Abstract:
A method for forming a unit layout pattern includes: forming first through third active regions in the unit layout pattern, each of the first through third active regions aligning and extending along a length in a first direction and having a width in a second direction perpendicular to the first direction; forming first and second gate regions on the first and second active regions, the first and second gate regions electrically connected to each other; forming the first active region of a first conductive type within a second conductive type well region; forming the second active region of a second conductive type; and forming the third active region connected with the first and second gate regions to form a junction diode, the third active region being located between the first or the second active region and an end of the length in the first direction of the unit pattern.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application is a Continuation of and claims priority to U.S. patent application Ser. No. 13/364,362 filed on Feb. 2, 2012 which is a Divisional of U.S. patent application Ser. No. 12/047,071 filed on Mar. 12, 2008, which claims priority under 35 USC §119 to Korean Patent Application No. 10-2007-0030043, filed on Mar. 27, 2007 in the Korean Intellectual Property Office, the disclosure of each of which is incorporated herein in its entirety by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a layout method of a semiconductor device, and more particularly, to a layout method of junction diodes for preventing damage caused by plasma charge. 
     2. Description of the Related Art 
     Due to increasing demands for high integration, very small patterns, and high performance semiconductor devices, various plasma processes are typically required in fabricating the semiconductor devices. The various plasma processes can include a dry etching process, a thin film deposition process using a plasma-enhanced chemical vapor deposition (PE-CVD) process, an ashing process, and a blanket etchback process. The dry etching process is generally used in fabricating highly integrated semiconductor devices because the dry etching process has an advantage in that even very small patterns can be processed to have an anisotropic etch characteristic, in comparison with a conventional wet etching process. 
     However, when the plasma process is applied to fabricate a metal-oxide-semiconductor (MOS) transistor, unequal charge is accumulated in the dry etching process for forming a gate line and a wiring line, or in the ashing process for removing a photosensitive pattern. Accordingly, a gate insulating layer can be damaged (referred to as “plasma damage”) due to the plasma charge which migrates to both edge side walls and a surface of a conductive layer forming the gate line or the wiring line. A defect of the semiconductor device caused by the plasma damage is mainly found during use by a customer after sale, whereas other initial defects can be screened in advance of delivery to the customer. 
     To address the plasma damage problem, a method of disposing a junction diode on a gate pattern has been developed. In other words, by using an NP diode for an N-type metal-oxide-semiconductor (NMOS) transistor and a PN diode for a P-type metal-oxide-semiconductor (PMOS) transistor, the unequal charge caused by the plasma process flows toward a circuit board through the junction diode rather than accumulating in undesired locations. 
       FIG. 1  illustrates a conventional layout method of a junction diode  150  for minimizing plasma damage. Referring to  FIG. 1 , for example, the junction diode  150  for minimizing plasma damage is provided in addition to providing a P-type metal-oxide-semiconductor (PMOS) transistor  110  and an N-type metal-oxide-semiconductor (NMOS) transistor  130 , thereby forming an inverter circuit. A P-active layer  114   a  and a gate poly layer  116   a  included in the PMOS transistor  110  are disposed in an N-well layer  112 . Bit poly layers  122   a  surrounding a contact layer  120   a  are disposed on the P-active layer  114   a  included in the PMOS transistor  110 . One bit poly layer  122   a  on the P-active layer  114   a  connects with a metal layer  126   a  through a via layer  124   a . A power supply voltage (VINT) is applied to the metal layer  126   a . Another bit poly layer  122   a  on the P-active layer  114   a  connects with one bit poly layer  122   b  which is connected with an N-active layer  118   b  through a contact layer  120   b  which are included in the NMOS transistor  130 . The P-active layer  114   a  forms a P-type doped active region and the N-active layer  118   b  forms an N-type doped active region. 
     A metal layer  126   c  to which a well bias voltage (VINTW) is applied, connects with a bit poly layer  122   d  through a via layer  124   c  and the bit poly layer  122   d  connects with an N-active layer  118   a  through a contact layer  120   d . Thus, the N-active layer  118   a  forms a well guard ring in the N-well layer  112 . 
