JP2005340758A - Transparent body for plasma treatment apparatus, and plasma treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent body which is reinforced in durability to the plasma of site glass or a transparent chamber inner face, for a plasma treatment apparatus. <P>SOLUTION: The plasma treatment apparatus is characterized in that an upper electrode 2 and a lower electrode 3 are arranged in a chamber body composed of an aluminium alloy, that a chuck 4 mounting a processed work W is provided on the lower electrode 3, that site glass 5 is inserted in an aperture formed in the chamber body 1, and that a transparent plasma-proof layer 5a composed of yttrium oxide (Y<SB>2</SB>O<SB>3</SB>) polycrystalline is formed at the inner side of the site glass 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a translucent body excellent in plasma resistance and a processing apparatus using the translucent body.

  In order to form a multilayer wiring on the surface of a semiconductor wafer or glass substrate, surface treatment such as etching or ashing is repeated in a plasma atmosphere. A plasma processing apparatus that performs this processing is provided with a table for placing an object to be processed in a chamber, and an electrode is disposed inside or outside the chamber, the chamber is decompressed, and a high frequency is applied between the electrodes to generate plasma. It is generated.

  As the chamber, there is a chamber in which sight glass is fitted in a part of an aluminum alloy chamber, or a chamber in which the whole chamber is made of synthetic quartz. Becomes thin (so-called thinning), the light transmittance of the transparent portion is lowered and internal monitoring cannot be performed, and particles are generated, resulting in a decrease in yield.

Therefore, Patent Document 1 proposes to use a high-purity alumina sintered body or a yttrium oxide sprayed film in a place where plasma resistance is required.
Further, Patent Document 2 applies a mechanical impact force by causing a brittle material to collide with a base at a high speed, causing a crystal lattice to be displaced along a wall open surface such as an interface between crystallites, or crushing. It is disclosed that a new surface having a high surface energy is formed on a slip surface or a fracture surface, and that these new surfaces are bonded together to form a transparent layer of a dense brittle material, and in particular, yttrium oxide is disclosed as a brittle material. Yes.
JP 2002-252209 A (Page 2) JP 2003-183848 A paragraph (0021)

When the above-described prior art is applied to a plasma processing apparatus, early devitrification and generation of particles of a light transmitting body such as sight glass are likely to occur.

  That is, the present invention provides a light transmitting body for a plasma processing apparatus that simultaneously satisfies the maintenance of transparency and particle resistance during plasma exposure.

In order to solve the above problems, the present invention provides a transparent body for a plasma processing apparatus in which a workpiece is set in a chamber, plasma is generated in the chamber under reduced pressure, and the workpiece is subjected to surface treatment. A transparent plasma-resistant layer is formed on the inner surface of the light body. This transparent plasma-resistant layer is mainly composed of a yttrium oxide (Y ₂ O ₃ ) polycrystal, has a thickness of 1 μm to 100 μm, and an average crystal grain size of 100 nm. Below, it was set as the structure which the grain boundary layer which consists of a glass layer does not exist substantially in the interface of crystals.

As the translucent body, the chamber itself or sight glass is conceivable. Further, in order for the translucent body to be transparent, it is necessary to have the above thickness range (100 μm or less) and the average crystal grain size (100 nm or less). The reason why the thickness is 1 μm or more is that if it is less than this, the plasma resistance is poor.

  Here, in the present invention, the translucent material refers to a material that can transmit light having a specific wavelength of 200 nm to 1000 nm. Whether or not the light transmitting body is transparent means that the light transmittance at a wavelength of 550 nm of the light transmitting body on which the transparent plasma-resistant layer is formed is 50% or more.

The transparent plasma-resistant layer is characterized in that the yttrium oxide (Y ₂ O ₃ ) polycrystal has substantially no crystal orientation, and a part thereof forms an anchor portion that bites into the inner surface of the translucent body. Can be mentioned.

