JP2017020880A - Film thickness unevenness inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film thickness unevenness inspection device capable of discriminating a portion where film thickness is thick and a portion where the film thickness is thin, when thickness unevenness of a resin film applied onto a substrate is inspected.SOLUTION: A film thickness unevenness inspection device 1 for inspecting thickness unevenness of a rein film 2 applied onto a substrate, includes: a stage 4 which holds the substrate; a light irradiation section 5 which irradiates the resin film 2 with light having a predetermined wavelength region; an imaging section 6 which acquires intensity distribution of fluorescent light emitted from the resin film 2 as an image; and a control section 7 which control the operations of the stage 4, the light irradiation section 5, and the imaging section 6, and has a function of processing an image signal acquired by the imaging section 6. The control section 7 specifies a portion where film thickness is thick and a portion where the film thickness is thin of the resin film 2 from fluorescence intensity distribution acquired by the imaging section 6.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a film thickness nonuniformity inspection apparatus that inspects a thickness nonuniformity of a resin film applied on a substrate.

  When a resin film such as a resist film is applied on a substrate such as a wiring substrate, thickness unevenness may occur. If this thickness unevenness exceeds the allowable range, it may adversely affect the processing conditions of the subsequent process and the quality of the final product. For this reason, the inspection of the film thickness nonuniformity of the resin film apply | coated on the board | substrate is performed conventionally.

  As an inspection of film thickness unevenness, a method of irradiating a resin film on a substrate with monochromatic light as described in Patent Document 1 and visually observing or imaging an interference fringe caused by a difference in film thickness to determine pass / fail Is conventionally known.

  An example of an apparatus for imaging interference fringes and inspecting film thickness unevenness is shown in FIG. In the optical interference type film thickness unevenness inspection apparatus 100 of FIG. 8, the light emitted from the light source 105 is converted into a single wavelength by the optical filter 106 (if the light source 105 is a single wavelength light source such as a sodium lamp, the optical filter 106 is not required), and the substrate 3, the camera 107 irradiates the resin film 2 on the surface 3 and images the reflected light from the resin film 2. Here, the reflected light intensity from the resin film 2 is such that the reflected light on the resin film surface 2a interferes with the reflected light on the resin film back surface 2b (substrate 3 side), and the film thickness T of the resin film 2 and the reflected light intensity. The relation of PR is as shown in FIG. 9, and if there is a change in the film thickness 2 in the plane on the substrate 3, interference fringes are generated. For this reason, the presence or absence of a film thickness change is known from the interference fringes in the captured image. That is, the film thickness unevenness can be inspected.

JP-A-9-329423

  When thickness unevenness occurs in the resin film applied on the substrate, it is necessary to analyze the cause of the thickness unevenness and take specific measures in the application process or the like. For this reason, it is necessary to grasp the state where the thickness unevenness occurs, that is, the thick and thin portions.

  By the way, in the method of inspecting the film thickness unevenness by optical interference, it can be seen that interference fringes occur in both cases where the film thickness becomes thicker and thinner, as shown in FIG. For this reason, in the method using the interference fringes, the portion where the film thickness is changed can be recognized, but it cannot be determined whether the film is thick or thin. For example, when the resin film 2 has a film thickness portion B2 and a thin film portion D2 as shown in FIG. 10 (the AA cross-sectional view of FIG. 10A viewed from the top is as shown in FIG. 10B). 11), the reflected light image VR showing the in-plane distribution of the reflected light intensity PR is as shown in FIG. 11, and interference fringes appear in a ring shape in the film thickness part B2 and the thin film part D2.

  The present invention has been made in view of the above problems, and a film thickness unevenness inspection capable of distinguishing between a thick part and a thin part when inspecting a thickness unevenness of a resin film applied on a substrate. A device is provided.

In order to solve the above problems, the invention described in claim 1
A film thickness non-uniformity inspection apparatus for inspecting a thickness non-uniformity of a resin film applied on a substrate,
A stage for holding the substrate;
A light irradiation unit for irradiating the resin film with light in a predetermined wavelength range;
An imaging unit that acquires an intensity distribution of fluorescence emitted from the resin film as an image;
A control unit that controls operations of the stage, the light irradiation unit, and the imaging unit, and that has a function of processing an image signal acquired by the imaging unit;
The control unit has a function of specifying a thin part and a thick part of the resin film from the fluorescence intensity distribution acquired by the imaging unit.

