CN114735927A - Method for producing synthetic quartz material for semiconductor mask plate - Google Patents
Method for producing synthetic quartz material for semiconductor mask plate Download PDFInfo
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- CN114735927A CN114735927A CN202210396733.6A CN202210396733A CN114735927A CN 114735927 A CN114735927 A CN 114735927A CN 202210396733 A CN202210396733 A CN 202210396733A CN 114735927 A CN114735927 A CN 114735927A
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 139
- 239000010453 quartz Substances 0.000 title claims abstract description 57
- 239000000463 material Substances 0.000 title claims abstract description 42
- 239000004065 semiconductor Substances 0.000 title claims abstract description 24
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 20
- 238000000151 deposition Methods 0.000 claims abstract description 43
- 238000000034 method Methods 0.000 claims abstract description 40
- 230000008021 deposition Effects 0.000 claims abstract description 37
- 238000005245 sintering Methods 0.000 claims abstract description 32
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 31
- 229910052681 coesite Inorganic materials 0.000 claims abstract description 25
- 229910052906 cristobalite Inorganic materials 0.000 claims abstract description 25
- 229910052682 stishovite Inorganic materials 0.000 claims abstract description 25
- 229910052905 tridymite Inorganic materials 0.000 claims abstract description 25
- 239000007789 gas Substances 0.000 claims abstract description 21
- 238000010438 heat treatment Methods 0.000 claims abstract description 20
- 239000001301 oxygen Substances 0.000 claims abstract description 17
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 17
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 16
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 14
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000010703 silicon Substances 0.000 claims abstract description 13
- 238000004017 vitrification Methods 0.000 claims abstract description 12
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims abstract description 11
- 238000000137 annealing Methods 0.000 claims abstract description 11
- 230000018044 dehydration Effects 0.000 claims abstract description 10
- 238000006297 dehydration reaction Methods 0.000 claims abstract description 10
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 10
- 239000011737 fluorine Substances 0.000 claims abstract description 10
- 239000011261 inert gas Substances 0.000 claims abstract description 9
- 238000005137 deposition process Methods 0.000 claims abstract description 6
- 238000005906 dihydroxylation reaction Methods 0.000 claims abstract description 6
- 238000002156 mixing Methods 0.000 claims abstract description 3
- 239000012535 impurity Substances 0.000 claims description 22
- 239000002184 metal Substances 0.000 claims description 17
- 229910052751 metal Inorganic materials 0.000 claims description 17
- 238000006243 chemical reaction Methods 0.000 claims description 8
- 239000000460 chlorine Substances 0.000 claims description 8
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 7
- 229910052801 chlorine Inorganic materials 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 239000002274 desiccant Substances 0.000 claims description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 3
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 239000001307 helium Substances 0.000 claims description 3
- 229910052734 helium Inorganic materials 0.000 claims description 3
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 3
- 239000001257 hydrogen Substances 0.000 claims description 3
- 229910052739 hydrogen Inorganic materials 0.000 claims description 3
- 235000012239 silicon dioxide Nutrition 0.000 description 46
- 230000007547 defect Effects 0.000 description 24
- 230000008569 process Effects 0.000 description 21
- 230000003287 optical effect Effects 0.000 description 15
- 238000002834 transmittance Methods 0.000 description 14
- 239000011521 glass Substances 0.000 description 11
- 239000002994 raw material Substances 0.000 description 10
- 238000005516 engineering process Methods 0.000 description 8
- 229910003910 SiCl4 Inorganic materials 0.000 description 5
- 239000002912 waste gas Substances 0.000 description 5
- 229910002808 Si–O–Si Inorganic materials 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 4
- 238000000280 densification Methods 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 150000004820 halides Chemical class 0.000 description 4
- 239000013307 optical fiber Substances 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 3
- OBNDGIHQAIXEAO-UHFFFAOYSA-N [O].[Si] Chemical compound [O].[Si] OBNDGIHQAIXEAO-UHFFFAOYSA-N 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 238000005229 chemical vapour deposition Methods 0.000 description 3
- 238000002485 combustion reaction Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 3
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 3
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 206010021143 Hypoxia Diseases 0.000 description 2
- 239000006004 Quartz sand Substances 0.000 description 2
- 229910008045 Si-Si Inorganic materials 0.000 description 2
- 229910006411 Si—Si Inorganic materials 0.000 description 2
- 125000004429 atom Chemical group 0.000 description 2
- 239000002585 base Substances 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 230000031700 light absorption Effects 0.000 description 2
- 239000004973 liquid crystal related substance Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 229910001510 metal chloride Inorganic materials 0.000 description 2
- 229910001507 metal halide Inorganic materials 0.000 description 2
