Structure for reducing stress-induced voiding in an interconnect of integrated circuits
A structure for reducing stress-induced voiding in an interconnect of an integrated circuit, the interconnect having a first portion and at least a second portion narrower than the first portion. The structure comprises at least one interior slot disposed in the first portion in proximity to the intersection of the first portion and the second portion. The present invention also includes methods of making the interconnect and the structure. A conductive interconnect structure comprises a first portion and at least a second portion narrower than the first portion; and a stress reducing structure comprising a transition portion formed at an intersection of the first portion and the second portion.
The present invention relates to integrated circuits and more particularly to structures in an interconnect and methods of manufacture thereof.
BACKGROUNDWith broad utilization of integrated circuits, the reliability of conductive connection becomes increasingly important. Among corrosion and electromigration, stress-induced voiding is one of major causes resulting to the malfunction of integrated circuits on chips. The reason is speculated to be that small notches usually originate at grain boundaries and migrate slowly towards low-stress region according to stress gradient to relieve the stress. Along the time, small voiding distributed in conductive material such as metals grows, moves, and accumulates in low-stress regions. As a result, stress-induced voiding causes discontinuities in conductive connections of the integrated circuits. The discontinuity results in open circuit failure in one layer metallization structures and an increase in the line resistance in the metallization structure formed by multiple layers of refractory metals such as W, TiW, Ta, TaN, and Ti.
Void growth is governed by some variables such as the properties, microstructure, and processing of the metallization. The circuit failure by stress-induced voiding depends upon void morphology such as size, shape, and density of voids and the geometry of the metallization. Voiding becomes a serious problem in particular in narrow aluminum lines. Some approaches are employed to improve the stress-induced voiding phenomena such as using copper and other additives as alloying elements, reducing contaminant concentrations like nitrogen and oxygen, and producing metallization films with larger grain sizes.
SUMMARY OF THE INVENTIONA structure for reducing stress-induced voiding in an interconnect of an integrated circuit, the interconnect having a first portion and at least a second portion narrower than the first portion. The structure comprises at least one interior slot disposed in the first portion in proximity to the intersection of the first portion and the second portion. The present invention also includes methods of making the interconnect and the structure. A conductive interconnect structure comprises a first portion and at least a second portion narrower than the first portion; and a stress reducing structure comprising a transition portion formed at an intersection of the first portion and the second portion.
BRIEF DESCRIPTION OF THE DRAWINGSA more complete understanding of the present invention can be obtained by reference to the detailed description of embodiments in conjunction with the accompanying drawings, in which:
Several models are suggested to explain the migration of stress-induced vacancies. It is believed that vacancies nucleated from grain boundaries of conductive materials can be driven by thermal stress to migrate. Structures such as a connection between a via and an interconnect; and a sharp transition from a wide portion to a narrow portion of an interconnect, attract vacancies generated in the connecting conductive materials. As a result, it is likely that vacancies, accumulated around these regions, cause the failure of an integrated circuit.
Two structure designs can resolve the problem. Firstly, a slot disposed in an appropriate position of an interconnect can interrupt the migration of vacancies from the connecting conductive materials by blocking or delaying vacancies from arriving to these regions. In addition, a slot can also modify the local thermal stress profile. Secondly, because a sharp transition from a wide portion to a narrow portion of an interconnect creates a higher thermal stress gradient to attract vacancies, a stress reducing structure can be employed to reduce the stress gradient by smoothening the sharp transition corners. These two features can be applied separately or at the same time. Accordingly, a possible circuit failure caused by voiding is delayed or prevented. The lifetime of an integrated circuit is increased.
This description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. in the description, relative terms such as “narrower” and “longer” should be construed to refer to the quantity of the characteristic under discussion. Relative terms such as “right,” “left,” “lower,” “higher,” “lowest,” “highest,” “top,” “bottom,” “parallel” and “perpendicular” should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation.
In another embodiment, the first portion 110 can be a flat polygon solid or a flat irregular shape. The second portion 120 can have any elongated shape. The first portion 110 and the second portion 120 comprise electrically conductive materials such as metals or doped polysilicon. In some embodiments, the first portion 110 and the second portion 120 comprise a layer of aluminum, aluminum alloy, or copper. In other embodiments, the first portion 110 and the second portion 120 comprise multiple layers of metals chosen from such as titanium layer, titanium nitride layer, tungsten layer, and copper layer. Each layer may have different thickness. The first portion 110 can have different number of layers, different thickness of layers, and different layer materials from the second portion 120.
