Patent Application
20070248832
The electrically conductive, plasma-resistant member of the invention is an erosion-resistant member having formed, on at least part of a side thereof to be exposed to a halogen-based gas plasma environment, a thermal spray coating of yttrium metal, a mixture of yttrium metal and yttrium oxide, a mixture of yttrium metal and yttrium fluoride, or a mixture of yttrium metal, yttrium oxide and yttrium fluoride.
It is preferable here that the thermal spray powder used to form the thermal spray coating be one having an iron content that is low so as minimize the iron content within the thermal spray coating. The trend in recent years has been to manufacture semiconductor devices and the like to smaller feature sizes and larger diameters. In so-called dry processes, particularly etching processes, use is coming to be made of low-pressure, high-density plasmas. When such low-pressure, high-density plasmas are used, the effect on plasma-resistant members is greater than prior-art etching conditions, leading to major problems, such as erosion by the plasma, member ingredient contamination arising from such erosion, and contamination arising from reaction products due to surface impurities. With regard to iron in particular, when iron is present in a plasma-resistant material, the etching rate rises, raising the concern that the chamber interior and the wafer being treated may be subject to contamination. Accordingly, it is desirable to minimize the iron content within the plasma-resistant material.
The concentration of iron in the conductive plasma-resistant coating should be held to preferably not more than 500 ppm, based on the total amount of yttrium element. The total amount of yttrium element means the following. When the thermal spray coating is composed of only yttrium metal, the total amount of yttrium element is the amount of the yttrium metal. When the thermal spray coating is composed of yttrium metal in admixture with yttrium oxide and/or yttrium fluoride, the total amount of yttrium element is the sum of the amount of the yttrium metal and the amount of yttrium element in the yttrium oxide and/or yttrium fluoride. To this end, the concentration of iron impurities in the thermal spray powder must be held to not more than 500 ppm. The thermal spray powder can generally be prepared by an atomizing process such as gas atomization, disc atomization or rotating electrode atomization.
To hold the iron concentration to 500 ppm or below, the incorporation of iron in these atomizing processes must be minimized. However, there is a factor that tends to raise the iron concentration above this level; namely, the inadvertent incorporation of iron powder when yttrium oxide is converted to yttrium fluoride at the start of yttrium metal preparation. It is preferable that deironing treatment is conducted to yttrium oxide and yttrium fluoride during their preparation. For example, deironing in which the iron powder that has been incorporated into the yttrium fluoride is attracted with a magnet may be carried out. The concentration of iron within the thermal spray powder is held in this way to 500 ppm or below with respect to the total amount of yttrium element.
A precursor powder for thermal spraying having a controlled conductivity is thus prepared by mixing yttrium metal powder having a reduced iron concentration with an yttrium oxide thermal spraying precursor powder having a reduced iron concentration, with an yttrium fluoride thermal spraying precursor powder having a reduced iron concentration, or with both yttrium oxide and yttrium fluoride each having a reduced iron concentration.
By thermally spraying these precursor powders, electrically conductive thermal spray coatings having an iron impurity concentration of 500 ppm or below can be obtained.
To achieve electrical conductivity, it is desirable for the thermal spray coating to be prepared from a thermal spray powder containing preferably at least 3 wt % and up to 100 wt % of metallic yttrium, with the remainder being atomized yttrium oxide or yttrium fluoride. To measure the yttrium metal concentration, given that the thermal spray powder is a mixture of yttrium metal with yttrium oxide or yttrium fluoride, first the oxygen concentration or fluorine concentration in the material is measured and the equivalent as Y2O3 or YF3 is determined. The remaining yttrium is then treated as a metallic component.
It is preferable for the substrate on which the above thermal spray coating (yttrium metal thermal spray coating, or a mixed thermal spray coating of yttrium metal with yttrium oxide and/or yttrium fluoride) is formed to be at least one selected from among titanium, titanium alloys, aluminum, aluminum alloys, stainless steel, quartz glass, alumina, aluminum nitride, carbon and silicon nitride.
