JP5213227B2 - Method for producing amorphous carbon thin film - Google Patents

Description

  The present invention relates to a method for producing an amorphous carbon thin film.

  Low dielectric constant (1ow-k) thin film fabrication technology used in semiconductor fabrication is one of the important technologies in the semiconductor industry. In the conventional thin film formation by chemical vapor deposition (CVD) method, a raw material hydrocarbon or the like is heated and decomposed to about 900 ° C. in a chamber and deposited on a substrate such as silicon.

  However, in the CVD method, since the heating temperature is 900 ° C. or higher, it is difficult to produce a thin film having no heat resistance. Moreover, the manufacturing apparatus used for the CVD method is large and expensive. Therefore, a simple and inexpensive method for producing a thin film has been demanded.

Several techniques have been proposed as means for solving the above problems (for example, see Patent Document 1), but there is still room for improvement.
JP 2006-144084 A

  An object of this invention is to provide the amorphous carbon thin film preparation method which can be produced simply and cheaply.

  A feature of the present invention is an amorphous structure including a step of enclosing carbon dioxide and hydrocarbons in a fluid layer of a supercritical fluid cell to form a supercritical state, and a step of irradiating the fluid layer with laser light having an ultraviolet wavelength. The gist of the carbon thin film manufacturing method.

  The present invention provides a method for producing an amorphous carbon thin film that can be produced easily and inexpensively.

  Hereinafter, the present invention will be described with reference to embodiments, but the present invention is not limited to the following embodiments. In addition, about what has the same function or a similar function in a figure, the same or similar code | symbol is attached | subjected and description is abbreviate | omitted.

(Amorphous carbon thin (ac) film making device)
An amorphous carbon thin film production apparatus 1 used for an amorphous carbon thin film production method according to an embodiment is disposed on a supercritical fluid cell 6 including a fluid layer 5 in which a supercritical atmosphere is formed, and on the supercritical fluid cell 6. A synthetic quartz glass 4, a substrate 8 disposed on the bottom of the fluid layer 5 on which a thin film grows, a laser 2 for irradiating the supercritical fluid cell 6 with laser light, and a mirror 3 for changing the path of the laser light from the light source; And a temperature controller 9 disposed around the supercritical fluid cell 6.
As the substrate 8 on which the thin film is to be grown, a silicon substrate can be used.

(Amorphous carbon thin film production method)
(A) An amorphous carbon thin film forming apparatus 1 as shown in FIG. 1 is prepared.

(B) Carbon dioxide and hydrocarbons are enclosed in the fluid layer 5 of the supercritical fluid cell 6. Examples of the hydrocarbon that is a raw material source for the thin film include benzenes such as benzene and 1,3,5-trichlorobenzene. This is because benzenes have high dispersibility in supercritical carbon dioxide, and thus have good compatibility with supercritical carbon dioxide as a reaction solvent.

(C) A supercritical state is formed in the fluid layer 5 of the supercritical fluid cell 6. Generally, at the critical point of carbon dioxide, the critical density is 466 kg / m ³ , the critical pressure is 7.38 MPa, and the critical temperature is 304.2K. Therefore, the supercritical state of carbon dioxide can be formed by adjusting the temperature and pressure in the supercritical fluid cell 6 to the above numerical values.

  In this case, the temperature in the fluid layer 5 can be adjusted so that the temperature difference T-Tc when the supercritical carbon dioxide temperature is T and the critical temperature is Tc is 3 ° C. or more, more preferably 5 ° C. or more. convenient. This is because a flat thin film can be formed.

  Since the critical temperature varies depending on the type and amount of benzenes put into the fluid layer 5 and it is difficult to indicate the absolute temperature, the temperature in the fluid layer 5 is determined from the gas-liquid critical point temperature of the binary mixture system here. The difference is described. In this case, although there is no particular limitation, when 1,3,5-trichlorobenzene shown in the column of an example described later is mixed, the temperature in the fluid layer 5 is 3 ° C. higher than the critical temperature (35 ° C.). The temperature is preferably adjusted to 38 ° C. or higher, and more preferably 5 ° C. or higher to 40 ° C. or higher.

