Light irradiation device

Abstract

The present invention provides a light irradiation device capable of stably irradiating illumination light having a desired wavelength at a desired light intensity. [Solution] The light irradiation device 70 provided in the observation device for observing a semiconductor wafer W comprises a light bulb 701 having a filament, a power supply 704 that supplies power to the light bulb 701 at a voltage such that the light from the light bulb has a predetermined spectral distribution, a housing 710 that houses the light bulb 701, an outlet 711 provided in the housing 710 that transmits the light irradiated from the light bulb 701, a relative distance adjustment means 703 that changes the relative distance between the light bulb 701 and the outlet 711, and a light intensity control means 707 that controls the amount of light emitted from the outlet 711. When changing the amount of light, the light intensity control means 707 changes the relative distance using the relative distance adjustment means 703 while keeping the voltage of the power supplied from the power supply 704 constant so as to suppress changes in the spectral distribution of the light from the light bulb 701.

Description

Technical Field

[0001] The present invention relates to a light irradiation device using a light bulb having a filament, and more particularly to a light irradiation device suitably provided in an observation device for observing a semiconductor wafer.

Background Art

[0002] Generally, a light irradiation device is employed as a light source in a microscope or a processing apparatus. When broadband light is required or when light in a band that cannot be obtained with an LED (Light Emitting Diode) lamp is needed, a light irradiation device using a light bulb (filament lamp) having a filament is used.

[0003] In this type of light irradiation device, the light quantity is controlled by controlling the voltage applied to the light bulb so as to obtain an image with appropriate brightness. At this time, since the illuminance of the light bulb changes non-linearly with respect to the voltage, the voltage is adjusted so as to set the desired light quantity.

[0004] For example, the light quantity control device of the filament lamp described in Patent Document 1 includes a current detection sensor connected in series to a filament lamp having a characteristic that the change in the light quantity of the lamp is substantially proportional to the square of the power consumption, a multiplication circuit that generates a voltage proportional to the product of the terminal voltage of the filament lamp and the output voltage of the current detection sensor, a square root circuit that generates a voltage proportional to the square root of the control voltage, a comparison of the output voltage of the multiplication circuit and the output voltage of the square root circuit, an error amplifier circuit that minimizes the error, and a constant voltage power supply device connected to the output terminal of the error amplifier circuit that supplies power to the filament lamp.

[0005] Thereby, the light quantity control device described in Patent Document 1 can change the light quantity of the filament lamp substantially linearly with respect to the voltage applied by the constant voltage power supply device.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2004-030927 [Overview of the project] [Problems that the invention aims to solve]

[0007] Light intensity control devices that change the voltage applied to a filament lamp to control the light intensity may have difficulty stably controlling the light to obtain light of a desired wavelength at a desired intensity because the spectral distribution of the light from the filament lamp changes in response to the voltage change.

[0008] In view of these circumstances, the present invention aims to provide a light irradiation device capable of stably irradiating illumination light having a desired wavelength with a desired light intensity. [Means for solving the problem]

[0009] To achieve the object of the present invention, a light irradiation device according to a first aspect of the present invention is a light irradiation device provided in an observation device for observing a semiconductor wafer, comprising: a light bulb having a filament; a power supply for supplying power to the light bulb; a housing for housing the light bulb; an outlet provided in the housing for transmitting light emitted from the light bulb; relative distance adjustment means for changing the relative distance between the light bulb and the outlet; and light intensity control means for controlling the amount of light emitted from the outlet, wherein when changing the amount of light, the light intensity control means changes the relative distance using the relative distance adjustment means while keeping the voltage of the power supplied from the power supply constant.

[0010] According to this embodiment, the amount of light is adjusted by changing the relative distance between the light bulb and the light outlet while keeping the voltage applied to the light bulb constant. This eliminates the need for a complex circuit to adjust the voltage of the power supplied to the light bulb in order to adjust the light intensity. Furthermore, since the amount of light can be adjusted while keeping the voltage of the power supplied to the light bulb constant, changes in the spectral distribution of the light from the light bulb caused by voltage changes are suppressed. Consequently, it becomes possible to irradiate with illumination light having a desired wavelength at a desired light intensity.

[0011] According to a second aspect of the present invention, the light irradiation device according to the first aspect further comprises a shutter for blocking light and a shutter driving means for driving the shutter, wherein when the amount of light is to be reduced to zero, the light intensity control means moves the shutter on the light path from the light bulb to the light outlet using the shutter driving means while the light bulb is lit.

