Patent Application
20190019814
The present application claims the benefit of Chinese Patent Application No. 201610666482.3, filed on Aug. 12, 2016, the entire disclosure of which is incorporated herein by reference.
The present disclosure relates to the field of display technology, and particularly to a display substrate, a method for fabricating the same, and a display panel.
A thin film transistor (TFT) acts as a switching control unit, and has been widely applied in the display field. A TFT array substrate comprises a display region in which a plurality of pixel units are arranged in an array. Each of the pixel units is provided with a TFT switch for controlling the pixel unit.
An amorphous silicon TFT has excellent performance, a mature process and low cost, so that it has been applied extensively. In the amorphous silicon TFT, an active layer comprises an amorphous silicon active layer and an n+ amorphous silicon ohmic contact layer. Forming the active layer generally involves two etching processes. A first etching process is used to form a silicon island pattern of the active layer, and a second etch process is used to etch gaps among n+ amorphous silicon ohmic contact layers.
Embodiment of the present disclosure provide a display substrate, a method for fabricating the same, and a display panel, which can alleviate or solve one or more problems in the art.
In a first aspect, it is provided a method for fabricating a display substrate, comprising forming a TFT on a substrate. Forming the TFT comprises forming a gate, a gate insulating layer, an active layer, an ohmic contact layer, a source and a drain on the substrate in sequence. After forming the active layer, and prior to forming the ohmic contact layer, the method further comprises forming a first pattern in a non-TFT region. The first pattern in the non-TFT region is configured to cover the gate insulating layer.
For example, the method further comprises: forming a second pattern in a channel region of the active layer by using a same insulating material as the first pattern and at a same time as forming the first pattern in the non-TFT region.
For example, the method comprises: at a same time as forming the ohmic contact layer, partially etching the second pattern to partially retain a thickness of the second pattern and form a protection insulating layer pattern.
For example, the protection insulating layer pattern has a thickness of 5-15 nm.
For example, forming the ohmic contact layer, the protection insulating layer pattern, the source and the drain comprises:
forming the first pattern and the second pattern on the substrate on which the active layer has been formed;
forming an ohmic contact transitional pattern on the substrate on which the first pattern and the second pattern have been formed, wherein the ohmic contact transitional pattern has a same shape as the active layer; and
forming the source and the drain on the substrate on which the ohmic contact transitional pattern has been formed, and etching the ohmic contact transitional pattern, the first pattern and the second pattern to form the ohmic contact layer and the protection insulating layer pattern.
For example, the first pattern is etched away. Alternatively, the first pattern is etched to a thickness smaller than that of the protection insulating layer pattern.
For example, after forming the first pattern and the second pattern, the method further comprises:
forming an ohmic contact transitional pattern on the substrate on which the first pattern and the second pattern have been formed, wherein the ohmic contact transitional pattern is arranged in a source region and a drain region of the TFT region; and
forming the source and the drain on the substrate on which the ohmic contact transitional pattern has been formed.
For example, after forming the source and the drain, the method further comprises: etching the first pattern and the second pattern to have a same thickness.
For example, both the first pattern and the second pattern are etched away.
For example, the active layer is formed by amorphous silicon, and the ohmic contact layer is formed by n+ amorphous silicon.
For example, the insulating material comprises at least one of SiO2, SixNy, and SiOxNy.
For example, the ohmic contact transitional pattern, the first pattern and the second pattern are etched by dry etching in a mixture comprising SF6 and O2, Cl2 and O2, or CF4 and O2.
In a second aspect, it is provided a display substrate, comprising a TFT which is arranged on a substrate. The TFT comprises a gate, a gate insulating layer, an active layer, an ohmic contact layer, a source and a drain which are arranged on the substrate in sequence. The TFT comprises a protection insulating layer pattern which is arranged on a side of the active layer away from the substrate, and is arranged in a channel region.
For example, the protection insulating layer pattern has a thickness of 5-15 nm.
For example, the active layer is formed by amorphous silicon, and the ohmic contact layer is formed by n+ amorphous silicon.
For example, the protection insulating layer pattern comprises at least one of SiO2, SixNy, and SiOxNy.
