JP3338203B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plasma processing apparatus such as a magnetron reactive ion etching apparatus used for a dry etching operation and an ashing apparatus used for an ashing operation in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art As one of dry etching methods in a semiconductor device manufacturing process, a reactive ion etching (RIE) method is known.
As an application of the method, for example, a magnetron reactive ion etching apparatus as shown in FIG.
RIE apparatus) is known. This M-RI
The E apparatus applies a high frequency (RF) power to the square plate-shaped cathode electrode 40 on which the wafer 50 is mounted, and a box disposed so as to surround the cathode electrode 40, the wafer 50, and the cathode electrode 40. An electric field E is generated between the anode coil 30 and the electromagnetic coils 10, 1 disposed around the anode electrode 30 surrounding the wafer 50.
A magnetic field B perpendicular to the electric field E by passing a current through 1, 20, 21
Is generated, the plasma 70 generated in the vacuum atmosphere in the anode electrode 30 is confined in the space near the wafer 50. Here, inside the plasma 70 generated in this way, the electric field E and the magnetic field B orthogonal to each other cause the electrons to drift, that is, to move in a cycloidal manner, thereby increasing the frequency of inelastic collisions. The plasma density increases. Note that the electromagnetic coils 10 and 11 are arranged to face each other with the wafer 50 interposed therebetween, and are usually a pair of electromagnetic coils connected in series. Similarly, the electromagnetic coils 20 and 21 are also a pair of electromagnetic coils. I have.

In such an M-RIE apparatus, if the direction of the magnetic field B with respect to the wafer 50 is relatively fixed, the plasma density distribution on the surface of the wafer 50 is greatly deviated. It is necessary to relatively rotate the direction of the magnetic field B with respect to 50. However, rotating the wafer 50 while fixing the direction of the magnetic field B involves difficulties in terms of hardware such that the RF power supply and the like must also be rotated at the same time. The direction of the magnetic field B is rotated by controlling the current. That is, conventionally, the current I ₁ between the electromagnetic coils 10 and 11 and the current I ₂ between the electromagnetic coils 20 and 21 are respectively

## EQU1 ## I ₁ = I ₀ cos (2πft)

I ₂ = I ₀ sin (2πft) where I ₀ : amplitude, f: frequency, t: time, whereby a phase difference π / 2 is provided between the two.

[0004]

However, this M
-The RIE apparatus has the following disadvantages. This M-
In the RIE device, the phase 2πf between the electromagnetic coils
When t = 0, as shown in FIG. 7A, the interval between the magnetic flux lines 75 increases on the surface of the wafer 50, that is, the magnetic field gradient decreases. Although the plasma regions 71 are generated, the drift motion of the electrons in the plasma 70 (see FIG. 6) is stabilized on the surface of the wafer 50, and the degree of deviation of the plasma density distribution is minimized. On the other hand, the phase 2πft =
In the case of π / 4, as shown in FIG. 7B, the interval between the lines of magnetic force 76 becomes smaller toward the center of the wafer 50, that is, the magnetic field gradient becomes larger. Compared with plasma 70 (see FIG. 6)
The drift motion of electrons in the inside becomes active, and the high-density plasma regions 71, 71 and the quasi-high-density plasma regions 72, 72 also occur at the corners, so that the degree of bias of the plasma density distribution becomes maximum. The magnetic field gradient is a spatial gradient of the magnetic field strength, and its unit is Ga.
uss / cm.

However, even if the degree of deviation of the plasma density distribution on the surface of the wafer 50 is minimized and the plasma density distribution is substantially uniform, if the difference from the vicinity is large, the plasma is not etched. Since the plasma current flowing through the wafer 50 becomes uneven, for example, when gate etching is performed using the M-RIE apparatus, the semiconductor substrate, the gate insulating film, A phenomenon generally called charge-up damage may occur such that a large potential difference is generated between each of the gate electrodes, thereby destroying a relatively thin gate insulating film. Moreover, in this M-RIE device, charge-up damage may occur not only in the case of gate etching but also in other metal or insulating film etching processes and ashing processes. There are still points to be improved as a dry etching apparatus and an ashing apparatus.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to uniform the plasma density generated between a cathode electrode and an anode electrode, thereby preventing the occurrence of charge-up damage. An object of the present invention is to provide a plasma processing apparatus such as a magnetron reactive ion etching apparatus and an ashing apparatus.

