CN111785814A - A substrate and its processing method, light-emitting diode and its manufacturing method - Google Patents

Abstract

The invention provides a substrate and a processing method thereof, a light emitting diode and a manufacturing method thereof. By determining the asymmetric surface type and asymmetric orientation presented by the substrate, the substrate is scanned on the asymmetric orientation, and the The modified points are formed by adjusting the spacing distance of the scan lines in the asymmetric direction, so that the scan lines in the same direction are parallel to each other, while the spacing distances of the scan lines in the asymmetric direction are different, resulting in modified points with different spacing distances in the asymmetric direction , by forming the above modification points, the stress of the substrate is changed, the stress distribution of the entire substrate is uniform, and different bending value changes are generated in different directions, and finally the bending amplitude of the substrate in each radial direction and The bending directions tend to be the same, and the substrate surface type converges to a symmetrical surface type. Symmetrical surface substrates are beneficial to improve the wavelength convergence of subsequent epitaxial layers, thereby greatly improving the device yield.

Description

A substrate and its processing method, light-emitting diode and its manufacturing method

technical field

The present invention relates to the technical field of semiconductor manufacturing, in particular to a substrate and a processing method thereof, a light emitting diode and a manufacturing method thereof.

Background technique

In the manufacturing process of semiconductor devices, the growth of epitaxial layers is usually performed by means of a growth substrate. For the growth substrate, substrate twist/bend is the most important factor affecting the uniformity of epitaxy. For example, the sapphire substrate, which is usually used as the growth substrate of the GaN epitaxial layer, will produce uneven stress during the machining process of the sapphire substrate, thereby causing the substrate to be distorted; for example: in the process of multi-wire cutting , due to the hard sapphire, the diamond line is subjected to a large cutting resistance, which will cause jitter and deformation, and the positions of the lines on both sides of the substrate are asymmetrical, resulting in uneven stress on the substrate and distortion; As time goes by, the abrasive particles will gradually decrease, and the pressure of particles of different sizes on the substrate is different, resulting in different residual stress of the substrate; after single-side polishing, the roughness of both sides of the final substrate will be different, which will lead to The stress conditions on the two sides of the substrate are different, and the distortion is further exacerbated. The bending/twisting of the substrate causes the substrate to present an asymmetric surface shape, and the non-surface shape of the substrate will reduce the convergence of the wavelength of the subsequently formed epitaxial layer. The uniformity of the wavelength of the epitaxial layer directly affects the yield of the devices in this later stage.

In the prior art, the warpage shape or warpage amount of the substrate is generally controlled by controlling the flat wafer processing process of the substrate, such as processes such as crystal growth, cutting, grinding, annealing, copper polishing and polishing. However, such an approach does not allow the substrate to fully converge to a symmetric surface type. Therefore, it is necessary to provide a method for effectively converging the substrate into a symmetrical plane.

SUMMARY OF THE INVENTION

In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a processing method of an asymmetric planar substrate, a light emitting diode and a manufacturing method thereof. Firstly, the asymmetric surface type presented by the substrate is determined, and the asymmetric orientation of the asymmetric surface type is determined, the substrate is scanned on the asymmetric orientation, and modified spots are formed in the substrate so that the substrate is formed by Asymmetric facets converge to symmetric facets. A substrate with a symmetrical surface type, such as a bowl type, is beneficial to the wavelength uniformity of the subsequently formed epitaxial layer.

To achieve the above object and other related objects, an embodiment of the present invention provides a method for processing a substrate that presents an asymmetric surface type: the method comprises the following steps:

providing a substrate, and determining the asymmetric surface type presented by the substrate;

determining an asymmetric orientation of the asymmetric facet, and measuring the curvature of the substrate in the asymmetric orientation;

In the asymmetric orientation, the substrate is scanned by laser along the scan line, and modified spots are formed in the substrate so that the substrate converges from an asymmetric surface type to a symmetrical surface type.

Optionally, on the asymmetric orientation, laser scanning is performed on the substrate along a scan line, further comprising the following steps:

determining a target curvature bow0 of the substrate according to the curvature of the substrate in the asymmetric orientation;

calculating the curvature value of the base in the asymmetric orientation and the curvature difference Δbow of the target curvature;

determining the scanning depth for laser scanning on the substrate according to the curvature difference Δbow;

The spacing between scan lines in different orientations is adjusted according to the curvature difference Δbow.

Optionally, the above processing method further includes: adjusting the scanning lines in the same orientation to be parallel to each other.

Optionally, the above processing method further includes: adjusting the spacing between scan lines in the same orientation to be the same, and adjusting the spacing between scan lines in different orientations to be different.

Optionally, determining the asymmetric orientation of the asymmetric surface type, and measuring the curvature of the substrate on the asymmetric orientation, further comprising the steps of:

determining a first orientation and a second orientation of the asymmetric surface type, the first orientation and the second orientation being an intersecting asymmetric orientation;

measuring a first bow1 of the substrate in the first orientation;

measuring a second bow2 of the substrate in the second orientation;

Calculate a first curvature difference Δbow1 between the first curvature of the substrate in the first orientation and the target curvature, and a second curvature of the substrate in the second orientation Degree difference Δbow2.

Optionally, on the asymmetric orientation, laser scanning is performed on the substrate along a scan line, further comprising the following steps:

According to the first curvature difference Δbow1 and the second curvature difference Δbow2, determine the scanning depth for laser scanning on the substrate;

Adjust the first spacing between scan lines on the first orientation according to the first curvature difference Δbow1 on the first orientation;

The second spacing between scan lines in the second orientation is adjusted according to the second curvature difference Δbow2 in the second orientation.

Optionally, the scanning depth for performing laser scanning on the substrate determined according to the curvature difference Δbow is any depth within a thickness range of 2% to 98% of the substrate.

