Semiconductor device and method for manufacturing same
According to an embodiment, a semiconductor device, includes a substrate, an inter-layer insulating layer provided above the substrate, a first interconnect provided in a first trench, and a second interconnect provided in a second trench. The first interconnect is made of a first metal, and the first trench is provided in the inter-layer insulating layer on a side opposite to the substrate. The second interconnect is made of a second metal, and the second trench is provided in the inter-layer insulating layer toward the substrate. A width of the second trench is wider than a width of the first trench. A mean free path of electrons in the first metal is shorter than a mean free path of electrons in the second metal, and the first metal is a metal, an alloy or a metal compound, including at least one nonmagnetic element as a constituent element.
1. A semiconductor device, comprising:
a substrate;
an inter-layer insulating layer provided above the substrate;
a first interconnect provided in a first trench, and made of a first metal, the first trench being provided in a direction toward the substrate from a front surface of the inter-layer insulating layer on a side opposite to the substrate; and
a second interconnect provided in a second trench, and made of a second metal, the second trench being provided in a direction from the front surface of the inter-layer insulating layer toward the substrate, a width of the second trench being wider than a width of the first trench,
a mean free path of electrons in the first metal being shorter than a mean free path of electrons in the second metal, and the first metal being a metal, an alloy or a metal compound, including at least one nonmagnetic element as a constituent element.
2. The device according to claim 1 , wherein the first metal includes at least one selected from aluminum, rhodium, molybdenum, iridium, tungsten, zinc, ruthenium and indium.
3. The device according to claim 1 , wherein the first metal is an alloy or a metal compound, which includes at least one selected from iron, cobalt and nickel, and a nonmagnetic element.
4. The device according to claim 1 , wherein the first metal is a silicide including at least one selected from iron, cobalt and nickel, or a boride including at least one selected from iron, cobalt and nickel.
5. The device according to claim 1 , wherein the first metal is tungsten or molybdenum, and the second metal is copper.
6. The device according to claim 1 , wherein a resistivity of the second interconnect is higher than a resistivity of the first interconnect when a width of the first interconnect and a width of the second interconnect are set to be the same as the width of the first trench.
7. The device according to claim 1 , wherein the second interconnect is filled into the second trench with a metal film interposed, the metal film being made of the first metal.
8. The device according to claim 7 , further comprising a barrier metal layer between the metal film and the second interconnect.
9. The device according to claim 8 , wherein the barrier metal layer includes one selected from titanium, titanium nitride, tantalum, tantalum nitride, a stacked structure of titanium and titanium nitride, and a stacked structure of tantalum and tantalum nitride.
10. The device according to claim 7 , wherein a thickness of the metal film made of the first metal inside the second trench is less than a depth of the second trench and not less than half of the width of the first trench.
11. The device according to claim 7 , further comprising: a film including at least one of titanium and titanium nitride between the first interconnect and the inter-layer insulating layer and between the metal film and the inter-layer insulating layer.
12. The device according to claim 1 , wherein
the inter-layer insulating layer includes a first inter-layer insulating layer provided above the substrate and a second inter-layer insulating layer provided above the first inter-layer insulating layer, and
each of the first trench and the second trench pierces the second inter-layer insulating layer, and is communicated with the first inter-layer insulating layer.
13. The device according to claim 12 , wherein
the second interconnect is filled into the second trench with a metal film interposed, the metal film being made of the first metal, and
a thickness of the metal film made inside the second trench is less than a thickness of the second inter-layer insulating layer and not less than half of the width of the first trench.
14. The device according to claim 12 , wherein the width of the first trench is less than twice a thickness of the second inter-layer insulating layer.
15. The device according to claim 1 , wherein
the substrate has a memory cell region and a peripheral circuit region, the memory cell region including a memory element,
the first trench is provided above the memory cell region, and
the second trench is provided above the peripheral circuit region.
16. A method for manufacturing a semiconductor device, comprising:
forming an inter-layer insulating layer above a substrate;
forming a first trench and a second trench in a direction from a front surface of the inter-layer insulating layer toward the substrate, a width of the second trench being wider than a width of the first trench;
forming a first metal film made of a first metal to fill the first trench and cover the front surface of the inter-layer insulating layer, a side wall of the second trench, and a bottom surface of the second trench;
forming a second metal film with the first metal film interposed on the first trench, on the front surface of the inter-layer insulating layer, on the side wall of the second trench, and on the bottom surface of the second trench, the second metal film being made of a second metal; and
removing the second metal film and the first metal film until the front surface of the inter-layer insulating layer is exposed,
a mean free path of electrons in the first metal being shorter than a mean free path of electrons in the second metal, and the first metal being a metal, an alloy or a metal compound, including at least one nonmagnetic element as a constituent element.
17. The method according to claim 16 , wherein
a first interconnect made of the first metal film filling the first trench, a second interconnect made of the second metal film filling the second trench, and a metal film made of the first metal film between the inter-layer insulating layer and the second interconnect are formed by removing the second metal film and the first metal film until the front surface of the inter-layer insulating layer is exposed.
18. The method according to claim 16 , wherein a barrier metal layer is formed on the first metal film after the forming of the first metal film and before the forming of the second metal film.
19. The method according to claim 18 , wherein the barrier metal layer includes one selected from titanium, titanium nitride, tantalum, tantalum nitride, a stacked structure of titanium and titanium nitride, and a stacked structure of tantalum and tantalum nitride.
20. The method according to claim 16 , wherein a film thickness of the first metal film formed on the bottom surface of the second trench is not less than half of the width of the first trench and less than a depth of the second trench.