Overlay alignment measurement of wafers
OwnerNoah Bareketinventor
Life of this patent
Estimating the term…
Abstract
The present invention is a new target, and associated apparatus and methods, for determining offset between adjacent layers of a semiconductor device. The target disclosed here includes a first periodic structure to be placed on a first layer of the device and a second periodic structure, that complements the first periodic structure, placed on a second layer of the device at a location that is adjacent the first periodic structure when the second layer is placed on the first layer. Any offset that may occur is detected by the present invention either optically, micro-mechanically or with electron beams using any of various methods and system embodiments.
Claims45
A target for use in measuring the relative position between two substantially coplanar layers of a device wherein a second layer of said two layers is located on a first layer of said two layers, said target comprising:
- a first periodic structure to be placed on said first layer of said device that is visible through said second layer;
- and
- a second periodic structure that complements said first periodic structure with said second periodic structure placed on said second layer of said device at a location that is adjacent said first periodic structure when said second layer is placed on said first layer with said first and second layers being in fixed position with respect to each other.
An apparatus to measure the relative position between two substantially coplanar layers of a device wherein a second layer of said two layers is located on a first layer of said two layers utilizing a target including a first periodic structure on said first layer of said device that is visible through said second layer and a second periodic structure that complements said first periodic structure with said second periodic structure on said second layer of said device at a location that is adjacent, and in a fixed position with respect to, said first periodic structure, said apparatus comprising:
- a optical scan head positioned relative to said device to gather optical data from said target, said optical scan head including:
- a light source to provide a light beam;
- a birefringent polarizing prism to receive said light beam from said light source and to split said light beam into first and second linearly and orthogonally polarized light beams, each of said first and second light beams having a selected angular deviation from the other of said first and second polarized light beam;
- a non-polarizing beam splitter to transmit said first and second polarized light beams from said birefringent polarizing prism to physically separated locations on said target, and to independently receive and selectively direct each of a first and a second reflected polarized light beam from said separate locations on said target wherein each of said first and second reflected polarized light beams corresponds to said first and second polarized light beams, respectively;
- and
- a detector positioned to independently receive each of said first and second reflected polarized light beams from said non-polarizing beam splitter to independently generate a first and a second electrical signal proportional to the intensity of the corresponding one of said first and second reflected polarized light beams;
- and
- a computing and control system coupled to said optical scan head and said device to provide movement therebetween to cause said first and second polarized light beams from said non-polarizing beam splitter to scan physically separated paths across said target, and coupled to said detector to receive said signals therefrom to calculate any offset between said first periodic structure and said second periodic structure of said target.
An apparatus to measure the relative position between two substantially coplanar layers of a device wherein a second layer of said two layers is located on a first layer of said two layers utilizing a target including a first periodic structure on said first layer of said device that is visible through said second layer and a second periodic structure that complements said first periodic structure with said second periodic structure on said second layer of said device at a location that is adjacent, and in a fixed position with respect to, said first periodic structure, said apparatus comprising:
- an optical scan head positioned relative to said device to gather optical data from said target, said optical scan head including:
- a light source to provide a light beam;
- a beam splitter to transmit said light beam from said light source to said target, and to receive and selectively direct a reflected light beam from said target wherein said reflected light beam corresponds to said light beam directed to said target;
- a mirror selectively rotatable about an axis wherein said axis has a selected angular relationship to a top surface of said device to reflect said light beam from said beam splitter to said target, and to direct said reflected light beam from said target to said beam splitter;
- a scan transducer coupled to said mirror to rotate said mirror about said axis through a selected angular range to cause said light beam to scan across said target in a selected scan path, and to position said axis of said mirror to select between two angular relationships between said axis and said top surface of said device to provide the capability to cause said light beam to scan through two physically separated scan paths each being related directly to said angular relationship between said axis of said mirror and said surface of said device;
- and
- a detector positioned to receive said reflected light beam from said beam splitter to generate an electrical signal proportional to the intensity of said reflected light beam;
- a memory coupled to said detector to store scan signals for comparison with later received scan signals produced when said axis of said mirror is in another position relative to said device to calculate any offset between said first and second periodic structures of said target;
- and
- a computing and control system coupled to said scan transducer to cause said light beam to scan across said target and to sequentially vary the angular relationship between said mirror axis and said surface of said device in two such angular relationships, and coupled to receive signals from said detector and said memory to calculate any offset between said first periodic structure and said second periodic structure of said target with two scan signals, one from each of said detector and said memory.
