JP2020119912A - Laser annealing apparatus and laser annealing method - Google Patents

Abstract

To provide a laser annealing apparatus capable of manufacturing a TFT whose transistor characteristics do not change regardless of a direction of an electric current flowing to a channel region.SOLUTION: A laser annealing apparatus, which modifies an amorphous silicon film to a crystallization silicon film by irradiating the amorphous silicon film with laser light for a processing target substrate obtained by forming gate wiring on a substrate and forming the amorphous silicon film on the gate wiring through a gate insulation film, comprises: an electric current generation unit for causing the gate wiring to generate heat by causing the gate wiring to generate an electric current; a laser light source unit for oscillating laser light; and a laser irradiation unit for irradiating the amorphous silicon film along the gate wiring with the laser light oscillated from the laser light source unit.SELECTED DRAWING: Figure 2

Description

The present invention relates to a laser annealing apparatus and a laser annealing method.

A thin film transistor (TFT) is a switching element for actively driving a flat panel display (FPD) such as a liquid crystal display (LCD) and an organic light emitting display (OLED). Is used as. As a material of a semiconductor layer of a thin film transistor (hereinafter referred to as a TFT), amorphous silicon (a-Si:amorphous Silicon), polycrystalline silicon (p-Si:polycrystalline Silicon), or the like is used.

In recent years, a laser annealing method has been known in which pseudo single crystal silicon is laterally (laterally) grown to increase the mobility of a channel region in a TFT (see Patent Document 1). In this laser annealing method, first, a polycrystalline silicon film formed by annealing an amorphous silicon film with an excimer laser is prepared. Then, the polycrystalline silicon film is partially scanned with a laser beam to melt the silicon, and the crystal grains remaining in the vicinity of the melted portion are used as seed crystals for lateral crystal growth in the scanning direction. Is disclosed.

JP, 2003-124136, A

In the above-mentioned laser annealing method, since the lateral crystal growth process is used, the mobility of the crystal depends on the direction. Therefore, when the TFT is manufactured, there is a problem that the transistor characteristics change depending on the direction of the current flowing in the channel region. Further, in the above-described laser annealing method, when it is attempted to partially form the pseudo single crystal silicon in the channel region of the TFT, it is necessary to precisely irradiate the laser beam to the polycrystalline silicon film in the portion laminated on the gate wiring. It was

The present invention has been made in view of the above problems, and provides a laser annealing apparatus and a laser annealing method that make it possible to fabricate a TFT whose transistor characteristics do not change regardless of the direction of a current flowing in a channel region. With the goal. It is another object of the present invention to provide a laser annealing apparatus and a laser annealing method capable of forming a channel region having good characteristics in a self-aligned manner in a region overlapping a gate wiring.

In order to solve the above problems and to achieve the object, an aspect of the present invention is that a gate wiring is formed on a substrate, and an amorphous silicon film is formed on the gate wiring via a gate insulating film. A laser annealing apparatus for irradiating a laser beam on the amorphous silicon film with respect to a substrate to be processed, for modifying the amorphous silicon film into a crystallized silicon film, wherein a current is generated in the gate wiring. And a laser light source that oscillates laser light, and a laser that irradiates the amorphous silicon film along the gate wiring with laser light oscillated from the laser light source. And an irradiation unit.

In the above aspect, the current generation unit includes a first prober connected to one end of the gate line for applying a voltage, and a second prober used for grounding connected to the other end of the gate line, Is preferably provided.

In the above aspect, it is preferable that the laser irradiation unit emits a laser beam for projecting an elongated laser spot on the surface of the amorphous silicon film in a direction perpendicular to the extending direction of the gate wiring. ..

In the above aspect, it is preferable that the laser light source unit includes a CW laser light source that oscillates continuous wave laser light.

In the above aspect, it is preferable that the laser light source unit is capable of converting continuous wave laser light oscillated from the CW laser light source into pulsed laser light.

According to another aspect of the present invention, a gate wiring is formed on a base body, and the amorphous silicon film is formed on the gate wiring via a gate insulating film. A laser annealing method for irradiating a film with laser light to modify the amorphous silicon film into a crystallized silicon film, the method comprising: a gate wiring heating step of generating a current in the gate wiring to heat the gate wiring. A laser annealing step of irradiating the amorphous silicon film with laser light along the gate wiring during the gate wiring heating step.

In the above aspect, it is preferable that in the gate wiring heating step, a voltage is applied to one end of the gate wiring and the other end of the gate wiring is grounded.