When a thermal spray coating is formed as described above on the surface portion of these substrates to be exposed to plasma, a metal layer (nickel, aluminum, molybdenum, hafnium, vanadium, niobium, tantalum, tungsten, titanium, cobalt or an alloy thereof) or a ceramic layer (alumina, yttria, zirconia) may first be formed on the substrate. Even in such a case, an outermost layer of yttrium metal, a mixture of yttrium metal and yttrium oxide, a mixture of yttrium metal and yttrium fluoride, or a mixture of yttrium metal with yttrium oxide and yttrium fluoride is formed by thermal spraying, thereby providing the halogen plasma-resistant thermal spray coating having electrical conductivity on at least part of the substrate surface which is a characteristic feature of the invention.
It is desirable for the thermal spray coating to have an electrical conductivity greater than 0 Ω·cm but not more than 5,000 Ω·cm, and preferably in a range of from 10−4 to 103 Ω·cm. By conferring the thermal spray coating with such an electrical conductivity, abnormal discharge within the chamber does not occur, making it possible to prevent arc damage.
In particular, even if the substrate is a dielectric material or the substrate is electrically conductive but an intermediate layer made of a dielectric material has been formed thereon, the characteristic features of the invention can be fully achieved by suitable modification, such as forming holes in the substrate and embedding conductive pins or the like therein, then depositing as the outermost layer a conductive, halogen plasma-resistant thermal spray coating, or making the thermal spray coating continuous from the front side to the back side of the substrate and connecting an electrically conductive portion to a ground or the like.
Thermal spraying may be carried out by any thermal spraying process cited in Yosha Handobukku [Thermal Spraying Handbook], such as gas thermal spraying and plasma spraying. In recent years, there has existed a related process known as aerosol deposition which, although not thermal spraying per se, may be used as the spraying process for the purposes of the invention. With regard to the thermal spraying conditions, a known method such as atmospheric-pressure thermal spraying, controlled-atmosphere thermal spraying or low-pressure thermal spraying may be used. The precursor powder is loaded into the thermal spraying apparatus and a coating is deposited to the desired thickness while controlling the distance between the nozzle or thermal spraying gun and the substrate, the velocity of movement between the nozzle or thermal spraying gun and the substrate, the type of gas, the gas flow rate, and the powder feed rate.
It is desirable for the thermal spray coating which has been conferred with electrical conductivity to have a thickness of at least 1 μm. The thickness may be set within a range of from 1 to 1,000 μm. However, because corrosion is not entirely absent, to increase the life of the coated member, it is generally preferable for the coating thickness to be from 10 to 500 μm, and especially from 30 to 300 μm.
When yttrium metal has been plasma sprayed under atmospheric conditions, yttrium nitride sometimes forms on the surface of the plasma sprayed coating. Because yttrium nitride is hydrolyzed by atmospheric moisture and the like, if surface nitridation has occurred, the yttrium nitride should be promptly removed.
The conductive, plasma-resistant member of the invention obtained in the foregoing manner has a portion which is electrically conductive and which both enhances the erosion resistance to halogen-based plasmas and also confers electrical conductivity to the interior of the plasma chamber. As a result, particle formation due to abnormal discharge is suppressed and an even more stable plasma is generated, enabling improvements to be made in the wafer etching performance and the formation of stable coatings by plasma CVD.
Examples of the invention and Comparative Examples are given below by way of illustration and not by way of limitation.
A thermal spray powder was prepared by weighing out 15 g of disc-atomized metallic yttrium powder having an iron content of 352 ppm and 485 g of yttrium oxide powder, and mixing the powders for 1 hour in a V-type mixer. Next, an aluminum alloy substrate measuring 100×100 ×5 mm was degreased with acetone, then roughened on one side by blasting with alumina grit. The thermal spray powder was then sprayed onto the substrate with a plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
Another test specimen was formed in the same manner as above except that an alumina substrate was used instead of the aluminum alloy substrate. The thermal spray coating deposited on the alumina substrate was then dissolved in hydrochloric acid and the resulting solution was analyzed by inductively coupled plasma (ICP) emission spectrometry, whereupon the coating was found to have an iron concentration, based on the total yttrium element, of 40 ppm.
