A method for repairing defects in a photomask

Abstract

The present application relates to a kind of preventive repair of damaged photomask defect repair method, comprising the following steps: confirming the type of defect on photomask;According to the type of defect, PSM vapor deposition and / or quartz etching are selected to repair defects;And defect analysis is carried out using a spatial image measurement system to determine the eligibility of the repaired photomask.The method can prevent the problem of repeated repair caused by washing off the deposited material when the traditional deposition repair mode is washed in the back-end cleaning, and can ensure that the PSM phase of the repaired mask is reversed by 180 degrees and its light transmittance.

Description

Technical Field

[0001] This invention relates to the field of photomask repair technology, and in particular to a method for repairing defects in photomasks to prevent damage. Background Technology

[0002] Common defects in the Hole layer of a photomask include repairable pinholes and white bumps. Figure 1 ), including the peeling type, covering type, pattern enlargement type, overall small enlargement type, and white convex type spanning three sides ( ) among the difficult repair types. Figure 2 ).

[0003] Currently, the method for repairing white defects involves using a deposition method to fill in the extra parts on the image. Afterwards, the deposition residue is cleaned off, and the image is then checked against an Aerial Image Measurement System (AIMS) to confirm whether it meets the acceptance requirements. However, this repair method has the following drawbacks:

[0004] 1. For white convex and peeling types, although the extra part of the pattern defect can be filled by deposition and it looks no different from the normal pattern, it may not actually meet the requirements. Therefore, it is easy to cause repeated corrections and eventually scrap.

[0005] 2. For minor changes in size, the entire pattern is usually framed and repaired by deposition. The disadvantage is that it will affect the light transmittance inside the Hole, causing the light transmittance to exceed the standard specification, which is unqualified and may even lead to scrapping in severe cases.

[0006] 3. For white defects, if the deposition thickness and time are insufficient, they are easily removed, either entirely or partially, during cleaning.

[0007] Therefore, for defects such as peeling, covering, enlarged pattern, overall small enlargement, and white convexity across three sides, a repair method is needed that can meet the requirements for both appearance and light transmittance after the defect is repaired. Summary of the Invention

[0008] To address at least some of the problems mentioned above in the prior art, the present invention provides a method for preventing and repairing defects in photomasks, characterized by comprising the following steps:

[0009] Identify the type of defects on the photomask;

[0010] Depending on the type of defect, PSM vapor deposition and / or quartz etching may be selected to repair the defect; and

[0011] Defect analysis was performed using a spatial image measurement system to determine the suitability of the repaired photomask.

[0012] Furthermore, when defects on the photomask are of the peeling type, covering type, pattern enlargement type, or white convex type spanning three sides, the PSM vapor deposition method is used for repair.

[0013] Furthermore, the steps for repairing defects using the PSM vapor deposition method are as follows:

[0014] Take a normal pattern with the same CD line width, and deposit a repair layer directly at the defect location according to the shape of the normal pattern; and

[0015] After repair, the photomask is cleaned, and a spatial imaging system is used to simulate imaging and perform defect analysis to determine whether the transmittance of the repaired photomask is up to standard.

[0016] Furthermore, if the transmittance of the photomask is confirmed to be acceptable through a spatial image measurement system, the defect repair is complete.

[0017] If the transmittance of the photomask is confirmed to be substandard by a spatial image measurement system, quartz etching is performed for repair.

[0018] Furthermore, when the defects on the photomask are of the overall size variation, quartz etching is used to repair the defects.

[0019] Furthermore, when the appearance of the defect has been corrected to match the normal pattern, but the light transmittance does not meet the requirements, quartz etching is used for repair.

[0020] Furthermore, the steps for repairing defects using the quartz etching method are as follows:

[0021] The spatial imaging measurement system was used to confirm the difference in transmittance at the defect location compared to the normal pattern; and

[0022] Select 1 / 3 or 1 / 4 of the area within the defect as the etching range, input the information into the repair machine, and set the number of etching layers or the ion repair energy of the repair machine.

[0023] The repair machine directly sprays etching gas onto the set etching area for repair.

