JPH04273434A - Optical cvd method - Google Patents

Abstract

PURPOSE:To permit pattern transfer which allows excellent space selection by using spatially shaped ultrashort wavelength light. CONSTITUTION:After the process of cleaning a poly film 13 by electron beam shower 17, ultrashort wavelength light 15 such as synchrotron irradiation beams, etc., is space-shaped in thermal CVD using a mask 16, thermal CVD reaction at the irradiating part is suppressed, and the film of Al wiring 14 is formed selectively at the non-irradiating part. Since the wavelength of the irradiation light is short and that the influence by vapor phase active pieces is eliminated, a patterned film shaped as an inverted opening of the mask 16 is formed and the blur of the pattern is suppressed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CVD method for patterning various materials with good spatial selectivity by utilizing light without processes such as resist coating, exposure, and resist peeling.

0002

[Prior Art] Photo-reversal CVD, which directly patterns a CVD film by irradiating light during thermal CVD and suppressing the growth of the CVD film in the light-irradiated area, uses ordinary light to grow a film in the light-irradiated area. Compared to the CVD method, it is possible to eliminate the influence of accumulation due to vapor phase decomposition, and thus it is possible to improve the resolution of pattern transfer. As a conventional example of this method, Japanese Patent Application Laid-open No. 116786/1986 (invented by Kishida)
Patent Application No. 60-254582) "Surface selective treatment method" and Sugita et al.'s presentation at the 36th Applied Physics Association Lectures (Spring 1989) Volume 2, page 592, lecture number 2p.
-L-5 There is an example of "positive pattern transfer CVD using synchrotron radiation". To summarize these methods, the adsorbent is detached by infrared light irradiation that resonates with the vibrational energy of the bond between the substrate and the adsorbent, or the adsorbent is detached by severing the bond between the substrate and the adsorbent by vacuum ultraviolet light irradiation. This method takes advantage of the detachment of

0003

[Problem to be solved by the invention] C by the above conventional method
A method for patterning a VD film is to perform patterning by irradiating light only onto a desired portion of a substrate and suppressing CVD at the light irradiated portion. Suppression of CVD,
When the adsorbent is detached by irradiation with infrared light that resonates with the vibrational energy of the bond between the substrate and the adsorbent, the substrate is heated by the infrared light, so not only the adsorbent is detached but also deposited due to thermal decomposition. This results in insufficient control of CVD. Also,
When CVD is suppressed by detachment of the adsorbent due to the bond breaking between the substrate and the adsorbent due to vacuum ultraviolet light irradiation, photochemical CVD occurs not only due to the bond breaking between the substrate and the adsorbent but also due to the bond breaking within the adsorbent. , CVD control becomes insufficient.

[0004] In addition to the insufficiency caused by such a CVD suppression mechanism, there are also restrictions on the type of light source. In the method of detaching adsorbents by irradiation with infrared light that resonates with the vibrational energy of the bond, it is necessary to make the energy of the irradiated light resonate with the vibrational energy. In addition, since there is usually more than one type of adsorbent, in order to desorb all the adsorbents, it is necessary to use light that resonates with each adsorbent, which increases the number of light sources that must be prepared, and the equipment configuration. It becomes an obstacle above.

On the other hand, in a method in which the adsorbent is detached by breaking the bond between the substrate and the adsorbent using ultraviolet light irradiation, the electrons in the bonding orbital are moved to the antibonding orbital by excitation of the valence electrons of the adsorbent. To do something. This means that the initial state and final state of photoexcitation are determined, so the use of light with a wavelength corresponding to this energy is limited. In addition, when vacuum ultraviolet light with an even shorter wavelength is used,
Ionization of the adsorbent occurs, which breaks the bond between the adsorbent and the substrate, causing desorption of the adsorbent, thereby suppressing CVD in the vacuum ultraviolet light irradiation region. In this case, the energy of the light used only needs to be greater than the ionization threshold energy, so the restrictions on the wavelength are less strict than in the above two methods. However, ionization by valence electron excitation has the problem that CVD caused by adsorbent desorption is still insufficiently suppressed, and is not practical.

[0006] Furthermore, there is a problem in patterning the CVD film due to the diffraction effect of light. The light irradiation area is determined by the shape of the opening in the mask, and the sharpness of the edge shape of the CVD film after patterning is the best way to suppress light from going around to non-irradiated areas due to light diffraction at the opening in the mask. It depends. Since the magnitude of this wraparound is proportional to the wavelength of the light, it is better to use vacuum ultraviolet light, which has a shorter wavelength, than to use infrared light to suppress the wraparound of light due to diffraction. However, at the wavelengths used so far,
Suppression of diffraction effects is still insufficient.

It is an object of the present invention to effectively suppress CVD by promoting the detachment of adsorbents at the light irradiation part, and to have a wide selection range of light sources that emit a desired wavelength. It is an object of the present invention to provide a light inversion patterning CVD method that suppresses diffraction effects, has sharp edges at the boundary between light irradiated areas and non-irradiated areas, and has good spatial selectivity.

