Method for manufacturing a transistor with a gate-all-around structure
A method for manufacturing a pFET transistor, the method for manufacturing the transistor including providing a base structure comprising a silicon channel and a gate structure, the gate structure surrounding the channel leaving two flanks of the channel free; growing a first layer made from silicon-germanium alloy on the flanks of the channel; enriching the channel with germanium atoms from the first layer; and forming a drain region and a source region on either side of the channel.
1. A method for manufacturing a pFET transistor, the method comprising:
providing a base structure comprising a silicon channel and a gate structure, the gate structure comprising a gate electrode, a gate dielectric and lateral spacers, the gate dielectric separating the gate electrode from the channel, the lateral spacers being arranged on both sides of the gate structure, the gate structure surrounding the channel leaving two flanks of the channel free;
after said providing, growing a first silicon-germanium alloy layer on the flanks of the channel;
enriching the channel with germanium atoms from the first silicon-germanium alloy layer; and
forming a drain region and a source region on either side of the channel.
2. The method for manufacturing a pFET transistor according to claim 1 , wherein the channel of the base structure comprises at least one silicon nano-sheet or at least one silicon nano-wire or at least one silicon fin.
3. The method for manufacturing a pFET transistor according to claim 1 , wherein the channel of the base structure comprises a plurality of silicon fins parallel to one another and wherein the base structure comprises pads made of dielectric material arranged on either side of the channel between each silicon fin.
4. The method for manufacturing a pFET transistor according to claim 3 , comprising the removal of pads after the enriching of the channel.
5. The method for manufacturing a pFET transistor according to claim 2 , wherein the growth of the first silicon-germanium alloy layer is initiated from flanks of each silicon nano-sheet or from flanks of each silicon nano-wire or from flanks of each silicon fin.
6. The method for manufacturing a pFET transistor according to claim 1 , wherein the enriching is carried out by application of a diffusion anneal configured to diffuse germanium atoms from the first silicon-germanium alloy layer in the channel.
7. The method for manufacturing a pFET transistor according to claim 1 , wherein the enriching is carried out via oxidation of the first silicon-germanium alloy layer configured to condense germanium atoms from the first silicon-germanium alloy layer in the channel.
8. The method for manufacturing a pFET transistor according to claim 1 , wherein the forming of the drain and source regions is carried out by the forming of a second layer on the first silicon-germanium alloy layer on either side of the channel, the forming of the second layer being configured to apply a compressive stress on the channel.
9. The method for manufacturing a pFET transistor according to claim 1 , wherein the providing of the base structure comprises:
forming, on a substrate, an active zone, a sacrificial gate on a portion of the active zone and first lateral spacers on either side of the sacrificial gate;
delimiting the channel from the active zone by forming the free flanks of the channel in line with the first lateral spacers, and
forming the gate structure by replacing the sacrificial gate.
10. The method for manufacturing a pFET transistor according to claim 9 , wherein the active zone comprises a stack of layers comprising at least one silicon-germanium layer and at least one silicon layer in alternation, the stack of layers starting, from the substrate, with a silicon-germanium layer.
11. The method for manufacturing a pFET transistor according to claim 10 , wherein the forming of the gate structure comprises a replacing of said at least one silicon-germanium layer with a gate dielectric and a gate electrode.
12. A method for cointegrating a first pFET transistor and a second nFET transistor, the method comprising the following steps:
providing a first base structure and a second base structure identical to the first base structure, each base structure of the first base structure and the second base structure comprising a silicon channel, a gate structure and lateral spacers, the gate structure comprising a gate electrode, a gate dielectric and lateral spacers, the gate dielectric separating the gate electrode from the channel, the lateral spacers being arranged on both sides of the gate structure, the gate structure surrounding the channel leaving two flanks of the channel free;
after said providing, on the first base structure:
growing a first layer made from silicon-germanium alloy on the flanks of the channel;
enriching the channel with germanium atoms from the first layer made from silicon-germanium alloy;
forming a first drain region and a first source region on either side of the channel; and
on the second base structure, forming a second drain region and a second source region on either side of the channel of the second base structure.
13. The method for cointegrating a first pFET transistor and a second nFET transistor according to claim 12 , comprising, before the step of growing applied to the first base structure, protecting the second base structure by means of a first protective layer.
14. The method for cointegrating a first pFET transistor and a second nFET transistor according to claim 13 , comprising, before the step of forming applied to the second base structure, releasing the second base structure by removing the first protective layer.
15. The method for cointegrating a first pFET transistor and a second nFET transistor according to claim 12 , comprising, before the step of forming applied to the second base structure, protecting the first pFET transistor by means of a second protective layer.