TWI705229B - Wafer thickness detecting device and method thereof - Google Patents

Abstract

The invention discloses a wafer thickness detecting device comprising a first detecting group, a second detecting group and a calculating module. The wafer has a known diameter length M and an unknown thickness d1. The angle between the wafer and the horizontal plane is unknown θ1. The first detecting group includes a first transmitting component and a first receiving component. The first radiating element emits a horizontal light source to the wafer, and the first receiving component measures a vertical projection amount of the wafer in a vertical plane. The second detecting group includes a second transmitting component and a second receiving component. The second emitting element emits a known θ2 source to the wafer at an angle to the horizontal plane. The second receiving component measures the vertical projection amount of the wafer relative to the light source of the second emitting element. The calculation module is connected to the first receiving component and the second receiving component signal, and receives the vertical projection amount measured by the first receiving component and the second receiving component, and substitutes the wafer diameter length M and the second emitting component light source angle θ2, Calculate the thickness of the wafer d1.

Description

Wafer thickness detecting device and method

This creation is a wafer thickness detection device and method, especially a wafer thickness detection device and method that calculates the wafer thickness by illuminating the wafer and measuring the projection amount.

Various manufacturing processes in the semiconductor industry, such as epitaxy, etching, etc., have very precise requirements for thickness. If the wafer has an appropriate thickness, it can effectively increase the yield.

But in fact, in the whole process, the wafer is continuously undergoing different processes. Due to factors such as transportation, process processing, human operations, etc., defects such as wafer thickness changes, wafer cracks, and wafer damage may occur. Sometimes defects Quite subtle is only reflected in the small thickness difference, but it will eventually cause the yield to drop.

Therefore, to ensure that the wafer has the proper thickness, that is, the thickness of the wafer can fall within the standard thickness range, in addition to improving the yield, it can also reduce the damage of the wafer in the machine, avoiding the contamination of the machine, and saving extra The labor and time cost of processing.

Therefore, accurate and rapid pre-measurement of wafer thickness before each process will help improve the process efficiency of the semiconductor industry.

A conventional method is to use the blocking light sensing method to measure the thickness of the wafer, that is, the laser beam is used to penetrate the wafer to measure the deviation of the light spot, and then the wafer thickness is obtained by inverse calculation. Recently, the thickness of the wafer may have been smaller than the laser spot, causing the measurement of this method to be inaccurate.

Another common method for measuring wafer thickness is to set up a measuring machine, place the wafers one by one on the carrier plate of the measuring machine, and then use the probe on the measuring machine to perform Wafer thickness measurement, but the disadvantages of this probe measurement method are as follows:

1. Additional procedures must be added: the robot arm is used to move the wafer back and forth between the wafer boat and other storage devices and the measuring machine, and a slight displacement deviation during the movement may cause the wafer transfer to fail, slide, and drop. Pieces, missing corners, fragments, etc.

2. Additional machines must be added: increasing equipment costs and making the manufacturing process laborious and time-consuming.

In addition, since the wafer may not be perfectly level when placed, it may have an angle with the horizontal plane. How to take the non-horizontal and slightly tilted condition of the wafer into account to obtain the true wafer thickness is an urgent problem in the industry. .

Therefore, how to solve the above-mentioned conventional problems and deficiencies is the direction that the creators of this creation and the related manufacturers engaged in this industry urgently want to study and improve.

Therefore, a device and method that can conveniently, accurately and safely detect the thickness of a wafer is one of the research and development goals of the relevant industry.

Therefore, the purpose of this creation is to provide a device and method that can detect wafer thickness conveniently, accurately and safely.