[0024] Furthermore, the number of etching layers or the ion repair energy of the repair machine include:

[0025] Set the number of etched layers to 30% to 60% of the maximum number of etched layers on the repair machine, or set the ion repair energy to 30% to 60% of the total energy.

[0026] The present invention has at least the following beneficial effects: The present invention discloses a method for repairing defects in photomasks to prevent damage during repair. This method prevents the traditional deposition repair method from washing away the deposited material during the later cleaning stage, which would otherwise require repeated repairs. The method can ensure that the PSM phase of the repaired photomask is reversed by 180° and its transmittance is maintained. This method prevents situations where the traditional deposition repair method can repair the defect appearance to match the normal pattern, but the transmittance cannot meet the requirements, leading to scrap. The method can improve yield, reduce costs, and improve product quality. Attached Figure Description

[0027] To further illustrate the above and other advantages and features of the various embodiments of the present invention, a more specific description of the embodiments of the invention will be presented with reference to the accompanying drawings. It is to be understood that these drawings depict only typical embodiments of the invention and are therefore not intended to limit its scope. In the drawings, identical or corresponding parts will be indicated by identical or similar reference numerals for clarity.

[0028] Figure 1 A schematic diagram of a repairable defect is shown;

[0029] Figure 2 A schematic diagram of a difficult-to-repair defect is shown;

[0030] Figure 3 A schematic diagram of a white convex defect is shown;

[0031] Figure 4 A schematic diagram of an overall micro-to-large defect is shown;

[0032] Figure 5 The flowchart of a photomask defect repair method for preventing and repairing damage according to an embodiment of the present invention is shown;

[0033] Figure 6 and 7 A schematic diagram of a quartz etching repair process according to an embodiment of the present invention is shown;

[0034] Figure 8 A schematic diagram of a photomask structure is shown; and

[0035] Figure 9 A schematic diagram of another photomask structure is shown. Detailed Implementation

[0036] It should be noted that the components in the accompanying drawings may be shown exaggerated for illustrative purposes and may not be to scale.

[0037] In this invention, the various embodiments are merely intended to illustrate the solutions of the invention and should not be construed as limiting.

[0038] In this invention, unless otherwise specified, the quantifiers “a” and “one” do not exclude scenarios involving multiple elements.

[0039] It should also be noted that, in the embodiments of the present invention, only a portion of the parts or components may be shown for clarity and simplicity. However, those skilled in the art will understand that, under the teachings of the present invention, the required parts or components can be added as needed for specific scenarios.

[0040] It should also be noted that within the scope of this invention, the terms "same", "equal", and "equal to" do not mean that the two values ​​are absolutely equal, but allow for a certain reasonable error. In other words, the terms also cover "substantially the same", "substantially equal", and "substantially equal to".

[0041] It should also be noted that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not explicitly or implicitly suggest that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] Furthermore, the embodiments of the present invention describe the process steps in a specific order. However, this is only for the convenience of distinguishing each step, and is not a limitation on the order of each step. In different embodiments of the present invention, the order of each step can be adjusted according to the process.

[0043] Generally, deposition methods can be divided into:

[0044] 1) Ion beam deposition, using a deposition gas (Depo GAS) of silica-like carbon, commonly known as diamond-like carbon (DLC).

[0045] 2) Electron beam deposition using chromium hexacarbonyl Cr(CO)6.

[0046] Different deposition gases can be used for different substrates (blanks). The following example uses a phase-shifted mask (PSM). It's explained that a phase-shifted mask provides a slight increase in transmittance to the light-blocking area. A 180-degree phase-shifted KrF PSM (248-wavelength phase-shifted mask) will have approximately 6% more transmittance than a traditional Binary mask, while an ArFPSM (193-wavelength phase-shifted mask) will have approximately 20% more transmittance. However, transmittance may vary slightly depending on the manufacturing process of different mask manufacturers. Both DLC and Cr(CO)6 are primarily composed of chromium, which is the opaque layer of the mask. Therefore, when repairing white defects, the transmittance of the PSM due to phase reversal must be considered.

[0047] like Figure 3 As shown, taking the white convex defect as an example, the two sides of the normal pattern 1 have defects 2 that need to be repaired. The conventional repair method is to deposit DLC or Cr(CO)6 in an area larger than the defect 2. There is no need to repair the left and bottom of the hole. The X and Y directions can each retain the phase shift. The transmittance of the Shift Mask does not affect the 180-degree phase reversal.

