JPS61230323A - Etching apparatus - Google Patents

Abstract

PURPOSE:To improve the precision of the etching process, yield and efficiency by automatically correcting a change in the illuminance by a photo transistor, and causing the power supply voltage to correspond to a change in the distance between the light source and the object to be etched. CONSTITUTION:The surface of a wafer 6 is observed through a cylindrical lens 12, an interference filter 13 and an objective lens 14 which are arranged in front of a charge transfer device CCD 11. Image information changing with time due to the etching is inputted through CCD driver 15 to a data processing unit 16, and the process and end point of the etching are determined by a determination and control unit of the etching end point 17, thereby controlling the switching of a high-frequency power supply 9. Fluctuation of a light source 1 is corrected through a controller by control of an illumination power supply 2, based on the feedback signal of a photo transistor 3. With this, the precision of the process, yield and efficiency of LSI wafers or the like are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an etching apparatus that visually recognizes the progress of etching.

[Background of the Invention] Currently, in semiconductor manufacturing technology, the mainstream method of etching monitoring and etching end point detection in ultra-LSI processing and etching technology is based on emission spectrometry, and other methods such as laser interferometry are also used. However, none of them are equipped with a high-precision illumination device with excellent reproducibility.

With the shift to ultra-large scale integrated circuits, the etching technology that requires high precision is shifting from a batch processing method to a single wafer processing method. Therefore, measures to increase processing capacity (throughput) include improving the etching rate and increasing the diameter of wafers. In addition, increasing the speed of etching is greatly influenced by the selectivity, dimensional controllability, and uniformity of etching.Therefore, it is important to accurately and precisely detect the end point of etching, and to detect unfinished etching points and excessive etching. It is important to prevent this.

For information on this technology, see the Special Publication No. 58-424.
57 and Japanese Patent Publication No. 58-52572, etc., the former assumes that the object to be irradiated is uniformly illuminated), while the latter deals with changes in the dimensions of the object to be irradiated, such as paper size A4 size, etc. This invention relates to an exposure method that can accommodate changes in size such as A3 size.

[Purpose of the Invention J The present invention has been made to solve the above-mentioned problems of the prior art, and aims to improve the etching accuracy of fi, LSI, and VLSI, and to improve the yield efficiency. Etching device! The aim is to provide l.

[Summary of the Invention] In order to achieve the above object, in the etching apparatus of the present invention, changes in illuminance due to fluctuations in the illumination power supply and attenuation of the light source are automatically corrected by a phototransistor, and changes in the illumination intensity between the light source and the object to be etched are automatically corrected. By adjusting the power supply voltage to changes in distance, constant illumination can be obtained at all times.

[Embodiment j of the invention j Hereinafter, an etching apparatus which is an embodiment of the invention will be described with reference to FIGS. 1 and 2.

First, the general configuration of the embodiment is such that attenuation due to changes in the light source 1 over time and changes in illuminance due to the electric power of the illumination power source 2 are detected by the phototransistor 3 and corrected. The distance between the pair of upper and lower electrodes 4.5 that face each other varies depending on the etching conditions, but the distance between the light source 1 and the unino 6, which is the object to be etched and also the object to be observed, is also 250 to 350%, for example. The structure is designed to accommodate this change.

In detail, in FIG. 1, a pair of upper and lower electrodes 4.5 are provided inside the etching processing chamber 7, the upper electrode 4 is connected to a ground 8 potential, and the lower electrode 5 is connected to a high frequency power source 9. ing.

The object to be etched 16 is supported and attached to the center of the upper surface of the lower electrode 5, and is passed through the entire transparent viewing window 10 from above the etching processing chamber 7 to the C0D (charge transfer device) 1.
The system is such that it can be observed with 1.