For example, the display substrate is an array substrate.
In a third aspect, it is provided a display panel, comprising the display substrate as described above.
In order to explain the technical solutions in the embodiments of the present disclosure or the prior art more clearly, the drawings to be used in the description of the embodiments or the prior art will be introduced briefly in the following. Apparently, the drawings described below are only some embodiments of the present disclosure.
The display substrate, the method for fabricating the same, the display panel, and the display apparatus in embodiments of the present disclosure will be described in detail hereinafter with reference to the accompanying drawing.
Reference numerals: 01 substrate; 02 TFT; 11 gate; 12 gate insulating layer; 13 amorphous silicon active layer; 14 protection insulating layer; 141 first pattern; 142 second pattern; 143 protection insulating layer pattern; 15 n+ amorphous silicon ohmic contact layer; 151 n+ amorphous silicon film; 152 n+ amorphous silicon transitional pattern; 16 source; 17 drain; 18 photoresist; 181 retained portion of photoresist; 19 pixel electrode; 30 non-TFT region.
During forming an ohmic contact layer of n+ amorphous silicon, since shielding is absent over the gate insulating layer, the gate insulating layer generally has a reduced thickness in the non-TFT region, which will damage the gate insulating layer. For instance, when the thickness of the active layer is etched by 100 nm during a second etching, the thickness of the gate insulating layer generally is reduced by 80 nm. It is one of the objectives of embodiments of the present disclosure to alleviate or eliminate the damage to the gate insulating layer during forming ohmic contact layer.
Embodiments of the present disclosure provide a method for fabricating a display substrate. As shown in
As shown in
In the TFT with the configuration as shown above, a leakage current mainly comprises: a first leakage current between the source and the drain, and a second leakage current consisting of a leakage current between the gate and the source and a leakage current between the gate and the drain. When the gate insulating layer at sides of the amorphous silicon active layer provides a poor coverage or the gate insulating layer is relatively thin, a large parasitic capacitance is developed between the gate and the source as well as between the gate and the drain. As a result, the second leakage current is large, and the leakage current of the TFT accordingly is large. According to embodiments of the present disclosure, since the first pattern 141 is formed in the non-TFT region 30 and covers the gate insulating layer 12, the gate insulating layer 12 at sides of the amorphous silicon active layer 13 provides good coverage, and the thickness of the gate insulating layer 12 is retained. Therefore, the parasitic capacitance between the gate 11 and the source 16 as well as between the gate 11 and the drain 17 is small. As a result, the second leakage current is small, and the leakage current of the TFT is small.
In embodiments of the present disclosure, the method further comprises: at a same time forming the first pattern 141 in the non-TFT region 30, forming a second pattern 142 in a channel region of the active layer 13 by using a same insulating material as the first pattern. The term “channel region” as used herein refers to a region between a source region and a drain region in a TFT region.
In embodiments of the present disclosure, the protection insulating layer 14 for example can be made from any suitable material which does not affect the channel region.
In embodiments of the present disclosure, the first pattern 141 of the protection insulating layer 14 is retained or removed. In an embodiment, only some thickness of the first pattern 141 is retained. In another embodiment, all thickness of the first pattern 141 is retained.
In embodiments of the present disclosure, the second pattern 142 of the protection insulating layer 14 is retained or removed. In an embodiment, only some thickness of the second pattern 142 is retained. In another embodiment, all thickness of the second pattern 142 is retained.
In embodiments of the present disclosure, when both the first pattern 141 and the second pattern 142 are removed, they can be removed at a same time.
In embodiments of the present disclosure, during the process for fabricating the display substrate, in case it is required to remove the first pattern 141, it is not intended to limit the step in which the first pattern 141 is removed, provided that the damage to the gate insulating layer 12 is avoided during the steps after forming the gate insulating layer 12.
Although the following embodiments are described by taking the active layer 13 of amorphous silicon and the ohmic contact layer 15 of n+ amorphous silicon as an example, embodiments of the present disclosure are not limited in terms of materials for the active layer and the ohmic contact layer.