This invention creates a wafer thickness detection device, which is configured in a semiconductor machine. A wafer has a known diameter length M and an unknown thickness d1. The angle between the wafer and the horizontal plane is unknown θ1. The wafer The thickness detection device includes a first detection group, a second detection group, and a calculation module. The first detection group includes a first emitting element and a first receiving element. The first emitting element emits A horizontal light source to the wafer, the first receiving element measures the amount of vertical projection produced by a vertical surface of the wafer, the second detection group includes a second emitting element and a second receiving element, the first The two emitting elements emit a light source with a known angle θ2 from the horizontal plane to the wafer. The second receiving element measures the vertical projection of the wafer to the light source of the second emitting element. The calculation module and the The first receiving element and the second receiving element are signal-connected to receive the vertical projection measured by the first receiving element and the second receiving element, and substitute the known wafer diameter length M and the known second The angle θ2 of the light source emitted by the emitting element is calculated to obtain the thickness d1 of the wafer.

In the wafer thickness detection device of the present invention, the first emitting element and the second emitting element are located on the same vertical line.

In the wafer thickness detection device of this creation, in the calculation module, set the relational expression group (1):

θ1＜2°;

θ2＜2°;

β=π÷180=0.0175;

sinθ1≅ β×θ1;

cosθ1≅1;

sinθ2≅β×θ2;

cosθ2≅ 1 (1), (1),

Wherein, θ1 is the unknown angle between the wafer and the horizontal plane, θ2 is the known angle between the light source emitted by the second emitting element and the horizontal plane, and β is a known coefficient.

In the wafer thickness detection device of this invention, in the calculation module, the relationship between the reading value of the first receiving element and the vertical projection amount of the wafer on the vertical plane caused by the first transmitting element is set ( 2):

α×Y1 = M×sinθ1+d1×cosθ1 (2),

Among them, α is a known unit conversion parameter, Y1 is the known reading value of the first receiving element, M is the known wafer diameter and length, θ1 is the unknown angle between the wafer and the horizontal plane, and d1 is unknown The thickness of the wafer.

In the wafer thickness detection device of the present invention, in the calculation module, the reading value of the second receiving element is set, and the second emitting element makes the wafer on the vertical plane relative to the light source of the second emitting element The relationship between the vertical projection amount produced (3):

α×Y2 = M×sin(θ2-θ1)+d1×cos(θ2-θ1) (3),

Among them, α is a known unit conversion parameter, Y2 is a known reading value of the second receiving element, M is a known wafer diameter and length, and θ2 is a known light source emitted by the second emitting element and The angle between the horizontal plane, θ1 is the unknown angle between the wafer and the horizontal plane, and d1 is the thickness of the unknown wafer.

In the wafer thickness detection device of this creation, in the calculation module, the conditional expression group (1) is substituted into the relational expression (2), and the relational expression (4) is calculated:

α×Y1 = M×sinθ1+d1×cosθ1

= M×sinθ1+d1

= M × β × θ1 + d1 (4),

Among them, α is the known unit conversion parameter, Y1 is the known reading value of the first receiving element, M is the known wafer diameter and length, β is the known coefficient, and θ1 is the unknown wafer and horizontal plane. The included angle, d1 is the thickness of the unknown wafer.

In the wafer thickness detection device of this creation, in the calculation module, the conditional expression group (1) is substituted into the relational expression (3), and the relational expression (5) is calculated:

α×Y2 = M×sin(θ2-θ1)+d1×cos(θ2-θ1)

= M×β×(θ2-θ1)+d1 (5),

Among them, α is the known unit conversion parameter, Y2 is the known reading value of the second receiving element, M is the known wafer diameter and length, β is the known coefficient, and θ2 is the known second transmitter. The angle between the light source emitted by the element and the horizontal plane, θ1 is the unknown angle between the wafer and the horizontal plane, and d1 is the thickness of the unknown wafer.

In the wafer thickness detection device of this creation, in the calculation module, the relationship (4) and the relationship (5) are subtracted, and the relationship (6) is calculated:

α×(Y1-Y2) = M×β×(2θ1-θ2),

θ1 =[α×(Y1-Y2)÷(M×β) + θ2]÷2

=[sin-1(α×(Y1-Y2)÷M) + θ2] ÷2 (6),

Among them, θ1 is the unknown angle between the wafer and the horizontal plane, α is the known unit conversion parameter, Y1 is the known reading value of the first receiving element, Y2 is the known reading value of the second receiving element, M is a known wafer diameter and length, β is a known coefficient, and θ2 is a known angle between the light source emitted by the second emitting element and the horizontal plane.

