JP2012208185A - Resist inspection apparatus and defect inspection method of mask substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for performing a resist pattern inspection without deteriorating the performance of the inspection apparatus in which, when inspecting a resist pattern of a mask substrate using a short-wavelength and high output light source, outgas is generated to cause the deterioration of the performance of an optical system of the inspection apparatus.SOLUTION: A mask substrate 7 is fixed to a mask fixing holder 19 of the resist inspection apparatus to form a sealed space 31 with the surface of a resist 7a, a support 21, and a translucent protective member 22, and inert gas 27 is supplied to and exhausted from the sealed space 31 through vent holes 23 and 24 provided in the support 21. The outgas 28 generated by the application of the light 29 to the resist 7a is forcibly exhausted outside the sealed space 31 so as to prevent the deterioration of the inspection apparatus and allow the resist defect inspection in a mid-flow of a mask manufacturing step.

Description

  The present invention relates to a defect inspection method for a mask substrate of a reticle or photomask, and a resist inspection apparatus used therefor.

  In the manufacturing process of a semiconductor device, a reticle or a photomask (hereinafter referred to as “mask”) is used to form a pattern on a substrate. If there is a defect in the mask, the defect is transferred to the pattern, so that a defect inspection for detecting the defect present in the mask is performed.

  Known mask inspection methods include die-to-die inspection, die-to-database inspection, and foreign matter inspection.

  In die-to-die inspection, optical images of the same pattern regularly arranged on the mask are compared, whereas in die-to-database inspection, from the design data (CAD data) used when creating the mask The reference image to be created is compared with the pattern drawn on the mask.

  In a mask inspection apparatus, generally, a method of acquiring an optical image while moving the mask in the X direction and the Y direction while being held on a stage in the inspection apparatus. At this time, since the position of the stage is controlled by a laser interferometer or the like, the optical image of the mask to be acquired and the reference image are always aligned.

  A general mask manufacturing process includes a drawing device (electron beam drawing device or laser drawing device), a developing device, an etching device, and a defect inspection device.

  In the mask manufacturing process, specifically, the mask is generally manufactured through the following processes.

  Mask blanks, in which a light shielding film such as a Cr film or MoSi film is formed on a glass substrate, and a resist is applied thereon, are loaded onto a stage of a drawing apparatus. In a drawing apparatus, drawing data created from design data is drawn on a mask blank by a laser or an electron beam. The drawn mask is patterned by a developing device and an etching device.

  The patterned mask is subjected to defect inspection by a defect inspection apparatus. In the defect inspection system, an optical image that has passed through the mask pattern is acquired. For die-to-die inspection, images on the same mask are compared. For die-to-database inspection, the design data is referenced. A defect on the mask is detected by comparing the images. That is, in the mask inspection apparatus, a place where the degree of coincidence between the shape of the optical image and the reference image is determined as a defect.

  However, in the above process, the presence or absence of defects cannot be detected until the final defect inspection of the mask, it is possible to know where the defect has occurred in the mask manufacturing process, and the corresponding mask is a non-defective product. Therefore, it is difficult to know at an early stage of the mask manufacturing process whether or not the product can be shipped, and therefore, it is necessary to inspect defects during the mask manufacturing process such as after the development process and after the etching process.

Conventional defect inspection apparatuses for masks are for detecting defects present on a mask pattern. This mask defect inspection apparatus cannot cope with a defect inspection in the middle of a mask manufacturing process in which a resist remains on a mask substrate. Rather, a resist inspection apparatus that inspects a resist pattern is more suitable for defect inspection during the mask manufacturing process.
In the past, a relatively long wavelength such as i-line has been used as the inspection wavelength of the resist inspection apparatus, and outgassing has not been a major problem even when resist pattern inspection is performed.
However, due to the miniaturization of mask patterns accompanying the recent miniaturization of semiconductors, the inspection wavelength of inspection equipment has also become shorter, and the output has also increased. Outgas is released. The outgas remains as an adhering substance on the surface of an optical element such as a lens in the inspection apparatus.
If this phenomenon occurs for a long time, the performance of the optical element such as a lens deteriorates, and eventually the inspection performance is hindered.
In the unlikely event that such performance degradation occurs, the performance of the optical element may be restored by removing the degraded optical element such as a lens from the device and performing cleaning. This is not realistic because it takes a long time and there are problems such that the apparatus cannot be used during the work and the work cost is high.

