Abstract:
A method for photolithography in semiconductor device manufacturing comprises defining test critical dimension target for a photolithography mask, measuring a mask critical dimension, comparing mask critical dimension to the test critical dimension target and determining a critical dimension deviation, determining a photolithography light base energy in response to the critical dimension deviation, and exposing the wafer according to the photolithography light base energy.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of commonly assigned U.S. Provisional Application No. 60/669,524 entitled “A System and Method for Photolithography in Semiconductor Manufacturing” filed on Apr. 8, 2005, the entirety of which is hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     Since the inception of the semiconductor industry, photolithography has been used for forming the components of integrated circuits. Generally, light beams pass through a mask, which has been patterned with a magnified image of the relevant integrated circuits. The light beams are then focused by a projection lens onto a wafer, resulting in an image of the integrated circuits in the photoresist layer of the wafer. 
     Among other factors, mask defects constitute a source of yield reduction. Specifically, the deviation of the mask image will result in the imperfection of the image on the wafer. 
     Even though the defects of the mask image are detected during mask verification and validation, traditional approaches for wafer fabrication fail to take advantage of such information. As shown in  FIG. 1 , after a customer  2  completes the design of the integrated circuits, the design data may be stored in a tape and forwarded to a mask formation unit  4  for purposes of generating a corresponding mask. Then, the completed mask may be dispatched to a wafer fabrication unit  6  to be used for semiconductor integrated circuit fabrication. Because mask formation is often imperfect and causes deviation in mask dimensions, wen the wafer fabrication facility performs mask verification and validation, a trial-and-error process is often used, which results in wasted time, funds and energy. The resultant product cycle time for product verification and validation and time-to-market is prolonged. This problem is only aggravated by the shrinking device dimensions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  is a simplified diagram of selected components of a semiconductor manufacturing facility; 
         FIG. 2  is a simplified flowchart of an embodiment of a new method of photolithography; 
         FIG. 3  is a simplified flow diagram of selected components of a semiconductor manufacturing facility. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the following disclosure provides many different embodiments or examples for implementing different features of the disclosure. Specific examples of components and arrangements are described below. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. 
     In one embodiment, the present disclosure relies on the collaboration between the mask formation unit  4  and the wafer fabrication unit  6 . Instead of merely forwarding the completed mask to the wafer fabrication unit  6 , data indicating mask defects are also forwarded to the wafer fabrication unit  6 . As a result, prior to the first run of the exposure process, the wafer fabrication unit  6  may derive compensation energy based on the mask defects, and optimize the base energy accordingly. 
     Referring now to  FIG. 2 , shown therein is a simplified flowchart of an embodiment of a new photolithography method  10 . Referring also to  FIG. 3  for a simplified diagram of a data flow diagram. In step  12 , the wafer fabrication business unit  6  defines a test CD line pattern target width  32  for a particular mask and provides this target width to the mask formation business unit  4 . The mask formation business unit  4  makes the mask according to specifications from the customer and takes measurements of the mask test CD line width of the mask in step  13 . The measurement may be conducted by one or more metrology instruments and/or other methods known in the art. The resultant mask may include defects, which may be caused by erred design of mask patterns, flaws occurred during the pattern generation process, fabrication process, handling of the mask, and other defective manufacturing steps. In one example, during the fabrication of the mask, defects of the mask may be caused by bubbles, scratches, pits, fractures, and other factors. The wafer fabrication unit  6  transmits the test CD line target to the mask formation unit  4 . The transmission of this data may be done electronically such as using file transfer protocol (FTP), electronic mail, or another suitable way. A more formalized communication portal or interface may also be provided between the customer  2 , mask formation unit  4 , and wafer fabrication unit  6 . In step  14 , the measured line width is compared with the pre-defined mask CD line target width. In step  15 , a delta, delta_DOM, between the measured line width is compared with the pre-defined mask CD line target width is determined. 
     The mask that has been constructed as well as the delta width  34  are then supplied to the wafer fabrication business unit  6  in step  16 . The transmission of this data may be done electronically such as using file transfer protocol (FTP), electronic mail, or another suitable way. In step  17 , a compensation energy is calculated based on the delta width. The compensation energy is an amount to be applied to a base energy that is representative of the intensity of the photolithography light. Therefore, an adjustment or modulation of the base energy will vary the intensity of the light used in photolithography. In one embodiment, the calculation may include the following formula: compensation energy=ƒ(delta_DOM), wherein ƒ is a linear or nonlinear function. The function ƒ may be derived based on a variety of factors, such as the specific manufacturing technology, the mask layer, and/or a variety of other factors. Further, the function ƒ may be refined to achieve greater precision by several approaches, such as regressing the original formula in a polynomial form or other forms by a statistical tool, and/or using a greater collection data to refine the function as the manufacturing activity progresses. The function ƒ may also be determined by a number of methods, such as experiments, first data analysis, and/or other methods. For example, for the manufacturing of 0.15 μm logic devices, the function ƒ may be: compensation energy=33.83×delta —DOM− 2.0726. As noted above, the function ƒ is not fixed. For example, in another case, if delta_DOM is equal to about 0.002 um, the resulting compensation energy may be determined to be about 2.73426 mj. In step  18 , the base energy is adjusted by the amount of the compensation energy so that the wafer is exposed using the. adjusted base energy. The adjusted base energy may be equal to the sum of the original base energy and the compensation energy. Alternatively, the adjusted base energy may be equal to the difference between the original base energy and the compensation energy. The exposure may be accomplished by any methods know in the art, and may include dry lithography or wet lithography. In the case of wet lithography, the wavelength of the radiation may be 193 nm, 157 nm, and/or other figures. 
     The method  10  described above may be utilized in the manufacturing of a variety of semiconductor devices, such as memory devices (including but not limited to a static random access memory (SRAM)), logic devices (including but not limited to a metal-oxide semiconductor field-effect transistor (MOSFET)), and/or other devices. The transfer of various data may be performed via electronic transmissions such via electronic mail, web interface (Hypertext Transfer Protocol (HTTP) or Hypertext Transfer Protocol Secure (HTTPS)), File Transfer Protocol (FTP), Extensible Markup Language (XML), and/or any other suitable means now known or to be developed. 
     Many variations of the above example are contemplated herein. In one example, the mask formation unit  4  and the wafer fabrication unit  6  may belong to one business entity. In another example, deviation of the mask dimension delta_DOM may include any data relating to mask defects that may be used to adjust the lithography process other than or including the base energy. In another example, the mask formation unit  4  may simply forward data relating to the mask  24 , while the wafer fabrication unit  6  may compare the data with the original specification to determine the CD line width deviation or delta. Therefore, a variety of modifications are contemplated by the present disclosure. 
     Although only a few exemplary embodiments of this disclosure have been described in details above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this disclosure. Also, features illustrated and discussed above with respect to some embodiments can be combined with features illustrated and discussed above with respect to other embodiments. Accordingly, all such modifications are intended to be included within the scope of this disclosure.