JPH01189912A - Method and apparatus for photo-assisted cvd - Google Patents

Abstract

PURPOSE:To decrease the number of processes, by etching the region around a pattern simultaneously with formation of a film within the same reaction chamber. CONSTITUTION:A thin film forming gas of Si2H6 for example is introduced into a reaction chamber 1 while light from an ArF laser 6 is applied to a quartz substrate 2 through a pattern mask 7 to form a pattern thin film 5 of amorphous silicon. Simultaneously with the introduction of Si2H6, Cl2 gas for etching is introduced while light from a XeCl laser 10 is applied to the rear face of the substrate 2. As soon as a thickness of the amorphous silicon pattern film 5 attains a value as desired, introduction of disilane is stopped and light from the ArF laser 6 is interrupted. If deposit around the pattern has disappeared to such an extent that it does not cause a problem in application of the substrate for a device, introduction of Cl2 gas is also stopped and light from the XeCl laser 10 is interrupted. In this manner, deposit on the region around the pattern can be eliminated in parallel with the formation of the pattern thin film. Thus, a number of required devices as well as the number of processes can be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a film forming method, and more particularly to a photo-CVD method.

(Problems to be Solved by the Prior Art and the Invention) As devices become more highly integrated, more advanced miniaturization techniques are required. In pattern formation by photo-CVD, a film with a desired pattern can be directly formed by condensing laser light or by transferring, so the pattern formation process can be significantly shortened. Furthermore, by using a short wavelength laser, it is also possible to form fine patterns on the submicron order.

However, while photo-CVD, which utilizes photochemical reactions, has the advantage of being able to form films at low temperatures, it has the serious drawback of causing vapor-phase reaction products to accumulate around the pattern (48th 1987 Autumn Applications). Proceedings of the Physical Society of Japan Academic Conference P, 443.18P-H-3). Such accumulation is a major problem in device manufacturing because it causes electrical troubles such as short circuits and poor connections. Conventionally, in order to remove this deposit, a method was used in which the entire surface of the substrate was etched after film formation. However, this method requires three steps, namely film formation, cleaning, and etching, and therefore requires two or more processing apparatuses, and has the disadvantage that the number of steps increases due to switching from one chamber to another, etc. Furthermore, since the entire surface of the substrate is etched, the surface of the patterned thin film is also damaged.

As described above, in the conventional method, it is difficult to remove the accumulation around the pattern using a single device and a single process without damaging the pattern portion.

An object of the present invention is to provide a film forming method and apparatus that solve the problems of the conventional method and apparatus.

(Means for Solving the Problems) In the first invention, a thin film forming gas is introduced into a reaction chamber, and light for decomposing the gas is irradiated onto a desired part of the surface of a substrate installed in the reaction chamber. In photo-CVD for forming a patterned thin film in the desired portion by:
Provided is a photo-CVD method, characterized in that an etching gas having a property of etching the patterned thin film when excited by light is introduced into the reaction chamber, and the excitation light is irradiated from the back surface of the substrate. It is something.

In the second invention, a thin film forming gas is introduced into a reaction chamber, and a desired portion of the surface of a substrate placed in the reaction chamber is irradiated with light for decomposing the gas, whereby the desired portion is patterned. In a photo-CVD apparatus for forming a thin film, the thin film is provided with an etching gas supply mechanism, an inlet for introducing the etching gas into the reaction chamber, and a light source having an emission wavelength corresponding to the decomposition and absorption wavelength of the etching gas. and a window portion provided in the reaction chamber so as to irradiate the light emitted from the light source onto the back surface of a substrate installed in the reaction chamber.

(Function) In the case of laser CVD that utilizes photochemical reactions, gas phase reaction products accumulate near the irradiation area. The film in areas other than the desired areas due to such accumulation can be removed by introducing an etching gas into a chamber containing the CVD substrate, and selectively irradiating areas other than the desired areas with a laser to excite the etching gas. can be removed. Furthermore, when the formed patterned thin film exceeds a certain thickness, it hardly transmits light of a wavelength that excites a general etching gas, and can function as a mask for light of this wavelength.

The present invention utilizes the fact that selective etching is possible by light irradiation and that the formed thin patterned film itself can be used as a mask pattern to perform laser CVD.
During pattern formation, not only CVD gas but also etching gas is introduced, and second light that excites the etching gas is irradiated from the back surface of the substrate to remove deposits around the pattern. Since the second light does not pass through the patterned thin film, etching of the patterned thin film does not occur, but since the second light passes through the deposited portion, which is much thinner than the patterned thin film, etching progresses only on the deposited portion. At the early stage of growth, when the patterned thin film is thin and allows light for excitation of the etching gas to pass through, the patterned thin film may also be etched. However, etching of the patterned thin film in the early stage of growth can be avoided by monitoring the light transmitted through the patterned thin film by the light for excitation of the etching gas and introducing the etching gas only when the intensity of the transmitted light has sufficiently decreased.

In the present invention, etching around the pattern can be performed in parallel with film formation in the same reaction chamber, so the number of steps is reduced compared to the conventional method of etching the entire surface of the substrate, and only one process device is required.

Further, in the present invention, since only the peripheral portion of the pattern is selectively etched, the surface of the pattern thin film is not damaged.

