JP2009107864A - Parts for manufacturing semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide parts for manufacturing semiconductor which can maintain high performance and high reliability of the semiconductor. <P>SOLUTION: The parts are made by providing a substrate 1 comprised of silicon nitride crystal particles 3 and grain boundaries and composed of a silicon nitride sintered compact having a relative density of at least 98%, by removing the grain boundaries from the outer layer of the substrate 1 and providing a porous layer 5 having three-dimensionally connected silicon nitride crystal particles 3 on the substrate 1, wherein even when conveying silicon wafers laid on the porous layer 5, the silicon wafers do not contact with elements, for example rare earth elements, aluminium or the like, which would conventionally constitute grain boundaries, thereby the silicon wafers are not contaminated and the performance and the reliability of the semiconductor are not dameaged. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor manufacturing component, and more particularly to a semiconductor manufacturing component for supporting or transporting a silicon wafer.

  In the manufacturing process of a semiconductor device, a semiconductor manufacturing component such as a susceptor for supporting or holding a silicon wafer, an electrostatic chuck, a support base on which these are mounted, an insulating ring, or various jigs are mainly used. In addition, ceramics such as alumina are used.

Alumina ceramics are widely used because they are relatively inexpensive and chemically stable. However, since alumina ceramics are heavy with a density of 4.0 g / cm ³ and have a large coefficient of thermal expansion of 5 × 10 ⁻⁶ / ° C. at 20 to 40 ° C., deformation due to temperature is large when performing microfabrication. There is a problem that the accuracy is lowered and a defect occurs.

  Therefore, recently, it is known that such a semiconductor manufacturing component is formed of a silicon nitride sintered body (see, for example, Patent Documents 1 and 2). Such a silicon nitride sintered body has high purity and high strength in addition to light weight and low thermal expansion coefficient, and has been proposed as a component for semiconductor manufacturing.

Such a silicon nitride sintered body is generally increased in its sinterability and densified by a combination with rare earth oxides such as Y ₂ O ₃ as a sintering aid, and optionally aluminum oxide. Thereby, a sintered body having high strength and high fracture toughness can be obtained.

  Patent Document 3 discloses that as a member for molten aluminum, the surface of a silicon nitride sintered body is etched to remove the grain boundary phase, thereby forming a porous layer having a thickness of 5 to 300 μm. .

Patent Document 4 discloses a semiconductor manufacturing member in which the surface of an alumina base material is chemically etched to have a surface roughness Ra of 4 to 10 μm. Patent Document 5 discloses a surface of the alumina base material. A semiconductor manufacturing member having a surface layer with a porosity of 20 to 60% and a porosity of 10 to 100 μm by etching is disclosed.
JP 2001-302353 A JP 2007-39306 A JP 2005-177850 A JP 2006-8474 A JP 2006-13288 A

However, the silicon nitride sintered body is generally enhanced in sinterability by combining with rare earth oxides such as Y ₂ O ₃ as a sintering aid, and aluminum oxide if desired. In the semiconductor manufacturing apparatus 2, for example, an element such as a rare earth element or aluminum as a grain boundary phase contaminates the silicon wafer when supporting or holding the silicon wafer and impairs the performance or reliability of the semiconductor. was there.

  In addition, although the member for aluminum melt is described in patent document 3, the point which uses the silicon nitride sintered compact which has a porous layer for a semiconductor manufacturing apparatus is not described.

  An object of this invention is to provide the component for semiconductor manufacture which can maintain the performance and reliability of a semiconductor highly.

  The semiconductor manufacturing component of the present invention comprises a silicon nitride sintered body having a relative density of 98% or more, and the grain boundary phase on the surface layer of the base is removed from the base made of silicon nitride crystal grains and a grain boundary phase. In addition, a porous layer in which the silicon nitride crystal particles are three-dimensionally connected is provided.

  In such a semiconductor manufacturing component, the porous layer is composed of silicon nitride crystal particles and voids formed three-dimensionally continuously at the grain boundaries of the silicon nitride crystal particles. Since it does not exist, even when a silicon wafer is placed on the porous layer and transported, elements such as rare earth elements and aluminum constituting the conventional grain boundary phase do not come into contact with the silicon wafer. This prevents contamination of the silicon wafer and impairs the performance and reliability of the semiconductor.

