JP2678343B2 - Drive circuit TFT manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention relates to a drive circuit TFT.
The present invention relates to a method of manufacturing (thin film transistor).

[0002]

2. Description of the Related Art For example, an active matrix type liquid crystal display device will be described with reference to FIG. 1B. An active circuit TFT is formed in a substantially square pixel switching element forming region 6 on a glass substrate 1. , The glass substrate 1
The strip-shaped signal line drive circuit TFT on one side (upper side in FIG. 1B) and the other side (left side in FIG. 1B) of the predetermined two sides of the pixel switching element forming region 6 which are orthogonal to each other. There is one in which a signal line drive circuit TFT and a scanning line drive circuit TFT are respectively formed in the formation region 7 and the scanning line drive circuit TFT formation region 8 which are also strip-shaped.

By the way, in a method of manufacturing a TFT of each circuit in such a liquid crystal display device, an amorphous silicon thin film is formed on the entire upper surface of a relatively large glass substrate, and the amorphous silicon thin film is irradiated with an excimer laser beam. There is a method in which the amorphous silicon thin film is crystallized to form a polysilicon thin film, and the polysilicon thin film is separated into elements to form TFTs for each circuit.
In this case, the spot size of the excimer laser beam is 10 mm × 10 mm at the maximum with respect to the size of the glass substrate.
Since it is quite small, the excimer laser beam is scanned in the X and Y directions to irradiate the entire amorphous silicon thin film.

[0004]

However, in the conventional method of manufacturing a TFT as described above, in order to reliably irradiate the entire amorphous silicon thin film on the glass substrate, for example, as shown by hatching in FIG. , It is necessary to irradiate the boundary portions of the four laser beam irradiation regions adjacent to each other in the horizontal direction and the vertical direction in an overlapping manner.
Therefore, the size of the crystal grains of the polysilicon thin film varies, and in particular, the carrier mobility also varies. However, since the mobility of a TFT is considerably inferior to that of a single crystal, there is a problem that even a slight variation in carrier mobility causes a fatal defect. This characteristic requirement is required for the signal line drive circuit TFT that shifts data vigorously. An object of the present invention is to provide a method of manufacturing a drive circuit TFT that can make the crystal grain size of a polysilicon thin film for forming the drive circuit TFT uniform.

[0005]

According to a first aspect of the present invention, a strip-shaped signal line drive circuit TFT forming region and a strip-shaped scanning line drive circuit TFT forming region are arranged orthogonally on a substrate, and Signal line drive circuit TFT
When the signal line drive circuit TFT is formed in the formation region, the shape of the laser beam is a band longer than the longitudinal direction of the signal line drive circuit TFT formation region,
By scanning and irradiating in the direction orthogonal to the longitudinal direction of the signal line drive circuit TFT formation region in a state where both ends of the laser beam are located outside both ends in the longitudinal direction of the signal line drive circuit TFT, respectively.
The amorphous silicon thin film formed on the substrate is crystallized to form a polysilicon thin film, and the signal line drive circuit TFT including a plurality of TFTs having the polysilicon thin film as an active layer is formed. Claim 2
According to the invention, an active circuit TFT is formed in a substantially rectangular pixel switching element formation region on a substrate, and one side and the other of predetermined two sides of the pixel switching element formation region orthogonal to each other on the substrate. When the signal line drive circuit TFT and the scanning line drive circuit TFT are formed in the strip-shaped signal line drive circuit TFT formation region and the strip-shaped scanning line drive circuit TFT formation region, respectively, the shape of the laser beam is changed to the signal line. A belt-like shape extending parallel to the drive circuit TFT formation region is provided, and the laser beam is applied to the signal line drive circuit TF.
The amorphous silicon thin film formed on the substrate is crystallized into a polysilicon thin film by scanning and irradiating in a direction orthogonal to the longitudinal direction of the T formation region, and the active circuit TFT and the signal line drive are formed by the polysilicon thin film. A circuit TFT and the scanning line drive circuit TFT are formed.

