JPH09148403A - In-cassette substrate detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To insert a carry arm so that it may not interfere with a substrate within a cassette, by detecting each positional range of substrate existing within a cassette, from the output waveform generated by a photosenser when the optical sensor and the cassette shift vertically relatively. SOLUTION: A board detector is equipped with bracket 21 which go up and down around each cassette C arranged on a cassette table 3, and these bracket 21 are arranged each in the position surrounding each cassette C, and a photosensor consisting of a light casting element 22 and a light receiving element 23 is attached to the tip of the bracket 21. And, the positions of the light casting element 22 and the light receiving element 23 are set so that the light L may pass the two openings Ca and Cb provided in front and in rear of the cassette C, and from the output waveform of the photosenser, the positional range in vertical direction of the wafer W within the cassette is detected. Hereby, the carry arm can be inserted without interfering with the wafer W.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a substrate such as a semiconductor wafer contained in a cassette.

[0002]

2. Description of the Related Art As a device for detecting a substrate stored in a cassette, for example, one disclosed in Japanese Patent Application Laid-Open No. 3-298156 disclosed by the present applicant is known. In this device, at each predetermined storage position in the cassette, it is determined whether the light receiving element of the optical sensor is in the light receiving state or the non-light receiving state, and according to the result, it is determined whether or not the substrate is present in each storage position. doing.

[0003]

By the way, the groove for accommodating the substrate, which is provided in the cassette, is often manufactured so as to be raised rearward. Also, the cassette itself may be distorted. For this reason, the substrates stored in the cassette are often slightly tilted forward. Therefore, when the substrate is taken out from the cassette, in order to insert the transfer arm so as not to interfere with the substrate in the cassette, not only whether the substrate is in the predetermined storage position but also the vertical direction of each substrate It is desirable to know the position range of. However, with the above-mentioned device, it is impossible to know the vertical position range of each substrate stored in the cassette.

The present invention has been made to solve the above-mentioned problems in the prior art, and an object thereof is to detect the vertical position range of each substrate housed in a cassette.

[0005]

Means for Solving the Problem and Its Action / Effect To solve at least a part of the above-mentioned problems, a first invention is an apparatus for detecting a substrate contained in a cassette, wherein the cassette is An optical sensor including a light projecting element and a light receiving element that are arranged so as to face each other, a vertical driving unit that relatively moves at least one of the optical sensor and the cassette in a vertical direction, the optical sensor and the cassette. Substrate position detecting means for detecting the vertical position range of each substrate existing in the cassette from the output waveform generated by the optical sensor when the substrate moves relatively vertically.

The light of the optical sensor is shielded by the substrate and becomes a non-light receiving state. Therefore, from the output waveform generated by the optical sensor when the optical sensor and the cassette move relatively vertically,
It is possible to detect the vertical position range of each substrate housed in the cassette.

The cassette has a substrate insertion opening for inserting / removing a substrate, and an opening provided on the opposite side of the substrate insertion opening. Is preferably arranged at a position where the light emitted from the light projecting element passes through the substrate insertion opening and the opening and is received by the light receiving element.

In this way, it is possible to determine the vertical position range of the substrate projected substantially along the direction in which the transfer arm enters (the direction connecting the substrate insertion opening and the opening).

Further, it is preferable that the light projecting element and the light receiving element are arranged substantially horizontally.

In this way, the vertical position range of the substrate can be accurately determined.

Further, it is preferable that the substrate position detecting means includes a position determining means for determining a range of an output level of the optical sensor indicating that the light receiving element is in a non-light receiving state as a position range of the substrate.

Further, the substrate position detecting means includes a position pulse signal generating means for generating a position pulse signal of one pulse each time the optical sensor and the cassette are vertically moved relative to each other by a constant distance, and the position pulse signal. A counter that counts the number of pulses, storage means that sequentially stores the count value of the counter at the timing when the output level of the optical sensor is switched, and the count value stored in the storage means that is stored in the cassette. Position determining means for determining the respective position ranges of the substrate are preferably provided.

With this configuration, the output level of the optical sensor is switched depending on whether or not the substrate shields the optical sensor. Therefore, each position range of the substrate can be determined from the count value at the timing when the output level switches.

