WO2012111868A1

WO2012111868A1 - Substrate-processing system

Info

Publication number: WO2012111868A1
Application number: PCT/KR2011/001231
Authority: WO
Inventors: 강진기; 마재용; 박홍진; 이경호
Original assignee: 한솔테크닉스(주)
Priority date: 2011-02-16
Filing date: 2011-02-23
Publication date: 2012-08-23

Abstract

The present invention relates to a substrate-processing system, which imparts a uniform roughness to a back surface of the substrate using sand blasting. The substrate-processing system includes: a slicing unit for slicing an ingot into a wafer shape; a sand blasting unit for spraying a polishing material onto at least one surface from among the two surfaces of the substrate sliced into the wafer shape so as to perform sand blasting; a heat treatment unit for heat-treating the sand-blasted substrate; and a polishing unit for polishing the entire surface of the heat-treated substrate.

Description

Substrate Processing System

The present invention relates to a substrate processing system for manufacturing a substrate for a semiconductor device, and more particularly to a substrate processing system for manufacturing a substrate that can be used for high brightness light emitting diodes (LEDs).

Light emitting diodes (LEDs) have advantages in comparison with conventional light sources (fluorescent lamps, incandescent lamps), which are superior in brightness and power consumption, and have a small volume, a thin thickness, and no harmful substances such as mercury. The light emitting diode is a directional light source, which enables selective illumination for each area. Therefore, the light emitting diode is used in various lightings, traffic lights, and electronic displays. In addition, light emitting diodes are now widely used as back light units (BLUs) for displays such as mobile phones and LCDs.

In particular, since the blue light emitting diode was developed in 1995, since it is possible to implement all colors, it is possible to realize a light of a desired color by combining three color light emitting diodes, and the application fields are becoming more diverse. Blue and green light emitting diodes are generally manufactured by epitaxially growing a GaN active layer on a sapphire substrate.

On the other hand, in the light emitting diode, the biggest problem is low luminous efficiency. In general, the light emitting efficiency of a light emitting diode is classified into an efficiency in which light is generated (internal quantum efficiency) and an efficiency in which generated light is emitted out of the device (external light extraction efficiency). In order to increase the output power of the light emitting diode, it is important to improve the characteristics of the active layer in terms of internal quantum efficiency, but to increase the light emission efficiency, it is more important to increase the external light extraction efficiency.

The biggest obstacle to the emission of light generated in the active layer of the light emitting diode to the outside is the internal total reflection due to the difference in refractive index between each layer of the light emitting diode. The light emitted by the total internal reflection is emitted to the outside is only about 20% of the generated light. In addition, the light that is not emitted to the outside is converted to heat while moving inside the light emitting diode, which shortens the life of the light emitting diode.

In order to improve the external light extraction efficiency, the surface roughness of the semiconductor layer (p-GaN layer or n-GaN layer) formed on the sapphire substrate is increased, or the surface of the sapphire substrate is roughened to be fine for several micrometers. A method of forming a groove pattern has been studied. The sapphire substrate on which the bending pattern is formed is called a patterned sapphire substrate (PSS). When epitaxially growing a GaN-based active layer on the PSS, the density of dislocations, which causes the luminance of the active layer, may be greatly reduced, and total internal reflection may be reduced, thereby improving luminous efficiency of the light emitting diode.

The back surface roughness of the substrate is conventionally determined in a lapping process. The lapping process is a process in which a single crystal sapphire ingot is sliced in the form of a wafer to reduce thickness variation of the wafer and provide surface roughness. This lapping process is a double-sided lapping process, in order to have the desired surface roughness through the lapping process, not only the process time is long, but also the problem of using a large amount of abrasives and excessive waste of the lapping process, There is also difficulty in making one surface roughness.

The technical problem to be solved by the present invention is to provide a substrate processing system that is given a uniform roughness on the back.

In order to solve the above technical problem, the substrate processing system according to the present invention is a cutting unit for cutting the ingot (ingot) in the form of a wafer (slicing), and spraying abrasives on at least one surface of both sides of the substrate cut in the wafer form And a sand blasting unit for sand blasting, a heat treatment unit for heat-treating the sand blasted substrate, and a polishing unit for mirror polishing the entire surface of the heat-treated substrate.

