JPS59124729A - Formation of insulating film - Google Patents

Abstract

PURPOSE:To enable formation of an even insulating film by forming fluid product on a substrate by plasma polymerization with introducing monomer into a reactor followed by irradiation of radiant ray or heat treatment upon said product. CONSTITUTION:An usual plasma CVD system is available for a reactor and the discharging type and the structure of electrodes thereof are arbitrary. As monomer, proper organic compound can be used, thereby it becomes easy to form fluid product under the condition of low substrate temperature, low applied electrical power, high monomer supply and high pressure. Next, this product is irradiated with radiant rays, for example, one within a region from ultraviolet to far ultraviolet, or is subjected to heat treatment or combination of these treatments so as to form the insulating film 3 being stable and whose surface is even compared with unevenness of the lower substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an insulating film forming method for forming an insulating film such as an interlayer insulating film in a semiconductor device manufacturing process.

Conventional methods for forming this type of insulating film include the CVD method, plasma CVD method, and sputtering method as vapor phase growth methods, but all methods require a high quality inorganic film (Sin2
．． Si, N4. PSG, etc.), however, the formation temperature is high, defects are likely to occur in the crystal of the substrate, and it is not possible to form a flat film directly on the unevenness of the substrate surface due to wiring, etc. Too 7
However, there are drawbacks such as the need to perform complex process operations such as manipulation for planarization.

In particular, when the film obtained in this way is used as an interlayer insulating film, if the surface of the film is uneven after being formed for flattening, for example, metal may be deposited by means of vacuum evaporation to form wiring. If the metal film is adhered by the step, the metal film becomes thinner on the side surface of the stepped portion, and wire breakage is likely to occur, which in turn tends to lead to a decrease in yield.

In order to solve these problems such as cost and yield, the so-called Glass 70-method, in which phosphor glass is made to plastically flow through high-temperature treatment at nearly 1000°C, is used to easily form an insulating film with a smooth or flat surface. A known method is to spin-code an organic material such as polyimide and heat cure it.

However, the use of the glass flow method is strongly limited, as the distribution of impurities in the semiconductor becomes blurred due to its high-temperature treatment, and it is necessary to use high-melting point metals for the electrodes. The disadvantage is that it cannot be used.

In addition, when using organic materials, since the film formation is wet, it is easy for impurities to get mixed in, it is difficult to obtain a dense film, there are problems with hygroscopicity, pinholes are likely to occur, and microfabrication is difficult. There are drawbacks such as problems.

The purpose of the present invention is to solve the above-mentioned drawbacks, and to form a high-quality film with a flat surface directly over unevenness such as wiring on the surface of a substrate using a vapor phase growth method at a relatively low temperature. An object of the present invention is to provide a method for forming an insulating film.

In order to achieve such an objective, in the present invention, a substrate is placed in a reaction vessel for plasma polymerization, a monomer is introduced into the reaction vessel, and a fluid product is formed on the substrate by the plasma polymerization method. Then, by subjecting the resulting product to radiation irradiation such as light irradiation or electron beam irradiation, heat treatment, or a combination thereof, an insulating film with a flat surface is formed on the substrate.

As a reactor for carrying out the present invention, an ordinary plasma CVD apparatus can be used, and its discharge type.

Any desired electrode structure can be used and is not limited in any way. As the monomer, any suitable organic compound can be used, whereby under the conditions of low substrate temperature, low applied power, high monomer supply amount, and high pressure,
A free-flowing product can be easily formed. next,
This product is irradiated with radiation such as light in the ultraviolet to vacuum ultraviolet range, electron beams, X-rays, etc., or /! ;0-. 2! By applying heat treatment at around 0°C or a combination of these treatments, it is possible to form an insulating film that is stable and has a smooth surface compared to the unevenness of the underlying substrate. can.

In plasma polymerization, almost any organic compound can be used as a monomer, but if heat resistance of the resulting film is required, an insulating film with excellent heat resistance can be formed by using an organic silicon compound as a monomer. can. As such organic silicon compounds,
Cyclomethylsiloxane and its derivatives such as octamethylsiloxane, hexamethylsiloxane, hexamethyldisiloxane, octamethyltetrasiloxane (,t
), alkoxysilanes and their derivatives such as tetramethoxysilane and tetraethoxysilane, cyclic and chain silazane and their derivatives such as hexamethylcyclotetrasilazane and hexamethyldisilazane, etc. Can be used.

Furthermore, in order to reduce the unevenness of the surface of the formed insulating film and make it flat, it is preferable to lower the temperature of one substrate during film formation to a temperature lower than (the melting point of the monomer) +10°C. Under such conditions, an insulating film with a flat surface can be easily formed according to the present invention.

Embodiments of the present invention will be described below with reference to the drawings.

