Generally, integrated circuits and other semiconductor devices are used in a variety of electronic applications, such as computers, cellular phones, personal computing devices, and many other applications. Home, industrial, and automotive devices, which in the past included only mechanical components, now have electronic parts that require semiconductor devices.
Semiconductor devices are manufactured by depositing many different types of material layers over a semiconductor workpiece or wafer, and patterning the various material layers using lithography. The material layers typically include thin films of conductive, semiconductive, and insulating materials that are patterned and etched to form integrated circuits (IC's). There may be a plurality of transistors, memory devices, switches, conductive lines, diodes, capacitors, logic circuits, and other electronic components formed on a single die or chip.
Lithography involves the transfer of an image of a mask to a material layer of a die or chip, also referred to as a wafer. The image is formed in a layer of photoresist, the photoresist is developed, and the photoresist is used as a mask during a process to alter the material layer, such as etching and patterning the material layer.
As feature sizes of semiconductor devices continue to decrease, as is the trend in the semiconductor industry, transferring patterns from a lithography mask to a material layer of a semiconductor device becomes more difficult, due to the effects of the light or energy used to expose the photoresist. A phenomenon referred to as the “proximity effect” results in the line width of patterns varying, depending the proximity of a feature to other features. Closely-spaced features tend to be smaller than widely-spaced features, although on a lithography mask they include the same dimensions. It is important in many semiconductor device designs for features to have uniform, predictable dimensions across a surface of a wafer to achieve the required device performance.
To compensate for the proximity effect, optical proximity corrections (OPC) are often made to lithography masks, which may involve adjusting the widths or lengths of the lines on the mask. More advanced methods of OPC correct corner rounding and a general loss of fidelity in the shape of features by adding small secondary patterns referred to as serifs to the corners of patterns. The serifs, together with line width changes, enhance the amount of light transmitted through the transparent mask patterns.
The OPC design phase is time-consuming, and therefore costly. Often, it is desirable to introduce a product as quickly as possible to the market in the semiconductor device industry. However, it may take up to two or three weeks for OPC calculations to be performed on a semiconductor device design.
As such, it is desirable to provide faster and more efficient methods of calculating and determining OPC for lithography masks used to fabricate semiconductor devices. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.
USPTO Backgrounds
USPTO Backgrounds