BERYLLIUM OXIDE PEDESTALS
A base plate containing a having a top and a bottom and comprising a beryllium oxide composition containing at least 95 wt % beryllium oxide and optionally fluorine/fluoride ion. The base plate demonstrates a clamping pressure of at least 133 kPa at a temperature of at least 600° C. and a bulk resistivity greater than 1×10 5 ohm-m at 800° C.
1 . A base plate having a top and a bottom and comprising a beryllium oxide composition, containing at least 95 wt % beryllium oxide and optionally fluorine/fluoride ion;
wherein the base plate demonstrates a clamping pressure of at least 133 kPa at a temperature of at least 600° C. and a bulk resistivity greater than 1×10 5 ohm-m at 800° C.
2 . The base plate of claim 1 , wherein the base plate comprises a beryllium oxide composition comprising from 1 ppm to 5 wt % ppm magnesium oxide and from 1 ppm to 5 wt % silicon dioxide and from 1 ppm to less than 5 wt % ppm magnesium trisilicate.
3 . The base plate of claim 1 , wherein the base plate demonstrates:
a temperature variance of less than ±3%, when heated to a temperature over 700° C.; and/or
a decomposition change of less than 1 wt % at temperatures greater than 1600° C.; and/or
a dielectric constant less than 20; and/or
a surface hardness of at least 50 Rockwell on a 45N scale; and/or
a coefficient of thermal expansion ranging from 5 to 15 throughout the base plate.
4 . The base plate of claim 1 , wherein a coefficient of thermal expansion varies from top-to-bottom by less than 25%.
5 . The base plate of claim 1 , wherein the base plate demonstrates a corrosion loss of less than 0.016 wt %.
6 . The base plate of claim 1 , wherein the base plate demonstrates a cleaning cycle time less than 2 hours and a temperature variance of less than ±3%.
7 . The base plate of claim 1 , wherein the base plate contains no discrete layers.
8 . The base plate of claim 1 , wherein the base plate demonstrates a temperature variance of less than ±3%, when heated to a temperature over 700° C.
9 . The base plate of claim 1 , wherein the base plate has:
a decreasing top-to-bottom thermal conductivity gradient;
a decreasing top-to-bottom resistivity gradient; and
a decreasing top-to-bottom purity gradient.
10 . The base plate of claim 1 , wherein the top purity is at least 0.4% greater than the bottom purity.
11 . A pedestal assembly comprising:
a shaft containing a first beryllium oxide composition containing beryllium oxide and fluorine/fluoride ion; and
a base plate containing a second beryllium oxide composition containing at least 95 wt % beryllium oxide;
wherein the base plate demonstrates a clamping pressure of at least 133 kPa at a temperature of at least 600° C. and a bulk resistivity greater than 1×10 5 ohm-m at 800° C.
12 . The assembly of claim 11 , wherein the first beryllium oxide composition has average grain boundaries greater than 0.1 micron.
13 . The assembly of claim 11 , wherein the first beryllium oxide composition has an average grain size less than 100 microns.
14 . The assembly of claim 11 , wherein the first beryllium oxide composition comprises from 10 ppb to 800 ppm fluorine/fluoride ion.
15 . The assembly of claim 11 , wherein the first beryllium oxide composition comprises more fluorine/fluoride ion than the second beryllium oxide composition.
16 . The assembly of claim 11 , wherein the first beryllium oxide composition further comprises:
from 1 ppb to 50 wt % ppm alumina;
from 1 ppb to 10000 ppm sulfites; and/or
from 1 ppb to 1 wt % ppm boron, barium, sulfur, or lithium, or combinations thereof including oxides, alloys, composites, or allotropes, or combinations thereof.
17 . The assembly of claim 11 , wherein first beryllium oxide composition comprises less than 75 wt % aluminum nitride and the second beryllium oxide composition comprises less than 5 wt % aluminum nitride.
18 . A shaft for a pedestal assembly comprising a beryllium oxide composition containing beryllium oxide and from 10 ppb to 800 ppm fluorine/fluoride ion;
wherein the beryllium oxide composition has average grain boundaries greater than 0.1 micron or an amorphous grain structure and an average grain size less than 100 microns.
19 . A process for making a base plate, the process comprising the steps of:
providing a first BeO powder and a third BeO powder;
forming a second powder from the first and third powders;
forming a first (bottom) region from the first powder;
forming a second (middle) region from the second powder;
forming a third (top) region from the third powder to form a base plate precursor, wherein the second region is disposed between the first and third regions; and
firing the base plate precursor to form the base plate.
20 . The process of claim 19 , wherein the first and third, and optionally second, powders comprise different grades of raw BeO.