In the wafer thickness detection device of this creation, in the calculation module, substitute relation (6) into relation (4):

θ1 =[sin-1(α×(Y1-Y2)÷M) + θ2] ÷2 (6),

d1=α×Y1-M×sinθ1 (4),

Among them, θ1 is the unknown angle between the wafer and the horizontal plane, α is the known unit conversion parameter, Y1 is the known reading value of the first receiving element, Y2 is the known reading value of the second receiving element, M is the known diameter and length of the wafer, and θ2 is the known angle between the light source emitted by the second emitting element and the horizontal plane, and the wafer thickness d1 is known.

This invention creates a wafer thickness detection method, which is suitable for a semiconductor machine. A wafer has a known diameter length M and an unknown thickness d1. The angle between the wafer and the horizontal plane is unknown θ1, and the wafer thickness The detection method includes the following steps:

A first detection step: a first emitting element emits a horizontal light source to the wafer, and then a first receiving element measures the amount of vertical projection produced by a vertical surface of the wafer;

A second detection step: a second emitting element emits a light source with a known angle θ2 from the horizontal plane to the wafer, and then a second receiving element measures the distance between the wafer and the light source of the second emitting element Vertical projection; and

A calculation step: a calculation module receives the vertical projections measured by the first receiving element and the second receiving element, and substitutes the known wafer diameter length M and the known amount emitted by the second transmitting element The light source included angle θ2, and the thickness d1 of the wafer is calculated.

The effect of this creation is to use the vertical projection measured by the first receiving element and the second receiving element to substitute the known wafer diameter length M and the known angle between the light source emitted by the second emitting element θ2, the thickness d1 of the wafer is calculated, and the purpose of conveniently, accurately and safely detecting the thickness of the wafer is indeed achieved.

The aforementioned and other technical content, features and effects of this creation will be clearly presented in the following detailed description of a preferred embodiment with reference to the drawings.

Before this creation is described in detail, it should be noted that in the following description, similar elements are represented by the same numbers.

Referring to FIG. 1, a wafer thickness detection device 1 of the present invention is configured in a semiconductor machine 2. The semiconductor machine 2 of this creative crystal usually uses the wafer carrier load port to transfer the LPT (Load Port Transfer) machine, and can also be set up on the thin film process machine, the yellow light process machine, the etching process machine, and the chemical polishing process machine. 、On the diffusion process machine, it is convenient to measure the thickness during the process.

A wafer 3 has a known diameter length M and an unknown thickness d1, and the angle between the wafer 3 and the horizontal plane is unknown θ1.

The wafer thickness detection device 1 includes a first detection group 11, a second detection group 12, and a calculation module 13.

The first detection group 11 includes a first emitting element 111 and a first receiving element 112. The first emitting element 111 emits a horizontal light source to the wafer 3, and the first receiving element 112 measures the wafer 3 The amount of vertical projection produced on a vertical plane.

The second detection group 12 includes a second emitting element 121 and a second receiving element 122. The second emitting element 121 emits a light source with a known angle θ2 from the horizontal plane to the wafer 3, and the second receiving element 122 measures the vertical projection of the wafer 3 relative to the light source of the second emitting element 121.

It is worth mentioning that the wafer 3 is fixed in the wafer boat, and the wafer boat is covered with a wafer transfer box 4 (SMIF Pod). The wafer transfer box 4 is placed on the semiconductor machine 2 and the semiconductor machine 2 will Open the wafer transfer box 4. The first detection group 11 and the second detection group 12 are fixedly installed on the semiconductor machine 2. The first transmitting element 111 is arranged opposite to the first receiving element 112, and the second transmitting element 121 is arranged opposite to the first receiving element 112.