[0007]

In a plasma processing apparatus according to the present invention, a cathode electrode on which a wafer is mounted, a cathode electrode
Polygonal upper electrode and the cathode
The lower part is opened with the side electrode arranged surrounding the ground electrode.
Box-shaped anode electrode and anode electrode
It is arranged opposite to each other with the cathode electrode on the outside.
And a plurality of pairs of electromagnetic coils. And especially
The side electrodes constituting the node electrode are arranged next to each other.
Between the electromagnetic coils,
It has a protruding part that protrudes outward, and
The upper electrode constituting the pole closes the upper opening of the protrusion
It is characterized by: Note that an exhaust port may be provided at the protruding portion of the anode electrode so as to be openable and closable. Further, a portion of the cathode electrode corresponding to the position of the protruding portion may be formed to extend in a protruding direction of the protruding portion. Further, the ends of the electromagnetic coils arranged on both sides of the protrusion of the anode electrode may be bent outward along the protrusion, respectively, and may be opposed to each other.

[0008]

According to the present invention, since the protruding portions are provided at the corners of the anode electrode so as to protrude in the direction between the adjacent electromagnetic coils of the respective electromagnetic coils, the high density generated at the corners within the anode electrode is provided. The plasma region moves away in the direction of protrusion of the protrusion, and thus the high-density plasma region moves away from the vicinity of the wafer. In addition, since the surface area of the corner portion of the anode electrode is increased, the probability of the recombination of the charged particles on the inner surface of the anode electrode is increased. Therefore, the plasma density in the high-density plasma region generated at the corner portion is reduced, and The entire plasma density distribution is made uniform.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magnetron reactive ion etching apparatus according to the present invention will be described in detail. FIG.
FIG. 2 is a view showing a first embodiment in which the plasma processing apparatus of the present invention is applied to a magnetron reactive ion etching apparatus, and is a magnetron reactive ion etching apparatus (hereinafter abbreviated as M-RIE apparatus) shown in FIG. Figure 6
Is different from the conventional M-RIE apparatus shown in FIG. 1 in that a projection 81 is formed at a corner of an anode electrode 80 functioning as a chamber wall.

That is, the M-RIE apparatus shown in FIG. 1 has a square plate-shaped cathode electrode 40 on which a wafer 50 constituting a semiconductor device is mounted, and covers the upper surfaces of the wafer 50 and the cathode electrode 40 so as to cover the upper surface of the cathode electrode 40. An anode electrode 80 having a substantially square shape in plan view surrounding the anode electrode 80;
And a plurality of electromagnetic coil pairs disposed to face each other with the wafer 50 interposed therebetween. The cathode electrode 40 is formed sufficiently larger than the wafer 50, and is connected to a grounded radio frequency (RF) power supply 60. On the other hand, the anode electrode 80 constitutes a chamber together with the cathode 40, and has a box-like shape comprising a side electrode and an upper electrode for closing an upper opening thereof, and thus opening downward. As described above, the anode electrode 80 is disposed so as to surround the wafer 50 and the cathode electrode 40 on which the wafer 50 is mounted, and is grounded to generate plasma inside the wafer 50. The space surrounded by the cathode electrode 40 and the anode electrode 80, that is, the inside of the chamber is closed so that an airtight state is maintained as described later.
A negative pressure source such as a vacuum pump is connected to this space, whereby the inside of the chamber is depressurized and a vacuum atmosphere is created.