  In order to obtain a more uniform thin film, it is preferable to apply an electric field. Specifically, it is preferable to apply an electric field higher than 0.40 kV / mm, more preferably 0.50 kV / mm or more, and still more preferably 0.60 kV / mm or more.

(D) Irradiating the fluid layer 5 with laser light having an ultraviolet wavelength. Examples of ultraviolet laser light include YAG-THG (three-dimensional frequency): wavelength 355 nm, YAG-THG (four-dimensional frequency): wavelength 266 nm, KrF excimer: wavelength 248 nm, and the like.

  Low dielectric constant (1ow-k) thin film fabrication technology used in semiconductor fabrication is one of the important technologies in the semiconductor industry. In the thin film production by the CVD method, a raw material hydrocarbon or the like is heated and decomposed to about 900 ° C. in a chamber and deposited on a substrate such as silicon. However, according to the present embodiment, unlike a conventional thin film production technique, a thin film can be produced at a room temperature of about 35 ° C. In addition, according to the present embodiment, benzenes that are relatively inexpensive and easily available are dispersed in supercritical carbon dioxide, and irradiated with a YAG laser, the dispersed benzenes are photodecomposed and supercritical. It can be deposited on a silicon substrate installed in the fluid cell 6. That is, according to this embodiment, a thin film can be produced easily and inexpensively.

  Moreover, according to this embodiment, since an amorphous carbon thin film can be produced at a low temperature, it can be used for producing a biosemiconductor chip or the like using a heat-sensitive protein.

Example 1
A thin film was produced by the same method as in the embodiment using the amorphous carbon thin film production apparatus 1 of FIG. 1 under the following conditions.
Conditions: carbon dioxide as a reaction solvent, 1,3,5-trichlorobenzene as a carbon source (hydrocarbon), YAG-THG four-dimensional frequency (wavelength 266 nm) as an ultraviolet wavelength laser beam, fluid layer temperature: 40 ° C. The experiment was conducted at a critical density.

  The obtained thin film was subjected to atomic force microscope (AFM) observation, structural analysis of the thin film with a Raman scatterometer, and component analysis using an energy dispersive X-ray analyzer (EDS). The obtained results are shown in FIG. 3, FIG. 4, and FIG.

(Comparative Example 1)
The experiment was conducted in the same manner as in Example 1 except that the temperature in the fluid layer was adjusted to 25 ° C. and the critical density so as to be in the subcritical state. The obtained thin film was observed with AFM. The obtained results are shown in FIG.
Example 1 showed that a thin film having a uniform thickness was formed in the supercritical state of carbon dioxide (room temperature of about 35 ° C.). On the other hand, according to Comparative Example 1, it was shown that a thin film having a uniform thickness was not formed in the subcritical state of carbon dioxide.

(Example 2, Example 3), (Comparative Example 2, Comparative Example 3,)
In order to show the relationship between the temperature of the supercritical carbon dioxide in which the benzene in the supercritical fluid cell 6 is dispersed and the uniformity of the thin film, benzene is used as the carbon source, T-Tc = 0 ° C., 1 ° C., 3 ° C., The experiment was performed in the same manner as in Example 1 except that the temperature was 5 ° C. The obtained thin film was observed with AFM. FIG. 6 (Comparative Example 2, T-Tc = 0 ° C.), FIG. 7 (Comparative Example 3, T-Tc = 1 ° C.), FIG. 8 (Example 2, T-Tc = 3 ° C.) It shows in FIG. 9 (Example 3, T-Tc = 5 degreeC). Moreover, in order to quantitatively evaluate the uniformity of the thin film, the value obtained by calculating the RMS of the thin film surface height calculated from the image obtained by AFM observation is shown in FIG.
6 to 9, it was found that the surface of the thin film becomes uniform as the temperature of supercritical carbon dioxide increases.

