JP2003086475A - Dummy wafer, manufacturing method therefor and detection method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dummy wafer, which is required to be highly resistant to a corrosive gas or plasma thereof in semiconductor manufacturing steps and is superior in plasma resistance, heat resistance and shock resistance, and has light-shielding performance. SOLUTION: A ceramic dummy wafer, used in semiconductor manufacturing steps, consists of a compound of yttria and aluminum as a main crystal phase. The phase consists of YAG (yittium, aluminum and garnet), the YAG and aluminum or the YAG and yttria.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dummy wafer required to have high corrosion resistance against corrosive gas or its plasma in a semiconductor manufacturing process, and more particularly to a ceramic dummy wafer.

[0002]

2. Description of the Related Art In various processes such as a dry etching process and a film forming process in semiconductor manufacturing, a technique utilizing plasma is widely used. In this plasma process, a high reactivity is obtained especially for etching and cleaning. Halogen-based corrosive gases such as fluorine and chlorine are often used.

Silicon wafers are generally used as substrates in the film forming process and etching process in the production of these semiconductors. With the increase in the performance and the integration density, various kinds of processing precision, cleaning degree, etc. have been used. Inspections and operation tests of equipment are being confirmed in advance. A dummy wafer is used as a test wafer for such a test.For example, the relationship between film forming conditions such as film forming time and film forming temperature and the thickness of the formed thin film, components, constituent phases, etc. is actually formed on the dummy wafer. The film is examined and the film forming conditions at the time of production are determined based on the result.

Since such a dummy wafer comes into contact with corrosive gas or plasma, it is required to have high corrosion resistance and high strength.
Generally, silicon, quartz, etc. have been used.

However, these dummy wafers made of silicon, quartz, etc., are difficult to analyze when analyzing the components of the formed thin film.
Accurate analysis is not possible because silicon is also detected from the dummy wafer at the same time.Since the silicon wafer is corroded by the acid cleaning process, it is difficult to regenerate it, and even if it can be successfully regenerated without changing its properties, it will gradually become thinner. Therefore, there is a problem that the number of times of use is significantly limited.

Further, the strength against strain caused by heat change is low, and when the cleaning gas temperature rising time is shortened, cracks occur due to heat shock, and corrosive gas directly touches the wafer holding member or the like through the gap to contact the member. It had a problem that it was significantly deteriorated.

In order to solve the above problems, a silicon oxide film is formed on a thick silicon wafer to improve the strength against strain, and the silicon oxide film is used for self-cleaning (fluorine trioxide gas) (chamber). It has been proposed to perform gas cleaning / film removal inside (Japanese Patent Laid-Open No. 4-61331).

Further, by using a high-purity alumina ceramics, a dummy wafer made of high-purity alumina ceramics in which crystal grains such as silicon carbide or zirconia are dispersed in the alumina particles and at the grain boundaries is used to prevent contamination of the thin film. However, a dummy wafer has been proposed which can be repeatedly used by improving corrosion resistance and cleaning with a chemical.

[0009]

In recent years, with the goal of improving productivity, the corrosiveness of the cleaning gas used has become extremely strong and the heating time has been shortened in order to further shorten the cleaning time. For this reason, more severe conditions such as a rapid temperature rise are becoming more severe.

However, the conventionally used dummy wafer, in which a silicon oxide film is formed on a large-thickness silicon wafer, has insufficient strength against a highly corrosive cleaning gas and corrosion resistance, resulting in a rapid temperature rise. On the other hand, it had a drawback that it was easily cracked and dust and contamination could not be prevented.

Further, since the thickness of silicon is large, there is a drawback in that the weight cannot be reduced and a load is imposed on the transportation system in the manufacturing process.

Further, the dummy wafer made of high-purity alumina ceramics has a weakness in thermal shock resistance and has a drawback that it is easily damaged when used in a process in which heating and cooling are repeatedly applied.

Further, since the ceramic has a high purity and has a light-transmitting property, a transmission type or a reflection type utilizing an optical effect such as visible light and ultraviolet rays for measuring and controlling the timing of positioning and processing steps is used. When an optical system sensor is used, a light wave such as visible light is difficult to detect by passing through the dummy wafer, and there is a drawback that detection is omitted.

The present invention has been devised in view of the above-mentioned drawbacks, and an object thereof is to have a high corrosion resistance to a cleaning gas having a very strong corrosive property and to have a thermal shock property due to a rapid temperature rise. Another object is to provide a dummy wafer that is less likely to be damaged and has a light shielding property.

[0015]

The dummy wafer of the present invention is characterized in that it is made of a ceramic containing a compound of yttria and alumina as a main crystal phase.

The dummy wafer of the present invention is characterized in that the main crystal phase is made of YAG (yttrium aluminum garnet), YAG and alumina, or YAG and yttria.

Further, the dummy wafer of the present invention is characterized by having an average crystal grain size of 8 μm or less and a porosity of 0.2% or less.

Furthermore, the dummy wafer of the present invention contains 500 parts of zirconia containing ceria as a stabilizer as a subcomponent.
.About.50000 weight ppm is contained.

The dummy wafer of the present invention is characterized by being made of a ceramic containing 50 to 80% by weight of alumina and 20 to 50% by weight of YAG.

