Patent Application
20140042152
The present disclosure relates to a device and a method using the same for rectifying wafer warpage. In particular, it relates to a variable frequency microwave (VFM) device and a method for rectifying the wafer warpage.
Wafer warpage commonly occurs in a microelectronic or semiconductor fabricating process. The warpage degrades device performance, reliability and line width control in various processing steps. Therefore, early detection and precise rectification of the wafer warpage can minimize cost and processing time, and ensure quality of semiconductor products as desired.
In semiconductor processing, when using lower cure temperature materials, coefficients of thermal expansion of molding compounds and silicon cause significant wafer bow, handling problems, and longer curing time, thus resulting in low throughput, as measured in wafers per hour (WPH).
Thus, there is a need to solve the above-mentioned problems.
For a more complete understanding of the present embodiments, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
The present disclosure will be described with respect to particular embodiments and with reference to certain drawings, but the disclosure is not limited thereto but is only limited by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not necessarily correspond to actual reductions to practice.
Furthermore, the terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments described herein are capable of operation in other sequences than described or illustrated herein.
Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments described herein are capable of operation in other orientations than described or illustrated herein.
It is to be noticed that the term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.
Similarly it should be appreciated that in the description of exemplary embodiments, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed disclosure requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment.
Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the disclosure, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.
In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
The disclosure will now be described by a detailed description of several embodiments. It is clear that other embodiments can be configured according to the knowledge of persons skilled in the art without departing from the true technical teaching of the present disclosure, the claimed disclosure being limited only by the terms of the appended claims.
Variable frequency microwave (VFM) devices, used in packaging procedures of the semiconductor industry and the electronic components industry for example, offer controlled and uniform distribution of microwave energy for a broad range of thermal applications, so that wafer warpage is cured and finally the dies are packaged with polymeric adhesives or solders. With a high microwave power and a high temperature supply, a large number of dies/electronic components packaged within molding materials (or polymeric adhesives) on a carrier are cured for warpage and further processing, and such a VFM curing process is useful for BGA (Ball Grid Array), eWLB (embedded wafer-level BGA), chip scaled packaging, wafer level chip scaled packaging (WLCSP), fan-out WLCSP processes, and on the like. Nevertheless, wafer warpage still exists, or worsens, after the conventional VFM rectification process, and rectification on the warped wafers is essential.
The structure of the wafer to be cured is schematically depicted as shown in
In the VFM process, the cavity magnetron of the conventional VFM device converts high-voltage electric energy to microwave radiation and simultaneously radiates to heat the wafer, and the glass carrier expands/shrinks with the dramatically high temperature, leading to no rectification in wafer warpage. After the molding process, in which the wafer may become warped, the molding compound needs to be fully cured. Less warpage of the wafer 10 after full curing of the molding compound is desired. Otherwise, subsequent semiconductor manufacturing processes, such as a redistribution layer (RDL) process, and the reliability tests, will be adversely affected.
Please refer to
Furthermore, the temperature of the first layer 7 and the carrier 10 in the ambient atmosphere before rectification may be about 25° C. The change in temperature T1 is formulated as “ΔT1=T1=25° C.” and the change in temperature T2 is formulated as “ΔT2=T2−25° C.” accordingly. In accordance with various embodiments, not only is the temperature T1 of the first layer 7 significantly higher than the temperature T2 of the carrier 10, but also the change in temperature ΔT1 of the first layer 7 is significantly higher than the change in temperature ΔT2 of the carrier 10. Since the coefficient of thermal expansion of an article is proportional to the change in temperature, the conformation of the molding compound 7 will be influenced by the changes in temperature ΔT1, and thus the wafer warpage will be rectified by the configuration and operation of the WFM device in the present disclosure.
In addition, since the warped wafer has been processed with the molding compound, the temperature difference present in the glass/silicon substrate is less than that in the molding compound after rectification, and thus the glass shrinkage caused by the temperature difference will be reduced.
For providing the cold air flow, the cooler 4 can be configured as an air cooling device, and includes but is not limited to any of a ventilator, a fan, a cooling plate, an air conditioner, a fin heat sink and a combination thereof. The cooling device 6 can also be configured as a water cooling device, such as a looped heat pipe system, a condenser, other apparatuses and the like.
In an example, the temperature T1 is higher than the temperature T2, and the temperature T1 has any value in a range of about 100° C. to about 200° C., or in a range of about 150° C. to about 160° C., or up to 265° C. (a temperature monitored by the VFM device), for instance. Since increasing the curing temperature is beneficial in reducing the curing time, the number of wafers per hour (WPH) is increased.
Please refer to
To sum up, wafer warpage or wafer bowing can be rectified and cured by the VFM device and the rectifying method of the present disclosure, and WPH is correspondingly increased. The design of the VFM device and the rectifying method of the disclosure offer advantages for semiconductor fabricating processes. Based on the concept/spirit of the present disclosure, the heat from two different heat sources can be applied on the article at a heating device with an adequate time period to enable the article to have two or more temperatures or temperature differences/gradients to cure the warpage or bends of the articles.
In accordance with various embodiments, a variable frequency microwave (VFM) device includes a chamber including top and bottom walls; a heater installed in the top wall of the chamber; and a cooler installed in proximity to the bottom wall of the chamber.
In accordance with various embodiments, a VFM device is provided and includes a chamber including a bottom wall; and a cooling device installed in proximity to the bottom wall.
In accordance with various embodiments, a method of rectifying warpage of a wafer is provided, the wafer includes a first layer and a second layer, and the method includes: providing a variable frequency microwave to the first layer; and cooling a position in proximity to the second layer of the wafer.
While the disclosure has been described in terms of what is presently considered to be the most practical and preferred Embodiments, it is to be understood that the disclosure needs not be limited to the disclosed Embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.
