I get the Same Z-Depth value for two different Pixels

Hello,
I need very precise Z-depth values from Eevee. Is it Possible to Increase the Resolution in Z-direction to get better results? I created a Scene with only one Plane. My Camera looks in Y direction with a small Angle. The Z-Depth shold increase each pixel. If i Use Cycles it works but because of performance i need to use Eevee. Eevee has the same Z-Depth for 2 to 3 Pixel so the Results are not continues rising.

Greetings CVDH