JPH03126225A - Dry etching apparatus - Google Patents

Abstract

PURPOSE:To obtain a dry etching apparatus by which high homogenity is maintained all the time by arranging a ring-shaped permanent magnet so that the position of the magnet can be adjusted in the vertical direction, and continuously changing the relative position of the ring-shaped permanent magnet and a sample. CONSTITUTION:A ring-shaped permanent magnet 8 is provided at the outside of a vacuum container 21 and can be rotated in the circumferential direction. The magnet is mounted on a driving and position-adjusting stage 30 whose relative height with respect to a wafer 25 can be adjusted. Under this state, the magnet is attached horizontally with respect to the wafer 25. The attaching position is determined so that the height, at which the upper surface of the ring-shaped permanent magnet 8 viewed from the horizontal direction agrees with at least the surface of the wafer 25, is made to be a starting point. The height can be adjusted in the down-ward direction. At first, the height of the ring-shaped permanent magnet 8 is adjusted so that a parallel magnetic field region 16 is positioned directly on the wafer 25. Then, etching is performed. The distribution of the etching at this time is examined. The ring-shaped permanent magnet 8 is moved to a position where the magnetic field distribution becomes the etching distribution so as to offset the above described etching distribution. The etching is performed again, and excellent homogenity is obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a plasma dry etching device used in the manufacture of semiconductor integrated circuits, and particularly relates to a magnetron etching device that applies a magnetic field to a plasma radiation region. .

(Conventional technology) Magnetron etching equipment is capable of etching with higher accuracy, less damage, and higher speed than conventional dry etching equipment, and is extremely effective for the mass production of semiconductor integrated circuits, which will continue to become even finer in the future. It is a great device. However, in the magnetron etching apparatus, it is very difficult to obtain high uniformity because the distribution of magnetic lines of force of the magnetic field applied to the plasma discharge region directly affects the uniformity of etching.

Magnetron etching devices proposed to solve these problems are described in, for example, Japanese Patent Laid-Open No. 63-99530 and Japanese Patent Laid-Open No. 63-186429.

FIG. 5 is a sectional view of such a conventional magnetron etching device.

In this figure, 1 is a vacuum container, 2 is an etching gas introduction pipe, 3 is an exhaust pipe, 4 is a cathode electrode, 5 is a wafer to be etched, and 6 is an RF (Radio).

7 is a magnetron discharge, 8 is a ring-shaped permanent magnet, 9 is a main magnetic pole layer, 10 is an auxiliary magnetic pole layer, 11 is an anode electrode, B is a magnetic field, and E is an alternating electric field.

As shown in FIGS. 2 and 3 (details will be described later), the ring-shaped permanent magnet 8 constituting the magnetic field generator is divided into two parts by diameter, with an N pole 12 in one half and an S pole in the other half. pole 1
4 is magnetized to form a main magnetic pole layer 9 on the outer circumference of the ring, and on the opposite side of these N poles 12 and 5i14, that is, on the inner circumference of the ring, 5i13 and N pole 15, which are opposite to the main magnetic pole layer 9, are formed. An auxiliary magnetic pole layer lO is formed. Such a magnetic pole structure is
It can be formed spontaneously by using a permanent magnet material with a high coercive force of 1000 Oe and magnetizing the ring parallel to the radial direction. Further, in the ring-shaped permanent magnet 8, uniform lines of magnetic force 18 are formed in the hollow part of the ring due to the above-described magnetic pole structure. In particular, the lines of magnetic force 18 seen in the cross-sectional direction have an appropriate thickness including the hollow portion and are completely parallel.

