JPS62108527A - Dry etching apparatus - Google Patents

Abstract

PURPOSE:To uniformize a current density by increasing the impedance of a cover as compared with that of a substrate, and disposing the surfaces of the cover and the substrate substantially in the same plane. CONSTITUTION:A chamber 1 is evacuated by an evacuating system to a predetermined pressure, and CF4 gas is fed, for example, from a gas feeding system. A high frequency voltage is applied by a high frequency power source 11 between an anode 9 and a cathode 2 to generate a plasma 13 to dry etch a substrate 5. In this case, since an ion current by the plasma 13 is concentrated at the substrate 5 having small impedance, the ion current density flowing to the substrate 5 becomes high, and the etching rate becomes high. Since the surface 5a of the substrate 5 and the surface 23a of the cover 23 are disposed in the same plane, an electric field density becomes uniform in a boundary between the surfaces 5a and 23a, and does not become irregular on the surface of the substrate 5. Thus, ion current of uniform density flows on the surface 5a of the substrate 5 to uniformly etch the substrate 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a dry etching apparatus that performs dry etching using plasma.

(Prior Art) Conventionally, a dry etching apparatus, as shown in FIG.
A substrate 5 is placed on a cathode 2 installed in a chamber 1 (via a metal stage 3 when necessary). The surface of the cathode 2 protruding from the substrate 5 is covered with a cover 7 to prevent it from being etched by the generated plasma. 9 is the 7th node and is grounded together with chamber l.

When performing dry etching, the inside of the chamber I is evacuated to a predetermined pressure by an exhaust system (not shown), and CF4 gas, for example, is introduced from a gas introduction system (not shown). A high frequency voltage is applied between the cathode and the anode by a high frequency power supply 11 to generate plasma I3, and the substrate 5 is dry etched by this plasma 13.

(Problems to be Solved by the Present Invention) However, the cover 7 is made of Teflon or quartz (relative dielectric constants are approximately 2.1 and 3.8), and the thickness d is usually about 3 mm. of that high frequency (for example 13
．． The impedance Zc at 5 MHz) is on a substrate 5 made of silicon (with a relative dielectric constant of about 11 and usually extremely high resistance) with a thickness of about 1 mm (usually on a metal stage 3 made of aluminum, stainless steel, etc. with a thickness of about 2 mm). )
Since the impedance is approximately equal to or less than the impedance Zv, a considerable amount of ion current also flows to the cover 7, which causes a problem in that the density of the ion current flowing to the substrate decreases. Further, since there is a step at the boundary between the surface 7a of the cover 7 and the surface 5a of the substrate 5, the electric field density becomes non-uniform near the boundary. For this reason, the density of the ion current flowing through the substrate 5 becomes non-uniform at the edges of the substrate, resulting in problems such as the inability to perform uniform etching.

An object of the present invention is to provide a dry etching apparatus that can solve the problems such as the decrease in current density.

(Means for Solving the Problem) In order to achieve the above object, the present invention makes the impedance of the cover larger than the impedance of the substrate, and the surface of the cover on the anode side and the surface of the substrate on the anode side. are arranged so that they are almost on the same plane.

(Action of the present invention) Since the impedance of the cover is made larger than the impedance of the substrate, more ionic current flows through the substrate than through the cover. Also with the surface of the cover.

Since the surface of the substrate is made to be on the same plane, the electric field density becomes uniform at the boundary between these surfaces.

(Effects of the Present Invention) Since more ion current flows through the substrate than through the cover, the density of the ion current flowing through the substrate increases, thereby increasing the etch rate. Further, since the electric field density becomes uniform at the boundary of the surface, the electric field density on the substrate near the boundary becomes uniform. Therefore, the density of the ion current flowing through the substrate becomes uniform, and the substrate is etched uniformly.

(Embodiment of the invention) In FIG. 1, 5 is approximately 11 m1 having the same diameter as the metal stage 21 placed on the cathode via the metal stage 21.
The thick substrate 23 is a Teflon cover that protects the surface of the cathode protruding from the substrate 5, and its thickness d is approximately so that the impedance Zw of this cover is greater than twice the impedance Zc of the substrate 5. It is made thicker than 5mm. Fig. 2 shows the thickness d and Zw/Zc of the cover 23.
showed the relationship between

On the other hand, the thickness of the metal stage 21 is selected so that the surface 23a of the cover 23 on the 7th node 9 side and the surface 5a of the substrate 5 on the 7th node 9 side are on the same plane. As in the past, the metal stage 21 is made of aluminum, stainless steel, etc., and its impedance can be considered to be almost zero. 25 is a capacitor, and 27 is an insulator that electrically insulates the chamber 1 from the cupid 2. Furthermore, the fourth
Components that are the same as those shown in the figures are given the same reference numerals, and therefore their descriptions will be omitted.

Now, the inside of the chamber 1 is evacuated to a predetermined pressure by an exhaust system (not shown), and then, for example, CF is injected from a gas introduction system (not shown).
4 Introduce gas. Then, a high frequency voltage is applied between the seven nodes and the 9φ cutweed 2 by a high frequency power source 11 to generate plasma 13. This plasma 13 causes the substrate 5 to
is dry etched.

At this time, since the ion current generated by the plasma 13 is concentrated on the substrate 5 having a low impedance, the density of the ion current flowing through the substrate 5 becomes high, and the etching rate becomes high. FIG. 3 shows the relationship between etch rate and Zw/Zc. It is clearly seen that the etching rate rises from around Z/Zc~2 and suddenly shows a high value.

Furthermore, since the surface 5a of the substrate 5 and the surface 23a of the cover 23 are on the same plane, the electric field density becomes uniform at the boundary between the surfaces 5a and 23a, so that the electric field density is non-uniform on the surface of the substrate 5. Therefore, since an ion current with uniform density flows through the surface 5a of the substrate 5, the substrate 5 is etched uniformly.

In the above embodiment, the impedance Zc is increased by increasing the thickness of the cover 23, but the impedance can also be increased by selecting a material with a high dielectric constant without increasing the thickness. , and further metal stage 2
1 may be omitted and the electrode surface of that portion may be raised.

[Brief explanation of drawings]

Figure 1 is a sectional view of the embodiment, Figure 2 is the thickness and Z of the cover.
FIG. 3 is a graph showing the relationship between etch rate and Zw/Zc, and FIG. 4 is a cross-sectional view of a conventional etching apparatus. 1...Chamber 2...Cathode 5...
・Substrate 5a...Surface 9...Anode 21...Metal stage 23...Cover 23a...Surface Agent Patent attorney
Nobuyuki Shima 1 Ku6 2 KutL(-Ichie 3 Kut”%・

Claims (1)

[Claims] A device that places a substrate on a cathode installed in a chamber, covers the surface of the cathode that protrudes from the substrate with a cover, applies a high-frequency voltage to the cathode to generate plasma, and uses this plasma to dry-etch the substrate. A dry etching apparatus characterized in that the impedance of the cover is made larger than the impedance of the substrate, and the surface of the cover and the surface of the substrate are substantially on the same plane.