- 150000005309 metal halides Chemical class 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 125000004430 oxygen atom Chemical group O* 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
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- 238000007670 refining Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000001308 synthesis method Methods 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- 150000003624 transition metals Chemical class 0.000 description 2
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 229910001413 alkali metal ion Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000005388 borosilicate glass Substances 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000003889 chemical engineering Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
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- 238000007872 degassing Methods 0.000 description 1
- 108700041286 delta Proteins 0.000 description 1
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- 238000002438 flame photometric detection Methods 0.000 description 1
- 125000000623 heterocyclic group Chemical group 0.000 description 1
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- 230000001788 irregular Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000010309 melting process Methods 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 238000004377 microelectronic Methods 0.000 description 1
- -1 oxygen ions Chemical class 0.000 description 1
- 238000000059 patterning Methods 0.000 description 1
- 150000002978 peroxides Chemical class 0.000 description 1
- 125000000864 peroxy group Chemical group O(O*)* 0.000 description 1
- 238000001259 photo etching Methods 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 229920002120 photoresistant polymer Polymers 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 239000005373 porous glass Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
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- 230000009467 reduction Effects 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 239000005049 silicon tetrachloride Substances 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
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- 230000003595 spectral effect Effects 0.000 description 1
- 230000007847 structural defect Effects 0.000 description 1
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B19/00—Other methods of shaping glass
- C03B19/14—Other methods of shaping glass by gas- or vapour- phase reaction processes
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B19/00—Other methods of shaping glass
- C03B19/14—Other methods of shaping glass by gas- or vapour- phase reaction processes
- C03B19/1453—Thermal after-treatment of the shaped article, e.g. dehydrating, consolidating, sintering
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B19/00—Other methods of shaping glass
- C03B19/14—Other methods of shaping glass by gas- or vapour- phase reaction processes
- C03B19/1453—Thermal after-treatment of the shaped article, e.g. dehydrating, consolidating, sintering
- C03B19/1461—Thermal after-treatment of the shaped article, e.g. dehydrating, consolidating, sintering for doping the shaped article with flourine
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
- Y02P40/57—Improving the yield, e-g- reduction of reject rates
Abstract
The invention relates to a method for producing a synthetic quartz material for a semiconductor mask, which comprises the following steps: (1) depositing a silicon source on the guide rod by adopting a gas-phase axial deposition method to obtain low-density SiO2A loose body; wherein in the deposition process, the interior of the deposition cavity is controlled to be in a negative pressure environment, and the temperature is not higher than 500 ℃; (2) mixing low density SiO2Transferring the loose body to a sintering furnace, heating to 1100-1300 ℃ in a closed environment filled with dehydroxylation airflow and oxygen, and enabling the low-density SiO to be in a state of being heated2Dehydrating the loose body; (3) introducing fluorine-containing gas into the sintering furnace in an inert gas environment, and heating to 1400-1600 ℃ to ensure that the low-density SiO2Vitrifying the loose body to form transparent quartz glass; low density SiO during dehydration and vitrification2The loose body keeps not moving longitudinally, and a deposition cavity is formedThe temperature gradient between the inner longitudinal direction and the radial direction is less than or equal to 2 ℃; (4) and annealing the transparent quartz glass to obtain the synthetic quartz material. The method has high continuity of the production process and synthesizes the quartz product T170‑193nm≥95％。
Description
Technical Field
The invention relates to the technical field of quartz preparation, in particular to a method for producing a synthetic quartz material for a semiconductor mask.
Background
Quartz glass is a special glass consisting of a single component of silicon dioxide, the chemical formula of which is SiO2. Quartz has unique optical, mechanical, and thermal properties, including: the softening temperature is high, and the heat resistance is strong; high purity and corrosion resistance; low thermal expansion coefficient and thermal shock resistance; the light transmittance is better from the ultraviolet band to the infrared band; the radiation resistance is strong; excellent electrical insulation properties, and the like. The properties enable the quartz product to be widely applied to the high-end manufacturing fields of aerospace, laser optics, semiconductors, optical communication, metallurgy, chemical engineering and the like.
