KR100573144B1 - A method for manufacturing polycrystalline semiconductor active layer, the active layer by the same method, and flat panel display with the active layer - Google Patents

Abstract

The present invention provides a semiconductor active layer crystallization method comprising a laser irradiation step for polycrystallizing a semiconductor active layer, wherein the atmosphere in which the laser irradiation step is performed contains oxygen, and the oxygen content of the atmosphere is determined in advance of the semiconductor active layer. Provided are a semiconductor active layer crystallization method and a semiconductor active layer, and a flat panel display device having the same, wherein the semiconductor active layer has a predetermined oxygen content to have a value of less than or equal to a set surface roughness.

Description

A method for manufacturing polycrystalline semiconductor active layer, the active layer by the same method, and flat panel display with the active layer}

1 is a schematic diagram of a laser annealing apparatus for performing laser annealing according to the present invention;

2A to 2C are SEM images of the surface of a semiconductor active layer under an atmosphere of varying oxygen content under a pressure condition of 10 Torr,

3A to 3C are SEM images of the surface of a semiconductor active layer under an atmosphere of varying oxygen content under a pressure condition of 100 Torr;

4A and 4B are graphs showing Raman spectra under an atmosphere of oxygen content change under a pressure condition of 100 Torr;

5 is a diagram showing a degree of crystallinity for the case shown in FIGS. 2A-3C,

6A and 6B are schematic perspective and partial cross-sectional views of an electroluminescent display device having a semiconductor active layer according to an embodiment of the present invention;

FIG. 7 is a diagram showing surface roughness change with oxygen content change under pressure conditions of 10 Torr and 100 Torr. FIG.

<Brief description of symbols for the main parts of the drawings>

10 ... support 11 ... board support

12 ... Conveyor 13 ... Fixed bar

14 ... feed support 15 ... drive

21, 22 ... N2, O2 supply unit 23 ... discharge unit

30 Chamber 40 Laser generator

41 Laser oscillator 42 Control unit

43 ... slit 44 ... optical system

45 ... reflection means 100 ... substrate

110 substrate 130 semiconductor active layer

200 ... sealing substrate 300 ... sealing material

400 electrical element 700 wiring

The present invention relates to a method for polycrystallizing a semiconductor active layer, and more particularly, to a semiconductor active layer crystallization method for polycrystallizing through a laser beam, a semiconductor active layer thereby, and a flat panel display device having the same.

In displaying an image, many kinds of display apparatuses are used. In recent years, various flat panel display apparatuses are used to replace conventional cathode ray tubes, that is, cathode ray tubes (CRTs). Such flat panel display devices can be classified into self-emissive and non-emissive types according to the light emission type. Representative self-emissive display devices include plasma display panel devices and organic electric fields. An organic electroluminescent display device and the like, and a typical non-luminescent display device is a liquid crystal display device (liquid crystal display device).

In the case of a liquid crystal display and an organic electroluminescent display, an active driving liquid crystal display (AMLCD) and an active driving organic electroluminescent display in which a driving element, that is, a thin film transistor (TFT), adjusts a voltage or a current applied to a pixel (AMOLED) and the like are emerging. Amorphous silicon and polycrystalline silicon are used for the thin film transistor as a driving element, and since the polycrystalline silicon, especially polycrystalline silicon having a large particle diameter, has better field effect mobility than amorphous silicon or polycrystalline silicon having a small particle diameter, Polycrystalline silicon is mainly used as an element forming the.

Methods for producing polycrystalline materials, for example polycrystalline silicon, are classified into low temperature processes and high temperature processes depending on the production temperature. In the case of high temperature processes, there is a problem that the film thickness becomes uneven due to high surface roughness during film formation. In the case of low temperature processes, laser processing, or laser annealing, which irradiates a laser beam onto a thin film substrate, is typically used. Since crystallization of amorphous silicon by the laser beam is performed in nanosecond units, the substrate under the thin film is used. It has the advantage of minimizing the damage to it.