Here, the interpretation of the words that are important for understanding the present invention will be described below.
(Polycrystalline) In this case, it refers to a structure in which crystallites are joined and accumulated. The crystallite is essentially one crystal, and its diameter is usually 5 nm or more. However, the case where the fine particles are taken into a transparent structure without being crushed rarely occurs, but is substantially polycrystalline.
(Film thickness) In this case, the film thickness is measured with a stylus type surface shape measuring instrument (Nihon Vacuum Technology Co., Ltd./Dectak3030), a scanning electron microscope (Hitachi, Ltd./S-4100), or a transmission electron microscope. The height of the transparent structure formed on the substrate measured and calculated by observation from the cross-sectional direction. Moreover, when an anchor part is formed in the interface of a base material and a transparent structure, the formation height measured and calculated from the outermost surface of a base material is said.
(Average crystal grain size) In this case, the average crystal grain size means the crystallite size calculated by the Scherrer method in the X-ray diffraction method, and is measured and calculated using MXP-18 manufactured by Mac Science. .
(Crystal orientation) In this case, it refers to the degree of orientation of crystal axes in a transparent structure that is polycrystalline, and whether or not there is orientation is generally X-ray powder diffraction, which is considered to be substantially non-oriented. JCPDS (ASTM) data, which is standard data by the above, is judged as an index. The peak intensity of the three major diffraction peaks in this index, which is the material constituting the brittle material crystal in the transparent structure, is defined as 100%. In this case, it is assumed that there is substantially no orientation in a state where the deviation of the peak intensity of the other two peaks is within 30% of the index value.
(Interface) In this case, it refers to the region that forms the boundary between crystallites.
(Grain boundary layer) A layer with a certain thickness (usually several nanometers to several micrometers) located at the grain boundary in the interface or sintered body, and usually takes an amorphous structure different from the crystal structure in the crystal grain, and in some cases Is accompanied by segregation of impurities.
(Anchor part) In the case of this case, it refers to the unevenness formed at the interface between the base material and the transparent structure, and in particular, it is not necessary to form the unevenness in the base material in advance. It refers to irregularities formed by changing the surface accuracy of the substrate.

In order to form the transparent plasma-resistant layer having the above characteristics on the substrate surface, for example, an aerosol deposition method (AD method) described later can be used. Here, the substrate is not particularly limited as long as it has translucency (transparency). For example, quartz glass, silicate glass, soda lime glass, lead alkali glass, borosilicate glass , Aluminosilicate glass, phosphate glass, alkali silicate glass, barium glass, potassium lime glass, lithium silicate glass, and sapphire.
In the AD method, a transparent plasma-resistant layer is formed on the substrate by the following mechanism.
Specifically, when a mechanical impact force is applied to a brittle material (ceramics) that does not have spreadability, the crystal lattice shifts along the wall open surface such as the interface between crystallites or is crushed. When these phenomena occur, a new surface is formed on the slipping surface or fracture surface, in which atoms originally present inside and bonded to other atoms are exposed. The part of the atomic layer on the new surface is exposed to an unstable surface state by an external force from a stable atomic bond state, and the surface energy is high. This active surface joins to the adjacent brittle material surface, the newly formed brittle material surface, or the surface of the base material, and shifts to a stable state. The addition of a continuous mechanical impact force from the outside causes this phenomenon to occur continuously, and does not deform or crush fine particles.
The repetition and densification of bonding are performed by any repetition, and a transparent layer of a brittle material is formed.

  According to the light transmitting body for a plasma processing apparatus according to the present invention, it is possible to obtain a plasma processing apparatus that is excellent in plasma durability and in which a transparent member such as sight glass is not devitrified for a long time.

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 and 2 are sectional views of an example of a plasma processing apparatus to which a light transmitting body according to the present invention is applied. The plasma processing apparatus shown in FIG. 1 includes an upper electrode 2 and a lower part in a chamber body 1 made of an aluminum alloy. The electrode 3 is disposed, the chuck 4 for placing the workpiece W on the lower electrode 3 is provided, and the sight glass 5 is fitted into the opening formed in the chamber body 1, and the inner surface of the sight glass 5 is oxidized. A transparent plasma-resistant layer 5a made of yttrium (Y ₂ O ₃ ) polycrystal is formed.

In the plasma processing apparatus shown in FIG. 2, sheet electrodes 6 and 7 are disposed on the outer periphery of the upper portion of the chamber body 1 made of synthetic quartz, and a chuck 4 on which the workpiece W is placed faces the lower portion of the chamber body 1. Not. A transparent plasma-resistant layer 1 a made of a yttrium oxide (Y ₂ O ₃ ) polycrystal is formed on the inner surface of the chamber body 1.

