WO2016061881A1

WO2016061881A1 - Method for patterning substrate

Info

Publication number: WO2016061881A1
Application number: PCT/CN2014/093457
Authority: WO
Inventors: 刘海鹰
Original assignee: 北京北方微电子基地设备工艺研究中心有限责任公司
Priority date: 2014-10-20
Filing date: 2014-12-10
Publication date: 2016-04-28
Also published as: CN105514243B; CN105514243A

Abstract

Provided is a method for patterning a substrate, which comprises: a main etching process, performing a main etching on a substrate (1) on the surface of which a mask (2) is formed, and completing the main etching process before the cover area of the mask (2) is reduced; and an over etching process, performing an over etching on the substrate (1) which has experienced the main etching, the etching rate of the mask (2) during the over etching being less than the etching rate of the mask (2) during the main etching. The provided method for patterning a substrate avoids the occurrence of an abrupt corner on a side wall of a PSS pattern during the main etching process through completing the main etching process before the cover area of the mask (2) is reduced, and thereafter reduces the inward-shrinkage rate of the mask (2) by reducing the etching rate of the mask (2) during the over etching, such that the angle of the corner on the side wall of the finally formed PSS triangle taper (11) is increased, thereby improving the smooth flatness of the side wall of the triangle taper (11).

Description

Method for patterning a substrate

Technical field

The present invention relates to the field of semiconductor technology, and in particular, to a method of patterning a substrate.

Background technique

With the development of process technology in the field of LED (Light-Emitting Diode) and the rapid growth of the entire LED industry, research on GaN (GaN-based) LED devices PSS (Patterned Sapphire Substrates) It is also gradually increasing, manufacturers have adopted PSS technology to improve the light extraction efficiency of LED devices.

PSS technology refers to coating a mask for dry etching (generally photoresist) on a sapphire substrate, and then etching the mask by photolithography, and then using ICP (Inductive Coupled Plasma). The etching technique etches the sapphire substrate exposed by the mask, forms a PSS pattern on the surface of the sapphire substrate, and then removes the mask to grow GaN on the substrate. Due to the existence of PSS pattern, the growth of GaN changes from longitudinal epitaxy to lateral epitaxy. This aspect can effectively reduce the dislocation density of the GaN epitaxial layer, thereby reducing the non-radiative recombination of the active region, reducing the reverse leakage current, and improving The lifetime of the LED, on the other hand, the light emitted by the active region, through multiple scattering of the interface between the GaN and the sapphire substrate, changes the exit angle of the total reflected light, thereby increasing the probability of light exiting the sapphire substrate and increasing the light. Extraction efficiency.

As shown in Fig. 1, a PSS pattern generally accepted in the industry is a triangular pyramid shape, and the smooth flatness of the triangular pyramidal sidewall is the key to ensure that the GaN epitaxial layer formed on the surface has good film quality.

The process of forming a triangular pyramid by PSS in the prior art generally includes a two-step etching: a first etching (Main Etch, ME), which is mainly used to form a preliminary shape of the PSS pattern, and the second step is an overcut. Over Etch (OE) is mainly used to modify the outer contour of the PSS pattern to make the surface smooth and flat. The above two-step etching forms a triangular pyramid and can be divided into four In the same stage: the first stage, as shown in FIG. 2a, the main etching step starts, etching the region where the sapphire substrate 1 is not covered by the photoresist 2; as the main etching proceeds, the second stage is entered, as shown in the figure 2b, at this time, due to the bombardment by the etching gas, the outer surface of the photoresist 2 is etched away, the bottom is retracted, the covering area becomes small, and the edge of the area originally covered by the photoresist 2 is exposed. Further etched; as the etch continues, as shown in Figure 2c, entering the third stage, where the sidewall of the PSS pattern on the sapphire substrate 1 has a prominent corner α, typically 150°, the main etch phase Then, in the fourth stage, as shown in FIG. 2d, etching is performed to modify the corner α of the main etching stage, and the sidewall of the triangular pyramid 11 obtained by etching is made smooth and flat as much as possible.

