TECHNICAL FIELD

The present disclosure relates generally to spectroscopic metrology and, more particular, to bandgap measurements of patterned film stacks using spectroscopic metrology.

BACKGROUND

Demand for electronic devices with ever-smaller footprints presents a wide range of manufacturing challenges beyond fabrication at a desired scale. For example, as the physical size of electronic components such as transistors shrinks, electrical and optical properties of the constituent film layers become increasingly dependent on physical geometry. In particular, leakage current through thin insulating layers presents a significant challenge for devices manufactured with lithography tools incorporating wavelengths lower than 65 nm. This leakage current negatively impacts device performance and may lead to increased operating temperatures as well as increased power consumption. It is therefore desirable to closely monitor and control the properties of insulating layers during fabrication to ensure that a fabricated device operates within design specifications.

Metrology targets are commonly used to monitor various aspects of fabricated layers of a semiconductor device. Metrology targets typically consist of a series of target features fabricated on the same layers as device features and are designed to be sensitive to one or more fabrication parameters of interest such as, but not limited to, a layer thickness, layer optical properties (e.g., dispersion, bandgap, and the like), a critical dimension, a sidewall angle, relative alignment of two or more layers (e.g., overlay), focal position of a target, or exposure dose during a lithography step. In this regard, measurements of a metrology target may provide sensitive data representative of fabricated device features.

In many applications, metrology targets are designed to facilitate a measurement of a desired fabrication parameter and may thus have a different physical configuration than a corresponding device feature. However, an increased dependence of electrical and optical properties of fabricated layers on the physical geometry may reduce a correlation between measurements of metrology targets and device features with different geometries. This may be particularly true for, but is not limited to, multilayer grating structures including periodic features formed from multiple thin film layers fabricated with increasingly small dimensions. Therefore, it would be desirable to provide a system and method to address deficiencies such as those identified above.

SUMMARY

A spectroscopic metrology system is disclosed in accordance with one or more illustrative embodiments of the present disclosure. In one illustrative embodiment, the system includes a spectroscopic metrology tool to provide a spectroscopic signal indicative of the radiation emanating from a multilayer grating including two or more layers in response to incident illumination. In another illustrative embodiment, the system includes a controller communicatively coupled to the spectroscopic metrology tool. In another illustrative embodiment, the controller generates a model of a multilayer grating including two or more layers, the model including one or more parameters associated with multilayer grating in which the one or more parameters include geometric parameters indicative of a geometry of a test layer of the multilayer grating and one or more dispersion parameters indicative of a dispersion of the test layer. In another illustrative embodiment, the controller receives a spectroscopic signal of a fabricated multilayer grating corresponding to the modeled multilayer grating from the spectroscopic metrology tool. In another illustrative embodiment, the controller determines values of the one or more parameters of the modeled multilayer grating providing a simulated spectroscopic signal corresponding to the measured spectroscopic signal within a selected tolerance. In another illustrative embodiment, the controller predicts a bandgap of the test layer of the fabricated multilayer grating based on the determined values of the one or more parameters of the test layer of the fabricated structure.

A bandgap quantification method is disclosed in accordance with one or more illustrative embodiments of the present disclosure. In one illustrative embodiment, the method includes generating a model of a metrology target, the metrology target including a multilayer grating formed from two or more layers, the model parameterized with one or more parameters associated with the multilayer grating in which the one or more parameters include geometric parameters associated with the multilayer grating and one or more dispersion parameters indicative of a dispersion of a test layer of the two or more layers. In another illustrative embodiment, the method includes measuring a spectroscopic signal of a fabricated multilayer grating corresponding to the modeled multilayer grating. In another illustrative embodiment, the method includes determining values of the one or more parameters of the modeled multilayer grating providing a simulated spectroscopic signal corresponding to the measured spectroscopic signal within a selected tolerance. In another illustrative embodiment, the method includes calculating a metrology metric for the metrology target indicative of a bandgap of the test layer of the fabricated multilayer grating based on the determined values of the one or more parameters.

A fabrication system is disclosed, in accordance with one or more illustrative embodiments of the present disclosure. In one illustrative embodiment, the system includes one or more process tools for fabricating multilayer gratings including two or more layers based on a process recipe. In another illustrative embodiment, the system includes a spectroscopic metrology tool to provide a spectroscopic signal indicative of the radiation emanating from a multilayer grating in response to incident illumination, the multilayer grating fabricated by the one or more process tools. In another illustrative embodiment, the system includes a controller communicatively coupled to the spectroscopic metrology tool and the one or more process tools. In another illustrative embodiment, the controller generates a model of a multilayer grating including two or more layers, the model including one or more parameters associated with multilayer grating in which the one or more parameters include geometric parameters indicative of a geometry of a test layer of the multilayer grating and one or more parameters include dispersion parameters indicative of a dispersion of the test layer. In another illustrative embodiment, the controller receives a spectroscopic signal of a fabricated multilayer grating corresponding to the modeled multilayer grating from the spectroscopic metrology tool, the fabricated multilayer grating fabricated by the one or more process tools based on a selected process recipe. In another illustrative embodiment, the controller determines values of the one or more parameters of the modeled multilayer grating providing a simulated spectroscopic signal corresponding to the measured spectroscopic signal within a selected tolerance. In another illustrative embodiment, the controller calculates a bandgap of the test layer of the fabricated multilayer grating based on the determined values of the one or more parameters of the test layer of the fabricated structure. In another illustrative embodiment, the controller adjusts the process recipe for the one or more process tools for fabricating multilayer gratings based on the predicted bandgap of the test layer.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and together with the general description, serve to explain the principles of the invention.

