JPS59148341A - Insulating film forming method - Google Patents

Abstract

PURPOSE:To form an insulating film including impurities on a substrate readily, by performing the high frequency sputtering of the target of an insulating film in a gas including impurities. CONSTITUTION:A gas including phosphorus other than argon, e.g., phosphine, is introduced from a gas introducing port. Argon plasma 8 is yielded from argon in a high frequency electric field. Argon ions impinge on silicon oxide target 6, and the silicon oxide is sputtered. The atoms of part of the sputtered silicon and the atoms of oxygen are reacted with the atoms of the phosphorus activated in the plasma, and a mixture of the silicon oxide and phosphorus oxide is formed. The mixed film of the silicon oxide and the phosphorus oxide, i.e., a phosphorus glass film, is formed on a substrate 7. Therefore, the concentration of the phosphorus is accurately controlled by the flow rate of the phosphine.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for forming an insulating film containing impurities.

[Prior art]

FIG. 1 shows an apparatus for performing a method of forming a silicon oxide film by sputtering, which is one of the conventional methods of forming an insulating film. In the figure, (1) is a vacuum container, (2) is a vacuum exhaust port, (3) is a gas inlet, (4) is a high frequency power supply, and (5)
(6) is a silicon oxide target, (7) is a substrate on which a dielectric film is formed by sputtering, and (8) is an argon plasma formed by high frequency discharge.

In the above configuration, after the vacuum container 11) is evacuated, argon gas is introduced, and a radio frequency electric field (RF) is applied to the electrode of the silicon oxide target (6) to generate argon plasma (8). Argon ions in the plasma,
The electric field generated in a self-biased manner causes the silicon oxide target (6) to collide with the silicon oxide target (6) to form silicon oxide (SiO2).
is sputtered and deposited on the substrate (7) to form a silicon oxide film. At this time, the substrate bias power supply (5)
By applying negative/bias pressure to the substrate side, the quality of the silicon oxide film deposited on the substrate is improved, and a flat film with good step coverage at the stepped portion is deposited. can do.

However, in the conventional method for forming such an insulating film, in order to introduce impurities into the silicon oxide film, it is necessary to mix the impurity into the silicon oxide target (6) in advance, so the formed oxide It has been impossible to optimally control the amount of impurities in the silicon film or to freely vary the amount of impurities in the depth direction.

Furthermore, as a method for depositing a silicon oxide film containing impurities, there is a CVD method in which a mixed gas of silane (SiH4) and a gas containing impurities is reacted in a thermal furnace.
The CVD method requires high-temperature heat treatment of about 450°C or higher, so when depositing on an aluminum wiring film,
There are disadvantages such as the formation of protrusions called hillocks on the aluminum wiring film and the formation of needle-like crystals called whiskers.

In addition, the film quality itself was low in density and not dense, and the step coverage at stepped portions was also poor.

[Summary of the invention]

This invention was made in view of the above points, and a gas containing impurities such as phosphorus is introduced during high-frequency sputtering of an insulating target such as silicon oxide, and is combined with the insulating target to form a phosphorous glass film. In this method, an insulating film such as the following is formed, and the impurity concentration in the insulating film is controlled by continuously changing the amount of gas containing impurities introduced.

[Embodiments of the invention]

