According to the Russian phonology wiki (https://en.m.wikipedia.org/wiki/Russian_phonology) :
The pronunciation of unstressed /o ~ a/ is as follows: (...)
When a soft consonant or /j/ precedes, both /o/ and /a/ merge with /i/ and are pronounced as [ɪ].
Examples: язы́к ( [jɪˈzɨk] ) and "ýчасть" ( [ˈut͡ɕɪsʲtʲ] )
However, it seems that the phonem /a/ in я at the end of a word seems to not follow this rule and is pronounced [ə], such as in "тётя" ( [ˈtʲɵtʲə] ) or "деревня" ( [dʲɪˈrʲevnʲə ] ) . Am I missing a pronunciation rule or are these words which end in я exceptions?