Optionally, the asymmetric surface type presented by the substrate includes any one of the following types:

Concentric ellipse, the substrates are bent in the same direction in asymmetrical directions but with different degrees of curvature;

Through type, the substrate is bent in one direction and not bent in another direction that is asymmetric to this direction;

Saddle type, the substrates are bent in opposite directions in asymmetrical directions.

Optionally, the modified spots are distributed along the first orientation and the second orientation, and form a grid-like distribution inside the substrate.

Optionally, the modified spots include voids formed in the substrate.

Optionally, the modified spots include cavities formed in the substrate, the cavities forming trenches in the substrate.

Another embodiment of the present invention provides a method for preparing a light-emitting diode, the method comprising the following steps:

providing a substrate, and determining the asymmetric surface type presented by the substrate;

determining an asymmetric orientation of the asymmetric facet, and measuring the curvature of the substrate in the asymmetric orientation;

On the asymmetric orientation, laser scanning is performed on the substrate along the scanning line, and modified spots are formed in the substrate to make the substrate converge from an asymmetric surface type to a symmetrical surface type;

A light emitting structure is formed over the substrate that converges to a symmetrical plane.

Optionally, forming the light emitting structure over the substrate includes the following steps:

forming a first semiconductor layer over the substrate;

forming multiple quantum wells over the first semiconductor layer;

A second semiconductor layer of opposite conductivity to the first semiconductor layer is formed over the multiple quantum well.

Optionally, on the asymmetric orientation, laser scanning is performed on the substrate along a scan line, further comprising the following steps:

determining a target curvature bow0 of the substrate according to the curvature of the substrate in the asymmetric orientation;

calculating the curvature value of the base in the asymmetric orientation and the curvature difference Δbow of the target curvature;

determining the scanning depth for laser scanning on the substrate according to the curvature difference Δbow;

The spacing between scan lines in different orientations is adjusted according to the curvature difference Δbow.

Optionally, the above light-emitting diode manufacturing method further includes: adjusting the scanning lines in the same orientation to be parallel to each other.

Optionally, the method further includes: adjusting the spacing between scan lines in the same orientation to be the same, and adjusting the spacing between scan lines in different orientations to be different.

Another embodiment of the present invention provides a substrate for epitaxial growth, the substrate has a first surface and a second surface, the inside of the substrate has a plurality of modified spots formed by multiphoton absorption, In the plan view direction of the first surface of the substrate, the modified spots form a grid-like distribution along two different radial directions of the substrate.

Yet another embodiment of the present invention provides a light emitting diode, comprising a substrate and a light emitting structure formed above the substrate, where the substrate is the substrate for epitaxial growth provided by the present invention.

As mentioned above, the substrate provided by the present invention and its processing method, light-emitting diode and its manufacturing method have at least the following beneficial technical effects:

In the method of the present invention, the asymmetric surface type presented by the substrate is first determined, and the asymmetric orientation of the asymmetric surface type is determined, the substrate is scanned on the asymmetric orientation, and modified spots are formed in the substrate to The substrate is made to converge from an asymmetric face shape to a symmetrical face shape, such as a bowl shape. By adjusting the spacing distance of the scan lines in the asymmetric direction, the scan lines in the same direction are parallel to each other, while the spacing distance of the scan lines in the asymmetric direction is different, resulting in different bending value changes in the asymmetric direction, making the substrate Finally, the bending degrees in all directions tend to be the same, so that the surface shape of the substrate converges to a symmetrical surface shape (for example, a concentric circle shape or a bowl shape). Growing the epitaxial layer on the substrate that converges to a symmetrical plane is beneficial to reduce the dispersion of the wavelength of the epitaxial layer, that is, to make the wavelength of the epitaxial layer more convergent, and the improvement of the convergence of the wavelength of the epitaxial layer directly affects the yield of subsequent devices, so that The device yield is greatly improved.

In addition, the present invention uses a laser to irradiate the substrate, and adjusts parameters such as the spot size, pulse wavelength, power, pulse time, irradiation (or scanning) time of the laser pulse according to the type and size of the substrate, and determines the modification point. The depth (voids or bubbles) in the substrate, and the size of the modified spots. The control process is easy to operate and the control precision is high. In addition, the cost of laser irradiation is relatively low, thereby reducing the cost of substrate processing.

The substrate for epitaxy and the semiconductor device of the present invention can be processed by the above-mentioned method, and thus also have the above-mentioned beneficial effects.

Description of drawings

Figures 1a to 1c are schematic diagrams showing the bending distribution of substrates with different surface types that are distorted due to uneven stress distribution tested by a flatness measuring instrument.

FIG. 1 d shows a schematic diagram of the bending distribution of the substrate with uniform stress distribution as measured by a flatness measuring instrument.

FIG. 2 shows a flow chart of a method for manufacturing an epitaxial substrate according to different embodiments of the present invention.

Figures 3a-3c show schematic representations of defined asymmetric orientations for substrates of asymmetric facet types.

Figure 4 is a graph showing the relationship between the curvature of the substrate before and after laser scanning and the focal depth of the laser pulse under the condition of a certain scanning line spacing.

Fig. 5 is a graph showing the relationship between the scanning line spacing and the curvature of the substrate under the condition that the focal depth of the laser pulse is constant.

Figure 6 shows a schematic diagram of scan lines for scanning the substrate of the concentric elliptical profile shown in Figure 3a.

FIG. 7 is a schematic diagram showing scan lines for scanning the through-profile substrate shown in FIG. 3b.

FIG. 8 is a schematic diagram of scan lines for scanning the saddle-shaped substrate shown in FIG. 3c.

Figure 9 shows a schematic view of modified spots formed in the substrate viewed from the side of the substrate.

Figure 10 shows a boxplot of the ratio of warpage to bow for a substrate that has not been laser scanned and a substrate that has been laser scanned in the method of the present invention.

FIG. 11 is a schematic flowchart of a method for fabricating a semiconductor device according to another embodiment of the present invention.

