JP2002009047A - Plasma processor and plasma processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniform the peak-to-peak of a high frequency voltage in an electrode face which is the cause of the improvement of the uniformity of a plasma processing, in a plasma processor where a planar electrode in which an object to be processed is installed in a vacuum chamber, high frequency power is applied at the back of the electrode, plasma is generated on a side where the processed object is installed for plasma-processing. SOLUTION: A first dielectric 13 which is formed in such a way that it is sequentially thickened along a direction to an outer peripheral part from a center where high frequency power is applied is arranged in a lower electrode 5 and the impedance of the lower electrode 5 is varied in the periphery of the center and the outer peripheral part. Thus, voltage drops differ in respective parts in the lower electrode 5 and the peak-to-peak of the high frequency voltage in the lower electrode 5 is uniformed. Consequently, electric field intensity in the lower electrode 5 is uniformed, ion energy accelerated by an electric field is uniformed in the substrate face and the uniformity of the plasma processing is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a plasma processing apparatus and method for performing plasma processing such as dry etching, plasma CVD, and sputtering.

[0002]

2. Description of the Related Art In recent years, plasma processing has been widely used for surface processing of substances such as fine processing by dry etching, thin film formation, and surface modification. It is an indispensable technology in doing so.

[0003] As a conventional plasma processing apparatus, a capacitively coupled parallel plate plasma processing apparatus has been widely used. The reason is that, while uniform plasma processing is required, uniform low-density plasma can be easily generated under a relatively low degree of vacuum.

However, as the miniaturization of semiconductor integrated circuits has progressed, it has become necessary to generate high-density plasma under a high degree of vacuum, and a high-frequency current is passed through a coil to induce an induced magnetic field in a space under reduced pressure. Inductively coupled plasma generators that generate plasma by acting on them, and plasma processing apparatuses using the same have attracted attention.

When plasma is generated in a high vacuum,
In the case of a dry etching apparatus, the probability that ions collide with ions or other neutral gas particles in the ion sheath formed on the substrate surface is reduced, so that the direction of the ions is aligned toward the substrate and the etching anisotropy is increased. And high aspect ratio processing becomes possible. In the case of a plasma CVD apparatus, a fine pattern is buried and flattened by the sputtering effect of ions, and processing with a high aspect ratio becomes possible. As the sputtering device, R
2. Description of the Related Art An F (Radio Frequency) magnetron sputtering apparatus is known. In this RF magnetron sputtering apparatus, an RF voltage is applied between a target and a substrate to discharge a sputtering gas and generate plasma in a space near a cathode. To deposit a thin film on the substrate.

As an example of a plasma processing apparatus, a conventional parallel plate type dry etching apparatus described above will be described with reference to the drawings. As shown in FIG. 3, the chamber 1 includes a loading / unloading unit and an exhaust unit (not shown) for taking a workpiece into and out of the chamber 1, a reaction gas introducing unit 2 for introducing a reaction gas, and a chamber 1.
Pressure control means 3 for keeping the inside at a predetermined pressure is provided. Inside the chamber 1, a flat upper electrode 4 and a lower electrode 5 are provided in parallel with each other. The lower electrode 5 is provided with an object to be processed such as a liquid crystal glass substrate 6 on which etching or film deposition is performed. The lower electrode 5 is provided with a high-frequency power source 7 outside the chamber 1 at the center or in the vicinity of the lower surface thereof. High frequency power is applied via the device 8.

[0007] As shown in FIG.
, A dielectric 10 disposed under the electrode 9 to insulate it from the bottom of the chamber, and an insulating block 11 surrounding the periphery of the electrode 9 and the dielectric 10. The electrode 9 is made of a conductive material, for example, a single material such as alumite-treated aluminum, in a flat plate shape or a disk shape having a flat surface, and its impedance is not biased depending on the position and the center of the electrode. And the outer periphery of the electrode are substantially equal.

In order to perform dry etching using such a plasma processing apparatus, first, the substrate 6 is loaded into the chamber 1 by a loading / unloading means (not shown) and placed on the lower electrode 5. Thereafter, the gas in the chamber 1 is exhausted by an exhaust means (not shown), the reaction gas is introduced into the chamber 1 by the reaction gas introduction means 2, and the pressure is maintained at a predetermined pressure by the pressure control means 3. Then
High-frequency power is applied to the lower electrode 5 from the high-frequency power source 7 via the impedance matching device 8 to generate plasma between the lower electrode 5 and the upper electrode 4, thereby etching the substrate 6. When the etching is completed, the supply of the high-frequency power is stopped, the introduction of the reaction gas is stopped, the residual gas in the chamber 1 is exhausted, and then the substrate 6 is taken out of the chamber 1.

