JP2862088B2 - Plasma generator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a plasma generator used for dry etching, CVD, and the like, which are one of the steps of manufacturing a semiconductor device.

[Prior Art] A conventional plasma generator will be described with reference to FIG.

A plate electrode (cathode electrode) 2 connected to a high-frequency power supply 1 via a DC blocking capacitor 8;
Electrode (anode electrode) 3 at ground potential relative to
Is installed. The cathode electrode 2 and the anode electrode 3 are housed in a vacuum vessel 4, and the cathode electrode 2 is made of an insulating material 5.
Is insulated from the vacuum container 4.

The vacuum vessel 4 is provided with an introduction system 6 for introducing a reactive gas and an exhaust system 7 for keeping the pressure inside the vacuum vessel 4 constant.

An object to be processed, for example, a silicon wafer 9 is usually mounted on the cathode electrode 2.

When a high-frequency power, for example, 13.56 MHz is applied between the two electrodes 2 and 3 to generate plasma between the two electrodes, a large difference in the moving speed of electrons and positive ions in the plasma causes the high-frequency power to be applied (cathode). A cathode drop (self-bias) occurs on the electrode 2 side). The reactive gas ions are accelerated by the drop of the cathode and vertically incident on the object 9 to be processed, whereby the etching in the vertical direction proceeds.

[Problems to be Solved by the Invention] When an etching process is performed by such an apparatus, the cathode fall voltage (ion energy) and the number of ions (ion density = plasma) incident on the object to be processed are main factors that determine the etching rate. Density).

In order to increase the etching rate, it is necessary to particularly increase the plasma density among the ion energy and the plasma density. To increase the plasma density, it is sufficient to increase the applied high frequency power.

However, when the high-frequency power is increased, the cathode drop voltage (ion energy) naturally increases.

Therefore, in the case where the object to be processed is a wafer for manufacturing a semiconductor device, in the conventional case, if the etching rate is increased, the ion energy increases, and if the ion energy further increases, a film is formed on the surface of the wafer. There is a problem that a damaged mask, a layer under the etching layer, or a base material may be damaged.

The present invention has been made in view of the above circumstances, and has as its object to provide a plasma generator for preventing damage under a mask and a layer to be etched and realizing a high etching rate.

[Means for Solving the Problems] According to the present invention, an anode electrode having a ground potential is provided so as to face a high-frequency cathode electrode, and a DC cathode electrode is provided so as to face the anode electrode. A required number of holes are provided in a portion facing the high-frequency cathode electrode and the anode electrode to discharge by applying high-frequency power between the high-frequency cathode electrode and the anode electrode, and discharge by applying DC power between the DC cathode electrode and the anode electrode. It is characterized by the following.

[Operation] A high-frequency plasma is generated between the high-frequency cathode electrode and the anode electrode, and a DC plasma is generated between the DC cathode electrode and the anode electrode. The high frequency plasma has a positive potential with respect to the DC plasma by separating the two plasmas at the anode electrode at the ground potential provided with a large number of holes. It is taken into the plasma and increases the density of the high-frequency plasma. The cathode drop voltage of the high-frequency cathode electrode is mainly determined by high-frequency power, and does not significantly affect the cathode drop voltage, that is, ion energy, by taking in electrons from the DC plasma.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the basic configuration of the embodiment, and FIG.
FIG. 3 shows the electrode positions corresponding to the figure and the potential distribution of plasma generated therebetween.

A high-frequency cathode electrode 11 and a DC cathode electrode 12 are arranged to face each other, and an anode electrode 13 is arranged between the electrodes 11 and 12. The anode electrode 13 is a perforated plate having a large number of holes,
Or a mesh-like plate.

The high frequency cathode electrode 11 is connected to a DC blocking capacitor 8
Connected to the high-frequency power source 1 via the DC cathode electrode
12 is connected to the negative side of the DC power supply 15 via the resistor 14. The + side of the DC power supply 15 and the anode electrode 13 are set to the ground potential.

In the above-described configuration, high-frequency power and DC power are applied between the high-frequency cathode electrode 11 and the anode electrode 13 and between the DC cathode electrode 12 and the anode electrode 13, respectively. , DC plasma 17 is generated.

Thus, the above-mentioned plasma potential distribution between the electrodes is the second
It looks like the figure. That is, the anode electrode 13 becomes the ground potential, and the vicinity of the DC cathode electrode 12 and the high-frequency cathode electrode
A cathode drop of V ₁ and V ₂ occurs near 11 respectively. or,
Plasma potential of -V _P1 is in a space excluding the electrode near the direct current plasma 17, the space excluding the electrode near the high-frequency plasma 16 generated plasma potential of + V _P2.

