JP2727781B2 - Dry etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method for generating a plasma by a magnetic field and a microwave electric field to etch an oxide film.

[0002]

2. Description of the Related Art As the density of semiconductor integrated circuits has increased, patterns have become finer and surface steps have increased. Therefore, there is a demand for a processing method capable of obtaining a high selectivity of the oxide film with respect to silicon and polysilicon (the ratio of the etching rate of the oxide film to the etching rate of silicon and polysilicon) in the dry etching step of the oxide film. In the conventional dry etching method, a high selectivity with the underlying silicon is obtained by changing the operating conditions such as the mixing ratio of the etching gas, the high frequency power applied to the substrate, and the pressure to obtain the selectivity with the underlying silicon film. I was trying to improve it. As related to the present invention, for example, JP-A-60-154620 and JP-A-63-6
No. 5,624, JP-A-63-69232, JP-A-63-77119, and the like.

[0003]

In the conventional method, no consideration is given to the etching rate of the oxide film, and the etching rate of the oxide film decreases in order to obtain a selectivity with respect to the underlying silicon film. there were.

An object of the present invention is to provide a dry etching method capable of controlling a taper angle of a contact hole while obtaining a high selectivity with an underlying silicon film without reducing the etching rate of the oxide film in the etching of the oxide film. It is in.

[0005]

The above object is achieved by using one or more kinds of carbon fluoride gas as an etching gas, generating a plasma in a plasma generation chamber by a magnetic field and a microwave electric field, and forming a plasma on the underlying silicon film. In the dry etching method for etching an oxide film, the point of the magnetic flux density satisfying the electron cyclotron resonance conditions formed in the plasma generation chamber and the range of the distance from the substrate have substantially the same etching rate of the oxide film. The etching rate is reduced by periodically changing the position of the point of the magnetic flux density within such a range and within a range where the selectivity with the silicon film becomes higher as the distance becomes shorter. This can be achieved by increasing the selectivity with respect to the silicon film and controlling the taper shape of the contact hole without increasing the selectivity.

[0006]

[Function] The magnetic flux density formed in the plasma generation chamber is increased,
That is, a magnetic flux density satisfying the electron cyclotron resonance condition (875 μm when a microwave of 2.45 GHz is used)
By bringing the position of Gs where the magnetic flux density satisfies the electron cyclotron resonance condition) close to the electrode on which the substrate is mounted, only the etching rate of the underlying silicon film decreases without decreasing the etching rate of the oxide film. This phenomenon was discovered through experiments. Thus, by changing the magnetic flux density formed in the plasma generation chamber during the etching, a high selectivity with respect to the underlying silicon film can be obtained without reducing the etching rate of the oxide film. In this way, by simply bringing the position of the magnetic flux density satisfying the electron cyclotron resonance condition close to the electrode on which the substrate is mounted, a high selectivity with respect to the underlying silicon film can be obtained. In the etching step, the etching shape becomes a gentle taper shape (taper angle of 84 degrees or less). For this reason, the magnetic flux density changes periodically during the etching, that is, the distance from the substrate at the point of the magnetic flux density that satisfies the electron cyclotron resonance condition is periodically changed to reduce the etching rate and the selectivity without decreasing the taper shape. It is necessary to avoid this.

[0007]

An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows a carbon fluoride gas as an etching gas. For example, the position of the magnetic flux density (referred to as the position of the ECR point) that satisfies the electron cyclotron resonance condition when a mixed gas of C ₂ F ₆ and CH ₂ F ₂ is used, the etching rate of the oxide film, And the selection ratio. As can be seen from the figure, by bringing the position of the ECR point closer to the substrate placed on the electrode, a high selectivity with respect to the underlying silicon film can be obtained without significantly reducing the etching rate of the oxide film. In this case,
The etching rate and the selectivity when the position of the ECR point, that is, the distance from the substrate to the ECR point is 85 mm, are each represented as 1.0.

Table 1 shows that C ₂ F ₆ and C
Using a mixed gas of H ₂ F ₂ , the position of the ECR point (in this case,
(60 mm and 70 mm) shows the etching rate of the oxide film, the selectivity to the underlying silicon, and the taper angle of the contact hole when the etching is performed by periodically changing the etching stepwise during the etching. As can be seen from the table, by changing the position of the ECR point periodically during etching, a high selectivity with the underlying silicon film can be obtained without reducing the etching rate of the oxide film, and the taper angle of the contact hole can be controlled. be able to.

[0009]

[Table 1]

FIG. 2 shows an example of a microwave apparatus having a magnetic field. Reference numeral 10 denotes a vacuum processing chamber, 11 denotes a processing gas supply device for supplying a processing gas into the vacuum processing chamber 10, and 12 denotes a vacuum processing chamber. An exhaust device for exhausting the interior of the chamber 10 to a predetermined pressure;
Reference numeral 13 denotes a sample stage (electrode) for disposing the substrate 14 in the vacuum processing chamber 10, reference numeral 15 denotes a waveguide for introducing microwaves from the magnetron 16 into the vacuum processing chamber 10, and reference numerals 17 and 18 denote vacuum processing. An electromagnetic coil 19 for generating a magnetic field in the chamber 10 is a control device for adjusting and controlling the intensity of the magnetic flux density of the electromagnetic coils 17 and 18. The ECR point 20 in the plasma moves periodically in the direction of the arrow by periodically adjusting and controlling the magnetic flux density of the electromagnetic coils 17 and 18 by the control device 19 using the device configured as described above.

According to this embodiment, the position of the ECR point is periodically changed in a stepwise manner during the etching with respect to the substrate, so that the position of the ECR point can be selected higher than the underlying silicon without reducing the etching rate of the oxide film. The taper angle of the contact hole can be controlled while maintaining the ratio.

[0012]

According to the present invention, there is an effect that the taper shape of the contact hole can be controlled while obtaining a high selectivity with respect to the underlying silicon without reducing the etching rate of the oxide film.

[Brief description of the drawings]

FIG. 1 is a diagram showing an etching rate of an oxide film and a selectivity of silicon when the position of an ECR point is changed.

FIG. 2 is a configuration diagram showing an example of an apparatus for performing the method of the present invention.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshie Sato 794, Higashitoyoi, Kazamatsu-shi, Yamaguchi Pref. Kasado Plant, Hitachi, Ltd. (56) References JP-A-64-81225 (JP, A) JP-A Sho 60-134423 (JP, A) JP-A-3-218018 (JP, A) JP-A-6-1996447 (JP, A)

Claims (1)

(57) [Claims] At least one kind of carbon fluoride gas is used as an etching gas, a plasma is generated in a plasma generation chamber by a magnetic field and a microwave electric field, and an oxide film on an underlying silicon film is etched. In the dry etching method, the point of the magnetic flux density satisfying the electron cyclotron resonance conditions formed in the plasma generation chamber and the range of the distance from the substrate are within a range where the etching rate of the oxide film becomes substantially the same, and Within a range in which the selectivity with the silicon film becomes higher as the distance becomes shorter, the position of the point of the magnetic flux density is periodically changed to thereby select the silicon film without reducing the etching rate. A dry etching method characterized by increasing the ratio to control the taper shape of the contact hole.