An apparatus to measure the relative position between two substantially coplanar layers of a device wherein a second layer of said two layers is located on a first layer of said two layers utilizing a target including a first periodic structure on said first layer of said device that is visible through said second layer and a second periodic structure that complements said first periodic structure with said second periodic structure on said second layer of said device at a location that is adjacent, and in a fixed position with respect to, said first periodic structure, said apparatus comprising:
- an optical scan head positioned relative to said device to gather optical data from said target, said optical scan head including:
- a light source to provide a light beam;
- a birefringent polarizing prism to receive said light beam from said light source and to split said light beam into first and second linearly and orthogonally polarized light beams, each of said first and second light beams having a selected angular deviation from the other;
- a non-polarizing beam splitter to transmit said first and second polarized light beams from said polarizing prism to physically separate locations on said target, and to independently receive and selectively direct each of a first and a second reflected polarized light beam from said target with each of said first and second reflected polarized light beams corresponding to said first and second polarized light beams, respectively;
- a selectively rotatable mirror to reflect each of said first and second polarized light beams from said non-polarizing beam splitter through a selected angle to said target, and to independently direct each of said first and second reflected light beams from said target to said non-polarizing beam splitter;
- a scan transducer coupled to said mirror to rotate said mirror through a selected range of angles to cause each of said first and second polarized light beams to scan across said target in two scan paths;
- a polarizing beam splitter to receive each of said first and second reflected polarized light beams directed thereto by said non-polarizing beam splitter, and to separate the paths of said first and second reflected polarized light beams by passing said first reflected polarized light beam therethrough and reflecting said second reflected polarized light beam into another path;
- a first detector positioned to receive said first reflected polarized light beam from said polarizing beam splitter to generate a first electrical signal proportional to the intensity of said first reflected polarized light beam;
- and
- a second detector positioned to receive said second reflected polarized light beam from said polarizing beam splitter to generate a second electrical signal proportional to the intensity of said second reflected polarized light beam;
- and
- a computing and control system coupled to said scan transducer to cause each of said first and second polarized light beams to scan across said target, and coupled to receive signals from said first and second detectors to calculate any offset between said first periodic structure and said second periodic structure of said target.
An apparatus to measure the relative position between two substantially coplanar layers of a device wherein a second layer of said two layers is located on a first layer of said two layers utilizing a target including a first periodic structure on said first layer of said device that is visible through said second layer and a second periodic structure that complements said first periodic structure with said second periodic structure on said second layer of said device at a location that is adjacent, and in a fixed position with respect to, said first periodic structure, said apparatus comprising:
- an optical scan head positioned relative to said device to gather optical data from said target, said optical scan head including:
- a light source to provide a light beam;
- an optical grating to receive said light beam from said light source and to split said light beam into first and second light beams with a selected angular deviation between said first and second light beams;
- a beam splitter to transmit said first and second light beams from said optical grating to physically separate locations on said target, and to receive and selectively direct each of a first and a second reflected light beam from said target wherein each of said first and second reflected light beams corresponds to said first and second light beams, respectively;
- and
- a detector positioned to independently receive said first and second reflected light beams from said beam splitter and to independently generate a first and a second electrical signal proportional to the intensity of the corresponding one of said first and second reflected light beams;
- and
- a computing and control system coupled to said optical scan head and said device to provide movement therebetween to cause said first and second light beams from said beam splitter to scan across said target, and coupled to said detector to receive said signals therefrom to calculate any offset between said first periodic structure and said second periodic structure of said target.
An apparatus to measure the relative position between two substantially coplanar layers of a device wherein a second layer of said two layers is located on a first layer of said two layers utilizing a target including a first periodic structure on said first layer of said device that is visible through said second layer and a second periodic structure that complements said first periodic structure with said second periodic structure on said second layer of said device at a location that is adjacent, and in a fixed position with respect to, said first periodic structure, said apparatus comprising:
- an optical scan head positioned relative to said device to gather optical data from said target, said optical scan head including:
- first and second light sources;
- a pulse generator coupled to each of said first and second light sources to alternately ignite each of said first and second light sources at a selected frequency to provide first and second light beams of substantially the same intensity 180.degree. out of phase from each other;
- a first beam splitter to which each of said first and second light beams from said first and second light sources, respectively, are directed to substantially the same point on opposite sides of said first beam splitter to separate said first and second light beams into separate paths with each directed to a different point on said target;
- a second beam splitter having a first and a second surface thereof, to receive on said first surface each of said first and second light beams from said first beam splitter at different points thereon to be transmitted therethrough toward said target, and to receive on, and reflect from, said second surface a first and a second reflected light beam reflected from said target in a selected direction wherein said first and second reflected light beams correspond to said first and second light beams, respectively;
- and
- a first detector positioned to alternately receive said first and second reflected light beams from said second surface of said second beam splitter and to alternately and independently generate a first and a second electrical signal proportional to the intensity of said first and second reflected light beams, respectively;
- and
- a computing and control system is coupled to said optical scan head and said device to provide movement therebetween to cause said first and second light beams from said second beam splitter to scan across said target in physically separated paths;
- and coupled to, and strobes at twice said selected frequency and synchronized with said selected frequency, said first detector to receive said signals therefrom to calculate any offset between said first periodic structure and said second periodic structure of said target.