The traditional optical quartz glass preparation process comprises electric melting, gas refining, Chemical Vapor Deposition (CVD), indirect synthesis method, sol-gel method and the like. The electric melting and refining process uses high-purity quartz sand as raw material, and the quartz sand is melted at a high temperature of more than 1800 ℃ to prepare quartz glass, and the prepared quartz glass has low purity and has the defects of more bubbles, more impurities and the like due to the limitations of the purity of the raw material and the melting process, thereby greatly influencing the physical and chemical properties of the glass.
The CVD direct synthesis process mainly adopts a vertical process at present, but has a remarkable defect that the content of hydroxyl is too high, so that the high-temperature resistance of the prepared quartz glass is reduced, the physical properties such as refractive index, thermal expansion coefficient and the like are influenced, and the application requirements in the fields of high-end photoelectric technology and semiconductors cannot be met.
The indirect synthesis method is a process technology developed in the last decade, and quartz prepared by the technology has the advantages of small light absorption coefficient, controllable hydroxyl content (1-1000 ppm) and spectral transmittance T157-4000The nm is more than or equal to 80 percent, and the defects are easy to dope and control.
The photomask is a graphic master mask used in a photoetching process in microelectronic manufacturing, and has the core functions of: as a mold, a circuit pattern on a mask is transferred to a chip or a liquid crystal panel glass by a photolithography technique, thereby mass-producing products such as integrated circuits or liquid crystal panels. Photomask substrate materials must have no defects on both the inner and outer surfaces and high optical transmittance at the exposure wavelength of the photoresist. The current integrated circuit industry is rapidly developing, the size of the silicon chip is expanded to 8 → 12 → 16, the integration level is higher and higher, and the exposure light is also converted from visible light to near ultraviolet light, even far ultraviolet light. Since any defect such as micro-bubble in the quartz glass substrate can cause a fatal error in the chip patterning, the chip performance is seriously affected, which also puts higher requirements on the quartz glass substrate for the photomask: high ultraviolet transmittance, high optical uniformity, high intrinsic quality, and high surface finish quality.
The glass used for manufacturing the photomask plate comprises synthetic quartz, borosilicate glass and soda glass, wherein the synthetic quartz is the most chemically stable, has the advantages of high hardness, low expansion coefficient, strong light transmittance and the like, is not the second choice for the production of products with higher precision requirements, and is widely applied to the manufacture of photomasks for LSIs and large masks for FPDs. Synthetic quartz can provide a wide light projection area, low impurity content, and few physical defects, and its deep UV, high uniformity requirement for synthetic quartz is increasing with the development of semiconductors. The conventional synthetic quartz cannot satisfy a high-precision mask blank for a semiconductor.
Therefore, to satisfy the requirement of high uniformity and high transmittance of the semiconductor photomask, the following 2 aspects need to be solved in an important way: controlling the content of metal impurities and defects in quartz;
1) the existence of transition metal impurities in the synthetic quartz glass causes absorption of light passing through the glass, which causes the transition metal to absorb a large amount of energy, and when alkali metal impurities exist in the quartz, the network formed by silicon-oxygen tetrahedrons is broken, and alkali metal ions are uniformly and disorderly distributed in the gaps of some tetrahedrons, so that the silicon-oxygen structure of the quartz is changed, non-bridge oxygen ions are formed, and the absorption is caused.
In the deposition process, the silicon tetrachloride raw material is hydrolyzed at high temperature to generate silicon dioxide. The process involves high temperature reactions (reaction temperatures typically exceeding 1000 ℃) with the concomitant production of large amounts of hydrogen chloride. Because most of the materials in the deposition cavity are made of metal materials, metal chloride gas is easily generated under high-temperature conditions and high-corrosion environments, and the metal chloride gas flows along with the airflow in the deposition cavity and is deposited on the quartz materials to pollute the deposited materials. The corrosion of the cavity in the high-temperature hydrolysis reaction process inevitably causes the pollution of metal impurities in the quartz material, and the reduction of the content of the metal impurities in the quartz material becomes more difficult.
