TWI414647B - Method for fabricating submicro patterned-sapphire substrate - Google Patents

Abstract

The present invention provides a method for fabricating a submicron patterned sapphire substrate to be able to apply in GaN light emitting diode. The method includes the following steps: forming an etching stop layer on a sapphire substrate; forming a photoresist layer on the etching stop layer; making a photo mask to contact with the photoresist layer; illuminating the photoresist layer with a beam of light by using the photo mask, and developing the photoresist layer to transfer a submicron pattern from the photo mask to the photoresist layer; etching the etching stop layer by using the photoresist layer with the submicron pattern as a mask to form a first etching stop layer; and etching the sapphire substrate with the first etching stop layer to acquire a submicron patterned sapphire substrate.

Description

Method of making submicron patterned sapphire substrate

This invention relates to a method for making sub-micron patterned sapphire substrates, and in particular, to a sub-micron patterned sapphire substrate suitable for use in gallium nitride light-emitting diodes.

The light-emitting diode is a semiconductor component that was originally used as a light source for an indicator light or a display panel. However, with the appearance of a white light diode, it is also used for illumination. Compared with the traditional light source, the light-emitting diode has the advantages of high efficiency, long life and not easy to be damaged, so it is regarded as a new light source in the 21st century. When a forward voltage is applied, the light-emitting diode emits monochromatic light, and depending on the chemical composition of the semiconductor material used, the light-emitting diode emits near-ultraviolet, visible or infrared light.

However, conventional light-emitting diodes are still insufficient in luminous efficiency. Therefore, in order to simultaneously improve the quantum efficiency and light extraction efficiency inside the light-emitting diode, a patterned sapphire substrate is used as a substrate of the light-emitting diode. The patterned sapphire substrate can increase the radiation bonding effect by lateral epitaxial growth to reduce the density of misalignment in the gallium nitride crystal lattice, and further enhance the internal quantum efficiency. On the other hand, by patterning the pattern on the sapphire substrate, the light limited to the light-emitting diode can be extracted with a higher probability, so that the light extraction rate of the light-emitting diode can be improved.

In the prior art, the line width of the patterned sapphire substrate applied to the gallium nitride light-emitting diode is on the order of several micrometers. In order to further improve the luminous efficiency, the sub-micron patterned sapphire substrate has been applied to the light-emitting diode. The method of fabricating the sub-micron patterned sapphire substrate is to form a sub-micron pattern photoresist on the substrate, and then etching the substrate by the photoresist to obtain a sub-micron patterned substrate. In addition, a thin film layer is formed as an etch stop layer by physical vapor deposition or chemical vapor deposition before the photoresist is formed, which can increase the etching depth of the sub-micron patterned substrate, so that the light has more contact area. Increase the light extraction rate.

In the prior art, there are three methods for fabricating sub-micron patterned substrates. The first method is to use a polystyrene to lay a nanosphere on the substrate as an etch stop. However, this method is difficult to control in uniformity and causes the wafer to be incomplete. Another method uses electron beam evaporation on a substrate to form a nickel layer as an etch stop, followed by annealing to self-assemble the nickel. However, this method is time consuming and does not control the uniformity of the structure. Furthermore, sub-micron patterned substrates can also be obtained by a stepwise exposure method commonly used in semiconductor processes. However, this method requires expensive equipment and a machine.

The above method for fabricating a sub-micron pattern has the disadvantages of incomplete, time-consuming or high cost of the fabricated substrate structure, which is disadvantageous for the production of sub-micron patterned sapphire substrates.

Accordingly, it is an object of the present invention to provide a method of fabricating a sub-micron patterned sapphire substrate that can be fabricated in a simple and stable process to solve the above problems.

