JPS59189632A - Dry etching method - Google Patents

Abstract

PURPOSE:To easily detect the end of etching and improve accuracy of mask and productivity by introducing the reactive gas with nitrogen gas into the container accommodating sample to be processed and by removing a film through formation of gas plasma condition by applying a high frequency power. CONSTITUTION:A mask blank having completed the developing process of resist is placed at the specified position on the electrode 3 in a processing container 1 as a sample 18 to be processed. CCl4 and O2 are put in the processing container 1 with the ratio, for example, of about 3:2 and N2 is also usually put into it with the ratio of 10% or less for the total amount of CCl4 and O2. The pressure in the processing container 1 is kept to the specified value. The etching is started by applying a DC voltage and required high frequency power with the electrodes 3, 3' used as the positive electrodes. When the etching of Cr film comes close to the end, an impedance between the electrodes 3 and 3' changes and reflection of high frequency power increases. Accordingly, the increased reflection is accurately detected by a reflection measuring apparatus 15 and the dry etching processing is suspended by a system control apparatus 17.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a dry etching method applied to the manufacture of semiconductor devices, masks, etc., in which a film is removed by reactive gas plasma and its completion is completed. This invention relates to a dry etching method that is easily detected.

(bl Background of technology) In order to increase the scale of semiconductor integrated circuit devices, miniaturization and higher integration of semiconductor integrated circuit devices are being promoted. This is a composite technology that uses this as a mask to etch basic semiconductor materials.

As an etching method in the manufacturing process of semiconductor devices, wet etching using a chemically selected solution is based on a long technological accumulation (it has been widely used as a slurry, but etching is It is necessary to improve the loading capacity, reduce the complexity of the process, and furthermore, there are problems such as environmental protection.

(cl. Prior Art and Problems) Techniques collectively referred to as dry etching methods include etching methods based on chemical reactions, physical reactions, and chemical and physical reactions.

The physical dry etching method is an etching method that utilizes the sputtering phenomenon that occurs when ions with large kinetic energy collide with a solid surface.This method involves patterning the sample surface in advance. 9th grade 2-F
In this method, the entire surface of the sample is irradiated with an ion beam by masking it with a small piece of material made of a metal ion beam. There is an ion beam etching method that selectively etches.Kowa et al.'s method uses a uniformly incident ion beam with uniform directionality, which can suppress undercuts below the mask and improve microfabrication. However, it has poor selectivity with respect to the material to be treated, and there is a high risk of damage due to ion bombardment.

An example of a chemical dry etching method is a plasma etching method. The low-temperature gas plasma normally used in Plasma Erasen is obtained by introducing an appropriate reactive gas into a reaction tube at a pressure of about 0.1 to 10 Torr (1 Torr), and then applying high-frequency power to it. The degree of ionization of this low-temperature gas plasma is small, but it contains atoms and molecules that have been brought into an excited state by various collision processes.Atoms and molecules in such an excited state have low chemical activity. When a chemical reaction occurs between the atoms on the surface of the sample that the gas plasma contacts, and volatile substances are formed as a result of this reaction, atoms are removed from the sample surface and etched. That will happen.

Although this plasma etching method has selectivity with respect to the material to be processed, the etching direction is isotropic and the microfabriability is poor.

In the sputter etching method described above, an inert gas is used as the atmosphere, but by using a reactive gas, chemical and physical reactions coexist.
Selectivity to the material to be processed is obtained, and furthermore, it becomes possible to increase the etching rate for the intended material.

This etching method is called an active ion etching method or a reactive sub-etching method, but in many cases high-frequency power is used to form a plasma. This etching method uses a small IS of undercut.
Highly anisotropic etching is possible.

Dry etching methods that have been put to practical use in the manufacturing process of semi-quadruple integrated circuit devices are often optimized by combining and combining the etching methods described above.
The etching mechanism is also not pure. Reliably detecting the end point of the advancing dry etching process in this manner is extremely important for the reliability of etching and for automating the etching process. For this reason, conventionally, many end point detection means have been implemented depending on the conditions such as the dry etching method and material. Conventionally known detection means include the following examples.

(Measurement of E refractive index, absorption coefficient, and film thickness of the film formed by the chemical etch process, which utilizes the light emitted during the reaction between SL and activated oak, using an ellipsometer. optical measurement method, (/1 laser detection method that detects by irradiating the laser source onto the sample and detecting the reflected +e anti-shape l, (-4 discharge l, which is excited and passes the external line, and detects the molecules ζ in the discharge space. Infrared absorption spectroscopy, which measures the absorption spectrum of gases, and mass spectrometry, which analyzes the mass of exhaust gas and detects it by the intensity change of a specific mass spectrum. In addition, the probe method, which judges changes in plasma-like defects by current-voltage percentage, (7) the discharge impedance method, which uses the fact that the discharge impedance changes before and after etching, and (1)
A pressure change method that detects pressure changes before and after etching halumium (A-1). and so on.

The dry etching method as described above is also suitable for the manufacturing process of masks used in manufacturing semiconductor devices. In other words, an etching process for forming a mask pattern of a chromium mask in which a chromium ((,:r) film of, for example, about 70 μm thick is formed by vapor deposition or sputtering on a high-quality glass substrate, for example, using tetrachloride). Carbon (CCt, ) and oxygen (0,
), it is possible to form a pattern with less dimensional change than the conventional wet-enching method using, for example, ceric ammonium nitrate.