According to the present invention, it is possible to give uniform roughness to the rear surface of the substrate through sand blasting. In addition, the process of imparting roughness to the rear surface of the substrate by sand blasting may reduce the process time compared to the process of imparting roughness to the rear surface of the substrate by the conventional double-sided lapping process. In addition, since the sand blasting process does not use the expensive abrasive used in the conventional double-sided lapping process, it is possible to reduce the production cost when manufacturing the substrate.

1 is a schematic configuration diagram of a substrate processing system according to an embodiment of the present invention.

2 and 3 are schematic configuration diagrams of the blasting unit shown in FIG.

4 is a view illustrating a state of blasting the substrate in the blasting unit.

5 is a flowchart illustrating a process of processing a substrate with the substrate processing system according to the present embodiment.

Fig. 6 is a schematic diagram showing the shape of the sapphire wafer before sandblasting, after processing and after heat treatment.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the substrate processing system according to the present invention. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you.

1 is a schematic configuration diagram of a substrate processing system according to an embodiment of the present invention, FIGS. 2 and 3 are schematic configuration diagrams of a blasting unit shown in FIG. 1, and FIG. 4 is a blasting substrate in a blasting unit. The figure expresses the appearance.

1 to 4, the substrate processing system 100 according to the present embodiment includes a cutting unit 10, a lapping unit 20, a heat treatment unit 30, a polishing unit 40, and a sand. The blasting unit 50 is included.

The cutting unit 10 cuts the ingot into a wafer form, wherein the ingot may be made of at least one of sapphire, LiTaO _3, and LiNbO ₃ . As the cutting unit, a wire saw or a multi wire saw can be employed.

The lapping unit 20 is an apparatus for wrapping both sides of a substrate cut in a wafer form. As the lapping unit, an apparatus in the form as mentioned in the prior art, that is, in the form of lapping the substrate by contacting the polishing portion (polishing plate) to the substrate while supplying a slurry may be employed.

The heat treatment unit 30 is a device for heating the substrate to relieve damage (stress) accumulated in the substrate.

The polishing unit 40 is a device for polishing or mirror polishing a substrate.

Since the cutting unit 10, the lapping unit 20, the heat treatment unit 30, and the polishing unit 40 are well known devices, the description thereof will be omitted.

The sand blasting unit 50 is for imparting uniform roughness to the substrate by spraying abrasives onto the substrate. In the present embodiment, the sand blasting unit 50 includes a table 51, a storage unit 52, and an injection unit. 53, a recovery part 54, and a filter part 55 are included.

The table 51 is where the substrate is seated. In the present embodiment, as shown in FIG. 4, a plurality of substrates w are seated on the table 51, and the seated substrates are fixed to the table 51 by a vacuum suction method. And this table 51 is rotatably provided.

The storage unit 52 is a space in which the abrasive is stored. As the abrasive, SiC, B ₄ C, CeO ₂ , SiO ₂ , Al ₂ O ₃ , metal particles, and combinations thereof may be used. It is preferable that they are 50 micrometers-100 micrometers.

The injection unit 53 is for injecting the abrasive stored in the storage unit to the substrate, it is configured in the form of a nozzle. The spraying unit 53 sprays the abrasive at a pressure of 0.25 MPa to 0.35 MPa at a position of about 10 to 20 cm away from the substrate seated on the table. And injection pressure is for optimizing the surface roughness of the substrate. Meanwhile, as shown in FIG. 4, in the state in which the table rotates, the injection unit 53 injects abrasive into the substrate while reciprocating, and a plurality of injection units may be provided to increase sandblasting efficiency.

The recovery unit 54 is for recovering the abrasive injected to the substrate, and may include a pump installed in the lower part of the table. In this case, the through hole is provided in the table so that the abrasive injected into the substrate can be introduced into the pump. (Flow path of the abrasive) (not shown) can be formed.

