KR20060086169A - Intensity controlling mask for laser, laser apparatus comprising the same and making method of thin film transistor using the same - Google Patents

Abstract

The present invention relates to a laser intensity control mask, a laser device comprising the same, and a method of manufacturing a thin film transistor using the same. Laser intensity control mask according to the present invention is characterized in that it comprises an intensity maintenance region and the intensity reduction region provided on both sides of the intensity maintenance region. Thereby, the intensity | strength of a laser beam can be made uniform.

Description

Intensity control mask for laser, laser device including the same, and manufacturing method of thin film transistor using same

1 is a diagram showing the intensity distribution of the laser light generated in the conventional laser device,

Figure 2 is a graph showing the intensity distribution of the laser light generated in the conventional laser device,

3 is a schematic diagram showing the irradiation of the laser light to the amorphous silicon layer in the laser device including the intensity control mask for laser according to the first embodiment of the present invention,

Figure 4 is a perspective view showing a laser intensity control mask according to a first embodiment of the present invention,

5 is a schematic diagram showing the intensity distribution of the laser beam passing through the intensity control mask for laser according to the first embodiment of the present invention,

6 is a schematic view showing a mask used in the laser device of FIG.

7 is a schematic diagram showing the intensity distribution of the laser light reflected from the intensity control mask for laser according to the first embodiment of the present invention,

8 is a schematic view showing that a pair of laser intensity control masks according to a first embodiment of the present invention is provided in pairs,

9 is a perspective view showing a laser intensity control mask according to a second embodiment of the present invention,

10 is a cross-sectional view showing the structure of a polysilicon thin film transistor according to an embodiment of the present invention,

11A to 11E are cross-sectional views illustrating a method of manufacturing a polysilicon thin film transistor according to an embodiment of the present invention.

12 is a schematic diagram illustrating a sequential lateral solid phase crystallization process of irradiating a laser to crystallize an amorphous silicon layer into a polysilicon layer,

FIG. 13 illustrates a microstructure of a polysilicon layer in a process in which an amorphous silicon layer is crystallized into a polysilicon layer through a sequential side solid phase crystallization process.

Figure 14 is a schematic diagram showing the irradiation of the laser light to the amorphous silicon layer in another laser device including a laser intensity control mask according to a first embodiment of the present invention.

Explanation of Signs of Major Parts of Drawings

10: laser generating unit 20: the first optical system

30a, 30b, 30c: reflection mirror 40: mask

41: light emitting part 45: the matting part

50: second optical system 60: projection lens unit

70: protective mirror 80: laser intensity control mask

The present invention relates to a laser intensity control mask, a laser device including the same, and a method of manufacturing a thin film transistor using the same.

Recently, flat display devices have come into the spotlight among display devices. The flat panel display device includes a liquid crystal display (LCD) and an organic electroluminescent device (OLED).

The liquid crystal display and the organic electroluminescent display display an image by different mechanisms, but have a thin film transistor to display the image in common.

The thin film transistor includes a channel portion, a gate electrode, a source contact portion, a data contact portion, and the like. The channel portion may be formed of amorphous silicon. However, amorphous silicon has low electrical characteristics and reliability due to low mobility, and it is difficult to make a large display area.

To overcome this problem, a polysilicon thin film transistor liquid crystal display using polysilicon having a mobility of about 20 to 150 cm 3 / Vsec as a channel portion has been developed. Polysilicon thin film transistors have a relatively high mobility and can implement chip in glass in which a driving circuit is directly embedded in a liquid crystal panel.

As a technology for forming a thin film of polysilicon, a method of depositing polysilicon directly on the substrate material at a high temperature, a high temperature crystallization method of laminating amorphous silicon and crystallizing it at a high temperature of about 600 ° C, laminating amorphous silicon and a laser, etc. The method of heat treatment using the said, etc. were developed. However, these methods are difficult to apply to the glass substrate because the high temperature process is required, there is a disadvantage that the electrical characteristics between the thin film transistors are not uniform due to non-uniform grain boundaries.

Among them, lasers include a sequential lateral solidification (SLS) method and an excimer laser annealing (ELA) method. In the SLS method, grains of polysilicon grow in parallel with the substrate, and in the ELA method, grains of polysilicon grow in the vertical direction of the substrate.

In both methods, the laser beam is irradiated to the amorphous silicon in a band shape. 1 is a view showing the intensity distribution of the laser light generated in the conventional laser device, Figure 2 is a graph showing the intensity distribution of the laser light generated in the conventional laser device. As shown in the figure, the intensity of the laser beam is higher in the part along the edge of the long axis than in the center part. The crystallization characteristics of the polysilicon produced by the intensity distribution of the non-uniform laser light is changed, and the characteristics between the thin film transistors are also changed.

