TWI745721B - Method for reducing substrate warpage - Google Patents

Abstract

A method for reducing substrate warpage including steps below is provided. First, providing a first substrate and a second substrate. The first substrate includes a first surface and a second surface opposite to the first surface. The second substrate includes a third surface and a fourth surface opposite to the third surface. The first surface is subject to a compression stress and the second surface is subject to a tensile stress. The third surface is subject to a compression stress and the fourth surface is subject to a tensile stress. Then, bonding the first substrate and the second substrate to form a composite substrate. The first surface of the first substrate is faced with the third surface of the second substrate, or the second surface of the first substrate is faced with the fourth surface of the second substrate.

Description

Method of reducing substrate warpage

The present invention relates to a method for reducing the warpage of a substrate, and particularly relates to a method for reducing the warpage of the substrate during high-temperature thermal annealing.

During the manufacturing process, the substrate often undergoes shaping or heat treatment to have residual stress in its interior, and the formed substrate will be warped due to the residual stress when it is subsequently subjected to high temperature thermal annealing. The conventional methods for solving the warpage of the substrate include improving the characteristics of the substrate material to reduce the residual stress or using a jig to flatten the warpage of the substrate. However, both of these methods will increase the manufacturing cost.

The present invention provides a method for reducing the warpage of the substrate, which can solve the problem of the warpage of the substrate without changing the original characteristics of the material, so as to reduce the manufacturing cost.

The method for reducing the warpage of the substrate of the present invention includes the following steps. First, a first substrate and a second substrate are provided. The first substrate includes a first surface and a second surface opposite to the first surface, and the second substrate includes a third surface and a fourth surface opposite to the third surface. The first surface is subjected to compressive stress and the second surface is subjected to tensile stress, the third surface is subjected to compressive stress and the fourth surface is subjected to tensile stress. Afterwards, the first substrate and the second substrate are bonded to form a composite substrate. The first surface of the first substrate faces the third surface of the second substrate, or the second surface of the first substrate faces the fourth surface of the second substrate.

In an embodiment of the present invention, at least one of the above-mentioned first substrate and second substrate is a glass substrate.

In an embodiment of the present invention, the above-mentioned glass substrate is a float glass substrate.

In an embodiment of the present invention, one of the above-mentioned first substrate and second substrate is a plastic substrate.

In an embodiment of the present invention, at least one of the aforementioned first substrate and second substrate includes a multilayer structure.

In an embodiment of the present invention, the above-mentioned first substrate and the second substrate have substantially the same total thickness.

In an embodiment of the present invention, the step of bonding the first substrate and the second substrate includes forming an adhesive layer between the first substrate and the second substrate to bond the first substrate and the second substrate.

In an embodiment of the present invention, the aforementioned adhesive layer includes optically transparent glue or optically transparent resin.

Based on the above, the present invention can offset the residual stresses of the first substrate and the second substrate by making the surfaces of the first substrate and the second substrate that are attached to each other have residual compressive stress or both have residual tensile stress, so that the formation of The composite substrate may not warp during subsequent high-temperature thermal annealing, so as to reduce the manufacturing cost.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail in conjunction with the accompanying drawings.

1A and 1B are schematic flowcharts of a method for reducing substrate warpage according to an embodiment of the present invention.