Further, in the dummy wafer of the present invention, the average crystal grain size of the alumina is 2 to 10 μm, the average crystal grain size of the YAG is 1.5 to 5 μm, and the average crystal grain size of the alumina is based on the average crystal grain size of the YAG. It is characterized in that the ratio of the average crystal grain size is larger than 1 and smaller than 7.

Furthermore, the dummy wafer of the present invention is characterized by having a porosity of 0.2% or less.

Furthermore, the dummy wafer of the present invention is characterized by having a relative reflectance of 70% or more.

Further, the dummy wafer of the present invention is characterized in that at least one of the main surfaces has a surface roughness Ra of 0.1 to 0.4 μm.

Further, according to the method for producing a dummy wafer of the present invention, a raw material powder obtained by adding and mixing at least alumina powder and yttria powder is molded into a predetermined shape, and then the obtained molded body is degreased at 300 to 600 ° C. , Heating in the air atmosphere and heating rate from about 1200 ° C. to 15 to 20
C./hour, the temperature is kept constant for a period of 3 to 10 hours every 3 to 6 hours, and firing is performed at a maximum temperature of 1500 to 1750 ° C.

Furthermore, the present invention is characterized by a detection method for investigating the film formation, etching conditions and the like in the film forming step and the etching step in the semiconductor manufacturing process using the dummy wafer.

According to the dummy wafer of the present invention, a compound of yttria and alumina is used as a main crystal phase, and the main crystal phase is composed of YAG (yttrium aluminum garnet), YAG and alumina, or YAG and yttria. Even if these ceramics react with corrosive gas or plasma to form halides,
Since it has a high melting point and is stable, it can have excellent corrosion resistance.

Further, according to the dummy wafer of the present invention, since the average crystal grain size is 8 μm or less and the porosity is 0.2% or less, it is possible to prevent the progress of corrosion as a dense ceramic and to improve the corrosion resistance. can do.

Further, according to the dummy wafer of the present invention,
50 parts of zirconia containing ceria as a stabilizer as a sub ingredient
Since the content is 0 to 50,000 ppm by weight, it is possible to improve the thermal shock resistance against heat shock due to a rapid temperature rise.

According to the dummy wafer of the present invention, since it is made of ceramics containing 50 to 80% by weight of alumina and 20 to 50% by weight of YAG, alumina can increase mechanical strength and hardness and can be corrosive by YAG. The corrosion resistance to gas and its plasma can be made excellent.

Further, according to the dummy wafer of the present invention, the average crystal grain diameter of the alumina is 2 to 10 μm, the average crystal grain diameter of YAG is 1.5 to 5 μm, and the alumina is relative to the average crystal grain diameter of the YAG. Since the ratio of the average crystal grain size of is larger than 1 and smaller than 7, it reduces the pores in the ceramics and improves the bending strength and hardness,
It is possible to suppress the progress of corrosion in plasma. Further, the fracture toughness value can be suppressed to an appropriate value to obtain free-cutting property and workability.

Further, according to the dummy wafer of the present invention,
Since the porosity is 0.2% or less, the progress of corrosion can be prevented as a dense ceramic and the corrosion resistance can be further enhanced.

Furthermore, according to the dummy wafer of the present invention, since the relative reflectance is 70% or more, it is possible to improve the detection accuracy of the measurement using the optical sensor.

Furthermore, since the surface roughness of at least one of the main surfaces is (Ra) of 0.1 to 0.4 μm, the light wave of the optical system sensor is not scattered and a higher reflectance is obtained. be able to.

In the dummy wafer of the present invention, at least alumina powder and yttria powder are added and mixed to form a raw material powder into a predetermined shape, and the obtained formed body is degreased at 300 to 600 ° C. It is heated in the atmosphere and the temperature rising rate is set to 15 to 20 ° C / hour from about 1200 ° C, and the temperature is kept constant for 3 to 10 hours every 3 to 6 hours, and 1500 to 1750 ° C. Since it is fired at the highest temperature, it is possible to prevent a rapid shrinkage, obtain a dense, high-strength gray-white dummy wafer having a light-shielding property.

Further, since it is the detection method using the dummy wafer of the present invention, it is possible to accurately search the film forming and etching conditions in the film forming step and the etching step in the semiconductor manufacturing process.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION The dummy wafer of the present invention has an orientation flat in a part thereof as shown in FIG. 1, and is used in each process such as a dry etching process and a film forming process in a semiconductor manufacturing process. The halogen-based corrosive gas used in the present invention is used for exploring the film forming and etching conditions of the halogen-based corrosive gas, and examples of the halogen-based corrosive gas include SF ₆ , CF ₄ , CHF ₃ , ClF ₃ and NF. ₃ , C
Fluorine gas such as ₄ F ₈ and HF, Cl ₂ , HCl, BC
l ₃ , chlorine gas such as CCl ₄ , or Br ₂ , HB
There are bromine-based gases such as r and BBr ₃ , and when microwaves or high frequencies are introduced in these halogen-based corrosive gas atmospheres, these gases are turned into plasma, and the etching effect is further enhanced. Therefore, plasma may be generated by introducing an inert gas such as Ar together with the halogen-based corrosive gas.

