Applied Materials, Inc.

Kla Tencor Corporation

Kla-Tencor Technologies Corporation

Bo Su

Gaurav Verma

Kevin P Fairbairn

Rui-Fang Shi

Mircea Dusa

Carl Hess

Scott A Andrews

William Volk

Harold William Lehon

Hong Du

Zoe Osborne

Computer-implemented methods and systems for determining different process windows for a wafer printing process for different reticle designs are provided. One method includes generating simulated images illustrating how each of the different reticle designs will be printed on a wafer at different values of one or more parameters of the wafer printing process. The method also includes detecting defects in each of the different reticle designs using the simulated images. In addition, the method includes determining a process window for the wafer printing process for each of the different reticle designs based on results of the detecting step.

Computer-implemented methods and systems for determining different process windows for a wafer printing process for different reticle designs

Computer-implemented methods, systems, and computer-readable media for determining a model for predicting printability of reticle features on a wafer are provided. One method includes generating simulated images of the reticle features printed on the wafer using different generated models for a set of different values of exposure conditions. The method also includes determining one or more characteristics of the reticle features of the simulated images. In addition, the method includes comparing the one or more characteristics of the reticle features of the simulated images to one or more characteristics of the reticle features printed on the wafer using a lithography process. The method further includes selecting one of the different generated models as the model to be used for predicting the printability of the reticle features based on results of the comparing step.

Computer-implemented methods, systems, and computer-readable media for determining a model for predicting printability of reticle features on a wafer

A method and apparatus for processing a semiconductor wafer to reduce CD variation feeds back information gathered during inspection of the wafer to a previously visited processing tool and feeds forward information to adjust the next process the wafer will undergo. The inspection and processing are performed at a single processing module without exposing the wafer to ambient atmospheric conditions. Embodiments include removing a wafer from a wafer cassette, and measuring a dimension of a feature on the surface of the wafer, such as the feature's CD using an optical measuring tool. A process, such as an etch process, is then performed on the wafer using a set of process parameter values, such as an etch recipe, selected based on the CD measurement, and the wafer is returned to a cassette. The CD measurements are also linked to photolithography adjustable parameters such as stepper focus and exposure settings. The linked information on focus and exposure is fed back to the previously visited photo cell so the stepper can be adjusted, either automatically or at the user's discretion, to correct the deviation in following lots. In some embodiments, post-etch processing, such as ash stripping, wet cleaning and/or further CD measurement, are performed by the module before the wafer is returned to a cassette. All of the transfer and processing steps performed by the module are performed in a clean environment, thereby increasing yield by avoiding exposing the wafer to the atmosphere and possible contamination between steps. This feedback and feed-forward mechanism improves CD control by adjusting processing parameters for every wafer based on the wafer's measured CD.

Semiconductor processing module with integrated feedback/feed forward metrology

In a process for measuring the CD of a mask pattern transferred to a semiconductor wafer, in which a series of dies are sequentially inspected by first locating a target area on the die and then vectoring to a CD measurement area, a technique is used whereby the stored image of an alignment target is used for pattern recognition in the process of acquiring each subsequent die's target. The stored image is updated with each new die inspected, using an image of the most recently acquired target area. In this manner, the stored target image always closely approximates the next target to be acquired. Thus, according to the invention, difficulties in recognizing and centering on the target are minimized, and CD measurements of much higher reliability can be effected.

Target acquisition technique for CD measurement machine

A method for monitoring the focus-exposure settings of a stepper in a photolithography process is disclosed. A golden image of the target is stored in the CD-SEM. Then, during the FEM measurements, the target of each die is compared to the golden image, and a PR score is stored. Thus, a matrix, or a look-up table, is constructed which provides a PR score for each die with respect to the golden image. Then, during a line monitoring, when a target image is obtained it is compared to the golden image and a PR score is obtained. If the measured CD turns out to be out of bound, the PR score is checked against the PR matrix of the FEM to see the focus-exposure parameters that resulted in such a PR score. Such a matching would indicate the actual drift of the focus or exposure of the stepper.

Photolithography monitoring using a golden image

A method and apparatus for reducing lot to lot CD variation in semiconductor wafer processing feeds back information gathered during inspection of a wafer, such as after photoresist application, exposure and development, to upcoming lots that will be going through the photolithography process, and feeds forward information to adjust the next process the inspected wafer will undergo (e.g., the etch process). Embodiments include forming a feature such as an etch mask on a semiconductor wafer at a &ldquo;photo cell&rdquo; by a photolithography process, then conventionally imaging the feature with a CD-SEM to measure its CD and other sensitive parameters. The measured parameters are linked, via the feature's SEM waveform, to photolithography adjustable parameters such as stepper focus and exposure settings. If the measured parameters deviate from design dimensions, the linked information on focus and exposure is fed back to the photo cell so the stepper can be adjusted, either automatically or at the user's discretion, to correct the deviation in following lots. The measured parameters are also linked to etch process adjustable parameters such as etch recipes for different over-etch and/or etch chemistry. If the measured parameters deviate from desired values, a linked etch recipe to correct the error is fed forward to the etcher and implemented automatically or at the user's discretion. This feedback and feed-forward mechanism improves lot to lot CD control at inspection following photoresist development and at final inspection as well.

Integrated critical dimension control for semiconductor device manufacturing

A method and apparatus is provided for inspecting a semiconductor wafer for field-to-field critical dimension (CD) variations using statistical techniques, such that an optimal number of fields on the wafer under inspection are measured, thereby increasing the accuracy of the results of the inspection procedure and avoiding unnecessary sampling. Embodiments include randomly selecting a predetermined number of fields on a semiconductor wafer to be inspected, and measuring the CD of a comparable feature in each of the sample fields, as by a critical dimension scanning electron microscope (CD-SEM). A statistical function, such as an average or standard deviation, of the measured CDs is calculated. Further fields are the randomly selected, CDs measured, and the running average or standard deviation calculated after each CD is measured. If the last acquired CD does not change the average or standard deviation by a predetermined amount, the inspection procedure for the wafer under inspection is terminated. Otherwise, the random field sampling, CD measurement and running average or standard deviation calculation continues. Because the number of fields to be sampled is not fixed, sampling continues as necessary without oversampling or undersampling, thereby obtaining statistically accurate results and increasing production throughput.

Automatic field sampling for CD measurement

A method and apparatus for inspecting a feature formed on the surface of a semiconductor wafer predicts the profile of the feature and pinpoints the stepper settings of the inspected feature by inspecting the feature using standard SEM imaging techniques. Embodiments include forming and SEM-imaging a plurality of reference features, comparable to the target feature to be inspected, on a reference semiconductor wafer, each of the reference features associated with a known profile and stepper setting. The reference SEM waveform associated with an optimal profile is selected as a golden waveform, then a waveform corresponding to the target feature is compared with the golden waveform. If the target waveform does not substantially match the golden waveform, the reference waveform which most closely matches the target waveform is identified, to determine the profile and stepper settings of the target feature. The difference between the golden waveform stepper setting and the target feature stepper setting is then determined. Thus, the profile and stepper settings of the inspected feature are pinpointed, thereby facilitating investigation of the causes of feature defects or variations from optimal dimensions and enabling effective corrective action to be implemented.

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San Jose, CA, United States of America

Bo Su