JPS62271432A - Dry etching apparatus - Google Patents

Abstract

PURPOSE:To improve the efficiency of electric discharge and thereby to etch at high speed a material to be etched, by disposing above or below an electrode a magnet having a gap of a closed circuit, so as to cause electrons to make a magnetron movement by perpendicularly-intersecting electromagnetic fields generated on the electrode or the magnet. CONSTITUTION:A permanent magnet 1, together with a pole piece 3 made of soft iron, generates a magnetic line of force B substantially parallel to an opposite electrode 4 made of stainless steel in a gap 2. An electric component 6 is cooled by a water cooling pipe 7. When a magnetic field exists in the gap 2, perpendicularly-intersecting-electromagnetic fields are generated in the vicinity of the gap 2 by said magnetic field and an electric field which is determined by DC self-bias and high-frequency power. Electrons near the gap 2 are subjected to a drift field, and thereby the efficiency of ionization in the vicinity 15 thereof is increased remarkably in comparison with that in the surroundings 16 thereof. Thereby the efficiency of discharge is improved, and thus a material to be etched is etched at high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the use of Si and 5i0 in the manufacturing process of integrated circuits, etc.
This invention relates to a dry etching device used for etching films such as 2 or M.

In recent years, integrated circuits have become increasingly finer, and recently, prototype LSIs with a minimum pattern size of 1 to 2 μm have been developed. Plasma etching technology is indispensable for this ultra-fine processing. The technique typically involves introducing a reactive gas such as CF4 into a reaction vessel with parallel plate electrodes, placing the sample on the electrode (cathode) upon application of radio frequency ('f) power such as 13.58 MHg, and Positive ions from the gas plasma generated by the glow discharge are accelerated by a voltage drop (V dc) generated at the cathode, impact the sample, and etch it.

This method is called reactive ion etching (RIE). However, with the glow discharge generated by applying high frequency (r) to parallel plates, for example, in RIE of 5i02 using CF4+H2 gas, the etching rate is at most 300 people/minute, and in the case of etching of 5i02 with a film thickness of 1 μm, the etching rate is 40 This extremely low etching speed is currently a serious problem in terms of mass production.
Usually, CCl4 gas is mainly used, and the etching speed is about 1000 people/min, which takes several tens of minutes for a thickness of 1 μm.
In the RIE of phosphorus-doped Po1y-St, CBrF3 gas was used, and the etching rate was 500 people/min.
Although not as high as 8 minutes and 5i02 for human thickness, these fast etches are desired as well, as they are relatively low.

In order to improve the etching speed, for example, increasing the rrm force may improve the etching speed somewhat, but the advantage of increasing the number of etching species is outweighed by the rf'
The loss due to the conversion of electric power to heat is large (and the cathode drop voltage increases, etc.), which leads to deterioration and deterioration of the photoresist that serves as an etching mask, and electrical damage to the St substrate. Considering harmful effects, it is customary to lower the RFM power as much as possible even at the expense of etching speed.The essential reason for this is that in parallel plate glow discharge, the gas ionization efficiency is at most 5. ~
It is said that it is about 3%.

On the other hand, there has recently been a report that high-speed etching of St and Al2O3 was achieved using a three-electrode device equipped with a means for supplying electrons into the plasma, but this was not possible using a hot filament. As a result, the filament is corroded by the reactive gas, which poses a problem for long-term continuous use. (N, Ie1man et al., J.
Mac, Sci.

Technol, 1? (3), 731.1 (18G
) Furthermore, a method has been proposed in which a laser is used to increase the density of etching species in plasma. (
J.I.

5telnfeld et al., J. Electroche
m, Soc, 127,514゜1980) According to this method, the density of etching species certainly increases,
Although the etching rate has also increased, the increased etching species are mainly neutral radicals, and therefore, the etching species does not result in etching with vertical walls, but is thought to include side etching, and it is thought that etching occurs with a thickness of 1 μm. The following submicron processing is unacceptable.

This situation is the same in the type in which rr is applied to the electrode on which electrical parts are placed in the reaction vessel made of insulating material and the reaction vessel support is grounded, or in the type in which a DC power source is used instead of f.

Therefore, in order to avoid the above damage and increase the etching rate, it is necessary to use as much applied force as possible to perform efficient discharge, dissociate the introduced gas, and create many reactive species.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a dry etching apparatus that is high-speed and has fewer problems such as electrical damage. .

