JPS58225637A - Ion beam apparatus - Google Patents

Abstract

PURPOSE:To realize uniform etching to the entire part of material to be etched by forming plasma with a high frequency power source and extracting an ion current in such a direction as orthogonally crossing with the electrode provided in a plane. CONSTITUTION:Reservoirs 1 and 2 are exhausted to a high degree of vacuum with a vacuum pump 16. Next, a high frequency power is applied across electrodes 7 and 8 from a high frequency power source 13 and discharge gas is supplied from a discharge gas supply hole 17. Thereby, if discharge occurs in the space formed between the electrodes 7 and 8, the ionization effect of gas is further enhanced by the magnetic field generated by a field generating means 12 and stable discharge can be maintained. Charged particles are extracted by control electrodes 10 and 11 from the plasma generated in this space 9 in the direction almost orthogonal to the surface direction of electrodes 7, 8 and these are irradiated to a material 3 to be etched. Thereby, the material 3 is etched. Accordingly, the ion beam can be irradiated uniformly to the etching surface and thereby uniform etching can be realized.

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.

For this etching, ion beam etching (or ion milling, hereinafter referred to as IM) is widely used as a dry etching method. This ion beam etching is classified into two types depending on the type of gas used. That is, one is ion beam etching using an inert gas such as Ar + Her Ne, and the other is CF etching.
4. Ion beam etching that uses a highly reactive gas such as CCl2.0□ is called active ion beam etching (
or reactive ion milling) (hereinafter referred to as RI
(abbreviated as M).

In the case of the IM method, the Kaufman type is generally used.

A Kaufmann-type ion source heats a filament and accelerates the hot electrons emitted from it using a direct current electric field, and increases the probability of collision between electrons and gas molecules by applying a magnetic field to generate a glow discharge (or plasma). It is something that makes you Such an ion source is suitable when using an inert gas, but since an active gas is used in the above-mentioned RIM method, the discharge of the active gas causes rapid deterioration of the filament, and the discharge may cause permanent damage. It is not stable and cannot withstand long-term use. However, the above R
The IM method 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, differences in etching speed (referred to as etching selectivity) depending on the material of the object to be etched can be obtained by selecting the discharge gas, making it suitable for selective etching. It has many advantages. Furthermore, in this RIM method,
In addition to the scattering effect caused by ion collisions, the chemical reaction of activated ions and activated neutral radical molecules removes the etched material as a volatile reactant, so that the etched material can be etched again. No problem of sticking to surfaces. Furthermore, in the RIM method, compared to the IM method using an inert gas, the charge-up phenomenon due to secondary electron emission from the etched surface tends to occur less easily, and like the IM method, the kinetic energy of ions incident on the etched surface is less likely to occur. Furthermore, since the direction of incidence can be controlled with a high degree of freedom, the etching shape of the object to be etched can be controlled. Furthermore, RIM
This method can also use chemically active ions and neutral radicals for etching, so it is best when using only an inert gas.
This method has the advantage that the etching rate of the material to be etched can be increased or decreased, making it easy to control.

As mentioned above, the RIM method has many advantages.
It is something that you have. However, as described above, since a reactive gas is used in this case, conventionally a problem arises in emitting a stable ion beam for a long time. On the other hand, in this RIM method, various methods for emitting the ion beam have been studied.
There is an invention described in No. 3577 (Japanese Patent Publication No. 57-2788).

The present invention provides an ion beam device that can perform the above-mentioned RIM method, for example, and can perform etching stably and uniformly over a wide area.1. .

Prior to the description of 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) When the gas pressure is 10-5 to 10-'
rr), that is, when using ion milling, the ions are extracted from the discharge and etched, but in order to increase the etching efficiency, the mean free path of the gas molecules and ions must be several times larger. Since a gas pressure of about 100 to 100 liters is required, this gas pressure must be selected.

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

(3) When the object to be etched is, for example, a semiconductor wafer, for the sake of mass production, it is possible to perform uniform etching over the entire surface of the wafer or on multiple wafers at once. In addition, 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 (5).

