JPH01296627A - Film formation - Google Patents

Abstract

PURPOSE:To enable a fine ruggedness to be flattened exercising no unfavorable effect on the electrical properties of a device by a method wherein the local selective etching process is performed by photoexcitation. CONSTITUTION:A CVD chamber 3 is simultaneously fed with disilane as a material for forming silicon thin film as well as Cl2 gas for etching silicon and then a substrate 1 is irradiated with the beams of an ArF laser 9 in parallel with the substrate 1 through a window 10 to decompose the disilane gas for forming a silicon thin film. At this time, an Al pattern 11 only is irradiated with the beams of an XeCl laser 7 through a pattern mask 6, a lens 5 and another window 4 to excite the Cl2 gas for etching the silicon thin film. Then, ozone gas is fed to the CVD chamber 3 to reform the silicon thin film into silicon oxide. Through these procedures, a fine ruggedness can be flattened exercising no unfavorable effect on the electrical properties of a device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a film forming method, and more specifically to a film forming method capable of flattening minute irregularities.

[Prior Art and Problems to be Solved by the Invention] Amid the trend toward miniaturization and multilayering accompanying higher integration of devices, planarization of devices has become an important issue. For example, when manufacturing an LSI with a multilayer structure, it is desired to flatten unevenness caused by underlying metal wiring by CVD or the like of an interlayer insulating film.

Adams et al., 1981, Journal of the Electrochemical Society, Vol. 128.

On page 428 (1981), he published a planarization method using etchback. In this method, a 5i film with undulations is formed on a substrate having unevenness due to metal wiring so that the film thickness at the bottom is higher than the film thickness at the convex part of the underlying metal wiring.
02 film is formed, an organic material is applied to the undulating surface of this 5i02 film, and it is heated and melted to flatten the undulating surface. Then, reactive ions with the same etching rate as that of the organic material and 8102 are selected, and etched from the surface. The uneven substrate is planarized by etching until all organic matter is removed.

However, this method has the disadvantage that when the width of the recess is less than one willow, organic matter cannot enter, resulting in insufficient flattening. A method to overcome this drawback was proposed by III Naka et al. in the proceedings of the 44th Japan Society of Applied Physics, 1983, 427.
This is planarization using the bias sputtering method published in p. This method uses the angular dependence of sputtering to perform flattening, and can perform flattening even if the convex portion has a height of one leg and a width of less than one leg. However, this method causes electrical instability due to trapping of charged particles in the film.

As described above, with the conventional method, it is extremely difficult to flatten unevenness caused by fine metal wiring or the like having a width of 1 μs or less without causing a problem in the electrical characteristics. It is an object of the present invention to solve the problems of the conventional methods and to provide a film forming method that can flatten fine irregularities without affecting the electrical characteristics of a device.

[Means for Solving the Problems] The present invention provides a film forming method for forming a flat oxide film on a substrate having a patterned first thin film formed on the surface. In an atmosphere containing a source gas for forming a second thin film and a gas for etching the second thin film by photoexcitation, the light is selectively irradiated onto the patterned first thin film while etching the second thin film. This film forming method consists of a step of forming a thin film and a step of oxidizing the second thin film formed in the step, and is characterized in that each step is repeated to obtain a flat oxide film surface.

[Operation] In an atmosphere containing a raw material gas that forms a thin film and a gas that generates an active species that etches the thin film when excited by light, light is irradiated only onto desired areas on the substrate. When the film is formed, the areas irradiated with light are selectively etched, and the areas not irradiated with light form a thin film.

Therefore, the patterned first thin film -F is formed into this first thin film -F. N
If film formation is performed while flowing both raw material waste and etching gas without irradiating light only to the film part, the film thickness in the gaps of the patterned first thin film becomes large, and the film thickness of the first thin film part becomes large. is formed into an extremely small film.