By partially shielding the light source emitted by the first emitting element 111 and the second emitting element 121 by the wafer 3, the first receiving element 112 and the second receiving element 122 then receive other unshielded light sources. The area of the light source emitted by the first emitting element 111 and the second emitting element 121 is greater than the thickness of the single wafer 3. In addition, when the number of the first detection group 11 and the second detection group 12 is multiple, they can correspond to the position of each wafer 3, and the thickness of multiple wafers 3 can be measured at the same time. However, only one group is shown in Figure 1. It is worth mentioning that the first emitting element 111 and the second emitting element 121 are not particularly limited here. They can be laser light transmitters, infrared transmitters, etc., and the sending and receiving modes can be separate sending and receiving modes, One-piece method, retro-reflective transmission and reception methods, etc.

It is further explained that the first emitting element 111 and the second emitting element 121 are located on the same vertical line. It is worth mentioning that the first detection group 11 and the second detection group 12 can also be fixed on both sides of the semiconductor machine 2 (not shown) so as to facilitate the transfer of the wafer transfer box 4 .

In addition, the thickness measurement can be performed when the wafer transfer box 4 is not opened. The first emitting element 111 and the second emitting element 121 emit a light source that can penetrate the wafer transfer box 4, and the wafer 3 Measure the thickness and calculate after deducting the light refraction error of the wafer transfer box 4. If a wafer 3 with abnormal thickness is found, then open the wafer transfer box 4 and take out the specified wafer 3 to reduce the opening time of the wafer transfer box 4 To avoid pollution.

The calculation module 13 is connected to the signals of the first receiving element 112 and the second receiving element 122, receives the vertical projections measured by the first receiving element 112 and the second receiving element 122, and substitutes it into a known crystal. The diameter and length M of the circle 3 and the known angle θ2 of the light source emitted by the second emitting element 121 are calculated to obtain the thickness d1 of the wafer 3.

With reference to Figures 2 and 3, in the wafer thickness detection device 1 of the present invention, since the angle between the wafer 3 and the horizontal plane is extremely small, the second emitting element 121 is also close to the level, so the calculation module 13 , You can set the following relational expression group (1), which will effectively simplify subsequent calculations:

θ1＜2°;

θ2＜2°;

β=π÷180=0.0175;

sinθ1≅ β×θ1;

cosθ1≅1;

sinθ2≅β×θ2;

cosθ2≅ 1 (1), (1),

Among them, θ1 is the unknown angle between the wafer 3 and the horizontal plane, θ2 is the known angle between the light source emitted by the second emitting element 121 and the horizontal plane, β is a known coefficient, and β will be used in later calculations. Simplify the calculation process.

Next, in the calculation module 13, set the relationship (2) between the reading value of the first receiving element 112 and the vertical projection amount of the wafer 3 on the vertical plane by the first transmitting element 111:

α×Y1 = M×sinθ1+d1×cosθ1 (2),

Among them, α is the known unit conversion parameter (mm/ADC), Y1 is the known reading value (ADC) of the first receiving element 112, M is the known diameter and length of the wafer 3, and θ1 is the unknown The angle between the wafer 3 and the horizontal plane, d1 is the unknown thickness of the wafer 3.

Then, in the calculation module 13, set the reading value of the second receiving element 122 to be perpendicular to the vertical plane of the wafer 3 relative to the light source of the second emitting element 121 by the second emitting element 121 Relational equation of projection amount (3):

α×Y2 = M×sin(θ2-θ1)+d1×cos(θ2-θ1) (3),

Among them, α is the known unit conversion parameter (mm/ADC), Y2 is the known reading value (ADC) of the second receiving element 122, M is the known diameter and length of the wafer 3, and θ2 is the known The angle between the light source emitted by the second emitting element 121 and the horizontal plane, θ1 is the unknown angle between the wafer 3 and the horizontal plane, and d1 is the unknown thickness of the wafer 3.

