CN1275291C - Method for making polysilicon film by excimer laser recrystallization process - Google Patents

Abstract

The invention provides a method for manufacturing a polycrystalline silicon film by using an excimer laser recrystallization process. The method comprises providing a substrate with a first region, a second region and a third region defined on the surface, forming an amorphous silicon film on the substrate, removing part of the amorphous silicon film to form an alignment mark in the third region, forming a shielding layer on the amorphous silicon film, and removing the shielding layer in the first region to perform the excimer laser recrystallization process to recrystallize the amorphous silicon film in the first region into a polysilicon film.

Description

Method for making polysilicon film by excimer laser recrystallization process

technical field

The invention provides a method for manufacturing a polysilicon film, especially a method for manufacturing a polysilicon film by using an excimer laser crystallization (ELC) process.

Background technique

With the rapid development of technology, thin, light, power-saving and portable smart information products have filled our living space, and monitors have played a very important role in it, whether it is mobile phones, personal digital assistants or notebook computers , both require a display as a human-machine communication interface. However, the amorphous silicon thin-film transistor liquid crystal display (a-TFT LCD), which has been mass-produced today, is difficult to further meet the requirements of thinness, power saving, and high-quality image due to the limitation of carrier mobility. Next will be low temperature polysilicon (LTPS) thin film transistor liquid crystal displays.

In liquid crystal displays, since the heat resistance of general glass substrates can only reach 600°C, if polysilicon thin films are directly fabricated at high temperatures, the glass substrate will be distorted and deformed. Therefore, traditional polysilicon thin film transistor liquid crystal displays often have to To use expensive quartz as a substrate, the scope of application is often limited to small-sized liquid crystal panels. Therefore, at present, another low-temperature polysilicon thin film production method using amorphous silicon thin film recrystallization has gradually become the mainstream, and the excimer laser crystallization (excimer laser crystallization, ELC) process has received special attention.

In addition, the display panel of a liquid crystal display often includes a plurality of low-temperature polysilicon thin film transistors arranged in a matrix to drive the pixel electrodes in the display panel to generate images. Therefore, the formed polysilicon thin film usually includes a plurality of The polysilicon island structures are respectively used as active areas of the LTPS TFTs to form the source, drain and channel regions therebetween.

For the convenience of description, only a polysilicon island structure is taken as an example in the following figure to illustrate the existing method of manufacturing a polysilicon thin film by excimer laser recrystallization process. Please refer to FIG. 1 to FIG. 4 . FIG. 1 to FIG. 4 are schematic diagrams of a method for fabricating a polysilicon thin film by an excimer laser recrystallization process in the prior art. As shown in FIG. 1, a display panel 10 is first provided, and the display panel 10 includes a substrate 12, then a sputtering process is performed to form a metal layer (not shown) on the surface of the substrate 12, and then a first light The metal layer is patterned by the etching and etching process to form an alignment mark 14 on the surface of the substrate 12 . Wherein, the substrate 12 is a glass substrate, and the alignment mark 14 includes at least one protruding structure, which is located in the peripheral area where the circuit layout will not be performed, so even after several deposition processes, the alignment mark 14 can still be used. For equipment to be clearly identified.

Generally speaking, multiple photolithography processes are often used in the polysilicon thin film and subsequent display panel manufacturing process. Once the alignment deviation occurs in these photolithography processes, it is easy to reduce the reliability of the components. Serious defects even lead to loss of function. Therefore, in order to improve the alignment capability of each device, each device will be positioned according to the alignment mark 14 before performing various operations (especially the photolithography process), so as to reduce Defects caused by misalignment.

