Charge transfer device having a bulged portion for clock frequencies from 100 MHz
A charge transfer device having a charge transfer channel in a semiconductor substrate. The charge transfer channel is formed by overlap of the possible electrostatic effect of the gates with the conduction layer. A clock generator has a clock frequency of more than 100 MHz which applies changes in potential at the clock frequency to the gates, for transporting charge carriers at the clock frequency from adjacent regions of the overlap between adjacent gates and the conduction layer. The charge transfer channel in the region of one gate has a region of a constriction in which the cross-section in the flow direction decreases, and is arranged at least in the region of the gate upstream of the region of the protuberance or in the regions of the gate upstream of the protuberance and the adjoining gate of the protuberance.
1 . A charge transfer device
having a charge transfer channel in a semiconductor substrate
having a doped conduction layer
for movably accepting the charge carriers,
having a sequence of at least two electrically isolated gates
which adjacently succeed one another
for transferring the charge carriers in the conduction layer in a flow direction,
wherein the charge transfer channel is formed by overlap of the possible electrostatic effect of the gates with the conduction layer,
and having a clock generator
having a clock frequency of more than 100 MHz,
which applies changes in potential at the clock frequency to the gates,
for transporting charge carriers at the clock frequency from adjacent regions of the overlap between adjacent gates and the conduction layer,
wherein
the charge transfer channel
and one gate or the sequence of two adjoining gates
has a region of a protuberance
in which the cross-section in the flow direction first increases by more than 20% and then decreases by more than 20%, and
which is arranged in a manner extending over the region of one or two mutually adjoining gates, and
has a region of a constriction
in which the cross-section in the flow direction decreases continuously in a constant fashion, and
is arranged at least in the region of the gate upstream of the region of the protuberance or in the regions of the gate upstream of the protuberance and the adjoining gate of the protuberance.
2 . The charge transfer channel as claimed in claim 1 , wherein
the region of the constriction
is embodied as beveled in the flow direction
and is embodied as funnel-shaped.
3 . The charge transfer channel as claimed in claim 1 , wherein
the constriction reduces the spillback or the flow resistance or the loss of the charge carriers in the protuberance.
4 . The charge transfer channel as claimed in claim 1 , wherein
the semiconductor substrate is p+ doped, and/or
the conduction layer is weakly n− doped, and/or
the gates are formed from metal, and/or
a nonconducting layer is arranged between the gates and the conduction layer, and/or
the gates are separated in a manner electrically insulated from one another.
5 . The charge transfer channel as claimed in claim 1 , wherein the cross-section in the flow direction first increases by more than 40% and then decreases by more than 40%.
6 . The charge transfer channel as claimed in claim 1 , wherein the cross-section in the flow direction first increases by more than 80%.
7 . The charge transfer channel as claimed in claim 1 , wherein the cross-section in the flow direction first increases by more than 100%.
8 . The charge transfer channel as claimed in claim 1 , wherein
the region of the constriction
is arranged upstream of the protuberance at a distance of less than the maximum width of the region of the protuberance at a distance of less than one-half of the width of the protuberance, and
adjoins the protuberance directly upstream of the protuberance.
9 . The charge transfer channel as claimed in claim 8 , wherein the region of the constriction
is arranged upstream of the protuberance at a distance of less than one-fourth of the width of the protuberance.
10 . The charge transfer channel as claimed in claim 1 , wherein
the region of the protuberance
has a length of less than one-half of the maximum width.
11 . The charge transfer channel as claimed in claim 10 , wherein the length of the region of the protuberance is less than one-fourth of the maximum width.
12 . The charge transfer channel as claimed in claim 10 , wherein the length of the region of the protuberance is less than one-eighth of the maximum width.
13 . The charge transfer channel as claimed in claim 1 , wherein
the region of the protuberance
has a maximum width whose ratio to the width of the conduction channel upstream of the constriction or downstream of the protuberance
is more than around 110%, and/or
is less than 200%.
14 . The charge transfer channel as claimed in claim 2 , wherein the ratio of the maximum width of the region of the protuberance to the width of the conduction channel upstream of the constriction or downstream of the protuberance
is more than around 130%, and/or
is less than 180%.
15 . The charge transfer channel as claimed in claim 13 , wherein the ratio of the maximum width of the region of the protuberance to the width of the conduction channel upstream of the constriction or downstream of the protuberance
is more than around 150%, and/or
is less than 160%.
16 . The charge transfer channel as claimed in claim 1 , wherein the clock frequency is more than 150 MHz.
17 . The charge transfer channel as claimed in claim 16 , wherein the clock frequency is more than 200 MHz.
18 . The charge transfer channel as claimed in claim 17 , wherein the clock frequency is more than 250 MHz.
19 . The charge transfer channel as claimed in claim 18 , wherein the clock frequency is more than 300 MHz.
20 . The charge transfer channel as claimed in claim 19 , wherein the clock frequency is more than 400 MHz.