Hermetic-sealing package member, production method therefor, and hermetically-sealed package production method using this hermetic-sealing package member

Abstract

The present invention is to provide an hermetic-sealing package member including a substrate and at least one frame-like sealing material for defining a sealing region formed on the substrate, in which the sealing material is formed of a sintered body obtained by sintering at least one metal powder selected from gold, silver, palladium, or platinum having a purity of 99.9 wt % or greater and an average particle size of 0.005 m to 1.0 m, and with respect to an arbitrary cross-section toward an outside from the sealing region, a length of an upper end of the sealing material is shorter than a length of a lower end. Examples of a cross-sectional shape of the sealing material may include one formed to have a base portion having a certain height and at least one mountain portion protruding from the base portion or one formed to have a mountain portion having substantially a triangular shape in which the length of the lower end of the sealing material is a bottom. By use of the hermetic-sealing package member of the present invention, a load is reduced at the time of hermetic-sealing and a sufficient sealing effect can be obtained.

Claims

1. A hermetic-sealing package member comprising a substrate and at least one frame-like sealing material for defining a sealing region formed on the substrate, wherein the sealing material is formed of a sintered body obtained by sintering of at least one metal powder selected from gold, silver, palladium, or platinum having a purity of 99.9 wt % or greater and an average particle size of 0.005 m to 1.0 m, and the sealing material is formed such that a shape of an arbitrary cross-section toward an outside from the sealing region includes a base portion having a certain height and at least one mountain portion protruding from the base portion, and a length of an upper end of the sealing material is shorter than a length of a lower end.

2. The hermetic-sealing package member according to claim 1, wherein a ratio (h/h) of a height (h) of the mountain portion to a height (h) of the base portion of the sealing material in the arbitrary cross-section is 0.2 to 5.0.

3. The hermetic-sealing package member according to claim 1, wherein a path traced by an apex of the mountain portion is a net shape or a grid shape when being viewed in a plane parallel to a planar surface of the substrate.

4. A production method for the hermetic-sealing package member defined in claim 1, comprising the steps of: placing a mask having a mesh-like opening on a surface of a substrate; applying a metal paste containing at least one metal powder selected from gold, silver, palladium, or platinum having a purity of 99.9 wt % or greater and an average particle size of 0.005 m to 1.0 m and a solvent, filling the metal paste in the opening, and then pulling out the mask; and forming a sealing material formed of a sintered body by firing of the metal paste.

5. The production method for the hermetic-sealing package member according to claim 4, wherein the metal paste has a thixotropy index (TI) value of 3 to 15 which is calculated from a measurement value of viscosity at a shear rate of 4/s with respect to viscosity at a shear rate of 40/s at 23 C. by use of a rotation viscometer and viscosity of 30 to 1000 Pa.Math.s at a shear rate of 4/s.

6. A production method for a hermetically-sealed package using the hermetic-sealing package member defined in claim 1, comprising the steps of: overlapping the substrate of the hermetic-sealing package member and another substrate through a sealing material to each other; and densifying the sealing material by heating at 80 to 300 C. and pressing in one direction or both directions.

7. The hermetic-sealing package member according to claim 2, wherein a path traced by an apex of the mountain portion is a net shape or a grid shape when being viewed in a plane parallel to a planar surface of the substrate.

8. A production method for the hermetic-sealing package member defined in claim 2, comprising the steps of: placing a mask having a mesh-like opening on a surface of a substrate; applying a metal paste containing at least one metal powder selected from gold, silver, palladium, or platinum having a purity of 99.9 wt % or greater and an average particle size of 0.005 m to 1.0 m and a solvent, filling the metal paste in the opening, and then pulling out the mask; and forming a sealing material formed of a sintered body by firing of the metal paste.

9. A production method for the hermetic-sealing package member defined in claim 3, comprising the steps of: placing a mask having a mesh-like opening on a surface of a substrate; applying a metal paste containing at least one metal powder selected from gold, silver, palladium, or platinum having a purity of 99.9 wt % or greater and an average particle size of 0.005 m to 1.0 m and a solvent, filling the metal paste in the opening, and then pulling out the mask; and forming a sealing material formed of a sintered body by firing of the metal paste.

10. A production method for a hermetically-sealed package using the hermetic-sealing package member defined in claim 2, comprising the steps of: overlapping the substrate of the hermetic-sealing package member and another substrate through a sealing material to each other; and densifying the sealing material by heating at 80 to 300 C. and pressing in one direction or both directions.

11. A production method for a hermetically-sealed package using the hermetic-sealing package member defined in claim 3, comprising the steps of: overlapping the substrate of the hermetic-sealing package member and another substrate through a sealing material to each other; and densifying the sealing material by heating at 80 to 300 C. and pressing in one direction or both directions.

