JPH0481325B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In manufacturing various devices including semiconductor devices, etching operations such as drilling and removing various materials such as semiconductors, magnetic materials, and insulators are often performed.

Ion beam etching (or ion milling, hereinafter abbreviated as IM) is widely used for this etching, particularly as dry etching. This ion beam etching is classified into two types depending on the type of gas used. That is, one of them is Ar,
Ion beam etching uses inert gases such as He and Ne; other methods include CF ₄ , CCl ₄ , O ₂
Ion beam etching that uses a highly reactive gas such as ion beam etching is called reactive ion beam etching (or reactive ion milling) (hereinafter abbreviated as RIM). .

When using the IM method, the Kaufmann type is generally used. A Kaufmann-type ion source heats a filament and accelerates the hot electrons emitted from the filament using a DC electric field, and increases the probability of collision between electrons and gas molecules by applying a magnetic field, creating a glow discharge (or plasma). It is something that generates (call). Such an ion source is suitable when using an inert gas, but since an active gas is used in the RIM method mentioned above, the filament is rapidly deteriorated due to the discharge of the active gas, and the discharge is unstable and cannot withstand long-term use. However, the RIM method described above has many advantages over the IM method described above. That is, in the case of this RIM method, since active ions with high reactivity are used, etching rate differences (referred to as etching selectivity) depending on the material of the object to be etched can be obtained by selecting the discharge gas, resulting in selective etching. It has the advantage of being suitable for Furthermore, in this RIM method, in addition to the sputtering effect caused by ion collisions, the etched material is removed as a volatile reactant by a chemical reaction between activated ions and activated neutral radical molecules. There is no problem that the etching material will adhere to the surface to be etched again. Furthermore, the RIM method tends to be less likely to cause a charge-up phenomenon due to secondary electron emission from the surface to be etched than the IM method using an inert gas, and does not require much neutralization of the beam by a so-called neutralizer. Yet again
In the case of the RIM method, as with the IM method using an inert gas, the kinetic energy and direction of incidence of ions incident on the surface to be etched can be controlled with a high degree of freedom, making it possible to control the etched shape of the object to be etched. It has the advantage of Yet again
Since the RIM method can also use chemically active ions and neutral radicals for etching, it has advantages such as increasing or decreasing the etching rate of the material to be etched compared to the case of using an inert gas alone, and making it easier to control. has.

As mentioned above, the RIM method has many advantages. However, as described above, since a reactive gas is used in this case, conventionally a problem arises in extracting a stable ion beam for a long time. On the other hand, various methods for extracting the ion beam in this RIM method have been studied, for example, Japanese Patent Application Laid-Open No. 56-3577 (Japanese Patent Publication No. 56-3577).
57-2788).

The present invention provides an ion beam apparatus which can perform the above-mentioned RIM method, and can perform etching stably and uniformly over a wide area, for example.

Prior to explaining the present invention, in order to facilitate understanding of the present invention, conditions required for an ion source in the RIM method will be further listed.

(1) In the case of discharging at a gas pressure of 10 ^-5 to ^{10 -3} Torr, that is, in the case of ion milling, the ions are extracted from the discharge and etching is performed, but the etching efficiency is In order to increase the pressure, the mean free path of gas molecules and ions must be on the order of several centimeters to several tens of centimeters, so selection of this gas pressure is required.

(2) In addition, stable discharge can be maintained for a long period of time regardless of the use of this reactive gas.

(3) When the object to be etched is, for example, a semiconductor wafer, in order to enable uniform etching over the entire surface of the wafer or on multiple wafers at once for the sake of mass productivity, it is necessary to The etching area requires an ion beam with a large diameter, at least the diameter of the wafer or larger.

(4) It is desirable to be able to extract the ion beam from the discharge and control the energy of the ions and electrons.

In the apparatus of the present invention, it is possible to obtain an ion flow that satisfies all of these conditions (1) to (4).

An example of an etching apparatus according to the present invention will be explained with reference to FIG.

In this example, a closed container 1 made of, for example, quartz glass is provided, and a transparent container 2, also made of, for example, quartz glass, which constitutes a high frequency excitation type ion source, is arranged airtightly below it. A support 4 for supporting an object 3 to be etched, such as a silicon wafer 3, is arranged in the container 1. The support stand 4 is provided with a cooling means (not shown) in which cooling water is circulated, for example, to maintain a cooled state. A rotary table 5 is provided below the support table 4 and is cooled by the support table 4 and rotates about the axis O-O', for example.
Furthermore, an auxiliary stand 6 is provided which is adapted to rotate with respect to the turntable 5, and to which the pair 3 to be etched, for example a silicon wafer, is attached.

