Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of...
Reexamination Certificate
1999-01-15
2001-03-20
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
C438S765000, C438S778000, C438S782000, C438S785000
Reexamination Certificate
active
06204194
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of Invention
The present invention relates to a method for producing a semiconductor device. The present invention aims to improve a conventional batch system, in which a plurality of semiconductor-silicon wafers are treated by chemical vapor deposition (CVD) or a direct reaction of the wafers with a reaction gas, so that the growth rate of the CVD films and the like is enhanced. The present invention also relates to an apparatus for producing a semiconductor device.
2. Description of Related Art
Long history is involved in the LP (low-pressure)-CVD methods using the hot-wall type heating furnace. A plurality of the semiconductor silicon wafers are located horizontally in the reaction tube which is installed in the furnace. The LP-CVD methods reported in the literature are related to the formation of SiO
2
film for example with the use of TEOS and ozone, PSG (phosphosilicate glass) film, BPSG (borophospho-silicate glass) film, HTO (high-temperature oxidation) film with the use of SiH and N
2
O or NO, Si
3
N
4
film, Ta
2
O
5
film, WSi
2
film or the like.
In a conventional vertical hot-wall type heating furnace approximately 150 wafers can be treated in one batch. Although the treatment time is long in such a furnace, since the thermal stress can be mitigated, the above-mentioned furnace is advantageous for producing fine devices. Each wafer is or a plurality of wafers together are loaded into and unloaded from such a furnace by means of a fork-shaped wafer-loading and unloading jig.
In a vertical hot-wall type heating furnace from approximately 100 to 150 wafers are arranged with a clearance distance of 5-9 mm, and the arranged wafers are located in a temperature-equalizing zone, the length of which is from 700 to 900 mm. The internal pressure of such furnace is kept as low as possible, for example approximately 0.3 to 1.0 torr so as to attain uniform growth of the film on each wafer. The reaction gas is introduced into a furnace at a speed as high as approximately 3 to 7 m/second. The introduced reaction gas first flows along the peripheral edges of the wafers within a quartz reaction tube in a direction perpendicular to the surface of wafers. The reaction gas is then engulfed into a clearance between the wafer surfaces.
Under such low-pressure condition, the growth rate of films ranges from 20 to 100 angstroms/minute and is slow. The growth rate of a film in the LP-CVD is influenced by the pressure and also by the length of the temperature-equalizing region. The growth rate of a film varies greatly dependent upon the position of the wafers with increase in the length of the temperature-equalizing zone. This length and hence the treated number of the 6-inch wafers are limited to keep the variation of film thickness usually within a range of from 1 to 3%. Especially, the growth rate of an HTO film ranges from 15 to 20 angstroms/minute at 800° C. under the pressure of from 0.3 to 1.0 torr. Variation of the HTO film-thickness is from 3 to 6.5% on an 8-inch wafer and from 2 to 5% on a 6-inch wafer.
In the case of forming a P-doped or non-doped polycrystalline Si film with the use of SiH
4
under the LP-CVD conditions of: 5 to 7 mm of the wafer-distance; 625° C. of temperature; 200 mL/minute of the SiH
4
flow rate; 50 to 150 8-inch wafers; and 0.6 torr of pressure, the growth rate is from 50 to 80 angstroms/minute. This growth rate is considerably less than the growth rate of a polycrystalline Si by means of a conventional single-wafer process by means of the lamp heating, which is the so-called cold-wall process.
The total processing time of 150 wafers, including the temperature-elevating and lowering stages, ranges from approximately 120 to 600 minutes. The total processing time is greatly dependent upon the kind and thickness of the film to be formed. An example of the long total processing time, i.e., 600 minutes or more, is the formation of an approximately 1 &mgr;m thick amorphous Si.
As is described above, since the growth rate of a CVD film or a direct-reaction film is slow in the hot-wall process, its productivity can be enhanced by increasing the number of wafers treated in one batch, for example to 150 wafers.
SUMMARY OF INVENTION
It is an object of the present invention to provide an improved batch method for producing a semiconductor device, in which a CVD film or a direct-reaction film is formed at a high growth rate on a plurality of semiconductor silicon wafers.
It is another object to provide an apparatus for producing a semiconductor device, in which a CVD film or a direct-reaction film is formed at a high growth rate on a plurality of semiconductor-silicon wafers.
In accordance with the objects of the present invention, there is provided a method for producing a semiconductor device, in a heating furnace, in which a reaction tube is installed and a temperature-equalizing zone is formed in the reaction tube, comprising:
locating semiconductor-silicon wafers, preferably approximately seventy five or fewer wafers, in the temperature-equalizing zone horizontally and parallel to one another, thereby the surfaces of the semiconductor-silicon wafers are placed face to face;
introducing a reaction gas into the clearances between the semiconductor silicon wafers, thereby forming on said semiconductor-silicon wafers a CVD film or a direct reaction film;
said method further comprising:
setting the distance of said clearance at approximately 5 mm or more;
rotating said semiconductor-silicon wafers around an axis perpendicular to the wafer surface; and,
discharging essentially all of the reaction gas from a first position in the proximity of the edges of the semiconductor-silicon wafers into each of said clearances.
The method according to the present invention may further comprise a step of sucking essentially all of the reaction gas discharged from the clearances between the semiconductor-silicon wafers, from a second positiion opposite to the first position.
The apparatus for producing a semiconductor device comprises:
a heating furnace;
a reaction tube installed in the heating furnace and including a temperature-equalizing zone;
a reaction zone formed in said temperature-equalizing zone and providing a space for forming a film on said semiconductor-silicon wafers, preferably approximately seventy-five or fewer wafers, by CVD or a direct reaction using a reaction gas;
a jig for holding a plurality of semiconductor-silicon wafers in the temperature-equalizing zone horizontally and parallel to one another and forming between the semiconductor silicon wafers a clearance of approximately 5 mm or more;
a driving means for rotating said semiconductor-silicon wafers around an axis perpendicular to the wafer surface;
a first gas-guiding means for guiding said reaction gas into the reaction tube in the proximity of the edges of the semiconductor-silicon wafers, while impeding contact of the reaction gas with an interior gas of the heating furnace; and,
discharging ports of the first gas-guiding means, for discharaging essentially all of the reaction gas at the first position into each of said clearances.
The wafer-holding jig according to the present invention consists of a single monotlithic sheet having a holding portion(s) and a vacant space(s) formed by removing non-holding portion(s) of the single monolithic sheet. Alternatively, the wafer-holding jig according to the present invention comprises an outer annular portion and an inner annular portion and a joint portion connecting the outer and inner annular portions.
Preferably, the apparatus according to the present invention further comprises:
a second gas-guiding means for sucking essentially all of the reaction gas discharged from each of the clearances and guiding the reaction gas, while impeding its contact with the interior gas of the heating furnace;
sucking ports of the second gas-guiding means for sucking the reaction gas discharged from the clearances between the semiconductor silicon wafers; and,
a gas-exhausting means connected to said second gas-guiding means.
The present inv
Armstrong Westerman Hattori McLeland & Naughton LLP
F.T.L. Co., Ltd.
Smith Matthew
Yevsikov Victor V.
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