[0009]

In the above-mentioned conventional parallel plate type plasma processing apparatus, the point of application of high frequency power to the lower electrode 5 is set at the center of the lower surface, and Ti (titanium) is used.
The 550 mm × 670 mm liquid crystal glass substrate 6 on which the film was deposited was used as an object to be processed, and high frequency power of 13.56 Mhz was output from the high frequency power supply 7 to perform etching. The distribution of the etching rate in the substrate surface is shown in FIG. It became so. In the drawing, A and B indicate measurement values on two lines A and B set in directions perpendicular to each other so as to pass right above the application point. Looking at this distribution, the etching rate is low at and around the application point of the high-frequency power, and increases as the distance from the application point increases.

Further, when the VPP (peak-to-peak of the high-frequency voltage) on the lower electrode surface was examined in a non-discharge state in which high-frequency power was applied to the lower electrode 5, as shown in FIG.
It was found that the frequency was low at and around the application point of the high-frequency power, and increased as the distance from the application point increased.

From these facts, as shown in FIG. 6, the VPP of the lower electrode surface changes according to the distance from the point to which the high-frequency power is applied, and the electric field intensity corresponding to the VPP is given in the lower electrode surface. It is considered that the ion energy accelerated according to the electric field intensity was applied, and as a result, the etching rate distribution in the substrate surface as shown in FIG. 5 was obtained.

The change (variation) of the VPP on the lower electrode surface is caused by the fact that when a cable end of a transmission cable is opened and a standing wave generated on the cable or a radio wave is radiated from an antenna, the potential at the open end becomes one. Highest, 1 from open end
This is considered to be the same as that the potential becomes minimum at a position / 4λ away. Under the above conditions, the frequency is 13.56 Mhz
Thus, although the size of the lower electrode 5 is sufficiently smaller than １ ／ λ, it can be said that the size is not negligible.

In this regard, in recent years, in the manufacturing process of semiconductors and liquid crystal panels, the size of wafers and substrates on which etching and film deposition are performed has been increasing, and the electrodes of plasma processing apparatuses have also increased in size. I have. For this reason, it is becoming difficult to secure the in-plane uniformity of the etching rate in the dry etching apparatus and to secure the in-plane uniformity of the deposited film thickness in the CVD / sputtering apparatus.

In particular, in the production of liquid crystal panels, the size of a substrate has conventionally been 370 mm × 470 mm or the like in the past, but now 550 mm × 670 mm or the like, and it is 1000 mm square in 3 to 4 years from now. The size is expected to increase. As the size of the electrode increases, the distance from the high-frequency power application point to the outer peripheral portion increases, and the change (variation) in the VPP of the lower electrode surface becomes more remarkable, and the in-plane uniformity of the process is ensured. It is expected to be even more difficult.

An object of the present invention is to solve the above-mentioned problem, and an object of the present invention is to provide a plasma processing apparatus capable of uniformizing VPP on an electrode surface, which is a factor for improving uniformity of plasma processing.

[0016]

In order to solve the above-mentioned problems, according to the present invention, a plate-like electrode on which an object to be processed is placed is arranged inside a vacuum chamber, and high-frequency power is applied to the back of the electrode to apply the object. In a plasma processing apparatus that generates plasma on the processing object installation surface side and performs plasma processing on an object to be processed, a dielectric body that is formed sequentially thicker in a direction from a high frequency application unit to an outer peripheral portion is disposed inside the electrode. The impedance of the electrode is different between the periphery of the high-frequency application section and the outer periphery. When forming the dielectric sequentially thicker, it may be made gently thicker continuously,
The thickness may be increased stepwise.

Further, according to the present invention, a plate-like electrode for placing an object to be processed is arranged inside a vacuum chamber, and high-frequency power is applied to the back of this electrode to generate plasma on the side of the object-to-be-processed and to generate a plasma. When the object is subjected to the plasma treatment, the impedance of the electrode is arranged around the periphery of the high-frequency application unit by placing a dielectric formed in the electrode in the order of thickness from the high-frequency application unit in the direction from the high-frequency application unit to the outer periphery. The process is performed in a state where the peak-to-peak of the high-frequency voltage in the electrode surface is made uniform.

