Low CTE boro-aluminosilicate glass for glass carrier wafers

Abstract

A low CTE boro-aluminosilicate glass having a low brittleness for use in wafer-level-packaging (WLP) applications is disclosed. The glass comprises a composition in mol-% of SiO.sub.2: 60-85, Al.sub.2O.sub.3: 1-17, B.sub.2O.sub.3: 8-20, Na.sub.2O: 0-5, K.sub.2O: 0-5, MgO: 0-10, CaO: 0-10, SrO: 0-10, and BaO: 0-10. An average number of non-bridging oxygen per polyhedron (NBO) is equal to or larger than 0.2 and a ratio B.sub.2O.sub.3/Al.sub.2O.sub.3 is equal to or larger than 0.5. The NBO is defined as NBO=2O.sub.mol/(Si.sub.mol+Al.sub.mol+B.sub.mol)4. A glass carrier wafer made from the low CTE boro-aluminosilicate glass and a use thereof as a glass carrier wafer for the processing of a silicon substrate are also disclosed, as well as a method for providing a low CTE boro-aluminosilicate glass.

Claims

1. An article of manufacture, comprising: a glass carrier wafer for use in wafer-level-packing (WLP) applications formed of a boro-aluminosilicate glass comprising a composition in mol-% of: TABLE-US-00006 SiO.sub.2 60-85; Al.sub.2O.sub.3 1-10; B.sub.2O.sub.3 11-20; Na.sub.2O 0-5; K.sub.2O 0-5; MgO 0-10; CaO 0-10; SrO 0-10; and BaO 0-10, wherein an average number of non-bridging oxygen per polyhedron (NBO) is equal to or larger than 0.18 and a ratio B.sub.2O.sub.3/Al.sub.2O.sub.3 is equal to or larger than 1.1, wherein the NBO is defined as NBO=2O.sub.mol/(Si.sub.mol+Al.sub.mol+B.sub.mol)4, wherein a coefficient of thermal expansion of the glass is in a range from 2.6 ppm/K to 3.8 ppm/K.

2. The article according to claim 1, wherein the glass is an alkali-free glass and comprises a composition in mol-% of: TABLE-US-00007 SiO.sub.2 60-70; Al.sub.2O.sub.3 7-10; B.sub.2O.sub.3 11-15; MgO 0-10; CaO 0-10; SrO 0-10; and BaO 0-10.

3. The article according to claim 1, wherein the glass is an alkali containing glass and comprises a composition in mol-% of: TABLE-US-00008 SiO.sub.2 75-85; Al.sub.2O.sub.3 1-5; B.sub.2O.sub.3 11-20; Na.sub.2O >0-5; K.sub.2O >0-5; MgO 0-10; CaO 0-10; SrO 0-10; and BaO 0-10.

4. The article according to claim 1, wherein the composition of the boro-aluminosilicate glass is essentially free of Li.sub.2O.

5. The article according to claim 1, wherein: the NBO of the glass is equal to or larger than 0.17.

6. The article according to claim 5, wherein the NBO of the glass is equal to or larger than 0.16.

7. The article according to claim 1, wherein the NBO of the glass is equal to or less than 0.1 and the ratio B.sub.2O.sub.3/Al.sub.2O.sub.3 is equal to or less than 10.

8. The article according to claim 1, wherein the boro-aluminosilicate glass has a transition temperature T.sub.g higher than 550 C.

9. The article according to claim 1, wherein a transition temperature T.sub.g of the glass is higher than 650 C.

10. The article according to claim 1, wherein a brittleness index H.sub.V/K.sub.IC of the glass is equal to or less than 10 m.sup.1/2, wherein H.sub.V refers to a Vicker's hardness of the boro-aluminosilicate glass and K.sub.lc refers to a fracture toughness of the boro-aluminosilicate glass.

11. The article according to claim 10, wherein the brittleness index H.sub.V/K.sub.IC of the glass is equal to or less than 8 m.sup.1/2.

12. The article according to claim 1, wherein the glass carrier wafer has a thickness of 1.2 mm or less.

13. The article according to claim 1, wherein a maximum edge chipping size after dicing of the glass carrier wafer is equal to or less than 20 m.

14. The article according to claim 1, further comprising a silicon substrate bonded to the glass carrier wafer.

15. The article according to claim 14, further comprising an adhesive layer bonding the silicon substrate to the glass carrier wafer.

