Semiconductor device and method for manufacturing thereof
The present disclosure provides a forksheet structure in a semiconductor device and methods of manufacturing thereof. The forksheet structure according to the present disclosure includes a dielectric wall disposed between two channel regions inside a gate structure and without extending through the sidewall spacers to the source/drain regions. In some embodiments, a cut metal gate (CMG) dielectric structure is formed in the gate structure along with the dielectric walls. A gate dielectric layer is in contact with the dielectric wall. In some embodiments, the dielectric layer surrounds semiconductor channels in the channel region. In other embodiments, the gate dielectric layer surrounds a portion of the semiconductor channels in the channel region, for example forming a π-shape cross sectional profile around the semiconductor channel.
1 . A method, comprising:
forming a first fin structure and a second fin structure along a first direction;
forming a sacrificial gate structure along a second direction and across the first and second fin structures;
forming first and second sidewall spacers on opposing sidewalls of the sacrificial gate structure;
etching back the first and second fin structures to form source/drain openings on opposing sides of the sacrificial gate structure;
forming epitaxial source/drain regions in the source/drain openings;
forming a wall opening in the sacrificial gate structure between the first and second sidewall spacers and between the first and second fin structures;
forming a dielectric wall in the wall opening between the first and second sidewall spacers;
removing the sacrificial gate structure; and
forming a first replacement gate structure and a second replacement gate structure, wherein the dielectric wall isolates the first replacement gate structure from the second replacement gate structure.
2 . The method of claim 1 , wherein forming the sacrificial gate structure comprises:
depositing a sacrificial gate dielectric layer;
depositing a sacrificial gate electrode layer over the sacrificial gate dielectric layer; and
patterning the sacrificial gate electrode layer and the sacrificial gate dielectric layer to form the sacrificial gate structure, wherein the wall opening is formed through the sacrificial gate electrode layer, and the sacrificial gate dielectric layer is exposed in the wall opening.
3 . The method of claim 2 , wherein forming the dielectric wall comprises:
removing the sacrificial gate dielectric layer from the first fin structure and second fin structure;
depositing a dielectric liner layer in the wall opening; and
depositing a dielectric filling layer over the dielectric liner layer.
4 . The method of claim 3 , wherein the first fin structure comprises two or more first semiconductor layers alternatively stacked with two or more second semiconductor layers, the method further comprising:
after removing the sacrificial gate structure, removing the two or more second semiconductor layers from the first fin structure; and
removing at least a portion of the dielectric liner layer disposed between the two or more first semiconductor layers and the dielectric filling layer.
5 . The method of claim 1 , wherein forming the sacrificial gate structure comprises:
depositing a first sacrificial gate dielectric layer;
depositing a second sacrificial gate dielectric layer over the first sacrificial gate dielectric layer;
depositing a sacrificial gate electrode layer over the second sacrificial gate dielectric layer; and
patterning the sacrificial gate electrode layer, the second sacrificial gate dielectric layer, and the first sacrificial gate dielectric layer to form the sacrificial gate structure, wherein the wall opening is formed within the sacrificial gate electrode layer, and a gap volume of the sacrificial gate electrode layer remains between the wall opening and the first fin structure.
6 . The method of claim 5 , wherein forming the dielectric wall comprises:
depositing a first dielectric filling layer in the wall opening;
removing the sacrificial gate electrode layer and forming an air gap in the gap volume; and
depositing a second dielectric filling layer in the air gap.
7 . A method, comprising:
forming a first fin structure and a second fin structure along a first direction;
forming a sacrificial gate structure along a second direction and across the first and second fin structures;
forming first and second sidewall spacers on opposing sidewalls of the sacrificial gate structure;
etching back the first and second fin structures to form source/drain openings on opposing sides of the sacrificial gate structure;
forming a first source/drain region and a second source/drain region in the source/drain openings, wherein the first source/drain region is connected to the first fin structure, and the second source/drain region is connected to the second fin structure; and
forming a forksheet structure between the first and second sidewall spacers, wherein the forksheet structure comprises:
a first channel region comprising a portion of the first fin structure;
a second channel region comprising a portion of the second fin structure; and
a dielectric wall disposed between the first channel region and the second channel region, wherein the dielectric wall has a first surface facing the first channel region, a second surface facing the second channel region, a third surface connecting the first and second surfaces, and a fourth surface opposing the third surface, the first sidewall spacer is disposed on a first side of the forksheet structure, and the second sidewall spacer is disposed on a second side of the forksheet structure, wherein the dielectric wall comprises a dielectric filling layer, wherein the dielectric filling layer includes a first dielectric filling layer extending from the third surface to the fourth surface of the dielectric wall, and a second dielectric filling layer disposed on a lower portion of the first surface and second surface of the dielectric wall.