The electromagnetic coil pair is composed of electromagnetic coils 10 and 11 and electromagnetic coils 20 and 21 similarly to the one shown in FIG. 1, and as described above, the anode electrode is held with the wafer 50 interposed therebetween. 80, they are arranged facing each other outside and are connected in series. In the anode electrode 80, each of the electromagnetic coils 10, 1 forming a pair of electromagnetic coils is provided at a corner thereof.
Projections 81,... Projecting in the direction between adjacent electromagnetic coils 1, 20, 21 are formed. The protruding portions 81 have side electrodes at the corners of the anode electrode 80 extending in a diagonal direction of the anode electrode 30 shown in FIG.
In addition, the upper electrode is provided and formed in a state where the upper opening is closed.

In order to perform an etching process using an M-RIE device having the anode electrode 80 having such a shape,
6, the wafer 50 is set on the cathode electrode 40 in advance in the same manner as in the conventional apparatus shown in FIG. 6, and then the pressure in the chamber between the anode electrode 80 and the cathode electrode 40 is reduced by a vacuum pump (not shown). Create a vacuum atmosphere. Next, an etching gas, for example, a gas such as Cl _{2 is} introduced between the anode electrode 80 and the cathode electrode 40 in a vacuum atmosphere from a gas introduction hole (not shown). Next, an RF electric field is applied to the cathode electrode 40 to generate an electric field E in a direction from the anode electrode 80 toward the cathode electrode 40, and a current is applied to the electromagnetic coils 10, 11, 20, 21 to cause a magnetic field orthogonal to the electric field E. B is generated, whereby a plasma 70 is generated between the anode electrode 80 and the cathode electrode 40.

Then, the ions in the plasma 70 are converted by the electric field E into the cathode electrode 40 or the wafer 5 thereon.
It collides with 0 and secondary electrons are emitted. The emitted secondary electrons cause cycloidal motion by an electric field E and a magnetic field B which are orthogonal to each other and collide with etching gas molecules, thereby generating new ions. Then, in the same manner as described above, the ions collide with the cathode electrode 40 or the wafer 50 thereon, and secondary electrons are emitted again. This is repeated, thereby increasing the plasma density.
By increasing the plasma density in this manner, a large number of reactive ions are supplied from the plasma 70 to the wafer 50, and Si or its compound, various metals, and the like are etched at a high speed.

At this time, in the M-RIE apparatus of the present embodiment, the high density plasma region 71 generated at the corner of the chamber wall 30 as shown in FIG. And the semi-high-density plasma region 72 can be generated in the protruding direction of the protrusions 81, that is, in a position away from the wafer 50, and therefore, these high-density plasma regions can be separated from the vicinity of the wafer 50, and thereby the plasma Thus, the plasma current flowing through the wafer 50 to be etched can be made uniform, and charge-up damage can be prevented. Also,
By forming the protruding portions 81...
The surface area of the corner side electrode of the conventional M shown in FIG.
As a result, the probability of recombination of charged particles on the inner surface of the side electrode of the anode electrode 80 is increased when plasma is generated.
The plasma density in the high-density plasma region generated at the position of the corner shown in (1) becomes low, and the plasma density distribution in the anode electrode 80 becomes uniform.

FIG. 2 is a view showing a second embodiment of the present invention. The M-RIE apparatus shown in FIG.
The difference from the IE device is that an exhaust port 82 is formed in the protruding portion 81 of the anode electrode 80. Exhaust port 8
Reference numeral 2 denotes an opening formed in the upper electrode portion of the protruding portion 81 of the anode electrode 80 and a peripheral portion of the opening so as to adjust the degree of opening of the opening and to hermetically seal the opening. It is formed from a movable lid (not shown). By providing such an exhaust port 82, the M-RIE apparatus shown in FIG. 2 can control the pressure in the anode electrode 80 by adjusting the opening degree of the exhaust port 82, and thus can perform high-density plasma. Can be prevented from being re-dissociated due to the generation of slag at the corners of the anode electrode 80, whereby the etching reaction can be stabilized.