Lasers used for laser annealing can be classified into pulse lasers and continuous wave lasers according to the waveform of the laser beam being oscillated. The pulse laser is a method of periodically oscillating a laser beam having a short irradiation time of several tens of nanoseconds, such as a yag laser, an excimer laser, and the like. Continuous oscillation laser is a laser beam irradiated continuously irrespective of the oscillation cycle, such as an argon laser, a semiconductor laser.

On the other hand, in the case of the method of polycrystallizing the amorphous silicon layer by laser irradiation, the factors for evaluating the polycrystalline silicon include those such as the size of grains, the uniformity of grain size, the direction of grains, and the like. Among these factors, increasing the proportion of polycrystalline silicon, that is, increasing the degree of polycrystallization, is also one of important factors for evaluating polycrystallization. Various methods for enhancing such polycrystallinity have been studied. In one example, there is a method of multiple irradiation of the laser beam to the amorphous silicon layer. However, such laser beam multi-irradiation increases the processing time by increasing the processing time, and also causes laser beam irradiation such that the position error of the irradiated region is generated due to disturbances such as vibration generated in the multi-irradiation process, resulting in different grain sizes. Problems are involved, such as causing nonuniformity of device characteristics throughout the region.

On the other hand, Japanese Patent Laid-Open No. 1997-102467 discloses a laser annealing method in which nitrogen gas is filled in a laser irradiation area in order to improve work efficiency.

In addition, Japanese Patent Laid-Open No. 1998-149984 discloses a method of performing laser annealing in an atmosphere in which at least one or more kinds of gases of hydrogen, nitrogen, and an inert gas are circulated. According to this prior art, only to disclose a method of performing laser annealing in an atmosphere of a stable gas such as nitrogen, in order to prevent a decrease in work efficiency due to blurring of the laser beam introduction window due to repetitive laser irradiation, to increase the degree of polycrystallization. There is no mention of how to change the atmosphere.

In addition, the surface roughness of the semiconductor active layer is one of the important factors that determine the device characteristics of the semiconductor active layer. If the surface roughness is too large, the breakdown voltage may be reduced. Therefore, in order to improve the surface roughness, as disclosed in Japanese Patent Laid-Open No. 2002-252181, laser annealing is performed in a state filled with a stable gas such as nitrogen. However, under such a stable gas atmosphere, the intended purpose of improving surface roughness is achieved, but problems such as enhancement of crystallinity and grain size are not solved.

It is an object of the present invention to provide a semiconductor active layer polycrystallization method by laser irradiation which solves the above problems and can increase the crystallinity and grain size in a simple manner and at the same time have the required surface roughness.

Another object of the present invention is to provide a semiconductor active layer formed by the method of the present invention, and a flat panel display device having the same.

According to an aspect of the present invention for achieving the above object, in the semiconductor active layer crystallization method comprising a laser irradiation step to polycrystallize the semiconductor active layer, the atmosphere in which the laser irradiation step is performed contains oxygen, The oxygen content of the atmosphere provides a semiconductor active layer crystallization method, characterized in that the oxygen content in the atmosphere is a predetermined oxygen content to have a value below the predetermined surface roughness of the semiconductor active layer.

According to another aspect of the present invention, the predetermined surface roughness is 130 GPa, and the predetermined oxygen content is 2% or less.

According to another aspect of the present invention, a semiconductor active layer crystallized by laser irradiation, wherein the semiconductor active layer is laser polycrystallized under a predetermined oxygen atmosphere to have a roughness below a predetermined surface roughness of the semiconductor active layer crystallization. To provide.

According to another aspect of the invention, the surface roughness of the polycrystalline semiconductor active layer provides a semiconductor active layer, characterized in that less than 130Å.

