JP2004221457A - Semiconductor processing equipment - Google Patents

Abstract

An object of the present invention is to provide a semiconductor processing apparatus which is a vertical heat diffusion furnace capable of performing a uniform heat treatment on a wafer and preventing metal contamination.
A porous partition wall (3) separates a gas inlet (6) for introducing an atmospheric gas into a furnace tube (2) and a wafer boat (13) holding wafers inside the furnace tube (2).
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor processing apparatus such as a heat treatment furnace for annealing a semiconductor wafer in an atmosphere of, for example, 1000 ° C. or higher.
[0002]
[Prior art]
In a manufacturing process of a semiconductor wafer (hereinafter, referred to as a wafer), a silicon single crystal is gradually pulled up from a heating furnace by a CZ (Czochralski) method or the like as shown in a general schematic flow chart in FIG. Is grown (S11), the pulled silicon ingot is cut into blocks, and the blocks are sliced (S12). The surface of the cut wafer is subjected to lapping, and is further subjected to mirror finishing to form a mirror surface (S13). After the mirror polishing, cleaning is performed (S14), and a heat treatment is performed in a high-temperature (1000 ° C. or higher) atmosphere using a heat treatment furnace (for example, a vertical thermal diffusion furnace) in order to secure a complete crystal layer on the wafer surface. (S15). Thereafter, final cleaning is performed (S16), and a wafer is completed (S17).
[0003]
Among these manufacturing processes, wafer heat treatment using a heat treatment furnace involves a process in which fine crystal defects generated in a wafer are accompanied by an increase in the degree of integration of a semiconductor, and the electrical characteristics of each element such as a transistor and a capacitor formed in the wafer are changed. For example, in the case of a wafer manufactured by the conventionally used CZ method, when the crystal defect density in the element active layer is high, the yield is reduced in the device manufacturing process because the wafer is manufactured by the conventionally used CZ method. I will.
[0004]
Therefore, although the manufacturing cost is increased, annealing for several hours in an H ₂ atmosphere exceeding 1000 ° C. inside the thermal diffusion furnace reduces the crystal defect density in the element active layer. By using a hydrogen-annealed wafer or an epitaxial wafer that has been subjected to the annealing process as described above, the yield reduction rate in the process of manufacturing a highly integrated semiconductor device is suppressed. As described above, the wafer heat treatment by the heat treatment furnace for making the wafer suitable for the formation of the semiconductor element is usually performed by a batch method in which the heat treatment is performed while a plurality of wafers are placed on a wafer boat. .
[0005]
FIG. 3 is a perspective view showing an outline of the appearance of a conventional vertical heat diffusion furnace, and FIG. 4 is a partial cross-sectional view showing an upper part of the conventional vertical heat diffusion furnace.
[0006]
The vertical heat diffusion furnace 50 has a cylindrical shape, and a gas introduction pipe 51 for supplying gas from the outside is connected to the top of the vertical heat diffusion furnace 50.
[0007]
In the actual heat treatment, a boat 52 on which wafers W are horizontally placed is inserted from below into the vertical thermal diffusion furnace 50, and a predetermined gas is supplied from outside through a gas introduction pipe 51, and a predetermined gas is supplied. The heat treatment is performed by exposing the wafer W to the gas for a period of time. That is, the upper chamber 53, which is the upper part of the furnace 50 to which the gas is supplied, has a structure in which there is no obstacle to the gas flow. Go through 53. In the furnace tube portion 54 below the wafer W, the wafers W are held at equally spaced gaps in the wafer boat, so the temperature here is controlled to 1000 ° C. or higher, the gas flows near the wafer W, and the wafer W Heat treatment is performed in a gas atmosphere. A reflector (not shown) having a complicated shape is provided below the furnace tube portion 54 so that high heat does not reach further below. The gas passes through this portion and is exhausted from the furnace 50 through an exhaust pipe (not shown) (for example, see Patent Document 1).
[0008]
As shown in FIG. 5, a partition wall 56 having a hole 56 a is provided at the upper part of the furnace 50, and the partition wall 56 separates the upper chamber 53 of the furnace 50 from the furnace cylinder 54. It is disclosed (for example, see Patent Document 1).
[0009]
[Patent Document 1]
JP-A-10-22291 (paragraphs 0006 to 0038, FIGS. 1, 9, and 10)
[0010]
[Problems to be solved by the invention]
The flow of gas inside the conventional vertical thermal diffusion furnace will be described with reference to the explanatory view shown in FIG. 6. In the conventional vertical thermal diffusion furnace 50, since there is no obstacle at the upper part inside the furnace 50, The gas G is supplied from the gas introduction pipe 51, flows into the upper chamber 53, flows further below, and is supplied so as to collide with the wafer W. In this case, the gas G flows from a wide area without obstacles to an area where the wafer boat 52 on which the wafer G is mounted is provided. That is, the gas G flows from a wide area to a narrow area at a flow rate substantially supplied from the gas introduction pipe 51. Therefore, the flow becomes unstable, and the gas G forms vortices A1 and A2 in the upper chamber 53 and the upper part of the furnace tube.
