JP2001345369A - Substrate sensor and method for sensing substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a damage due to a substrate conveying error by erroneously recognizing a substrate sensor provided at a substrate conveyor or the like of a semiconductor manufacturing apparatus, to recognize the presence or absence of the substrate due to a substrate material or a difference of reflectivity of a film on the surface of the substrate. SOLUTION: The substrate sensor comprises a light emitting element H for emitting an illumination light t to the surface of a wafer W, a photodetector J for receiving a reflected light (h) from the wafer W and a plate-like partial shield plate P installed between the element H and the photodetector J. If the wafer W excessively approaches a sensor mounting part S in the case of conveying, the light (t) or the light (h) is automatically shielded by the plate P so that the photodetector J does not detect the light (h) and can judge as the absence of the wafer. Even when the reflectivity of the wafer is different, a damage due to contact of the wafer with the mounting part S is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate sensor and a substrate detection method for performing stable detection of a difference in light reflectance on a wafer measurement surface.

[0002]

2. Description of the Related Art In a manufacturing apparatus such as a semiconductor device, it is necessary to confirm each wafer by a sensor whether or not the wafer is normally transferred in a portion where a wafer is supplied from a wafer cassette into a processing chamber of the apparatus. And This wafer has different materials such as a silicon substrate and a transparent quartz substrate, and the color of the wafer varies depending on the processing method such as the film quality and film thickness that adheres to the back surface of the wafer as it goes through the manufacturing process. The light reflectivity varies depending on For example, when a film is deposited by a furnace tube type CVD apparatus such as a low pressure CVD, the film grows also on the back surface of the wafer, but a silicon oxide film, a silicon nitride film and the like have a low reflectance and a metal film such as a high melting point metal film and an aluminum film. Has high reflectance. In such a situation where the back surface of the wafer is in such a state, in checking the presence or absence of the wafer on the semiconductor manufacturing apparatus, the reliability of a sensor capable of accurately detecting the presence or absence of the wafer with respect to the difference in light reflectance is required.

FIG. 2 is a diagram showing a configuration example of a conventional apparatus for detecting the wafer. What is shown in this figure is
A light emitting element H and a light receiving element J are obliquely installed on a sensor mounting section S, which is a wafer detection section at a transfer site of a semiconductor manufacturing apparatus, and usually has a flat surface. Then, the wafer W is transferred from the wafer cassette onto the sensor mounting portion S by, for example, a metal fork (not shown) without contacting the sensor portion.

In FIG. 1, the detection of the wafer W is performed by irradiating the light t emitted from the light emitting element H with the reflected light h
And enters the light receiving element J. Amplifier A
The sensitivity adjustment section K is set so that it is determined that there is a wafer when the amount of received light is appropriate, and the presence or absence of the wafer W is detected. This sensor is configured to detect a wafer when the wafer on the surface of the sensor mounting portion S passes a certain distance L away. When it is determined from the measurement result that there is a wafer W, the result is displayed by an LED or the like attached to the amplifier A.

FIGS. 5A to 5C are diagrams showing how a sensor detects the distance of a wafer when measuring a certain wafer. FIG. 5A shows a state in which the distance L between the wafer W and the sensor mounting portion S is shorter than the set distance, and the reflected light h of the wafer W hardly enters the light receiving element J as can be seen from the arrangement in the figure. FIG. 5B shows a state in which the distance L between the wafer W and the sensor mounting portion S is appropriate, and shows a state in which the reflected light h enters the light receiving element J. FIG. 5C shows a state in which the distance L between the wafer W and the sensor mounting portion S is longer than the set distance. At this time, as is clear from the path of the reflected light h in FIG. I hardly enter J.

FIG. 3 is a graph showing the dependence of the amount of light received by the light receiving portion J on the distance L between the flat portion of the sensor mounting portion S and the wafer assuming that the irradiation light t is constant. Are shown. Curve 1 is for a wafer with a high reflectivity, and curve 2 is for a wafer with a low reflectivity. In the case of a wafer having a high reflectivity, the reference light receiving amount for determining the presence or absence of the wafer by the amplifier A is set to a level of four. Then, the distance L at which the amplifier A can confirm that a wafer is present is 5, that is, the area L surrounded by the intersection of the dotted lines of the curves 1 and 4. On the other hand, when such a criterion is provided, the light receiving amount curve of a wafer having a low reflectance is 2, and
Since the level is always lower than level 4, the wafer cannot be detected.

