JPS58112344A - Heat treatment for substrate-coating film - Google Patents

Abstract

PURPOSE:To remove irregularity in thickness, bubbles, and distortion from a coating formed by a rotational coating method and thereby to form a free of- bubble, homogeneous, fine, and flat film by a method wherein a substrate is subjected to ultrasonic vibration while under-going heat treatment. CONSTITUTION:Vibration of a vibrating piece is transmitted via a support 7 to a semiconductor substrate when the vibrating piece is fixed to the support 7 by soldering or brazing. Vibration is generally effective when it is applied simultaneously with heat. By way of example, an approximately 1mum-thick Al wiring on an SiO2 coating is rotationally applied with an approximately 1mum-thick coating of polyimide resin, which is followed by a 90-100 deg.C heat treatment for 30min in an ultrasonic heat treatment furnace generating a 49KHz frequency. The ultrasonic wave reduces the difference in thickness between the upwind and downwind portions. Air bubbles and distortion in thicker portions are also greatly reduced. The coating solidified in the first heating grows drier and stronger after repeated treatment under 200 deg.C/30min and 350 deg.C/30min conditions.

Description

[Detailed description of the invention] This invention I! A: Thermal coating method is used to coat semiconductor substrates, especially to smooth the surface of semiconductor substrates, and to form smooth and uniform coatings used for interlayer insulating films in 4IK multilayer wiring structures. The present invention relates to a heat treatment method.

As semiconductor devices, especially integrated circuits, become faster and more dense, the manufacturing process becomes more complex.

The irregularities on the surface become increasingly large (sP), which causes failures in the multilayer wiring due to open circuits and short circuits.

Therefore, the semiconductor base 74ILI! ! The coating film formed on the surface needs to be useful for smoothing and free from bubbles.

Recently, polyimide film, silica film, etc. have been used as coating films suitable for these purposes.

These films are coated using a rotary coating machine and then solidified by heat treatment, but since the surface of the substrate is highly uneven, it is difficult to form a smooth, textured film.

FIGS. 1 and 2 are explanatory diagrams showing the state of a coating film formed on the surface of a living and dead conductor substrate by coating and heat treatment using a conventional method. In Fig. 1, l is a semiconductor substrate, 2 is a silicon oxide film formed on it, and 3 is an aluminum wire, but the overall O
The structure is uneven like a snow eave. If the direction of the arrow is the windward direction or the leeward direction, the coating film 4 is more abundant and thicker on the windward side than on the leeward side. Under good wind conditions, the coating film and the convex parts do not come into close contact and there are bubbles in some parts. Such inconsistency in film thickness and bubble formation may cause defects in the bladder. If there are irregularities on the semiconductor substrate (for example, as shown in Figure 2), the coating film 4' will have different thicknesses on the windward and leeward sides; it will be thinner on the windward side and thicker on the leeward side. There is a high possibility that cracks will occur after the part has solidified.

Therefore, the present invention has been made to address the above-mentioned problems, and the spin-coated film is not excessively dependent on the condition of the substrate surface.
Another object of the present invention is to provide a method for heat treating a coating film that does not cause defects.

In other words, this invention O1! The purpose is to provide a heat treatment method for a coating film spin-coated on a substrate, in which the substrate is heat-treated without applying ultrasonic vibration to the substrate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the drawings. FIG. 3 is a diagram illustrating the construction of a heat treatment furnace used for heat treatment during coating of semiconductor substrates according to an embodiment of the present invention.

In the figure, 1 is a dead conductor substrate coated with a coating film, 7 is a support stand on which the medium conductor Go board 1 is placed, and 9 is a support body that supports the Hiro support stand. Further, 8 is an ultrasonic transducer fixed to the support base 7. Further, 10 is a heater for heating, and 11 is a heating furnace main body. Various types of ultrasonic vibrators can be used; for example, when a crystal vibrator is used, electrodes are formed on both sides of the crystal, and the ultrasonic vibrator can be vibrated by applying a κ voltage.