In the present invention, a dummy wafer exposed to these halogen-based corrosive gas and its plasma is formed of ceramics containing a compound of yttria and alumina as a main crystal phase, and the main crystal phase is YAG (yttrium). -Aluminum garnet), or ceramics composed of YAG and alumina, or YAG and yttria.

These ceramics composed of yttria and alumina compounds mainly produce YF ₃ and AlF ₃ when they react with a fluorine-based gas which is a halogen-based corrosive gas, and YCl ₃ and AlCl when they react with a chlorine-based gas. ₃ generates a but, melting halides of yttria (YF _3: 1
152 ° C., YCl ₃ : 680 ° C.) is the melting point (SiF ₄ : −90 ° C., SiC of a conventional halide produced by reaction with silicon, quartz, or alumina ceramics).
_{l 4: -70 ℃, AlF 3} : 1040 ℃, AlCl 3: 1
Since it is higher than 78 ° C., it has stable corrosion resistance even when exposed to a halogen-based corrosive gas or its plasma at a high temperature.

However, yttria alone has a very low sinterability, its porosity is 2% or more, a dense body cannot be obtained, and the corrosion resistance to halogen-based corrosive gas and plasma is significantly lowered. On the other hand, by using a compound with alumina, the porosity is reduced, dense ceramics can be obtained, and the formation of yttria halide can suppress the formation of halide of the alumina component.

Therefore, the present inventors use the compound of yttria and alumina as the main crystal phase to increase the melting point of the halide formed by the reaction with the halogen-based corrosive gas or plasma, and to use the primary raw material as the primary raw material. 1-2 μm
Adjusting the degree to increase the sinterability, the average crystal grain size is 8μm
Hereafter, a dense body having a porosity of 0.2% or less has high mechanical strength and has very few pore edges that are susceptible to corrosion.

As a result, it is possible to obtain a highly corrosion-resistant dummy wafer which is resistant to corrosion even in the acid cleaning step and can be used any number of times, and which can prevent dusting and contamination even when a highly corrosive cleaning gas is used.

Regarding the crystal phase of ceramics, X
By the line diffraction, the porosity can be obtained by the Archimedes method.

Here, YAG is formed at the composition ratio of yttria and alumina at the composition ratio shown in the following formula. Then, if this ratio is variously changed to a range other than the following formula range, YA
A mixed phase of G and alumina or YAG and yttria is obtained. (Formula) A + B = 1 0.365 ≦ A ≦ 0.385 A: Yttria molar amount 0.615 ≦ B ≦ 0.635 B: Alumina molar amount Also, the thermal shock resistance of ceramics composed of yttria and alumina compounds. In order to improve the temperature, tetragonal zirconia containing ceria as a secondary component in a stabilizer is added in an amount of 500 to 5
By adding 0000 ppm, it is possible to disperse zirconia in a sintered body composed of a compound of yttria and alumina without impairing the corrosion resistance of the above-mentioned ceramics, so that the progress of cracks generated during thermal shock is prevented by zirconia. Can have thermal shock resistance,
The strength against strain caused by heat change is high, and cracks and the like are less likely to occur even when the temperature rising time of the cleaning gas is shortened.

This is because zirconia in ceramics is present in a tetragonal crystal form and the thermal shock resistance ΔT is 100 ° C.
As described above, the development of cracks caused by thermal shock is prevented by absorbing the propagation energy of cracks by causing the phase transformation of tetragonal zirconia into monoclinic crystals.

By using ceria as a stabilizer for stabilizing the zirconia in the tetragonal system, thermal deterioration of the zirconia to a temperature of 100 to 200 ° C. can be prevented by heating the lamp, and the addition of the ceria is performed. The amount of zirconia can be stabilized by adding 1% by weight or more to 100% by weight of zirconia.

The zirconia content is 500 weight pp.
If it is less than m, the thermal shock resistance of the ceramics decreases,
Cracks and cracks are likely to occur on the dummy wafer, while
When it exceeds 50,000 ppm by weight, the corrosion resistance of zirconia is poor and it becomes susceptible to corrosion by a halogen-based corrosive gas or its plasma.

The contents of these components can be determined by ICP emission analysis or fluorescent X-ray.

Further, the dummy wafer of the present invention preferably has a relative reflectance of 70% or more. This is a transmission type or a reflection type that uses optical effects such as visible light and ultraviolet rays to control the positioning when mounting semiconductor elements on the upper surface of a dummy wafer, the timing measurement of film formation processing, and the transfer of wafers. This is because the optical system sensor detects the light wave such as visible light and prevents the light wave such as visible light from passing through or scattering through the dummy wafer, thereby performing high-precision detection without detection omission.

The reflectance of the dummy wafer is 70%.
To achieve the above, it is necessary to make the ceramics light-shielding and reduce the surface roughness.

Generally, ceramics have a light-transmitting property as they become higher in purity. However, in the dummy wafer of the present invention, when zirconia is contained in an amount of 500 to 50,000 ppm by weight, a ceramic composed of a compound of yttria and alumina is relatively contained. The purity can be reduced and the light-shielding property can be adjusted by specifying firing conditions in the production method as described later.

Here, the above yttria-alumina compound is used as the main crystal phase, and this main crystal phase is YAG or Y
A method of manufacturing a dummy wafer made of a ceramic composed of AG and alumina or YAG and yttria will be described.