[0014]

Other Embodiments of the Invention The present invention includes the following other embodiments. A first aspect is a method of detecting a substrate housed in a cassette, comprising: an optical sensor including the cassette and a light projecting element and a light receiving element that are arranged to face each other with the cassette interposed therebetween. From at least one of the output waveforms generated by the optical sensor when the optical sensor and the cassette are moved in the vertical direction relative to each other, at least one of them is moved in the vertical direction. Detect the position range.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

A. Configuration of Apparatus: Next, an embodiment of the present invention will be described based on examples. FIG. 1 is a perspective view showing a semiconductor wafer processing apparatus equipped with an apparatus according to an embodiment of the present invention. This semiconductor wafer processing apparatus is an apparatus for heat-treating a substrate such as a semiconductor wafer, and includes an indexer unit (substrate loading / unloading unit) 1 for loading and unloading a wafer W into a cassette C, and a cassette C. And a process unit group 2 for performing various processes on the taken-out wafer W. The indexer unit 1 includes a cassette table 3 for mounting the cassette C and a cassette C.
Substrate unloading mechanism 4 for loading and unloading wafer W to and from wafer 4
And Further, the process unit group 2 includes the rotation processing units 111 and 112 and the heat treatment unit 121.
To 123 and a substrate transfer mechanism 9 for transferring the wafer W to each of these units.

FIG. 2 is a plan view of the indexer unit 1. On the cassette table 3 of the indexer unit 1, a plurality of cassettes C that store the wafers W in multiple stages are installed. Inside the cassette table 3, a main part of a substrate detection device described later is provided.

The substrate take-out mechanism 4 includes a substrate transfer arm 5 which can be moved up and down and moved back and forth. The substrate transfer arm 5 has a function of taking out the wafer W stored in the groove in each cassette C or storing the wafer W in the groove in the cassette C. The substrate unloading mechanism 4 further includes three vertically movable support pins 61 to 63 for mounting the wafer W taken out by the substrate transfer arm 5.
And alignment plates 71 to 72 for performing center alignment of the wafer W supported by the support pins 61 to 63. A plurality of projections 8 arranged on the alignment plates 71 to 72 so as to have a curvature substantially the same as the outer diameter of the wafer W.
When the alignment plates 71 to 72 are horizontally reciprocated, the projections 8 are brought into contact with and separated from the periphery of the wafer W, and the center alignment of the wafer W is performed.

The wafer W taken out of the cassette C by the substrate take-out mechanism 4 is transferred to the substrate transfer position (position P shown in FIG. 1) and then received by the substrate transfer mechanism 9 (FIG. 1) of the process unit group 2. Passed.

The substrate transfer mechanism 9 has two substantially U-shaped substrate support arms 10 for mounting the wafer W thereon. The substrate transfer mechanism 9 sequentially transfers the wafers W in each unit of the process unit group 2 in accordance with a preset processing recipe (data defining a processing procedure). The wafer W processed by the process unit group 2 has the substrate transfer mechanism 9 at the substrate transfer position P.
From the board take-out mechanism 4 to the board take-out mechanism 4
Is returned to the cassette C by.

FIG. 3 is a partially cutaway front view showing the mechanical structure of the substrate detection device. The substrate detection device includes a bracket 21 that moves up and down (vertically moves) around each cassette C placed on the cassette table 3. As shown in FIG. 2, the bracket 21 has a substantially U-shape and is arranged at a position surrounding each cassette C. An optical sensor 24 including a light projecting element 22 and a light receiving element 23 is attached to the tip of the bracket 21 to detect the wafer W stored in the cassette C. The light receiving element 23 is provided on the front side of the substrate insertion port Ca on the front surface of the cassette C. In addition, the light projecting element 22
Is provided on the rear side of the opening Cb on the side opposite to the board insertion port Ca. The light projecting element 22 and the light receiving element 23 are attached such that their optical axes are substantially horizontal and parallel to the substrate transfer arm 10. The light L emitted from the light projecting element 22 enters the cassette C through the opening Cb at the rear end, exits from the substrate insertion port Ca, and is received by the light receiving element 23. When the wafer W is stored in the cassette C, the light L is blocked by the wafer W. Thus, the positions of the light projecting element 22 and the light receiving element 23 are set so that the light L passes through the two openings Ca and Cb provided in the front and rear of the cassette C. As a result, the light L can be reliably blocked by the wafer W stored in the cassette C. The vertical range in which the light L is blocked by the wafer W corresponds to the range in which the wafer W is projected along the entering direction of the substrate transfer arm 5 (the direction connecting the substrate insertion opening 5a and the opening 5b). The positions of the light projecting element 22 and the light receiving element 23 can be reversed.