  From FIG. 10, it was found that the uniformity of the surface of the thin film was improved as the critical carbon dioxide temperature, that is, the temperature in the supercritical fluid cell 6 increased. The uniformity of the thin film surface height at T-Tc = 0 ° C. is improved compared to the case at T-Tc = 1 ° C., but in this case, there are many carbon dioxide molecules due to the generation of critical protein light. Caused by disassembling. However, regarding the characteristics of the thin film, since many carbon dioxide molecules decomposed are contained and become impurities, T-Tc = 0 ° C. is not a good condition for the thin film. Therefore, in this thin film production experiment, it was found that it is possible to produce a uniform a-c thin film in a temperature environment where the supercritical carbon dioxide in the chamber is about T-Tc> 3 ° C.

(Effect of electric field on surface roughness of amorphous carbon (ac) thin film)
In order to show the relationship between the electric field strength and the uniformity of the thin film, an experiment was conducted in the same manner as in Example 3 except that the electric field strength was changed. FIG. 11 shows the RMS change of the surface of the a-c thin film when the electric field strength is changed at the fluid temperature T−Tc = 5 ° C. It was found that by increasing the electric field, the surface of the ac thin film becomes uniform. Moreover, a big difference was seen between electric field strength 0.38 kV / mm and 0.63 kV / mm, and it turned out that a 10-fold or more uniform thin film is formed in the electric field strength of 0.63 kV / mm.

(Other embodiments)
As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, since it is considered that a fluorine-containing thin film is good for the 1ow-k thin film, hexafluorobenzene may be dispersed in supercritical carbon dioxide instead of 1,3,5-trichlorobenzene. Furthermore, a thin film can be produced with high efficiency and uniformity by applying an electric field in the supercritical fluid cell 6.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

The schematic block diagram of an amorphous carbon thin film production apparatus is shown. The figure obtained by atomic force microscope (AFM) observation about the thin film of the comparative example 1 is shown. The figure obtained by AFM observation about the thin film of Example 1 is shown. The structural analysis result by a Raman scatterometer about the thin film of Example 1 is shown. The EDS component analysis result about the thin film of Example 1 is shown. The figure obtained by AFM observation about the thin film of the reference example 2 is shown (T-Tc = 0 degreeC). The figure obtained by AFM observation about the thin film of the reference example 3 is shown (T-Tc = 1 degreeC). The figure obtained by the AFM observation about the thin film of Example 2 is shown (T-Tc = 3 degreeC). The figure obtained by AFM observation about the thin film of Example 3 is shown (T-Tc = 5 degreeC). The value which calculated RMS of the thin film surface height calculated from the image obtained by AFM observation is shown. The value which calculated RMS of the thin film surface height calculated from the image obtained by AFM observation is shown.

Explanation of symbols

1: Amorphous carbon thin film forming apparatus 2: Laser 3: Mirror 4: Synthetic quartz glass 5: Fluid layer 6: Supercritical fluid cell 8: Substrate 9: Temperature controller

Claims (5)

Encapsulating carbon dioxide and hydrocarbons in the fluid layer of the supercritical fluid cell to form a supercritical state;
Irradiating the fluid layer with laser light of an ultraviolet wavelength ,
A method for producing an amorphous carbon thin film , further comprising a step of applying an electric field of 0.50 kV / mm or more .   The method for producing an amorphous carbon thin film according to claim 1, wherein the hydrocarbon is 1,3,5-trichlorobenzene.   2. The method for producing an amorphous carbon thin film according to claim 1, wherein the hydrocarbon is hexafluorobenzene.   2. The method of claim 1, further comprising a step of adjusting the temperature in the fluid layer so that a temperature difference T-Tc is 3 ° C. or more when the supercritical carbon dioxide temperature is T and the critical temperature is Tc. The method for producing an amorphous carbon thin film as described.   2. The method of claim 1, further comprising a step of adjusting the temperature in the fluid layer so that the temperature difference T-Tc is 5 ° C. or more when the supercritical carbon dioxide temperature is T and the critical temperature is Tc. The method for producing an amorphous carbon thin film as described.