JPH01503580A - Mask repair using an optimized focused ion beam device - Google Patents

Abstract

Apparatus and method for repairing semiconductor masks (32) and reticles is disclosed, utilizing a focused ion beam system (8) capable of delivering, from a single ion column, several different species of focused ion beams (12), each of which is individually optimized to meet the differing requirements of the major functions to be performed in mask repair. This method allows the mask (32) to be imaged with high resolution and minimum mask damage. Opaque defects are removed by sputter etching at high rates with minimum damage to the mask substrate (32), with the optional use of a sputter rate enhancing gas such as chlorine, and clear defects are filled in at high rates by deposition of a metallic or other substance compatible with the mask materials by condensation of metal-containing vapor such as chromium hexacarbonyl using a focused ion beam. A focused ion beam column able to produce precisely focused ion beams (12) is employed and is operated at high energies for imaging and sputter etching, and at low energies for imaging and deposition. A liquid metal alloy source (10) containing a plurality of suitable atomic species is employed.

Description

[Detailed description of the invention] Background of the invention of mask repair using an optimized focused ion beam device 1. Technical field of invention The present invention relates to a focused ion beam device. The present invention also relates to chemical vapor deposition and substrate materials. Focused ion beams to accelerate sputter etching and chemical vapor deposition rates of materials. It concerns the use of the system. In particular, the present invention applies to photomasks and reticles. It concerns the use of said technique for repair.

2. Conventional technology Conventional technologies include KLA/Micron SOS and Seiko 5IR100O.

and Ion Beam System's Microtrim.

These three types of devices all provide a kind of focused ion beam to the mask during repair, i.e. 20~ Only a gallium ion beam with an energy of 30 KeV is emitted. A video like this The high sputtering speed of the gallium ion beam caused significant mask damage during imaging. occurs. However, during imaging and opaque defect repair, a large amount of gallium is deposited on the mask substrate. and later identified as opaque defects by standard industrial mask inspection equipment. The so-called ``gallium staining'' that causes a localized decrease in the transparency of a dark substrate. arise. Clear defect repair has been attempted with these devices, but eventually Even if the existing metal film (usually chromium) covers part of the mask, Unable to attach compatible material to clear defects.

Detailed description of the invention The present invention uses a single ion beam column, each to be performed with mask repair. Several types of ion beams optimized to meet different requirements for main functions Novel semiconductor masks and reticles that utilize focused ion beam devices that can emit Includes Kuru's restoration techniques. These main functions are mask imaging (localized on the mask surface). creation of images of microscopic structures), opaque defect repair (localized defects on the surface of the mask substrate, Rear defect repair (addition of chromium alloy material to undesired voids on the surface of the mask substrate) (the use of a focused ion beam to catalyze deposition).

A feature of the present invention is that a complex ion beam is generated by a single ion beam column. Use of the system for mask repair, mask imaging with significantly reduced damage levels and contamination , either sputter etching or chemically promoted sputter etching. repair of opaque defects due to Repairs clear defects by adhering metallic materials whose optical properties are strictly balanced. be.

The present invention provides high resolution imaging of masks and reduces damage to the mask substrate. Removes opaque defects more efficiently with fewer scratches, and is compatible with the mask's original material. Clear defects at high speed using a beam that directly catalyzes the deposition of metal materials to be combined. Can fill cavities.

The invention has five major components. Target typically 0.5 micron It is possible to generate a precisely focused ion beam with a beam diameter of less than Ions that can be operated at voltages ranging from 4 to 120 KV with a current density of 5 A/cm” A beam column is used.

The liquid metal alloy source for the ion beam column is a low atomic weight source that is compatible with the mask substrate material. optically opaque metal films for rapid repair of opaque defects High atomic weight elements (e.g. gold), resulting in high sputter etching rates, Ion beam of metallic materials compatible with those commonly used to cover transparent areas Elements used in accelerated formulations (e.g., hexacarbonylchromium vapor or other ) Gold, chromium, or silicon used to promote the deposition of chromium from compounds. Contains suitable atomic species, including (recon).

The mass filter provides rapid selection of the desired beam ion species at the mask.

