JPH0518908B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for dry etching a sample using a dry etching apparatus equipped with an electrostatic chuck mechanism. [Technical Background of the Invention and Problems Therewith] In recent years, integrated circuits have become increasingly miniaturized, and even ultra-LSIs with minimum dimensions of 1 to 2 [μm] have recently been prototyped. Such microfabrication is usually performed by introducing a reactive gas such as _CF4 into a reaction vessel with parallel plate electrodes, and applying high frequency power (e.g. 13.56MHz) to the electrode on which the sample is placed. A discharge is generated, positive ions in the plasma are accelerated by the cathode drop voltage (hereinafter referred to as V _DC ) generated on the cathode (electrode to which high-frequency power is applied), and the ions are perpendicularly incident on the sample to etch the sample. The so-called reactive ion etching ( R eactive
ion etching (RIE) is used. However, in RIE using parallel plate electrodes, for example,
The etching rate of SiO ₂ using CF ₄ + H ₂ gas is:
300 to 400 [Å/min] at most, and 1 [μm] thick
It takes about 40 minutes to etch SiO ₂ , which is extremely inconvenient in terms of mass production. Therefore, it is desired to increase the etching speed. To improve the etching speed, e.g. RF
It is conceivable to increase the power, but in this case, conversely, the loss due to conversion of RF power to heat will increase the deterioration and deterioration of the photoresist, and the V _DC
As a result, damage to the device is also exacerbated by the increase in the amount of damage to the device. Therefore, in order to avoid these problems, the current practice is to lower the RF power as much as possible even at the expense of etching speed. The essential reason for this is that in glow discharge by RF, the ionization efficiency of the introduced gas is extremely low at 1% or less. In response to this, the present inventors have recently installed a magnetic field generating means consisting of a permanent magnet under the RF applying electrode instead of RF glow discharge, and created a magnetic field orthogonal to the electric field caused by RF power to generate electrons (electric field). ) We proposed a dry etching device using magnetron discharge that improves discharge efficiency by promoting collisional dissociation between electrons and gas molecules by drifting in the direction of ) × (magnetic field) and making these electron orbits a closed circuit. (Special Application No. 173821, 1982). FIG. 1 is a schematic diagram showing a dry etching apparatus using the magnetron discharge described above. Vacuum container 4 equipped with a gas inlet 1 and exhaust systems 2 and 3
A room 6 in which a glow discharge 5 is generated and a room 8 in which a magnet assembly (magnetic field generating means) 7 is arranged are connected to a cathode 12 and a cathode 12 connected to a conduit that also serves as a water cooling pipe 11 through which a high frequency power 9 passes through a matching box 10. It is separated by a valve 13. The etching process is carried out as follows. First, the threaded rod 15 rotated by the rotary introduction device 14 from outside the vacuum container 4 moves the valve 13 downward according to the guide 16, and the valve 13 opens. Next, both rooms 6 and 8 are evacuated to below 10 ^-4 Torr by the exhaust system 3. When the air is exhausted below 10 ^-4 Torr, the valve 13 is closed by the reverse operation, and both rooms 6 and 8 are exhausted. Thereafter, the reaction gas is introduced through the gas inlet 1 and at the same time is exhausted from the exhaust system 2, and the pressure is controlled to be on the order of 10 ^-1 to 10 ^-2 [Torr], and high frequency power 9 is applied to the cathode 12. Then, a magnetron discharge 17 is generated by the orthogonal electromagnetic field of ExB, and the material to be etched (sample) 19 such as a Si wafer of an electrostatic chuck mechanism, which will be described later, is etched.Permanent magnets 7a, 7b, The magnetic pole gap between the N and S poles 7c is rectangular and forms a closed loop.On the other hand, when the magnet assembly 7 is scanned by the rotation introducing system 20 such as a motor as in FIG. scan above,
Etch evenly. At that time, room 8 is 10 ^-4
Since the pressure was maintained at [Torr], no electrical discharge occurred, and the material to be etched 19 could be etched at the same rate with half the high frequency power as shown in FIG. That is, in FIG. 1, when SiO 2 is etched by introducing halogen gas, for example CHF ₃ gas, at 5×10 ^-2 [Torr] with the valve ₁₃ open, approximately 300 [W] of high frequency power is applied.
An etching rate of 7000 Å/min was obtained, but when the valve 13 was closed and only the chamber 6 was discharged in the manner described above, the same etching rate was obtained by applying a high frequency power of 150 W. By lowering not only the etching speed but also the high-frequency power, the heat loss was reduced, and damage to the resist that serves as a mask on the SiO ₂ was eliminated or extremely reduced. The high-speed RIE method that is the basis of this proposal embodies the miniaturization of etching equipment for mass production, which is part of the production equipment whose diameters continue to increase to 5 inches and 6 inches as the ultra-LSI becomes finer. That is, with conventional low etching speeds, it is necessary to batch-etch as many wafers as possible for mass production, which requires the RIE apparatus to be larger. However, high-speed etching allows for mass production by processing only one or a small number of wafers.
