CN1933098B - A mask for continuous lateral crystallization technology and a method for using the mask - Google Patents

Abstract

The invention provides a mask for a continuous lateral crystallization technology and a use method of the mask. The mask includes: the transparent grating comprises two long edges, a front edge and a rear edge, the two long edges are parallel to each other and have the same length, the front edge protrudes towards the outer side of the transparent grating, and the rear edge is recessed towards the inner part of the transparent grating. The invention can effectively eliminate the uneven area and avoid the problem of process speed reduction. With the improvement of the process speed, the continuous transverse crystallization process can simultaneously reduce the overlapping area of the melting area so as to prevent the polycrystalline silicon layer from absorbing excessive laser energy and reduce the possibility of the polycrystalline silicon layer breaking due to agglomeration.

Description

A mask for continuous lateral crystallization technology and a method for using the mask

technical field

The present invention relates to a mask, in particular to a mask for SLS (Sequential Lateral Solidification) technology and a method for using the mask.

Background technique

In recent years, liquid crystal displays (LCD: Liquid Crystal Display) have gradually replaced traditional cathode ray tube (CRT: Cathode Ray Tube) displays due to their advantages of thinness, power saving, and no radiation, and are widely used in desktop computers, personal In electronic products such as digital assistants, notebook computers, digital cameras and mobile phones.

As shown in FIG. 1 , it is a schematic diagram of a typical active matrix liquid crystal display panel. The liquid crystal display panel 10 has a plurality of pixel elements 12 arranged in a matrix. Each pixel element 12 is connected to a thin film transistor (TFT: Thin Film Transistor) 14 as a switch to control the charging and discharging of the pixel element 12 . The source of the thin film transistor 14 is electrically connected to a source driving circuit (not shown) through a signal line 16 , and its gate is electrically connected to a scanning driving circuit (not shown) through a scanning line 18 . Therefore, the display signal input from the outside can be converted into a source driving voltage Vs and a scanning driving voltage Vg respectively input to the source and gate of each thin film transistor 14 to generate a picture.

Generally speaking, the TFT 14 directly fabricated on the liquid crystal display panel 10 adopts an amorphous silicon (Amorphous Silicon) design due to the limitation of the temperature that the glass substrate can withstand. However, the switching speed, electrical effect and reliability of the amorphous silicon thin film transistor (a-TFT: Amorphous This Film Transistor) are not enough to meet the high computing speed required by the driving circuit. Therefore, the driving circuit must use polysilicon thin film transistors as switching elements, so that the driving circuit must be fabricated on a silicon chip and connected to the liquid crystal display panel 10 through wiring to control the display of the pixel elements 12 .

However, as the size of the liquid crystal display panel 10 increases, the switching speed provided by the traditional amorphous silicon thin film transistor is gradually insufficient. In order to improve the display effect of the liquid crystal display panel, and in order to make the driving circuit on the display panel to achieve light and thin requirements, it is necessary to try to fabricate polysilicon thin film transistors on the glass substrate. Therefore, it is necessary to try to make a high-quality polysilicon layer on the glass substrate.

As shown in FIG. 2 , it is a schematic diagram of a typical low temperature polysilicon process. As shown in the figure, an amorphous silicon layer 120 is formed on the surface of a substrate 100 , and a laser forms a molten layer 122 on the surface of the amorphous silicon layer 120 . The unmelted amorphous silicon material under the molten layer 122 acts as a seed crystal required for crystallization, and grows upward to form crystal grains 126 . However, the grain size 126 provided by this process is often less than one micron, which cannot effectively improve the electrical properties of the thin film transistor.

In order to increase the grain size, please refer to FIG. 3 , in a typical lateral crystallization (LateralSolidification) process, the laser passes through the mask 200 to melt the specific region A of the amorphous silicon layer 120, and at the same time, a lateral solidification is also produced in the molten region A. thermal gradient. The non-melted amorphous silicon material at the side of the molten region A acts as a seed crystal and grows toward the center of the molten region A to generate larger-sized crystal grains 128 .