As shown in Figure 2, a buffer layer 16 and an amorphous silicon film 18 are sequentially formed on the surface of the substrate 12, and the surface of the amorphous silicon film 18 defines a first region 20 and a second region 30, and then as follows As shown in FIG. 3 , a patterned mask layer (masklayer) 22 is formed on the surface of the amorphous silicon film 18 to cover the second region 30 . Wherein, the shielding layer 22 can be a single-layer material comprising a metal layer and a silicon nitride layer or a multi-layer structure composed of the above materials, and its function is to increase the reflectivity of the second region 30 by the metal layer to The heat absorption of the lower amorphous silicon film 18 is reduced or the high thermal conductivity of the silicon nitride layer is used to make the amorphous silicon film 18 covered with the shielding layer 22 form a crystal nucleus first. In general, the purpose of forming the shielding layer 22 is to make the amorphous silicon film 18 in the second region 30 (the region covered with the shielding layer 22) become partially molten, while the first region 20 (the region not covered with the shielding layer 22) ) of the amorphous silicon film 18 reaches a completely molten state, so when the excimer laser irradiation ends, when the molten amorphous silicon layer 18 starts to solidify, it will be partly melted and completely melted due to a heterogeneous interface between the regions. The melted area is the base point of nucleation, and lateral grain growth occurs from the partially melted second area 30 to the fully melted first area 20 to form a polysilicon film 24 in the first area 20 .

As shown in FIG. 4 , a photolithography and etching process is then performed to remove the masking layer 22 and the polysilicon layer 18 on the second region 30 to form a polysilicon island structure 24 in the first region 20 . Finally, the subsequent liquid crystal display panel process is performed, and the polysilicon island 24 is used as an active area in the liquid crystal display to form a driving circuit in the liquid crystal display panel.

In the above-mentioned excimer laser recrystallization process, after defining the position of the alignment mark, patterning the masking layer, and finally forming the polysilicon island, each photolithography process needs to be used once, that is to say, on the entire polysilicon It is necessary to use three photolithography processes to form a polysilicon film with the polysilicon island structure. Therefore, although the above method can control the position of the grain boundary formation, the production process is quite complicated, and it requires a lot of time. More process time will also lead to an increase in manufacturing cost. Therefore, how to simplify the excimer laser recrystallization process is an important research topic at present.

Contents of the invention

The main purpose of the present invention is to provide a method for producing a polysilicon thin film by using an excimer laser recrystallization process, which improves the disadvantages of complex processes in the prior art, so as to reduce manufacturing costs and shorten process time.

The present invention provides a method for producing a polysilicon film by using an excimer laser recrystallization process. First, a substrate is provided, and the surface of the substrate defines a first region, a second region surrounding the first region, and a third region, and then an amorphous silicon film is formed on the substrate, and then by A first photolithography and etching process, removing part of the amorphous silicon film in the third area, and forming an alignment mark in the third area, and then forming a masking layer, which covers the substrate, on the amorphous silicon film and the alignment mark, and perform a second photolithography and etching process, remove the shielding layer in the first region above the amorphous silicon film and perform the excimer laser recrystallization process, The amorphous silicon film in the first region is recrystallized into a polysilicon film. Finally, an etching process is performed to remove the masking layer.

The present invention also provides a method for making a polysilicon film by using an excimer laser recrystallization process, the method includes the following steps: providing a substrate, the surface of the substrate defines a first region, a second region around In the first area and a third area; forming an amorphous silicon film above the substrate; performing a first photolithography and etching process to remove the amorphous silicon film in the third area, and Forming an alignment mark in the third area; forming a heat-containing cover layer covering the substrate, the amorphous silicon film and the alignment mark; forming a shielding layer on the heat-containing cover layer; performing a first 2. photolithography and etching process, remove the shielding layer in the first region above the amorphous silicon film; and perform the excimer laser recrystallization process to recrystallize the amorphous silicon film in the first region into a polysilicon film.

The polysilicon thin film manufacturing method of the present invention only needs to use two photolithography processes to form a polysilicon island structure that can control the position of the grain boundary, so the process can be greatly simplified, and the shortcomings of complicated processes in the prior art can be improved to reduce manufacturing costs and shorten the production process. Craft time.

Description of drawings

1 to 4 are schematic diagrams of a method for making a polysilicon film with an excimer laser recrystallization process in the prior art;

5 to 9 are schematic diagrams of a method for producing a polysilicon film with an excimer laser annealing process in the first embodiment of the present invention;

10 is a schematic diagram of a method for fabricating a polysilicon film by an excimer laser annealing process in the second embodiment of the present invention; and

FIG. 11 is a schematic diagram of a method for fabricating a polysilicon film by an excimer laser annealing process in the third embodiment of the present invention.