Therefore, a cathode electrode 4 and an anode electrode 11 are disposed facing each other inside a vacuum container 1 for processing a wafer to be etched (hereinafter simply referred to as a wafer) 5, and an RF power source 6 is connected to the cathode electrode 4. , the anode electrode 11 is grounded. The wafer 5 is placed horizontally on the cathode electrode 4, and the ring-shaped permanent magnet 8 is attached to the outside of the vacuum container 1 so that the parallel magnetic field regions are horizontal just above the wafer 5 when viewed from the cross-sectional direction. , and is configured to be able to automatically rotate in the circumferential direction. Here, etching gas is introduced into the vacuum vessel 1 through the introduction pipe 2, and is evacuated at an appropriate flow rate through the exhaust pipe 3 using a vacuum pump (not shown) to appropriately adjust the gas pressure within the vacuum vessel 1. Meanwhile, when a voltage of 13.56 MHz is applied to the cathode electrode 4 from the RF power source 6, a magnetron discharge 7 is generated due to the action of an alternating current electric field E generated perpendicularly to the surface of the cathode electrode 4 and a magnetic field B orthogonal thereto. The plasma intensity of the magnetron discharge 7 portion is equal to the alternating current electric field E
and the strength of the magnetic field B. In this case, since the intensity distributions of the AC electric field E and the magnetic field B are both approximately uniform on the wafer 5, the plasma intensity is also approximately uniform. In addition, the ionization rate of plasma caused by magnetron discharge is more than two orders of magnitude higher than that of plasma caused by ordinary RF discharge.In other words, with this magnetron etching device, it is faster than conventional etching by more than one order of magnitude, and it has not been a problem since then. The problem of poor etching uniformity has been resolved, and highly uniform etching is now possible.

(Problems to be Solved by the Invention) However, the high uniformity obtained with the magnetron etching apparatus having the above configuration is not universally achieved under any etching conditions. For example, when etching is dominated by reactive active species with relatively long lifetimes, etching uniformity strongly depends on the flow and retention of the reactive gas, or when the applied RF power is increased, the wafer or cathode electrode The electric field is concentrated around the
A phenomenon occurs in which the uniformity is strongly dependent on this, and in some cases, excellent uniformity cannot be obtained even with the magnetron etching device.

The present invention makes it possible to continuously change the relative positions of the wafer, the cathode electrode, and the permanent magnet in the vertical direction in order to solve the above-mentioned deterioration in etching uniformity that depends on the etching conditions. It is an object of the present invention to provide a dry etching device that always maintains high uniformity under any conditions.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a ring-shaped permanent magnet in a space above a sample mounted on a cathode electrode and installed in a vacuum container. A dry etching device comprising means for applying a horizontally rotating magnetic field and means for supplying an RF voltage to the cathode electrode, and generating a magnetron discharge by the action of the RF voltage and the rotating magnetic field, wherein the ring-shaped permanent The magnets are arranged so that their positions can be adjusted in the vertical direction, and the relative position between the ring-shaped permanent magnet and the sample is continuously changed.

(Function) According to the present invention, by configuring as described above,
In a magnetron etching apparatus, the relative position of a rotating ring-shaped permanent magnet and a wafer can be continuously changed in the vertical direction.

Therefore, the position of the ring-shaped permanent magnet is adjusted so that the tendency of change in the etching speed distribution within the wafer plane due to a change in etching conditions and the tendency of change in the speed distribution due to a change in the position of the ring-shaped permanent magnet are offset. However, high uniformity of etching can always be maintained under any etching conditions.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a magnetron etching device showing an embodiment of the present invention, FIG. 2 is a plan view of a ring-shaped permanent magnet that obtains a magnetic field applied to the plasma discharge region of the magnetron etching device, and FIG. It is a sectional view taken along the line AA in the figure.

In FIG. 1, 8 is a ring-shaped permanent magnet, 21 is a vacuum container, 22 is an etching gas introduction pipe, 23 is an exhaust pipe, 2
4 is a cathode electrode, 25 is a wafer to be etched, 2
6 is an RF (high frequency) power supply, 27 is a magnetron discharge, 2
30 is a drive and position adjustment pedestal for the ring-shaped permanent magnet 8, B is a magnetic field, and E is an alternating current electric field.

Here, the ring-shaped permanent magnet 8 that generates the magnetic field B is
As shown in the figures and FIG. 3, the magnet is magnetized so that one half of the diametrically divided portion forms a north pole and the other half forms a south pole. Here, the material of the ring-shaped permanent magnet 8 is Aj2. Ni, Co.

It is necessary to use an alnico magnet or the like whose main components are Fe or Cu, and to have a high coercive force of 1000 Oe or more. In other words, by using a ring-shaped magnet with a high coercive force, the divergence of the direction of the magnetic domain near the end faces of the magnet's poles and the magnet surface parallel to the magnetic flux is suppressed, and the inner periphery of the ring appears to have an outer periphery. It appears that a weak opposite pole with a different polarity has been formed.