However, since the protruding corner α of the PSS pattern formed in the main etching step is relatively abrupt, after the over-etching step is completed, the bottom of the obtained triangular pyramid is still likely to leave a corner β, resulting in a triangular pyramid. The sidewalls are not smooth enough to affect the quality of the film grown thereon.

Summary of the invention

In order to overcome the above drawbacks in the prior art, the technical problem to be solved by the present invention is to provide a method for patterning a substrate to increase the corner angle on the triangular pyramidal sidewall obtained by the patterned substrate, thereby improving Smooth flatness of the side walls.

In order to achieve the above object, the present invention adopts the following technical solutions:

The invention provides a method for patterning a substrate, comprising: a main etching process, performing main etching on a substrate having a mask formed on a surface thereof, ending the main engraving before the coverage area of the mask is reduced An etching process, the substrate processed by the main etching process is over-etched, and the etching rate of the mask in the over-etching process is less than that in the main etching process The etch rate of the mask.

The etching rate of the mask in the over-etching process is less than the etching rate of the mask in the main etching process, specifically: the gas pressure used in the over-etching process is less than Said The gas pressure used in the main etching process.

The gas pressure used in the main etching process is 2 mT to 4 mT, and the gas pressure used in the over-etching process is 1.5 mT to 2.5 mT.

The etch rate of the mask in the over etch process is less than the etch rate of the mask in the main etch process, specifically: the gas flow rate used in the over etch process is less than The flow rate of gas used in the main etching process.

Wherein, the gas flow rate used in the main etching process is 80 sccm to 150 sccm, and the gas flow rate used in the over-etching process is 50 sccm to 80 sccm.

The duration of the main etching process is 10 min to 15 min, and the duration of the over-etching process is 10 min to 20 min.

The lower electrode RF power used in the over-etching process is not less than the lower electrode RF power used in the main etching process.

The radio frequency of the lower electrode used in the main etching process is 300W-600W, and the RF power of the lower electrode used in the over-etching process is 500W-700W.

The selection of the mask in the over-etching process is the same as the selection ratio of the substrate to the mask in the main etching process.

Wherein, the selection ratio of the substrate to the mask etching is greater than or equal to 0.8.

In the method for patterning a substrate provided by the present invention, by ending the main etching before the coverage area of the mask is reduced, the occurrence of abrupt corners of the sidewall of the PSS pattern during the main etching process is avoided, and then During the etching process, the etching rate of the mask is reduced to reduce the rate of shrinkage of the mask, so that the corner angle of the finally formed PAS triangular tapered sidewall is increased, thereby improving the smoothness of the triangular tapered sidewall.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art description will be briefly introduced below, and it is obvious that The drawings in the following description are only some of the embodiments of the present invention, and those skilled in the art can obtain other drawings according to the drawings without any creative work.

1 is a structural view of a sapphire substrate obtained by using PSS technology;

2a is a schematic diagram showing the results of the first stage when preparing a triangular pyramidal PSS pattern in the prior art;

2b is a schematic diagram showing the results of the second stage in the preparation of the triangular pyramidal PSS pattern in the prior art;

2c is a schematic diagram showing the results of the third stage in the preparation of the triangular pyramidal PSS pattern in the prior art;

2d is a schematic diagram showing the results of the fourth stage in the preparation of the triangular pyramidal PSS pattern in the prior art;

3a is a schematic diagram showing the result of step S1 when preparing a triangular pyramidal PSS pattern according to an embodiment of the present invention;

FIG. 3b is a schematic diagram showing the result of step S2 when preparing a triangular pyramidal PSS pattern according to an embodiment of the present invention; FIG.