The reference signs in the accompanying drawings are explained as follows:

10 Display panel 12 Substrate

14 alignment mark 16 buffer layer

18 Amorphous silicon thin film 20 The first area

22 Shielding layer 24 Amorphous silicon film

30 Second area 110 Display panel

112 substrate 114 buffer layer

116 Amorphous silicon film 118 Alignment mark

120 First area 122 Covering layer

124 Polysilicon film 130 Second area

140 Third area 210 Display panel

212 Substrate 214 Buffer layer

216 Amorphous silicon film 218 Alignment mark

220 The first area 222 Covering layer

223 Thermal coating layer 224 Polysilicon thin film

230 Second Area 240 Third Area

322 Shielding layer 323 Heat containing covering layer

324 polysilicon film

Detailed ways

Please refer to FIG. 5 to FIG. 9 . FIG. 5 to FIG. 9 are schematic diagrams of a method for fabricating a polysilicon thin film by an excimer laser annealing process in the first embodiment of the present invention. As shown in FIG. 5, a display panel 110 is first provided, and the display panel 110 includes a substrate 112, and the surface of the substrate 112 defines a first region 120, a second region 130 surrounding the first region 120 and a third region. area. Next, a buffer layer 114 is formed on the surface of the substrate 112 to prevent the impurity in the substrate 112 from being diffused upward in the subsequent process and affecting the quality of the polysilicon film, and then an amorphous silicon film 116 is formed on the buffer layer 114 . In a preferred embodiment of the present invention, the substrate 110 is a glass substrate, and the buffer layer 114 is a silicon-oxygen layer or a polycrystalline structure composed of a silicon-oxygen layer and a silicon-nitride layer, and the methods for forming the above layers include: There are many kinds, such as low-pressure chemical vapor deposition (LPCVD) process, plasma-assisted chemical vapor deposition (PECVD) process, and sputtering (sputtering) process, which are all existing standard processes, so they will not be repeated here.

As shown in FIG. 6, a first photolithography and etching process is then carried out to pattern the amorphous silicon film 116, and simultaneously remove part of the amorphous silicon film 116 in the third region 140, so that the amorphous silicon film 116 in the third region A pair of alignment marks 118 are formed within 140 . The alignment mark 118 includes at least one protruding structure and is located in the peripheral area where circuit layout will not be performed. Therefore, even after several deposition processes, the alignment mark 118 can still be clearly identified by the equipment.

Then, as shown in FIG. 7 , a masking layer 122 is formed on the display panel 110 to cover the buffer layer 114 , the amorphous silicon film 116 and the alignment marks 118 . Wherein, the shielding layer 122 is a single-layer structure including a silicon oxide layer (SiO _x ), a silicon nitride layer (SiN), a metal layer, and a silicon oxynitride (SiON) layer, or a multilayer stack composed of the above materials. structure, and can be formed according to the materials used, using appropriate process methods, such as the existing low-pressure chemical vapor deposition (LPCVD) process, plasma-assisted chemical vapor deposition (PECVD) process, and sputtering (sputtering) process.

As shown in FIG. 8 , a second photolithography and etching process is then performed to remove the masking layer 122 in the first region 120 to expose the amorphous silicon film 116 in the first region 120 . Then irradiate with an excimer laser, no matter whether the shielding layer 122 uses a metal layer to increase the reflectivity or utilizes a high thermal conductivity material to increase the heat dissipation rate, the amorphous silicon film 116 in the first region 120 will reach a completely molten state. , and keep the amorphous silicon film 116 in the second region 130 still in an unmelted or partially melted state. Then the irradiation of the excimer laser is stopped, and the molten amorphous silicon film 116 is recrystallized into a polysilicon film 124 .

