JPS6227537B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method suitable for manufacturing semiconductor devices that require highly accurate fine pattern electrodes.

Conventionally, aluminum (Al) has been widely used as an electrode/wiring material for semiconductor devices. To form the electrodes and wiring, an aluminum film formed by vapor deposition, for example, on the semiconductor substrate is photo-photographed.
Patterning is typically done using photolithography techniques that utilize resist masks and chemical etching.

In this case, the etching solution is phosphoric acid alone,
Alternatively, a mixture containing a small amount of nitric acid or acetic acid and heated to a temperature of 50 [°C] or higher is used.

When a phosphoric acid solution alone is used as an etching solution, hydrogen (H ₂ ) generated by corrosion of Al becomes bubbles and stays at the pattern edges of the photoresist film, and will separate unless it becomes enlarged to a certain extent. Therefore, the processed pattern tends to be non-uniform, making precise patterning difficult. For this reason, conventional methods have been used such as applying ultrasonic vibration to force stirring. Therefore, the processing capacity at one time is one wafer unit, and there is a significant lack of workability.

When a mixed acid is used, the gas generated due to the presence of nitric acid is mainly nitrogen oxide (NO _x ), so that the generated gas does not stay at the pattern edges. However, since it is still a hot bath, the drawback remains that the corrosion rate is strongly dependent on the temperature distribution. Therefore, this problem is solved by circulating or stirring the etching solution, but a similar dependence also exists in the direction of flow of the etching solution, so there is no difference in etching time within a wafer or between wafers. resulting in batch processing,
For example, when processing 20 wafers/batch, considerable skill is required to judge the end point.
Such non-uniform corrosion rate inevitably leads to undercuts in aluminum electrodes and wiring.
So-called wire thinning occurs, leading to increased electrical resistance and disconnection accidents.

The present invention uses an etching solution at room temperature, eliminates the influence of temperature distribution and the problems of stirring associated with it, and
This makes it possible to manufacture a semiconductor device having a highly accurate fine pattern electrode, and this will be explained in detail below.

The basic principle of the present invention is to pattern an aluminum film using a solution containing at least an aqueous choline solution (HOCH ₂ CH ₂ N (CH ₃ ) ₃ OH) as a main component as an etching solution.

The composition of the etching solution used in the present invention is exemplified as follows.

(1) Choline aqueous solution (2) Choline aqueous solution (10 [ml]) + Potassium hydroxide (KOH1 [g]) (3) Choline aqueous solution (10 [ml]) + Potassium hydroxide (1 [g]) + Isopropanol ( (CH ₃ ) ₂ CHOH2 [ml]) The concentration of the choline aqueous solution in (1) above is 5 to 8.
[%], which is 1.0 [%] in (2) and (3) above.

For example, an Al film with a thickness of about 4 [μm] is formed by vapor deposition on a silicon semiconductor wafer of 7.5 [cm]φ (3 [inches]φ), and a minimum line width of 10 [μm] is formed on the Al film using the vapor deposition method.
When a photoresist film with a geometric pattern of 1 was baked and the Al film was etched using an etching solution having the composition shown in (3) above, the results shown in FIG. 1 were obtained.

As is clear from the figure, because the linearity of the etching rate is extremely good, the etching time difference within a wafer or between wafers is extremely small, and a thickness of 4 [μm] was completed in a batch process of 20 wafers. The difference was within 1 minute.

The cross-sectional shape of the patterned aluminum film has an inclination of 45° or more as shown in Figure 2, and the photoresist film P _R and the aluminum film A _L
W/d at the interface with was around 0.5. Therefore, when an insulating film such as a phosphosilicate glass film is formed on the aluminum electrode/wiring, there will be no step breakage, which is particularly effective in multilayer wiring.

Next, various data obtained when the test was carried out on samples similar to those described above will be explained.

Figure 3 shows that the composition of the etching solution is ``choline aqueous solution (1 [%] aqueous solution 10 [ml]): H ₂ O (10
[ml]): (CH ₃ ) ₂ CHOH (4 [ml]): KOH (2
[g])', time [minutes] versus corrosion amount [μ
m], and the measurement was performed using a surface roughness meter.

Figure 4 shows an etching solution whose composition is the same as that shown in Figure 3, with KOH in n [g].
This is data regarding W/d and corrosion rate when changing.

FIG. 5 shows data regarding W/d and corrosion rate when the type of alcohol used as a surfactant was changed.

FIG. 6 shows data regarding W/d and corrosion rate when the alcohol is n [ml] and the value n is changed.

As can be seen from the above explanation, according to the present invention, an aluminum film is patterned using an etching solution whose main component is an aqueous solution of choline plus potassium hydroxide, and the etching is carried out at room temperature. Therefore, equipment such as heating and stirring is not required. Furthermore, since the etching rate is uniform, it is easy to determine the end point when batch processing is performed. Furthermore, the processed shape is good,
In particular, since it is easy to taper around 60 degrees, it is convenient for multilayer wiring.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between time and corrosion amount in one embodiment of the present invention, Fig. 2 is a sectional side view of the main part explaining the etching shape, and Figs. 3 to 6 are the effects of the present invention. FIG. In the figure, A _L is an aluminum film and P _R is a photoresist film.

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device, comprising the step of patterning an aluminum film using an etching liquid whose main component is a choline aqueous solution plus potassium hydroxide.