[0008]

[Means for Solving the Problems] According to the photo-CVD method of the present invention, in a CVD method in which light is irradiated during thermal CVD, at least one type of atoms among atoms constituting a substrate or a source gas is The method is characterized in that by irradiating light with an energy that can ionize the inner shell and suppressing CVD in the light irradiated area, a CVD film is formed only in the non-light irradiated area, and the CVD film is directly patterned.

[0009] Furthermore, in a CVD method in which light is irradiated during thermal CVD, patterning of the CVD film is performed by changing the surface composition of the irradiated area to that of the non-irradiated area through light irradiation and suppressing the CVD reaction in the irradiated area. It is characterized by

[0010] Furthermore, the above-mentioned photo-CVD method is characterized in that it includes a step of exposing the clean surface of the substrate prior to the step of light irradiation during the above-mentioned CVD. The surface can be cleaned by electron or particle beams or by high-energy light irradiation.

[0011]

[Operation] The operational features of the present invention are (1) promotion of decomposition and desorption of the adsorbent by inner shell excitation of at least one atom among the atoms constituting the substrate or the adsorbent;
(2) inhibition of adsorption due to surface composition modification using short-wavelength light, and (2) suppression of diffraction effects due to the wavelength of light that can excite the inner shell being shorter than that of conventionally used light. This comes down to two factors.

[0012] Method 1 of suppressing CVD by the method of the present invention
The first is the decomposition and desorption of unstable multivalent ions from the adsorbent, which are formed by the cascade Auger transition of the core holes formed by core excitation. Until now,
In the decomposition reactions of organometallic compounds and SiH4 in the gas phase, it is known that excitation of the inner shells of the constituent atoms produces decomposition products with a higher degree of dissociation than excitation of the valence electrons. ing. These things are discussed, for example, in the paper published by Nagaoka et al. in Chemical Physics Letters, Volume 154 (1988), pages 363 to 368, and by Yagishita et al. Chemical Physics Letters (Ch.
em. Phy. Lett. ) Volume 132 (1986), pages 437 to 440.

[0013] In addition to the gas-phase reactions that have been reported so far, excitation of the inner shell of adsorbed molecules on the substrate not only increases the degree of dissociation but also increases the rate of desorption of dissociation products. It was found from the experimental results of the present inventor that this was promoted. Therefore, rather than suppressing CVD using conventional infrared light or vacuum ultraviolet light, using light with a short wavelength sufficient to excite the inner shell is more effective in suppressing CVD. Therefore, when CVD is performed on the light irradiation area, the decrease in spatial selectivity due to the diffusion of active species generated in the gas phase to areas other than the light irradiation area can be avoided by the desorption of the active species that diffuse in the light irradiation area. By performing patterning by suppressing CVD by desorption of adsorbed molecules, spatial selectivity can be significantly improved compared to conventional techniques.

A second method for suppressing CVD according to the method of the present invention is to inhibit the adsorption of source gas by modifying the surface composition of adsorbents through photodecomposition. From the experimental results of the present inventors, it was found that although this modification effect occurs even with light of a wavelength that cannot excite the inner shell, it is more pronounced when using light of a wavelength that can excite the inner shell. Therefore, when light of such a wavelength is used, the difference in composition between the irradiated part and the non-irradiated part can be increased, and as a result, the CVD suppressing effect in the irradiated part is increased. Furthermore, CVD suppression by this surface modification utilizes the difference in rate of adsorption reaction between the light irradiated area and the non-irradiated area.

[0015] If the substrate surface 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 a surface modification step by light irradiation, the CVD suppressing effect can be achieved over a wide temperature range. Regarding spatial selectivity, even if the active species generated in the gas phase diffuse to areas other than the light irradiation area, the degree of modification is lower than that of the dense surface composition modification in the irradiation area, so it does not suppress CVD. , the spatial selectivity can be greatly improved compared to the prior art.

Furthermore, when patterning a film by suppressing CVD in the light irradiation area, the diffracted light diffracted at the edge of the opening of the mask that determines the light irradiation area on the substrate also irradiates the non-irradiation area. . As a result, not only the irradiated area by the light that goes straight without being diffracted, but also the non-irradiated area is caused by the diffracted light.
VD is partially suppressed, and CVD is not applied to the desired shape.
The film cannot be patterned. However, when the wavelength of the light used becomes short enough to excite the inner shell, compared to the infrared light or vacuum ultraviolet light that has been used so far, which can excite valence electrons,
Since the intensity of the diffracted light and the wraparound are reduced by 2 to 3 orders of magnitude, CVD can be suppressed only by the irradiation area with the straight light.
A CVD film can be patterned into a desired shape.