12. A hermetic-sealing package member comprising a substrate and at least one frame-like sealing material for defining a sealing region formed on the substrate, wherein the sealing material is formed of a sintered body obtained by sintering at least one metal powder selected from gold, silver, palladium, or platinum having a purity of 99.9 wt % or greater and an average particle size of 0.005 m to 1.0 m, and the sealing material is formed such that a shape of an arbitrary cross-section toward an outside from the sealing region includes a mountain portion having substantially a triangular shape in which a length of a lower end of the sealing material is a bottom, and a length of an upper end of the sealing material is shorter than the length of the lower end.

13. The hermetic-sealing package member according to claim 12, wherein a ratio (h/L) of a height (h) of the mountain portion of the sealing material in the arbitrary cross-section to a length (L) of the bottom is 0.1 to 3.0.

14. A production method for the hermetic-sealing package member defined in claim 12, comprising the steps of: placing a mask having a mesh-like opening on a surface of a substrate; applying a metal paste containing at least one metal powder selected from gold, silver, palladium, or platinum having a purity of 99.9 wt % or greater and an average particle size of 0.005 m to 1.0 m and a solvent, filling the metal paste in the opening, and then pulling out the mask; and forming a sealing material formed of a sintered body by firing of the metal paste.

15. A production method for the hermetic-sealing package member defined in claim 13, comprising the steps of: placing a mask having a mesh-like opening on a surface of a substrate; applying a metal paste containing at least one metal powder selected from gold, silver, palladium, or platinum having a purity of 99.9 wt % or greater and an average particle size of 0.005 m to 1.0 m and a solvent, filling the metal paste in the opening, and then pulling out the mask; and forming a sealing material formed of a sintered body by firing of the metal paste.

16. A production method for a hermetically-sealed package using the hermetic-sealing package member defined in claim 12, comprising the steps of: overlapping the substrate of the hermetic-sealing package member and another substrate through a sealing material to each other; and densifying the sealing material by heating at 80 to 300 C. and pressing in one direction or both directions.

17. A production method for a hermetically-sealed package using the hermetic-sealing package member defined in claim 13, comprising the steps of: overlapping the substrate of the hermetic-sealing package member and another substrate through a sealing material to each other; and densifying the sealing material by heating at 80 to 300 C. and pressing in one direction or both directions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1(a) to 1(c) are views illustrating processes of forming a recrystallized region in a sealing material of the present invention.

(2) FIG. 2 is a view illustrating a dimension of a mountain portion of a sealing material having a base portion and the mountain portion.

(3) FIG. 3 is a view illustrating a path of a mountain portion of a sealing material in plane view.

(4) FIG. 4 is a view illustrating an example of a shape of a mountain portion of a sealing material having a base portion and the mountain portion.

(5) FIG. 5 is a view illustrating another cross-sectional shape (mountain portion having substantially a triangular shape) of a sealing material in the present invention.

(6) FIGS. 6(a) to 6(c) are views illustrating processes of forming a sealing material.

(7) FIG. 7 is a photograph showing an appearance of a sealing material produced in a first embodiment.

(8) FIG. 8 is a photograph showing an appearance of a sealing material produced in a second embodiment.

DESCRIPTION OF EMBODIMENTS

(9) Preferred embodiments of the present invention will be described below.

First Embodiment

(10) A silicon wafer having a diameter of 4 inches was prepared as a substrate, and a three-layered metal film of Ti (0.05 m)/Pt (0.01 m)/Au (0.2 m) (Ti being provided toward a surface of the wafer) was formed, as an underlying film, on a surface of the silicon wafer by a sputtering method.

(11) Then, a metal paste serving as a raw material of a sintered body was adjusted to form a sealing material. A metal paste was used which was adjusted by mixture of 96 wt % metal powders produced by a wet reduction method and 4 wt % isobornyl cyclohexanol (MTPH) being an organic solvent. In this embodiment, a metal paste of each metal powder such as gold, silver, palladium, or platinum was prepared.