16. The article according to claim 1, further comprising a dicing film applied to the silicon substrate.

17. The article according to claim 16, wherein the dicing film is a dicing tape.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1 is a schematic cut view of an exemplary dicing process in a wafer level packaging (WLP) application;

(3) FIG. 2 is a schematic view of cutting edges of a glass wafer with edge chipping after cutting;

(4) FIG. 3 is a diagram of NBO vs. brittleness for several exemplary glass compositions;

(5) FIG. 4 is a diagram of NBO vs. maximum edge chipping size for several exemplary glass compositions;

(6) FIG. 5 is a diagram of the ratio B.sub.2O.sub.3/Al.sub.2O.sub.3 vs. brittleness for several exemplary glass compositions;

(7) FIG. 6 is a diagram of the ratio B.sub.2O.sub.3/Al.sub.2O.sub.3 vs. maximum edge chipping size for several exemplary glass compositions;

(8) FIG. 7 is an enlarged view of cutting edges of a glass sample formed in accordance with the present disclosure having an NBO of 0.162;

(9) FIG. 8 is an enlarged view of cutting edges of a glass sample formed in accordance with the present disclosure having an NBO of 0.140; and

(10) FIG. 9 is an enlarged view of cutting edges of a glass sample formed in accordance with the present disclosure having an NBO of 0.129.

(11) Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

(12) FIG. 1 shows an exemplary dicing process in a wafer level packaging (WLP) application. A silicon substrate 2 is adhered via an adhesive layer 3 to a glass wafer 1. The glass wafer 1 has a thickness t. In a first cutting step, the glass wafer 1 is cut with a first blade 4 having a first width w.sub.1. The cut thereby extends into the adhesive layer 3, but not into the silicon substrate 2. The cut is achieved via a rotating blade 4.

(13) Once the cut with the first blade 4 is established, a second cut with a second blade 5 is performed. The second blade 5 has a second width w.sub.2, which is smaller than the width w.sub.1 of the first blade 4. The second cut is made within the cutting groove from the first cutting step. Due to the smaller width w.sub.2 of the second cutting blade 5, the second cutting step can be performed without affecting the glass wafer 1. The second cut extends through the silicon substrate 2 and may extend into a dicing tape 6 preventing the now completely separated dies from falling apart. The dicing tape 6 is applied before the second cutting step, before or after the first cutting step.

(14) After cutting, the glass wafer 1 has fresh cutting edges 10, as schematically shown in FIG. 2. The cutting edges 10 usually show a certain degree of edge chipping 11 as a result from the first cutting process. Such edge chipping 11 can, e.g., give rise to propagating cracks that ultimately result in breakage of the glass wafer 1 during cutting or further processing. Furthermore, the edge chipping 11 reduces the effective usable area A after dicing. Reducing edge chipping 11 can therefore increase the dicing yield. Generally, a characteristic maximum edge chipping size C can be identified, which depends on e.g., the used cutting blades and other cutting parameters such as feeding speed and rotation rate of the blade. For a given set of cutting parameters, however, the maximum edge chipping size C can be reduced by the specific glass material used for the glass wafer 1.

(15) A glass wafer 1 made from exemplary embodiments of the glass thereby provides a low tendency to edge chipping and, as such, allows for high dicing yield as can be seen from the following examples.

EXAMPLES

(16) The following Table 1 shows compositions of 11 exemplary glasses formed according to the present disclosure. Examples 12 to 14 show exemplary comparative glasses that do not fall within the scope of the disclosure. Examples 1 to 5 and 7 to 11 show alkali free glass compositions whereas example 6 describes an alkali containing glass.

(17) TABLE-US-00004 TABLE 1 Compositions of examples 1 to 11 formed in accordance with the present disclosure and comparative examples 12 to 14. Mol-% SiO.sub.2 Al.sub.2O.sub.3 B.sub.2O.sub.3 Na.sub.2O K.sub.2O MgO CaO BaO Glass 1 60 16 9.5 6.6 6.5 1.4 Glass 2 62.5 14 10 7.6 5.5 0.4 Glass 3 67 12 9.6 4.58 4.5 2.4 Glass 4 67.166 11.32 9.9 4.58 5.5 1.4 Glass 5 66 11 10.6 6.58 5 0.9 Glass 6 82.50 1.52 11.67 3.91 0.39 Glass 7 67.125 9.625 11.225 5.125 5.5 1.4 Glass 8 64.5 10 12 6.6 5.5 1.4 Glass 9 65.5 9 12 7.6 4.5 1.4 Glass 65.375 8.375 12.375 6.975 5.5 1.4 10 Glass 64.5 8 13 7.5 6 1 11 Glass 62.6 16.5 8 7.5 4 1.4 12 Glass 60 19 8.6 6 5 1.4 13 Glass 60 21 8.6 5 4 1.4 14

(18) The following Table 2 lists selected relevant parameters of the glass compositions of examples 1 to 11 and comparative examples 12 to 14 according to Table 1.

