# Patent

## Title
Method for making semiconductor device with stacked analog components in back end of line (BEOL) regions

## Abstract

A method for making a semiconductor device may include forming a first dielectric layer above a semiconductor substrate, forming a first trench in the first dielectric layer, filling the first trench with electrically conductive material, removing upper portions of the electrically conductive material to define a lower conductive member with a recess thereabove, forming a filler dielectric material in the recess to define a second trench. The method may further include filling the second trench with electrically conductive material to define an upper conductive member, forming a second dielectric layer over the first dielectric layer and upper conductive member, forming a first via through the second dielectric layer and underlying filler dielectric material to the lower conductive member, and forming a second via through the second dielectric layer to the upper conductive member.

## Background
BACKGROUND
Technical Field
The present invention relates to the field of electronic devices and, more particularly, to semiconductor devices and related methods.
Description of the Related Art
Semiconductor device manufacturing generally involves two phases, the first being the Front-End-of-Line (FEOL) processing in which the digital circuitry (e.g., transistors, etc.) are formed on a semiconductor substrate. The second phase is the Back-End-Of-Line (BEOL) processing, in which the analog components and conductive or metal traces are formed to connect various active semiconductor components together and to corresponding input/output connectors of the device package.
As technology nodes continues to scale down, the density of the digital circuitry continues to increase. However, the rate of increase in the analog circuitry density is generally less than that of the digital circuits. Resistors and capacitors are sometimes formed during BEOL processing for use as frequency filters, etc. Yet, the ability to produce an appropriate number of such analog resistors, capacitors, and inductors in the space available for BEOL processing for the ever-increasing density of digital components in a semiconductor device may be difficult. As such, further advances in BEOL processing may be desirable in some applications.
BRIEF SUMMARY
A method for making a semiconductor device may include forming a first dielectric layer above a semiconductor substrate, forming a first trench in the first dielectric layer, filling the first trench with electrically conductive material, removing upper portions of the electrically conductive material to define a lower conductive member with a recess thereabove, forming a filler dielectric material in the recess to define a second trench. The method may further include filling the second trench with electrically conductive material to define an upper conductive member, forming a second dielectric layer over the first dielectric layer and upper conductive member, forming a first via through the second dielectric layer and underlying filler dielectric material to the lower conductive member, and forming a second via through the second dielectric layer to the upper conductive member.
In accordance with one example implementation, forming the first conductive via may include forming a first pair of conductive vias coupled to opposing lateral ends of the lower conductive member to define a first resistor therewith, and forming the second conductive via may include forming a second pair of conductive vias coupled to opposing lateral ends of the upper conductive member to define a second resistor therewith. In an example embodiment, the first and second resistors may include different electrically conductive materials.
In accordance with another example implementation, forming the first via may include forming a single via to the lower conductive member to define a lower capacitive plate therewith, and forming the second via may include forming a single via to the upper conductive member to define an upper capacitive plate therewith. The upper and lower capacitive plates may define a capacitor with the dielectric filler therebetween.
The method may further include forming at least one integrated circuit on the substrate. Furthermore, the first and second dielectric layers may comprise first and second inter-level dielectric (ILD) layers. By way of example, the electrically conductive material may include at least one of tungsten, copper, and aluminum. The method may also include forming a first nitride liner in the first trench prior to filling the first trench with electrically conductive material, and forming a second nitride liner in the second trench prior to filling the second trench with electrically conductive material. The filler dielectric material may comprise a high density plasma (HDP) oxide, for example.
A related semiconductor device may include a first dielectric layer above a semiconductor substrate and having a first trench therein, a lower conductive member in the first dielectric layer, a filler dielectric material over the lower conductive member having a second trench therein and within the first dielectric layer, and an upper conductive member in the second trench in the filler dielectric material and within the first dielectric layer. The semiconductor device may further include a second dielectric layer over the first dielectric layer and upper conductive member, a first via extending through the second dielectric layer and underlying filler dielectric material to the lower conductive member, and a second via extending through the second dielectric layer to the upper conductive member.



BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1a is a top view of an inter-level device (ILD) layer with a master layer metal area therein used for making a semiconductor device in accordance with the present invention.
FIG. 1b is a cross-sectional view of ILD layer and master layer metal area of FIG. 1a taken along line b-b.
FIGS. 2a and 2b are top and cross-sectional views respectively corresponding to FIGS. 1a and 1b, after recess of the master layer metal area to form a lower conductive member.
FIGS. 3a and 3b are top and cross-sectional views respectively corresponding to FIGS. 2a and 2b, after deposition of a conformal dielectric layer.
FIGS. 4a and 4b are top and cross-sectional views respectively corresponding to FIGS. 3a and 3b, after deposition of a metal liner and metal layer over the conformal dielectric layer.
FIGS. 5a and 5b are top and cross-sectional views respectively corresponding to FIGS. 4a and 4b, after patterning of the metal layer over the conformal dielectric layer to form an upper conductive member.
FIGS. 6a and 6b are top and cross-sectional views respectively corresponding to FIGS. 5a and 5b, after deposition of an upper dielectric layer and via trench formation to the upper and lower conductive members.
FIGS. 7a and 7b are top and cross-sectional views respectively corresponding to FIGS. 6a and 6b, after lining and filling the vias so that the upper and lower conductive members define upper and lower plates of a capacitor.
FIG. 8 is a cross-sectional view similar to that of FIG. 7b, but for another example embodiment including a double vertical capacitor arrangement.
FIG. 9 is a cross-sectional view similar to that of FIG. 7b, but for another example embodiment including a double vertical resistor arrangement.



