1. A phase change memory device comprising:
a semiconductor substrate provided with a switching device;
a lower electrode contact formed over the switching device, the lower electrode contact having a specific resistance which gradually increases from a lower part to an upper part of the lower electrode contact; and
a phase change pattern layer formed over the lower electrode contact.
2. The phase change memory device of claim 1, wherein the lower electrode contact includes:
a crystalline conductive layer formed over the switching device; and
an amorphous conductive layer formed over the crystalline conductive layer.
3. The phase change memory device of claim 2, wherein the crystalline and amorphous conductive layers each comprise an SEG (Selective Epitaxial Growth) layer.
4. The phase change memory device of claim 2, wherein the crystalline conductive layer is thicker than the amorphous conductive layer.
5. The phase change memory device of claim 1, wherein the lower electrode contact includes:
a first SEG (Selective Epitaxial Growth) layer formed over the switching device, the first SEG layer having conductive impurities at a first density; and
a second SEG layer formed over the first SEG layer, wherein the second SEG layer has conductive impurities at a second density such that the second density is less than the first density.
6. The phase change memory device of claim 5, wherein the conductive impurities are p-type impurities.
7. The phase change memory device of claim 5, wherein the second SEG layer is undoped and only has intrinsic levels of conductive impurities.
8. The phase change memory device of claim 5, wherein the first SEG layer is thicker than the second SEG layer.
9. The phase change memory device of claim 1, wherein the lower electrode contact comprises:
a germanium-rich SiGe SEG (Selective Epitaxial Growth) layer formed over the switching device wherein the germanium-rich SiGe SEG layer comprises a SixGe(1-x) stoichiometric ratio where x<0.45; and
a silicon-rich SiGe SEG layer formed over the germanium-rich SiGe SEG wherein the silicon-rich SiGe SEG layer comprises a SixGe(1-x) stoichiometric ratio where x>0.55.
10. The phase change memory device of claim 9, further comprising a normal SiGe SEG layer formed over the silicon-rich SiGe SEG layer, wherein the normal SiGe SEG layer having a stoichiometric ratio of SixGe1-x where x is between 0.45 and 0.55.
11. The phase change memory device of claim 1, wherein the lower electrode contact comprises:
a SiGe SEG (Selective Epitaxial Growth) layer formed over the switching device; and
a Si SEG layer formed over the SiGe SEG layer.
12. A method for manufacturing a phase change memory device, the method comprising:
forming a first interlayer dielectric layer over a semiconductor substrate in which the semiconductor includes a switching device;
forming a second interlayer dielectric layer having a lower electrode contact hole over the first interlayer dielectric layer;
forming a lower electrode contact within the contact hole, wherein the lower electrode contact has a specific resistance that increases from a lower part of the lower electrode contact to an upper part of the lower electrode contact; and
forming a phase change pattern over the lower electrode contact.
13. The method of claim 12, wherein the forming of the lower electrode contact includes forming a SiGe layer such that the specific resistance of the lower electrode contact increases from the lower part to the upper part of the lower electrode contact.
14. The method of claim 12, wherein the forming of the lower electrode contact includes:
forming a crystalline SEG layer within a lower portion of the contact hole; and
forming an amorphous SEG layer over the crystalline SEG layer.
15. The method of claim 12, wherein the forming of the lower electrode contact includes:
growing a lower SEG layer in a temperature range about 500\xb0 C. to about 650\xb0 C. to fill in the lower portion of the contact hole with the SEG layer; and
growing an upper SEG layer in a temperature range of about 650\xb0 C. to about 700\xb0 C. to fill in an upper portion of the contact hole with the SEG layer.
16. The method of claim 12, wherein, when the lower electrode contact is formed, an amount of dangling bond source gas is gradually decreased.
17. The method of claim 12, wherein the forming of the lower electrode contact includes:
forming a first SEG layer within the contact hole, the first SEG layer comprises conductive impurities at a first density; and
forming a second SEG layer over the first SEG layer, the second SEG layer comprises conductive impurities at a second density which is less than the first density.
