TWI406106B - System and method for manufacturing multi-chip silicon pattern by laser - Google Patents

Abstract

The invention provides a method and a system for manufacturing polycrystalline silicon patterns by femtosecond laser, comprising generating a laser beam by a femtosecond laser source; focusing the laser beam onto the surface of a substrate by a focusing lens and scanning the substrate surface to form a polycrystalline silicon material, wherein the frequency and energy of the laser beam is adjusted and controlled by a frequency adjusting unit and a energy adjusting unit; and etching to remove the amorphous silicon material to achieve polycrystalline silicon patterns. The invention utilizes the femtosecond laser technique to form polycrystalline silicon patterns that have line widths smaller than the laser gathering spots by controlling the frequency and energy thereof.

Description

Method and system for producing polycrystalline germanium patterns by femtosecond laser

This invention relates to the fabrication of polycrystalline germanium patterns, and more particularly to a method of fabricating a polycrystalline germanium pattern from a femtosecond laser and a system for fabricating the polycrystalline germanium pattern.

In optoelectronic products such as thin-film solar cells or flat-panel displays, in order to improve the performance of components, amorphous materials are usually heat treated to make the material polycrystalline germanium to improve carrier mobility. The typical polysilicon patterning process is to produce an amorphous germanium pattern through five processes such as exposure and development, and then solid phase crystallization (SPC), which is melted and recrystallized at a process temperature higher than 600 ° C to complete the polysilicon pattern. Production. However, since the maximum temperature of glass and flexible plastic substrates is only 650 ° C and 300 ° C, this method is not suitable for displays, thin film solar cells and soft electronics.

U.S. Patent Nos. 2008087889A1, 2005028729A1, 2002185059A1, 7507645, and 7381600, and Taiwan Patent Nos. I258810 and I245321 disclose the use of laser selective irradiation of an amorphous enamel pattern produced by an exposure development process to melt and recrystallize to complete a polycrystalline germanium structure. Production. Although these techniques improve the high temperature process, the process pattern is still limited by the mask process, the degree of change is low, and the laser needs to be accurately irradiated on the formed pattern area, which requires high precision positioning to accurately scan, which is not conducive to the pattern line. The width is further reduced.

Therefore, how to simplify the process steps, improve the smoothness and change of the pattern, satisfy the high-precision scanning and reduce the line width of the polysilicon pattern, which is a technical problem that is currently being solved.

Accordingly, the present invention provides a method of fabricating a polysilicon pattern by femtosecond laser, comprising: providing a substrate having a layer of amorphous germanium material on the surface; focusing a femtosecond laser beam onto the surface of the substrate, and scanning the surface of the substrate to form a polycrystalline germanium material; and etching to remove the amorphous germanium material to obtain a polycrystalline germanium pattern.

In practice, the present invention generates the femtosecond laser beam by a femtosecond laser source, and the pulse width of the two laser beams is less than or equal to 500 fs.

In one embodiment, the frequency of the femtosecond laser beam conforms to the following equation such that the polysilicon pattern line width is less than the laser focused spot diameter:

f ≧D _t /d ²

Where f is the frequency of the femtosecond laser beam, D _{t is} the thermal diffusivity of the amorphous germanium material, and d is the laser concentrated spot diameter.

In addition, the present invention also provides a system for fabricating a polysilicon pattern, comprising: a carrier for carrying a substrate having an amorphous germanium material layer; a femtosecond laser source for generating a femtosecond laser beam; and a frequency adjustment unit, Positioning along the femtosecond laser beam transmission path to control the frequency of the femtosecond laser beam; an energy adjustment unit disposed along the femtosecond laser beam transmission path to control the energy of the femtosecond laser beam; And a focusing lens for collecting the femtosecond laser beam of the controlled frequency and energy to the surface of the amorphous germanium material layer of the substrate carried by the stage.

In one embodiment, the system of the present invention includes a displacement control mechanism coupled to the stage to move the stage relative to the femtosecond laser beam.

In another embodiment, the displacement control mechanism of the present invention is coupled to the femtosecond laser source to cause the generated femtosecond laser beam to move relative to the stage to form a modified pattern and a crystalline pattern.

