I'm french too, thanks to everyone, i've done this and its working.

I use luks encryption for home and root files.
If it can help some guys

 vim /etc/vconsole.conf

Add this

 KEYMAP=fr-latin9

and also check this

 vim /etc/mkinitcpio.conf

It MUST be in the good order

 HOOKS=(base udev autodetect keyboard keymap consolefont modconf block encrypt lvm2 filesystems fsck)

Regenerate initrd

 mkinitcpio -P