A thermal spray powder was prepared by weighing out 25 g of gas-atomized metallic yttrium powder having an iron content of 120 ppm and 475 g of yttrium oxide powder, and mixing the powders for 1 hour in a V-type mixer. Next, an aluminum alloy substrate measuring 100×100×5 mm was degreased with acetone, following which the thermal spray powder was sprayed onto the substrate with a plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
Another test specimen was formed in the same manner as above except that an alumina substrate was used instead of, the aluminum alloy substrate. The thermal spray coating deposited on the alumina substrate was then dissolved in hydrochloric acid and the resulting solution was analyzed by ICP emission spectrometry, whereupon the coating was found to have an iron concentration, based on the total yttrium element, of 15 ppm.
A thermal spray powder was prepared by weighing out 50 g of rotating electrode-atomized metallic yttrium powder having an iron content of 80 ppm and 450 g of yttrium oxide powder, and mixing the powders for 1 hour in a V-type mixer. Next, an aluminum alloy substrate measuring 100×100×5 mm was degreased with acetone, following which the thermal spray powder was sprayed onto the substrate with a plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
Another test specimen was formed in the same manner as above except that an alumina substrate was used instead of the aluminum alloy substrate. The thermal spray coating deposited on the alumina substrate was then dissolved in hydrochloric acid and the resulting solution was analyzed by ICP emission spectrometry, whereupon the coating was found to have an iron concentration, based on the total yttrium element, of 17 ppm.
A thermal spray powder was prepared by weighing out 250 g of gas-atomized metallic yttrium powder having an iron content of 120 ppm and 250 g of yttrium oxide powder, and mixing the powders for 1 hour in a V-type mixer. Next, a stainless steel substrate measuring 100×100×5 mm was degreased with acetone, following which the thermal spray powder was sprayed onto the substrate with an atmospheric pressure plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
Another test specimen was formed in the same manner as above except that an alumina substrate was used instead of the stainless steel substrate. The plasma spray coating deposited on the alumina substrate was then dissolved in hydrochloric acid and the resulting solution was analyzed by ICP emission spectrometry, whereupon the coating was found to have an iron concentration, based on the total yttrium element, of 72 ppm.
It is apparent from the results obtained in the above examples of the invention that the iron concentration of the plasma spray coating is most greatly affected by the iron content within the metallic yttrium powder, and substantially does not increase as a result of thermal spraying per se.
A thermal spray powder was prepared by weighing out 15 g of gas-atomized metallic yttrium powder having an iron content of 120 ppm and 485 g of yttrium fluoride powder, and mixing the powders for 1 hour in a V-type mixer. Next, an aluminum alloy substrate measuring 100×100×5 mm was degreased with acetone, following which the thermal spray powder was sprayed onto the substrate with a plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
Another test specimen was formed in the same manner as above except that an alumina substrate was used instead of the aluminum alloy substrate. The thermal spray coating deposited on the alumina substrate was then dissolved in hydrochloric acid and the resulting solution was analyzed by ICP emission spectrometry, whereupon the coating was found to have an iron concentration, based on the total yttrium element, of 13 ppm.
A thermal spray powder was prepared by weighing out 25 g of gas-atomized metallic yttrium powder having an iron content of 120 ppm and 475 g of yttrium fluoride powder, and mixing the powders for 1 hour in a V-type mixer. Next, an aluminum alloy substrate measuring 100×100×5 mm was degreased with acetone, following which the thermal spray powder was sprayed onto the substrate with a plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
Another test specimen was formed in the same manner as above except that an alumina substrate was used instead of the aluminum alloy substrate. The thermal spray coating deposited on the alumina substrate was then dissolved in hydrochloric acid and the resulting solution was analyzed by ICP emission spectrometry, whereupon the coating was found to have an iron concentration, based on the total yttrium element, of 18 ppm.