The filter part 55 is for separating the crushed abrasive particles among the recovered abrasives. That is, the abrasive may be crushed while hitting the substrate during the sand blasting process, the filter unit filters the crushed abrasive particles. The filter unit may be configured in various forms. For example, by using a net having a plurality of holes having a predetermined size, particles smaller than the reference size and particles larger than the reference size may be separated from each other. In addition, the filter unit may be configured to separate only particles smaller than the reference size using centrifugal force.

On the other hand, as shown in Figure 2, the crushed particles separated in the filter unit 55 is stored (discarded) separately, only the uncrushed particles are supplied back to the storage unit 52. At this time, since the amount of the abrasive supplied from the reservoir to the injection unit is always maintained, the new abrasive is supplied to the reservoir 52 as much as the amount of the crushed particles, as shown in FIG. The abrasive of size may be sprayed onto the substrate.

Hereinafter, the process of processing a board | substrate using the above-mentioned board | substrate processing system is demonstrated. FIG. 5 is a flowchart showing a process of processing a substrate by the substrate processing system according to the present embodiment, and FIG. 6 is a schematic view showing the shape of the sapphire wafer before sandblasting, after processing, and after heat treatment.

Referring to FIGS. 5 and 6, first, ingots are cut into wafers in a cutting unit (S110). Then, the substrate cut in the lapping unit is double-sided wrapped. Through this double-sided lapping process, the thickness variation of the substrate is reduced to become a substrate having a uniform thickness, and the cutting traces generated during ingot cutting (S110) are removed. However, as described below, the double-sided lapping step S120 may be omitted as necessary.

Next, sandblasting the double-sided wrapped substrate (S130). The sand blasting step S130 is performed on both surfaces or one surface of the substrate. In particular, the back side of the substrate is sandblasted, and the front side of the substrate may be sandblasted as necessary. Through the sand blasting step (S130), to make the substrate to the desired thickness, to make the back surface of the substrate to the desired roughness.

The sand blasting step S130 will be described in more detail. The wrapped substrate is mounted on a table, and the table is rotated at a constant speed of 150 rpm or more and 2400 rpm or less. At the same time, the abrasive is sprayed at a constant pressure. At this time, if the conditions such as the type of abrasive particles, the size of the abrasive particles, the abrasive pressure of the abrasive particles, the spraying range of the abrasive from the spraying part, and the conditions such as the rotation speed of the table are adjusted, the thickness of the substrate and the roughness of the substrate may be adjusted. I can regulate it. Preferably, the roughness of the substrate after the sand blasting process is preferably about Ra 0.6μm ~ 1.2μm.

On the other hand, before proceeding the sand blasting step (S130), after confirming the warpage phenomenon of the sapphire wafer (that is, the substrate), it is necessary to distinguish between the + side and-side. Here, the + plane means a convex surface as shown in (b) and (c) of Figure 6, the-plane means a concave surface. This is because the abrasive should be sprayed on the negative side of the sapphire wafer where the warpage phenomenon is distinguished during sandblasting. Hereinafter, the reason will be described.

As shown in (a) of FIG. 6, when sand blasting the sapphire wafer (Sand Blasting), a convex warp occurs toward the processed surface, and the wafer is flattened when the stress is reduced by heat treatment.

However, if the sand blasting on the + surface as shown in Figure 6 (b) is more bent the wafer, even if the stress is lowered through the heat treatment has a limit to flatten the wafer, so that the wafer remains bent to some extent do.

Therefore, as shown in FIG. 6C, when sandblasting is performed on the − surface, the wafer may be flattened by appropriately restoring stress through heat treatment.

Next, the sand blasted substrate is heat treated (S140). The sand blasted substrate has a processing stress, and it is necessary to relieve the processing stress, for which heat treatment (S140) is performed. Heat treatment step (S140) is preferably performed in a temperature range of about 900 ~ 1600 ℃. The heat treatment step S140 is a step for releasing the stress formed in the sand blasting step S130. It eliminates surface stresses during double side lapping and sand blasting, and optimizes the conditions that minimize wafer warpage by a combination of temperature, time and atmosphere. That is, the curved substrate is flattened by releasing the stress formed on the substrate through the heat treatment step.