In the above aspect, in the laser annealing step, a laser beam for projecting an elongated laser spot on the surface of the amorphous silicon film in a direction perpendicular to the extending direction of the gate wiring may be emitted as laser light. preferable.

In the above aspect, it is preferable that the laser light is continuous wave laser light.

With the laser annealing apparatus and the laser annealing method according to the present invention, it is possible to manufacture a TFT whose transistor characteristics do not change regardless of the direction of the current flowing in the channel region. Further, according to the laser annealing apparatus and the laser annealing method according to the present invention, the channel region having no direction dependence on the mobility can be formed in a self-aligned manner with respect to the gate wiring, thus increasing the number of manufacturing steps of the TFT. Can be suppressed.

FIG. 1 is a schematic configuration diagram of a laser annealing apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional explanatory diagram of the laser annealing apparatus according to the embodiment of the present invention. FIG. 3 is a plan view showing a state in which the amorphous silicon film is laser-annealed by using the laser annealing apparatus according to the embodiment of the present invention. FIG. 4 is a view showing the structure of the IV-IV cross section of FIG. 3 and the temperature distribution in the W direction of the substrate corresponding to this cross sectional area.

The details of the laser annealing apparatus and the laser annealing method according to the embodiment of the present invention will be described below with reference to the drawings. However, it should be noted that the drawings are schematic, and the number of each member, the size of each member, the ratio of the sizes, the shape, and the like are different from the actual ones. In addition, the drawings include portions having different dimensional relationships, ratios, and shapes.

[Embodiment]
Prior to the description of the configuration of the laser annealing apparatus according to the present embodiment, an example of a substrate to be subjected to laser annealing processing by the laser annealing apparatus and a pseudo single crystal silicon film will be briefly described with reference to FIGS. 1 to 3. .. In FIG. 1, a gate insulating film 4 and an amorphous silicon film 5 described later are omitted.

(Substrate to be processed)
As shown in FIGS. 1 and 2, a substrate 1 to be processed includes a glass substrate 2 as a base, a plurality of gate wirings 3 arranged on the surface of the glass substrate 2 in parallel with each other, and a glass substrate 2 And a gate insulating film 4 (see FIG. 2) formed on the gate wiring 3, and an amorphous silicon film 5 (see FIG. 2) deposited on the entire surface of the gate insulating film 4.

As shown in FIG. 2, in the present embodiment, both ends 3A and 3B in the longitudinal direction of the gate wiring 3 are exposed without being covered with the gate insulating film 4 and the amorphous silicon film 5. ing.

The substrate 1 to be processed finally becomes a TFT substrate in which TFTs and the like are formed. As shown in FIGS. 1 to 3, in the present embodiment, the substrate 1 to be processed is transferred along the longitudinal direction (transfer direction T) of the gate wiring 3 in the laser annealing process.

(Pseudo single crystal silicon film)
In the present embodiment, the laser-annealed amorphous silicon film 5 is modified into pseudo single crystal silicon films 5B and 5C as crystallized silicon films. The pseudo single crystal silicon film 5B formed on the gate wiring 3 is finally patterned as a channel region (not shown) of the TFT. As a result, such a channel region is provided along the gate wiring 3 for each pixel region on the TFT substrate of the liquid crystal display panel.

The quasi-single-crystal silicon film 5B described above has small mobility direction dependence, as described later. Therefore, when the source/drain is provided in the channel region formed of the pseudo single crystal silicon film 5B, the transistor characteristics are the same even if the direction connecting the source/drain (channel length direction) is different. The reason why the direction dependency of mobility is reduced in the pseudo single crystal silicon film 5B will be described later.

(Schematic configuration of laser annealing device)
Hereinafter, the schematic configuration of the laser annealing apparatus 10 according to the present embodiment will be described with reference to FIGS. 1 and 2. The laser annealing apparatus 10 includes a base 11, a laser light source unit 12, a laser irradiation unit 13, a first prober 14 and a second prober 15 as a current generation unit, a control unit 16, and a control unit 16 for position information of the substrate 1 to be processed. A position sensor (not shown) that outputs to

In the present embodiment, the laser irradiation unit 13 does not move during the laser annealing process, but the substrate 1 to be processed is moved. That is, the base 11 is provided with a substrate transfer means (not shown). In the laser annealing apparatus 10, the substrate 1 to be processed is placed on the base 11 and is transported along the transport direction (scanning direction) T by a substrate transport means (not shown). As shown in FIGS. 2 and 3, the transport direction T is the same as the extending direction (longitudinal direction) of the gate wiring 3.