On the contrary, if the detection level of the amplifier A is set at the position indicated by the dotted line 3 so that the presence or absence of a wafer having a low reflectance can be detected, the low reflectance wafer has a light receiving curve 2 It can be determined that there is a wafer at a distance L of a portion sandwiched between intersections with the straight line indicating level 3. However, in this state, the distance L between the wafer and the sensor mounting portion of the wafer having a high reflectance is 0, that is, the sensor mounting portion S
It is determined that there is a wafer even when the wafer and the wafer W are in contact with each other.

If it is determined that there is a wafer even when the wafer W comes into contact with the sensor mounting portion S, the semiconductor manufacturing apparatus transports the wafer to another place while keeping the contact with the sensor mounting portion S in order to proceed to the next step. However, at this time, the wafer W is damaged or damaged. In order to prevent this, conventionally, the reference light receiving amount setting of the amplifier A is changed and used for each wafer having a different light reflectance.

[0009]

As described above, in the above-described conventional wafer detection method, every time the type or state of film formation on the surface of the wafer changes, the work of resetting the reference light receiving amount of the sensor amplifier occurs. Was.

In a semiconductor manufacturing apparatus, a sensor for confirming the presence or absence of a wafer is used in a part where a wafer is taken out of a carrier before processing or a part where a wafer is stored in a carrier after processing, and it takes a lot of time to adjust the position. There is a problem.

Conversely, if such an operation is omitted, when the light receiving amount is set as a reference for a wafer with a low reflectance, the range of the distance L for determining that there is a wafer in a wafer with a high reflectance is widened. Causes a transport error at the transport site. Further, if it is determined that there is a wafer even in a state where the wafer is in contact with the sensor mounting portion S, there is a problem that the wafer is damaged.

The present invention solves the problem of the conventional sensor for detecting the presence / absence of a wafer as described above. Even if the reflectance differs for each substrate, the substrate comes too close to the substrate sensor and contacts the substrate sensor. It is an object of the present invention to provide a substrate sensor and a substrate detection method that can prevent the substrate from being damaged.

[0013]

According to a first aspect of the present invention, there is provided a substrate sensor, wherein a light irradiating means for irradiating a predetermined area on one principal surface of a substrate with light, and a light receiving means for receiving reflected light from a predetermined area of the substrate. And, installed between the light irradiating means and the light receiving means, it is possible to shield the irradiation light or reflected light beyond a predetermined shielding amount when the substrate approaches a predetermined distance to the light irradiating means or light receiving element,
A shielding body having an adjustable shielding amount, and a determining unit for determining that there is a substrate when the amount of reflected light received by the light receiving unit is equal to or greater than a predetermined value corresponding to the predetermined shielding amount. .

According to the substrate sensor of the first aspect, if a substrate such as a wafer is too close to the sensor, the shield is also relatively close to the substrate, so that irradiation light or reflected light is further blocked. Therefore, the amount of light reaching the light receiving means is equal to or less than a predetermined value, and it is not determined that the substrate is present. As a result, the device equipped with the substrate sensor is stopped, and the substrate is not damaged by excessive transport. Therefore, even if the reflectance is different for each substrate, it is possible to prevent the substrate from being too close to the substrate sensor and coming into contact with and being damaged.

According to a second aspect of the present invention, in the first aspect, the shielding amount of the shield is adjusted by moving the shield.

According to the substrate sensor of the second aspect, the same effect as that of the first aspect is obtained.

According to a third aspect of the present invention, there is provided a substrate sensor comprising: a light irradiating means for irradiating a predetermined area on one main surface of the substrate with light; a light receiving means for receiving light reflected from a predetermined area of the substrate; The light irradiating means and the light receiving means are installed substantially perpendicular to one principal surface of the substrate in the vicinity including a predetermined area, and when the substrate approaches the light irradiating means or the light receiving element by a predetermined distance, irradiating light or reflected light A shield capable of shielding a predetermined amount of shielding,
A determination unit that determines that there is a substrate when the amount of reflected light received by the light receiving unit is equal to or more than a predetermined value corresponding to a predetermined shielding amount.

According to the substrate sensor of the third aspect, the same effect as that of the first aspect is obtained.

