JPH01306568A - Hot wall type vacuum cvd device - Google Patents

Abstract

PURPOSE:To make the thickness of films and the concn. of an impurity uniform by introducing a doping gas to be added to formed films into an inner tube through plural openings which become gradually smaller toward the downstream side in the wall of the tube so that the partial pressure of the gas can be made uniform. CONSTITUTION:A double-walled reaction tube consisting of an outer tube 1 and an inner tube 2 is used as a reaction chamber and heating means 31-33 are arranged around the chamber. Holders 7 holding substrates 8 such as Si wafers on which films are formed, a baffer 6 and a pipe (gas nozzle) 5 for introducing a reactive gas are arranged in order toward the throat in the inner tube 2 and a doping gas to be added to formed films is fed to the gap 9 between the outer and inner tubes 1, 2. Plural openings which become gradually smaller in area toward the downstream side are pierced is inlets 11-14 for introducing the gas into the inner tube 2 in the wall of the tube 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention heats a semiconductor substrate or the like in a reaction chamber from outside the reaction chamber to form an oxide film containing impurities such as PSGIII on the substrate at a low temperature. True wall type low pressure CVD
Regarding equipment.

[Conventional technology]

FIG. 2 is a schematic cross-sectional view of the gas inlet 4 x 9 pipes and the gas exhaust port of a conventional (known) real wall type low-pressure CVD device for forming a low-temperature oxide film. This device is used to form PSG. When performing the membrane, first, the double quartz reaction tube parts 1 and 2
Resistance heater divided into three areas 31.32.3
3, the psc film formation temperature is fixed in advance at 300 to 400°C. However, for aft MN adjustment, the furnace temperature on the furnace opening side (upstream) is set to be about 7% lower than the temperature at the hearth center, and the furnace temperature on the furnace back side (downstream) is set to be about 7% higher. This is due to the CV introduced from the furnace mouth 41, 42 as described later.
By gradually increasing the reaction temperature, the reaction gas for D is consumed sequentially from the upstream, and the partial pressure of the reaction gas decreases as it goes downstream, and the deposition rate of the CVD film would gradually decrease if left as it was. Oxygen (O) and helium gas are supplied from the upper part of the furnace mouth 41 into the inner tube 1, which has been sufficiently purged with nitrogen under a reduced pressure of about 1 mbar, and a gas nozzle is supplied from the lower part of the furnace mouth 42. Monosilane (S1114) and phosphine (PHs) are introduced via 5. Since the diffusion constant is inversely proportional to pressure, the reaction gas diffuses more quickly under reduced pressure than at normal pressure, and is uniformly supplied into the reaction tube. , the uniformity of the film thickness is improved.Furthermore, since helium gas is a carrier gas with a large mean free path, a more uniform film thickness can be obtained than when monosilane is diluted with other inert gases. The reactive gas flow starts to react with O□, but since the quartz buffer 6 is provided, the flow of the reactive gas is particularly affected by the narrow gap between the inner wall of the inner tube 2 and the buffer and the quartz support 7. By using this special technique, it is possible to supply the reaction gas almost uniformly onto the surface of the silicon wafer 8 supported by the support 7. In the low pressure CVD method in the low temperature region, Sl
When l+4-02 series gas is used, SIH* and PH
, reacts as the temperature increases to 08°C, and oxidation has already progressed at about l < 300°C. Therefore, unless the reaction chamber is carefully designed, reaction products will form on the inlet and outlet sides of the furnace, as well as on the walls of the reaction chamber. This is because 5iO1 is frequently formed into flakes, and this must be avoided as much as possible so that the reaction can take place effectively only on the wafer surface.

[Problem to be solved by the invention]

If the above-mentioned measures are taken, the uniformity within the thickness of the CVD-degraded film will be very good and the reproducibility will be good. However, there is still a problem with the uniformity of the concentration of phosphorus as an impurity within a batch, and the reality is that it is difficult to control it. In other words, 5il14+(h→510. +2
The reaction of It can occur almost uniformly in the furnace by the above-mentioned measures, and the oxide film (Slow) is deposited uniformly. However, 2PL+40□-PJs +311.
Even with the above-mentioned measures, the 0 reaction cannot be caused uniformly in the furnace with good controllability; for example, the phosphorus concentration (pzos) gradually decreases in waves from the upstream to the bottom. There were problems with controllability.

The object of the present invention is to suppress rapid oxidation by devising the structure of the reaction chamber of the hot wall type low-pressure CVD apparatus for forming a low-temperature oxide film, and to achieve a uniform film thickness within the coating. In addition to forming the film, it is also necessary to make the concentration of impurities such as eborin, which are added into the film, uniform within the batch.