[0006]

According to the first aspect of the present invention, the amorphous silicon provided in the signal line drive circuit TFT forming region on the substrate has the both ends of the laser beam at the two ends in the longitudinal direction of the signal line drive circuit TFT. Since the scan irradiation is performed in the direction orthogonal to the longitudinal direction of the signal line drive circuit TFT formation region in a state of being located outside, amorphous silicon is not overlapped in the longitudinal direction, and amorphous silicon is a polysilicon thin film having a uniform crystal grain size. It is possible to manufacture a signal line drive circuit TFT having no variation in characteristics. According to the second aspect of the present invention, the shape of the laser beam is a strip shape extending parallel to the strip-shaped signal line drive circuit TFT formation region, and the laser beam is orthogonal to the longitudinal direction of the signal line drive circuit TFT formation region. By scanning and irradiating in the direction, the amorphous silicon thin film formed on the substrate is crystallized into a polysilicon thin film, and the active thin film transistor TFT, the signal line drive circuit TFT, and the scanning line drive circuit TFT are collectively formed by the polysilicon thin film. Therefore, among the semiconductor layers of the signal line drive circuit and the scanning line drive circuit, the variation of the characteristics of the semiconductor layer of the signal line drive circuit, which is most affected by the variation of the display characteristics, is prevented and the polysilicon thin film of the signal line drive circuit is prevented. And the scanning line drive circuit polysilicon thin film can be formed together. Throughput can be improved because it is.

[0007]

1 to 6 show respective manufacturing steps of a TFT in a liquid crystal display device to which an embodiment of the present invention is applied. Therefore, the method of manufacturing the TFT of this embodiment will be described with reference to these drawings in order.

First, as shown in FIG. 1A, a gate electrode 2 made of aluminum and having a thickness of about 1000 Å is patterned on the upper surface of the glass substrate 1, and then the gate electrode 2 and the upper surface of the glass substrate 1 are formed. A gate insulating film 3 made of silicon oxide and having a thickness of about 1500 Å is formed, and an amorphous silicon thin film 4 having a thickness of about 500 Å is formed on the upper surface thereof.
To form a film. Next, the amorphous silicon thin film 4 is crystallized into a polysilicon thin film 5 by irradiating it with an excimer laser beam.

Here, an irradiation method of the excimer laser beam in this case will be described with reference to FIG. Although the amorphous silicon thin film 4 is formed on the entire surface of the glass substrate 1, the substantially square area indicated by reference numeral 6 is a pixel switching element forming area, and the upper portion of the pixel switching element forming area 6 is indicated by reference numeral 7. The strip-shaped area is the signal line drive circuit TFT formation area,
A strip-shaped region indicated by reference numeral 8 on the left side of the pixel switching element formation region 6 is a scanning line drive circuit TFT formation region. Although not shown, the signal line drive circuit TFT formed in the signal line drive circuit TFT formation region 7 is CM
It has a shift register circuit element composed of an OS TFT and a transfer gate circuit element composed of a combined C-MOS TFT, and each circuit element is aligned linearly in the longitudinal direction corresponding to each pixel column by the method described below. It is formed by being arranged. In other words, the TFTs, which are the circuit elements forming the shift register circuit and the transfer gate circuit, are arranged at the same position in the width direction of the signal line drive circuit TFT formation region 7. It In this case, the channel width of the TFT that constitutes the shift register of the signal line drive circuit is 20 to 30 μm.
The channel width of the TFT forming the transfer gate is about 200 to 300 μm.

The excimer laser beam irradiation area 9 has a belt shape because the laser beam shape is made into a belt shape extending in parallel to the signal line drive circuit TFT forming area 7 by an optical system (not shown). In this case, since the irradiation energy of the laser beam corresponds to the irradiation area, for example, when the irradiation area of the excimer laser beam is a square of 10 mm × 10 mm and when it is 100 mm.
The irradiation energy is the same as in the case of a strip shape of × 1 mm or 200 mm × 0.5 mm. That is, the beam width of the excimer laser beam is, for example, 0.5 to 1.0 mm.
And irradiate the entire area in the longitudinal direction on the uppermost end side of the signal line drive circuit TFT formation region 7, and then the laser beam irradiation position is set to 1 in the width direction of the signal line drive circuit TFT formation region 7.
The laser beam is emitted by moving the line. On this occasion,
The movement amount is adjusted so that the laser beam irradiation area of this time partially overlaps the irradiation area of the previous time. Thereafter, similarly, scanning irradiation is performed while shifting the laser beam in the width direction of the signal line drive circuit TFT formation region 7. This scan irradiation is similarly performed on the scanning line drive circuit TFT formation region 8 and the pixel switching element formation region 6, and ends at the termination region of the scanning line drive circuit TFT formation region 8 and the pixel switching element formation region 6. . In the case of the embodiment, the length of the laser beam irradiation region is equal to or longer than the length of the glass substrate 1, and the length of one irradiation region is
The length is made sufficiently longer than the total length of the scanning line drive circuit TFT formation region 8 and the pixel switching element formation region 6.

