JPS6217854B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a thin film by sputtering for electronic devices such as semiconductor devices and liquid crystal devices.

Among electronic devices, for example, in the manufacture of semiconductor devices, after forming a wiring layer 5 of aluminum (Al) or the like as shown in FIG. As the protective film 6, a phosphorous-containing SiO ₂ film (hereinafter referred to as a PSG film) is formed by vapor phase growth, or a sputtered silica film is formed. In addition, in a liquid crystal display panel as shown in FIG. 2, a silicon oxide film (SiO ₂ film) is formed directly on the substrate glass 7 in order to improve the reliability of the display panel.
For example, a SiO ₂ film is formed on a conductive film (for example, an indium oxide or tin oxide film).

Since the PSG film formed by vapor phase growth as a surface protective film does not have very high mechanical strength, cracks may occur in the film when sealing with resin the semiconductor substrate 1 on which the surface protective film 6 and below are formed. Many defects occur. Furthermore, the number of defects increases due to temperature changes even after sealing with a polymer resin. If a defect exists in the surface protection film 6, the wiring layer 5 made of Al or the like will corrode or the device characteristics will change due to moisture that has permeated through the polymer resin or impurities in the polymer resin. On the other hand, since the sputtered SiO ₂ film has excellent mechanical strength, cracks do not occur in the film unlike the PSG film. However, sodium (Na) adhering to the walls of the sputtering equipment during film formation
Since impurities such as these easily enter the film, the device characteristics become unstable. The only way to prevent this is to regularly clean the sputtering equipment.

On the other hand, in liquid crystal display panels as well, it is necessary to prevent impurities (particularly Na) in the panel constituent materials that cause deterioration and short circuits between electrodes. However, soda glass is often used as the substrate glass due to its smooth surface, and in this case, a large amount of
Since it contains Na, simply forming a SiO ₂ film cannot completely prevent Na from being mixed in from the substrate glass.

An object of the present invention is to improve the reliability of electronic devices by developing a new film forming technique for thin films used as surface protection films and interlayer insulating films for electronic devices such as semiconductor devices and liquid crystal devices.

In the present invention, when forming a thin film on an electronic device using sputtering, a solid plate made by mixing and firing a fine powder of the same material as the main constituent material of the thin film and a fine powder of phosphorus pentoxide is used as a target. By mixing phosphorus into the film during the film formation process, the film has a dense film quality unique to sputtering thin films, and has the ability to capture mobile ions caused by contamination during film formation. It is characterized by having both.

For example, when forming a sputtering SiO ₂ film, the present inventors used a solid plate prepared by mixing and firing a fine powder of silicon oxide (SiO ₂ ) and a fine powder of phosphorus pentoxide (P ₂ O ₅ ) as a target. In this case, the formed film has phosphorus added thereto, and it has been found that this film has the density characteristic of sputtering thin films and also has a getter effect due to the phosphorus in the film.

Figure 3 shows a case in which a solid plate obtained by mixing and firing the above-mentioned SiO ₂ fine powder and P ₂ O ₅ fine powder was used as a target (experimental data (b)), and a case in which fused silica was used (experimental data (b)). Regarding data (a)),
The results of fabricating a MOS structure and measuring the amount of change (ΔV _FB ) in the flat band voltage V _FB in the MOS structure due to BT treatment (300° C., 10 ⁶ V/cm environmental conditions) are shown. From the same figure, SiO ₂ is used as a target.
It can be seen that the instability caused by the BT treatment can be resolved when a solid plate prepared by mixing and firing a fine powder of P ₂ O ₅ and a fine powder of P 2 O 5 is used. It was found that phosphorus was mixed into the film formed by sputtering using the above-mentioned target, and that this phosphorus captured mobile ions (Na ⁺ ) caused by contamination during film formation in the film. confirmed.

In addition, fine powder of SiO ₂ and P ₂ O ₅ were used as targets.
The solid plate made by mixing and firing the fine powder of
This is because P ₂ O ₅ fine powder deliquesces at room temperature and is unstable because it is easily elevated at relatively low temperatures, so a mixed and fired solid plate is suitable for incorporating P ₂ O ₅ as a target in a stable state. be.

In addition, after the film is formed using the above-mentioned target, heat treatment in an atmosphere of nitrogen N ₂ and hydrogen H ₂ can not only recover damage caused by sputtering but also turn the film into honey. confirmed.

