Patent Publication Number: US-2023154790-A1

Title: Preventing electrode discontinuation on microdevice sidewall

Description:
FIELD ON THE INVENTION 
     This invention relates to the process of etching and treatment of sidewalls while processing microdevices. 
     SUMMARY 
     The present invention relates to a method to planarize sidewalls of microdevices, the method comprising, coating a microdevice with a polymer, and removing the polymer by a dry etching process and leaving the polymer in a sidewall indentation to planarize the sidewalls. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The foregoing and other advantages of the disclosure will become apparent upon reading the following detailed description and upon reference to the drawings. 
         FIG.  1    shows an example of a device  100  where the walls have indentation. 
         FIG.  2 A  shows a polymer coating a wall of a device. 
         FIG.  2 B  shows a polymer as etched back by dry etching. 
         FIG.  2 C  shows a conductive layer on the wall after dry etching. 
         FIG.  3 A  shows a polymer material coated to cover the wall of the device where there is a film/s that exists between at least a part of the polymer and the wall. 
         FIG.  3 B  shows the polymer after the etch process. 
         FIG.  3 C  shows that a conductive layer is formed on the wall after etching. 
         FIG.  4    shows where the wall forms a VIA in the device layers. 
     
    
    
     While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments or implementations have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
     In this description, the term “device” and “microdevice” are used interchangeably. However, it is clear to one skilled in the art that the embodiments described here are independent of the device size. 
     During processing microdevices, the sidewalls (or internal walls of a VIA) can have some indentation. This could happen as part of etching or treatment of the sidewalls. 
     If a conductive layer needs to sit (cover) on the walls, the indentation can cause discontinuation and so the conductive layer can be disconnected. 
       FIG.  1    shows an example of a device  100  where the walls have an indentation  102 . The conductive layers  104  and  106  are disconnected due to this indentation  102 . 
     Depending on the depth of the indentation, it may be hard to fill it with a thin film deposition process. 
     The present invention is to fill the device wall indentation with a polymer. A polymer layer covers the wall. The polymer layer can also be spin coated or printed (or other methods). 
     After the coverage of the wall by the polymer, there is excess material on the wall. This excess material is removed by a process of dry etching to leave polymer in the indentation. It is possible to have a thin layer of the polymer still left on the wall after dry etching. This thin layer reduces the sharpness of the indentation edge and as such results in better coverage for subsequent films that will be deposited (or formed) on the walls. The films can be conductive, dielectric, or a combination of them. 
     In another case, other materials can be used to fill the indentation such as a dielectric, conductive material, and others. 
       FIG.  2    (comprising  FIG.  2 A,  2 B &amp;  2 C ) highlights an approach to fill the indentation. In  FIG.  2 A , a polymer material  208  is coated (or formed by other means) to cover the wall of the device  200 . The polymer can be cured after the coating. The curing (thermal or light based) can have a reflow cycle where the polymer can fill the spaces before hard curing. A reflow cycle is a form of curing under temperature of light where the material is soft enough that it can move to small spaces. The polymer is etched backed by a dry etching process ( FIG.  2 B ). The dry etching process can be RIE (reactive-ion etching), ion milling, or ICP (inductively coupled plasma RIE). This process is fairly directional and as a result, the material will stay inside the indentation area  202 . After the etching process, conductive layer  204  can form on the wall as demonstrated in  FIG.  2 C . 
       FIG.  3    (comprising  FIG.  3 A,  3 B &amp;  3 C ) highlights a case where there is another film  310  (or combination of films) that is formed on the wall before planarization of indentation. 
     In  FIG.  3 A , a polymer material  308  is coated (or formed by other means) to cover the wall of the device  300  where there is a film  310  (or combination films) that exists between at least part of the polymer  308  and the wall. The polymer (or other material) can be cured after the coating. The curing can have a reflow cycle where the polymer can fill the spaces before hard curing. 
     In  FIG.  3 B , the polymer, covering the wall of the device  300  where there is a film  310 , is etched backed by a dry etching process. The dry etching process can be RIE, ion milling, or ICP. This process is fairly directional and as a result, the material will stay inside the indentation area  302 . 
     After the etching process, a conductive layer  304  can form on the wall as demonstrated in  FIG.  3 C . The film  310  can be dielectric or conductive or a combination of them. In one case, at least one of the film  310  can be a mask for the etching of the polymer. This layer will protect the device  300  during the etch back of the polymer  308 . The film  310  can cover the walls or the surface of the device. The film  310  can also be removed. 
       FIG.  4    shows an example where the wall forms a VIA in the device  400  layers. Here indentation  402  is filed with polymer (or other film) with the method described above. There can be a film  410  (or combination of films) prior to filling the indentation  402 . Another film  404  is deposited after the indentation  402  is filled. Here the film  404  can be conductive to bring a signal from top of the via to the bottom. The VIA can be at the bottom and be coupled to another film. 
     Method Aspects 
     The invention discloses a method to planarize sidewalls of microdevices. The method comprises, coating a microdevice with a polymer, and removing the polymer by a dry etching process leaving the polymer in a sidewall indentation to planarize the sidewalls. Here, the polymer is cured. Also, a conductive layer may cover part of the planarized sidewall, and there may be another dielectric between the conductive layer and the planarized sidewall, wherein the dielectric is placed before or after the planarization. Further, the curing may be thermal, or light based and the curing can have a reflow cycle. In one instance, the dry etching process can be RIE, ion milling, or ICP. Additionally, a film can exist between part of the polymer and the sidewall. In one instance, combination films may exist between part of the polymer and the sidewall, wherein the additional film acts as a mask for the dry etching process. Here, the combination films may act as a mask for the dry etching process, and the films comprise of dielectric and conductive layer. Moreover, the additional film can either be a conductive layer or a dielectric. In another aspect, the sidewall is a wall of a VIA, wherein the conductive layer brings a signal from the top to the bottom of the VIA. 
     The foregoing description of one or more embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.