  In addition, the presence of a substrate made of a silicon nitride sintered body having a relative density of 98% or more has high rigidity, can improve strength, and has a low thermal expansion coefficient. In addition, since a porous layer including silicon nitride crystal particles and voids formed three-dimensionally continuously at the grain boundaries of the silicon nitride crystal particles is provided on the surface of the substrate, the weight can be reduced. In addition, since the porous layer has no grain boundary phase, as described above, the amount of impurities other than silicon nitride can be almost eliminated, and contamination of the silicon wafer can be prevented.

  In particular, when the silicon wafer is supported or held at the tip of the fine silicon nitride crystal particles, the contact with the semiconductor manufacturing component becomes a point contact, thereby further preventing contamination.

  In the semiconductor manufacturing component of the present invention, silicon oxide is present on the surface of the silicon nitride crystal particles of the porous layer. In such a semiconductor manufacturing component, the bonding between the silicon nitride crystal particles in the porous layer is strengthened, and the strength of the porous layer can be improved. Thereby, the reliability of the semiconductor manufacturing component can be improved.

  Furthermore, the semiconductor manufacturing component of the present invention is characterized in that the tips of the silicon nitride crystal particles of the porous layer are rounded. In such a semiconductor manufacturing component, the tips of the silicon nitride crystal particles are rounded and smooth, so that the silicon wafer can be prevented from being damaged.

  The thickness of the porous layer is 0.01 to 0.7 mm, preferably 0.02 to 0.6 mm, more preferably 0.03 to 0.5 mm.

  The semiconductor manufacturing component of the present invention has high rigidity due to the presence of the substrate, can improve strength, and has a low coefficient of thermal expansion. Moreover, since the porous layer is provided on the surface layer of the substrate, the weight can be reduced, and the porous layer has no grain boundary phase. And contamination of the silicon wafer can be prevented.

  The present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the vicinity of the surface of a semiconductor manufacturing component according to the present invention. According to FIG. 1, the semiconductor manufacturing component of the present invention includes a base body 1 and a porous layer 5 provided on the surface of the base body 1, and a silicon wafer is placed on the surface of the porous layer 5. Is done.

  The substrate 1 is preferably a silicon nitride sintered body containing a sintering aid in a proportion of 1 to 20% by mass and having a relative density of 98% or more from the viewpoint of thermal shock resistance and strength. In particular, the strength of the silicon nitride sintered body of the substrate 1 does not generate much stress when supporting or holding a silicon wafer, and the internal cutout strength at room temperature may be 200 MPa or more.

  Known components can be used as the sintering aid. For example, an oxide of a group 3a element such as Y, Er, Yb, or Lu, or an oxide such as Al or Mg can be used. From the viewpoint of promoting sinterability, the group 3a element can be used. The oxide is excellent. What is necessary is just to mix | blend these sintering adjuvant components so that the total amount of oxide conversion may become a ratio of 1-20 mass% with respect to silicon nitride.

  If the content of the sintering aid is less than 1% by mass, the densification is insufficient and sufficient strength cannot be obtained, and if it exceeds 20% by mass, the absolute amount of the grain boundary becomes large. The amount of voids increases due to the impact resistance and surface strength. Therefore, in order to have sufficient strength and to further improve the peeling and deficiency of the porous layer 5, the content is particularly preferably 2 to 15% by mass, and more preferably 3 to 10% by mass.

  It is desirable that the average particle diameter of the silicon nitride crystal particles 3 in the porous layer 5 is substantially the same as the average particle diameter of the silicon nitride crystal particles of the silicon nitride sintered body constituting the substrate 1. By making the average particle diameters of the silicon nitride crystals of the substrate 1 and the porous layer 5 substantially the same, the structure is difficult to peel off, and the strength is not drastically reduced. As shown in FIG. 1, it is desirable that the lower end portion of the silicon nitride crystal particles 3 of the porous layer 5 is embedded in the substrate 1. The silicon nitride crystal particles 3 have a hexagonal column shape.

