CN1501065A - Detection device for polycrystalline silicon thin film crystallization quality and detection and control method thereof - Google Patents

Abstract

The invention discloses a detection device for the crystallization quality of a polycrystalline silicon thin film and a detection and control method thereof. First, a first substrate is provided, and a first amorphous silicon layer is covered on the first substrate. Then, the first amorphous silicon layer is annealed by laser with different energy densities to form a plurality of first polysilicon regions. Then, a light source is split into a first light beam and a second light beam for irradiating the first polysilicon region by a beam splitter. Then, the light intensity of the first light beam and the second light beam reflected from the first polysilicon layers is detected to obtain a plurality of light intensity ratios, and a second predetermined energy density is determined according to the light intensity ratios. Finally, the laser with the second set energy density is used for carrying out annealing treatment on the second substrate with the surface covered with the second amorphous silicon layer so as to form a second polycrystalline silicon layer.

Description

Polysilicon thin film crystal quality detection device and its detection and control method

technical field

The present invention relates to a semiconductor thin film detection device and its detection and control method, in particular to a polysilicon thin film crystal quality detection device and its detection and control method to monitor the polysilicon thin film crystal quality and adjust the crystallization laser energy density.

Background technique

The current thin film transistor liquid crystal display (thin film transistor-liquid crystal display, TFT-LCD) technology is divided into two types, one is the traditional amorphous silicon thin film transistor, and the other is polysilicon thin film transistor. The electron movement speed of the polysilicon thin film transistor is between 10 times and 100 times that of the amorphous silicon thin film transistor. Therefore, the TFT-LCD industry has begun research and development, using polysilicon thin film transistors as pixel switching elements and driving circuits around the LCD.

The above-mentioned polysilicon thin film transistors are generally manufactured using a low temperature polysilicon (LTPS) process. The so-called LTPS process uses excimer laser annealing (ELA) to transform the original amorphous silicon film into a polysilicon structure. Since the process temperature is below 600°C, it is suitable for transparent glass substrates. The electron movement speed of the polysilicon thin film transistor is related to the crystalline quality of the polysilicon thin film. That is, the electron movement speed of the polysilicon thin film transistor increases as the grain size of the polysilicon thin film increases. Furthermore, the grain size of the polysilicon film is related to the laser energy density applied to the amorphous silicon film. Therefore, it is necessary to inspect the polysilicon film to regulate the applied laser energy, so as to obtain the best crystal quality of the polysilicon film.

In order to detect the crystalline quality of polysilicon thin films, traditionally, an optical microscope with a power of 500 to 1000 times more is used to observe the surface roughness of the film as an indicator of the crystalline quality of polysilicon thin films. Since this method relies heavily on human eyes, it is impossible to obtain accurate Measured results and not applicable to large size substrates. Furthermore, another traditional detection method is to use a scanning electron beam microscope (SEM) to detect the crystalline quality of the polysilicon thin film. However, the above method is a destructive detection, and it takes a lot of time to make samples and observe, which seriously affects the productivity.

Contents of the invention

Therefore, the object of the present invention is to provide a detection method and detection device for a polysilicon film, to quickly and accurately detect the crystalline quality of a polysilicon film, and to replace the traditional offline (off-line) destructive detection, and to be able to Effectively monitor the crystalline quality of polysilicon thin films and increase productivity.

According to the above purpose, the present invention provides a detection method for a polysilicon thin film. Firstly, a substrate is provided, covered with a polysilicon layer. Next, a light source with a predetermined wavelength is provided, and passes through a beam splitter to form a first beam and a second beam for irradiating the polysilicon layer. The light intensities of the first light beam and the second light beam reflected from the polysilicon layer are detected to obtain a light intensity ratio. Finally, the crystalline quality of the polysilicon layer is monitored according to the light intensity ratio. Wherein, the light source is a laser and the predetermined wavelength is in the range of 266nm to 316nm.

Furthermore, the intensity ratio of the first light beam and the second light beam is 30-40%:70-60%.

According to the above purpose, the present invention provides a detection device for the crystal quality of polysilicon thin film. The detection device includes a beam splitter, a first detection device, a second detection device and a control unit. The beam splitter is used for receiving a light source with a predetermined wavelength to form a first light beam and a second light beam irradiated on the substrate covered with a polysilicon layer. The first detecting device is used for detecting the light intensity of the first light beam, and the second detecting device is used for detecting the light intensity of the second light beam reflected from the polysilicon layer. The control unit is coupled between the first and second detection devices, and is used for monitoring the crystal quality of the polysilicon layer according to the light intensity ratio of the first and second light beams. Wherein, the light source is a laser and the predetermined wavelength is in the range of 266nm to 316nm.

