"""Greek cross test structure."""
from itertools import product
import numpy as np
import gdsfactory as gf
from gdsfactory.components.cross import cross
from gdsfactory.components.pad import pad
from gdsfactory.components.rectangle import rectangle
from gdsfactory.components.via_stack import via_stack, via_stack_m1_m3, via_stack_npp_m1
from gdsfactory.cross_section import metal1
from gdsfactory.typings import ComponentSpec, CrossSectionSpec, Floats, LayerSpecs
[docs]
@gf.cell
def greek_cross(
length: float = 30,
layers: LayerSpecs = (
"WG",
"N",
),
widths: Floats = (2.0, 3.0),
offsets: Floats | None = None,
via_stack: ComponentSpec = via_stack_npp_m1,
) -> gf.Component:
"""Simple greek cross with via stacks at the endpoints.
Process control monitor for dopant sheet resistivity and linewidth variation.
Args:
length: length of cross arms.
layers: list of layers.
widths: list of widths (same order as layers).
offsets: how much to extend each layer beyond the cross length
negative shorter, positive longer.
via_stack: via component to attach to the cross.
.. code::
via_stack
<------->
_________ length ________
| |<-------------------->|
2x | | | ↓ |<-->|
| |======== width =======|
|_______|<--> | ↑ |<-->|________
offset offset
References:
- Walton, Anthony J.. “MICROELECTRONIC TEST STRUCTURES.” (1999).
- W. Versnel, Analysis of the Greek cross, a Van der Pauw structure with finite
contacts, Solid-State Electronics, Volume 22, Issue 11, 1979, Pages 911-914,
ISSN 0038-1101, https://doi.org/10.1016/0038-1101(79)90061-3.
- S. Enderling et al., "Sheet resistance measurement of non-standard cleanroom
materials using suspended Greek cross test structures," IEEE Transactions on
Semiconductor Manufacturing, vol. 19, no. 1, pp. 2-9, Feb. 2006,
doi: 10.1109/TSM.2005.863248.
- https://download.tek.com/document/S530_VanDerPauwSheetRstnce.pdf
"""
c = gf.Component()
if len(layers) != len(widths):
raise ValueError("len(layers) must equal len(widths).")
offsets = offsets or (0.0,) * len(layers)
# Layout cross
for layer, width, offset in zip(layers, widths, offsets):
cross_ref = c << gf.get_component(
cross,
length=length + 2 * offset,
width=width,
layer=layer,
port_type="electrical",
)
cross_offset = offset
port_at_length = [
port.move_polar_copy(d=cross_offset, angle=180 + port.orientation)
for port in cross_ref.get_ports_list()
]
# Add via
for port in port_at_length:
via_stack_ref = c << gf.get_component(via_stack)
via_stack_ref.connect("e1", port, allow_layer_mismatch=True)
c.add_port(name=port.name, port=via_stack_ref.ports["e3"])
c.auto_rename_ports()
return c
[docs]
@gf.cell
def greek_cross_with_pads(
pad: ComponentSpec = pad,
pad_spacing: float = 150.0,
greek_cross_component: ComponentSpec = greek_cross,
pad_via: ComponentSpec = via_stack_m1_m3,
xs_metal: CrossSectionSpec = metal1,
) -> gf.Component:
"""Greek cross under 4 DC pads, ready to test.