When such laser beam scanning irradiation is performed, the signal line drive circuit TFT forming region 7 has a predetermined width (for example, 0.5 to 1.0) in the longitudinal direction thereof.
(mm) is irradiated only once, so there is no overlapping irradiation area. Therefore, the amorphous silicon thin film 4 formed in the signal line drive circuit TFT formation region 7 is given uniform energy over the entire length of the signal line drive circuit TFT formation region 7 to be crystallized. Therefore, the size of the crystal grains of the polysilicon thin film 5 for forming the signal line drive circuit TFT can be made uniform, and the carrier mobility can be made uniform. In this case, in the width direction of the signal line drive circuit TFT formation region 7, there are overlapping irradiation regions at predetermined intervals, but the irradiation width of the laser beam is different for each TFT.
Is sufficiently larger than the large
It can be removed from the T formation position. However,
It is not always necessary to remove the overlapping laser beam irradiation region from the TFT formation position. As described above, each TFT formed in the signal line drive circuit TFT formation region 7 is arranged in a straight line at a predetermined position in the width direction of the signal line drive circuit TFT formation region 7. Even if there is, that region corresponds to the same region in each TFT, and this does not impair the uniformity of the element characteristics of each TFT. For example, even if the source areas of all the TFTs are the overlapping irradiation areas,
The uniformity of TFT device characteristics is maintained. The pixel switching element forming region 6 and the scanning line drive circuit T
In the FT formation region 8, overlapping irradiation regions are generated in the vertical direction of the boundary portion of the laser beam irradiation region, but in the case of the pixel switching element TFT and the scanning line drive circuit TFT, the carrier mobility has some variation. There is not much problem.

After the amorphous silicon thin film 4 is crystallized in this way, as shown in FIG. 2, the upper surface of the polysilicon thin film 5 is made of silicon nitride to a thickness of 200.
An impurity implantation mask forming layer 11 of about 0Å is formed, and a positive type photoresist layer 12 is formed on the upper surface thereof. Next, exposure is performed from the lower surface (back surface) side of the glass substrate 1 using the gate electrode 2 as a mask. Next, when development is performed, as shown in FIG. 3, a photoresist pattern 12a is formed on the upper surface of the impurity implantation mask forming layer 11 in a portion corresponding to the gate electrode 2.
Is formed. Next, the impurity implantation mask forming layer 11 is etched with hydrofluoric acid (BHF) using the photoresist pattern 12a as a mask, and then the photoresist pattern 12a is peeled off, so as to correspond to the gate electrode 2 as shown in FIG. An impurity implantation mask 11a is formed on the upper surface of the polysilicon thin film 5 in the desired portion. Next, impurities such as phosphorus ions and boron ions are implanted using the impurity implantation mask 11a as a mask to form impurity implantation regions 5a in the polysilicon thin film 5 in regions other than under the impurity implantation mask 11a. After that, the impurity implantation mask 11a
Is peeled off.

Next, as shown in FIG. 5, unnecessary portions of the polysilicon thin film 5 are removed by element isolation. FIG.
In the process shown in FIG. 5, the TFTs that are shift register circuit elements and transfer gate circuit elements formed in the signal line drive circuit TFT formation region 7 are
The signal line drive circuit TFT is formed so as to be formed on a straight line in the longitudinal direction of the TFT formation region 7. Next, FIG.
As shown in, an interlayer insulating film 13 made of silicon nitride is deposited on the entire upper surface by plasma CVD. Plasma CV
When the interlayer insulating film 13 made of silicon nitride is deposited by D, if the substrate temperature is about 250 to 350 ° C., the impurity implantation region 5a of the polysilicon thin film 5 is activated at the same time, and the polysilicon thin film 5 is hydrogenated. This reduces sled dangling bonds. Note that hydrogenation may be performed in a separate step, and activation may be performed by thermal annealing before depositing the interlayer insulating film 13.