Furthermore, the splitting ratio of the first light beam and the second light beam is 30-40%:70-60%.

According to the above purpose, the present invention provides a method for controlling the crystal quality of polysilicon thin films. Firstly, a first substrate is provided, covered with a first amorphous silicon layer. The first amorphous silicon layer is respectively annealed with lasers having different first predetermined energy densities to form a plurality of first polysilicon regions in the first amorphous silicon layer. Then, a light source with a predetermined wavelength is provided, and passes through a beam splitter to form a first beam and a second beam for irradiating the first polysilicon regions. Then, detecting the light intensity of the first light beam and the second light beam reflected from the first polysilicon regions to obtain a plurality of light intensity ratios, and determining a second predetermined energy density according to the light intensity ratios. Finally, a second substrate is provided, covered with a second amorphous silicon layer, and the second amorphous silicon layer is annealed with a laser having a second predetermined energy density to convert the second amorphous silicon layer into a second polysilicon layer.

Wherein, the laser is an excimer laser, and the first predetermined energy density is in the range of 300 to 500 mJ/cm ² .

Furthermore, the light source is a laser with a predetermined wavelength in the range of 266nm to 316nm.

Furthermore, the splitting ratio of the first light beam and the second light beam is 30-40%:70-60%.

Furthermore, the second predetermined energy density is an energy density capable of forming the largest polysilicon grain size.

Description of drawings

In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and understandable, the preferred embodiments are specifically cited below, together with the accompanying drawings, and are described in detail as follows:

1 is a flow chart showing a method for detecting the crystal quality of a polysilicon thin film according to an embodiment of the present invention;

2 is a schematic diagram showing a detection device for the crystal quality of a polysilicon thin film according to an embodiment of the present invention;

3 is a flow chart showing a method for controlling the crystalline quality of a polysilicon thin film according to an embodiment of the present invention; and

FIG. 4 is a graph showing phase difference versus photon energy according to an embodiment of the present invention.

The reference signs in the accompanying drawings are explained as follows:

100～substrate; 102～polysilicon layer;

200～light source generator; 202～beam splitter;

204～the first detection device; 206～the second detection device;

208～control unit; L～measurement light source;

L1～first beam; L2, L2’～second beam;

I1, I2'～light intensity.

Detailed ways

FIG. 1 is a flowchart showing a method for detecting crystal quality of a polysilicon thin film according to an embodiment of the present invention. First, step S10 is performed to provide a substrate, such as a transparent glass substrate, on which an amorphous silicon (α-Si) layer is formed. In this embodiment, this substrate is used to fabricate a thin film transistor liquid crystal display (TFT-LCD). The amorphous silicon layer on the substrate is used for subsequent fabrication of the channel layer of the thin film transistor. The amorphous silicon layer can be formed by chemical vapor deposition (CVD), and its thickness is in the range of about 300 Å to 500 Å.

Next, step S12 is performed to anneal the amorphous silicon layer with a laser with a predetermined energy density, such as excimer laser annealing (ELA), to convert the amorphous silicon layer into a polysilicon (p-Si) layer . In this embodiment, the predetermined energy density of the laser is in the range of 300 to 500 mJ/cm ² .

Next, proceed to step S14 , provide a measurement light source, such as a laser, and divide the measurement light source into a first light beam and a second light beam through a beam splitter. In this embodiment, the measurement light source has a predetermined wavelength, such as in the range of 266nm to 316nm. Wherein, the splitting ratio of the first light beam and the second light beam is 30-40%:70-60%.

Next, step S16 is performed, irradiating the polysilicon layer on the substrate with a second light beam. Afterwards, step S18 is performed to simultaneously detect the light intensity of the first light beam passing through the polysilicon layer and the light intensity of the second light beam reflected from the polysilicon layer.

Finally, step S20 is performed to obtain a light intensity ratio (light intensity of the first light beam/light intensity of the second light beam) according to the detection result. The crystalline quality of the polysilicon layer is monitored by the light intensity ratio.

The surface roughness (grain size) of the polysilicon layer formed by laser annealing will increase with the increase of laser energy density, and after the formation of the maximum grain size (optimum laser energy density), the increase and decrease. The inventors have found through experiments that the light intensity of the light beam reflected from the polysilicon layer will decrease as the surface roughness increases. Likewise, after the maximum grain size is formed, the light intensity increases as the grain size decreases. With this feature, the crystalline quality of the polysilicon layer can be monitored. However, the detected light intensity is affected by the attenuation or interference of the measuring light source, which reduces the accuracy of the detection result. Therefore, the detection method of the present invention uses the ratio of light intensity as an index for detecting crystal quality, so as to effectively eliminate the above-mentioned problems.