  FIG. 3 is a schematic configuration diagram of a production apparatus for forming the transparent plasma-resistant layers 1a and 5a. Various gas cylinders 11 of nitrogen, dry air, and helium are connected to an aerosol generator 13 through a transport pipe 12, and A nozzle 15 is arranged in the structure forming apparatus 14 through the transport pipe 12. A base material 16 installed on the XY stage 17 is disposed at the tip of the nozzle 15 so as to face the nozzle 15 with an interval of 10 mm. The structure forming chamber 14 is connected to an exhaust pump 18.

  Then, after the material powder is filled in the aerosol generator 13, the gas cylinder 11 is opened, and dry air is introduced into the aerosol generator 13 through the transport pipe 12, thereby generating an aerosol in which the material powder is dispersed in the gas. This aerosol is further transported in the direction of the structure forming chamber 14 through the transport pipe 12, and the material powder is sprayed toward the base material 16 from the nozzle 15 while being accelerated at a high speed.

In this embodiment, a mixed powder of yttrium oxide (Y ₂ O ₃ ) fine particles and aluminum (Y ₂ O ₃ ) fine particles having a larger particle diameter than that is used as a material for forming the transparent plasma-resistant layers 1a and 5a. Used.

As shown in FIG. 4 (a), when the mixed powder is ejected from the nozzle onto the base material at a high speed, the yttrium oxide (Y ₂ O ₃ ) fine particles are deformed or crushed by the impact that hits the base material to form a new surface. The newly formed surfaces are bonded to form a dense film. When large particles are mixed, as shown in FIG. 4B, the large particles are converted to small yttrium oxide particles. By crushing from the back, a new surface is formed more effectively.

(Example)
Yttrium oxide (Y ₂ O ₃ ) fine particles and aluminum oxide (Al ₂ O ₃ ) particles were prepared. The 50% average particle size based on volume of the aluminum oxide particles was 2.1 μm, and the particle size of the yttrium oxide fine particles was 0.47 μm. Here, the 50% average particle size based on the volume refers to particles when the cumulative volume of particles from the smaller particle size reaches 50% in the particle size distribution measurement data measured using a laser diffraction particle size distribution meter. The particle size of Further, the particle diameter of the yttrium oxide fine particles is a particle diameter calculated from the specific surface area measured by a Fischer sub-sieve sizer.

  Next, these fine particles were mixed at a number ratio of (aluminum oxide fine particles) :( yttrium oxide fine particles) = 1: 10 to obtain a particle mixture.

  The above particle mixture is loaded into the aerosol generator of the production apparatus shown in FIG. 3, and aerosol is generated while flowing nitrogen gas as a carrier gas at a flow rate of 5 liters / minute, and is jetted onto the quartz substrate. It was. In this manner, a light-transmitting yttrium oxide film having a height of 10 μm and an area of 20 mm × 20 mm was formed on the substrate.

  On the other hand, the average particle diameter of the yttrium oxide fine particles is 0.47 μm, the average particle diameter of the aluminum oxide fine particles is 5.9 μm, and the particle mixture is mixed at a number ratio of (aluminum oxide fine particles) :( yttrium oxide fine particles) = 1: 100. Was used, it became a black yttrium oxide film.

Thus, the particle size and mixing ratio of the aluminum oxide fine particles and the yttrium oxide fine particles are indispensable conditions for the yttrium oxide film to exhibit translucency. When the light transmittance (wavelength 550 nm) of the base material (transparent member such as a glass plate) is 95%, the light transmittance (wavelength 550 nm) of the base material + transparent anti-plasma layer (yttrium oxide film) performs internal monitoring. In order to achieve 50% or more required above, yttrium oxide (Y ₂ O ₃ ) fine particles having an average particle size of 0.010 μm to 1.0 μm and fine particles having an average particle size of 1.0 μm to 5.0 μm (such as aluminum oxide fine particles) ) Is preferably used in a ratio of 1: 1 to 1: 1000.

  Aluminum oxide fine particles are for deforming or crushing yttrium oxide fine particles to form a new surface, and since they are reflected after collision and inevitably mixed in, they do not directly constitute the material of the film. The material is not limited to aluminum oxide, and yttrium oxide may be used, but aluminum oxide is optimal in consideration of cost.

FIG. 5A is an SEM photograph showing a state before the plasma resistance test of the yttrium oxide (Y ₂ O ₃ ) film, which is a transparent plasma resistance layer obtained by the AD method, and FIG. 5B is a plasma resistance test of the film. It is a SEM photograph which shows a back state.