According to a fourth aspect of the present invention, there is provided a substrate detecting method for detecting a substrate having one principal surface having a different reflectance using the substrate sensor according to the first, second, or third aspect. Then, a predetermined value of the amount of received light of the reflected light is set to the amount of light received by the substrate having the minimum reflectance.

According to the substrate detecting method of the fourth aspect, even if the reflectance differs for each substrate, the substrate does not come too close to the substrate sensor and is not damaged by contact.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows a configuration of a sensor according to an embodiment of the present invention. In FIG.
J is a light receiving element, A is an amplifier constituting a determination unit, W is a wafer, P is a shielding plate, t is irradiation light, h is reflected light, K is a sensitivity adjustment unit, and S is a sensor mounting unit. The mounting angle of the light emitting element H and the light receiving element J is adjusted such that the reflected light h enters the light receiving element J when the distance L between the plane of the sensor mounting portion S and the wafer W is at an appropriate allowable distance. , The light emitting element H and the light receiving element J are embedded from the plane of the sensor mounting portion S. The tip of the shielding plate P is located above the plane of the sensor mounting portion S. Further, the horizontal position of the shielding plate P is attached immediately below a point on the surface of the wafer W to which the irradiation light t from the light emitting element H is applied when the distance L is at an appropriate allowable distance. More specifically, a recess 10 having a V-shaped cross section, for example, is formed substantially at the center of the upper surface of the sensor mounting portion S, and a hole 1 is formed on the opposite slope of the recess 10.
1 and 12 are provided, and the light emitting element H and the light receiving element J are buried in the bottoms of the holes 11 and 12. The light-shielding plate P is, for example, plate-shaped, and its lower end is buried in the center of the concave portion 10 to stand.

In the sensor configured as described above, the irradiation light t is emitted from the light emitting element H toward the wafer W. The irradiation light t passes between the wafer W and the shielding plate P to irradiate the surface of the wafer W, and therefore the amount of the reflected light h is limited. Then, the reflected light h limited by the distance between the wafer W and the shielding plate P enters the light receiving element J.

FIG. 2 shows the amount of received light in the sensor of the present invention.
5 is a graph showing a relationship between a sensor attachment portion plane and a distance L between a wafer W. Curve 1 is for a wafer with a high reflectivity, and curve 2 is for a wafer with a low reflectivity. In the case of a wafer having a high reflectivity, if the reference value of the amount of received light, which is the boundary at which the amplifier A determines that there is a wafer, is set to the line 4, the region where the amplifier A determines that there is a wafer is defined by the curve 1 and the line 4 This is when the wafer is located at a distance L between the intersections.

However, if the reference value of the amount of received light is set to the level of 4, a low-reflectance wafer cannot be detected as shown in FIG. Then, the received light amount reference value is lowered to level 3. In this way, the distance L between the intersections of the curves 1 and 2 and the straight line 3 with respect to the high-reflectance and low-reflectance wafers
The wafer can be detected.

In the present invention, when L passes through a small value,
As can be seen from FIG. 1, the light path width of the irradiation light t is restricted by the shielding plate P and the wafer surface, and the light amount received by the light receiving element J decreases sharply. When L is small, the amount of received light is further reduced.
It becomes 2. Thus, even if the reference value of the amplifier A is set to the level of 3 for a wafer having a low reflectance, even when the wafer W having a high reflectance approaches, the area is equal to or less than the reference value of the amplifier A, that is, the wafer W When approaching, there is a region where the shielding plate P blocks more than a predetermined shielding amount and reduces the received light amount to a predetermined value or more, and it can be determined that there is no wafer.

Thus, the criterion value of the amplifier A is set to 3
It is possible to make a correct judgment regardless of the level of the wafer reflectance even if the level is set to one type and fixed, and when the sensor comes into contact with the sensor mounting portion, the wafer transfer is stopped in the semiconductor manufacturing apparatus, The wafer will not be damaged and become a defective product. In addition, when the amplifier A determines the presence or absence of a wafer, the reference value for determining the amount of received light only needs to be set once, which eliminates the time required for setting and adjusting the reference value in accordance with the difference in the reflectance of the semiconductor substrate surface. Has an effect.

