JPS60128264A - Formation of thin film - Google Patents

Abstract

PURPOSE:To prevent unnecessary atoms of a decomposition product from entering a deposited thin film as an impurity when a gaseous compound is decomposed by irradiating light to form a thin film of a specified substance on the surface of a substrate, by irradiating other light which is absorbed in the unnecessary atoms. CONSTITUTION:A substrate 1 is placed in a deposition chamber 2, and a gaseous mixture of gaseous Mo(CO)3 with Ar, He or other gas is fed to the chamber 2 from a gas feeding source 11. At the same time, ultraviolet rays are irradiated from the 1st light source 4 to decompose the Mo(CO)3 into Mo and CO. This Mo forms a thin film 5 on the substrate 1. When light of specified wavelengths emitted from the 2nd light source 7 is irradiated, the CO moves lively and leaves the Mo deposition region, so it does not enter a thin Mo film, and a thin Mo film 5 of high purity is obtd.

Description

Detailed Description of the Invention The present invention relates to a method for forming a thin film using photodissociation of compound molecules. Conventionally, as a method for forming a thin film using light, a substrate is exposed to molecules of a compound containing atoms to be deposited, and the molecules are exposed to light. A method is known in which a substrate is irradiated with light having a wavelength that causes dissociation, and a deposited film containing the atoms is formed on the irradiated portion of the substrate.

At that time, lasers are increasingly being used as light sources in order to improve the deposition rate and localization of deposition. However, in this case, impurities are generally mixed into the deposited film, which poses a problem in terms of film quality.

For example, when a metal is precipitated and deposited from an organometallic compound gas, compositional analysis of the deposited film reveals that carbon (C) and oxygen (0
) are detected at modest concentrations, and the physical or chemical properties of the deposited metal film are often far from those expected of a pure metal film.

Specifically, when depositing molybdenum (MO), which is important as a metal for LSI wiring and electrodes, vapor of Mo(Co)6, which is a carbonyl compound, is used as the compound, and A and R lasers are used as the light source. A method is known in which photodissociation is caused by irradiation with the second harmonic of or an ultraviolet laser such as an excimer laser, but in many cases more than 10% of impurities are detected in the deposited film. There is. The causes of this can be roughly divided into cases where impurity gas in the compound gas mixes into the deposited film, cases where impurities adsorbed on the substrate mix, and cases where atomic groups that have been separated from metal atoms during photodissociation of the compound mix. There are three cases in which the substance is mixed into the deposited film by adsorption or as a compound.

The first two cases can be dealt with by increasing the purity of the raw material gas and cleaning the substrate, respectively, but in the third case, no effective measures have been taken to date, and impurity It is assumed that this is a strong cause of contamination.

An object of the present invention is to eliminate this third cause and obtain a deposited film with high purity.

The present invention irradiates a substrate exposed to a compound gas with a first light having a wavelength that causes total photodissociation of the metal, and deposits a deposited film by the photodissociation on a portion of the substrate irradiated with the light. In the method for forming a thin film, the second light absorbed by an atomic group that is separated from the compound by the photodissociation and does not contribute to deposition on the deposited film is irradiated simultaneously with the first light. It is characterized by irradiating the area.

The thin film forming method according to the present invention will be specifically explained below with reference to the drawings. Figure ○ is a conceptual diagram of one embodiment of the thin film deposition apparatus based on the present invention. A substrate] is mounted in the deposition chamber 2. The light for deposition passes through the lens 3 which also serves as the window of the deposition chamber 2, and the substrate l.
The light is focused on l. From the raw material gas supply system 11 to the cock 12
Mo(Co)s gas and buffer gas, which is a rare gas such as Ar or He, are supplied through the tube. At this time, it may be operated in a so-called flow state with a cock 13 provided for evacuation of the deposition chamber 2, or it may be operated in a closed state. Next, when the substrate is irradiated with ultraviolet light from the second harmonic generator of an Ar laser, which is the first light source 4 for No(CO)60 photolysis, a local Mo thin film 5 is formed on the substrate. be done. At this time, in the present invention, the deposited portion on the substrate 1 is also irradiated with light from another second light source 7 via the multiplexer 6. In this case, Mo(CO)eF
Since it decomposes into p Mo and CO gas by photodissociation, the second
As the light source 7, we use one that emits light with a wavelength that is absorbed by molecules, specifically, a variable wavelength light source with a wavelength of around 4.7 μm.
A parametric oscillator using a LiNbO5 crystal with YAG laser light as the fundamental wave, or a difference frequency oscillator that combines a two-wavelength light source such as a two-wavelength alexandrite laser, a two-wavelength chromatic laser, a dye laser light and its excitation light, and LiNbO3, etc. A second light source 7 can also be used if another compound for Mo deposition, bisbenzene molybdenum Mo(CaHa), is used.
As, the wavelength absorbed by benzene C, H, 3.26μ
It is sufficient to use a similar light source that emits light of m, 6.75 μm, 9.64 μm, etc. As described above, by simultaneously irradiating the second light according to the present invention, the movement of unnecessary molecules etc. is activated. However, since these unnecessary molecules quickly leave the deposition region, the impurities in the obtained local metallic N film 5 are significantly reduced, and the film quality is significantly improved. In many cases, the second light is also absorbed by the substrate 1 and the deposited thin film 5, so if it is irradiated with a strong illumination intensity, the deposition area will expand due to the thermal effect, making it impossible to form a fine pattern. It is important to irradiate at a certain illumination intensity.0 Although one embodiment in which the thin film forming method according to the present invention is applied has been described above, it goes without saying that several modifications are possible without departing from the spirit of the present invention. O For example, the second light does not need to be placed coaxially with the light from the first light source 4, and it is sufficient to irradiate the thin film 5 on the substrate 1 at the same time. On the other hand, if there is no absorption by the substrate 1,
Alternatively, both lights may be irradiated from the back side by turning the substrate 1 upside down.Also, in this embodiment, metal deposition was explained as an example.
It goes without saying that the present invention is also applicable to the deposition of semiconductors and dielectrics.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of an embodiment of a thin film forming apparatus based on the present invention, and each component is as follows: 1...Substrate, 2...Deposition chamber, 3...Lens, 4...
・First light source, ・Thin film, 6... Multiplexer, 7...
・81.52 light source, 11... Raw material gas supply system, 12
...Cock, I3...Cock used for exhaust.

Claims (1)

[Claims] In a thin film forming method, a substrate exposed to a compound gas is irradiated with first light having a wavelength that photodissociates the compound, and a deposited film is formed by the photodissociation on a portion of the substrate irradiated with the light. , simultaneously irradiating the irradiated portion with a second light that is absorbed by an atomic group that is separated from the compound by the photodissociation and does not contribute to the deposition on the deposited film; Thin film formation method with percentage characteristics〇