JP2732663B2 - Copper thin film patterning method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a device using a semiconductor or a thin film, for example, a thin film magnetic head, a thin film transformer, etc.
TECHNICAL FIELD The present invention relates to a copper thin film patterning method for performing patterning with high accuracy when a pattern using the same is included.

(Prior art) Conventionally, when a Cu film is used for a part of a thin film device and a desired Cu pattern is obtained by patterning the Cu film,
The patterning methods include (1) electroplating and (2)
Lift-off method, (3) ion etching method by reaction and the like. However, (1) is that it is necessary to remove a conductor thin film formed in advance in order to impart conductivity.
(2) The pattern collapse occurs, and (3) the etching selectivity between Cu and the mask is small (about 20).
There is a drawback that a fine pattern of a thick film having a thickness of 3 to 10 μm cannot be patterned with high accuracy.

(Problems to be Solved by the Invention) An object of the present invention is to provide a copper thin film patterning method for forming a Cu pattern in a thin film device with high accuracy and efficiency.

(Means for Solving the Problems) In the copper thin film patterning method of the present invention, when forming a Cu pattern by ion etching using a metal mask,
Ta, Nb or Zr is used as a mask material, and when patterning Cu using this mask, a mixed gas of nitrogen and hydrogen or a mixed gas of nitrogen and ammonia is used as an operating gas.

Conventionally, to form a Cu pattern of a thin film device, as described above, using an electroplating method, using a lift method,
Either reactive ion etching using an etching selectivity with Cu using a metal mask, or either method has been adopted. As a working gas for reactive ion etching, it is possible to use a halogen-based gas in addition to a mixed gas of Ar and oxygen. Further, in the case of a Cu pattern having a high aspect ratio, it has been difficult to perform high-precision patterning by the conventional method.

(Example) FIG. 1 is a diagram showing the relationship between the etching rate of Cu and Ta and the ion acceleration voltage according to the present invention. The etching was performed by a Kauffman-type ion beam etching apparatus. First
The figure shows the ion acceleration voltage dependence of the etching rate when a mixed gas of nitrogen: ammonia (2: 1) is used as the etching gas and the operating gas pressure is 1 × 10 ⁻⁴ Torr. From this figure, it was found that the etching rate of Cu tends to increase as the accelerating voltage increases, whereas Ta is hardly etched. In addition, ion acceleration voltage is 300V
In this case, the etching rate ratio between Cu and Ta can be 50 or more, so if Ta is used as a mask, the mask can be made thinner.
It has been found that patterning is possible. This is because, by using a mixed gas of nitrogen and ammonia, Cu reacts with the mixed gas, whereas Ta has excellent corrosion resistance. In this embodiment, the substrate temperature was set at room temperature, but it is clear that etching at 200 to 300 ° C. in order to increase the reactivity further improves the etching characteristics.

FIGS. 2 (a) to 2 (d) are views showing a step of patterning a Cu coil for a thin film magnetic head by reactive ion beam etching according to the present invention. In FIG. 2, 1 is a coil-shaped photoresist mask, 2 is a Ta film, 3 is a Cu film,
Is an Altic substrate used for the slider. First thickness 5
After forming a Cu film having a thickness of 0.1 μm and a Ta film having a thickness of 0.1 μm or less by ion beam sputtering, a photoresist AZ135 having a thickness of 0.5 μm is formed.
Spin coat 0 (product name) and cure. afterwards,
Exposure and development were performed using a coil-shaped mask 1 (FIG. 2A). Then, using this photoresist pattern as a mask, Ar is used as an operating gas and ion etching
The film is patterned into a coil shape (FIG. 2 (b)).
Using this Ta film as a mask 22 (FIG. 2 (c)), the Cu film is subjected to reactive ion beam etching using a mixed gas of nitrogen and ammonia as an etching gas to obtain a desired Cu.
A coil pattern 33 was obtained (FIG. 2 (d)). According to this method, a sharply-cut coil pattern having an angle of 85 ° or more with respect to the substrate was obtained without the re-adhesion of the etching product to the Cu side wall surface, which was conventionally observed.

It was also found that high-precision patterning can be performed even with a fine pattern having a high aspect ratio of 1 μm, a coil width of 1 μm, and a coil height of 5 μm. In the above example, the Ta film was used as a mask to form the Cu pattern.However, when a mixed gas of nitrogen and ammonia gas was used as the etching gas, a mask material capable of obtaining a selectivity of 50 or more with respect to Cu was obtained. , Nb, and Zr, the same effect can be obtained when these are used as a mask material, and even when a mixed gas of nitrogen and hydrogen is used as an etching gas, the etching rate is reduced, but the etching is The selectivity was found to be over 50.

(Effects of the Invention) As described above, according to the copper thin film patterning method of the present invention, when patterning a Cu film using a mixed gas of nitrogen and hydrogen or nitrogen and ammonia gas as an operating gas, 50 for Cu film such as Ta, Nb or Zr
If a material that can obtain the above high etching selectivity is used, a sharp pattern side angle can be obtained, and thus a Cu pattern with a high aspect ratio and high accuracy can be easily obtained. If this technique is used, a low-resistance Cu film can be used for thin-film magnetic heads, thin-film transformers, and other wirings in semiconductor devices, and the field of application of thin-film devices is widened.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the etching rate of Cu and Ta and the ion acceleration voltage according to the present invention, and FIGS. 2 (a) to (d) are Cu coils for a thin film magnetic head by reactive ion beam etching according to the present invention. FIG. 4 is a view showing a patterning step of FIG. 1 ... Coil-shaped photoresist mask 2 ... Ta film 3 ... Cu film 4 ... Substrate 22 ... Ta mask 33 ... Cu coil pattern

Claims (1)

(57) [Claims] When patterning a Cu film in a thin film device including a Cu coil, a wiring, and the like manufactured using a photolithography technique and a dry etching technique,
A copper thin film patterning method characterized in that a thin film of Ta, Nb or Zr is used as a mask material and processing is performed by ion beam etching using a mixed gas of nitrogen and hydrogen or a mixed gas of nitrogen and ammonia as an operating gas. .