[0048] like Figure 4 As shown, taking the overall small-to-large defect as an example, defect 2 surrounds normal pattern 1, and the area surrounded by defect 2 is slightly larger than that of normal pattern. If DLC or Cr(CO)6 is deposited in an area larger than defect 2 using conventional repair, the transmittance of the phase shift mask will affect the 180-degree phase reversal, causing the slight loss of transmittance of its light-blocking part, which cannot meet the specifications and leads to scrap.

[0049] Based on the aforementioned problem that normal repair methods can easily affect the phase reversal transmittance of PSM, this invention provides a method for repairing photomask defects to prevent damage during repair. It employs two repair methods: PSM vapor deposition and quartz etching. These two methods correspond to different defects and can be used interchangeably to compensate for the deficiencies of each method, thereby meeting the repair needs of white convex, peeling, and overall small-to-large defects.

[0050] PSM vapor deposition is suitable for patterns where the defect location covers more than three sides of the hole, such as peeling, covering, enlarged pattern, and three-sided white convex pattern.

[0051] Quartz etching is suitable for the following three situations:

[0052] 1. The overall size changes from small to large.

[0053] 2. The appearance and shape have been corrected to match the normal pattern using PSM vapor deposition, but the light transmittance still exceeds the specifications.

[0054] 3. When normal hole defects are not properly repaired during etching, resulting in light transmittance exceeding specifications, this part also needs to be corrected to match the normal pattern through deposition mode.

[0055] Therefore, for special white defects that appear normal, quartz etching can be used for repair. This involves applying etching energy to the center of the pattern to reduce its light transmittance and achieve compliance with specifications. Quartz etching is a method of reducing light transmittance by causing damage to the quartz glass.

[0056] like Figure 5 As shown, a method for repairing defects in a photomask to prevent damage includes the following steps:

[0057] Step 1: Identify the type of defect on the photomask.

[0058] Step 2: Select PSM vapor deposition and / or quartz etching to repair the defect, depending on the type of defect.

[0059] Step 3: Use a spatial image measurement system to perform defect analysis to determine whether the repaired photomask is qualified.

[0060] If the defects on the photomask are of the peeling type, peeling type, large pattern size, or white convex type spanning three sides, they can be repaired using the PSM vapor deposition method. The specific steps are as follows:

[0061] Step 1: Take a normal pattern with the same CD line width, and deposit a repair layer directly on the defect according to the shape of the normal pattern.

[0062] Step 2: After repair, clean the photomask and use a spatial imaging system to simulate imaging and analyze defects to determine if the repaired photomask is acceptable. If the spatial imaging system confirms that the photomask is acceptable, proceed to the next engineering station. If the spatial imaging system confirms that the photomask's transmittance does not meet the requirements, quartz etching repair is necessary.

[0063] Quartz etching includes the following steps:

[0064] Step 1: Use a spatial image measurement system to confirm the difference in transmittance at the defect location compared to the normal pattern.

[0065] Step 2, as follows Figure 6 and 7As shown, first, select 1 / 3 or 1 / 4 of the area within the hole-pattern defect (quartz region) as the etching range 100, input it into the repair machine, and set the number of etching layers or the ion repair energy of the repair machine. The repair machine directly sprays etching gas into the set etching range. Reduce the number of etching layers or the ion repair energy of the repair machine, setting the number of etching layers to 30%–60% of the maximum number of etching layers of the repair machine, or setting the ion repair energy to 30%–60% of the full energy.

[0066] For cases where the repaired shape is normal and the pattern is consistent, but the light transmittance does not meet the requirements, the 1 / 3 or 1 / 4 area located in the center of the defect should be selected as the etching range.

[0067] This method uses etched gas to etch quartz, rather than typical chromium or molybdenum silicide layers. Therefore, the etching range must be matched with the number of etched layers or the ion repair energy.