Then, in the calculation module 13, the conditional expression group (1) is substituted into the relational expression (2), and the relational expression (4) is calculated:

α×Y1 = M×sinθ1+d1×cosθ1

= M×sinθ1+d1

= M×β×θ1+d1 (4),

Among them, α is the known unit conversion parameter (mm/ADC), Y1 is the known reading value (ADC) of the first receiving element 112, M is the known diameter and length of the wafer 3, and β is the known coefficient , Θ1 is the unknown angle between the wafer 3 and the horizontal plane, and d1 is the thickness of the unknown wafer 3.

Then, in the calculation module 13, the conditional expression group (1) is substituted into the relational expression (3), and the relational expression (5) is calculated:

α×Y2 = M×sin(θ2-θ1)+d1×cos(θ2-θ1)

= M×β×(θ2-θ1)+d1 (5),

Among them, α is the known unit conversion parameter (mm/ADC), Y2 is the known reading value (ADC) of the second receiving element 122, M is the known diameter and length of the wafer 3, and β is the known coefficient , Θ2 is the known angle between the light source emitted by the second emitting element 121 and the horizontal plane, θ1 is the unknown angle between the wafer 3 and the horizontal plane, and d1 is the unknown thickness of the wafer 3.

Then, in the calculation module 13, the relationship (4) is subtracted from the relationship (5), and the relationship (6) is calculated:

α×(Y1-Y2) = M×β×(2θ1-θ2),

θ1 =[α×(Y1-Y2)÷(M×β) + θ2]÷2

=[sin-1(α×(Y1-Y2)÷M) + θ2] ÷2 (6),

Among them, θ1 is the unknown angle between the wafer 3 and the horizontal plane, α is the known unit conversion parameter (mm/ADC), Y1 is the known reading value (ADC) of the first receiving element 112, and Y2 is the known The reading value (ADC) of the second receiving element 122, M is the known diameter and length of the wafer 3, β is a known coefficient, and θ2 is the known angle between the light source emitted by the second emitting element 121 and the horizontal plane .

In the wafer thickness detection device 1 of the present invention, in the calculation module 13, the relational expression (6) is substituted into the relational expression (4):

θ1 =[sin-1(α×(Y1-Y2)÷M) + θ2] ÷2 (6),

d1=α×Y1-M×sinθ1 (4),

Among them, θ1 is the unknown angle between the wafer 3 and the horizontal plane, α is the known unit conversion parameter (mm/ADC), Y1 is the known reading value (ADC) of the first receiving element 112, and Y2 is the known The reading value (ADC) of the second receiving element 122, M is the known diameter and length of the wafer 3. In the first preferred embodiment, M is 200mm, and θ2 is the known second transmitting element 121 The angle between the emitted light source and the horizontal plane is used to determine the thickness d1 of the wafer 3.

With reference to Fig. 4, a method for detecting the thickness of wafer 3 according to the present invention includes the following steps:

A first detection step 100: the first emitting element 111 emits a horizontal light source to the wafer 3, and then the first receiving element 112 measures the vertical projection of the wafer 3 on the vertical plane.

A second detection step 200: the second emitting element 121 emits a light source with a known angle θ2 from the horizontal plane to the wafer 3, and then the second receiving element 122 measures that the wafer 3 is relative to the second emitting element 121 The amount of vertical projection of the light source.

A calculation step 300: the calculation module 13 receives the vertical projections measured by the first receiving element 112 and the second receiving element 122, and substitutes the known diameter length M of the wafer 3 and the known second The angle θ2 of the light source emitted by the emitting element 121 is calculated to obtain the thickness d1 of the wafer 3.

It is worth noting that the first detection step 100 and the second detection step 200 can be sequenced interchangeably, or can be performed simultaneously. Anyone with ordinary knowledge in the field can reasonably deduce it according to the manual of this creation. Such transformations are still within the scope of this creation.