[0012] According to this embodiment, for example, the frequency of turning the light bulb on and off during observation by an observation device can be reduced. Consequently, the time required for soft start to suppress the inrush current that occurs when turning on the light can be reduced. Furthermore, by reducing the frequency of turning the light bulb on and off, the shortening of the light bulb's lifespan can also be suppressed.

[0013] According to a third aspect of the present invention, the light irradiation device according to the first or second aspect further comprises a bandpass filter between the light bulb and the output port that limits the wavelength band of light.

[0014] According to this embodiment, the bandpass filter makes it possible to selectively transmit light in a wavelength range suitable for observation from the broadband light emitted from the light bulb, while blocking light in other wavelength ranges.

[0015] According to a fourth aspect of the present invention, in the light irradiation device according to the third aspect, the relative distance adjustment means changes the relative distance while keeping the positional relationship between the light bulb and the bandpass filter constant.

[0016] According to this embodiment, by maintaining a constant positional relationship between the light bulb and the bandpass filter, changes in the transmission characteristics of the bandpass filter due to temperature fluctuations can be suppressed. Consequently, the wavelength of light emitted from the light irradiation device can be stabilized, making it possible to stably adjust the brightness of the observed image. [Effects of the Invention]

[0017] According to the present invention, since the amount of illumination light can be changed while keeping the voltage applied to the light bulb constant, it is possible to stably irradiate illumination light having a desired wavelength with a desired amount of light.

Brief Description of the Drawings

[0018] [Figure 1] It is a schematic diagram of the appearance of a laser processing apparatus having an observation apparatus to which the light irradiation apparatus according to the present invention is applied. [Figure 2] It is an example of a plan view of a wafer. [Figure 3] It is a functional block diagram of the light irradiation apparatus. [Figure 4] It is a graph showing an example of the spectral distribution of the light of the light bulb. [Figure 5] It is a graph showing an example of the characteristics of the bandpass filter. [Figure 6] It is an explanatory diagram of the principle of light amount adjustment. [Figure 7] It is a graph showing an example of the sensitivity of the InGaAs sensor.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a schematic diagram of the appearance of a laser processing apparatus having an observation apparatus to which the light irradiation apparatus according to the present embodiment is applied. In Fig. 1, the X direction, Y direction, and Z direction are shown. The X direction and the Y direction intersect each other. For example, the X direction and the Y direction are orthogonal to each other. The Z direction intersects the X direction and the Y direction. For example, the Z direction is orthogonal to the X direction and the Y direction. Hereinafter, the lengths in the X direction and the Y direction may sometimes be referred to as thickness or width. The length in the Z direction may sometimes be referred to as thickness, depth, and height. Also, in the Z direction, the direction toward the tip side of the arrow in the Z direction may be referred to as the upward direction, upper side, or up, and the direction opposite to the upward direction may be referred to as the downward direction, lower side, or down.

[0020] As shown in Figure 1, the laser processing apparatus 10 comprises a base 12, an XYZθ stage 14, a suction stage 16, a processing unit 18, a monitor 20, and a control device 22.

[0021] The base 12 has a horizontal surface, and an XYZθ stage 14 is provided on the base 12. The XYZθ stage 14 is provided on the base 12 so as to be movable in the XYZ direction and rotatable in the θ direction. This XYZθ stage 14 is moved in the XYZ direction and rotated in the θ direction by a moving mechanism (not shown) that includes actuators and motors.

[0022] The adsorption stage 16 is provided on the XYZθ stage 14 and adsorbs and holds a flat wafer W. Figure 2 is a plan view of the wafer W. As shown in Figure 2, the wafer W is divided into multiple regions by a plurality of streets CH (also called division lines) arranged in a grid, and various devices 4 constituting a semiconductor chip are formed in each of these divided regions. In this embodiment, the case in which wafer W is used as the workpiece is described, but the present invention is not limited to this, and for example, glass substrates, piezoelectric ceramic substrates, glass substrates, etc. can also be used.

[0023] A wafer W is placed on an adsorption stage 16 with the back surface facing upwards, and a back grind tape (hereinafter referred to as BG tape) having an adhesive material is attached to the surface (device surface) on which the device is formed. There are no particular restrictions on the thickness of the wafer W, but for example, it is 700 μm or more or 700 μm to 800 μm.

