TWI787785B - Wafer testing method - Google Patents

Abstract

A wafer testing method adapted to test wafers is disclosed. The wafer is combined with a first vacuum-release substrate to form a wafer assembly. An attaching surface of the first vacuum-release substrate attaches a front surface of the wafer with an attaching force which is sensitive to the air pressure. The method includes transporting the wafer assembly to a first chuck and making a back surface of the first vacuum-release substrate face down and the front surface of the wafer face up. The method also includes attaching a second vacuum-release substrate to the front surface of the wafer and removing the attaching force between the first vacuum-release substrate and the wafer. The method also includes transporting the second vacuum-release substrate and the wafer to a second chuck. The method also includes eliminating the attaching force between the second vacuum-release substrate and the wafer and removing the second vacuum-release substrate to expose the front surface of the wafer. The method also includes performing a wafer test procedure to the wafer by a testing apparatus.

Description

Wafer Test Method

The invention relates to a wafer testing method, in particular to a wafer testing method applied to thin wafers.

After the wafer surface has gone through multiple processes, in addition to undergoing multiple heat treatments, the surface will also be covered with multiple coatings, wiring and components. Due to the different thermal expansion rates of the wafer, plating, wiring and components, the surface of the wafer will bear a certain degree of shrinkage stress and/or tensile stress, resulting in a certain degree of warpage in the product wafer itself . This kind of warping will become more significant as the thickness of the wafer becomes thinner, and even severe warping like "potato chips" will appear.

In practice, the fact that the wafer needs to be ground to such a thin thickness is mostly due to the trend of mobile electronic devices becoming thinner, lighter and smaller. In particular, various chips used in smartphones, including vertical cavity surface laser chips (VCSEL) for face recognition, photosensitive elements behind the camera lens, and system chips related to the operating performance of mobile phones, etc., all require Thinning as much as possible can meet the thickness specifications of subsequent assembled products.

The "thin wafer" mentioned in this specification generally refers to wafers with a thickness of less than 200 microns. Wafers with a thickness below this thickness are very obvious, which makes subsequent inspection procedures very difficult.

The invention provides a wafer testing method, which is suitable for testing a wafer. wafer with A first vacuum release type substrate constitutes a wafer assembly. The first vacuum release substrate has an attachment surface and a back surface opposite to the attachment surface, and the attachment surface of the first vacuum release substrate is attached to the back surface of the wafer with an adhesive force that is sensitive to air pressure. The method comprises the following steps: using a robotic arm to transport the wafer assembly to a first wafer chuck, wherein the back side of the first vacuum release substrate faces the first wafer chuck, and the front side of the wafer faces upward; The robot arm or another robot arm transports a second vacuum release type substrate to the top of the first wafer chuck, and makes the attachment surface of the second vacuum release type substrate face the front side of the wafer; The attachment surface is attached to the front side of the wafer of the wafer assembly; the first wafer chuck is used to provide a negative pressure on the first vacuum release type substrate of the wafer assembly to remove the adhesion between the first vacuum release type substrate and the wafer force; using the robot arm or the other robot arm to transport the second vacuum release type substrate and the wafer to a second wafer chuck, and provide an adsorption force to the wafer with the second wafer chuck; The robot arm or the other robot arm provides a negative pressure to the second vacuum release type substrate to remove the adhesion between the second vacuum release type substrate and the wafer; the robot arm or the other machine arm The arm removes the second vacuum release type substrate to expose the front side of the wafer; and tests the wafer with a testing device.

One of the characteristics of this case is to propose a new wafer inspection process to solve the problem that warped wafers are difficult to inspect.

100: Wafer

110: The front of the wafer

120: The back side of the wafer

200A: The first vacuum release type substrate

210A: Attachment surface of the first vacuum release type substrate

220A: the back side of the first vacuum release type substrate

200B: Second vacuum release type substrate

210B: Attachment surface of the second vacuum release type substrate

220B: the back side of the second vacuum release type substrate

300: wafer assembly

400:Robot Arm

420: negative pressure

500:Wafer Cassette

600: Warpage detection device

601: Optical transmitter

602: Optical receiver

620: The first wafer chuck

700: Test device

720: Second wafer chuck

OP: Optical path

S11~S17: Steps

[ FIG. 1 ] is an exemplary flow chart of the wafer testing method of the present invention.

