JPH0330424A - Plasma etching device - Google Patents

Abstract

PURPOSE:To manufacture the title plasma etching device in the structure capable of miniaturization and power saving using no electromagnetic coil while uniforming the plasma by a method wherein rotary electric field generating parts composed of electrode members in specific shape respectively making mechanical differential angles are provided on one side of parallel electrodes arranged in a chamber. CONSTITUTION:Rotary electric field generating electrode parts composed of divided electrode member in specific shape are provided on one side of parallel electrodes 7, 8 arranged in a chamber so that the electric field distribution in the chamber 9 may be turned to the rotary electric field by transmitting electric signals in differential phases corresponding to the said mechanical differential angles to the electrode parts. For example, two opposite electrodes are composed of conical electrodes 5a-5d cut into quarters while high-frequency SIN wave signals and COS wave signals in 90 degree of electric phase difference are transmitted from secondary coil 3a and pi/2 phase-shifting device 4 of respec tive transformers 3 to the said electrodes so as to generate the rotary electric field.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dry etching apparatus that performs etching using plasma, and particularly to a mechanism that averages the plasma distribution in the plasma chamber and increases the plasma density. Revised JIL plasma etching equipment with
This is related to K.

[Conventional technology]

As a conventional plasma etching apparatus, a reactive ion etching (hereinafter referred to as RIE) apparatus will be described as an example, as shown in FIG. This RIE apparatus has 1
A disk-shaped upper electrode 21 and a lower electrode 22 are arranged in parallel with each other in a cavity 24 serving as a vacuum chamber, a wafer 23 to be etched is placed on the lower electrode 22, and an etching gas is introduced through the gas inlet 25. Introduce the system. Then, high frequency power is applied from a high frequency (RF) power source 28 between the electrodes 21 and 22 to create a parallel alternating electric field (13.56 MHz), causing a glow discharge and turning the etching gas into plasma. The wafer 23t-etches using radical molecules, ionized ions, and electrons. In addition, in FIG. 5, 26 is a vacuum inlet, and 27 is a matching circuit.

9. In order to average the plasma distribution in the chamber, there is also a magnetic field RIE device that generates a magnetic field perpendicular to the electric field and uses this magnetic field as a rotating magnetic field. A cross-sectional view of its schematic structure is shown in Figure 6. . Here, 31& and 31b are paired coils, and 32a and 32b and 33& and 33b are similarly paired coils, forming three pairs of coils. And these three pairs of coils ata, 3
1b, 328, 32b, 33&, 33b are installed outside the plasma chamber 34 that accommodates the wafer 35, and generate a magnetic field perpendicular to the electric field of parallel electrodes (not shown) disposed opposite to each other inside the plasma chamber 34. By forming a rotating magnetic field and generating a rotating magnetic field, a synergistic effect of these magnetic fields and an electric field, i.e., an increase in plasma density due to the E-B effect, and an averaging of υ due to plasma rotation are achieved.

At this time, each of the coils 311 to 33b is driven by a signal having a phase difference in electrical angle corresponding to a difference in mechanical arrangement angle. For example, if the three pairs of coils 31 & ~ 33b are spatially (mechanically arranged) at an angle of 120 degrees, the three-phase alternating current (electrical difference of 120 degrees) is sta,
31b pair coil - +33m, 33b pair coil →
The etching action can be averaged by generating a multi-rotation magnetic field by flowing it through the pair of coils 32 & 32b, narrowing the plasma and rotating the plasma distribution. Also, if the current is supplied with a phase difference of 60 degrees, the pair of coils of aia, 31b /
M32&, 32b pair coil → a3m, 33b
By passing the current through the pair of coils in this order, a rotating magnetic field is generated, and the same effect as described above can be obtained. Also, by sharing the electric and magnetic fields, the E-B effect can be obtained, so electrons can be
These electrons can be used to increase the efficiency of plasma generation.

