JPS63202890A - Transparent conductive thin film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a transparent conductive thin film (hereinafter abbreviated as ITO thin film) made of indium and tin mixed crystal oxide, and relates to a transparent conductive thin film made of indium and tin mixed crystal oxide (hereinafter abbreviated as ITO thin film). It is widely used as an electrode for displays, plasma displays, electrocomic displays, etc.

Conventional technology ITO thin films are typically made from an alloy of indium and tin (approximately 1% tin
It is manufactured by direct current magnetron active sputtering method, targeting 0%).

As a result, the electrical resistivity of 10 Ω/1 unit and the optical wavelength of 50
ITO with a light transmittance of 90% or more near 0 nm
A thin film is obtained. When an ITOfi film having such characteristics is incorporated into a device, microfabrication is performed by etching using photolithography technology. At this time, for example, the ITO pattern edge along the edge of a straight resist pattern is not a smooth straight line, but often becomes a jagged edge with many irregularities.

Problems to be Solved by the Invention The present invention attempts to eliminate the disorder of pattern edges (uneven etching) of ITO after etching that often occurs when ITO is microfabricated using photolithography technology.

Means for solving the problem Only the (222) or (400) plane parallel to the substrate surface is 6
The crystals are oriented at a ratio of 0 or more, and the particle size is 25
A transparent conductive thin film is made of an indium and tin mixed crystal oxide characterized by a range of 0 to 400%.

Effect■ Disturbance of pattern edge after etching of TO thin film is
As a result of detailed examination, it was found that the problem was largely due to the microstructure of the thin film. That is, it depends on the crystallographic orientation and particle size of the particles in the thin film. The present invention solves the problem of ITO-<turn edge by specifying both of these factors.

By specifying the particle orientation and particle size of the ITO thin film, it is possible to achieve an appropriate etching speed for the thin film and to make the etching speed uniform depending on the location, making it possible to form an ITO pattern edge with an even and uniform shape. Ta.

EXAMPLE First, the particle orientation and particle size, which are the basis of the present invention, will be explained for three types of IT◯ thin film samples. Indium containing 10% by weight of tin in all three samples,
Using tin and alloy targets, substrate temperature (200°C)
Although the substrate-to-target separation distance (607 rrm) was the same, the conditions of gas pressure, oxygen mixing ratio, and power were changed for each sample, and the samples were prepared by direct current magnetron activated sputtering. The results for each film thickness are shown for different samples.

The half-value width was measured from the (222) peak of these X-ray diffraction patterns, and the particle size was first determined.

The half-width β is the straight line β′ obtained by the modified Lorentz approximation of the (222) peak, and the half-width 0 of the silicon powder measured at the same time.
．． It was calculated using equation (1) (Warren's correction equation) with a correction of 1°.

β(0)=,/”'core (1) Particle size d was calculated from equation (2) (Scherer's equation) using β in equation (1).

0.9　λ d(A)=　□　　・・・・・・(2) βcosθ λ: X-ray wavelength 1.64 people θ: (222) % of peak diffraction angle 2θ The calculation results are shown in Table 1.

The samples in Table 1 correspond to the lines in the X-ray diffraction pattern in the figure. Next, from the peak intensity of the diffraction pattern in Figure 4 (222
), (400) and (440) plane orientation degrees were determined.

In most of the ITO thin films, these planes are oriented either singly or in a mixed state parallel to the substrate plane. Especially (2
22) and (400) plane orientation are strong. The degree of orientation Q(l) was calculated using the Lotgering equation shown in equation (3).

Here, ΣWork'' and ΣWork0 mean the surface of interest, and Σ means adding a surface equivalent to that surface.

hkJ is a surface index.

■■ Lotus 77' /L/, ■• is the X-ray reflection intensity of the powder (random state). Reflection intensity in random state A
Obtained from STM card.