According to yet another aspect of the present invention, in a flat panel display device having a semiconductor active layer crystallized by laser irradiation, the semiconductor active layer is formed by the method of claim 1 so that the semiconductor active layer has a value of less than or equal to a predetermined surface roughness. A flat panel display apparatus is provided.

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

1 shows a laser annealing apparatus for forming a semiconductor active layer and a flat panel display device having the same according to the present invention. The laser annealing apparatus 1 is comprised with the laser generation part 40, the chamber 30, the support apparatus 10, and the atmosphere apparatus.

One side of the chamber 30 of the apparatus 1 for thin film laser processing, ie, laser annealing, on the substrate is formed with a substrate window 35 for introducing the substrate 100 on which the thin film of amorphous material is formed into the chamber 30.

At the upper end of one side of the chamber 30 as an atmosphere device for forming the atmosphere in the chamber 30, a nitrogen supply device 21 for supplying nitrogen and an oxygen supply device 22 for supplying oxygen, each nitrogen inlet port. It is in fluid communication with chamber 30 via 31 and oxygen inlet 32.

In addition, when switching the atmosphere in the chamber 30, a pump system 23 for discharging the previous atmosphere in the chamber 30 is in fluid communication with the chamber 30 through the outlet 33.

The support device 10 is disposed inside the chamber 30, and the support device 10 includes a substrate support 11 and a transfer device 12. The substrate part 100 is seated on one surface of the substrate support 11, and the substrate part 100 includes a substrate 110 having a semiconductor active layer 130 to be polycrystalline.

The conveying apparatus 12 includes a driving apparatus 15 for driving the substrate support 11, a fixing bar 13 for guiding the driving apparatus 15, and a conveying support 14 for supporting the fixing bar 13. It is composed. During the laser annealing of the semiconductor active layer 130, the driving device 15 moves along the fixing bar 13 fixed by the transfer support 14 of the lower surface of the chamber 30 by an electrical signal applied thereto. Although the driving device 15 is illustrated in FIG. 1 as being disposed below the substrate support 11, the driving device 15 is not limited thereto and may be directly connected to the fixed bar 13 to directly drive the fixed bar 13. You can also take

On the other hand, the laser generating unit 40 is composed of a laser oscillator 41, a control unit 42, a slit 43, an optical system 44, a reflecting means 45 and the like. The laser beam generated from the laser oscillator 41 is divided at a predetermined ratio via the slit 43, a part of the laser beam is introduced into the controller 42 via the slit 43, and a part of the laser beam penetrates the slit 43.

The control unit 42 monitors the energy of the laser beam through the partially transmitted laser beam and generates a control signal from the difference between the energy level of the monitored laser beam and the targeted energy level and returns it to the laser oscillator 41. By performing the feedback closed loop control to output, it controls so that the laser beam which is output uniformly and uniformly may be produced by the laser oscillator 41. FIG.

Some other laser beam that passes through the slit 43 enters the optical system 44, where the size and energy distribution of the laser beam can be adjusted. Such an optical system 44 is, for example, a homogenizer that makes the energy distribution of the laser beam uniform, or a mechanical shutter or an optical light valve that can change the cross-sectional shape of the laser beam. Although this configuration is just an example, the optical system is not limited thereto and may take various forms and configurations.

The laser beam passing through the optical system 44 is incident into the chamber 30 via a modification window 34 formed at the upper end of the chamber 30. The laser beam incident on the chamber 30 is reflected by the reflecting mirror 45 as the reflecting means. The reflecting mirror 45 is movable by a driving means not shown, and the driving of the reflecting mirror 30 as the reflecting means is made by the reflecting driving means 45a and the laser processing conditions, namely, substrate transfer speed, thin film thickness, It may be determined based on conditions such as the width of the laser beam, and the controller for generating a signal for rotating or moving the reflecting mirror 45 as the reflecting means may be a separate controller.