As shown in FIG. 4A , it is a schematic diagram of a mask 300 typically used in a sequential lateral solidification (SLS: Sequential Lateral Solidification) process. As shown in the figure, the mask 300 has a plurality of first transparent slits 310 and a plurality of second transparent slits 320 arranged thereon. The front edge and the rear edge of the first transparent grating 310 and the second transparent grating 320 adopt a triangular symmetrical pattern design respectively. Each first transparent grating 310 is aligned with the opaque area between two adjacent second transparent gratings 320 . Moreover, the width of the first transparent grating 310 is greater than the distance between two adjacent second transparent gratings 320 .

4B and 4C show schematic diagrams of other mask 301, 302 designs for continuous lateral crystallization processes. Compared with the design of the mask 300 in FIG. 4A , the front and rear edges of the transparent gratings on the masks 301 and 302 respectively adopt rectangular and semicircular symmetrical patterns.

As shown in FIG. 5 , it is a schematic diagram of a continuous lateral crystallization process using the mask of FIG. 4A . First, in the first laser melting step (as shown by the dotted line in the figure), the laser passes through the first transparent grating 310 and the second transparent grating 320 on the mask 300, and irradiates the amorphous silicon layer at a certain reduction ratio. Instead, a molten region is formed on the amorphous silicon layer. Meanwhile, as shown in FIG. 6 , the first crystalline region A1 formed in this laser melting step is enlarged. Since the inhomogeneous region a with disordered crystal direction will be generated around the transparent gratings 310 and 320 due to light interference and scattering, only the central part of the first crystallization region A1 can be an ideal uniform lateral crystallization region b. Therefore, the length L of the lateral crystalline region b in FIG. 6A can only be at most equal to the length L1 of the projection of the long side of the transparent grating on the amorphous silicon layer.

In the second laser melting step (as shown by the solid line in FIG. 5 ), the mask 300 is moved to the right, so that the first transparent grating 310 is aligned with the uncrystallized portion between the first crystallization regions A1 . Since the width of the first transparent grating is greater than the distance between two adjacent second transparent gratings, as shown in FIG. 6B, the second crystallization region A2 produced in this laser irradiation step and the long side of the first crystallization region A1 There will be some overlap. Therefore, the inhomogeneous region a located around the long side of the first crystallization region A1 can be re-melted through this step to improve its crystallization effect.

As for the uneven region a near the leading edge and the trailing edge of the first crystalline region A1, it must be improved by reducing the moving distance of the mask. Further, as shown in FIG. 6C, the distance D between the first crystalline region A1 formed in the first laser melting step and the third crystalline region A3 formed in the second laser melting step must be smaller than the length of the lateral crystalline region b L1, to ensure that the leading edge of the first crystalline region A1 fully overlaps the trailing edge of the third crystalline region A3, so as to effectively eliminate the uneven region a. Therefore, the mask moving distance cannot be increased and the process speed is limited. At the same time, since the overlapping area of the first crystalline region A1 and the third crystalline region A3 increases, the possibility of agglomeration causing holes in the polysilicon layer increases.

Contents of the invention

The object of the present invention is to provide a mask applied to continuous lateral crystallization, which can effectively eliminate the non-uniform region a and avoid the problem of process speed reduction.

The present invention provides a continuous lateral crystallization technique for crystallizing an amorphous silicon layer to form a polycrystalline layer mask, comprising:

At least one transparent grating, the transparent grating includes two long sides, a front edge and a rear edge, the two long sides are parallel to each other and have the same length, the front edge protrudes toward the outside of the transparent grating, and the rear edge faces The interior of the transparent grating is concave.

The shape of the front edge is V-shaped, arc-shaped or trapezoidal.

The shape of the trailing edge is V-shaped, arc-shaped or trapezoidal.

The shape of the front edge is V-shaped, the shape of the trailing edge is V-shape, and the top angle of the V-shaped front edge is smaller than or equal to the top angle of the V-shaped trailing edge.

The top angle of the V-shaped leading edge ranges from 10 degrees to 90 degrees.

The top angle of the V-shaped trailing edge ranges from 90 degrees to 170 degrees.

The present invention also provides a mask for crystallizing an amorphous layer to form a polycrystalline layer by a lateral crystallization technique, comprising:

At least one transparent grating, the transparent grating includes two long sides, a front edge and a rear edge, the two long sides are parallel to each other and have the same length, the front edge protrudes toward the outside of the transparent grating, and the rear edge forms a A straight line connects to the two long sides.