Fig. 12 is a graph showing the comparison of mean and standard deviation of bending at different stages of epitaxial layer growth between a substrate fabricated by the method of the present invention and a substrate without laser scanning in the prior art.

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

It should be noted that the diagrams provided in this embodiment are only to illustrate the basic concept of the present invention in a schematic way, although the diagrams only show the components related to the present invention rather than the number, shape and the number of components in actual implementation. For dimension drawing, the shape, quantity, positional relationship and proportion of each component can be changed at will under the premise of realizing the technical solution of this party, and its component layout shape may also be more complicated.

The preparation of the substrate is a very important link in the manufacturing process of semiconductor devices, and the yield of the substrate directly affects the performance of the device. Since the substrate is usually a very thin sheet, during the machining process of the substrate, due to uneven stress distribution, the substrate inevitably has defects such as bending, twisting, and warping. It directly affects the quality of the subsequent epitaxial film formation.

The uneven stress distribution of the substrate causes the substrate to bend, warp or twist in different directions, and the degree of bending and/or the direction of bending in different directions are different, which makes the substrate exhibit an asymmetric surface shape. If the stress distribution of the substrate is relatively uniform, the bending direction and bending degree of the substrate in each radial direction tend to be the same, and the substrate exhibits a symmetrical surface type. Symmetrical surface substrates have better bending convergence, and when such substrates are used for epitaxial film formation, it is beneficial to the wavelength convergence of the epitaxial film formation layer.

As shown in FIGS. 1 a to 1 d , taking a sapphire substrate as an example, the substrate has a first surface and a second surface opposite to it, and the horizontal and vertical directions are defined as two vertical directions extending radially from the substrate. A surface of the sapphire substrate is tested for the curvature distribution of the substrate by a flatness measuring instrument. The sapphire substrate usually has four different surface types. As shown in Figure 1a, if the peripheral region of the substrate is curved toward the first surface in the lateral direction, and the peripheral region of the substrate is curved toward the second surface in the longitudinal direction, the substrate presents a saddle-like shape, Therefore, such a substrate surface type is usually called a saddle type; as shown in Fig. 1b, if part of the peripheral area of the substrate in the lateral direction is bent to the same surface (ie, the first surface or the second surface), in the longitudinal direction On the other hand, if part of the peripheral area of the substrate is flat and free of warpage, the substrate surface type that exhibits this type of curvature is usually called the penetration type; as shown in Figure 1c, if the The peripheral regions of the bottom are all curved toward the same surface (ie, the first surface or the second surface), and at the same distance from the center of the substrate, the degree of curvature in the lateral direction is greater than that in the longitudinal direction. , the substrate surface is concentric elliptical.

For the substrate surface types shown in Figures 1a to 1c, the substrate has different bending directions and/or bending degrees in different radial directions due to uneven stress distribution. A substrate that is completely symmetrical in the direction exhibits asymmetric features in some radial directions, so the substrate surface types shown in FIGS. 1 a to 1 c are collectively referred to as asymmetric surface types.

In the substrate shown in Figure 1d, the stress distribution is relatively uniform, and the substrate has almost the same degree of curvature at radial positions of the same distance from the center of the substrate in the peripheral region, and all face the same surface (that is, the first surface or The second surface) is curved, and the curved surface of the substrate is concentric or bowl-shaped. Due to the relatively uniform stress distribution of the concentric substrate, the bending direction of the peripheral area in each radial direction is the same and the degree of bending tends to be the same. At this time, the substrate is basically still symmetrical in each radial direction, so This face shape may be referred to as a symmetrical face shape. The concentric surface type substrate has better bending convergence, and when this type of substrate is used for epitaxial film formation, it is beneficial to the wavelength convergence of the epitaxial film formation layer.

In view of the above-mentioned characteristics of substrate bending, this embodiment aims to provide a substrate processing method capable of improving the convergence of the surface shape of the substrate.

As shown in FIG. 1, in an embodiment of the present invention, the manufacturing method of the epitaxy substrate of the present invention includes the following steps:

S01: Provide a substrate, and determine the asymmetric surface type presented by the substrate;

S02: determine the asymmetric orientation of the asymmetric surface type, and measure the curvature of the substrate on the asymmetric orientation;

S03: On the asymmetric orientation, laser scanning is performed on the substrate along the scanning line, and modified spots are formed in the substrate to make the substrate converge from an asymmetric surface type to a symmetrical surface type.

In this embodiment, the above-mentioned substrate may be any substrate used for semiconductor manufacturing, for example, may be a substrate suitable for epitaxial layer growth. In an alternative embodiment, the substrate is a substrate capable of absorbing laser light and forming modified spots inside to improve stress distribution, such as a sapphire substrate. The thickness of the sapphire substrate is about 50 μm˜20 mm, and the diameter thereof may be 4 inches˜18 inches.

Taking a sapphire substrate as an example, the substrate has a first surface and a second surface, and a flatness measuring instrument is used to test the curvature distribution of the substrate from one of the surfaces of the substrate, thereby determining the surface type presented by the substrate.

In an optional embodiment of this embodiment, as shown in FIG. 3a, in two different radial directions of the substrate surface, the peripheral regions of the substrate all face the same surface (that is, the first surface or the second surface However, at the same distance from the center of the substrate, in the above two different radial directions, the degree of curvature of the substrate is different. At this time, the surface shape of the substrate is a concentric ellipse, which is Asymmetrical face.

After the face shape of the substrate is determined, it is determined that the substrate exhibits two asymmetrical orientations of asymmetrical curvature. For the concentric elliptical-shaped substrate shown in FIG. 3a, the first orientation 101 and the second orientation 102 of the elliptical-shaped substrate are determined, and the substrate faces the same in the first orientation 101 and the second orientation 102 The surface (ie, the first surface or the second surface) is curved, but at the same distance from the center of the substrate, the degree of curvature of the substrate is different.