Compared with the prior art, the present invention focuses on a femtosecond laser beam in a single step and scans the amorphous germanium material layer instead of the exposure, development and crystallization steps in the conventional process, simplifying the multi-step process without The entire substrate is heat-treated, the degree of pattern change is not limited to the mask, and the laser-free annealing is limited by the high precision of the alignment, and has the advantages of greatly reducing the process, time, and obtaining a high-precision microstructure.

The embodiments of the present invention are described below by way of specific examples, and those skilled in the art can readily appreciate other advantages and functions of the present invention from the disclosure herein.

The present invention relates to a method for fabricating a polycrystalline germanium pattern by femtosecond laser. In the present invention, a substrate having an amorphous germanium material layer on a surface is scanned using a laser source to form a polycrystalline germanium material, wherein no limitation is imposed on any form. The laser source, in one embodiment of the invention, uses a titanium-sapphire femtosecond laser source. On the other hand, the object to be treated by the present invention is a substrate having a layer of amorphous germanium material on its surface, especially those that have not undergone a patterning process. Typically, the substrate comprises a substrate that is itself amorphous or has a layer of amorphous germanium material on its surface.

Further, the laser beam used in the present invention has a pulse width of less than or equal to 500 fs. Within this short pulse width range, the time at which the workpiece is processed is released (eg, the time at which free electrons release energy to the crystal lattice) is greater than the pulse width of the laser. At this time, the absorption of energy by the workpiece exhibits a nonlinear relationship with the nth power of the laser power density, where n is the number of photons absorbed. Under laser irradiation, electrons can absorb n photon energy transitions to conduction bands to form free electrons due to multiphoton-Ionization. Therefore, under the multiphoton absorption mechanism, the laser pulse power density is controlled. Therefore, only the center of the Gaussian laser beam produces nonlinear absorption, so the line width of the polysilicon pattern smaller than the diameter of the laser concentrated spot is realized.

The femtosecond laser beam for scanning the surface of the substrate is adjusted to an appropriate interval by the energy, and then the femtosecond laser beam is focused by the lens to the surface of the substrate so that the substrate surface accepts a range of 0.001 to 0.02 J/cm ² The laser dose is insufficient due to the energy of the laser defocusing position, so that the above-mentioned multiphoton absorption does not occur to form a polycrystalline germanium material.

In a second step of the method of the present invention, the present invention finds that when the frequency ( f ) of the femtosecond laser beam is adjusted to a specific value, the femtosecond laser beam produces nonlinear absorption in the focused amorphous germanium material portion. Can break through the optical diffraction limit. Specifically, the frequency of the femtosecond laser beam is in accordance with the following formula.

f ≧D _t /d ²

Where f is the frequency of the femtosecond laser beam, D _{t is} the thermal diffusivity of the amorphous germanium material, and d is the laser concentrated spot diameter. D _t can be calculated from the formula D _t =κ/ρ Cp , where κ is the heat transfer coefficient (W/m‧K); ρ is the density (kg/m ³ ); and Cp is the specific heat (J/(Kg‧K) )).

In one embodiment of the invention, the femtosecond laser beam is focused by a lens.

In another embodiment of the invention, the amorphous germanium material layer has a thickness of from 20 to 5000 nm.

Since the portion of the focused laser scan forms a polycrystalline germanium material, the polycrystalline germanium material has high acid corrosion resistance compared to the amorphous germanium material. Therefore, in order to obtain the polycrystalline germanium pattern structure of the present invention, the amorphous germanium material is removed by etching in the final step to obtain a polycrystalline germanium pattern. In one embodiment, the etching is performed using a mixture of hydrofluoric acid and potassium dichromate, and the ultrasonic oscillation can be used simultaneously to accelerate the etching.

In addition, the present invention also provides a system for fabricating a polysilicon pattern, as shown in FIG. 1A, the system comprising: a carrier 101 carrying a substrate 100 having an amorphous germanium material layer; a femtosecond laser source 103 for generating a femtosecond laser beam 105; a frequency adjustment unit 107 disposed along the femtosecond laser beam 105 transmission path to control the frequency of the femtosecond laser beam 105; an energy adjustment unit 109 along the femtosecond laser The beam 105 is disposed in a path to control the energy of the femtosecond laser beam 105; and a focusing lens 111 is used to concentrate the controlled frequency and energy femtosecond laser beam 105 onto the surface of the substrate 100 carried by the stage 101. It should be noted that the settings of the frequency adjustment unit 107 and the energy adjustment unit 109 of the present invention are not limited in sequence, and the energy re-adjustment frequency may be adjusted first.