  In the present invention, the term “substantially identical” means that the average particle size AL of the silicon nitride crystal particles 3 of the porous layer 5 is 0.95 AS ≦ AL ≦ 1 with respect to the average particle size AS of the silicon nitride crystal particles of the substrate 1. .05AS means a value that satisfies the relational expression.

  Further, it is important that the porous layer 5 is composed of the silicon nitride crystal particles 3 and the voids 4 surrounding the silicon nitride crystal particles 3 three-dimensionally. The porous layer 5 removes the grain boundary phase containing the sintering aid and impurities existing at the grain boundary of the silicon nitride crystal grain 3 from the surface 2 of the porous layer in direct contact with the silicon wafer to a specific depth. It can be produced by forming the voids three-dimensionally.

  Thus, there is a sintered body with high strength and high impact resistance inside, and the silicon nitride crystal 3 formed by sintering integrally with the sintered body is three-dimensionally bonded, and the silicon nitride Since the structure in which the grain boundaries of the crystal grains 3 are formed three-dimensionally is adopted, even if a silicon wafer is placed on the surface 2 of the porous layer 5 without the sintering aid, rare earth elements, aluminum Such an element does not come into contact with the silicon wafer, so that the silicon wafer is not contaminated and the performance and reliability of the semiconductor are not impaired. Further, even if there are many voids, the silicon nitride crystal particles are continuous from the substrate 1 and are three-dimensionally sintered and integrated, so that the porous layer 5 is difficult to peel off from the substrate 1 and is highly reliable. A semiconductor manufacturing component can be realized. The semiconductor manufacturing component of the present invention in which a porous layer is provided on a substrate can also be used as a liquid crystal panel manufacturing component.

  The meaning of “three-dimensionally continuous” in the present invention means three-dimensional continuity and spatial connection, though not necessarily continuous on a flat surface such as a polished surface. Yes. That is, the voids 4 formed at the grain boundaries of the silicon nitride crystal grains are connected, and there is no or almost no grain boundary phase. In addition, the silicon nitride crystal particles are partly sintered and integrated with other crystal grains in which at least a part of each crystal particle is adjacent, and the parts that are partially connected are connected in a three-dimensional manner. Is in a state of being.

  The thickness of the porous layer 5 is preferably 10 μm or more, particularly 20 μm, further 30 μm or more, and more preferably 50 μm or more. Silicon nitride itself is made of a chemically stable compound having a covalent bond, so it has excellent corrosion resistance, but if there is a sintering aid or impurity at the grain boundary, it contaminates the silicon wafer, but the thickness of the porous layer is reduced. By setting the thickness to 10 μm or more, the silicon wafer does not come into direct contact with a sintering aid component such as a rare earth element or aluminum.

  The upper limit of the thickness of the porous layer 5 is not particularly limited, but there is no change in the function and effect even when the thickness is 500 μm or more, for example. In order not to extremely reduce the strength of the semiconductor manufacturing component, 1 mm or less, particularly 700 μm or less, further 600 μm or less, more preferably 500 μm or less is desirable.

  Even if such a semiconductor manufacturing component places a silicon wafer on the porous layer 5 and transports it, elements such as rare earth elements and aluminum constituting the conventional grain boundary phase are silicon wafers. This prevents contamination of the silicon wafer and impairs the performance and reliability of the semiconductor.

  Next, the manufacturing method of the component for semiconductor manufacture of this invention is demonstrated. The silicon nitride sintered body serving as the substrate can be produced by a known method.

Specifically, the silicon nitride powder is mixed with a Group 3a elemental oxide such as Y ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ , Al ₂ O ₃ , MgO, AlN. , SiO ₂ and other sintering aids added in a total amount of 1 to 20% by mass, particularly 2 to 15% by mass, and further 3 to 10% by mass, in a desired molding means such as cold static After forming into an arbitrary shape by hydraulic press, cast molding, extrusion molding, etc., firing is performed.

  Firing is performed in a nitrogen-containing atmosphere at a temperature of 1500 to 1950 ° C. for about 0.5 to 10 hours to obtain a sintered body having a relative density of 98% or more, particularly 98.5% or more, and further 99% or more.