As a method for detecting the end point of the dry etching process for this chrome mask, a method such as irradiating laser light and detecting the reflected light can be applied, but the irradiation position needs to be adjusted depending on the pattern, and mass spectrometry etc. This method is also not easy to implement. In order to avoid the complexity of detecting the end point, the dry etching execution time is sometimes standardized and managed by time, but the actual time required varies depending on the area to be removed by etching, so it is usually The margin time becomes excessive, which reduces etching accuracy and is also a waste of time.

There is a need for an end point detection means that is easy to implement in such embodiments of the dry enching method.

+d+ OBJECTS OF THE INVENTION An object of the present invention is to provide a dry etching method in which a film is removed using reactive gas plasma, in which the completion of intended film removal can be easily detected.

[el Structure of the Invention The above-mentioned object of the present invention is to accommodate a sample to be treated with a film to be removed exposed in a container, introduce a reactive gas to which nitrogen gas is added into the container, and remove the reactive gas. Applying high-frequency power to the gas to form a gas plasma state, removing the film by the gas plasma, and detecting completion of removal of the film by an increase in reflected waves generated in the high-frequency power supply circuit. This is achieved by

It should be noted that this phenomenon is caused by the fact that it is generally known that the bias voltage increases when nitrogen gas is introduced into the container and high-frequency power is applied to the seal. It is presumed that this leads to a significant increase in reflected waves.

tfJ EXAMPLES OF THE INVENTION The present invention will be specifically explained below by way of examples with reference to the drawings.

1 is a diagram illustrating an example of an apparatus suitable for carrying out the present invention. In the figure, 1 is a processing container, 2 is a waste outlet pipe, 3 and 3' are electrodes, 4.5 and 6 are gas containers, and 7
Reggie relays 118 and 8' are shirt valves, 9 is a flow meter, 10 is a leak valve,] l is a air force, 11; t)
Lap, 1:H; the vacuum pump, 14 is the noble e power supply, 1
5 is a reflected wave measuring device, 16 is a direct a power source, 17 is a system control device, and 18 is a sample to be processed.

When the present invention is applied to pattern formation of a mask in which a CrfL film is provided on a glass substrate, the gas container 4 is filled with carbon tetrachloride (CCt), and the gas container 5 is filled with oxygen ('J2).

6. Prepare nitrogen (N2). The pre-f4e mask grunk, on which the resist development process has been completed, is placed at a predetermined position on the electrode 3 in the processing container 1 as the sample 18 to be processed. CCt,
and 02, for example, at a ratio of about 3:2, and N2 is introduced into the processing vessel 1 at a ratio of usually 10 [ch] or less, for example, about 4 [ch] to the total flow rate of cc4 and O7. The pressure inside is set to a predetermined pressure. In this embodiment, it is set to about 0.1 to 1 (Torr).

For example, 1. In which the electrode 3 and the electrode 3' are of positive polarity.
Etching is started by applying a direct current of about 00 (V) to a ratio and a frequency power of f9r, approximately soo [W] in this embodiment. At this time, impedance matching is performed for the high frequency power, and reflected waves from the electrodes 3 and 3' side to i) the power source are eliminated to about 0.2 [chi] or less.

Impedance matching is maintained during the progress of the Cr film's error, but near the end of the Cr film's error.

Then, the impedance between the electrodes 3 and 3' changes, and the reflected waves of high-frequency power increase.

This increase in reflected waves 7J11 is due to the fact that when N2 is not added to the reaction gas, as illustrated by the chain line A in FIG. Compared to this, the present invention increases the change in impedance by adding N2, and increases the reflected power to 10 [ν■], as illustrated by the solid line B in FIG. ] In other words, it can be about 2 [chi].

The thus magnified reflected waves are accurately measured by the reflected wave measurement device 15, and the system control device 17 stops the dry etching process.

The embodiments described above include Cr film CC74 and (J).

Although this is an etching process using CF4 as a reactive gas, the present invention can also be applied to other types of dry etching processes. For example, using Freon (CF4) and oxygen
A mixed gas of 2) may also be used.

tgl As described in detail, according to the present invention, it is possible to easily determine the end point of dry etching in which a film is removed using reactive gas plasma, and it is suitable for use in semiconductor devices and their manufacturing. The effect of improving the precision and productivity of masks, etc. that can be used contributes to the advancement and spread of semiconductor devices, especially large-scale integrated circuit devices.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a device suitable for implementing the present invention, and FIG. 2 is a diagram showing an example of changes in reflected waves of high-frequency power. In the figure, 1 is a processing container, 3 and 3' are '[h poles, 4
．． 5 and 6 waste containers, 13 is a vacuum pump, 4 is a high frequency power source, 15 is a reflected wave measuring device, 1664 is a DC power source, 1
7 is a system control device, and 18 is a sample to be processed. Book I Senkyou 2 Close L...7 Temporary Open End Top

Claims (1)

[Claims] The sample to be treated with the film to be removed exposed is placed in a container, a reactive gas to which nitrogen gas has been added is introduced into the container, and high frequency power is applied to the reactive gas to remove the gas. A dry etching method characterized by forming a plasma state, removing the film by the gas plasma, and detecting completion of removal of the pre-distribution film by an increase in reflected waves generated in the high-frequency power supply circuit.