The shape of the front edge is V-shaped, arc-shaped or trapezoidal.

The front edge is V-shaped with a top angle ranging from 10° to 90°.

The present invention also provides a method for crystallizing an amorphous silicon layer using a mask having at least one transparent grating with two long sides, a leading edge and a trailing edge, the leading edge facing the The outside of the transparent grating protrudes, and the trailing edge is recessed toward the inside of the transparent grating. The method at least includes the following steps:

providing a substrate;

making an amorphous silicon layer on the substrate;

aligning the mask to the substrate;

melting the amorphous silicon layer through the mask to generate a plurality of first crystalline regions in the amorphous silicon layer respectively corresponding to the transparent grating;

laterally moving the mask such that a leading edge or a trailing edge of the transparent grating overlaps the first crystallized region;

The amorphous silicon layer is melted through the mask to produce a plurality of second crystalline regions.

The distance that the mask moves laterally is less than the length of the long side of the transparent grating.

The distance that the mask moves laterally is greater than the length of the long side of the transparent grating minus the distance of the trailing edge depression.

The advantage of the present invention is that it can effectively eliminate the non-uniform area, and also avoid the problem of process speed reduction. As the process speed increases, the continuous lateral crystallization process of the present invention can simultaneously reduce the overlapping area of the melting region, so as to prevent the polysilicon layer from absorbing too much laser energy and reduce the possibility of polysilicon layer being broken due to agglomeration.

Description of drawings

1 is a schematic diagram of an active matrix liquid crystal display panel;

2 is a schematic diagram of a low-temperature polysilicon process;

3 is a schematic diagram of a lateral crystallization process;

4A, 4B and 4C are schematic diagrams of masks used in a continuous lateral crystallization process;

5 is a schematic diagram of a continuous lateral crystallization process using the mask of FIG. 4A;

6A is an enlarged view of the first crystalline region formed in the continuous lateral crystallization process of FIG. 5;

FIG. 6B is an enlarged view showing the second crystalline region and the first crystalline region formed in the continuous lateral crystallization process of FIG. 5;

6C is an enlarged view of the first crystalline region and the third crystalline region formed in the continuous lateral crystallization process of FIG. 5;

7A to 7I are schematic diagrams of the first to ninth embodiments of the transparent grating of the mask of the present invention;

FIG. 8A is a schematic diagram of mask movement when using the mask of FIG. 7A for a continuous lateral crystallization process;

8B and 8C are diagrams respectively showing the first crystallization region and the second crystallization region formed in the continuous lateral crystallization process of FIG. 8A .

Description of figure number:

LCD panel 10 pixel element 12

Thin film transistor 14 Signal line 16

Scanning line 18 Amorphous silicon layer 120

Substrate 100 Fusion layer 122

Die 126, 128 Mask 200, 300, 301, 302

The first transparent grating 310 The second transparent grating 320

Inhomogeneous region a Uniform lateral crystallization region b

Detailed ways

As shown in FIG. 7A , it is a schematic view of the first embodiment of the transparent grating included in the mask of the present invention. As shown in the figure, the transparent grating has two corresponding long sides, a leading edge and a trailing edge. Wherein, the two corresponding long sides are parallel to each other and have the same length (the lengths are both X1). The front edge is V-shaped, its tip is located on the center line of the transparent grating, and protrudes a predetermined distance F1 toward the outside of the transparent grating (ie, the right side in the figure). The trailing edge is V-shaped, its tip is located on the center line of the transparent grating, and is recessed toward the inside of the transparent grating (ie, the right side in the figure) for a predetermined distance R1.

Although in this embodiment, the V-shaped front edge and the V-shaped trailing edge have the same shape, the protruding distance F1 of the V-shaped leading edge and the concave distance R1 of the V-shaped trailing edge are also the same. However, the present invention is not limited thereto. As shown in FIG. 7B , in the second embodiment of the transparent grating of the present invention, the protruding distance F2 of the V-shaped front edge is greater than the concave distance R2 of the V-shaped trailing edge. In other words, the apex angle c of the V-shaped leading edge of the transparent grating is smaller than the apex angle d of the V-shaped trailing edge. As for a preferred embodiment, the top angle c of the V-shaped leading edge is preferably between 10° and 90°, and the top angle d of the V-shaped trailing edge is preferably between 90° and 170°.