     The N-active layer  118   b  and a gate poly layer  116   b  are included in the NMOS transistor  130 . The bit poly layers  122   b  surrounding the contact layer  120   b  are disposed on the N-active layer  118   b . Another bit poly layer  122   b  on the N-active layer  118   b  connects with a metal layer  126   b  through a via layer  124   b  and then connects with a P-active layer  114   b  through a contact layer  120   e . A ground voltage (VSS) is applied to the metal layer  126   b . The P-active layer  114   b , to which the VSS is applied, forms a P-substrate bias. 
     The gate poly layers  116   a  and  116   b , respectively included in the PMOS transistor  110  and the NMOS transistor  130 , connect with a bit poly layer  122   c  through a contact layer  120   c . The bit poly layer  122   c  connects with an N-active layer  118   c  through a contact layer  120   f . The N-active layer  118   c  forms the NP junction diode  150  for preventing damage caused by plasma charge. 
       FIG. 2  illustrates an example wherein a dummy gate poly layer  116   c  is disposed in a region close to the gate poly layer  116   b  when the layout shown in  FIG. 1  is disposed uniformly on a substrate. The dummy gate poly layer  116   c  is used in order to reduce step coverage in a gate poly region when the layout is formed repeatedly. Referring to  FIG. 2 , the dummy gate poly layer  116   c  overlaps with the N-active layer  118   c  forming the junction diode  150  for preventing damage caused by plasma charge, and hereinafter, this overlapped region is defined as region “A”. Although region “A” is not a transistor according to design rules, the region “A” may be misrecognized as a transistor region. 
     Therefore, a layout method of the junction diode  150  for preventing damage caused by plasma charge is needed for the dummy gate poly layer  116   c  such that it does not overlap with the N-active layer  118   c , even though a unit layout is disposed uniformly on a substrate. 
     SUMMARY 
     The present invention provides a layout method of junction diodes for preventing damage caused by plasma charge. 
     According to an aspect of the present invention, there is provided a layout method for a unit layout pattern, the method including: forming an active layer so as to form a plurality of active regions in the unit layout pattern; forming a gate layer so as to form a plurality of gate regions on the active regions; forming a first conductive type doping region in at least one of the plurality of active regions which is within a well layer where a second conductive type well region is formed so as to form a first conductive type active region; forming a second conductive type doping region in at least one of the plurality of active regions which is outside of the second conductive type well region so as to form a second conductive type active region; and forming a second conductive type doping region which is connected with the gate regions so as to form a junction diode in at least one active region between the first and second conductive type active regions. 
     Accordingly, when laying out a unit layout pattern according to the layout method of the junction diode for preventing damage caused by plasma charge, a dummy gate poly is not required in order to reduce a step coverage in the gate poly region, since the gate poly region is disposed at regular intervals. Further, the width of the unit layout pattern is substantially equal to the widths of the NMOS and PMOS transistors. Therefore, a layout area can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  illustrates a conventional method of laying out a junction diode for preventing damage caused by plasma charge; 
         FIG. 2  illustrates an example where a dummy gate poly layer is disposed in order to reduce a step coverage in a gate poly region, in the layout method shown in  FIG. 1 ; 
         FIG. 3  illustrates a layout method of a junction diode for preventing damage caused by plasma charge according to an embodiment of the present invention; 
         FIG. 4  illustrates a layout method of a junction diode for preventing damage caused by plasma charge according to another embodiment of the present invention; 
         FIG. 5  illustrates a layout method of a junction diode for preventing damage caused by plasma charge according to another embodiment of the present invention; and 
         FIG. 6  illustrates a layout method of a junction diode for preventing damage caused by plasma charge according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The attached drawings for illustrating exemplary embodiments of the present invention are referred to in order to gain a sufficient understanding of the present invention, the merits thereof, and the objectives accomplished by implementation of the present invention. 
     Hereinafter, the present invention will be described in detail by explaining exemplary embodiments of the invention with reference to the attached drawings. Like reference numerals in the drawings denote like elements. 