DETAILED DESCRIPTION
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and prime and multiple prime notation are used to indicate similarly elements in different embodiments.
Referring initially to FIGS. 1a-7b, a method for making a semiconductor device 30 which provides enhanced analog circuit density in Back-End-Of-Line (BEOL) regions is first described. The method may include forming a first dielectric layer 31, such as an ultra low K (ULK) inter-level dielectric (ILD) layer, above a semiconductor substrate 32. By way of example, the substrate 32 may be a silicon substrate, although other suitable semiconductor substrate materials may also be used. As will be understood by those skilled in the art, during the Front-End-of-Line (FEOL) processing active circuit regions (e.g., “digital” circuitry) are formed in the substrate 32. The first dielectric layer 31 may be formed directly on the substrate 32 in some embodiments, or there may be one or more intervening levels (e.g., metal interconnect layers, etc.) between the first dielectric layer and the substrate, as will also be understood by those skilled in the art.
A first trench is formed in the first dielectric layer 31, and then filled with an electrically conductive material 33, such as a metal or metal alloy. By way of example, the metal or alloy may include one of more of tungsten, copper, and aluminum, although other suitable conductive materials may be used in different embodiments. Furthermore, prior to filling the first trench with the electrically conductive material 33, a liner 34 (e.g., TiN, etc.) may be formed in the trench. This accordingly forms a master layer metal area that will be processed to produce a multi-level metal component stack that may be used for the formation of resistors, capacitors, and/or inductors, as will be discussed further below. A dielectric insulator layer 35, such as a high density plasma (HDP) oxide layer, is formed over upper portions of the electrically conductive material 33 and adjacent upper portions of the first dielectric layer 31.
As seen in FIGS. 2a and 2b, the method further illustratively includes removing or recessing upper portions of the electrically conductive material 33 (and liner 34) to define a lower conductive member 36 with a recess 37 thereabove, which may be done using conventional metal etching techniques, for example. Furthermore, the recess 37 may have a filler dielectric material 38 formed therein, which again may be an HDP oxide, for example, although other suitable dielectric materials may also be used in different embodiments. In other words, the filler dielectric material may be deposited as a conformal layer, although other approaches may also be used. To this end, the filler dielectric material 38 may serve as the dielectric or insulator of a capacitor(s) later formed in the master metal layer area, and thus different dielectric materials may be selected depending upon the desired capacitive properties for the given implementation, as will be understood by those skilled in the art.
The filler dielectric material 38 has a second trench 39 therein, as seen in FIG. 3b. The second trench 39 may then be filled with a liner 41 (e.g., TiN, etc.) and an electrically conductive material 40, which may similarly include a metal or alloy such as those described above. Another patterning (e.g., CMP) or etching step may be performed to define an upper conductive member 42 from the electrically conductive material 40, as seen in FIGS. 5a and 5b. The lower conductive member 35 and upper conductive member 42 are therefore elongate, planar metal conductive elements formed within the same master level metal layer, with the “footprint” of the upper conductive member being smaller than, and laterally inside of, the footprint of the lower conductive member. Stated alternatively, the lower conductive member 35 is wider than the upper conductive member 42, and the upper conductive member vertically overlaps portions of the lower conductive member.
A second dielectric layer 43 is formed over the upper conductive member 42 and dielectric material 38, a first opening 45 for a first via 46 may be formed through the second dielectric layer and underlying filler dielectric material to the lower conductive member 34, and a second opening 47 for a second via 48 may be formed through the second dielectric layer to the upper conductive member 42, as seen in FIGS. 6a, 6b. The first and second vias 46, 48 may include a metal, such as those discussed above, and respective liners 49, 50 may be formed in the first and second recesses 45, 47 prior to formation of the metal vias 46, 48 (see FIGS. 7a, 7b)
In the illustrated example, a single first via 46 extends to the lower conductive member 35 to define a lower capacitive plate, and a single second via 48 extends to the upper conductive member 42 to define an upper capacitive plate therewith. As such, the lower and upper capacitive plates 35, 42 define a capacitor with the dielectric filler 38 therebetween. In accordance with another example embodiment shown in FIG. 8, a double or two-level capacitive stack arrangement may also be formed. Here, a first capacitor is formed between the conductive members 35′ and 42′ and the intervening dielectric filter 38′, as before. Yet, here the conductive member 42′ is an intermediate conductive member vertically positioned between the lower conductive member 35′, and another (upper) conductive member 55′ (which may have its own liner 56′, as with the other conductive members). As such, the intermediate conductive member 42′ and the upper conductive member 55′ define a second capacitor in a vertically stacked with the first capacitor. As before, a single via 57′ (which also has a liner 58′) extends through the second dielectric layer 43′ to the upper conductive member 55′, as shown.
In accordance with still another example implementation now described with respect to FIG. 9, rather than a using single vias as described above, a first pair of conductive vias 46′′ may be formed which are coupled to opposing lateral ends of the lower conductive member 35′′ to define a first resistor therewith, and a second pair of conductive vias 48′′ are coupled to opposing lateral ends of the upper conductive member 42′′ to define a second resistor therewith above the first resistor. In some embodiments, the conductive members 35′′, 42′′ members may include different materials to provide different resistance values, for example, although the same material may also be used for both. In other configurations, conductive members may be interconnected to form an inductor(s), as will be appreciated by those skilled in the art.
The above-described techniques therefore provide an approach to make relatively high density RLC integrated circuits within a given master metal layer. Moreover, this may advantageously be done with the double or multi-stack conductive members being formed in a single master lithography step, as will be appreciated by those skilled in the art. As a result, this may help reduce chip “real estate” or surface area usage by putting the analog circuitry (e.g., resistors, capacitors, inductors) in the BEOL metal layers rather than on the periphery of the chip. The above-noted approach may also relax the requirements of the lithography tool capability significantly, and also potentially save BEOL manufacturing costs. It should also be noted that the above-described process may be implemented for a number of different circuit chips, including digital devices (processors, microcontrollers, memory, etc.), analog devices, mixed signal devices (such as, for example, consumer, tablet, phone, computer, servers, gaming, set top box, TV, and automotive devices), Micro-Electro-Mechanical Systems (MEMS) devices, sensors, etc.
Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.