[0024] Alternatively, the wafer W may have a dicing tape with adhesive material attached to one side, and may be placed on the suction stage 16 in an integrated state with the frame via this dicing tape.

[0025] By moving the XYZθ stage 14 in the XYZθ direction using a moving mechanism (not shown), the processing unit 18 is moved relative to the wafer W on the adsorption stage 16 in the XYZθ direction. As a result, the laser processing apparatus 10 forms a laser processing area inside the wafer W along the street CH.

[0026] The processing unit 18 includes a laser optical system 25 and an observation optical system 30. This processing unit 18 is positioned above the adsorption stage 16 in the Z direction (facing the wafer W) and is controlled by a control device 22.

[0027] The laser optical system 25 irradiates laser light L toward a street CH on the wafer W. This laser optical system 25 includes a laser light source 26 (laser oscillator), a collimating lens 27, a half mirror 28, and a focusing lens 29 (condensing lens).

[0028] The laser light source 26 emits processing laser light L (e.g., pulsed laser light) toward the collimating lens 27 to form a laser processing area inside the wafer W, according to the control of the control device 22. The conditions for the laser light L are, for example, that the light source is a semiconductor laser-pumped Nd:YAG (Neodym: Yttrium Aluminum Garnet) laser, the wavelength is 1.1 μm, and the laser light spot cross-section is 3.14 × 10⁻⁶. -8 cm 2 The oscillation mode is Q-switched pulse, the repetition frequency is 80kHz to 200kHz, the pulse width is 180ns to 370ns, and the output power is 8W.

[0029] The collimating lens 27 converts the laser light L incident from the laser light source 26 into a parallel beam, and then emits this laser light L toward the half mirror 28.

[0030] The half mirror 28 is positioned on the optical axis of the focusing lens 29 and reflects a portion of the laser light L incident from the collimating lens 27 toward the focusing lens 29. The half mirror 28 also transmits a portion of the illumination light IL incident from the half mirror 33 (described later) toward the focusing lens 29 and transmits a portion of the reflected light of the illumination light IL incident from the focusing lens 29 toward the half mirror 33.

[0031] The focusing lens 29 focuses the laser light L and / or illumination light IL incident from the half mirror 28 onto the wafer W.

[0032] The observation optical system 30 is mounted coaxially with the laser optical system 25. The observation optical system 30 is used to align the wafer W before laser processing and to observe the processing points (modified regions) formed within the wafer W after laser processing.

[0033] The observation optical system 30 includes a collimating lens 32, a half mirror 33, a focusing lens 34, an observation device 35, and a light irradiation device 70, etc. Furthermore, the observation optical system 30 shares the half mirror 28 and the focusing lens 29 with the laser optical system 25.

[0034] The light irradiation device 70 irradiates illumination light IL toward the collimating lens 32. The configuration of the light irradiation device 70 will be described later. The collimating lens 32 converts the illumination light IL incident from the light irradiation device 70 into a parallel light beam, and then emits this illumination light IL toward the half mirror 33.

[0035] The half mirror 33 is positioned on the optical axis of the focusing lens 29 and reflects a portion of the illumination light IL incident from the collimating lens 32 toward the half mirror 28. As a result, the illumination light IL is focused onto the surface of the wafer W via the half mirror 28 and the focusing lens 29. The half mirror 33 also transmits a portion of the reflected illumination light IL incident from the wafer W through the focusing lens 29 and the half mirror 28 toward the focusing lens 34.

[0036] The focusing lens 34 concentrates the reflected light IL of the illumination light incident from the half mirror 33 onto the observation device 35.

[0037] The observation device 35 is a so-called digital camera. Examples of image sensors that the observation device 35 may have include CCD (Charged Coupled Device), CMOS (Complementary Metal Oxide Semiconductor), and InGaAs (Indium Gallium Arsenide) sensors. However, the image sensor is not limited to these examples, and any type of image sensor can be appropriately selected and used depending on the type of illumination light IL, the type of wafer W to be observed, the observation area, etc.

[0038] The observation device 35 captures the reflected light of the illumination light IL focused by the focusing lens 34 and outputs observation images (captured image data) of each part of the wafer W to the control device 22. The control device 22 displays the observation images and input / output screens related to laser processing on the monitor 20.

[0039] The control device 22 comprehensively controls the operation of each part of the laser processing apparatus 10, such as the moving mechanism (not shown), the laser optical system 25, and the observation optical system 30, to perform alignment of the processing unit 18, laser processing, acquisition of observation images of the wafer W, and other operations.