First, when ceramics composed of YAG, YAG and alumina, or YAG and yttria as the main crystal phase is used, alumina powder, YAG powder, yttria powder as a starting material and, if necessary, auxiliary agents such as a sintering aid are used. Prepare the ingredients.

Then, a predetermined amount of these powders is added and mixed, and further, a desired organic binder such as wax emulsion (wax + emulsifier), PVA (polyvinyl alcohol), PEG (polyethylene glycol) is added and mixed, and kneaded. A slurry is obtained or kneaded and dried to obtain granulated powder.

Next, the slurry is molded into a predetermined shape by a tape molding method such as a casting method, an injection molding method, a doctor blade method, or the granulated powder is filled in a mold and uniaxially pressed. It is molded into a predetermined shape by using a pressure molding method or an equal pressure molding method such as rubber press molding.

After that, the obtained molded body is 300 to 60
After degreasing at 0 ° C, heat in air atmosphere to 1200
It is important that the temperature rising rate is 15 to 20 ° C./hour from around 0 ° C. to make the temperature rising curve gentle and to keep the temperature constant for a period of 3 to 10 hours every 3 to 6 hours.

The above-mentioned temperature rising rate has been conventionally about 30 ° C./hour, but the temperature rising curve is made gentle from around 1200 ° C. in order to prevent firing cracking due to abrupt shrinkage of a material such as YAG in the atmosphere. Therefore, it is preferable to set the temperature to 15 to 20 ° C./hour in order to perform the firing so as to reduce the temperature variation of the product. If the rate of temperature rise is less than 15 ° C., only the firing time is extended and the production takes a long time. On the other hand, if the heating rate exceeds 20 ° C., firing cracks and cracks are likely to occur.

Also, the above temperature rising curve is conventionally a continuous curve, but for the same reason as the temperature rising rate, the temperature is kept constant for every 3 to 6 hours for a length of 3 to 10 hours. The pattern is preferable. When the interval for holding at the above-mentioned constant temperature is less than 3 hours or the holding time is less than 3 hours, the temperature variation of the product cannot be suppressed and firing cracks and cracks are likely to occur. On the other hand, if the temperature keeping interval exceeds 6 hours, or if the holding time exceeds 10 hours, only the firing time is extended and it takes a long time to manufacture.

When the shrinkage behavior of the molded body containing yttria, YAG, etc. used in the present invention was examined, it was 99.5% alumina.
It was found that the product contracted more rapidly than the molded product of No. Examination of the shrinkage behavior of the molded product of the present invention during firing reveals that the molded product undergoes rapid shrinkage as compared with, for example, a molded product of 99.5% alumina. That is, the shrinkage of a molded body of 99.5% alumina starts at around 1100 ° C. and ends at around 1640 ° C., whereas in the case of the material containing yttria or YAG as in the present invention, these materials are fine powders. Therefore, degreasing is difficult, and shrinkage starts at about 1300 ° C. and finishes at around 1700 ° C. in air atmosphere firing.

Therefore, in order to prevent firing cracking due to abrupt shrinkage in the air atmosphere, the temperature rise curve is made gentle from around 1200 ° C. to reduce the temperature variation of the product, and firing is performed in the temperature range of 1500 to 1750 ° C. As a result, it is possible to obtain a ceramic that is sufficiently sintered and densified, and has excellent mechanical properties such as bending strength, hardness, and fracture toughness value without abnormal grain growth of alumina particles and YAG particles.

Here, if firing is carried out in the air atmosphere in a temperature range of less than 1500 ° C., the sintering becomes insufficient and the mechanical strength is lowered. On the other hand, if the temperature exceeds 1750 ° C., it becomes oversinter, abnormal grain growth occurs, the porosity increases and the mechanical properties deteriorate.

Further, by setting the firing atmosphere to be the atmospheric atmosphere, it is possible to obtain a grayish white light-shielding ceramic. On the other hand, in the past, it was transparent in that it was fired at a temperature of 1750 to 1900 ° C. in a vacuum or a reducing atmosphere.

Finally, the surface of the obtained ceramic is processed by lapping with a diamond grindstone or loose abrasive grains.

Next, as another embodiment of the present invention, a dummy wafer made of ceramics containing alumina as a main component and YAG as a sub-component will be described.

The above-mentioned ceramic contains alumina in an amount of 50 to 8
It is characterized by comprising 0% by weight and ceramics containing 20 to 50% by weight of YAG. YAG suppresses the grain growth of alumina, and therefore densifies the ceramics and improves bending strength and hardness. it can.

When the alumina content is less than 50% by weight, the main component is YAG, and the mechanical properties of the ceramics are governed by the mechanical properties of YAG, and the bending strength and hardness do not include YAG. Significantly lower than alumina ceramics. On the other hand, if it exceeds 80% by weight,
Since the content of YAG is small, the effect of suppressing the grain growth of alumina is small, the ceramics cannot be densified, and the bending strength and hardness decrease, and the corrosion resistance may decrease.

In the ceramics, the average crystal grain size of alumina is 2 to 10 μm, the average crystal grain size of YAG is 1.5 to 5 μm, and the average crystal grain size of alumina is the average crystal grain size of YAG. Ratio of 1
It is preferable to make it larger and smaller than 7, so that the porosity in the ceramic is reduced and the porosity is 0.2%.
By increasing the bending strength and hardness,
It is possible to suppress the progress of corrosion in plasma. Further, the fracture toughness value can be suppressed to an appropriate value to obtain free-cutting property and workability.