[Problem to be solved by the invention]

However, in the conventional R [device shown in Fig. 5], plasma is generated by an alternating electric field on parallel electrodes, but the electric field is distorted due to differences in electrode finishing accuracy, and due to slight differences in the wafer multiplier. There is a problem in that the uniformity of the plasma distribution is poor due to the sagging electric field, non-uniform etching gas flow, etc.

In addition, in the conventional magnetic field RIE apparatus shown in Fig. 6, plasma uniformity is improved by rotating the plasma using a rotating magnetic field, but since an electromagnetic coil is provided inside or outside the chamber, the plasma is relatively large. Drive current is required. For this reason, the amount of heat generated is large, a cooling mechanism is required, it is difficult to miniaturize the device, and power consumption also increases.

The present invention was made to solve the above-mentioned problems, and instead of using a rotating electric field, it is possible to average the plasma (uniformity), and the structure of the device also has electromagnetic coils, etc. It is not used and is miniaturized.

The purpose of this invention is to obtain a plasma etching device that can save power.

[Means to solve the problem]

In order to make the plasma distribution uniform, the plasma etching apparatus according to the present invention divides electrode members of a predetermined shape on one side of parallel electrodes arranged in a chamber, and rotates each electrode member nine times with a mechanical angle difference. An electric field generating electrode section is provided,
By feeding electrical signals with a phase difference corresponding to the mechanical angle difference to this electrode part and making the electric field distribution in the chamber a rotating electric field, the etching action on the wafer is made uniform and etching with good reproducibility is achieved. This is what I tried to accomplish.

[Effect]

The plasma etching apparatus of the present invention can uniformize the plasma by generating an alternatingly rotating high-frequency electric field, improve the reproducibility of etching on wafers, and reduce the size of the apparatus and save energy. It can also be measured.

(Example) An example of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 is a schematic diagram showing the overall configuration of a plasma etching apparatus according to the present invention, FIG. 2 is a sectional view taken along line A-A in FIG. 1, and FIG. It is an electrical system diagram showing an electrode structure and its power supply system.

In these figures, 1 is the frequency, for example 13, 5
A high frequency (R, F) power supply using 6MHz, 2 a matching circuit for matching the power supply and the load, and 3 a power divider for supplying power to two electrodes to be described later to create a rotating electric field. It is a trance. Also, 4
5 is a π/2 phase shifter for obtaining an electrical phase difference corresponding to the mechanical angular difference of the electrodes, and 5 is a conical plate for generating a rotating electric field consisting of nine electrodes 50 to 5d divided into four parts. Electrode part, 6
is an insulating electrode holding ring such as 8103 which is resistant to etching and depositing and is used to hold the electrodes 5a to 5d divided into four parts.

Further, T is a ring-shaped upper electrode placed at a predetermined location in the vacuum chamber 9, and near the inner peripheral surface of this upper electrode 7, a lower part of a conical electrode portion 5 for generating a rotating electric field is located. The electrodes 51 to 5d are arranged symmetrically about the axis as shown in FIG. At this time, the quarter-divided conical electrodes 5a to 5d constitute two electrodes facing each other, and these electrodes have a mechanical angle difference of 90 degrees. And the electrical phase is also 90 degrees (π/2)
A high frequency 5IN (sine) wave signal Ex with a difference of .

A rotating electric field is generated by feeding a C05 (cosine) wave signal [7 from the secondary coil 3a of the transformer 3 and the /2 phase shifter 4, respectively. Reference numeral 8 denotes a disk-shaped lower electrode disposed parallel to the upper electrode 7 including the conical electrodes 5 &~5d;
A wafer 10 to be etched is placed thereon. A SIN wave signal is supplied to the secondary coil 3a of the transformer 3 between the lower electrode 8 and the upper electrode 1.

11 is a gas inlet with a rectifying plate for introducing etching gas, and 12 is a vacuum outlet.

According to the configuration of the above embodiment, two electrodes 5m and 5b are arranged in a conical shape with respect to one upper electrode I forming parallel electrodes.
, 5c and 5d are formed as the rotating electric field generating electrode section 5, and these electrodes sa, sb and 5c.