An object of the present invention is to provide a laser intensity control mask that can make the intensity of laser light uniform.

Another object of the present invention is to provide a laser device comprising a laser intensity control mask capable of making the intensity of laser light uniform.                         

Still another object of the present invention is to provide a method of manufacturing a thin film transistor using a laser intensity control mask that can make the intensity of laser light uniform.

The above object can be achieved by an intensity control mask for a laser including an intensity maintenance region and an intensity reduction region provided on opposite sides of the intensity maintenance region.

The intensity maintaining region may transmit or reflect incident laser light.

The closer the intensity reduction region is to the intensity maintenance region, the lower the laser beam intensity reduction ratio is.

The laser intensity control mask may include a slit pattern formed on the base substrate and the intensity reduction region, and the slit pattern may be formed of a chromium layer.

The slit pattern may be formed parallel to the boundary between the strength maintenance region and the strength reduction region or in a vertical direction.

Another object of the present invention can be achieved by a laser device including a laser generator and an intensity control mask for adjusting the intensity pattern of the laser light incident and incident on the laser generator.

The intensity control mask preferably includes a pair of intensity reduction regions facing each other and an intensity maintenance region located between the pair of intensity reduction regions.                     

It is preferable that the intensity control mask is provided in pairs facing each other.

It is preferable to further include a projection lens unit for adjusting the focus of the laser light to irradiate the amorphous silicon layer, wherein the intensity control mask is located between the laser generation unit and the projection lens unit.

Still another object of the present invention is to form an amorphous silicon layer on a substrate material, a laser device including a laser generation unit, and an intensity control mask for adjusting the intensity pattern of the laser light generated and incident on the laser generation unit Forming a polysilicon layer by crystallizing the amorphous silicon layer through a sequential lateral solid-phase crystallization process, forming a gate insulating film on the polysilicon layer, and forming a gate electrode on the gate layer of the polysilicon layer Forming a source region and a drain region by implanting impurities into the polysilicon layer; forming an interlayer insulating layer on the gate electrode; etching the gate insulating layer or the interlayer insulating layer to etch the source region and the interlayer insulating layer. Respectively forming contact holes exposing the drain region, It can be achieved by a thin film transistor manufacturing method comprising the steps of forming each group through the contact hole of the source region and the drain region and the parts of the source contact and the drain contact portion to be connected, respectively.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

Figure 3 is a schematic diagram showing the irradiation of the laser light to the amorphous silicon layer in the laser device including a laser intensity control mask according to a first embodiment of the present invention. The laser device shown in FIG. 3 relates to a laser device used in the SLS method.

The laser device is largely comprised of a laser generating unit 10, optical systems 20 and 50, reflective mirrors 30a, 30b and 30c, a mask 40, a projection lens unit 60, a protective mirror 70 and a first optical system ( And a laser beam intensity control mask 80 provided in 20).

The laser generator 10 generates raw raw laser light. The laser generation unit 10 may include a laser generation tube (not shown). Each laser generating tube includes an upper electrode and a lower electrode, and is a structure in which Ze, Cl, He, Ne gas, etc. are filled therebetween. The size of the raw laser light is about 12mm x 36mm and the pulse holding time is about 20ns.

The raw laser light generated by the laser generator 10 is supplied to the first optical system 20. The first optical system 20 includes a plurality of mirrors and lenses. The first optical system 20 is provided with a pulse duration extender (PDE) to increase the pulse duration from 20ns to 200ns. The longer the pulse holding time, the larger the crystal size of the polysilicon formed and the better the quality. The first optical system 20 also functions to adjust the laser light to the desired size. The laser beam passes through the laser intensity control mask 80 positioned in the first optical system 20, thereby making the intensity pattern uniform. The configuration and operation of the laser intensity control mask 80 will be described later.

As the pulse holding time increases and the size of the laser beam is adjusted while passing through the first optical system 20, the laser beam is reflected by the first reflection mirror 30a and then passes through the mask 40. The laser beam passes through the mask 40 to have a predetermined pattern.                     

The laser light having a predetermined pattern through the mask 40 passes through the second reflecting mirror 30b, the second optical system 50, and the third reflecting mirror 30c and then enters the projection lens unit 60. The projection lens unit 60 focuses the laser light and reduces the size of the laser light. The size of the laser light actually irradiated on the amorphous silicon layer 210 is about 1/5 of the laser light passing through the mask 40. The larger size of the mask 40 than the laser light actually used is to facilitate pattern formation of the mask 40.