[0011]
Thereafter, the gas G flows downward along the surface of the wafer W while forming an unstable flow, and enters the furnace tube portion 54. The gas G also proceeds in an unstable flow inside the furnace tube portion 54, and flows through the flow path according to the shape of the wafer boat 52 on which the wafer W placed inside the furnace tube portion 54 is placed. A vortex A3 may be generated in a portion having a small cross-sectional area, and a large convection B may be generated inside the furnace tube portion 54.
[0012]
As a result, the gas flow near the wafer W becomes non-uniform, and uneven heat treatment occurs. Further, extremely fine metal-contaminated particles precipitated in the lower portion of the furnace tube portion 54 due to large convection are transported to the wafer W above the furnace tube portion 54, and the wafer W may be metal-contaminated.
[0013]
Further, as shown in Patent Document 1, even if a partition plate 56 having a large number of holes is inserted between the furnace tube portion 54 of the upper chamber 53 of the furnace 50 shown in FIG. Since the velocity of the gas G is not uniform behind (below) the hole immediately after 56, the instability of the flow of the gas G is not solved.
[0014]
The present invention has been made based on these circumstances, and an object of the present invention is to provide a semiconductor processing apparatus which is a vertical heat diffusion furnace capable of performing uniform heat treatment on a wafer and preventing metal contamination. And
[0015]
[Means for Solving the Problems]
According to the means of the present invention, a semiconductor process for performing a heat treatment on a wafer placed on a wafer boat disposed inside the heat treatment furnace by an atmospheric gas supplied from a gas inlet formed in the heat treatment furnace. An apparatus, wherein the gas inlet and the wafer boat are separated by a porous partition.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
The inventor has foreseen that in order to perform processing uniformly and efficiently in a heat treatment furnace (vertical heat diffusion furnace) that anneals the wafer and to prevent metal contamination, the wafer inside the vertical heat diffusion furnace is required. Therefore, it is important to form a uniform and stable gas flow and prevent convection around the wafer, and the gas flow inside the vertical thermal diffusion furnace is considered important. We have studied flow control.
[0018]
As a result, in recent years, by using the following structure inside the vertical thermal diffusion furnace, the gas flow to the wafers inside the vertical thermal diffusion furnace has been made uniform and stable. It was also confirmed that convection around the wafer could be prevented from occurring.
[0019]
FIG. 1 is a schematic cross-sectional view showing an example of the vertical heat diffusion furnace of the present invention.
[0020]
In the vertical heat diffusion furnace 1, a heat treatment chamber is formed by a cylindrical furnace core tube 2 made of a material such as quartz glass glass or SiC and closed at the top. The furnace tube 2 is separated into an upper chamber 4 and a furnace tube 5 by a partition wall 3 joined to the side wall 2a by welding.
[0021]
The partition 3 is made of a porous material through which gas G can flow, and has a heat-resistant temperature of at least 1000 ° C. and a thermal expansion coefficient of a predetermined value or less. These members are, for example, silicon carbide (SiC), alumina or quartz glass. The partition wall 3 is welded to the side wall 2a of the furnace tube 2 so as to be substantially parallel to a plane of a wafer W which is an object to be processed placed on a wafer boat described later. Note that the partition wall 3 may be formed by one sheet, or may be formed by a plurality of sheets having a predetermined thickness.
[0022]
On the side wall 2a of the furnace tube 2, a predetermined heat treatment gas G for performing a heat treatment on the wafer W to be processed is supplied from the upper gas inlet 6 inside the furnace tube 2 to the upper chamber portion 4. A gas introduction pipe 7 to be introduced is arranged. Further, a gas outlet 8 for discharging the heat treatment gas G is arranged on the side wall 2 a of the furnace core tube 2 facing the gas inlet tube 7. The gas G is a reducing atmosphere gas containing H _2.
[0023]
In addition, in order to prevent metal contamination of the wafer W, the material of the gas introduction pipe 7 and the side wall 2a of the upper chamber 4 is made of high-purity quartz glass having few metal components such as Fe and Cu which cause metal contamination. Is preferred.
[0024]
Further, it is preferable that the material of the side wall 2a of the upper chamber portion 4 has a lower concentration of both Fe and Cu which cause metal contamination than the material of the side wall 2a of the furnace tube portion 5.
[0025]
Accordingly, the material of the gas introduction pipe 7 and the side wall 2a of the upper chamber 4 is made of high-purity quartz glass, and the purity of the quartz glass is set to be higher than that of the material of the side wall 2a of the furnace tube 5 by the material of the side wall 2a of the upper chamber 4. If the material is made higher, the contamination of the metal from the side wall 2a of the upper chamber 4 which occurs inside the upper chamber 4 can be prevented.
[0026]
Further, inside the furnace tube 2, a lower heat insulating tube 11, an upper heat insulating tube 12, and a wafer board 13, which are sequentially laminated on a hearth 9 made of stainless steel, for example, are arranged.
[0027]
