by taking wiring formation as an example.

[Explanation of symbols]

 Reference Signs List 11 Si substrate 12 Thermal oxide film 13 Poly-Si film 14 Al wiring 15 Light 16 Mask 17 Electron beam shower

Claims (2)

(57) [Claims] In a CVD method of irradiating light during thermal CVD, a surface composition of an irradiated portion is changed to a non-irradiated portion by light irradiation to suppress a CVD reaction in the irradiated portion,
An optical CVD method characterized by selectively forming a CVD film only on a non-irradiated portion. Wherein after the step of exposing the clean surface of the substrate, the optical CVD method according to claim 1, characterized in that the CVD process using the light irradiation.