1A, a first substrate 100 and a second substrate 200 are provided. Each of the first substrate 100 and the second substrate 200 includes two surfaces facing each other. In detail, the first substrate 100 includes surfaces 100a and 100b, and the second substrate 200 includes surfaces 200a and 200b. In one embodiment, the first substrate 100 and the second substrate 200 each have residual stress due to the shaping or heat treatment experienced during the manufacturing process. For example, the surface 100a of the first substrate 100 bears the residual compressive stress C1, and the surface 100b of the first substrate 100 bears the residual tensile stress T1; similarly, the surface 200a of the second substrate 200 bears the residual compressive stress C2, and the second substrate 200 bears the residual compressive stress C2. The surface 200b of the substrate 200 bears the residual tensile stress T2. When the first substrate 100 (or the second substrate 200) is subjected to high temperature thermal annealing, the first substrate 100 (or the second substrate 200) will endure the residual compressive stress C1 (or the residual compressive stress C2) due to the above residual stress The direction of the surface is warped. The residual stress value and the residual stress direction of the first substrate 100 and the second substrate 200 can be measured, for example, by using the sharp color method, the circular polarization method, the orthogonal polarization method, or a combination thereof. In detail, the sensitive color method distinguishes the stress status of the measured object by color, and can display the residual stress value and the direction of the residual stress of the measured object; the circular polarization method can directly identify the occurrence of the residual stress of the measured object; and Polarization method can detect whether there is hidden residual stress and distinguish the direction of residual stress. Through the above-mentioned measurement method, the residual stress value and the residual stress direction of the first substrate 100 and the second substrate 200 can be accurately confirmed, so as to facilitate the subsequent finding of the best bonding method. However, the present invention is not limited to this. For two test objects that include the same or similar materials and undergo the same or similar manufacturing process, their residual stress values and residual stress directions should be similar. Based on this, the two test objects can be used instead of the above-mentioned measurement method. The total thickness of the object is equal to the bonding method.

1B, the first substrate 100 and the second substrate 200 are bonded together to form a composite substrate 10. In order to avoid warpage of the first substrate 100 or the second substrate 200 due to residual stress, the surface 100a of the first substrate 100 that bears the residual compressive stress C1 and the surface 200a of the second substrate 200 that bears the residual compressive stress C2 can be combined. Adhere to each other, and by making the residual stresses of the two offset each other, the problem of warpage of the composite substrate 10 during high-temperature thermal annealing is improved. In contrast, the surface 100b of the first substrate 100 that bears the residual tensile stress T1 and the surface 200b of the second substrate 200 that bears the residual tensile stress T2 can be bonded to each other to improve the performance of the composite substrate 10 during high-temperature thermal annealing. There is a problem of warpage.

In one embodiment, the adhesive layer 300 may be used to bond the first substrate 100 and the second substrate 200. The adhesion layer 300 may include, for example, an optically transparent glue or an optically transparent resin. When optically transparent glue or optically transparent resin is used to bond the first substrate 100 and the second substrate 200, a full bonding method is used to bond the first substrate 100 and the second substrate 200 to provide a bonded composite substrate 10 Has good flatness. In this embodiment, the first substrate 100 and the second substrate 200 are bonded together in a fully bonded manner using an optical transparent glue.

In an embodiment, at least one of the first substrate 100 and the second substrate 200 is a glass substrate. In more detail, at least one of the first substrate 100 and the second substrate 200 is a float glass substrate. The method of manufacturing a float glass substrate (float method) is, for example, to first contact one surface of the molten glass with a tin solution, and expose the other opposite surface of the glass to the air, and then to remove the molten glass After solidification and annealing, a solid float glass substrate is formed. The surface of the float glass substrate that was in contact with the tin solution is called the tin surface, and the surface of the float glass substrate that was exposed to the air is called the air surface. Since the number of tin particles on the tin surface of the float glass substrate is relatively large, the tin surface of the float glass substrate will bear residual compressive stress, and the air surface of the float glass substrate will bear residual tensile stress. In contrast, the glass formed by the overflow down-draw method is not suitable for the material included in the first substrate 100 or the second substrate 200 due to relatively little residual stress, and the manufacturing cost of the glass formed by the overflow down-draw method is also greater than The manufacturing cost of glass formed by the float method. The residual stress value and the residual stress direction of the float glass can be measured by the aforementioned measurement method, and will not be repeated here.

In an embodiment, one of the first substrate 100 and the second substrate 200 is a plastic substrate. The plastic substrate selected here needs to have residual stress. For example, a polyimide substrate that has undergone shaping or heat treatment can be selected. One surface of the polyimide substrate bears residual compressive stress, and the other side The surface is subjected to residual tensile stress. The value of residual stress and the direction of residual stress on the surface of the polyimide substrate can be measured by the aforementioned measuring method, which will not be repeated here. The other of the first substrate 100 and the second substrate 200 in this embodiment is a float glass substrate.

