JP2748819B2 - Patterning 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 in which steps such as resist application, exposure, and resist stripping are omitted in VD, and patterning can be performed with good spatial selectivity by using light or an electron beam.

[0002]

2. Description of the Related Art A general patterning method using a resist process is described in Kazuo Maeda's book "Latest L.
It is described in many publications such as "SI process technology" (Industry Research Institute Co., Ltd.).

[0003] There are many reports on the method of directly patterning using light without the resist step, including the comprehensive report "Photoexcitation Process Handbook" (Science Forum, 1987) edited by Kiyoshi Takahashi. is there.

[0004] As an example of a method of patterning aluminum by light, an example using an excimer laser is disclosed in G. Okayama et al. S.
Appl. Phys. Let
t. It is reported on page 1051 of Volume 56 (1986).

[0005]

The resist process has been established as a patterning method and is widely used.
To perform one patterning process, resist coating,
The disadvantage is that many steps such as exposure, etching, resist stripping, and cleaning are required.

The method of directly patterning by omitting the resist process using light is an effective method for shortening the process. However, a major disadvantage is that the film forming speed in the photo-CVD process is generally low. Optical CVD can be broadly classified into two types according to its reaction mechanism. In other words, there are two methods: a method in which the substrate is locally heated using light energy to selectively perform CVD by a thermal reaction, and a method in which a raw material gas or a raw material adsorbed on the substrate is photoexcited to perform CVD by a photochemical reaction. is there. In any case, the photo-CVD has a limitation in the film forming speed for the following reasons, and the speed is generally lower than that of the thermal CVD or the CVD using plasma.

A patterning CV for locally heating a substrate
In the D method, since it is necessary to heat to a temperature sufficient to induce a thermal reaction, generally, a large energy is required, and in many cases, the laser beam is condensed and realized. In order to form a desired pattern by this method,
Inevitably, the laser light must be spatially manipulated, and the film forming speed is lower than in the method of transferring the pattern all at once. Although a method of avoiding one-point light condensing and transferring a pattern blocked to some extent at a time is also conceivable, it is basically a method limited by light energy (output), so that it is difficult to use it for large-area CVD. It is.

Further, in the CVD method using photochemical excitation, since a photon is directly absorbed by a molecule which should cause a reaction, there is no limitation in energy (output) of a light source as in the case of using a thermal reaction. In this case, the absorption coefficient (absorption cross section) determines the limit of the film formation rate. In general, the absorption cross section of a molecule is 10 ^-18 cm even if it is large.
Is ² mm, to form with the photochemical reaction. The materials for forming requires a large flux of light source results in.

Also, a normal patterning CV using light
In the D method, in addition to the problem of the film forming speed, the limit of the resolution is also a serious problem. The major factors that determine the resolution limit of photo-CVD are the essential limitations due to the wavelength limit,
There are limitations due to technical issues such as a reduction in resolution due to heat diffusion (in the case of thermal excitation) and a problem of peripheral deposition caused by the excitation of gas molecules (in the case of optical excitation).

Generally, in laser CVD, since visible light or ultraviolet light is used, its essential resolution limit is sub-μm, which is almost equal to the fineness of LSI. On the other hand, even if the required resolution is within the wavelength limit and the optical resolution is satisfied, the problem of heat diffusion and peripheral deposition often remains as a cause of lowering the resolution.

An object of the present invention is to solve such a problem and to provide a method for forming a patterned CVD thin film using a light or an electron beam without going through a resist process.

[0012]

Patterning method of the present invention, in order to solve the problem] is a method for forming a patterned thin film on a substrate surface, a step of terminating the substrate surface with hydrogen, before
By irradiating light or electron beams to the end surface in serial hydrogen, removing the hydrogen irradiation portion, organic a CVD material
Using metal, the organic metal and the hydrogen in the irradiation part are removed.
Between the exposed surface and the hydrogen-terminated surface
And setting a substrate temperature to a temperature at which a difference is exhibited, and using a selective CVD method to grow a metal thin film only on the irradiated portion.

[0013] The patterning method of the present invention can be applied to a substrate.
How to form a patterned thin film on a surface
Te, a step of terminating the substrate surface with hydrogen, with the hydrogen
Irradiate the terminated surface with light or electron beam
Removing part of hydrogen, and adding dimethyl alcohol
Using minium hydride, set the substrate temperature during CVD to 1
Set the temperature in the range of 00 to 200 ° C and use the selective CVD method.
And grow an aluminum thin film only on the irradiated part
And a step.

[0014]

The operational features of the present invention can be summarized in the following four points.

(1) A photo-CVD process is performed by separately performing a patterning process for producing a difference in surface chemical reactivity using light or electrons and a thermal CVD process for forming a thin film using a thermal reaction. The disadvantage of the method is that the low deposition rate is solved.

