Abstract:
Methods and structures for critical dimension or profile measurement are disclosed. The method provides a substrate having periodic openings therein. Material layers are formed in the openings, substantially planarizing a surface of the substrate. A scattering method is applied to the substrate with the material layers for critical dimension (CD) or profile measurement.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the fabrication of integrated circuit devices on semiconductor substrates and, more particularly relates to methods and structures for critical dimension (CD) or profile measurement. 
   2. Description of the Related Art 
   The Complementary Metal Oxide Semiconductor (CMOS) technology has been recognized as the leading technology for use in digital electronics in general and for use in many computer products in particular. The miniaturization of CMOS technology according to a scaling rule is used in a semiconductor device to achieve large-scale integration and high-speed operation. Due to minimization of integrated circuits, control of dimensions of devices becomes more important. In order to precisely control the dimensions of the devices, measurement for control dimension (CD) has been paid more attention during the process of manufacturing integrated circuits. 
     FIG. 1A  shows a prior art method for measuring critical dimension of (CD) of a structure. The prior art method first provides a substrate  100   a  with periodic trenches  110   a  therein. A scatterometry optical critical dimension (OCD) method is used to measure the dimension of the trenches  110   a . Light beams  120   a  arrive at the periodic trenches  110   a  and reflects so as to create a scattering spectrum. According to the scattering spectrum, the dimension of the trenches  110   a  can be measured. 
     FIG. 1B  shows a prior art method for measuring critical dimension of (CD) of another structure. The prior art method also provides a substrate  100   b  with periodic trenches  110   b  therein. Spacers  115  are formed on the sidewalls of the trenches  110   b . A scatterometry optical critical dimension (OCD) method is used to measure the dimension of the trenches  110   b  and the spacers  115 . Light beams  120   b  arrive at the periodic trenches  110   b  and reflects so as to create a scattering spectrum. According to the scattering spectrum, the dimension of the trenches  110   b  and the spacers  115  can be measured. 
   These prior art methods described above use a non-planarized grating structure for Scatterometry OCD measurement. 
   U.S. Patent Application No. 2004/0058460 A1 discloses scatterometry test structures stacked over same footprint area. The prior art describes a plurality of scatterometry test structures for use in process control during fabrication of a semiconductor wafer having multilevel integrated circuit chips. Many of said levels have a feature size of a critical dimension. The scatterometry test structures on the wafer are at each level, suitable to measure critical dimensions. The second level and each subsequent level of the test structures are located to fit into the same footprint area as the first level. This prior art method also uses a non-planarized grating structure for Scatterometry OCD measurement. After Scatterometry OCD measurement, the periodic pattern is planarized with a dielectric layer. 
   Accordingly, methods and structures for CD or profile measurement are desired in this industry. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a method for measuring critical dimension (CD) or profile of a structure. A substrate comprising periodic openings therein is provided. Material layers are formed in the openings, substantially planarizing a surface of the substrate. A scattering method is applied to the substrate with the material layers for CD or profile measurement. 
   The present invention also discloses a structure for critical dimension (CD) or profile of a structure. The structure comprises a substrate having periodic openings therein, and material layers formed in the openings substantially planarizing a surface of the substrate so as to measure dimensions of the structure by using a scattering method. 
   The present invention also discloses a structure for critical dimension (CD) or profile of a structure, which comprises a substrate having periodic trenches therein, and oxide layers formed in the trenches substantially planarizing a surface of the substrate so as to measure dimensions of the trenches by using a scatterometry optical critical dimension (OCD) method without a shielding layer formed over the trenches. 
   The above and other features of the present invention will be better understood from the following detailed description of the preferred embodiments of the invention that is provided in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  shows a prior art method for measuring critical dimension of (CD) of a structure. 
       FIG. 1B  shows a prior art method for measuring critical dimension of (CD) of another structure. 
       FIGS. 2A and 2B  are a series of schematic cross sectional diagrams illustrating an exemplary method for forming a structure for measuring critical dimension (CD) and profile of the structure. 