In an embodiment, at least one of the first substrate 100 and the second substrate 200 includes a multilayer structure. For example, the first substrate 100 and the second substrate 200 may have a structure with the same number of layers; or, the first substrate 100 and the second substrate 200 may have a structure with a different number of layers. When the first substrate 100 and the second substrate 200 have structures with different numbers of layers, the total thickness of the first substrate 100 and the second substrate 200 may be substantially the same. For example, when the first substrate 100 has a relatively large number of layers, each layer of the second substrate 200 can be made relatively thick so that the total thickness of the first substrate 100 and the second substrate 200 are substantially the same, and The residual compressive stresses C1, C2 (or residual tensile stresses T1, T2) of the surfaces where the first substrate 100 and the second substrate 200 are attached to each other are substantially the same, so as to improve the warpage of the composite substrate 10. In an embodiment, the first substrate 100 may have a single-layer structure with a thickness of 1 mm, and the second substrate 100 may have a double-layer structure with a thickness of 0.5 mm. Alternatively, when the first substrate 100 has a structure with a larger number of layers and has a relatively large thickness, the second substrate 200 can be made of a material different from that of the first substrate 100, so that the first substrate 100 and the second substrate 200 The residual compressive stresses C1, C2 (or residual tensile stresses T1, T2) of the surfaces that are attached to each other are substantially the same, so as to improve the problem of warpage of the composite substrate 10 during high-temperature thermal annealing. In the above-mentioned embodiments, those with ordinary knowledge in the field can freely select the number and thickness of the first substrate 100 and the second substrate 200, and the present invention is not particularly limited.

In summary, without changing the material properties of the first substrate and the second substrate, the present invention makes the surfaces of the first substrate and the second substrate have residual compressive stress or both have residual compressive stress. The tensile stress can offset the residual stress of the first substrate and the second substrate, so that the formed composite substrate may not warp during subsequent high-temperature thermal annealing, so as to improve the yield.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the relevant technical field can make some changes and modifications without departing from the spirit and scope of the present invention. The protection scope of the present invention shall be subject to those defined by the attached patent application scope.

10: Composite substrate 100: first substrate 100a, 100b, 200a, 200b: surface 200: second substrate 300: Adhesive layer C1, C2: Residual compressive stress T1, T2: Residual tensile stress

1A and 1B are schematic flowcharts of a method for reducing substrate warpage according to an embodiment of the present invention.

10: Composite substrate

100: first substrate

100a, 100b, 200a, 200b: surface

200: second substrate

300: Adhesive layer

Claims (7)

A method for reducing the warpage of a substrate includes: providing a first substrate and a second substrate each having residual stresses that have undergone shaping or heat treatment during the manufacturing process, the first substrate including a first surface and the first substrate A second surface opposite to the surface, the second substrate includes a third surface and a fourth surface opposite to the third surface, wherein the first surface bears compressive stress and the second surface bears tensile stress, the The third surface is subjected to compressive stress and the fourth surface is subjected to tensile stress; and the first substrate and the second substrate are bonded to form a composite substrate, wherein the first surface of the first substrate can be selected Facing the third surface of the second substrate or the second surface of the first substrate facing the fourth surface of the second substrate, wherein the first substrate And an adhesive layer is formed between the second substrates to bond the first substrate with the residual stress value and the second substrate with the residual stress value in a fully bonded manner. The method for reducing the warpage of a substrate as described in the scope of the patent application, wherein at least one of the first substrate and the second substrate is a glass substrate. According to the method for reducing the warpage of the substrate as described in item 2 of the scope of patent application, the glass substrate is a float glass substrate. According to the method for reducing the warpage of a substrate as described in claim 1, wherein one of the first substrate and the second substrate is a plastic substrate. The method for reducing the warpage of a substrate as described in the scope of the patent application, wherein at least one of the first substrate and the second substrate includes a multilayer structure. According to the method for reducing the warpage of a substrate as described in the first item of the scope of patent application, the total thickness of the first substrate and the second substrate is substantially the same. According to the method for reducing the warpage of a substrate as described in item 1 of the scope of the patent application, the adhesive layer includes an optically transparent glue or an optically transparent resin.

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