This apparent dividing boundary (strictly speaking, it is not distinguished by a fixed position) is shown by a broken line in the figure, where:
The main magnetic pole layer 9 is composed of N poles 12.5i14 and 5i13
, N pole 15 constitute an auxiliary magnetic pole layer 10. In a ring-shaped permanent magnet having such a magnetic pole structure, the distribution of magnetic lines of force 18 is as shown in the figure. In particular, the distribution of magnetic lines of force seen from the cross-sectional direction is characteristic, and the lines of magnetic force 18 connecting both poles of the main magnetic pole layer 9 are
does not simply diverge in the area near the magnet;
Due to the action of the auxiliary magnetic pole layer IO in the inner circumferential portion, it is drawn into the hollow portion. Due to this action, a horizontally uniform and completely parallel magnetic field region 16 can be obtained within a region of appropriate thickness including the hollow portion of the ring-shaped permanent magnet 8. In the space further outside the parallel magnetic field region 16, lines of magnetic force 18
A diverging magnetic field region 17 is obtained due to the repulsion of .

In magnetron etching, the wafer 25 to be etched is fixed in the parallel magnetic field region 16 parallel to the lines of magnetic force 18, and the ring-shaped permanent magnet 8 is rotated in the circumferential direction. On the other hand, when the wafer 25 to be etched is placed horizontally in the diverging magnetic field region 17 and the ring-shaped permanent magnet 8 is rotated, a unique etching speed distribution is created within the wafer plane. Become. The present invention attempts to achieve high uniformity by inversely utilizing this unique distribution, and the details will be shown in the experimental results described later.

As shown in FIG. 1, a vacuum container 2 for processing a wafer 25
1, a cathode electrode 24 and an anode electrode 28 are arranged facing each other, and an RF power source 26 is connected to the cathode electrode 24.
The anode electrode 28 is grounded. Further, the wafer 25 is placed horizontally on the cathode electrode 24.

On the other hand, the ring-shaped permanent magnet 8 is provided outside the vacuum container 21, rotates in the circumferential direction, and is placed on a drive and position adjustment pedestal 30 whose height relative to the wafer 25 can be adjusted. Then, it is attached horizontally to the wafer 25. The mounting position is ring-shaped permanent magnet 8 when viewed from the horizontal direction.
Starting from a height at which the upper surface of the wafer 25 is at least flush with the surface of the wafer 25, the height can be adjusted downward from this point.

At this time, the height 1i1 node range allows both the parallel magnetic field region 16 and the diverging magnetic field region 17 in FIG. 3 to be moved and adjusted to the surface of the wafer 25.

Using the apparatus configured as described above, etching gas is introduced from the inlet pipe 22, and is evacuated from the exhaust pipe 23 at an appropriate flow rate using a vacuum pump, while the gas pressure inside the vacuum container 21 is adjusted appropriately. , RF power supply 26 to cathode 1 and 24
When a power of 13.56 MHz is applied, a magnetron discharge 27 is generated due to the action of an alternating current electric field E generated perpendicularly on the surface of the cathode electrode 24 and a magnetic field B perpendicular to the alternating current electric field E. The plasma intensity of this magnetron discharge 27 is:
Since it is proportional to the strength of the AC electric field E and the magnetic field B, if the height position of the ring-shaped permanent magnet 8 is appropriately adjusted and the shape of the magnetic field distribution located directly above the wafer 25 is selected, etching with an appropriate distribution can be achieved. becomes possible.

In actual etching, first, the height of the ring-shaped permanent magnet 8 is adjusted so that the parallel magnetic field region 16 (see FIG. 3) is located directly above the wafer 25, and etching is performed.
After examining the etching distribution at this time, the ring-shaped permanent magnet 8 is moved to a position where a magnetic field distribution with an etching distribution that cancels out the etching distribution is obtained, and etching is performed again to obtain excellent uniformity. can get.

Next, the present invention will be explained in detail while showing experimental results.

FIG. 6 shows the etching rate distribution within the wafer surface when a wafer is etched using a normal dry etching apparatus in which there is no effect of the magnetic field B.

Two types of parallel plate type reactive ion etching equipment are available as dry etching equipment, in which the symmetry of equipment elements such as electrode shape, wafer placement position, etching gas introduction route, exhaust route, etc. is well considered.1. Using apparatus ■, the wafer is
N, S++ polycrystalline 5i (Poly-3i) with resist deposited thereon was used.

In Fig. 6, A is the A2 etching distribution (Sicj2
a/Cf, , equipment 1), B is the stz etching distribution (CFa, equipment 1t), C is the polycrystalline St etching distribution (C1t, equipment 1), D is the etching rate of the resist etching distribution (0□, equipment ■) It shows.

