Patent Application
20110201260
The present methods, devices, and systems relate generally to the field of semiconductor fabrication, and more particularly to the backgrinding of substrates to produce through vias.
Fabrication of vertically integrated semiconductor devices, commonly referred to as “3D interconnect,” may involve the formation of through vias by backgrinding a substrate to expose fill material (e.g., conductor material) from the substrate back side (the side of the substrate from which backgrinding process removes material). Backgrinding using a grinding wheel may result in removed portions of the fill material adhering to the abrasive material of the grinding wheel. This build up of accumulated fill material may cause degradation of the performance of the grinding wheel, resulting in decreased grinding efficiency during the backgrinding process.
Embodiments of the present methods for retaining grinding efficiency during a backgrinding process include backgrinding a substrate using a grinding wheel, and using a grinding fluid during the backgrinding of the substrate. The grinding wheel may have an abrasive material configured to remove a substrate material from the substrate during the backgrinding process. The grinding fluid may include a chemical agent that is configured to remove an accumulated portion of the substrate material from the abrasive material.
In some embodiments, the chemical agent is configured to remove the accumulated portion from the abrasive material by chelating the accumulated portion. In some embodiments, the chemical agent includes a citrate. In some embodiments, chemical agent includes a succinate. In some embodiments, the chemical agent includes a benzotriazole.
In some embodiments of the present methods, the grinding fluid further includes a second chemical agent that is configured to etch the accumulated portion. Some embodiments further include adjusting the pH of the grinding fluid to facilitate the chelating of the accumulated portion.
Some embodiments of the present methods further include cleaning the grinding wheel prior to backgrinding the substrate using a pre-grinding chemical agent. The pre-grinding chemical agent may be configured to remove a previously accumulated portion of a previous substrate material from the abrasive material. In some embodiments, the pre-grinding chemical agent may be configured to remove the previously accumulated portion from the abrasive material by chelating the previously accumulated portion.
In some embodiments, the pre-grinding chemical agent may include a citrate. In some embodiments, the pre-grinding chemical agent may include a succinate. In some embodiments, the pre-grinding chemical agent may include a benzotriazole.
In some embodiments, cleaning the grinding wheel prior to backgrinding the substrate further includes using sonic agitation. In some embodiments, cleaning the grinding wheel prior to backgrinding the substrate further includes using a contact-cleaning brush.
Embodiments of the present systems for performing a backgrinding process include a pedestal configured to support a substrate, a grinding wheel configured to backgrind the substrate, and a fluid source configured to deliver a grinding fluid to the substrate while the grinding wheel backgrinds the substrate. The grinding wheel may include an abrasive material configured to remove a substrate material from the substrate during the backgrinding process. The fluid source may be configured to deliver a grinding fluid to the substrate while the grinding wheel backgrinds the substrate. The grinding fluid may include a chemical agent that is configured to remove an accumulated portion of the substrate material from the abrasive material by chelating the accumulated portion.
In some embodiments of the present systems, the chemical agent may include a citrate. In some embodiments, the chemical agent may include a succinate. In some embodiments, the chemical agent comprises a benzotriazole.
Some embodiments further include a cleaning extension configured to deliver a cleaning fluid to the grinding wheel. The cleaning fluid may include a pre-grinding chemical agent that is configured to remove a previously accumulated portion of a previous substrate material from the abrasive material by chelating the previously accumulated portion.
In some embodiments of the present systems, the pre-grinding chemical agent may include a citrate. In some embodiments, the pre-grinding chemical agent may include a succinate. In some embodiments, the pre-grinding chemical agent may include a benzotriazole.
Any embodiment of any of the present methods and systems may consist of or consist essentially of—rather than comprise/include/contain/have—the described functions, steps and/or features. Thus, in any of the claims, the term “consisting of” or “consisting essentially of” may be substituted for any of the open-ended linking verbs recited above, in order to change the scope of a given claim from what it would otherwise be using the open-ended linking verb.
The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present methods and systems. The drawings illustrate by way of example and not limitation. Identical reference numerals do not necessarily indicate an identical structure. Rather, the same reference numeral may be used to indicate a similar feature or a feature with similar functionality. Not every feature of each embodiment is labeled in every figure in which that embodiment appears, in order to keep the figures clear.