The laser passing through the projection lens unit 60 is irradiated to the amorphous silicon layer 210 via the protective mirror 70 to crystallize the amorphous silicon into polysilicon.

The distance between the projection lens unit 60 and the amorphous silicon layer 210 is very small, about 25 mm. Since the gap is narrow, the silicon may splash during the silicon crystallization process and damage the projection lens unit 60, but the protective mirror 70 serves to prevent this. Since the protective mirror 70 may also be damaged by silicon, it is replaced after a certain time of use.

 The substrate 200, on which the amorphous silicon layer 210 is formed, is located under the protective mirror 70. The amorphous silicon layer 210 may be deposited on the substrate 200 by a plasma enhanced chemical vapor deposition (PECVD) method. The substrate 200 is seated on the stage 300. The stage 300 moves the substrate 200 in the X-Y direction so that the entire amorphous silicon layer 210 can be crystallized.

Hereinafter, the configuration and operation of the laser intensity control mask 80 according to the first embodiment of the present invention will be described with reference to FIGS. 4 and 5.

The laser intensity control mask 80 includes a base substrate 81 made of quartz, glass, or the like. On the base substrate 81, an intensity holding region 82 provided in the center portion and an intensity decreasing region 85 provided opposite to each other facing the strength holding region 82 are formed. The intensity of the laser beam passing through the intensity maintenance region 82 is maintained as it is, and the intensity of the laser beam passing through the intensity reduction region 85 is somewhat reduced.

The intensity reduction region 85 is provided with a plurality of slit patterns 86 parallel to the boundary between the two regions 82 and 85. The interval between the slit patterns 86 becomes wider as the intensity holding region 82 gets closer, and becomes narrower as it gets farther from the strength holding region 82. The slit pattern 81 is not limited to this, but is made of chromium or the like to reduce the reflectance or transmittance of the laser light. The slit pattern 86 may be made of MgF ₂ , Al ₂ O ₃ , SiO ₂ , CaF ₂ , AlF ₃ , or the like. The denser the slit pattern 86, the lower the intensity of the laser light.

The laser light incident on the laser intensity control mask 80 has a stronger intensity in the intensity reduction region 85 than in the intensity maintenance region 82. The intensity of the laser beam having a relatively low intensity through the intensity maintaining region 81 is maintained while the intensity of the laser beam having a relatively high intensity through the intensity reduction region 85 is reduced by the slit pattern 85. . The laser beam passing through both sides having particularly strong intensity is further reduced in intensity by the slit pattern 86 which is densely formed. As a result, the laser beam passing through the laser intensity control mask 80 has a uniform intensity pattern regardless of the position.                     

The laser beam having a uniform intensity pattern through the laser intensity control mask 80 has a constant pattern while passing through the mask 40. 6 is a schematic diagram showing a mask 40 used in the laser device of FIG.

The mask 40 is made of quartz and includes a transmission region 41 through which incident laser light is transmitted and a blocking region 45 surrounding the transmission region 41. In the blocking region 45, a chromium layer is formed.

In the transmission region 41, slits are arranged in a row and have two rows of slits 42a and 42b arranged side by side. Here, the slits of the slit rows 42a and 42b are alternately arranged. The size d1 x d2 of the two slit rows 42a and 42b is about 10 mm x 90 mm, which is similar to the size of the laser light incident on the mask 40.

7 is a schematic view showing the intensity distribution of the laser light reflected from the laser intensity control mask 80 according to the first embodiment of the present invention, Figure 8 is a laser intensity control mask according to the first embodiment of the present invention ( It is a schematic diagram which shows that 80) was provided in pair.

As shown in FIG. 7, the intensity adjusting mask 80 for a laser according to the first embodiment may be provided to reflect incident laser light instead of transmitting it. In this case, the laser intensity control mask 80 may further include a separate coating layer for reflection on the back surface of the base substrate 81. As in the case of transmission, the intensity of the laser beam passing through the intensity reduction region 85 is also reduced, so that the intensity pattern becomes uniform.

As shown in FIG. 8, the intensity control mask 80 according to the first embodiment may be provided in a pair facing each other to effectively reduce the intensity.                     

9 is a perspective view showing a laser intensity control mask according to a second embodiment of the present invention. Unlike the first embodiment, the slit pattern 86 is formed in the vertical direction with respect to the boundary between the two regions 81 and 85. In addition, the width of the slit pattern 86 decreases as it approaches the strength maintenance region 81.

Unlike the first and second embodiments, the slit pattern 86 provided in the strength reduction region 85 may be variously modified to have a lattice shape or the like.