## Claims

1. A device, comprising:
a substrate;
a plurality of active circuit regions in the substrate;
a first dielectric layer on the substrate and on the plurality of active circuit regions;
a first opening in the first dielectric layer;
a first conductive layer in the first opening;
a second dielectric layer on the first dielectric layer and on the first conducive layer in the first opening;
a second opening in the second dielectric layer;
a second conductive layer in the second opening; and
a third dielectric layer on the second dielectric layer and on the second conductive layer, the first conductive layer being separated from the third dielectric layer by the second dielectric layer.

2. The device of claim 1, further comprising a first liner between the first dielectric layer and the first conductive layer.

3. The device of claim 2, further comprising a second liner between the second dielectric layer and the second conductive layer.

4. The device of claim 1 wherein the first conductive layer has a first shape and the second conductive layer has a second shape, the first shape being larger than the second shape and the first shape being different from the second shape.

5. The device of claim 4, further comprising a first via, the first shape including a protrusion, the first via being coupled to the protrusion, the first via extending through the second dielectric layer.

6. The device of claim 5 wherein the second shape is rectangular.

7. The device of claim 5, further comprising a second via that is coupled to the second conductive layer.

8. A device, comprising:
a substrate;
a first dielectric layer on the substrate;
a trench in the first dielectric layer;
a first conductive layer in the trench;
a second dielectric layer on the first conductive layer in the trench;
a first opening in the second dielectric layer, the first opening being in the trench;
a second conductive layer in the first opening; and
a first via extending into the trench, past the second conductive layer, the first via electrically coupled to the first conductive layer.

9. The device of claim 8, further comprising:
a second opening in the trench; and
a third conductive layer in the second opening.

10. The device of claim 9, further comprising a second via coupled to the second conductive layer and a third via coupled to the third conductive layer.

11. The device of claim 8, further comprising a second via coupled to the second conductive layer.

12. The device of claim 11, further comprising a third via coupled to the first conductive layer and a fourth via coupled to the second conductive via.

13. The device of claim 8 wherein the first dielectric layer has a first surface, the trench extending into the first dielectric layer from the first surface, the first conductive layer having a first surface that is spaced from the first surface of the first dielectric layer and a second surface that faces a bottom surface of the trench.

14. A method, comprising:
forming a first dielectric layer on a substrate, the substrate including active circuit elements;
forming a trench in the first dielectric layer;
forming a first conductive layer in the trench;
forming a second dielectric layer in the trench on the first conductive layer;
forming a first opening in the second dielectric layer in the trench;
forming a second conductive layer in the first opening; and
forming a third dielectric layer on the second conductive layer, the first conducive layer being separated from the third dielectric layer by the second dielectric layer and the second conductive layer.

15. The method of claim 14, further comprising:
forming a first via through the second conductive layer; and
coupling the first via to the first conductive layer.

16. The method of claim 15, further comprising:
forming a second via through the third conductive layer; and
coupling the second via to the second conductive layer.