The invention described in claim 2
The film thickness nonuniformity inspection apparatus according to claim 1,
The imaging unit includes an imaging device and an imaging unit optical filter disposed on an optical path from the resin film to the imaging device,
The imaging unit optical filter has a characteristic of blocking the wavelength range of light emitted from the light irradiation unit while transmitting the wavelength range of fluorescence emitted from the resin film.

The invention according to claim 3
The film thickness nonuniformity inspection apparatus according to claim 1 or 2,
The light irradiator includes a light source, and a light irradiator optical filter disposed on an optical path leading to the light source and the resin film,
The said light irradiation part optical filter has the characteristic which interrupts | blocks the wavelength range of the fluorescence emitted from the said resin film.

The invention according to claim 4
It is a film thickness nonuniformity inspection apparatus in any one of Claims 1-3,
The wavelength of the light irradiated to the resin film by the light irradiation unit is in the range of 390 nm to 550 nm,
The imaging unit has a characteristic of blocking wavelengths shorter than 550 nm.

The invention described in claim 5
It is a film thickness nonuniformity inspection apparatus in any one of Claims 1-4,
Using a TDI camera for the imaging device,
Fluorescence image distribution is obtained by imaging while moving the stage relative to the imaging unit and the light irradiation unit.

  With the film thickness unevenness inspection apparatus of the present invention, it is possible to easily distinguish between a thick part and a thin part when inspecting the thickness unevenness of the resin film applied on the substrate.

It is a figure which shows the structure of the film thickness nonuniformity inspection apparatus which concerns on one Embodiment of this invention. It is a figure for demonstrating the function of the film thickness nonuniformity inspection apparatus which concerns on one Embodiment of this invention. (A) It is a figure which shows an example of the fluorescence intensity distribution in the cross section of the board | substrate obtained with the film thickness nonuniformity inspection apparatus which concerns on one Embodiment of this invention. (B) The in-plane distribution of the fluorescence intensity obtained with the same inspection apparatus. It is an example. (A) It is a figure explaining that film thickness nonuniformity is difficult to detect when the irradiation light intensity distribution is nonuniform in the film thickness nonuniformity inspection apparatus according to one embodiment of the present invention. (B) The intensity distribution is nonuniform. It is a figure which shows the standard intensity distribution of the fluorescence which should be obtained in such a case. It is a figure which shows the structure of the modification of the film thickness nonuniformity inspection apparatus which concerns on one Embodiment of this invention. It is a figure for demonstrating the function of the modification of the film thickness nonuniformity inspection apparatus which concerns on one Embodiment of this invention. It is a figure which shows the structure of another modification of the film thickness nonuniformity inspection apparatus which concerns on one Embodiment of this invention. It is an example of the apparatus which test | inspects film thickness nonuniformity by optical interference. It is a figure explaining the principle in which an interference fringe appears in reflected light by a film thickness change. (A) It is the figure which looked at the case where there exist a thick part and a thin part in the resin film apply | coated on the board | substrate from the upper surface. (B) It is a figure which shows the linear cross section in which the thick part and thin part exist in the resin film. It is a figure which shows the reflected light when a monochromatic light is irradiated to what has a thick part and a thin part in the resin film apply | coated on the board | substrate.

Embodiments of the present invention will be described with reference to the drawings.
First, the film thickness nonuniformity inspection apparatus 1 which is one embodiment according to the present invention shown in FIG. 1 will be described. 2 is a diagram used when explaining the function of the film thickness inspection apparatus 1, and shows a state seen from the X direction of FIG.

  A resin film 2 to be inspected by the film thickness unevenness inspection apparatus 1 is applied on a substrate 3. The film thickness unevenness inspection apparatus 1 includes a stage 4, a light irradiation unit 5, an imaging unit 6, and a control unit 7. In the present embodiment, the surface holding the substrate 3 is the XY plane, and the direction orthogonal to the XY plane is the Z direction.

  The resin film 2 is mainly composed of a resin such as epoxy or polyimide, and emits fluorescence while being extremely weak against visible light irradiation. For this reason, it is not necessary to add a fluorescent material to the resin film 2. Note that “fluorescence” refers to light having a longer wavelength than the irradiation light emitted when the molecule irradiated with light is excited, and includes phosphorescence as well as fluorescence. Here, since the emitted light is emitted by exciting the molecules in the film, the number of excited molecules increases and the fluorescence intensity tends to increase as the film thickness increases.