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 used.
and a transparent container (2) made of quartz glass, for example, below which constitutes a high-frequency excited ion source.
be placed airtight. The object to be etched (3) is placed in the container (1).
) For example, a support stand that supports a silicon wafer (3) (
4) Place. The support base (4) is provided with a cooling means (not shown) in which cooling water is circulated so as to maintain a cooled state. Under this support table (4) is a rotary table (5) which is cooled by this and is configured to rotate about the d-axis 0-σ.
Further, an auxiliary table (6) is provided which is adapted to rotate with respect to the rotary table (5), and an object to be etched (3), for example, a silicon wafer, is attached to this auxiliary table (6). ) can be done.

Inside the ion source container (2), for example, a plate-shaped first plate is provided on the bottom surface of the container (2), facing the surface on which the object to be etched (3) is arranged.
electrodes (7) are 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 this first electrode (7) and the object to be etched (3), an electrode is formed that faces parallel to the first electrode (7) over the entire area of the entire arrangement surface of the object to be etched (3). A second electrode (8) consisting of an electrode plate 9 having a mesh shape or having a plurality of through holes through which ions can pass is arranged. There is a required space (9) between these electrodes (7) and '(8).
) is formed.

Further, a mesh-like or a large number of through-holes which similarly transmit ions are bored between the second electrode (8) and the entire arrangement of the object to be etched (3) in parallel with the second electrode (8). Control electrodes such as metal plates, for example, first and second control electrodes 01, which are arranged parallel to each other in the figure, are arranged.

Further, on the outside of the ion source container (2), a magnetic field generating means a'4, such as a permanent magnet or an electromagnet, is arranged in the space (9) between the first and second electrodes (7) and the second electrode (8). The ion source container (2) forms a unidirectional magnetic field extending in the direction of or across the axis of the ion source container (2). This magnetic field is preferably an alternating magnetic field whose direction is reversed.

Furthermore, means for applying a high frequency voltage is connected between the first and second electrodes (7) and (8). In the figure, the α force is a high frequency power source, and the α force is a matching device.
This is a case where a fixed, for example, ground potential is applied to the first electrode (7) so as to connect the power. Although the figure shows a case where a high frequency power source is connected to the second electrode (8), the second electrode (8) is set to a fixed voltage and a high frequency power source is connected to the first electrode (7). You can also do something like this.

Further, the first control electrode has a ground potential, for example,
A positive or negative DC control voltage with respect to the first control electrode is applied to the second control electrode a9.

Also, containers (1) and (2) contain, for example, open-close pulp α!
A vacuum pump is connected via 1. Further, α power is a gas supply port that feeds gas into the ion source container (2), and 6 o'clock indicates a discharge gas supply source connected to the discharge gas supply port 0η. The gas used here is a reactive gas, for example CHF3.
rcF 4 +C2F6, CIFB +C4FB,
or ccz4゜CxCtyF3(x=1.21y-1
-6+s=1-6)+8F6*81F4 or other halodane compound gas, or Ar, H@.

Inert gases such as N2 and other gases such as N2,0□ may be used alone or as a mixture thereof. In addition, the α Samurai is a mass flow controller installed between the discharge gas supply port α force and the discharge gas source (1. Indicates opening/closing or adjusting pulp.

To perform ion beam etching with 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'' Torr, using a vacuum pump (g), and then the first and second electrodes (7) and (8) In the meantime, a high frequency power of, for example, 13.56 MHz is applied from a high frequency power source 0, and a matching device α◆ performs a matching adjustment so that the reflected power is minimized. Thereafter, the discharge gas (9) is supplied through the supply port 025, and the gas pressure is momentarily set to a high gas pressure of, for example, 10-5 Torr so that the discharge can easily start. In order to increase this instantaneous gas pressure, for example, discharge gas is stored in advance in the aforementioned gas reservoir (), and when discharge starts, the valve () is opened and the discharge gas stored in () is introduced into this gas reservoir. In particular, the first and second electrodes (
Increase the discharge gas pressure between 7) and (8).

When doing this, the discharge can be easily started due to the relatively high gas pressure. After such discharge is started, a gas flow rate automatically controlled by the mass flow controller α is again introduced into the reaction vessel, and the degree of vacuum is set to about 10 −5 to 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 matching of the incidence of high-frequency power is slightly shifted, but since the discharge is continued, the matching can be readjusted. In this way, a discharge occurs in the space (9) between the first and second electric poles (10) and the poles (7) and (8). The ionization effect is enhanced and stable discharge is maintained.