In another embodiment illustrated in FIG. 1B, the system for fabricating a polysilicon pattern includes a mirror 113 for changing the path of the femtosecond laser beam 105, as illustrated in the exemplary embodiment, the fly The path of the second laser beam 105 changes by about 90 degrees.

Referring to another embodiment shown in FIG. 2A, the system of the present invention includes a displacement control mechanism 115 that is coupled to the stage 101 to move the stage 101 relative to the femtosecond laser beam 105 to facilitate formation. microstructure. Since the displacement control mechanism is implemented in many ways and is known to those of ordinary skill in the art, it will not be described herein.

Referring to another embodiment shown in FIG. 2B, the system of the present invention includes a displacement control mechanism 115' connected to the femtosecond laser source 103 to command the generated femtosecond laser beam 105 relative to the The stage 101 is moved to form a modified pattern and a crystalline pattern. In a specific implementation, as shown in FIG. 2B, the femtosecond laser source 103, the frequency adjusting unit 107, the energy adjusting unit 109, and the focusing lens 111 can be installed in the housing 117, and the displacement control mechanism 115' is The housing and/or femtosecond laser source 103 is coupled to control the displacement of the femtosecond laser beam 105. Of course, the femtosecond laser source 103, the frequency adjusting unit 107, and the energy adjusting unit 109 can also be fixed to each other simply by the connecting member, as long as the frequency adjusting unit 107 and the energy adjusting unit 109 are arranged along the femtosecond laser. The beam 105 can be set in the transmission path.

Example 1 Production of a polycrystalline germanium pattern

In this embodiment, a substrate having an amorphous germanium material layer is scanned by using a femtosecond laser beam of three different laser energies, such as 67 mW, 112 mW, and 202 mW, wherein the amorphous germanium material has a thermal diffusivity of about 8×10 ^{− 5} m ² /s, the laser concentrated spot diameter is about 5 μm, and after adjusting the frequency of the laser beam to be greater than D _t /d ² , the laser beam is focused on the surface of the substrate for scanning to form polycrystalline germanium material, and finally by concentration. 8 wt% of hydrofluoric acid and potassium dichromate having a concentration of 0.15 mole/L, the mixture ratio of the mixture is 2:1, and the amorphous germanium material is removed by ultrasonic vibration for 1 minute to obtain polycrystalline germanium. pattern.

As shown in the SEM images shown in Figures 3A, 3B and 3C, the polysilicon pattern widths produced on the scanning surfaces of 67 mW and 112 mW were 1.3 μm and 2.8 μm, respectively, and the laser-concentrated spot diameter was 5 μm. The polysilicon pattern line width of the energy on the 202 mW scanning surface was 5 μm.

As shown in Fig. 4, the relationship between the laser dose and the line width of the polycrystalline germanium pattern confirms that the adjustment of the energy at a dose of less than 0.012 J/cm ² or less makes it possible to make the polycrystalline germanium pattern line width smaller than the laser concentrated spot diameter by 5 μm.

It can be seen that the present invention uses a femtosecond laser to produce a polycrystalline germanium pattern through a maskless manner, and further reduces the line width of the polycrystalline germanium pattern to enhance the pattern accuracy, breaks through the bottleneck of the prior art, and opens up the advantages of the femtosecond laser application.

The above-described embodiments are merely illustrative of the principles of the invention and its effects, and are not intended to limit the invention. Modifications and variations of the above-described embodiments can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be as set forth in the scope of the claims described below.

100. . . Substrate

101. . . Loading platform

103. . . Femtosecond laser source

105. . . Femtosecond laser beam

107. . . Frequency adjustment unit

109. . . Energy adjustment unit

111. . . Focusing lens

113. . . Reflector

115, 115’. . . Displacement control mechanism

117. . . case

1A is a schematic view of a system for manufacturing a polycrystalline germanium pattern according to the present invention; FIG. 1B is a schematic view of another system for manufacturing a polycrystalline germanium pattern according to the present invention; FIG. 2A is a schematic diagram of a system having a displacement control mechanism of the present invention; Another schematic diagram of a system having a displacement control mechanism according to the present invention; FIG. 3A is a SEM photograph of a polycrystalline germanium pattern produced by the method and system of the present invention; and FIG. 3B is another SEM photograph of a polycrystalline germanium pattern produced by the method and system of the present invention; 3C is a further SEM photograph of a polycrystalline germanium pattern produced by the method and system of the present invention; and FIG. 4 is a graph showing the relationship between the pattern line width and the irradiated laser dose of a polycrystalline germanium pattern produced by the method and system of the present invention.