Therefore, in the plasma space in which the potential distribution as shown in FIG. 2 is formed, the electrons in the DC plasma 17 are always accelerated by the accelerating electric field of _VP1 + _VP2 and supplied to the high-frequency plasma 16 through the anode electrode 13. You. With the supplied electrons, the plasma density of the high-frequency plasma 16 can be higher than the plasma density using only the high-frequency power. Also, the high-frequency power is dominant for the cathode drop voltage V ₂ on the high frequency side,
It is substantially constant even when the plasma density increases. Thus, the plasma density can be controlled by controlling the DC power applied by the DC power supply 15, and the ion energy is determined by the cathode fall (self-ias) governed by the RF power, so that the RF power is controlled. As a result, the plasma density and ion energy can be controlled individually and independently. The spatial distribution of the plasma density can be adjusted by changing the distribution state of the holes of the anode electrode 13.

FIG. 3 shows another embodiment of the present invention, in which the direct current cathode electrode 12 is a so-called hollow electrode 18 in the above embodiment so that plasma is generated efficiently.

A number of holes 19 are dug in the hollow electrode 18 to generate a hollow cathode discharge in the hole 19.

The shape of the hole 19 is optimally such that twice the thickness of the cathode drop of the glow discharge is slightly smaller than the diameter of the hole 19, and the depth of the hole is about twice the diameter or more. It is preferred that

Further, when the hollow electrode 18 is used, it is possible to change the distribution of the plasma density by changing the distribution of the dug holes 19. In the uniform distribution of the holes 19, the peripheral plasma density is high and the etching rate of the wafer 9 is high in the periphery (curve A). However, the hole distribution can be made uniform by making the center dense (curve B). it can.

FIG. 5 shows the relationship between the DC discharge current and the etching rate when the high-frequency power is constant using the hollow electrode 18, and it can be seen that the etching rate can be controlled by changing the DC discharge current. You.

The hollow electrode 18 may of course be a groove instead of the hole 19.

FIG. 6 shows a third embodiment. The anode electrode 20 is formed in a cylindrical shape having only one end surface opened, and a large number of holes 22 (or slits) are formed on the same circumference of the cylindrical wall 21, and a ring-shaped DC cathode 23 is arranged to face the holes 22. The ring-shaped DC cathode 23 has a hole 19 formed in the inner peripheral surface thereof to serve as a hollow electrode.

The high-frequency cathode electrode 23 is provided at the opening of the anode electrode 20 so as to face the bottom surface.

By applying a high-frequency power between the anode electrode 20 and the high-frequency cathode electrode 24, a high-frequency plasma is generated inside the anode electrode 20, and a DC power is further applied between the anode electrode 20 and the DC cathode electrode 23. By doing
DC plasma is generated between the anode electrode 20 and the DC cathode electrode 23, and electrons in the DC plasma are supplied to the high-frequency plasma through the holes 22.

In the third embodiment, a plurality of rows of holes 22 may be provided, and a plurality of DC cathode electrodes 24 may be provided so as to face the holes 22. In this case, the discharge current of each DC cathode electrode 24 is reduced. By changing them, it becomes possible to control the number of electrons to be supplied and the spatial distribution of the plasma density in the high-frequency plasma, respectively. Further, the concave portion of the DC cathode 23 may be a continuous groove.

[Effects of the Invention] As described above, according to the present invention, ion energy and plasma density, which are factors that determine the etching rate in plasma dry etching, can be individually controlled.
The plasma density can be increased while keeping the ion energy at the optimum value, and an excellent effect that the etching rate can be increased without damaging the non-etched portion of the object to be processed is exhibited.

[Brief description of the drawings]

FIG. 1 is a basic structural diagram showing a first embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing a plasma potential distribution in the embodiment, FIG. 3 is a diagram showing a basic configuration of the second embodiment, FIG. 4 is a diagram showing an etching rate distribution, and FIG. FIG. 6 is a basic configuration diagram showing a third embodiment, and FIG. 7 is a basic configuration diagram showing a conventional example. 11, 24 are high-frequency cathode electrodes, 12, 23 are DC cathode electrodes, 13, 20 are anode electrodes, 18 is hollow electrodes, 19 is holes, 2
2 indicates a hole.

Continuation of the front page (56) References JP-A-60-195939 (JP, A) JP-A-61-2328 (JP, A) JP-A-62-120479 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) H05H 1/46 H01L 21/3065 H01L 21/205

Claims (5)

(57) [Claims] An anode electrode having a ground potential is provided opposite to a high-frequency cathode electrode, and a DC cathode electrode is provided opposite to the anode electrode. A plasma generating apparatus characterized in that holes are provided, high-frequency power is applied between the high-frequency cathode electrode and the anode electrode to discharge, and DC power is applied and discharged between the DC cathode electrode and the anode electrode. . 2. The plasma generator according to claim 1, wherein a concave portion is provided in said DC cathode electrode to form a hollow electrode. 3. The plasma generator according to claim 2, wherein the distribution state of the concave portions provided on the DC cathode electrode is changed to change the spatial distribution of the plasma density. 4. The plasma generator according to claim 1, wherein the spatial distribution of the plasma density is changed by changing the hole distribution state of the anode electrode. 5. The plasma according to claim 1, wherein at least one of high-frequency power applied between the high-frequency cathode electrode and the anode electrode and DC power applied between the DC cathode electrode and the anode electrode are independently controlled. Generator.