8 . The method of claim 7 , wherein the forksheet structure further comprises:
a first gate dielectric layer disposed on the first channel region; and
a first gate electrode layer disposed on the first gate dielectric layer, wherein the first gate dielectric layer is in contact with the first surface of the dielectric wall.
9 . The method of claim 8 , wherein the dielectric wall comprises one or more low-k dielectric material.
10 . The method of claim 9 , wherein the dielectric wall comprises:
a dielectric liner layer,
wherein the dielectric filling layer is disposed over the dielectric liner layer, wherein the third surface and fourth surface of the dielectric wall comprises the dielectric liner layer.
11 . The method of claim 10 , wherein the first surface and second surface of the dielectric wall comprise the dielectric filling layer.
12 . The method of claim 11 , wherein a portion of the first surface and second surface of the dielectric wall comprise the dielectric liner layer.
13 . The method of claim 9 , wherein the dielectric wall further comprises:
a sacrificial dielectric layer disposed on the second dielectric filling layer.
14 . The method of claim 8 , further comprising forming a cut gate dielectric feature extending between the first and second sidewall spacers, wherein the cut gate dielectric feature and the dielectric wall are disposed on opposing sides of the first channel region.
15 . A method, comprising:
forming a semiconductor device comprising:
a first source/drain region;
a second source/drain region;
a first channel region disposed between and connected to the first source/drain region and the second source/drain region;
a first gate structure comprising:
a first gate dielectric layer disposed on the first channel region; and
a first gate electrode layer disposed on the first gate dielectric layer;
first and second sidewall spacers disposed on opposite sides of the first gate structure, wherein the first source/drain region is in contact with the first sidewall spacer, and the second source/drain region is in contact with the second sidewall spacer;
a dielectric wall, wherein the dielectric wall has a first end, a second end, and a first surface connecting the first end and the second end, the first end of the dielectric wall terminates at the first sidewall spacers, the second end of the dielectric wall terminates at the second sidewall spacer, and the first gate dielectric layer in contact with the first surface of the dielectric wall, wherein the dielectric wall comprises:
a dielectric liner layer; and
a dielectric filling layer disposed over the dielectric liner layer, wherein the first surface includes the dielectric filling layer and a portion of the dielectric liner layer extending from the dielectric filling layer, and the portion of the dielectric liner layer is in contact with the first channel region.
16 . The method of claim 15 , wherein the first channel region comprises two or more semiconductor channels, and the first gate dielectric layer is formed on each of the semiconductor channel, and the portion of the dielectric liner layer has a height shorter than a height of the semiconductor channels.
17 . The method of claim 16 , wherein the first gate dielectric layer has a T-shaped profile.
18 . The method of claim 15 , further comprising:
a third source/drain region;
a fourth source/drain region;
a second channel region disposed between and connected to the third source/drain region and the fourth source/drain region; and
a second gate structure comprising:
a second gate dielectric layer disposed on the second channel region; and
a second gate electrode layer disposed on the second gate dielectric layer, wherein the dielectric wall has a second surface opposing the first surface and connecting the first end and second end of the dielectric wall, and the second gate dielectric layer in contact with the second surface of the dielectric wall.
19 . The method of claim 7 , wherein forming the sacrificial gate structure comprises:
depositing a first sacrificial gate dielectric layer;
depositing a second sacrificial gate dielectric layer over the first sacrificial gate dielectric layer; and
depositing a sacrificial gate electrode layer over the second sacrificial gate dielectric layer,
wherein the dielectric filling layer is disposed over the second sacrificial gate dielectric layer.
20 . The method of claim 19 , wherein the first sacrificial gate dielectric layer is a nitrogen containing layer and the second sacrificial gate dielectric layer is an oxygen containing layer.