2) The main intrinsic defects in the quartz material have absorption and emission characteristics in the material body and on the material surface, the more common defects such as oxygen defect centers and non-bridged oxygen vacancy centers have absorption and emission characteristics, and even if the same type of defects exist, the properties on the material surface and in the material body are slightly different. Visible structural defectTraps have a significant effect on the optical properties of quartz materials, and this effect can often be the result of the co-existence of a variety of defects. In theory, quartz glass should be a complete Si-O network tetrahedron, with each Si atom being bonded to four O atoms, each O atom being bonded to two Si atoms, thereby forming a three-dimensional silicon-oxygen tetrahedron. The structure has several key parameters, including bond length d (Si-O), on average about
Tetrahedral corner
Average bond angle about 109 °; a meta-tetrahedral angle α (Si-O-Si) having an average bond angle of about 144 ° -150 ° ranging from 120 ° to 180 °; the bond twist angles delta 1, delta 2 and the like are also included, and it is because the continuous change and twist of the bond angle between Si-O-Si results in the remote disordered structural characteristics of the quartz optical fiber material. The (Si-O) n topological ring structure is distributed in the irregular grid structure of the quartz optical fiber material, and a three-ring, four-ring to ten-ring or heterocyclic ring structure exists, wherein the three, four, six or seven rings are the majority. In the structure of the silica optical fiber material, if a deviation from the above-mentioned ideal random lattice structure composed of Si-O-Si occurs, a point defect structure is formed. The common point defect structure in the high-purity quartz optical fiber material mainly comprises an oxygen-deficient defect and an oxygen-enriched defect. The oxygen deficiency type defects comprise E' color centers, Si-Si bonds and the like; oxygen-rich defects include nonbridging oxygen defects (NBOHCs), peroxy radicals, and peroxy linkages.
In view of the above, there is a need for a method for producing a photomask for a semiconductor to produce a synthetic quartz product with high ultraviolet transmittance and high optical uniformity.
Disclosure of Invention
Therefore, the invention provides a method for producing synthetic quartz material for semiconductor mask plate, which has high continuity of production process and synthetic quartz product T170-193 nm≥95％。
In order to solve the technical problem, the invention provides a method for producing a synthetic quartz material for a semiconductor mask, which comprises the following steps:
(1) depositing a silicon source on the guide rod in the deposition cavity by adopting a gas-phase axial deposition method to obtain low-density SiO2A loose body; wherein the silicon is derived from a chemical reaction in a burning oxyhydrogen flame to form silica particles and deposit to form low density SiO2A loose body; in the deposition process, controlling the interior of the deposition cavity to be in a negative pressure environment, wherein the temperature is not higher than 500 ℃;
(2) mixing low density SiO2Transferring the loose body to a sintering furnace, and heating to 1100-1300 ℃ in a closed environment filled with dehydroxylation airflow and oxygen to ensure that the low-density SiO2Dehydrating the loose body;
(3) introducing fluorine-containing gas into a sintering furnace in an inert gas environment, and heating to 1400-1600 ℃ to ensure that the low-density SiO2Vitrifying the loose body to form transparent quartz glass; the low density SiO is formed during dehydration and vitrification2The loose body keeps not moving longitudinally, and the temperature gradient between the longitudinal direction and the radial direction in the deposition cavity is less than or equal to 2 ℃;
(4) and (4) annealing the transparent quartz glass obtained in the step (3) to obtain the synthetic quartz material for producing the semiconductor mask plate.
Further: in the step (1), the silicon source is SiCl with the purity of more than 99.9999 percent4The purity of the introduced hydrogen and oxygen reaches more than 99.999 percent, and the inner wall of the deposition cavity adopts a high-purity quartz lining.
Further: in the step (1), the low-density SiO is controlled by a motor2The rotational speed of the loose body is 20-50 rpm/min, and the lifting speed is 0.4-1.2 mm/min.
Further: in the step (1), the obtained low-density SiO2The content of metal impurities in the loose body is less than or equal to 10 ppb.
Further: in the step (2), the dehydroxylation gas flow comprises inert gas and chlorine-based drying agent.
Further: in the step (2), the inert gas comprises helium or argon, and the chlorine-based drying agent comprises chlorine; the flow rate of the oxygen is 0.5-2L/min.
Further: in the step (3), the fluorine-containing gas includes CF4、C2F6、C3F8One or more of (a).
Further: in the step (3), 2-4 layers of heating elements are arranged outside the furnace wall of the sintering furnace, 6-14 thermocouples are uniformly and symmetrically distributed, the thermocouples are respectively connected into the PLC system, the temperatures of different areas in the sintering furnace are monitored through the thermocouples and fed back to the PLC system, and then the heating power of different heating elements is adjusted according to the fed back temperature data, so that the longitudinal and radial temperature gradients in the sintering furnace are less than or equal to 2 ℃.