According to this configuration, the dielectric material is thinner at places where the peak-to-peak (VPP) of the high-frequency voltage is originally low, such as the high-frequency application section and its periphery (hereinafter referred to as the high-frequency application section periphery). However, where the VPP is originally high, such as the outer peripheral portion, the thickness of the dielectric is increased, and the impedance of the electrode itself is made different between the periphery of the high-frequency application portion and the outer peripheral portion. The difference is that the VPP in the electrode surface is made uniform. As a result, the electric field intensity in the electrode surface is made uniform, and the ion energy accelerated by the electric field becomes uniform in the substrate surface, so that the uniformity of the plasma processing is improved.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plasma processing apparatus and a plasma processing method according to an embodiment of the present invention will be described with reference to the drawings. (Embodiment 1) The plasma processing apparatus according to Embodiment 1 of the present invention has substantially the same configuration as the conventional parallel plate plasma processing apparatus described above with reference to FIG.
With reference to FIG. 3, illustration and detailed description of the entire configuration are omitted, and a lower electrode, which is a characteristic member of the plasma processing apparatus, will be described.

As shown in FIG. 1, the lower electrode 5
Has a first electrode 12 on which an object to be processed such as a glass substrate for liquid crystal 6 is placed, a first dielectric 13 for adjusting impedance, A second electrode 14 for applying power and a second dielectric 15 for insulating the chamber from the bottom surface are arranged in this order from above and are in contact with each other. Insulation block 1
6 are arranged.

The first electrode 12 is made of a single material that is a conductive material, for example, alumite-treated aluminum. The upper surface on which the substrate 6 is mounted has a flat surface, in this case, a length of 780 mm. , 660 mm in width.

The second electrode 14 is made of a conductive material, for example, aluminum. A high-frequency power source 7 outside the chamber 1 is connected to a central portion of the lower surface (or in the vicinity thereof) via an impedance matching device 8. are doing.

The first dielectric 13 is made of a dielectric material such as a fluorocarbon resin such as Teflon (trademark), and has a thick outer peripheral portion and a peripheral portion to which high-frequency power is applied and a peripheral portion thereof (hereinafter referred to as a peripheral portion of the central portion). It is formed in a shape with a gentle inclination so as to be thin. In the above-described conventional device, the VPP distribution on the lower electrode surface was ± 5.7%, so that the thickness a was 10 mm around the center and the thickness b was 11.4 mm around the periphery. The lower surface of the first electrode 12 in contact with the first dielectric 13 has a shape having a gentle inclination along the first dielectric 13.

A temperature control mechanism (not shown), for example, a coolant circulation path, is provided inside the first electrode 12.
Is maintained at a predetermined temperature.

In general, the impedance Z of a dielectric is Z
= 1 / 2πfC. (F is the high frequency, C is the capacitance of the dielectric) The capacitance C of the dielectric is C = ε × S /
It is determined by d.

(Ε is the dielectric constant, S is the dielectric area, and d is the thickness of the dielectric) From such a relationship, the thick part of the dielectric (the part where d is large) has a small capacitance C and a large impedance Z. ,
A thin portion (a portion where d is small) has a large capacitance C and a small impedance Z.

Accordingly, the first dielectric 13 has a large impedance at the outer peripheral portion and a large voltage drop when a high frequency is applied, and has a small impedance around the central portion and a small voltage drop when a high frequency is applied. .

As a result, the conventional problem of the lower electrode 5, that is, the phenomenon that VPP is low around the central portion to which high-frequency power is applied and VPP becomes higher toward the outer peripheral portion can be mitigated. The VPP distribution in the surface of the first electrode 12 to be mounted can be made uniform.

Therefore, when high-frequency power is applied to the lower electrode 5 from the high-frequency power source 7 through the impedance matching device 8, the electric field intensity in the plane of the lower electrode 5 becomes uniform, and the ion energy accelerated by the electric field is reduced in the plane of the substrate 6. And uniform plasma processing can be performed. At this time, since the impedance is matched with the plasma, a stable plasma discharge can be generated. (Embodiment 2) In the plasma processing apparatus according to Embodiment 2 of the present invention, as shown in the vertical sectional view of FIG. Has a shape in which the thickness is changed stepwise so as to increase the thickness. That is, in the above-described conventional device, the VPP distribution on the lower electrode surface was ± 5.7%, so that the thickness c = 10 mm around the central portion and the thickness d = 11.4 m around the peripheral portion.
m, and a thickness e = 10.7 at an intermediate portion between the central portion and the outer peripheral portion.
mm. The lower surface of the first electrode 18 in contact with the first dielectric 17 has a shape having a stepwise inclination along the first dielectric 17.