According to a specific embodiment, the method for fabricating a sub-micron patterned sapphire substrate of the present invention comprises the steps of: first forming an etch stop layer on a sapphire substrate; then forming a photoresist layer on the etch stop layer; The cover directly contacts the photoresist layer; then, the light beam is transmitted through the photomask through the photomask, and then the photoresist layer is developed to transfer the sub-micron pattern on the photomask to the etch stop layer; then, the photoresist having the sub-micron structure is transmitted through The layer etches the etch stop layer to form a first etch stop layer; finally, the sapphire substrate having the first etch stop layer is etched to obtain a sub-micron patterned sapphire substrate.

In this embodiment, the reticle directly contacts the photoresist layer, so that when the light passes through the reticle, the diffraction phenomenon is prevented to cause the scale of the structure to be too large and the uniformity to be affected.

Another aspect of the present invention is to provide a method of making a sub-micron patterned sapphire substrate to solve the above problems.

According to a specific embodiment, the method for fabricating a sub-micron patterned sapphire substrate of the present invention comprises the steps of: first, fabricating a master mold having a sub-micron pattern; and then, filling a soft material into the master mold to convert a sub-mold, Therefore, the sub-mold will have a relative pattern with respect to the sub-micron pattern of the master mold; after that, the imprint material is filled into the relative pattern of the sub-mold; after that, the sapphire substrate is imprinted by the sub-mold, so The embossing material in the relative pattern of the mold can be formed on the sapphire substrate to form a photoresist layer having a sub-micron pattern; finally, the sub-micron patterned sapphire substrate can be obtained by etching the sapphire substrate by the photoresist layer.

In this embodiment, the sub-micron pattern on the photoresist layer is formed in a mold having a sub-micron pattern, thereby avoiding the effect of the diffraction phenomenon of the exposure development method of the prior art on the photoresist layer.

The advantages and spirit of the present invention will be further understood from the following detailed description of the invention.

Referring to FIG. 1 and FIG. 2A to FIG. 2G together, FIG. 1 is a flow chart showing the steps of a method for fabricating a sub-micron patterned sapphire substrate 3 according to an embodiment of the present invention, and FIG. 2A to FIG. G is a schematic diagram showing the steps of the method of FIG.

As shown in FIG. 1, the method of this embodiment may include steps S10 to S22. In step S10, a sapphire substrate 20 is prepared as shown in FIG. 2A. Next, in step S12, an etch stop layer 32 is disposed on the sapphire substrate 30, as shown in FIG. 2B, wherein the material of the etch barrier layer 32 may be yttrium oxide, nitrided, or hafnium oxynitride. It can be a general physical vapor deposition method or a chemical vapor deposition method, such as Plasma Enhanced Chemical Vapor Deposition (PECVD) or high density plasma chemical vapor deposition (HDPCVD; High Density). Plasma Chemical Vapor Deposition) method. In step S14, a photoresist layer 34 is disposed on the etch stop layer 32, as shown in FIG. In step S16, the photomask M is contacted with the photomask M as shown in FIG. In step S18, the exposure process is performed by irradiating the photoresist layer 34 with the light beam through the mask M, as shown in FIG. 2D, and then the development process of the photoresist layer 34 is performed to transfer the sub-micron pattern on the mask M to the light. The resist layer 34 is as shown in FIG. 2E. In step S20, the etch stop layer 32 is etched through the photoresist layer 34 having the sub-micron pattern to form the first etch stop layer 320, and the photoresist layer 34 is removed, as shown in FIG. 2F; then, in the step In S22, the sapphire substrate 30 having the first etch stop layer 320 is etched by a wet etching process to obtain the sub-micron patterned sapphire substrate 3, as shown in FIG. The wet etching process described above is carried out by mixing between phosphoric acid and nitric acid at a ratio of from 1 to 3 to 1 to 5, wherein the etching temperature is between about 200 and 350 °C. Please note that in practice, the user or designer can change the sub-micron pattern on the reticle M to cause a change in the sub-micron pattern on the sub-micron patterned sapphire substrate 3.

