Compositions: ceramic – Ceramic compositions – Carbide or oxycarbide containing
Reexamination Certificate
2002-01-23
2003-12-30
Group, Karl (Department: 1755)
Compositions: ceramic
Ceramic compositions
Carbide or oxycarbide containing
C501S090000, C501S092000, C501S091000, C501S097100, C501S097200, C501S097300
Reexamination Certificate
active
06670294
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to high-purity and corrosion-resistive ceramic materials, method of producing the same, and members for semiconductor manufacturing which utilize the ceramic materials.
(2) Related Art Statement
In accordance with an increase of memory capacities in super LSI, micro-fabrication technique has been progressed, so that processes requiring chemical reactions have been widely used. Particularly, halogen-based gases such as chlorine-based gases and fluorine-based gases are used as a deposition gas, an etching gas or a cleaning gas in the semiconductor manufacturing apparatus requiring a super clean state.
In the semiconductor manufacturing apparatus such as a hot CVD apparatus as a heater for heating a wafer in contact with such a corrosive gas, the semiconductor cleaning gas of a halogen-based corrosive gas such as ClF
3
, NF
3
, CF
4
, HF or HCl is used after the deposition. During the deposition, another halogen-based gas such as WF
6
or SiH
2
Cl
2
is also used as a film-forming gas.
Since silicon nitride is a compound containing Si as a main component constituting wafers, silicon nitride is used for members in semiconductor manufacturing apparatuses, particularly chambers, together with Si, SiO
2
and SiC.
Up to now, as a chamber member used in the semiconductor manufacturing apparatuses, use is made of silicon or quartz glass. However, since silicon and quartz glass become high purity but have a low fracture toughness, chipping and cracks easily occur on their surfaces during a machining work, and thus this causes a generation of particles. Moreover, in the semiconductor manufacturing apparatuses, respective members are exposed to halogen-based corrosive gases or its plasma. For example, in the ether, corrosion of the members is accelerated with ion bombardment, or a component in the member is sputtered with plasma ion bombardment, thereby causing pollution of the wafers. Since a design rule approaches 0.1 &mgr;m, such problems become more elicit than before. Moreover, in the present states, life of the members made of silicon or quartz glass is short. Further, the present applicant disclosed in JP-A-5-251365 that is a silicon nitride sintered body is exposed to a ClF
3
gas at high temperatures, its surface state changes to generate particles.
SUMMARY OF THE INVENTION
An object of the invention is to provide corrosion-resistive materials used suitably for an application exposing to a corrosive gas such as members for semiconductor manufacturing, which achieve high corrosion resistance and decrease of particle generation due to an exposure to a corrosive gas, and wherein chippings and cracks do not occur easily during a machining work.
According to the invention, corrosion-resistive ceramic materials which are to be exposed to a corrosive gas comprise a ceramic including silicon atom wherein a percentage of respective metal elements other than metal elements constituting sintering agents and silicon atom is not more than 10 weight ppm.
Moreover, according to the invention, a method of producing the corrosion-resistive ceramic materials mentioned above comprises the steps of: preparing raw materials wherein a percentage of respective metal elements other than metal elements constituting sintering agents and silicon atom is not more than 10 weight ppm; and mixing the thus prepared raw materials by means of balls to which resins are coated. Further, according to the invention, members for semiconductor manufacturing comprise a base member made of the corrosion-resistive ceramic materials mentioned above.
The present inventors found that if silicon atom used as a main metal element of ceramic and a percentage of respective impurity metal elements in ceramic is made not more than 10 weight ppm, the corrosion resistance with respect to corrosive substances, particularly halogen-based corrosive gas or its plasma, is extremely improved and particle generation is decreased, thereby reaching to the present invention.
The corrosion resistance of the members according to the invention is extremely high as compared with, for example, quartz glass or silicon, and is also extremely high as compared with a normal silicon nitride sintered body or a silicon carbide sintered body. Such a relationship between a low amount of impurity metal elements and the corrosion resistance with respect to halogen-based corrosive gases or their plasmas has not been discussed up to now.
In addition, since the members according to the invention are made of a ceramic including silicon atom as a main metal component, chippings and cracks do not occur easily during machining, and thus it is possible to prevent particle generation due to chippings.
Further, since the members according to the invention are made of a ceramic including silicon atom as a main metal component and the percentage of impurity metal elements other than silicon atom and metal atoms constituting sintering agents is low, there is no fear of polluting the inside of the semiconductor manufacturing apparatus.
The kind of ceramic including silicon atom as a main metal elements is not limited, but it is preferred to use a ceramic such as silicon nitride, silicon carbide and sialon, particularly silicon nitride and silicon carbide.
As metal elements constituting sintering agents, use is made of magnesium, silicon, yttrium, zirconium, elements belonging to lanthanide series, ytterbium and cerium.
In the preferred embodiment, a silicon nitride sintered body is used and the metal elements constituting sintering agents are selected from a group of magnesium, silicon, yttrium, zirconium and elements belonging to lanthanide series. If these metal elements are included, it is possible to decrease the corrosion of the corrosion-resistive ceramic materials more and more. As the metal elements mentioned above, use may be made of metal elements which react with the halogen and form a stable haloid. Here, lanthanide series means La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.
Particularly, it is further preferred to use (heavy) elements having a larger atomic weight (such as Sr, Y, and lanthanide elements).
Among the metal elements mentioned above, it is further preferred to use one or more elements selected from a group of magnesium, yttrium, ytterbium, cerium, samarium and lanthanum.
It is most preferred to include the metal elements mentioned above in the form of oxide, but it may be possible to include them in the form of element itself or nitride.
In the silicon nitride sintered body, if an amount of additives is too large, a so-called boundary phase is precipitated to a level such that it is easily detected by XRD, and selective corrosion due to the difference in the etch rate between the boundary and the silicon nitride particle is promoted. As a result, particle pollutions easily occur, and the rate of being sputtered by ion bombardment becomes larger. Moreover, since the thermal expansion coefficient becomes larger, the positional relation with respect to the wafer is varied in response to a variation of thermal expansion coefficient when heated, and thus, the yield ratio of manufacturing devices becomes worse. Therefore, it is preferred that the amount of metal elements constituting sintering agents (preferably metal elements selected from a group of magnesium, silicon, yttrium, zirconium and elements belonging to lanthanide series) is not more than 15 mol % with respect to 1 mol of ceramic as calculated in the form of metal elements. This amount is further preferred to be not more than 12 mol %.
Moreover, in the case of adding sintering agents, it is preferred that the amount of metal elements constituting sintering agents (preferably metal elements selected from a group of magnesium, silicon, yttrium, zirconium and elements belonging to lanthanide series) is not less than 1.0 mol % with respect to 1 mol of ceramic as calculated in the form of metal elements.
In the silicon nitride sintered body, an amount of metal elements other than the metal elemen
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