  The substrate 3 forms a wiring substrate or the like. The substrate 3 is mainly composed of an inorganic material such as glass, ceramics, or silicon, and does not emit fluorescence under the condition that the resin film 2 emits fluorescence (or the resin film 2 does not emit light). Those which are extremely weak compared with each other are effective in the present invention. In addition, since metal does not emit fluorescence, metal wiring such as copper may be provided on the substrate 3.

  The stage 4 is disposed on a flat table (not shown), and has a function of holding the substrate 3 by vacuum suction or the like and a function of moving on the table in the XY plane while holding the substrate 3. .

  The light irradiation unit 5 has a function of irradiating the resin film 2 with light in a predetermined wavelength range. The light irradiating unit 5 includes a light source 51 and a light irradiating unit optical filter 52 that transmits light in a predetermined wavelength range.

  A white light source may be used as the light source 51, but if a monochromatic light source such as a light emitting diode (hereinafter referred to as an LED light source) or a semiconductor laser (hereinafter referred to as an LD light source) is used, the light irradiation unit filter 52 may be omitted. There is.

  As a function of the optical filter 52, it is necessary to transmit light in a predetermined wavelength region and to block the wavelength region of fluorescence emitted from the resin film 2 (by irradiating light in the predetermined wavelength region). That is, since the fluorescence emitted from the resin film 2 is weak, it is necessary to exclude light that becomes a disturbance when detecting the fluorescence from the irradiation light. For example, even when a monochromatic light source such as an LED light source or an LD light source is used as the light source 51, the light irradiation unit optical filter 52 can be omitted if there is a portion where the emission wavelength overlaps the fluorescent wavelength region. Absent. However, if the light source 51 includes a light emission wavelength that is included in a predetermined wavelength range and does not include a wavelength that overlaps the fluorescence wavelength range, the light irradiation unit optical filter 52 can be omitted.

  In order to increase the fluorescence intensity as a predetermined wavelength range, it is desirable to be on the short wavelength side, but there is a concern that light in the short wavelength range may adversely affect the resin film 2, especially when the resin film 2 is a photosensitive resist. In this case, ultraviolet light is not preferable. For this reason, it is desirable that the wavelength in the predetermined range is longer than the visible range, that is, 390 nm. However, it is not preferable to irradiate the resin film 2 with light having a wavelength longer than 550 nm because fluorescence emission that can be detected by the imaging unit 6 is difficult to obtain. That is, the predetermined wavelength range is desirably in the range of 390 nm to 550 nm.

  The range of the resin film 2 to which the light irradiation unit 5 emits light varies depending on the field of view of the imaging unit 6, but in FIG. 1, the field region 2L of the imaging unit 6 is linear as will be described later. For this reason, the light source 51 and the light irradiation unit optical filter have a shape that uniformly irradiates the visual field region 2L. Although not shown, a lens for condensing light in the visual field region 2L may be disposed on the optical path of the resin film 2 from the light source 51.

  The imaging unit 6 has a function of acquiring the intensity distribution of fluorescence emitted from the resin film 2. The imaging unit 6 includes an imaging device 61 and an imaging unit optical filter 62 as constituent elements. The imaging unit optical filter 62 has a function of transmitting the wavelength range of the fluorescence emitted by the resin film 2 while blocking the wavelength range of the light irradiated by the light irradiation unit 5 onto the resin film 2.

  The imaging device 61 has a function of converting the light intensity of each pixel in the field of view into an electrical signal. For example, a CCD solid-state imaging device, a MOS image sensor, a CMOS image sensor, or the like is used. As the imaging device 61, either an area camera having two-dimensional pixels or a line sensor camera having one-dimensional pixels is used. When a line sensor camera is used as the imaging device, the visual field region 2L is linear in the X direction as shown in FIG. 1, but the stage 4 is (relatively) arranged relative to the light irradiation unit 5 and the imaging unit 6. A two-dimensional fluorescence distribution can be acquired by taking an image every time a certain distance is moved in the Y direction.

  In the present embodiment, when irradiating light of uniform intensity to the visual field region, the one-dimensional visual field is easier to construct as the visual field region 2L as shown in FIG. 1 than the two-dimensional visual field. Yes. In addition to a general line sensor camera, a TDI camera (Time Delay Integration Camera) can be applied to the linear visual field 2L. The TDI camera has a one-dimensional field of view, but uses a two-dimensionally arranged pixel to increase the light receiving sensitivity. Since the TDI camera has high sensitivity, it is suitable for measuring the intensity of faint light, and is particularly suitable for measuring the intensity of extremely weak fluorescence emitted when receiving visible light.