[FIG. 2A] is an exploded schematic diagram of a wafer assembly.

[FIG. 2B] is a schematic diagram of the assembly of wafer components.

[FIG. 3A] is a schematic diagram (1) of the operation of the wafer testing method of the present invention.

[FIG. 3B] is a schematic diagram (2) of the operation of the wafer testing method of the present invention.

[FIG. 3C] is a schematic diagram (3) of the operation of the wafer testing method of the present invention.

[FIG. 3D] is a schematic diagram (4) of the operation of the wafer testing method of the present invention.

[FIG. 3E] is a schematic diagram (5) of the operation of the wafer testing method of the present invention.

[FIG. 3F] is a schematic diagram (6) of the operation of the wafer testing method of the present invention.

[FIG. 3G] is a schematic diagram (7) of the operation of the wafer testing method of the present invention.

[ FIG. 3H ] is a schematic diagram (8) of the operation of the wafer testing method of the present invention.

[FIG. 3I] is a schematic diagram (9) of the operation of the wafer testing method of the present invention.

[FIG. 3J] is a schematic diagram (10) of the operation of the wafer testing method of the present invention.

[FIG. 3K] is a schematic diagram (11) of the operation of the wafer testing method of the present invention.

[FIG. 3L] is a schematic diagram (11) of the operation of the wafer testing method of the present invention.

[FIG. 3M] is a schematic diagram (11) of the operation of the wafer testing method of the present invention.

[FIG. 3N] is a schematic diagram (11) of the operation of the wafer testing method of the present invention.

[ FIG. 4A ] is a schematic diagram (1) of warpage detection of the wafer testing method of the present invention.

[ FIG. 4B ] is a schematic diagram (2) of warpage detection of the wafer testing method of the present invention.

In the description of this case and the scope of the patent application, "upper" or "lower" is only used to describe its orientation shown in the drawings, not to limit its actual orientation. The term "front side" of a wafer refers to the main processing surface of the semiconductor manufacturing process, that is, the surface on which multiple semiconductor devices are formed. The "back" of the wafer is relative to the "front" of the wafer, which is generally a smooth surface, but the back of some wafers is a conductive plane, such as a VCSEL wafer.

The relative sizes and thicknesses of the components in the drawings are for illustration only, and are not intended to limit the components The actual relative size relationship.

Referring to FIG. 1 , FIG. 2A and FIG. 2B , they are respectively an exemplary flow chart of the wafer testing method of the present invention and an exploded schematic diagram and a schematic assembly schematic diagram of the wafer assembly. The wafer testing method of the present invention is suitable for testing the wafer 100, especially suitable for testing the wafer 100 with a thickness below 200 microns. The wafer 100 is disposed on the first vacuum release substrate 200A to form a wafer assembly 300 together with the first vacuum release substrate 200A. The first vacuum release substrate 200A has an attachment surface 210A and a back surface 220A opposite to the attachment surface 210A. The attachment surface 210A of the first vacuum release substrate 200A is attached to the back surface 120 of the wafer 100 with an adhesive force.

The first vacuum release type substrate 200A is a substrate widely used by semiconductor manufacturers, and its characteristic is that the adhesion provided by it is sensitive to air pressure. When the pressure difference between the back surface 220A of the first vacuum releasing substrate 200A and the attaching surface 210A is zero or less than a preset value, the attaching surface 210A of the first vacuum releasing substrate 200A can provide adhesion to the surface of the wafer 100 . When the pressure difference between the back surface 220A of the first vacuum release substrate 200A and the attachment surface 210A is greater than the preset value, the adhesion provided by the attachment surface 210A of the first vacuum release substrate 200A to the surface of the wafer 100 will be reduced. significantly lower, so that the first vacuum release type substrate 200A and the wafer 100 can be separated from each other. The wafer testing method of the present invention will be described below with reference to the drawings.

