GLASS-CERAMICS WITH PLASMA RESISTANCE AND PARTS FOR DRY ETCHING COMPRISING THE SAME

Abstract

A crystallized glass includes crystalline and vitreous structures, in which the crystalline structure includes lithium disilicate as a main crystalline phase and at least one crystalline phase among lithium phosphonate (Li.sub.3PO.sub.4), lithium metasilicate (Li.sub.2SiO.sub.3), silica (SiO.sub.2), and zirconia (ZrO.sub.2) as a sub-crystalline phase, has an excellent processability and an excellent plasma corrosion resistance, thereby being useful as a material for production of parts for various dry etching apparatuses.

Claims

1. A plasma corrosion-resistive crystallized glass comprising crystalline and vitreous structures, wherein the crystalline structure comprises lithium disilicate as a main crystalline phase and at least one crystalline phase among lithium phosphonate (Li.sub.3PO.sub.4), lithium metasilicate (Li.sub.2SiO.sub.3), silica (SiO.sub.2), and zirconia (ZrO.sub.2) as a sub-crystalline phase.

2. The crystallized glass according to claim 1, wherein the silica crystalline phase is at least one selected from the group consisting of cristobalite, α-quartz, and tridymite.

3. The crystallized glass according to claim 1, wherein the crystalline phase has an average grain size of 0.05 μm to 5 μm.

4. The crystallized glass according to claim 3, wherein the crystalline phase has an average grain size of 0.05 μm to 0.5 μm.

5. The crystallized glass according to claim 3, wherein the crystalline phase has an average grain size of 0.5 μm to 5 μm.

6. The crystallized glass according to claim 1, wherein the crystallized glass has a surface roughness Ra of 0.1 μm at a maximum.

7. A method of preparing a plasma corrosion-resistive crystallized glass, the method comprising: performing a primary crystallization heat treatment at a temperature in the range of 400° C. to 850° C. on a melt of a glass composition comprising: 60% to 85% by weight of SiO.sub.2; 10% to 15% by weight of Li.sub.2O; 1% to 6% by weight of P.sub.2O.sub.5; 0.1% to 5% by weight of a divalent element oxide alone represented by Me.sup.IIO (where, Me.sup.II is Ca, Mg, Zn, Ba, or Be) or a mixture of the divalent element oxides; 0.1% to 5% by weight of a monovalent element oxide alone represented by Me.sup.I.sub.2O (where Me.sup.I is K, Na, Rb, or Cs) or a mixture of the monovalent element oxides; and 1% to 10% by weight of a trivalent element oxide alone represented by Me.sup.III.sub.2O.sub.3 (where, Me.sup.III is Al, B, Y, La, Ga, or In) or a mixture of the trivalent element oxides.

8. The method according to claim 7, further comprising performing a secondary crystallization heat treatment at a temperature in the range of 800° C. to 950° C. after the primary crystallization heat treatment.

9. The method according to claim 7, further comprising: performing a grinding process after performing the primary crystallization heat treatment; and performing a polishing process after performing the secondary crystallization heat treatment at a temperature in the range of 800° C. to 950° C.

10. The method according to claim 8, further comprising: performing a grinding process and a polishing process after the secondary crystallization heat treatment.

11. The method according to claim 9, wherein the polishing process is performed so that an average surface roughness Ra becomes 0.1 μm at a maximum.

12. A dry etching process component comprising the plasma corrosion-resistive crystallized glass of claim 1.

13. A dry etching process component made of the plasma corrosion-resistive crystallized glass of claim 1.

14. The dry etching process component according to claim 12, wherein the part is at least one selected from a focus ring, an electrostatic chuck, and an edge ring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 illustrates an example flow chart for producing a crystallized glass according to one embodiment of the present disclosure;

[0038] FIGS. 2A, 2B and 2C are 3K-magnification SEM images of a microstructure after dry etching embodiments of the present disclosure: FIG. 2A represents a crystallized glass (glass-ceramics) specimen according to one embodiment of the present disclosure; FIG. 2B represents an alumina specimen according to one embodiment of the present disclosure, and FIG. 2C represents a zirconia specimen according to one embodiment of the present disclosure; and

[0039] FIG. 3 is an example diagram illustrating a method of masking a specimen using Kaptone tape made of polyimide to measure an etch rate.