Operation of the laser annealing device 1 is performed by the following process. First, the driving means 15 is operated by the output signal of the controller 42 to move the substrate support 11 to the vicinity of the substrate window 35. After the substrate 110 on which the thin film such as the semiconductor active layer 130 is formed through the substrate window 35 is introduced into the chamber 30 and seated on the substrate support 11, the driving means 15 is controlled by the controller 42. The substrate support 11 is moved to an area to receive a signal from and irradiate a laser beam.

At this time, the atmosphere in the chamber 30 is established through the nitrogen supply device 21 and controlled through the oxygen supply device 22. After the atmosphere in the substrate 100 and the chamber 30 is formed, a laser beam is irradiated onto the semiconductor active layer 130 as a thin film layer formed on one surface of the substrate 110. That is, the laser beam generated from the laser oscillator 41 is irradiated to the semiconductor active layer 130 via the slit 2, the optical system 44, and the reflecting mirror 45.

On the other hand, the atmosphere in the chamber 30 in which the laser polycrystallization process of the semiconductor active layer according to the present invention is performed is formed through the nitrogen supply device 21 and controlled through the oxygen supply device 22. That is, according to the method for laser polycrystallizing the semiconductor active layer according to the present invention, the oxygen in the atmosphere in the chamber as a way to increase the crystallinity of the polycrystals and to improve the uniformity of the crystallization, as well as to not only create a nitrogen atmosphere as in the prior art To optimize the content (or oxygen fraction), such an atmosphere is formed by operating the respective supply devices 21 and 22 by a signal input from the controller 42 (or a separate controller).

It is important to enhance the appropriate oxygen content of the atmosphere in the chamber, that is, the crystallinity of the semiconductor active layer, while maintaining an oxygen content sufficient to maintain uniformity of crystallization. On the other hand, when a very small amount of oxygen is contained in the atmosphere, the oxygen content in the atmosphere is preferably 0.1% or more because it is difficult to achieve the desired crystallization enhancement and the oxygen content is difficult to control.

On the other hand, when excessive oxygen is contained in the atmosphere, for example, the crystallization may be hindered by excessive reaction with oxygen in the crystallization process after melting by, for example, a laser beam. Is preferably less than 20%.

As an embodiment according to the invention, the experiment was carried out while varying the oxygen content of the atmosphere in the chamber. The experiment was carried out by setting the pressure conditions in the chamber to two cases of reduced pressure conditions, that is, 10 Torr and 100 Torr, and changing the oxygen content in the atmosphere to 0%, 2%, 5% and 20%.

Chamber pressure condition: 10 Torr

2A to 2C are SEM images of the polycrystalline semiconductor active layer after laser annealing performed for each case where the pressure condition in the chamber was set to 10 Torr and the oxygen content in the atmosphere was set to 0%, 2%, and 20%. to be. These figures are images taken at the same magnification.

FIG. 2A shows the surface of the laser annealed semiconductor active layer in an atmosphere formed only of nitrogen, and FIG. 2B shows the surface of the laser annealed semiconductor active layer in an atmosphere having an oxygen content of 2%. It can be seen that the degree of crystallization is clearly different, and that the uniformity of the crystallization formed is even over the entire surface. 2C shows an SEM image showing the surface of the laser annealed semiconductor active layer in an oxygen content of 20%. It can be seen that there is little change in grain size and crystallinity. 2b and 2c seem to show a slight difference in grain uniformity, but this is within the margin of error in terms of repeated experiments. In the case of the semiconductor active layer according to the present invention, the effective radius when the size of the crystal grains, that is, the area of the crystal grains is indicated by a circle may be about 250 nm or more.

Chamber Pressure Condition: 100Torr

3A to 3C show SEM images of the polycrystalline semiconductor active layer after laser annealing performed for each case in which the pressure condition in the chamber was set to 100 Torr and the oxygen content in the atmosphere was set to 0%, 2%, and 5%. to be. These figures are images taken at the same magnification.

