JPS60113429A - Evaluation method of plasma etching uniformity - Google Patents

Abstract

PURPOSE:To evaluate etching uniformity in high sensitivity stressing uneven etching by providing a coated layer made of a material which is slower in etching speed on the upper surface of a substrate being etched and plasma-etching. CONSTITUTION:On the upper surface of a substrate 1 being etched, a coated layer 3 made of a material which is slower in etching speed than that of the substrate is formed and etched by plasma current 2. If the plasma current 2 is uneven, the etching on the coated layer 3a is also uneven. Since the etching speed of the layer 3a is slower than the etching speed of the substrate 1, etching unevenness is greatly stressed at the time when the remaining part of the layer 3a is completely removed by etching.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for evaluating the uniformity of etching effect in each case of plasma etching necessary for manufacturing semiconductor devices.

[Prior art]

Although plasma etching has become widely used in the manufacturing process of semiconductor devices, fine irregularities may be formed on the surface of the member to be etched due to the presence of uneven plasma flow.

The unevenness ranges from several A to several tens of digits, but as the degree of integration of semiconductor devices becomes higher and higher, etching unevenness of several tens of digits has reached a level that can cause a fatal defect in the characteristics of the device.

Therefore, prior to application to actual device manufacturing.

Evaluation of the uniformity of the etching effect of the plasma etching equipment used for this purpose is an essential technique.

FIG. 1 is a cross-sectional view showing a conventional evaluation method, in which the surface of a substrate to be etched (1) is etched by a plasma stream (2) under conditions similar to those used in actually manufacturing semiconductor devices. If the plasma flow (2) is uneven, minute irregularities Δ will appear on the surface of the substrate to be etched (1), as shown in Figure 2.
yields 1. These irregularities were evaluated using a highly sensitive surface roughness inspection device.

However, as mentioned above, this unevenness Δ is extremely small, ranging from several A to several A, so even when measured with a high-sensitivity surface roughness meter, a sufficiently accurate measurement value cannot be obtained, making the necessary evaluation difficult. there were.

[Overview of the invention]

The present invention has been made in view of the above points, and involves providing a coating layer made of a material whose etching speed is slower than that of the substrate on the upper surface of the substrate to be etched, and then performing plasma etching.

The present invention provides a method that can extremely emphasize etching unevenness and evaluate etching uniformity with high sensitivity.

[Embodiments of the invention]

FIG. 3 is a sectional view showing the state of each stage of an embodiment of the present invention. First, as shown in FIG. A coating layer (3) is formed, and a plasma flow (
When etching is performed in accordance with 2), if the plasma flow (2) is uneven, etching unevenness with a depth Δ2 occurs as shown as a coating layer (3a) in FIG. 3B. This coating 1
In the portion (3a) where etching progresses quickly, etching of the substrate to be etched (1') starts earlier than in the portion where etching progresses slowly.

Here, the rate at which the coating layer (3a) is etched is slower than the rate at which the substrate (1) to be etched is etched.

At the time when the remaining portion of the coating layer (3a) is completely etched away, the portion of the substrate to be etched (1) where etching begins earlier has a depth of Δ3, which is larger than the above Δ, as shown in FIG. 3C. The unevenness of the etching is greatly accentuated.

^ Well, the substrate to be etched (1) is polycrystalline silicon, and the etching gas is carbon dichloride tetrafluoride (C2C12F).
4) - 1 Use a film containing iron as the main component for the coating layer (3).
In the case of fc, the depth Δ3 of the etching unevenness produced on the surface of the substrate to be etched (1) by the above procedure is about 150 A, and the etching unevenness on the surface can be sufficiently determined by visual inspection. Good results can also be obtained by using tungsten for the coating layer (3).

Although the above explanation has been given as a method for evaluating the uniformity of plasma etching, this method also makes it possible to directly visualize local fluctuations in plasma pressure, etc., which have been difficult to observe in the past.

〔Effect of the invention〕

As described above, in this invention, a coating layer made of a material whose etching speed is slower than that of the substrate to be etched is provided on the substrate to be etched, and the plasma etching to be evaluated is performed on the coating layer, so that uneven etching due to uneven plasma flow is avoided. Even minute etching non-uniformities can be highlighted and evaluated with high sensitivity.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the implementation status of the conventional evaluation method;
The figure is a sectional view showing unevenness due to etching unevenness caused by this conventional method, and FIGS. 3A to 3C are sectional views showing states at each stage of an embodiment of the present invention. In the figure, (1) is the substrate to be etched, (2) is the plasma flow, and (3) is the coating layer. In each figure, the same reference numerals indicate the same or corresponding parts. Agent Masuo Oiwa Figure 1 Figure 2 Figure 3

Claims (3)

[Claims] (1) A coating III made of a member whose etching speed is slower than that of the substrate to be etched on the surface of the substrate to be etched.
is formed, plasma etching to be evaluated is performed on the coating layer, and uniformity is determined based on the pattern of protrusions and recesses caused by etching on the surface of the substrate to be etched at the stage when the coating layer is etched away. A method for evaluating the uniformity of plasma etching. (2) The method for evaluating the uniformity of plasma etching according to claim 1, characterized in that a tungsten film is used as the coating layer. (3) The method for evaluating the uniformity of plasma etching according to claim 1, characterized in that a film containing iron as a main component is used as the coating layer.