After the above-mentioned asymmetric orientation of the substrate is determined, the value of the curvature of the substrate in the asymmetric orientation is calculated respectively. Referring to FIG. 3 a , the bow 1 of the substrate in the first orientation 101 and the bow ₂ of the substrate in the _second orientation 102 are measured.

After determining the curvature of the substrate in the asymmetric orientation, the substrate is scanned with a laser, in this embodiment, a pulsed laser is selected to scan the substrate. A single pulse with a certain spot size can produce modified spots with a certain size and depth on a specific material. The modified spots can be voids or recast spots. The overlapping voids or recast spots form grooves in the substrate. Or recast the line. The size and depth of the modified spots described above are related to the hardness and melting point of the material and the spot size, energy and wavelength of a single pulse. By adjusting the pulse frequency and scanning speed, the width and depth of the modified spots (or the grooves or recast lines formed by the modified spots) can be regulated. The parameters of the laser pulse used in this embodiment are described in Table 1 below:

Table 1 Parameters of the laser pulses used to scan the substrate

scope pulse time Wavelength (nm) Power (W) Frequency (kHz) Spot size (μm) Scanning speed (mm/s) Min 1as 200 0.1 1 1 10 Max 1ms 5000 100 1000 10⁵ 10000

According to the parameters such as the type and thickness of the substrate, select the appropriate parameters to scan the substrate within the range of each laser parameter shown in Table 1 above. In a preferred embodiment, the substrate is laser scanned from the first surface of the substrate.

As shown in Fig. 4, it is a graph showing the relationship between the curvature of the substrate before and after laser scanning and the focal depth of the laser pulse under the condition that the distance between the scanning lines of the laser pulse is constant. Here, the focal depth of the laser pulse is Defined as the depth of the focal point of the laser pulse from the first surface of the substrate. Figure 4 shows the change of the curvature of the substrate before and after laser scanning with the focal depth of the laser pulse when the scanning line spacing of the laser pulse is 100 μm and 500 μm, respectively. It can be seen from Fig. 4 that when the distance between the scanning lines is constant, the greater the distance between the focal depth of the laser pulse and the mid-depth plane of the substrate, the greater the change in the curvature of the substrate. According to the curve shown in Fig. 4, when the surface shape and curvature of the substrate are determined, an appropriate focal depth of the laser pulse can be selected. In this embodiment, for the sapphire substrate, the first surface of the sapphire substrate is regarded as a surface with a depth of 0, and the depth increases from the first surface to the second surface. In a preferred embodiment, appropriate laser pulse parameters can be selected such that the depth of focus of the laser pulse is in the range of 2% to 98% of the substrate thickness.

In addition, it can also be seen from Fig. 4 that under the premise that the focal depth of the laser pulse is constant, the change of the curvature of the substrate is related to the spacing between the scanning lines of the laser scanning. Referring to FIG. 5 , it is a graph showing the relationship between the scanning line spacing p and the curvature of the substrate under the condition that the focal depth of the laser pulse is constant. It can be seen from Figure 5 that when the focal depth of the laser pulse is constant, the larger the distance p between the scan lines, the smaller the change in the curvature of the substrate before and after laser scanning, and the smaller the distance p between the scan lines. , before and after laser scanning, the greater the curvature of the substrate changes.

As shown in Fig. 3a, after determining the presented asymmetric surface type and asymmetric orientation of the substrate, and the curvature of the substrate on the asymmetric orientation, determine the curvature of the symmetrical surface type finally converged by the substrate . As shown above, the concentric substrate has relatively uniform stress distribution, and the peripheral area has the same bending direction and the same degree of bending in each radial direction, and the bending convergence of the substrate is better. During epitaxial film formation, it is beneficial to the wavelength convergence of the epitaxial film formation layer. Therefore, the concentric surface type substrate is used as the target surface type of the asymmetric surface type substrate. And the target curvature bow ₀ of the target surface shape is determined.

A first difference in curvature, Δbow ₁ , between the bow ₁ of the substrate in the first orientation 101 and the target bow ₀ , and the bow ₂ of the substrate in the second orientation 102 and the target bow are then calculated The second curvature difference Δbow ₂ between the degrees bow ₀ . Then, based on the relationship between the curvature of the substrate and the focal depth of the laser pulse and the spacing p between the scan lines shown in FIGS. 4 and 5 , according to the above-mentioned first curvature difference value Δbow ₁ and the second curvature difference The value Δbow ₂ determines the depth of focus of the laser pulse and adjusts the spacing p between scan lines.

As described above, since the substrate shown in FIG. 3a exhibits a concentric elliptical profile, the first difference in curvature Δbow ₁ and the second difference in curvature Δbow ₂ are different. The scanning depth of the laser pulse is determined according to the relationship between the curvature of the substrate and the focal depth of the laser pulse and the spacing p between the scanning lines shown in FIGS. 4 and 5 . In an alternative embodiment, the depth of focus of the laser pulses is in a thickness range of 2% to 98% of the thickness of the substrate 100, more preferably, the depth of focus of the laser pulses is in a thickness of 10% to 40% of the thickness of the substrate range or the 60%-96% thickness range position (where the 10%-40% thickness range is located closer to the first surface of the substrate for epitaxial growth than the 60%-96% thickness range). In a preferred embodiment of this embodiment, when scanning the first orientation 101 and the second orientation 102 of the substrate, the scanning depth is fixed and unchanged. After the depth of focus of the laser pulse is determined, the spacing between the scan lines in the first orientation 101 and the second orientation 102 is adjusted. As shown in FIG. 6 , a schematic diagram of scan lines for scanning the substrate of the concentric elliptical surface type shown in FIG. 3 a is shown. As shown in FIG. 6 , the scan lines are line segments extending along the first orientation and the second curve respectively, and form grid lines. In the same orientation (the first orientation or the second orientation), the scan lines are mutually In parallel. In the first orientation 101, there is a first spacing D11 between scan lines, and in the second orientation, there is a second spacing D12 between scan lines, and D11 is different from D12. As shown in FIG. 3a, the first curvature bow ₁ of the substrate in the first orientation 101 is smaller than the second curvature bow ₂ in the second orientation 102. In a more preferred embodiment, the target curvature is bow0 greater than bow ₂ , that is, bow ₁ ≤bow ₂ ≤bow ₀ . Accordingly, the first curvature difference Δbow ₁ of the substrate is greater than the second curvature difference Δbow ₂ . According to 5, at this time, it can be determined that the distance D11 between the scan lines in the first orientation of the substrate is smaller than the distance D12 between the scan lines in the second orientation. It should be noted that the first curvature difference Δbow ₁ and the second curvature difference Δbow ₂ described above are both absolute values of the curvature difference.

