Semiconductor device manufacturing: process – With measuring or testing
Reexamination Certificate
2001-05-10
2004-07-06
Zarabian, Amir (Department: 2822)
Semiconductor device manufacturing: process
With measuring or testing
C438S017000, C324S765010, C324S762010
Reexamination Certificate
active
06759255
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to detecting metal contamination. Certain embodiments relate to determining metal contamination in a semiconductor substrate or a dielectric material by measuring electrical parameters of the semiconductor substrate or the dielectric material.
2. Description of the Related Art
Metal contamination on a semiconductor substrate may degrade the electrical properties of the semiconductor substrate. For example, metal contamination in the bulk semiconductor substrate may cause the bulk minority carrier lifetime to decrease because the metal contamination may assist in the recombination of electrons and holes in the semiconductor substrate. When metal contamination is present in a dielectric material formed upon the semiconductor substrate or on a surface of the semiconductor substrate, the metal contamination may cause the electrical properties of the dielectric material to degrade. As such, the electrical properties of the dielectric material and the semiconductor substrate may be measured to determine the amount of metal contamination. Metal contamination may have a significant impact on the performance and reliability of semiconductor devices. Metal contamination may be deposited on a semiconductor wafer during processing and manufacturing of semiconductor devices. In many cases, a portion or substantially all of the metal contamination may be deposited on the surface of the semiconductor substrate due to problems in processing or improper handling of the semiconductor substrates.
The metal contamination may currently be measured by physical analysis of a dielectric material or a semiconductor substrate. Examples of physical analysis techniques include, but are not limited to, secondary ion mass spectroscopy (SIMS), total reflection x-ray fluorescence (TXRF), and vapor phase decomposition inductively coupled plasma mass spectroscopy (VPD-ICPMS). The disadvantage to using one of these physical analysis techniques to determine the metal contamination is that these measurement techniques generally take a very long time. As such, the throughput or the number of wafers which may be processed in a given period of time may be relatively low compared to the number of wafers which may need to be examined during a manufacturing process. In addition, SIMS and VPD-ICPMS are destructive techniques which generally require removal of a portion of the dielectric material or semiconductor substrate during the measurement process.
The metal contamination may also currently be measured using device-based electrical characterization. These testing techniques may provide a measurement of the metal contamination that is very similar to metal contamination found on manufactured semiconductor devices. This type of testing, however, requires forming semiconductor devices on the dielectric material or on the semiconductor substrate. As such, device-based electrical characterization may be expensive and time consuming. In addition, analyzing the data also becomes complicated due to the number of processing steps that may be performed in order to form the semiconductor devices on the dielectric material or on the semiconductor substrate.
The metal contamination, however, may also be determined by using a non-contact work function and a surface photo-voltage measurement technique. This testing technique may include biasing the wafer using a corona charge deposited by a corona charge deposition system. The testing technique may also include measuring the surface voltage by using a work function sensor. Additionally, the band bending of the semiconductor substrate may also be measured using a surface photo-voltage sensor. As such, the surface voltage and the band bending of the semiconductor substrate may be functions of the electrical bias, which may be generated by the charge deposited by using a corona charging device. Examples of non-contact corona charging devices are illustrated in U.S. Pat. No. 4,599,558 to Castellano et al., U.S. Pat. No. 5,594,247 to Verkuil et al., and U.S. Pat. No. 5,644,223 to Verkuil, which are incorporated by reference as if fully set forth herein. Examples of work function sensors and surface photo-voltage sensors are illustrated in U.S. Pat. No. 4,812,756 to Curtis et al., U.S. Pat. No. 5,485,091 to Verkuil, U.S. Pat. No. 5,650,731 to Fung, and U.S. Pat. No. 5,767,693 to Verkuil, which are incorporated by reference as if fully set forth herein. Examples of using work function sensors and surface photo-voltage sensors to measure the electrical properties of dielectric materials are illustrated in U.S. Pat. No. 6,202,029 to Verkuil et al. and U.S. Pat. No. 6,191,605 to Miller et al., which are incorporated by reference as if fully set forth herein. Additional examples of systems and devices which may be used to determine the metal contamination in a semiconductor substrate includes “A New Approach for Measuring Oxide Thickness”, Miller, Semiconductor International, July 1995, and is incorporated by reference as if fully set forth herein.
Accordingly, it would be advantageous to develop a nondestructive testing method to rapidly and accurately measure the metal contamination on a semiconductor topography without sacrificing product wafers and without forming semiconductor devices on the semiconductor topography.
SUMMARY OF THE INVENTION
In an embodiment, metal contamination in a dielectric material disposed upon a semiconductor substrate may be detected by annealing the semiconductor substrate such that a portion of the metal contamination is driven into the dielectric material. In some embodiments, the annealing process may be effective to drive only one type of metal contamination into the dielectric material. The annealing process, however, may also be effective to drive at least two types of metal contamination into the dielectric material. After the semiconductor substrate is annealed, an electrical property of the dielectric material may be measured. The electrical property may include a surface voltage, a flatband voltage, an interface trap density, a total dielectric charge of the charged dielectric material, or a determined resistivity of the dielectric material. The measured electrical property may be used to determine a characteristic of the metal contaminant. Characteristics may include determining the presence of metal contaminants, the identity of the metal contaminant, and the concentration of the metal contaminants, or all of the above.
In one embodiment, a charge may be deposited on an upper surface of the dielectric material to facilitate measurement of the electrical property. The charge may be deposited using, e.g., a corona charging technique. The deposited charge may be effective to cause a tunneling condition of the dielectric material. After the charge is deposited on the dielectric material, the tunneling voltage of the dielectric material may be measured. The tunneling voltage may be used to determine a tunneling field of the dielectric material. The tunneling voltage and/or the tunneling field may be used to determine the presence of metal contamination in the dielectric material.
The characteristic of the metal contamination in the dielectric material may be determined as a function of the measured electrical property (e.g., tunneling voltage or the tunneling field). Determining the characteristic of the metal contamination in the dielectric material may include determining a characteristic of one type of metal contamination or characteristics of at least two types of metal contamination. Alternatively, the surface voltage may be measured as a function of time. In this manner, a resistivity of the dielectric material may also be determined.
In a further embodiment, a method for detecting metal contamination in a semiconductor substrate is provided. The semiconductor substrate may have a dielectric material formed thereon. The method may include annealing the semiconductor substrate such that the annealing process is effective to drive only one type of metal contamina
Horner Greg
Miller Thomas G
Samsavar Amin
Srivatsa Arun
Weinzierl Steven
Conley & Rose, P.C.
KLA-Tencor Technologies Corp.
Mewherter Ann Marie
Vockrodt Jeff
Zarabian Amir
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