A cylindrical lens 12, an interference filter 13, and an objective lens 14 are arranged in this order on the front side of the CCD 11, and the surface of the Unino S6 can be observed through these members. Image information that changes over time due to etching is input to the data processing device 16 via the COD drive 15, and the etching end point determination control device 17 determines the etching process and end point, and turns the high frequency power source 9 on and off.
' control switching. The monitor lighting device is composed of a lighting power source 2, a light source 7, a lens 18, and a no-7 mirror 19, of which the amount of light of the light source #2 can be controlled arbitrarily.

Next, in FIG. 2, when the distance between the light source 1 and the sea urchin 6 is fixed and unchanged, the light intensity of the light source 1 is adjusted by the controller 20 so as to give an appropriate illuminance to the surface of the sea urchin 6. Then, the power source 2 for lighting is set. or,
The output of the phototransistor 3 provided in the storage box of the No.7 mirror 19 is introduced into one input terminal A of the comparator 21 via the amplifier 22t. An analog subtracter is used as the comparator 21 used here, and by setting the voltage of the other input terminal B to be balanced with the voltage of terminal A, the surface of the sea urchin/S6 is set using this balanced voltage as a reference value. The illuminance change, that is, the fluctuation of the light source 1 is caused by the feedback signal of the phototransistor 3,
This is corrected by controlling the illumination power source 2 via the controller 20, and as a result, stable illumination is obtained.

In this way, when considering the distance between the light source 1 and the unit 6 as fixed, the reference voltage input to the input terminal B of the comparator 21 can be set with a simple circuit configuration.

However, as a practical matter, the distance between the light source 1 and the sample sea urchin 16 changes, and the amount of light is adjusted with high precision in response to this change.

That is, if the illuminance on the surface of the wafer 6 is L, this illuminance is a function inversely proportional to the square of the distance 1.
In illumination control, the voltage E of the reference signal of the comparator 21 becomes a function proportional to the square of the distance β. Tsuma, B=R1,2CVノ ・・・・・・・・・・・・
......It can be expressed as (1).

Here, R indicates an illuminance coefficient.

Therefore, if the illuminance coefficient R is calculated from the relationship between the distance 1 and E in the above equation (1), the distance 1 set by the digital switch of the presetter 25 is !・The V converter 24 converts the voltage into a reference voltage that corresponds to the change in distance r, and inputs it to the D/A converter 25 and then to the comparator 21, so that stable illumination with good reproducibility can always be obtained. .

The illumination of the etching monitor varies depending on the etching distance, the material to be etched, and other etching conditions.
This is handled by creating a table of each data obtained experimentally under various conditions and setting the illuminance coefficient R in the above equation (1), and basically the method of this embodiment is established.

As is clear from the above, this example is strongly influenced by illumination in order to observe the contrast on the surface of the quay 16 that changes over time due to etching. 6, the attenuation of the source rA1, and other changes in conditions can be greatly reduced, and stable illumination with good reproducibility can be obtained.

〔Effect of the invention〕

As can be understood from the above, the etching apparatus of the present invention enables quantitative image processing and highly accurate detection of the end point of etching, thereby improving processing accuracy and yield for LSI etching etc. and is effective in improving efficiency.

[Brief explanation of the drawing]

The first factor is a block diagram of an etching apparatus employing an etching monitor illumination apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram of the illumination apparatus of this embodiment. DESCRIPTION OF SYMBOLS 1...Light source 2...Illumination power source 3...Phototransistor 4.5...Upper and lower electrodes 6...Wafer 18 as an object to be etched 18...Lens 19...Half mirror 20 ...Lighting controller

Claims (1)

[Claims] This is an etching apparatus designed to visually recognize the progress of etching on the surface of an etched object to be patterned, in which a phototransistor is installed at a certain position from a light source, and the illuminance is controlled by the output signal of the phototransistor. corrected and a change in distance between the light source and the object to be etched is set in a presetter;
An etching apparatus characterized in that the etching apparatus is controlled so that a constant illuminance is always obtained on the object to be etched by converting the voltage into a voltage corresponding to the change in the distance.