FIG. 3A shows the surface of the laser annealed semiconductor active layer in an atmosphere formed only of nitrogen, and FIG. 3B shows the surface of the laser annealed semiconductor active layer in an atmosphere having an oxygen content of 2%, as can be seen in the figure. It can be seen that the degree of crystallization is clearly different, and that the uniformity of the crystallization formed is even over the entire surface. 3C shows an SEM image showing the surface of the laser annealed semiconductor active layer in an atmosphere having an oxygen content of 5%. It can be seen that there is little change in grain size and crystallinity. Also in these cases, as in the case of FIGS. 2B and 2C, the effective radius when the size of the crystal grains, that is, the area of the crystal grains is indicated by a circle may be about 250 nm or more.

Crystallinity calculation

The Raman spectrum is used as a method for deriving each crystallinity, ie, the ratio of crystalline peaks to amorphous peaks, from the experimental results. 4A and 4B show the Raman spectra of the polycrystalline thin film, which was set in a pressure condition of 100 Torr during the above experiment and carried out in an atmosphere of nitrogen and oxygen of 2%. In each plot, line 2a refers to raw data, and lines 2a 'and 2a "refer to crystalline data having crystalline peaks and amorphous data deconvolved from the raw data of line 2a, respectively.

In the case of the polycrystalline thin film run in a nitrogen atmosphere, it can be seen that the width of the amorphous peak of the line 2a "is considerably larger than the width of the crystalline peak of the line 2a '. That is, the crystallinity is very small in this case. On the other hand, as shown in Fig. 4B, in the case of the polycrystalline thin film carried out in the atmosphere having an oxygen content of 2%, the width of the amorphous peak of the line 3a "is not large or large compared with the width of the crystalline peak of the line 3a '. Able to know. In other words, it can be seen that the crystallinity is quite large in this case.

The crystallinity obtained from the Raman spectrum for the semiconductor active layer obtained from the above experiments is shown in FIG. 5. From this, it can be seen that the pressure conditions in the chamber do not have a great influence on the polycrystallization of the semiconductor active layer if oxygen in the atmosphere is included, except that the pressure conditions in the chamber are executed only in the nitrogen atmosphere. In addition, as the oxygen content in the atmosphere increases, the degree of crystallinity increases (or slightly decreases), but since it is almost within the error range, it can be seen that the increase in crystallinity is almost saturated when the oxygen content in the atmosphere is 20% or more. . Rather, as described above, when the oxygen content is 20% or more, the degree of crystallinity may be inhibited or uniformity may be inhibited.

As another embodiment of the present invention, the semiconductor active layer according to the present invention can be used in a variety of products, inter alia, can be used in a flat panel display device having a TFT layer.

For example, the semiconductor active layer according to the present invention, as shown in Figure 6a, the substrate 110 and the sealing substrate 200, the sealing material 300 for sealing these substrates, and the substrate through the sealing material 300 The display device may be provided in an electroluminescent display device composed of an electrical element 400 such as a horizontal driving circuit part and a wiring part 700, etc., in which electrical communication is made between the display area sealed between the 110 and the sealing substrate 200.

FIG. 6B is a cross-sectional view of some pixels of the EL display device of FIG. 6A. On one surface of the substrate 110, the buffer layer 120, the semiconductor active layer 130, the gate electrode layer 150, the source / drain electrode layers 170a and b, the gate insulating layer 140 disposed between the respective layers, A TFT layer composed of an insulating layer such as the intermediate layer 160 may be disposed. The passivation layer 180 is formed on one surface of the source / drain electrode layers 170a and b, and the first electrode layer 190 is disposed through the via hole 181 formed on one side of the passivation layer 180. The pixel defining layer 191 may be formed on the passivation layer 180, and an opening region 194 is disposed in the corresponding region on the first electrode layer 190. An electroluminescent part 192 including a light emitting layer or the like may be formed on one surface of the first electrode layer 190 as the opening region 194, and the second electrode layer 193 may be entirely deposited on the top surface thereof. In the electroluminescent display device, the semiconductor active layer 130 through which the channel is energized by an electrical signal applied to the gate electrode 150 may be formed of a polycrystalline thin film according to the present invention.