1 Charged particles are transferred from the plasma generated between the first and second parallel electrodes to the control electrodes αQ and H01 in a direction substantially perpendicular to the surface direction of these electrodes (7) and (8).
and irradiate it onto the object to be etched (3). In this way, the object to be etched (3) is etched. In this case, the amount of the ion beam can be controlled by the voltages applied to the first and second control electrodes 01 and 01 and their polarities.

As mentioned above, when using the apparatus of the present invention, a high frequency power source is used to form plasma and a flow of ions is deposited, so that stable ion supply, that is, supply of an ion flow can be performed over a long period of time. . In addition, especially in the device of the present invention, as mentioned above, the ion flow is extracted in a direction perpendicular to the planarly arranged electrode (8), 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 emitted. 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 for the material to be etched can be selected by selecting the gas.
5102, such as when the S1 wafer has two coatings.
It is possible to create a difference in the etching speed between the wafer and 81, and to have selectivity in the etching of the two.

This etching can have both the effects of sputtering and chemical etching.
The etching speed of to2 can be increased. Furthermore, there is no fear of the etched 5to2 being reattached. Furthermore, by controlling the ion flow control electrode (6) and Al, the etching surface is coated with Teno J? Processing such as adding .

In the example explained in FIG. 1, the first and second discharge electrodes (7) and (8) are parallel plate-shaped electrodes, but for example, as shown in FIG. The electrode, for example, the first electrode (7), may have one or more coiled electrode configurations. 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 orthogonal thereto.

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 α and the gas reservoir are placed in parallel with the gas supply source α, and the mass flow controller is placed downstream of the mass flow controller. (to the pulp) and mass flow controller (
(2) to set the gas pressure in the container (2) to the low gas pressure desired for etching, and open the valve (2) at a predetermined time to increase the supply of discharge gas from the gas reservoir (2). You can also do that. Figure 4 shows the time relationship in the supply of the amount of discharge gas when using the device explained in Figure 1, and Figure 5 shows the time relationship in the gas supply in the example of Figure 3. .

In addition, each electrode, for example, in the example of FIG. 1, electrodes (7) (8)
) (At least the surface of each of 10 (1) facing the discharge space (9) is coated with a protective film, such as Teflon (trade name), to avoid damage to the electrodes due to the impact of the ion flow. Alternatively, in the example of FIG. 2, a similar Teflon protective coating can be applied to the surface of the coiled electrode.

(14) Although the above example is applied to etching using an ion beam, the apparatus of the present invention can also be used for ion beam deposition depending on the selection of the gas type.

[Brief explanation of the drawing]

FIG. 1 is a line 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 the same. It is a curve diagram showing a gas flow rate mode of a 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 an object to be etched, (7)
) and (8) are first and second electrodes, (t) and ← are control electrodes, a'3 is a high frequency power source, 0'4 is a magnetic field generating means, and ii) is a discharge gas supply source. (15) Procedural amendment dated 10/22/1980 Patent Application No. 107794 2, Title of invention: Ion beam device 3, Relationship to the person making the amendment case: Patent applicant's representative enforcement officer, Nori Ohga J, 1t . 4. Agent 6. Number of inventions increased by amendment 7. Subject of amendment Detailed explanation of the invention in the specification, column 9. 8. Contents of amendment (1) In the specification, page 8, lines 4-5, "This magnetic field is...desirable." is deleted. (2) Ibid., page 13, line 17, “You can choose.” Next to [
Further, the coiled electrode can be provided around the container (2) so as to be contained therein. ” to join. (3) Same, p. 14, line 17, ``For example, Teflon'' is corrected to ``For example, quartz, Teflon''. (4) Same, @ p. 15, after the third line ``Deposition'', add [ and high vacuum plasma CVD J. Above 1

Claims (1)

[Claims] 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 electrodes; and means for introducing gas into the space; the ions of the gas caused by plasma discharge are guided through the second electrode in a direction perpendicular to the second electrode, and the surface of the sample is An ion beam device that irradiates