\documentclass[border=0mm]{standalone}

\usepackage{cmap}
\usepackage[cp1250]{inputenc}	
\usepackage[T1]{fontenc}
\usepackage{graphicx}
\usepackage{lmodern}
\usepackage{tikz}
\usepackage{float}
\usepackage{siunitx}
\usepackage{amsmath}
\usepackage{upgreek}
\usepackage{pgfplots}
\pgfplotsset{compat=1.17}
\usepgfplotslibrary{fillbetween}
\usepgfplotslibrary{units}
% \makeatletter
%\pgfplotsset{
%  unit code/.code 2 args=
%    \begingroup
%    \protected@edef\x{\endgroup\si{#2}}\x
%} 
%\makeatother

\pgfkeys{%
  /tikz/on layer/.code={
    \pgfonlayer{#1}\begingroup
    \aftergroup\endpgfonlayer
    \aftergroup\endgroup
  }
}

\begin{document}
	\begin{tikzpicture}
		\begin{axis}[
			height=7cm,	width=6cm,	grid=major,
    		x unit=\SI{}{\micro\ampere}, y unit=\SI{}{\pico\second},
			xlabel=$I_\mathrm{BIAS}$,	ylabel=$t_\mathrm{d}$,
			ymin=0,ymax=125,
			xmin=5, xmax=50,
			ytick distance = 25,
			xtick={5,10,20,30,40,50},
			set layers,
			%x tick label style={/pgf/number format/.cd, set thousands separator={}},
			xticklabel shift = 2 pt,
			legend pos=north east
		]					
			
			\addplot +[solid, smooth, thick,color=blue,mark=none] table [x expr=\thisrow{X1}*1e6, y expr=\thisrow{Y1}*1e12, col sep=semicolon] {../cadence_data/ccdlu_lowvt_3s_excel.csv};
			\addplot +[name path = FF, solid, smooth, thick,color=blue, draw=none,mark=none] table [x expr=\thisrow{X2}*1e6, y expr=\thisrow{max}*1e12, col sep=semicolon] {../cadence_data/ccdlu_lowvt_3s_excel.csv};
			\addplot +[name path = SS, solid, smooth, thick,color=blue,draw=none,mark=none] table [x expr=\thisrow{X3}*1e6, y expr=\thisrow{min}*1e12, col sep=semicolon] {../cadence_data/ccdlu_lowvt_3s_excel.csv};
			\addplot[blue, fill opacity = 0.15] fill between[of=SS and FF];
			
			%\addplot +[solid, smooth, thick,color=red,mark=none] table [x expr=\thisrow{X1}*1e6, y expr=\thisrow{Y1}*1e12, col sep=comma] {../cadence_data/ccdlu_normal_3s.csv};
			%\addplot +[name path = SSN, solid, smooth, thick,color=red,mark=none] table [x expr=\thisrow{X2}*1e6, y expr=\thisrow{Y2}*1e12, col sep=comma] {../cadence_data/ccdlu_normal_3s.csv};	
			%\addplot +[name path = FFN, solid, smooth, thick,color=red,mark=none] table [x expr=\thisrow{X3}*1e6, y expr=\thisrow{Y3}*1e12, col sep=comma] {../cadence_data/ccdlu_normal_3s.csv};
			%\addplot[red, fill opacity = 0.15] fill between[of=SSN and FFN];	
		\end{axis}
	\end{tikzpicture}
\end{document}