However, the present invention is not limited to the organic / inorganic electroluminescent display device. That is, various modifications are possible, such as being applicable to a liquid crystal display device within the limit provided with a semiconductor active layer.

On the other hand, when looking again at the crystallization process according to the present invention, the oxygen content in the atmosphere may be further limited if the crystallinity is increased through the laser annealing process and a predetermined degree of surface roughness is required. FIG. 7 shows the surface roughness of the polycrystalline semiconductor active layer for cases in which the pressure conditions in the chamber are set to 10 Torr and 100 Torr and the oxygen content in the atmosphere is less than 20%, in accordance with the present invention. As the oxygen content in the atmosphere is increased, the surface roughness is increased, but the oxygen content is saturated at about 10%. Since the roughness is preferably 130 kPa or less in order to secure an appropriate process margin necessary for later processing and to prevent degradation such as a decrease in breakdown voltage, the oxygen content in the atmosphere is more preferably 2% or less. However, as can be seen from the crystallinity diagram shown in Figure 5, when the oxygen content in the atmosphere is too small, it is difficult to form the crystal grain of the desired size, it is difficult to achieve the desired crystallinity, and difficult to control the inflow of oxygen into the chamber. . Therefore, the crystallization degree greater than the crystallinity obtained in the nitrogen atmosphere of the semiconductor active layer is obtained through laser crystallization according to the present invention, but the oxygen content in the atmosphere is preferably 0.1% or more to satisfy the grain size of 250 nm or more and the surface roughness of 130 GPa or less. Do.

The present invention having the above-described configuration can obtain the following effects.

In the method of crystallizing a semiconductor active layer by laser irradiation according to the present invention, the laser crystallization is carried out in an atmosphere containing oxygen during laser irradiation, particularly in an atmosphere having an oxygen content of less than 20%, thereby maintaining a uniformity of crystallization and increasing polycrystallization. The semiconductor active layer as a thin film layer can be provided.

Further, by performing laser annealing in an atmosphere containing a predetermined amount of oxygen, it is possible to provide a polycrystalline semiconductor active layer having an average effective length of crystal grains of 250 nm or more, and a flat panel display having a TFT layer composed of such a polycrystalline semiconductor active layer. A device, in particular an electroluminescent display device, may be provided.

In addition, by performing laser polycrystallization in an atmosphere containing 2% or less of oxygen, deterioration such as reduction in breakdown voltage due to increase in surface roughness and increase in average effective length of crystal grains and increase in surface roughness can be prevented. A flat panel display device having a semiconductor active layer or a TFT layer having the same can be provided.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. . Accordingly, the protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (5)

In the semiconductor active layer crystallization method comprising the step of irradiating the laser to polycrystalline the semiconductor active layer, The atmosphere in which the laser irradiation step is carried out contains oxygen, wherein the oxygen content of the atmosphere is a predetermined oxygen content such that the crystallized semiconductor active layer has a value of less than or equal to a predetermined surface roughness of 130 kPa. A semiconductor active layer crystallization method. The method of claim 1, And said predetermined oxygen content is 2% or less. In the semiconductor active layer crystallized by laser irradiation, And wherein the semiconductor active layer crystallized is laser polycrystallized under a predetermined oxygen atmosphere to have an illuminance below a predetermined surface roughness of 130 kPa. delete A flat panel display device comprising a semiconductor active layer crystallized by laser irradiation, A flat panel display device characterized in that the semiconductor active layer is obtained by the method of claim 1 so that the crystallized semiconductor active layer has a value of less than or equal to a predetermined surface roughness of 130 kPa.

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