DETAILED DESCRIPTION

[0040] The foregoing and other aspects of the present disclosure will become more clearly apparent through preferred embodiments described with reference to the accompanying drawings. Hereinafter, embodiments of the present disclosure will be described in detail such that those skilled in the art can easily understand and reproduce them.

[0041] The present disclosure relates to a crystallized glass having excellent processability (machinability) and plasma corrosion resistance and to dry etching parts including the same.

[0042] In order for materials to be applied to the dry etching process, the materials need to withstand harsh environments such as fluorinated gas. As a result of development of a glass composition that can be applied to an environment in which fluorinated gas is used and that exhibits easy processability compared to conventional ceramic materials, the present disclosure proposes crystallized glass having plasma corrosion resistance and exhibiting easy processability required for a dry etching process, and a method for preparing the same.

[0043] Specifically, crystallized glass having such plasma corrosion resistance includes crystalline and vitreous structures. The crystalline structure includes lithium disilicate as a main crystalline phase and at least one among lithium phosphonate (Li.sub.3PO.sub.4), lithium metasilicate (Li.sub.2SiO.sub.3), silica (SiO.sub.2), and zirconia (ZrO.sub.2) as a sub-crystalline phase.

[0044] In terms of processability and plasma corrosion resistance, the crystallized glass may contain at least 30% by weight of the crystalline structure and preferably 40% to 80% by weight of the crystalline structure.

[0045] In the above and below description, the term “main crystalline phase” will be understood as a crystalline phase occupying at least 50% by weight or more with respect to the total weight of the crystalline phases. In terms of processability and plasma corrosion resistance, the crystallized glass may contain at least 55% by weight of the lithium disilicate as the main crystalline phase and preferably 60% to 95% by weight of the lithium disilicate.

[0046] In the corrosion-resistive crystallized glass of the present disclosure, the silica crystalline phase as the sub-crystalline phase may have various crystalline forms but may not be limited thereto. Preferably, the silica crystalline phase includes at least one selected from cristobalite, α-quartz, and tridymite in terms of plasma corrosion resistance, strength, and processability, but the examples of the silica crystalline phase may not be limited thereto.

[0047] Preferably, the crystallized glass may have a hardness (Vickers hardness, Hv) of 720 to 750 kg/mm.sup.2 in terms of processability.

[0048] In addition, the plasma corrosion-resistive crystallized glass of the present disclosure preferably has an average grain size of 0.05 μm to 5 μm in terms of strength, plasma corrosion resistance, and processability. In terms of processability, the crystalline phase may have an average grain size of 0.05 μm to 0.5 μm. However, in terms of strength and plasma corrosion resistance, the crystalline phase may have an average grain size of 0.5 μm to 5 μm.

[0049] The crystallized glass having plasma corrosion resistance according to the present disclosure expresses a high strength different from that of general glass materials in terms of strength. Specifically, the crystallized glass is a high strength material having a breaking strength of 350 to 500 MPa based on three-point flexural strength (ISO 4049, ANSI/ADA Specification No. 27).

[0050] The plasma corrosion-resistive crystallized glass having a maximum surface roughness Ra of 0.1 μm may be useful as fine ceramics for dry etching processes.

[0051] As long as the crystallized glass satisfies these conditions, the preparation method thereof is not limited. For example, the plasma corrosion-resistive crystallized glass may be prepared from a glass composition including: 60% to 85% by weight of SiO.sub.2; 10% to 15% by weight of Li.sub.2O; 1% to 6% by weight of P.sub.2O.sub.5; 0.1% to 5% by weight of a divalent element oxide alone represented by Me.sup.IIO (where, Me.sup.II is Ca, Mg, Zn, Ba, or Be) or a mixture of the divalent element oxides; 0.1% to 5% by weight of a monovalent element oxide alone represented by Me.sup.I.sub.2O (where Me.sup.I is K, Na, Rb, or Cs) or a mixture of the monovalent element oxides; and 1% to 10% by weight of a trivalent element oxide alone represented by Me.sup.III.sub.2O.sub.3 (where, Me.sup.III is Al, B, Y, La, Ga, or In) or a mixture of the trivalent element oxides.