As is clear from this figure, under conditions where etching uniformity is not particularly optimized, there is a tendency for the etching rate around the wafer to become faster, except for the case of resist D. This tendency was also the same in the magnetron etching apparatus shown in the conventional example.

FIG. 7 shows the above-mentioned device n, in which a ring-shaped permanent magnet is attached outside the vacuum container so that its relative position with respect to the wafer is variable, and the ring-shaped permanent magnet is not rotated.
It shows the relationship between the relative position of the upper surface of a wafer ring-shaped permanent magnet and the etching distribution when resist is etched using gas.

Here, the 8%g curve shows characteristics that depend on the relative height of the wafer surface as seen from the top surface of the ring-shaped permanent magnet.
The height of the wafer surface as seen from the top of the ring-shaped permanent magnet is
In case of a, it is Oam+, in case of b, it is 14m, in case of c, it is 34M, in case of d, it is 54m, in case of e, 74-1f is 94M, and in case of H is 124mm.

As is clear from this figure, excellent uniformity was obtained when the relative position of the top surface of the wafer ring permanent magnet was 0, but as the relative position was increased, the etching rate at the center of the wafer tended to increase. Can be seen. Therefore, it is easy to imagine that the etching distribution can be corrected by adjusting the position of the ring-shaped permanent magnet under etching conditions that increase the etching rate around the wafer.

FIG. 4 shows the etching distribution when magnetron etching is performed on the polycrystalline St shown in FIG. 6 using a ring-shaped permanent magnet and optimizing the relative position with respect to the wafer.

As is clear from this figure, in this example, the tendency of the etching rate to increase at the outer periphery of the wafer shown in FIG. 6 is corrected, and excellent uniformity is obtained.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) As described above in detail, according to the present invention, in a magnetron etching apparatus using a rotating ring-shaped permanent magnet, by adjusting the position of the permanent magnet in the vertical direction, the wafer and the ring The magnetic field distribution directly above the wafer can be selected by continuously changing the relative position with the shaped permanent magnet. Therefore, it is possible to arbitrarily control the etching distribution within the wafer surface, and regardless of the material to be etched and the etching conditions, the etching distribution can be controlled each time, and excellent etching uniformity can always be obtained.

In addition, from the perspective of being able to control the relative position between the ring-shaped permanent magnet and the wafer, changing the magnetic field distribution near the wafer, and freely controlling the spatial plasma density, plasma deposited silane, magnetron sputtering, etc. It can be applied to many semiconductor manufacturing devices that use low-temperature plasma.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a magnetron etching device showing an embodiment of the present invention, FIG. 2 is a plan view of a ring-shaped permanent magnet that obtains a magnetic field applied to the plasma discharge region of the magnetron etching device, and FIG. 4 is a cross-sectional view taken along line A-A in the figure, FIG. 4 is a polycrystalline silicon etching rate characteristic diagram with the ring-shaped permanent magnet obtained by applying the magnetron etching apparatus of the present invention and the wafer position optimized, and FIG. 6 is a cross-sectional view of a conventional magnetron etching device, FIG. 6 is an etching speed characteristic diagram using a conventional dry etching device that does not apply a magnetic field, and FIG. 7 is a resist etching speed characteristic diagram depending on the relative position of the ring-shaped permanent magnet to the wafer. It is. 8... Ring-shaped permanent magnet, 21... Vacuum container, 22
...Etching gas introduction pipe, 23...Exhaust pipe, 2
4... Cathode electrode, 25... Wafer to be etched, 26... RF (high frequency) power supply, 27... Magnetron discharge, 28... Anode electrode, 30... Drive of ring-shaped permanent magnet Position adjustment pedestal, B...magnetic field, E...
...AC electric field.

Claims (1)

[Claims] Means for applying a rotating magnetic field horizontally to the sample using a ring-shaped permanent magnet in a space above the sample mounted on the cathode electrode and placed in a vacuum container; and a means for supplying a voltage, the dry etching apparatus generating a magnetron discharge by the action of the RF voltage and the rotating magnetic field, wherein the ring-shaped permanent magnet is arranged so as to be adjustable in position in a direction perpendicular to the sample. A dry etching apparatus characterized in that the relative position between the ring-shaped permanent magnet and the sample is continuously changed.