Phase-change memory cell
The memory cell includes a memory area which is formed in a phase-change material pattern based on chalcogenide. An electric p/n-type junction is series-connected between electrodes. The p/n junction is formed in a crystalline area by the interface between first and second doped areas of the phase-change material pattern. The memory area is formed in one of the two doped areas, at a distance from the junction.
1. A memory cell comprising:
a first pattern made of a first phase-change material of a first conductivity type, the first pattern having a first thermal resistance value,
a second pattern made of a second phase-change material of a second conductivity type, the second pattern having a second thermal resistance value,
an electric p/n-type junction located between two electrodes, and formed at the interface between the first and second patterns, in an area where both patterns are polycrystalline,
a heating element connected to the first pattern, the heating element being separated from the second pattern by the first pattern, the heating element having a third thermal resistance value, the ratio of the third thermal resistance to the sum of the first and second thermal resistances ranging between 0.9 and 1.1,
a phase-change memory area formed in contact with the heating element in a portion of the first pattern.
2. Memory cell according to claim 1 , wherein the first pattern and the second pattern are made of the same phase-change material.
3. Memory cell according to claim 1 , comprising a circuit for applying a first current configured to melt the first phase-change material.
4. Memory cell according to claim 3 , comprising a circuit for applying a second current configured to cause the crystallization of the first phase-change material.
5. Memory cell according to claim 1 , wherein the first pattern and/or the second pattern are formed by elementary layers of phase-change materials having different compositions.
6. Memory cell according to claim 1 , wherein the thicknesses of the heating element, of the first phase-change material pattern, and of the second phase-change material pattern are configured to fulfill the following equation:
0.9
≤
T
2
a
·
ρ
th
2
a
+
T
2
b
·
ρ
th
2
b
T
7
·
ρ
th
7
≤
1.1
,
where:
T 2a is the thickness of the first pattern
T 2b is the thickness of the second pattern
ρ th 2a th is the thermal conductivity of the material forming the first pattern
ρ th 2b th is the thermal conductivity of the material forming the second pattern
T 7 is the thickness of the heating element
ρ th 7 th is the thermal conductivity of the heating element.