4 is a comparison diagram of step S2 when the mask etching rate is reduced and the mask etching rate is not reduced in the embodiment of the present invention;

Figure 5 is a comparison diagram of step S2 when the gas pressure is reduced and the gas pressure is not reduced in the embodiment of the present invention;

6 is a comparison diagram of step S2 when the gas pressure is reduced, the gas flow rate is reduced, the lower electrode RF power is increased, the lower electrode gas pressure is increased, the gas flow rate is not decreased, and the lower electrode RF power is not increased.

detailed description

In order to make the above objects, features and advantages of the present invention more apparent, the following will be The technical solutions in the embodiments of the present invention are clearly and completely described in conjunction with the drawings in the embodiments of the present invention. It is apparent that the described embodiments are only a part of the embodiments of the invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

Embodiments of the present invention provide a method of patterning a substrate, the method comprising the following steps:

Step S1: The main etching process performs main etching on the substrate 1 on which the mask 2 is formed, and ends the main etching process before the coverage area of the mask 2 is reduced, as shown in FIG. 3a.

In the above steps, the main etching process forms a preliminary topography of the triangular pyramid 11.

During the etching process, the mask 2 is also etched while the substrate 1 is being etched, but the amount of the mask 2 is etched away during the period from the beginning of the etching, and the concentration is mainly concentrated. In the upper middle portion of the mask 2, the bottom of the mask 2 is hardly etched away, so that it does not have a reduced influence on the area of the substrate 1 to be covered, and it can be considered that during the period from the start of etching The coverage area of the mask 2 does not change. As the etching continues, the amount of the bottom portion of the mask 2 is etched away, and the reduction in the bottom cover area becomes apparent. The end time of the main etching stage in this step is before the coverage area of the mask 2 is reduced, thereby effectively avoiding the edge of the original covered area of the substrate 1 being etched due to the reduction of the bottom cover area of the mask 2. The problem of corners appearing on the side wall of the triangular pyramid 11 provides a good basis for the subsequent over-etching process to modify the surface of the formed pattern.

Based on ensuring that the substrate 1 is sufficiently etched in the main etching stage to form a preliminary topography of the closer triangular pyramid 11, and ensuring that the cover area of the mask 2 does not reduce the two aspects of causing the occurrence of corners, The end time of the main etch in the embodiment may preferably be a critical point at which the coverage area of the mask 2 is to be reduced without being reduced. More specifically, the duration of the main etch process may be 10 min to 15 min.

Step S2: over-etching, etching the substrate 1 after the main etching, the etching rate of the mask 2 during the over-etching process is smaller than the etching rate of the mask 2 in the main etching process, as shown in the figure 3b is shown.

In this step, the outer contour of the preliminary topography of the triangular pyramid 11 formed in step S1 is modified to make the surface of the triangular pyramid 11 smooth and flat, and the desired triangular pyramid 11 is obtained.

Since the etching rate of the mask 2 of the over-etching process is smaller than the etching rate of the mask 2 of the main etching process, the bottom retraction of the mask 2 is slowed down, so that when the sidewall of the triangular pyramid 11 is modified The sidewall can be gradually etched, the sidewall surface is smoothly transitioned, and no abrupt corners are formed, that is, the corner angle becomes larger, which alleviates the rapid shrinkage of the mask 2 in the prior art, and the sidewall is unevenly engraved. The etch (the amount of the upper surface of the sidewall is etched away), the sidewall surface cannot be smoothly transitioned, and the problem of abrupt corners occurs.

It has also been experimentally confirmed that reducing the etching rate of the mask 2 can increase the angle of the side wall corners, resulting in a triangular cone 11 having a smoother surface. As shown in FIG. 4, the selection ratio of (1) and (2) substrate 1 to the mask 2 is 0.8, but the etching rate of the mask 2 in (1) is 66 nm/min, (2) The etching rate of the mask 2 is 77 nm/min, and the bottom diameter m1 of the mask 2 in (1) is 902 nm, the side angle β1 of the triangular pyramid 11 is 165 degrees, and the bottom of the mask 2 in (2) The diameter m2 is 387 nm, and the side angle β2 of the triangular pyramid 11 is 155 degrees. It can be seen that the etch rate of the smaller mask 2 results in a larger sidewall corner and a smoother surface.

