A wafer positioning and detection method for semiconductor wet process equipment

Abstract

This invention discloses a wafer positioning and detection method for semiconductor wet process equipment, comprising the following steps: calibration of detection algorithm data; placing a wafer cassette containing wafers at known positions in a housing; scanning the wafer cassette at a set speed and direction, and recording the time of each trigger signal; processing the acquired trigger signals; in the calibration state, calculating the spacing between adjacent layers of the wafer cassette and the position of the first layer wafer based on the first processed signal and the relative position of the known wafers; entering the working state, placing a wafer cassette containing wafers at unknown positions in the housing; scanning the wafer cassette at a set speed and direction, and recording the time of each trigger signal; processing the acquired trigger signals; and obtaining the relative position information of all wafers within the wafer cassette. This invention solves the problem of inaccurate positioning and detection when wafers are tilted within a wafer cassette containing a fluid medium, providing accurate positioning and detection for subsequent wafer handling.

Description

Technical Field

[0001] This invention belongs to the field of wafer positioning and inspection technology, and in particular relates to a wafer positioning and inspection method for semiconductor wet process equipment. Prior Technology

[0002] In existing wet process applications, some equipment uses a "wet-in, wet-out" wafer transfer scheme, where wafer cassettes are placed in a tank filled with liquid, and a robotic arm retrieves wafers from the liquid. In current practices, the equipment does not perform wafer positioning detection; the wafer position and quantity are manually input into the controller. This method suffers from an asymmetry between the input information and the actual wafer information in the cassette, potentially leading to collisions during wafer retrieval by the robotic arm, thereby damaging the robotic arm or the wafers. Therefore, effective detection of the wafer status within the cassette is necessary to ensure accurate and safe wafer retrieval and transport by the robotic arm.

[0003] In addition, the above-mentioned "wet in, wet out" transmission scheme faces the following difficulties in achieving automatic detection of wafer position and quantity: (1) To ensure the stability of the wafer position in the liquid and facilitate transmission, the wafer cassette opening is usually facing upwards and the wafer is placed at an angle, which makes wafer positioning detection difficult; (2) After the wafer cassette is placed or loaded, the wafer will shake in the liquid, causing the sensor's detection signal to have a positional deviation and the wafer position calculation to be incorrect; (3) The wafer is subject to buoyancy in the liquid and or there is a suction force between the wafer and the wafer cassette, which causes the position of each layer of wafers in the wafer cassette to be uneven, making it difficult to detect the wafer position. (4) When the wafer is in the liquid and the sensor is outside the liquid, the sensor is easily affected by ambient light and liquid surface fluctuations, which will also cause positional deviation of the sensor signal; (5) Some wafer substrate materials have high transparency and thin thickness, such as SiC or glass, making it difficult to trigger the sensor signal, with a short trigger time, and more susceptible to the influence of liquid fluctuations, resulting in positional deviation of the sensor signal and making positional calculation difficult; (6) In order to detect wafers with high transparency and thin thickness, the sensor light intensity is usually increased or the threshold is lowered, which makes the sensor susceptible to the influence of reflected light from other objects, such as wafer cassette bases and water waves. (7) Conventional wafer detection sensors cannot perform effective wafer detection when the medium changes. For example, some sensors cannot be immersed in water for detection, or they can be immersed in water, but due to the change of the medium, the light propagation path changes and they cannot detect stably and accurately. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides a wafer positioning and detection method for semiconductor wet process equipment, which can adapt to wafer positioning and detection in fluid media, is accurate, and can adapt to different types of wafer positioning and detection.

[0005] The technical solution adopted by this invention to solve its technical problem is: a wafer positioning and detection method for semiconductor wet processing equipment, comprising the following steps:

[0006] The detection algorithm data is calibrated. A wafer cassette containing wafers at known locations is placed inside a housing containing a fluid medium. The wafer cassette has a multi-layered structure for placing the wafers.

[0007] The sensor scans the chip box at a set speed and direction, and records the time of each triggered signal;

[0008] The acquired trigger signal is processed to remove interference signals caused by the fluid medium;

[0009] In calibration mode, based on the first processed signal after removing interference signals and the known relative positions of the wafers, the interval time between two adjacent layers of the wafer cassette and the signal trigger time of the first wafer layer are calculated. The interval distance between two adjacent layers of the wafer cassette and the position of the first wafer layer are also calculated based on the sensor scanning speed.

[0010] Upon entering the working state, a wafer cassette containing wafers at unknown locations is placed inside a housing containing a fluid medium. Sensors scan the wafer cassette at a set speed and direction, and record the time of each trigger signal.

[0011] The acquired trigger signal is processed to remove interference signals caused by the fluid medium;

[0012] The second processed signal, after removing interference signals in the working state, is converted into wafer position information according to the sensor scanning speed. It is then calculated with the spacing between two adjacent layers of the wafer cassette and the position of the first layer wafer obtained in the calibration state to obtain the relative position information of all wafers in the wafer cassette. The position information of the wafers in the wafer cassette is then transmitted to the controller to control the transmission device to pick up the wafers.