Next, please refer to FIG. 2 , which shows a schematic diagram of a detection device for crystal quality of a polysilicon film according to an embodiment of the present invention. A light source generator 200 provides a measuring light L, such as a laser, for irradiating a substrate 100, such as a glass substrate, covered with a polysilicon layer 102 on its surface. The measuring light L is received by a beam splitter 202 and split into a first light beam L1 and a second light beam L2. In this embodiment, the measurement light L has a predetermined wavelength, such as in the range of 266nm to 316nm. Wherein, the splitting ratio of the first light beam L1 and the second light beam L2 is 30-40%:70-60%, and the second light beam L2 is used to irradiate the polysilicon layer 102 .

A first detection device 204 is used to detect the light intensity I1 of the first light beam L1, and a second detection device 206 is used to detect the light intensity 12' of the second light beam L2' reflected from the polysilicon layer 102.

A control unit 208, coupled between the first detection device 204 and the second detection device 206, is used to determine the light intensity ratio (I1/I2') of the first light beam L1 and the reflected second light beam L2' The crystalline quality of the polysilicon layer 102 is monitored.

Since the detection device of the present invention does not need to destroy the substrate 100, the manufacturing cost can be reduced and the detection time can be shortened. Furthermore, the detection device can be integrated into the laser annealing processing system, so it can be used for in-line detection. When the grain size does not meet the process requirements, a warning can be issued immediately, so that the process personnel can immediately check and adjust the energy density of the laser to obtain the best grain size again to ensure the good rate of subsequent products. Furthermore, the laser tempering process belongs to the front-stage process of the low-temperature polysilicon process, and the process detects abnormal products and scraps or reworks them in time, which can effectively reduce costs.

The invention further proposes a method for controlling the crystal quality of the polysilicon thin film. Please refer to FIG. 3 , which shows a flowchart of a method for controlling the crystal quality of a polysilicon film according to an embodiment of the present invention. First, step S20 is performed to provide a test substrate, such as a transparent glass substrate, on which an amorphous silicon (α-Si) layer is formed. In this embodiment, the test substrate is used for the measuring machine.

Next, step S22 is performed, respectively annealing the amorphous silicon layer on the test substrate with lasers with different predetermined energy densities, such as excimer laser annealing (ELA), to form a plurality of Polysilicon (p-Si) region. In this embodiment, the predetermined energy density of the laser is in the range of 300 to 500 mJ/cm ² .

Next, proceed to step S24 , using the light source generator 200 in FIG. 2 to provide a measurement light source L, and split the measurement light source L into a first light beam L1 and a second light beam L2 through the beam splitter 202 . Likewise, the measurement light source L has a predetermined wavelength, such as in the range of 266nm to 316nm. Wherein, the splitting ratio of the first light beam and the second light beam is 30-40%:70-60%.

Next, step S26 is performed, irradiating the polysilicon regions on the test substrate with the second light beam L2. Afterwards, step S28 is performed, by using the first detection device 204 and the second detection device 206 to simultaneously detect the light intensity I1 of the first light beam L1 that has not passed through the polysilicon layer and the light intensity I1 reflected from the polysilicon layer on these test substrates. The light intensity I2' of the second light beam L2'.

Next, step S30 is performed. Since the laser energy density applied to each test substrate is different, the crystal quality of the polysilicon regions formed on the test substrates is also different. Different light intensity ratios (I1/I2') can be obtained by the control unit 208 according to the detection results, and the preferred laser energy density for the annealing process is determined from these light intensity ratios.

For example, select different predetermined laser energy densities in the energy density range of 300 to 400mJ/cm ² , such as 330mJ/cm ² , 340mJ/cm ² , 350mJ/cm ² , 360mJ/cm ² , 370mJ/cm ² , and 380mJ/cm ² , respectively annealing the test substrates to form polysilicon regions with different crystalline qualities on the test substrates. Then, each polysilicon region is detected to obtain the relationship curve of the light intensity ratio (I1/I2') with the laser energy density and the grain size, and the results are shown in FIG. 4 . As shown in FIG. 4 , the polysilicon layer annealed with a laser having a predetermined energy density of 350 mJ/cm ² may have the largest grain size (300 nm). Therefore, the preferred laser fluence that can form the largest polysilicon grain size is 350 mJ/cm ² .

Next, step S32 is performed to provide a product substrate, such as a transparent glass substrate, on which an amorphous silicon layer is formed. Here, the product substrate is used to manufacture a thin film transistor liquid crystal display (TFT-LCD), and the amorphous silicon layer is used to subsequently manufacture a channel layer of a thin film transistor.

