METHOD TO FORM A THIN SEMICONDUCTOR LAMINA ADHERED TO A FLEXIBLE SUBSTRATE
A semiconductor donor body such as a wafer is implanted with ions to form a cleave plane. The donor wafer is affixed to a polyimide receiver element, for example by applying polyimide in liquid form to the donor wafer, then curing, or by affixing the donor wafer to a preformed polyimide sheet. Annealing causes a lamina to cleave from the donor wafer at the cleave plane. The resulting adhered lamina and polyimide body are not adhered to another rigid substrate and can be jointly flexed.
1 . A method to form a plurality of flexible structures, the method comprising:
providing a polyimide substrate;
affixing a plurality of substantially crystalline semiconductor wafers to the polyimide substrate, each semiconductor wafer having a cleave plane defined within; and
cleaving a semiconductor lamina from each wafer of the plurality at the cleave plane, the semiconductor laminae remaining affixed to the polyimide substrate.
2 . The method of claim 1 wherein the semiconductor wafers are monocrystalline silicon wafers.
3 . The method of claim 1 wherein the semiconductor laminae have a thickness less than about 50 microns.
4 . The method of claim 1 wherein each of the semiconductor laminae has a thickness between about 0.5 and about 20 microns.
5 . The method of claim 1 further comprising fabricating electronic devices in the semiconductor laminae.
6 . The method of claim 5 wherein the electronic devices comprise infrared detection devices.
7 . The method of claim 1 wherein the cleave plane of each semiconductor wafer was defined by implanting hydrogen and/or helium ions into the semiconductor wafer before the affixing step.
8 . A method to form a flexible structure, the method comprising
providing a substantially crystalline semiconductor donor body having a cleave plane defined within;
providing a cured polyimide receiver affixed to the donor body at a first surface of the donor body, wherein one or more layers have previously been formed on the first surface, and wherein the polyimide is affixed only to the semiconductor donor body and is not affixed to any other substrate; and
cleaving a semiconductor lamina from the semiconductor donor body at the cleave plane, the semiconductor lamina remaining affixed to the cured polyimide receiver.
9 . The method of claim 8 wherein the step of providing the cured polyimide receiver comprises:
applying polyimide in liquid form to the first surface of the donor body, wherein zero, one, or more layers have previously been formed on the first surface; and
curing the polyimide to form the cured polyimide receiver.
10 . The method of claim 8 wherein the semiconductor lamina has a thickness between about 0.2 microns and about 50 microns.
11 . The method of claim 10 wherein the semiconductor lamina has a thickness between about 0.5 microns and about 20 microns.
12 . The method of claim 8 further comprising fabricating a photovoltaic cell, the photovoltaic cell comprising the semiconductor lamina.
13 . The method of claim 8 wherein the semiconductor donor body is a monocrystalline, multicrystalline, or polycrystalline silicon wafer.
14 . The method of claim 8 further comprising fabricating electronic devices in the semiconductor lamina.
15 . The method of claim 8 wherein the step of providing a cured polyimide receiver affixed to the donor body comprises:
providing a pre-cured polyimide sheet;
and affixing the donor body to the polyimide sheet.
16 . A method to form a plurality of photovoltaic structures, the method comprising:
providing a polyimide substrate;
affixing a plurality of substantially crystalline semiconductor wafers to the polyimide substrate, each semiconductor wafer having a cleave plane defined within;
cleaving a semiconductor lamina from each wafer of the plurality at the cleave plane, the semiconductor laminae remaining affixed to the polyimide substrate; and
fabricating a plurality of photovoltaic cells, wherein each photovoltaic cell comprises one of the semiconductor laminae.
17 . The method of claim 16 wherein the polyimide substrate is a pre-cured polyimide sheet.
18 . The method of claim 16 wherein the semiconductor wafers are monocrystalline silicon wafers.
19 . The method of claim 16 wherein the semiconductor laminae have a thickness between about 0.5 microns and about 20 microns.
20 . The method of claim 16 wherein the cleave plane of each semiconductor wafer was defined by implanting hydrogen and/or helium ions into the semiconductor wafer before the affixing step.
21 . The method of claim 16 wherein a conductive layer intervenes between at least one lamina and the polyimide substrate.
22 . The method of claim 21 wherein the conductive layer comprises a metal layer.
23 . The method of claim 22 wherein the metal layer comprises aluminum.
24 . The method of claim 22 wherein the metal layer comprises silver.
25 . The method of claim 21 wherein a dielectric layer intervenes between the conductive layer and the semiconductor lamina.
26 . The method of claim 16 further comprising, before the affixing step, doping a first surface of at least one semiconductor wafer, wherein during the affixing step the lamina is affixed to the polyimide substrate at the first surface with zero, one, or more layers intervening between the first surface and the polyimide substrate.
27 . A method to form a photovoltaic cell, the method comprising:
providing a polyimide sheet;
affixing a substantially crystalline semiconductor wafer to the polyimide sheet, the semiconductor wafer having a cleave plane defined within;
cleaving a semiconductor lamina from the wafer at the cleave plane, the semiconductor lamina remaining affixed to the polyimide sheet, the lamina having a thickness between about two and about six microns; and
fabricating a photovoltaic cell, wherein the photovoltaic cell comprises the semiconductor lamina.