JP2003031555A - Surface treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent abnormal discharges in a gas hole, by strengthening a magnetic field of a surface treating apparatus, utilizing a plasma near a gas plate and weakening the field near a substrate and to prevent damages from affecting magnets, even if abnormal discharges occur. SOLUTION: The surface treatment apparatus comprises the gas hole 11a of the gas plate 11 at a position of a zero magnetic field, by deviating the shifting the hole 11a and the magnets (a), (b).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for manufacturing semiconductors and the like, and more particularly to a structure of a point cusp magnetic field and a gas hole provided in a parallel plate surface treatment apparatus using plasma.

[0002]

2. Description of the Related Art Conventionally, in semiconductor manufacturing processes, etching and plasma CVD (chemical vapor depo
In the case of surface treatment such as sition) and ashing, a surface treatment apparatus configured to generate plasma in a vacuum container and perform a predetermined treatment on the surface of a substrate to be processed or a wafer has been used.

Nowadays, the degree of integration of devices is getting higher and the improvement of throughput is also very important. Therefore, in these surface treatment apparatuses, not only the yield is improved, but also fine processing is performed at high speed. Is especially emphasized. Further, when etching a contact hole having a high aspect ratio, increasing the plasma density reduces the sheath width as will be described later, and reduces the amount of ions scattered by colliding with the neutral gas in the sheath. Therefore, the problem that ions collide with the side wall of the contact hole in an oblique direction and the contact hole has a swollen bowing shape, or the vertical hole shape cannot be obtained, and the vertical shape contact hole can be etched. . Further, high plasma density enables high speed etching.

Therefore, it is a recent technical trend in the etching process to increase the plasma density to enable high-speed processing of the substrate and reduce the pressure to prevent the scattering of ions in the sheath where the ions are accelerated. Further, even in the case of ashing, when the pressure is low, a substance having a low vapor pressure does not remain as a residue, and when the plasma density is high, high-speed processing becomes possible. When performing plasma CVD, when the pressure is low, the gas phase reaction is suppressed and dust is not generated.

The plasma density and the sheath width, which are one of the grounds for the above explanation, will be described.

The Debye length of plasma is given by the following equation.

Λ_De= 743 (T_e/ N_e)^0.5 Where λ_DeIs the Debye length in cm, T_eIs vol
electron temperature represented by t, n _eIs cm^ThreeElectronic density per hit
It is degree. With this device length, the plasma sheath length
From the Child formula, S is as follows.

[0008] S = [(2^1/2) / 3] λ_De(2V_o/ T_e)^3/4 Where V_oIs the voltage on the sheath. For example,
T_e= 3 eV, n_e= 10¹¹Pieces / cm^Three, V_o
= 600V, the sheath width is 0.1
7 cm = 1.7 mm. Ar: 30 at gas pressure 4Pa
0 sccm, C _FourF₈: 10 sccm standard process
In the case of Ar, the mean free path of Ar is 3.5 mm, so
The scattering of Ar in the source is about 40%. Furthermore, C
_FourF₈ Mean free path in Ar is 1 / 3.5 times that of Ar
Ionized C because there is only a degree_FourF₈Average of
The free path is about 1 mm and there is no collision scattering in the sheath.
I can't see. In fact, the proportion of particles that run without collision at the distance x is
Exp (-x / λ), where λ is mean free
Stroke, x is the flight distance), Exp (-x
/Λ)=0.18 is obtained. Therefore, it is incident on the sheath.
82% of all the ions that are generated will collide and scatter. C_Four
F₈Since the ionization rate of is much larger than Ar
The scattering rate is a value that cannot be ignored. This is the side wall etch
And cause the blistering of the inside blisters.
Become. If the plasma density is doubled, the sheath length will be
It becomes about 0.7 times and can suppress the bowing shape
It

To increase the plasma density, the frequency may be increased and the high frequency power may be increased.
When the frequency is raised to the HF band, for example, 60 MHz or higher, the transmission condition of the high frequency becomes strict, and there is a problem that it cannot be coupled well with the plasma load. Therefore, great efforts are required to use it in the parallel plate type surface treatment device. . There is also a problem that abnormal discharge is likely to occur when the high frequency power is increased.