Further: in the step (3), the content of metal impurities in the obtained transparent quartz glass is less than or equal to 8 ppb.
Further: in the step (4), the optical uniformity of the obtained quartz material reaches 1.2 multiplied by 10-6The external passing rate level of the transmittance is more than or equal to 90.5 percent (5mm), and the internal passing rate level is more than or equal to 99.5 percent.
Compared with the prior art, the technical scheme of the invention has the following advantages:
1. usually, the vitrification of the synthetic quartz by an indirect method needs to adopt a zone sintering technology, a porous loose body is sintered and densified in a zone of a resistance furnace so as to become a transparent glass prefabricated rod without bubbles, and because the sintering technology is a zone sintering technology, the stress of the quartz glass is overlarge due to longitudinal movement and longitudinal temperature difference of the loose body in the vitrification process. According to the method for synthesizing the quartz material, the adopted sintering furnace is provided with the multiple layers of heating elements, so that the loose body can be ensured not to move longitudinally in the processes of dehydration, doping, vitrification and annealing, and the loose body is ensured not to be influenced by mechanical longitudinal movement in the vitrification process; meanwhile, the temperature feedback and PLC control system of the multiple thermocouples ensures that the temperature field in the furnace is highly stable in the dehydration, doping, vitrification and annealing processes of the loose body, and the influence of temperature gradient caused by lifting on the stress of the glass is avoided, so that the optical uniformity of the synthetic quartz is improved, the synthetic quartz glass produced by the device has the aperture of 120, and the optical uniformity reaches 1.2 multiplied by 10-6。
2. The production of silica agglomerates is mainly based on the production of halide raw materials (SiCl) from gas supply systems4) The flame hydrolysis reaction produces fine glass particles which are subsequently deposited on the growth surface to form a porous bulk. During the deposition production process, most of H generated by the reaction is generated due to the higher deposition temperature2The O and HCl, as well as residual glass particles that have not yet deposited on the surface, will be exhausted from an exhaust vent located near the deposition zone. However, due to the higher reaction temperature, a portion of H2O and HCl can diffuse to the inner wall of the deposited metal chamber to corrode the chamber and deposit on the quartz material to pollute the deposited loose body. The invention realizes the high purity of the loose body by using high-purity raw materials and gases, adopting corrosion-resistant materials for the deposition cavity and using high-purity quartz lining and other deposition process protection technologies. The loose body treated by the method has the advantages that the content of metal impurities is obviously reduced, and the content of the metal impurities can be controlled to be less than or equal to 10 ppb.
3. The porous body is generally sintered and densified in an electric resistance furnace area at present, and the method mainly comprises two steps: 1) the densification of the porous glass is increased, and the open pores are converted into closed pores in the process; 2) the shrinkage of the closed pores disappeared. Through these two processes, the loose body becomes a bubble-free synthetic quartz glass. In the densification process of the loose body, the internal temperature field of the resistor is generally controlled to be more than 1500 ℃, in the sintering process, fluorine-containing gas with certain concentration is introduced to generate gaseous metal halide with metal oxide under the high-temperature condition, the highest boiling point of the chloride is 1500 ℃, and the halide can be removed through sintering, so that the purification of the synthetic quartz glass is realized. The synthetic quartz glass treated by the method has the advantages that the content of metal impurities is obviously reduced, and the content of the metal impurities can be controlled to be less than or equal to 8 ppb.
4. The structural defect of quartz glass is [ SiO ]4]The tetrahedral network structure is self-defective, including oxygen deficiency type defects (. ident.Si,. ident.Si-Si ≡) and peroxide type defects (. ident.Si-O.,. ident.Si-O-Si ≡). The VAD sintering atmosphere of the present invention may be an inert atmosphere or an oxidizing atmosphere. The oxidizing atmosphere is likely to create an oxygen-rich environment, thereby causing oxygen-rich defects. The invention is implemented by doping fluorineThe formed E' defect and NBOHC defect are repaired, the requirement on the density of a loose body is low, the corresponding adjustment of process parameters for the loose body with different densities is not needed, the ultraviolet transmittance level of the synthesized quartz material is obviously optimized, the transmittance external excess rate level is more than or equal to 90.5 percent (5mm), and the transmittance internal excess rate level is more than or equal to 99.5 percent.