To sum up, the effect of this creation is to use the vertical projection measured by the first receiving element 112 and the second receiving element 122 into the known diameter and length M of the wafer 3 and the known second The angle θ2 of the light source emitted by the emitting element 121 is calculated to obtain the thickness d1 of the wafer 3, and the purpose of conveniently, accurately and safely detecting the thickness of the wafer 3 is indeed achieved.

In addition, since the wafer 3 may not be perfectly level when placed, how to take the non-horizontal and slightly inclined condition of the wafer 3 into account to obtain the true wafer thickness d1. The above description will clearly solve this problem. Really achieve the purpose of cost creation.

However, the above are only the preferred embodiments of this creation, and should not be used to limit the scope of implementation of this creation, that is, all simple equivalent changes and modifications made according to the scope of patent application and description of the invention in this creation are all It is still within the scope of this creation patent.

1 Wafer thickness detection device 11 First detection group 111 First transmission component 112 First reception component 12 Second detection group 121 2nd reception component 13 Compute module 2 4 Wafer transport box M Wafer diameter length θ2 The angle between the light source emitted by the second emitting element and the horizontal plane θ1 The angle between the wafer and the horizontal plane d1 The second detection step 200 The detection step 300

Figure 1 is a perspective view illustrating the first preferred embodiment of the inventive wafer thickness detection device;

Figure 2 is a schematic diagram illustrating the first detection group and the second detection group of the first preferred embodiment;

FIG. 3 is a schematic diagram illustrating the equivalent schematic diagram of the first detection group and the second detection group of the second preferred embodiment; and

FIG. 4 is a flowchart illustrating the first preferred embodiment of the method for detecting the thickness of a creative wafer.

111 First emitting element 121 Second emitting element 3 Wafer M Wafer diameter length θ1 The angle between the wafer and the horizontal plane θ2 The angle between the light source emitted by the second emitting element and the horizontal plane d1 Wafer thickness

Claims (10)