[0052] In the glass composition, P.sub.2O.sub.5 acts as a nucleating agent, the divalent element oxide represented by Me.sup.IIO may serve to increase the softening point and plasma corrosion resistance of glass, the monovalent element oxide represented by Me.sup.I.sub.2O may serve to lower the glass melting temperature, and the trivalent element oxide represented by Me.sup.III.sub.2O.sub.3 may serve as an intermediate agent for glass and affect corrosion resistance.

[0053] FIG. 1 illustrates an example flow chart of a method for producing a crystallized glass according to one embodiment of the present disclosure. The method for producing a crystallized glass from such a glass composition first prepares a glass melt by the various melting methods.

[0054] The glass melt is prepared by weighing and mixing the ingredients of the glass composition in step S11. In this step, Li.sub.2CO.sub.3 may be added instead of Li.sub.2O because carbon dioxide (CO.sub.2) in Li.sub.2CO.sub.3 is discharged and removed as a gas in the glass melting process. In addition, as the monovalent element oxides represented by Me.sup.I.sub.2O, for example, K.sub.2CO.sub.3 or Na.sub.2CO.sub.3 may be added instead of K.sub.2O or Na.sub.2O, respectively because carbon dioxide (CO.sub.2) is discharged and removed as a gas in the glass melting process.

[0055] The glass composition may be mixed using a dry mixing process, and a ball milling process may be used as the dry mixing process. The ball milling process will be described in detail. Starting materials are charged into a ball milling machine, and the ball mill is rotated at a constant speed to mechanically pulverize and uniformly mix the starting materials. The balls used in the ball mill may be balls made of a ceramic material such as zirconia or alumina, and the balls may have the same size or may have at least two different sizes. Depending on the target particle size, the sizes of the balls, the milling time, and the rotation speed per minute of the ball mill are controlled. For example, to achieve the target particle size, the size of the balls may be set in a range of about 1 mm to 30 mm, and the rotational speed of the ball mill may be set in a range of about 50 to 500 rpm. Ball milling is preferably performed for 1 to 48 hours depending on the target particle size. Through the ball milling, the starting materials are pulverized into fine particles having a uniform particle size, and the particles are uniformly mixed.

[0056] The mixed starting materials are put into a crucible and then heated so that the glass composition is melted in step S12. Here, “melting” means that the glass composition is changed to a liquid state having a viscosity from a solid state. The melting furnace is preferably made of a material having a high melting point, high strength, and a low contact angle in order to suppress the sticking of the melt. To this end, the melting furnace is preferably made of platinum (Pt), diamond-like-carbon (DLC), or chamotte or is preferably coated with platinum (Pt) or diamond-like-carbon (DLC).

[0057] Melting is preferably performed at 1,400° C. to 2,000° C. under normal pressure for 1 to 12 hours. When the melting temperature is lower than 1,400° C., the starting material may not be completely melted. When the melting temperature exceeds 2,000° C., it is not economical because excessive energy is consumed. Therefore, it is preferable that the melting is performed at a temperature in the above-mentioned range. In addition, when the melting time is too short, the glass composition may not be sufficiently melted whereas when the melting time is too long, excessive energy is consumed, resulting in being not economical. It is preferable that the temperature increase rate of the melting furnace is about 5° C./min to 50° C./min. When the temperature increase rate of the melting furnace is low, it takes a long time to melt the glass composition, resulting in reduction in productivity. On the other hand, when the temperature increase rate of the melting furnace is excessively high, the amount of volatilization of the starting material may increase due to a rapid temperature increase, resulting in deterioration of the physical properties of the crystallized glass. Therefore, it is preferable to raise the temperature of the melting furnace at a temperature increase rate in the above-described range. The melting may be preferably performed in an oxidizing atmosphere such as oxygen (O.sub.2) or air.