[0013] Furthermore, the trigger signal is a time-series signal, which is a rising edge, or a falling edge, or a combination of rising and falling edges.

[0014] Furthermore, the step of calculating the spacing between two adjacent layers of the wafer cassette and the position of the first wafer layer includes the following sub-steps:

[0015] Calculate the weighted average of at least multiple rising or falling edge time differences of the first processed signal after processing to obtain the interval time between two adjacent layers of the cassette.

[0016] Calculate the difference between the time interval of each rising or falling edge of the first processed signal and the time interval of the corresponding layer, and then take the weighted average of all differences to obtain the time of the first layer wafer;

[0017] Multiply the interval time between two adjacent layers of the wafer cassette and the time of the first wafer by the sensor scanning speed under calibration conditions to obtain the interval distance between two adjacent layers of the wafer cassette and the position of the first wafer.

[0018] Furthermore, the step of calculating the spacing between two adjacent layers of the wafer cassette and the position of the first wafer layer includes the following sub-steps:

[0019] Place the chip cassette within the sensor's detection range;

[0020] Obtain the distance Xa between the wafer placement surface within the wafer cassette terminal cavity slot layer structure and the edge of the wafer cassette frame terminal; obtain the distance Xt between the placement surfaces of adjacent cavity slot layer structures.

[0021] The sensor scans the wafers within the wafer cassette at a specific speed and records the time corresponding to the trigger signal at the edge of the wafer cassette border.

[0022] Record all wafer trigger signals and convert them into wafer position information relative to the edge of the wafer cassette edge, Xx, based on the sensor scan speed;

[0023] By determining whether Xx is located between (Xa+(k-1)Xt) and (Xa+kXt), where k is the layer number, the number of layers in the cavity trench structure of the wafer can be determined.

[0024] Alternatively, calculate the position Xk of all theoretical wafer placement surfaces relative to the wafer cassette edge, and determine that Xx is between Xk and Xk+1 to determine that the number of layers in the cavity trench structure where the wafer is located is K layers.

[0025] Furthermore, the interference signals include water wave interference signals and reflected light interference signals, wherein the water wave interference signals include water surface interference and / or wafer wobble interference.

[0026] Furthermore, the process of removing interference signals includes the following sub-steps:

[0027] Compare the time difference between adjacent rising or falling edges of each trigger signal and determine if it is less than the median value of all adjacent rising or falling edge time differences multiplied by a set coefficient. If the result is less than this, the trigger signal is filtered out.

[0028] and / or,

[0029] Compare the time difference between adjacent rising and falling edges of each trigger signal and determine whether it is greater than the median value of the time differences between all adjacent rising and falling edges multiplied by a set coefficient. If the result is greater, then the trigger signal is filtered out.

[0030] Furthermore, the step of obtaining the relative position of the wafer within the wafer cassette under the operating state includes the following sub-steps:

[0031] Multiply the time of all trigger signals by the sensor scanning speed during operation to obtain the positions of all trigger signals;

[0032] Subtract the first-layer wafer position obtained from calibration from all trigger signal positions, divide by the distance between two adjacent layers of the wafer cassette obtained from calibration, round the result to the nearest integer, and add one to obtain the relative positions of all wafers within the wafer cassette.

[0033] Furthermore, the signal emitted by the sensor is parallel or nearly parallel to the crystal plane direction. This ensures that the vertical distance between the sensor and the edge of each wafer within the wafer cassette is equal or nearly equal during movement.

[0034] Furthermore, the sensor is an optical sensor and is located outside the fluid medium of the housing.

[0035] Furthermore, the wafer substrate material is an opaque material, namely Si; or, the wafer substrate material is a transparent material, namely SiC or glass; the wafer thickness is 0.3mm-0.8mm, and the wafer diameter is 6 inches-12 inches.

[0036] Furthermore, the wafer is placed vertically in a container containing a fluid medium, with the angle between the wafer surface and the liquid surface being 45°-90°, and the wafer being completely submerged in the fluid medium.

[0037] Furthermore, the fluid medium is a transparent liquid, which is either pure water or a sodium hydroxide solution.

[0038] Furthermore, the sensor scanning direction is either an increasing or decreasing direction of the number of layers; the sensor scanning speed in the calibration state is the same as or different from the sensor scanning speed in the working state.

[0039] Furthermore, the wafer cassette can hold 50, 25, 13, or 12 wafers.

[0040] Furthermore, the step of the sensor scanning the cartridge at a set speed and direction can be performed before the cartridge is loaded into the working position of the corresponding transmission device in the housing, or after the cartridge is loaded into the working position of the corresponding transmission device in the housing, or during the process of loading the cartridge into the working position of the corresponding transmission device in the housing.

[0041] Furthermore, the tank is equipped with a liquid level sensor, which is used to monitor changes in the liquid level and the amount of change in the liquid level.

[0042] The present invention also discloses a semiconductor wet process apparatus, comprising:

[0043] The enclosure contains a fluid medium.

