Hi! Jeff Kettle,

I have known that it's hard to scratch a ideal grating by AFM so simply.
However, I only use AFM scratching to form patterns in photoresist just like
conventional lithography does.
Then, I think there are two ways to fabricate micro-nano structure.

1. sputter chrome(about 50nm) on silicon substrate—spin photoresist (AZ
series)—AFM scratching on films—wet etch chrome or RIE—remove photoresist

2. spin photoresist on silicon substrate—AFM scratching on films to form
pattern—sputter chrome or other metal (scratched photoresist as sacrificial
layer)—remove photoresist—wet etch silicon—remove chrome

Recently, I am trying the first process.And I have transfered pattern from
photoresist to chrome layer.

Please give me your suggestion about the two methods. Is it worth to follow?

Your help will be highly appreciated.

Liuchang


2008/6/3, Jeff Kettle :
>
> Afternoon Liuchang,
>
> This can be quite a common problem with AFM "scratching" lithography onto
> polymers. Generally, after spin coating of the polymer film, a tensile
> strain is created between the polymer chains in the film. When you cut the
> polymer using an AFM probe, the strain is released, widening the trench to a
> distance greater than the AFM tip diameter.
>
> You have a couple of alternatives to reduce line widths; add solvents to
> the PR to dilute it, trying different lithography parameters. Try
> controlling the way in which the polymer contracts after scracthing can help
> also.
>
> The depth-to-width ratio  10:1 is typical for AFM work; I'm not surprised
> you can't get higher. If you want high aspect ratios, you're using the wrong
> technology!