[0040] The control device 22 is composed of an arithmetic unit such as a personal computer and includes an arithmetic circuit composed of various processors and memory. Examples of various processors include CPUs (Central Processing Units), GPUs (Graphics Processing Units), ASICs (Application Specific Integrated Circuits), and programmable logic devices. Examples of programmable logic devices include SPLDs (Simple Programmable Logic Devices), CPLDs (Complex Programmable Logic Devices), and FPGAs (Field Programmable Gate Arrays). The various functions of the control device 22 may be implemented by a single processor, or by multiple processors of the same or different types.

[0041] Next, the configuration of the light irradiation device 70 will be described using Figure 3. Figure 3 is a functional block diagram of the light irradiation device 70. In Figure 3, as an example, the light irradiation device 70 is shown irradiating light via the connector 720 and the optical fiber 730. However, this example is not intended to limit the connection configuration between the observation device 35 and the light irradiation device 70.

[0042] As shown in Figure 3, the light irradiation device 70 comprises a light bulb 701, a bandpass filter 702, a relative distance adjustment unit (relative distance adjustment means) 703, a power supply 704, a shutter 705, a shutter drive unit (shutter drive means) 706, a light intensity control unit (light intensity control means) 707, a housing 710, and an output port 711. The light bulb 701, the bandpass filter 702, and the shutter 705 are installed inside the housing 710. The output port 711 is a through-hole formed in the housing 710, and the light from the light bulb 701 is emitted from the output port 711 to the outside of the housing 710 as illumination light IL.

[0043] The light bulb 701 emits light using power supplied from the power supply 704. The light bulb 701 is a so-called filament lamp having a filament. More specifically, for example, the light bulb 701 is a xenon arc lamp, a tungsten lamp, or a halogen lamp. When the observation device 35 is applied to the laser processing device 10, the light bulb 701 is particularly preferably a halogen lamp.

[0044] For example, during laser processing, the wafer W may be held on the XYZθ stage 14 with its back surface (the side opposite to the device surface) facing upwards and opposite the processing unit 18. In this case, when aligning the wafer W before laser processing or observing the processing points (modified regions) formed within the wafer W after laser processing, it is necessary to observe the inside of the wafer W by transmitting illumination light IL through the substrate.

[0045] The following describes a light bulb 701 that allows for clear observation of wafer W when the substrate of the wafer W is made of silicon, by transmitting light through the substrate. Figure 4 is a graph showing an example of the spectral distribution near the wavelength of light from the light bulb 701. In Figure 4, the horizontal axis represents the wavelength of light, in units of μm. The vertical axis represents the relative intensity of the light. The solid line shows an example of the spectral distribution of a typical halogen lamp, and the dashed line shows an example of the spectral distribution of a halogen lamp (Hysil 1500, manufactured by Kahoku Lighting Solutions Co., Ltd.) that has been improved so that the central wavelength is shifted further into the infrared region than that of a typical halogen lamp.

[0046] When observing a wafer W through a silicon substrate, a light bulb 701 capable of generating relatively high-intensity light in the infrared wavelength band is well used, as shown in Figure 4. This example is not intended to limit the use of light bulb 701. Naturally, the light bulb 701 can be appropriately selected depending on the material of the wafer W and the observation area.

[0047] Returning to Figure 3, the bandpass filter 702 is located near the light bulb 701 in the optical path between the light bulb 701 and the output port 711. For example, if the light from the light bulb 701, which has a broadband spectral distribution as shown in Figure 4, is used for observation, the observation image tends to be poor. Therefore, in order to obtain a clearer observation image, the bandpass filter 702 selectively transmits light in wavelength bands suitable for observation from the broadband light emitted from the light bulb 701, and blocks light in other bands.

[0048] For example, in the laser processing apparatus 10 shown in Figure 1, when alignment is performed before processing with the wafer W held on the adsorption stage 16 with the wafer W surface (device surface) facing downwards, and when observing the laser processing area formed inside the wafer W after processing, preferably the bandpass filter 702 selectively transmits light in a specific wavelength band that can penetrate the substrate of the wafer W.