[0044] The wafer cassette, housed within a box, has a multi-cavity, slotted structure for placing wafers;

[0045] The sensor can move relative to the wafer cassette and detect the wafer's position information according to the detection method described above.

[0046] The beneficial effects of this invention are: 1) It solves the problem of inaccurate positioning and detection when wafers are tilted in a wafer cassette containing a fluid medium, providing accurate positioning and detection for subsequent wafer handling; 2) It solves the problems of water waves, reflected light, and large wafer position deviations, and can achieve positioning and detection of wafers of different sizes and types in water; 3) The equipment operates automatically, with high detection efficiency and reduced human error; 4) The presence, tilt, or stacking of wafers is determined by a sensor above the fluid medium. Simple Explanation of the Diagram

[0047] Figure 1 is a simplified diagram of the housing of the present invention.

[0048] Figure 2 is a flowchart of the wafer positioning and detection method of the present invention.

[0049] Figure 3 shows the sensor signal feedback diagram affected by water wave interference.

[0050] Figure 4 shows the sensor signal feedback diagram affected by other reflected light after reducing the number of wafers.

[0051] Figure 5 is a simplified diagram of the cassette of the present invention.

[0052] Figure 6 is a simplified diagram of the cassette of the present invention.

[0053] Figure 7 is a partial simplified diagram of the cassette of the present invention.

[0054] Figure 8 is a simplified diagram illustrating the principle of abnormal slice differentiation. Implementation

[0055] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0056] A wafer positioning and detection method for semiconductor wet process equipment includes the following steps:

[0057] The detection algorithm data is calibrated. A wafer cassette containing wafers at known locations is placed inside a housing 3. The housing 3 contains a fluid medium 5. The wafer cassette 2 has a multi-layer structure for placing wafers 1.

[0058] In this embodiment, wafer 1 is placed vertically inside the housing 3 containing fluid medium 5. Specifically, wafer 1 is placed vertically one by one inside the wafer cassette 2, with the angle between the wafer surface and the liquid surface being 45°-90°, and the fluid medium 5 completely submerging the wafer 1. The fluid medium 5 is a transparent liquid, which can be pure water or a sodium hydroxide solution. The substrate material of wafer 1 is an opaque material, such as Si, or it can be a transparent material, such as SiC or glass. The thickness of wafer 1 is 0.3mm-0.8mm, and the diameter of wafer 1 is 6 inches-12 inches. The number of layers in the wafer cassette 2 is 50, 25, 13, or 12. The step of placing the wafer cassette 2 inside the housing 3 can be either placing the wafer cassette 2 directly at the working position of the corresponding transmission device in the housing 3 (specifically, the position where the transmission device picks up and places wafers), or placing the wafer cassette 2 at the transfer position in the housing 3 and then loading it into the working position of the corresponding transmission device in the housing 3 (specifically, the position where the transmission device picks up and places wafers). The transmission device can specifically be a robotic arm.

[0059] Sensor 4 scans the chip box 2 at a set speed and direction, and records the time of each triggered signal;

[0060] In the above steps, the trigger signal is a time-series signal, which can be a rising edge, or a falling edge, or a combination of rising and falling edges.

[0061] In the above steps, the scanning direction of sensor 4 is either the direction of increasing layer number or the direction of decreasing layer number, which is not limited, as long as the scanning starts from the end side of wafer cassette 2; sensor 4 is set in the area outside the fluid medium 5 of housing 3, and sensor 4 can be an optical sensor, and the signal emitted by sensor 4 is parallel or nearly parallel to the crystal plane direction of wafer 1;

[0062] The step of the sensor 4 scanning the cartridge 2 according to the set speed and direction can be performed before, after, or during the loading of the cartridge 2 into the working position of the corresponding transmission device in the housing 3. The acquired trigger signal is processed to remove interference signals caused by the fluid medium 5.

[0063] The interference signals in the above steps include water wave interference signals and reflected light interference signals. Water wave interference signals include simple water surface interference, simple wafer wobble interference, and combined interference from both water surface interference and wafer wobble interference.

[0064] Water wave interference signal filtering is not limited to preliminary hardware condition filtering when the water surface interference signal is not within the sensor's detection range; reflected light interference signal filtering is not limited to a wafer housing mounting base material that is not a strongly reflective dark substrate.

[0065] The interference signal removal step in the above steps includes the following sub-steps: for the removal of dense small-segment interference signals caused by water waves and wafer shaking, compare the time difference between adjacent rising or falling edges of each trigger signal, and determine whether it is less than the median value of the time difference between all adjacent rising or falling edges multiplied by a set coefficient. If the result is less than, then the trigger signal is filtered out; the set coefficient can specifically be 0.5.

[0066] Of course, the above steps for removing interference signals may also include the following sub-steps: for removing large segments of reflected light interference signals such as those from the base, compare the time difference between adjacent rising and falling edges of each trigger signal, and determine whether it is greater than the median value of the time difference between all adjacent rising and falling edges multiplied by a set coefficient. If the result is greater, then the trigger signal is filtered out; the set coefficient can specifically be 1.5.