Further, other application examples of the method of the present invention will be shown. A wiring 5 made of Al or the like is formed on a semiconductor substrate ₁ on which an integrated circuit having the structure shown in FIG. A solid plate prepared by mixing and firing fine powders of O ₅ and SiO ₂ was set in an ordinary high-frequency sputtering device as a target, and the sputtering conditions were as follows: a gap between the sample and the target of 50 mm, an argon atmosphere pressure of 0.7 Pa, and a high-frequency power of 500 W. As the surface protection film 6, a sputtered SiO ₂ film containing phosphorus was formed to a thickness of 1 μm. In FIG. 1, 2 is a P-type diffusion layer formed within the N-type semiconductor substrate 1, and 3 is an N-type diffusion layer formed within the P-type diffusion layer 2. Reference numeral 4 denotes a thermal oxide film formed on the semiconductor substrate 1, which is selectively removed by etching to form a window for leading out wiring.

After that, the semiconductor substrate 1 was heat-treated for 10 minutes in a nitrogen and hydrogen atmosphere at 500°C, immersed in saline solution (50%, 100°C) for 10 minutes, dried naturally, and heated to 500°C.
After heat treatment in an air atmosphere at a temperature of 4 hours, changes in the base-collector current I _CBO of the transistor in the semiconductor substrate 1 were examined. The results are shown in experimental data b in FIG. For comparison, a wiring 5 made of Al or the like was formed and heat-treated according to the conventional technique, and then a sputtered SiO ₂ film was formed by high-frequency sputtering using fused silica as a target, and then changes in I _CBO were investigated using the same process as described above. The results are shown in data (a) in FIG.

From Figure 4, it can be seen that the sputtering SiO ₂ film using a solid plate made by mixing and firing fine powders of P ₂ O ₅ and SiO ₂ as a target is more effective than the case where fused silica is used as a target due to the forced contamination of saline water. It can be seen that characteristic fluctuations can be greatly reduced. Furthermore, when a PSG film was formed by chemical vapor deposition, it was confirmed that cracks occurred after the film was formed when the film thickness was about 1 μm.

Further, an example of application of the method of the present invention to a liquid crystal display panel is shown in FIG. On the glass substrate 7, P ₂ O ₅ and
Sputtering SiO ₂ containing phosphorus in the film using a solid plate prepared by mixing and firing SiO _{2 fine} powder as a target.
A film 8 is formed, and then a conductive electrode 9 is formed by spraying indium oxide or the like, vapor deposition or sputtering. After the substrate surface is aligned in the layer 10, spacers 11 are made of mylar film, Teflon film, etc. to keep the thickness of the liquid crystal layer 12 constant, and after the liquid crystal is sealed in the panel, metal electrodes are formed. do. Note that after forming the sputtered SiO ₂ film 8 containing phosphorus in the film and the conductive electrode 9, the sputtered SiO ₂ film 8
may be formed.

In this way, sputtering SiO ₂ films using a solid plate prepared by mixing and firing fine powders of SiO ₂ and P ₂ O ₅ as a target does not allow phosphorus to be mixed into the film during the film formation process. As shown in Figure 3, it has the effect of capturing mobile ions and the like caused by contamination during film formation. Furthermore, it has a dense film quality unique to sputtering thin films, and as shown in FIG. 4, it is possible to improve the reliability of semiconductor devices.

As described above, in the present invention, a solid plate is created by mixing and firing a fine powder of the same material as the main constituent material of the thin film and a fine powder of phosphorus pentoxide, and a thin film is created by sputtering using this as a target. In this case, since phosphorus is mixed into the film in parallel with the process of film formation, the phosphorus concentration can be controlled, and it can also have the effect of capturing mobile ions, etc. caused by contamination during film formation. . Further, since this film has a density peculiar to a sputtering thin film, the thin film formed using the target has the effect of being of high quality as a thin film of an electronic device and improving the reliability of the electronic device.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part of a semiconductor device for explaining an example of application of the method of the present invention, FIG. 2 is a cross-sectional view of a main part of a liquid crystal display panel for explaining an example of application of a method of the present invention, and FIG. and FIG. 4 are diagrams comparing experimental results obtained by the method of the present invention and the conventional method, respectively. 1... Semiconductor substrate, 5... Aluminum wiring,
6... Sputtered SiO ₂ film containing phosphorus in the film,
7... Glass substrate, 8... Sputtered SiO ₂ film containing phosphorus in the film, 12... Liquid crystal layer.

Claims (1)

[Claims] 1 A solid plate is created by mixing and firing a fine powder of the same material as the main constituent material of the thin film and a fine powder of phosphorus pentoxide, and using this as a target, a thin film is created on a substrate by sputtering method, and the film is formed. A method for forming a thin film characterized by mixing phosphorus into the film in parallel with the process.