Generally speaking, the used excimer laser is generated by molecules such as XeCl, ArF, KrF or XeF, and different molecules will produce different wavelengths, and the output power and irradiation time of the excimer laser can be determined according to the thickness of the amorphous silicon thin film 116. The thickness is adjusted appropriately, since the adjustment of this part of the process parameters should be well known to those skilled in the art, so it will not be repeated here. It is worth noting that, except that the excimer laser used in the method of the present invention includes a short pulse laser (about 20 to 50 ns) widely used in the prior art, it also includes a long pulse period laser, and its pulse time is about 150 to 250 ns, to increase the size of the formed crystal grains, thereby increasing the mobility of carriers in the formed polysilicon thin film 124 and improving the device performance of the low temperature polysilicon thin film transistor.

As shown in FIG. 9 , an etching process is then performed to remove the shielding layer 122 on the surface of the display panel 110 to form a polysilicon island structure, which can then continue to be used as a low-temperature polysilicon film. The active area of the transistor is used for the subsequent fabrication of the display panel. Since the subsequent process should be easily completed by those skilled in the art, it will not be described in detail here.

Based on the above, the method of the present invention uses the amorphous silicon film 116 to form the alignment mark 118 , so one deposition process and one photolithography process can be reduced, thereby shortening the process time and reducing the manufacturing cost.

Please refer to FIG. 10 , which is a schematic diagram of a method for fabricating a polysilicon film by an excimer laser annealing process in a second embodiment of the present invention. The process method of this embodiment is similar to that of the first embodiment, the only difference is that after the second photolithography and etching process is performed to pattern the shielding layer 222, a thermal covering layer 223 is first formed to cover the shielding layer 222 and the amorphous silicon film 216, and then irradiated with an excimer laser to recrystallize the amorphous silicon film 216 in the first region 220 into a polysilicon film 224, and then remove the masking layer 222 and the thermal cover by an etching process. Layer 223. Wherein, the heat-containing covering layer 223 is composed of silicon oxide (SiO _x ), silicon nitride (SiN), silicon oxynitride (SiON) or a combination of the above materials, which can be used to reduce heat loss, so that the melting in the first region 220 The amorphous silicon film 216 in the molten state can be recrystallized at a higher ambient temperature, thereby increasing the size of the formed grains.

Please refer to FIG. 11 , which is a schematic diagram of a method for fabricating a polysilicon film by an excimer laser annealing process in the third embodiment of the present invention. The process principle of this embodiment is the same as that of the aforementioned second embodiment, except that in this embodiment, the shielding layer 322 is formed after the thermal covering layer 323 is formed first. Since the masking layers 122 and 222 in the aforementioned embodiments are all directly formed on the amorphous silicon films 116 and 226, once the metal layer or the nitrogen-silicon layer is used as the main material below the masking layer, polysilicon formation is often easy to occur. The film is contaminated by metal or the semiconductor film is peeled off due to stress. Therefore, the third embodiment of the present invention can solve this problem by forming the heat-containing covering layer 323 first, thereby increasing the reliability of the product.

Compared with the process method in the prior art which first forms the alignment mark and then performs the amorphous silicon thin film, the present invention integrates the patterning of the amorphous silicon thin film and the production of the alignment mark, so the process can be greatly simplified, the process time can be shortened, and Reduce manufacturing costs. In addition, the embodiment of the present invention also discloses a polysilicon thin film manufacturing method including forming a heat-containing covering layer and using a long pulse period laser, in addition to further increasing the size of the crystal grains in the formed amorphous silicon thin film In addition, it can effectively solve problems such as metal pollution or semiconductor film peeling that are easily generated in the prior art, so as to effectively improve the electrical performance and reliability of components.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the patent of the present invention.

Claims (20)

1. one kind is utilized the excimer laser crystallization processes method of making a polysilicon membrane again, and this method includes the following step:

One substrate is provided, and this substrate surface definition has a first area, a second area around this first area, and one the 3rd zone;

Form an amorphous silicon membrane in this substrate top;

Carry out one first photoetching and etch process, remove this amorphous silicon membrane in the 3rd zone, and in the 3rd zone, form an alignment mark;

Form a shielding layer, this shielding layer is covered on this substrate, this amorphous silicon membrane and this alignment mark;

Carry out one second photoetching and etch process, remove this shielding layer in this this first area, amorphous silicon membrane top; And

Carry out this excimer laser crystallization processes again, make this amorphous silicon membrane in this first area recrystallize into a polysilicon membrane.