Next, the edge of the heat-treated substrate is polished using an polishing unit (S150) and mirror-polished the entire surface of the substrate (S160). The mirror polishing step (S160) is performed in the order of a wax mounting process (S161), a polishing (polishing) process, and a demounting process (S164) of the substrate. The wax mounting process S161 is a process of attaching the back side of the substrate to the ceramic block using wax. The polishing process is a process of polishing the entire surface of the substrate into a mirror surface, and is divided into a diamond polishing process (S162) and a pad polishing process (chemical mechanical polishing (CMP)) (S163). Diamond polishing process (S162) is to remove the mechanical damage or rough surface using a diamond abrasive to start the mirror surface of the front surface of the substrate, such as total thickness variation (TTV), local thickness variation (LTV) The flatness is improved. The pad polishing process (S163) removes damages caused by the diamond polishing process, removes defects such as microscratch, particles, stains, and pit on the front surface of the substrate, and minimizes surface roughness. Thus, the front surface of the substrate is mirrored.

In the substrate mirror polished wafer, the wafer of stains, scratches or poor transparency can be quantified by controlling the processing method of sand blasting through a sand blasting step.

As described above, in the present embodiment, since roughness is provided to the rear surface of the substrate through sand blasting, uniform roughness may be imparted to the rear surface of the substrate.

That is, in the conventional case, the surface roughness and the thickness of the substrate were matched through a double-sided lapping process, but since the particles of the abrasive are reduced due to the lapping process, the abrasive should be replenished or exchanged at any time during the processing. Therefore, the size of the abrasive particles cannot always be maintained at a constant level (i.e., the newly supplemented large particles and the used small particles coexist), and as a result, it is not only difficult to accurately control the surface roughness thickness, but also the amount of abrasive used. There is a problem that increases the number and decreases the productivity as the process manufacturing time increases. However, in the present invention, since the particle size of the abrasive and the amount of the abrasive are maintained at a constant level, there is an advantage that the surface roughness and thickness of the wafer can be precisely processed.

And if the conditions of sandblasting are selected suitably, the roughness of the back surface of a board | substrate can be adjusted easily. In addition, the sand blasting process can reduce the production cost because expensive abrasives are not used as in the conventional double-sided lapping process.

On the other hand, in the previous embodiment provided with a wrapping unit, it may not be provided with a wrapping unit. In this case, the sandblasting process replaces the lapping process. That is, by sandblasting both surfaces of the substrate immediately without undergoing a double-side lapping process after the cutting process, the thickness of the substrate can be made uniform, and a uniform roughness can be formed at the same time as the cutting marks are removed. In this case, the conventional double-sided lapping process can reduce the time than giving the thickness uniformity and roughness of the substrate.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific preferred embodiments described above, and the present invention belongs to the present invention without departing from the gist of the present invention as claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

Claims

Cutting unit for cutting the ingot (ingot) in the form of a wafer (slicing);

A sand blasting unit for sand blasting by spraying abrasives on at least one surface of both surfaces of the substrate cut into the wafer form;

A heat treatment unit for heat treating the sand blasted substrate; And

And a polishing unit for mirror-polishing the entire surface of the heat-treated substrate.
The method of claim 1,

And a lapping unit for lapping both sides of the substrate before sandblasting the substrate.
The method of claim 1,

The abrasive material comprises at least one of SiC, B 4 C, CeO 2 , SiO 2 , Al 2 O 3 and metal particles.
The method of claim 3,

The abrasive is sprayed at a pressure of 0.25MPa ~ 0.35MPa substrate processing system.
The method of claim 3,

The abrasive is sprayed at a position 10 ~ 20cm away from the substrate.
The method of claim 3,

The diameter of the abrasive particles is a substrate processing system, characterized in that 50μm ~ 100μm.
The method of claim 1,

The sand blasting unit,

A table on which the substrate is mounted and rotatably installed;

A storage unit in which the abrasive is stored;

An injection unit for injecting the abrasive stored in the storage unit into the substrate;

A recovery part for recovering the abrasive injected into the substrate;

And a filter unit for separating the crushed abrasive particles among the abrasives recovered by the recovery unit.