An apparatus to measure the relative position between two substantially coplanar layers of a device wherein a second layer of said two layers is located on a first layer of said two layers utilizing a target including a first periodic structure on said first layer of said device that is visible through said second layer and a second periodic structure that complements said first periodic structure with said second periodic structure on said second layer of said device at a location that is adjacent, and in a fixed position with respect to, said first periodic structure, said apparatus comprising:
- an optical scan head positioned relative to said device to gather optical data from said target, said optical scan head including:
- a spectral multiplexed light source including a first and a second light source providing a first and a second light beam, respectively, each of a different wavelength and a same relative intensity;
- a first beam splitter having a first and a second side with each of said first and second light beams directed to substantially the same point on said first and second sides of said first beam splitter, respectively, to direct said first and second light beams into separate paths with each directed to different points on said target;
- a second beam splitter having a first and a second surface with said first surface receiving and transmitting therethrough each of said first and second light beams from said first beam splitter at different points thereon to physically separate locations on said target, and said second surface receiving and reflecting therefrom a first and a second reflected light beam from said target wherein said first and second reflected light beams correspond to said first and second light beams, respectively;
- a dichroic type beam splitter, being selected to pass light therethrough having a bandwidth that includes the wavelength of the light in said first light beam and excludes the wavelength of the light in said second light beam, positioned to receive said first and second reflected light beams from said second surface of said second beam splitter, to pass said first reflected light beam therethrough, and to reflect said second reflected light beam therefrom in a different direction;
- a first detector positioned to receive said first reflected light beam passed through said dichroic type beam splitter to generate a first electrical signal proportional to the intensity of said first reflected light beam from said target;
- and
- a second detector positioned to receive said second reflected light beam from said dichroic type beam splitter to generate a second electrical signal proportional to the intensity of said second reflected light beam from said target;
- and
- a computing and control system coupled to said optical scan head and said device to provide movement therebetween to cause said first and second light beams from said second beam splitter to scan across said target in physically separated paths, and coupled to said first and second detectors to receive said signals therefrom to calculate any offset between said first periodic structure and said second periodic structure of said target.
A method for measuring the relative position between two substantially coplanar layers of a device in a selected direction wherein a second layer of said two layers is located on a first layer of said two layers, said method comprising the steps of:
- a. placing a first periodic structure of a first target on said first layer of said device oriented to facilitate measurement of said relative position between said two layers in said selected direction;
- b. placing a second periodic structure of said first target on said second layer, wherein said second periodic structure complements said first periodic structure, at a location that is adjacent said first periodic structure and oriented similarly to the orientation of said first periodic structure in step a. to facilitate measurement of said relative position between said two layers in said selected direction with said first periodic structure being visible through said second layer, and said first and second periodic structures in a fixed relationship with respect to each other;
- c. scanning a radiation beam in a first path across portions of both said first and second periodic structures of steps a. and b.;
- d. scanning a radiation beam in a second path across portions of both said first and second periodic structures of steps a. and b. wherein said first and second paths are physically separated from each other;
- e. detecting radiation reflected from said first and second periodic structures in said first path as the scanning of step c. is performed;
- f. detecting radiation reflected from said first and second periodic structures in said second path as the scanning of step d. is performed;
- g. generating a first signal proportional to the intensity of the detected reflected radiation in step e.;
- h. generating a second signal proportional to the intensity of the detected reflected radiation in step f.;
- and
- i. calculating any offset between said first periodic structure and said second periodic structure of said first target from said signals generated in steps g. and h.
Dependencies are inferred from the claim text.