A magnetron type parallel plate surface treatment apparatus which solves this problem and uses a magnetic field to raise the plasma density and lower the pressure is considered promising.

For example, Japanese Patent Laid-Open No. 11-283926 discloses a plasma processing apparatus shown in FIG. The plasma processing apparatus shown in FIG. 5 is an apparatus in which a large number of small columnar magnets Ma are arranged on the back side of the counter electrode 2 facing the substrate mounting electrode 3 with their polarities alternately changed in order to generate a point cusp magnetic field. . The magnetic field structure and action in this case will be described. Since the magnets Ma have opposite polarities, a magnetic flux is generated between the adjacent magnets Ma, electrons in the plasma generated by the high frequency are trapped, the neutral particles are efficiently ionized, and the plasma density is increased. In this way, it is said that the plasma density can be increased with a low gas pressure to enable accurate etching.

[0012]

However, the following problems are recognized in the above-mentioned prior art.

That is, as the plasma density increases, the plasma enters the gas holes formed in the gas plate of the counter electrode 2 to cause abnormal discharge, the inside of the gas holes is etched, and the diameter of the gas holes expands. As the plasma density inside the gas holes becomes denser and diffuses to the outside of the gas holes, the decomposition of the gas in that part proceeds more than in other parts, and in the etching apparatus, the gas density of the substrate 4 facing the gas plate is increased. There is a problem that the etching rate of the portion becomes faster.
Further, in the plasma CVD apparatus, there are problems that the amount of deposit in the relevant portion becomes too large and particles are generated due to gas phase reaction. There is a problem that uniform processing is difficult even with ashing.

The present invention solves such a problem and is composed of two N-poles and two S-poles arranged so that the N-pole and the S-pole for generating a point cusp magnetic field alternate.
An object of the present invention is to provide a surface treatment device in which gas holes are arranged in a portion where the plasma density is low by providing gas holes in a gas plate in a zero magnetic field portion generated at an intermediate position of each magnet, and the gas holes are not exposed to dense plasma. I am trying.

[0015]

That is, according to the present invention, a substrate mounting electrode having a substrate mounting surface on which a substrate is mounted, and a counter electrode having a facing surface facing the substrate mounting surface. , A power supply unit that supplies power to at least one of the substrate mounting electrode and the counter electrode so that plasma is generated between the substrate mounting electrode and the counter electrode, and uses the plasma A surface treatment apparatus for performing a predetermined treatment on the surface of the substrate, wherein a gas plate disposed on the opposite surface side of the counter electrode with a constant distance from the counter surface; A point cusp magnetic field generation unit that is disposed between the facing surface of the counter electrode and the gas plate and that generates a point cusp magnetic field on the gas plate surface side of the gas plate facing the substrate mounting surface. , The gas plate faces the counter electrode And a plurality of gas holes perforated in a direction substantially perpendicular to the gas plate, the plurality of gas holes are provided at a plurality of zero magnetic field positions of the point cusp magnetic field in the gas plate. A surface treatment device for

Further, according to the present invention, the point cusp magnetic field generating section has a plurality of magnets arranged between the facing surface of the counter electrode and the gas plate, and the plurality of magnets are Two first magnets with one of N and S poles facing the gas plate, and two second magnets with the other of the N and S poles facing the gas plate. And one of the north and south poles of the two first magnets,
The other of the N and S poles of the two second magnets forms a square quadrangle, and the one of the N and S poles of the two first magnets. Forms one diagonal of the square, and the other of the north and south poles of the two second magnets forms another diagonal of the square,
A surface treatment apparatus is obtained in which the center of the square is the zero magnetic field position.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a case where the present invention is applied to an etching apparatus which is an example of a surface treatment apparatus will be described below. Not only etching equipment, ashing, P
The same applies to a surface treatment apparatus such as (plasma) -CVD.

