Assuming this is a URL or formula URL field then you can choose to open it in the same page, a new window, or in a pop-up in the field options themselves. It is under "Open Target" which is in the Display section.
If this opens in a new tab or a new window will depend on the end users browser. On my browser it opens in a new tab because I have it set that way. However if I do this in another browser I get a new window. A pop-up window is probably your best bet here but I know it is annoyingly small when it opens.
There is a second way to do this via a formula Rich Text field and creating the link via html and giving it a target of "_blank" but I tested this just now and it also opens in a new tab for me instead of a new window. Again likely due to my specific browser settings. Another downside to this is it is a text link but you may be able to style it into a button, I didn't try.
