METHOD FOR SEPARATING SUBSTRATES

• US 20190322564A1
• Filed: 07/02/2019
• Published: 10/24/2019
• Est. Priority Date: 01/02/2017
• Status: Active Grant

• Current Assignee: Schott AG (Carl-Zeiss-Stiftung)
• Original Assignee: Schott AG (Carl-Zeiss-Stiftung)
• Inventors: WAGNER, Fabian, PLAPPER, Volker, ORTNER, Andreas, SCHMITT, Simon, LENTES, Frank-Thomas, SEIDL, Albrecht, MAKACS, Antal, BARTHOLOME, Patrick
• Granted Patent: US 11,618,707 B2
• Time in Patent Office: Days
• CPC Class Codes: B23K 2103/54 Glass
• CPC Class Codes: B23K 26/0006 taking account of the properties of the material involved B23K26/32, B23K26/40 take precedence
• CPC Class Codes: B23K 26/53 for modifying or reforming the material inside the workpiece, e.g. for producing break initiation cracks
• CPC Class Codes: C03B 33/0222 Scoring using a focussed radiation beam, e.g. laser
• CPC Class Codes: Y02P 40/57 Improving the yield, e-g- reduction of reject rates

Abstract

A method for separating a substrate of a brittle-hard material is provided. The method includes the steps of introducing defects into the substrate at a spacing from one another along a separation line using at least one pulsed laser beam; selecting an average spacing between neighboring defects and a number of laser pulses for generating a respective defect such that a breaking stress (σ_B) for separating the substrate along the separation line is smaller than a first reference stress (σ_R1) of the substrate and such that an edge strength σ_K of the separation edge obtained after separation is greater than a second reference stress (σ_R2) of the substrate; and separating the substrate after introducing the defects by applying a stress along the separation line.

Claims

1. A method for separating a substrate made of brittle-hard material, comprising:

introducing defects into the substrate at a spacing from one another along a separation line using at least one pulsed laser beam;

selecting an average spacing between neighboring defects and a number of laser pulses for generating a respective defect such that a breaking stress (σ

_B) for separating the substrate along the separation line is smaller than a first reference stress (σ

_R1) of the substrate and such that an edge strength σ

_K of the separation edge obtained after separation is greater than a second reference stress (σ

_R2) of the substrate; and

separating the substrate after introducing the defects by applying a stress along the separation line.

2. The method of claim 1, setting the first reference stress (σ

_R1) and the second reference stress (σ

_R2) identical to one another and to a maximum thermal stress (σ

_th) that depends on a material of the substrate.

3. The method of claim 2, further comprising determining the maximum thermal stress (σ

_th) according to a formula σ

_th=0.5·

α

·

E·

(T_g−

100°

C.), wherein α

is the coefficient of thermal expansion of the material of the substrate, E is the Young'"'"'s modulus of the material of the substrate, and T_g is the glass transition temperature of the material of the substrate.

4. The method of claim 1, further comprising setting the first reference stress according to a formula σ

_R1≤

C_R1·

α

·

E·

(T_g−

100°

C.) and the second reference stress according to a formula σ

_R2≥

C_R2·

α

·

E·

(T_g−

100°

C.),

wherein C_R1 and C_R2 are reference stress coefficients with C_R1=0.5/k and C_R2=0.5·

k,

wherein k is 1.5,

wherein α

is the coefficient of thermal expansion of the material of the substrate,

wherein E is the Young'"'"'s modulus of the material of the substrate, and

wherein T_g is the glass transition temperature of the material of the substrate.

5. The method of claim 1, wherein, when the substrate is a chemically toughened substrate, the method comprises:

setting the first reference stress (σ

_R1) and the second reference stress (σ

_R2) identical to one another and to an inner tensile stress (σ

_CT) that depends on properties of the chemically toughened substrate; and

determining the inner tensile stress (σ

_CT) according to the formula σ

_CT=(σ

_CS·

d_L)/(d−

2d_L),

wherein σ

_CS denotes a surface compressive stress of the chemically toughened substrate, d_L is a penetration depth of a preliminary stress, and d is a thickness of the chemically toughened substrate.

6. The method of claim 1, wherein, when the substrate is a thermally toughened substrate, the method comprises:

setting the first reference stress (σ

_R1) and the second reference stress (σ

_R2) identical to one another and to an inner tensile stress (σ

_CT) that depends on properties of the thermally toughened substrate; and

determining the inner tensile stress σ

_CT according to the formula σ

_CT=σ

_CS/2,

wherein σ

_CS denotes a surface compressive stress of the thermally toughened substrate.

7. The method of claim 1, wherein the step of separating the substrate comprises moving a point of incidence of a laser radiation over the substrate along the separation line to cause the stress to be applied along the separation line.

8. The method of claim 1, wherein the step of selecting the average spacing between neighboring defects comprises selecting from an interval [1 μ

m, 10 μ

m] or from an interval [5 μ

m, 7 μ

m].

9. The method of claim 1, wherein the step of selecting the number of laser pulses comprises selecting from an interval [1, 20] or from an interval [2, 8].