Further, it is preferable that the ratio of the average crystal particle diameter of alumina to the average crystal particle diameter of YAG is larger than 1 and less than 7, and the average crystal particle diameter of YAG is larger than the average crystal particle diameter of alumina. Since it is small, the four-point bending strength can be improved to 300 MPa or more and the Vickers hardness can be improved to 15 GPa or more, and the fracture toughness value can be maintained.

The average crystal grain size of alumina is 3 to 7
It is more preferable that the average crystal grain size of μm and YAG is in the range of 1.8 to 2.5 μm.

Ceramics composed of alumina and YAG within the above range have high strength and hardness, and can have a thermal shock resistance (ΔT) of 150 ° C. or higher, and can be used for a short time in a semiconductor manufacturing process or the like. It is possible to obtain a dummy wafer that can withstand repeated use by being prevented from being damaged by thermal shock even when used in an environment where the temperature is extremely high.

The dummy wafer of the present invention preferably has a relative reflectance of 70% or more. This is a transmission type or a reflection type that uses optical effects such as visible light and ultraviolet rays to control the positioning when mounting semiconductor elements on the upper surface of a dummy wafer, the timing measurement of film formation processing, and the transfer of wafers. This is because the optical system sensor detects the light wave such as visible light and prevents the light wave such as visible light from passing through or scattering through the dummy wafer, thereby performing high-precision detection without detection omission.

The reflectance of the dummy wafer is 70%.
To achieve the above, it is necessary to make the ceramics light-shielding and reduce the surface roughness.

Generally, ceramics have a light-transmitting property as they become higher in purity, but the dummy wafer of the present invention can be adjusted to have a light-shielding property by specifying firing conditions in the manufacturing method as described later. .

At least one main surface of the ceramic is polished to have a surface roughness (Ra) of 0.1 to 0.4.
It is preferable that the thickness is set to μm, and higher reflectance can be obtained without scattering of light waves of the optical system sensor.

Here, when (Ra) is less than 0.1 μm, higher reflectance can be obtained but processing becomes difficult. On the other hand, when (Ra) exceeds 0.4 μm, the scattering of light waves becomes large and a high reflectance cannot be obtained.

The surface roughness Ra is 0.1 to 0.4 μm.
To achieve this, a diamond grindstone having a higher count, for example, a grindstone of # 600 or more, may be used for processing, and more preferably lapping using free abrasive grains may be performed.

Further, the relative reflectance was measured by a detector using a reflection type sensor having a red LED as a light emitting portion, which was installed perpendicularly to the dummy wafer.

Furthermore, when the dummy wafer of the present invention is used as a film thickness monitor during film formation, the specific electric resistance value is controlled to adjust the film thickness, or a numerical value is obtained with respect to an actually measured value on a wafer such as silicon. It can be applied by correcting.

Now, a method for manufacturing a dummy wafer made of ceramics containing alumina as a main component and YAG as a sub-component will be described.

First, alumina powder and YA were used as starting materials.
G powder and, if necessary, auxiliary components such as sintering auxiliary are prepared. It is preferable to use alumina powder having an alumina purity of 95% or more, an average particle diameter of 1 to 15 μm, and a BET specific surface area of 1 to 4 m ² / g.

The YAG powder was prepared by mixing alumina powder and yttria powder in the same ratio as in the above-mentioned embodiment, and
It can be obtained by calcination after calcination at 000 to 1600 ° C., and average particle diameter of 0.6 to 1.2 μ.
It is preferable to use a powder having a BET specific surface area of 2 to 5 m2 / g.

Then, the above alumina powder is mixed in the range of 50 to 80% by weight and the above YAG powder is mixed in the range of 20 to 50% by weight, and further a desired organic binder is added and mixed and kneaded to prepare a slurry, or Knead and dry to produce granulated powder.

Next, a green body having a predetermined shape is obtained, and the obtained green body is fired under the same firing conditions as those of the above-mentioned embodiment, whereby a grayish white and light-shielding ceramic can be obtained. It is possible to obtain a ceramic that is excellent in mechanical properties such as bending strength, hardness, and fracture toughness value without causing abnormal grain growth of alumina particles and YAG particles as the sintering progresses and becomes dense.

Finally, the dummy wafer of the present invention can be obtained by processing the surface of the obtained ceramics by lapping using a diamond grindstone or loose abrasive grains.

The dummy wafer thus obtained is
The relative reflectance becomes 70% or more, and in order to investigate the film forming and etching conditions in the film forming process and etching process in the semiconductor manufacturing process, for example, positioning when mounting a semiconductor element, film forming process, etc. Timing measurement of
The control of wafer transportation and the like can be performed by detecting it with an optical system sensor that utilizes optical effects such as visible light and ultraviolet rays.

By using the dummy wafer of the present invention, it has good corrosion resistance against a cleaning gas having a very strong corrosive property, and is less likely to be cracked by a thermal shock due to a rapid temperature rise. By constructing a high dummy wafer, the cleaning time can be significantly shortened and the detection by the optical sensor can be performed accurately.