A high-frequency signal block having an electrical phase angle of 90 degrees equal to its mechanical angle difference with respect to 5d, the SIN shown in FIG. 4(a)
By respectively feeding the wave signal EX and the CO8 wave signal EF shown in FIG. 4, a rotating electric field vector resulting from the combination of both can be generated as an alternating rotating electric field 9 as shown in FIG. 4(c). However, the composite rotating electric field vector shown in FIG. 4(0) is obtained when a cosine wave is fed to the Y axis and a sine wave is fed to the X axis.

Therefore, in the etching method of this embodiment, after introducing the plasma etching gas from the gas inlet 11, this gas is applied to the two opposing electrodes 5m, 5b and 5c.
By passing through the alternating rotating electric field generated by the conical electrode part 5 consisting of 5d, it is excited by high frequency, and the radical molecules, ionized molecules (ions) and electrons promote the separation of the sheath layer. .

Furthermore, because of the conical electrode section 5, it has downward speed while rotating in a circle, and the upper electrode 7, which forms a parallel electrode. Plasma molecules are caused to enter the parallel electric field region formed between the lower electrodes 8. In this case, the motion of the plasma molecules is changed from circular motion to linear motion by the parallel electric field, and etching is performed by colliding the plasma molecules onto the Ueno layer 10. This has the advantage of increasing the plasma density and increasing the efficiency of plasma generation, as well as ensuring uniformity of the plasma.

In the above example, the electrode structure for generating a rotating electric field is shown as a conical plate, but this can also be constructed by a combination of parallel flat plates as in a synchroscope, or by dividing a cylindrical plate. . In addition, the power feeding method has an electrical phase angle of π/2
However, power may be supplied using polyphase alternating current. Furthermore, in the example of the seven upper electrodes forming parallel plate electrodes, the rotating electric field generating electrode section 5 is arranged under the rotating electric field generating electrode part 5, but the rotating electric field generating electrode part 5 is arranged under the upper electrode 7 and parallel A rotating electric field generator is provided above the electric field, or a π/2 phase shifter 4
It is also possible to use the phase delay caused by the cable length.

〔Effect of the invention〕

As described above, according to the present invention, in order to increase the efficiency of plasma generation, the rotating electric field section is configured in the chamber.
Along with promoting the ionization of plasma molecules, the uniformity of the plasma can be measured. Therefore, compared to the conventional method of measuring plasma uniformity using a rotating magnetic field, the device can be made at a lower cost. Furthermore, the high frequency signal for power supply can be easily obtained by dividing the conventional power supply using a high frequency lance or the like.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a plasma etching apparatus according to the present invention, FIG. 2 is a sectional view taken along line A-A in FIG.
Figure 3 is an electrical system diagram showing the electrode structure and power supply system for generating the rotating electric field shown in Figure 1. Figure 4 is a diagram showing the power supply signal waveform and composite rotating electric field vector for the rotating electric field. FIG. 6 is a schematic diagram illustrating an RIE apparatus using parallel flat plates, and FIG. 6 is a cross-sectional view of a schematic structure showing the same conventional RIE apparatus using a rotating magnetic field. 1・φ・・High frequency power supply, 3・・・Transformer, 4e**
-π/2 phase shifter, 5, writing... Electrode section for generating rotating electric field, 6
... Electrode holding ring, T ... Upper electrode, 8 -
Sleep-lower electrode, 9.Vacuum chamber 10-@Φ
・Wafer, 11・Fist・Gas inlet, 12@φ self-evacuation port.

Claims (1)

[Claims] In a dry etching device that uses plasma, an electrode part of a predetermined shape is divided into two parts on one side of parallel electrodes arranged in a chamber, and an electrode part for generating a rotating electric field is provided in each part with a mechanical angle difference. A plasma etching apparatus characterized in that the electric field distribution in the chamber is made into a rotating electric field by feeding an electric signal having a phase difference corresponding to the mechanical angle difference to the electrode portion.