A wafer thickness detection device is configured in a semiconductor machine. A wafer has a known diameter length M and an unknown thickness d1. The angle between the wafer and the horizontal plane is an unknown θ1. The wafer thickness detection The measurement device includes: a first detection group, including a first emitting element and a first receiving element, the first emitting element emits a horizontal light source to the wafer, and the first receiving element measures the wafer The amount of vertical projection produced by the vertical plane; a second detection group, including a second emitting element and a second receiving element, the second emitting element emits a light source with a known angle θ2 from the horizontal plane to the wafer, The second receiving element measures the vertical projection of the light source of the wafer with respect to the second emitting element; and a calculation module connected to the first receiving element and the second receiving element signal to receive the first The vertical projection measured by the receiving element and the second receiving element is substituted into the known wafer diameter length M and the known angle θ2 of the light source emitted by the second emitting element, and the thickness of the wafer is calculated d1. According to the wafer thickness detection device described in claim 1, wherein the first emitting element and the second emitting element are located on the same vertical line. According to the wafer thickness detection device described in item 2 of the scope of patent application, in the calculation module, set the relational expression group (1): θ1＜2°; θ2＜2°; β=π÷180= 0.0175; sinθ1≅ β×θ1; cosθ1≅1; sinθ2≅β×θ2; cosθ2≅1 where the angle of the second θ1 and the plane of the θ2 is known to be 1 The angle between the light source and the horizontal plane, β is a known coefficient. The wafer thickness detection device according to claim 3, wherein, in the calculation module, the reading value of the first receiving element and the first transmitting element are set so that the wafer is generated on a vertical plane The relationship formula (2) of the vertical projection amount: α×Y1 = M×sinθ1+d1×cosθ1 (2), where α is the known unit conversion parameter, and Y1 is the known reading value of the first receiving element , M is the known wafer diameter and length, θ1 is the unknown angle between the wafer and the horizontal plane, and d1 is the unknown thickness of the wafer. The wafer thickness detection device according to claim 4, wherein, in the calculation module, the reading value of the second receiving element is set, and the second transmitting element makes the wafer relative to the first The relationship between the vertical projection amount produced by the vertical plane of the light source of the two emitting elements (3): α×Y2 = M×sin(θ2-θ1)+d1×cos(θ2-θ1) (3), where α is Known unit conversion parameters, Y2 is the known reading value of the second receiving element, M is the known wafer diameter length, θ2 is the known angle between the light source emitted by the second emitting element and the horizontal plane, θ1 is the unknown angle between the wafer and the horizontal plane, and d1 is the thickness of the unknown wafer. According to the wafer thickness detection device described in item 5 of the scope of patent application, in the calculation module, the conditional formula group (1) is substituted into the relational formula (2), and the relational formula (4) is calculated: α ×Y1 = M×sinθ1+d1×cosθ1 = M×sinθ1+d1 = M×β×θ1+d1 (4), where α is the known unit conversion parameter of the known element, and Y1 Read the value, M is the known wafer diameter and length, β is the known coefficient, θ1 is the unknown angle between the wafer and the horizontal plane, and d1 is the unknown thickness of the wafer. According to the wafer thickness detection device described in item 6 of the scope of patent application, in the calculation module, the conditional expression group (1) is substituted into the relational expression (3), and the relational expression (5) is calculated: α ×Y2 = M×sin(θ2-θ1)+d1×cos(θ2-θ1) = M×β×(θ2-θ1)+d1 (5), where α is a known unit conversion parameter, and Y2 is a known unit conversion parameter. Knowing the reading value of the second receiving element, M is the known wafer diameter and length, β is the known coefficient, θ2 is the known angle between the light source emitted by the second emitting element and the horizontal plane, and θ1 is unknown The angle between the wafer and the horizontal plane, d1 is the thickness of the unknown wafer. According to the wafer thickness detection device described in item 7 of the scope of patent application, in the calculation module, the relationship (4) and the relationship (5) are subtracted, and the relationship (6) is calculated: α×(Y1-Y2) = M×β×(2θ1-θ2), θ1 =[α×(Y1-Y2)÷(M×β) + θ2]÷2 =[sin-1(α×(Y1- Y2)÷M) + θ2] ÷2 (6), where θ1 is the unknown angle between the wafer and the horizontal plane, α is the known unit conversion parameter, and Y1 is the known reading value of the first receiving element. Y2 is the known reading value of the second receiving element, M is the known wafer diameter and length, β is a known coefficient, and θ2 is the known angle between the light source emitted by the second emitting element and the horizontal plane. According to the wafer thickness detection device described in item 8 of the scope of patent application, in the calculation module, the relational expression (6) is substituted into the relational expression (4): θ1 =[sin-1(α×(Y1) -Y2)÷M) + θ2] ÷2 (6), d1=α×Y1-M×sinθ1 The conversion between the plane and the angle (4) is the known angle of α, where the angle of α is unknown, and the angle of θ is unknown. Y1 is the known reading of the first receiving element, Y2 is the known reading of the second receiving element, M is the known wafer diameter and length, and θ2 is the known emitted by the second transmitting element. The angle between the light source and the horizontal plane, and the wafer thickness d1. A method for detecting wafer thickness is suitable for a semiconductor machine. A wafer has a known diameter length M and an unknown thickness d1. The angle between the wafer and the horizontal plane is unknown θ1. The wafer thickness detection The method includes the following steps: A first detection step: a first emitting element emits a horizontal light source to the wafer, and then a first receiving element measures the amount of vertical projection produced by a vertical surface of the wafer; Two detection steps: a second emitting element emits a light source with a known angle θ2 from the horizontal plane to the wafer, and then a second receiving element measures the vertical projection of the wafer with respect to the light source of the second emitting element And a calculation step: a calculation module receives the vertical projections measured by the first receiving element and the second receiving element, and substitutes the known wafer diameter length M and the known second transmitting element The angle θ2 of the emitted light source is calculated to obtain the thickness d1 of the wafer.

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