According to the present invention, a magnetic field orthogonal to the electric field is formed between the electrodes by a permanent magnet and/or an electromagnet on or under the electrode, causing electrons to drift, promoting collisional dissociation between electrons and gas, and discharging the gas. By improving the efficiency, a large number of etching species are generated, and the material to be etched placed on the electrode or magnet, that is, on the cathode surface, is etched at high speed.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view for explaining one embodiment of the present invention. This device has a rectangular (or circular) closed gap (discharge path) (2) for one permanent magnet (1). In the figure, (1) is a permanent magnet made of, for example, cobalt samarium, and together with a pole piece (3) made of a magnetic material, here soft iron, a counter electrode (anode) made of stainless steel ( Normal earth potential (17)) (
Generate lines of magnetic force (B) that are approximately parallel to 4). A non-magnetic material can be used for the counter electrode (4). Further, the permanent magnet (1) and the pole piece (3) are connected to the anode (4).
A non-magnetic material (5), here carbon (C)vi, is provided on this electrode, which forms part of a cathode (8). Electrical components (6) are cooled by water cooling pipes (7).

The pole piece (3) is box-shaped, and the part surrounded by the gap (2) forming a closed loop on the top surface is a permanent magnet (1).
is supported by The upper surface of the permanent magnet (1) is N1
Since the lower surface is the south pole, lines of magnetic force are formed in an arch shape on the pole piece (3) following the gap (2).

First, the case where there is no magnetic field in the gap will be explained. First, open the vacuum partition valve (13), create a vacuum inside the reaction vessel (4), and then open the gas inlet (18).
After introducing a raw material gas in which ions generated by dissociation show reactivity, high frequency 1! The source ([2) is connected to the matching circuit (1
1) to the cathode (8).

Then, this high-frequency power causes a glow discharge of the introduced gas, and as described above, a cathode drop voltage (DC self-bias) is generated on the cathode, resulting in a dark area of discharge light called the cathode dark area (10). is observed.

Next, if a magnetic field exists in the gap (2), the same operation as in the case without a magnetic field is performed, but due to this magnetic field and the electric field determined by the DC self-bias and high-frequency power mentioned above, the gap (2) Since an orthogonal electromagnetic field is generated in the vicinity, electrons near the gap receive a drift electric field in the IEXIB direction and are trapped in the drift orbit near the gap. Therefore, the ionization efficiency in the vicinity (15) is
It increases significantly compared to its surroundings (16). In fact, when the inventors observed the thickness of the cathode dark area on the cathode with and without a magnetic field, they found that in the presence of a magnetic field, it was so narrow that it could hardly be observed with the naked eye. I confirmed that it would happen. This means that the plasma density is locally very high near the gap where the orthogonal electromagnetic field exists, and as a result, compared to the size of the conventional DC self-bias, a large amount of power is generated with a small value. This means that density can be added. This is the basis of high-speed etching, which is the object of the present invention. That is, for example,
CF< (Freon) was selected as the introduced gas, and silicon oxide (S i 02 ) was selected as the electrical component to be etched (including those in the process of being manufactured in this specification) (6). When the etching conditions are CF4 pressure 0, 04 Torr, power density 0.2 W/ad, and the etching material mounting table is C plate, the etchant is formed on the St substrate. A high etching speed of about 1 μm/min was achieved for the 5i02 film, and the ion damage to the St substrate was small. Also, 5
After forming a resist pattern on the i02 film and etching the 5i02 film, its profile was observed by SEM,
We realized that this is anisotropic etching with vertical etching walls.

Figure 2 shows 5i02. when N2 is added to C2F in the same apparatus. The etching characteristics of Si (a) are compared with those of a conventional example (b) where the material to be etched is placed on the cathode (8). As is clear from the figure, when 5i02 is etched using the method of the present invention, an etching speed several tens of times faster than that of the conventional example is achieved, and S
The selectivity ratio with respect to i was also 10 or more, which was comparable to the conventional value.

The present inventors also investigated the strength of the magnetic field on the sample surface as shown in FIG. 3 and the 5i02. We discovered a peculiar phenomenon between the etching rates of SL. Etching condition is 0.04 Tor
r, 250 W using C2F6 gas. The strength of the magnetic field shown in Figure 4 refers to the magnetic field above the discharge gap (2) on the surface of the C temporary (5) placed on the pole piece (3) that constitutes a part of the cathode (8) in Figure 1. was measured using a Hall sensor. 5i when the strength of the magnetic field near the gap is changed by gradually increasing the thickness h of the C plate.
As the strength of the magnetic field increases, the etching rate of 02°Sl becomes larger for 5to2 than the etching rate of St, and as a result, the ratio of the etching wall of 5i02 to Si also increases with the strength of the magnetic field. There was found. In other words, from this experimental fact, in order to achieve selective etching of 5i02 on Si, the magnetic field and strength near the gap (2) must be 350 Gauss or more, and the height from the gap surface must be 8 + I11 or less. I found out that it doesn't happen. In addition, when the etching material was placed directly on the magnetic material (3) and etched (h-0), an ultra-high etching speed of 3 μm/minute was obtained for 5to2, and it was also The selectivity ratio of C21'e
A value of about 5 to 6 is obtained with a single gas, and this value is 5i02. It was found that the value was higher than that obtained when St was etched (approximately 2).