The laser light source unit 12 includes a CW laser light source that oscillates continuous wave laser light (CW laser light). In addition, the laser light source unit 12 also includes a pulse generator (not shown) for pulsing the CW laser light to generate pulsed light. Various lasers such as a semiconductor laser, a solid-state laser, a liquid laser, and a gas laser can be used as the CW laser light source provided in the laser light source unit 12. Here, the continuous wave laser beam (CW laser beam) is a concept including so-called pseudo continuous wave that continuously irradiates the target region with the laser beam. That is, the laser light may be a pulsed laser or a pseudo continuous wave laser whose pulse interval is shorter than the cooling time of the silicon thin film after heating (irradiation with the next pulse before hardening).

The laser irradiation unit 13 is arranged above the base 11 by a support frame (not shown) or the like. The laser irradiation unit 13 includes an incident-side image forming system, a rod integrator as a homogenizing element, and an emitting-side image forming system, which are not shown.

As shown in FIG. 1, the laser irradiation unit 13 forms a laser beam LB having a shape extending in a width direction W of the substrate 1 to be processed. As shown in FIGS. 1 and 3, the laser beam LB is set so as to project an elongated rectangular beam spot BS on the surface of the target substrate 1 (the surface of the amorphous silicon film 5). In the present embodiment, the length of the beam spot BS in the longitudinal direction is set so as to extend over the plurality of gate wirings 3 along the width direction W of the substrate 1 to be processed.

The first prober 14 includes an elongated rectangular prober body 14A and a plurality of probe pins 14B protruding from a side portion of the prober body 14A. In the present embodiment, the number of probe pins 14B is set to be equal to the number of gate wirings 3 on the substrate 1 to be processed. The first prober 14 is set so that a predetermined voltage is applied to each probe pin 14B. The plurality of probe pins 14B are arranged so as to have the same pitch as the gate wirings 3 formed on the substrate 1 to be processed.

The second prober 15 includes a prober body 15A and a plurality of probe pins 15B protruding from a side portion of the prober body 15A. In the present embodiment, the number of probe pins 15B is set to be equal to the number of gate wirings 3 on the substrate 1 to be processed. In the second prober 15, each probe pin 15B is grounded. The plurality of probe pins 15B are arranged so as to have the same pitch as the gate wirings 3 formed on the substrate 1 to be processed.

As shown in FIG. 1 and FIG. 2, the probe pins 14B of the first prober 14 are provided at the end portions 3A of the gate wiring 3 which are exposed at one end edge portion of the target substrate 1 with respect to the target substrate 1, respectively. The position is fixed so as to come into contact with. Similarly, the probe pin 15B of the second prober 15 is fixed in position so as to come into contact with each of the end portions 3B of the gate wiring 3 exposed at the other end edge portion of the target substrate 1 with respect to the target substrate 1. To be done. Therefore, when a voltage is applied from the prober main body 14A of the first prober 14, the current I is set to flow in the gate wiring 3 as shown in FIG. In addition, in the present embodiment, the first prober 14 and the second prober 15 are integrally carried with respect to the substrate 1 to be processed by a substrate carrying means (not shown).

The control unit 16 controls the substrate transfer means (not shown) provided on the base 11, the laser light source unit 12, and the first prober 14. Specifically, the control unit 16 is set to drive and control a substrate transfer unit (not shown) to move the target substrate 1 in the transfer direction T at a predetermined speed.

Further, the control unit 16 drives and controls the laser light source unit 12 to irradiate the processing target substrate 1 with the laser beam LB. The control unit 16 controls the laser light source unit 12 to selectively generate the CW laser light and the pulsed laser light. At the first stage of the laser annealing process, the control unit 16 controls the laser light source unit 12 to emit pulsed laser light based on the positional information of the substrate 1 to be processed. The pulsed laser light is used to form a seed crystal on one edge of the amorphous silicon film 5. In this embodiment, the output of the pulsed laser light emitted from the laser light source unit 12 is set to a relatively low energy.

(Laser annealing method)
The configuration of the laser annealing apparatus 10 according to the present embodiment has been described above, but a laser annealing method using the laser annealing apparatus 10 will be described below.

First, as shown in FIG. 1, the first prober 14 is connected to the target substrate 1. Specifically, the probe pin 14B of the first prober 14 is set so as to come into contact with each of the ends 3A of the gate wiring 3 exposed at one end of the substrate 1 to be processed. Similarly, the second prober 15 is connected to the target substrate 1. Specifically, the probe pin 15B of the second prober 15 is set so as to come into contact with each of the ends 3B of the gate wiring 3 exposed at the other end of the substrate 1 to be processed.