  Specifically, the control unit 7 may have a configuration in which a CPU, a ROM, a RAM, an HDD, and the like are connected by a bus, or may be configured by a one-chip LSI or the like. The control unit 7 has a function of controlling the functions of the stage 4, the light irradiation unit 5, and the imaging unit 6 and processing the fluorescence distribution acquired by the imaging device 61 of the imaging unit 6 as an image signal.

  The control unit 7 is connected to the stage 4 and has a function of controlling the holding of the substrate 3 and the movement of the stage 4 in the XY directions. The control unit 7 is connected to the light irradiation unit 5 and has a function of controlling the direction of light irradiation, blinking of the light source 51 and lighting power. The control unit 7 is connected to the imaging unit 6 and has a function of controlling adjustment of the imaging field of view and image capture by the imaging device 61. The control unit 7 also has a function of processing an image acquired by the imaging device 61.

  In the film thickness unevenness inspection apparatus 1 according to the present invention, light is irradiated to the visual field region 2L of the resin film 2 shown in FIG. Here, as shown in FIG. 2, what is irradiated to the visual field region 2L is light LI emitted from the light source 51 and transmitted through the light irradiation unit optical filter 52 to become a predetermined wavelength region. Here, it is desirable that the predetermined wavelength range is in the range of 390 to 550 nm as described above.

  As shown in FIG. 2, the resin film 2 in the visual field region 2L emits fluorescent FO by receiving the light LI. The fluorescent FO passes through the imaging unit optical filter 62 and is converted into an electrical signal by the imaging device 61. The light LI is partially reflected by the visual field region 2L, but the reflected light is blocked by the imaging optical filter 62.

  The fluorescence FO emitted from the visual field region 2L is converted into an electric signal by the imaging device 61. An example thereof is shown in FIG. FIG. 3A shows a portion corresponding to AA in FIG. 10A, that is, a region having a cross-sectional shape as shown in FIG. 10B as a visual field region 2L. It is strong at the thick part and weak at the thin part. Therefore, it is possible to determine that a certain range G is provided for the fluorescence intensity PF, the portion where the fluorescence intensity PF exceeds the upper limit of the range G is thick, and the portion where the fluorescence intensity PF is less than the lower limit of the range G is thin. . Such a determination is performed by the control unit 7 having a function of processing an image acquired by the imaging device 61.

  In the present embodiment, the visual field region 2L is one-dimensional in the X direction in FIG. 1 by the line sensor camera. Therefore, in order to perform the film thickness nonuniformity inspection on the entire surface of the substrate 3, the stage 4 is moved in the Y direction by a certain amount in the Y direction at least in the range where the inspection region (for example, Y0 to Y1 in FIG. 10A) is included. While moving, the control unit 7 controls the stage 4 and the imaging device 61 so that the imaging device 61 captures an image. Instead of moving the stage 4, the imaging unit 6 may be moved in the Y direction. Note that the amount of movement when the stage 4 is moved in the Y direction by a certain amount for each imaging may be arbitrarily set as necessary, but is preferably about the same as the resolution in the X direction determined by the number of pixels of the licensor camera.

  An example of the two-dimensional intensity distribution of fluorescence obtained by relatively moving the stage 4 and the imaging unit 6 in the Y direction is shown in FIG. In FIG.3 (b), the part which is not emitting fluorescence is blackened, and it changes from gray to white as fluorescence intensity increases. Since the film thickness is thick when the fluorescence is strong and the film thickness is thin when the fluorescence is weak, in FIG. 2B, the thick part and the thin part of the resin film 2 can be easily distinguished on the surface of the substrate 3. . This is very different from the result obtained by the method using optical interference (FIG. 11).