The dummy wafer of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention.

[0087]

Example 1 First, alumina powder, YAG powder, yttria powder, etc. were prepared as starting materials in the proportions shown in Table 1, and ion-exchanged water and a binder were further added and kneaded and dried. Granulated powder was produced. The obtained granulated powder is filled in a mold, and a diameter of 6 is obtained by a press molding method.
A disk-shaped compact having a thickness of 0 mm and a thickness of 5 mm was obtained.

Then, the obtained molded body was degreased at 400 ° C., the temperature rising rate was set to be within the range of 20 ° C./hour from 1200 ° C., and the temperature was kept constant for about 6 hours every 5 hours. Meanwhile, firing was performed at a temperature of about 1600 ° C. in the air atmosphere.

Then, each ceramic was ground to a thickness of 3 mm, and then the surface was lapped to obtain a mirror wafer dummy wafer sample.

As a comparative example, a dummy wafer sample made of alumina ceramics having a purity of 99.5% by weight and quartz and having a mirror-finished surface was obtained in the same manner as above.

The average crystal grain size of each dummy wafer sample was measured by an image analyzer (Luzex), the porosity was measured by the Archimedes method, and the surface roughness was calculated according to JIS B0601. The four-point bending strength was determined by a gauge according to JIS R1601.

Furthermore, each sample was subjected to RIE (Reactiv).
e Ion Etching) device
After exposing to ₂ gas atmosphere and SF ₆ gas atmosphere for 3 hours,
The etching rate per minute was calculated from the weight reduction value before and after the treatment.

The numerical value of the etching rate is 9
The relative comparison is made assuming that the etching rate of 9.5 wt% alumina ceramics is 1.

Further, in order to investigate the thermal shock resistance of each sample, each ceramic sample was 3 mm × 4 mm × 40 mm.
The bending resistance test piece was prepared, heated to a predetermined temperature, and then dropped in water to evaluate the thermal shock resistance by the presence or absence of cracks generated on the ceramic surface.

The presence or absence of cracks was judged by the flaw detection liquid, and the maximum temperature difference without cracks was defined as the thermal shock resistance temperature ΔT.

Further, the ceramics shown in Table 1 were ground and polished to prepare a dummy wafer sample having a diameter of 100 mm, a thickness of 0.65 mm, and a surface roughness Ra of the sensing surface of 0.1 to 1.0 μm. Red LE with the relative reflectance of the dummy wafer installed vertically at a distance of 30 mm from the dummy wafer
The measurement was performed by a detector using a reflection type sensor having D (600 nm) as a light emitting portion.

The results are shown in Table 1.

[0098]

[Table 1]

As is clear from Table 1, the dummy wafer samples (Nos. 2 to 12) of the present invention have an average crystal grain size of 1
It was 5.4 μm or less, the porosity was 0.5% or less, and the four-point bending strength was a large value of 245 to 265 MPa. In addition, the ratio of the etching rate to Cl ₂ gas is 0.6.
Below, the ratio of the etching rate to the SF ₆ gas is 0.
It can be seen that it has a very high corrosion resistance of 45 or less.
Furthermore, the thermal shock resistance is as high as 100 ° C. or higher. Further, the relative reflectance was 70% or more, which is a practical level at which detection omission did not occur.

Particularly, zirconia is added as an auxiliary component in an amount of 500-500.
The samples (No. 2, 4 to 6, 8 to 10) containing 50,000 ppm by weight and having an average crystal grain size of 8 μm or less have a porosity of 0.2% or less and a small four-point bending strength of 255.
It became larger than MPa. Further, the ratio of the etching rate to Cl ₂ gas is 0.50 or less, SF
The ratio of the etching rate to ₆ gases was 0.24 or less, and the corrosion resistance was excellent.

On the other hand, the sample (No.
1, 13 and 14) have a very low corrosion resistance with an etching rate ratio to Cl ₂ gas of 0.41 to 4.6 and an etching rate ratio to SF ₆ gas of 1 to 18.26, and a relative reflectance of 20. It was as small as ~ 65%, and it was found that it was not sufficiently sensed by the optical sensor.

(Example 2) Next, a dummy wafer sample was prepared in the same manner as in Example 1, except that the contents of alumina and YAG and the average crystal grain size of alumina and YAG were as shown in Table 2.

As a comparative example, YAG and a purity of 99.
Samples made of 5 wt% alumina ceramics were prepared.

Each sample was observed with a scanning electron microscope, and each average crystal grain size of alumina and YAG was measured with an image analyzer (Luzex).

The porosity of each sample was measured by the Archimedes method in accordance with JIS R1601 for four-point bending strength, JIS R1610 for Vickers hardness, and JIS R1607 for fracture toughness.

Next, these ceramics were formed to a thickness of 3 m.
After grinding to m, a sample with a mirror surface on the surface was obtained, and each sample was set in the RIE device and Cl
After being exposed to a ₂ gas atmosphere for 3 hours, the etching rate per minute was calculated from the weight reduction value before and after the treatment.
The above etching rate is 99.5% by weight.
It is shown by relative comparison when the etching rate of the aluminous ceramics of 1 is set to 1.

The thermal shock resistance and relative reflectance of each sample were measured in the same manner as in Example 1.