       FIGS. 3A and 3B  are a series of schematic cross sectional diagrams illustrating an exemplary method for forming another structure for measuring critical dimension (CD) and profile of the structure. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 2A and 2B  are a series of schematic cross sectional diagrams illustrating an exemplary method for forming a structure for measuring critical dimension (CD) and profile of the structure. 
     FIG. 2A  shows that periodic openings  210  are formed in a substrate  200 . The substrate  200  can be, for example, a silicon substrate, a III–V compound substrate, a glass substrate, a liquid crystal display (LCD) substrate or the other substrate similar to those described above. The openings  210  can be trenches, holes or any other periodic topographic structures. In this embodiment, the openings  210  are trenches which can be formed, for example, by a photolithographic process and an etch process. The depth of the openings  210  can be, for example, from about thousands of angstroms to about tens of thousands of angstroms. 
   Referring to  FIG. 2B , material layers  220  are formed in the openings  210  shown in  FIG. 2A  and substantially planarize the surface  203  of the substrate  200 . The material layers  220  can be a dielectric layer such as oxide, nitride or oxy-nitride. In this embodiment, the material layers  220  are oxide. The material layers  220  can be formed, for example, by forming a material (not shown) over the substrate  200 , filling the openings  210 . An etch-back process or chemical-mechanical polishing (CMP) process is used to remove the material above the surface  203  of the substrate  200 . 
   A scattering method is used to measure the dimension and profile of the structure, such as the depth, the top width and the bottom width of the openings  210 , the space between two neighboring openings  210 , or the other dimension. The scattering method can be, for example, a scatterometry optical critical dimension (OCD) method. Light beams  230  are polarized and arrive at the periodic structure area. Due to scattering phenomenon, a scattering spectrum is generated which varies with the dimension and profile of the structure. According to the scattering spectrum, the dimension and profile of the structure are thus measured. 
     FIGS. 3A and 3B  are a series of schematic cross sectional diagrams illustrating an exemplary method for forming another structure for measuring critical dimension (CD) and profile of the structure. 
     FIG. 3A  shows that periodic openings  310  are formed in a dielectric layer  305  which is formed on a substrate  300 . The substrate  300  is similar to the substrate  200  described in  FIG. 2A . Detailed descriptions are not repeated. The dielectric layer  305  can be, for example, oxide, nitride, oxy-nitride or other dielectric material. The dielectric layer  305  can be formed, for example, by chemical vapor deposition (CVD). The openings  310  can be, for example, contact holes, via holes, dual damascene profile patterns, trenches or other periodic topographic structures. In this embodiment, the openings  310  are dual damascene profile patterns. 
     FIG. 3B  shows that material layers  320  are formed in the openings  310  shown in  FIG. 3A  and substantially planarize the surface  303  of the substrate  300 . The material layers  320  can be a metal layer such as copper, aluminum-copper or tungsten. In this embodiment, the material layers  320  are copper. The material layers  320  can be formed, for example, by forming a copper layer (not shown) over the substrate  300 , filling the openings  310 . A chemical-mechanical polishing (CMP) process is used to remove the copper layer above the surface  203  of the substrate  200 . 
   A scattering method is used to measure the dimension and profile of the structure, such as the depth, the top width and the bottom width of the openings  310 , the space between two neighboring openings  310 , or the other dimension. In this embodiment, the scattering method is a scatterometry optical critical dimension (OCD) method. Light beams  330  are polarized and arrive at the periodic structure area. Due to scattering phenomenon, a scattering spectrum is generated which varies with the dimension and profile of the structure. According to the scattering spectrum, the dimension and profile of the structure are thus measured. 
   In these embodiments described above, no shielding layer is required to be formed over the material layers  210  and  310 . In some embodiments with stacked test structure, a shielding layer might be required to be disposed between the upper and the lower test structures so as to curb the interference resulting from the reflection of the light beams from the lower test structure. 
   Although the present invention has been described in terms of exemplary embodiment, it is not limit thereto. Rather, the appended claims should be constructed broadly to include other variants and embodiments of the invention which may be made by those skilled in the field of this art without departing from the scope and range of equivalents of the invention.