Next, a contact hole 14 is formed in the interlayer insulating film 13 in a portion corresponding to the impurity implantation region (source / drain region) 5a. Next, the contact hole 14
A source / drain electrode 15 made of aluminum is formed on the upper surface of the interlayer insulating film 13 so as to be connected to the impurity implantation region 5a via the. Thus, the active circuit TFT is formed in the substantially square pixel switching element formation region 6 on the glass substrate 1, and one side of the predetermined two sides of the pixel switching element formation region 6 on the same glass substrate 1 which intersect at right angles ( In FIG. 1B, the upper side and the other side (FIG. 1).
A signal line drive circuit TFT and a scanning line drive circuit TFT are formed in the signal line drive circuit TFT formation region 7 and the scanning line drive circuit TFT formation region 8 on the left side in (B), respectively.

In the above embodiments, the case where the present invention is applied to the drive circuit of the liquid crystal display device has been described, but the present invention is not limited to this and can be applied to the drive circuit of a light receiving device such as a photo sensor. .

[0016]

As described above, according to the present invention, the signal line drive circuit TFT forming region of the amorphous silicon thin film formed on the substrate is formed in the laser beam shape in the longitudinal direction of this region. Since the irradiation is performed with a laser beam in the form of a longer band, the amorphous silicon thin film in the drive circuit TFT formation region can be crystallized without overlapping irradiation in the longitudinal direction of the drive circuit TFT formation region. The crystal grain size of the polysilicon thin film for forming the drive circuit TFT can be made uniform, and the carrier mobility can be made uniform.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view of a state in which an amorphous silicon thin film is crystallized by irradiation of an excimer laser into a polysilicon thin film when manufacturing a TFT to which an embodiment of the present invention is applied, and FIG. The top view shown in order to demonstrate the laser irradiation method.

FIG. 2 is a cross-sectional view of a state in which an impurity implantation mask forming layer and a photoresist layer are formed on the upper surface of a polysilicon thin film and then exposed from the lower surface side of a glass substrate in manufacturing the same TFT.

FIG. 3 is a cross-sectional view of a state in which the TFT is developed in manufacturing the same.

FIG. 4 is a cross-sectional view of a state in which impurities are injected in manufacturing the same TFT.

FIG. 5 is a cross-sectional view showing a state where elements are separated in manufacturing the same TFT.

FIG. 6 is a sectional view of the TFT in a completed state.

FIG. 7 is a plan view shown for explaining scan irradiation of a conventional excimer laser.

[Explanation of symbols]

 1 Glass Substrate 4 Amorphous Silicon Thin Film 5 Polysilicon Thin Film 6 Active Circuit TFT Forming Area 7 Signal Line Drive Circuit TFT Forming Area 8 Scanning Line Drive Circuit TFT Forming Area 9 Excimer Laser Beam Irradiation Area

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 27/12 H01L 29/78 627G

Claims (2)

(57) [Claims] 1. A strip-shaped signal line drive circuit on a substrate.
TFT forming area and strip-shaped scanning line drive circuit
The TFT formation region is arranged orthogonally, and the signal line drive
A signal line drive circuit TFT is formed in the circuit TFT formation area
To time, the longitudinal direction and longer strip than the other hand, both end portions the signal line drive each of the laser beams of the laser beam shape the signal line drive circuit TFT forming region
Positioned outside both ends of the circuit TFT in the longitudinal direction
In this state, by scanning and irradiating in the direction orthogonal to the longitudinal direction of the signal line drive circuit TFT formation region,
A drive circuit characterized by crystallizing an amorphous silicon thin film formed on the substrate to form a polysilicon thin film, and forming the signal line drive circuit TFT composed of a plurality of TFTs using the polysilicon thin film as an active layer. Method of manufacturing TFT. 2. A substantially rectangular pixel switching on a substrate.
Forming an active circuit TFT in the element formation area
, The orthogonal predetermined two sides one side and the other side signal line drive circuit TFT forming region and also the scanning line drive circuit TFT forming region of the strip shape of the strip shape of the pixel switching element forming region A on the substrate When each of the signal line drive circuit TFT and the scanning line drive circuit TFT is formed in, the shape of the laser beam is formed into a band shape extending parallel to the signal line drive circuit TFT formation region, and the laser beam is formed into the signal line drive circuit TFT. The amorphous silicon thin film formed on the substrate is crystallized into a polysilicon thin film by scanning irradiation in a direction orthogonal to the longitudinal direction of the formation region, and the active thin film transistor TF is formed by the polysilicon thin film.
T, forming the signal line drive circuit TFT and the scanning line drive circuit TFT, a method of manufacturing the drive circuit TFT.