By doing so, the VPP distribution in the surface of the first electrode 18 on which the substrate 6 is mounted can be made uniform, and the same effect as in the first embodiment can be obtained. As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to such a configuration, and may be modified or changed within the scope of the technical idea described in the claims. It belongs to the scope of the present invention. For example, in the above embodiment, the parallel plate type plasma processing apparatus has been described as an example, but the configuration of the present invention can be applied to an inductively coupled plasma processing apparatus in which a coil for generating plasma is arranged at an upper portion of a chamber or the like. It is. Also, an example in which an etching process is performed on a liquid crystal substrate has been described. However, a process using semiconductor or electronic component wear as an object to be processed,
The structure of the present invention can be applied to various plasma treatments such as CVD and sputtering.

[0031]

As described above, according to the present invention, an object such as a liquid crystal substrate is placed and the thickness of the electrode along the direction from the high-frequency application section toward the outer periphery is set inside the electrode for applying the high-frequency power. By arranging a dielectric which changes sequentially, and making the impedance of the electrode itself different between the periphery and the outer periphery of the high-frequency application section, the peak-to-peak distribution of the high-frequency voltage in the electrode plane can be made uniform. As a result, the electric field intensity in the electrode surface can be made uniform, the ion energy accelerated by the electric field can be made uniform in the substrate surface, and the uniformity of the plasma processing can be improved.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a lower electrode constituting a plasma processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional view of a lower electrode constituting a plasma processing apparatus according to a second embodiment of the present invention.

FIG. 3 is a schematic overall configuration diagram of a conventional parallel plate type plasma processing apparatus.

FIG. 4 is a longitudinal sectional view of a conventional lower electrode installed in the plasma processing apparatus of FIG. 3;

FIG. 5 is a distribution diagram of an etching rate in a plane of a substrate provided on a lower electrode of FIG. 4;

FIG. 6 is a VPP distribution diagram on the lower electrode surface of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chamber 2 Reaction gas introduction means 3 Pressure control means 4 Upper electrode 5 Lower electrode 6 Substrate 7 High frequency power supply 8 Impedance matching device 9 Electrode 10 Dielectric 11 Insulation block 12 First electrode 13 First dielectric 14 Second electrode 15 Second Dielectric (for insulation) 16 Insulation block 17 First dielectric 18 First electrode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme coat ゛ (Reference) H01L 21/31 H01L 21/302 C 5F103 F-term (Reference) 4K029 BD01 CA05 DC35 FA05 4K030 DA04 FA03 KA15 KA30 LA15 4K057 DA11 DA16 DB06 DB20 DD01 DG15 DM03 DM06 DM09 DN01 5F004 BA06 BB13 BD04 BD05 5F045 AA08 AE01 BB02 DP02 EH14 EH20 5F103 AA08 BB09 BB33 HH03 HH04 RR06

Claims (2)

[Claims] A flat electrode for placing an object to be processed is disposed inside a vacuum chamber, and a high-frequency power is applied to the back surface of the electrode to generate plasma on the side where the object is to be placed, thereby generating a plasma. In the plasma processing apparatus for performing processing, a dielectric formed sequentially thicker in a direction from the high-frequency application unit to the outer peripheral portion is disposed inside the electrode, and the impedance of the electrode is set to the periphery and the outer peripheral portion of the high-frequency application unit. And a plasma processing apparatus characterized in that: 2. A plate-like electrode on which an object to be processed is placed is disposed inside a vacuum chamber, and high-frequency power is applied to the back of the electrode to generate plasma on the side where the object to be processed is installed. In performing the process, by arranging a dielectric formed sequentially thicker along the direction from the high frequency applying unit to the outer peripheral portion inside the electrode, the impedance of the electrode is changed between the periphery and the outer peripheral portion of the high frequency applying unit. A plasma processing method characterized by processing an object to be processed in a state where peak-to-peak of a high-frequency voltage in an electrode surface is made uniform.