18. The method of claim 17, wherein the second SEG layer is an undoped SEG layer.
19. The method of claim 12, wherein the forming of the lower electrode contact includes:
forming a germanium-rich SiGe SEG layer within a lower portion of the contact hole wherein the germanium-rich SiGe SEG layer comprises a SixGe(1-x) stoichiometric ratio where x<0.45; and
forming a silicon-rich SiGe SEG layer over the germanium-rich SiGe SEG layer wherein the silicon-rich SiGe SEG layer comprises a SixGe(1-x) stoichiometric ratio where x>0.55.
20. The method of claim 19, further comprising forming a normal SiGe SEG layer over the silicon-rich SiGe SEG layer, wherein the normal SiGe SEG layer comprises a SixGe(1-x) stoichiometric ratio where 0.45<x<0.55.
21. The method of claim 12, wherein the forming of the lower electrode contact includes:
forming a SiGe SEG layer in a lower portion of the contact hole; and
forming a Si SEG layer over the SiGe SEG layer.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A measuring method of internal information of a scattering medium, comprising:
a light injecting step of injecting pulsed light of two or more predetermined wavelengths into a scattering medium at a light injection position;
a light detecting step of detecting the light of said two or more predetermined wavelengths having propagated inside said scattering medium, at a photodetection position to acquire a photodetection signal;
a signal processing step of acquiring waveform data indicating a temporal change of intensity of the detected light, based on said photodetection signal;
a mean pathlength and variance computing step of performing an operation to compute a mean pathlength of plural photons composing said detected light, and a variance, based on said waveform data; and
an absorption coefficient difference calculating step of calculating a difference between absorption coefficients at said predetermined wavelengths, based on a predetermined relation holding among said mean pathlength, said variance, and the difference between the absorption coefficients at said two or more predetermined wavelengths.
2. A measuring method of internal information of a scattering medium according to claim 1, wherein said absorption coefficient difference calculating step comprises a step of further calculating a concentration of an absorber, based on said difference between the absorption coefficients at said two or more predetermined wavelengths and a difference between extinction coefficients of the absorber thereat.
3. A measuring method of internal information of a scattering medium according to claim 1, wherein said operation carried out in said mean pathlength and variance computing step is an operation executed using a mean pathlength and a variance of said photodetection signal and a mean pathlength and a variance of an instrumental function.
4. A measuring method of internal information of a scattering medium according to claim 1, wherein said predetermined relation used in said absorption coefficient difference calculating step is a relation among said mean pathlength, said variance, and said difference between the absorption coefficients at said two or more predetermined wavelengths derived from the Microscopic Beer-Lambert law.
5. A measuring method of internal information of a scattering medium according to claim 1, wherein said pulsed light used in said light injecting step is said pulsed light of said predetermined wavelengths of n1 kinds (where n is an integer not less than 1), said photodetection signal detected in said light detecting step is said photodetection signals of n1 kinds,
said waveform data acquired in said signal processing step is said waveform data of n1 kinds,
said mean pathlength and said variance computed in said mean pathlength and variance computing step are said mean pathlengths and said variances of n1 kinds, and
said difference between the absorption coefficients calculated in said absorption coefficient difference calculating step is said differences of n kinds between the absorption coefficients at said predetermined wavelengths of n1 kinds.
6. A measuring method of internal information of a scattering medium according to claim 5, wherein said absorption coefficient difference calculating step comprises a step of further calculating concentrations of absorbers of n kinds, based on said differences of n kinds between the absorption coefficients at said predetermined wavelengths of n1 kinds and differences between extinction coefficients of the absorbers of n kinds thereat.
