Process for operating a gas inlet device for reactors

Technical area

p0001The invention relates to a method for operating a gas inlet device for reaction vessels, in particular for the III-V semiconductor production according to the preamble of claim 1.

p0002In the case of reaction vessels, which are particularly suitable for III-V semiconductor manufacture, there is generally the problem of successively introducing a series of reaction gases as well as a carrier gas or protective gas into the reaction vessel. In doing so, the reaction gases should be introduced not only at certain pressures, but also in a precisely defined chronological sequence with "sharp" concentration transitions.

State of the art

p0003In the past, gas inlet devices, which have a shut-off valve as well as, if appropriate, metering devices, have been used for each reaction or carrier gas. In this connection, valves have been considered, for example, as described in "PATENTS ABSTRACT OF JAPAN" M-201, Vol. 7, 1983 or US Pat. No. 3,556,147.

p0004However, it has been found that it is not suitable with gas inlet devices in which known valve types, for example, the four-way valves described in "PATENTS ABSTRACT OF JAPAN" or in US Pat. No. 3,506,147 are used with two independent valve pistons It is possible to introduce the reaction gases into the reaction vessel successively in rapid succession without causing any residual gas contamination. In particular, the switching delays occurring in the known gas inlet devices interfere due to the inevitable dead volumes and / or of simultaneously closed lines. In addition, pressure fluctuations in the reaction system, which can be interfering with the process, can occur by switching on or off various gas flows.

p0005Furthermore, with the known valve devices, it is only possible with great difficulty to achieve the leak rates of less than 10⁻⁸ mbar * 1 / sec required for the III-V semiconductor production.

DESCRIPTION OF THE INVENTION

p0006The invention is based on the object of specifying a method for operating a gas inlet device for reaction vessels, in particular for the III-V semiconductor production, in which the switching delays are minimal due to the switching over of different reaction gas streams and practically no pressure fluctuations occur during switching .

p0007A solution according to the invention of this object is characterized in its patent claims.

p0008In the method according to the invention, a valve device is used, which for each reaction gas has a multi-way valve which has a through-passage continuously through which the carrier gas flows. Depending on the switching position of the valve, the reaction gas inlet is connected to the through-passage channel through which the carrier gas flows and thus to the reaction gas inlet of the reaction vessel or to a second outlet connection so that no reaction gas flowing into this reaction can enter the reaction vessel. The method according to the invention has a number of advantages: Since the reaction gas stream is not switched on or off, but merely switched between the passage channel and the second output connection, practically no pressure fluctuations occur. Furthermore, the switching delays due to dead volumes, etc., are negligible in practice, since all the reaction gas inlets are connected to the channel, which is continuously traversed by the carrier gas, in the operating state in which this reaction gas is to flow into the reaction space.

p0009Advantageous further developments of the invention are characterized in the subclaims: The design characterized in claim 2 with a common exhaust passage, to which the second outlets of the individual multi-way valves are connected, is particularly advantageous when the exhaust gases contain toxic constituents and / or components which are to be recovered from the exhaust gas.

p0010As multi-way valves, for example, 4-way valves (claim 3) or 5-way valves (claim 6) can be used.

p0011A particularly simple embodiment of a four-way valve used in the method according to the invention for operating a gas inlet device for reaction vessels is described in claim 4. The 4-way valve consists of two individually operated shut-off valves, one of which is normally closed and the other normally open. The normally-closed shut-off valve is arranged in the connection between the passage channel and the reaction-gas inlet port while the normally-open shut-off valve is arranged in the connection between the reaction-gas inlet port and the second outlet port via which the reaction gas flows off, Reaction space.

p0012As a result of the arrangement of the inlet and outlet connections as well as the shut-off valves, the shortest possible connections between the individual connections and the valves are obtained with 4-way valves so that any remaining dead volumes are further reduced.

p0013The use of 5-way valves as multi-way valves has the advantage that the valve block can additionally have an exhaust gas passage channel through which not only the line effort for connecting the individual valves but also the volume of the exhaust line is further reduced .

p0014The use of bellows-sealed shut-off valves according to claim 7 makes it possible in a simple manner to realize the leakage rate of less than 10⁻⁸ mbar * l / sec, which is required in particular for the III-V semiconductor production.

p0015It is of particular advantage in any case if, according to claim 8, the valves can be actuated electrically or pneumatically. Such an electrical or pneumatic actuation makes it possible to provide a control unit for the gas inlet device according to the invention. This control unit can switch the individual multi-way valves according to the desired inlet program for the different reaction gases. In addition, the control unit can also control the individual reaction gas streams to predetermined stationary values, for example with a corresponding throttle or throttle valve. Adjust the proportional valve.