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

[0018]

Embodiment A first embodiment of the photo-CVD method of the present invention will be described below with reference to FIG. In this example, S
A case will be described in which Al wiring is selectively formed in the formation of an i-device.

In FIG. 1(a), a thermal oxide film 12 is patterned on a Si substrate 11, and a pol film is formed on the entire surface of the thermal oxide film 12.
A y-Si film 13 is formed.

In FIG. 1(b), on the substrate of FIG. 1(a),
A method is shown in which the Al wiring 14 is deposited while being directly patterned using light 15, and 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 is shown below.

A substrate having the structure shown in FIG. 1(a) was placed in a CVD chamber, dimethylaluminum hydride, Al(CH3)2H, as an Al raw material was introduced into the chamber, and the substrate temperature was set at 300° C. to perform thermal CVD. conduct. light 1
As step 5, synchrotron radiation with energy higher than 100 eV that can excite the inner shells of Al atoms, C atoms, and Si atoms is used, and a mask 16 is used to prevent the light 15 from hitting the wiring formation area. C of Al only in the part
VD is performed to form Al wiring 14. In other words, the wiring is an inversion of the mask pattern. In this way, the Al wiring 1
4 can be deposited with direct patterning using light 15 to form electrical contacts.

After this, using the deposited Al as a mask,
Poly-Si is removed by plasma etching and Al
The wiring formation process ends. After forming an Al wiring using this method, the resistance between this wiring and a wiring with no contact formed therein was measured and found that there was no electrical leakage and that the insulation 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 example will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view illustrating the CVD process. A substrate with the same structure as in the previous example was placed in an ultra-high vacuum chamber, and
As shown in (a), the electron beam shower 17 is irradiated and the po
Hydrogen atoms terminating on the surface of the ly-Si film 13 are removed to reveal a clean surface.

Next, Al(CH3) as an Al raw material
2 H is introduced into the chamber, the substrate temperature is set at 200° C., and thermal CVD is performed. If the clean surface is not exposed, 25
Although CVD does not occur below 0°C, CVD occurs even at 200°C by exposing a clean surface. 4 nm that can excite the inner shells of Al atoms, C atoms, and Si atoms as light 15
Using synchrotron radiation of a nearby wavelength, the mask 16 is used to prevent the light 15 from hitting the wiring formation area, and the Al
CVD is performed to form Al wiring 14 as shown in FIG. 2(b). In this way, the Al wiring 14 can be deposited while being directly patterned using the light 15 to form electrical contacts.

After this, using the deposited Al as a mask,
Poly-Si is removed by plasma etching and Al
The wiring formation process ends. The effect of suppressing CVD in the light irradiation section is greater than that in the first example in which the poly-Si film 13 was not cleaned. Furthermore, in this example, the wraparound of the diffracted light was sufficiently small, so the inverted pattern of the mask was accurately reflected, and a pattern with sharp edges could be formed.

In this example, an electron beam shower was used to produce a clean surface, but ion beams or high-energy light may also be used. Further, if cleaning by heating is possible due to the structure of the device, this method may be used.

In the above examples, Al(CH3)2
Although the inverse CVD of Al using H as a raw material has been described, the raw material is not limited to this, and other organic metals such as triisobutylaluminum and Al-iso(C4H9)3 may be used, and materials that do not contain chlorine atoms may also be used. It's okay to stay. Further, the substrate is not limited to the embodiment, and other semiconductor substrates are also effective.

Furthermore, the material to be subjected to reverse CVD is not limited to Al, but may also be metals such as Cu and Au, semiconductors such as Si and GaAs, and mixed crystals thereof, as well as non-green materials such as SiO2. It may be a film. Depending on what is to be grown, growth conditions such as the substrate, raw material gas, light energy, substrate temperature, etc. may be changed to suit the principles described in the operation section.

[0029]

[Effects of the Invention] According to the present invention, in CVD of various materials, a mask pattern can be reversed even in a desired fine pattern shape by using high-energy light without processes such as resist coating, exposure, and resist peeling. ,
An optical CVD method that allows patterning with good spatial selectivity can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the photo-CVD method of the present invention using wiring formation as an example.

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

[Explanation of symbols]

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

Claims (3)

[Claims] Claim 1: In a CVD method in which light is irradiated during thermal CVD, light is irradiated with energy capable of ionizing the inner shell of at least one type of atoms among the atoms constituting the substrate or the source gas, and the light irradiation is performed. A photo-CVD method characterized in that patterning of a CVD film is performed by suppressing CVD in the area. 2. In a CVD method in which light is irradiated during thermal CVD, the surface composition of the irradiated area is changed from that of the non-irradiated area by light irradiation, and the CVD reaction in the irradiated area is suppressed, thereby causing CVD to occur only in the non-irradiated area. A photo-CVD method characterized by selectively forming a film. 3. The photo-CVD method according to claim 2, wherein after the step of exposing the clean surface of the substrate, a CVD step using light irradiation is performed.