In this embodiment, the etch stop layer 32 can be grown on the sapphire substrate 30 by physical vapor deposition (PVD) or chemical vapor deposition (CVD). Next, the photoresist layer 34 can be applied to the etch stop layer 32 by spin coating. Please note that in practice, the thickness of the photoresist layer 34 is as thin as possible to facilitate fabrication of the sub-micron pattern. For example, the photoresist layer 34 can be from 0.4 μm to 0.8 μm. In addition, the photoresist layer 34 is also kept clean after coating, and the gap between the two is formed by the particles on the surface of the photoresist layer 34 when the mask M contacts the photoresist layer 34, thereby causing the diffraction phenomenon of the light beam. The line width of the sub-micron pattern.

In step S16, the photomask layer 34 is directly contacted with the photoresist layer 34, and then the subsequent exposure and development process is performed. Therefore, there is no gap between the mask M and the photoresist layer 34. When a light beam (for example, 365 nm ultraviolet light) is irradiated onto the photoresist layer 34 through the mask M, the diffraction phenomenon due to the void can be prevented from causing the line width of the submicron pattern to become large. The mask M is in hard contact with the photoresist layer 34. For the method of contacting the lens, refer to FIG. 3. FIG. 3 is a flow chart showing the detailed steps of the step S16 of the method of FIG. As shown in FIG. 3, step S16 further includes step S160 and step S162. In step S160, the photoresist layer 34 is soft baked, and then, in step S162, the photomask M is biased to closely contact the photoresist layer 34.

Since the soft baking can make the photoresist layer 34 in a state of optimum viscosity, the photoresist layer 34 can be attached to the etching barrier layer 32 without falling off. In addition, when the photomask M contacts the photoresist layer 34, the viscosity of the photoresist layer 34 can bring the photomask M and the photoresist layer 34 into close contact to avoid a gap between the two.

In this embodiment, the portion of the photoresist layer 34 that is illuminated by the beam is removable during development, that is, the photoresist layer 34 is made of a positive photoresist. However, in practice, the photoresist layer can also be made of negative photoresist. The photoresist layer is made of a positive photoresist or a negative photoresist, depending on the needs of the user or the designer, and the invention is not limited thereto.

In the above step S20, the etch stop layer 32 may be etched using the etching system and the photoresist layer 34 having the sub-micron pattern developed as a barrier layer, so that the etch stop layer 32 has the same submicron as the photoresist layer 34. The etch stop layer 32 having the sub-micron pattern is the first etch stop layer 320.

Referring to FIG. 2G again, as shown in FIG. 2G, step S22 uses the barrier structure 36 as a barrier layer and etches the sapphire substrate 30 by a wet etching process to obtain a sub-micron patterned sapphire substrate 3. Since the wet etching process etches the entire substrate by immersing it in the etching liquid, the etching of the sapphire substrate has a certain degree of isotropic property. In other words, the size of the pattern etched on the sub-micron patterned sapphire substrate 3 where it is intended to be etched may be greater than or equal to the size of the sub-micron pattern of the first etch stop layer 320, depending on the etchant used. However, by the hard mask of the mask M in step S16 and the photoresist layer 34 to avoid the diffraction phenomenon, the size of the sub-micron pattern of the first etch stop layer 320 can be controlled and the pattern on the sub-micron patterned sapphire substrate 3 can be indirectly controlled. The size of A is maintained at the sub-micron level. On the other hand, as shown in FIG. 2G, the two etched portions (pattern A) on the sub-micron patterned sapphire substrate 3 can also be regarded as another sub-micron pattern B, since the etching liquid will have different degrees. Isotropic, so the size of the pattern B can easily reach the sub-micron level.

In addition, in the specific embodiment, step S22 further removes the first etch stop layer 320 after etching the sapphire substrate 30 to obtain the sub-micro pattern sapphire substrate 3, and is produced by the method of the specific embodiment. The micropatterned sapphire substrate 3 can be directly used in a gallium nitride light emitting diode.

The above specific embodiment etches the sapphire substrate by wet etching, and therefore, the etched submicron pattern has a certain degree of isotropic. However, the method of the present invention can also etch a sapphire substrate by dry etching.

