THIN FILM CAPACITOR, MANUFACTURING METHOD THEREFOR, AND SUBSTRATE WITH BUILT-IN ELECTRONIC COMPONENT

• US 20200135406A1
• Filed: 10/21/2019
• Published: 04/30/2020
• Est. Priority Date: 10/31/2018
• Status: Active Grant

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: ABURAKAWA, Yuuki, NAMIKAWA, Tatsuo, ANDOH, Suguru, SAITA, Hitoshi
• Granted Patent: US 11,398,354 B2
• Time in Patent Office: Days
• CPC Class Codes: H01G 4/008 Selection of materials
• CPC Class Codes: H01G 4/0085 Fried electrodes
• CPC Class Codes: H01G 4/012 Form of non-self-supporting electrodes
• CPC Class Codes: H01G 4/306 made by thin film techniques
• CPC Class Codes: H01G 4/33 Thin- or thick-film capacitors thin- or thick-film circuits H01L27/00; capacitors without a potential-jump or surface barrier specially adapted for integrated circuits, details thereof, multistep manufacturing processes therefor H01L28/40
• CPC Class Codes: H05K 1/115 Via connections; Lands around holes or via connections H05K1/112 takes precedence
• CPC Class Codes: H05K 1/162 incorporating printed capacitors

Abstract

A thin film capacitor is provided with a lower electrode made of a metal foil containing many metal grains, a dielectric thin film formed on an upper surface of the lower electrode, and an upper electrode formed on an upper surface of the dielectric thin film. A lower surface of the lower electrode is an etched surface from which cross sections of the metal grains appear. The height difference between the cross sections of adjacent metal grains in the etched surface is 1 μm or more and 8 μm or less.

Claims

1. A thin film capacitor comprising:

a lower electrode made of a metal foil containing many metal grains;

a dielectric thin film formed on an upper surface of the lower electrode; and

an upper electrode formed on an upper surface of the dielectric thin film, wherein

a lower surface of the lower electrode is an etched surface from which cross sections of the metal grains appear, and

a height difference between the cross sections of adjacent metal grains in the etched surface is 1 μ

m or more and 8 μ

m or less.

2. The thin film capacitor as claimed in claim 1, wherein

a number of the metal grains each of whose cross section of (111) plane ±

20°

appears from the etched surface is N₁₁₁,

a number of the metal grains each of whose cross section of (100) plane ±

20°

appears from the etched surface is N₁₀₀,

a number of the metal grains each of whose cross section of (110) plane ±

20°

appears from the etched surface is N₁₁₀, and

a relationship;

N₁₁₁>

N₁₀₀>

N₁₁₀ is satisfied.

3. The thin film capacitor as claimed in claim 1, wherein

an average grain size of the metal grains is 10 μ

m or more and 25 μ

m or less.

4. The thin film capacitor as claimed in claim 1, wherein

the metal foil is an Ni foil, and the metal grains are Ni grains.

5. The thin film capacitor as claimed in claim 1, wherein

a side surface of the lower electrode is the etched surface from which the cross sections of the metal grains appear like the lower surface of the lower electrode.

6. A thin film capacitor manufacturing method comprising steps of:

forming a dielectric thin film on an upper surface of a lower electrode;

forming an upper electrode on an upper surface of the dielectric thin film; and

thinning the lower electrode, wherein

the step of thinning the lower electrode includes a step of etching a lower surface of the lower electrode using an etching solution mainly containing Na₂SO₈.H₂SO₄.

7. The thin film capacitor manufacturing method as claimed in claim 6, wherein the etching solution contains an additive used as a leveling agent in an electrolytic plating process.

8. The thin film capacitor manufacturing method as claimed in claim 6, wherein

the step of forming the dielectric thin film on the upper surface of the lower electrode includes

a step of annealing the lower electrode at a temperature of 300°

C. or higher,

a step of forming a precursor layer of the dielectric thin film on the upper surface of the lower electrode, and

a step of sintering the precursor layer.

9. The thin film capacitor manufacturing method as claimed in claim 6 further includes a step of covering the upper surface of the lower electrode on which the dielectric thin film and upper electrode are formed in this order with an upper resin layer before the step of thinning the lower electrode.

10. The thin film capacitor manufacturing method as claimed in claim 9 further includes a step of covering the lower surface of the lower electrode with a lower resin layer after the step of thinning the lower electrode.

11. The thin film capacitor manufacturing method as claimed in claim 10 further includes a step of forming a side surface of the lower electrode by etching after the step of thinning the lower electrode and before the step of covering the lower surface of the lower electrode with the lower resin layer, wherein

the lower electrode is etched using an etching solution mainly containing Na₂SO₈.H₂SO₄ in the step of forming the side surface of the lower electrode by etching, and

the side surface of the lower electrode is covered with the lower resin layer in the step of covering the lower surface of the lower electrode with the lower resin layer.

12. A substrate with built-in electronic component comprising:

a multilayer substrate;

a thin film capacitor embedded in an inside of the multilayer substrate and including a lower electrode made of a metal foil containing many metal grains, a dielectric thin film formed on the upper surface of the lower electrode, and an upper electrode formed on the upper surface of the dielectric thin film;

a first via hole electrode formed in the multilayer substrate so as to be electrically connected to the lower electrode of the thin film capacitor; and

a second via hole electrode formed in the multilayer substrate so as to be electrically connected to the upper electrode of the thin film capacitor, wherein

the lower surface of the lower electrode is an etched surface from which cross sections of the metal grains appear,

the height difference between the cross sections of adjacent metal grains is 1 μ

m or more and 8 μ

m or less.

13. The substrate with built-in electronic component as claimed in claim 12, wherein

the multilayer substrate includes a first insulating layer and a second insulating layer formed on the upper surface of the first insulating layer,

the thin film capacitor is provided on the upper surface of the first insulating layer,

the second insulating layer is formed on the upper surface of the first insulating layer so as to embed therein the thin film capacitor,

the first via hole electrode is provided in a first contact hole formed in the second insulating layer so as to expose therethrough the lower electrode, and

the second via hole electrode is provided in a second contact hole formed in the second insulating layer so as to expose therethrough the upper electrode.