Referring to FIG. 1, there is shown a surface treatment apparatus (etching apparatus) according to a first embodiment of the present invention. In FIG. 1, 1 is a processing chamber, 2 is a counter electrode, 3 is a substrate mounting electrode, 5 is an electrostatic chuck that electrostatically adsorbs a substrate 4,
Reference numeral 6 is a water-cooled electrode, 6a is a water-cooled electrode cooling water inlet, 6b is a water-cooled electrode cooling water passage, 6c is a water-cooled electrode cooling water outlet, and 12 is a counter electrode power source. 13 is a power source for the substrate mounting electrode, 13a
Is a blocking capacitor, 15 is a power supply for the electrostatic chuck electrode, 15a is a high frequency filter, 10 is an insulator, 2
Reference numeral 1 is a gas supply system, 22 is an exhaust valve, and 31 is a push-up pin used for attaching and detaching the substrate. A gas hole 11a is formed in the counter electrode 2.
A large number of gas plates 11 and a water cooling holder 8 for cooling the gas plates 11 with water are installed, and magnets a and reverse polarity magnets b are alternately arranged in a lattice shape in the gaps formed in the water cooling holder 8. These magnets a and b are fixed to the magnet supporting plate c with screws by means of screw holes formed in the yoke bonded to the magnets a and b. On the back of the magnet support plate c, there is a gas dispersion plate 9 having a gas dispersion hole 9a formed therein, which serves to make the gas uniform. The water cooling holder 8 has a water cooling pipe 8b, cooling water is supplied from the water cooling pipe inlet 8a, and goes out from the water cooling pipe outlet 8c. The magnet support plate c is also provided with a large number of gas holes, and plays a part in gas dispersion.

In order to operate this etching apparatus, first, the inside of the processing chamber 1 is evacuated through the valve 22 connected to the exhaust system, and then a voltage is applied to the electrode from the electrostatic chuck power supply 15 to adsorb and fix the substrate 4. The processing gas is sent from the gas supply system 21 to the counter electrode 2 so that the inside of the processing chamber 1 has a constant pressure.

Thereafter, the counter electrode power supply 12 supplies high frequency power in the VHF band (eg, 60 MHz) to the counter electrode 2, and the substrate mounting electrode 3 is supplied from the substrate mounting electrode power supply 13 to HF.
A high frequency power of a band (for example, 1.6 MHz) is supplied. Then, the high frequency power in the VHF band generates relatively high density plasma and etchant, and the high frequency power in the HF band controls the ion bombardment energy independently of the plasma density. Here, the electrons in the plasma are trapped by the magnetic flux 111 generated by the magnets a and b having polarities opposite to each other, and the electrons collide with the neutral particles many times to ionize the neutral particles. Produces high-density plasma.

In this way, a high density plasma can be obtained at a target low pressure and a uniform etching process can be performed. The conditions such as gas pressure are the same as those shown in the prior art. In the case of oxide film etching, add 5 sc of oxygen
It is usual to add about cm. In this case, the substrate temperature is kept at 60 ° C and the counter electrode temperature is kept at 90 ° C.

Although the high-density plasma is confined in the magnetic field, the electrons are cycloidally moved by ExB drift to reach a weak point magnetic field at the point cusp, escape from the magnetic field, and diffuse into bulk plasma having no magnetic field. Ions are not trapped in a magnetic field of several hundred Gauss as in this embodiment. In this way, due to the diffusion of electrons in the high-density plasma, the ions are also dragged by the electrons and diffuse, the plasma density around the substrate 4 also increases, and the plasma density becomes uniform during the diffusion. Further, since the dissociation and ionization of the process gas also progress, the etching rate is improved. This is a feature of etching using a point cusp magnetic field.