5. The invention has good process repeatability, the produced synthetic quartz has large size and high quality, the fluorine base is introduced in the densification stage, the concentration, the flow and the gas partial pressure of the fluoride entering the sintering device are controlled, the radial refractive index uniformity of the synthetic quartz glass is less than or equal to 5ppm, the purity of the produced synthetic quartz material is higher, the 120-caliber of the product is measured through slicing → polishing → testing, and the optical uniformity reaches 1.2 multiplied by 10-6。
Drawings
FIG. 1 is a process flow diagram of the present invention;
FIG. 2 is a schematic structural view of a deposition apparatus according to the present invention;
FIG. 3 is a schematic structural view of a sintering apparatus according to the present invention;
FIG. 4 is a graph showing a comparison of the transmittance of a synthetic quartz glass (A) produced by the present invention and that of a conventional synthetic quartz (B);
FIG. 5 is a graph showing a refractive index profile of a synthetic quartz glass produced by the present invention;
wherein, 1, a guide rod; 2. a deposition chamber; 3. a high efficiency filter; 4. a silicon source combustion device; 5. a valve; 6. a distribution system; 7. a feeding pipe; 8. SiCl4Raw materials; 9. an air draft device; 10. a waste gas discharging pipe; 11. a valve; 12. low density SiO2A loose body; 13. sintering furnace; 14. a furnace core tube orifice outlet; 15. transparent quartz glass; 16. a heating member; 17. a furnace core pipe bottom air inlet; 18. and a thermocouple.
Detailed Description
The present invention is further described below in conjunction with specific examples to enable those skilled in the art to better understand the present invention and to practice it, but the examples are not intended to limit the present invention.
Referring to FIG. 1, the present invention provides a method for manufacturing a semiconductor maskThe method for synthesizing quartz material for plate includes four main procedures of loose body deposition, loose body dehydration, vitrification and fluorine base introduction and furnace annealing, i.e. adopting vapor axial deposition process (VAD) to firstly deposit and form low-density SiO2Loosening the body 12 and sintering; dehydrating, dehydroxylating, degassing and densifying are carried out in the sintering process until vitrification is achieved; and annealing the obtained quartz glass after sintering is finished so as to fully release the stress in the quartz glass to ensure the uniformity of the quartz glass, and finally obtaining an annealed quartz glass 26 finished product, namely high-quality high-purity high-uniformity low-hydroxyl quartz glass. The steps are described in detail below.
1. Deposition of bulk
Referring to FIG. 2, low density SiO2The deposition of the loose body 12 is carried out in the deposition chamber 2, and in the deposition chamber 2, a silicon source is deposited on the guide rod 1 by VAD technology to obtain low-density SiO2The loose body 12. Wherein the silicon source is SiCl4Feedstock 8, via the carrier gas, enters distribution system 6 and then enters the silicon source combustion device 4 via valve 5 and the mass flow controller. Simultaneously, purified Ar and H2And O2Through a metal conduit into the distribution system 6 and through a metal line into the silicon source combustion device 4. SiCl4The raw material 8 is subjected to chemical reaction in a burning oxyhydrogen flame to form silicon dioxide particles, and the silicon dioxide particles are deposited on the guide rod 1 in the deposition cavity 2 to obtain the low-density SiO2The loose body 12. The distribution system 6 is a gas flow controller for controlling the flow of different gases. In the present invention, SiCl4The purity of the raw material 8 is preferably more than 99.9999%, and the hydrogen and the oxygen are preferably high-purity gases with the purity of more than 99.999%, so that the purity of the quartz glass finished product is favorably improved. Ar is used as a protective gas, and plays a role in physical isolation in the combustor, so that the combustor is prevented from being damaged.
The flow rates of the above-mentioned raw material gases can be set as required by those skilled in the art, or can be set by conventional flow rates. SiCl4The flow rate of the raw material 8 can be 80-120 g/min, and preferably 80g/min in the embodiment; h2、O2And flow rates of ArCan be 110-130L/min, 70-90L/min and 15-17L/min, preferably 120L/min, 80L/min and 16L/min in the embodiment.