7. A measuring method of internal information of a scattering medium, comprising:
a light injecting step of injecting modulated light of two or more predetermined wavelengths modulated at a predetermined frequency, into a scattering medium at a light injection position;
a light detecting step of detecting said light of said two or more predetermined wavelengths having propagated inside said scattering medium, at a photodetection position to acquire a photodetection signal;
a signal processing step of extracting a signal of said predetermined frequency component from said photodetection signal;
a group delay and second-partial-derivative-of-logarithm-of-amplitude computing step of computing a group delay of the signal of said predetermined frequency component and a second partial derivative of logarithm of amplitude with respect to the modulation frequency, based on said signal of the predetermined frequency component; and
an absorption coefficient difference calculating step of calculating a difference between absorption coefficients at said predetermined wavelengths, based on a predetermined relation holding among said group delay, said second partial derivative of logarithm of amplitude with respect to the modulation frequency, and the difference between the absorption coefficients at said two or more predetermined wavelengths.
8. A measuring method of internal information of a scattering medium according to claim 7, wherein said absorption coefficient difference calculating step comprises a step of further calculating a concentration of an absorber, based on said difference between the absorption coefficients at said two or more predetermined wavelengths and a difference between extinction coefficients of the absorber thereat.
9. A measuring method of internal information of a scattering medium according to claim 7, wherein said predetermined relation used in said absorption coefficient difference calculating step is a relation among said group delay, said second partial derivative of logarithm of amplitude with respect to the modulation frequency, and the difference between the absorption coefficients at said two or more predetermined wavelengths derived from the Microscopic Beer-Lambert law.
10. A measuring method of internal information of a scattering medium according to claim 7, wherein said modulated light used in said light injecting step is said modulated light of said predetermined wavelengths of n1 kinds (where n is an integer not less than 1),
said photodetection signal detected in said light detecting step is said photodetection signals of n1 kinds,
said signal of the predetermined frequency component extracted in said signal processing step is said signals of predetermined frequency components of n 1 kinds,
said group delay and said second partial derivative of logarithm of amplitude with respect to the modulation frequency computed in said group delay and second-partial-derivative-of-logarithm-of-amplitude computing step are said group delays and said second partial derivatives of logarithm of amplitude with respect to the modulation frequency of n1 kinds, and
said difference between the absorption coefficients calculated in said absorption coefficient difference calculating step is said differences of n kinds between the absorption coefficients at said predetermined wavelengths of n1 kinds.
11. A measuring method of internal information of a scattering medium according to claim 10, wherein said absorption coefficient difference calculating step comprises a step of further calculating concentrations of absorbers of n kinds, based on said differences of n kinds between the absorption coefficients at said predetermined wavelengths of n1 kinds and differences between extinction coefficients of the absorbers of n kinds thereat.
12. A measuring apparatus of internal information of a scattering medium, comprising:
light injecting means for injecting pulsed light of two or more predetermined wavelengths into a scattering medium at a light injection position;
light detecting means for detecting the light of said two or more predetermined wavelengths having propagated inside said scattering medium, at a photodetection position to acquire a photodetection signal;
signal processing means for acquiring waveform data indicating a temporal change of intensity of the detected light, based on said photodetection signal;
mean pathlength and variance computing means for performing an operation to compute a mean pathlength of plural photons composing said detected light, and a variance, based on said waveform data; and
absorption coefficient difference calculating means for calculating a difference between absorption coefficients at said predetermined wavelengths, based on a predetermined relation holding among said mean pathlength, said variance, and the difference between the absorption coefficients at said two or more predetermined wavelengths.
13. A measuring apparatus of internal information of a scattering medium according to claim 12, wherein said absorption coefficient difference calculating means further calculates a concentration of an absorber, based on said difference between the absorption coefficients at said two or more predetermined wavelengths and a difference between extinction coefficients of the absorber thereat.
14. A measuring apparatus of internal information of a scattering medium according to claim 12, wherein said operation carried out by said mean pathlength and variance computing means is an operation executed using a mean pathlength and a variance of said photodetection signal and a mean pathlength and a variance of an instrumental function.
