Process Flow: 1. Multiple layers (Ni/SiO2/HfO2) deposition on InGaAs/InP substrate

Modified Figure: 2. Bonding at 400’C, followed by lapping and HCl etching

Modified Figure: 3. Write global/chip marks, and location numbers in the 1 st EBL step , followed by

evaporation of Au/Ni

sorry, I don’t not quit get the idea of the orientation mark?

4.[2.] Write Ni Lines in the 2 nd EBL step , with 2um width and 3um space. These Ni line are used as support for InGaAs membrane as well as the source for alloy reaction Need also larger spacing than 3 um in order to first learn how to control the reaction and reach steady state while still you have unreacted InGaAs layers in the center. Yes, I think I can vary the spacing larger or smaller by put some anchors in between the Fins.

5.[3.] Write Fin structures in the 3 rd EBL step , with two different orientations: (111) and (100)

6.[4.] After Cl-ICP etching and HSQ removal, protect the top surface with photoresist, and etch the Si aperture grid from the backside, in order to remove Ni (with diluted HNO3), and SiO2 (with diluted BOE) Where is the SiO2? . It’s corrected in the schematic figures. After these etching steps, there will be only a 15nm HfO2 layer underneath the InGaAs.

Problems to be discussed: In step 3, the alignment marks need to be written according to the center of bonded

membrane. However, because of the InGaAs/HfO2/SiO2/Ni multiple stacks, it’s hard to find the open window in SEM. How shall I locate the center of the TEM grid?In SEM mode, go to the 4 corners of the TEM grid, write down the coordinates, and then take the average value to be the center of the TEM grid. Write your pattern there. Previously, I was trying to generate the mask to pattern the Ni for the TEM grid bonding, in order to leave the open window without Ni. I checked with the TEM company with the specific dimension. They told me that the Si frame is not always regularly cut and the window might be slightly off center. I also check with the microscope with x-y coordination, and realize that sometimes the edge cutting is not parallel with the window edge. So that’s the reason I’m worried about the marker position.

This is the optical and SEM images of the window, it’s quite blur from the normal SEM, so I think the EBL’s SEM will be even hard to find it.

This morning, I tried to write the markers on the TEM grid. It looks good after spin coating. But after 180’C bake, the window broke. I’m not sure whether it’s due to the thermal stress or the stress from the resist? I will bond more samples today for these tests.

Ni Pad

Ni Pad

Ni Pad

(110) Fin

(100) Fin

In step 4, as Minh pointed out, this process will keep the InGaAs underneath the Ni pads non-attacked during RIE etching, which will consume the Ni during annealing. Can this be counteracted by a thicker Ni evaporation? and is this ok for TEM observation? Yes, it will be Ok to deposit thicker Ni layers there and it should be Ok for TEM observation.

In step 6, I’m not sure whether wet BOE etching is so controllable. However, if RIE dry etch is introduced here, I haven’t think out thought of a good way to arrange the dielectric layers: (1) F-etch will also attack HfO2 I don’t think so, didn’t Daisy found out that the etch rate

for HfO2 by also F-etch is slow?(2) If change SiO2 with Al2O3 and use Cl-ICP etch, the HfO2 layer can probably

survive, but Al2O3 cannot stand the BOE dip during HSQ removal correct(3) If use HfO2 as BOE stop layer, then thin layer of Al2O3 as F-etch stop layer, and

bulk dielectric of SiO2 at the bottom, F-etch is ok for this process. But the F-ICP etches Si grid even faster than SiO2.

So, maybe still use BOE wet etching at this moment? Yes, I think so too. We should be able to control the etch rate of PECVD SiO2 or thermal SiO2 with BOE. Here, PECVD SiO2 grown at 180 C could be etched ok…I think I need to test the etching rate with our own recipe here, and see how different dielectric layers can be used.

As Daisy previously found that the HfO2 will change to crystalline during bonding annealing, is this 15nm crystalline HfO2 will affect the TEM observation? Maybe. We will be able to see contrast change in the stack a Ni eats through the InGaAs, so I wouldn’t worry too much about it for now.