In the invention, in order to ensure the stability of the airflow in the deposition cavity 2 and ensure stable deposition, the side wall of the deposition cavity 2 is respectively provided with the high-efficiency filter 3 and the air draft device 9, and the height of the air draft device 9 is slightly lower than the position of the high-efficiency filter. Through high efficiency filter 3 and updraft ventilator 9, updraft ventilator 9's height is slightly less than high efficiency filter 3 position. The interior of the deposition cavity 2 is slightly negative pressure, preferably 50-150 Pa lower than the standard atmospheric pressure, so that the stability of air flow in the deposition cavity 2 is ensured, impurities are not easy to introduce, and the introduction of external impurities into the loose body is effectively reduced. Preferably, a pressure gauge is provided at the suction opening so that the pressure can be monitored and dynamic pressure regulation can be performed. Through the dynamic control of pressure, the stability of the airflow in the deposition cavity 2 is ensured, so that impurities are not easy to introduce. Preferably, a temperature sensor is provided in the deposition chamber 2 for monitoring and ensuring that the temperature in the deposition chamber 2 is not higher than 500 ℃ to reduce the introduction of metal impurities.
In the invention, a guide rod 1 to be deposited is suspended in a deposition cavity 2, and a driving device is arranged on the deposition cavity 2, wherein the driving device is a motor in the embodiment. The motor can drive the guide rod 1 to lift and rotate, so that the uniformity of loose body deposition is improved. The rotating speed of the motor is 20-50 rpm/min, preferably 30 rpm/min. To improve the homogeneity of the quartz glass, the rotation speed of the motor can be suitably increased. The motor lifting speed is 0.4-1.2 mm/min, preferably 0.8mm/min, so as to ensure the diameter of the loose body. And a waste gas discharging pipe 10 is arranged on the side wall of the deposition cavity 2, waste gas generated in the deposition cavity 2 is discharged through the waste gas discharging pipe 10, and a valve 11 is arranged on the waste gas discharging pipe 10.
2. Dewatering of loose bodies
Referring to FIG. 3, the low density SiO2The loose body 12 is transferred into a sintering furnace 13, and Cl is introduced into the sintering furnace 13 through the inlet of the furnace core pipe orifice2Or other chlorine-based drying agents and inert gases, using a heating element 16 arranged on the sintering furnace 13 to heat the low-density SiO2Heating the loose body 12 to 1100-1300 DEG CThermal, physical and chemical reaction of low density SiO2The loose body 12 is removed of hydroxyl, moisture and the like, and then discharged out of the sintering furnace 13 through the furnace core nozzle outlet 14. In the invention, in order to ensure the stability and uniformity of the temperature field of the loose body, a plurality of layers (2-4) of heating elements are set on the outer wall of the sintering furnace, a plurality of thermocouples (6-14) with the same model are uniformly and symmetrically distributed in the effective temperature field area of the furnace core pipe (the model of the thermocouple is B type), and are respectively connected into a PLC system, and the heating power of different heating elements is respectively adjusted by monitoring the temperature of the thermocouples, so that the longitudinal and radial temperature gradient in the furnace core pipe is ensured to be less than or equal to 2 ℃. Therefore, the loose body does not need to move longitudinally in the dehydration and vitrification stages, thereby avoiding the influence of temperature gradient on the stress of the glass during lifting and improving the optical uniformity of the synthetic quartz. In order to further ensure the optical uniformity of the quartz material, O with a certain flow rate is synchronously introduced in the dehydration and dehydroxylation processes2，O2The feeding amount of the catalyst is controlled to be 0.5-2L/min, preferably 1L/min, and the catalyst is used for improving the optical uniformity of products.
3. Vitrification and fluorine radical introduction
Low density SiO2After the loose body 12 is dehydrated, the loose body is placed in an inert gas environment of helium or argon gas, and is heated to 1400-1600 ℃ at the same time, and the loose body is vitrified under the condition to form transparent quartz glass 23. Obviously, during the dehydration and sintering processes of the loose body, the loose body must be placed in a closed environment to provide a corresponding atmosphere environment for the dehydration and the complete transparentization of the loose body, and meanwhile, external impurities are prevented from entering the loose body. In the present invention, a flow of a fluorine-containing gas, such as CF, is introduced during the densification of the bulk4、C2F6、C3F8Etc., preferably CF4The fluorine-containing gas and the metal oxide can generate gaseous metal halide under the high-temperature condition, the maximum boiling point of the halide is 1500 ℃, and the halide can be removed through sintering, so that the purification of the synthetic quartz glass is realized. The metal impurity content of the synthetic quartz glass treated by the step is obviously reduced, and the metal impurity content can be controlled to be less than or equal to 8 ppb.