The substrate is scanned in the first orientation and the second orientation from the first surface of the substrate with the scan lines shown in FIG. 6 , so that the curvature of the scanned substrate in the first orientation and the curvature in the second orientation are The curvature tends to be consistent, and the entire substrate converges to a concentric surface type. As shown in Fig. 9, after laser scanning is performed on the substrate, modified spots 500 are formed inside the substrate, and the modified spots can be formed in a circle, an ellipse, a polygon, or any combination thereof. The formation shape and type of modified spots can be changed and/or controlled by controlling the wavelength, pulse time, pulse shape, etc. of the laser. The modified spots 500 shown in FIG. 9 may be polycrystals (also referred to as thermally modified regions) or voids formed inside the substrate. Taking a cavity as an example, multiple cavities are formed inside the substrate. When the size of the cavities is larger than the spacing distance between adjacent cavities, the adjacent cavities will overlap to form trenches in the substrate.

After the laser scanning shown in Table 1, the formed modified spots 500 are correspondingly distributed in the thickness range of 2% to 98% of the thickness of the substrate 100, and the size of the formed modified spots 500 is between 1 μm and 5 mm. In a preferred embodiment of this embodiment, the above-mentioned modified spots are formed in a thickness range of 10% to 40% of the thickness of the substrate or a position in a thickness range of 60% to 96% (wherein the position of the thickness range of 10% to 40% is relatively The position in the thickness range of 60% to 96% is closer to the first surface of the substrate for epitaxial growth). In a more preferred embodiment of this embodiment, in the sapphire substrate shown in Figure 3a, the formed modified spots or grooves are distributed along the first orientation and the second orientation, and a grid-like distribution is formed inside the substrate.

In another optional embodiment of the present invention, as shown in FIG. 3b, a part of the peripheral region of the substrate in one radial direction is curved toward the first surface, and in another radial direction, a part of the peripheral region of the substrate The regions are flat, warp-free, and the substrate exhibits an asymmetrical punch-through profile. According to the surface shape of the substrate, the direction in which part of the peripheral region is curved toward the first surface of the substrate is defined as the first orientation 201 , and the direction in which part of the peripheral region is flat without warping is defined as the second orientation 202 . The substrate is measured for a first bow ₁ in a first orientation 201 and a second bow ₂ in a second orientation 202 . And according to the surface shape of the substrate, determine the curvature of the symmetric concentric surface shape that the substrate will eventually converge into, that is, the target curvature bow ₀ of the substrate, and then calculate the first curvature and the second curvature respectively and Differences in target curvature: the first curvature difference Δbow ₁ and the second curvature difference Δbow ₂ . In a preferred embodiment, for a sapphire substrate exhibiting a penetration profile, the target curvature is selected to be slightly smaller than the second curvature bow ₂ , that is, Δbow ₁ >Δbow ₂ . It should also be noted that the first curvature difference Δbow ₁ and the second curvature difference Δbow ₂ described above are both absolute values of the curvature difference.

As described above, the relationship Δbow ₁ > Δbow ₂ of the difference in curvature of the substrate in the first orientation 201 and the second orientation 202 is determined, and the focal depth of the laser pulse is determined according to FIG. 4 . In a preferred embodiment, in order to make The scanning process is easier to control. In the first orientation and the second orientation, then, according to the relationship between the variation of the substrate curvature and the spacing between the scanning lines shown in FIG. 5, the scanning lines in the first orientation and the second orientation are determined. Pitch. For the through-surface type substrate shown in this embodiment, the selected scan lines are shown in FIG. 7 . As shown in FIG. 7 , the scan lines are line segments extending along the first orientation and the second orientation respectively, and the scan lines in the two orientations form grid lines. In the first orientation, the scan lines are parallel to each other, and in the second orientation Upward, the scan lines are also parallel to each other; however, the spacing D21 between the scan lines in the first orientation is smaller than the spacing D22 between the scan lines in the second orientation.

Laser scanning is performed on the substrate showing the penetration profile from the first surface of the substrate along the scanning line shown in FIG. 7, and the modified spot 500 shown in FIG. 9 is formed inside the substrate. The modified spot can be formed as Circle, oval or polygon, or any combination of them. The formation shape and type of modified spots can be changed and/or controlled by controlling the wavelength, pulse time, pulse shape, etc. of the laser. The modified spots 500 may be polycrystals (also referred to as thermally modified regions) or voids formed inside the substrate. Taking a cavity as an example, multiple cavities are formed inside the substrate. When the size of the cavities is greater than the spacing distance between adjacent cavities, the adjacent cavities will overlap to form trenches in the substrate.

The above modified spots 500 are also distributed in a thickness range of 2% to 98% of the thickness of the substrate 100 , and the size of the formed modified spots 500 is between 1 μm and 5 mm. In a preferred embodiment of the present embodiment, the above-mentioned modified spots are formed in a thickness range of 10% to 40% of the thickness of the growth substrate or a position of a thickness range of 60% to 96% (wherein the thickness range of 10% to 40% is The position is closer to the first surface of the substrate for epitaxial growth than the position in the thickness range of 60% to 96%). In the through-face type sapphire substrate shown in Fig. 3b, the modified point is formed at a position of 40% of the thickness of the substrate. The formed modified spots or grooves are distributed along the first orientation and the second orientation, forming a grid-like distribution inside the substrate.