Examples of the firing method include normal pressure firing, nitrogen gas pressure firing, and hot isostatic firing, and in some cases, these can be combined.

  Next, it is important to etch the silicon nitride sintered body obtained as described above to remove the grain boundary phase. As the etching process, three kinds of heat etching process in a corrosive gas, plasma etching process in a corrosive gas plasma, and pressure heating process in an acid can be adopted. Halogen gas and / or hydrogen can be used as the corrosive gas, and hydrochloric acid as the acid.

  In particular, hydrogen is preferable for the heat etching process, and halogen gas is preferable for the plasma etching process. Since halogen gas is highly corrosive, it is suitable for plasma etching. As the halogen gas, at least one of chlorine gas, bromine gas and iodine gas can be adopted, and chlorine gas is preferable in consideration of cost and grain boundary phase removal efficiency.

  In the case of the heat etching process, the etching process is performed in a temperature range of 800 to 1900 ° C. in a gas atmosphere containing at least the above corrosive gas. By removing the grain boundary phase component on the surface of the sintered body by this etching treatment, a surface layer composed of a porous layer can be formed.

  When the temperature during this etching process is less than 800 ° C., the removal rate of the grain boundary phase is small. For example, even if the etching process is continued for 30 hours or more, a porous layer having a thickness of 5 μm or more may not be obtained. Not suitable for. In order to complete the treatment in a short time, a temperature of 900 ° C. or higher, further 1000 ° C. or higher, more preferably 1100 ° C. or higher is desirable. However, at temperatures exceeding 1900 ° C., silicon nitride itself is actively decomposed and large surface erosion occurs. Therefore, the pressure is set to 1900 ° C. or lower at atmospheric pressure. Needless to say, when the etching process is performed at a high pressure exceeding 1 atm, the upper limit of the etching process temperature is raised.

  Furthermore, in order to suppress a decrease in the bending strength of the substrate 1, it is desirable to perform an etching process at a temperature of 1600 ° C. or lower. In addition, with respect to the etching process time, it is desirable to perform the etching process for 10 minutes or more in any temperature condition in order to sufficiently remove.

  In the case of the plasma etching process, the corrosive gas is discharged into a plasma state, and the silicon nitride sintered body is disposed so as to be in contact with the plasma. In this treatment, it is not particularly necessary to raise the temperature, but in order to suppress temperature variation due to plasma, it is preferable to set the temperature to a constant temperature of 50 ° C. or higher by heating. Since the plasma etching process can be performed at a low temperature, it is preferable in terms of safety.

  According to such an etching treatment method, it can be easily applied to a complicated member or a large member, and a substrate having a porous layer can be manufactured.

  In addition, in the pressure heat treatment in acid, the porous material is removed by removing the grain boundary phase components on the surface of the sintered body by treating at a temperature of 120 to 200 ° C. under an equilibrium vapor pressure of water for 1 to 100 hours. A surface layer composed of layers can be formed.

  In the semiconductor manufacturing component of the present invention, it is desirable that silicon oxide is present on the surface of the silicon nitride crystal particles of the porous layer. In such a semiconductor manufacturing component, the bonding between the silicon nitride crystal particles in the porous layer is strengthened, and the strength of the porous layer can be improved. Thereby, the reliability of the semiconductor manufacturing component can be improved.

  In order to make silicon oxide exist on the surface of the silicon nitride crystal particles and strengthen the bonding between the silicon nitride crystal particles of the porous layer, after forming the porous layer by etching, the temperature is 800 to 1200 ° C. for 1 to 50 hours. This can be achieved by heat treatment.

  Furthermore, in the semiconductor manufacturing component of the present invention, it is desirable that the tips of the silicon nitride crystal particles of the porous layer are rounded. In such semiconductor manufacturing parts, the tips of the silicon nitride crystal particles are rounded and smooth, and even when the silicon wafer is placed (contacted) to support or hold, the silicon wafer may be damaged. Absent. Smoothing the tips of the silicon nitride crystal particles can be achieved by plasma etching with fluorine plasma or pressure heat treatment in hydrofluoric acid. In addition, when removing the grain boundary phase by pressurizing and heating in an acid, the tip of the silicon nitride crystal particles is rounded to some extent, but the etching process and the corrosive gas plasma in corrosive gas. When the grain boundary phase is removed by plasma etching treatment in the inside, since corners are formed on the surface of the silicon nitride crystal particles, plasma etching with fluorine plasma or pressure heating treatment in hydrofluoric acid is performed. It is desirable to smooth the tips of the silicon nitride particles.