Finally, step S34 is performed, using a laser with a predetermined energy density of 350mJ/cm ² to perform annealing treatment on the amorphous silicon layer on the product substrate, so as to control the crystalline quality of the amorphous silicon layer transformed into a polysilicon layer. Furthermore, steps S14 to S20 in FIG. 1 can be performed to implement online detection. When the grain size does not meet the process requirements, a warning can be issued immediately, so that the process personnel can immediately check and adjust the energy density of the laser to obtain the best grain size again to ensure the good rate of subsequent products.

Compared with the prior art, the method of the invention can quickly and accurately detect the crystallization quality of the polysilicon film on-line, so it can effectively monitor the crystallization quality of the polysilicon film and improve the production capacity. Furthermore, since the detection by the detection device of the present invention is a non-destructive detection, the manufacturing cost can be reduced.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Those skilled in the art can make changes and modifications to it without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be determined by the appended claims.

Claims (16)

1. the detection method of a polysilicon membrane crystalline quality comprises the following steps:

One substrate is provided, is coated with a polysilicon layer on this substrate;

One light source with a set wavelength is provided, and by an optical splitter to form one first light beam and in order to shine one second light beam in this polysilicon layer;

Detect this first light beam and from the light intensity of this second light beam of this polysilicon layer reflection to obtain a light intensity ratio; And

Monitor the crystalline quality of this polysilicon layer according to this light intensity ratio.

2. the detection method of polysilicon membrane crystalline quality as claimed in claim 1, wherein this substrate is a glass substrate.

3. the detection method of polysilicon membrane crystalline quality as claimed in claim 1, wherein this light source is a laser and this set wavelength arrive 316nm at 266nm a scope.

4. the detection method of polysilicon membrane crystalline quality as claimed in claim 1, wherein the splitting ratio of this first light beam and this second light beam is 30～40%: 70～60%.

5. the pick-up unit of a polysilicon membrane crystalline quality comprises:

One light source, it has a set wavelength, in order to shine the substrate that a polysilicon layer is arranged in a surface coverage;

One optical splitter forms one first light beam and and shines second light beam in this polysilicon layer in order to receive this light source;

One first arrangement for detecting is in order to detect the light intensity of this first light beam; And

One second arrangement for detecting is in order to the light intensity of detecting from this second light beam of this polysilicon layer reflection.

6. the pick-up unit of polysilicon membrane crystalline quality as claimed in claim 5, also comprise a control module, be coupled to this first and this second arrangement for detecting between, in order to first to monitor the crystalline quality of this polysilicon layer with the light intensity ratio of this second light beam according to this.

7. the pick-up unit of polysilicon membrane crystalline quality as claimed in claim 5, wherein this light source is a laser and this set wavelength arrive 316nm at 266nm a scope.

8. the pick-up unit of polysilicon membrane crystalline quality as claimed in claim 5, wherein this substrate is a glass substrate.

9. the pick-up unit of polysilicon membrane crystalline quality as claimed in claim 5, wherein the splitting ratio of this first light beam and this second light beam is 30～40%: 70～60%.

10. the control method of a polysilicon membrane crystalline quality comprises the following steps:

One first substrate is provided, is coated with one first amorphous silicon layer on this first substrate;

With laser this first amorphous silicon layer is implemented annealing in process respectively, in this first amorphous silicon layer, to form a plurality of first multi-crystal silicon areas with different first set energy densities;

One light source with a set wavelength is provided, and by an optical splitter to form one first light beam and in order to shine one second light beam in those first multi-crystal silicon areas;

Detect this first light beam and from the light intensity of this second light beam of those first multi-crystal silicon areas reflection to obtain a plurality of light intensity ratio;

Decide one second set energy density according to those light intensity ratio;

One second substrate is provided, is coated with one second amorphous silicon layer on this second substrate; And

With laser this second amorphous silicon layer is implemented annealing in process, so that this second amorphous silicon layer is transformed into one second polysilicon layer with this second set energy density.

11. the control method of polysilicon membrane crystalline quality as claimed in claim 10, wherein those first substrates and this second substrate are glass substrate.

12. the control method of polysilicon membrane crystalline quality as claimed in claim 10, wherein this laser is an excimer laser.

13. the control method of polysilicon membrane crystalline quality as claimed in claim 12, wherein this first set energy density is 300 to 500mJ/cm ²Scope.

14. the control method of polysilicon membrane crystalline quality as claimed in claim 12, wherein this light source is a laser and this set wavelength arrive 316nm at 266nm a scope.

15. the control method of polysilicon membrane crystalline quality as claimed in claim 12, wherein the splitting ratio of this first light beam and this second light beam is 30～40%: 70～60%.

16. as the control method of claim 12 a described polysilicon membrane crystalline quality, wherein this second set energy density is the energy density that can form maximum polysilicon grain size.

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