FIG. 3 is a view showing a third embodiment of the present invention. The M-RIE apparatus shown in FIG.
The difference from the IE device is that a substantially square plate-shaped cathode electrode 90 is used instead of the square plate-shaped cathode electrode 40. The cathode electrode 90 is formed by forming the square plate-shaped cathode electrode 40 shown in FIG. 2 with its corners extending diagonally, and extending outwardly from these. Is the anode electrode 8
Are arranged so as to correspond to the positions of the 0 protruding portions 81.

According to such an M-RIE device, since the cathode electrode 90 having the extended portions 91 is used, the electric field E is smaller than that in the case where the conventional cathode electrode 40 is used.
Are located farther away from the wafer 50, and therefore, the generation position of the high-density plasma region can be separated from the wafer 50 as compared with the case where the cathode 40 is used. That is, although the electron drift motion does not occur unless the electric field E and the perpendicular magnetic field B exist, in the present embodiment, the electron drift motion is more distant from the wafer 50 due to the formation of the extending portions 91. It is because it occurs up to.

FIG. 4 is a view showing a fourth embodiment of the present invention. The M-RIE apparatus shown in FIG.
The difference from the IE device is that the electromagnetic coils 10, 11, 2
This is a point that both end portions of 0 and 21 are bent outward along the protruding portion 81 of the anode electrode 80, respectively. That is, the electromagnetic coils 10, 11, 20, 21 have bent portions 101, 101 (111, 111, 201, 2
01, 211, 211), and these bent portions are arranged such that adjacent bent portions between adjacent electromagnetic coils face each other with the protruding portion 81 of the anode electrode 80 interposed therebetween. It is arranged.

According to such an M-RIE apparatus, FIG.
As can be seen from the magnetic field line distribution shown in FIG. 1, the magnetic field gradient at the corner of the anode electrode 80 can be suppressed, and the plasma density distribution in the anode electrode 80 can be made uniform. That is, when the phase between the electromagnetic coils is 2πft = 0, FIG.
As shown in (a), the interval between the lines of magnetic force 77 does not become small in the projection 81 formed at the corner of the anode electrode 80 and in the vicinity thereof, so that a high-density plasma region is not generated in these locations. of course,
Even in the entire anode electrode 80, the interval between the magnetic force lines 77 becomes substantially constant, and therefore the plasma density distribution becomes uniform. On the other hand, the phase between the electromagnetic coils is 2πft = π
Also in the case of / 4, as shown in FIG. 5B, the interval between the lines of magnetic force 78 does not become small at the corners of the anode electrode 80, so that the plasma density distribution within the anode electrode 80 is also uniformed.

In the above embodiment, an example is shown in which the plasma processing apparatus of the present invention is applied to a magnetron reactive ion etching apparatus. However, the present invention can also be applied to, for example, an ashing apparatus. In the magnetron reactive ion etching apparatus, it is only necessary to change the gas used to oxygen. Further, in the above-described embodiment, the anode electrode 80 has a substantially square shape in a plan view. However, the present invention is not limited to this. Further, in the above embodiment, the projections 81 are formed at all corners of the anode electrode 80. However, the projections 81 may be formed only partially depending on other conditions. Similarly, the extension 91 of the electrode 90 may be provided only partially.

[0021]

As described above, in the plasma processing apparatus, the protruding portion is provided at the corner of the anode electrode so that the high-density plasma region generated at the corner in the anode electrode is kept away from the wafer. Therefore, by keeping these high-density plasma regions away from the vicinity of the wafer, the plasma current flowing from the plasma to the wafer to be etched can be made uniform, thereby preventing charge-up damage from occurring.
In addition, since the surface area of the corner portion of the anode electrode becomes larger than that of the conventional M-RIE device due to the formation of the protrusion, as a result, the probability of recombination of the charged particles on the inner surface of the anode electrode when plasma is generated is reduced. As a result, the plasma density in the high-density plasma region generated at the corner portion can be reduced, and the plasma density distribution in the anode electrode can be made uniform.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment when the present invention is applied to a magnetron reactive ion etching apparatus,
(A) is a plan sectional view, and (b) is a sectional view taken along line AA.