As shown in FIG. 3, an elevating mechanism 25 for elevating the bracket 21 is provided below the cassette table 3. The elevating mechanism 25 includes a rodless cylinder 26 that is supported in parallel in the vertical direction on the support plate 20,
The rodless cylinder 26 is provided with a movable member 28 slidably fitted therein. A vertical member 29 penetrating the cassette table 3 is provided on the movable member 28.
The vertical member 29 is connected to the bracket 21. A light shield plate 30 is provided on the side surface of the movable member 28, and a timing sensor 32 formed of a photo interrupter is provided below the light shield plate 30. In the stopped state, the light shield plate 30 is inserted in the gap of the timing sensor 32, and the timing sensor 32 is kept in the non-light receiving state. When the elevating mechanism 25 starts its operation and the light shielding plate 30 brings the timing sensor 32 into the light receiving state,
The timing sensor 32 generates a signal indicating that the bracket 21 (that is, the optical sensor 24) is at the predetermined origin position. The movable member 28 is further provided with a linear scale sensor 34 that generates a position pulse signal indicating the vertical position of the optical sensor 24. The optical sensor 24
As a sensor that generates a signal indicating the vertical position of
Not limited to the linear scale sensor, other means such as various encoders can be used.

When a drive mechanism (not shown) of the rodless cylinder 26 supplies air from the upper and lower ends of the rodless cylinder 26, a magnet (not shown) in the rodless cylinder 26 moves up and down. Then, along with this, the movable member 28 moves up and down, and the optical sensor 24 attached to the bracket 21 is moved.
Moves up and down along the circumference of the cassette C. At this time, the linear scale sensor 34 generates a position pulse signal of 1 pulse each time the movable member 28 moves up and down by a predetermined distance.

The elevating mechanism 25 is not limited to the rodless cylinder 26 as described above, but may be an ordinary air cylinder or a screw feeding mechanism using a motor.

FIG. 4 is a conceptual diagram showing the electrical construction of the substrate detection device. The light receiving element 23 generates a light receiving signal SL indicating whether or not the light L is being received. The timing sensor 32 generates an origin position signal SREF indicating that the bracket 21 is at a predetermined origin position. The linear scale sensor 34 also generates a position pulse signal SP1 indicating the moving distance of the optical sensor 24. These signals SL, SP1,
SREF is input to the board position detection device 40.

The board position detecting device 40 includes a CPU 42 connected to a bus 41 and a main memory 44.
, A FIFO memory 46, and a first up / down counter 48. The board position detecting device 40 further includes two selectors 51 and 52, a chattering prevention circuit 54, a latch 56, a second up / down counter 58, and a PLL circuit 60.

The light receiving signal SL from the light receiving element 23 for each cassette C on the cassette table 3 is input to the first selector 51. In the example of FIG. 1, since four cassettes C can be installed on the cassette table 3,
One light reception signal SL is input to the first selector 51.
The position pulse signal SP1 from the linear scale sensor 34 for each cassette is input to the second selector 52. The two selectors 51 and 52 are CP
According to the selection signal SEL given from U42, one is selected from four signals.

The position pulse signal SP1 selected by the second selector 52 is input to the PLL circuit 60 and converted into a second position pulse signal SP2 having a frequency that is an integral multiple of the frequency of the position pulse signal SP1. . For example, when the original position pulse signal SP1 is a signal that generates one pulse every 0.1 mm, if the frequency is multiplied by 4 by the PLL circuit 60, the second position pulse signal SP2 becomes 1 every 0.025 mm. It becomes a signal to generate a pulse. The PLL circuit 60 is provided in order to make the resolution (distance corresponding to one pulse) of the position pulse signal SP2 sufficiently small. Therefore, when the resolution of the original position pulse signal SP1 is sufficiently small, the PLL circuit 60 can be omitted. The linear scale sensor 34 and the PLL circuit 60 correspond to the position signal generating means in the present invention.