[0058] After obtaining the melt of the glass composition in the above manner, the melt is poured into a predetermined mold to obtain crystallized glass for producing a molded article of a desired shape and size in step S13. The mold is preferably made of a material having a high melting point, high strength, and a low contact angle in order to suppress the sticking of the glass melt. To this end, the mold may be made of a material such as graphite or carbon. To prevent thermal shock, it is preferable that the melt is poured into the mold after the mold is preheated to a temperature in the range of 200° C. to 300° C.

[0059] In order to prepare a plasma corrosion-resistive crystallized glass according to one embodiment of the present disclosure from the melt of the glass composition prepared in the way described above, it is preferable to perform a heat treatment at a temperature in the range of 400° C. to 850° C. in step S14. After this primary crystallization heat treatment, it is possible to obtain a crystallized glass including lithium disilicate as a main crystalline phase and at least one crystalline phase among lithium phosphonate (Li.sub.3PO.sub.4), lithium metasilicate (Li.sub.2SiO.sub.3), silica (SiO.sub.2), and zirconia (ZrO.sub.2) as a sub-crystalline phase. The crystallized glass may be crystallized glass including such a crystalline phase and the remaining vitreous phase. The crystalline phase may have an average grain size of 0.05 to 0.5 μm, so that the crystallized glass has a satisfiable final strength and an adequate cutting strength, thereby being easily processed.

[0060] On the other hand, in order to further enhance the strength of the crystallized glass having undergone the primary crystallization heat treatment, an additional heat treatment may be further performed in step S15 (hereinafter in the description, this additional heat treatment will be referred to as “a secondary crystallization heat treatment”). The secondary crystallization heat treatment may be preferably performed at a temperature in the range of 800° C. to 950° C., and the crystalline phase grows through such heat treatment and the grain size of the crystalline phase increases. Preferably, through the secondary crystallization heat treatment under the above conditions, the average grain size of the crystalline phase becomes 0.5 to 5 μm, so that the processability can be maintained while the strength is improved.

[0061] In order to use the crystallized glass of the present disclosure as fine ceramics for a semiconductor process, a grinding or polishing process may be involved in step S16. The grinding or polishing process may be performed after the first crystallization heat treatment and may be performed even after the second heat treatment.

[0062] For example, the grinding process may be performed after the primary crystallization heat treatment, and the polishing process may be performed after the secondary crystallization heat treatment. Alternatively, both of the grinding process and the polishing process may be performed after the secondary crystallization heat treatment.

[0063] In this case, the polishing process may be performed so that the average roughness Ra ultimately becomes at most 0.1 μm which is a useful roughness for fine ceramics.

[0064] It can be confirmed from the hardness value that the crystallized glass (hereinafter, referred to as glass-ceramics) according to the present disclosure is advantageous in terms of processability (cuttability). Table 1 below shows the result of measuring the hardness (Vickers hardness, Hv) of the glass-ceramics compared to the alumina and zirconia that are commonly used as materials for focus rings among parts for semiconductor manufacturing processes.

[0065] The size of the specimens used was 15×15×0.6 (mm), and the specimens had a surface roughness Ra of 0.5 μm.

[0066] As shown in the results of Table 1, the hardness of the crystallized glass proposed in the present disclosure is about ½ that of other materials, indicating that the cuttability is excellent. From this, it can be predicted that a lot of time and money will not be consumed in grinding and polishing when manufacturing parts such as a focus ring from the crystallized glass of the present disclosure.

TABLE-US-00001 TABLE 1 Hardness values of materials Sample name Zirconia Alumina Glass-Ceramics Hardness (Hv, 1351.6 ± 17.35 1653.1 ± 162.93 733.81 ± 1.16 kg/mm.sup.2)

[0067] Next, in order to examine the plasma corrosion resistance of the crystallized glass of the present disclosure, a dry etching process was performed under the conditions described below. Specifically, for the three types of specimens (having a size of 15×15×0.6 (mm)), dry etching was performed by the Korea Institute of Industrial Technology under the following conditions by request. [0068] (1) Equipment: 2300 Poly Lam Research (USA) [0069] (2) Test Condition [0070] 1) Power—RF Power (Source): 1,000 W; RF Power (Bias): 500 W [0071] 2) Gas: Total 10 mmTorr [0072] CF.sub.4: 120 sccm/Ar: 60 sccm/O.sub.2: 20 sccm [0073] 3) Time—repeat 6 times the event of a 10-minute exposure and a 5-minute pause

[0074] After a dry etching was performed in the same manner as described above, the microstructure of each specimen was observed under a scanning electron microscope (SEM). The result is shown in FIGS. 2A to 2C.