The conditions for the plasma resistance test are as follows.
Equipment: RIE type etcher equipment (DEA-506 / Nippon Anelva)
Gas: CF ₄ + (40 SCCM) + O ₂ (10 SCCM)
High frequency power supply: 1 kW (0.55 W / cm ² )
Frequency: 13.56MHz
Plasma irradiation time: 180 min
Degree of vacuum: 5-7 torr
Evaluation Method Erosion Depth and Surface Roughness: After exposing the sample to the plasma atmosphere, the level difference between the portion where the sample was masked and the portion where the sample was not applied was measured with a stylus type surface shape measuring instrument (manufactured by Nippon Vacuum Technology Co., Ltd./Dectak 3030 ).
Surface SEM observation: Surface observation before and after exposure to the plasma atmosphere was performed by SEM (scanning electron microscope: S4100 manufactured by Hitachi, Ltd.).

FIGS. 6A to 9B are SEM photographs of the surface of the other material before and after exposure to the plasma atmosphere, and FIG. 6 shows yttrium oxide (Y ₂ O ₃ ) formed by sintering (HIP). 7 shows a yttrium oxide (Y ₂ O ₃ ) film obtained by thermal spraying, FIG. 8 shows a sapphire film, and FIG. 9 shows quartz.

  From FIG. 6 to FIG. 9, the transparent yttrium oxide film according to the present invention is not observed to have pores like quartz and sapphire before exposure to the plasma atmosphere, and the yttrium oxide film formed by sintering (HIP) and the thermal spraying method. A pore of several μm is observed in the yttrium oxide film obtained by the above method.

  In addition, after the plasma atmosphere exposure, the transparent yttrium oxide film according to the present invention had no change in the surface state like sapphire, and the yttrium oxide film formed by sintering (HIP) existed before the exposure. The pores were eroded and the size of the pores increased, and the yttrium oxide film obtained by thermal spraying was cracked on the surface, and the pores that were not present before exposure were observed for quartz.

  FIG. 10 is a graph comparing the surface roughness before and after the plasma test. The surface roughness of the transparent yttrium oxide film according to the present invention before the plasma test is slightly inferior to that of sapphire and quartz, but even after the plasma test. It can be seen that the surface roughness hardly changes.

  FIG. 11 is a graph comparing the erosion depth after the plasma test. It can be seen that the erosion depth after the plasma test of the transparent yttrium oxide film according to the present invention is extremely small as compared with other materials.

  FIG. 12 shows the relationship between the film thickness and the transmittance of the yttria film prepared by the AD method before plasma irradiation. In three types of film thicknesses of 2.0 μm, 5.0 μm, and 8.5 μm, light having a wavelength of 200 nm to 800 nm is shown. It is the graph which compared the transmittance | permeability. In this graph, it can be seen that the transmittance decreases gradually as the film thickness increases before plasma irradiation. As described in paragraph 0009, whether or not the transparent body is transparent is determined by whether or not the light transmittance at a wavelength of 550 nm of the transparent body on which the transparent plasma-resistant layer is formed is 50% or more. However, the transmittance is 81% at a film thickness of 2.0 μm, the transmittance is 76.5% at a film thickness of 5.0 μm, and the transmittance is 73% at 8.5 μm, both of which exceed 50%. It can be said that it is transparent.

  As the yttria film forming conditions by the above-mentioned AD method, alumina particles (mother particles, bomber particles) having an average particle diameter of 2.1 μm and yttria particles (child particles, film forming particles) having an average particle diameter of 0.5 μm are in a number ratio. Powder was adjusted so that mother particle: child particle = 1: 10, and nitrogen (5 L / min) was used as a carrier gas.

Moreover, as a plasma resistance test condition in the transmittance measurement before and after plasma irradiation, an RIE type etcher (DEA-506 / manufactured by Anelva) was used for the apparatus, and CF 4 (40 sccm) and O 2 (10 sccm) were used for the corrosive gas. . The high frequency power of the apparatus was 1 kW (0.55 W / cm ² , the frequency was 13.56 MHz), and the irradiation time was 6 hours (360 minutes).

  Furthermore, the apparatus used for the transmittance measurement is a spectrophotometer (UV-3150 / manufactured by Shimadzu Corporation), and the measurement of the AD film is measurement data including the thickness of the quartz substrate (3 mmt).