[0067] Of course, it can also be a combination of the two filtering methods mentioned above. That is, compare the time difference between adjacent rising or falling edges of each trigger signal and determine whether it is less than the median value of the time differences between all adjacent rising or falling edges multiplied by a set coefficient. If the result is less, then the trigger signal is filtered out. At the same time, compare the time difference between adjacent rising and falling edges of each trigger signal and determine whether it is greater than the median value of the time differences between all adjacent rising and falling edges multiplied by a set coefficient. If the result is greater, then the trigger signal is filtered out.

[0068] In calibration mode, based on the first processed signal after removing interference signals and the known relative position of wafer 1, the interval time between two adjacent layers of wafer cassette 2 and the signal trigger time of the first layer wafer are calculated. To adapt to detection calculations at different scanning speeds and increase the applicability of the algorithm, the time unit is converted to a distance unit, and the interval distance between two adjacent layers of wafer cassette 2 and the position of the first layer wafer are calculated based on the scanning speed of sensor 4.

[0069] Specifically, the above steps involve calculating the weighted average of the time differences of at least a number of rising or falling edges of the first processed signal after processing to obtain the interval time between two adjacent layers of wafer cassette 2; calculating the difference between the interval time of all rising or falling edges of the first processed signal and the corresponding layer number, and then taking the weighted average of all differences to obtain the time of the first layer wafer; multiplying the interval time between two adjacent layers and the time of the first layer wafer by the scanning speed of sensor 4 in the calibration state to obtain the distance between two adjacent layers of wafer cassette 2 and the position of the first layer wafer.

[0070] Upon entering the working state, the wafer cassette 2 containing the wafer 1 at an unknown location is placed inside the housing 3, which contains a fluid medium 5. The sensor 4 scans the wafer cassette 2 at a set speed and direction, and records the time of each trigger signal.

[0071] In the above steps, the scanning speed of sensor 4 can be the same as or different from the scanning speed of sensor 4 in the calibration state, and the direction must be consistent with that in the calibration state.

[0072] The acquired trigger signal is processed to remove interference signals caused by the fluid medium 5;

[0073] The interference signals and methods for filtering interference signals in the above steps are the same as those in the calibration steps, and will not be repeated here.

[0074] The second processed signal, after removing interference signals in the working state, is converted into wafer 1 position information according to the scanning speed of sensor 4. This information is then compared with the spacing distance between two adjacent layers of wafer cassette 2 and the position of the first wafer layer obtained in the calibration state to calculate the relative position of wafer 1 within wafer cassette 2.

[0075] The step of obtaining the relative position of wafer 1 in wafer cassette 2 under working conditions in the above steps includes the following sub-steps: multiply all trigger signal times by the scanning speed of sensor 4 under working conditions to obtain all trigger signal positions; subtract the first layer wafer position obtained by calibration from all trigger signal positions, divide by the distance between two adjacent layers of wafer cassette 2 obtained by calibration, round to the nearest integer, and add one to obtain the relative position information of all wafers 1 in wafer cassette 2.

[0076] The position signal of wafer 1 in wafer cassette 2 is transmitted to the controller to control the transmission device, which can be a robotic arm that picks up wafer 1.

[0077] To ensure the stable position of wafer 1 in the fluid medium 5 and facilitate transmission, wafer cassette 2 is typically placed with its opening facing upwards and at an angle. However, the relative position of the wafer cassette 2 base and sensor 4 makes structural calibration difficult. To reduce detection difficulty and simplify the detection structure, this invention places the wafer at a designated position and performs a pre-scan, i.e., performs detection algorithm data calibration, obtaining signals at known positions to calculate the spacing between adjacent layers of the wafer cassette and the position of the first-layer wafer. This method eliminates the requirement for the sensor and wafer positions to remain fixed, thus removing the step of structural calibration. Furthermore, changes to wafer transparency and thickness do not require recalibrating the detection algorithm data. Even if wafer cassette specifications (wafer spacing, quantity changes) or wafer size are altered, only a pre-scan calibration is needed, without altering the detection structure or algorithm parameters, thus increasing the algorithm's applicability.

[0078] Specifically, as shown in Figure 3, even when wafer 1 is placed at an angle, its position will fluctuate within a certain range due to the buoyancy and fluctuations of the fluid medium 5, resulting in significant differences in wafer 1 spacing. If the detection algorithm directly uses the first set of detection signals as the time of the first layer wafer and the difference between any two adjacent signals as the interval time between adjacent layers in the wafer cassette, it is easily affected by interference, leading to distorted calibration data and incorrect wafer position calculation in the working state. To solve the above problems, we considered increasing the amount of data and calculating the average value to reduce the calibration data deviation caused by wafer position fluctuation. However, at the same time, to shorten the calibration time and avoid using a large number of wafers 1 for calibration, testing and calculation revealed that by placing wafers in the first, second, twenty-fourth, and twenty-fifth cavity slot layers of wafer cassette 2 for calibration scanning, and calculating the weighted average of the interval differences between multiple sets of first and last signals to obtain the time of the first layer wafer and the interval time between adjacent layers in the wafer cassette, the theoretical position of each layer wafer is converted to a theoretical position with a small deviation from the wafer position obtained from multiple sets of actual scans. This allows for accurate calculation of the wafer position and solves the problem of inaccurate positioning of wafers in water due to inconsistent spacing.