The results are shown in Table 2.

[0109]

[Table 2]

As is clear from Table 2, 50% alumina was added.
The samples (No. 17 to 22) containing 20 to 50% by weight of YAG and 20 to 50% by weight of YAG have a very low porosity of 0.1% or less, a 4-point bending strength of 300 MPa or more, and a Vickers hardness of 15 GPa or more. And excellent mechanical properties, and the etching rate ratio to Cl ₂ gas is 0.65 or less,
It was found that the corrosion resistance to SF ₆ gas was 0.31 or less, the thermal shock resistance was 140 ° C. or more, and the relative reflectance was more than 70% of the practical level at which detection leakage did not occur.

In particular, a sample in which the ratio of the average crystal grain size of alumina to the average crystal grain size of YAG was 1 to 7 (N
o. 17-20, 22) has a 4-point bending strength of 320MP
a or more, the Vickers hardness is 16 GPa or more, which is extremely high, and the fracture toughness value is 2.1 to 2.5 MPa · √m.
And it turned out that the processing accuracy is also excellent.

On the other hand, a sample containing 90 to 98% by weight of alumina and 2 to 10% by weight of YAG (No. 1).
5, 16) has a porosity of 0.3 to 0.5%, an etching rate ratio of 0.8 to 0.9 with respect to Cl ₂ gas,
SF ₆ it can be seen that large corrosion resistance and 0.5 to 0.65 is smaller than the gas.

Also, a sample (N
o. 23, 13) has a large etching rate and a relative reflectance as low as 60% or less, and thus it was found that they were not sufficiently sensed by the optical sensor.

(Example 3) Next, No. 1 in Table 1 was used.
The firing conditions of the sample of No. 5 were changed as shown in Table 3, and the characteristics were measured by the same method as in Examples 1 and 2.

The presence / absence of cracks on the surface of the sintered body was judged by a flaw detection liquid, and a sample having no cracks was evaluated as ◯, and a sample having minute cracks was evaluated as Δ.

The results are shown in Table 3.

[0117]

[Table 3]

As is clear from Table 3, the firing temperature under the firing conditions is 1500 to 1750 ° C.
The temperature rising rate after 0 ° C. is 15 to 20 ° C./hour, and 3
Samples (No. 5-2, 5-4, 5-7, 5-9, 5- held at a constant temperature every 3 to 6 hours for 3 to 10 hours)
11, 5-14) has a small porosity of 0.2% or less,
It was also found that the four-point bending strength was as high as 255 to 2565 MPa, the thermal shock resistance was 120 ° C. or higher, and there was no crack or breakage due to abrupt shrinkage.

Further, the sample (N
o. 5-3), the sample for holding the constant temperature for more than 10 hours (No. 5-10), and the sample for holding the constant temperature for more than 6 hours (No. 5-12),
Each of them has a porosity as small as 0.2% or less, excellent opportunistic properties, and has no cracks or cracks, but it takes a long time to manufacture, which is not preferable.

On the other hand, a sample with a low firing temperature (No.
5-1) has a 4-point bending strength of 245 MPa, and the sample with a high firing temperature (No. 5-15) has a porosity of 0.
It becomes as high as 29%, the 4-point bending strength also decreases, and cracks and breakages easily occur.

Samples that are not kept at a constant temperature (No. 5-5), samples that are kept at a constant temperature at short intervals (No. 5-6), and samples that are kept at a constant temperature for a short time (No. 5-8), and a sample with a high heating rate (No.
It was found that in No. 5-13), variations in temperature occur and cracks and breaks easily occur.

Example 4 Next, N in Example 2
o. The firing conditions of the sample No. 19 were changed as shown in Table 4, and the characteristics were measured by the same method as in Examples 1 to 3.

The results are shown in Table 4.

[0124]

[Table 4]

As is clear from Table 4, for the ceramics containing alumina as the main component and YAG as the accessory component, the heating rate after 1200 ° C. was set to 15 to 20 ° C./hour as in Example 3. And 3-1 every 3-6 hours
A sample in which the temperature was kept constant for a period of 0 hour (No. 19)
-2, 19-4, 19-7, 19-9, 19-11, 1
9-14) has a small porosity of 0.08% or less, a high four-point bending strength of 320 to 340 MPa, a thermal shock resistance of 160 ° C. or more, and is free from cracks and cracks due to rapid shrinkage. .

Further, the sample (N
o. 19-3), a sample which is kept at a constant temperature for more than 10 hours (No. 19-10), and a sample which is kept at a constant temperature for more than 6 hours (No. 19-1).
In the case of 2), the porosity is as small as 0.08% or less, the opportunity characteristics are excellent, and no cracks or cracks are generated, but it takes a long time to manufacture, which is not preferable.

On the other hand, a sample with a low firing temperature (No.
19-1), the four-point bending strength was reduced to 300 MPa,
The sample (No. 19-15) having a high firing temperature has a high porosity of 0.1% and a four-point bending strength of 300 MPa, which is likely to cause cracks and cracks.

Further, a sample which is not kept at a constant temperature (No. 19-5), a sample which is kept at a constant temperature at short intervals (No. 19-6), and a sample which is kept at a constant temperature for a short time (No. 19-8) and the sample with a high temperature rising rate (No. 19-13) were found to be susceptible to temperature variations and cracks.