In the exemplary embodiment, the laser intensity control mask 80 is located in the first optical unit 20, but the laser intensity control mask 80 may vary between the laser generation unit 10 and the projection lens unit 60. May be placed in position. In addition, the laser intensity control mask 40 is preferably provided to be adjustable in the X-Y direction on the laser light path.

Hereinafter, a thin film transistor manufactured using the intensity control mask 80 for a laser according to an embodiment of the present invention will be described.

10 is a cross-sectional view showing the structure of a polysilicon thin film transistor according to an embodiment of the present invention.

As shown in FIG. 10, the buffer layer 111 is formed on the substrate material 110, and the polysilicon layer 130 is positioned on the buffer layer 111. The buffer layer 111 is mainly made of silicon oxide, and prevents alkali metals and the like from the substrate material 110 from entering the polysilicon layer 130. In the polysilicon layer 130, LDD layers (lightly doped domains 132a and 132b) and source / drain regions 133a and 134b are formed around the channel portion 131. LDD layers 132a and 132b are n-doped and are formed to disperse hot carriers. On the other hand, the channel portion 131 is not doped with impurities, and the source / drain regions 133a and 133b are n + doped. A gate insulating layer 141 made of silicon oxide or silicon nitride is formed on the polysilicon layer 130, and a gate electrode 151 is formed on the gate insulating layer 141 on the channel portion 131. An interlayer insulating layer 152 is formed on the gate insulating layer 141 to cover the gate electrode 151. The gate insulating layer 141 and the interlayer insulating layer 152 are formed of the source / drain region 133a of the polysilicon layer 130. 133b has contact holes 181 and 182 for exposing it. The contact hole is formed on the interlayer insulating layer 152 to face the source contact part 161, which is connected to the source region 133a and the gate electrode 151, through the contact hole 181. A drain contact portion 162 connected to the drain region 133b is formed through 182. The interlayer insulating layer 152 is covered with the passivation layer 171, and a contact hole 183 exposing the drain contact portion 162 is formed in the passivation layer 171, and an indium tin oxide (ITO) is formed on the passivation layer 171. Alternatively, a pixel electrode 172 made of indium zinc oxide (IZO) or a conductive material having a reflectance is formed and connected to the drain contact part 162 through the contact hole 183.

Hereinafter, a method of manufacturing a polysilicon thin film transistor according to an embodiment of the present invention will be described.

11A to 11E are cross-sectional views illustrating a method of manufacturing a polysilicon thin film transistor according to an exemplary embodiment of the present invention, and FIG. 12 illustrates a sequential side solid state crystallization process of crystallizing an amorphous silicon layer into a polysilicon layer by irradiating a laser. 13 is a schematic diagram illustrating a microstructure of a polysilicon layer in a process of crystallizing an amorphous silicon layer into a polysilicon layer through a sequential side solid phase crystallization process.

First, as shown in FIG. 11A, the buffer layer 111 and the amorphous silicon layer 121 are deposited on the substrate material 110, and the amorphous silicon layer 121 is crystallized by the sequential side solid state crystal method. At this time, the laser intensity control mask 80 according to the embodiment of the present invention is used. The crystallization process is as follows.

 As shown in FIG. 12, in the sequential side solid-state crystal process, a laser beam is irradiated using a mask 40 having a transmissive region 41 formed in a slit pattern to locally melt the amorphous silicon layer 121 to completely dissolve the transmissive region. The liquid region 122 is formed in the amorphous silicon layer 121 corresponding to 41. The laser beam passing through the mask 40 passes through the laser intensity control mask 80 and has a uniform intensity distribution, and thus the polysilicon layer formed has uniform characteristics.

At this time, the crystal grains of the polysilicon layer grow in a direction perpendicular to the boundary surface at the boundary between the liquid region 122 irradiated with the laser and the solid state region not irradiated with the laser. Growth of the grains stops when they meet each other in the center of the liquid region 122, and when the laser beam is irradiated while moving the slit pattern in the growth direction of the grains, the lateral growth of the grains may continue to grow to a desired degree.

13 illustrates a grain structure of the polysilicon layer 130 when the slit pattern is formed in the horizontal direction. It can be seen that the grains grow vertically with respect to the slit pattern.

FIG. 11B shows the patterning of the polysilicon layer 130 where crystallization is completed.

Next, as shown in FIG. 11C, silicon oxide or silicon nitride is deposited to form a gate insulating layer 121. Subsequently, the gate electrode 151 is formed by depositing and patterning a conductive material for gate wiring. Subsequently, n-type impurities are ion-implanted using the gate electrode 151 as a mask to form channel portions 131, LDD layers 132a and 132b, and source / drain regions 133a and 133b in the polysilicon layer 130. . There are various methods of manufacturing the LDD layers 132a and 132b. For example, the gate electrode 151 may be made of a double layer, and then a method of making an overhang through wet etching may be used.