(19) TABLE-US-00005 TABLE 2 Structure parameters, properties and performance of glass examples 1 to 11 and comparative examples 12 to 14. Property Performance Structure parameters T.sub.g CTE H.sub.V0.2 K.sub.IC Brittleness Chipping size Z R NBO B.sub.2O.sub.3/Al.sub.2O.sub.3 ( C.) (10.sup.6/K) (MPa) (MPa .Math. m.sup.1/2) (m.sup.1/2) (m) Glass 1 4 1.901 0.198 0.594 707 3.23 5322 0.45 11.90 30 Glass 2 4 1.905 0.190 0.714 705 3.21 5256 0.47 11.20 28 Glass 3 4 1.91 0.184 0.800 712 3.14 5361 0.51 10.52 26 Glass 4 4 1.911 0.178 0.875 710 3.15 5471 0.54 10.07 23 Glass 5 4 1.92 0.167 0.964 715 3.10 5524 0.64 8.58 18 Glass 6 4 1.918 0.163 7.651 557 3.27 5463 0.73 7.46 10 Glass 7 4 1.919 0.162 1.166 711 3.12 5626 0.77 7.35 14 Glass 8 4 1.92 0.157 1.200 703 3.25 5325 0.74 7.20 13 Glass 9 4 1.93 0.140 1.333 706 3.22 5519 0.80 6.90 12 Glass 10 4 1.94 0.129 1.478 709 3.19 5723 0.88 6.50 9 Glass 11 4 1.94 0.122 1.625 708 3.23 5653 0.87 6.50 11 Glass 12 4 1.896 0.208 0.485 702 3.18 5360 0.43 12.5 32 Glass 13 4 1.868 0.264 0.453 695 3.11 5385 0.41 13.2 33 Glass 14 4 1.839 0.322 0.410 691 3.05 5410 0.39 13.8 35

(20) The examples 1 to 11 formed in accordance with the present disclosure cover a range of NBO numbers from (rounded) 0.2 to 0.12. The ratio of B.sub.2O.sub.3/Al.sub.2O.sub.3 thereby lies in the range from (rounded) 0.6 to approximately 1.6. The glass transition temperatures range from (rounded) 560 C. to 715 C. As can be seen from Table 2, the Vicker's hardness H.sub.V of all glass samples 1 to 11 lies in the range from (rounded) 5255 MPa to 5725 MPa and the fracture toughness K.sub.IC ranges from 0.45 MPa.Math.m.sup.1/2 to 0.88 MPa.Math.m.sup.1/2. The resulting brittleness, defined as H.sub.v/K.sub.IC ranges from 6.5 m.sup.1/2 to 11.9 m.sup.1/2.

(21) The comparative examples 12 to 14 have NBO numbers below 0.2 and a ratio B.sub.2O.sub.3/Al.sub.2O.sub.3 of less than 0.5.

(22) Table 2 also shows (in the right-most column) the resulting chipping performance during cutting of the glass samples. Chipping size hereby refers to the maximum chipping size C, as schematically shown in FIG. 2. The samples were cut with a soft 600 mesh dicing blade having a diameter of 56 mm and width w.sub.1 of 0.15 mm, with a feeding rate of 5 mm/s at a rotation speed of 20,000 rpm. It has been found that the chipping performance is not very sensitive to the dicing parameters and corresponding results were found for a range of dicing parameters as they are usually applied in the art in, e.g., WLP applications.

(23) The thickness t of the glass samples was 0.5 mm for all glass compositions of examples 1 to 14. It can be seen that, for all NBO numbers equal or above a value of 0.2, the resulting maximum edge chipping size is equal to or smaller than 30 m, whereas the maximum edge chipping size for the comparative examples 12 to 14 is above 30 m.

(24) FIG. 3 shows the values of the brittleness H.sub.v/K.sub.IC in dependence on the NBO number, whereas FIG. 4 shows the corresponding values for the chipping size. FIGS. 5 and 6 show the corresponding diagrams in dependence on the ratio of B.sub.2O.sub.3/Al.sub.2O.sub.3. All plots show a clear trend to decreasing brittleness and chipping size in dependence on the relevant parameters NBO and B.sub.2O.sub.3/Al.sub.2O.sub.3, where a transition of the brittleness index H.sub.V/K.sub.IC from above 12 m.sup.1/2 (dashed line) to below and a transition of the maximum chipping size from above 30 m (dashed line) to below occurs at an NBO value of 0.2 and a ratio B.sub.2O.sub.3/Al.sub.2O.sub.3 of 0.5.

(25) FIGS. 7 to 9 show enlarged views of cutting edges of selected samples of examples 7, 9 and 10 according to Table 1. FIG. 7 shows a sample of a glass according to example 7 having an NBO of 0.162. As can be seen from FIG. 7, the maximum edge chipping size is 14.42 m, which has been rounded to 14 m in Table 1. Similarly, FIG. 8 shows a sample of a glass according to example 9 of Table 1 having an NBO of 0.140 and a resulting maximum edge chipping size of 12.25 m. FIG. 9 shows a sample of a glass according to example 10 having an NBO of 0.129 with a maximum edge chipping size of 9.48 m. The corresponding values for the maximum edge chipping sizes in Table 1 were rounded to the next whole number in each case.

(26) While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.