Depending on whether sputter etching or deposition is chosen, low atomic weight Either an element or a high atomic weight element is selected.

In the present invention, a gas supply device is utilized. During clear defect repair, negative ions A metal-laden vapor stream is provided near the intersection of the beam and the target surface.

In addition, the gas supply device is connected to the ion beam and the target surface during opaque defect repair. It is also possible to provide an etching rate-enhancing gas flow near the intersection of . deer However, this device is optional and includes a gas supply device used for releasing said metal-containing vapor. It may be partially composed of the same thing as .

Brief description of the drawing Figure 1 shows a focused ion beam mask repair device, and Figure 2 shows the mask imaging process. A diagram showing FIG. 3 is a diagram showing the opaque defect repair process, FIG. 4 is a diagram showing the clear defect repair process, Figure 5 is a flowchart for clear defect repair, and Figure 6 is a flowchart for opaque defect repair. It is a chart.

Detailed explanation of the most important To image the photomask or reticle to be repaired, quality! Filter is low atomic The ion column is set to select the mass element beam, and the ion column is placed on the target surface. The beam is set to produce a finely focused beam that produces an image of the mask structure. scanned in a raster pattern to ensure consistency. Low atomic weight elements are mask substrate materials It may be made of silicone that is compatible with the material. In this mode of operation, the ion beam The mask surface (transparent and opaque areas). Furthermore, the ionic species is compatible with the mask substrate. Contamination of the transparent areas of the mask is also minimized.

Efficient removal of large portions of undesirable optically opaque materials to repair opaque defects A first beam of a high atomic weight element is generated to remove the high atomic weight element. This first beam is Set the quantity filter to select the beam of high atomic mass elements and set the ion column to Set to generate a fine focused ion beam, and remove unwanted ion beams. generated by scanning only the area covered by the optically opaque material. It will be done. The first ion beam sputter-etches this undesirable material. This can be achieved through the use of etching rate accelerating gases such as chlorine. can be accelerated arbitrarily.

Once this undesirable material has been largely removed, the device can optionally use lower atomic weight elements. You can switch to the second beam. This second ion beam is substantially the same as the first ion beam. the first (high-atom A very thin film (approximately 0.01 The sputter etching rate is sufficient to remove micrometers.

The implanted atoms from this second ion beam are injected into the mask substrate material by the second ion beam species. Because it is compatible with the mask substrate, it does not contaminate or stain the mask substrate.

To repair clear defects, the mass filter is set to select ionic species that stimulate beam-enhanced deposition. this The ion beam is scanned by the ion beam to leave behind an optically opaque metal film. has sufficient energy to promote vapor decomposition only in the area of the mask surface that is It is necessary. At the same time, the ion beam is capable of sputter etching that exceeds the deposition rate. It is not possible to have slow speed. Mass filter selects desired ion species for beam The ion column is set to produce finely focused ion beams on the target surface. The beam is then scanned over the clear defect area. metal The metal elements of the vapor contained must be compatible with the metal film that normally covers part of the mask. is selected.

FIG. 1 shows a focused ion beam generator 8 according to the present invention. The ion source 10 is Ion source for mixed ion beam 12 which is a mixture of multiple ion species in the invention It may be. Mixed ion beam 12 first passes through extraction hole 14 . Io In order to generate a high electric field at the emission end of the ion source 10, the extraction hole 14 and the ion source 10 are connected to each other. A voltage is applied between them. This electric field causes the ions to be ejected into the optical column, creating a mixed ion A beam 12 is formed. The mixed ion beam 12 then passes through the remainder of the optical column. Beam regulating hole 16 including a small hole regulating the half angle of the ion beam 12 passing through the encounter. The portion of the mixed ion beam 12 passing through the beam regulating hole 16 is The light is focused by the lens 18 onto the surface of the mass separation hole 240. through the upper electrostatic lens 18. After passing through, mixed ion beam 12 passes through mass filter 20 . This mass The function of filter 20 is to separate the various ion beams in mixed ion beam 12. That is. The figure shows two ion beams, that is, a mass-separated beam. A beam 26 and an ion beam 39 are shown.

