JPS6376889A - Dry etching device - Google Patents

Abstract

PURPOSE:To form a uniform etching pattern by providing an AC power source connected to the electrode on the substrate side separately from a plasma generating high-frequency power source in the title dry etching device, and separating the electrode on the substrate side to control the energy of the ion to be injected into the substrate. CONSTITUTION:The inside of a dry etching chamber 1 is evacuated, then a gaseous reactant such as CF4 is introduced, and a high-frequency power is supplied to an electrode 2 from the high-frequency power source 6. An electric current flows through capacitors 7a-7c connected to the slit electrodes 3a-3c of an electrode 3, hence plasma 10 is generated between both electrodes 2 and 3, and the SiO2 in a material to be etched on a substrate 5 is etched. An electric power is supplied to the electrode 3 provided on the substrate side from the AC power source 8, most of the electric current flows through variable resistors 9a-9c to generate an electric potential between both ends, different potentials for discharge plasma are provided to the respective split electrodes 3a-3c by controlling the resistance values of the variable resistors 9a-9c, and the whole surface of the substrate 5 is uniformly etched by the uniform plasma.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a dry etching apparatus used for etching in a semiconductor manufacturing process, and particularly to a dry etching apparatus suitable for forming a uniform etching pattern. Regarding.

[Conventional technology]

Currently, dry etching apparatuses utilizing reactive ion etching are widely used in the etching process for forming semiconductor device patterns. This device introduces etching gas into a processing chamber that is controlled to the required pressure.
This is a configuration in which high-frequency power is applied between opposing parallel plate electrodes to generate discharge plasma. Etching is performed using a chemical reaction caused by neutral radicals generated by plasma and a physical sputtering effect caused by the impact of ions on a semiconductor substrate (hereinafter referred to as the substrate). Ions are accelerated in a sheath region formed between the plasma and the substrate and are incident perpendicularly to the substrate, resulting in an etched shape with less side etching and excellent microfabrication.

In these etching techniques, it is important to obtain a uniform pattern over the entire surface of the substrate, but the uniformity of the etching speed with current dry etching equipment is
．． It is about 10% for a 5isO4 substrate. However, with the recent miniaturization of device patterns, the underlying film of the etched material tends to become thinner, and uneven etching rates affect the device characteristics themselves by exposing the underlying material to plasma unevenly. Uniformity of 10% has become insufficient as an etching property. Furthermore, since it is expected that the diameter of substrates will further increase in the future, improvement of uniformity is an issue for M9 from this point of view as well.

Conventionally, in order to improve uniformity, inventions in which features were added to the electrode structure of parallel plate electrodes for the purpose of making plasma uniform on the electrode surface were disclosed in Japanese Patent Laid-Open Nos. 57-19577 and 1983.
Publication No. 7-23227, and JP-A-57-19226
There is a dry etching apparatus described in Japanese Patent No. 8. These devices divide the parallel plate electrode that faces the electrode on which the substrate is placed into multiple parts, connect a high frequency power source to these divided electrodes, and connect each divided electrode to one part with the substrate electrode.
! The structure has a variable pole spacing. With this structure, the electric field strength of the discharge plasma can be locally controlled by changing the amount of high-frequency power supplied to each divided electrode and the electrode spacing, thereby achieving uniform plasma throughout the processing chamber. It is.

This configuration that locally changes the electrode spacing makes the plasma uniform and improves the uniformity of the etching rate;
There was a problem in that uniformity deteriorated rapidly when the pressure and high frequency power changed. That is, the range of discharge conditions with good uniformity was narrow, and stability was insufficient.

[Problem that the invention seeks to solve]

Regarding the uniformity of etching speed, the current equipment has
Uniformity of about 10% obtained by controlling pressure, high frequency power, and electrode spacing is insufficient, and although good uniformity can be obtained with the configuration of the known technology shown in the above-mentioned patent publication, Stability was insufficient, with uniformity rapidly deteriorating when pressure and high-frequency power changed.

The purpose of the present invention is to partially control the ion energy to improve the uniformity of 3 to 5%, which is about 10% with current devices.
The object of the present invention is to provide a dry etching apparatus which has improved uniformity against changes in pressure and high-frequency power to the same level as current apparatuses.

[Means for solving problems]

In addition to the high-frequency power source that generates plasma, the above purpose is to
By providing an AC power supply connected to the electrode on the substrate side, dividing the electrode on the substrate side, and applying a potential to each of them to control the energy of the ions incident on the substrate,
achieved.

[Effect]

Etching speed is related to ion density and ion energy. When a potential is applied to each part of the divided electrode by an AC power supply connected to the electrode on the substrate side, the ion energy of that part increases. When a potential is applied to a portion where the etching rate is slow, the ion energy increases in that portion and the etching rate increases, but other portions remain unchanged.

Therefore, this method allows uniform etching rates across the entire substrate.

Note that the AC power supply connected to this substrate electrode only applies a potential to the electrode, and supplies only a few percent of the power to the plasma, and the discharge state of the plasma does not change. Therefore, the parallel plate dry etching device and electrode structure may be the same as those currently used, and the same stable characteristics with respect to pressure and high frequency power can be obtained.

