I found the solution and I post here to help other people with the same problem.

We use the Last MultiSSOV2, so we have to customize the SSO following this article :

https://support.servicenow.com/kb?id=kb_article_view&sysparm_article=KB0778203

In our instance, i have modify the Saml custom script : SAML2_custom by adding this function :

    customizeAuthnRequest: function() {

        //Customization through Request DOM Element
        var xmlRequestElement = this.glidesaml2api.getGeneratedReqElemDOM();
        var nodeList = xmlRequestElement.getChildNodes();
        var RequestedAuthnContextElement = null;
        for (var i = 0; i < nodeList.getLength(); i++) {
            if ("saml2p:RequestedAuthnContext".equalsIgnoreCase(nodeList.item(i).getNodeName())) {
                RequestedAuthnContextElement = nodeList.item(i);
                break;
            }
        }
        if (RequestedAuthnContextElement != null) {
            RequestedAuthnContextElement.setAttribute("Comparison", "minimum");
        }
        this.glidesaml2api.setCustomizedReqElemDOM(xmlRequestElement);

    },