Rare-earth-containing glass material and substrate and device comprising such substrate
A rare-earth-containing glass material having a composition, expressed in mole percentages on and oxide basis, comprising: SiO 2 : 66-75 Al 2 O 3 : 11-17 B 2 O 3 : 0-4 MgO: 1-6.5 CaO: 2-7 SrO: 0-4 BaO: 0-4 Y 2 O 3 : 0-4 La 2 O 3 : 0-4 Y 2 O 3 +La 2 O 3 : 0.1-4. The inclusion of Y 2 O 3 and/or La 2 O 3 in the composition reduces the T2.3 of the glass thereby allowing higher annealing-point glasses to be produced. The glass is particularly useful for low-temperature polycrystalline silicon-based semiconductor devices.
1. A rare-earth-containing glass material having a composition, expressed in mole percentages on an oxide basis, comprising:
SiO 2 : 66-75
Al 2 O 3 : 11-17
MgO: 1-6.5
CaO: 2-7
SrO: 0-4
BaO: 0-4
Y 2 O 3 : 0-4
La 2 O 3 : 0-4
Y 2 O 3 +La 2 O 3 : 0.1-4
wherein the glass material has:
(i) a strain point that is equal to or greater than 750°; and
(ii) a B 2 O 3 content which is essentially zero.
2. A glass material according to claim 1 , comprising at most 3 mol % of RE 2 O 3 , where RE 2 O 3 represents the rare earth oxides in the glass material including the amounts of Y 2 O 3 and/or La 2 O 3 .
3. A glass material according to claim 1 , which is essentially free of BaO.
4. A glass material according to claim 1 , comprising 1-4 mol % of BaO.
5. A glass material according to claim 1 , which is essentially free of As 2 O 3 and Sb 2 O 3 .
6. A glass material according to claim 1 having at least one of the following compositional characteristics:
(i) up to 2 mol % TiO 2 ; and/or
(ii) up to 3 mol % ZnO.
7. A glass material according to claim 1 , comprising ZnO and B 2 O 3 , in total, from 0 to 4 mol %.
8. A glass material according to claim 1 , having a [R′O]/[Al 2 O 3 ] ratio from 0.75 to 1.8, where [Al 2 O 3 ] is the mole percent of Al 2 O 3 and [R′O] equals [RO]+1.5[RE 2 O 3 ], where [RO] is the sum of the mole percents of MgO, CaO, SrO, and BaO, and [RE 2 O 3 ] is the sum of the mole percents of rare earth oxides including Y 2 O 3 and/or La 2 O 3 in the glass material.
9. A glass material according to claim 1 , having an annealing point of higher than 790° C.
10. A glass material according to claim 1 , having a T2.3 lower than 1680° C., where T2.3 is the temperature at which a homogeneous composition of the glass material has a viscosity of 200 poise.
11. A glass material according to claim 1 , having a density lower than 3.2 gm/cm 3 .
12. A glass material according to claim 1 , having a liquidus temperature lower than 1250° C.
13. A glass material according to claim 1 , having a liquidus viscosity greater than 60 kPoise.
14. A glass substrate for TFT liquid crystal display, photovoltaic or other opto-electric devices, comprising a glass material according to claim 1 .
15. A glass substrate according to claim 14 made by a down-draw process such as a fusion down-draw process, or a slot down-draw process.
16. A device comprising a substrate comprising a glass material according to claim 1 .
17. A device according to claim 16 , comprising a thin film of polycrystalline or single-crystalline semiconductor material or a semiconductor device made thereof, formed over a surface of the substrate.
18. A device according to claim 16 , comprising a layer of a material differing from the glass material, such as a semiconductor material, formed by a process including a step at a temperature higher than 350° C.
19. A process for making a glass material according to claim 1 , comprising:
(i) providing a batch mixture comprising source materials that upon melting transforms into a glass melt having a composition corresponding to the glass material;
(ii) melting the batch mixture to obtain a fluid glass; and
(iii) forming a glass sheet from the fluid glass via a down-draw process.
20. A process according to claim 19 , wherein: in step (iii), the down-draw process comprises a fusion process.
21. A process according to claim 19 , wherein subsequent to step (iii) but prior to the end use of the glass sheet:
the as-formed glass sheet is not subjected to a heat treatment at a temperature around or higher than the annealing point thereof.
22. A rare-earth-containing glass material having a composition, expressed in mole percentages on an oxide basis, comprising:
SiO 2 : 66-75
Al 2 O 3 : 11-17
B 2 O 3 : 0-4
MgO: 1-6.5
CaO: 2-7
SrO: 0-4
BaO: 0-4
Y 2 O 3 : 0-4
La 2 O 3 : 0-4
Y 2 O 3 +La 2 O 3 : 0.1-4
wherein the glass material has:
(i) a strain point that is equal to or greater than 750°; and
(ii) an annealing point of higher than 790° C. and a T2.3 lower than 1580° C., where T2.3 is the temperature at which a homogeneous composition of the glass material has a viscosity of 200 poise.