The second position pulse signal SP2 generated by the PLL circuit 60 has two up / down counters 48, 5
8 and the chattering prevention circuit 54.
The position pulse signals SP1 and SP2 include an up signal that generates a pulse when the bracket 21 (that is, the optical sensor 24) rises and a down signal that generates a pulse when the bracket 21 (that is, the optical sensor 24) descends. The two up / down counters 48 and 58 count up / down the number of pulses of these up and down signals. Therefore, the up / down counter 48,
The count value of 58 indicates the vertical position of the optical sensor 24.

Two up / down counters 48,
58 is enabled by the origin position signal SREF generated by the timing sensor 32 and starts its operation. At this time, the count values of the two counters 48 and 58 are simultaneously cleared to 0. The origin position signal SREF for each cassette is wired OR, and when the origin position signal SREF for any cassette is turned on, the operation of the up / down counters 48 and 58 is started.

The CPU 42 monitors the count value of the first up / down counter 48 and determines whether or not the bracket 21 has risen to its upper end position. That is, when the count value of the up / down counter 48 reaches a predetermined upper limit value, it is determined that the bracket 21 has risen to the upper end, the raising operation is stopped, and the bracket 21 is lowered in reverse.

The chattering prevention circuit 54 receives the received light signal S.
Timing signal S indicating that the L level has been switched
Is producing T. However, the chattering prevention circuit 54
Generates a one-pulse timing signal ST when a predetermined number of pulses (for example, 5 pulses) of the position pulse signal SP2 are continuously generated after the level of the light receiving signal SL is switched. As a result, even if chattering occurs in the light receiving signal SL, the chattering of the timing signal ST can be prevented.

The count value CNT of the second up / down counter 58 is latched according to the timing signal ST generated by the chattering prevention circuit 54 and written in the FIFO memory 46, so the count value at the time when the level of the light receiving signal SL is switched. The CNTs will be sequentially stored in the FIFO memory 46.

B. Structure of Cassette C and Substrate Transfer Arm 5 and Wafer Position Detection Operation: FIG.
FIG. 3 is an explanatory diagram showing the configuration of FIG. That is, FIG.
FIG. 5 is a plan view showing a state where the substrate transfer arm 5 holding the wafer W is inserted into the cassette C, and FIG. 5B is a side view thereof. However, in FIG. 5B, a mechanism for driving the substrate transfer arm 5 is illustrated, and the cassette C and the bracket 21 are omitted.

As shown in FIG. 5B, the substrate transfer arm 5 is a plate-shaped member, and has a thick plate-shaped portion 5a at the rear end, a thin plate-shaped portion 5b at the center, and a thin plate-shaped portion 5b. And a projection 5c provided at the tip of the. The thickness t1 of the thick plate portion 5a is, for example, about 1.5 mm, and the thickness t2 of the thin plate portion 5b.
Is about 1.0 mm, the thickness t3 of the protrusion 5c is about 1.0 mm
It is.

An arm drive mechanism 80 for driving the substrate transfer arm 5 is provided near the rear end of the thick plate portion 5a. The arm drive mechanism 80 includes a vertical shaft 82 connected to the substrate transfer arm 5, a vertical drive unit 84 for moving the vertical shaft 82 up and down, a horizontal guide 86 for guiding the vertical drive unit 84 along the horizontal direction, and a vertical drive. A horizontal drive unit 88 that horizontally moves the unit 84 along the horizontal guide 86, and a drive control unit 89 that controls the vertical drive unit 84 and the horizontal drive unit 88.
And The drive controller 89 is electrically connected to the substrate position detecting device 40.

FIG. 6A is a plan view showing the structure of the cassette C, and FIG. 6B is a sectional view taken along the line BB of FIG. However, in FIG. 6B, for convenience of illustration, a line having a structure close to the opening Cb at the rear of the cassette C is omitted. Inside the side plate 90 of the cassette C, there are many grooves 92.
Are provided, and the wafer W is accommodated along the groove 92. Further, the cassette C has an upper surface plate 94 at its upper end, and has a structural member 96 called an H bar near its lower end. The name of the H bar 96 is derived from the fact that its planar shape is substantially H-shaped.

As shown in FIG. 6A, the light L emitted from the light projecting element 22 enters the cassette C through the opening Cb at the rear end of the cassette C, passes through the substrate insertion port Ca, and is received. The light is received by the element 23. Therefore, as shown in FIG. 6B, when the optical sensor 24 (light projecting element 22 and light receiving element 23) moves in the vertical direction along the circumference of the cassette C installed on the cassette table 3, the light projecting is performed. The light L emitted from the element 22 is blocked by the cassette table 3, the H bar 96 of the cassette, the wafer W housed in the cassette, and the top plate 94 of the cassette.