The mass separated beam 26 separates ions from among the ion species contained in the mixed ion beam 12. Beam 39 represents undesired ion species. For example, during imaging, the ion beam 39 is formed from a lightweight ionic species, e.g. silicon, while the mass separated beam 26 is Formed by high atomic mass ionic species that are undesirable in the image. Passes through mass filter 2o After that, the ions are separated into a mass separated beam 26 and an ion beam 39 as shown in the figure. The beam 12 passes through a beam plunker 22. beam plunker 22 machine The function is to blank the ion beam 39 with the target, that is, to blank the ion beam 39 with the target. It means turning on and off.

The beam plunker 22 prevents the ion beam 39 from passing through the mass separation hole 24 any further. By deflecting the ion beam 39 away from the axis of the ion column, The ion beam 39 is turned off. The ion beam 39 is the beam plunker 2 It is restored by inactivating 2. The ion beam 39 has mass separation After passing through the hole 24 , the ion beam 39 passes through the upper deflector 28 . is aligned with the lower electrostatic lens 30. Beam mass ion beam 39 The light passes through a lower electrostatic lens 30 that focuses the light onto the surface of the lens 32.

The main deflector 34 serves to deflect the ion beam 39 laterally across the surface of the mask 32. It is an 8-pole electrostatic type with variable 2-pole electrostatic voltages in the X and Y directions. Cha Is the channel electron multiplier (CEM or channeltron) 36 on the surface of the imaging mask? It is shown as a means of collecting secondary electrons or ions from the electrons.

Ion source 10 is FEI Co., Hillspolo, Oregon; V.G. Instruments, Inc., Stamford, CT Horated (V, G, I instruments.

Inc.) or Microbeam Inc., Nikobary Park, California. Obtained from Microbeam, Inc, etc. The standard liquid metal type you get. The ion source 1o is attached to the ion gun structure. The extraction hole 14 is also supported by this.

This gun structure is also a standard type available from each of the above companies. Beam regulating hole 16 The diameter of the beam is determined by the beam entering the upper lens 18 and mass filter 20. Determine the total current in system 12. This hole typically extends the beam half angle from 1 to 4 milliradians. A beam current of 100 to 100 OPA is given. The hole is Masatini Seso. Advanced Laser System (Advanced La) 5er System) and National Kong Co., Lantana, Florida. This is a standard product. Upper lens 18 images ion source 10 with mass separation aperture 24 .

When the mass filter 20 is operated, the ion beam 12 is separated into several parts by the mass separation hole 24. is divided into two beams. Mass separated beam 26 is one of these beams. Show one.

By appropriate selection of the mass filter settings, some of the mixed ion beams 12 The desired species pass through mass separation aperture 24 to form ion beam 39 . The relevant technology Preferred embodiments of mass filter 20 will be understood by those of ordinary skill in the art. One method is to use crossed electric and magnetic fields to separate beams with different velocities. It will be understood that this is the Uniin (EXE) filter used. AEON B To select the desired species for the mass filter, the electric field and Properly balancing the magnetic fields and magnetic field strengths is within the skill of those of ordinary skill in the art. It will be easily understood by those who understand.

In general, lenses, mass filters, deflectors and plunkers are not standard products, but These are Microbeam Incoho in Newbury Park, California. Rated and JOEL of Boston, Mass. Commercially available ion beam systems, such as those manufactured by Ion Beam Systems of Beverly, Sachusetts, It is an integral component of the ion column.

The ion beam 39 is not necessary for any of the mask repair processes shown in FIGS. 2 to 4. When necessary, the ion beam 39 is stopped by the beam plunker 22.

This prevents unnecessary irradiation of the ion beam 39 onto the mask. .

- is used to image the image on the surface of the mask 32. Using the main deflector 34 , the ion beam is usually scanned by a raster pattern for imaging, as is well known. Ru. For defect repair, the main deflector 34 directs the beam within the image raster pattern. Scan only the defective area within the area. The channel type electron multiplier 36 is a focused ion beam. Secondary ions or secondary electrons emitted from the mask 32 due to collision with the beam 39 Collect any of them. This is Galileo in Sturbridge, Massachusetts. Galileo Electro-Optics Or Detector Chikunoroshii of Brookfield, Massachusetts. (Detector Technology) Standard products supplied by various companies are good quality. stomach.