[0075] As described above, not only wafers but also process parts such as focus rings and edge rings are etched through the general dry etching process, and pores are generated. This can be easily confirmed from an SEM image after the etching of alumina (FIG. 2B) and a SEM image after the etching of zirconia (FIG. 2C). However, in contrast to the conventional materials, in the case of the crystallized glass of the present disclosure, an SEM image (FIG. 2A) shows that pores and etching traces rarely occur through etching.

[0076] In addition, the surface roughness was measured for each specimen, before and after the etching process. The results are shown in Table 2 below. The surface roughness was measured under an atomic force microscope (AFM).

[0077] In Table 2 below, the mean change in surface roughness for each specimen is obtained by subtracting the surface roughness value before etching (Ra) from the surface roughness value after etching (Ra), and the average value of these changes in surface roughness is then calculated.

[0078] From the results in Table 2, the amount of change in surface roughness before and after dry etching for the crystallized glass is about ¼ times that of alumina and about 1/1.5 times that of zirconia. In addition, it is seen that the corrosion resistance of the crystallized glass of the present disclosure is excellent because the surface after the etching is even as shown in FIGS. 2A to 2C.

TABLE-US-00002 TABLE 2 Surface roughness Surface roughness Mean change in before etching after etching surface (Ra, nm) (Ra, nm) roughness (nm) Glass- 1 4.4 54.0 43.08 Ceramics 2 4.9 45.0 3 3.3 46.4 4 3.1 42.2 5 3.8 47.3 Alumina 1 4.0 130.0 171.0 2 5.0 171.0 3 15.4 211.0 4 6.3 178.0 5 65 260.7 Zirconia 1 8.0 78.0 60.61 2 2.5 49.0 3 2.2 93.0 4 2.0 48.9 5 2.554 51.4

[0079] In addition, the weight change before and after dry etching was measured using a precision electronic scale, and the results are shown in Table 3 below. As a result of the measurement, it was found that the weight loss of the crystallized glass according to the present disclosure was smaller by about 11% compared to the existing materials. This is a result that shows that the crystallized glass according to the present disclosure is etched less in a severe plasma atmospheric condition. In Table 3 below, the average weight change is calculated by obtaining a weight change value for each specimen by subtracting the weight value after etching from the weight value before etching and then averaging the weight change values.

TABLE-US-00003 TABLE 3 Weight before Weight after Average weight etching (g) etching (g) change (mg) Glass- 1 0.39230 0.38989 2.308 Ceramics 2 0.39415 0.39169 3 0.39398 0.39172 4 0.39448 0.39222 5 0.39359 0.39144 Alumina 1 0.72264 0.72001 2.586 2 0.72124 0.71868 3 0.71924 0.71669 4 0.72042 0.71783 5 0.72219 0.71959 Zirconia 1 1.09921 1.09653 2.592 2 1.10173 1.09905 3 1.10192 1.09934 4 1.10176 1.09928 5 1.09843 1.09589

[0080] When performing the dry etching, as shown in FIG. 3 for each specimen, half (referred to as exposed surface) of the specimen was covered with a Kaptone tape (a polyimide tape) not to be exposed to the plasma and the other half (referred to as a non-exposed surface) was exposed to the plasma so as to be etched. Then, the step difference between the exposed surface and the non-exposed surface was measured with a confocal microscope, and the etch rate was measured therefrom. The results are shown in Table 4. Referring to the results in Table 4, it is possible to confirm that the etch rate of the crystallized glass according to the present disclosure is only half that of alumina and is similar to that of zirconia.