From the above, according to the present invention, both improved uniformity and stability can be obtained.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5. FIG. 1 is a schematic configuration diagram of an apparatus according to an embodiment of the present invention;
FIG. 2 is a diagram showing the etching rate distribution when the incident ion energy to the substrate is controlled, and FIG. 6 is a schematic diagram of the apparatus of another embodiment.

The following description will be made by taking as an example a system in which substrates are processed one by one, such as in a single-wafer system, using the apparatus shown in FIGS. 1 and 5.

In FIG. 1, 1 is a processing chamber, 2.5 is an electrode facing each other, and a lower electrode 5 has a substrate 5 placed thereon, and three concentric ring-shaped electrodes are placed on the lower electrode 5 through an insulating material 4. Split electrode 3
It is divided into a, 3b, and 3c. 6 is the frequency fa (for example, IA56MHz) for generating plasma in the processing chamber 1.
This is a high frequency power source. Reference numerals 7a, 7b, and 7c are bypass capacitors that are connected to the divided electrodes 3a, 3b, and 3c of the electrode 3 on which the substrate is placed, respectively, and flow the high frequency power from the high frequency power source 6 to the ground. 8 is a frequency f for providing a potential to draw ions in the plasma to the substrate 5
L (e.g., 1 ooxuz) AC power supply; 9 is a resistor with a resistance equal to the output impedance (e.g., 50Ω) of the AC power supply 8, and is used to apply a desired potential to each divided electrode 5a, 5b% 3c of the electrode 5. The variable ends are respectively divided electrodes 3a.

Variable resistors 9a, 9b, 9 connected to 3b, 3c
c (each total resistance value is, for example, 150Ω).

Further, 10 is plasma. The above capacitors 7a, 7
b, 7c have a capacitance value of 1000 pF, for example, and their impedance is the same as the above-mentioned high frequency fB156
12Ω for MHz, variable resistor 9as 9bs
The resistance value is 1/10 of the resistance value of 9C, and is 1600Ω for the above-mentioned low frequency fI of 100KHz, which is more than 10 times the resistance value of the variable resistors 9a, 9b, and 9o.

Next, the operation of this embodiment will be explained in detail with reference to FIGS. 1 and 2. In FIG. 1, the inside of a processing chamber 1 is evacuated by a vacuum evacuation system (not shown), a reaction gas (e.g., fluorocarbon gas CF4) is introduced from a gas supply system (not shown), and a predetermined pressure (e.g., from IPa to several 10 Pa). Here, when high frequency power is applied to the electrode 2 from the high frequency power supply 6, the divided electrodes 38 to 38 of the electrode 5
Since the capacitors 7a to 7C connected to the capacitor 3c have low impedance with respect to the frequency fH of the high frequency power source 6 as described above, current flows through the capacitors 78 to 7C. The combined impedance of the capacitors 7a to 7C is only 59 ohms with the above-mentioned capacitance value of 1000 pF, which is similar to the dry etching device of the known anode coupling method (configuration in which the electrode 6 mounted on the substrate is directly connected to the ground). Plasma 10 is stably generated between electrodes 2 and 3, and etches the material to be etched 5102 on substrate 5. Next, when power is applied to the electrode 3 from the AC power supply 8, the electrode 3
Capacitors 78-7 connected to divided electrodes 38-3C of
Since C has a high impedance with respect to the frequency fL of the AC power source 8, most of the current from the AC power source 8 flows through the variable resistors 9a to 90, and a potential is generated at both ends thereof. Here, if the pure resistance value of each of the variable resistors 98 to 9c is 1500 as described above, the combined impedance is 50Ω.
Therefore, a matching circuit between the AC power supply 8 and the resistor 9 is unnecessary. Then, by adjusting the variable ends of the variable resistors 9a to 90, the potential is divided, and a potential is applied to the divided electrodes 38 to 3C, which are electrically separated by the insulating material 4, independently of the discharge plasma. I have to.

Next, the energy of ions incident on the substrate during etching and the distribution of etching speed within the substrate will be explained with reference to FIG.

In the figure, the horizontal axis represents the distance from the center of the substrate (which coincides with the center of the electrode 5), and the vertical axis represents the etching rate. In the figure,
The distribution shown by the broken line uses fluorocarbon gas CF4 as the reaction gas, and the pressure is 30 Pa.

The etching speed distribution when etching 8102 using the conventional method at high frequency power of 200 W is shown. Uniformity is 10%. On the other hand, electricity is supplied from the AC power supply 8, and the electrode 3 having an electrode diameter of 1701 IIll is divided into divided electrodes 38 to 3c at radii of 40 m and 60 m from the center, respectively, to generate a potential having a peak value v0 at a frequency f of 100 KHz. The solid line in the figure shows the etching rate distribution when . Peak value V0 = 660V on divided electrode 3a, similarly 3 bc63
0V.

When a potential of 600V is applied to 3o by adjusting the variable resistors 98 to 90, the ion energy increases in the order of 3a%, 5bs, 3c, and the uniformity of the etching rate improves to 5% as shown in the figure. .