p0016An advantageous embodiment of a 4-way valve designed according to the invention is specified in claim 9. By modifying a commercially available 3-way valve, it is possible to manufacture the 4-way valves according to the invention at low cost. For example, the 4-way valves according to the invention can be produced by modification of a commercially available ASM 3-way valve.

p0017The dead volumes, control times and gas consumption can be further reduced if the inlets and outlets of the valves have connections which allow direct connection of the individual valves of the gas inlet device as well as of the reaction vessel. Such connections are, for example, VCR-male and VCR-FEMALE screw connections. For example, the inlet for the carrier gas stream is provided with a VCR-MALE connector, while the outlet is provided with a VCR-FEMALE connector (claim 10).

p0018In particular in the case of expensive reaction gases, the use of the control unit according to the invention (claim 11) makes it possible for the control unit to switch the steady-state reaction gas stream to a predeterminable temperature range only briefly before the time at which the reaction gas stream is to be introduced into the reaction vessel Steady-state value so as not to allow "unnecessary" expensive reaction gas to flow out through the second output terminal.

p0019A further advantage of the method according to the invention for operating a gas inlet device for reaction vessels is that both shut-off valves can be closed for leakage. The leak test can also be automated by the control unit which, for leakage, closes both shut-off valves and measures the leak rate.

BRIEF DESCRIPTION OF THE DRAWING

p0020BRIEF DESCRIPTION OF THE DRAWINGS The invention is described in more detail below with the aid of an exemplary embodiment, with reference to the drawing, in which: FIG.<dl id="dl0001"><dt>FIG</dt><dd>Schematically a gas inlet device used in the method according to the invention,</dd><dt>2a and 2b</dt><dd>The structure of a 4-way valve provided with a through-channel,</dd><dt>Figures 3a, 3b and 3c</dt><dd>The construction of a 5-way valve provided with a plurality of through-passages.</dd></dl>

DESCRIPTION OF EXEMPLARY EMBODIMENTS

p0021FIG. 1 shows schematically a gas inlet device for reaction vessels used in the method according to the invention, in particular for the III-V semiconductor production. The gas inlet device according to the invention has a series of 4-way valves 1₁, 1₂, to 1 nur, shown only schematically. The 4-way valves 1, the construction of which will be explained in more detail in conjunction with FIGS. 2a and 2b, have in each case 4 connections 2, 3, 4 and 5. Connections 3 and 5 are thereby continuously connected by a passage channel 6, The connection 2 is connected, depending on the switching position of the valve, either to the through-passage channel 6 or the connection 4.

p0022The individual valves 1₁ to 1₇ are interconnected in such a way that a line 7 for a carrier gas stream is connected to the connection 3 of the valve 1₁ while the connections 5 are each connected to the connection 3 of the next valve. The port 5 of the valve 1₇ is connected to the reaction vessel via a line 8. This creates a continuous channel for the carrier gas stream. The connections 2 of the various valves are connected to supply vessels for the individual reaction gases, while the connections 4 are connected to a common exhaust air channel 9. The exhaust air duct 9 is continuously purged by means of an exhaust air purge line 10. Metering or proportional adjusting valves (not shown) can also be provided with which the individual reaction gas streams can be adjusted.

p0023The gas inlet device explained in connection with FIG. 1 makes it possible to admix the individual reaction gases to the carrier gas stream constantly flowing into the reactor via the line 7, the individual through-passages 6 and the line 8, depending on the switched position of the individual valves 1 1 to 1.

p0024Since the reaction gas streams are simply switched over by the valves 1, there are no pressure fluctuations when the reaction gases are switched on or off. Furthermore, the dead volume of the gas inlet device according to the invention is, on the one hand, extremely small as a result of the construction of the individual valves explained in more detail in connection with FIGS. 2 a and 2 b as well as by the constant carrier gas purge of the channels so that fast switching times for the individual reaction gases can be achieved . The rise and fall times of the individual reaction gas admixtures can be in the range well below one second.

p0025FIG. 2a shows a cross-section through a 4-way valve according to the invention, FIG. 2b shows a cross section through the valve at line II-II in FIG. 2a.