(Example) Hereinafter, an example in which the present invention is applied to pattern thin film formation of amorphous silicon will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, and FIG. 2 shows a modification of the embodiment. First, the apparatus of the present invention will be explained. 1st
As shown in the figure, a substrate 2 is fixed in a reaction chamber 11 by a holder 8, and a thin film forming gas and an etching gas are supplied thereto. A pattern thin film 5 is formed by irradiating laser light onto the substrate 2 in a pattern through a pattern mask 7, a lens 9, and a front window 3. The light from the etching gas decomposition laser 10 passes through the rear window 4 to the substrate 2.
The patterned thin film 5 is irradiated from the back side to etch and remove the deposits around the patterned thin film 5.

Next, an example will be described in which the photo-CVD method of the present invention is implemented using the photo-CVD apparatus of the present invention described above. First, a quartz substrate was used as the substrate 2, Si2H6 was introduced into the reaction chamber as a thin film forming gas, and at the same time ArF laser light was irradiated through a pattern mask to form a patterned thin film of amorphous silicon. Si2H6
Simultaneously with the introduction of C12 gas for etching, XeC laser light was irradiated from the back surface of the quartz substrate 2.

When the thickness of the amorphous silicon pattern thin film 5 reaches a desired thickness, disilane is stopped and light from the ArF laser 6 is blocked. At this point, if the accumulation has disappeared to an extent that is not considered appropriate for device applications, C1□ gas is sought and the light from the XeC laser 10 is also blocked, but if it remains, C12 gas is and irradiate the light from the XeC laser 10. Using the amorphous silicon pattern thin film 5 as a mask, only the falling part is XeCIL/-The 10
and C1□ gas, it was possible to obtain an amorphous silicon pattern thin film 5 with no deposits.

In the present invention, it is not necessary to etch the entire surface of the substrate, and the deposition around the pattern can be removed in parallel with the formation of the patterned thin film, so compared to the conventional method of etching the entire surface of the substrate, it requires less equipment. The number of steps required is small, and the number of man-hours is also reduced. Furthermore, damage to the surface of the patterned thin film that would occur in the conventional method of etching the entire surface of the substrate does not occur because the etching is performed selectively, avoiding the patterned portion.

In this example, since etching is performed at the same time as the start of film formation, when the amorphous silicon pattern thin film 5 is thin at the early stage of film formation, the light from the xeC laser 10 passes through it, and the amorphous silicon pattern thin film 5 is thin. Etching also occurs on 5. If such etching causes problems with the device, as shown in Figure 2,
The light transmitted from the XeC laser 10 through the amorphous silicon pattern thin film 5 is transmitted through the front window 3, the lens 9, and the quartz reflector 11.
．． In order to transmit wavelengths longer than 200 nm, the light from the ArF laser 6 is passed through a filter 12 that blocks it and is received by a photodiode 13, and the intensity is observed. Only when the transmitted light intensity becomes sufficiently small is C12 gas introduced into the CVD chamber 1. Etching at the initial stage of film formation can be avoided by introducing a method of etching and removing the deposits around the amorphous silicon pattern thin film 5.

Note that the present invention is not necessarily applied only to the formation of amorphous silicon patterns, but can be applied to the formation of any thin film pattern within the scope of the invention, that is, as long as the laser used for etching can pass through the substrate. I can do it. For example, in the case of forming a polysilicon pattern, the method of this embodiment as well as the apparatus of this embodiment can be applied as is by simply changing the experimental conditions, such as increasing the substrate temperature.

(Effects of the Invention) As described above, according to the present invention, by etching the peripheral portion of the patterned thin film from the back side of the substrate at the same time as forming the patterned thin film, it is possible to obtain a patterned thin film without deposition on the periphery.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment to which the present invention is applied,
FIG. 2 is a schematic diagram of an apparatus in which a XeC laser light monitoring mechanism is added to this embodiment. 1...Reaction chamber 2...Substrate 3...Front window 4...Rear window 5...Pattern thin film 6...Laser 7...Pattern mask 8...Holder 9...
Lunz 10...Luza 11...Quartz reflector 1200. Filter 13...photodiode

Claims (2)

[Claims] (1) A thin film forming gas is introduced into the reaction chamber, and a patterned thin film is formed on the desired portion by irradiating a desired portion of the surface of a substrate placed in the reaction chamber with light for decomposing the gas. In the photo-CVD method for forming a substrate, an etching gas having a property of etching the patterned thin film when excited by light is introduced into the reaction chamber, and the excitation light is irradiated from the back surface of the substrate. Optical CVD method. (2) A thin film forming gas is introduced into the reaction chamber, and a patterned thin film is formed on the desired portion by irradiating a desired portion of the surface of the substrate installed in the reaction chamber with light for decomposing the gas. In the optical CVD apparatus for forming the thin film, a supply system for the etching gas for the thin film, an inlet for introducing the etching gas into the reaction chamber, and a light source having an emission wavelength in the decomposition and absorption wavelength of the etching gas; A photo-CVD apparatus comprising: a window portion provided in a reaction chamber so as to irradiate light emitted from the light source onto the back surface of a substrate placed within the reaction chamber.