In this configuration, only the potential is set as described above, so only a few percent of the power is supplied to the plasma, and the discharge state of the plasma does not change. Therefore, the same stable characteristics as current devices can be obtained with respect to pressure and high frequency power.

In the above example, the frequency f of the high frequency power source for generating plasma is 1i56 MHz, the frequency fL of the AC power source provided on the substrate mounting electrode side is 100 KHz, the capacitor capacity is 1000 PF, and the output impedance of the AC power source is 500. The frequency of each power source is not limited to this, and it is of course possible to configure other configurations as long as the high frequency power source and the AC power source have combinations of frequencies, capacitances, and output impedances that do not affect each other. . Furthermore, the waveform of the AC power supply is not limited to a sine wave, but may be a special waveform such as the potential waveform (a waveform that unifies the ion energy incident on the substrate) disclosed in Japanese Patent Laid-Open No. 60-126852. It may also be a waveform. Furthermore, the electrode diameter of the substrate mounting side electrode was increased to 170 mm.
am, radius 40■ from center of division position, 6011I11
Although the description has been made assuming that the position and the number of divisions are 3, these parameters are not limited to the above values. Further, the divided shape of the electrodes does not have to be concentric ring shapes, but can also be shaped like squares in accordance with the shapes of the counter electrode and the substrate (sample to be etched).

The present invention is not only effective for a counter-electrode type dry etching apparatus, but also for β-wave ECR, (electron cyclotron resonance, Electron C7clotror Re5
It is clear that the present invention can also be applied to a dry etching apparatus of the onancs type. This will be explained next.

FIG. 5 shows a case where the present invention is applied to a μ-wave ECR type dry etching apparatus. In Figure 5, Figure 1 and 閜-
Items with symbols indicate the same or equivalent parts. Third
In the figure, 20 is a waveguide, 21 is a magnetron, 22
is a coil. A magnetron 2 is installed at one end of the waveguide 20.
1 is attached, the other end of the waveguide 20 extends through the processing chamber 1, and a coil 22 is placed around it. At the bottom of the processing chamber 1 there is an electrode 3 on which a substrate 5 is placed. The electrode 3 is divided into a plurality of ring-shaped parts via an insulating material 4 (divided electrode 38 in the figure).
~3cl: divided into three), each divided electrode is connected to an AC power source 8 that controls the ion energy incident on the substrate and a variable resistor 9a~
9C, and variable resistors 98 to 9.
It is grounded via c. The plasma of this device is a μ wave (for example, 2.45 GH2) generated by the magnetron 21.
is generated by electron cyclotron resonance due to the magnetic field of the coil 22. In this case, since plasma is generated without electrodes, there is no need to connect a capacitor to the substrate mounted electrode as in the previous embodiment, and by adjusting the variable resistors 98 to 9C, the divided electrodes 58 to 3C can be connected to the divided electrodes 58 to 3C. Applying the desired potential,
The ion energy incident on the substrate can be controlled.

As described above, the present invention is not limited to the plasma generation method.

〔Effect of the invention〕

As explained above, according to the present invention, in a dry etching apparatus, the AC power supply for controlling the ion energy incident on the substrate is installed separately from the high frequency power supply for generating plasma, and Since the structure is such that the etching is applied independently, it is possible to compensate for the slow etching rate in current dry etching equipment by increasing the ion energy, improving uniformity to 3 to 5%. can. Note that the potential application to the substrate is performed separately from the high frequency power source that generates plasma as described above, and the plasma discharge itself is not changed. Therefore,
The same stable custom etching can be achieved against the pressure and high frequency power of conventional equipment.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a dry etching apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing the etching rate distribution when the incident ion energy to the substrate is controlled, and FIG. 3 is a diagram showing another example of the dry etching apparatus according to the present invention. FIG. 1 is a schematic configuration diagram of an apparatus according to an embodiment. 1... Processing chamber, 2, 5... Electrode, 3a-3
c...Divided electrode, 4...Insulating material, 5...
Board, 6...High frequency power supply, 78~7c...
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Claims (1)

[Scope of Claims] 1. A means for generating plasma in a vacuum processing chamber, an electrode on which a substrate to be exposed to the plasma and to be processed is placed, and a means connected to the electrode on which the substrate is placed to apply an electrode potential. A dry etching apparatus comprising a power supply having means, the electrode on which the substrate is placed is divided into a plurality of parts, and each divided electrode is provided with an adjustment means capable of applying and adjusting an electrode potential from an AC power supply. A dry etching device characterized by: 2. The dry etching apparatus according to claim 1, characterized in that the means for adjusting the potential to the electrode on which the substrate is placed is constituted by means for applying a divided potential using a variable resistor. dry etching equipment. 3. In the dry etching apparatus according to claim 1, the means for generating plasma in the vacuum processing chamber is provided with a flat plate electrode facing the electrode on which the substrate is placed, and a high frequency power source is connected to the flat plate electrode. A dry etching device characterized by: 4. The dry etching apparatus according to claim 1, wherein the means for generating plasma within the vacuum processing chamber is a plasma generating apparatus using microwaves.