(Gate wiring heating process and laser annealing process)
Next, in the laser annealing device 10, the substrate 1 to be processed is run in the transport direction T at a predetermined scan speed. The controller 16 applies a predetermined voltage to the probe pin 14B of the first prober 14 when the substrate 1 to be processed reaches a predetermined position based on position information from a position sensor (not shown). At the same time, the control unit 16 drives and controls a CW laser light source and a pulse generator (not shown). A CW laser light source (not shown) oscillates CW laser light. At this time, the CW laser light emitted from the CW laser light source is converted into pulse laser light by a pulse generator (not shown).

Next, as shown in FIG. 2, the surface of the amorphous silicon film 5 at one end of the substrate 1 to be processed is irradiated with a laser beam LB of pulsed laser light to end 3A of the gate wiring 3. A seed crystal region 5A (see FIG. 3) is formed in the amorphous silicon film 5 located above the vicinity. In the present embodiment, as described above, the output of the pulsed laser light is set relatively low, and the heating temperature of the pulsed laser light is added to the temperature of the resistance heat generation by the current I passing through the gate wiring 3, It is set so that the seed crystal region 5A can be formed in the amorphous silicon film 5. Therefore, as shown in FIG. 3, in the present embodiment, seed crystal region 5A made of microcrystalline silicon is formed only in the region above the end portion of gate wiring 3.

In the present embodiment, the seed crystal region 5A is formed only on the gate wiring 3, and the output condition of the pulsed laser light is changed to change the amorphous state at one edge of the substrate 1 to be processed. The seed crystal region 5A may be formed over the entire width direction W of the edge portion of the high-quality silicon film 5.

As described above, after the seed crystal region 5A is formed in the edge portion of the amorphous silicon film 5 (only the region above the gate wiring 3 in the present embodiment), the control unit 16 causes the pulse generation not shown. The drive is stopped and the CW laser light is oscillated from the laser light source unit 12. As a result, the laser irradiation unit 13 irradiates the amorphous silicon film 5 with the laser beam LB of CW laser light. Then, the substrate 1 to be processed is moved in the transport direction T as shown in FIG. 3 while being irradiated with the laser beam LB of CW laser light. At this time, the current I is applied to the gate wiring 3.

By simultaneously performing such a gate wiring heating step and a laser annealing step, the amorphous silicon film 5 located above the gate wiring 3 changes into a pseudo single crystal silicon film 5B. Specifically, as shown in FIG. 3, the amorphous silicon film 5 located above the gate wiring 3 generates heat due to resistance heating of the gate wiring 3 and heat from the laser beam LB of CW laser light. receive. As a result, the amorphous silicon film 5 is changed to the pseudo single crystal silicon film 5B. Further, the amorphous silicon film 5 located on the lateral side of the gate wiring 3 (outer in the width direction W of the gate wiring 3) becomes a pseudo single crystal silicon film 5C by receiving heat from the laser beam LB. Change.

In the present embodiment, when the amorphous silicon film 5 is irradiated with the laser beam LB of CW laser light, the current I flows through the gate wiring 3 to generate resistance heat. The temperature of the amorphous silicon film 5 in the located region is also raised. Due to the resistance heat generation of the gate wiring 3 in this way, the amorphous silicon film 5 is previously formed between the region above the gate wiring 3 and the peripheral (side) region of the gate wiring 3. There is a temperature gradient.

FIG. 4 shows the structure of the IV-IV cross section (cross section of the portion subjected to the laser annealing process) in FIG. 3 and the relationship between the coordinate position of the amorphous silicon film 5 in the width direction W and the temperature (temperature distribution). FIG. As shown in FIG. 4, a temperature gradient is generated between the region where the gate wiring 3 is formed and the lateral region in the width direction W. Therefore, the amorphous silicon film 5 above the gate wiring 3 is melted and then crystallized by cooling (lateral crystal growth), in addition to the transport direction T, a direction orthogonal to the transport direction T (width). The pseudo single crystal silicon film also grows in the direction W).

Therefore, in the pseudo single crystal silicon film 5B formed above the gate wiring 3, the mobilities in the x direction and the y direction shown in FIG. 3 are equal. Therefore, by using this pseudo single crystal silicon film 5B as the channel region of the TFT, it is possible to equalize the mobilities of the TFTs having different channel length directions. That is, by forming the pseudo single crystal silicon film 5B using the laser annealing apparatus 10 according to the present embodiment, it is possible to reduce the change in transistor characteristics due to the arrangement of the TFTs.

