Protection against in-process charging in silicon-oxide-nitride-oxide-silicon (SONOS) memories
View Patent ↗A pre-metal dielectric structure of a SONOS memory structure includes a UV light-absorbing film, which prevents the ONO structure from being electronically charged in response to UV irradiation. In one embodiment, the pre-metal dielectric structure includes a first pre-metal dielectric layer located over the SONOS memory structure, a light-absorbing structure located over the first pre-metal dielectric layer, and a second pre-metal dielectric layer located over the light-absorbing structure. The light-absorbing structure can be a continuous polysilicon or amorphous silicon layer. Alternately, the light-absorbing structure can include one or more patterned polysilicon layers. In another embodiment, the SONOS transistors include UV light absorbing polysilicon spacers.
1. A pre-metal dielectric structure for a silicon-oxide-nitride-oxide-silicon (SONOS) memory transistor comprising:
a first pre-metal dielectric layer located over the SONOS memory transistor;
a light-absorbing structure located over the first-pre-metal dielectric layer;
a second pre-metal dielectric layer located over the light-absorbing structure;
a first metal layer located over the second pre-metal dielectric layer; and
a barrier film located between the SONOS memory transistor and the first pre-metal dielectric layer.
2. The pre-metal dielectric structure of claim 1 , wherein the barrier film comprises silicon nitride.
3. A pre-metal dielectric structure for a silicon-oxide-nitride-oxide-silicon (SONOS) memory transistor comprising:
a first pre-metal dielectric layer located over the SONOS memory transistor;
a light-absorbing structure located over the first-pre-metal dielectric layer, wherein the light-absorbing structure comprises a continuous layer of polycrystalline silicon;
a second pre-metal dielectric layer located over the light-absorbing structure; and
a first metal layer located over the second pre-metal dielectric layer.
4. A pre-metal dielectric structure for a silicon-oxide-nitride-oxide-silicon (SONOS) memory transistor comprising:
a first pre-metal dielectric layer located over the SONOS memory transistor;
a light-absorbing structure located over the first-pre-metal dielectric layer, wherein the light-absorbing structure comprises a first patterned layer of polycrystalline silicon;
a second pre-metal dielectric layer located over the light-absorbing structure; and
a first metal layer located over the second pre-metal dielectric layer.
5. The pre-metal dielectric structure of claim 4 , wherein the first patterned layer of polycrystalline silicon comprises a plurality of polycrystalline silicon islands.
6. The pre-metal dielectric structure of claim 5 , wherein the polycrystalline silicon islands are separated by spacing corresponding to the minimum design rule spacing.
7. A pre-metal dielectric structure for a silicon-oxide-nitride-oxide-silicon (SONOS) memory transistor comprising:
a first pre-rnetal dielectric layer located over the SONOS memory transistor;
a light-absorbing structure located over the first-pre-metal dielectric layer, the light-absorbing structure comprising:
a first patterned layer of polycrystalline silicon;
a second patterned layer of polycrystalline silicon; and
an intermediate pre-metal dielectric layer located between the first and second patterned layers of polycrystalline silicon;
a second pre-metal dielectric layer located over the light-absorbing structure; and
a first metal layer located over the second pre-metal dielectric layer.
8. A pre-metal dielectric structure for a silicon-oxide-nitride-oxide-silicon (SONOS) memory transistor comprising:
a first pre-metal dielectric layer located over the SONOS memory transistor;
a light-absorbing structure located over the first-pre-metal dielectric layer, wherein the light-absorbing structure comprises amorphous silicon;
a second pre-metal dielectric layer located over the light-absorbing structure; and
a first metal layer located over the second pre-metal dielectric layer.
9. A pre-metal dielectric structure for a silicon-oxide-nitride-oxide-silicon (SONOS) memory transistor comprising:
a first pre-metal dielectric layer located over the SONOS memory transistor;
a light-absorbing structure located over the first-pre-metal dielectric layer;
a second pre-metal dielectric layer located over the light-absorbing structure; and
a first metal layer located over the second pre-metal dielectric layer;
wherein the first and second pre-metal dielectric layers comprise barrier films adjacent to the light-absorbing structure, wherein the barrier films suppress out-diffusion of impurities from other portions of the first and second pre-metal dielectric layer to the light-absorbing structure.
10. A pre-metal dielectric structure for a silicon-oxide-nitride-oxide-silicon (SONOS) memory transistor comprising:
a first pre-metal dielectric layer located over the SONOS memory transistor;
a light-absorbing structure located over the first-pre-metal dielectric layer;
a second pre-metal dielectric layer located over the light-absorbing structure;
a first metal layer located over the second pre-metal dielectric layer;
one or more contact openings formed through the first and second pre-metal dielectric layers and the light-absorbing structure, wherein the contact openings expose one or more surfaces of the light-absorbing structure; and
sidewall dielectric material located on the one or more exposed surfaces of the light-absorbing structure.
11. A method for fabricating a pre-metal dielectric structure for a silicon-oxide-nitride-oxide-silicon (SONOS) memory transistor, the method comprising:
forming a first pre-metal dielectric layer over the SONOS memory transistor;
forming a light-absorbing structure over the first-pre-metal dielectric layer;
forming a second pre-metal dielectric layer over the light-absorbing structure;
forming a first metal layer over the second pre-metal dielectric layer; and
forming a silicon nitride barrier film over the SONOS memory transistor and below the first pre-metal dielectric layer.
12. A method for fabricating a pre-metal dielectric structure for a silicon-oxide-nitride-oxide-silicon (SONOS) memory transistor, the method comprising:
forming a first pre-metal dielectric layer over the SONOS memory transistor;
forming a light-absorbing structure over the first-pre-metal dielectric layer wherein the light-absorbing structure is formed by depositing a first layer of polycrystalline silicon over the first pre-metal dielectric layer;
forming a second pre-metal dielectric layer over the light-absorbing structure;
forming a first metal layer over the second pre-metal dielectric layer.
13. The method of claim 12 , further comprising the step of patterning the first polycrystalline silicon layer.
14. The method of claim 13 , wherein the light-absorbing structure is further formed by:
depositing an intermediate pre-metal dielectric layer over the patterned first polycrystalline silicon layer;
depositing a second layer of polycrystalline silicon over the intermediate pre-metal dielectric layer; and
patterning the second polycrystalline silicon layer.
15. The method of claim 13 , wherein the step of patterning comprises creating a plurality of polycrystalline silicon islands from the first polycrystalline silicon layer, wherein spacing between the polycrystalline silicon islands corresponds to a minimum design rule spacing.
16. A method for fabricating a pre-metal dielectric structure for a silicon-oxide-nitride-oxide-silicon (SONOS) memory transistor, the method comprising:
forming a first pre-metal dielectric layer over the SONOS memory transistor;
forming a light-absorbing structure over the first-pre-metal dielectric layer;
forming a second pre-metal dielectric layer over the light-absorbing structure;
forming a first metal layer over the second pre-metal dielectric layer;
forming one or more contact openings through the first and second pre-metal dielectric layers and the light-absorbing structure, wherein the contact openings expose one or more surfaces of the light-absorbing structure; and
forming sidewall dielectric material on the one or more exposed surfaces of the light-absorbing structure.