It is noted that, embodiments of the present disclosure and all of the accompanying drawings are presented only for purpose of describing structures relevant with the inventive concept of the present disclosure, and irrelevant structures are not illustrated or partially illustrated.
Embodiments of the present disclosure provide a method for fabricating a display substrate. After forming the amorphous silicon active layer 13, and prior to forming the n+ amorphous silicon ohmic contact layer 15, the protection insulating layer 14 comprising the first pattern 141 in the non-TFT region 30 and the second pattern 142 in the channel region is formed. During forming the n+ amorphous silicon ohmic contact layer 15, the protection insulating layer 14 keeps the gate insulating layer 12 intact, the damage to the gate insulating layer 12 is avoided, and the performance of the display substrate is ensured. Since the protection insulating layer 14 is made from an insulating material, pollution to the channel region of the amorphous silicon active layer 13 (i.e., a portion of the amorphous silicon active layer 13 which correspond sto a gap between the source 16 and the drain 17) is avoided, so that the performance of the TFT 02 is ensured.
For example, as shown in
Here, the first pattern 141 and the second pattern 142 comprise a same material and have a same thickness, and the n+ amorphous silicon film is directly formed on the first pattern 141 and the second pattern 142. Thus, at a same time as the second pattern 142 is etched, the first pattern 141 will also be etched. On basis of this, embodiments of the present disclosure are not limited to the case in which the first pattern 141 is completely removed (
As an example, as shown in
It is noted that, since the first pattern 141 and the second pattern 142 comprise a same material and have a same thickness, for purpose of completely removing the first pattern 141 while partially retaining the second pattern 142, it is required that, prior to forming the n+ amorphous silicon ohmic contact layer 15 by etching, there is no n+ amorphous silicon film on the first pattern 141 or the n+ amorphous silicon film on the first pattern 141 has a thickness smaller than that of the n+ amorphous silicon film on the second pattern 142. On basis of this, it is further required to ensure that the n+ amorphous silicon can be etched in a same etching environment in which the material of the first pattern 141 and the second pattern 142 is etched.
In embodiments of the present disclosure, the protection insulating layer pattern 143 is formed on the channel region of the amorphous silicon active layer 13, so that the channel is prevented from being polluted by external electrically conductive particles, and the leakage current of the TFT 02 is reduced. The second pattern 142 is partially etched, so that electrically conductive particles accumulated on the surface of the second pattern 142 is prevented from penetrating the channel.
For example, the protection insulating layer pattern 143 has a thickness of 5-15 nm.
In embodiments of the present disclosure, the protection insulating layer pattern 143 is set to have a thickness of 5-15 nm. On one hand, this thickness is sufficient to prevent external electrically conductive particles from polluting the channel. On the other hand, the thickness of 5-15 nm is negligible, and thus avoids effects on an overall thickness of the display substrate.
The method for fabricating a display substrate will be described hereinafter with reference to a specific embodiment. As shown in
S10, as shown in
In particular, a metal film with a thickness of 100 nm-700 nm is formed on the substrate 01 by a magnetron sputtering method. For example, a metal film with a thickness about 300 nm is formed. The metal film generally comprises metals such as Mo, Al, Al—Ni alloy, Mo—W alloy, Cr, or Cu, or a combination thereof. Then, the gate 11 is formed in the TFT region of the display substrate (i.e., a region between two non-TFT regions 30 in
Of course, in case the display substrate is an array substrate, for example a gate line is formed at a same time as forming the gate 11.
Furthermore, an insulating film with a thickness of 100 nm-600 nm is deposited on the display substrate on which the gate 11 has been formed, by plasma enhanced chemical vapor deposition (PECVD). The insulating film generally comprises silicon nitride, silicon oxide, silicon oxynitride, or the like. For example, the gate insulating layer 12 of silicon nitride with a thickness of about 400 nm is formed.
It is noted that, prior to forming the metal film, the substrate 01 for example is cleaned in advance.
S11, as shown in
In particular, an amorphous silicon film with a thickness of 100 nm-600 nm is deposited by PECVD on the substrate 01 on which the gate insulating layer 12 has been formed. For example, an amorphous silicon film with a thickness about 200 nm is formed. The amorphous silicon active layer 13 is formed on the gate 11 in the TFT region of the display substrate by patterning processes comprising exposure with a mask, development, etch, and lifting off.