       FIG. 3  illustrates a layout method of a junction diode for preventing damage caused by plasma charge according to an embodiment of the present invention. Referring to  FIG. 3 , a junction diode  350  for preventing damage caused by plasma charge is between gates of a P-type metal-oxide-semiconductor (PMOS) transistor  310  and an N-type metal-oxide-semiconductor (NMOS) transistor  330 . A P-active layer  314   a  and a gate poly layer  316   a  included in the PMOS transistor  310  are disposed in an N-well layer  312 . Bit poly layers  322   a  surrounding a contact layer  320   a  are disposed on the P-active layer  314   a . One bit poly layer  322   a  on the P-active layer  314   a  connects with a metal layer  326   a  through a via layer  324   a . An internal voltage (VINT) is applied to the metal layer  326   a . Another bit poly layer  322   a  on the P-active layer  314   a  connects with one bit poly layer  322   b  which is connected with an N-active layer  318   b  through a contact layer  320   b  which are included in the NMOS transistor  330 . 
     The N-active layer  318   b  and a gate poly layer  316   b  are included in the NMOS transistor  330 . The bit poly layers  322   b  surrounding the contact layer  320   b  are disposed on the N-active layer  318   b . Another bit poly layer  322   b  on the N-active layer  318   b  connects with a metal layer  326   b  through a via layer  324   b  and then connects with a P-active layer  314   b  through a contact layer  320   c . A ground voltage (VSS) is applied to the metal layer  326   b . The P-active layer  314   b , to which the VSS is applied, forms a P-substrate bias. 
     The junction diode  350  for preventing damage caused by plasma charge includes an N-active layer  318   c  forming an NP diode. The N-active layer  318   c  connects with a bit poly layer  322   c  through a contact layer  320   d . The bit poly layer  322   c  connects with the gate poly layer  316   a  in the PMOS transistor  310  and the gate poly layer  316   b  in the NMOS transistor  330  through contact layers  320   e . Thus, according to some embodiments, the junction diode  350  may be disposed between the NMOS transistor  330  and the PMOS transistor  310 . 
     A metal layer  326   c  to which a well bias internal voltage (VINTW) is applied, connects with a bit poly layer  322   d  through a via layer  324   c . The bit poly layer  322   d  connects with an N-active layer  318   a  through a contact layer  320   f  and thus the N-active layer  318   a  forms a well bias in the N-well layer  312 . 
     When laying out a unit layout pattern uniformly across a substrate, according to the layout method of the junction diode shown in  FIG. 3 , a gate poly region is disposed at regular intervals such that a dummy gate poly is not required to reduce step coverage in the gate poly region. Further, the widths of the N-active layer  318   a  and P-active layer  314   a  are substantially equal to the width of the unit layout pattern. Therefore, the layout method of the junction diode for preventing damage caused by plasma charge can reduce the layout area, in comparison to conventional methods. 
       FIG. 4  illustrates a layout method of a junction diode for preventing damage caused by plasma charge according to another embodiment of the present invention. Comparing the layout method shown in  FIG. 4  to that of  FIG. 3 , a PMOS transistor  410  and an NMOS transistor  430  are disposed close to each other and a junction diode  450  for preventing damage caused by plasma charge is disposed below the NMOS transistor  430 . Thus, according to some embodiments, the NMOS transistor  430  may be disposed between the junction diode  450  and the PMOS transistor  410 . 
       FIG. 5  illustrates a layout method of a junction diode for preventing damage caused by plasma charge according to another embodiment of the present invention. Referring to  FIG. 5 , a junction diode  550  for preventing damage caused by plasma charge is a PN diode, while the junction diode  350  for preventing damage caused by plasma charge is an NP diode in the layout shown in  FIG. 3 . In a structure for the junction diode  550  for preventing damage caused by plasma charge, the junction diode  550  connects with the bit poly layer  322   c  through the contact layer  320   e  connecting with the gate poly layer  316   a  in a PMOS transistor  510  and the gate poly layer  316   b  in an NMOS transistor  530 . The bit poly layer  322   c  connects with a P-active layer  314   c  through the contact layer  320   d . Thus, unlike conventional layout methods, the junction diode  550  is disposed between the NMOS transistor  530  and the PMOS transistor  510 . 
