JPH0616505B2 - Insulation film formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [b] Field of Use of the Invention The present invention uses an organic silicon compound, for example, tetraethoxysilane (TEOS), to form a high-speed and high-quality insulating film on a surface to be formed by plasma chemical vapor reaction. The present invention provides a method for forming under pressure.

[B] Prior Art Recently, the area of wiring occupied in an IC chip is increasing with the high integration and large scale of LSI.

Therefore, it is becoming more and more important to make the wiring multi-layered and the pattern and wiring width finer.

The horizontal dimension of the pattern such as wiring and connection hole is miniaturized according to the scaling rule, while the vertical dimension such as the thickness of electrode wiring and insulating film is wiring resistance, stray capacitance, withstand voltage and migration resistance. It is necessary to meet the device specifications, and it is not easy to miniaturize it in the horizontal direction.

Further, since the patterns of the wirings and the connection holes are formed by etching with strong anisotropy for miniaturization, the shape of the end face of the LSI pattern becomes sharp.

Further, since the wiring is multi-layered, the unevenness on the LSI chip surface is naturally severe. Such unevenness on the surface of the LSI chip leads to a decrease in pattern processing accuracy and a decrease in reliability such as disconnection of wiring.

As a means for solving such a problem, a technique for flattening an interlayer insulating film is emphasized.

As a method of forming this interlayer insulating film, the thermal CVD method is widely known as a conventional thin film forming technology by chemical vapor reaction (hereinafter referred to as CVD). In this thermal CVD method, heat energy is applied to a reaction gas for film formation introduced into a reaction chamber to decompose or activate the gas to form a film. In this case, since the energy supply for the reaction is only heat, the temperature is also high, and it is performed in the range of 500 to 800 ° C.

For this reason, it is impossible to fabricate a semiconductor element that is susceptible to high temperatures, and there has been a demand for a technique for forming a film at a low temperature, which is promising as a next-generation LSI element.

In addition, plasma CVD is used as a method to form a film at a lower temperature.
The law is known. In this case, high frequency power is applied to the reactive gas introduced into the reaction chamber from the outside to decompose the gas,
It is activated to form a film on a heated substrate. In this case, the heating temperature is in the range of 200 to 400 ℃, but because of the high energy state of plasma, the reactive species decomposed and activated hit the film-forming surface and damage it, so that it is formed. Moreover, it has a drawback that it is difficult to obtain good characteristics at the interface between the coating film and the base substrate. In this case as well, as in the case of thermal CVD, it could not be used for compound semiconductors such as GaAs.

On the other hand, recently, as a technique to solve these problems, photo CVD
There is a law. This method applies light energy to a reactive gas to decompose and activate it to form a film on the substrate, which does not require high temperature as in the thermal CVD method.
Moreover, unlike the plasma CVD method, it is an ideal film formation method without physically damaging the underlying material.

As a method of flattening the insulating film formed by the above-described manufacturing method, a method of applying a liquid of an organic silicon compound onto a substrate surface having an uneven shape and subjecting it to vitrification by heat treatment, or having an uneven shape Various methods such as an etch-back method, in which the insulating film is etched back to smooth the uneven shape, are used. Each of these methods for forming a flat interlayer insulating film is divided into a step of forming an insulating film and a step of flattening, resulting in an increase in the number of steps, an increase in the number of manufacturing apparatuses, and a high cost.

[C] Object of the present invention The present invention solves these conventional problems, and an object of the present invention is to form an interlayer insulating film without abrupt steps.

[Configuration of the present invention]

The present invention is a plasma CV using the reaction of TEOS and N ₂ O.
According to the method D, a silicon oxide film is further formed to a predetermined film thickness, and then an etchback process is performed in the same reaction chamber.

Further, if necessary, these steps are repeated to form an insulating film having no sudden uneven steps.

In other words, it provides a method for forming an oxygen silicon insulating film without forming abrupt uneven steps without forming it on the substrate to be processed after forming the insulating film.

Examples will be shown below to show a method for producing the oxygen silicon film shown in the present invention.

Example 1 FIG. 2 shows a schematic view of a silicon oxide film forming apparatus used in this experiment.

In the drawing, a plurality of ultraviolet light sources (6) are installed in the ultraviolet light source chamber (4) in the reaction chamber (1), and the ultraviolet light source chamber (4) is almost equal to the pressure in the reaction chamber (1). Has been adjusted to The film-forming substrate (3) is installed in the reaction chamber (1) with the film-forming surface facing downward by the substrate support (2) which also functions as a substrate heating heater. This equipment uses a deposition-up method so that dust such as flakes generated during film formation does not adhere to the substrate.