[0079] As shown in Figure 4, the sensor signal changes from 0 to 1 as a rising edge and from 1 to 0 as a falling edge. The rising edge times are recorded as Tr1, Tr2...Trn, and the falling edge times are recorded as Td1, Td2...Tdn.

[0080] As can be seen from Figure 3, since the wafer is placed in a fluid medium, it is affected by the reflected light of the water wave and the shaking of the wafer, generating multiple short signals, which affect the detection. To filter this interference, an algorithm is added to compare the difference between adjacent rising-edge signals in each group with the median value Trm of the time difference [Tr(n) - Tr(n - 1)] of all adjacent rising-edge signals multiplied by a coefficient Trx. If [Tr(n) - Tr(n - 1)] < Trm * Trx, then the signals Tr(n) and Td(n) in this group are filtered out, and the signals Tr(n - 1) and Td(n - 1) are retained. Through multiple groups of tests, calculate the ratio of the length of the small-segment interference signal to the length of the normal wafer signal, take the maximum value, and add 0.2 to obtain Trx. Substituting it into the calculation can effectively remove the small-segment interference signal and retain the normal wafer signal.

[0081] As can be seen from Figure 4, since wafer 1 is placed in water, after reducing wafer 1, the light of sensor 4 directly irradiates the bottom of cassette 2, and it is easily affected by the reflected light of the base of cassette 2, generating continuous long-segment interference signals, which affect the detection. To filter this interference, an algorithm is added to compare the difference between the adjacent rising-edge signal Tr(n) and the falling-edge signal Td(n) in each group with the median value Tdm of the difference [Td(n) - Tr(n)] between all adjacent rising-edge signals and falling-edge signals multiplied by a coefficient Tdx. If [Td(n) - Tr(n)] > Tdm * Tdx, then the signals Tr(n) and Td(n) in this group are filtered out. Through multiple groups of tests, calculate the ratio of the length of the large-segment interference signal to the length of the normal wafer signal, take the minimum value, and subtract 0.5 to obtain Tdx. Substituting it into the calculation can effectively remove the large-segment interference signal and retain the normal wafer signal.

[0082] Adding the above two groups of filtering algorithms can effectively remove the dense small-segment interference signals caused by water waves and wafer shaking and the large-segment reflected light interference signals such as the cassette base. However, if the filtering intensity is too large, it is easy to remove the normal wafer signals. Therefore, by adjusting the magnitudes of Tdx and Trx, appropriately weakening the filtering effect, and calculating and filtering similar signals again through the final step, the data can be guaranteed to be relatively accurate.

[0083] More specifically, a wafer positioning detection method for a semiconductor wet equipment includes the following steps:

[0084] Step 1, calibration scanning. Place wafers on the first layer, the second layer, the twenty-fourth layer, and the twenty-fifth layer of the cassette, place the cassette in a box filled with liquid, perform the cassette loading box operation, and move the cassette to the pick-and-place position of the box transfer device. The sensor scans the cassette above the liquid at a speed of V1 in the direction of increasing layer number, and sequentially records the rising-edge and falling-edge times of all signals.

[0085] Step 2, signal processing. Compare the difference between each pair of adjacent rising-edge signals with the median value Trm of all adjacent rising-edge signal time differences [Tr(n) - Tr(n - 1)] multiplied by the coefficient Trx. If [Tr(n) - Tr(n - 1)] < Trm * Trx, then filter out the signals of Tr(n) and Td(n) in this group, and retain the signals of Tr(n - 1) and Td(n - 1). Compare the difference between each pair of adjacent rising-edge signal Tr(n) and falling-edge signal Td(n) with the median value Tdm of all adjacent rising-edge signal and falling-edge signal differences [Td(n) - Tr(n)] multiplied by the coefficient Tdx. If [Td(n) - Tr(n)] > Tdm * Tdx, then filter out the signals of Tr(n) and Td(n) in this group.

[0086] Step 3, calibration value calculation. Record the processed rising-edge signal times as t1, t2, t24, t25 in sequence. Calculate the average time interval Tt between adjacent two layers of the cassette and the average trigger time Tf of the first-layer wafer. The calculation formulas are as follows:

[0087] Tt = ((t25 - t1) / 24 * wt1 + (t24 - t1) / 23 * wt2 + (t25 - t2) / 23 * wt3 + (t24 - t2) / 22 * wt4) / (wt1 + wt2 + wt3 + wt4),

[0088] Tf = ((t1 * wf1 + (t2 - Tt) * wf2 + (t24 - Tt * 23) * wf3 + (t25 - Tt * 24) * wf4) / (wf1 + wf2 + wf3 + wf4),

[0089] Among them, the weighting coefficients wt1, wt2, wt3, wt4, wf1, wf2, wf3, wf4 are empirical values and can all be 1.