Next, the positional relationship between the magnets a and b and the gas hole 11a, which is the main part of the present invention, will be described with reference to FIG. In FIG. 2, a is a magnet and b is a reverse polarity magnet, which are alternately installed on the back surface of the gas plate 11 (FIG. 1) at intervals of about 1 cm. Reference numeral 100 represents a magnetic flux created by the magnet a and the opposite polarity magnet b, and forms a point cusp magnetic field. In such an arrangement of the magnets a and b, the magnetic field is canceled and becomes zero at the center of the square formed by the two magnets a and the two opposite polarity magnets b which are adjacent to each other. In the present embodiment, the gas hole 11a is provided in the gas plate 11 at this zero magnetic field point so that the gas hole 11a penetrates the gas plate 11 at the zero magnetic field point. In this case, since the magnetic field strength near the gas hole 11a is almost zero, the etching of the gas plate 11 does not proceed as compared with other places, and the inside of the gas hole 11a is not etched either. Therefore, the length of the gas hole 11a is shortened, and the amount of increase in the inner diameter of the gas hole 11a is also reduced, so that the conductance of the gas hole 11 does not change so much, and the processing conditions change even if the substrate processing is continued for a long time. There is nothing to do.

In FIGS. 1 and 2, the surface treatment apparatus according to the first embodiment of the present invention described above is summarized. In the first embodiment, a substrate mounting surface having a substrate mounting surface on which the substrate 4 is mounted is mounted. In order to generate plasma between the mounting electrode 3, the counter electrode 2 having a facing surface facing the substrate mounting surface, and the substrate mounting electrode 3 and the counter electrode 2, the substrate mounting electrode 3 and the counter electrode 2
And a power supply unit 12 or 13 for supplying power to at least one of the two, and is a surface treatment apparatus that performs a predetermined treatment on the surface of the substrate 4 by using the plasma.
Of the gas plate 11 on the opposite surface side of the gas plate 11 and a gas plate 11 arranged at a certain distance from the opposite surface, and between the opposite surface of the counter electrode 2 and the gas plate 11. A point cusp magnetic field (see FIG. 1) is formed on the gas plate surface side facing the substrate mounting surface.
No. 111 or 100 in FIG. 2), the point cusp magnetic field generator (a, b, c) is further provided, and the gas plate 11
Has a plurality of gas holes 11a bored in a direction substantially perpendicular to the facing surface of the counter electrode 2, and the plurality of gas holes 11a are a plurality of zero points of the point cusp magnetic field in the gas plate 11. It is characterized in that it is provided at a magnetic field position.

Typically, the point cusp magnetic field generator includes a plurality of magnets (a, b) arranged between the facing surface of the counter electrode 2 and the gas plate 11, as shown in FIG. The plurality of magnets include two first magnets (a) in which one of the N pole and the S pole faces the gas plate 11, and the N pole and the S pole of the gas plate. Two second facing each other
Magnet (b) of the two first magnets (a) and one of the north and south poles of the two first magnets (a) and the north and south poles of the two second magnets (b). The other of the poles forms a square corner, and the one of the north and south poles of the two first magnets (a) forms one diagonal of the square. The other of the north and south poles of the two second magnets (b) forms another diagonal of the rectangle, and the center of the rectangle is at the zero magnetic field position. Is characterized by.

The following are conceivable as promising proposals other than the first embodiment. If the position of the magnet and the gas hole are the same, the electron density and hence the plasma density will be reduced just above the magnet due to the divergent magnetic field effect. Therefore, the same effect as when the gas hole is penetrated to the zero magnetic field can be expected. But,
If the positions of the gas holes and the magnet are the same, the following problems will occur.

The closer the magnet is to the plasma, the more efficiently the plasma can be generated. In particular, the characteristic of the point cusp is that a strong magnetic field is generated near the gas plate, and the magnetic field rapidly weakens when it is separated from the gas plate, and becomes almost zero near the substrate. The reason for using the point cusp where the magnetic field approaches zero near the substrate is as follows. When there is a magnetic field near the substrate, there is a difference in the plasma density, the current flowing into the substrate becomes uneven, and uneven charge accumulates on the substrate, causing breakdown of the insulation, etc., and causing definite damage to the device. . The point cusp can prevent this.

