Infra red detectors and a method of manufacturing infra red detectors using MOVPE
View Patent ↗A method of forming infra red detector arrays is described, starting with the manufacture of a wafer. The wafer is formed from a GaAs or GaAs/Si substrate having CMT deposited thereon by MOVPE. The CMT deposited can include a number of layers of differing composition, the composition being controlled during the MOVPE process and being dependent on the thickness of the layer deposited. A CdTe buffer layer can aid deposition of the CMT on the substrate. Once the wafer is formed, the buffer layer, an etch stop layer and any intervening layers can be etched away leaving a wafer suitable for further processing into an infra red detector.
1. A method of producing an infrared detector comprising:
forming a cadmium mercury telluride (CMT) wafer that includes active device layers having an absorber layer that is sandwiched between two layers with higher x(Cd) that will passivate a diode pn junction where it reaches a surface of a CMT heterostructure;
forming a buffer layer on a substrate, the buffer layer ensuring the absorber layer does not contain dislocations produced by a lattice mismatch between the CMT heterostructure and the substrate;
forming a spacer layer on the buffer layer to space the active device layers from the buffer layer;
forming an etch stop layer on the spacer layer and directly adjacent to the active device layers;
dicing the CMT wafer into an individual CMT die;
bonding the CMT die to an integrated circuit wafer, wherein the active device layers have a uniform thickness;
selectively etching remaining material of the substrate and remaining material of the buffer layer of the CMT die;
forming a loophole focal plane array having a plurality of diodes in CMT monoliths of the active device layers on the integrated circuit wafer; and
dicing the integrated circuit wafer (IC) into an individual IC die following formation of the loophole focal plane array.
2. The method of producing an infra red detector according to claim 1 comprising:
b) bonding the CMT die of the CMT wafer to desired tested sites on readout integrated circuit (ROIC) wafer; and
c) removing the remaining material of the substrate and the remaining material of the buffer layer by selective or non-selective etching to form the CMT monoliths.
3. The method according to claim 2 wherein forming the loophole focal plane array comprises:
forming the array of loophole diodes in the CMT monoliths by ion beam milling through a photo-resist mask and depositing metal through the same mask to form contacts; and
b) dicing said ROIC wafer into individual dies.
4. The method of producing an infra red detector according claim 1 , comprising:
a) bonding the CMT die to tested good sites on an ROIC wafer; and
b) removing the remaining material of the substrate and the remaining material of the buffer layer by selective or non-selective etching to form monoliths.
5. The method according to claim 1 , wherein forming the loophole focal plane array comprises:
forming the array of loophole diodes in the CMT monoliths by ion beam milling through a photo-resist mask and depositing metal through the same mask to form contacts.
6. The method of producing an infrared detector according to claim 2 , wherein forming the loophole focal plane array comprises:
a) forming arrays of pseudo-loophole diodes in the CMT wafer by ion beam milling through a photo-resist mask, and depositing metal through the same photo-resist mask to form contacts;
b) dicing the CMT wafer into individual arrays;
c) bump-bonding said individual arrays to ROICS; and
d) removing the remaining material of the substrate from the arrays by etching.
7. The method of producing an infrared detector according to claim 3 , wherein forming the loophole focal plane array comprises:
a) forming arrays of pseudo-loophole diodes in the CMT wafer by ion beam milling through a photo-resist mask, and depositing metal through the same photo-resist mask to form contacts;
b) dicing the CMT wafer into individual arrays;
c) bump-bonding said individual arrays to ROICS; and
d) removing the remaining material of the substrate from the arrays by etching.
8. The method of producing an infrared detector according to claim 1 , wherein forming the loophole focal plane array comprises:
a) forming arrays of pseudo-loophole diodes in the CMT wafer by ion beam milling through a photo-resist mask, and depositing metal through the same photo-resist mask to form contacts;
b) dicing the CMT wafer into individual arrays;
c) bump-bonding said individual arrays to ROICS; and
c) removing the remaining material of the substrate from the arrays by etching.