[0049] Using Figure 5 as an example, the transmission characteristics of a bandpass filter 702 that selectively transmits light of a wavelength that allows for good observation of wafer W by passing through the substrate of wafer W, when the substrate of wafer W is made of silicon, will be explained. Figure 5 is an example graph showing the transmission characteristics of a bandpass filter 702 (TS OD 4.0 25nm bandpass filter, 1300nm 50nm, product code #87-841, manufactured by Edmund Optics Co., Ltd.). In Figure 5, the horizontal axis represents the wavelength of light, in μm. The vertical axis represents the transmittance, in %. The bandpass filter 702 shown in Figure 5 transmits infrared wavelength light with a center wavelength of 1.3 μm and a full width at half maximum of 25 nm, and blocks other light. This allows the light irradiation device 70 to irradiate light with characteristics suitable for observation as illumination light IL. Naturally, the bandpass filter 702 can be appropriately selected according to the spectral characteristics of the light bulb 701, the material of wafer W, and the observation area.

[0050] Returning to Figure 3, the relative distance adjustment unit 703 includes a drive unit (not shown) which includes a motor and a transmission mechanism. Based on the control by the light intensity control unit 707, the relative distance adjustment unit 703 adjusts the relative distance between the light bulb 701 and the light outlet 711 by moving at least one of the light bulb 701 and the light outlet 711. Here, when adjusting the relative distance between the light bulb 701 and the light outlet 711, it is preferable that the relative distance adjustment unit 703 does not change the positional relationship between the light bulb 701 and the bandpass filter 702 (described later).

[0051] The shutter 705 blocks the light that has passed through the bandpass filter 702. The shutter drive unit 706 includes a drive unit (not shown) that includes a motor and a transmission mechanism. Based on the control of the light intensity control unit 707, the shutter drive unit 706 selectively moves the shutter 705 forward and backward between an insertion position in which it is inserted into the optical path between the light bulb 701 and the light outlet 711, and a retracted position where it is moved out of the optical path. Preferably, the insertion position of the shutter 705 is in the optical path between the light bulb 701 and the light outlet 711, and is in the vicinity of the light outlet 711.

[0052] The illumination light IL emitted from the output port 711 is directed towards the collimating lens 32 (see Figure 1) via the connector 720 and the optical fiber 730. The user observes the wafer W illuminated by the illumination light IL using the observation device 35. For example, when adjusting the brightness of the observation image, the user inputs an instruction to the light intensity control unit 707 to adjust the light intensity of the illumination light IL via an input / output unit (not shown).

[0053] The light intensity control unit 707 controls the light intensity of the illumination light IL based on instructions output from the input / output unit. Specifically, the light intensity control unit 707 controls the light intensity of the illumination light IL by changing the relative distance between the light bulb 701 and the output port 711 using the relative distance adjustment unit 703. Furthermore, the light intensity control unit 707 controls the light intensity of the illumination light IL to 0 (zero) by moving the shutter 705 to the insertion position using the shutter drive unit 706. The principle of light intensity adjustment by the light irradiation device 70 will be described in detail later.

[0054] The light intensity control unit 707, like the control device 22, is composed of an arithmetic unit such as a personal computer, and includes an arithmetic circuit composed of various processors and memory. Examples of processors are as described above, so their explanation is omitted. Furthermore, the light intensity control unit 707 may be provided within the control device 22, or it may be provided separately from the control device 22.

[0055] The light irradiation device 70 may further include a half-mirror (not shown) and an illuminance sensor 712 located near the output port 711. The half-mirror guides a portion of the illumination light IL emitted from the output port 711 to the illuminance sensor 712. The illuminance sensor 712 measures the amount of illumination light IL incident from the half-mirror and outputs (feeds back) the measurement result to the light intensity control unit 707. Based on the measurement result, the light intensity control unit 707 can monitor whether the light intensity is adjusted according to the instructions output from the input / output unit.

[0056] Since the amount of illumination light IL emitted from the light irradiation device 70 is inversely proportional to the square of the relative distance between the light bulb 701 and the output port 711, it tends to be difficult to control the light intensity linearly. However, by feeding back the measurement results of the illumination light IL to the light intensity control unit 707, the light intensity control unit 707 can control the light intensity more reliably.

[0057] The principle of light intensity adjustment by the light irradiation device 70 will be explained below using Figure 6. Reference numerals 6A to 6C in Figure 6 indicate the positional relationships of the light bulb 701, the bandpass filter 702, and the shutter 705 inside the housing 710 of the light irradiation device 70, respectively. Reference numeral 6A in Figure 6 indicates the positional relationship when the light intensity of the illumination light IL is high, reference numeral 6B indicates the positional relationship when the light intensity of the illumination light IL is low, and reference numeral 6C indicates the positional relationship when the light intensity of the illumination light IL is 0 (zero).

