Abstract: A method for analyzing overlay errors in lithography is described. Interfield sampling and intrafield sampling are first conducted to sample multiple positions on each of the wafers, and then the overlay error value at each of the positions is measured. An overlay error model including coefficients of intrafield and interfield overlay errors of different types is used to fit the measured overlay error values with respect to the sampled positions. In the overlay error model, the intrafield overlay errors include intrafield translation, isotropic magnification, reticle rotation, asymmetric magnification and asymmetric rotation, and the interfield overlay errors include interfield translation, scale error, wafer rotation and orthogonality error.

Abstract: A method for analyzing overlay errors in lithography is described. Interfield sampling and intrafield sampling are first conducted to sample multiple positions on each of the wafers, and then the overlay error value at each of the positions is measured. An overlay error model including coefficients of intrafield and interfield overlay errors of different types is used to fit the measured overlay error values with respect to the sampled positions. In the overlay error model, the intrafield overlay errors include intrafield translation, isotropic magnification, reticle rotation, asymmetric magnification and asymmetric rotation, and the interfield overlay errors include interfield translation, scale error, wafer rotation and orthogonality error.

Abstract: A cooling system for a hot plate. The cooling system includes a plurality of pipelines inside the hot plate. Each pipeline has an inlet and an outlet. The inlet permits a cooling fluid to enter and the outlet permits the cooling fluid to leave. The cooling fluid running inside the pipelines picks up heat from the hot plate and carries away so that the hot plate is cooled.

Abstract: A method of fabricating a phase shift mask (PSM) is described. A patterned photoresist layer is formed on an opaque layer over a transparent plate. A thin mask layer is formed on the sidewalls of the patterned photoresist layer. The exposed opaque layer and transparent plate thereunder are then removed while using the patterned photoresist layer and mask layer as a mask. A phase shift opening is formed in the transparent plate, and thereby a phase shift layer is formed at the place where the phase shift opening is located. The patterned photoresist layer and the opaque layer thereunder are then removed to expose the transparent plate. The opaque layer under the mask layer can precisely self-align the phase shift layer to prevent alignment deviation caused by multiple lithography processes. The precision of the phase shift mask can be increased, and mask manufacture cost can be lowered.

Abstract: A method of fabricating a phase shift mask (PSM) is described. A patterned photoresist layer is formed on an opaque layer over a transparent plate. A thin mask layer is formed on the sidewalls of the patterned photoresist layer. The exposed opaque layer and transparent plate thereunder are then removed while using the patterned photoresist layer and mask layer as a mask. A phase shift opening is formed in the transparent plate, and thereby a phase shift layer is formed at the place where the phase shift opening is located. The patterned photoresist layer and the opaque layer thereunder are then removed to expose the transparent plate. The opaque layer under the mask layer can precisely self-align the phase shift layer to prevent alignment deviation caused by multiple lithography processes. The precision of the phase shift mask can be increased, and mask manufacture cost can be lowered.

Abstract: First of all, an adjusting step is performed to change a first optical parameter and a second optical parameter, so as to adjust the positions of two side-lobes of the main feature's exposure peak and overlap with the main feature's exposure peak and two side-lobes thereof, wherein the first optical parameter is the Numerical Aperture (NA) and the second optical parameter is the sigma(&sgr;). Afterward, a lithography process is performed by using a translucent mask to pattern the semiconductor devices, wherein the translucent mask can equalize the intensity of the main feature's exposure peak and the side-lobes thereof from each other. Therefore, this invention can reduce the pitch to decrease the critical dimension of the semiconductor devices.

Abstract: First of all, an adjusting step is performed to change a first optical parameter and a second optical parameter, so as to adjust the positions of two side-lobes of the main feature's exposure peak and overlap with the main feature's exposure peak and two side-lobes thereof, wherein the first optical parameter is the Numerical Aperture (NA) and the second optical parameter is the sigma(&sgr;). Afterward, a lithography process is performed by using a translucent mask to pattern the semiconductor devices, wherein the translucent mask can equalize the intensity of the main feature's exposure peak and the side-lobes thereof from each other. Therefore, this invention can reduce the pitch to decrease the critical dimension of the semiconductor devices.

Abstract: A method of forming a pattern according to a set of ROM codes in a photoresist layer is performed on a wafer coated with a photoresist layer. A projection lens is positioned atop a top surface of the wafer. An exposure light source having a pre-selected wavelength for generating a dipole exposure ray is provided. And a ROM code mask is positioned between the projection lens and the exposure light source. The ROM code mask has a plurality of ROM code openings arranged in a non-periodic manner and a plurality of assistant features arranged among the plurality of ROM code openings. The assistant features function as image enhancement elements that render a combined pattern consisting of the plurality of ROM code openings and the plurality of assistant features that are substantially periodic along an x-axis.

Abstract: A method for improving the resolution limits of a stepper is described. The region between the mask and the projection lens of the stepper is filled with a transparent material, wherein the reflection index of the transparent material is greater than one. Since the reflection index of the transparent material is greater than one, the diffracted angle of the diffracted light, formed after the parallel light from the light source passes through the mask, is reduced. A majority of the diffracted light can thus pass through the projection lens to improve the resolution limits of the stepper.

Abstract: A method for removing a photoresist layer on wafer edge is disclosed. The invention uses a light source located under a spin on coated wafer mounted on a supporting mean of a rotatable chuck to expose the photoresist material on the wafer edge. First of all, the spin on coated wafer is mounted on the supporting mean of the rotatable chuck. Then the rotatable chuck is rotated and the wafer is exposed to the light source. Finally, the wafer is developed.

Abstract: A method of transferring photomask patterns of a single photomask to a semiconductor wafer. The photomask patterns include at least a first pattern and a second pattern. The semiconductor wafer includes at least a photoresist layer positioned on the surface of the semiconductor wafer. A first exposure process is performed through the first pattern and the second pattern of the photomask to expose a first region and a second region in the photoresist layer, respectively. A second exposure process is then performed through the first pattern and the second pattern of the photomask in order to expose the second region and a third region in the photoresist layer, respectively. The combination of the first pattern and the second pattern in the second region in the photoresist layer is a latent pattern. Lastly, a development process is performed in order to transfer the latent pattern to the photoresist layer.

Abstract: A method for removing a photoresist layer on wafer edge is disclosed. The invention uses a light source located under a spin on coated wafer mounted on a supporting mean of a rotatable chuck to expose the photoresist material on the wafer edge. First of all, the spin on coated wafer is mounted on the supporting mean of the rotatable chuck. Then the rotatable chuck is rotated and the wafer is exposed to the light source. Finally, the wafer is developed.

Abstract: A cooling system for a hot plate. The cooling system includes a plurality of pipelines inside the hot plate. Each pipeline has an inlet and an outlet. The inlet permits a cooling fluid to enter and the outlet permits the cooling fluid to leave. The cooling fluid running inside the pipelines picks up heat from the hot plate and carries away so that the hot plate is cooled.