S12, as shown in
In particular, an insulating film with a thickness of 40 nm-60 nm is deposited by PECVD, on the substrate 01 on which the amorphous silicon active layer 13 has been formed. Then, the first pattern 141 in the non-TFT region 30 and the second pattern 142 in the channel region are formed, by patterning processes comprising exposure with a mask, development, etch, and lifting off. For example, the protection insulating layer 14 of silicon dioxide (SiO2) with a thickness of about 50 nm is formed. In other embodiments, the protection insulating layer 14 comprises silicon nitride (SixNy) or silicon oxynitride (SiOxNy).
A side wall of the amorphous silicon active layer 13 can be well controlled during dry etching, so that the resulting active layer has an improved performance. Thus, in embodiments of the present disclosure, the insulating film is etched for example by dry etching.
As for the dry etching, for example plasma etching, reactive ion etching (RIE), inductively coupled plasma (ICP) etching or the like can be used. As for an etching gas, for example a fluorine or chlorine containing gas can be used. For example, CF4, CHF3, SF6, CCl2F2, or a mixture of these gases with oxygen (O2) can be used.
S13, as shown in
In particular, as shown in
Since the n+ amorphous silicon transitional pattern 152 has a same shape as that of the amorphous silicon active layer 13, a mask for forming the amorphous silicon active layer 13 can be used in step S13.
In addition, for example, the n+ amorphous silicon film 151 is etched by dry etching.
S14, as shown in
In particular, as shown in
Of course, in case the display substrate is an array substrate, for example, data lines are formed at a same time as forming the source 16 and the drain 17.
Furthermore, as shown in
For example, the n+ amorphous silicon transitional pattern 152, the first pattern 141, and the second pattern 142 are etched by dry etching.
It is noted that, prior to the n+ amorphous silicon transitional pattern 152, the first pattern 141, and the second pattern 142 are etched, the second pattern 142 is shielded by the n+ amorphous silicon transitional pattern 152, while there is no shielding on the first pattern 141, as shown in
SiO2, SixNy, and SiOxNy are excellent insulating materials with a low cost. Thus, in embodiments of the present disclosure, the first pattern 141 and the second pattern 142 for example comprises at least one of SiO2, SixNy, and SiOxNy. Namely, the protection insulating layer 14 comprises at least one of SiO2, SixNy, and SiOxNy.
On basis of this, in the above step S14, the n+ amorphous silicon transitional pattern 152, the first pattern 141 and the second pattern 142 are etched, by dry etching in a mixture comprising e.g., SF6 and O2.
By taking SiO2 as an example, in the mixture comprising SF6 and O2, an etching rate of silicon is larger than that of SiO2. Thus, n+ amorphous silicon on the second pattern 142 is etched away quickly, until the first pattern 141 of SiO2 is completely etched away and the etching process is stopped. At this time, a partial thickness of SiO2 in the second pattern 142 is etched away, and the remaining thickness of SiO2 is retained to form the protection insulating layer pattern 143.
Of course, a mixture comprising Cl2 and O2, or a mixture comprising CF4 and O2 has a similar effect as the mixture comprising SF6 and O2, which are not repeated here for simplicity. In these mixtures, SixNy and SiOxNy also have a same effect as SiO2.
On basis of this, for example, the thickness of n+ amorphous silicon is set to be equal to or slightly larger than that of the first pattern 141. As a result, when the first pattern 141 is etched away, n+ amorphous silicon has been etched away. The first pattern 141 and the second pattern 142 have a same thickness.
In embodiments of the present disclosure, the n+ amorphous silicon transitional pattern 152, the first pattern 141 and the second pattern 142 are etched by dry etching in the mixture comprising SF6 and O2, the mixture comprising Cl2 and O2, or the mixture comprising CF4 and O2. In this way, the process for forming the protection insulating layer pattern 143 can be easily controlled.