FIG. 7 is an explanatory diagram showing the waveform of the light receiving signal SL generated by the light receiving element 23 when the optical sensor 24 rises. That is, FIG. 7B schematically shows the structure corresponding to FIG. 6B, and FIG. 7A shows the waveform of the received light signal SL corresponding thereto. In this embodiment, as shown in FIG. 7A, 25 wafers W are stored in the cassette C.
It is assumed that one wafer can be stored, and a part of the wafer W
Is supposed to be actually stored. Light receiving element 23
Is in the light receiving state, the light receiving signal SL shows 0 level (L level), and the light receiving element 23 is in the non-light receiving state (light blocking state)
When it is at, the received light signal SL shows 1 level (H level).

FIG. 8 shows a board position detecting device 40 shown in FIG.
6 is a timing chart showing the operation of FIG. 8A shows the second position pulse signal SP2 generated by the PLL circuit 60, FIG. 8B shows the origin position signal SREF generated by the timing sensor 32, and FIG. 8C shows the light receiving element 23 generated. The received light signal SL is shown in FIG. 8, and the count value CNT stored in the FIFO memory 46 is shown in FIG.

When the optical sensor 24 starts to move up and the origin position signal SREF of the timing sensor 32 becomes H level, the operation of the substrate position detecting device 40 is started in response to this.
At this time, the count values of the up / down counters 48 and 58 are also initialized to 0. As shown in FIG. 8A, the position pulse signal SP2 is generated by one pulse each time the optical sensor 24 moves by a predetermined distance (for example, 0.025 mm). The up / down counters 48 and 58 count up the number of pulses of the position pulse signal SP2. In this embodiment, it is assumed that the optical sensor 24 rises at a constant speed. Therefore, the position pulse signal SP2 shown in FIG. 8A is an up signal. Further, no pulse is generated in the down signal.

When the level of the light receiving signal SL (FIG. 8 (c)) generated by the light receiving element 23 is switched, the count value C of the second up / down counter 58 is changed as shown in FIG. 8 (d).
NT is held by the latch 56 and stored in the FIFO memory 46. Therefore, the count value CNT at each of the times T1, T2, ... At which the level of the received light signal SL is switched is sequentially stored in the FIFO memory 46.

The count value CNT is measured by the timing sensor 3
2 shows the distance in the vertical direction from the origin position defined by 2. That is, the vertical position of the optical sensor 24 at each time T1, T2, ... Can be calculated from the count value CNT stored in the FIFO memory 46. Cassette C
The positions of the H bar 96 and the upper plate 94 are known in advance. Therefore, the CPU 42 determines each vertical position range of the wafer W stored in the cassette C from the count value CNT stored in the FIFO memory 46. Further, when the vertical position range of the wafers W is determined, the clearance between the wafers W can be determined at the same time.

Substrate position determining device 40 in this embodiment
Corresponds to the substrate position detecting means and the clearance measuring means in the present invention. Further, the CPU 42 has a function as position determining means in the present invention. A software program (application program) for realizing the function as the position determining means is stored in a portable storage medium (portable storage medium) such as a floppy disk or a CD-ROM, and is transferred from the portable storage medium to the main memory 4
4 or an external storage device (not shown) and is stored in the main memory 44 at the time of execution.

As described above, in practice, the chattering prevention circuit 54 shown in FIG. 4 continues the predetermined number (for example, 5 pulses) of the position pulse signal SP2 after the level of the light receiving signal SL is switched. 1 when it occurs
The pulse timing signal ST is generated. Therefore,
The timing at which the latch 56 holds the count value CNT is delayed by 5 pulses. Therefore, the position obtained by subtracting 5 pulses from the position calculated from the count value CNT stored in the FIFO memory 46 becomes the accurate measurement position.

