JPS6063932A - Reactive ion beam etching device - Google Patents

Abstract

PURPOSE:To contrive the prolongation of the lifetime of a cathode by a method wherein the cathode of lanthanum hexaboride which radiates thermal electrons to generate reactive gas ions is stably operated in the atmosphere of an inert gas. CONSTITUTION:For example, Ar gas is introduced inside a cathode cover 8, and the reactive gas is introduced into an ion source chamber 1. Thereafter a positive high bias voltage of several hundred V is impressed on an electron lead- out electrode 10, and a negative one of several hundred V on an accelerating electrode 5. Next, when the thermal electrons are radiated by heating the LaB6 cathode 9, the Ar gas inside the cover 8 is activated and then comes to the state of plasma of isolation into Ar ions and electrons. The reactive gas in the chamber 1 is activated by the electrons in the Ar plasma. The positive ions are led out through a window by the negative high bias voltage impressed on the electrode 5, and perform etching by irradiating the film to be etched formed on the main surface of an Si wafer 6. The cathode 9 is then protected by the inert gas, and besides the heating temperature is low.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a reactive ion beam etching apparatus for etching metal films and insulating films formed on the main surface of a silicon substrate by irradiation with a reactive ion beam. It is.

[Prior art]

FIG. 1 is a diagram schematically showing the main components of an example of a conventional reactive ion beam etching apparatus.

In the figure, (1) has carbon tetrachloride A (OCI) inside.
! 4) an ion source chamber that activates a reactive gas such as a chlorine-based gas or a fluorine-based gas such as carbon tetrafluoride (OF4) to a plasma state to generate positive ions (■ in the figure) of the reactive gas; (2) is a gas introduction pipe that is installed in a part of the side wall of the ion source chamber (1) and introduces the reactive gas into the ion source chamber (1), and (3) is a gas introduction tube that is installed in the ion source chamber (1). The ion source chamber (1
) is a tungsten (W) filament that emits thermionic electrons (θ′″ in the figure) that activate the reactive gas introduced into the ion source chamber (
The positive ions of the reactive gas generated at Vcg inside the ion source chamber (1) are sent to the outside of the ion source chamber (1) by being provided on a part of the side wall other than the side wall where the gas introduction pipe (2) of 1) is installed. A net-like window (5) is provided outside the Vi ion source chamber (1) so as to face the window (4) with a gap h between the window (4) and has a negative height with respect to the window (4). A lattice-shaped accelerating electrode (6) is an accelerating electrode (5) which pulls out positive ions of a reactive gas generated in the ion source chamber (1) through a window (4) in the direction of the arrow shown when a bias voltage is applied. Metal films such as aluminum (Al), silicon oxide (S10□), silicon nitride (81
A silicon (Sl) wafer (7) on which an etched film (not shown) of an insulating film such as 3N4) is formed on the main surface.
is a cassette that supports the B1 wafer (6). Note that the cassette (7) is configured to be cooled by water or other coolant.

In this conventional apparatus, positive ions of a reactive gas extracted from an ion source chamber (1) by an accelerating electrode (5) are applied to a film to be etched (Fig. (not shown) to irradiate the film to be etched. This etching is called reactive ion beam etching (R over B), which enables plasma etching and anisotropic etching through chemical reactions with high etching speed and high selectivity, and is a physical method that facilitates microfabrication. It is a combination of ion milling by target removal, and it can process aluminum (Al), silicon (Sl), copper (Ou) alloys, etc., which is impossible with normal plasma etching or reactive ion etching (R process Ic). Etching of A1 alloy is now possible. For example, if chlorine-based gas is used as a reactive gas, 'AI!・Sl・
The Ou gold alloy AA' element is converted to volatile Al01x,
81 elements are volatile 5inl! , and evaporate into O
The u element is converted to nonvolatile Curl, but this Ou O
No. 12 is removed by sloping by chlorine-based gas ions. As a result, fine patterns of lpm or less of A1 alloy such as Al-Si.Ou gold alloy can be easily formed.

However, in this conventional device, the W filament (3) is heated to a high temperature in an atmosphere of reactive gas in the ion source chamber (1), so the W filament (3) reacts with the reactive gas and the W filament ( The lifespan of 3) was short, about 20 hours, which was a practical problem.

[Summary of the invention]

This invention was made for the purpose of eliminating the above-mentioned problems, and has a work function 74% lower than that of the W filament, and activates the reactive gas at a lower temperature than that of the W filament. By making the Rankan hexaboride (LaB6) cathode, which emits thermionic electrons to generate ions, operate stably in an inert gas atmosphere, the lifespan of the LaBe cathode is longer than that of the W filament. The object of the present invention is to provide a reactive ion beam etching apparatus which has a long length and is free from practical problems.

[Embodiments of the invention]

FIG. 2 is a diagram schematically showing the main components of a reactive ion beam etching apparatus according to an embodiment of the present invention.

In the figure, the same reference numerals as those in the conventional example shown in FIG. 1 indicate equivalent parts. (8) is provided in a part of the side wall of the ion source chamber (1) other than the side wall where the gas introduction pipe (2) and the window (4) are provided, with one end passing through this part. An aperture (8a) opening into the ion source chamber (1) is formed in the center of the cathode cup-1 (9) in which a La Be cathode, which will be described later, is accommodated. A directly heated La Be cathode has a work function smaller than that of W and emits thermoelectrons when heated to a temperature of about 1500°C. θ0 is the ion source chamber (
1) A positive voltage of several hundred V with respect to the cathode cover (8) is provided so as to face the cathode cover (8) at a distance from the end in which the opening (8a) of the cathode cover (8) is formed. This is an electron drawing electrode that draws electrons from the cathode cup (-(8)) into the ion source chamber (1) by applying a high bias voltage of . Inert gas such as Ar and He is introduced and LaB
It is configured to protect the cathode (9).