[0058] As shown in reference numeral 6A, when increasing the light intensity of the illumination light IL, the light irradiation device 70 reduces the relative distance between the light bulb 701 and the output port 711 by moving the light bulb 701 using the relative distance adjustment unit 703 while keeping the voltage of the power supplied from the power supply 704 constant. Since the light intensity of the illumination light IL that passes through the output port 711 is inversely proportional to the square of the distance between the light bulb 701 and the output port 711, the light intensity of the illumination light IL can be increased by reducing the relative distance between the light bulb 701 and the output port 711.

[0059] Conversely, as shown in reference numeral 6B, when the light intensity of the illumination light IL is to be reduced, the light irradiation device 70 increases the relative distance between the light bulb 701 and the light outlet 711 by moving the light bulb 701 using the relative distance adjustment unit 703, while keeping the voltage of the power supplied from the power supply 704 constant. This reduces the light intensity of the illumination light IL. In this way, the light intensity control unit 707 adjusts the light intensity by changing the relative distance between the light bulb 701 and the light outlet 711 while keeping the voltage of the power supplied from the power supply 704 constant.

[0060] Conventional light irradiation devices adjust the light intensity by changing the voltage of the power supplied to the light bulb 701. In this case, since the light intensity changes nonlinearly with respect to voltage, a complex circuit is required to adjust the voltage to set the desired light intensity. On the other hand, in the light irradiation device 70 of this embodiment, the light intensity is adjusted by changing the relative distance between the light bulb 701 and the output port 711 while keeping the voltage applied to the light bulb 701 constant, thus eliminating the need for such a complex circuit.

[0061] Furthermore, in conventional light irradiation devices, the voltage of the power supplied to the light bulb 701 is changed, so the spectral distribution of the light from the light bulb 701 changes in accordance with the voltage change. Therefore, it is difficult to stably control the illumination light to obtain the desired wavelength at the desired light intensity. On the other hand, in the light irradiation device 70 of this embodiment, the light intensity of the illumination light IL can be adjusted while keeping the voltage of the power supplied to the light bulb 701 constant. As a result, changes in the spectral distribution of the light from the light bulb 701 caused by voltage changes are suppressed. Therefore, the light irradiation device 70 makes it possible to control the illumination light to obtain the desired wavelength at the desired light intensity more stably than in conventional devices.

[0062] Incidentally, in halogen lamps, the lifespan of the bulb is extended by the halogen cycle, in which metal particles evaporated from the filament, which becomes hot when the lamp is lit, return to the filament. However, when using a halogen lamp as a light bulb, conventional light irradiation devices reduce the voltage when reducing the light intensity, so this halogen cycle tends not to occur at low light levels. In other words, at low light levels, the metal particles evaporated from the filament do not return to the filament but instead precipitate on the glass surface of the bulb 701, causing the filament to gradually become thinner and shortening the lifespan of the bulb 701.

[0063] On the other hand, in the light irradiation device 70 of this embodiment, the light intensity can be adjusted while keeping the voltage applied to the light bulb 701 constant, so that the halogen cycle can be maintained well, and consequently, the shortening of the lifespan of the light bulb 701 can be suppressed. It is desirable that the voltage supplied to the light bulb 701 be, from the viewpoint of the lifespan of the light bulb 701, a voltage at which the halogen cycle of the light bulb 701 can be stably produced.

[0064] In the light irradiation device 70 of this embodiment, as shown by reference numerals 6A and 6B, when changing the relative distance between the light bulb 701 and the output port 711 to adjust the light intensity, it is desirable to keep the positional relationship between the light bulb 701 and the bandpass filter 702 constant. More specifically, for example, if the relative distance adjustment unit 703 is configured to move the light bulb 701 in order to change the relative distance between the light bulb 701 and the output port 711, the relative distance adjustment unit 703 moves the bandpass filter 702 together with the light bulb 701. By keeping the positional relationship between the light bulb 701 and the bandpass filter 702 constant, fluctuations in the transmission characteristics of the bandpass filter 702 can be suppressed, and consequently, the wavelength of the illumination light IL irradiated from the light irradiation device 70 can be stabilized. This makes it possible to stably adjust the brightness of the observation image of the observation device 35.

