Glass-ceramic substrates for semiconductor processing

Abstract

Embodiments are directed to glass-ceramic substrates with a III-V semiconductor layer, for example, a GaN layer that can be used in LED lighting devices. The glass-ceramics material is in the anorthite-rutile (CaAl.sub.2Si.sub.2O.sub.8+TiO.sub.2) family or in the cordierite-enstatite (SiO.sub.2Al.sub.2O.sub.3MgOTiO.sub.2) family.

Claims

1. An article comprising a glass-ceramic substrate; and a layer comprising a III-V semiconductor disposed on a surface of the substrate, wherein the substrate comprises a cordierite-enstatite (SiO.sub.2Al.sub.2O.sub.3MgOTiO.sub.2) material having a coefficient of thermal expansion (GTE) of 6010.sup.7510.sup.7, and further wherein the cordierite-enstatite material comprises in weight percent: 40-55 SiO.sub.2; 10-15 Al.sub.2O.sub.3; 20-30 MgO; 1-5 CaO; and 5-15 TiO.sub.2 wherein the III-V semiconductor is GaN, GaP, AlGaAs, InGaAs, InGaN, AlGaP, or a combination thereof.

2. The article according to claim 1, wherein the substrate is crystalline phase throughout 80 percent or more of its volume.

3. The article according to claim 2, wherein the crystalline phase is dispersed throughout the volume.

4. The article according to claim 1, wherein the substrate is glassy phase throughout 20 percent or less of its volume.

5. The article according to claim 4, wherein the glassy phase is dispersed throughout the volume.

6. The article according to claim 1, wherein the CTE of the layer and the substrate are within 510.sup.7 of each other.

7. The article according to claim 1, wherein the CTE of the substrate and the layer are both 6010.sup.7+5.

8. The article according to claim 1, wherein the surface has an average roughness of 100 nm or less.

9. The article according to claim 1, wherein the substrate has an average grain size of 5 microns or less.

10. The article according to claim 1, wherein the substrate is alkali free.

11. The article according to claim 1, wherein the substrate is Au, Pd, Ag, or Pt free.

12. The article according to claim 1, wherein the substrate is Au, Pd, Ag, and Pt free.

13. The article according to claim 1, wherein the substrate is As free.

14. The article according to claim 1, wherein less than 500 ppm of each of Ni, Na, Cu, Fe, Cr, Ca, Ti, K, Mg, or Zn diffuse out of the substrate.

15. The article according to claim 1, wherein the substrate comprises a cordierite-enstatite material comprising in weight percent: 45-50 SiO.sub.2; 10-15 Al.sub.2O.sub.3; 20-30 MgO; 1-5 CaO; and 5-15 TiO.sub.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph showing average thermal expansion of state-of-the-art substrates for GaN growth.

(2) FIG. 2 is a graph showing average thermal expansion of one exemplary glass-ceramic from the anorthite-rutile family, compared to GaN.

(3) FIG. 3 is a graph showing average thermal expansion of a second exemplary glass-ceramic from the anorthite-rutile family, compared to GaN.

(4) FIG. 4 is a graph showing average thermal expansion of a glass-ceramic from the cordierite-enstatite family, compared to GaN.

(5) FIG. 5 is a graph showing X-Ray Diffraction (XRD) data of Example 2 in its final, crystallized state.

(6) FIGS. 6A and 6B are top down Secondary Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) images, respectively, showing crystal grain size of about 1 micron or less.

DETAILED DESCRIPTION

(7) Reference will now be made in detail to various embodiments of glass-ceramics and their use in LED articles, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

(8) One embodiment is an article comprising a glass-ceramic substrate; and a layer comprising a III-V semiconductor disposed on a surface of the substrate, wherein the substrate comprises an anorthite-rutile (CaAl.sub.2Si.sub.2O.sub.8+TiO.sub.2) or a cordierite-enstatite (SiO.sub.2Al.sub.2O.sub.3MgOTiO.sub.2) material. The III-V semiconductor can comprise Al, Ga, In, or combinations thereof and N, P, As, or combinations thereof. The III-V semiconductor can be GaN, GaP, AlGaAs, InGaAs, InGaN, AlGaP, or a combination thereof. The III-V semiconductor in one embodiment is GaN.

(9) Another embodiment is an article comprising a glass ceramic substrate; and a layer comprising GaN disposed on a surface of the substrate, wherein the substrate comprises an anorthite-rutile (CaAl.sub.2Si.sub.2O.sub.8+TiO.sub.2) or a cordierite-enstatite (SiO.sub.2Al.sub.2O.sub.3MgOTiO.sub.2) material.