  FIG. 13 compares the transmittance of quartz glass before plasma irradiation and after irradiation for 6 hours. At a wavelength of 550 nm of the light transmitting body, the light transmittance before plasma irradiation is reduced from 93% to 47.5%, and the rate of change is 48.9%. Since 50% is cut after 6 hours of plasma irradiation, it can be seen that the quartz glass after 6 hours of plasma irradiation cannot be said to be translucent.

  FIG. 14 compares the transmittance before plasma irradiation and after 6 hours of irradiation for an AD yttria film having a thickness of 5 μm. The transmittance is 76% before plasma irradiation, 73.5% after 6 hours irradiation, and the rate of change is 3.3%. In this case, it can be said that it has sufficient translucency even after plasma irradiation for 6 hours.

  The plasma processing apparatus to which the light transmitting body according to the present invention is applied can be used in an integrated circuit formation process.

Sectional drawing of an example of the plasma processing apparatus to which the transparent body which concerns on this invention is applied Sectional drawing of an example of the plasma processing apparatus to which the transparent body which concerns on this invention is applied Schematic configuration diagram of a composite structure manufacturing apparatus using the AD method Diagram explaining the process of film formation by AD method (A) is a SEM photograph showing the state before the plasma resistance test of the yttrium oxide (Y ₂ O ₃ ) film obtained by AD method, (b) is a SEM photograph showing the state after the plasma resistance test of the film, (A) and (b) are the same scale. (A) is an SEM photograph showing the state of the yttrium oxide (Y ₂ O ₃ ) film formed by sintering (HIP) before the plasma resistance test, and (b) is an SEM photograph showing the state of the film after the plasma resistance test. (A) and (b) are the same scale as FIG. (A) is a SEM photograph showing the state before the plasma resistance test of the yttrium oxide (Y ₂ O ₃ ) film obtained by the thermal spraying method, (b) is a SEM photograph showing the state after the plasma resistance test of the film, (A) and (b) are the same scale as FIG. (A) is a SEM photograph showing the state of the sapphire film before the plasma resistance test, (b) is a SEM photograph showing the state of the film after the plasma resistance test, and both (a) and (b) are 1 in FIG. / 2 scale. (A) is a SEM photograph showing the state of the quartz before the plasma resistance test, (b) is a SEM photograph showing the state of the film after the plasma resistance test, both (a) and (b) of FIG. 2 scale. Graph comparing surface roughness before and after plasma test Graph comparing erosion depth after plasma test Relationship between film thickness and transmittance of yttria film produced by AD method Change in transmittance of quartz glass (before plasma irradiation and after 6 hours) Change in transmittance of AD yttria film (5μm) (Plasma irradiation 6 hours)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Chamber main body, 1a, 5a ... Transparent plasma-resistant layer, 2 ... Upper electrode, 3 ... Lower electrode, 4 ... Chuck, 5 ... Sight glass, 6, 7 ... Sheet, 11 ... Gas cylinder, 12 ... Transfer pipe, 13 ... Aerosol generator, 14 ... structure forming device, 15 ... nozzle, 16 ... substrate, 17 ... XY stage, 18 ... exhaust pump, W ... workpiece.

Claims (6)

In a light transmitting body for a plasma processing apparatus in which an object to be processed is set in a chamber and plasma is generated in the chamber under reduced pressure to perform surface treatment on the object to be processed. This transparent plasma-resistant layer is mainly composed of a yttrium oxide (Y ₂ O ₃ ) polycrystal, the thickness of this layer is 1 μm to 100 μm, and the average crystal grain size of the polycrystal is 100 nm or less. A translucent material for plasma processing, characterized in that a grain boundary layer composed of a glass layer is substantially absent at an interface between crystals. The light transmitting body for plasma processing apparatus according to claim 1, wherein the yttrium oxide (Y ₂ O ₃ ) polycrystalline body has substantially no crystal orientation. 3. The light transmitting body for a plasma processing apparatus according to claim 1, wherein a part of the transparent plasma-resistant layer forms an anchor portion that bites into an inner surface of the light transmitting body. Translucent body. The light transmitting body for a plasma processing apparatus according to any one of claims 1 to 3, wherein the light transmitting body is a chamber itself or a sight glass. 5. The light transmitting body for a plasma processing apparatus according to claim 4, wherein the light transmitting body at a wavelength of 550 nm of the light transmitting body on which the transparent plasma-resistant layer is formed is 50% or more. body. A plasma processing apparatus comprising the light-transmitting body according to claim 1.