Further, when the thin film obtained above is a thin film as thin as a few atoms, it is possible to modify the entire thin film into an oxide film by an oxidation process.

By repeating the above two steps, the substrate surface can be flattened.

In the present invention, by utilizing the above-mentioned phenomenon, for example, a substrate having an uneven surface having a patterned metal thin film on an insulating thin film can be flattened with an insulating film. As an example of this, for example, while flowing both a silicon etching gas and a raw material gas for silicon formation, a metal thin film on a substrate is irradiated with light of a wavelength that excites the silicon etching gas, and an insulating film is etched. A silicon film is formed to a thickness of about several atomic layers. Since etching occurs on the metal thin film at the same time as the silicon film is formed, the film thickness is negligibly small compared to the film thickness on the insulating film. Thereafter, the silicon thin film thus formed is oxidized with ozone gas and modified into a silicon oxide film. By repeating this process of film formation and oxidation until the thickness of the silicon oxide becomes approximately equal to the thickness of the metal thin film, the uneven surface can be flattened.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

In this example, I, I
s; A substrate with an uneven cross-sectional shape having a # pattern is
An example applied to a planarization process using iO21PJ will be described.

FIG. 1 is a schematic diagram of a film forming apparatus used in this embodiment, and a substrate 1 is installed in a CVDVSO 4-tar 2. As shown in FIG. The temperature of the substrate 1 reaches 30°C, where silicon oxidation by ozone begins.
Set to around 0℃.

First, in the first step, disilane, which is a raw material gas for forming a CVDVSO4 silicon thin film, and CJ22 gas, which is used for etching a silicon thin film, are simultaneously flowed. Next, the light from the ArF laser 9 is irradiated onto the substrate 1 through the window 10 in parallel with the light to decompose the disilane gas, and a silicon thin film is formed in several evaporations. At this time, the light of the XerU laser 7 is irradiated only on the N pattern 11 through the pattern mask 6, lens 5, and window 4,
The silicon thin film is etched by exciting the Ci2+ scum. As a result, substantially no silicon thin film is deposited on the N pattern 11.

In the next step, ozone gas is introduced into the CVD chamber 3 through the ozone generator 8 to reform the silicon thin film into silicon oxide.

The above two steps are repeated until the thickness of the deposited 5i02 film becomes equal to the thickness of the N pattern 11, and the substrate 1 is planarized. As described above, in this example, fine irregularities on the order of submicrons could be flattened.

Furthermore, since no charged particles or the like were used in this example, electrical instability was not caused in the device. Furthermore, the concentration of CJ12 incorporated into the film was extremely small and did not affect the characteristics of the device, and was sufficiently low.

Although an ArF laser is used to form the silicon thin film in this embodiment, it does not necessarily have to be an ArF laser, and any energy source that can control the film thickness at the level of several atomic layers may be used.

For example, the glow discharge method and plasma CVD method are also applicable to the present invention.

[Effects of the Invention] As explained above, ``According to the present invention, locally selective etching by optical excitation is used, so unlike when applying an organic substance such as a resist, the organic substance does not completely enter into minute irregularities, resulting in flattening. There is no limit to the possible unevenness, and for example, it is possible to flatten minute unevenness such that the wiring film thickness is about one layer for a wiring width on the order of a micron.

Further, unlike conventional bias sputtering methods, charged particles are not introduced into the film, so planarization can be achieved without adversely affecting the electrical characteristics of the device.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a film forming apparatus used in an embodiment of the present invention.

Claims (1)

[Claims] (1) In a film formation method for forming a flat oxide film on a substrate on which a patterned first thin film is formed, a source gas that is oxidized to form a second thin film having the composition of an oxide film; forming the second thin film while selectively irradiating the patterned first thin film with the light in an atmosphere containing a gas that etches the second thin film by photoexcitation; A film forming method comprising a step of oxidizing the formed second thin film, and comprising repeating each of the above steps to obtain a flat oxide film surface.