As shown in FIG. 7B, for the wafer W housed horizontally, the period during which the received light signal SL is at the 1 level (H level) corresponds approximately to the thickness of the wafer W. . On the other hand, with respect to the wafer W that is stored in an inclined manner, the period when the light reception signal SL is at the 1 level (H level) corresponds to the thickness when the wafer W is projected by the light in the horizontal direction. Considerably wider than the actual thickness of. In this way, even when the wafer W is stored in an inclined state, the vertical storage range of the wafer W is known, and
The clearance between wafers can also be known. Therefore, in this embodiment, as described below, the substrate transfer arm 5 is operated in accordance with the clearance between the wafers to prevent the substrate transfer arm 5 and the wafer W from colliding with each other.

FIG. 9 is an explanatory view showing the operation mode of the substrate transfer arm 5 according to the clearance between the wafers.
FIG. 9 shows an example in which the standard wafer storage pitch in the cassette C is 6.35 mm. Further, it is assumed that the upper wafer W1 is taken out of the two wafers W1 and W2.

As shown in FIG. 9A, two wafers W1,
When the clearance CL between W2 is 4.5 mm or more, the lower surface of the substrate transfer arm 5 is set to 3.5 mm below the lower surface position of the upper wafer W1, and this height is maintained. The substrate transfer arm 5 is moved horizontally and inserted between the wafers W1 and W2. Since the maximum thickness of the substrate transfer arm 5 is 2.5 mm, even if it is inserted in this way, the distance between the upper end of the substrate transfer arm 5 (that is, the upper end of the protrusion 5c) and the lower surface of the upper wafer W1 is 1 mm or more. There is a gap. There is also a gap of 1 mm or more between the lower end of the substrate transfer arm 5 and the upper surface of the lower wafer 2. Therefore, even if the substrate transfer arm 5 is inserted horizontally, the substrate transfer arm 5 does not interfere with the wafers W1 and W2.

As shown in FIG. 9B, two wafers W1,
When the clearance CL of W2 is in the range of 3.1 mm or more and less than 4.5 mm, the lower surface of the substrate transfer arm 5 is
The distance d given by the following equation is set to the lower side from the lower surface position of the upper wafer W1.

D = 3.5− (4.5−CL) / 2 [mm]

If the distance d is determined according to the above equation,
The lower surface of the substrate transfer arm 5 is set above the position shown in FIG. 9A by 1/2 of the difference between 4.5 mm and the clearance CL. Even in this state, a gap is secured between the substrate transfer arm 5 and each wafer. Therefore, even if the substrate transfer arm 5 is inserted horizontally, the substrate transfer arm 5 does not interfere with the wafers W1 and W2.

As shown in FIG. 9C, two wafers W1,
When the clearance CL of W2 is in the range of 2.1 mm or more and less than 3.1 mm, it is considered that the two wafers W1 and W2 are both tilted forward. Therefore, in this case, first, the lower surface of the substrate transfer arm 5 is set to a height 2.8 mm below the lower surface position of the upper wafer W1. Then, the substrate transfer arm 5 is started to be inserted horizontally at this height, and the substrate transfer arm 5 is moved to 0.8 mm below the wafer W1.
Insert while raising.

FIG. 10 is an explanatory diagram showing the movement trajectory of the substrate transfer arm 5 in the case of FIG. 9 (C). FIG.
As shown in (A), first, the lower surface of the substrate transfer arm 5 is inserted in the horizontal direction while keeping the lower surface of the upper wafer W1 at a height of 2.8 mm below. Then, the substrate transfer arm 5 is linearly moved diagonally along the locus TR indicated by the alternate long and short dash line from the position where the protrusion 5c reaches below the front end (right end in FIG. 10) of the wafer W1. The locus TR is the locus of the corner portion 5p of the substrate transfer arm 5. FIG. 10 (B) shows a state in which the substrate transfer arm 5 has moved to the end of the diagonal trajectory. FIG. 10 (B)
At the position, since the substrate transfer arm 5 is raised by 0.8 mm from the position shown in FIG. 10A, the lower surface of the substrate transfer arm 5 does not contact the upper surface of the lower wafer W2.
From the position shown in FIG. 10B, the substrate transfer arm 5 moves up in the vertical direction to receive the upper wafer W1. FIG.
The operation of the substrate transfer arm 5 shown in FIG. 0 is achieved by the drive control unit 89 shown in FIG. 5 controlling the vertical drive unit 84 and the horizontal drive unit 88.