Among the reactive gases, the silicide gas and the oxide gas are mixed in the pipe, introduced into the reaction chamber through the gas nozzle (7), and mixed near the substrate (3). Ultraviolet light emitted from an ultraviolet light source (6) that undergoes a photochemical vapor phase reaction is transmitted through a transmission window (5).
A direct excitation method was adopted in which the reactive gas was irradiated through the glass. In addition, the reaction was carried out without coating low vapor pressure oil for preventing the formation of a film on the transmission window (5). In particular, in the case of the present invention, since a silicon oxide film is formed, even if a coating film is formed on the transmission window, ultraviolet light is sufficiently transmitted, and thus it is not particularly necessary.

Furthermore, a mesh electrode (8) for etching is placed on the transparent window (5). This Mesh Electrode (8)
Is configured so that high-frequency power can be applied between the substrate support (2) and the power supply (9). If necessary, power can be applied between the mesh electrode (8) and the substrate support (2). And applying bias voltage, etching of transmitted light window (5), substrate to be processed (3)
Etching back can be done in the same reaction chamber.

Using this device, the reaction pressure is 1500 Pa to 7000 Pa, (11 to 53 Torr), the substrate temperature is 200 ℃ to 400 ℃, and the input ultraviolet light source power is 13.56 MHz, 200 W on a substrate having irregularities as shown in FIG. 1 (A).
A silicon oxide film was formed by changing the ratio of monosilane and nitrous oxide as a reactive gas under the condition of ~ 300W.

In the case of photochemical gas phase reaction, the oxidizing gas has a high activation rate, so the ratio of N ₂ O to the amount of silicon is 0.005 to
It was added in a slight excess in the range of 0.05, formed on a single crystal silicon semiconductor substrate, and the film thickness and refractive index were measured by an ellipsometer. The reaction between SiH ₄ and N ₂ O is 6.eV (153Kcal / mol) 4.9eV (112.5Kcal / m) when the resonance line of 185nm and 254nm of a low pressure mercury lamp is used as an ultraviolet light source, respectively.
ol), it is easy to cut the interatomic bond energy if absorption can occur in the reactive gas molecule.

Each atomic bond energy is shown below.

Si-H 74.6 Kcal / mol Si-Si 76 Kcal / mol H-N 86 Kcal / mol H-H 104 Kcal / mol Si-N 105 Kcal / mol O-O 119 Kcal / mol N-O 149 Kcal / mol The light absorption edge of Si-O 192 Kcal / mol N-N 227 Kcal / mol SiH ₄ molecule has a peak on the shorter wavelength side than 185 nm, but it is considered that some light absorption is performed.

On the other hand, the photolysis reaction of N ₂ O is considered to be the following process.

N ₂ O + hr (185nm) → N ₂ + O ( ¹ D) When activated O ( ¹ D) attacks SiH ₄ molecule, weak bond Si−H is dissociated and replaced with oxygen radical to replace Si−O. A bond is formed.

The following reactions can be considered from the refractive index and infrared absorption of the oxygen-silicon coating in the range of SiH ₄ / N ₂ O of 0.005 to 0.05.

The formation of SiH ₄ + 2N ₂ O → SiO ₂ + 2N ₂ + 2H ₂ hydrazine and ammonia may be considered, but it is difficult to think from the results of this analysis.

FIG. 3 shows the relationship between the reaction pressure and the film formation rate. Gas composition ratio is SiH ₄ / N ₂ O ratio 0.01 Substrate temperature 400
The film was formed under the conditions of a temperature of 300 ° C., an ultraviolet light source power of 13.56 MHz and a power of 300 W.

As the reaction pressure increases, the amount of raw material (reaction) gas present in the gas phase per unit time increases, the number of active species that contribute to film formation increases, and the film formation rate increases, but peaks near 20-25 torr. In other regions, the number of times that the active species collide with other molecules increases and it does not contribute to film formation (for example, it becomes a secondary product), and it is expected that the film formation rate will decrease.

That is, it is considered that there is an optimum region in the reaction pressure.

FIG. 4 shows the film formation rate when the high frequency power density was varied in the plasma CVD method using the reaction of TEOS and nitric oxide.