p0026As already described in connection with FIG. 1, the valve, which is designated overall by 1, has four connections 2, 3, 4 and 5. The four connections 2-5 are arranged in a star shape. The connection 2 is connected via a channel 11 to a channel 12 whose two ends open into cavities 13 and 14 in which the valve tappets 15 and 16 of the bellows valves 17 and 18 are arranged. The valve tappets 15 and 16 in each case seal the ends of the channel 12. The terminal 4 is connected to the cavity 14 via a channel 19, while the terminals 3 and 5 are connected to the cavity 13 via channels 20 and 21.

p0027Furthermore, in the exemplary embodiments shown, the valves are pneumatically actuated, the valve 17 being normally opened and the valve 18 normally being closed. The pneumatic actuating device of the valves is known so that it will not be explained in more detail in the following.

p0028As already described in connection with FIG. 1, the connection 2 is connected to a reaction gas container and the connection 3 is connected to a line or to the connection 5 of the upstream valve through which a carrier gas stream flows. In this case, the carrier gas stream can flow through the connector 3, the channel 20, the cavity 13, the channel 21 and the connector 5 independently of the switching position of the tappets 15 and 16 through the 4-way valve. The reaction gas stream entering the valve through the port 2 flows in the non-actuated state through the channel 11, the channel 12, the cavity 14, the channel 19 to the port 4 and thus into the exhaust air channel 9. In the actuated state, In which the plunger 16 closes the channel 12 and the plunger 15 is retracted, the reaction gas flow flows via the channel 11 and the channel 12 into the cavity 13 and thus via the channel 21 to the outlet connection 5.

p0029FIG. 3a shows a longitudinal section through a 5-way valve according to the invention; FIG. 3b shows a cross section along the line III-III in FIG. 3a and FIG. 3c shows the connection of the individual valves 1 1, 1 2,... In a gas inlet device according to the invention as shown in FIG.

p0030Parts which correspond to parts in FIGS. 1 and 2 and / or perform a similar function are provided with the same reference numerals so that a detailed description can be dispensed with.

p0031The 5-way valve has five connections 2, 3, 4, 4 'and 5. The connections 3 and 5 are directly connected by a passage channel 6 in the valve block 1 'for the carrier gas and the connections 4 and 4' through a passage channel 9 'for the exhaust gas.

p0032When the bellows valve 17 is closed and the bellows valve 18 is opened, the reaction gas flows from the connection 2 via the channel 12 'and a bore 16 in the valve tappet 16 into the through-channel 6; When the valve 18 is closed and the valve 17 is open, the reaction gas flows from the inlet 2 into the exhaust gas passage 9 '.

p0033This valve has the advantage that the passage channel 6 for the carrier gas as well as the channel 9 for the exhaust gas is formed by simple connection of the same valves 1. This arrangement reduces dead volumes as well as the structural complexity to a minimum.

p0034DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The multi-way valves illustrated in FIGS. 2 and 3 with a passage channel for the carrier gas in combination with the gas inlet device according to the invention have a number of advantages in common: The valves according to the invention practically have no dead spaces, so that the switching times between the individual gas streams are very short.

p0035The individual reaction gas streams are not switched on or off, but merely switched between the outlet 4 and the outlet 5, so that no pressure fluctuations occur.

p0036Furthermore, the connections 5 and 3 as well as, if appropriate, the connections 4 and 4 'lying in one plane can be directly connected to one another by successive valves when they are provided with suitable screw connections, for example simple tube screw connections or advantageously VCR-MALE screw connections And VCR-FEMALE screw connections. If, for example, the connection 3 is implemented as a VCR-MALE connection and the connection 5 is a VCR-FEMALE connection, particularly short conduction paths result which further reduce the switching times when switching between the individual reaction gas streams.

p0037Furthermore, both valve tappets 15 and 16 can be closed, so that the system can be leak tested without difficulty.

p0038The invention has been described above with reference to exemplary embodiments. Within the scope of the general idea of ​​the invention - to use a gas inlet device consisting of multi-way valves with at least one passage channel for the carrier gas - the most diverse modifications are possible: The design of the multi-way valve is, of course, not limited to the embodiments shown in FIGS. 2 or 3, even if these have various advantages. For example, the valve according to FIG. 2 has the advantage that it can be easily realized by modifying a commercially available 3-way valve. For this purpose, only the 3-way valve is provided with an additional connection, namely the connection 5 as well as with the channel 21, which produces the continuous passage for the carrier gas.

p0039The valve according to FIG. 3 has the advantage that it is of compact construction and permits a simple construction of the device according to the invention.

p0040It is also possible to use manually operated or electrically actuatable valves. Electrically or pneumatically operable valves, however, have the advantage that the gas inlet device can be controlled by means of a control, so that the individual reaction gas streams can be directed into the reaction vessel at precisely defined times.