Question

I'm confused about how [110] direction is determined for (100), (110) or (111) wafers. I found a book chapter which just confused me even more. From the image below, I understand how [110] is determined on the (110) wafer but not the other two. I'm also having a hard time understanding what different planes would look like on the (111) and (110) wafer. I would appreciate a resource for silicon wafers specifically (not necessarily crystallography). Here are things I'm not understanding.

How is the [110] direction determined and why is it different for each of the three wafers below? For the (110) wafer [110] is between x and y axis which makes sense. But for (100) it seems to go from z to y and for (111) it's between x and z. From my understanding [110] intercepts x and y axis at 1 and doesn't intercept z axis but that doesn't seem to be the case for (100) and (111) wafers.

Does the definition of x,y and z axis change when we're talking about (100), (111) or (110) wafers? I know that whichever wafer it is, that direction will be pointing out from the wafer surface but when I draw planes with respect to [110] and [111] (for (111) wafer), I don't know where the (100) plane should be. (110) plane would be perpendicular to the [110] direction and would be normal to the surface and (111) would be 35° from it. I can't find a drawing for it which makes me think we don't need to show the (100) plane? But if not then what if I need to align my mask to (100) plane on (111) wafer?

How would I define higher miller index planes on the 3 wafers? For example I need to align my mask to (122) or (411) plane, how would I start with it? I understand that this might become clear once I learn about the primary planes on the wafers.

Answer 1

The [110] direction on (100), (110), and (111) wafers is determined by the orientation of the crystal lattice. The [110] direction is different for each wafer due to the varying orientations of the crystal lattice. The definition of the x, y, and z axes remains the same for all three wafers.

Step-by-step explanation:

The direction [110] represents a crystallographic direction on a silicon wafer and is determined by the orientation of the crystal lattice. The direction [110] is different for each type of wafer because the orientation of the crystal lattice changes. In a (110) wafer, the [110] direction is between the x and y axes because these axes align with the crystallographic planes. However, on a (100) or (111) wafer, the [110] direction does not align with the x or y axis, but instead intersects the z axis. The definition of the x, y, and z axes remains the same for all three wafers.

In terms of drawing planes on (100) or (111) wafers, the (100) plane would be perpendicular to the [110] direction and would be normal to the surface. The (111) plane would be at a 35° angle from the [110] direction. As for the (122) or (411) planes, you would need to refer to the primary planes on the wafers to determine their orientations.

If you need to align your mask to the (100) plane on a (111) wafer, you may need additional information to determine its location. It's possible that the (100) plane may not be directly relevant or necessary for your alignment process. A resource specifically focused on silicon wafers, rather than crystallography, may provide more detailed information on the orientations and planes of silicon wafers.