As shown in FIG. 9D, two wafers W1,
When the clearance CL of W2 is less than 2.1 mm and 1.0 mm or more, the lower surface of the substrate transfer arm 5 is set to a height 2.8 mm below the lower surface position of the upper wafer W1. This is similar to the case of FIG. Then, the insertion of the substrate transfer arm 5 is started at this height, and the wafer W1
Underneath, the substrate transfer arm 5 is inserted while being raised by 1.5 mm. This locus is almost the same as that shown in FIG. 10, and the only difference is the vertical movement distance (that is, the rising width) in the diagonal locus.

Clearance C between two wafers W1 and W2
When L is less than 1.0 mm, it is difficult to insert the substrate transfer arm 5 without interfering with the wafers W1 and W2, so the substrate position detection device 40 notifies the operator that the insertion is difficult. Generates an alarm (alarm sound or alarm display) to activate. The drive controller 89 also stops the substrate transfer arm 5. In this way, when the clearance CL is less than the predetermined limit value (for example, 1.0 mm), if the substrate transfer arm 5 is stopped and an alarm is issued, the substrate transfer arm 5 is forcibly inserted and the wafer W1. , W2 can be prevented from being damaged.

As described above, in this embodiment, the two wafers W1 and W measured along the direction in which the substrate transfer arm 5 enters.
The drive control unit 89 changes the locus of insertion of the substrate transfer arm 5 according to the clearance CL of 2. As a result, the tip of the substrate transfer arm 5 has two wafers W1 and W2.
It prevents the collision with the substrate transfer arm 5
It is also prevented that the lower surface of the above contacts the upper surface of the lower wafer W2. That is, the clearance CL has a predetermined margin (0.6 m) within the maximum thickness (2.5 mm) of the substrate transfer arm 5.
m) with a critical value (3.1 mm) or more (Fig. 9).
The substrate transfer arm 5 is horizontally inserted into (A) and (B). On the other hand, when the clearance CL is less than the critical value and equal to or more than the limit value (1.0 mm) (FIGS. 9C and 9D), the substrate transfer arm 5 is placed at the front end positions of the wafers W1 and W2.
The substrate transfer arm 5 is horizontally inserted until the front end of the substrate transfer arm reaches, and then the substrate transfer arm 5 is inserted while being raised along the oblique trajectory TR. The moving distance in the vertical direction on the trajectory TR in the oblique direction is determined by the substrate transfer arm 5
Of the lower surface of the wafer W2 so as not to contact the upper surface of the lower wafer W2,
It is determined according to the value of the clearance CL. Normally, the thickness of the front end portion of the substrate transfer arm 5 is smaller than the maximum thickness of the substrate transfer arm 5, so that such an oblique trajectory T
By inserting the substrate transfer arm 5 at R, it is possible to prevent interference between the substrate transfer arm 5 and the two wafers W1 and W2.

It should be noted that the respective values such as the above-mentioned critical value and limit value are merely examples, and appropriate values are set in accordance with the storage pitch of wafers in the cassette C, the thickness of the substrate transfer arm 5, and the like.

Wafer W1 taken out from cassette C
Are returned to the same cassette C after the processing in the process unit group 2 is completed. At this time, the drive control unit 89 (FIG. 5) of the substrate transfer arm 5 reversely follows the trajectory TR when the wafer W1 is taken out, and the wafer W1 is transferred to the cassette C.
Back. This makes it possible to prevent the substrate transfer arm 5 from interfering with the wafer W2 below it when the wafer W1 is stored in the cassette C. The storage state (including clearance CL) of each wafer in the cassette C is stored in the main memory 44 (FIG. 4) in the substrate position detecting device 40, and the drive control unit 89 executes the above-mentioned control according to the storage state. To do.

The present invention is not limited to the above-described examples and embodiments, but can be carried out in various modes without departing from the scope of the invention.
For example, the following modifications are possible.

(1) Instead of raising and lowering the optical sensor 24, the cassette C may be raised and lowered. That is, at least one of the optical sensor 24 and the cassette C may be relatively moved in the vertical direction.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a semiconductor wafer processing apparatus including an apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of the indexer unit 1.

FIG. 3 is a partially cutaway front view showing a mechanical configuration of a substrate detection device.

FIG. 4 is a conceptual diagram showing an electrical configuration of a substrate detection device.

FIG. 5 is an explanatory diagram showing a configuration of a board take-out mechanism 4.