Figure 4 uses C2F as the gas, and the pressure is 0.04T.
orr, when the thickness h) of C plate is 2 mm, rf
'The etching rate of Si, 5i02 was determined using the distance (x) from the center of the gap (2) as the horizontal axis for electric power of 250 W and 80 W. At the center of the gap, i.e. at x-0, the etching rate of 5i02 is 1μ at 250W.
m, but it is extremely low at 80W, which is probably due to the influence of deposition.

FIG. 5 also shows C2F fl, 0. (14To
rr, C When the thickness of the plate is 2 mm, r('St for the t4 force.

The etching speed of 5i02 was determined.

At 100W, the selectivity begins to increase rapidly, and the etching speed of 5i02 also increases rapidly, resulting in high speed and high selectivity.

In the 200-400W etching shown in Figure 5,
The cathode drop voltage hardly changed as the radio frequency power increased. When the cathode drop voltage Vdc at this time was plotted on the horizontal axis, a magnetron mode was observed in which the ion current sharply increased with respect to Vdc.

Vdc corresponds to DC11S pressure at DC bias.

In Figure 6, the cathode (8) is grounded, a flat plate anode is provided in the reaction vessel (4) so as to face the bow piece (3), and the DC
This is the relationship between DC voltage and ion current when the power source is connected. The C plate is removed, and C2F6 gas is used at a pressure of 2 x
10 Torr(a), 7 x 10-'Torr
(b), 3 x 10-'Torr (c), (a
), magnetron mode was observed in (b).

FIG. 7 is a view of the sample surface observed from directly above when Si is etched at around 70% H2a, where the selectivity between 5i02 and St described in FIG. 2 is best obtained. In the example shown in Figure 2, when the H2 concentration exceeds 60% in the sample etched by the conventional method, a Teflon-based organic film with C-F bonds is deposited over the entire surface of the wafer; In the embodiment of the invention, as shown in the figure, the discharge gap (19)-a, b is about 1
It was found that no organic film was deposited at all in (21)-a, b, and c of about cm, and that the deposition locations were limited to the surrounding areas (20)-a, b, and c. This organic film can be etched by placing it over the discharge gaps (19)-a, b, but especially 19-a.

When there are a plurality of plasma density maximum positions on 19-b, etching uniformity can be improved by narrowing the area so that even electrical parts between them can be etched. Taking Figure 3 as an example, the orthogonal component to the electric field is 3
Make sure it is at least 50 Gauss. This organic film deposition is
As explained in the embodiment of the invention in FIG. 5, the gap between the discharge gap (19)-a, t) is shortened;
Therefore, discharges in each discharge gap can be prevented by overlapping each other.

Further, in the apparatus shown in FIG. 1, the material to be etched is etched only in a rectangular or stripe (or ring) shape, and is not suitable for uniformly etching the entire sample.

FIG. 8 shows another embodiment of the present invention in which uniform etching can actually be performed. In the same figure, (22)-
Permanent magnets a, b, and c are arranged in a non-contact manner below a cathode (31) made of a non-magnetic material to which power from a high-frequency power source (27) is applied via a matching circuit (2B). There is. Further, (24) is a pole piece made of a magnetic material, for example soft iron, and is housed as a whole in a box-shaped container connected to a motor for scanning in one direction, for example. It has a structure that allows it to be driven and scanned as a whole. In addition, by arranging multiple permanent magnets, multiple discharge gaps (2
3) -a -f occurs, and the discharge in each discharge gap, that is, the magnetic field, is made to overlap according to the experimental facts shown in Fig. 7, and (23) between -a and f. This is so that there is a tendency for non-deposition or etching. Further, (25) is water cooling means for cooling the cathode (31). (29) is an insulating material.

The permanent magnet, pole piece, etc. that make up the lower part of the cathode described above are housed as a whole in a vacuum container (36), and are connected to the exhaust system (32) in a vacuum manner through the ventilation hole (34). There is. Moreover, (33) is a dark space shield for preventing the discharge on the cathode from entering the lower part of the cathode. With such an apparatus configuration, the magnetic field generated by the permanent magnet can be scanned over the wafer surface during etching, so that the material to be etched can be etched with good uniformity without being etched at high speed. became possible.