The device can be made smaller and does not take up much floor space in a clean room where purity must be maintained. As explained above, by using the high-speed dry etching apparatus shown in FIG. 1, an improvement in mass productivity can be achieved with a compact apparatus. It has been found that the time taken to attach and detach the chuck system is an important factor that greatly reduces mass productivity. Second
Figures a and b show the electrostatic chuck mechanism 18. Figure 2a is a plan view, and Figure 2b is a sectional view taken along the line A--A in Figure a. Reference numeral 21 in the figure is, for example, a sapphire substrate, on which semicircular electrostatic electrodes 22a and 22b are formed symmetrically.
Further, an insulating film 23 made of Mylar or the like is deposited on the electrodes 22a and 22b. A sample (dielectric material) 24 corresponding to the object to be etched 19 is placed on this insulating film 23. In the electrostatic chuck mechanism constructed in this way, as shown in FIG.
When a high voltage of about [KV] is applied, the lines of electric force come straight out from the electrode 22a and enter the sample 24, as shown in Figure 2b, and in the case of a material with low electrical resistance such as a Si wafer, It may be considered that no electric field is generated in the electrode 24 and that it exits from the side facing the electrode 22b and enters the electrode 22b straight. The magnitude of the suction force at that time is
It is known that it is proportional to the square of the applied voltage and inversely proportional to the square of the distance to the sample 24. That is, the larger the applied voltage, the greater the attraction force, and the greater the adhesion between the sample 24 and the electrodes 22a, 22b, the stronger the chuck force will be. FIG. 4 shows the time taken to test drop when the sample 24 was first fixed with an electrostatic chuck, then the whole was turned upside down and the high voltage power supply was turned off. As a result, it was found that even when the high voltage was turned off, the sample 24 hardly ever fell down due to its own weight, and it took 1 to 2 days or more for the sample 24 to fall. That is, this experimental fact suggests that the relaxation time of the dipole induced in the insulating film 23 such as Mylar is extremely long. In actual etching, as soon as the etching of the sample 24 is completed, the sample 24 must be quickly replaced with the sample to be etched next. The current situation is that some kind of compulsory means must be put in place to exchange samples. In the dry etching apparatus shown in FIG.
9 (reduces ion collision energy → reduces damage. For example, see Haruo Okano, Takashi Yamazaki, Yasuhiro Horiike, 3rd Dry Process Symposium, p. 69 (1981) Institute of Electrical Engineers of Japan). Therefore, the thickness of the water-cooled cathode 12 is extremely thin, less than 4 mm, and therefore it is extremely difficult to provide the external means by machining or the like. In this way, as shown in Figure 1, high-speed etching of the object to be etched has been achieved using an etching device that applies a magnetic field, but when considered as a whole system, the extremely long relaxation time mentioned above is not enough for mass production. It is a major factor leading to a significant decline in sexual performance. [Object of the Invention] An object of the present invention is to quickly exchange the sample between each etching process when chucking and etching the sample using an electrostatic chuck mechanism, thereby improving productivity. The object of the present invention is to provide a dry etching method that can be measured. [Summary of the Invention] The gist of the present invention is to combine the high voltage applied to the electrostatic chuck electrode and the high frequency power applied between the cathode and the anode.
By shifting the OFF timing, the purpose is to shorten the above-mentioned relaxation time. The inventors of the present invention discovered the following important fact by conducting the experiment described in FIG. 4 above in the plasma shown in FIG. 1 above. In other words, if you first turn off the high frequency power and then turn off the high voltage applied to the electrostatic chuck electrode, it will take about 1 to 2 days for the sample to fall, as in the case of Figure 4. However, it has been found that, conversely, by delaying the timing of turning off the high frequency power compared to the turning off of the high voltage applied to the electrostatic chuck electrode, the sample drops instantaneously. Although the details of this cause have not yet been completely elucidated, it is likely that
Since the frequency of 13.56 [MHz] is sufficiently lower than the dielectric relaxation frequency of an insulating film such as mylar, the oriented molecules that make up the insulating film easily rotate, and instantaneous changes occur at the boundary of molecular rotation following the high-frequency electric field. It is assumed that the sample falls down. Taking these circumstances into consideration, the present invention provides a vacuum vessel comprising a cathode to which high frequency power is applied and a sample placed on the surface thereof, an anode disposed opposite to the surface of the cathode, and a vacuum vessel within the vacuum vessel. means for introducing a reactive gas into the magnet, means for shielding a space in which the magnet is arranged from a space in which the sample is arranged, and a plurality of mutually insulated electrodes and an insulating film deposited on the electrodes. Using a dry etching device equipped with an electrostatic chuck mechanism attached to the surface of the cathode and means for applying a high voltage to the electrodes of the electrostatic chuck mechanism, a discharge is generated between the cathode and anode. In a dry etching method in which plasma is generated and magnetron discharge is generated to etch the sample, when etching of the sample is completed, a high voltage is first applied to the electrode of the electrostatic chuck mechanism while the discharge is maintained. In this method, the sample is removed from the electrostatic chuck mechanism by turning off the sample and then turning off the high-frequency power applied between the cathode and the anode. [Effects of the Invention] According to the present invention, by turning off the high voltage applied to the electrode of the electrostatic chuck mechanism and then turning off the high frequency power applied between the cathode and the anode,
A sample chucked onto the electrostatic chuck mechanism can be quickly removed from the chuck mechanism. Therefore, samples can be quickly replaced, and the overall productivity of etching can be greatly improved. Further, there is an advantage that it can be realized extremely easily by simply setting the OFF timing of the high voltage and high frequency power without using special members. [Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIGS. 5a to 5c are timing charts for explaining one embodiment of the present invention. Figure 5a
is the relationship between the scanning speed v and time t of the unidirectional scanning of the permanent magnets 7a to 7c in FIG. 1, b is the relationship between high frequency power P and time t, and c is the relationship between the high frequency power P and time t applied to the electrostatic electrode. The relationship between high voltage E and time t is shown. In this embodiment, first, at the etching end point A, the high voltage power applied to the electrostatic chuck electrodes 22a and 22b shown in FIG. The state is maintained for at least one cycle of scanning, and then, for example, at point B, the high frequency power is turned off and one wafer (sample) is removed.