It should be noted that there are various ways to reduce the etching rate of the mask 2, for example, reducing the RF power of the lower electrode, reducing the gas pressure, reducing the gas flow rate, etc., but reducing the etching of the mask 2 by lowering the RF power of the lower electrode. The etch rate will undoubtedly reduce the bombardment energy of the etched particles, resulting in a slower rate of sidewall corner modification, resulting in prolonged process time.

Preferably, in the embodiment, the gas pressure is reduced, that is, the gas pressure used in the over-etching process is lower than the gas pressure used in the main etching process to reduce the etching rate of the mask 2, and the sidewall of the pattern is realized. The increase of the corner angle; further maintaining the same high ratio of the substrate 1 to the mask 2 in the main etching and the over etching, by reducing the gas pressure The etch rate of the mask 2 is reduced, thereby ensuring that the etching time is not prolonged, and the etching rate of the mask 2 is reduced, thereby achieving the purpose of increasing the corner angle of the sidewall of the pattern.

The inventors have verified through experiments that reducing the gas pressure during over-etching (ie, the gas pressure used in the over-etching process is less than the gas pressure used in the main etching process) can effectively slow down the shrinkage of the mask 2 and increase the sidewall of the pattern. The corner. As shown in Fig. 5, the upper electrode RF power, the lower electrode RF power, the gas flow rate, and the etching selection ratio are the same in (1) and (2), and the gas pressure in (1) is lower than the gas pressure in (2). 1mT, the bottom diameter m1 of the mask 2 in (1) is 1190 nm, and the bottom diameter m2 of the mask 2 in (2) is 1093 nm, and the mask 2 in (1) is slower than in (2), The triangular pyramid 11 side wall corner β1 in the final (1) is 165 degrees, which is larger than the triangular pyramid 11 side wall corner β2 = 156 degrees in (2).

Specifically, the gas pressure used in the main etching process in the embodiment may be 2 mT to 4 mT, and the gas pressure used in the over-etching process may be 1.5 mT to 2.5 mT, and the gas pressure from the main etching to the over-etching is lowered. The magnitude can be determined based on actual conditions.

In this embodiment, it is preferable to reduce the etching rate of the mask 2 by reducing the gas flow rate during over-etching, that is, the gas flow rate used in the over-etching process is smaller than the gas flow rate used in the main etching process. Slowing down the bottom of the mask 2, increasing the angle of the corners on the side walls of the pattern, and improving the smoothness of the side walls of the pattern. Specifically, the gas flow rate used in the main etching process may be 80 sccm to 150 sccm, and the gas flow rate used in the over etching process is 50 sccm to 80 sccm. In practical applications, the magnitude of the flow reduction from the main etch to the over etch gas can be determined according to the actual situation.

In actual production, a more preferable solution is to reduce the etching rate of the mask 2 in combination with reducing the gas pressure of the over-etching process and reducing the gas flow rate of the over-etching process to achieve a better increase. The effect of the angle of the corners on the side walls of the graphic.

In this embodiment, the RF power of the lower electrode used in the over-etching process can be the same as the RF power of the lower electrode used in the main etching process, so that the duration of the over-etching is not extended, and the over-etching can be performed. The lower electrode RF power used in the process is greater than that used in the main etching process. The lower electrode RF power, that is, the RF power of the lower electrode is increased from the main etching into the over-etching. Experiments show that increasing the RF power of the lower electrode during the over-etching can significantly reduce the inflection point height of the corner on the sidewall of the pattern.

As shown in Fig. 6, the upper electrode RF power and the etching selection ratio are the same in (1) and (2), and the gas pressure and gas flow ratio (1) in (1) are lower than in (2), and The electrode RF power ratio is higher than 200W in (2), then the bottom diameter m1 of the mask 2 in (1) is 1109 nm, the corner angle β1 of the triangular pyramid 11 is 165.49 degrees, and the height h1 of the corner of the corner is 357 nm, (2) The bottom surface m2 of the mask 2 is 1190 nm, the side angle β2 of the triangular pyramid 11 is 165 degrees, and the height h2 of the corner of the corner is 595 nm, although it is seen that although the corner angle in (1) is increased relative to (2) Obviously, but it has been significantly increased compared to the 150 degree angle that can be achieved in the prior art, and the corner height of the corner in (1) is significantly reduced, which is advantageous for the modification of the side wall of the triangular pyramid 11 and further improvement The smoothness of the side walls.

