>>889
(describe-function 'modify-syntax-entry)を評価すると以下が表示されるので、

(modify-syntax-entry CHAR NEWENTRY &optional SYNTAX-TABLE)

Set syntax for character CHAR according to string NEWENTRY.
The syntax is changed only for table SYNTAX-TABLE, which defaults to
the current buffer's syntax table.
CHAR may be a cons (MIN . MAX), in which case, syntaxes of all characters
in the range MIN to MAX are changed.
The first character of NEWENTRY should be one of the following:
Space or - whitespace syntax. w word constituent.
_ symbol constituent. . punctuation.
( open-parenthesis. ) close-parenthesis.
" string quote. \ escape.
$ paired delimiter. ' expression quote or prefix operator.
< comment starter. > comment ender.
/ character-quote. @ inherit from `standard-syntax-table'.
| generic string fence. ! generic comment fence.


`をエスケープ文字としたいなら

(defvar hoge-mode-syntax-table
  (let ((table (make-syntax-table)))
    (modify-syntax-entry ?` "\\" table)
    table))

でしょうか。