  Various methods have been considered for preventing performance degradation of optical elements such as lenses, but fundamentally, a resist pattern is placed in a sealed space (for example, Patent Document 1). It is required not to touch the element.

  For this reason, a method of inspecting only a photomask in a sealed space is conceivable, but if it is a complete sealed space, the generated outgas will be filled in the sealed space, and the outgas will continue to enter the translucent part. As a result, the inspection light passes through the translucent part, resulting in a decrease in transmittance. As a result, a phenomenon occurs in which the inspection performance deteriorates in the same manner as when outgas adheres to an optical system such as a lens. .

JP2009-151197

  The present invention has been made in view of these circumstances, and resist inspection and resist in which outgas generated by resist inspection does not remain on the optical path of light for inspection and does not deteriorate the performance of optical elements such as lenses. An object of the present invention is to provide a resist inspection apparatus that enables pattern inspection and a useful mask defect inspection method that can be performed using the resist inspection apparatus.

In order to solve the above-described problem, a resist inspection apparatus according to the first aspect of the present invention includes:
In a resist inspection apparatus for inspecting a defect by detecting a resist pattern on the resist formation surface by reflected light of inspection light irradiated on a resist formation surface of a mask substrate,
A housing having an opening-shaped mask placement portion that is closed by placing the mask substrate;
An air supply passage and an exhaust passage that communicate with each other in the housing and supply and discharge air for air purge to and from the housing;
The inspection light for irradiating the resist forming surface exposed in the casing of the mask substrate that is provided in the casing and is placed on the mask mounting portion to seal the inside of the casing, and the resist forming surface A light transmissive portion through which the reflected light from each transmits.
It is characterized by providing.

  Further, the resist inspection apparatus according to the second aspect of the present invention includes a defect detection unit that detects a defect of the resist pattern by comparing the resist pattern detected from the reflected light with a resist pattern for comparison, and the defect detection unit. Detects the position of the resist pattern from which the defect has been detected from the irradiation position of the inspection light on the resist formation surface, and outputs the inspection result output of the defect detection unit and the detection result of the defect position detection unit And a section.

Furthermore, the resist inspection apparatus according to the third aspect of the present invention is characterized in that the light transmission part is a thin glass that transmits ultraviolet light.
The resist inspection apparatus according to the fourth aspect of the present invention further includes a pressure control unit that controls the pressure in the casing by air supplied to and discharged from the casing by the air supply passage and the exhaust passage. It is characterized by providing.

Furthermore, the defect inspection method for a mask substrate according to the fifth aspect of the present invention includes:
The pattern drawn on the resist is developed in the development process, the light shielding film is etched with the pattern in the etching process, and then the resist is peeled off in the film removal process. There,
The resist pattern defect on the mask substrate using at least one of the development process and before the etching process and after the etching process and before the film removal process using the resist inspection apparatus according to claim 1. Includes a resist defect inspection process to inspect,
It is characterized by that.

  In the mask manufacturing process, after a pattern is drawn on a mask blank by a drawing apparatus, patterning is performed by development and etching, and then a defect inspection is performed by a defect inspection machine. In other words, the presence or absence of defects can only be confirmed after the mask is in the final form. For this reason, as in the embodiment of the present invention, defect inspection is performed in a state where a resist such as after development and after etching exists on the mask, thereby making it possible to investigate the cause of the defect in the mask and to deal with the defect early.

  The resist inspection apparatus according to the present invention is useful for preventing the outgas generated from the resist from diffusing into the defect inspection apparatus and obtaining effects such as the performance position of the optical element and the replacement of the optical element. In addition, in order to eliminate the influence of outgas, only a mask mounting portion that becomes a sealed space when a mask substrate is mounted on a housing provided with a light transmitting portion that transmits inspection light and reflected light to the resist formation surface is provided. In addition, the air purge in the housing using the air supplied and exhausted through the air supply passage and the exhaust passage communicating the outgas generated in the housing so that the light transmission portion is not affected by the outgas. The air can be ventilated and discharged outside the housing.