100. . . Substrate

101. . . Loading platform

103. . . Femtosecond laser source

105. . . Femtosecond laser beam

107. . . Frequency adjustment unit

109. . . Energy adjustment unit

111. . . Focusing lens

Claims (19)

A method for fabricating a polysilicon pattern by femtosecond laser, comprising: providing a substrate having a layer of amorphous germanium material on a surface; focusing a femtosecond laser beam onto the surface of the substrate, and scanning the surface of the substrate to form a polysilicon material, wherein The frequency of the femtosecond laser beam is as follows: f ≧D _t /d ² where f is the frequency of the femtosecond laser beam, D _{t is} the thermal diffusivity of the amorphous germanium material, and d is the laser focused spot Diameter; and etching removes the amorphous germanium material to obtain a polysilicon pattern. The method of claim 1, wherein the femtosecond laser beam is generated by a femtosecond laser source. The method of claim 2, wherein the laser beam has a pulse width of less than or equal to 500 fs. The method of claim 1, wherein the femtosecond laser beam is energy-adjusted prior to focusing such that a laser dose concentrated on the surface of the substrate ranges from 0.001 to 0.02 J/cm ² . The method of claim 1, wherein the femtosecond laser beam is focused by a lens. The method of any one of claims 1 to 4, wherein the substrate provided is not subjected to a patterning process. The method of claim 1, wherein the amorphous germanium material layer has a thickness of 20 to 5000 nm. For example, the method of the first application of the scope is mixed with hydrofluoric acid and potassium dichromate. The liquid is etched. The method of claim 8, wherein the hydrofluoric acid concentration is 8 wt%, the potassium dichromate is 0.15 mole/L, and the mixture ratio of the two is 2:1. The method of claim 1, wherein the energy of the femtosecond laser beam is below 202 mW, and the line width of the polysilicon pattern produced by scanning the surface of the substrate is less than 5 μm of the diameter of the laser spot. The method of claim 1 or 10, wherein, when the energy of the femtosecond laser beam is 67 mW, the polysilicon pattern produced by scanning the surface of the substrate has a line width of 1.3 μm. The method of claim 1 or 10, wherein, when the energy of the femtosecond laser beam is 112 mW, the polysilicon pattern generated by scanning the surface of the substrate has a line width of 2.8 μm. The method of claim 1, wherein when the dose of the femtosecond laser beam is less than 0.012 J/cm ² , the line width of the polysilicon pattern generated by scanning the surface of the substrate is less than 5 μm of the laser spot diameter. A system for fabricating a polysilicon pattern comprising: a carrier for carrying a substrate having an amorphous germanium material layer; a femtosecond laser source for generating a femtosecond laser beam; and a frequency adjustment unit along the femtosecond The laser beam transmission path is set to control the frequency of the femtosecond laser beam, wherein the frequency of the femtosecond laser beam conforms to the following formula: f ≧D _t /d ² where f is the frequency of the femtosecond laser beam , d _t for the thermal diffusivity of the material, amorphous silicon, and aggregate spot diameter d of the laser; energy adjustment unit line arranged to control the energy of the femtosecond laser beam along the transmission path of the femtosecond laser beam; and A focusing lens is used to concentrate the femtosecond laser beam of controlled frequency and energy onto the surface of the amorphous germanium material layer of the substrate carried by the stage. The system of claim 14, wherein the system includes a displacement control mechanism that connects the stage to move the stage relative to the femtosecond laser beam. For example, the system of claim 14 includes a displacement control mechanism that connects the femtosecond laser source and causes the generated femtosecond laser beam to move relative to the stage to form a modified pattern and a crystalline pattern. A system as claimed in claim 14 includes a mirror for varying the femtosecond laser beam path. The system of claim 14, wherein the femtosecond laser source produces a laser beam pulse width of less than or equal to 500 fs. The system of claim 14, wherein the energy adjustment unit is configured to adjust the beam energy before focusing of the femtosecond laser beam so that the laser dose concentrated on the surface of the substrate ranges from 0.001 to 0.02 J/cm ² .