In order to avoid such a problem, it is preferable that the magnetic field rapidly decreases as it moves away from the magnet like a point cusp, and the magnetic field becomes almost zero near the substrate. However, if the magnet and the gas hole are located at the same position in the point cusp, the gas flows into the gas hole, so that the distance between the gas plate and the magnet must be kept constant and the distance must be constant. If this distance is not constant, the conductance changes from gas hole to gas hole and there is a difference in the flow rate of gas flowing into each gas hole, resulting in non-uniform etching characteristics near the gas holes. In order to determine this distance, the magnet and gas plate are screwed or glued, but it is difficult to give an accurate value. Furthermore, when the magnet and the gas position are the same, the distance from the magnet to the surface of the gas plate on the plasma side becomes longer in order to secure the gas flow, as compared with the case where the magnet and the gas hole are at the offset positions. The strength of the magnetic force changes with the square of the distance from the magnet (three-distance cube when viewed as a dipole), so the magnetic force near the gas plate decreases, but the magnetic field strength near the substrate remains almost unchanged. The beneficial features of the point cusp are diminished. Therefore, it is preferable that the positions of the magnet and the gas hole are displaced from each other so that the magnet can be brought close to the gas plate.

Furthermore, if the gas hole and the magnet are located at the same position as in a promising plan other than this embodiment, plasma may enter the gas hole and the plasma density may increase. This will be described with reference to FIG. When the gas hole 11a of the gas plate 11 is directly above the magnet a, the magnetic flux emerges vertically from the magnet a, so that the magnetic flux flows parallel to the side wall of the gas hole 11a. Then, the electrons in the plasma are trapped in the magnetic flux parallel to the side wall of the gas hole 11a, the time until it collides with the side wall of the gas hole 11a and disappears becomes long, and the efficiency of plasma generation in the gas hole 11a increases. To do. As a result, the plasma density increases, the inner diameter of the gas holes 11a increases, and the plasma density further increases. Eventually, a hollow cathode discharge occurs, and the diameter of the gas holes rapidly expands. The variation of the etching rate becomes large.

Even when such an abnormal discharge does not spread, the magnet comes into contact with the plasma and the temperature of the magnet rises due to the heating of the plasma, and the magnetic force disappears beyond the Curie point. Then, the initial magnetic field characteristics cannot be maintained, the plasma state changes, and the etching characteristics change. It is difficult to find such a slight change in the etching characteristics, and it will continue to produce devices for a long period of time while the problems are overlooked, and build a pile of defective products.

For these two reasons, it is preferable that the position of the gas hole is not directly below the magnet but at the position of the zero magnetic field deviated from the magnet.

Next, a surface treatment apparatus according to a second embodiment of the present invention will be described with reference to FIG.

In the second embodiment, the magnet a (or b) is used.
Is close to the plasma, and the space where the gas exists between the gas hole 11a and the magnet a (or b) is eliminated. In FIG. 4, the gas holes 11 of the gas plate 11
a is two adjacent magnets a and two opposite polarity magnets b
It is located at the zero field point in the center of the square (Fig. 1). The magnet a is installed so that a part thereof enters the magnet hole 11b formed in the gas plate 11, and the opposite side (back side) is held by the magnet support plate c (FIG. 1). Magnet a
The circumference of the magnet protection cylinder 11c prevents the magnet a from being exposed to the plasma even if the plasma wraps around the back side of the gas plate 11.
Is provided. In this way, the position of the magnet a and the gas hole 11
Offsetting the position of “a” also has the advantage that flexibility in design can be obtained.

When the etching substance is deposited on the back side of the gas plate 11, the deposit can be prevented by increasing the gas flow rate and decreasing the diameter of the gas hole 11a.
Since it is described in Japanese Patent No. 175627, this method can be used.