Inside the ion source container 2, a plate-shaped first electrode 7 is arranged, for example, on the bottom surface of the container 2, facing the surface on which the object to be etched 3 is arranged. The first electrodes 7 are arranged over a wide area so as to face each other over the entire area of the object to be etched 3. Further, between the first electrode 7 and the object to be etched 3, there is provided an electrode which faces parallel to the first electrode 7 over the entire area of the entire arrangement of the object to be etched 3 so that ions can pass therethrough. A second electrode 8 made of a mesh-like electrode plate or an electrode plate having a plurality of through holes is arranged. There is a required space 9 between these electrodes 7 and 8.
is formed.

Furthermore, a control device comprising a metal plate in which a mesh-like or a large number of through holes are perforated parallel to the second electrode 8 and which similarly transmit ions is provided between the second electrode 8 and the entire arrangement of the object to be etched 3. Electrodes, for example first and second control electrodes 10 and 11, which in the figure are arranged parallel to each other, are arranged.

Also, on the outside of the ion source container 2, first and second
A magnetic field generating means 12, such as a permanent magnet or an electromagnet, is arranged in the space 9 between the electrodes 7 and 8, and forms a magnetic field oriented in the direction of or across the axis of the ion source container 2.

Moreover, means for applying a high frequency voltage is connected between the first and second electrodes 7 and 8. In the figure,
13 is a high frequency power supply, 14 is a matching device,
In the figure, a high frequency power source 13 of, for example, 13.56 MHz is connected to the second electrode 8 made of a second mesh-like or porous electrode plate, and a fixed, for example, ground potential is applied to the first electrode 7. This is the case. Although the figure shows a case where a high frequency power source is connected to the second electrode 8, it is also possible to set the second electrode 8 at a fixed voltage and connect a high frequency power source to the first electrode 7. .

Further, to the first control electrode 10, for example, a ground potential is applied to the second control electrode 11, and a positive or negative DC control voltage is applied to the first control electrode.

In addition, for example, an on-off valve 15 is provided in the containers 1 and 2.
A vacuum pump is connected via. Further, 17 is a gas supply port for feeding gas into the ion source container 2;
18 indicates a discharge gas supply source connected to the discharge gas supply port 17. The gases used here are reactive gases, such as CHF ₃ , CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ , or CCl ₄ , C _x Cl _y F _z (z=1, 2, y =1~6,z
= 1 to 6), halogen gas compound gas such as SF ₆ and SiF ₄ , or inert gas such as Ar, He, N _2, etc., and other gases such as H ₂ and O ₂ , either alone or as a mixture thereof. Can be used. Note that 19 is a mass flow controller provided between the discharge gas supply port 17 and the discharge gas source 18, and a gas reservoir 20, for example, is disposed at the subsequent stage. Further, 21 and 22 indicate opening/closing or adjustment bubbles, respectively.

To perform ion beam etching using this device, first, the insides of the containers 1 and 2 are evacuated to a high degree of vacuum, for example, 10 ^-7 to 10 ^-6 Torr, using the vacuum pump 16, and then the first and second A high frequency power of, for example, 13.56 MHz is applied between the electrodes 7 and 8 by a high frequency power source 13, and matching adjustment is performed by an etching device 14 so that the reflected power is minimized. Thereafter, a discharge gas is supplied from the discharge gas supply port 17, and the gas pressure is instantaneously set to a high gas pressure of about 10 ^-3 Torr, for example, to facilitate the start of discharge. In order to increase this instantaneous gas pressure, for example, discharge gas is stored in advance in the gas reservoir 20 described above, and at the start of discharge, the valve 22 is opened and the discharge gas stored in this gas reservoir 20 is introduced. Then, the discharge gas pressure in the container 2, especially between the first and second electrodes 7 and 8, is increased.

When doing this, the discharge can be easily started due to the relatively high gas pressure. After such discharge has started, the gas flow rate automatically controlled by the mass flow controller 19 is again introduced into the reaction vessel, and the degree of vacuum is increased to 10 ^-5 ~
Take about 10 ^-4 . The required time is about a few seconds.
Once a discharge occurs in this manner, the discharge is sustained even at this relatively low gas pressure. At this time, the etching of the incidence of high-frequency power is slightly shifted, but since the discharge continues, the etching can be readjusted. In this way, a discharge occurs in the space 9 between the first and second electrodes 7 and 8, and at this time, the ionization effect of this gas is further enhanced by the magnetic field generated by the magnetic field generating means 12, resulting in a stable discharge. maintained.