When the wafer testing production line receives the wafer products to be tested, the wafer products to be tested are usually stored in wafer cassettes. Therefore, when performing wafer testing, the operator must first take out the wafer product to be tested (wafer assembly 300 ) stored in the wafer cassette and place it on the testing machine for testing. Usually, each wafer cassette stores more than one wafer assembly 300 , and usually stores 25 wafer assemblies 300 .

As shown in FIG. 3A , when wafer testing is performed, the robot arm 400 is firstly used to take out the wafer assembly 300 from the wafer cassette 500 or from other specific storage containers for storing the wafer assembly 300 . Then, as shown in FIG. 3B , the wafer assembly 300 is transported to the first wafer chuck 620 , and the wafer assembly 300 is placed on the first wafer chuck 620 (step S11 ). In this embodiment, when the wafer assembly 300 is placed on the first wafer chuck 620, the back side 220A of the first vacuum release type substrate 200A faces the first wafer chuck 620, and the front side 110 of the wafer 100 is up.

Then, as shown in FIG. 3C , the back surface 220B of the second vacuum release type substrate 200B is sucked by the robot arm 400 (or another robot arm) to transport a second vacuum release type substrate 200B to the first wafer chuck 620. above, and make the attachment surface 210B of the second vacuum release type substrate 200B face the front surface 110 of the wafer 100 . The characteristics and usage of the second vacuum-releasing substrate 200B are the same as those of the first vacuum-releasing substrate 200A, and will not be repeated here. It should be noted here that the testing method of the present invention can be operated with a single robot arm from the beginning, or with two or more robot arms to increase production capacity, depending on the actual production capacity requirements.

Next, as shown in FIG. 3D , attach the attachment surface 210B of the second vacuum release type substrate 200B to the front surface 110 of the wafer 100 (step S12 ), and then align the first vacuum release type substrate 200A with the first wafer chuck 620 The backside 220A provides a negative pressure 420 to remove the adhesion between the first vacuum release type substrate 200A and the wafer 100 (step S13 ). Step S12 and step S13 can be performed synchronously, or step S12 can be performed first and then step S13 can be performed.

Next, as shown in FIGS. 3E to 3F , the robotic arm 400 transports the second vacuum release type substrate 200B and the wafer 100 attached to the second vacuum release type substrate 200B to the second wafer chuck 720, and then, with The second wafer chuck 720 provides suction to the back side 120 of the wafer 100. Adhesion (step S14). In some embodiments, the surface of the second wafer chuck 720 is provided with a plurality of flow channels or microholes, and each flow channel or microholes are connected to a vacuum pump through pipelines, and are evacuated by the vacuum pump. The gas is used to apply a vacuum suction force to the back surface 120 of the wafer 100 . The reason why the suction force must be provided on the backside 120 of the wafer 100 is to prevent the wafer 100 from returning to the warped state due to the removal of the second vacuum release type substrate 200B in subsequent steps.

After step S14 is completed, the front side 110 of the wafer 100 is still covered by the second vacuum release substrate 200B, so the second vacuum release substrate 200B needs to be removed to test the wafer 100 later. As shown in FIG. 3G , the robot arm 400 provides a negative pressure 420 to the second vacuum release substrate 200B to remove the adhesion between the second vacuum release substrate 200B and the wafer 100 (step S15 ). Then, as shown in FIG. 3H , the front side 110 of the wafer 100 can be exposed by taking out the second vacuum release type substrate 200B through the robotic arm 400 (step S16 ). Finally, as shown in FIG. 3I , at this time, the die on the wafer 100 can be tested through the testing device 700 (step S17 ). It should be specially noted here that the above step S14 and step S15 can be performed synchronously, or step S14 can be performed first and then step S15 can be performed.