[0090] Convert the time unit to the distance unit. The sensor scanning speed is V1. The calculation formula is as follows:

[0091] The distance Xt between adjacent two layers of the cassette = Tt * V1;

[0092] The position Xf of the first-layer wafer = Tf * V1;

[0093] Enter the working state.

[0094] Step 4, Working Scan. Depending on the actual working conditions, place the wafers arbitrarily in the wafer cassette, place the cassette in a container filled with liquid, and perform a loading operation to move the cassette to the wafer pick-and-place position on the transport device. The sensor scans the wafer cassette above the liquid at a speed of V2, along the direction of increasing layer number, and sequentially records the rise and fall times of all signals.

[0095] Step 5, Signal Processing. Execute Step 2 again, and record the processed rising edge signals as T1, T2...Tn.

[0096] Step 6, Wafer Position Calculation. Multiply all rising edge signals Tn by the sensor scanning speed V2, converting the time unit to a distance unit. Subtract the calibrated first-layer wafer position Xf to obtain the difference Xx. Divide Xx by the calibrated distance Xt between adjacent layers of the wafer cassette, round to the nearest integer, and add 1 to obtain the actual position number of wafer 1. The calculation formula is as follows: Nn = ROUND((Tn*V2-Xf) / Xt)+1. After all calculations are complete, package them into an array and send it to the host computer. For example, if the calculated N1=1, N2=2, N3=2, N4=24, N5=25, then send 11000000000000000000000011, indicating that wafers are present in the 1st, 2nd, 24th, and 25th cavity slots of the wafer cassette, and there are no wafers in the other cavity slots.

[0097] By using the above data calculation method, similar signals are converted into the same result, so that the data can be processed again and the results can be avoided.

[0098] In summary, by adding algorithms in steps two and five, most of the signals generated by water ripples and wafer cassette base interference are filtered out. Combined with increasing the number of calibrated wafers in steps one and three, multiple sets of weighted average differences are calculated to solve the problems of wafer position fluctuation and inconsistent spacing, and appropriate calibration values ​​are obtained as the basis for subsequent wafer position judgment. Finally, by calculating and filtering out similar signals in step five, the relative position information of all wafers in the wafer cassette is obtained.

[0099] Alternatively, the process can be combined into two steps: calibration scan calculation and working scan calculation. Under normal operating conditions, a calibration scan calculation only needs to be performed once during the first run of the equipment, and subsequent working scan calculations can be performed continuously.

[0100] In calibration mode, based on the first processed signal after removing interference signals, although wafer cassette 2 is tilted and fixed, (ideally) the wafer is tightly attached to the placement surface. Considering that the wafer is placed in wafer cassette 2 with a fluid medium, but there is a possibility that the weight is insufficient to completely overcome the buoyancy of the fluid, the wafer in wafer cassette 2 may have a slight tilt to the left or right or forward or backward. The first layer of wafers will also have this situation. The signal triggering time needs to be effectively processed. For this purpose, a fixed reference point in the fluid medium can be found for data analysis.

[0101] When the edge of wafer cassette 2 is within the detection range of sensor 4, the edge of wafer cassette 2 is used as a fixed reference point in the fluid medium. Sensor 4 moves from the edge 22 of the wafer cassette terminal to the placement surface 21 of the wafer cassette terminal cavity slot structure. Assuming the wafer cassette tilts from left to right, the edge 22 of the wafer cassette edge is at its highest position. The scanning direction of sensor 4 is consistent with the tilt direction of wafer cassette 2. The sampling time increases. The sensor signal is triggered at a high level and not triggered at a low level. That is, the distance between the lower surface of the edge of wafer cassette 2 and the lower surface (mesa level, i.e., the wafer placement surface) of wafer 1 adjacent to the edge of wafer cassette 2 is Xa. Based on the spacing Xt between two adjacent layers of the wafer cassette, the wafer 1 inside the wafer cassette 2 is scanned using the scanning speed V2 of the sensor 4. After one scan is completed, the time T0 corresponding to the trigger signal at the lower edge of the wafer cassette 2 border, the rising edge TrX (X=1,2,.....,n) of all trigger pulse signals, and the lower edge TdX (X=1,2,.....,n) of all pulse trigger signals are recorded. At this time, the width MX of each trigger pulse can be obtained as MX=[TdX-TrX], (X=1,2,.....,n).

[0102] To adapt to detection calculations at different scanning speeds and expand the algorithm's applicability, the time unit is converted to a distance unit. Based on the time T0 corresponding to the trigger signal at the bottom edge of the chip box 2's border, the corresponding position X0 = T0 * V2.