The mask 32 allows for accurate positioning of the mask 32 under the ion beam 12. This figure shows the state in which it is attached to a movable stage 38. FIG. 1 shows the mask 32 with an accuracy of 1 micron in both the X and Y directions of the defect location. , an example of a known means for providing this mask positioning function, an X-Y target It shows the stage. The center of the field of view in the imaging process shown in Figure 2 is the ion column. Its size is well understood by those with ordinary knowledge in the technical field. As understood, the total accelerating voltage of the ion beam 39 (from the ion source 10 to the mask 32), and the field strength and length of the main deflector 34 .

In a preferred embodiment, the ion source IO is a conventional ion source containing an alloy of gold and silicon. An ion source may also be used. Also, ion sources containing alloys of chromium, gold and silicon good. Such an ion source produces a mixed ion beam, from which it is known to those skilled in the art. As shown, a single species is selected through the use of it filter 20.

In a preferred embodiment, the proportion of the alloying components of the gold-silicon ion source is silicon 15 ~25%, the rest being all. Typical alloy for ion source is Si 18.6 atomic% , a gold-silicon eutectic alloy (melting point: about 363° C.) consisting of 81.4 atomic percent gold.

Preferred composition when using a ternary chromium/gold/silicon alloy as an ion source is 20-45% chromium, 20-55% gold, and the remainder silicon. these alloys The manufacture of is well known to those skilled in the art. Also, those skilled in the art will understand that two binary alloy ions It is easy to understand that it can also be used as a source. For example, imaging (Figure 2) and Imaging (Figure 2) of the first binary alloy ion source used for transparent defect repair (Figure 3) and a second binary alloy ion source for clear defect repair. Wear. Selection of appropriate binary alloys for the first and second ion sources will be readily apparent to those skilled in the art. It will be understood.

The function of the mass filter 20 can be deduced by one of ordinary skill in the art. Select the ion beam type for imaging (Figure 2) and repair (Figures 3 and 4) as shown in It is a matter of choosing. Before performing defect repair, the defect area should be imaged in a clear or opaque manner. Necessary to scan only the actual defect area with the ion beam used for bright defect repair. be.

The device according to the invention can be used to repair opaque defects in masks using sputtering. It is also possible to use The sputtering speed is determined by the primary ion beam 39 at the mask surface. can be promoted at will by using a gas that reacts with the ions in It is. The focused ion beam of the ion species to be sputtered is in the range of 1 to 5 cm/cm. It is used at energies greater than 10 KeV with a current density of . gas supply Tube 13 directs an etching rate promoting gas, such as chlorine, near the target surface. . The design of this gas supply tube is well known to those skilled in the art. For preliminary restoration Imaging (FIG. 2) is also performed at the same voltage levels as the exact imaging.

For clear defect repair, the apparatus of the present invention deposits material on the mask 32 (fourth figure). The focused ion beam is 10Ke with a current density in the range of 1 to 5 cm/cm. Used with energy greater than V.

The gas supply pipe 13 targets metal-containing vapors such as carbonyl chromium. lead to the vicinity of the surface. To ensure accuracy, prerepair imaging (Figure 2) was also performed at the same voltage. It is done.

As those of ordinary skill in the art know, masks 32 The charge accumulated in the It is desirable to neutralize the substance before it reaches a level that affects energy. Io The currently preferred method of neutralizing a beam is by using a flood gun (as it is known). 37 to irradiate the surface of the mask 320 with a large amount of electrons. This irradiation The process may be performed simultaneously with imaging (Figure 2) or repair (Figures 3 and 4). It is possible to have them performed alternately.

Imaging is done using scanning microscopy using either secondary electrons or secondary ions. It is carried out using As is well known, the collector 36 is used for imaging. Collect secondary particles of any type. Imaging techniques are well known and However, it is outside the scope of the present invention.

FIG. 2a shows typical mask imaging performed in the prior art.

The mask substrate 4o consists of atoms 42 of the first atomic species, typically silicon.