The method for fabricating a display substrate will be described hereinafter with reference to another embodiment. As shown in
S20, as shown in
S21, as shown in
S22, as shown in
S23, as shown in
S24, as shown in
Here, as shown in
Furthermore, as shown in
Here, since the first pattern 141 and the second pattern 142 have a same thickness, both the first pattern 141 and the second pattern 142 are etched away.
On basis of this, as shown in
Embodiments of the present disclosure further provide a display substrate, as shown in
In embodiments of the present disclosure, the protection insulating layer 14 for example can be made from any suitable material which does not affect the channel region.
Embodiments of the present disclosure provide a display substrate. After forming the amorphous silicon active layer 13, and prior to forming the n+ amorphous silicon ohmic contact layer 15, the protection insulating layer 14 comprising the first pattern 141 in the non-TFT region 30 and the second pattern 142 in the channel region is formed. For example, during forming the n+ amorphous silicon ohmic contact layer 15, the first pattern 141 is completely removed, and the thickness of the second pattern 142 is partially retained to form the protection insulating layer pattern 143. On one hand, this ensures that the gate insulating layer 12 is kept intact, the damage to the gate insulating layer 12 is avoided, and the performance of the display substrate is ensured. On the other hand, the protection insulating layer pattern 143 is formed on the channel region, which prevents external electrically conductive particles from polluting the channel, and reduces the leakage current of the TFT 02.
For example, the protection insulating layer pattern has a thickness of 5-15 nm.
In embodiments of the present disclosure, the thickness of the protection insulating layer pattern 143 is set to 5-15 nm. On one hand, this thickness is sufficient to prevent external electrically conductive particles from polluting the channel. On the other hand, the thickness of 5-15 nm is negligible, and thus avoids effects on an overall thickness of the display substrate.
SiO2, SixNy, and SiOxNy are excellent insulating materials with a low cost. Thus, the protection insulating layer pattern for example comprises at least one of SiO2, SixNy, and SiOxNy.
For example the display substrate is an array substrate.
This avoids a deviation of a liquid crystal capacitance and a storage capacitance from a simulated result due to the damage to the gate insulating layer 12, and thus avoids problems of image flickering, as well as deviations of parameters like a coupling voltage, response time, and charging ratio.
As shown in
Furthermore, the array substrate for example further comprises a common electrode.
As for an IPS (In-Plane Switching) array substrate, the pixel electrode and the common electrode are arranged in a same layer and spaced apart from each other, and both electrodes are strip shaped electrodes. As for an ADS (Advanced-super Dimensional Switching) array substrate, the pixel electrode and the common electrode are arranged in different layers, in which the upper electrode is a strip shaped electrode, and the lower electrode is a plate shaped electrode.
Embodiments of the present disclosure further provide a display panel, comprising the above display substrate.
In addition, embodiments of the present disclosure further provide a display device, which comprises the above display panel.
The display device for example is any product or component with a display function, such as a liquid crystal display, a liquid crystal TV, a digital photo frame, a mobile phone, a tablet computer.
Embodiments of the present disclosure provide a display substrate, a method for fabricating the same, and a display panel. After forming the amorphous silicon active layer, and prior to forming the n+ amorphous silicon ohmic contact layer, the protection insulating layer comprising the first pattern in the non-TFT region and the second pattern in the channel region is formed. During forming the n+ amorphous silicon ohmic contact layer, the gate insulating layer is maintained intact. This prevents damage to the gate insulating layer, and the performance of the display substrate is ensured. Since the material of the protection insulating layer is an insulating material, this prevents the channel region of the amorphous silicon active layer (i.e., a portion of amorphous silicon active layer corresponding to the gap between the source and the drain) from being polluted, and the performance of TFT is ensured.
Apparently, the person with ordinary skill in the art can make various modifications and variations to the present disclosure without departing from the spirit and the scope of the present disclosure. In this way, provided that these modifications and variations of the present disclosure belong to the scopes of the claims of the present disclosure and the equivalent technologies thereof, the present disclosure also intends to encompass these modifications and variations.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201610666482.3 | Aug 2016 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2017/088645 | 6/16/2017 | WO | 00 |
