DIELECTRIC LAYERS FOR DIGITAL MICROFLUIDIC DEVICES
An electrowetting system is disclosed. The system includes electrodes configured to manipulate droplets of fluid in a microfluidic space. Each electrode is coupled to circuitry operative to selectively apply a driving voltage to the electrode. The system includes a dielectric stack including a first dielectric pair comprising a first layer having a first dielectric constant and a second layer having a second dielectric constant. The second dielectric constant is larger than the first dielectric constant. The dielectric stack includes a second dielectric pair comprising a third layer having a third dielectric constant and a fourth layer having a fourth dielectric constant. The fourth dielectric constant is larger than the third dielectric constant. A ratio of a thickness of the fourth layer to a thickness of the third layer (T 4 :T 3 ) is in the range from about 2:1 to about 8:1. The second dielectric pair is thinner than the first dielectric pair.
1 . An electrowetting system for performing droplet operations, the system including:
a plurality of electrodes configured to manipulate droplets of fluid in a microfluidic space, wherein each electrode is coupled to circuitry operative to selectively apply a driving voltage to the electrode; and
a dielectric stack comprising:
a first dielectric pair comprising a layer of alumina (Al 2 O 3 ) and a layer of hafnium oxide (HfO 2 ); and
a second dielectric pair comprising a second layer of alumina (Al 2 O 3 ) and a second layer of hafnium oxide (HfO 2 ); wherein:
the ratio of the thickness of the hafnium oxide:alumina layers in the second dielectric pair is in the range from about 2:1 to about 8:1; and
the total thickness of the second dielectric pair is thinner than the total thickness of the first dielectric pair.
2 . The electrowetting system of claim 1 , wherein the ratio of the thickness of the hafnium oxide:alumina layers in the second dielectric pair is in the range from about 4:1 to about 6:1.
3 . The electrowetting system of claim 1 , wherein the ratio of the thickness of the hafnium oxide:alumina layers in the second dielectric pair is in the range from about 4.5:1 to about 5.5:1.
4 . The electrowetting system of claim 1 further comprising a layer of silicon nitride (Si 3 N 4 ).
5 . The electrowetting system of claim 1 , wherein the dielectric pair layers are formed by atomic layer deposition (ALD).
6 . The electrowetting system of claim 1 , further comprising a third dielectric pair comprising a third layer of alumina (Al 2 O 3 ) and a third layer of hafnium oxide (HfO 2 ).
7 . The electrowetting system of claim 6 , wherein the ratio of the thickness of the hafnium oxide:alumina layers in the third dielectric pair is in the range from about 2:1 to about 8:1, wherein the total thickness of the third dielectric pair is thinner than the total thickness of the first dielectric pair.
8 . The electrowetting system of claim 6 , wherein the thicknesses of the layers in the second and third dielectric pairs are the same.
9 . The electrowetting system of claim 6 , wherein each layer of each thin dielectric pair is formed by atomic layer deposition (ALD).
10 . The electrowetting system of claim 1 , further comprising a third dielectric pair comprising a fourth layer of alumina (Al 2 O 3 ) and a fourth layer of hafnium oxide (HfO 2 ).
11 . The electrowetting system of claim 10 , wherein the ratio of the thickness of the hafnium oxide:alumina layers in the fourth dielectric pair is in the range from about 2:1 to about 8:1, wherein the total thickness of the fourth dielectric pair is thinner than the total thickness of the first dielectric pair.
12 . The electrowetting system of claim 10 , wherein the thicknesses of the layers in the second, third and fourth dielectric pairs are the same.
13 . The electrowetting system of claim 12 , wherein each layer of each thin dielectric pair is formed by atomic layer deposition (ALD).
14 . The electrowetting system of claim 1 , comprising a protective layer disposed over the dielectric stack.
15 . The electrowetting system of claim 14 , wherein the protective layer includes parylene.
16 . The electrowetting system of claim 1 , comprising a hydrophobic layer disposed over the dielectric stack.
17 . The electrowetting system of claim 16 , wherein the hydrophobic layer includes Teflon®.
18 . The electrowetting system of claim 1 , comprising:
a plurality of electrodes configured to manipulate droplets of fluid in a microfluidic space, wherein each electrode is coupled to circuitry operative to selectively apply a driving voltage to the electrode; and
a dielectric stack comprising:
a layer of silicon nitride;
a first dielectric pair comprising a layer of alumina (Al 2 O 3 ) and a layer of hafnium oxide (HfO 2 ); and
a second dielectric pair comprising a second layer of alumina (Al 2 O 3 ) and a second layer of hafnium oxide (HfO 2 ); wherein:
the ratio of the thickness of the hafnium oxide:alumina layers in the second dielectric pair is in the range from about 4:1 to about 6:1; and
the total thickness of the second dielectric pair is thinner than the total thickness of the first dielectric pair;
a protective layer comprising parylene disposed over the dielectric stack; and
a hydrophobic layer including Teflon®.
19 . The electrowetting system of claim 18 , wherein the dielectric pair layers are formed by atomic layer deposition (ALD).
20 . The electrowetting system of claim 1 comprising:
a layer formed of alumina (Al 2 O 3 ), the layer having a thickness of about 50 nanometers;
a layer formed of hafnium oxide (HfO 2 ), the layer having a thickness of about 50 nanometers;
a layer formed of alumina (Al 2 O 3 ), the layer having a thickness of about 5 nanometers; and
a layer formed of hafnium oxide (HfO 2 ), the layer having a thickness of about 28 nanometers.