Complete the entire etching process. By assembling such an etching sequence, it becomes possible to quickly exchange wafers between each etching process, thereby realizing a compact etching apparatus and etching method capable of processing one or a small number of wafers. Note that the time delay between point A and point B is due to the permanent magnet 7a~
It was confirmed that 7c scan half cycles were sufficient. Note that the present invention is not limited to the embodiments described above, and can be implemented with various modifications without departing from the gist thereof. For example, the OFF timing shift time between the high voltage applied to the electrostatic chuck electrode and the high frequency voltage applied between the cathode and the anode may be determined as appropriate depending on the specifications. Further, the configuration of the electrostatic chuck mechanism can be changed as appropriate depending on specifications. Furthermore, the dry etching apparatus is not limited to the type in which a magnet is provided on the surface of the cathode as in the above-described embodiment, but other dry etching apparatuses utilizing magnetron discharge may be used. Furthermore, it goes without saying that the present invention can be applied not only to dry etching apparatuses that utilize magnetron discharge, but also to dry etching apparatuses that utilize ordinary glow discharge.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram showing a high-speed dry etching device using magnetron discharge, Figures 2a and b are plan views and sectional views showing the electrostatic chuck mechanism used in the device, and Figures 3 and 4. The figures are for explaining the action of the electrostatic chuck mechanism mentioned above. Fig. 3 shows an example of its use, and Fig. 4 shows how the electrostatic chuck mechanism fixes the sample, turns it upside down, and turns off the high voltage. Figures 5a to 5c are timing charts for explaining one embodiment of the present invention. 1... Gas inlet, 2, 3... Exhaust system, 4...
Vacuum container (anode), 5... Glow discharge, 6... Vacuum chamber, 7... Magnet assembly, 8...
10 ^-4 [Torr] or less high vacuum chamber, 9...high frequency power supply, 10...matching circuit, 11...water cooling pipe, 12...cathode, 13...gate valve, 14...
Solenoid valve, 15... Threaded rod, 16... Guide, 17
... Magnetron discharge, 18 ... Electrostatic chuck mechanism, 19, 24 ... Object to be etched (sample), 2
0...Motor, 21...Saphire, 22a, 2
2b... Electrostatic electrode, 23... Insulating film.

Claims (1)

[Scope of Claims] 1. A vacuum vessel equipped with a cathode to which high-frequency power is applied and a sample placed on the surface thereof, and an anode placed opposite to the surface of the cathode, and a reactant gas in the vacuum vessel. an electrostatic chuck mechanism comprising an electrode and an insulating film deposited on the electrode and attached to the surface of the cathode; and means for applying a high voltage to the electrode of the electrostatic chuck mechanism. In a dry etching method, the sample is etched by generating discharge plasma between the cathode and the anode using a dry etching apparatus equipped with the following steps:
When the etching of the sample is completed, the high voltage applied to the electrode of the electrostatic chuck mechanism is turned off while the discharge is maintained, and then the high frequency power applied between the cathode and the anode is turned off.
A dry etching method characterized in that the electrostatic chuck mechanism is turned OFF and the sample is removed from the electrostatic chuck mechanism. 2. The dry etching method according to claim 1, wherein the discharge plasma generated between the cathode and the anode is plasma generated by magnetron discharge. 3. A magnet provided on the back surface of the cathode and applying a magnetic field to the surface of the cathode through a closed-loop magnetic pole gap, a means for scanning the magnet in a direction orthogonal to the direction of the electric field generated by the high-frequency power, and the magnet is arranged. 2. The dry etching method according to claim 1, further comprising means for shielding a space in which the sample is placed from a space in which the sample is placed. 4. Claim 1, wherein the electrostatic chuck has a plurality of electrodes that are insulated from each other, and the high voltage is applied between the electrodes of the electrostatic chuck. Drying method described in section.