In another alternative embodiment of the present invention, as shown in FIG. 3c, the substrate is curved toward the second surface of the substrate in one radial direction, and is curved toward the second surface of the substrate in a different radial direction One surface is curved, and the substrate presents a saddle-shaped surface. According to the surface shape of the substrate, as shown in FIG. 3 c , the direction in which the substrate is bent toward the second surface of the substrate is defined as the first orientation 301 , and the direction in which the substrate is bent toward the first surface is defined as the second orientation 302 . Measure the first curvature bow ₁ of the substrate in the first orientation 301 and the second curvature bow ₂ in the second orientation 302 respectively, and determine the target curvature of the symmetrical concentric surface shape that the substrate will eventually converge into Degree bow ₀ . In a preferred embodiment of this embodiment, the concentric surface shape into which the substrate finally converges is defined as a concentric surface shape curved toward the first surface of the substrate, and the target curvature bow ₀ is close to or slightly larger than or slightly smaller than the substrate. The bow ₂ of the base in the second orientation. Thus, the first curvature difference Δbow ₁ between the first curvature bow ₁ in the first orientation 301 and the target curvature bow ₀ is calculated, and the second curvature bow ₂ in the second orientation 302 and the target curvature The first curvature difference Δbow ₂ for bow ₀ . As can be seen from the above, Δbow ₁ >Δbow ₂ . It should be noted that, since the substrate shown in FIG. 3c is curved toward the second surface and the first surface of the substrate in the first orientation and the second orientation, respectively, the curvature toward the first surface is defined as a positive value, and the curvature toward the first surface is defined as a positive value. The curvature of the second surface curvature is negative. The first curvature difference Δbow ₁ and the second curvature difference Δbow ₂ described above are both absolute values of the curvature difference.

Then the focal depth of the laser pulse is determined according to Fig. 4. In a preferred embodiment, in order to make the scanning process easier to control, the same focal depth of the laser pulse is selected in the first orientation and the second orientation. Then, according to the relationship between the curvature of the substrate and the spacing between the scanning lines shown in FIG. 5, the spacing between the scanning lines in the first orientation and the second orientation is determined. For the through-surface type substrate shown in this embodiment, the selected scan lines are shown in FIG. 8 . As shown in FIG. 8 , the scan lines are line segments extending along the first orientation and the second orientation respectively, and the scan lines in the two orientations form grid lines. In the first orientation, the scan lines are parallel to each other, and in the second orientation Upwards, the scan lines are also parallel to each other; however, the spacing D31 between scan lines in the first orientation is smaller than the spacing D32 between scan lines in the second orientation.

Laser scanning is performed from the first surface of the substrate along the scanning line shown in FIG. 8 to a substrate showing a saddle surface shape, and a modified spot 500 as shown in FIG. 9 is formed inside the substrate, and the modified spot can be formed as a circle. shape, ellipse or polygon, or any combination of them. The formation shape and type of modified spots can be changed and/or controlled by controlling the wavelength, pulse time, pulse shape, etc. of the laser. The modified spots 500 may be polycrystals (also referred to as thermally modified regions) or voids formed inside the substrate. Taking a cavity as an example, a plurality of cavities are formed inside the substrate. When the size of the cavities is greater than the spacing distance between adjacent cavities, the adjacent cavities will overlap to form trenches in the substrate. The formed modified spots or grooves are distributed along the first orientation and the second orientation, forming a grid-like distribution inside the substrate.

The above modified spots 500 are also distributed in a thickness range of 2% to 98% of the thickness of the substrate 100 , and the size of the formed modified spots 500 is between 1 μm and 5 mm. In a preferred embodiment of the present embodiment, the above-mentioned modified spots are formed in a thickness range of 10% to 40% of the thickness of the growth substrate or a position of a thickness range of 60% to 96% (wherein the thickness range of 10% to 40% The position is closer to the first surface of the substrate for epitaxial growth than the position in the thickness range of 60% to 96%). As mentioned above, in the present invention, in the process of processing the substrate, the laser scanning is performed on the substrate by using the method of fixing the focal depth of the laser pulse and adjusting the spacing between the scanning lines in different orientations. It should be understood that, The focal depth of laser pulses in different orientations and the spacing between scan lines in different orientations can be adjusted simultaneously, that is, the above two parameters can be adjusted simultaneously to perform laser scanning on the substrate.

In order to verify the surface shape of the converged sapphire substrate, Fig. 10 shows the ratio of warpage to warpage before epitaxial growth between the substrate without laser scanning and the substrate after laser scanning in the method of the present invention As can be seen from Figure 10, the mean value of warpage/curvature of the untreated sapphire substrate is 3.18, and the standard deviation is 3.47; while the sapphire substrate processed by the laser scanning described in this embodiment has a mean value of 3.18 and a standard deviation of 3.47. The mean value of warpage/curvature is 1.01, and the standard deviation is 0.04 (warpage and curvature are measured by a flatness measuring instrument (eg, Zhengmei GSS machine) respectively).

According to different surface substrates, the ratio of warpage to curvature is shown in Table 2 below:

Table 2 Substrate profile and range of warpage/bend

face shape concentric saddle type Penetrating oval Warpage/Bend 1～1.5 >2.5 <1 1.5～2.5

It can be seen from this that after the laser scanning described in this embodiment, the average value of the warpage/curvature of the sapphire substrate is between 1 and 1.5, that is, the surface shape of the substrate is concentric circles. And the standard deviation of the warpage/bend of the substrate is as low as 0.04, and the convergence of the substrate surface profile is improved. The substrate converges to a concentric shape and has high convergence, which is beneficial to improve the wavelength convergence of the subsequent epitaxial layers.