[0065] The effects of temperature fluctuations on the bandpass filter 702 will be explained in more detail below using Figure 7. In the following explanation, we assume that the inside of the wafer W is observed using infrared wavelength illumination light IL. For example, when observing the inside of the wafer W using illumination light IL (see Figure 5) with a center wavelength of 1.3 μm and a full width at half maximum of 25 nm, an InGaAs sensor with high sensitivity in the near-infrared wavelength band can be suitably used as the image sensor of the observation device 35. Figure 7 is a graph showing the sensitivity change of the InGaAs sensor in the near-infrared wavelength band. In Figure 7, the horizontal axis represents the wavelength of the illumination light IL, and the unit is μm. The vertical axis represents the light receiving sensitivity of the InGaAs sensor, and the unit is A / W.

[0066] As shown in Figure 7, the light-receiving sensitivity of the InGaAs sensor is not constant in the near-infrared wavelength band, and near a wavelength of 1.3 μm, the light-receiving sensitivity tends to increase as the wavelength increases. If the distance between the light bulb 701 and the bandpass filter 702 changes, the temperature of the bandpass filter 702 will also change. Because the transmission characteristics of the bandpass filter 702 tend to change depending on the temperature due to thermal expansion or contraction of the filter, the wavelength of the illumination light IL transmitted through the bandpass filter 702 also tends to change when the temperature of the bandpass filter 702 changes.

[0067] For example, in the case of a bandpass filter 702 having the characteristics shown in Figure 5, as the temperature of the bandpass filter 702 rises, the wavelength of the light transmitted through the bandpass filter 702 drifts to the longer wavelength side. Specifically, if the temperature of the bandpass filter 702 having the characteristics shown in Figure 5 rises by 200°C from the temperature during normal use, the center wavelength of the illumination light IL transmitted through the bandpass filter 702 becomes longer from 1.3 μm to approximately 1.31 μm (wavelength drift).

[0068] As the central wavelength changes, the light-receiving sensitivity of the InGaAs sensor changes from approximately 0.67 A / W at a wavelength of 1.3 μm to approximately 0.69 A / W at a wavelength of approximately 1.31 μm, as shown in Figure 7 (sensitivity change). Thus, when the wavelength of the illumination light IL transmitted through the bandpass filter 702 changes, the brightness of the observation image on the observation device 35 changes due to the change in the light-receiving sensitivity of the InGaAs sensor accompanying the change in wavelength. This can lead to the problem that it becomes difficult to obtain an observation image of the desired brightness even when the light intensity is adjusted.

[0069] To suppress such problems, when changing the relative distance between the light bulb 701 and the output port 711 to adjust the light intensity, the positional relationship between the light bulb 701 and the bandpass filter 702 is kept constant. This suppresses temperature fluctuations of the bandpass filter 702 and, consequently, suppresses changes in the transmission characteristics of the bandpass filter 702. This makes it possible to stably adjust the brightness of the observation image of the observation device 35.

[0070] Returning to Figure 6, as shown by reference numeral 6C, when the light intensity of the illumination light IL is set to 0 (zero), the light intensity control unit 707 inserts the shutter 705 into the optical path between the light bulb 701 and the output port 711 using the shutter drive unit 706. Since it is not necessary to turn off the light bulb 701 to set the light intensity to 0 (zero), the frequency of turning the light bulb 701 on and off during observation by the observation device 35 can be reduced. Consequently, the time required for so-called soft start, which is necessary to suppress the inrush current that occurs when the illumination light IL is turned on during observation by the observation device 35, can be reduced. In addition, by reducing the frequency of turning the light bulb 701 on and off, it is possible to suppress the shortening of the lifespan of the light bulb 701.

[0071] <Other> In the above embodiment, the light irradiation device 70 and the observation device 35 are connected via an optical fiber 730, but instead of the optical fiber 730, an aperture may be provided near the output port 711.

[0072] In the above embodiment, a laser processing apparatus 10 was described as an example of a processing apparatus. Naturally, it is also possible to apply the light irradiation device 70 to a blade dicing apparatus or other processing apparatus.

[0073] In the above embodiment, the case of observing the inside of the wafer W using infrared light was described as an example. Naturally, it is also possible to apply the light irradiation device 70 when observing the surface of the wafer W. In this case, it is possible to appropriately select a light bulb 701 and a bandpass filter 702 that have characteristics suitable for observation.

[0074] In the above embodiment, the case in which the light irradiation device 70 is applied to the observation device 35 for observing the wafer W was described, but naturally, the object to be observed is not limited to the wafer W.