The reaction pressure is 0.4 torr, the substrate temperature is 200 ° C, and the nitrous oxide flow rate of the bubbling carrier gas is 100 SCCM.

Within this variable range, there is a linear increasing tendency with respect to the high frequency power density.

That is, the rate of TEOS supply is not limited.

TEOS usually does not thermally decompose below 600 ° C, so when it is introduced into the reaction space, it exists on the substrate surface or in the gas phase in a liquid or highly viscous gas state, so that the substrate temperature is low and the high frequency power density is small. Although it has good step coverage under the following conditions, the film quality is -OH group or C
Remains in the film and is not necessarily good.

On the other hand, under the condition that the substrate temperature is high and the high frequency power density is large, the step coverage is slightly reduced, but the film quality is improved. However, hillocks are often generated on Al, which is a problem.

From the above, it is considered that there are optimum conditions for the two parameters of the substrate temperature and the high frequency power density.

It was found that at a certain reaction pressure, the substrate temperature was not raised too much, the viscous flow was promoted, and the film quality was stabilized by applying high frequency power and bias power to the substrate.

The nitrous oxide used as the carrier gas here is also an oxygen supply source for the silicon oxide film formed.

FIG. 5 shows the film formation rate when the flow rate of nitrous oxide was varied in the plasma CVD method.

The reaction pressure is 0.4 torr, the substrate temperature is 200 ° C, and the high frequency power density is 0.35 W / cm ² . Nitrous oxide flow rate 5
Even if it is doubled, the film forming rate is increased only by about 15%.
That is, it is understood that the oxygen necessary for forming the silicon oxide film is sufficiently supplied by the decomposition of TEOS. Further, by using nitric oxide as shown in the present invention, nitrogen is allowed to exist in the silicon oxide film with Si-N bond, and the blocking effect of alkali resistance is improved, which is effective.
Further, the reaction was surface reaction and the life of radicals was long, and it was possible to form a silicon oxide film in the recesses sufficiently even for the unevenness of the base.

FIG. 6 shows the etching rate when the high frequency power density was varied when the silicon oxide film was plasma-etched using sulfur hexafluoride. The reaction pressure is 0.4 torr, the substrate temperature is 200 ° C, and the SF ₆ flow rate is 25 SCCM. 0.56W / c
It has been found that an isotropic or anisotropic etching shape can be controlled by applying a negative bias power to the substrate, which is sufficient for the etch-back process because it can obtain about 500 Å / min in m ² .

FIG. 7 shows the etching rate when the substrate temperature is changed.

Reaction pressure 0.4 torr High frequency power density 0.56 W / cm ² , SF
_{At 6} flow rate of 25 SCCM, there is almost no substrate temperature dependence, and it is considered that the high frequency power density determines the temperature.

It can be said that the substrate temperature is one of the important parameters because the process has selectivity in the etching process when the interlayer insulating film is continuously formed.

By such a photo-CVD method, a silicon oxide film was formed on the substrate having the uneven shape as shown in FIG.

The convex portion on this substrate has a height of 1 μm and a space of about 0.8.
It had a shape of μm. Since the silicon oxide film (10) was first formed on this substrate by the photo-CVD method, this uneven shape could be uniformly covered. (Fig. 1 (B)) After that, the pressure in the reaction chamber was adjusted to 10 Pa, and a power source (9) was used between the mesh electrode (8) on the transmitted light window (5) and the substrate support (2). High frequency power, for example, 13.56 MHz power of 80 W was applied. The reaction gas is TEOS / N ₂ O, the flow rate of N ₂ O for bubbling is 100 SCCM, and other conditions are the same as the photo-CVD, and the silicon oxide film (11) is about 1.5 μm by plasma CVD method.
This plasma CV was formed with a thickness of 2.0 μm (FIG. 1 (C)).
Silicon oxide formation by the D method has a step coverage of light C
It is slightly slower than VD, but the film formation rate is 0.5-1 μm
/ Min, fast and highly productive.

As shown in FIG. 1 (C), after a silicon oxide film is formed thickly so as to cover the irregularities, the reactive gas in the reaction chamber is exhausted and removed, and then a halide gas such as an etching gas is used.
SF ₆ , NF ₃ , CF ₄ , CF ₃ H, etc. were introduced into the reaction chamber, the pressure was adjusted to 10 Pa, and power was applied between the mesh electrode (8) and the substrate support (2) to cause plasma discharge. The formed coating film (11) was etched to eliminate the abrupt portions of uneven steps.
(FIG. 1 (D)) At this time, if a bias voltage was applied between the mesh electrode (8) and the substrate support (2) at the same time, the shape of the uneven step could be controlled by etching. That is, when a negative bias voltage was applied to the substrate side, the uneven step could be made smoother.