       FIG. 6  illustrates a layout method of a junction diode for preventing damage caused by plasma charge according to another embodiment of the present invention. Comparing the layout method shown in  FIG. 6  to that of  FIG. 5 , a PMOS transistor  610  and an NMOS transistor  630  are disposed close to each other and a junction diode  650  for preventing damage caused by plasma charge is disposed above the PMOS transistor  610 . Thus, unlike conventional layout methods, the PMOS transistor  610  is disposed between the junction diode  650  and the NMOS transistor  630 . 
     According to an aspect of the present invention, there is provided a layout method for forming a unit layout pattern, the method including: forming an active layer so as to form a plurality of active regions in the unit layout pattern; forming a gate layer so as to form a plurality of gate regions on the active regions; forming a first conductive type doping region in at least one of the plurality of active regions within a well layer where a second conductive type well region is formed so as to form a first conductive type active region; forming a second conductive type doping region in at least one of the plurality of active regions outside of the second conductive type well region so as to form a second conductive type active region; and forming a second conductive type doping region connected with the gate regions so as to form a junction diode in at least one active region between the first and second conductive type active regions, wherein a width of the first and second conductive type active regions is substantially equal to a width of the unit layout pattern. 
     The layout method may further include the operation of forming a first conductive type doping region so as to form a well guard ring region in at least one of the plurality of active regions within the second conductive type well region at an edge of the unit layout pattern. 
     The first and second conductive type active regions may form a source region and a drain region, respectively, of a metal-oxide-semiconductor (MOS) transistor. 
     According to another aspect of the present invention, there is provided a layout method for forming a unit layout pattern, the method including; forming an active layer so as to form a plurality of active regions in the unit layout pattern; forming a gate layer so as to form a plurality of gate regions on the active regions; forming a first conductive type doping region in at least one of the plurality of active regions within a well layer where a second conductive type well region is formed so as to form a first conductive type active region; forming a second conductive type doping region in at least one of the plurality of active regions outside of the second conductive type well region so as to form a second conductive type active region; and disposing a second conductive type doping region connected with the gate region so as to form a junction diode in at least one active region disposed below the second conductive type active region, wherein a width of the first and second conductive type active regions is substantially equal to a width of the unit layout pattern. 
     According to another aspect of the present invention, there is provided a layout method for forming a unit layout pattern, the method including: forming an active layer so as to form a plurality of active regions in the unit layout pattern; forming a gate layer so as to form a plurality of gate regions on the active regions; forming a first conductive type doping region in at least one of the plurality of active regions within a well layer where a second conductive type well region is formed so as to form a first conductive type active region; forming a second conductive type doping region in at least one of the plurality of active regions outside of the second conductive type well region so as to form a second conductive type active region; and forming a first conductive type doping region connected with the gate regions so as to form a junction diode in at least one active region within the second conductive type well region between the first and second conductive type active regions, wherein a width of the first and second conductive type active regions is substantially equal to a width of the unit layout pattern. 
     According to another aspect of the present invention, there is provided a layout method for forming a unit layout pattern, the method including: forming an active layer so as to form a plurality of active regions in the unit layout pattern; forming a gate layer so as to form a plurality of gate regions on the active regions; forming a first conductive type doping region in at least one of the plurality of active regions within a well layer where a second conductive type well region is formed so as to form a first conductive type active region; forming a second conductive type doping region in at least one of the plurality of active regions outside of the second conductive type well region so as to form a second conductive type active region; and forming a first conductive type doping region connected with the gate region so as to form a junction diode in at least one active region disposed above the first conductive type active region within the second conductive type well region, wherein a width of the first and second conductive type active regions is substantially equal to a width of the unit layout pattern. 
     Accordingly, when laying out a unit layout pattern uniformly across a substrate, according to the layout method of the junction diode for preventing damage caused by plasma charge, a dummy gate poly is not required to reduce a step coverage in the gate poly region, since the gate poly region is disposed at regular intervals. Further, the width of the unit layout pattern is substantially equal to the widths of the NMOS and PMOS transistors. Therefore, a layout area can be reduced. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.