[0129]

According to the dummy wafer of the present invention, a compound of yttria and alumina is used as a main crystal phase, and the main crystal phase is composed of YAG (yttrium aluminum garnet), YAG and alumina, or YAG and yttria. Therefore, even if these ceramics react with a corrosive gas or plasma to form a halide, the ceramics have a high melting point and are stable, so that they can have excellent corrosion resistance.

Further, according to the dummy wafer of the present invention, since the average crystal grain size is 8 μm or less and the porosity is 0.2% or less, it is possible to prevent the progress of corrosion as a dense ceramic and to improve the corrosion resistance. can do.

Further, according to the dummy wafer of the present invention,
50 parts of zirconia containing ceria as a stabilizer as a sub ingredient
Since the content is 0 to 50,000 ppm by weight, it is possible to improve the thermal shock resistance against heat shock due to a rapid temperature rise.

According to the dummy wafer of the present invention, since it is made of a ceramic containing alumina in an amount of 50 to 80% by weight and YAG in an amount of 20 to 50% by weight, alumina can increase mechanical strength and hardness, and YAG can corrode it. The corrosion resistance to gas and its plasma can be made excellent.

Further, according to the dummy wafer of the present invention, the average crystal grain diameter of the alumina is 2 to 10 μm, the average crystal grain diameter of YAG is 1.5 to 5 μm, and the alumina is larger than the average crystal grain diameter of the YAG. Since the ratio of the average crystal grain size of is larger than 1 and smaller than 7, it reduces the pores in the ceramics and improves the bending strength and hardness,
It is possible to suppress the progress of corrosion in plasma. Further, the fracture toughness value can be suppressed to an appropriate value to obtain free-cutting property and workability.

Further, according to the dummy wafer of the present invention,
Since the porosity is 0.2% or less, the progress of corrosion can be prevented as a dense ceramic and the corrosion resistance can be further enhanced.

Furthermore, according to the dummy wafer of the present invention, since the relative reflectance is 70% or more, it is possible to increase the detection accuracy of the measurement using the optical sensor.

Furthermore, since the surface roughness of at least one main surface is 0.1 to 0.4 μm in terms of arithmetic average roughness (Ra), the light wave of the optical system sensor is higher without scattering. The reflectance can be obtained.

In the dummy wafer of the present invention, a raw material powder obtained by adding and mixing alumina powder and yttria powder is molded into a predetermined shape, and then the obtained molded body is molded into 300 to 6 pieces.
After degreasing at 00 ° C, heat it in the air atmosphere for about 12
The temperature rise rate is set to 15 to 20 ° C./hour from 00 ° C., and the firing is performed at the maximum temperature of 1500 to 1750 ° C. while maintaining the temperature constant for 3 to 10 hours every 3 to 6 hours Therefore, it is possible to prevent a rapid contraction, obtain a dense, high-strength, gray-white dummy wafer having a light-shielding property.

Further, since it is the detection method using the dummy wafer of the present invention, it is possible to accurately search the film forming and etching conditions in the film forming step and the etching step in the semiconductor manufacturing process.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a dummy wafer of the present invention.

[Explanation of symbols]

1: Dummy wafer

Claims (11)

[Claims] 1. A dummy wafer comprising a ceramic containing a compound of yttria and alumina as a main crystal phase. 2. The main crystal phase is YAG (yttrium.
2. The dummy wafer according to claim 1, wherein the dummy wafer comprises aluminum garnet), YAG and alumina, or YAG and yttria. 3. The dummy wafer according to claim 1, which has an average crystal grain size of 8 μm or less and a porosity of 0.2% or less. 4. The dummy wafer according to claim 1, which contains 500 to 50,000 ppm by weight of zirconia containing ceria as a stabilizer as an auxiliary component. 5. Alumina 50 to 80% by weight and YAG 2
A dummy wafer comprising a ceramic containing 0 to 50% by weight. 6. The alumina having an average crystal grain size of 2 to 10.
μm, the average crystal grain size of YAG is 1.5 to 5 μm
The dummy wafer according to claim 5, wherein the ratio of the average crystal grain size of the alumina to the average crystal grain size of the YAG is larger than 1 and smaller than 7. 7. The dummy wafer according to claim 5, which has a porosity of 0.2% or less. 8. The dummy wafer according to claim 1, which has a relative reflectance of 70% or more. 9. The surface roughness is an arithmetic average roughness (Ra) of 0.
It is 1-0.4 micrometers, It is characterized by the above-mentioned.
The dummy wafer according to any one of 1. 10. A raw material powder obtained by adding and mixing at least alumina powder and yttria powder into a predetermined shape, degreasing the obtained molded body at 300 to 600 ° C., and then heating in an air atmosphere, Temperature increase rate of 1 from approx. 1200 ° C
5 to 20 ° C./hour and 3 to 3 every 3 to 6 hours
Hold the temperature constant for 10 hours, 1500-17
The method of manufacturing a dummy wafer according to claim 1, wherein the method is performed by baking at a maximum temperature of 50 ° C. 10. 11. A detection method for investigating the film formation, etching conditions and the like in a film forming step, an etching step and the like in a semiconductor manufacturing process using the dummy wafer according to claim 1.