Therefore, as shown in the drawing, if the oscillator is fixed to the support stand 7 by soldering or brazing, and this resonator is placed on the support body, the vibration of the resonator can be applied to the semiconductor substrate via the support stand. . Alternatively, it may be fixed to a support stand without coming into contact with the vibrator wire support.

The frequency and amplitude of vibration must be changed as appropriate depending on the coating material, substrate surface condition, etc. When the power of the oscillators is too strong, this can be compensated for by increasing the number of oscillators that are turned on.

Next, considering the timing of applying vibration, it depends on the material, but if vibration is applied before heating, it may cause the film to peel, and it may be less effective if the film has already hardened after heating. Generally, it is effective to apply vibration at the same time as heating.

For example, about 1 #m of polyvinyl resin was spin-coated onto a U wiring having a thickness of about 1 um on a silicon oxide film, and after coating, it was heat-treated at 90 to 100° C. for 30 minutes in the above-mentioned ultrasonic heat treatment furnace. A frequency of 49 kHz was added. In this case, the ultrasonic waves were smoothed and the difference in film thickness between upwind and leeward areas was small, and as a result, the need for air bubbles and thick areas could be significantly reduced. The coating film fixed by primary heating was further heated at 200℃ for 30 minutes and then at 350℃ for 3 minutes.
It is heat treated for 0 minutes to wither and become a strong film.

In addition, in this example, ultrasonic waves were applied only for the first heating.

For further heating, a heating furnace without an ultrasonic element was used. Therefore, some parts of the crystal oscillator operated well without any adverse thermal effects. As a result, air bubbles are removed from undesirable films with uneven thickness, pores, and distortions formed by spin coating, and the film thickness is smoothed and homogenized, resulting in a high-quality film. I was able to form it.

A similar method was also attempted for the formation of silica 7yl▲. In other words, as a silica film, OCD (manufactured by Tokyo Ohka Co., Ltd., trade name) is coated on a silicon oxide film with a thickness of approximately 1,000 ml by spin coating method, similar to the Borii-ken coating film, on the surface containing the wiring.
^Apply and apply ultrasonic waves at 300℃ for 60 minutes as primary heating 4
It was carried out while adding 9 kHz. Next, as a second step, 4
Heat treated at 50℃ for 60 minutes without applying ultrasound. As a result, in the conventional heat treatment without applying ultrasonic waves, the coating film adhered non-uniformly due to spin coating, and the coating film remained stuck as it was, and the film quality containing pores became uneven, resulting in good film quality. K〈It was. However, by the method of the present invention in which ultrasonic waves were added, the film quality could be made dense and homogenized, and the film thickness could also be averaged. Ultrasonic waves were applied only to the primary heating of the main heat treatment tunnel, and the secondary heating was performed in a heating furnace without a vibrator.

In addition, in the embodiment, only the coating film on the semiconductor substrate will be described, but it is not intended to say that the invention can also be applied to the formation of an insulating film of multilayer wiring formed on an insulating substrate.

That is, according to the method of the present invention, the pores are removed from the coating film which was formed by the spin coating method and has non-uniform thickness, pores and distortions, and the thickness of the coating is smoothed to be homogeneous and dense. A good quality film κ and ζ can be formed.

Incidentally, if the method of the present invention is carried out under reduced pressure, pores and bubbles can be removed more effectively.

[Brief explanation of the drawing]

Figures 1 and 2m are schematic cross-sectional views showing the surface condition of a coating film spin-coated onto the surface of a conductor substrate having irregularities and heat treated by a conventional method, and Figure 3 is a semiconductor substrate coating film according to an embodiment of the present invention. FIG. L...Semiconductor substrate, L2'...Silicon oxide film, 3...Electrode, 4...Coating film, 5...Empty Hole, 7...Support stand, 8...
... Vibrator, 9 ... Support, 10 ... Pa°
° Heating heater, 11... Heat treatment mP main body.

Claims (1)

[Claims] A method for heat treating a coating film spin-coated on a substrate, the method comprising heat treating the substrate while applying ultrasonic vibrations.