Aspects of this document relate generally to electrically conductive structures, such as vias having a flat top for forming electrical connections between various devices. More specific implementations involve vias having variable resistance.
Conventionally, interconnects have been incorporated within semiconductor devices to form electrical connections within the device as well as electrical connections between the device and exterior devices. Interconnects have included wire bonds, conductive routing, flip chips, and vias. Vias are used to form an electrical connection through a silicon wafer or a die.
Implementations of a via for a semiconductor devices may include a first tungsten layer deposited conformally within the via, and may be recessed within the via, and a second tungsten layer deposited into the recess over the first tungsten layer. A plane formed by the second tungsten layer may be substantially parallel with a plane aligned substantially perpendicularly with a longest dimension of the via viewed in cross section.
Implementations of vias may include one, all, or any of the following:
The second tungsten layer may be less than one-half a width of the via.
A first liner may be coupled to the first tungsten layer.
A second liner may be coupled between the second tungsten layer and the first tungsten layer.
The second liner may include either titanium nitride or tantalum nitride.
The material of the second liner may include a higher effective resistance than tungsten.
The first tungsten layer may be directly coupled to the second tungsten layer.
Implementations of a via for a semiconductor device may include a first liner coupled to a first portion of a surface of the via, a first layer coupled to the first liner, a second liner coupled to a second portion of the surface of the via and to the first layer, and a second layer coupled to the second liner. A material of the second liner may have a different effective resistance than a material of the second layer.
Implementations of vias may include one, all, or any of the following:
The first layer may be tungsten.
The second layer may be tungsten.
The second layer may be deposited into a recess of the first layer.
The second layer may be less than one half a width of the via.
A plane formed by the second tungsten layer may be substantially parallel with a plane aligned substantially perpendicularly with a longest dimension of the via.
Implementations of a method for forming a via may include depositing a first liner on a surface of a via, depositing a first tungsten layer over the first liner within the via, polishing the first tungsten layer, etching a portion of the first tungsten layer to form a recess in the via, depositing a second liner over the first tungsten layer into the recess, depositing a second tungsten layer over the second liner into the recess, and polishing the second tungsten layer.
Implementations of methods for forming a via may include one, all, or any of the following:
The second tungsten layer may be deposited using chemical vapor deposition.
A plane formed by the second tungsten layer may be substantially parallel with a plane aligned substantially perpendicularly with a longest dimension of the via.
The material of the second liner may be configured to adjust the effective resistance of the via.
The second liner may include either titanium nitride or tantalum nitride.
The material of the second liner may include a higher effective resistance than tungsten.
The second tungsten layer may not include a seam therein.
The foregoing and other aspects, features, and advantages will be apparent to those artisans of ordinary skill in the art from the DESCRIPTION and DRAWINGS, and from the CLAIMS.
Implementations will hereinafter be described in conjunction with the appended drawings, where like designations denote like elements, and:
This disclosure, its aspects and implementations, are not limited to the specific components, assembly procedures or method elements disclosed herein. Many additional components, assembly procedures and/or method elements known in the art consistent with the intended vias will become apparent for use with particular implementations from this disclosure. Accordingly, for example, although particular implementations are disclosed, such implementations and implementing components may comprise any shape, size, style, type, model, version, measurement, concentration, material, quantity, method element, step, and/or the like as is known in the art for such vias, and implementing components and methods, consistent with the intended operation and methods.
Referring to
A method for forming the via illustrated by
The method for forming the via illustrated by
The recess 10 may prove problematic in forming electrical connections to the via 2. Referring to
Referring to
As illustrated, the via includes a first tungsten layer 36 deposited conformally within the via. As described previously herein, the first tungsten layer could alternatively be a layer including any other conductive material, including any metal or metal alloy. In implementations where the via 26 includes a first liner 30, the first tungsten layer 36 may be coupled directly to the first liner 30. In implementations where a different conductive material is used in place of tungsten and there is no first liner, the layer of conductive material may be directly coupled to the first portion 32 of the surface 34 of the via 26. The tungsten layer 36 may be deposited using CVD. In the implementation illustrated by
In various implementations, the first tungsten layer 36 may be recessed within the via 26. In various implementations, the recess 40 extends into the via 26 less than ½ the width of the via 26. In other implementations, the recess 40 may extend deeper or less deep into the via 26 than ½ the width of the via depending on the geometry of the via. The surface 42 of the first tungsten layer 36 adjacent to the recess may be concave, convex, flat, or any combination thereof.
