JPS5846850B2 - Size selection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a size selection method, and more particularly to a method for selecting finished dimensions of a pattern formed by photolithography.

The following will explain the manufacture of a semiconductor device, particularly a Schottky barrier diode, which is a junction type device, as an example.

A Schottky barrier diode has a structure in which a semiconductor crystal and a metal electrode are in contact with each other, and FIG. 1 is a cross-sectional view showing an example thereof.

In the figure, 1 is a semiconductor crystal, 2 is a circular metal electrode with a diameter formed on the entire surface of the crystal, 3 is an insulating surface protection film,
4 is an ohmic contact to the other main surface of the semiconductor crystal;
5 is an interface between the semiconductor crystal 1 and the metal electrode 2, and a Schottky barrier is formed at this interface 5.

Schottky... The most important electrical property of the barrier is the barrier capacitance (Cjo) at zero bias, and its value is given by the following equation.

and k, q is the electron charge, ε8 is the permittivity of the semiconductor crystal 1, approximately is the carrier concentration of the semiconductor crystal 1, vbi is the built-in voltage, k is Boltzmann's constant, T is the absolute temperature, and D is the metal electrode 2. It is the diameter.

In recent years, with the improvement of semiconductor crystal growth technology, the carrier concentration N in the semiconductor substrate on which many such elements are formed has increased.

Since the non-uniformity of is extremely small, the barrier capacitance C
It can be said that the non-uniformity of jo depends exclusively on the non-uniformity of the diameter of the metal electrode 2.

As an example, carrier concentration N.

When using a GaAs crystal substrate of ”-2×1.Oon, when D=10μ, Cjo=0.11 pF'D=12
When μ, C,=0.16 pF O , and a difference in diameter of only 2 μ changes the barrier capacitance Cjo by a factor of about 45.

Barrier capacity Cj. Since the O value must normally be within a deviation of 10 to 20%, the diameter of the metal electrode 2 must be kept within an accuracy of 1 μm or less.

However, the metal electrode 2 cannot be placed on the semiconductor substrate with such precision.
Forming it over the entire surface of the substrate is a photolithography process,
This is extremely difficult considering the non-uniformity in the etching process.

Therefore, in order to select devices with barrier capacitance Cjo within a predetermined range, it is necessary to measure the barrier capacitance Cjo of all the devices or measure the diameter of the metal electrode 2.

This was a very time-consuming task.

This invention has been made in view of the above-mentioned drawbacks of the conventional method, and involves forming a monitor pattern on each element at the same time as the metal electrode 2, and visual inspection of the formation of the monitor pattern on the completed element. The present invention aims to provide a method for classifying the diameter of the metal electrode 2 by analogy.

FIG. 2 is a pattern diagram showing an embodiment of the present invention, in which 6 is a main pattern for forming metal electrodes, and 7 is a monitor pattern.

In the photolithography process for manufacturing Schottky barrier diodes, chemical resistance, adhesion, etc. are usually taken into consideration.
WAYCOATIC RESIST made by Phil ip A-Hunt Chemica 1 in the U.S. O made by Tokyo Ohka Kogyo Co., Ltd.
Negative photoresist materials such as MR are used.

When microfabricating the insulating surface protection film 3 with a film thickness of 0.5 to 1.0μ using these resist materials,
It is well known experimental experience that the pattern of μ is the limit.

Therefore, as shown in Figure 2, for each chip forming each Schottky barrier diode, the straight shape is 2μ, 3μ,
A monitor pattern 7 consisting of a dot pattern row of 4 μm, etc. is formed at the same time as the main pattern 6 for the metal electrode 2, for example, having a diameter of 12 μm.

The finished dimensions of the main pattern 6 can be estimated with an accuracy of within 1 .mu. by simply visually observing the thus-formed monitor pattern 7 and seeing whether a dot pattern up to .mu. is formed.

This is because the size of one chip is 250 to 1000 μm square, and the processing accuracy of the pattern is considered to be uniform within this range.

With this method, it is possible to estimate the finished size of a main pattern having a diameter of 8μ or more with an accuracy of 1μ as described above.

That is, for example, if all of the four types of dot patterns in the monitor pattern 70 are formed, the main pattern 6 has a diameter of 12 μm as desired, and if 2 μm of dots in the monitor pattern 7 have disappeared, the main pattern 6 If you measure in advance the correspondence between the formation status of the monitor pattern 7 and the finished size of the main pattern, for example, the finished size of the monitor pattern 7 is 10μ, then the main pattern can be determined simply by visually observing the formation status of the monitor pattern 7. 6 size selections are possible.

When there is only one main pattern 6 in one step as shown in FIG. 2, it is possible to sort by the monitor pattern 7 as described above, but a large number of chips having the main pattern 6 with the desired finished dimensions are required. In some cases, a larger number of steps must be manufactured and selected from among them, which poses problems in terms of product yield.

FIG. 3 is a pattern diagram showing another embodiment in which the present invention is applied to the prior art developed with this point in mind.
4μ, 13μ, 12μ.

Eight types are provided, 10μ, 9μ, and 8μ, and it is expected that any one of these will have the desired finished size of 12μ.

Therefore, a monitor pattern 7 similar to that shown in the case of the actual case shown in FIG. 2 is provided for each chip, and the formation status of this monitor pattern 7 is visually observed. It is easy to see that it is possible to determine which dimension is closest and use it in practice.

The shape and dimensions of the monitor pattern, as well as whether it will be a dot-like pattern or a hole-like open pattern, will depend on the type and thickness of the insulating surface protective film, the photolithography conditions, and the post-pattern formation process. Although it should be determined appropriately depending on the etching conditions, etc., the minimum pattern needs to be approximately the microfabrication limit value of the workpiece.

The above explanation took the example of processing an insulating surface protection film for forming a metal electrode of a Schottky barrier diode, but it can also be applied to checking processing accuracy in the manufacturing process of other semiconductor devices or the processing process of metal films, etc. It is possible.

As described in detail above, in this invention, when processing and forming a main pattern with predetermined dimensional accuracy on a workpiece, the minimum dimension is the dimension corresponding to the degree limit value of the processed sugar of the workpiece, and the predetermined dimensional difference is sequentially adjusted. Since a plurality of monitor patterns are simultaneously processed and formed in close proximity to the main pattern forming area of the workpiece, just visually observing the formation status of these monitor patterns is enough to ensure sufficient accuracy. This eliminates complicated procedures such as numerous dimensional measurements.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the structure of a Schottky barrier diode used to explain this invention, FIG. 2 is a pattern diagram showing one embodiment of this invention, and FIG. 3 is another embodiment of this invention. FIG. In the figure, 1 is a semiconductor crystal, 2 is a metal electrode, 3 is an insulating surface protective film, 6 is a main pattern, and 7 is a monitor pattern. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. When processing and forming a main pattern with a predetermined dimensional accuracy on a workpiece, a plurality of monitor patterns having a predetermined dimensional difference are sequentially formed on the workpiece, with the minimum dimension corresponding to the processing accuracy limit value of the workpiece. A size selection method characterized in that the main pattern is processed and formed at the same time in close proximity to the main pattern forming station, and the formed size of the main pattern is determined and selected by visually observing the formed state of the monitor pattern.