First, raw material powder is prepared. That is, silicon nitride powder (average particle size 0.6 μm, oxygen content 0.7 mass%, pregelatinization rate 92%), rare earth element oxide powder, and Al ₂ O ₃ powder so as to have the compositions shown in Table 1, respectively. After adding and thoroughly mixing with a ball mill, a granule is produced by drying and granulating with a spray dryer. The granule is filled into a mold and molded by pressing with a pressure of 100 MPa to produce a molded body. .

  The obtained molded body was put in a silicon carbide mortar, heated using a carbon heater to a temperature of 1750 ° C. in a normal pressure nitrogen atmosphere, held at this temperature for 5 hours, and further up to 1900 ° C. The temperature was raised and held for 5 hours. Thereafter, the furnace was cooled to produce a silicon nitride sintered body having a thickness of 5 mm.

  The obtained silicon nitride sintered body was subjected to etching treatment to produce a substrate on which a porous layer was formed. The etching process was a pressure heating process in hydrochloric acid under an equilibrium vapor pressure. The etching conditions are shown in Table 1.

  Next, the silicon nitride sintered body was processed into a 20 mm square shape with a thickness of 5 mm to prepare a test piece. The thickness of the porous layer was measured with a scanning electron microscope (SEM) after cutting the test piece.

  Then, after processing from the substrate to dimensions of 3 mm long × 4 mm wide × 40 mm long (the porous layer is formed on a surface 4 mm wide × 40 mm long), the 4-point bending strength of the substrate is measured at room temperature. did. The strength was measured according to JIS R 1601, and a load was applied from the opposite surface of the porous layer.

Sample No. 13 is a case where a Si powder was molded and nitrided to produce a porous body of 3 mm long × 4 mm wide × 40 mm long.

  Sample No. of the present invention. 1 to 11, the porous layer has a thickness of 10 μm, particularly 300 μm or more, and is not contaminated even when a silicon wafer is placed thereon. Further, since the strength is 300 MPa or more, damage or the like may occur. Absent. Furthermore, the tips of the silicon nitride crystal particles are rounded so that they are not damaged even when a silicon wafer is placed. Further, in the case of oxidation treatment, the sample No. 1, 2, Sample No. As can be seen from the comparison of 5 and 6, it can be seen that silicon oxide is present on the surface of the silicon nitride particles, the silicon nitride particles are sufficiently bonded to each other, and the strength is greater than when no oxidation treatment is performed.

  On the other hand, a sample No. outside the scope of the present invention that was not etched. No. 12 shows that although the strength is high, there is no porous layer, which may contaminate the silicon wafer. Also, high purity reaction sintered silicon nitride sample No. No. 13 does not contain a sintering aid, but the strength is as low as 150 MPa, and there is a risk of breakage.

BRIEF DESCRIPTION OF THE DRAWINGS The semiconductor manufacturing component of this invention is shown, (a) is sectional drawing, (b) is a schematic diagram which expands and shows a part of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base | substrate 2 ... Surface 3 of porous layer ... Silicon nitride crystal particle 4 ... Void 5 ... Porous layer

Claims (3)

  A silicon nitride sintered body having a silicon nitride crystal grain and a grain boundary phase and having a relative density of 98% or more is removed from the grain boundary phase on the surface layer of the base, so that the silicon nitride crystal grain is 3 A semiconductor manufacturing component comprising a dimensionally connected porous layer.   2. The semiconductor manufacturing component according to claim 1, wherein silicon oxide is present on the surface of the silicon nitride crystal particles of the porous layer.   The semiconductor manufacturing component according to claim 1, wherein tips of the silicon nitride crystal particles of the porous layer are rounded.

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