It is a flowchart of a general mask manufacturing process. 1 is a conceptual diagram of a resist inspection apparatus according to an embodiment of the present invention. It is a conceptual diagram of the mask fixing holder of the resist inspection apparatus according to the embodiment of the present invention. It is a flowchart of the mask manufacturing process performed by implementing the defect inspection method for the mask substrate according to the embodiment of the present invention using the resist inspection apparatus of FIGS.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of a general mask manufacturing process 1. The mask manufacturing process 1 includes processes performed using a drawing apparatus 2 (electron beam drawing apparatus or laser drawing apparatus), a developing apparatus 3, an etching apparatus 4, a resist stripping apparatus 5, and a defect inspection apparatus 6, respectively.

  FIG. 2 is a conceptual diagram showing the configuration of a resist inspection apparatus 6A in the embodiment of the present invention. The resist inspection apparatus 6A is a post-development inspection apparatus 6a for defect inspection after the development process by the development apparatus 3 and a defect inspection after the etching process by the etching apparatus 4 in a mask manufacturing process 1A described later with reference to FIG. It can be used as a post-etching inspection apparatus 6b. The resist inspection apparatus 6A includes a stage 8 that holds a mask 7 (reticle or photomask) to be inspected. When the resist inspection apparatus 6A is used as the post-development inspection apparatus 6a, the stage 8 is provided with a mask 7 with a pattern formed on the resist immediately after development by the development apparatus 3. When the resist inspection apparatus 6A is used as the post-etching inspection apparatus 6b, the mask 7 in which the pattern on the resist is also formed on the light shielding film immediately after the etching by the etching apparatus 4 is placed on the stage 8.

  The stage 8 can be driven in the X-axis direction and the Y-axis direction by an actuator such as a motor. The position of the stage 8 is monitored by an X-axis position sensor 9 and a Y-axis position sensor 10 and is driven and controlled by a control unit 11.

  The resist inspection apparatus 6A includes a light source 12 such as a laser. Light from the light source 12 is applied to the resist formation surface of the mask 7 through the optical system 13.

  The light reflected from the resist pattern surface of the mask 7 returns to the optical system 13 and forms an image on the light receiving unit 14. The light receiving unit 14 is an image sensor using an image sensor of a transfer method such as a CCD (Charge Coupled Device) or a TDI (Time Delayed Integration).

  The resist pattern image of the mask 7 captured by the light receiving unit 14 is sent to the image processing unit 15. At this time, position information obtained from the X-axis position sensor 9 and the Y-axis position sensor 10 is associated with the coordinates of the defect detected by the defect detection unit 16 of the image processing unit 15.

  When the defect inspection is completed, the result is sent to the inspection result storage unit 17 and stored as the inspection result.

  The data stored in the inspection result storage unit 17 can be output through the result output unit 18 as necessary.

  Next, a mask fixing holder provided on the stage 8 and a method of sealing the resist pattern surface there will be described with reference to FIG. The mask fixing holder 19 is a structure provided on the stage 8 in FIG. The mask fixing holder 19 is provided with a hollow portion having a predetermined shape that matches the shape of the mask 7, and is cut out in order to fix the mask 7 by contacting the outermost peripheral portion of the pattern surface (resist surface) of the mask 7. A placement surface 20 is provided at the bottom of the part.

  A frame-like support body 21 that holds the translucent protection member 22 is configured below the placement surface 20, and the translucent protection member 22 covers the entire opening of the support body 21. The housing 30 is constituted by the mask fixing holder 19, the support 21 and the translucent protective member 22. The translucent protective member 22 is preferably composed of, for example, a thin glass plate that transmits ultraviolet light having a short wavelength suitable for detection of a fine pattern. When the mask 7 is placed on the mask fixing holder 19, a sealed space 31 is formed in the housing 30 by the surface of the mask 7 on which the resist 7 a is formed, the support 21, and the translucent protective member 22.

