JPH01230236A - Dry etching method - Google Patents

Abstract

PURPOSE:To make it possible to detect the final point of etching accurately, by performing plasma treating of a wafer, introducing reacting gas in a chamber, and etching an Si oxide film. CONSTITUTION:A wafer 3 on which a silicon oxide film is formed is mounted on one of parallel planar electrodes 2 in a chamber 1. The inside of the chamber is evacuated so as to obtain a vacuum state. Inactive gas is introduced into the chamber 1. A high frequency is applied across the electrodes 2 from a power source 4. The gas is turned plasmatic. At this time, gases such as H2O, O2, CO and CO2 which are adsorbed in the wafer 3 when the wafer is introduced are removed by sputtering action at this time and exhausted together with exhausting N2 gas out of the chamber 1. After this treatment, reacting gas incorporating fluorine is introduced to become plasmatic. Thus, the silicon oxide film is etched.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a dry etching method for etching a silicon oxide film (SiO□) in the manufacturing process of semiconductor integrated circuits.

<Prior art> Conventionally, dry etching of a silicon oxide film has been carried out by placing a wafer 3 on which a silicon oxide film has been formed on one side of a parallel plate electrode 2 in a chamber 1, as shown in the schematic diagram of FIG. 12. C:
This is carried out by introducing a reactive gas containing fluorine such as 1 Fe, and applying high frequency waves between the electrodes 2 using a high frequency power source 4 to turn the reactive gas into plasma.

In this type of dry etching, C in the reaction gas is
(Carbon) reacts with O(W!IN') in the silicon oxide film, which is the material to be etched, and the CO generated emits light, and the end point of etching can be detected by monitoring the emission intensity of the CO. . That is, at the end point of etching, the 0 in the silicon oxide film disappears and no CO is produced, and the emission intensity of CO rapidly decreases, so that the end point of etching is detected. As a means for monitoring the change in the emission intensity of CO, as shown in FIG. The output signal of 7 is passed through a signal processing device 8 and outputted from an output device 9 as a light emission intensity.

In recent years, as wafers have become larger in diameter and devices have become more highly integrated, dry etching has shifted from a batch method in which a plurality of wafers are processed at a time to a branch method in which wafers are processed one by one. In this single-wafer type tri-etching, the etching speed is generally increased in order to obtain a throughput close to that of the batch type. Therefore, especially in this single-wafer type dry etching, it is necessary to accurately detect the end point of etching.

<Problem to be solved by the invention> However, when putting the wafer 3 into the chamber 1, N20.
N2. Atmospheric gases such as O□, co, and co□ are introduced into the chamber 1 while being adsorbed onto the wafer 3. Among these adsorbed gases, N20,02. Co, Co
When dry etching is performed on a silicon oxide film with two gases adsorbed, CO radicals are generated by the mutual reaction of the adsorbed gas, reaction gas, and silicon oxide film, which are generated by reaction and dissociation. 00 by etching
00 light emission, which is different from light emission, will occur. Moreover, the intensity of the 00 emission caused by the adsorbed gas gradually decreases during etching due to the desorption of the adsorbed gas.

Therefore, as shown in the characteristic diagram of the unsealed CO emission intensity during etching in Figure 3, the CO emission intensity rapidly increased after the start of etching.
The emission intensity gradually decreases until the etching end point te is reached, and the etching end point 1e becomes unclear.

Especially in single-wafer dry etching.

Since only one wafer is etched, the intensity of the original 00 emission due to etching is low, and therefore, in order to increase the detection sensitivity of the 60 emission, the 60
The influence of light emission becomes greater, making it more difficult to accurately detect the etching end point te.

As mentioned above, the conventional dry etching method has a problem in that the etching end point cannot be accurately detected due to the adsorbed gas.

<Means for Solving the Problems> The present invention has been proposed to solve the above-mentioned problems.The present invention has been proposed in order to solve the above-mentioned problems. , a dry etching method characterized in that the silicon oxide film is etched by introducing a reactive gas into the chamber.