Since high-density plasma is generated near the gas plate 11, it is preferable that the gas plate 11 is made of a scavenger material such as Si or SiO ₂ . Further, from the viewpoint of high frequency propagation, the gas plate 11 may be made of an insulator, a doped semiconductor or a metal.

[0036]

As described above, according to the present invention,
The flow rate of each gas hole can be controlled to be constant, the magnetic field can be made high near the gas plate and negligibly small near the substrate, and both high plasma density and uniform plasma density near the substrate can be achieved. By doing so, it is possible to realize substrate processing in which etching is performed at high speed and with good uniformity, and etching shape is uniform. Plasma CVD can realize substrate processing at high speed and with uniform film quality and film thickness.

Further, since the magnet and the gas hole are placed at mutually deviated positions, even if the plasma enters the gas hole, the plasma does not come into contact with the magnet, the temperature of the magnet rises and demagnetizes, and the magnetic field characteristics change. Prevent things. Therefore, there is no problem that the plasma characteristics change and the etching and plasma CVD characteristics change.

Further, in the ashing, it is possible to realize the uniformity of the ashing rate and the uniformity of the residue.

[Brief description of drawings]

FIG. 1 is a sectional view of a surface treatment apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a positional relationship between a magnet and a gas hole provided in a gas plate in the surface treatment apparatus of FIG.

FIG. 3 is a cross-sectional view of a gas plate and a magnet for explaining a promising plan other than the first embodiment.

FIG. 4 is a sectional view of a gas plate and a magnet of a surface treatment apparatus according to a second embodiment of the present invention.

FIG. 5 is a perspective view of a conventional plasma processing apparatus.

[Explanation of symbols]

1 processing room 2 Counter electrode 3 Substrate mounting electrode 4 substrates 8 water cooling holder 8b water cooling tube 8a Water cooling pipe inlet 8c Water cooling pipe outlet 9 gas dispersion plate 9a Gas dispersion hole 11 gas plate 11a gas hole 11b Magnet hole 11c Magnet protection tube 12 Counter electrode power supply 13 Power supply for substrate mounting electrodes a magnet b Magnet (reverse polarity magnet) c Magnet support plate

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Claims (2)

[Claims] 1. A substrate mounting electrode having a substrate mounting surface on which a substrate is mounted, a counter electrode having a facing surface facing the substrate mounting surface, and the substrate mounting electrode and the counter electrode. A power supply unit that supplies power to at least one of the substrate mounting electrode and the counter electrode so as to generate plasma therebetween, and performs a predetermined process on the surface of the substrate using the plasma. A surface treatment apparatus, comprising: a gas plate disposed on the facing surface side of the counter electrode with a constant distance from the facing surface; and the facing surface of the counter electrode and the gas plate. And a point cusp magnetic field generation unit that generates a point cusp magnetic field on the side of the gas plate facing the substrate mounting surface of the gas plate, the gas plate facing the counter electrode. Multiple holes drilled in a direction substantially perpendicular to the plane A surface treatment apparatus having a plurality of gas holes, the plurality of gas holes being provided at a plurality of zero magnetic field positions of the point cusp magnetic field in the gas plate. 2. The surface treatment apparatus according to claim 1, wherein the point cusp magnetic field generation unit has a plurality of magnets arranged between the facing surface of the counter electrode and the gas plate, The plurality of magnets are two first magnets with one of N and S poles facing the gas plate, and two with the other of N and S poles facing the gas plate. Second magnet of the two first magnets, and the one of the north and south poles of the two first magnets, and the north and south poles of the two second magnets.
The other of the poles forms a square corner, and the one of the north and south poles of the two first magnets forms one diagonal of the square. The surface treatment apparatus characterized in that the other of the N and S poles of the second magnets forms another diagonal of the rectangle, and the center of the rectangle is at a zero magnetic field position.