Although
As illustrated in
A method of manufacturing an interconnect structure embodying the present invention is shown in
In
In addition to the aforementioned method of fabricating an interconnect structure, another method of damascene process can also be used to manufacture an interconnect structure in accordance with the present invention. To increase the operating speed of an integrated circuit while reducing power consumption, conductive material with lower electrical resistance such as copper is used to replace aluminum. However, copper is difficult to etch in a semiconductor environment. As a result, a damascene approach, comprising of etching openings such as trenches and vias in the dielectric material and filling with copper, is used. After a layer of copper seed is deposited onto the surface of dielectric layer where openings for trenches and vias are formed, the bulk of the copper trench-fill and via-fill is performed using, for example, an electroplating technique.
In
Conductive material such as copper is then deposited to fill openings 570 and 575 by electroplating. The upper surface of the dielectric layer 520 is planarized by chemical mechanical polishing (CMP). The conductive portion 590 is the first portion 110 of the interconnect. The conductive portion 595 is the second portion 120 of the interconnect. The dielectric portion 580 is the slot 130.
As shown in
In this embodiment, the first portion 610 is a rectangle; the second portion 620 is a rectangular strip; the stress reducing structure 630 is a triangle; and the meeting angle 640 is a right angle (from top view). In another embodiment, the first portion 610 can be a polygon or an irregular shape (from the top view). The second portion 620 can be in any elongated shape. The stress reducing structure can be in any shape that can at least partially fit in the angle 630 to smoothen the sharp connection comers between the first portion 610 and the second portion 620. For example,
Although the invention has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the invention, which may be made by those skilled in the art without departing from the scope and range of equivalents of the invention.
Claims
1. A structure for reducing stress-induced voiding in an interconnect of an integrated circuit, said interconnect having a first portion and at least one second portion narrower than said first portion, said structure comprising:
- at least one interior slot disposed in the first portion in proximity to an intersection of said first portion and said second portion.
2. The structure of claim 1, wherein said first and second interconnect portions converge at said intersection, said intersection comprising a plane at a transition from said first interconnect portion to the second interconnect potion.
3. The structure of claim 1, wherein said structure further comprises an electrical connection between the first and second interconnect portions.
4. The structure of claim 1, wherein said slot is longer than a width of said intersection.
5. The structure of claim 1, wherein said first portion and said second portion comprise copper.
6. (canceled)
7. A structure for reducing stress-induced voiding in an interconnect of an integrated circuit, comprising:
- a first interconnect portion and at least one second interconnect portion narrower than said first interconnect portion; said first and second interconnect portions being connected at an intersection; and said second interconnect portion being connected to a via;
- wherein the first interconnect portion has at least one interior slot disposed portion in proximity to said intersection of said first and second interconnect portions, said interior slot having a length that is greater than a width of said intersection.
8. The structure of claim 7, wherein said intersection comprises a plane at a transition from said first interconnect portion to said second interconnect potion.
9. The structure of claim 8, wherein said intersection comprises an electrical connection between said first and second interconnect portions.
10. The structure of claim 7, wherein said interior slot has a length and a width, the length and width being unequal.
11. The structure of claim 10, wherein said interior slot is oriented approximately parallel to said intersection.
12. The structure of claim 7, wherein said interior slot has an elongated shape, said interior slot being oriented approximately parallel to said intersection.
13. The structure of claim 12, wherein a shortest distance from said interior slot to said intersection is smaller than 100 times of a critical dimension.
14. The structure of claim 12, wherein a shortest distance from said slot to said intersection is smaller than one half of a length of said first portion.
15. A structure for reducing stress-induced voiding in an interconnect of an integrated circuit, comprising:
- a first interconnect portion and at least one second interconnect portion narrower than said first interconnect portion;
- wherein said first interconnect portion comprises first and second elongated interior slots disposed adjacent to an intersection of said first and second interconnect portions, said first and second slots each having a longitudinal axis that is oriented approximately perpendicular to a plane of said intersection.
16. The structure of claim 15, wherein a shortest distance between said first and second slots is smaller than 10 times of a critical dimension, and wherein said shortest distance is greater than a width of said first interconnect portion.
17. The structure of claim 16, wherein a shortest distance from said first slot to said intersection is smaller than 100 times of said critical dimension.
18. The structure of claim 16, wherein a shortest distance from said first slot to said intersection is smaller than one half of a length of said first interconnect portion.
19-27. (canceled)
28. The structure of claim 14, wherein said structure comprises an electrical connection between said first and second interconnect portions.
29. The structure of claim 14, wherein said second interconnect portion is connected to a via.
30. The structure of claim 14, wherein said first and second interconnect portions comprise copper.
Type: Application
Filed: Jan 10, 2006
Publication Date: May 25, 2006
Inventors: Chih-Hsiang Yao (Taipei), Chin-Chiu Hsia (Taipei), Wen-Kai Wan (Hsinchu City)
Application Number: 11/328,614
International Classification: H01L 23/48 (20060101);