As shown in FIG. 7A to FIG. 7F , the first to sixth embodiments of the transparent grating of the present invention are shown. As shown in the figure, the leading edge of the transparent grating can be V-shaped (as shown in Figure 7A and Figure 7B ), arc-shaped (as shown in Figure 7C and Figure 7D ), or trapezoidal (as shown in Figure 7E and Figure 7F shown) and other different shapes; and the trailing edge can also be V-shaped (as shown in Figure 7A and Figure 7B), arc-shaped (as shown in Figure 7C and Figure 7D) or trapezoidal (as shown in Figure 7E and Figure 7F Show) and other different appearance.

In addition, the transparent gratings in each of the above embodiments adopt the same shape type at the leading edge and the trailing edge. That is to say, if the front edge of the transparent grating is V-shaped, its trailing edge is also V-shaped (as shown in FIGS. 7A and 7B ); if the front edge of the transparent grating is arc-shaped, its trailing edge is also arc-shaped. type (as shown in FIG. 7C and FIG. 7D ), and if the front edge of the transparent grating is trapezoidal, its trailing edge is also trapezoidal (as shown in FIG. 7E and FIG. 7F ).

Secondly, the protruding distance of the leading edge and the concave distance of the trailing edge of the transparent grating of the present invention can be the same (as shown in Figure 7A, Figure 7C and Figure 7E), or different (as shown in Figure 7B, Figure 7D and Figure 7F ). The distance by which the leading edge protrudes is preferably greater than the distance by which the trailing edge is recessed. In addition, please refer to FIG. 7G to FIG. 7I. In the seventh to ninth embodiments of the transparent grating of the present invention, the front edges of the transparent grating are respectively V-shaped, arc-shaped or trapezoidal, however, the distance of the trailing edge depression is reduced to Zero, that is, the trailing edge adopts the shape of a straight line.

As shown in FIG. 8A , it is a schematic diagram of a continuous lateral crystallization process using the mask of the present invention. In the figure, the transparent grating shown in FIG. 7A is taken as an example for illustration. In the continuous lateral crystallization process, firstly, a substrate is provided, and an amorphous silicon layer is formed on the substrate (please also refer to FIG. 2 ). Subsequently, the mask is aligned to the substrate in the first laser melting step, as indicated by the dotted line in FIG. 8A. The laser beam passes through the transparent grating on the mask and projects on the amorphous silicon layer with a certain scaling ratio, so as to generate a plurality of first crystalline regions B1 in the amorphous silicon layer (please refer to FIG. 8B ). Subsequently, as shown by the solid line in FIG. 8A , the mask is moved laterally for a subsequent second laser melting step. The laser passes through the mask to melt the amorphous silicon layer to generate a plurality of second crystalline regions B2 (please refer to FIG. 8C ).

It is worth noting that, as shown in Figure 8C, the leading edge of the second crystalline region B2 formed in the second laser melting step must fully overlap with the trailing edge of the first crystalline region B1, so as to ensure that the first crystalline The inhomogeneous region with disordered crystal direction at the trailing edge of region B1 can be repaired through this melting step. It can be seen that, in order to ensure a good crystallization effect, the distance D1 between the first crystalline region B1 and the second crystalline region B2 must be smaller than the length S1 of the long side of the first crystalline region B1. Therefore, the distance D1 must be smaller than the length X1 of the long side of the transparent grating (as shown in FIG. 8A ) multiplied by the reduction ratio of the projection of the transparent grating to the amorphous silicon layer. In addition, although in the above continuous lateral crystallization process, as shown in FIG. 8A , the mask is moved to the right in the figure to perform the subsequent laser melting step; however, the present invention is not limited thereto. As mentioned above, as long as the distance D1 between adjacent secondary laser melting steps is less than the length S1 of the long side of the crystallized region, there is no limitation on the moving direction of the mask.

