JPS6230688B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum film forming method, and particularly to an aluminum film forming method suitable for microfabrication.

The present invention will be described below, taking as an example a case where the invention is suitable for forming internal wiring of a semiconductor integrated circuit.

In recent years, integrated circuits have become more densely integrated, and internal wiring has also become finer.

In order to meet these demands and advance the miniaturization of internal wiring, conventional methods have encountered various problems.

In other words, when an aluminum film is formed by vapor deposition or sputtering, and internal wiring is formed by photoetching using a photoresist as a mask, in order to form a fine pattern, the finer the crystals of the aluminum film, the better the patterning. This is advantageous in that it results in a sharper pattern, but when considering the wiring life, the larger the crystal is, the more advantageous it becomes from the viewpoint of electromigration.

As shown in FIG. 1, the crystallinity of this aluminum film depends to some extent on the substrate temperature in both the evaporation method and the sputtering method.

Further, as shown in FIG. 2, the crystallinity also changes due to heat treatment after the aluminum film is formed, and the crystals become larger. Based on these facts, a method was devised to keep the substrate temperature low during aluminum film formation, form a fine pattern with photoresist, and then enlarge the crystals by heat treatment. However, the above-mentioned proposed method has serious drawbacks and has not been put into practical use.

The drawback is that after forming a fine pattern with photoresist, if the heat treatment temperature for fetetching is higher than the substrate temperature during aluminum film formation, the crystallinity changes and the sharpness of the fine pattern is simply lost. This will cause pinholes and open defects.

This invention allows the substrate temperature during aluminum film formation to be lower than the photoresist processing temperature (normally 100℃ to 200℃).
By keeping the temperature 10 to 20℃ higher,
The purpose is to eliminate the above drawbacks and enable fine processing.

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

An aluminum film 3 is deposited by vapor deposition on the silicon wafer 1 on which the contact window has been formed (FIG. 3).

The conditions at this time were to maintain the surface temperature of the silicon wafer at 170°C during vapor deposition. The crystals of the resulting aluminum film had a diameter of 0.3 to 0.4μ.

Next, photoresist is applied and prebaked at 100℃ for 10 minutes to increase sensitivity, and then light is applied through a photomask to form the desired pattern 4 (Figure 4).The change in crystal diameter before and after prebaking is Nakatsuta.

Next, post-bake at 150℃ for etching.
After etching with an aluminum etching solution containing mainly phosphoric acid for 60 minutes, the photoresist was removed (Figure 5).

The crystal size did not change after post-baking.

Finally, alloying was carried out at 450° C. for 30 minutes to obtain electrical conduction with the contact, thereby forming the desired aluminum wiring 3B (FIG. 6).

The crystal diameter after alloying was 1.0 to 1.2μ, which was sufficient for the life of the wiring.

Conversely, if the silicon wafer temperature during vapor deposition is lower than the post-bake temperature, below 150°C, the aluminum film crystals will have a smaller diameter of 0.2 to 0.3μ, making the edges of the pattern sharper. In fact, post-baking at 150℃ causes crystals to form.
The size increases to 0.5 to 0.6μ, and as it grows, it not only deteriorates the adhesion with the photoresist pattern on top, but also causes the aluminum crystals that grow upward to push up the photoresist film and create pinholes. Therefore, it is not possible to obtain good aluminum wiring.

As described above, according to the method of the present invention, when forming a photoresist pattern for wiring, the wiring can be formed on an aluminum film with sufficiently fine crystals, and the crystals do not become large at the post-baking temperature for etching, so that the photoresist pattern can be formed. Etching can be performed without losing sharpness, and the final alloy can have a crystal diameter sufficient for the life of the wiring, making it possible to obtain fine aluminum wiring without losing product yield reliability. I can do it.

Although the explanation is omitted in the examples, it goes without saying that similar results can be obtained even if the sputtering method or dry etching is used.

[Brief explanation of the drawing]

FIGS. 1 and 2 are tables showing the substrate temperature during vapor deposition sputtering, the crystal size of the aluminum film, and the size after heat treatment. 3 to 6 are cross-sectional views of each process showing a method for forming aluminum wiring using an embodiment of the present invention. In the figures, 1...semiconductor substrate, 2
...Insulating film formed on a semiconductor substrate, 3, 3
A, 3B...Aluminum film, 4...Photoresist pattern.

Claims (1)

[Claims] 1. A step of forming an aluminum film on the surface of the substrate by a vapor deposition method or a sputtering method, and a step of applying a photoresist to the surface of the aluminum film and pre-baking it.
A step of forming a predetermined pattern on the photoresist and post-baking at a temperature higher than that during the pre-baking and lower than that during the formation of the aluminum film, and forming an aluminum film pattern using the photoresist as a mask, and then forming the aluminum film at a temperature higher than that during the formation of the aluminum film. A method for forming an aluminum film pattern, comprising a step of alloying at a high temperature.