X-ray or gamma ray systems or devices – Specific application – Fluorescence
Reexamination Certificate
2002-09-12
2004-10-26
Glick, Edward J. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Fluorescence
C250S306000
Reexamination Certificate
active
06810105
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to the field of inspection and analysis of specimens and, more particularly, to dishing and erosion inspection and analysis for semiconductor integrated circuits.
2. Description of Related Art
The metallization and thin film layers of conventional integrated circuits contain interconnects. The interconnects are arranged to allow electrical contact between transistors and other circuitry in an integrate circuit. However, dishing and erosion may cause defective interconnects on an integrated circuit. Dishing is the concavity formed near the center of an interconnect. Erosion is the deterioration of interconnects along with the surrounding material, typically an oxide. Processes such as chemical mechanical polishing (CMP) can cause dishing and erosion. Variation in polished surfaces (cuts, dishing and erosion) affect signal uniformity due to variation in the conductance of the Cu layer/lines.
During CMP, a dielectric layer comprising an oxide typically works to control CMP to material above the dielectric layer. However, the CMP process may nevertheless remove material in the dielectric layer. Conductive material removed from near the center of an interconnect is referred to as dishing. Conductive material as well as surrounding dielectric material removed from an interconnect is referred to as erosion.
Both erosion and dishing can negatively impact operation of integrated circuit devices by causing open circuits.
Inspection of integrated circuit at various stages of manufacture can significantly improve production yield and product reliability. If erosion or dishing can be detected early in production, various production processes such as CMP can be modified. For example, the slurry composition, plate and carrier rotational speeds, pad hardness, and the pressure of the polish head can be varied to improve processing.
Conventional surface abrasion systems use a protocol comprising of a fine needle traversing a surface, thereby indicating surface/topographical variations.
A secondary electron detector can also be used to measure the intensity of the secondary electron emission that originates only at the path swept by the scanning electron beam. A defective portion can be identified from the potential state of the portion under inspection. In one form of inspection, the mismatched portion between the defective voltage contrast image and the defect free one reveals the general defect location.
Other techniques involve slicing a wafer into cross sections and using an electron microscope to detect defects. Intrusive methods, however, are both time consuming and wasteful. Accoustic and optical methods are also available, but these methods are typically effective only in very particular circumstances, such as when the conductive elements have been completely dished or eroded.
Accordingly, improved detection systems allowing more precise characterization of erosion and dishing are desirable.
SUMMARY
The present invention includes a system for efficient and effective detection and characterization of dishing and/or erosion. An x-ray emission inducer is used to scan a target on a sample. The target can be scanned from different directions to allow characterization of the dishing and/or erosion and analysis of the metallization or thin film layer topology.
According to various embodiments, a system for characterizing dishing and/or erosion associated with a sample having a first surface and a second surface is provided. The system includes a memory and a processor. The processor is coupled with memory and is configured to identify a first measurement of induced x-ray emissions characteristic of a first material emitted upon scanning a first scan target from a first direction. The processor is further configured to identify a second measurement of induced x-ray emissions characteristic of the first material emitted upon scanning the first scan target from a second direction. The first and second measurements provide information for characterizing dishing and/or erosion associated with the sample.
According to other embodiments, an apparatus for characterizing dishing and/or erosion in a first scan target associated with a sample having a first surface and a second surface is provided. The apparatus includes an x-ray emission inducer configured to scan a first scan target at an acute incident angle. The x-ray emission inducer causes the first scan target to emit x-rays from the first surface. The apparatus also includes an x-ray emission detection system configured to obtain a measurement of the x-rays emitted from the first surface of the sample. The x-ray measurement is compared to a control measurement to provide information for characterizing dishing and/or erosion in the first scan target.
According to still other embodiments, a method for characterizing dishing and/or erosion in a sample is provided. The method includes identifying a first measurement of induced x-ray emissions characteristic of a first material at a first scan target resulting from a first scan from a first direction, identifying a second measurement of induced x-ray emissions characteristic of the first material at the first scan target resulting from a second scan from a second direction, and providing the first and second measurements to allow characterization of dishing and/or erosion associated with the first scan target in the sample.
These and other features and advantages of the present invention will be presented in more detail in the following specification of the invention and the accompanying figures which illustrate by way of example various principles of the invention.
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Nasser-Ghodsi Mehran
Wood Phil
Beyer Weaver & Thomas LLP
Glick Edward J.
KLA-Tencor Technologies Corporation
Song Hoon
LandOfFree
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