A thermal spray powder was prepared by weighing out 50 g of gas-atomized metallic yttrium powder having an iron content of 120 ppm and 450 g of yttrium fluoride powder, and mixing the powders for 1 hour in a V-type mixer. Next, an aluminum alloy substrate measuring 100×100×5 mm was degreased with acetone, following which the thermal spray powder was sprayed onto the substrate with a plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
Another test specimen was formed in the same manner as above except that an alumina substrate was used instead of the aluminum alloy substrate. The thermal spray coating deposited on the alumina substrate was then dissolved in hydrochloric acid and the resulting solution was analyzed by ICP emission spectrometry, whereupon the coating was found to have an iron concentration, based on the total yttrium element, of 22 ppm.
A thermal spray powder was prepared by weighing out 250 g of gas-atomized metallic yttrium powder having an iron content of 120 ppm and 250 g of yttrium fluoride powder, and mixing the powders for 1 hour in a V-type mixer. Next, an aluminum alloy substrate measuring 100×100×5 mm was degreased with acetone, following which the thermal spray powder was sprayed onto the substrate with a plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
Another test specimen was formed in the same manner as above except that an alumina substrate was used instead of the aluminum alloy substrate. The thermal spray coating deposited on the alumina substrate was then dissolved in hydrochloric acid and the resulting solution was analyzed by ICP emission spectrometry, whereupon the coating was found to have an iron concentration, based on the total yttrium element, of 65 ppm.
An aluminum alloy substrate measuring 100×100×5 mm was degreased with acetone, following which a gas-atomized metallic yttrium powder having an iron content of 120 ppm was sprayed onto the substrate with a plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
Another test specimen was formed in the same manner as above except that an alumina substrate was used instead of the aluminum alloy substrate. The thermal spray coating deposited on the alumina substrate was then dissolved in hydrochloric acid and the resulting solution was analyzed by ICP emission spectrometry, whereupon the coating was found to have an iron concentration, based on the total yttrium element, of 121 ppm.
A thermal spray powder was prepared by weighing out both 150 g of gas-atomized metallic yttrium powder having an iron content of 120 ppm and 50 g of yttrium oxide powder, and mixing the powders for 1 hour in a V-type mixer. Next, an aluminum alloy substrate measuring 100×100×5 mm was degreased with acetone, following which the thermal spray powder was sprayed onto the substrate with a plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
Another test specimen was formed in the same manner as above except that an alumina substrate was used instead of the aluminum alloy substrate. The thermal spray coating deposited on the alumina substrate was then dissolved in hydrochloric acid and the resulting solution was analyzed by ICP emission spectrometry, whereupon the coating was found to have an iron concentration, based on the total yttrium element, of 92 ppm.
A thermal spray powder was prepared by weighing out 180 g of gas-atomized metallic yttrium powder having an iron content of 120 ppm and 20 g of yttrium fluoride powder, and mixing the powders for 1 hour in a V-type mixer. Next, an aluminum alloy substrate measuring 100×100×5 mm was degreased with acetone, following which the thermal spray powder was sprayed onto the substrate with a plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
Another test specimen was formed in the same manner as above except that an alumina substrate was used instead of the aluminum alloy substrate. The thermal spray coating deposited on the alumina substrate was then dissolved in hydrochloric acid and the resulting solution was analyzed by ICP emission spectrometry, whereupon the coating was found to have an iron concentration, based on the total yttrium element, of 110 ppm.