15. A measuring apparatus of internal information of a scattering medium according to claim 12, wherein said predetermined relation used in said absorption coefficient difference calculating means is a relation among said mean pathlength, said variance, and said difference between the absorption coefficients at said two or more predetermined wavelengths derived from the Microscopic Beer-Lambert law.
16. A measuring apparatus of internal information of a scattering medium according to claim 12, wherein said pulsed light used in said light injecting means is said pulsed light of said predetermined wavelengths of n1 kinds (where n is an integer not less than 1),
said photodetection signal detected by said light detecting means is said photodetection signals of n1 kinds,
said waveform data acquired by said signal processing means is said waveform data of n1 kinds,
said mean pathlength and said variance computed by said mean pathlength and variance computing means are said mean pathlengths and said variances of n1 kinds, and
said difference between the absorption coefficients calculated by said absorption coefficient difference calculating means is said differences of n kinds between the absorption coefficients at said predetermined wavelengths of n1 kinds.
17. A measuring apparatus of internal information of a scattering medium according to claim 16, wherein said absorption coefficient difference calculating means further calculates concentrations of absorbers of n kinds, based on said differences of n kinds between the absorption coefficients at said predetermined wavelengths of n1 kinds and differences between extinction coefficients of the absorbers of n kinds thereat.
18. A measuring apparatus of internal information of a scattering medium, comprising:
light injecting means for injecting modulated light of two or more predetermined wavelengths modulated at a predetermined frequency, into a scattering medium at a light injection position;
light detecting means for detecting said light of said two or more predetermined wavelengths having propagated inside said scattering medium, at a photodetection position to acquire a photodetection signal;
signal processing means for extracting a signal of said predetermined frequency component from said photodetection signal;
group delay and second-partial-derivative-of-logarithm-of-amplitude computing means for computing a group delay of the signal of said predetermined frequency component and a second partial derivative of logarithm of amplitude with respect to the modulation frequency, based on said signal of the predetermined frequency component; and
absorption coefficient difference calculating means for calculating a difference between absorption coefficients at said predetermined wavelengths, based on a predetermined relation holding among said group delay, said second partial derivative of logarithm of amplitude with respect to the modulation frequency, and the difference between the absorption coefficients at said two or more predetermined wavelengths.
19. A measuring apparatus of internal information of a scattering medium according to claim 18, wherein said absorption coefficient difference calculating means further calculates a concentration of an absorber, based on said difference between the absorption coefficients at said two or more predetermined wavelengths and a difference between extinction coefficients of the absorber thereat.
20. A measuring apparatus of internal information of a scattering medium according to claim 18, wherein said predetermined relation used in said absorption coefficient difference calculating means is a relation among said group delay, said second partial derivative of logarithm of amplitude with respect to the modulation frequency, and the difference between the absorption coefficients at said two or more predetermined wavelengths derived from the Microscopic Beer-Lambert law.
21. A measuring apparatus of internal information of a scattering medium according to claim 18, wherein said modulated light used in said light injecting means is said modulated light of said predetermined wavelengths of n1 kinds (where n is an integer not less than 1),
said photodetection signal detected by said light detecting means is said photodetection signals of n1 kinds,
said signal of the predetermined frequency component extracted by said signal processing means is said signals of predetermined frequency components of n 1 kinds,
said group delay and said second partial derivative of logarithm of amplitude with respect to the modulation frequency computed by said group delay and second-partial-derivative-of-logarithm-of-amplitude computing means are said group delays and said second partial derivatives of logarithm of amplitude with respect to the modulation frequency of n1 kinds, and said difference between the absorption coefficients calculated by said absorption coefficient difference calculating means is said differences of n kinds between the absorption coefficients at said predetermined wavelengths of n1 kinds.
22. A measuring apparatus of internal information of a scattering medium according to claim 21, wherein said absorption coefficient difference calculating means further calculates concentrations of absorbers of n kinds, based on said differences of n kinds between the absorption coefficients at said predetermined wavelengths of n1 kinds and differences between extinction coefficients of the absorbers of n kinds thereat.