Another embodiment of the present invention provides a preparation method of a semiconductor device, as shown in Figure 11, the method comprises the following steps:

Step S100: providing a substrate, and determining the asymmetric surface type presented by the substrate;

Step S200: determine the asymmetric orientation of the asymmetric surface, and measure the curvature of the substrate on the asymmetric orientation;

Step S300: on the asymmetric orientation, carry out laser scanning to the substrate along the scanning line, and form modified spots in the substrate to make the substrate converge from asymmetric surface type to symmetrical surface type;

Step S400 : forming at least one semiconductor epitaxial layer on the first surface of the substrate.

Wherein, the above steps S100 to S300 are the same as the processing method of the substrate with an asymmetric surface provided by the present invention in the previous embodiment of the present invention, and are not repeated here. Wherein, in step S400, forming at least one layer of semiconductor epitaxial layer above the first surface of the substrate includes the following steps:

forming a first semiconductor layer over the first surface of the substrate;

forming multiple quantum wells over the first semiconductor layer;

A second semiconductor layer having conductivity opposite to that of the first semiconductor layer is formed on the multiple quantum well.

In an optional embodiment, N number (N=1000) sapphire substrates are used for epitaxial growth, N/2 substrates are subjected to laser scanning processing through the scanning lines shown in FIGS. 6 to 8 , and the remaining N/2 2 number of substrates are not processed by laser scanning, the N/2 number of substrates and the remaining N/2 number of substrates also include the four surface types shown in Figures 1a to 1d. The mean and standard deviation STD of tortuosity of N/2 number of sapphire substrates and the rest of N/2 number of sapphire substrates without laser treatment at different epitaxial growth stages are measured, and the comparison of the obtained results is shown in Figure 12 .

As can be seen from Figure 11, the mean value of the curvature of the sapphire substrate processed by the method of the present invention and the untreated sapphire substrate at different stages of epitaxial growth are basically the same, and there is no major difference. However, the standard deviation of the curvature of the two is significantly different. For example, after the growth of the n-type GaN layer, the standard deviation STD of the curvature of the sapphire substrate processed by the method described in this embodiment is about 0.6, while the standard deviation STD of the unprocessed sapphire substrate is about 0.6. The standard deviation of the curvature of the sapphire substrate is about 9.85; during the growth of multiple quantum wells, the standard deviation STD of the curvature of the sapphire substrate processed by the method in this embodiment is about 1.21, while the untreated sapphire substrate has a standard deviation of about 1.21. The standard deviation of the curvature of the bottom is about 2.54; from the comparison of the above different epitaxy processes, it can be seen that compared with the standard deviation of the curvature of the untreated sapphire substrate, the sapphire substrate treated by the method in this embodiment is in The standard deviation of the curvature in the epitaxial growth process is significantly reduced, that is, the curvature of the sapphire substrate after the laser treatment in this embodiment is obviously converged in the epitaxial growth process.

In order to further verify the optimization of the wavelength standard deviation (STD) of the epitaxial layer subsequently formed on the substrate by the method described in this embodiment, different applications formed on the sapphire substrate processed by the method of the present invention were measured respectively. The wavelength standard deviation of the epitaxial wavelength of the product. As shown in Table 3 below, it shows the convergence improvement rate of the epitaxial wavelength of different products, that is, the reduction range of the wavelength standard deviation (assuming the epitaxial wavelength of each application product formed on the sapphire substrate processed by the method in this embodiment) The wavelength standard deviation STD1 of the sapphire substrate processed by this method is STD2 of the wavelength standard deviation of the epitaxial wavelength of each product formed on the sapphire substrate processed by this method, then the reduction range in Table 3 is ((STD2-STD1)*100%)/( STD1)).

Table 3 Decreases of wavelength standard deviation for different products

It can be seen from FIG. 12 and Table 3 above that the stress generated by the above-mentioned modified points 500 generated inside the substrate can effectively uniformize the stress distribution of the substrate, improve the convergence of the substrate, and make the substrate converge to the concentricity shown in FIG. 1d. Round shape. The concentric surface type substrate is beneficial to the wavelength convergence of the epitaxial layer, so that the standard deviation STD of the wavelength is reduced by nearly 11% to 25%.

As mentioned above, the substrate provided by the present invention and its processing method, light-emitting diode and its manufacturing method have at least the following beneficial technical effects:

In the method of the present invention, the asymmetric surface type presented by the substrate is first determined, and the asymmetric orientation of the asymmetric surface type is determined, the substrate is scanned on the asymmetric orientation, and modified spots are formed in the substrate to The substrate is made to converge from an asymmetric face shape to a symmetrical face shape, such as a bowl shape. By adjusting the spacing distance of the scan lines in the asymmetric direction, the scan lines in the same direction are parallel to each other, while the spacing distance of the scan lines in the asymmetric direction is different, resulting in different bending value changes in the asymmetric direction, making the substrate Finally, the bending degrees in all directions tend to be the same, so that the surface shape of the substrate converges to a symmetrical surface shape (for example, a concentric circle shape or a bowl shape). Growing the epitaxial layer on the substrate that converges to a symmetrical plane is beneficial to reduce the dispersion of the wavelength of the epitaxial layer, that is, to make the wavelength of the epitaxial layer more convergent, and the improvement of the convergence of the wavelength of the epitaxial layer directly affects the yield of subsequent devices, so that The device yield is greatly improved.

In addition, the present invention uses a laser to irradiate the substrate, and adjusts parameters such as the spot size, pulse wavelength, power, pulse time, irradiation (or scanning) time of the laser pulse according to the type and size of the substrate, and determines the modification point. The depth (voids or bubbles) in the substrate, and the size of the modified spots. The control process is easy to operate and the control precision is high. In addition, the cost of laser irradiation is relatively low, thereby reducing the cost of substrate processing.

