Apparatuses for heating semiconductor wafers, ceramic heaters and a process for manufacturing the same, a process for manufacturing ceramic articles

A mold for heat-treating a convolution of a spiral-coiled, high melting point metallic filament, comprising a groove for holding said convolution in a predetermined planar pattern, and composed of a material stable at a heat treatment temperature of said high melting point metal.

A ceramic heater, comprising:

• a ceramic substrate and a resistant heating element embedded within said substrate along a predetermined planar pattern, wherein said resistant heating element is obtained by heat-treating a convolution of a high melting point metallic, spiral-coiled filament at a temperature not higher than a primary recrystallization commencement temperature of said high melting point metal under a non-oxidative atmosphere, while said convolution is held in and along the predetermined pattern.

A ceramic heater, comprising:

• a ceramic substrate and a resistant heating element embedded within said ceramic substrate, said resistant heating element being a convolution of a spiral coil, the number of coils per a unit length of said convolution being set at a predetermined value in each of defined domains of the ceramic heater, and when the number of coils per a unit length of said convolution is determined, the relation of a maximal value, a minimal value and a mean value, of all the determined numbers of coils in the above domains, satisfies the following formula:
• (maximal value-minimal value)/mean value.ltoreq.0.1.

An apparatus for heating semiconductor wafers, comprising:

• a disc-shaped ceramic substrate;
• and a resistant heating element embedded within said ceramic substrate, wherein said resistant heating element has a planar shape comprising a plurality of concentric loops differing in diameter from each other and connecting portions which connect inner loops in sequence with outer loops to form a series of resistant heating elements.

A process for manufacturing ceramic articles comprising a ceramic substrate, an electroconducting body embedded within said ceramic substrate and a conduit or pit bored avoiding said electroconducting body in said ceramic substrate, comprising the steps of:

• taking an X-ray transmission photograph of said ceramic substrate and then forming said conduit or pit, based on the X-ray transmission photograph.

A ceramic heater, comprising:

• a board-shaped ceramic substrate for heating wafers and a resistant heating element embedded within said ceramic substrate, said resistant heating element being a convoluted spiral coil embedded in a fashion such that the spiral coil is flattened in the vertical direction of said ceramic substrate and that a ratio of a dimension in the horizontal direction to the dimension in the vertical direction of said spiral coil, is in the range between 1.5 and 3.0.