Method of forming a semiconductor device with air gaps for low capacitance interconnects

Abstract

This invention proposes a method for fabricating air gaps for low-capacitance interconnects in advanced semiconductor devices. The method includes exposing a substrate to a sequence of gas pulses to deposit material forming air gaps between raised features.

Description

[Technical Field] This invention relates to the fields of semiconductor manufacturing and semiconductor devices, and more specifically, to a method for forming a semiconductor device having an air gap for low-capacitance interconnects. [Cross-reference to related applications] This application relates to and claims priority to U.S. Provisional Patent Application No. 62 / 654,760, filed April 9, 2018, the entire contents of which are incorporated herein by reference. [Previous Technology] As component feature sizes shrink, interconnects are becoming a critical issue for performance improvements. This is partly due to the increasing resistivity (Rs) caused by the continuous reduction in component feature size and the resulting harmful capacitance between adjacent features. One way to reduce capacitance is to use ultra-low k dielectric materials, and air gaps provide a minimum dielectric constant (k) of approximately 1. Therefore, component manufacturers are adding air gaps to critical layers in advanced metallization schemes. [Summary of the Invention] This disclosure describes a novel method for creating air gaps in advanced semiconductor devices. According to one embodiment, the method includes providing a substrate comprising raised features and bottom regions between the raised features, the raised features having a top region and sidewalls; and exposing the substrate to a sequence of gas pulses to deposit material forming air gaps between the raised features, wherein the gas pulse sequence includes, in any order: a) firstly, sequentially exposing the substrate to a first precursor gas to non-conformally form a first precursor layer on the top region and on the upper portion of the sidewalls, but not on the lower portion of the sidewalls and the bottom region; and secondly, exposing the substrate to a second precursor gas, the second precursor gas reacting with the first precursor layer to form a material layer on the substrate; and b) firstly, sequentially exposing the substrate to the first precursor gas to conformally form a second precursor layer on the top region, on the sidewalls, and on the bottom region; and secondly, exposing the substrate to the second precursor gas, the second precursor gas reacting with the second precursor layer to form a second material layer on the substrate. Steps a), b), or a) and b), may be repeated at least once until the air gap is formed. According to another embodiment, the method includes providing a substrate comprising raised features and a bottom region between the raised features, the raised features having a top region and sidewalls; and exposing the substrate to a sequence of gas pulses to deposit material forming air gaps between the raised features, wherein the gas pulse sequence includes, in any order: a) firstly, sequentially, exposing the substrate to a first precursor gas to conformally form a first precursor layer on the top region, on the sidewalls, and on the bottom region; secondly, exposing the substrate to a plasma-excited halogen-containing gas to deactivate or at least partially remove the first precursor layer in the top and bottom regions; and thirdly, exposing the substrate to a second precursor gas, the second precursor gas reacting with the first precursor layer to form a material layer on the sidewalls; and b) First, the substrate is exposed to a first precursor gas to conformally form a second precursor layer on the top region, the sidewalls, and the bottom region. Second, the substrate is exposed to a second precursor gas, which reacts with the second precursor layer to form a second layer of material on the substrate. Steps a), b), or a) and b), may be repeated at least once until the air gap is formed.

Implementation Method

Claims

1. A substrate processing method, comprising: A substrate is provided, the substrate including a plurality of raised features and a plurality of bottom regions between the raised features, the raised features having a plurality of top regions and a plurality of sidewalls; and the substrate is exposed to a gas pulse sequence to deposit a material forming an air gap between the raised features, wherein the gas pulse sequence includes, in any order: a) sequentially, firstly exposing the substrate to a first precursor gas to nonconformally form a first precursor layer on the top regions and the upper portions of the sidewalls, but not on the lower portions of the sidewalls and the bottom regions, and secondly, exposing the substrate to a second precursor gas, the second precursor gas reacting with the first precursor layer to form a first layer of the material on the substrate; and b) Sequentially, the substrate is first exposed to the first precursor gas to conformally form a second precursor layer on the top regions, the sidewalls, and the bottom regions; and secondly, the substrate is exposed to the second precursor gas, which reacts with the second precursor layer to form a second layer of the material on the substrate.