In this way, charged particles are transferred from the plasma generated between the first and second parallel electrodes to the control electrode 10 in a direction substantially perpendicular to the surface direction of these electrodes 7 and 8.
and 11, and the object to be etched 3 is irradiated with this. In this way, the object 3 to be etched can be etched. In this case, the amount of the ion beam can be controlled by the voltages applied to the first and second control electrodes 10 and 11 and their polarities.

As described above, when using the apparatus of the present invention, a plasma is formed using a high frequency power source, and an ion flow is extracted from the plasma, so that stable ion supply, that is, supply of an ion flow can be performed for a long period of time. . In addition, especially in the device of the present invention, as described above, the ion flow is extracted in a direction perpendicular to the electrodes 8 arranged in parallel, that is, over a wide area, so that the area of the ion flow spot is sufficiently large. The object to be etched 3
For example, it is possible to uniformly irradiate a plurality of wafers with a uniform ion flow over the entire area of a semiconductor wafer, thereby making it possible to perform uniform etching in each part.

Furthermore, as in the example mentioned above, when the discharge electrodes are of a parallel plate type, equipotential surfaces are formed in parallel between the electrodes, making it possible to generate a uniform discharge over the entire surface of the electrodes. A uniform, large-diameter ion beam can be extracted. In addition, in parallel plate electrodes, the cathode drop voltage phenomenon occurring in the space near the electrodes, which is typical of capacitively coupled discharge using high frequencies, has an advantageous effect on extracting charged particles from the plasma.

Furthermore _, according to the apparatus of the present invention, _the etching characteristics of the material to be etched can be selected by selecting the gas. It is possible to create a difference in the etching speed between the two, and to have selectivity in etching between the two.

This etching can have both sputtering and chemical etching effects, and can increase the etching rate of SiO ₂ . Furthermore, there is no fear of re-deposition of etched SiO ₂ . Furthermore, an ion flow control electrode 10
By controlling steps 1 and 11, it is also possible to perform processes such as tapering the etched surface.

In the example illustrated in FIG. 1, the first and second discharge electrodes 7 and 8 are parallel plate electrodes, but as shown in FIG. The electrode 7 can also be configured to have one or more coiled electrodes. The axial direction is not limited to the ion beam extraction direction as shown in the figure, but can be arbitrarily selected such as a direction perpendicular thereto. Further, the coiled electrode can also be provided around the container 2 so as to be contained therein.

Furthermore, in the above configuration, in order to increase the gas pressure at the time of starting discharge, in the example shown in FIG. For example, as shown in FIG. 3, the mass flow controller 19 and the gas reservoir 20 are arranged in parallel with the gas supply source 18, and the valve 23 provided after the mass flow controller 19 is opened. The mass flow controller 19 sets the gas pressure in the container 2 to a low gas pressure desired for etching, and opens the valve 22 at a predetermined time to increase the supply of discharge gas from the gas reservoir 20. You can also do that. Figure 4 is the first
This figure shows the time relationship in the supply of the amount of discharge gas in the case of the apparatus described in the figure, and FIG. 5 shows the time relationship in the gas supply in the example of FIG. 3.

Further, each electrode, for example, in the example of FIG. 1, each of the electrodes 7, 8, 10, 11 has at least a discharge space
It is also possible to cover the opposite surface with a protective film such as quartz or Teflon (trade name) to avoid damage to the electrodes due to collisions of ion streams. In this example, a similar TEF protective coating can be applied to the surface of the coiled electrode.

Although the above-mentioned example is applied to etching using an ion beam, the apparatus of the present invention can also be used for ion beam deposition or high vacuum plasma CVD depending on the selection of the gas type.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of an example of an ion etching apparatus for carrying out the method of the present invention, FIGS. 2 and 3 are block diagrams of other examples of the same apparatus, and FIGS. 4 and 5 are respectively It is a curve diagram showing the gas flow rate mode of the gas supply channel. 1 is a reaction container, 2 is an ion source container, 3 is an object to be etched, 4 is a support for the object to be etched, 7 and 8 are first and second electrodes, 10 and 11 are control electrodes, 13 is a high frequency power source, 12 is a magnetic field generating means; 1
8 is a discharge gas supply source.

Claims (1)

[Claims] 1 a first electrode, a second electrode parallel to the first electrode and through which ions can pass; means for applying a high frequency voltage between the first and second electrodes; means for applying a magnetic field to the space between the two electrodes, and means for introducing gas into the space,
The ions of the gas caused by the plasma discharge are transferred to the second
An ion beam device that directs an ion beam through an electrode in a direction perpendicular to it and irradiates it onto the surface of a sample.