Next, one embodiment of the present invention will be described. The sputtering apparatus is the same as that shown in FIG. 1, but a gas containing phosphorus, such as phosphine (1'H3), in addition to argon (Ar) is introduced through the gas inlet (3). As schematically shown in Figure 2, argon (Ar) introduced into a vacuum generates argon plasma (8) in a high-frequency electric field, and argon ions (
Ar+) bombards the silicon oxide target (6), causing the silicon oxide to splatter. Some of the sputtered silicon (Si) and oxygen (0) atoms are
It reacts with activated phosphorus atoms in the plasma to form a mixture of silicon oxide (SiOz) and phosphorus oxide (P2O3). And on the substrate (7) is silicon oxide (SiO
As shown in Figure 3, the flow rate of phosphine (PH3) introduced into the plasma (flow rate ratio to argon) can be controlled with high accuracy. Furthermore, by changing the flow rate of phosphine (PH3) during the formation of phosphorus glass, it is possible to freely change the phosphorus concentration in the phosphorus glass film in the depth direction. Further, since the phosphor glass film formed in this embodiment is subjected to high frequency sputtering using a substrate bias, the step coverage of the stepped portion is significantly improved. That is, as shown in Fig. 4, compared to the glass film (10) formed by the conventional CVD method (Fig. 4 (a)
), the phosphor glass film (11 has good step coverage (FIG. 4(b))) formed by the step-cutting method of this embodiment. In FIG. 4, (9) is an aluminum wire. In addition, the etching rate with 6:1 buffer hydrofluoric acid, which indicates the density of the film itself, becomes extremely small.
As shown in FIG. 5, the etching characteristics of the phosphor glass film portion by the CVD method (A) and the etching characteristics of the phosphor glass film portion by the sputtering method (B) are significantly different.

Also, unlike the CVD method, it does not require high-temperature heat treatment1.
Therefore, inconveniences such as the formation of protrusions called hillocks or needle-shaped crystals called whiskers on the aluminum wire do not occur.

Furthermore, according to the method described above, a phosphorus glass film that has a gettering effect on harmful impurities such as sodium can be formed at low temperatures, and it is possible to use the usual sno-glass film that does not introduce conventional 7-osphine (PH3). Therefore, the lower layer of the insulating film in contact with the aluminum wire can be made of less corrosive silicon oxide (SiOz), and the upper layer can be made of highly concentrated phosphorus glass that has a strong gettering effect, providing ideal surface protection. It is possible to form a film.

In the above embodiments, the method of forming a phosphorus glass film was explained as an example, but the present invention can be applied to a method of forming a silicon oxide film containing impurities other than phosphorus, or an insulating film containing any impurity.

〔Effect of the invention〕

As described above, according to the present invention, an insulating film containing impurities can be easily formed on a substrate by high-frequency sputtering of an insulating target in a gas containing impurities, and the impurity concentration can be controlled with high precision, so an insulating film can be formed depending on the purpose.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a high-frequency sputtering apparatus used for conventional insulating film sputtering, Figure 2 is a schematic diagram showing the principle of the present invention, and Figure 3 is a diagram showing the ratio of phosphine and argon introduced into the plasma. Figure 4 is a diagram showing the relationship between the phosphorus concentration in the glass film. Figure 4 is a cross-sectional view comparing the step coverage of the phosphor glass film formed by the CVD method and the phosphor glass film formed by the present invention. Figure 5 is a diagram showing the relationship between the phosphorus concentration in the glass film. FIG. 3 is a diagram comparing the etching rates of a phosphorus glass film formed by a CVD method and a phosphorus glass film formed by a sputtering method. (3)... Gas inlet, (4)... High frequency power supply, (5)... Power supply for substrate bias, (6)...
Silicon oxide target, (7)...substrate, (8)
...Argon plasma, (9) ...aluminum! ,
(10)... -CVD phosphorus glass, (1,11...
・Sputtering glass. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Shin Kuzuno - Figure 1 Figure 2? Fig. 3 PH1/Ar>L+g+e/e) Fig. 4 (a) (b) Relationship with the case of the person making the amendment Patent Applicant Address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Corporation Representative Hitoshi Katayama 4, Agent Address Marunouchi, Chiyoda-ku, Tokyo 2-chome 2-3''
"I'm going to change it," he corrected.

Claims (3)

[Claims] (1) In an insulating film formation method in which an insulating target is sputtered in high-frequency plasma to deposit an insulating film on a substrate, by introducing a gas containing impurities into the high-frequency plasma, elements in the insulating material are 4? Combining impurities and depositing an insulating film containing impurities on a substrate. Characteristic insulating film formation method. (2) By using silicon oxide 7 (r-) as an insulator and using 7-Osfin as a gas containing impurities.
The method of forming an insulating film according to claim 1, characterized in that a glass film is deposited. (3) The phosphorus concentration in the phosphorus film is continuously changed in the depth direction by continuously changing the amount of phosphine introduced during the formation of the insulating film. Insulating film formation method.