10. The method of claim 1, wherein, when the substrate is made of a material with a coefficient of thermal expansion in an interval [3·

10<sup>−

6</sup> K<sup>−

1</sup>, 4·

10<sup>−

6</sup> K<sup>−

1</sup>], a Young'"'"'s modulus in an interval [69 kN/mm², 76 kN/mm²], and/or a glass transition temperature in an interval [700°

C., 800°

C.], the step of selecting the average spacing and the number of laser pulses comprises selecting the average spacing from an interval [6 μ

m, 8 μ

m] and the number of laser pulses from an interval [7, 9].

11. The method of claim 1, wherein, when the substrate is made of a material with a coefficient of thermal expansion in an interval [7·

10<sup>−

6</sup> K<sup>−

1</sup>, 8·

10<sup>−

6</sup> K<sup>−

1</sup>], a Young'"'"'s modulus in an interval [69 kN/mm², 76 kN/mm²], and/or a glass transition temperature in an interval [500°

C., 600°

C.], the step of selecting the average spacing and the number of laser pulses comprises selecting the average spacing from an interval [6 μ

m, 8 μ

m] and the number of laser pulses from an interval [1, 3].

12. The method of claim 1, wherein, when the substrate is made of a material with a coefficient of thermal expansion in an interval [3·

10<sup>−

6</sup> K<sup>−

1</sup>, 4·

10<sup>−

6</sup> K<sup>−

1</sup>], a Young'"'"'s modulus in an interval [60 kN/mm², 68 kN/mm²], and/or a glass transition temperature in an interval [500°

C., 600°

C.], the step of selecting the average spacing and the number of laser pulses comprises selecting the average spacing from an interval [4 μ

m, 8 μ

m] and the number of laser pulses from an interval [7, 9].

13. The method of claim 1, wherein, when the substrate is made of a material with a coefficient of thermal expansion in an interval [3·

10<sup>−

6</sup> K<sup>−

1</sup>, 4·

10<sup>−

6</sup> K<sup>−

1</sup>], a Young'"'"'s modulus in an interval [60 kN/mm², 68 kN/mm²], and/or a glass transition temperature in an interval [500°

C., 600°

C.], the step of selecting the average spacing and the number of laser pulses comprises selecting the average spacing from an interval [6 μ

m, 8 μ

m] and the number of laser pulses from an interval [3, 5].

14. A method for separating a substrate made of brittle-hard material, comprising:

providing a substrate with at least one known material parameter and/or a substrate property that is selected from a group consisting of a coefficient of thermal expansion, a Young'"'"'s modulus, a glass transition temperature, transmittance, and average roughness of a surface of the substrate;

defining at least one process parameter selected from a group consisting of a spacing of defects, a number of laser pulses, and a burst frequency, as a function of the at least one known material parameter and/or substrate property; and

introducing defects into the substrate at a spacing from one another along a separation line using laser pulses of a laser according to the at least one predetermined process parameter.

15. A workpiece comprising:

a glass product, glass ceramic product, or silicon product that has been pre-damaged along a separation line with defects at a spacing from one another along the separation line;

a breaking stress (σ

_B) along the separation line is smaller than a first reference stress (σ

_R1) of the glass product, glass ceramic product, or silicon product; and

an edge strength (σ

_K) of a separation edge obtained after separation at the separation line that is greater than a second reference stress (σ

_R2) of the glass product, glass ceramic product, or silicon product.

16. The workpiece of claim 15, wherein the first reference stress (σ

_R1) and the second reference stress (σ

_R2) are equal and are a maximum thermal stress (σ

_th) of the glass product, glass ceramic product, or silicon product,

wherein the maximum thermal stress (σ

_th) is defined according to a formula σ

_th=0.5·

α

·

E·

(T_g−

100°

C.),

wherein α

is a coefficient of thermal expansion of the glass product, glass ceramic product, or silicon product,

wherein E is a Young'"'"'s modulus of the glass product, glass ceramic product, or silicon product, and

wherein T_g is a glass transition temperature of the glass product, glass ceramic product, or silicon product.

17. The workpiece of claim 15, wherein σ

_R1≤

C_R1·

α

·

E·

(T_g−

100°

C.) applies to the first reference stress and σ

_R2≥

C_R2·

α

·

E·

(T_g−

100°

C.) applies to the second reference stress, wherein C_R1 and C_R2 are reference stress coefficients, with C_R1=0.5/k and C_R2=0.5*, and with k=1.5, and

wherein α

is a coefficient of thermal expansion of the glass product, glass ceramic product, or silicon product,

wherein E is a Young'"'"'s modulus of the glass product, glass ceramic product, or silicon product, and

wherein T_g is a glass transition temperature of the glass product, glass ceramic product, or silicon product.

18. The workpiece of claim 15, wherein the glass product, glass ceramic product, or silicon product has been pre-damaged along two separation lines that cross each other.

19. The workpiece of claim 18, wherein the two separation lines have breaking stresses for separation that differ by at least 3 MPa and/or wherein the two separation lines have spacings of the defects that differ.

20. The workpiece of claim 15, further comprising at least two sets of juxtaposed separation lines, wherein a first set of the juxtaposed separation lines has an average breaking force that differs from an average breaking force of a second set of the juxtaposed separation lines by at least 3 MPa.

22. The workpiece of claim 15, further comprising organic functional coating for protein or DNA analysis.

21. The workpiece of claim 21, wherein the first set of juxtaposed separation lines have ends that terminate at a distance from one of the edge such that a web or frame is formed between the ends and the edge so that separable elements remain attached to the web or frame after separation along the first set of juxtaposed separation lines.