[Means to solve the problem]

In order to achieve the above object, the apparatus of the present invention has a reaction chamber equipped with a heating means on the outside, which consists of a double reaction tube, and a support for a substrate to be formed into a film, a gas flow blocker, and a reaction gas inside the inner tube. A part of the introduction pipe is placed at 111a toward the furnace mouth, the gap between the outer pipe and the inner pipe is a passage for the other part of the reaction gas containing impurities added to the produced film, and the inner pipe It is assumed that a plurality of openings are formed in the wall, the area of which gradually decreases as the distance from the furnace mouth increases, as an inlet for introducing the other portion of the reaction gas.

[Effect]

The partial pressure of the other part of the reaction gas containing impurities that enters the reaction tube from the opening of the inner tube through the passage in the gap of the inner tube of the outer tube and reacts with the reaction gas separately introduced into the reaction tube is equal to that of the opening. Since the area becomes smaller as it goes downstream, it gradually becomes higher, and in order to compensate for the decrease in the partial pressure of the gas containing impurities due to the reaction, the impurity concentration of the produced film becomes uniform within the batch.

〔Example〕

FIG. 1 is a schematic cross-sectional view of the vicinity of a reaction tube of a real wall type low-pressure CVD apparatus for forming a low-temperature oxide film according to an embodiment of the present invention.
Components common to those in FIG. 2 are given the same reference numerals. In this device as well, the upper part of the furnace mouth 4 is placed inside the inner tube 2 of the double quartz reaction tube.
1 and the gas introduced from the lower part 42 of the furnace 1 via the gas nozzle 5 pass through the narrow gap between the inner wall of the inner tube 2 and the quartz buffer 6 and quartz support 7 at high speed. . At this time, the reaction between S I It and Ol occurs uniformly. However, the doping gas, PH, is not introduced from the nozzle 5, and the gap 9 between the inner tube 1 and the outer tube 2 is used as a path for the doping gas, and the doping gas is introduced into the inner tube through an opening along the upstream to downstream direction. This is carried out through a plurality of gas inlet ports 11, 12, 13, and 14 that are opened on the surface of the inner tube at equal intervals so that the area decreases, for example, exponentially.

- As an example, the amount of gas introduced during thin film deposition is S I 1
14 is 550”! / mln+Oz is 130 a7
/ win, lle is 3000 @ 17 sin,
When PH3 is 180 lIl / win,
The pressure inside the inner tube is 1.5a+bar, and the pressure inside the outer tube is 2000.
If the pressure is set to mbar, the inside of the inner tube can be made to have an almost completely negative pressure than the inside of the outer tube, so P]
! The reaction with P I can also occur uniformly within the inner tube.
+, the gas partial pressure becomes uniform in the furnace along with the Sth 14 gas partial pressure. As a result, a PSG film having a phosphorus content of 71IIO1% is obtained on the silicon wafer 8, with the impurity t1 degree, that is, P2O, in the thin film deposited on the silicon wafer 8 being uniform within the batch. Of course, the film thickness is also uniform.

〔Effect of the invention〕

According to the present invention, a gas containing impurities to be added to the produced film is introduced through an opening formed in the inner tube, the area of which decreases as it goes downstream. Since the partial pressure can be made uniform from upstream to downstream, C has a uniform film thickness and impurity concentration within the batch.
VDI# can be formed, for example PSGTf3. as an interlayer insulating film of MO5IC etc. This has the effect of improving the controllability of thin film formation, such as, and improving the yield rate.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the vicinity of the reaction tube in one embodiment of the present invention;
The figure is a sectional view of a reacting part of a conventional device. 1: Outer tube, 2; Inner tube, 31, 32, 33: Heater, 5
: Gas nozzle, 6; Quartz buffer, 7; Quartz support, 8
: Silicon wafer, 11, 12.13.14 : Gas inlet. Pa. Agent) Shibu-L Iwao Yamaguchi,

Claims (1)

[Claims] (1) The reaction chamber is equipped with a heating means on the outside and consists of a double reaction tube, in which the support for the substrate to be formed into a film, the gas flow blocker, and the inlet tube for a portion of the reaction gas are arranged in order toward the furnace mouth. The gap between the outer tube and the inner tube is a passage for other parts of the reaction gas containing impurities that are added to the produced film, and the inner tube wall has a plurality of holes whose area gradually decreases as it moves away from the furnace mouth. Hot wall type reduced pressure CVD characterized in that the opening is opened as an inlet for the other part of the reaction gas.
Device.