[0103] Based on the distance Xa from the edge of wafer cassette 2 to the placement surface 21 of the starting cavity slot layer structure, and the approximate distance Xt from the placement surface 21 of the adjacent cavity slot layer structures, the position Xk of all mezzanine surfaces relative to the edge of wafer cassette 2 can be calculated. Then, based on the position Xx of all wafers relative to the edge of wafer cassette 2, the specific number of cavity slot layer structures where the wafer trigger signal is located can be determined.

[0104] More specifically, it includes the following steps:

[0105] Obtain the theoretical position Xk of the placement surface 21 of the cavity slot layer structure of each chip box 2.

[0106] Xk(k=1,2,.....,25)=(X0+Xa)+(k-1)*Xt, where k is the number of layers in the groove structure of the inner cavity of wafer cassette 2.

[0107] The position Xx of the lower edge signal Tdx (wafer lower surface) of each trigger signal pulse obtained by scanning relative to the wafer cassette edge is determined.

[0108] Xx=[(Tdx-T0)*V2],(x=1,2,....,n)

[0109] Where Xx is the coordinate scale value of the lower surface of the wafer, T0 is the time value of the initial reference position of the wafer cassette 2 (the edge position of the cassette 2), Tdi is the time value of the extraction detection sensor 4 relative to the initial reference position when scanning the lower surface of the wafer, and V2 is the movement speed of the motion device.

[0110] By determining the location of the wafer trigger signal in the cavity slot, and whether Xx-X0 is between (Xa+(k-1)Xt) and (Xa+kXt), where k is the layer number, or by determining that Xx is between Xk and Xk+1, the number of layers in the cavity slot layer structure of the wafer can be determined to be K layers.

[0111] After determining the specific number of layers in the cavity slot structure where the trigger signal is located, it is determined whether the wafer is placed in a single layer, stacked (stacked), or tilted (tilted).

[0112] First, a skewed wafer determination is performed. Since tilted placement may result in left-right or front-back tilts, the position Xx corresponding to the trigger signal Tdi when the detection sensor 4 scans the lower surface of the wafer is not near the theoretical wafer placement surface Xk, as shown in Figure 8. It is then determined whether the position Xx corresponding to the trigger signal Tdi is located near the range Xk-1+Jm to Xk-Jm (Jm in Figure 8 is empirically derived and used for critical region division). If it falls within this range, it is considered a tilted placement; otherwise, it is a stacked or monolithic placement.

[0113] If Xx is between Xk+ / -Jm, the actual wafer thickness Mi(mm)*V2 is obtained based on the width and speed of each trigger pulse, which determines whether it is stacked or single-wafer placement.

[0114] In the above calculation of the spacing between two adjacent cavity slots of the wafer cassette and the position of the first wafer layer or the edge position of wafer cassette 2, in the embodiment, it is not limited to one type of wafer cassette, but can be different wafer cassettes. In that case, the distance between the placement surfaces of the adjacent wafer cavity slot layer structures will be different, and the value of the spacing Xt can be modified.

[0115] Of course, the fluid medium 5 can also be a non-transparent liquid. The wafer 1 can be vertically raised and lowered to increase its freedom. The above algorithm can also be used to ensure that the medium between the wafer 1 and the sensor 4 is the same.

[0116] Specifically, when using the above algorithm, sensor 4 is a reflective line laser sensor, which performs wafer detection outside the medium. The reflective structure allows sensor 4 to perform detection outside the medium in a stable air environment. The line laser has a large signal contact area, which can obtain more effective signals, thus solving the instability caused by the medium and filling the gap in detailed and effective detection of the wafer state in the liquid.

[0117] A liquid level sensor 6 is installed inside the housing 3 to monitor changes in the liquid level and the amount of change. Specifically, when wafer 1 is removed from the wafer cassette 2, the liquid level in the housing 3 decreases; when a new wafer 1 is placed into the wafer cassette 2, the liquid level in the housing 3 increases. By calculating the increase and decrease in the liquid level, the entry and exit of wafer 1 can be determined, and by calculating the amount of increase and decrease in the liquid level, the number of wafer 1s that have entered or exited can be determined.

[0118] The above specific embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

[0119] 1: Wafer 2: Tablet Box 21: Placement surface of cavity groove structure 22: Edge of the cartridge terminal 3: Box 4: Sensor 5: Fluid medium 6: Liquid level sensor