In some embodiments, before the attachment surface 210B of the second vacuum release substrate 200B is attached to the front surface 110 of the wafer 100, it further includes performing an alignment step, so that the attachment surface 210B of the second vacuum release substrate 200B is aligned with the front surface 110 of the wafer 100. The front sides 110 of the wafers 100 are aligned with each other.

In some embodiments, during the process of transporting the second vacuum release type substrate 200B and the wafer 100 to the second wafer chuck 720, the back side 120 of the wafer 100 is kept facing down, and the whole process of transporting is carried out with a photographic model. A group (such as a video camera, a camera, etc.) continuously captures images of the second vacuum releasing substrate 200B and the wafer 100 , and determines whether there is a gap between the second vacuum releasing substrate 200B and the wafer 100 by analyzing the images. If the analysis results show that a gap exists, immediately Flip the second vacuum release type substrate 200B and the wafer 100 through the robotic arm, make the back side 120 of the wafer 100 face up and transport the wafer 100 and the second vacuum release type substrate 200B back to the wafer cassette 500 to avoid the wafer 100 dropped during shipping.

In some embodiments, after the attachment surface 210B of the second vacuum-releasing substrate 200B is attached to the front surface 110 of the wafer 100, the robotic arm 400 will turn over so that the back surface 120 of the wafer 100 faces up, and transport the second vacuum During the transfer of the release substrate 200B and the wafer 100 to the second wafer chuck 720 , the back side 120 of the wafer 100 is kept facing upward. When the second vacuum release type substrate 200B and the wafer 100 are transported above the second wafer chuck 720, the robot arm 400 starts to turn over so that the back side 120 of the wafer 100 faces down, thereby reducing the time spent on the transport of the wafer 100. risk of falling.

As mentioned above, in the production line, the second vacuum release type substrate 200B has a service life specification, and will be replaced once the service life expires. Therefore, during the process of transporting the second vacuum release type substrate 200B and the wafer 100 to the second wafer chuck 720 , no matter whether the back side 120 of the wafer 100 is facing up or down, safety regulations can be complied with.

In some embodiments, after placing the wafer assembly 300 on the first wafer chuck 620 , a warpage detection step is further included. Referring to FIG. 4A and FIG. 4B , in the warpage detection step, the warpage detection device 600 is used to detect whether the warpage of the wafer 100 is less than a warpage threshold. In some embodiments, the warping detection device 600 is a light interruption sensing device as shown in FIG. 4B , and includes a light emitter 601 and a light receiver 602 . The light emitter 601 and the light receiver 602 are respectively located on opposite sides of the first wafer chuck 620, and an optical path OP is defined between the light emitter 601 and the light receiver 602, wherein the light emitted by the light emitter 601 (eg, infrared rays) will travel along the optical path OP and reach the optical receiver 602 . The vertical distance between the optical path OP and the back surface 120 of the wafer 100 is pre-set set up. When performing the warpage test, the first wafer chuck 620 rotates and drives the wafer assembly 300 on it to rotate together. If the optical path OP is blocked by the wafer 100 during the rotation, it is determined that the warpage of the wafer 100 is higher than the warpage threshold, and the robot arm 400 will transfer the wafer assembly 300 back to the wafer cassette 500 without Inspection is performed to avoid subsequent wafer breakage. If the optical path OP is not blocked by the wafer 100 during the rotation of the first wafer chuck 620 , it is determined that the warpage of the wafer 100 is lower than the warpage threshold, and the subsequent steps can be continued.

In some embodiments, the warpage detection device 600 is a camera module, and determines the degree of wafer warpage through image recognition means. The camera module and image recognition means form a visual recognition system.

In some embodiments, when the wafer assembly 300 is placed on the first wafer chuck 620, the wafer will be controlled through the pressure sensor disposed on the first wafer chuck 620 or the robot arm 400. The pressure when the wafer assembly 300 contacts the first wafer chuck 620 is less than a pressure threshold, thereby avoiding damage to the wafer 100 during placement.