Subsequently, as shown in FIG. 11D, an interlayer insulating layer 152 covering the gate electrode 151 is formed on the gate insulating layer 121, and then patterned together with the gate insulating layer 121 to form the polysilicon layer 130. Contact holes 181 and 182 exposing source / drain regions 133a and 133b are formed.

Subsequently, as shown in FIG. 11E, a metal layer for data wiring is deposited and patterned on the substrate material 110 to be connected to the source / drain regions 133a and 133b through the contact holes 181 and 182, respectively. 161 and the drain contact portion 162 are formed.

Subsequently, as shown in FIG. 10, after applying the protective film 171 on the upper portion, the contact hole 183 exposing the drain contact portion 162 is formed by patterning. Subsequently, the pixel electrode 172 is formed by stacking and patterning a transparent conductive material such as ITO or IZO or a conductive material having excellent reflectivity.                     

Figure 14 is a schematic diagram showing the irradiation of the laser light to the amorphous silicon layer in another laser device including a laser intensity control mask according to a first embodiment of the present invention. 14 shows a laser device used in the ELA method.

Unlike the laser device of FIG. 3, a long-axis shutter 90 is provided between the protective lens 70 and the amorphous silicon layer 210. In the ELA method, the length-to-width ratio of the laser light irradiated to the amorphous silicon layer 210 is larger than that of the SLS, but the long-term shutter 90 adjusts the laser light in the form of a band. Like the laser device of FIG. 3, the intensity of the laser light is made uniform by the laser intensity control mask 80.

The thin film transistor according to the present invention and the thin film transistor substrate using the same may be used in a display device such as a liquid crystal display or an organic light emitting diode.

The organic electroluminescent device is a self-luminous device using an organic material that emits light upon receiving an electrical signal. In the organic electroluminescent device, a cathode layer (pixel electrode), a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and an anode layer (counter electrode) are stacked. The drain contact portion of the thin film transistor substrate according to the present invention may be electrically connected to the cathode layer to apply a data signal.

As described above, according to the present invention, there is provided a laser intensity control mask capable of making the intensity of laser light uniform.

In addition, a laser device including a laser intensity control mask capable of uniformizing the intensity of a laser beam and a method of manufacturing a thin film transistor using the same are provided.

Claims (13)

A strength maintenance area; And an intensity reduction region provided on opposite sides of the intensity maintenance region. The method of claim 1, And the intensity maintaining region transmits incident laser light. The method of claim 1, The intensity maintenance region is a laser intensity control mask, characterized in that for reflecting the incident laser light. The method of claim 1, And the intensity reduction region decreases as the laser beam intensity decreases as the intensity decrease region approaches the intensity maintenance region. The method of claim 1, The intensity adjusting mask for laser comprises a slit pattern formed on the base substrate and the intensity reduction region. The method of claim 5, The slit pattern is a laser intensity control mask, characterized in that consisting of a chromium layer. The method of claim 5, And the slit pattern is formed parallel to the boundary between the intensity maintenance region and the intensity reduction region. The method of claim 5, And the slit pattern is formed in a direction perpendicular to the boundary between the intensity maintenance region and the intensity reduction region. A laser generator; And an intensity control mask for adjusting an intensity pattern of the laser light incident and generated by the laser generator. The method of claim 9, And the intensity control mask includes a pair of intensity reduction regions facing each other and an intensity maintenance region located between the pair of intensity reduction regions. The method of claim 10, The intensity control mask is provided with a pair of laser devices facing each other. The method of claim 9, Further comprising a projection lens unit for adjusting the focus of the laser light to irradiate the amorphous silicon layer, The intensity control mask is a laser device, characterized in that located between the laser generating portion and the projection lens portion. Forming an amorphous silicon layer on the substrate material; The amorphous silicon layer is crystallized to form a polysilicon layer through a sequential lateral solid-state crystallization process using a laser device including a laser generator and an intensity control mask for adjusting the intensity pattern of the laser light incident and generated by the laser generator. Doing; Forming a gate insulating film on the polysilicon layer; Forming a gate electrode on the gate film of the polysilicon layer; Implanting impurities into the polysilicon layer to form source and drain regions; Forming an interlayer insulating film on the gate electrode; Etching the gate insulating film or the interlayer insulating film to form contact holes exposing the source region and the drain region, respectively; And forming a source contact portion and a drain contact portion respectively connected to the source region and the drain region through the contact hole, respectively.

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