Claims

1. A wafer positioning detection method for a semiconductor wet process equipment, characterized by the following steps: Detection algorithm data calibration; a wafer cassette containing wafers at known positions is placed inside a housing containing a fluid medium; the wafer cassette has a multi-layer structure for placing wafers; a sensor scans the wafer cassette at a set speed and direction, and records the time of each trigger signal; the signal emitted by the sensor is parallel or nearly parallel to the crystal plane; the trigger signal is a time-series signal, which is a rising edge, or a falling edge, or a combination of rising and falling edges; the acquired trigger signal is processed to remove interference signals caused by the fluid medium; in the calibration state, based on the first processed signal after removing interference signals and the relative position of the known wafers, the interval time between two adjacent layers of the wafer cassette and the trigger time of the first layer wafer signal are calculated, and the interval distance between two adjacent layers of the wafer cassette and the position of the first layer wafer are calculated based on the sensor scanning speed; Upon entering the working state, a wafer cassette containing wafers at unknown locations is placed inside a housing containing a fluid medium. A sensor scans the wafer cassette at a set speed and direction, recording the time of each trigger signal. The acquired trigger signals are processed to remove interference signals caused by the fluid medium. The second processed signal, after removing interference signals during operation, is converted into wafer position information based on the sensor scanning speed. This information is then compared with the distance between adjacent layers of the wafer cassette and the position of the first layer of wafers obtained during calibration to obtain the relative position information of all wafers within the wafer cassette. This wafer position information is transmitted to the controller to control the transfer device to pick up the wafers.

2. The wafer positioning and detection method for semiconductor wet process equipment as described in claim 1, characterized in that: the step of calculating the spacing distance between two adjacent layers of the wafer cassette and the position of the first wafer layer includes the following sub-steps: calculating the weighted average of at least a plurality of rising edge or falling edge time differences of the processed first processing signal to obtain the spacing time between two adjacent layers of the wafer cassette; calculating the difference between all rising edges or falling edges of the processed first processing signal and the corresponding layer interval time, and then taking the weighted average of all differences to obtain the first wafer layer time; multiplying the spacing time between two adjacent layers of the wafer cassette and the first wafer layer time by the sensor scanning speed in the calibration state to obtain the spacing distance between two adjacent layers of the wafer cassette and the position of the first wafer layer.

3. The wafer positioning and detection method for semiconductor wet process equipment as described in claim 1, characterized in that: the step of calculating the spacing between two adjacent layers of the wafer cassette and the position of the first layer wafer includes the following sub-steps: placing the wafer cassette within the detection range of the sensor; obtaining the distance Xa between the wafer placement surface in the wafer cassette terminal cavity slot layer structure and the terminal edge of the wafer cassette edge, and obtaining the distance Xt between the placement surfaces of adjacent cavity slot layer structures; the sensor scans the wafers in the wafer cassette at a specific speed, and records the time corresponding to the trigger signal of the wafer cassette edge terminal edge; recording all wafer trigger signals, and converting them into wafer position information Xx relative to the wafer cassette edge terminal edge according to the sensor scanning speed; determining whether Xx is between (Xa+(k-1)Xt) and (Xa+kXt), where k is the layer number, thereby determining the layer number of the cavity slot layer structure where the wafer is located; Alternatively, calculate the position Xk of all theoretical wafer placement surfaces relative to the wafer cassette edge, and determine that Xx is between Xk and Xk+1 to determine that the number of layers in the cavity trench structure where the wafer is located is K layers.

4. The wafer positioning detection method for semiconductor wet process equipment as described in claim 1, characterized in that: the interference signal includes water wave interference signal and reflected light interference signal, wherein the water wave interference signal includes water surface interference and / or wafer sway interference.

5. The wafer positioning detection method for a semiconductor wet process equipment as described in claim 4, characterized in that: the step of processing and removing interference signals includes the following sub-steps: comparing the time difference between adjacent rising or falling edges of each group of trigger signals, determining whether it is less than the median value of all adjacent rising or falling edge time differences multiplied by a set coefficient, and if the result is less than, then filtering out the trigger signal; and / or comparing the time difference between adjacent rising and falling edges of each group of trigger signals, determining whether it is greater than the median value of all adjacent rising and falling edge time differences multiplied by a set coefficient, and if the result is greater than, then filtering out the trigger signal.

6. The wafer positioning and detection method for a semiconductor wet process equipment as described in claim 1, characterized in that: the step of obtaining the relative position of the wafer in the wafer cassette under the working state includes the following sub-steps: multiplying all trigger signal times by the sensor scanning speed under the working state to obtain all trigger signal positions; subtracting the calibrated first layer wafer position from all trigger signal positions, then dividing by the calibrated spacing between two adjacent layers in the wafer cassette, rounding the calculation result to the nearest integer, and then adding one to obtain the relative position of all wafers in the wafer cassette.

7. The wafer positioning detection method for a semiconductor wet process equipment as described in claim 1, characterized in that: the sensor is an optical sensor and is disposed in an area outside the fluid medium of the housing.

8. The wafer positioning and detection method for semiconductor wet process equipment as described in claim 1, characterized in that: the wafer is placed vertically in a box containing a fluid medium, the angle between the wafer surface and the liquid surface is 45°-90°, and the wafer is completely submerged in the fluid medium.

9. The wafer positioning detection method for semiconductor wet process equipment as described in claim 1, characterized in that: the fluid medium is a transparent liquid, which is pure water or a sodium hydroxide solution.

10. A semiconductor wet process apparatus, characterized in that it comprises: a housing containing a fluid medium; a wafer cassette placed within the housing, having a plurality of cavity groove structures for placing wafers; and a sensor movable relative to the wafer cassette and detecting wafer position information as described in any one of claims 1-9.

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