FIG. 6 is an explanatory view showing the structure of a cassette C.

FIG. 7 is an explanatory diagram showing a waveform of a light reception signal SL generated by the light receiving element 23 when the optical sensor 24 moves in the vertical direction.

FIG. 8 is a timing chart showing the operation of the substrate position detection device 40.

FIG. 9 is an explanatory diagram showing an operation mode of the substrate transfer arm 5 according to a clearance between wafers.

FIG. 10 is an explanatory diagram showing a movement trajectory when the substrate transfer arm 5 is obliquely inserted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Indexer unit 2 ... Process unit group 3 ... Cassette table 4 ... Substrate extraction mechanism 5 ... Substrate transfer arm 5a ... Thick plate-shaped portion 5b ... Thin-walled plate-shaped portion 5c ... Projection portion 5p ... Corner portion 8 ... Projection 9 ... Substrate Transport mechanism 10 ... Substrate support arm 20 ... Support plate 21 ... Bracket 22 ... Light emitting element 23 ... Light receiving element 24 ... Optical sensor 25 ... Elevating mechanism 26 ... Rodless cylinder 27 ... Drive mechanism 28 ... Movable member 29 ... Vertical member 30 ... Light shielding plate 32 ... Timing sensor 34 ... Linear scale sensor 40 ... Substrate position detection device 41 ... Bus 42 ... CPU 44 ... Main memory 46 ... FIFO memory 48 ... Up / down counter 51, 52 ... Selector 54 ... Chattering prevention circuit 56 ... Latch 58 ... Up-down counter 60 ... PLL circuit 61-63 ... Support pin 7 1 to 72 ... Alignment plate 80 ... Arm drive mechanism 82 ... Vertical shaft 84 ... Vertical drive unit 86 ... Horizontal guide 88 ... Horizontal drive unit 89 ... Drive control unit 90 ... Side plate 92 ... Groove 94 ... Top plate 96 ... H bar 111, 112 ... Rotation processing unit 121-123 ... Heat treatment unit C ... Cassette Ca ... Substrate insertion port Cb ... Opening portion SL ... Light receiving signal SP1, SP2 ... Position pulse signal SREF ... Origin position signal ST ... Timing signal SEL ... Selection signal W … Wafer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masayuki Itaba, Masayuki Itaba, 322 Hazushi, Furukawa-cho, Fushimi-ku, Kyoto City Dainichi Screen Manufacturing Co., Ltd. Rakusai Plant Address Dainichi Honsen Screen Mfg. Co., Ltd. Rakusai Plant

Claims (5)

[Claims] 1. An apparatus for detecting a substrate housed in a cassette, comprising: an optical sensor having a light projecting element and a light receiving element, which are opposed to each other with the cassette interposed therebetween; the optical sensor; and the cassette. Vertical drive means for relatively moving at least one of the two in the vertical direction, and an output waveform generated by the optical sensor when the optical sensor and the cassette are moved in the vertical direction, from the output waveform of the substrate existing in the cassette. And a substrate position detecting means for detecting a position range of each vertical direction. 2. The in-cassette substrate detection device according to claim 1, wherein the cassette includes a substrate insertion port for inserting and removing a substrate, and an opening provided on the opposite side of the substrate insertion port. The light projecting element and the light receiving element are arranged at positions where light emitted from the light projecting element passes through the substrate insertion opening and the opening and is received by the light receiving element. In-cassette substrate detection device. 3. The in-cassette substrate detection device according to claim 2, wherein the light projecting element and the light receiving element are arranged substantially horizontally.
Substrate detection device in cassette. 4. The in-cassette substrate detection device according to claim 1, wherein the substrate position detection means indicates an output level of the optical sensor indicating that the light receiving element is in a non-light receiving state. In-cassette substrate detection device, which comprises a position determining means for determining the range of 1) as the position range of the substrate. 5. The in-cassette substrate detection device according to claim 1, wherein the substrate position detection means outputs a position pulse signal of one pulse every time the optical sensor and the cassette vertically move by a fixed distance. Position pulse signal generating means, a counter for counting the number of pulses of the position pulse signal, a storage means for sequentially storing the count value of the counter at the timing when the output level of the optical sensor is switched, and the storage means A substrate detecting device in a cassette, comprising: a position determining unit that determines a position range of each of the substrates housed in the cassette from the stored count value.