[0075] <Effects of the invention> As described above, in the light irradiation device 70 of this embodiment, the light intensity of the illumination light IL is adjusted by changing the relative distance between the light bulb 701 and the output port 711 while keeping the voltage applied to the light bulb 701 constant. Therefore, a complex circuit for adjusting the voltage of the power supplied to the light bulb 701 to adjust the light intensity is unnecessary. Furthermore, since the light intensity of the illumination light IL can be adjusted while keeping the voltage of the power supplied to the light bulb 701 constant, changes in the spectral distribution of the light from the light bulb 701 caused by voltage changes are suppressed. Consequently, it becomes possible to control the illumination light having a desired wavelength at a desired light intensity more stably than in conventional devices.

[0076] In the light irradiation device 70 of this embodiment, when the light bulb 701 is a halogen lamp, the light intensity of the illumination light IL is adjusted while maintaining a constant voltage that allows the halogen cycle of the light bulb 701 to be stably generated. This makes it possible to suppress the shortening of the lifespan of the light bulb 701.

[0077] In the light irradiation device 70 of this embodiment, when changing the relative distance between the light bulb 701 and the output port 711 to adjust the light intensity of the illumination light IL, the positional relationship between the light bulb 701 and the bandpass filter 702 is kept constant. This makes it possible to suppress changes in the transmission characteristics of the bandpass filter 702 due to temperature fluctuations of the bandpass filter 702. Consequently, since the wavelength of the illumination light IL emitted from the light irradiation device 70 can be stabilized, the brightness of the observation image on the observation device 35 can be stably adjusted.

[0078] In the light irradiation device 70 of this embodiment, when the light intensity of the illumination light IL is set to 0 (zero), the shutter 705 is inserted into the optical path between the light bulb 701 and the output port 711. This reduces the frequency of turning the light bulb 701 on and off during observation by the observation device 35. Consequently, it becomes possible to reduce the time required for soft start to suppress the inrush current that occurs when the light bulb 701 is turned on during observation by the observation device 35. Furthermore, by reducing the frequency of turning the light bulb 701 on and off, it is also possible to suppress the shortening of the lifespan of the light bulb 701.

[0079] Although embodiments of the present invention have been described above, the present invention is not limited to the above examples, and various improvements and modifications may be made without departing from the spirit of the present invention. [Explanation of symbols]

[0080] 10…Laser processing device, 12…Base, 14…XYZθ stage, 16…Adsorption stage, 18…Processing unit, 20…Monitor, 22…Control device, 25…Laser optics, 26…Laser light source, 27…Collimating lens, 28…Half mirror, 29…Focusing lens, 30…Observation optics, 32…Collimating lens, 33…Half mirror, 34…Focusing lens, 35…Observation device, 70…Light irradiation device, 701…Light bulb, 702…Bandpass filter, 703…Relative distance adjustment unit, 704…Power supply, 705…Shutter, 706…Shutter drive unit, 707…Light intensity control unit, 710…Housing, 711…Outlet, 712…Illuminance sensor, 720…Connector, 730…Optical fiber, CH…Street, X,Y,Z…Axial direction, θ…Direction around the Z axis, W…Wafer

Claims

1. A light irradiation device provided in an observation apparatus for observing semiconductor wafers, A light bulb having a filament, A power supply that provides the light bulb with power at a voltage such that the light from the light bulb has a predetermined spectral distribution, A housing for the aforementioned light bulb, The housing is provided with an outlet that transmits light emitted from the light bulb, A relative distance adjustment means for changing the relative distance between the light bulb and the outlet, A light intensity control means for controlling the amount of light emitted from the outlet, Equipped with, When changing the light intensity, the light intensity control means changes the relative distance using the relative distance adjustment means while keeping the voltage of the power supplied from the power source constant in order to suppress changes in the spectral distribution of the light of the light bulb. Light irradiation device.

2. A shutter that blocks the aforementioned light, A shutter driving means for driving the shutter, Furthermore, When the light intensity is to be reduced to zero, the light intensity control means moves the shutter along the light path from the light bulb to the light outlet using the shutter driving means while the light bulb is lit. The light irradiation device according to claim 1.

3. A bandpass filter that limits the wavelength band of the light is further provided between the light bulb and the output port. The light irradiation device according to claim 1 or 2.

4. The light irradiation device according to claim 3, wherein the relative distance adjustment means changes the relative distance while keeping the positional relationship between the light bulb and the bandpass filter constant.

Images