  Further, at least two vent holes 23 and 24 communicating with the inside of the housing 30 are made in the support body 21, and a gas supply pipe 25 and a gas exhaust pipe 26 are connected to each, and the mask 7 is a mask fixing holder. 19, while forming the sealed space 31, an inert gas 27 such as nitrogen is always supplied from the gas supply pipe 25 into the housing 30 by the gas supply unit 32, and at the same time, the outgas in the housing 30 is The fan unit 33 connected to the gas exhaust pipe 26 is forcibly exhausted from the inside of the housing 30, whereby the outgas 28 from the resist 7 a generated in the sealed space 31 is discharged and the gas supply unit 32. By controlling the gas supply amount and the gas discharge amount of the fan unit 33 by the control unit 11, the pressure in the sealed space 31 is always kept constant.

  Therefore, it is possible to prevent the outgas 28 generated from the resist 7a from being released outside the sealed space 31 when the mask 29 is irradiated with the light 29 via the optical system 13. This helps prevent performance degradation of the optical elements such as the optical system 13, and does not require work for returning the apparatus to a normal state, such as replacement of the optical elements such as the optical system 13. Time can be saved.

Further, unlike the case where a mask is put in a simple sealed space to prevent the outgas from being emitted, the sealed space 31 is always filled with an inert gas 27 such as new nitrogen, and the outgas 28 generated from the resist 7a is also a gas. Since the exhaust pipe 26 is forcibly exhausted to the outside of the sealed space 31 (housing 30), the inside of the sealed space 31 is also minimized by the outgas 28, and the transmittance of the translucent protective member 22 is prevented from decreasing at the same time. Achieved.
As described above, the resist inspection apparatus 6A of the present embodiment receives the reflected light of the light (inspection light) from the light source 12 irradiated on the resist 7a formation surface of the mask 7 (mask substrate) by the light receiving unit 14. In order to detect the resist pattern on the surface on which the resist 7a is formed and inspect the defect, a mask fixing holder having an open mask mounting surface 20 (mask mounting portion) that is closed by mounting the mask 7 19 and a casing 30 composed of a translucent protective member 22 (light transmitting portion) held via a support 21, and formed in the support 21 and communicated with the interior of the casing 30. A vent hole 23 through a gas supply pipe 25 (supply passage) and a vent hole 24 through a gas exhaust pipe 26 (exhaust passage) for supplying and discharging an inert gas 27 (air purge air) to and from the body 30 are provided. Configuration and mask mounting Light that irradiates the resist 7a forming surface exposed in the housing 30 of the mask 7 that is placed on the surface 20 so that the inside of the housing 30 is a sealed space 31 (sealed state), and reflected light from the resist 7a forming surface However, it was set as the structure which permeate | transmits the translucent protection member 22, respectively.
Further, the resist inspection apparatus 6A of the present embodiment compares the pattern of the resist 7a detected by receiving the reflected light with the light receiving unit 14 with the comparison resist pattern, and detects the defect of the resist 7a pattern. And a defect detection unit that detects the position of the resist 7a pattern where the defect detection unit 16 has detected the defect from the irradiation position of the light 29 on the resist 7a formation surface based on the detection results of the X-axis position sensor 9 and the Y-axis position sensor 10. 16 (defect position detection unit) and an inspection result output unit 17 that outputs a detection result (defect detection, defect position) of the defect detection unit 16.
Note that the resist pattern for comparison used for the defect inspection is a pattern of the resist 7a in another portion on the same mask 7 in the case of die-to-die inspection, and is design data in the case of die-to-database inspection.
Furthermore, in the resist inspection apparatus 6A of the present embodiment, the translucent protective member 22 is made of thin glass that transmits ultraviolet light.
In addition, the resist inspection apparatus 6A of the present embodiment includes an inert gas 27 and an outgas 28 that are supplied to the inside of the housing 30 through the vent hole 23 through the gas supply pipe 25 and the vent hole 24 through the gas exhaust pipe 26. A control unit 11 that performs pressure control in the body 30 is further provided.

  In the general mask manufacturing process 1 shown in FIG. 1, if the resist pattern inspection can be performed in the middle of the mask manufacturing process 1, the inspection after the development in the middle of the mask manufacturing process and the inspection after the etching can be performed. By performing this resist pattern inspection using the resist inspection apparatus 6A according to the embodiment of the present invention, the mask manufacturing process 1 is as shown in FIG.