(10) The substrate can be crystalline phase throughout 80 percent or more of its volume, for example, 90 percent or more. The crystalline phase can be dispersed throughout the volume. The substrate can be glassy phase throughout 20 percent or less of its volume, for example, 10 percent or less. The glassy phase can be dispersed throughout the volume. The substrate can be, for example, 80 percent or more crystalline phase and 20 percent or less glassy phase.

(11) In one embodiment, the CTE of the GaN layer and the substrate are within 510-7 of each other. The CTE of the substrate and the layer are both 6010-7.

(12) The surface can have an average roughness of 100 nm or less, for example, 50 nm or less. The substrate can have an average grain size of 5 microns or less, for example, 4 microns or less, 3 microns or less, 2 microns or less, 1 microns or less, 0.5 microns or less.

(13) In one embodiment, the substrate is alkali free. The substrate can be Au, Pd, Ag, or Pt free, for example, Au, Pd, Ag, and Pt free. The substrate can be As free. In one embodiment, less than 500 ppm of each of Ni, Na, Cu, Fe, Cr, Ca, Ti, K, Mg, or Zn diffuse out of the substrate, for example, during subsequent device processing at elevated temperatures or immersion in wet chemical solutions.

(14) In one embodiment, the substrate comprises in weight percent: 15-20 CaO, 35-40 Al.sub.2O.sub.3, 35-40 SiO.sub.2, and 12-16 TiO.sub.2.

(15) In a further embodiment, the substrate comprises in weight percent: 40-55 SiO.sub.2, 10-15 Al.sub.2O.sub.3, 20-30 MgO, 1-5 CaO, and 5-15 TiO.sub.2.

(16) In a still further embodiment, the substrate comprises in weight percent: 45-50 SiO.sub.2, 10-15 Al.sub.2O.sub.3, 20-30 MgO, 1-5 CaO, and 5-15 TiO.sub.2.

(17) In one embodiment, the substrate can have a thickness of 5 mm or less, for example, 4 mm or less, for example, 3 mm or less, for example, 2 mm or less, for example, 1 mm or less, for example, 0.5 mm or less. The substrate can have a thickness in the range of from 0.5 mm to 4 mm.

(18) The glass-ceramic substrate can be from the anorthiterutile (CaAl.sub.2Si.sub.2O.sub.8+TiO.sub.2) family. The composition is given in oxide weight percent for two examples in Table 1. Of these, the composition in Example 2 is stoichiometric. The oxide mixtures were melted at 1650 C. for 16 hours, then poured into forms and annealed at 750 C. The forms were annealed at 900 C. over eight hours to nucleate, and then crystallized at 1250 C. for four hours.

(19) TABLE-US-00001 TABLE 1 wt % Example 1 Example 2 CaO 16.8 17.19 Al.sub.2O.sub.3 31.8 31.26 SiO.sub.2 36.7 36.84 TiO.sub.2 14.7 14.7

(20) In a another embodiment, the glass-ceramic is from the cordierite-enstatite (SiO.sub.2Al.sub.2O.sub.3MgOTiO.sub.2) family. The composition in Example 3 is given in oxide weight percent in Table 2. The oxide mixtures were melted at 1650 C. for 16 hours, then poured into forms and annealed at 750 C. The forms were annealed at 850 C. four two hours to nucleate, and then crystallized at 13501425 C.

(21) TABLE-US-00002 TABLE 2 wt % Example 3 SiO.sub.2 48.7 Al.sub.2O.sub.3 13.8 MgO 25.2 CaO 1.5 TiO.sub.2 10.8

(22) After crystallization, the forms of all three compositions were shaped into wafers and polished.

(23) FIG. 5 is a graph showing X-Ray Diffraction (XRD) data of Example 2 in its final, crystallized state. The data shows two crystalline phases anorthite and rutile, as well as some residual glass presence (advantageous for amortization of CTE mismatch induced stresses).

(24) FIGS. 6A and 6B are top down Secondary Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) images, respectively, showing crystal grain size of about 1 micron or less. This is advantageous for surface finishing due to GaN deposition process requirementssurface must be perfectly smooth.

(25) The GaN on the substrate or alone can be used to fabricate LED lights in, for example, fabrication processes such as wafer sized processes, for example, 6 inches by 6 inches or even larger. Multiple LEDs can be fabricated on the GaN and separated into single LEDs after fabrication.

(26) It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.