4. Annealing in a furnace
After the transparent quartz glass 15 is sintered, it is subjected to fine annealing using a precision annealing apparatus to eliminate the residual permanent stress and to meet the requirement of high uniformity. Obviously, the annealing process is divided into four stages, namely a heating stage, a heat preservation stage, a slow cooling stage and a fast cooling stage.
Fig. 4 is a graph showing a comparison of transmittance of the synthetic quartz glass of the present invention and conventional synthetic quartz, and fig. 5 is a refractive index profile of the synthetic quartz glass of the present invention.
As can be seen from the figure, the final annealed quartz glass of the invention has an optical uniformity of 1.2X 10 when the caliber of the product is 120mm-6The external passing rate level of the transmittance is more than or equal to 90.5 percent (5mm), and the internal passing rate level is more than or equal to 99.5 percent.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (9)
1. A method for producing a synthetic quartz material for a semiconductor mask, characterized by: the method comprises the following steps:
(1) depositing a silicon source on the guide rod in the deposition cavity by adopting a gas-phase axial deposition method to obtain low-density SiO2A loose body; wherein the silicon is derived from a chemical reaction in a burning oxyhydrogen flame to form silica particles and deposit to form low density SiO2A loose body; in the deposition process, controlling the interior of the deposition cavity to be in a negative pressure environment, wherein the temperature is not higher than 500 ℃;
(2) mixing low density SiO2Transferring the loose body to a sintering furnace, and heating to 1100-1300 ℃ in a closed environment filled with dehydroxylation airflow and oxygen to ensure that the low-density SiO2Dehydrating the loose body;
(3) in an inert gas ringIn the environment, introducing fluorine-containing gas into a sintering furnace, and heating to 1400-1600 ℃ to ensure that the low-density SiO2Vitrifying the bulk to form transparent quartz glass; the low density SiO is formed during dehydration and vitrification2The loose body keeps not moving longitudinally, and the temperature gradient between the longitudinal direction and the radial direction in the deposition cavity is less than or equal to 2 ℃;
(4) and (4) annealing the transparent quartz glass obtained in the step (3) to obtain the synthetic quartz material for producing the semiconductor mask plate.
2. The method of producing a synthetic quartz material for a semiconductor reticle according to claim 1, characterized in that: in the step (1), the silicon source is SiCl with the purity of more than 99.9999 percent4The purity of the introduced hydrogen and oxygen reaches more than 99.999 percent, and the inner wall of the deposition cavity adopts a high-purity quartz lining.
3. The method of producing a synthetic quartz material for a semiconductor reticle according to claim 1, characterized in that: in the step (1), the low-density SiO is controlled by a motor2The rotational speed of the loose body is 20-50 rpm/min, and the lifting speed is 0.4-1.2 mm/min.
4. The method of producing a synthetic quartz material for a semiconductor reticle according to claim 2, characterized in that: in the step (1), the obtained low-density SiO2The content of metal impurities in the loose body is less than or equal to 10 ppb.
5. The method of producing a synthetic quartz material for a semiconductor reticle according to claim 1, characterized in that: in the step (2), the dehydroxylation airflow comprises inert gas and chlorine-based drying agent.
6. The method of producing a synthetic quartz material for a semiconductor reticle according to claim 5, characterized in that: in the step (2), the inert gas comprises helium or argon, and the chlorine-based drying agent comprises chlorine; the flow rate of the oxygen is 0.5-2L/min.
7. The method of producing a synthetic quartz material for a semiconductor reticle according to claim 1, characterized in that: in the step (3), the fluorine-containing gas includes CF4、C2F6、C3F8One or more of (a).
8. The method of producing a synthetic quartz material for a semiconductor reticle according to claim 1, characterized in that: in the step (3), 2-4 layers of heating elements are arranged outside the furnace wall of the sintering furnace, 6-14 thermocouples are uniformly and symmetrically distributed, the thermocouples are respectively connected into the PLC system, the temperatures of different areas in the sintering furnace are monitored through the thermocouples and fed back to the PLC system, and then the heating power of different heating elements is adjusted according to the fed back temperature data, so that the longitudinal and radial temperature gradients in the sintering furnace are not more than 2 ℃.
9. The method of producing a synthetic quartz material for a semiconductor reticle according to claim 1, characterized in that: in the step (3), the content of metal impurities in the obtained transparent quartz glass is less than or equal to 8 ppb.
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