FIG. 9 also shows a further embodiment of the present invention having a so-called "-brush" discharge gap (38), but similar to FIG. On the other hand, it tends to be non-depositing or etching. By scanning in the same direction as in FIG. 7, uniform etching was also obtained.

FIG. 10 is an example of an application in which batch characteristics are further taken into consideration. (a) is a cross-sectional view of the device, (b) is a top view of the cathode, and (
The cross-sectional area of the permanent magnet shown in a) is indicated by X-X'. That is, by configuring the discharge gap (50) as shown in the figure below the rotary table (49) made of non-magnetic material,
During etching, the material to be etched (45
) is continuously rotated to provide an etching apparatus capable of performing batch processing at high speed and with good uniformity. In the figure, (47) is a permanent magnet, (48) is a dark space shield, (41) is a water cooling means, (3
9) is a high frequency power supply, (42) is a motor for rotation, (
44) is the exhaust system.

(48) is a gas introduction hole, (51) is a vacuum container, (52)
is an insulating material, (40) is a matching circuit, and (43) is a pulley.

As shown in the embodiments of the present invention, for example, in a parallel plate type plasma etching apparatus, a magnet having a closed circuit gap is placed above or below an electrode, and the orthogonal electromagnetic fields generated above the electrode or magnet cause etching. By moving the electron magnetron, a dry etching method and apparatus were obtained which improved the discharge efficiency and could rapidly etch the material to be etched placed on the electrode or magnet, and the productivity was greatly improved. Such dry etching methods are used for forming contact holes, patterning electrodes and wiring, and for manufacturing MOS devices and bipolar devices.

As the gas used for etching using the etching method of the present invention, gases containing fluorine such as CF are shown in the examples, but other reactive gases containing chlorine and bromine may also be used. Depending on the type of material to be processed, for example, for aluminum or aluminum alloy, CCl2°CCl2 +Cf12 gas is added,
For polycrystalline silicon molybdenum silicide etc., C
BrF3. CBrF3 +CJ2 By using CjJ2 gas, it is possible to perform selective etching at high speed and with good reliability, as in the case of 5i02.

Furthermore, although the sample was cooled together with the cathode and the permanent magnet, a liquefied gas such as Freon may be used in consideration of resist expansion caused by water cooling or alcohol cooling, or by high-speed etching.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram for explaining one embodiment of the present invention,
FIG. 2 shows 5i02. FIG. 3 is a diagram showing the etching characteristics when etching St. FIG. 3 is a diagram showing the relationship between the strength of the magnetic field and etching. FIGS. 4 to 6 are diagrams for explaining the present invention in detail. The figure is a view of the Si wafer surface when a Teflon-based organic film was deposited during the etching process shown in Figure 2.
FIG. 8 to FIG. 10 are configuration diagrams for explaining an embodiment of the pond of the present invention. In the figure, (1) (22) -a'~c, (37) (47)...
・Permanent magnet, <2) (23>-a - f, (38)
, (19)-a, b, (50)-discharge gap,
(5)...C board, (4) (3B) (51)...
Vacuum container, (3) (24)...Pole piece, (6)
(30) (45)...Material to be etched, (7)
(25) (41)...Water cooling means, (11) (31
) (49)...Cathode, (9) (29) (52)
...Insulating material (Teflon, etc.), (10) Cathode dark area, (
12) (27) (39)...High frequency power, (11)
(26) (40)... matching circuit, (13)...
Vacuum partition valve, (14) (32) (44)...
・Exhaust system, (15)...High density plasma, (16)・
... Glow discharge plasma, (17) ... Grounding, (11
1) (4B) = Gas inlet (20) -a -c Teflon-based organic film deposited area, (21) -a -c Teflon-based organic film not deposited area, (33) (4g
)...Dark space shield, (34)...Vent hole (vacuum connection port), (35)...Box containing permanent magnet, (28) (42)...Motor.

Claims (3)

[Claims] (1) A container in which an anode and a cathode on which the material to be etched is placed are placed facing each other, and ions generated by dissociation in this container exhibit reactivity, such as chlorine, bromine, or a raw material containing fluorine. means for introducing gas; means including a magnet for applying an arch-shaped magnetic field having a component perpendicular to the electric field between the two poles; and applying electric power between the two poles to generate plasma between the two poles. A dry etching apparatus comprising means for generating plasma, a member for shielding the magnet from the plasma, and a means for scanning the magnet. (2) The dry etching apparatus according to claim 1, wherein a mask pattern having a different etching rate is formed on the material to be etched. (3) The dry etching apparatus according to claim 1, wherein a carbon material, a film having a C-F bond or a C-H bond, or an alumina film is formed on the surface of the cathode.