Opaque region 44 is comprised of atoms 46 of a second atomic species, typically chromium. Imaging type a On-48 is used, which is injected into the transparent areas of the mask, and the mask as shown. The substrate 40 is contaminated or stained. Furthermore, due to the collision of -order ions 48, Sputter removal of substrate atoms 40 and opaque region atoms from the mask occurs. vinegar Both staining and sputter etching can cause unwanted damage to the mask. Ras.

FIG. 2 shows mask imaging performed according to the present invention, showing a mask substrate 40, a substrate Details of the atomic species 42, opaque region 44 and opaque region atomic species 46 are shown in FIG. 2a. It is the same as the thing. The present invention almost eliminates staining when implanted into a mask substrate. It is distinguished from the conventional technology by using the atom 40a of the imaging atomic species that does not cause Separated.

Furthermore, the substrate atoms 40 and the impurities under the mask caused by the collision of the -order ions 40a. Sputter removal of transparent region atoms 46 is extremely small.

The net result is that damage to transparent and opaque areas of the mask is substantially reduced.

FIG. 3a shows a typical opaque defect repair performed in the prior art. mask The substrate 40 is comprised of atoms 42 of a first atomic species, typically silicon, and has an opaque region 4 . 4 is an atom 46 of the second atomic species, typically chromium. Desired opaque area 44 Bounded by an opaque defect region 50 consisting of atomic species 52 . here The atomic species 52 is shown as being the same as the atomic species 46 in the opaque region. Opacity The defect region 50 may be entirely or partially composed of the third atomic species. Sara In addition, the opaque defect region 5o may be isolated from the desired opaque region, and It doesn't have to be bordering. Gallium ions 48 sputter etch the region 5o. As a result, gallium atoms 48a are implanted into the substrate 40. , causing staining and reducing the transmission of light from the mask substrate in the gallium implanted areas. Make it less.

FIG. 3 illustrates the repair of opaque defects performed in accordance with the present invention, and shows substrate 40. of the board Atomic species 42, opaque region 44, atomic species in opaque region 46, opaque defect region 50 and The details of the opaque and opaque defective atomic species 52 are the same as those in FIG. 38. The present invention Here, high atomic weight ionic species 54 are shown in sputter etched opaque areas 50. This method differs from conventional technology in that it uses . Atomic species 54 has sputter etching action selected to maximize efficiency. Rapid sputter etching accelerates erosion. Optionally it is possible to speed up by using advance gas 56. This system The system is optional and the same gas supply used to depressurize the metal-containing gas for deposition. A portion may be configured by a feeding device. The pressure of the nisoting speed accelerating gas is 1 to 1 O It is in the range of 0m1croTorr. This range targets some ion beams to provide enough gas to somewhat accelerate the etching rate while keeping it focused on the selected.

FIG. 4a shows a typical rear defect repair performed in the prior art. usually, An alternative method is used. The beam-enhanced carbon deposition method is shown on the top. be. The gallium ion 80 is a mask made of atomic species 42, typically silicon. Carbon-containing gas molecules 82 are caused to adhere to the surface of the substrate 400. This process A deposits an opaque spot on the defect, and this spot is typically composed of 46 atomic species. The optical properties are significantly different from the original opaque mask material 44 containing ROM. for example, The opaque spots reflect more reflected light than the relatively shiny chrome opaque areas of the mask. black. It also exhibits different behavior during the opaque defect repair process shown in FIG.

At the bottom of Figure 4, another method conventionally used for clear defect repair is shown. It is. Characteristics of the surface of the mask substrate 400 made of atomic species 42, typically silicon. Gallium ions 80 are used to sputter the special feature 82 . these The shape is designed to reflect light away from the clear defect area, making it visible in the dark. has been done.

This method is very slow, irreversible, and does not require the specific The disadvantage is that it is limited to the wavelength of the irradiated light.

FIG. 4 shows the repair of clear defects performed by the inventive method. -Next ion 100 is the region of clear defect 102, typically from atomic species 46 (typically chromium) scan for undesirable gaps in the opaque areas 44. -Next ion 100 scans the clear defect area, but the flow of metal-containing gas molecules 104 is partly ion 1 00 is an IJX seed 42, which is typically bombarded onto the surface of a mask substrate 40 made of silicon. directed toward the surface of the mask near the area of impact. -Next 100 ions directly in the beam It induces decomposition of metal-containing gas molecules 1040 only in the scanned area, and gold is removed in the defect area. This causes the attachment of genus atoms 106. The mass flow rate of metal-containing vapor is The pressure in the vicinity is adjusted to be in the range of 1 to 100ml croTorr.