TABLE-US-00004 TABLE 4 Glass-Ceramics Zirconia Alumina Step difference (μm) 2.83702 2.74467 5.24507 2.17369 2.60843 4.99973 Avg 2.505355 Avg 2.67655 Avg 5.1224 Average etch rate 41.75 44.61 85.37 (nm/min)

[0081] In the experimental examples described above, as the crystallized glass (Glass-Ceramics) of the present disclosure, a crystallized glass containing lithium disilicate as the main crystal phase and silica (SiO.sub.2) as a sub-crystalline phase was evaluated. However, it is possible to obtain a comparable effect in all kinds of crystallized glass satisfying the composition or physical properties according to the above-described embodiments of the present disclosure. For reference, Table 5 below shows examples of the types of fine ceramic parts used in dry etching processes, main application materials, and general replacement cycles.

TABLE-US-00005 TABLE 5 No. Name Material Replacement cycle 1 View port Quartz — 2 Battle Si—SiC 6 months to 1 year 3 Electrode Si 500 hours 4 Upper ring Quartz 300 hours 5 Upper confinement ring Quartz 300 hours 6 Lower confinement ring Quartz 300 hours 7 Hot edge ring Si, Al.sub.2O.sub.3 150 hours 8 Insulator pipe Quartz 300 hours 9 Inner focus ring Al.sub.2O.sub.3 300 hours 10 Outer focus ring Al.sub.2O.sub.3 300 hours 11 Lift pin Al.sub.2O.sub.3 — 12 ESC — — 13 Bottom Insulator Al.sub.2O.sub.3 —

[0082] From Table 5, it can be seen that various fine ceramic parts are required for dry etching processes, and most of these parts are consumable parts. In addition, it can be confirmed that alumina (Al.sub.2O.sub.3) is mainly used as the material of the parts. As described above, in the case of the crystallized glass proposed in the present disclosure, it is superior in processability and plasma corrosion resistance to conventional materials. Therefore, it is confirmed that the crystallized glass of the present disclosure will be useful as an alternative to conventional materials.

[0083] In one embodiment of the present disclosure, there is provided a dry etching process component including a plasma corrosion-resistive crystallized glass including crystalline and vitreous structures, in which the crystalline structure includes lithium disilicate as a main crystalline phase and at least one crystalline phase among lithium phosphonate (Li.sub.3PO.sub.4), lithium metasilicate (Li.sub.2SiO.sub.3), silica (SiO.sub.2), and zirconia (ZrO.sub.2) as a sub-crystalline phase.

[0084] Here, the dry etching process component including the plasma corrosion-resistive crystallized glass refers to all the cases in which the plasma corrosion-resistive crystallized glass of the present disclosure is provided as a laminate on a conventional heterogeneous material and in which the plasma corrosion-resistive crystallized glass of the present disclosure is provided as a coating layer.

[0085] Preferably, the dry etching process component according to an embodiment of the present disclosure may be made of a plasma corrosion-resistive crystallized glass including crystalline and vitreous structures, in which the crystalline structure includes lithium disilicate as a main crystalline phase and at least one selected from lithium phosphonate (Li.sub.3PO.sub.4), lithium metasilicate (Li.sub.2SiO.sub.3), silica (SiO.sub.2), and zirconia (ZrO.sub.2) as a sub-crystalline phase.

[0086] Such dry etching process parts have excellent plasma corrosion resistance and excellent processability, thereby being able to flexibly cope with the high integration of semiconductor elements and large-diameter Si-wafers.

[0087] While the present invention has been described with reference to exemplary embodiments, those skilled in the art will appreciate that the exemplary embodiments are presented only for illustrative purposes and the present invention is not limited to the disclosed exemplary embodiments. On the contrary, it will be understood that various modifications and equivalents thereto are possible.

[0088] The present disclosure can address the difficulty in processing and improve thermal shock stability during large-area fabrication of conventional semiconductor and electronic material ceramics by using crystallized glass having excellent processability. In addition, the present disclosure is useful for the production of dry etching process parts having improved durability during semiconductor plasma etching, thereby extending the part replacement cycle.