Further, as shown in FIG. 3, the pseudo single crystal silicon film 5B formed by using the laser annealing apparatus 10 according to the present embodiment has a region affected by resistance heating of the gate wiring 3, that is, the gate wiring 3 It is formed only in the upper region. The length (width dimension) w2 of the gate wiring 3 in the width direction W is substantially the same as the width dimension w1 of the gate wiring 3. Therefore, according to the present embodiment, there is an advantage that the pseudo single crystal silicon film 5B can be formed in self-alignment with the gate wiring 3.

[Other Embodiments]
Although the embodiments have been described above, it should not be understood that the description and drawings forming part of the disclosure of the embodiments limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

For example, in the above-mentioned embodiment, the substrate to be processed 1 is moved, but the position of the substrate to be processed 1 may be fixed and the laser irradiation unit 13 side may be moved.

In the above-described embodiment, the length of the laser beam LB in the longitudinal direction is set to extend over the plurality of gate wirings 3, but the laser beam LB having the length extending over all the gate wirings 3 may be set. ..

Although the pseudo single crystal silicon film 5B is formed as the crystallized silicon film in the above-described embodiment, the polycrystalline silicon film may of course be grown from the seed crystal region. Also in this case, it is possible to form a high-quality polycrystalline silicon film starting from the seed crystal region.

In the above embodiment, the first prober 14 and the second prober 15 that apply a current to the gate wiring 3 are used as the current generator. However, in order to selectively heat the gate wiring 3, induction heating, dielectric It may be configured to perform heating or the like.

Although the plurality of probe pins 14B and 15B are provided on the first prober 14 and the second prober 15 in the above-described embodiment, the plurality of gate wirings 3 exposed at the edge of the amorphous silicon film 5 are collectively formed. You may use the elongate connection piece in the width direction W which can be connected simultaneously.

1 substrate to be processed 2 glass substrate (base)
3 Gate wiring 3A, 3B Edge part 4 Gate insulating film 5 Amorphous silicon film 5A Seed crystal region 5B Pseudo-single-crystal silicon film (direction dependence of mobility is small)
5C Pseudo-single crystal silicon film 10 Laser annealing device 11 Base 12 Laser light source unit 13 Laser irradiation unit 14 First prober (current generation unit)
14A prober body 14B probe pin 15 2nd prober (current generator)
15A Prober body 15B Probe pin

Claims (9)

The amorphous silicon film is irradiated with laser light on the substrate to be processed in which the gate wiring is formed on the substrate and the amorphous silicon film is formed on the gate wiring via the gate insulating film. A laser annealing apparatus for modifying the amorphous silicon film into a crystallized silicon film,
A current generator that generates a current in the gate wiring to generate heat in the gate wiring;
A laser light source unit that oscillates laser light,
A laser irradiation unit that irradiates the amorphous silicon film with laser light oscillated from the laser light source unit along the gate wiring,
A laser annealing apparatus comprising. The current generator is
A first prober connected to one end of the gate line for applying a voltage;
A second prober used for grounding, which is connected to the other end of the gate wiring;
The laser annealing apparatus according to claim 1, further comprising: The laser irradiation unit emits a laser beam for projecting an elongated laser spot on a surface of the amorphous silicon film in a direction perpendicular to the extending direction of the gate wiring. The laser annealing apparatus described. The laser annealing device according to any one of claims 1 to 3, wherein the laser light source unit includes a CW laser light source that oscillates continuous wave laser light. The laser annealing device according to claim 4, wherein the laser light source unit is capable of converting continuous wave laser light oscillated from the CW laser light source into pulsed laser light. The amorphous silicon film is irradiated with laser light on the substrate to be processed in which the gate wiring is formed on the substrate and the amorphous silicon film is formed on the gate wiring via the gate insulating film. A laser annealing method for modifying the amorphous silicon film into a crystallized silicon film,
A gate wiring heating step of generating a current in the gate wiring to heat the gate wiring;
A laser annealing step of irradiating the amorphous silicon film with laser light along the gate wiring during the gate wiring heating step;
Laser annealing method for performing. The laser annealing method according to claim 6, wherein in the gate wiring heating step, a voltage is applied to one end of the gate wiring and the other end of the gate wiring is grounded. 8. The laser annealing step emits a laser beam as a laser beam for projecting an elongated laser spot on the surface of the amorphous silicon film in a direction perpendicular to the extending direction of the gate wiring. Laser annealing method according to. The laser annealing method according to claim 6, wherein the laser light is continuous wave laser light.

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