In various implementations, the via 26 may include a second liner 44 coupled to a second portion 46 of the surface 34 of the via 26 and to the first tungsten layer 36. In various implementations the second liner 44 may be directly coupled to the surface 42 of the first tungsten layer 36 and to the surface 34 of the via 26 formed in layer 28. In various implementations, the second liner 44 may include a material having a higher effective resistance (electrical resistance) than tungsten (or any other alternative material used in place of tungsten). In other implementations, the second liner 44 may include a material having a lower effective resistance than tungsten. In particular implementations, the material of the second liner may include, by non-limiting example, titanium, titanium nitride, tantalum, tantalum nitride, or any combination thereof. The second liner 44 may be of varying thickness. As the second liner has different resistance properties compared to the tungsten layers, the thickness of the second liner may be varied to correspondingly vary the resistance of the via. For example, titanium nitride has a resistance substantially ten times greater than the resistance of tungsten. Thus, by including the second liner it is possible to control the resistance among a plurality of vias all having the same critical dimensions by just changing the thickness and material used for the second liner 44 for those plurality of vias. This runs contrary to other via resistances where it was desirable to keep via resistances the same because the critical dimensions among the vias in a device were typically the same across a die in order to create optimum patterning control and to aid in processing of the vias in other process steps (like CMP). In this way, via resistances can be customized within a silicon die. Also, using these principles, the resistance of an entire set of vias in a layer on a die can be adjusted based on electrical test results to compensate for process variations or produce other desired performance characteristics. In other implementations including a conductive material rather than tungsten for the layer that fills the via 26, the via 26 may not necessarily include a second liner 44.
Still referring to
The depth of the second tungsten layer 50 may vary. In various implementations, the depth of the second tungsten layer 50 is less than the half the width of the via 26, though it may be more than half in various implementations. In various implementations the second tungsten layer 50 is a continuous layer of tungsten without any seams therein which is the result of filling an opening with much lower aspect ratios than the original via recess 40.
Referring to
Referring to
As illustrated by
Referring to
While this application focuses on forming a flat surface on a tungsten via and being able to vary the effective resistance of the tungsten via, one of ordinary skill in the art would understand that the elements of the vias and related methods disclosed herein may be applied to other vias that do not contain tungsten. As an example, in various implementations, rather than tungsten layers deposited in a via using CVD, copper (or any other metal or conductive material) may be formed in a via using a bottom-up deposition technique (electroplating or electroless plating). In various implementations, the via may be completely filled and then polished using CMP forming a recess. In other implementations, the via may not be completely filled, leaving a recess. A liner, or a seed layer, may then be deposited into the recess. This liner, or seed layer, may have a different effective resistance based on the material and thickness of the liner which works to vary the effective resistance of the via. The remainder of the via may be filled with copper (or any other metal or conductive material) and then CMP polished substantially flat to the top surface of the semiconductor layer.
In other implementations, rather than forming a recess in the via through polishing or etching the conductive material of the via, in implementations where the via is filled using a bottom-up process, the via may only be partially filled initially. A seed layer, or liner, having a varying effective resistance may then be deposited in the via and the remainder of the via may be filled. The top of the via may be polished if needed to ensure a smooth surface. In this manner, essentially any via may be formed with a varying resistance and a smooth surface that allows for reliable electrical connections to various components.
In places where the description above refers to particular implementations of vias and implementing components, sub-components, methods and sub-methods, it should be readily apparent that a number of modifications may be made without departing from the spirit thereof and that these implementations, implementing components, sub-components, methods and sub-methods may be applied to other vias.
This document claims the benefit of the filing date of U.S. Provisional Patent Application 62/503,815, entitled “Variable Resistance Flat Top Vias and Related Methods” to Cowell et al. which was filed on May 9, 2017, the disclosure of which is hereby incorporated entirely herein by reference.
Number | Date | Country | |
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62503815 | May 2017 | US |