Compared with the conventional continuous lateral crystallization process in FIG. 6C , the distance between the first crystallization region A1 and the third crystallization region A3 must be smaller than the length L1 of the lateral crystallization region b to obtain a good crystallization effect. As shown in FIG. 8B , in the continuous lateral crystallization process of the present invention, the distance D1 between the first crystallization region B1 and the second crystallization region B2 formed in two consecutive laser melting steps is not limited.

Further, assuming that the transparent grating of the present invention has the same length as the traditional transparent grating of FIG. The distance by which the triangular trailing edge of a conventional transparent grating protrudes. Please refer to FIG. 6A and FIG. 8A, the side length L of the first crystalline region A1 formed through the conventional transparent grating is equal to the long side length S1 of the first crystalline region B1 formed through the transparent grating of the present invention after subtraction The distance r of the edge depression. As shown in FIG. 8A, the continuous lateral crystallization process of the present invention obviously allows the separation distance D1 between the first crystallization region B1 and the second crystallization region B2 to be increased to be greater than the long side length S1 of the first crystallization region B1 minus the trailing edge depression The distance r. Therefore, the allowable moving distance of the mask in the continuous secondary laser melting step of the continuous lateral crystallization process of the present invention is greater than the allowable moving distance of the traditional continuous lateral crystallization process. Therefore, compared with the continuous lateral crystallization process using traditional mask design, the continuous lateral crystallization process of the present invention can achieve a higher process speed. As the process speed increases, the continuous lateral crystallization process of the present invention can simultaneously reduce the overlapping area of the melting region, so as to prevent the polysilicon layer from absorbing too much laser energy and reduce the possibility of polysilicon layer being broken due to agglomeration.

The above specific embodiments are only used to illustrate the present invention, but not to limit the present invention.

Claims (10)

1. A mask for continuous lateral crystallization technology, characterized in that it comprises: At least one transparent grating, the transparent grating includes two long sides, a front edge and a rear edge, the two long sides are parallel to each other and have the same length, the front edge protrudes toward the outside of the transparent grating, and the rear edge faces The interior of the transparent grating is concave. 2. The mask for continuous lateral crystallization according to claim 1, wherein the shape of the front edge is V-shaped, arc-shaped or trapezoidal. 3. The mask for continuous lateral crystallization according to claim 1, wherein the shape of the trailing edge is V-shaped, arc-shaped or trapezoidal. 4. The mask for continuous lateral crystallization technology according to claim 1, wherein the shape of the leading edge is V-shaped, the shape of the trailing edge is V-shaped, and the V-shaped front The apex angle of the edge is less than or equal to the apex angle of the V-shaped trailing edge. 5 . The mask for continuous lateral crystallization as claimed in claim 4 , wherein the top angle of the V-shaped front edge ranges from 10° to 90°. 6 . The mask for continuous lateral crystallization as claimed in claim 4 , wherein the top angle of the V-shaped trailing edge is between 90° and 170°. 7. A mask for continuous lateral crystallization technology, comprising: At least one transparent grating, the transparent grating includes two long sides, a front edge and a rear edge, the two long sides are parallel to each other and have the same length, the front edge protrudes toward the outside of the transparent grating, and the rear edge forms a A straight line connects to the two long sides. 8. The mask for continuous lateral crystallization according to claim 7, wherein the shape of the front edge is V-shaped, arc-shaped or trapezoidal. 9 . The mask for continuous lateral crystallization as claimed in claim 8 , wherein the leading edge is V-shaped and its top angle is between 10° and 90°. 10. A method for crystallizing an amorphous silicon layer using a mask, wherein the mask has at least one transparent grating, the transparent grating has two long sides, a leading edge and a trailing edge, the leading edge protruding toward the outside of the transparent grating, and the trailing edge is recessed toward the inside of the transparent grating, the method at least includes the following steps: providing a substrate; making an amorphous silicon layer on the substrate; aligning the mask to the substrate; melting the amorphous silicon layer through the mask to generate a plurality of first crystalline regions in the amorphous silicon layer respectively corresponding to the transparent grating; moving the mask laterally so that the leading edge or the trailing edge of the transparent grating overlaps the first crystallized region, wherein the distance the mask moves laterally is less than the length of the long side of the transparent grating and greater than the length of the transparent grating the length of the long side of the grating minus the distance of the trailing edge depression; The amorphous silicon layer is melted through the mask to produce a plurality of second crystalline regions.

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