  By the way, in FIG. 3A, if the resin film 3 has the same film thickness, the fluorescence intensity PF is the same regardless of the location, but depending on the light source 51, the intensity of the light LI irradiated to the resin film 2 is the same. May not be uniform in the X direction. That is, depending on the width (X direction) of the light source 61 with respect to the width (X direction) of the visual field region 2L, the light LI becomes weak at both ends of the visual field region 2L. In such a case, the intensity distribution of the light LI is reflected in the fluorescence FO. An example of this is shown in FIG. 4A in the case where the portion corresponding to AA in FIG. 10A, that is, the region having the cross-sectional shape as shown in FIG. In FIG. 4A, it can be seen that there are a portion where the fluorescence intensity PF is strong and a weak portion with respect to the periphery, but a range G is provided to discriminate whether the film thickness is thick or thin as shown in FIG. I can not. Therefore, when the fluorescence intensity PF differs depending on the location even if the resin film 2 has the same film thickness, a standard fluorescence intensity PF distribution as shown in FIG. 3B is obtained, and the standard fluorescence is obtained for each location. What is necessary is just to make it the control part 7 have the function to determine whether a film thickness is thick or thin compared with intensity | strength PF.

  The embodiment of the present invention has been described above by taking the film thickness unevenness inspection apparatus 1 of FIG. 1 as an example. FIG. 5 shows a modification of the embodiment of the present invention. In the film thickness nonuniformity inspection apparatus 11 of FIG. 5, the half mirror 8 is arrange | positioned on the optical path of the light irradiation part 5 and the resin film 2, and the resin film is reflected after the light LI is reflected by the half mirror 8, as shown in FIG. The fluorescent FO emitted from the resin film 2 is transmitted through the half mirror 8 and reaches the imaging unit 6. Here, if a dichroic mirror is used as the half mirror 8, the functions of the light irradiation unit filter 52 and the imaging unit optical filter 62 can be assigned to the half mirror 8 which is a dichroic mirror.

  FIG. 7 shows another modification of the embodiment of the present invention. In the film thickness nonuniformity inspection apparatus 21 in FIG. 7, an area camera that acquires a two-dimensional image is used as the imaging apparatus 61. In the above description, on the assumption that the fluorescence intensity is weak, a line sensor camera and preferably a TDI camera are preferably used as the imaging device 61. However, when the fluorescence intensity is relatively high, the field of view field 2A in FIG. You may employ | adopt the area camera which acquires a fluorescence image in such a two-dimensional area | region. For example, when a resin film 2 containing a fluorescent material is to be inspected, an area camera can also be employed.

DESCRIPTION OF SYMBOLS 1 Thickness nonuniformity inspection apparatus 2 Resin film 3 Substrate 4 Stage 5 Light irradiation part 6 Imaging part 7 Control part 8 Half mirror 10 Control part 51 Light source 52 Light irradiation part Optical filter 61 Imaging device 62 Imaging part Optical filter

Claims (5)

A film thickness non-uniformity inspection apparatus for inspecting a thickness non-uniformity of a resin film applied on a substrate,
A stage for holding the substrate;
A light irradiation unit for irradiating the resin film with light in a predetermined wavelength range;
An imaging unit that acquires an intensity distribution of fluorescence emitted from the resin film as an image;
A control unit that controls operations of the stage, the light irradiation unit, and the imaging unit, and that has a function of processing an image signal acquired by the imaging unit;
The film thickness nonuniformity inspection apparatus in which the control unit has a function of specifying a thin part and a thick part of the resin film from the fluorescence intensity distribution acquired by the imaging unit. The film thickness nonuniformity inspection apparatus according to claim 1,
The imaging unit includes an imaging device and an imaging unit optical filter disposed on an optical path from the resin film to the imaging device,
The film thickness nonuniformity inspection apparatus which has the characteristic which the said imaging part optical filter permeate | transmits the wavelength range of the fluorescence emitted from the said resin film, and interrupts | blocks the wavelength range of the light irradiated from the said light irradiation part. The film thickness nonuniformity inspection apparatus according to claim 1 or 2,
The light irradiator includes a light source, and a light irradiator optical filter disposed on an optical path leading to the light source and the resin film,
The film thickness nonuniformity inspection apparatus in which the light irradiation unit optical filter has a characteristic of blocking a wavelength range of fluorescence emitted from the resin film. It is a film thickness nonuniformity inspection apparatus in any one of Claims 1-3,
The wavelength of the light irradiated to the resin film by the light irradiation unit is in the range of 390 nm to 550 nm,
A film thickness unevenness inspection apparatus in which the imaging unit has a characteristic of blocking wavelengths shorter than 550 nm. It is a film thickness nonuniformity inspection apparatus in any one of Claims 1-4,
Using a TDI camera for the imaging device,
A film thickness nonuniformity inspection apparatus that obtains a fluorescence image distribution by imaging while moving the stage relative to the imaging unit and the light irradiation unit.

Images