2. the method for claim 1, wherein this substrate surface includes a resilient coating in addition, and this amorphous silicon membrane is formed at this buffer-layer surface.

3. the method for claim 1, wherein this method will remove this shielding layer again after forming this polysilicon membrane.

4. the method for claim 1, wherein this polysilicon layer is used as the active region of a thin-film transistor.

5. the method for claim 1, wherein this alignment mark is used for increasing the alignment ability of subsequent technique.

6. the method for claim 1, wherein this shielding layer is to include silica layer, nitrogen silicon layer, metal level, silicon oxynitride layer or the combination of above-mentioned material.

7. the method for claim 1, wherein this excimer laser again crystallization processes be to utilize an excimer laser to shine this amorphous silicon membrane, reach partially molten state so that be coated with interior this amorphous silicon membrane of this second area of this shielding layer, this amorphous silicon membrane reaches complete molten condition in this first area of this shielding layer and be not coated with, laterally long brilliant by the interface place of this first area and this second area again towards this first area, in this first area, to form a polysilicon membrane.

8. the method for claim 1 wherein includes a long pulse cycle laser in addition in this excimer laser.

9. method as claimed in claim 8, wherein the cycle of this long pulse cycle laser is 150 to 250ns.

10. the method for claim 1, wherein this method is in carrying out this excimer laser again before the crystallization processes, and other forms a heat and contains cover layer and be covered on this shielding layer and this amorphous silicon membrane, to increase the grain size of formed this polysilicon membrane.

11. one kind is utilized the excimer laser crystallization processes method of making a polysilicon membrane again, this method includes the following step:

One substrate is provided, and this substrate surface and definition have a first area, a second area around this first area, and one the 3rd zone;

Form an amorphous silicon membrane in this substrate top;

Carry out one first photoetching and etch process, remove this amorphous silicon membrane in the 3rd zone, and in the 3rd zone, form an alignment mark;

Forming a heat contains cover layer and is covered on this substrate, this amorphous silicon membrane and this alignment mark;

Contain formation one shielding layer on the cover layer in this heat;

Carry out one second photoetching and etch process, remove this shielding layer in this this first area, amorphous silicon membrane top; And

Carry out this excimer laser crystallization processes again, make this amorphous silicon membrane in this first area recrystallize into a polysilicon membrane.

12. method as claimed in claim 11, wherein this substrate surface includes a resilient coating in addition, and this amorphous silicon membrane is formed at this buffer-layer surface.

13. method as claimed in claim 11, wherein this method will remove this shielding layer and this heat contains cover layer again after forming this polysilicon membrane.

14. method as claimed in claim 11, wherein this polysilicon layer is used as the active region of a thin-film transistor.

15. method as claimed in claim 11, wherein this alignment mark is used to provide a mask alignment function, to increase the alignment ability of subsequent technique.

16. method as claimed in claim 11, wherein this shielding layer is to include silica layer, nitrogen silicon layer, metal level, silicon oxynitride layer or the combination of above-mentioned material.

17. method as claimed in claim 11, wherein to contain cover layer be to include silica layer, nitrogen silicon layer, silicon oxynitride layer or the combination of above-mentioned material to this heat.

18. method as claimed in claim 11, wherein this excimer laser again crystallization processes be to utilize an excimer laser to shine this amorphous silicon membrane, reach partially molten state so that be coated with interior this amorphous silicon membrane of this second area of this shielding layer, this amorphous silicon membrane reaches complete molten condition in this first area of this shielding layer and be not coated with, laterally long brilliant by the interface place of this first area and this second area again towards this first area, in this first area, to form a polysilicon membrane.

19. method as claimed in claim 11 wherein includes a long pulse cycle laser in addition in this excimer laser.

20. method as claimed in claim 19, wherein the cycle of this long pulse cycle laser is 150 to 250ns.

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