In the example shown in FIG. 1, the light shielding plate P has a plate shape and is perpendicular to the surface of the wafer W.
Any material may be used as long as it becomes a shield that limits the amount of light incident on the semiconductor substrate W. When the reference light receiving amount is determined by the amplifier A, the shielding body P is located between the light emitting element H and the light receiving element J with reference to FIG. And the distance L between the light emitting element H, the light receiving element J, or the sensor mounting portion S supporting them and the wafer W can be adjusted in an appropriate range so that it can be determined that there is a wafer.

Normally, however, it is sufficient to install the shield P near and immediately below the light irradiation point on the wafer W when L is an appropriate distance. In this case, the amount of received light automatically decreases, and the amplifier A can determine that there is no wafer in any case.

As described above, according to the present invention, in a sensor comprising a light emitting element H, a light receiving element J and a mounting portion S thereof, a shield is provided between the light emitting element H and the light receiving element J to limit the reflected light from the wafer. Accordingly, it is possible to stably determine the presence or absence of a wafer without bringing the sensor attachment portion S into contact with a wafer having a different reflectivity due to a difference in the material of the wafer or a film due to processing.

[0030]

According to the substrate sensor according to the first aspect, if a substrate such as a wafer is too close to the sensor, the shield is also relatively close to the substrate to further block the irradiation light or the reflected light. Therefore, the amount of light reaching the light receiving means is equal to or less than a predetermined value, and it is not determined that the substrate is present. As a result, the device equipped with the substrate sensor is stopped, and the substrate is not damaged by excessive transport. Therefore, even if the reflectance is different for each substrate, it is possible to prevent the substrate from being too close to the substrate sensor and coming into contact with and being damaged.

According to the substrate sensor of the second aspect, the same effect as that of the first aspect is obtained.

According to the substrate sensor of the third aspect, the same effect as that of the first aspect is obtained.

According to the substrate detecting method of the fourth aspect, even if the reflectance is different for each substrate, the substrate is not too close to the substrate sensor and does not contact and be damaged.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a substrate sensor according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a distance between a sensor and a wafer in a substrate sensor according to the present invention and a received light amount;

FIG. 3 is a configuration diagram of a conventional substrate sensor.

FIG. 4 is a diagram showing the relationship between the distance between a sensor and a wafer in a conventional substrate sensor and the amount of received light.

FIG. 5 is a diagram illustrating the principle of determining the presence or absence of a wafer by a substrate sensor.

[Explanation of symbols]

 H Light-emitting element J Light-receiving element A Amplifier W Wafer P Shielding plate t Irradiation light h Reflected light K Light-receiving amount adjustment unit L Distance between wafer and sensor mounting unit S Sensor mounting unit 1 Light-receiving amount curve of wafer with high reflectivity 2 Reflectivity Light reception curve of low wafer 3 Reference light reception level 4 Reference light reception level 5 Judgment area with wafer 6 Judgment area with wafer

Claims (4)

[Claims] A light irradiating means for irradiating a predetermined area on one main surface of the substrate with light; a light receiving means for receiving reflected light from a predetermined area of the substrate; and a light irradiating means and the light receiving means. Installed in between, the substrate can close the irradiation light or the reflected light beyond a predetermined shielding amount when the substrate approaches a predetermined distance to the light irradiating means or the light receiving element, and the shielding amount is adjustable A substrate sensor, comprising: a shield; and a determining unit that determines that the substrate is present when the amount of reflected light received by the light receiving unit is equal to or greater than a predetermined value corresponding to the predetermined shielding amount. 2. The substrate sensor according to claim 1, wherein the shielding amount of the shield is adjusted by moving the shield. 3. A light irradiating means for irradiating a predetermined area on one principal surface of a substrate with light, a light receiving means for receiving reflected light from a predetermined area of the substrate, and a plate-shaped light irradiating means. It is installed substantially perpendicular to one main surface of the substrate in the vicinity including the predetermined region between the light receiving means and the irradiation light or the light when the substrate approaches the light irradiation means or the light receiving element by a predetermined distance. A shield capable of blocking the reflected light exceeding a predetermined shielding amount, and determining that the substrate is present when the amount of reflected light received by the light receiving unit is equal to or greater than a predetermined value corresponding to the predetermined shielding amount. A substrate sensor comprising: 4. A substrate detection method for detecting a substrate having a different reflectance on one principal surface of a substrate using the substrate sensor according to claim 1, wherein the amount of the reflected light received is Wherein the predetermined value is set to the amount of light received by the substrate having the minimum reflectance.