(2) As a method for realizing the former patterning step in the above method, the surface of silicon is first passivated by terminating the surface with hydrogen, and then the desired surface is formed using light or an electron beam. Is used to remove the hydrogen at the point (2) to enhance the chemical reaction.

(3) When the above method is applied to aluminum film formation, dimethyl aluminum hydride and S
A difference in reactivity (selective CVD) between the i-surface and the hydrogen-terminated Si surface develops from 100 ° C to 200 ° C
During this time, the substrate temperature is controlled.

(4) As a method for removing hydrogen, short-wavelength light or an electron beam, which has a high resolution limit due to wavelength and has a high hydrogen removing effect, is used.

First, the present invention is intended to overcome the disadvantage that the film forming rate is small while maintaining the advantage of forming a patterned thin film without using a resist step, which is an excellent feature of the photo-CVD method. The operational feature of the above (1) is used. That is, the patterning by light is used only in the step of changing the chemical reactivity of the surface, and the actual thin film is formed by the thermal CVD step. Therefore, the deposition rate is determined by the rate of thermal CVD, and the light CV
The small deposition rate of D is solved.

Next, as a specific method for causing a difference in chemical reactivity on the surface, the above-mentioned method (2) of hydrogen termination and local removal thereof is used. The fact that the silicon surface is chemically passivated by hydrogen termination is described in Takaha
gi et al. Appl. Phys. 64 volumes (1
988), p. 3516. There are many other reports, and it has already been confirmed as a fact that the hydrogenated silicon surface has a function of suppressing natural oxidation in the atmosphere. Many reports use the resistance to oxidation reactions as described above, but the mechanism is due to the difference in chemical reactivity between the clean silicon surface and the silicon hydride surface, and is limited to oxidation reactions. It is not something to be done. In the method of the present invention, this property of chemical reactivity is applied to selective CVD.

Next, as a method of reactivating only a required portion of the passivated surface, local removal of hydrogen by light or electrons is used. The fact that short-wavelength light has such properties is exemplified in the report of lecture number 11a-ZF-11 described by Mr. Nishiyama et al. There is.
In this report, hydrogen terminating the silicon surface is 4n
The fact that desorption occurs by irradiation with synchrotron radiation, which is continuous light having a wavelength of m or more, has been confirmed by a temperature-programmed desorption method.

Further, when the above method is applied to aluminum film formation, dimethyl aluminum hydride
Reactivity difference between Si and hydrogen terminated Si surface (selection C
The substrate temperature is controlled between 100 ° C. and 200 ° C. at which VD) appears. This temperature condition is based on C
FIG. 2 shows the temperature dependency of the CVD rate on the clean surface, and FIG. 3 shows the data of the temperature dependency of the CVD rate on the hydrogen-terminated substrate. As can be seen, 15 on the clean Si substrate.
From 0 ° C to 175 ° C on the hydrogen-terminated substrate
It can be seen that VD is started. This difference between the CVD start temperatures is due to the passivation treatment by hydrogen termination.
At a temperature higher than this, aluminum growth starts regardless of the difference in the substrate surface. Once the growth of aluminum is started, as shown in the results of FIG.
Aluminum also shows CVD characteristics on the surface of the aluminum after the start of CVD (at the same time as the surface). Note that the temperature dependence of the CVD characteristics shown here slightly changes depending on the completeness of the hydrogen termination and the like. Therefore, in the claims, at least 100 ° C. to 200 ° C. including the temperature ranges of FIGS. 2 and 3 is claimed as a temperature range in which the basic mechanism of the present invention is established.

Further, as an action for overcoming the resolution limit of the photo-CVD method, the entirety of the above-mentioned characteristics (1) to (4) of the action is used. That is, as described in (4), since a short-wavelength light or an electron beam having an essentially high resolution limit is used for patterning, the resolution limit caused by the wavelength is overcome.

Further, as described in (1) to (3), the patterning step using a light or an electron beam is a step of removing adsorbed hydrogen on the surface, and is essentially a surface photochemical reaction, and gas excitation is performed. Therefore, there is no problem of peripheral deposition and heat diffusion.

[0025]

Next, an embodiment of the patterning method of the present invention will be described with reference to the drawings.

In this embodiment, an example of selectively forming aluminum used for wiring in a Si device will be described as an example of a thin film formed by patterning.

FIG. 1 (a) shows an S-type semiconductor having a hydrogen-terminated surface 2.
The i-single-crystal substrate (100) 1 is irradiated with synchrotron radiation 4 through a mask 3 having a desired pattern shape,
The step of selectively desorbing hydrogen from the irradiation unit is illustrated. In FIG. 1A, as a method of forming a hydrogen-terminated substrate, a method of cleaning with hydrofluoric acid diluted to about 1.6% with pure water is used. In this processing method, it was confirmed by Auger electron spectroscopy and thermal desorption that the formation of the natural oxide film was suppressed by removing the Si oxide film on the surface and maintaining the hydrogen termination even immediately before the start of CVD. did. The hydrogen-terminated substrate was irradiated with synchrotron radiation using the method shown in the figure.