  The mask manufacturing process 1 includes development processes in addition to general processes performed using the drawing apparatus 2 (electron beam drawing apparatus or laser drawing apparatus), the developing apparatus 3, the etching apparatus 4, the film removal apparatus 5, and the defect inspection apparatus 6, respectively. It has a post-development inspection process performed after the development process using the post-inspection apparatus 6a and a post-etching inspection process performed after the etching process using the post-etching inspection apparatus 6b. Each of these post-development inspection apparatus 6a and post-etching inspection apparatus 6b detects and inspects the pattern of the resist 7a of the mask 7 at the time after development and the time after etching. The inspection device 6A can be used.

  The resist inspection apparatus 6A according to the aspect of the present invention is used for defect inspection of the pattern of the resist 7a after development and after etching, where the resist 7a still exists on the mask 7 after each process step. As a result, it is possible to detect the defect generation process early and determine whether the mask 7 is a non-defective product at an earlier stage than the defect inspection performed using the final defect inspection apparatus 6.

DESCRIPTION OF SYMBOLS 1 ... Mask manufacturing process 2 ... Drawing apparatus 3 ... Development apparatus 4 ... Etching apparatus 5 ... Resist film removal apparatus 6 ... Mask inspection apparatus 6A ... Resist inspection apparatus 6b ... -Post-etching inspection device 7 ... Mask 7a ... Resist 8 ... Stage 9 ... X-axis position sensor 10 ... Y-axis position sensor 11 ... Control unit 12 ... Light source 13 ... Optical system 14: light receiving unit 15 ... image processing unit 16 ... defect detection unit 17 ... inspection result storage unit 18 ... result output unit 19 ... mask fixing holder 20 ... Mask mounting surface 21 ・ ・ ・ Support 22 ・ ・ ・ Translucent protective member 23 ・ ・ ・ Vent hole 24 ・ ・ ・ Vent hole 25 ・ ・ ・ Gas supply pipe 26 ・ ・ ・ Gas exhaust pipe 27 ・ ・ ・ Not used Active gas (nitrogen, etc.)
28 ・ ・ ・ Outgas 29 ・ ・ ・ Light 30 ・ ・ ・ Case 31 ・ ・ ・ Sealed space 32 ・ ・ ・ Gas supply unit 33 ・ ・ ・ Fan unit

Claims (5)

In a resist inspection apparatus for inspecting a defect by detecting a resist pattern on the resist formation surface by reflected light of inspection light irradiated on a resist formation surface of a mask substrate,
A housing having an opening-shaped mask placement portion that is closed by placing the mask substrate;
An air supply passage and an exhaust passage that communicate with each other in the housing and supply and discharge air for air purge to and from the housing;
The inspection light for irradiating the resist forming surface exposed in the casing of the mask substrate that is provided in the casing and is placed on the mask mounting portion to seal the inside of the casing, and the resist forming surface A light transmissive portion through which the reflected light from each transmits.
A resist inspection apparatus comprising:   A defect detection unit that detects a defect in the resist pattern by comparing the resist pattern detected from the reflected light with a resist pattern for comparison, and the position of the resist pattern in which the defect detection unit has detected a defect, 2. The apparatus according to claim 1, further comprising: a defect position detection unit that detects from an irradiation position of the inspection light in the step; and an inspection result output unit that outputs a detection result of the defect detection unit and the defect position detection unit. Resist inspection equipment.   The resist inspection apparatus according to claim 1, wherein the light transmission portion is a thin glass that transmits ultraviolet light.   The pressure control part which performs the pressure control in the housing | casing with the air supplied and discharged | emitted with respect to the inside of the housing | casing by the said air supply path and the said exhaust passage is further provided in any one of Claim 1 to 3 characterized by the above-mentioned. The resist inspection apparatus described. The pattern drawn on the resist is developed in the development process, the light shielding film is etched with the pattern in the etching process, and then the resist is peeled off in the film removal process. There,
The resist pattern defect on the mask substrate using at least one of the development process and before the etching process and after the etching process and before the film removal process using the resist inspection apparatus according to claim 1. Includes a resist defect inspection process to inspect,
A defect inspection method for a mask substrate, characterized in that:

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