[0068] Generally, deposition repair methods can be divided into two categories: ion beam deposition of carbonaceous material (DLC) and electron beam deposition of Cr(CO)6 hexacarbonyl chromium. Currently, ion beam deposition cannot achieve the phase effect of a Mosi (molybdenum silicide) layer on a PSM (photomask), so electron beam deposition is still the primary method of development. In electron beam deposition, the existing Cr(CO)6 on the equipment can be used with different gases to simulate the Chrome (chromium) or Mosi (molybdenum silicide) layers formed on the photomask, allowing for different deposition compositions to be created depending on the substrate. For example... Figure 8 As shown, the photomask consists of a quartz substrate 11 and a chromium layer 12. For this photomask, conventional deposition methods use gases such as XeF2, Cr(CO)6, etc., to deposit and repair the chromium layer of the photomask. Figure 9 As shown, the photomask consists of a quartz substrate 21, a silicon dioxide layer 22, a chromium layer 23, and another silicon dioxide layer 22 from bottom to top. For this photomask, PSM vapor deposition is used to deposit and repair gases such as XeF2, TEOS, and Cr(CO)6.

[0069] When a menu is created for repairing white defects, although the appearance can be repaired to be indistinguishable from the normal pattern, if the defect is too large or is a solid white defect, the light transmittance may not meet the requirements. Therefore, it is necessary to use the Qz (Quartz) Etch repair mode to make up for the problem of excessive light transmittance.

[0070] Based on the aforementioned PSM vapor deposition repair principle, PSM vapor deposition can be used to repair white defects of several types, including peeling, covering, enlarged patterns, and white convexity across three sides. However, as mentioned earlier, for larger or completely transparent white defects, the appearance may not match the transmittance requirements, so the Qz (Quartz) Etch repair mode is still needed as an auxiliary repair method.

[0071] If the overall size changes from small to large, it must first be confirmed whether it is no different from the normal pattern. If it is consistent with the normal pattern but the light transmittance still exceeds the customer's specifications, PSM GAS repair is not applicable. It must be repaired using the Qz (Quartz) Etch repair mode. If the appearance is larger than the normal pattern, it can be repaired according to the PSM GAS repair mode.

[0072] While some embodiments of the present invention have been described in this application, those skilled in the art will understand that these embodiments are merely illustrative. Numerous variations, alternatives, and improvements will arise in those skilled in the art under the teachings of this invention without departing from its scope. The appended claims are intended to define the scope of the invention and thereby cover methods and structures within the scope of the claims themselves and their equivalents.

Claims

1. A method for repairing defects in a photomask to prevent damage, characterized in that, Includes the following steps: Identify the type of defects on the photomask; Depending on the type of defect, PSM vapor deposition and / or quartz etching are selected to repair the defect. Specifically: PSM vapor deposition is used to repair defects on the photomask that are peeling, covering, enlarged, or three-sided white convex. Quartz etching is used to repair defects on the photomask that are generally small-to-large enlarged. Quartz etching is used to repair defects whose appearance has been corrected to match the normal pattern, but whose transmittance does not meet the requirements. Defect analysis was performed using a spatial image measurement system to determine the quality of the repaired photomask. The steps for repairing defects using PSM vapor deposition are as follows: Take a normal pattern with the same CD line width, and deposit a repair layer directly at the defect location according to the shape of the normal pattern; and After repair, the photomask is cleaned, and a spatial imaging system is used to simulate imaging for defect analysis to determine whether the transmittance of the repaired photomask is acceptable. If the transmittance of the photomask is confirmed to be acceptable by the spatial imaging system, the defect repair is complete. If the transmittance of the photomask is confirmed to be unacceptable by the spatial imaging system, quartz etching repair is performed. The steps for repairing defects using quartz etching are as follows: The spatial imaging measurement system was used to confirm the difference in transmittance at the defect location compared to the normal pattern; and Select 1 / 3 or 1 / 4 of the area within the defect as the etching range, input the information into the repair machine, and set the number of etching layers or the ion repair energy of the repair machine. The repair machine directly sprays etching gas onto the set etching area for repair.

2. The method according to claim 1, characterized in that, The number of etching layers or ion repair energy settings for the repair equipment include: Set the number of etching layers to 30% to 60% of the maximum number of etching layers on the repair machine, or set the ion repair energy to 30% to 60% of the full energy.

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