A thermal spray powder was prepared by weighing out 160 g of gas-atomized metallic yttrium powder having an iron content of 120 ppm, 20 g of yttrium oxide and 20 g of yttrium fluoride powder, and mixing the powders for 1 hour in a V-type mixer. Next, an aluminum alloy substrate measuring 100×100×5 mm was degreased with acetone, following which the thermal spray powder was sprayed onto the substrate with a plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
Another test specimen was formed in the same manner as above except that an alumina substrate was used instead of the aluminum alloy substrate. The thermal spray coating deposited on the alumina substrate was then dissolved in hydrochloric acid and the resulting solution was analyzed by ICP emission spectrometry, whereupon the coating was found to have an iron concentration, based on the total yttrium element, of 100 ppm.
An aluminum alloy substrate measuring 100×100×5 mm was degreased with acetone, following which yttrium oxide powder was sprayed onto the substrate with a plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
An aluminum alloy substrate measuring 100×100×5 mm was degreased with acetone, following which alumina powder was sprayed onto the substrate with a plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
A test specimen obtained by effecting anodic oxidation treatment to the surface of an aluminum alloy substrate measuring 100×100×5 mm was used.
The plasma-sprayed surfaces of the test specimens were polished, and the resistivity of the plasma spray coating in each example of the invention and each comparative example (in Comparative Example 3, the anodic oxidation coating) was measured with a resistivity meter (Loresta HP, manufactured by Mitsubishi Chemical Corporation (now Dia Instruments)). The results obtained are shown in Table 1.
As is apparent from the resistivity results in Table 1, the thermal spray coatings of yttrium oxide and aluminum oxide and the anodic oxidation coating were all insulators. It was confirmed, however, that electrical conductivity is conferred by including metallic yttrium in the plasma spray powder.
In each example, the test piece was cut to dimensions of 20×20×5, then surface polished to a roughness Ra of 0.5 or below. The surface was then masked with polyimide tape so as to leave a 10 mm square area exposed at the center, and an irradiation test was carried out for a given length of time using a reactive ion etching (RIE) system in a mixed gas plasma of CF4 and O2. The erosion depth was determined by measuring the height of the step between the masked and unmasked areas using a Dektak 3ST stylus surface profiler
The plasma exposure conditions were as follows: output, 0.55 W; gas, CF4+O2 (20%); gas flow rate, 50 sccm; pressure, 7.9 to 6.0 Pa. The results obtained are shown in Table 2.
From the results in Tables 1 and 2, plasma spray coatings containing metallic yttrium exhibit a good electrical conductivity without a loss of plasma resistance. Because such coatings have conductivity, abnormal discharges do not arise within the chamber and arc damage does not occur. Hence, it was confirmed that a good performance characterized by a suppressed erosion rate is exhibited even with exposure to a halogen-based gas plasma atmosphere.
By using such thermal spray coatings endowed with both plasma resistance and electrical conductivity at the interior of plasma chambers within semiconductor manufacturing equipment and liquid crystal manufacturing equipment, desirable effects such as plasma stabilization and a reduction in abnormal discharges can be expected.
A thermal spray powder was prepared by weighing out 200 g of gas-atomized metallic yttrium powder having an iron content of 120 ppm, 25 g of yttrium oxide powder and 25 g of yttrium fluoride powder, and mixing the powders for 1 hour in a V-type mixer. Next, a stainless steel substrate measuring 100×100×5 mm was degreased with acetone, following which the thermal spray powder was sprayed onto the substrate with an atmospheric-pressure plasma sprayer using argon and hydrogen as the plasma gases at an output of 40 kW, a spray distance of 120 mm and a powder feed rate of 20 g/min so as form a coating having a thickness of about 200 μm, thereby giving a test specimen.
The test specimen was sectioned, and the sectioned specimen was prepared for examination by setting it in epoxy resin and polishing the sectioned plane to be examined. Examination was carried out with a JXA-8600 electron microprobe manufactured by JEOL Ltd. Investigation of the elemental distribution of nitrogen by surface analysis confirmed that nitrogen was distributed over the surface, indicating that the thermal spraying of yttrium metal powder under atmospheric conditions is characterized by surface nitridation.
Japanese Patent Application No. 2006-116952 is incorporated herein by reference.
Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-116952 | Apr 2006 | JP | national |