The configuration of this example is as follows: cathode cover (8) *LaB
The structure is the same as that of the conventional example shown in FIG. 1 except for the aLaB6 cathode and the electron extraction electrode θυ.

Next, the operation of this embodiment will be explained.

Immediately, for example, Ar gas is introduced into the cathode cover (8) and a reactive gas is introduced into the ion source chamber (1), and then the cathode cover (8) is connected to the electron extraction electrode (Id).
A high positive bias voltage of several hundred μ is applied to the accelerating electrode (5), and a high negative bias voltage of several hundred μ is applied to the accelerating electrode (5). Then, the La Bs cathode (9) was
When heated to a temperature of about 00°C and emitted thermoelectrons,
The Ar gas in the cathode cover (8) is activated by these thermoelectrons and becomes a plasma state in which Ar ions and electrons are separated. - The density of this Ar plasma is increased by the high bias voltage applied between the electron extraction electrode 00 and the cathode cover (8), and the voltage between the electron extraction electrode α0 and the cathode cover (8) is increased by several 10V
K decreases, and Ar plasma is maintained between these electron extraction electrodes 00 and the cathode cover (8). In this way, the electron extraction electrode θ0 and the cathode cover (8
) The reactive gas in the ion source chamber (1) is activated by electrons in the Ar plasma held between the ion source chamber (1) and the ion source chamber (1). Similar to the conventional example shown in FIG. 1, the positive ions of the activated reactive gas are passed through the window (3) by the negative high bias voltage applied to the accelerating electrode (5), as indicated by the arrow in the figure. A broken etching film (not shown) formed on the main surface of the S1 wafer (6) by being pulled out in the same direction is irradiated, and the film to be etched is etched. Therefore, the film to be etched is AI! Etching of this A1 alloy film can be easily performed no matter which A1 alloy film is used, such as the φ81.Ou gold alloy.

In the apparatus of this embodiment, inert gas such as Ar or He is introduced into the LaB6 cathode (9) or the cathode cover (8) to prevent it from coming into contact with the reactive gas in the ion source chamber (1). Since it is protected, the La Bs cathode (9) can operate stably for a long time without reacting with reactive gases. Moreover, LaB6 cathode (
Since the heating temperature in 9) is lower than the heating temperature of the W filament, the life of the LaB cathode is longer than that of the W filament, and practical problems can be eliminated.

〔Effect of the invention〕

As explained above, in the reactive ion beam etching apparatus of the present invention, an opening is provided in a part of the side wall of the ion source chamber so that one end passes through this part and opens into the ion source chamber. A cathode cover configured to allow introduction of an inert gas into the cathode cover, and a hexaboride compound housed in the cathode cover and emitting thermoelectrons to activate the inert gas introduced into the cathode cover. The lanthanum cathode and the end of the cathode cover where the aperture is formed in the ion source chamber are provided to face each other with a gap between them, and the electrons of the inert gas activated in the cathode cover are used as an ion source. It has an electron extraction electrode that activates the reactive gas introduced into the ion source chamber by drawing it into the chamber,
+□lnc) 11+t in the ion source chamber □1!1 death? ,
□j is also brought out to the outside of 11□□ to perform etching by accelerating φ and irradiating the film to be etched, so that the ion source is Since it is protected from contact with reactive gases in the room, the lanthanum hexaboride cathode can operate stably for a long time without reacting with reactive gases. Moreover, since the heating temperature of the lanthanum hexaboride cathode is lower than that of the tungsten filament, the life of the lanthanum hexaboride cathode is longer than that of the tungsten filament, and practical problems can be eliminated.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing the main components of an example of a conventional reactive ion beam etching device, and FIG. 2 is a diagram schematically showing the main components of a reactive ion beam etching device according to an embodiment of the present invention. FIG. In the figure, (1) is the ion source chamber, (4) is the window, and (5)
is the addition Q (e is the electron extraction electrode. In addition, the same symbols in the figures indicate the same or corresponding parts. Agent Masuo Oiwa Figure 1 Figure 2

Claims (1)

[Claims] (1) An ion source chamber having a window into which a reactive gas is introduced and which guides the ions of the reactive gas generated inside to the outside, with one end penetrating a part of the side wall of the ion source chamber. a cathode cover provided with an opening opening into the ion source chamber at its end and configured to allow introduction of an inert gas therein; a cathode cover housed within the cathode cover; lanthanum hexaboride cathode, which emits thermionic electrons that activate the inert gas;
The cathode cover is provided in the ion source chamber so as to be opposed to the end of the cathode cover with a gap formed therein, and the electrons of the inert gas activated in the cathode cover are transferred to the opening. an electron extraction electrode that is drawn into the ion source chamber through a hole to activate the reactive gas introduced into the ion source chamber; and an electron extraction electrode that is drawn out into the ion source chamber through the hole and activates the reactive gas introduced into the ion source chamber; 1. A reactive ion beam etching apparatus comprising an accelerating electrode for accelerating gas ions, and etching a film to be etched by irradiating the accelerated ions of the reactive gas.