() I = Σ1”k7ΣWork ・・・・・・(4
)bkl, Ql becomes ΣI°/Σ”b
The degree of orientation is determined by whether kl υ is large. If it is large, the degree of orientation is positive and the plane of interest is oriented, but if it is small, it is negative and it is not oriented rather than in a random state. Table 2 shows the calculation results of the degree of orientation.

Table 2 ΣI' = 270 kl Similarly, the sample plane corresponds to the black part of the X-ray diffraction turn in the figure.The blank column in the table is where Q is smaller than ΣI0/ΣWork0hM.

Finally, we examined the surface flatness of the thin film after deposition and the edge properties of the etched pattern using a scanning electron microscope.
SEM) and compared with the results of the microstructure described above.

For etching, after forming the resist pattern, H process + H3P
This was done using O2 etching solution.

Table 3 summarizes the flatness of the thin film surface and the edge properties of the etching pattern for the three types of samples, as well as the grain size and degree of orientation determined by the method described above.

In Table 3, ◯ indicates excellent results, × indicates poor performance, and ∆ indicates intermediate values, and ◯ indicates the practical level desired by the present invention.

In the table, Sample Flat 1 has a broad (222) peak, and as a result, the particle size is small. That is, as can be seen from the X-ray pattern, the overall reflection intensity is weak and the crystallinity is poor. The degree of orientation is also relatively large for the (222) plane, but for the (440) plane.
The planes are also oriented parallel to the substrate. This ITO thin film had many small depressions on the surface, and had difficulty in surface flatness. Because the etching speed was too fast, the pattern edges after etching tended to be over-etched, and some edge disturbances were also observed.

The A2 sample has good crystallinity, but the (222) plane and (4
00) planes are moderately oriented in similar proportions on the substrate surface. Although such a thin film had good surface flatness, the edges of the pattern after etching had irregular etching speeds depending on the location, resulting in uneven and disordered edges.

Sample &3 has good crystallinity and relatively large particles. Further, since only the (222) plane was arranged parallel to the substrate surface and oriented on only one plane, etching was uniformly performed without unevenness in etching speed depending on the location, resulting in clean and straight pattern edges.

Although the above three types of IT○ thin film samples have been described in detail, other ITO thin films prepared under different film forming conditions were similarly measured and statistically investigated, and the following results were obtained.

Of course, the resistivity and light transmittance are within the usable range described above, but the orientation of only the − plane eliminates unevenness in etching speed depending on location and prevents uneven pattern edges. It turned out to be essential. It was also perfect when the degree of orientation was 60 inches or more.

At this time, only the (222) plane may be oriented, or the (4OO)
It may be oriented only in planes. Generally, when the formation rate is high (
400) Increased orientation. However, it is difficult to create an alignment film with only - planes when the particles become large, and the size must be kept below 400 Å.

In other words, when the thickness is higher than 400, the orientation of two or more planes parallel to the substrate surface is strong. Even if the degree of orientation of the grain plane is considerably high, the etching speed is high, over-etching is likely to occur, and control is difficult. In addition, local pattern edge disturbances are observed, and the surface flatness is generally poor.

Combining the above results, the microstructure (2
22) Or only the (400) plane is 5o parallel to the substrate surface.
% or more, and the grain size is 260 or more and 400
It has become clear that A or lower is optimal. The IT◯ thin film having this specified microstructure has excellent microprocessability.

Effects of the Invention Ir having the microstructure specified in the present invention
When using an O2 film, it has excellent patterning properties when performing etching and microfabrication using photolithography technology.
It is possible to obtain an ITO pattern with a clean, undisturbed shape that is faithful to the resist pattern and has a high yield.

Claims (1)

[Scope of Claims] Only (222) or (400) planes are oriented parallel to the substrate surface at a ratio of 50% or more, and the grain size is 2.
A transparent conductive thin film made of an indium and tin mixed crystal drinkide having a thickness in the range of 50 to 400 Å.