The substrate for epitaxy and the semiconductor device of the present invention can be processed by the above-mentioned method, and thus also have the above-mentioned beneficial effects.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (18)

1. A method of processing a substrate exhibiting an asymmetrical profile, comprising the steps of:

providing a substrate and determining an asymmetric profile exhibited by the substrate, the substrate having a first surface and a second surface;

determining an asymmetric orientation of the asymmetric profile and measuring a degree of curvature of the substrate in the asymmetric orientation;

and in the asymmetric orientation, performing laser scanning on the substrate along a scanning line, and forming a modified spot in the substrate so as to make the substrate converge from an asymmetric plane to a symmetric plane.

2. A method of processing a substrate exhibiting an asymmetrical profile as set forth in claim 1 wherein the substrate is laser scanned along a scan line in the asymmetrical orientation, further comprising the steps of:

determining a target curvature bow of the substrate from the curvature of the substrate in the asymmetric orientation₀；

Calculating a curvature difference value A bow of the target curvature for a curvature value of the base in the asymmetric orientation;

determining the scanning depth of laser scanning on the substrate according to the bending degree difference value delta bow;

and adjusting the spacing between the scanning lines in different orientations according to the bending degree difference delta bow.

3. The method of processing a substrate exhibiting an asymmetrical profile as set forth in claim 1, further comprising: the scanning lines in the same orientation are adjusted to be parallel to each other.

4. The method of processing a substrate exhibiting an asymmetrical profile as set forth in claim 1, further comprising: the distances between the scanning lines in the same orientation are adjusted to be the same, and the distances between the scanning lines in different orientations are different.

5. A method of processing a substrate presenting an asymmetric profile as claimed in claim 1, wherein the orientation of the asymmetry of the asymmetric profile is determined and the degree of curvature of the substrate in the asymmetric orientation is measured, further comprising the steps of:

determining a first orientation and a second orientation of the asymmetric face, the first orientation and the second orientation being intersecting asymmetric orientations;

measuring bow a first curvature of the substrate in the first orientation along the first surface₁；

Measuring a second curvature bow of the substrate in the second orientation along the first surface₂；

Calculating a first tortuosity difference Δ bow of the first tortuosity of the substrate in the first orientation and the target tortuosity₁And a second difference in bow, Δ bow, of the substrate in the second orientation₂。

6. The method of claim 5, wherein the substrate is laser scanned along a scan line in the asymmetric orientation, further comprising the steps of:

according to the first bending degree difference delta bow₁And said second difference in curvature Δ bow₂Determining a scanning depth for laser scanning of the substrate;

according to a first difference of curvature Δ bow in the first orientation₁Adjusting a first pitch between scan lines in the first orientation;

according to a second difference of curvature Δ bow in the second orientation₂Adjusting a second pitch between scan lines in the second orientation.

7. The method as claimed in claim 2 or 6, wherein the scanning depth of the laser scanning on the substrate is any depth in the range of 2-98% of the thickness of the substrate.

8. The method for processing a substrate having an asymmetric profile as claimed in claim 1, wherein the asymmetric profile presented by the substrate comprises any one of the following profiles:

the substrates are in the same bending direction but different in bending degree in the asymmetric direction;

a penetration type in which the substrate is bent in one direction and is not bent in another direction asymmetrical to the one direction;

saddle-shaped, the substrate bending in opposite directions in an asymmetrical direction.

9. The method according to claim 1, wherein the modified spots are distributed along the first orientation and the second orientation, and are distributed in a grid pattern inside the substrate.

10. The method of claim 1, wherein the modified spots comprise voids formed in the substrate.

11. The method of claim 1, wherein the modified spots comprise voids formed in the substrate, the voids forming trenches in the substrate.

12. A preparation method of a light-emitting diode is characterized by comprising the following steps:

providing a substrate, and determining an asymmetric surface type presented by the substrate;

determining an asymmetric orientation of the asymmetric profile and measuring a degree of curvature of the substrate in the asymmetric orientation;

in the asymmetric orientation, laser scanning is carried out on the substrate along a scanning line, and a modified point is formed in the substrate so that the substrate is converged from an asymmetric surface type to a symmetric surface type;

forming a light emitting structure over the substrate converging to a plane of symmetry.

13. The method of claim 12, wherein forming a light emitting structure over the substrate comprises:

forming a first semiconductor layer over the substrate;

forming a multiple quantum well over the first semiconductor layer;

forming a second semiconductor layer over the multiple quantum wells of opposite conductivity to the first semiconductor layer.

14. A method of processing a substrate exhibiting an asymmetrical profile as set forth in claim 12 wherein the substrate is laser scanned along a scan line in the asymmetrical orientation, further comprising the steps of:

determining a target bow of the substrate from a bow of the substrate in the asymmetric orientationDegree bow₀；

Calculating a curvature difference value A bow of the target curvature for a curvature value of the base in the asymmetric orientation;

determining the scanning depth of laser scanning on the substrate according to the bending degree difference value delta bow;

and adjusting the spacing between the scanning lines in different orientations according to the bending degree difference delta bow.

15. The method of processing a substrate exhibiting an asymmetrical profile as set forth in claim 12, further comprising: the scanning lines in the same orientation are adjusted to be parallel to each other.

16. The method of processing a substrate exhibiting an asymmetrical profile as set forth in claim 12, further comprising: the distances between the scanning lines in the same orientation are adjusted to be the same, and the distances between the scanning lines in different orientations are different.

17. A substrate for epitaxial growth, the substrate having a first surface and a second surface, characterized in that the substrate has a plurality of modified spots formed therein by multiphoton absorption, the modified spots forming a grid-like distribution in two different radial directions of the substrate in a plan view direction along the first surface of the substrate.

18. A light-emitting diode comprising a substrate and a light-emitting structure formed over the substrate, wherein the substrate is the substrate for epitaxy of claim 17.

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