(Example 1) ' Plasma polymerization was carried out using a normal plasma (3VD device, and a high frequency of /3.!A MHz was applied to the upper and lower parallel plate electrodes to generate a discharge. The substrate was placed on the lower electrode, and the substrate temperature (6°C) was controlled by passing cold or hot water through the lower electrode.

In this example, octamethylcyclotetrasiloxane was used as the monomer. The melting point of this monomer is 16 to 77°C, but the substrate temperature is 10/θ to the melting point of the monomer /6 to /7°C.
The temperature should be set at 70-9°C, which is lower than 26-1°C plus 100°C.

Set the monomer supply meter to about 3cm/min.

Yaria gas (nitrogen) flow meter 3θCCZ, total pressure 2T
When a film was formed on a silicon substrate for 5 minutes under the condition that the applied power was set to SW, a highly fluid liquid product was obtained. By irradiating this product with light using a low-pressure mercury lamp at an irradiation intensity of approximately lx/θ-2W/σ2 for over 700 minutes, the film thickness is increased by 3μ.
An insulating film was obtained which was stable in m and had good adhesion to the substrate. The volume resistivity was lθ16Ωα or more, indicating good insulation.

Further, even when heat treated in nitrogen at poo° C. for 30 minutes, no weight loss or cracks were observed, indicating good heat resistance. The results of thermogravimetric analysis in nitrogen are shown in FIG. Here, the curve line indicates the case of the photocurable film obtained according to the present invention, and the curve (2) indicates the case of the usual thermally polymerized polydimethylsiloxane for comparison. Both lines I
Comparison of ① and ① suggests that the film formed according to the present invention has good heat resistance.

In addition, we used a silicon substrate with polycrystalline silicon on which unevenness of 005 μm in height had been formed in advance to form an insulating film under the above conditions to examine the coverage. As shown in Figure 2. It was found that the surface was flat and a good coating was formed. In FIG. 2, / is a substrate, C is an uneven surface wiring formed in advance on the substrate l, and 3 is an insulating film formed according to this embodiment.

It has been found that when forming a highly fluid film as described above, the formation is facilitated by cooling the substrate temperature to a temperature lower than (monomer melting point) +/θ°C.

(Example 2) Using the plasma 0VD apparatus described in Example 1, hexamethylcyclotrisilazane (melting point -70°C) was used as a monomer.
was used, and nitrogen was used as the carrier gas. Monomer flow rate 3θ~/min, carrier gas flow rate 30cc/min,
When a film was formed on a silicon substrate for 5 minutes at a total pressure of 8, t T Orr % applied power, jW1 and a substrate temperature of 0° C., a highly fluid product was obtained. Approximately /X/θ-2W/cm2 was applied to this product using a low-pressure mercury lamp.
A stable insulating film with a film thickness of j μm was obtained by irradiating with light for 200 minutes or more at an irradiation light amount of . The volume resistivity of this film was lθ16Ω or higher, and no cracks were observed even after heat treatment at aOO°C for 30 minutes in nitrogen, showing good heat resistance. Furthermore, when a silicon substrate on which uneven surface wiring with a height of O.S.mu.m was previously formed was used, the surface was flat as shown in FIG. 2, and good coverage was exhibited.

As explained above, according to the present invention, a thin film with good surface flatness and excellent heat resistance can be easily formed directly by vapor phase growth using a low-temperature process.

Therefore, (9
) The present invention can be effectively used in manufacturing an interlayer insulating film.

[Brief explanation of drawings]

FIG. 1 is a temperature-weight residual ratio characteristic curve showing the results of a heat radiation test of a flat film formed according to the present invention, and FIG. 2 is a cross-sectional view showing the surface coverage of an insulating film formed according to the present invention. l...insulating film, c...surface wiring, 3...lower substrate. Patent applicant Nippon Telegraph and Telephone Public Corporation (10) ■ (Light 4 history film) Onma (C) Figure 2 Hm

Claims (1)

[Claims] 1) A substrate is placed in a reaction vessel for plasma polymerization, a monomer is introduced into the reaction vessel, a fluid product is formed on the substrate by plasma polymerization, and the product is exposed to radiation. An insulating film forming method comprising forming an insulating film with a flat surface on the substrate by performing one of irradiation and heat treatment or a combination of radiation irradiation and heat treatment. 2) The method for forming an insulating film according to claim 1, wherein the monomer is an organic silicon compound. 3) The method for forming an insulating film according to claim 1 or 2, characterized in that the temperature of the substrate is set at a humidity lower than the temperature obtained by adding +70° C. to the melting point of the monomer. . 4) The insulating film forming method according to any one of claims 1 to 3, wherein the radiation irradiation is light irradiation, electron beam irradiation, or X-ray radiation.