In some embodiments, after the wafer 100 is tested, because the wafer 100 is very thin, it is usually necessary to combine the tested wafer 100 with the second vacuum-released substrate 200B to prevent the wafer 100 from being transported in the subsequent transportation process. damaged in. At this time, as shown in FIG. 3J , the attachment surface 210B of the second vacuum-releasing substrate 200B is reattached to the front surface 110 of the wafer 100 through the robotic arm 400 . Next, as shown in FIG. 3K , the robotic arm 400 transports the second vacuum release type substrate 200B together with the wafer 100 to the first wafer chuck 620 . Next, as shown in FIG. 3L , the robotic arm 400 makes the backside 120 of the wafer 100 face down to combine with the attachment surface 210A of the first vacuum release type substrate 200A on the first wafer chuck 620 . Next, as shown in FIG. 3M and FIG. 3N , the robot arm 400 provides negative pressure to the second vacuum release type substrate 200B to remove the second vacuum release type substrate 200B. Adhesion between the vacuum release type substrate 200B and the wafer 100, and then take out the second vacuum release type substrate 200B. Next, the robotic arm 400 takes the wafer assembly 300 out of the first wafer chuck 620 and transports it back to the original wafer cassette 500, or transports it to another wafer used to store the tested wafer assembly 300 box. Subsequently, the aforementioned steps can be performed on another wafer assembly 300 , and all the wafer assemblies 300 in the wafer cassette 500 can be tested by repeating this cycle. The step of combining the wafer 100 with the first vacuum release type substrate 200A and the step of removing the adhesion between the second vacuum release type substrate 200B and the wafer 100 may be performed simultaneously, or the former step is performed first and the latter step is performed.

In the above-mentioned embodiments, the wafer assembly or the first/second vacuum release type substrate can be transported by a robotic arm with a Bernoulli chuck, a vacuum chuck or other end effectors capable of absorbing the surface of the substrate. It should be noted that the robotic arm referred to in this case generally refers to a mechanism or system that can be used to transport wafer assemblies or first/second vacuum release substrates. In some embodiments, in the process of combining the vacuum release type substrate with the surface of the wafer 100, a downward force must be applied by the robot arm 400, and the applied downward force is controlled between an upper limit and a lower limit. value between. If the applied force is too large, the wafer 100 will be damaged. If the applied force is too small, the attachment surface of the vacuum release type substrate may not be completely attached to the surface of the wafer 100, so that it is applied to the surface of the wafer 100. Insufficient adhesion may cause the wafer 100 and the vacuum release substrate to be separated from each other during subsequent processing or transportation.

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

S11~S17: Steps

Claims (14)