In FIG. 1B, a dimethylaluminum hydride gas 5 is applied to the substrate prepared in the step of FIG.
Are formed by selective CVD. At this time, the temperature of the substrate is controlled at 180 ° C.
After 10 minutes of CVD, it was confirmed that an aluminum film was formed only on the surface of the surface irradiated with synchrotron radiation.

When the electrical resistance of the Al film after the formation of the wiring was measured, it was confirmed that a resistance value close to that of bulk Al was obtained. Further, when the leak current between the wirings was measured, there was no electric leak, and it was confirmed that the selectivity of CVD was sufficiently good.

Although a single crystal surface of Si (100) was used here to describe the gist of the present invention, it was confirmed that wiring could be formed in the same manner even in a polysilicon state. This process can be applied to the connection of the Al wiring to the polysilicon electrode and the like.

In this embodiment, dilute hydrofluoric acid cleaning is used as the step of terminating the silicon surface with hydrogen.
Other methods include boiling hydrofluoric acid followed by boiling with pure water, or irradiating the surface with atomic hydrogen that has been dissociated using a tungsten filament or plasma after cleaning the surface by heating and heating in vacuum. It is known, and it is clear that any of them can be used to implement the method of the present invention.

Although the example of using synchrotron radiation as the step of desorbing hydrogen from the surface has been described, the same effect can be achieved by using an electron beam as described in the claims. In this case, there are a drawing method and a block exposure method as a method of forming a pattern, and it is clear that the method of the present invention can be applied to both cases.

In this embodiment, dimethylaluminum hydride is used as a CVD raw material. However, other aluminum raw materials such as diethyl aluminum hydride and triisobutylaluminum may be used by adjusting the CVD temperature conditions according to the raw material. It can be applied only by changing. Similarly, the basic method of the present invention using hydrogen termination and local desorption thereof can be applied to CVD of a film other than aluminum. In addition, the reactivity is reduced by hydrogen termination on not only silicon-based substrate materials but also other semiconductor surfaces and metal surfaces, and the hydrogen can be removed using light or an electron beam. The method of the present invention is effective in a system in which the property is lower than that of the non-hydrogen-terminated surface.

[0034]

As described above, according to the present invention, in CVD using various materials, steps such as resist coating, exposure, and resist stripping are omitted, and the spatial selectivity is improved by utilizing light or an electron beam. A CVD method that can be well patterned can be obtained.

[Brief description of the drawings]

FIG. 1 is a view for explaining a patterning method of the present invention by taking a pattern formation of an aluminum thin film as an example.

FIG. 2 is a diagram for explaining the operation principle of the present invention;
FIG. 5 is a graph showing the temperature dependence of the deposition rate when aluminum is deposited from dimethyl aluminum on the silicon surface.

FIG. 3 is a diagram for explaining the operation principle of the present invention;
FIG. 5 is a graph showing the temperature dependence of the deposition rate when aluminum is deposited from dimethyl aluminum on the surface of hydrogen-terminated silicon.

[Explanation of symbols]

 Reference Signs List 1 silicon substrate 2 hydrogen-terminated surface 3 mask 4 light 5 dimethyl aluminum hydride gas 6 aluminum

Claims (3)

(57) [Claims] 1. A method for forming a patterned thin film on a substrate surface, comprising the steps of: terminating the substrate surface with hydrogen; and irradiating the hydrogen-terminated surface with a light or an electron beam. Removing the hydrogen of the above, using an organic metal as a CVD raw material,
Surface with hydrogen removed and a table terminated with hydrogen
Set the substrate temperature to the temperature where the difference in reactivity with the surface appears
Growing a metal thin film only on the irradiated portion using a selective CVD method. 2. A method for forming a patterned thin film on a substrate surface, comprising: terminating the substrate surface with hydrogen; and applying a light or electron beam having an energy of 10 eV or more to the hydrogen-terminated surface. Irradiating to remove hydrogen from the irradiated portion; and using an organic metal as a CVD raw material;
Surface with hydrogen removed and a table terminated with hydrogen
Set the substrate temperature to the temperature where the difference in reactivity with the surface appears
Growing a metal thin film only on the irradiated portion using a selective CVD method. 3. Forming a patterned thin film on a substrate surface
A method of the step of terminating the substrate surface with hydrogen, a light or an electron beam to the end surface by the hydrogen irradiation
To remove hydrogen from the irradiated area, and use dimethyl aluminum hydride as the CVD material
The substrate temperature during CVD ranges from 100 ° C to 200 ° C
And the selective CVD method is used to apply
Patterning method which comprises the steps of growing a thin film of Miniumu, the.