(12) Viscosity of each metal paste, which has been adjusted, was measured in advance. With a cone-type rotation viscometer (Rheostress RS75 manufactured by HAAKE GmbH, (cone plate: made of titanium and having a diameter of 35 mm, and a gap being set to be 0.05 mm)), the viscosity of each metal paste was continuously measured in such a manner each metal paste was maintained for 30 seconds at respective shear rates of 4/s, 20/s, and 40/s in this order, at a measurement temperature of 23 C. A thixotropy index (TI) value was calculated on the basis of the measured value from the following equation.
TI=(viscosity at shear rate of 4/s)(viscosity at shear rate of 40/s)

(13) The metal paste was applied onto the substrate. In this embodiment, 10 rectangular sealing regions made of the sealing material having a width of 300 m and a pattern shape of 10 mm-square were set on the wafer. The metal paste was applied through a screen mask (suspend metal mask) along the pattern of the sealing material. The screen mask (product name: ESP metal mask, Taiyo Kagaku Corporation) used herein is obtained in such a manner that an emulsion part of a general emulsion mask is substituted for Ni foil metal. The Ni foil has a thickness of 30 m and is provided with meshes of a hole density of 500, which are woven by metal wires having a diameter of 16 m, on an upper surface of an opening, wherein an opening of a hole is 33 m.

(14) The metal paste was applied onto the wafer by a screen printing in a state where the metal mask was placed on the wafer. After the metal paste was filled in an opening of the metal mask, the metal mask was moved upward in an approximately vertical direction, and thus a mountain portion was formed by the meshes provided in the opening.

(15) After being applied, the metal paste was dried at 150 C., and thus a solvent and gas components contained in the metal paste were removed. Thereafter, the metal paste was fired under nitrogen 4% hydrogen atmosphere of 200 C., and thus a solvent and gas components contained in the metal paste were removed. An appearance of the sealing material obtained after the sintering is showed in FIG. 7. A cross section of the sealing material was observed with a scanning electron microscope to obtain an image of the cross section, the image was subjected to binarization processing by image analysis, and thus a relative density of the sealing material was calculated on the bases of a ratio of a pore portion and a non-pore portion.

(16) Similarly, a silicon wafer of 4 inches serving as an upper substrate formed with the underlying film of Ti (0.05 m)/Pt (0.01 m)/Au (0.2 m) was hermetically-sealed by boding to the hermetic-sealing package member produced in the above manner. In a vacuum atmosphere, the wafer was placed on the sealing material of the hermetic-sealing package member set on a heater. After a load was applied to the wafer from the above, the wafer was heated to 200 C. at a temperature rising rate of 30 C./min and was kept for 30 minutes after the reach of 200 C.

(17) The load was removed after the heating and pressing of the wafer at 200 C. for 30 minutes, and a helium leak test (bell jar method) was performed to confirm airtightness of the sealing region inside the sealing material. In this evaluation, helium leak was acceptable when being 10.sup.9 Pa.Math.m.sup.3/s or less.

(18) In this embodiment, the airtightness inside the sealing region was examined in such a manner that the wafers were bonded to each other by a change of a pressing load during the hermetic-sealing for each metal of the metal paste. Additionally, for comparison with the conventional example, the package member having an upper surface on which a flat sealing material was formed was produced, and airtightness of the package member was also confirmed. In the conventional example, a metal paste was used similarly to this embodiment, the metal paste was dried and fired after being formed into a pattern having a height size of 20 m by metal mask printing to have a planar shape (sealing material having a width of 300 m and a pattern shape of 10 mm-square) in the same manner as in this embodiment, and then a rectangular frame-like sealing material was formed. The wafers were hermetically-sealed by bonding to each other under the same condition as in this embodiment. The results are indicated in Table 1.