Specifically, the RF power of the lower electrode used in the main etching process may be 300 W to 600 W, and the RF power of the lower electrode used in the over etching process may be 500 W to 700 W, and the RF power of the lower electrode is reduced from the main etching to the over etching. The magnitude can be determined based on actual conditions.

On the other hand, increasing the RF power of the lower electrode during over-etching can enhance the bombardment energy of the etched particles, which is beneficial to increase the rate of sidewall corner modification and shorten the process time. The duration of the over-etching process may preferably be 10min ~ 20min.

It should be noted that, in the present embodiment, the selection of the substrate 2 for etching the mask 2 during the over-etching process is preferably the same as the selection ratio of the substrate 1 to the mask 2 during the main etching process. Preferably, a higher etching selectivity ratio is used in the two etching processes, for example, greater than or equal to 0.8 to ensure better etching of the substrate 1 during overetching and main etching.

In addition, the same upper electrode RF power can be set in the main etching and over-etching process, preferably 1400W-1900W, to ensure that the etched particles have high bombardment energy.

The substrate 1 mentioned in this embodiment may preferably be a sapphire substrate, and the mask 2 may preferably be a photoresist mask, but before the basic idea of the technical solution provided by the present invention is unchanged It is noted that the method of patterning a substrate in the present invention is also applicable to a process of patterning other substrates using other masks.

The above description is only the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any change or replacement that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention is It should be covered by the scope of the present invention. Therefore, the scope of the invention should be determined by the scope of the appended claims.

Claims

A method of patterning a substrate, comprising:

a main etching process, performing main etching on the substrate on which the mask is formed on the surface, and ending the main etching process before the coverage area of the mask is reduced;

An over-etching process, the substrate processed by the main etching process is over-etched, and the etching rate of the mask in the over-etching process is less than that in the main etching process The etch rate of the mask.
The method of patterning a substrate according to claim 1, wherein an etching rate of the mask in the over-etching process is smaller than an etching of the mask in the main etching process The rate is specifically: the gas pressure used in the over-etching process is less than the gas pressure used in the main etching process.
The method of patterning a substrate according to claim 2, wherein the gas pressure used in the main etching process is 2 mT to 4 mT, and the gas pressure used in the over etching process is 1.5 mT to 2.5 mT.
The method of patterning a substrate according to claim 1, wherein an etching rate of the mask in the over-etching process is smaller than an etching of the mask in the main etching process The rate is specifically: the gas flow rate used in the over-etching process is smaller than the gas flow rate used in the main etching process.
The method of patterning a substrate according to claim 4, wherein the gas flow rate of the main etching process is 80 sccm to 150 sccm, and the gas flow rate of the overetching process is 50 sccm to 80 sccm.
The method of patterning a substrate according to any one of claims 1 to 5, wherein the duration of the main etching process is 10 min to 15 min, and the duration of the overetching process is 10 min to 20 min. .
The method for patterning a substrate according to any one of claims 1 to 5, wherein the lower electrode RF power used in the overetching process is not less than the lower electrode RF used in the main etching process. power.
The method of patterning a substrate according to claim 7, wherein the RF power of the lower electrode used in the main etching process is 300 W to 600 W, and the RF power of the lower electrode used in the over etching process is 500W ~ 700W.
The method of patterning a substrate according to any one of claims 1 to 5, wherein a selection ratio of the substrate to the mask during the overetching process and the main engraving The substrate in the etch process has the same selection ratio for the mask etch.
The method of patterning a substrate according to claim 9, wherein the substrate has a selectivity ratio to the mask etch of greater than or equal to 0.8.