You can do this with a shader.
First you make a Texture map in black and white with your Text. The Text should have soft border or vignette (I do not know exactly the english word)
Second you make a shader with a Multi Channel Mixer for your flat vertex plane.
In source 1 you make a Multi Channel and in its Color Channel you put your Texture map with the Text. This is only for controling. If the Text is on the right place on your plane, you copy the color channel and paste it in the bump channel. The bump should for controlling be very high, like 250%.
Then you can delete the Textur map from the color channel and put in color or want you want.
Make a quick render to see your text embossed on the plane.
Third you copy the Multi Channel from source 1 and paste it on source 2.
In the Multi channel of source 2 you set the bump channel to none.
Finally you set the Blender to Value and you can blend between source 1 and source 2.
Using your method, you could also use it as a displacement map. Might have to play around with the polygon count in the plane. Generally, you should get better results with a higher polygon count (with caution). The nice thing about using displacement is, I believe you can export the plane as an .obj with the displacement baked in to the geometry, though I could be wrong about that. Might have to test it.