Please refer to Figure 4A, Figure 4B and Figure 4C. 4A is a flow chart showing the steps of a method of fabricating a sub-micron patterned sapphire substrate 6 in accordance with another embodiment of the present invention. Figure 4B is a schematic diagram showing the step S50 of the method of Figure 4A. Figure 4C is a schematic view showing the sub-micron patterned sapphire substrate 6 produced by the method of Figure 4A.

As shown in FIG. 4A, the specific embodiment is different from the above specific embodiment in that the method of the specific embodiment includes step S50 and step S52. In step S50, the etch stop layer 62 is etched through the photoresist layer 64 having the sub-micron pattern, and the photoresist layer 64 having the sub-micro pattern and the etched etch layer 62 are formed to form the barrier structure 66, as shown in FIG. 4B. Shown. In step S52, the sapphire substrate 60 having the barrier structure 66 is etched by a dry etching process to obtain the sub-micron patterned sapphire substrate 6 as shown in FIG. 4C, wherein the dry etching can be performed by inductively coupled plasma (ICP; Inductively Coupled Plasma). ) or reactive ion etching (RIE; Reactive Ion Etching). It should be noted that since the other steps of the method of the specific embodiment are substantially the same as the steps corresponding to the above specific embodiments, the details are not described herein.

In the method of the present embodiment, the sub-micron patterned sapphire substrate 6 is formed by an isotropic dry etching method, and thus its cross-sectional view is as shown in FIG. In practice, dry etching can be, but is not limited to, plasma etching.

Similarly, since the reticle of the present embodiment is in direct contact with the photoresist layer, the sub-micron pattern on the reticle can be directly transferred to the photoresist layer and the etch stop layer to form a barrier structure having a sub-micron pattern. Since the thickness of the barrier structure 66 is the thickness of the etch stop layer 62 plus the photoresist layer 64, the submicron structure patterned sapphire substrate 6 having a deeper depth can be etched by the barrier structure 66. In addition, the sapphire substrate may have a sub-micron pattern due to the anisotropic etch of the dry etch process and the presence of the barrier structure.

In the above embodiment, the photomask is directly contacted with the photoresist layer disposed on the sapphire substrate, and then the exposure and development process is performed, so that the submicron pattern on the photomask can be directly transferred to the photoresist layer and the etch barrier layer to form the submicron pattern. An etched barrier or barrier structure. The submicron patterned sapphire substrate can be easily fabricated by a dry etching or wet etching process by means of an etch stop or barrier structure having a submicron pattern. Compared with the prior art, the direct contact of the photoresist layer with the reticle can avoid the diffraction phenomenon during exposure and affect the line width of the sub-micron pattern. In addition, since the process of the method can achieve the sub-micron pattern on the yellow lithography process end. The production has the advantages of shortening process time, good structural uniformity and low cost.

Referring to FIG. 5 and FIG. 6A to FIG. 6G, FIG. 5 is a flow chart showing the steps of the method for fabricating the sub-micron patterned sapphire substrate 8 according to another embodiment of the present invention, FIG. 6A to FIG. A schematic diagram showing the steps of the method of FIG.

As shown in FIG. 5, the method of this embodiment may include steps S70 to S78. In step S70, a master 90 having a sub-micron pattern 900 is produced, as shown in FIG. Next, in step S72, a soft material is poured into the master mold 90 to reproduce a sub-mold 92, wherein the sub-mold 92 cooperates with the master mold 90 to have a relative pattern 920 with respect to the sub-micron pattern 900, as shown in FIG. Figure 6C shows. Thereafter, in step S74, the imprint material 84 is poured into the opposite pattern 920 of the sub-mold 92, as shown in FIG. Thereafter, in step S76, the sapphire substrate 80 is imprinted by the sub-mold 92 and the imprint material 84 is formed on the sapphire substrate 80 to form a photoresist layer 82 having the same sub-micron pattern 900 as the master 90. The pattern is shown in Figure 6E and Figure 6F. Finally, in step S78, the sapphire substrate 80 is etched through the photoresist layer 82 to obtain a sub-micron patterned sapphire substrate 8, as shown in FIG.