The lower heat insulating cylinder 11 is formed of a quartz glass glass plate 14a in which four holes (not shown) formed through four pillars 9a erected on the hearth 9 and electrically connected to each other in a skewered manner. They are formed by being laminated at a predetermined pitch.
[0028]
The upper heat insulating cylinder 12 is provided at a position corresponding to the column 9a of the lower heat insulating cylinder 11, and for example, four holes formed in the column 9b electrically connected to the column 9a penetrate in a skewered manner. Formed quartz glass plates 14b are laminated at a predetermined pitch.
[0029]
The heat retaining cylinders 11 and 12 serve as heat reflecting plates, and serve to prevent heat from escaping downward when the wafer W stored in the wafer W board 13 is subjected to heat treatment. The reason why the lower heat insulating cylinder 11 and the upper heat insulating cylinder 12 are separately provided is that the upper heat insulating cylinder 12 is exposed to a high temperature, and there is a possibility that the quartz glass glass plate 14a may be drooped due to aging. This is because of the ease of exchange and the economics of partial exchange.
[0030]
As shown in FIG. 1, a heater 15 is provided around the core tube 2 so as to surround the inserted wafer boat 13, and the outside of the core tube 2 and the heater 15 is provided by a casing 16. Concealed.
[0031]
Due to the structure of these vertical heat diffusion furnaces, the gas G introduced from the gas introduction pipe 7 into the upper chamber 4 at the upper part of the furnace tube 2 at a predetermined flow rate is supplied to the upper chamber 4 facing the flow of the gas G. Since the bottom is closed by the porous partition wall 3, it temporarily stays inside the upper chamber 4 and is heated. After that, it is dispersed at a very high density over the entire surface of the partition wall 3 and flows into the furnace tube portion 5 with a uniform flow velocity distribution so as to seep through the porous holes of the partition wall 3. In this case, since the partition wall 3 is welded to the side wall 2a of the furnace core tube 2 so as to be substantially parallel to the plane of the wafer W to be processed placed on the wafer boat, The gas G that has leaked out through the holes flows in a direction substantially perpendicular to the surface of the wafer W.
[0032]
The gas G flowing into the furnace tube 5 flows near the wafer W. Thereby, the wafer W is heat-treated. Then, the gas G passes through the portion where the heat retaining tubes 11 and 12 are installed, and is exhausted from the gas outlet 8 to the outside of the furnace tube 2.
[0033]
In this case, the flow of the gas G inside the furnace tube part 5 is dispersed at a very high density from the entire surface of the partition wall 3 and flows in with a uniform flow velocity distribution. A uniform flow is also formed inside the cylindrical portion 5, and a uniform gas G flows near the wafer W. As a result, temperature and airflow are not disturbed, and uniform heat treatment can be performed.
[0034]
Further, by avoiding the instability of the flow of the gas G inside the furnace tube 5, large convection inside the furnace tube 5 can also be suppressed. Thus, even if metal contamination precipitated at the lower portion of the furnace tube 2 occurs, the metal contamination is not transferred to the wafer W inside the furnace tube 5. Thereby, metal contamination of the wafer W can be prevented.
[0035]
In addition, the inflow position of the gas introduction pipe 7 into the furnace tube portion 5 can be arbitrarily arranged on the side wall 2 a or the top of the furnace tube 2. In addition, the number of the gas introduction pipes 7 can be arbitrarily selected from one or a plurality. In addition, the above-described embodiment can be variously modified in accordance with the gist of the invention.
[0036]
Further, in the above-described embodiment, the case of hydrogen annealing has been described. However, the present invention is not limited to hydrogen annealing but can be applied to N ₂ , Ar, or an oxidizing atmosphere.
[0037]
【The invention's effect】
According to the present invention, it is possible to realize a semiconductor processing apparatus such as a vertical thermal diffusion furnace or the like that can perform a uniform heat treatment on a wafer and that prevents metal contamination.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an example of a vertical thermal diffusion furnace of the present invention.
FIG. 2 is a general schematic flowchart of a semiconductor wafer manufacturing process.
FIG. 3 is a perspective view showing an outline of the appearance of a conventional vertical heat diffusion furnace.
FIG. 4 is a partial sectional view showing an upper part of a conventional vertical thermal diffusion furnace.
FIG. 5 is a partial sectional view showing an upper part of a conventional vertical heat diffusion furnace.
FIG. 6 is an explanatory view of a gas flow inside a conventional vertical thermal diffusion furnace.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Vertical thermal diffusion furnace, 2 ... Furnace tube, 3 ... Partition wall, 4 ... Upper chamber part, 5 ... Furnace cylinder part, 6 ... Gas introduction port, 7 ... Gas introduction pipe, 13 ... Wafer boat

Claims (2)

A semiconductor processing apparatus for performing a heat treatment on a wafer mounted on a wafer boat disposed inside the heat treatment furnace by an atmosphere gas supplied from a gas inlet formed in the heat treatment furnace,
A semiconductor processing apparatus, wherein the gas inlet and the wafer boat are separated by a porous partition. 2. The semiconductor processing apparatus according to claim 1, wherein said partition is made of silicon carbide, alumina or quartz glass.

Images