Arguments:
pad: component to use for probe pads
pad_spacing: spacing between pads
greek_cross_component: component to use for greek cross
pad_via: via to add to the pad
xs_metal: cross-section for cross via to pad via wiring
"""
c = gf.Component()
# Cross
cross_ref = c << gf.get_component(greek_cross_component)
cross_ref.x = (
2 * pad_spacing - (pad_spacing - gf.get_component(pad).info["size"][0]) / 2
)
cross_pad_via_port_pairs = {
0: ("e1", "e2"),
1: ("e4", "e2"),
2: ("e2", "e4"),
3: ("e3", "e4"),
}
# Vias to pads
for index in range(4):
pad_ref = c << gf.get_component(pad)
pad_ref.x = index * pad_spacing + pad_ref.xsize / 2
via_ref = c << gf.get_component(pad_via)
if index < 2:
via_ref.connect("e2", destination=pad_ref.ports["e4"])
else:
via_ref.connect("e4", destination=pad_ref.ports["e2"])
route = gf.routing.get_route(
cross_ref[cross_pad_via_port_pairs[index][0]],
via_ref[cross_pad_via_port_pairs[index][1]],
cross_section=xs_metal,
bend=gf.c.wire_corner,
start_straight_length=5,
end_straight_length=5,
)
c.add(route.references)
return c
[docs]
@gf.cell
def greek_cross_offset_pads(
cross_struct_length: float = 30.0,
cross_struct_width: float = 1.0,
cross_struct_layers: LayerSpecs = ("WG",),
cross_implant_length: float = 30.0,
cross_implant_width: float = 2.0,
cross_implant_layers: LayerSpecs = ("N",),
contact_layers: LayerSpecs = ("WG", "NPP"),
contact_offset: float = 10,
contact_buffer: float = 10,
pad_width: float = 50,
) -> gf.Component:
"""Greek cross, with silicon islands on each side of the cross to place larger contacting regions.
Args:
cross_struct_length: length of structural part of cross e.g. silicon core.
cross_struct_width: width of structural part of cross e.g. silicon core.
cross_struct_layers: layers to be considered "structural".
cross_implant_length: length of implantation part of cross.
cross_implant_width: width of implantation part of cross.
cross_implant_layers: layers to be considered "implants".
contact_layers: layers to include under and around the pad.
contact_offset: fudge factor to move pad relative to cross.
contact_buffer: amount of dopants around pad in contact.
pad_width: pad size.
.. code::
pad_width
<------->
_________ cross_implant_length, cross_struct_length
| |<------->
4x | | ↓
| |======== cross_implant_width, cross_struct_width
|_______| ↑
<-------------->
contact_offset (fudge)
References:
- Walton, Anthony J.. “MICROELECTRONIC TEST STRUCTURES.” (1999).
- W. Versnel, Analysis of the Greek cross, a Van der Pauw structure with finite
contacts, Solid-State Electronics, Volume 22, Issue 11, 1979, Pages 911-914,
ISSN 0038-1101, https://doi.org/10.1016/0038-1101(79)90061-3.
- S. Enderling et al., "Sheet resistance measurement of non-standard cleanroom
materials using suspended Greek cross test structures," IEEE Transactions on
Semiconductor Manufacturing, vol. 19, no. 1, pp. 2-9, Feb. 2006,
doi: 10.1109/TSM.2005.863248.
"""
c = gf.Component()
# Layout cross
for layer in cross_struct_layers:
c << gf.get_component(
cross,
length=2 * cross_struct_length + cross_struct_width,
width=cross_struct_width,
layer=layer,
)
for layer in cross_implant_layers:
c << gf.get_component(
cross,
length=2 * cross_implant_length + cross_implant_width,
width=cross_implant_width,
layer=layer,
)
pad_offset = pad_width / 2 + cross_implant_length / 2
# contact vias and pads
for sgnx, sgny in product([1, -1], [1, -1]):
pad_rotation = np.arctan2(sgny, sgnx) * 180 / np.pi - 45
c2 = gf.Component(f"contact_{sgnx}_{sgny}")
c2 << gf.get_component(via_stack, size=(pad_width, pad_width))
c2 << gf.get_component(pad, size=(pad_width, pad_width))
for layer in contact_layers:
w = gf.get_component(
rectangle,
size=(
pad_width + contact_buffer,
pad_width + cross_implant_length / 2 + contact_buffer,
),
layer=layer,
)
ref = c2 << w
ref.move(
np.array(
[
-1 * pad_offset + cross_implant_length / 2 - contact_buffer / 2,
-1 * pad_offset - contact_offset / 2,
]
)
)
contact = c << c2
contact.rotate(pad_rotation)
contact.move(np.array([sgnx * pad_offset, sgny * pad_offset]))
return c.flatten()
if __name__ == "__main__":
# c = greek_cross_offset_pads()
c = greek_cross_with_pads()
c.show(show_ports=True)
