Fix the glassivation layer's micro crack point...

Semiconductor device manufacturing: process – With measuring or testing

Reexamination Certificate

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C324S760020

Reexamination Certificate

active

06248601

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and, more particularly, to a method to detect pinholes in dielectric layers (or other glassivation layers such as passivation layers) by using electroplating.
(2) Description of the Prior Art
Glassification layers in the structure of a semiconductor device serve the purpose of protecting active device regions of an integrated circuit. Examples of glassification layers are dielectric layers, passivation layers, insulating encapsulation layers overlying electrical circuits and in general thin material films that are used for the manufacturing of semiconductor devices.
Imperfections that occur in these glassification layers can lead to shorts or unacceptably low breakdown voltages between different conductor levels. These imperfections can take the form of pinholes or weak spots that can be caused by a variety of reasons such as poor planarity of the underlying layer, poor alignment of the patterns during successive processes of patterning, high level of particulates in the processing environment, uneven distribution of deposited materials such as photoresist over device features that have regions of high angularity such as sharp corners, issues related to line coverage due to poor topography definition causing line thinning or opens in metal lines.
Glassification problems can be of particular devastating effect where they occur in Poly-Metal interlevel Dielectrics (PMD) or in Inter-Level Dielectric (ILD) layers. Electromigration, the phenomenon where ions of a conductor are re-located in the direction of the conducting current within a metal conductor, is also a frequently cited cause for surface defects. Electromigration causes an uneven distribution of ions within the metal conductor; this uneven distribution can lead to ion voids, which can result in open circuit failure of the metal conductor. Electromigration can, by its very nature, occur in any surface where electrical current is conducted, including metal contact areas.
Undesirable surface material distribution can have many causes. For instance stress related impact between overlying dielectric layers or different coefficients of thermal expansion between layers of material that are in contact with each other. It is apparent that, for micron and submicron devices, the impact of glassification problems becomes, due to the relative size of the glassification areas and irregularities, even more severe.
Numerous approaches and solutions have been proposed and implemented to eliminate or alleviate these occurrences of glassification such as using and matching materials according to their compressive values, adding certain elements to glassification layers to reduce the formation of weak spots in the surface of the layer, applying multiple layers where the interaction of these layers from a thermal and stress creating point of view are understood and matched, applying techniques during the formation of the glassification layers that minimize the probability of weak spots being created by for instance using a temperature profile of the glassification layer during its deposition, reducing angular features or adopting special processing techniques to eliminate areas where the uniform deposition of a layer can be questioned.
Where weak spots in glassification layer are of an extreme nature to the point where openings in a the glassification layer occur, the underlying layer may be exposed. The underlying layer can, as a consequence, form an oxidation layer on its surface or can be further exposed to contaminants. Corrosion of the underlying layer, such as conducting lines, may also occur.
It is clear from the above that the problem of weak spots and pinholes in glassification layers requires detailed attention. This implies that dependable, cheap methods must be available to detect such weak spots and pinholes so that remedial action can be taken to either eliminate these areas or to eliminate any negative effect that these areas might have on device yield and reliability.
Due to the microscopic nature of many of the indicated defects, it is also a requirement that any device or method of detection have great accuracy in locating the defect. The impact that the identification of a defect has on the manufacturing cycle must also be held to a minimum which means that the method used to identify these defects must not be time consuming.
A number of methods have been proposed and are in use for the localization of defects. Some of these methods combine chemical deposition on the glassification surface with electrical analysis of the surface after the chemical reaction has taken place. Other methods teach the deposition of chemical elements over the glassification layer whereby these elements cause chemical or electrochemical reactions with the layer in such a manner that any defects in the glassification layer are highlighted and are made visible for further analysis.
One previous method for identifying weak spots or pinholes in the glassification layer is by submerging the wafer that is being tested into a dish that contains a solution of DI water and isopropyl alcohol (IPA). A dc voltage of about 15 volt is applied to the dish; this voltage is applied between the body of the dish and the wafer under test so that dc current flows between the wafer and the dish. The surface of the glassification layer is, during the time that the dc current flows, observed with a microscope where bubbles emanating from the glassification surface indicate the formation of hydrogen and therefore the presence of surface weak spots or pinholes. This method has two major disadvantages: it is difficult to determine the exact location of the identified defect after the wafer under test is removed from the dish while this wafer analysis is time consuming.
U.S. Pat. No. 3,719,884 (Laroche) shows a method and apparatus to find pinholes by electroplating a component (varnish) and measuring the current consumed. The prior art section describes electroplating defect/pinholes with Cu to visually mark the defect. This is extremely close to the invention.
U.S. Pat. No. 5,076,906 (Dermarderosian, Jr.) teaches a method for testing pinholes in dielectric layers (glassivation) by using electrolyte test and by looking for gas bubbles. This is close to the invention, but does not claim electroplating specifically.
U.S. Pat. No. 4,514,436 (Moerschel) “Methods of highlighting pinholes in a surface layer of an article” shows a method of highlighting pinholes in a surface layer (
37
), such as a photoresist layer, of an article (
31
), such as a semiconductor wafer, using an electrolytic treatment step. The electrolytic treatment process dissolves the photoresist around each of the pinholes. The resulting enlarged areas (
46
) of missing photoresist around each of the pinholes are readily recognized by visual inspection of the wafer (
31
) at the conclusion of the electrolytic treatment.
U.S. Pat. No. 4,919,766 (Kotowski et al.) shows an etching technique for locating defects.
U.S. Pat. No. 4,180,439 (Deines et al.) teaches a method to anodic etch active defects in a silicon wafer.
U.S. Pat. No. 4,019,129 teaches a method of scanning the glassification surface by using the glassification surface as an anode and subsequently and sequentially energizing a coordinate array of cathode conductors. The conductive current occurring between the anode and cathode indicates the absence or presence of surface irregularities in the glassification layer.
U.S. Pat. No. 4,599,241 teaches the deposition on the surface of the glassification layer a layer of reactive material and further identifying any existing weak spots or pin holes by chemical treatments of the reactive material.
SUMMARY OF THE INVENTION
A principle objective of the invention is to locate defects in a glassification layer.
It is another objective of the invention to rapidly locate defects in a glassification layer.
It is another objective of the invention is to locate defects in a glassification l

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