In this particular embodiment, the master mold 90 can be comprised of, but not limited to, a tantalum material. In addition, in practice, a sub-micron pattern 900 can be formed on the master mold 90 by an etch process of an electron beam or an exposure machine. The soft material used to form the sub-mold 92 can be, but is not limited to, polydimethylsiloxane (PDMS) in this embodiment. In addition, the imprinting material that is filled in the opposite pattern 920 of the sub-mold 92 can be, but is not limited to, polymethylmethacrylate (PMMA) in this embodiment. As in the above specific embodiment, the sapphire substrate 80 of the present embodiment can also obtain the sub-micron patterned sapphire substrate 8 through a dry etching or wet etching process. The difference between the two etching processes is that the dry etching is an isotropic etching and wet etching. It is an isotropic etching process. In practice, the above two etching processes can be arbitrarily selected by the user or the designer, and the invention is not limited thereto.

Therefore, by the method of the present embodiment, the photoresist layer can be formed on the sapphire substrate by a sub-micron pattern through a mold and by direct contact. Since the photoresist layer does not need to be exposed and developed as in the prior art, the influence of the diffraction phenomenon on the submicron pattern of the photoresist layer can be avoided. At the same time, the method of fabricating the photoresist layer by the mold is simple, and the disadvantages of the prior art are time-consuming or high-cost.

If the sapphire substrate has an etch stop layer, the method may first transfer the sub-micron pattern to the etch stop layer, and etch the sapphire substrate through an etch stop layer having a sub-micron structure to obtain a sub-micron patterned sapphire substrate. .

Referring to FIG. 7 and FIG. 8A to FIG. 8E, FIG. 7 is a flow chart showing the steps of the method for fabricating the sub-micron patterned sapphire substrate 8 according to another embodiment of the present invention, FIG. 8A to FIG. A schematic diagram showing the steps of the method of Figure 7. Please note that the sapphire substrate 80 of the present embodiment further includes an etch stop layer 800.

As shown in FIG. 7, the specific embodiment is different from the previous embodiment in that the method of the specific embodiment further includes steps S760, S780, step S782, and step S784. In step S760, the sapphire substrate 80 is embossed by the sub-mold 92 and the embossed material 84 is formed on the etch stop layer 800 of the sapphire substrate 80. Similarly, the photoresist layer 82 has the same shape as the sub-micron pattern 900 of the master 90. The pattern is shown in Figure 8A and Figure 8B. In step S780, the etch stop layer 800 is etched through the photoresist layer 82 having the sub-micron pattern to transfer the sub-micron pattern on the photoresist layer 82 to the etch stop layer 800, as shown in FIG. In step S782, the photoresist layer 82 is removed, as shown in FIG. Finally, in step S784, the sapphire substrate 80 is etched through the etch stop layer 800 having the sub-micron structure to obtain the sub-micro pattern sapphire substrate 8, as shown in FIG. It should be noted that the other steps of the method of the specific embodiment are substantially the same as the corresponding steps of the foregoing specific embodiments, and thus are not described herein again.

In this embodiment, after the sub-micron pattern is transferred from the photoresist layer 82 to the etch stop layer 800, the photoresist layer 82 is removed and the sapphire substrate 80 is etched only through the etch stop layer 800. However, in another embodiment, the photoresist layer may also remain and form a barrier structure with the etch barrier layer, and the sapphire substrate may be etched through the barrier structure to obtain a sub-micron patterned sapphire substrate. Therefore, whether the photoresist layer is left after transferring the sub-micron pattern to the etch stop layer can be etched according to the needs of the user or the designer.