(19) TABLE-US-00001 TABLE 1 Sealing material*.sup.1 Result of Metal paste Mountain portion sealing test Particle Paste Height of Leak Purity size of characteristics Cross- Number of mountain Height rate Metal of metal metal Viscosity sectional mountain portion*.sup.4 of base Relative Pressing (Pa .Math. Deter- powder powder powder TI (at 4/s) shape portions Maximum Minimum portion density load*.sup.2 m.sup.3/s) mination 1 Au 99.9% 0.3 m 6 730 Base 3 30 m 20 m 10 m 71% 12 kN 10.sup.11 Ac- portion + to 10.sup.13 ceptable 2 mountain 3 30 m 20 m 10 m 69% 9.6 kN 10.sup.11 Ac- portion to 10.sup.13 ceptable 3 3 30 m 20 m 10 m 70% 7.2 kN 10.sup.9 Ac- to 10.sup.11 ceptable 4 99.0% 0.3 m 6 720 3 30 m 20 m 10 m 73% 7.2 kN 10.sup.6 Not Ac- to 10.sup.8 ceptable 5 99.9% 1.2 m 6 730 3 30 m 20 m 10 m 70% 7.2 kN 10.sup.6 Not Ac- to 10.sup.8 ceptable 6 99.9% 0.3 m 6 730 Rectangular 72% 12 kN 10.sup.11 Ac- shape*.sup.3 to 10.sup.13 ceptable 7 6 72% 7.2 kN 10.sup.6 Not Ac- to 10.sup.8 ceptable 8 Ag 99.0% 0.3 m 6 730 Base 3 30 m 20 m 10 m 65% 7.2 kN 10.sup.11 Ac- portion + to 10.sup.13 ceptable mountain portion 9 99.9% 0.3 m 6 720 Rectangular 66% 7.2 kN 10.sup.6 Not Ac- shape to 10.sup.8 ceptable 10 Pd 99.0% 0.3 m 6 730 Base 3 30 m 20 m 10 m 73% 9.6 kN 10.sup.11 Ac- portion + to 10.sup.13 ceptable mountain portion 11 99.9% 0.3 m 6 730 Rectangular 74% 9.6 kN 10.sup.6 Not Ac- shape to 10.sup.8 ceptable 12 Pt 99.0% 0.3 m 6 730 Base 3 30 m 20 m 10 m 73% 9.6 kN 10.sup.11 Ac- portion + to 10.sup.13 ceptable mountain portion 13 99.9% 0.3 m 6 730 Rectangular 73% 9.6 kN 10.sup.6 Not Ac- shape to 10.sup.8 ceptable *.sup.1Cross-sectional shape is obtained by cutting from the center of gravity of an inner surface of the sealing region to the outside in a horizontal direction *.sup.2Pressing load is a load against an entire surface of a wafer (having diameter of 4 inches) *.sup.3No. 6, 7, 9, 11, and 13 are conventional examples and have a sealing material having a flat upper surface *.sup.4In the embodiments, since the shape of the mountain portion is uneven as illustrated in FIG. 6, the maximum height (apex portion) and minimum height (ridge portion) were indicated

(20) From Table 1, in the conventional example, the sealing region having sufficient airtightness can be formed when the pressing load is 12 kN (No. 6), but leak occurs and sealing is insufficient when the pressing load is lowered to 7.2 kN (No. 7). That is, since the sealing material of the conventional example has the flat upper surface and an area of the sealing material is 120 mm.sup.2 (having a width of 0.3 mm, a pattern shape of 10 mm-square, and 10 sealing regions), it means that the sealing can be achieved at a pressure of 100 MPa (12 kN), but the leak occurs at a pressure of 60 MPa (7.2 kN).

(21) In contrast, the leak does not appear even in the pressing load of 7.2 kN in this embodiment and a sealing region having sufficient sealing performance can be formed while the load is reduced. That is, as a result of stress concentration on the mountain portion, metal powders are preferentially plastically-deformed and recrystallized near directly below of the mountain portion, thereby being densified, and thus it is understood that the hermetic-sealing is established at a low load compared to the conventional example where the entire surface of the sealing material needs to be pressed. However, when the metal powders constituting the sealing material is out of a preferred range in purity and particle size, a leak occurs, resulting in an insufficient result.

Second Embodiment

(22) A sealing material was formed to have a cross section of only a triangular mountain portion in this embodiment, and sealing ability of the sealing material was confirmed. A sealing material was formed on the same substrate as in the first embodiment by use of a metal paste (No. 1) of the first embodiment. An arrangement pattern of the sealing material on the substrate was configured such that 100 sealing regions were formed in 10 mm-square with a width (bottom) of 20 m.

(23) Similarly to the first embodiment, a metal paste was applied through a screen mask (suspend metal mask), thereby forming a sealing material. In an ESP metal mask (Taiyo Kagaku Corporation) used herein, an Ni foil has a thickness of 24 m and is provided with meshes of a hole density of 325, which are woven by metal wires having a diameter of 16 m, on an upper surface of an opening, wherein an opening of a hole is 53 m. FIG. 8 shows an appearance of the sealing material formed in this embodiment. The sealing material had a width of a bottom of 20 m an apex height of 4 to 7 m, and a ratio (h/L) of a height (h) of a mountain portion to a length (L) of the bottom was 0.2 to 0.4.

(24) The package member was hermetically sealed by bonding to a wafer in the same manner as in the first embodiment. Thereafter, a leak test was performed, and helium leak was in the range of 10.sup.11 to 10.sup.13 Pa.Math.m.sup.3/s, which was acceptable.

INDUSTRIAL APPLICABILITY

(25) The present invention is intended to solve the problem of the increase in the pressing load, which may be caused at the time of production of the hermetically-sealed package in which the plurality of sealing regions are set on the substrate. In the present invention, reliable hermetic-sealing can be obtained while the pressing load is reduced, a plurality of regions can be hermetically-sealed by a relatively simple process, and thus the present invention can be expected to be applied to a wafer level package.