This range allows the ion beam to remain partially focused on the target while still allowing the beam to be efficiently selected to provide sufficient gas to effect deposition. The attached metal atoms are Since it is compatible with the previous opaque area 44, the repaired portion is removed during the opaque defect repair process shown in FIG. , which are almost indistinguishable from these opaque regions in appearance and properties.

The lower part of Figure 4 schematically shows the clear defect repair area finished according to the present invention. It is.

FIG. 5 shows an embodiment of the clear defect repair process. First, in block 200, mask The region containing the defect is imaged as described in FIG. Photograph the defective area After imaging, the beam is emptied (turned off with a mask). Then block 2 In 02, the exact area of the clear defect within the entire imaging area is determined. block 20 At 4, the flow of metal-containing gas is started. At block 206, the ion beam and During the flow of this metal-containing gas at the mask surface near the intersection of the mask substrate, the The on-beam is not blocked and is allowed to scan only the precise area of the clear defect. Figure 4 The process shown here involves layering a metallic material that is compatible with the opaque mask material itself. is formed. After a specified time to deposit a sufficient thickness of material, remove the block. 208, where the ion beam is again blanked and the metal-containing gas supply will be stopped. Next, at block 210, using the method described in FIG. The defective area is then imaged again as done in block 200. block 21 Using the image displayed as 0, the operator (module or system; A determination is made at block 212 as to whether the cleared defect has been completely repaired. trout If the image shows that the defect has not yet been fully repaired, the professional Branch wire 214 is taken from block 12 and returned to block 202 .

At block 202, the remaining defective area is again determined as described above. Block If the imaging from the block 210 shows that the defect is completely repaired:=, A branch line 216 is taken out of block 212 and leads to a process completion block 218.

FIG. 6 shows an embodiment of the opaque defect repair process. First, at block 250, defects are identified. The area on the mask containing the mask is imaged as described above in FIG. The defect area is imaged After that, the beam is emptied (off with a mask). Then, at block 252, all The exact area of the opaque defect within the imaged area is determined. At block 254, an optional However, the supply of the etching rate accelerating gas may also be started. At block 256, the Desired ion species for sputter etching of transparent defects are selected using a mass filter. A beam is emitted to scan only the defective area. Opaque defects removed After that, block 258 is entered where the beam is again interrupted and the block is Lock 254 stops the supply of etching accelerating gas if it has been started. Ru. Block 260 then uses the method previously described in FIG. The mask is imaged again as done at 250. displayed in block 260 Using the image, the operator (or system computer) at block 262 A determination is made as to whether the opaque defect has been completely repaired. Defects still intact If the mask image indicates that it has not been repaired, the support is returned from block 262. Line 264 is taken and returned to block 252. At block 252, the remaining The depressed area is again determined as described above. With the imaging obtained from block 260 When it is indicated that the defect has been completely repaired, branch line 266 moves to block 262. and is directed to block 268.

After defects are removed, some residual staining may remain on the mask substrate. Ru. At block 268, an ionic species compatible with the substrate is used to finish the mask. Optical scanning may also be performed. Plot Dan FIGURE7゜ FIGURE3゜ Figure 5 Figure 6 international search report

Claims (1)

[Claims] 1. a first ionic species compatible with the material of which the mask or reticle is constructed; a second ionic species having a relatively high atomic mass compared to the first ionic species; an ion source comprising an ionic species, an ion source comprising one of said first and second ionic species; Select on-beam and select the target consisting of the semiconductor mask or reticle to be repaired. means for directing a focused ion beam onto a target, a metal-containing vapor on the surface of said target; means for supplying air, applying a low or high voltage between the ion source and the target; means for selectively supplying; and means for forming an image of the target by secondary ion emitting means; Repair semiconductor masks and reticles using a focused ion beam consisting of equipment.