A wafer testing method suitable for testing a wafer which constitutes a wafer assembly with a first vacuum release type substrate, the first vacuum release type substrate having an attachment surface and a back surface opposite to the attachment surface , the attachment surface of the first vacuum-releasing substrate is attached to the back surface of the wafer with an adhesive force, the adhesive force is sensitive to air pressure, and the wafer testing method includes: transporting the wafer assembly to a first vacuum-released substrate with a robotic arm wafer chuck, wherein the back side of the first vacuum release type substrate faces the first wafer chuck, and the front side of the wafer faces up; transporting a second vacuum release type substrate to the robot arm or another robot arm above the first wafer chuck, and make the attachment surface of the second vacuum release type substrate face the front of the wafer; make the attachment surface of the second vacuum release type substrate attach to the wafer of the wafer assembly front side; using the first wafer chuck to provide a negative pressure to the first vacuum release type substrate of the wafer assembly to remove the adhesion between the first vacuum release type substrate and the wafer; using the robotic arm or The other robotic arm transports the second vacuum release type substrate and the wafer to a second wafer chuck, and uses the second wafer chuck to provide a suction force on the wafer; the robotic arm or the wafer Another robot arm provides a negative pressure to the second vacuum release type substrate to remove the adhesion between the second vacuum release type substrate and the wafer; take out the second vacuum with the robot arm or the other robot arm releasing the substrate to expose the front side of the wafer; and testing the wafer with a testing device. In the wafer testing method described in Claim 1, the robotic arm takes out the wafer assembly from a wafer cassette and transports the wafer assembly to the first wafer chuck. According to the wafer testing method described in Claim 1, during the process of transporting the wafer assembly to the first wafer chuck, the robotic arm is adsorbed to the back surface of the first vacuum release type substrate of the wafer assembly. The wafer testing method as described in Claim 1, before the step of attaching the attachment surface of the second vacuum release type substrate to the front surface of the wafer of the wafer assembly, further includes: performing an alignment step, so that the The attachment surface of the second vacuum release substrate is aligned with the front side of the wafer. In the wafer testing method described in claim 1, in the step of transporting the second vacuum release type substrate and the wafer to the second wafer chuck, the back side of the wafer is kept facing down, and the method is further comprising: capturing an image of the second vacuum-releasing substrate and the wafer with a camera module; and analyzing the image to determine whether there is a gap between the second vacuum-releasing substrate and the wafer, if the If there is a gap, the robotic arm is used to turn over the second vacuum-releasing substrate and the wafer so that the back side of the wafer faces upward. The wafer testing method as described in claim 1, after placing the wafer assembly on the first wafer chuck, further includes: using a warpage detection device to detect whether the warpage of the wafer is less than a warpage threshold value, if the warp degree of the wafer is less than the warp threshold value, the robot arm or the other robot arm is used to transport the second vacuum release type substrate to the top of the first wafer chuck. The wafer testing method according to Claim 6, wherein the warpage detection device is a light interruption sensing device. The wafer testing method as described in Claim 7, wherein the step of detecting the warpage of the wafer includes: arranging a light emitter and a light receiver of the light interruption sensing device on the first wafer Opposite sides of the round chuck, an optical path is defined between the optical emitter and the optical receiver; and rotating the first wafer chuck, if the optical path is during the rotation of the first wafer chuck If it is not blocked by the wafer, it is determined that the warpage of the wafer is less than the warpage threshold. The wafer testing method as described in Claim 1, wherein, in the step of attaching the attachment surface of the second vacuum release type substrate to the front side of the wafer, further comprising: attaching the second vacuum release type substrate along the A direction perpendicular to the surface applies a pressure to the wafer so that the attachment surface of the second vacuum release substrate is attached to the front surface of the wafer. The wafer testing method as claimed in claim 9, wherein the robot arm or the other robot arm moves downward along the vertical direction to exert the pressure on the wafer. The wafer testing method as claimed in claim 9, wherein the first wafer chuck moves upward along the vertical direction to apply the pressure to the wafer. The wafer testing method as described in Claim 1, wherein, before the step of attaching the attachment surface of the second vacuum release type substrate to the front surface of the wafer, it further includes: performing an alignment step, so that the second A vacuum release type substrate is aligned to the wafer. The wafer testing method as described in claim 1, after the testing device tests the wafer, further comprising: the robot arm or the other robot arm transports the second vacuum release type substrate to the second wafer chuck above, and make the attachment surface of the second vacuum release type substrate face the front side of the wafer; making the attachment surface of the second vacuum release type substrate attached to the front side of the wafer; removing the adsorption force between the second wafer chuck and the wafer; transporting the first robot arm or the other robot arm Two vacuum release type substrates and the wafer are placed above the first wafer chuck, and the back side of the wafer is facing down; the attachment surface of the first vacuum release type substrate located on the first wafer chuck is attaching to the back side of the wafer; using the robotic arm or the other robotic arm to provide a negative pressure to the second vacuum-releasing substrate to remove the adhesion between the second vacuum-releasing substrate and the wafer; The robot arm or the other robot arm takes out the second vacuum release type substrate; and the robot arm or the other robot arm takes out the wafer assembly from the first wafer chuck. The wafer testing method as described in claim 13, wherein, after taking out the wafer assembly from the first wafer chuck, it further includes: using the robot arm or the other robot arm to transport the wafer assembly to a wafer round box.

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