2. The substrate processing method as described in claim 1 further includes: Repeat steps a), b), or a) and b) at least once, until the air gap is formed.

3. The substrate processing method of claim 1, wherein the first precursor gas comprises a metal-containing precursor.

4. The substrate processing method of claim 1, wherein the first precursor gas comprises aluminum, titanium, or a combination thereof.

5. The substrate processing method of claim 3, wherein the first and second precursor layers are selected from the group consisting of Al, Al2O3, AlN, AlON, an Al-containing precursor, Al alloy, CuAl, TiAlN, TaAlN, Ti, TiAlC, TiO2, TiON, TiN, a Ti-containing precursor, Ti alloy, and combinations thereof.

6. The substrate processing method of claim 1, wherein the first and second layers of the material comprise SiO2.

7. The substrate processing method of claim 1, wherein the second precursor gas includes a silanol gas.

8. The substrate processing method of claim 7, wherein the silanol gas system is selected from the group consisting of tris(tert-pentoxy)silanol, tris(tert-butoxy)silanol, and bis(tert-butoxy)(isopropoxy)silanol.

9. The substrate processing method of claim 1, wherein the first precursor gas comprises AlMe3 and the second precursor gas comprises tris(tert-pentoxy)silyl alcohol.

10. The substrate processing method according to claim 1, wherein exposing the substrate to the second precursor gas includes: Without any oxidizing or hydrolyzing agents, the substrate is exposed to a processing gas containing a silicol at a substrate temperature of about 150°C or lower.

11. A substrate processing method, comprising: A substrate is provided, the substrate including a plurality of raised features and a plurality of bottom regions between the raised features, the raised features having a plurality of top regions and a plurality of sidewalls; and the substrate is exposed to a gas pulse sequence to deposit a material forming an air gap between the raised features, wherein the gas pulse sequence includes, in any order: a) sequentially, firstly exposing the substrate to a first precursor gas to conformally form a first precursor layer on the top regions, on the sidewalls, and on the bottom regions; secondly, exposing the substrate to a plasma-excited halogen-containing gas to deactivate or at least partially remove the first precursor layer in the top regions and the bottom regions; and thirdly, exposing the substrate to a second precursor gas, the second precursor gas reacting with the first precursor layer to form a first layer of the material on the sidewalls; and b) Sequentially, the substrate is first exposed to the first precursor gas to conformally form a second precursor layer on the top regions, the sidewalls, and the bottom regions; and secondly, the substrate is exposed to the second precursor gas, which reacts with the second precursor layer to form a second layer of the material on the substrate.

12. The substrate processing method as described in claim 11 further includes: Repeat steps a), b), or a) and b) at least once, until the air gap is formed.

13. The substrate processing method of claim 11, wherein the first precursor gas comprises a metal-containing precursor.

14. The substrate processing method of claim 11, wherein the first precursor gas comprises aluminum, titanium, or a combination thereof.

15. The substrate processing method of claim 14, wherein the first and second precursor layers are selected from the group consisting of Al, Al2O3, AlN, AlON, an Al-containing precursor, Al alloy, CuAl, TiAlN, TaAlN, Ti, TiAlC, TiO2, TiON, TiN, a Ti-containing precursor, Ti alloy, and combinations thereof.

16. The substrate processing method of claim 11, wherein the first and second layers of the material comprise SiO2.

17. The substrate processing method of claim 11, wherein the second precursor gas includes a silanol gas.

18. The substrate processing method of claim 17, wherein the silanol gas system is selected from the group consisting of tris(tert-pentoxy)silanol, tris(tert-butoxy)silanol, and bis(tert-butoxy)(isopropoxy)silanol.

19. The substrate processing method of claim 11, wherein exposing the substrate to the second precursor gas includes: Without any oxidizing or hydrolyzing agents, the substrate is exposed to a processing gas containing a silicol at a substrate temperature of about 150°C or lower.

20. The substrate processing method of claim 11, wherein the plasma-excited halogen-containing gas includes Cl2, BCl3, CCl4, HCl, HBr, or TiCl4, or a combination thereof.

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