<Operation> According to the above method, N20,02.
Adsorbed gases such as Co and Co2 gas are removed.

<Example> Hereinafter, an example of the present invention will be described with reference to the characteristic diagram of the unsealed CO emission intensity during etching shown in FIG. 1 and the schematic configuration diagram shown in FIG. 2.

The apparatus for the dry etching method of the present invention includes:
A dry etching device similar to the conventional one shown in FIG. 2 can be used.

First, a wafer 3 on which a silicon oxide film is formed is placed on one of the parallel plate electrodes 2 in a chamber 1, and the chamber 1 is evacuated, and an inert gas such as N2 gas is introduced into the chamber 1. In this state jK4, high frequency is applied between the electrodes 2 by the high frequency power source 4 to turn the N2 gas into plasma. Then, due to the sputtering action of this N2 gas plasma, the N20,02 adsorbed to the wafer 3 when the wafer was introduced
゜co, co□ gas, etc. are removed and discharged to the outside of the chamber i together with the exhausted N2 gas.

After the plasma treatment using N2 gas, C2F6 +CHF:I is applied as in the conventional tri-etching.

CF4+)i2. C: The silicon oxide film is etched by introducing a reactive gas containing fluorine such as IF8 and turning it into plasma.

In the dry etching method described above, since the adsorbed gas is removed, there is no 00 emission caused by the adsorbed gas.
Therefore, the intensity of 00 emission sharply decreases at the end point of etching, and the intensity of CO emission sharply decreases at the end point of etching.

FIG. 1 shows a 70mm thick thermoformed 6 inch diameter wafer.
[] This is a characteristic diagram of the unsealed CO emission intensity during etching when a silicon oxide film of OA is subjected to tri-etching by the method of the present invention. To measure the CO emission intensity, as in the conventional case, as shown in FIG. and an output device 9 are used.

The CO emission intensity measured as shown in FIG. 1 increases rapidly after the start of etching, and remains approximately constant during etching. Then, immediately before the etching end point te, the CO emission intensity begins to decrease rapidly, and at the etching end point 1e, the CO emission intensity becomes extremely low. In other words, the etching end point te can be accurately detected by rapidly decreasing the CO emission intensity in this manner.

(Effects of the Invention) As described above, according to the dry etching method of the present invention, it is possible to accurately detect the etching end point in etching a silicon oxide film.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram of the unsealed CO emission intensity during etching in the present invention, Fig. 2 is a schematic configuration diagram of the tri-etching device, and Fig. 3 is a characteristic diagram of the unsealed CO emission intensity during etching in the conventional example. . te...Etching end point. l...Chamber, 3...Wafer. Patent applicant: Oki Electric Industry Co., Ltd. -1--”l+ Agent: Toshiaki Suzuki, l, -t. C2 Am groan V d β cedar 9 Naka 2 No Figure 3 Procedural correction power (“boundary”) 1.1.13 1.・Indication of 1 item 1986 Patent Application No. 055021 2, Title of the invention Trial etching method 3, person making the amendment/relationship with case h Patent applicant office (105) 1.1-7 Toranomon, Minato-ku, Tokyo
No. 12 Name (029) Oki Electric Industry Co., Ltd. Representative Director and President Hikaru Kosugi 4,
Agent Address (108) 4-10-3 Shibaura, Minato-ku, Tokyo
No. 5, "Detailed Description of the Invention" column 6 of the specification subject to amendment, Contents of the amendment

Claims (1)

[Claims] In a dry etching method in which a silicon oxide film on a wafer is etched by turning a reactive gas into plasma, and the etching end point is detected from a change in the emission intensity of CO, the wafer is placed inside a chamber. A dry etching method, comprising: performing plasma treatment with an inert gas introduced into the chamber, and then introducing a reactive gas into the chamber to perform etching on the silicon oxide film.