This treatment was carried out to perform etching of about 0.2 to 0.5 μm, and as shown in FIG. In this way, an interlayer insulating film without abrupt steps could be produced in the same device and reaction chamber.

In addition, the coating on the reaction chamber inner wall and the transmitted light window (5) could be removed at the same time during the etching process, and it was not necessary to stop the device for cleaning, which led to improved productivity.

Further, although the plasma CVD method and the photo-CVD method are used in combination in the production of the silicon oxide film in the present embodiment, it is obvious that the photo-CVD method alone may be employed.

Example 2 Under the same conditions as in Example 1 on the substrate shown in FIG. 1 (A), a silicon oxide film was formed to about 5000 Å by a photo-CVD method, and then a reactive gas in the reaction chamber was replaced. Under the same conditions as in Example 1, about 500 Å of etch back was performed. After that, a reactive gas is further replaced, and a silicon oxide film is formed again by the photo-CVD method under the same conditions. Such a cycle is repeated a plurality of times, and the interlayer insulation without sharp irregularities and steps as in Example 1 is performed. A film could be formed.

In this embodiment, the film formation by photo-CVD and the plasma etching are alternately performed, so that the reaction chamber contaminated by the film formation can be simultaneously cleaned by the etching process.

In addition, it should be added that it is desirable that the uppermost part of the laminated structure of the interlayer insulating film is a photo CVD film. This is because when the second layer Al film is sputter-deposited, the TEOS silicon oxide film at the uppermost portion may adversely affect the Al film quality due to the gas (moisture, H ₂ etc.) emitted from the film. .

Therefore, the ideal laminated structure of the interlayer insulating film is photo CVD film / plasma CVD film / photo CVD film.

The withstand voltage, which is important as an interlayer insulating film, can be sufficiently given by the photo CVD film of the first layer.

For reference, the breakdown voltage of the photo CVD film is 5 MV / cm or more.

Although a silicon oxide film is disclosed as an insulating film in the above embodiments, other insulating films, silicon nitride films, PSG, BPS are disclosed.
It is also applicable to G and alumina films.

Further, not only silane but also other polysilanes (SinH _{2n + 2} ), dimethylsilane, tetramethylsilane, and other organosilicon compounds (SiH _r (CH ₄ ) _4-n ) are used as a reactive gas as needed. It is also possible.

[E] Effect As described above, the present invention is a method for forming a high-quality and high-quality silicon oxide film under conditions that are clearly different from the conditions conventionally used, such as LSI, VLSI, etc. It became possible to use the interlayer insulating film used for the first time only by the film formed by the photo-CVD method.

According to the method of the present invention, it is possible to form an interlayer insulating film having no abrupt unevenness in the same reaction chamber of the same device, and it is possible to reduce the manufacturing cost of the device.

In addition, it has the feature that the inner wall of the reaction chamber and the transmitted light window can be etched simultaneously during the etch back process.

[Brief description of drawings]

FIG. 1 shows a step of producing an interlayer insulating film of the present invention. FIG. 2 shows a schematic view of the apparatus used in the present invention. FIG. 3 shows the relationship between the reaction pressure of the silicon oxide film formed by the photo-CVD method and the film formation rate. Figure 4 shows the relationship between the deposition rate and the high-frequency power density of a silicon oxide film formed by the plasma CVD method. Fig. 5 shows the relationship between the deposition rate and the flow rate of nitrogen-zinc oxide by the plasma CVD method. FIG. 6 shows the relationship between the etching rate and the high frequency power density of the silicon oxide film. FIG. 7 shows the relationship between the substrate temperature and the etching rate during plasma etching of the silicon oxide film.

Claims (3)

[Claims] 1. An insulating process, which comprises a step of uniformly forming a silicon oxide insulating film on a substrate surface having uneven steps by a plasma CVD method using a reaction of an organic silicon compound and nitric oxide. Film forming method. 2. The method for forming an insulating film according to claim 1, wherein the plasma CVD method uses tetraethoxysilane (TEOS) and nitrous oxide as a bubbling gas. 3. The etch back can be continuously performed in the same chamber by plasma etching using a plasma CVD film and a halide gas and applying a negative bias. Insulating film forming method.