Semiconductor device, method of manufacturing the same and display device
Embodiments of the present application provide a semiconductor device and a method of manufacturing the same for implementing both polysilicon TFTs and oxide TFTs with less process complication. The semiconductor device includes first and second thin film transistor structures formed on a substrate. The first TFT structure includes a first transistor and a capacitor on the first transistor, and the second TFT structure includes a bottom metal layer, a second insulating layer on the bottom metal layer, and a second transistor on the second insulating layer. A lower electrode of the capacitor comprises the same metal material as the bottom metal layer, a dielectric layer of the capacitor comprises the same insulator material as the second insulating layer, and the upper electrode of the capacitor comprises the same oxide semiconductor material as a semiconductor active layer of the second transistor.
1 . A semiconductor device comprising:
a first thin film transistor (TFT) structure formed on a substrate, the first TFT structure including a first transistor and a capacitor on the first transistor; and
a second TFT structure formed on the substrate, the second TFT structure including a bottom metal layer, a second insulating layer on the bottom metal layer, and a second transistor on the second insulating layer,
wherein a lower electrode of the capacitor comprises the same metal material as the bottom metal layer,
a dielectric layer of the capacitor comprises the same insulator material as the second insulating layer, and
an upper electrode of the capacitor comprises the same oxide semiconductor material as a semiconductor active layer of the second transistor.
2 . The semiconductor device according to claim 1 , wherein the oxide semiconductor material comprised by the upper electrode of the capacitor and the semiconductor active layer of the second transistor is at least partially converted to a conductor.
3 . The semiconductor device according to claim 1 , wherein the first transistor comprises a polysilicon active layer, a gate insulating layer, and a gate electrode, and the gate electrode of the first transistor also serves as the lower electrode of the capacitor.
4 . The semiconductor device according to claim 3 , wherein the second TFT structure further includes a first insulating layer beneath the bottom metal layer, and
the gate electrode and the gate insulating layer of the first transistor have sidewalls aligned with each other and the bottom metal layer and the first insulating layer of the second TFT structure have sidewalls aligned with each other.
5 . The semiconductor device according to claim 1 , wherein each of the dielectric layer of the capacitor and the second insulating layer of the second TFT structure is a part of a continuous layer that covers the first transistor and the bottom metal layer.
6 . The semiconductor device according to claim 1 , wherein each of the dielectric layer of the capacitor and the second insulating layer of the second TFT structure comprises:
a silicon oxide layer; or
a silicon nitride layer and a silicon oxide layer covering the silicon nitride layer.
7 . The semiconductor device according to claim 1 , wherein the second transistor further comprises a gate insulating layer and a gate electrode over the semiconductor active layer, and the gate electrode of the second transistor includes an oxide semiconductor layer formed on the gate insulating layer.
8 . A method of manufacturing a semiconductor device, wherein the semiconductor device includes a first thin film transistor (TFT) structure formed on a substrate and includes a first transistor and a capacitor on the first transistor, and a second TFT structure formed on the substrate and includes a bottom metal layer, a second insulating layer on the bottom metal layer, and a second transistor on the second insulating layer, the method comprising:
depositing a first metal layer, which forms a lower electrode of the capacitor and the bottom metal layer,
depositing a second insulator layer, which forms a dielectric layer of the capacitor and the second insulating layer, and
depositing an oxide semiconductor layer, which forms an upper electrode of the capacitor and a semiconductor active layer of the second transistor.
9 . The method according to claim 8 , further comprising:
using a first photomask to pattern the first metal layer into the lower electrode of the capacitor and the bottom metal layer, and
using a second photomask to pattern the oxide semiconductor layer into the upper electrode of the capacitor and the semiconductor active layer of the second transistor.
10 . The method according to claim 9 , further comprising, before depositing the first metal layer:
forming a polysilicon active layer of the first transistor; and
depositing a first insulator layer over the polysilicon active layer,
wherein using the first photomask further includes patterning the first insulator layer into a gate insulating layer of the first transistor and a first insulating layer beneath the bottom metal layer, and
the lower electrode of the capacitor also serves as a gate electrode of the first transistor.
11 . The method according to claim 9 , further comprising, after using the second photomask to pattern the oxide semiconductor layer:
depositing a third insulator layer;
depositing a second metal layer on the third insulator layer; and
using a third photomask to pattern the second metal layer and the third insulator layer into a gate electrode and a gate insulating layer of the second transistor, respectively.
12 . The method according to claim 11 , wherein using the third photomask to pattern the second metal layer and the third insulator layer comprises etching the second metal layer and the third insulator layer using a plasma, and the plasma at least partially converts an oxide semiconductor material of the upper electrode of the capacitor and exposed portions of the semiconductor active layer of the second transistor to a conductor.
13 . The method according to claim 12 , further comprising, after using the third photomask to pattern the second metal layer and the third insulator layer:
depositing an interlayer dielectric layer over the first TFT structure and the second TFT structure using a plasma enhanced CVD (PECVD) process,
wherein a plasma used in depositing the interlayer dielectric layer also acts to convert the oxide semiconductor material of the upper electrode of the capacitor and the exposed portions of the semiconductor active layer of the second transistor to a conductor.
14 . The method according to claim 13 , further comprising, after depositing the interlayer dielectric layer:
using a fourth photomask to simultaneously form contact holes to source/drain regions of the first transistor and contact holes to source/drain regions of the second transistor by dry etching.
15 . The method according to claim 13 , wherein the interlayer dielectric layer is in contact with the second insulator layer, which forms the dielectric layer of the capacitor and the second insulating layer, and
the second insulator layer comprises:
a silicon oxide layer; or
a silicon nitride layer and a silicon oxide layer covering the silicon nitride layer.
16 . The method according to claim 11 , further comprising, after depositing the third insulator layer and before the step of depositing the second metal layer:
depositing another oxide semiconductor layer, wherein a partial pressure of oxygen is higher than when depositing the oxide semiconductor layer.
17 . The method according to claim 16 , further comprising:
using a heat treatment to cause excess oxygen contained in the another oxide semiconductor layer to reach an interface between the gate insulating layer and the semiconductor active layer of the second transistor so as to cure at least a part of defects at the interface.
18 . A display panel comprising:
a backplane including a semiconductor device comprising:
a first thin film transistor (TFT) structure formed on a substrate, the first TFT structure including a first transistor and a capacitor on the first transistor; and
a second TFT structure formed on the substrate, the second TFT structure including a bottom metal layer, a second insulating layer on the bottom metal layer, and a second transistor on the second insulating layer,
wherein a lower electrode of the capacitor comprises the same metal material as the bottom metal layer,
a dielectric layer of the capacitor comprises the same insulator material as the second insulating layer, and
an upper electrode of the capacitor comprises the same oxide semiconductor material as a semiconductor active layer of the second transistor, and
a front plane including a light emitting structure.
19 . The display panel according to claim 18 , wherein the light emitting structure comprises an organic light emitting diode (OLED) structure.
20 . A display device including the display panel according to claim 18 .