Why the copy figure tool in toolbar fail to copy a large fig file to the clipboard?

I usually use the copy figure tool in toolbar for pasting my matlab drawing in a word file and it is quite convenient and with high image resolution. However, when the figure is a bit complex(say over 20M), the copy figure tool just don't work and the Ctrl+V in word result in nothing, neither is there a error report in Matlab workplace.

What should I do to improve its adaptability in my application (large fig file)?