In summary, the method for fabricating a sub-micron patterned sapphire substrate of the present invention is to directly contact the photoresist layer on the sapphire substrate with a photomask and expose it to form a sub-micron structure on the photoresist layer; or directly by using a mold. A photoresist layer having a submicron structure is imprinted on the sapphire substrate. Compared to the prior art, the method of the present invention can avoid the influence of the diffraction phenomenon during exposure, and the photoresist layer can accurately develop the desired sub-micron pattern. By the method of the present invention, a submicron patterned sapphire substrate can be obtained by etching a sapphire substrate having a photoresist layer having a precise submicron pattern. In addition, since the method of the present invention is simple in process, the disadvantages of the prior art and the high cost can be avoided.

The features and spirit of the present invention will be more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents within the scope of the invention as claimed. Therefore, the scope of the patented scope of the invention should be construed as broadly construed in the

S10~S22. . . Process step

3, 6. . . Submicron patterned sapphire substrate

30, 60. . . Sapphire substrate

32, 62. . . Etch barrier

34, 64. . . Photoresist layer

320. . . First etch stop

A, B. . . pattern

S160～S162. . . Process step

S40～S52. . . Process step

66. . . Barrier structure

S70～S78. . . Process step

S760, S780～S784. . . Process step

90. . . Master model

900. . . Submicron pattern

92. . . Submodule

920. . . Relative pattern

80. . . Sapphire substrate

800. . . Etch barrier

82. . . Photoresist layer

84. . . Imprint material

8. . . Submicron patterned sapphire substrate

1 is a flow chart showing the steps of a method of fabricating a sub-micron patterned sapphire substrate in accordance with an embodiment of the present invention.

2A to 2G are schematic views showing the steps of the method of FIG. 1.

Figure 3 is a flow chart showing the detailed steps of the photomask contacting the photoresist layer of the method of Figure 1.

4A is a flow chart showing the steps of a method of fabricating a sub-micron patterned sapphire substrate in accordance with another embodiment of the present invention.

Figure 4B is a schematic diagram showing the step S50 of the method of Figure 4A.

Figure 4C is a schematic view showing a sub-micron patterned sapphire substrate produced by the method of Figure 4A.

Figure 5 is a flow chart showing the steps of a method of fabricating a sub-micron patterned sapphire substrate in accordance with another embodiment of the present invention.

6A to 6G are schematic views showing the steps of the method of FIG.

Figure 7 is a flow chart showing the steps of a method of fabricating a sub-micron patterned sapphire substrate in accordance with another embodiment of the present invention.

8A to 8E are schematic views showing the steps of the method of FIG.

S70~S78‧‧‧ Process steps

Claims (7)

A method of fabricating a sub-micron patterned sapphire substrate for fabricating a micron patterned sapphire substrate having a micron pattern, the method comprising the steps of: fabricating a master mold having a micron pattern thereon; and a soft material Filling the master mold to reproduce a sub-mold, the sub-mold has a relative pattern relative to the sub-micron pattern of the master mold; injecting an imprint material into the relative pattern of the sub-mold; Printing a sapphire substrate, and forming the embossed material on the sapphire substrate to form a photoresist layer having the sub-micron pattern; and etching the sapphire substrate through the photoresist layer to obtain an etch process The submicron patterned sapphire substrate. The method of claim 1, wherein the sapphire substrate further comprises an etch stop layer and the photoresist layer is disposed on the etch stop layer, the method further comprising the step of: transmitting through the sub-micron pattern The photoresist layer etches the etch stop layer to transfer the sub-micron pattern to the etch stop layer; and the etch process is performed on the sapphire substrate through the etch stop layer having the sub-micro structure to obtain the sub-micro pattern sapphire substrate . The method of claim 2, further comprising the following steps Step: After transferring the submicron pattern to the etch stop layer, the photoresist layer is removed. The method of claim 1, further comprising the step of etching the sapphire substrate by a wet etching process to obtain the sub-micropatterned sapphire substrate. The method of claim 1, further comprising the step of etching the sapphire substrate by a dry etching process to obtain the sub-micropatterned sapphire substrate. The method of claim 1, further comprising the step of: fabricating the master by an electron beam etching method. The method of claim 1, further comprising the step of: fabricating the master by an exposure machine etching method.