FIG. 2 is a view showing a second embodiment of the present invention, wherein (a)
Is a plan sectional view, and (b) is a sectional view taken along line AA.

FIG. 3 is a diagram showing a third embodiment of the present invention, wherein (a)
Is a plan sectional view, and (b) is a sectional view taken along line AA.

FIG. 4 is a diagram showing a fourth embodiment of the present invention, wherein (a)
Is a plan sectional view, and (b) is a sectional view taken along line AA.

5A and 5B are diagrams showing distributions of lines of magnetic force in the magnetron reactive ion etching apparatus shown in FIG. 4, and FIG.
(B) shows the case where the phase of the coil current is 0, and (b) shows the case where the phase of the coil current is π / 4.

6A and 6B are views showing an example of a conventional magnetron reactive ion etching apparatus, wherein FIG. 6A is a plan sectional view, and FIG. 6B is a sectional view taken along line AA.

FIG. 7 is a diagram showing a distribution of lines of magnetic force in the magnetron reactive ion etching apparatus shown in FIG. 6, (a).
(B) shows the case where the phase of the coil current is 0, and (b) shows the case where the phase of the coil current is π / 4.

[Explanation of symbols]

 10, 11, 20, 21 Electromagnetic coil 40, 90 Cathode electrode 50 Wafer 80 Anode electrode 81 Projection 82 Exhaust port 91 Extension 101, 111, 201, 211 Bent

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065 C23F 4/00 H05H 1/46

Claims (5)

(57) [Claims] 1. A cathode electrode on which a wafer is mounted, and a polygonal upper portion disposed to face the cathode electrode
An electrode and a side electrode disposed surrounding the cathode electrode;
An anode electrode formed in a box shape opening downward, and the cathode electrode is sandwiched outside the anode electrode.
A plurality of pairs of electromagnetic coils arranged opposite to each other.
The side electrodes forming the anode electrode are arranged adjacent to each other.
Box-shaped corners between the electromagnetic coils to be placed.
A protruding portion that protrudes outwardly from the
The upper electrode constituting the cathode electrode has an upper opening of the protrusion.
A plasma processing apparatus characterized in that the apparatus is closed . 2. The plasma processing apparatus according to claim 1, wherein an exhaust port is provided at a protruding portion of the anode electrode so as to be openable and closable. 3. The plasma processing apparatus according to claim 1, wherein a portion of the cathode electrode opposed to a position of the protruding portion of the anode electrode is formed to extend in a protruding direction of the protruding portion. . 4. An end portion of an electromagnetic coil disposed on both sides of the projection of the anode electrode is bent outwardly along the projection, and is opposed to each other. The plasma processing apparatus according to claim 1. 5. A cathode electrode on which a wafer is mounted, and
Polygonal upper electrode placed opposite the cathode electrode
And a side electrode disposed around the cathode electrode.
Between the anode electrode formed in a box shape opening one side,
With the etching gas introduced, the cathode electrode and the
An electric field is generated between the anode electrode and the anode electrode.
Outside the node electrode, sandwich the cathode electrode
Apply current to multiple pairs of electromagnetic coils
By generating a magnetic field orthogonal to the electric field,
Plasma is generated between the cathode and anode electrodes.
In the plasma processing method for processing the wafer by arranging, the side electrodes constituting the anode electrode are arranged adjacent to each other.
Box-shaped corners between the electromagnetic coils to be placed.
By projecting the over portion outwardly, it occurs in the corner portion
A high-density plasma region in the protruding direction to
A plasma processing method characterized in that it is kept away from c .