The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”) and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. Thus, a method comprising certain steps is a method that includes at least the recited steps, but is not limited to only possessing the recited steps. Likewise, a device or system comprising certain elements includes at least the recited elements, but is not limited to only possessing the recited elements.
The terms “substantially,” “about,” and their variations are defined as being largely but not necessarily wholly what is specified as understood by one of ordinary skill in the art, and in one non-limiting embodiment, the substantially refers to ranges within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5% of what is specified.
The terms “a” and “an” are defined as one or more than one, unless this application expressly requires otherwise. The term “another” is defined as at least a second or more.
In one aspect, the present disclosure provides embodiments that are methods for retaining grinding efficiency during a backgrinding process. Another aspect of the present disclosure provides systems for performing a backgrinding process. These systems may be configured to perform methods for retaining grinding efficiency during a backgrinding process such as, for example, backgrinding of a through-via substrate such as an embedded through silicon via wafer. A grinding fluid may include a chemical agent that is configured to remove accumulated materials from the grinding wheel.
An embodiment of the present system for performing a backgrinding process is depicted in
System 10 may also include grinding wheel 200 that is configured to backgrind substrate 500. Grinding wheel 200 may have an abrasive material 210 (see
Referring to
Continuing with
Referring also to
Embodiments of the present systems may be configured such that fluid source 300 supplies grinding fluid 310 that contains chemical agent 311. Grinding fluid 310 is generally provided to the region of abrasion of substrate 500 by grinding wheel 200 to facilitate removal of waste material that are removed from substrate 500 during the backgrinding process. In some embodiments, grinding fluid 310 may also serve to remove heat generated during the backgrinding process. The use of chemical agent 311 in the present embodiments may facilitate the retention of grinding efficiency during the backgrinding process. Chemical agent 311 may be configured to remove accumulated substrate material 530 from abrasive material 210. In some embodiments of the present systems, chemical agent 311 may comprise chelating agents such as, for example, citrates, succinates, and/or benzotriazoles. Grinding fluid 310 may also include a mild corrosion agent to facilitate etching of accumulated substrate material 530 from abrasive material 210 at a rate sufficient to prevent accumulation of accumulated substrate material 530 on grinding wheel 200, but at a rate low enough to prevent significant damage to the exposed fill material 520 within substrate 500. In some embodiments, the pH of grinding fluid 310 may be adjusted to optimize the chemical conditions for the removal of accumulated substrate material 530 from abrasive material 210 by chemical agent 311.
In some embodiments, chemical agent 311 may be selectively introduced into grinding fluid 310 at certain stages of the backgrinding process, and/or the concentration of chemical agent 311 within grinding fluid 310 may be varied during the process. For example, chemical agent 311 may be introduced after a set period of grinding (e.g., after a certain time period of backgrinding or the backgrinding of a certain number of substrates). In other embodiments, chemical agent 311 may be introduced after process monitoring determines that buildup of accumulated substrate material 530 may have occurred (e.g., measurement of process variables indicates that the backgrinding performance of grinding wheel 200 has degraded past a threshold). In some embodiments, chemical agent 311 may be introduced only at certain stages of the backgrinding process (e.g., at the later stages or the fine grinding stages of the backgrinding process).
Referring to
Some embodiments of the present disclosure may use sonic agitation and/or a contact-cleaning brush to enhance the removal of accumulated previous substrate material 630 from grinding wheel 200.
It should be understood that the operational flow diagram of
Descriptions of well known assembly techniques, components, and equipment have been omitted so as not to unnecessarily obscure the present methods, apparatuses, an systems in unnecessary detail. The descriptions of the present methods and apparatuses are exemplary and non-limiting. Certain substitutions, modifications, additions and/or rearrangements falling within the scope of the claims, but not explicitly listed in this disclosure, may become apparent to those of ordinary skill in the art based on this disclosure. For example, the fixing of substrate 500 to pedestal 100 may be accomplished by for example, various methods of mechanical clamping and/or electrostatic clamping.
The appended claims are not to be interpreted as including means-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) “means for” and/or “step for,” respectively.
