Method for producing semiconductor wafers with epitaxial layer in a chamber of a deposition reactor

Abstract

A method of producing epitaxial layer wafers in a chamber of a deposition reactor of a system, comprising: repeatedly depositing an epitaxial layer onto a substrate wafer in the chamber of the deposition reactor, thereby forming a first number of epitaxial layer wafers; and, at the same time, preparing a replacement chamber of the deposition reactor outside of the system by flushing the replacement chamber with a flushing gas; interrupting the repeated deposition of an epitaxial layer on a substrate wafer; replacing the chamber by the replacement chamber; and continuing the repeated deposition of an epitaxial layer onto a substrate wafer in the replacement chamber of the deposition reactor, thereby producing a second number of epitaxial layer wafers.

Description

[0001] Method for producing semiconductor wafers with epitaxial layer in a chamber of a deposition reactor

[0002] The invention relates to a method for producing semiconductor wafers with an epitaxial layer in a chamber of a deposition reactor by means of vapor deposition. Such a method is typically interrupted from time to time to maintain the chamber, in particular to remove material that has deposited on the chamber's inner walls. After this time, the chamber is in a state that does not yet allow for the coating of semiconductor wafers that meet expectations, particularly with regard to the required lifetime of minority charge carriers in the epitaxial layer. Therefore, conditioning of the chamber is necessary, which limits the productivity of the process.

[0003] State of the art / problems

[0004] US 20080219824 A1 describes a typical system with which a method for producing semiconductor wafers with an epitaxial layer can be carried out by means of vapor deposition. Such a system generally comprises several deposition reactors, a load lock chamber, and a transfer chamber. A deposition reactor comprises, in particular, an upper dorne, a lower dorne, a base ring, and an upper and lower liner, which jointly belong to a chamber in which the vapor deposition takes place. The chamber contains, in particular, a susceptor support shaft with support arms, a wafer lift shaft, and a susceptor. The susceptor support shaft and the wafer lift shaft are connected to a rotation-lift unit.Lamp modules and reflectors are arranged above the upper cover and below the lower cover to provide radiant energy in the chamber during vapor deposition. DE 11 2016003399 T5 proposes purging the chamber of a deposition reactor with nitrogen for conditioning purposes, heating the interior of the chamber, and measuring the lifetime of minority charge carriers on test wafers to determine whether production of semiconductor wafers with epitaxial layers can continue.

[0005] Such conditioning of the chamber considerably limits the productivity of the production of semiconductor wafers with epitaxial layers.

[0006] The object of the present invention is to reduce such a limitation and to propose a particularly effective conditioning.

[0007] The object of the invention is achieved by a method for producing semiconductor wafers with an epitaxial layer in a chamber of a deposition reactor of a plant, comprising the repeated deposition of an epitaxial layer on a substrate wafer in the chamber of the deposition reactor, whereby a first number of semiconductor wafers with an epitaxial layer is produced, and during this time the conditioning of a replacement chamber of the deposition reactor outside the plant by purging the replacement chamber with a purge gas; the interruption of the repeated deposition of an epitaxial layer on a substrate wafer; the replacement of the chamber with the replacement chamber; and the continuation of the repeated deposition of an epitaxial layer on a substrate wafer in the replacement chamber of the deposition reactor, whereby a second number of semiconductor wafers with an epitaxial layer is produced.

[0008] The time of reduced productivity due to conditioning the chamber is significantly reduced when using the method according to the invention and is due in particular to the time required to replace the chamber with the replacement chamber. After replacement, the chamber replaced by the replacement chamber itself becomes a replacement chamber that can be conditioned outside the plant. The plant comprises a deposition reactor, preferably at least one additional deposition reactor.

[0009] A replacement chamber preferably comprises an upper cover, a lower cover, a base ring, upper and lower clamp rings, a susceptor support shaft with support arms, a disk lift shaft, a susceptor, a lower lamp module with lower reflectors, and a rotation-lift unit for the shafts. These components are assembled during conditioning of the replacement chamber in the same manner as during vapor deposition.

[0010] An upper lamp module with upper reflectors can also optionally be part of the replacement chamber.

[0011] Conditioning the replacement chamber is performed outside the system at a conditioning station and includes purging the replacement chamber with a purge gas and preferably one or two additional measures. The purge gas is passed through the replacement chamber from at least one gas inlet to at least one gas outlet. The water content of the purge gas is preferably less than 100 ppm, particularly preferably less than 50 ppm, when the purge gas enters the replacement chamber. Furthermore, the purge gas is preferably free of particles, in particular free of metallic particles.

[0012] The purge gas is nitrogen, hydrogen, helium, argon, or a mixture of at least two of the above-mentioned gases. Nitrogen is the preferred purge gas. When purging the backup chamber, care should be taken to ensure that there are no dead spots inside the backup chamber where the flow velocity of the purge gas decreases to the point of disappearance.

[0013] Further measures include increasing the temperature inside the replacement chamber compared to the temperature of the replacement chamber's surroundings, for example by means of IR radiation, heat mats or heat exchangers or a combination thereof. The temperature at points on the replacement chamber components that come into contact with the interior of the replacement chamber is preferably more than 21 °C, more preferably more than 65 °C. The upper temperature limit is fundamentally only determined by the temperature resistance of the material being heated. Further measures also include changing the pressure inside the replacement chamber during conditioning, whereby the pressure change can be carried out in two different ways: either by lowering the pressure inside the replacement chamber compared to the pressure at the conditioning level or by increasing the pressure inside the replacement chamber compared to the pressure at the conditioning level.To reduce the pressure, valves and / or a vacuum pump can be used at the gas outlet of the replacement chamber.

[0014] In addition, a combination of the two types of pressure changes can also be carried out, for example by first increasing the pressure of the purge gas in the interior of the replacement chamber and then reducing it below the pressure at the conditioning stand by sucking off the purge gas at the gas outlet.

[0015] Conditioning of the backup chamber is carried out for a specified duration, or preferably until the water content in the purge gas upon leaving the backup chamber reaches or falls below a specified threshold. For this purpose, the humidity in the purge gas can be measured, for example, at the gas outlet of the backup chamber.

[0016] After conditioning, the replacement chamber can be sealed to prevent ambient atmosphere from entering the chamber during transport to the facility. The pressure difference between the pressure inside and the pressure outside the sealed replacement chamber should be as small as possible during transport of the replacement chamber to the facility to prevent possible implosion of the replacement chamber. Replacement of the chamber with the conditioned replacement chamber should then be carried out under a dry purge gas atmosphere to prevent moisture from entering the replacement chamber during chamber swapping.

[0017] Transport to the system and replacement of the chamber can alternatively also be carried out while continuously purging the replacement chamber with dry purge gas, so that there is no pressure difference between the interior and the environment. A flow rate of 3 Nl / min to 8 Nl / min is recommended in this case. The semiconductor wafers produced according to the invention are preferably made of silicon or comprise silicon substrate wafers with at least one epitaxial layer of silicon germanium or with at least one epitaxial layer of gallium nitride. The diameter of the semiconductor wafers is preferably at least 200 mm, particularly preferably 300 mm.

[0018] The invention is further explained below with reference to drawings.

[0019] Brief description of the figures Fig. 1 shows a flow chart for the conditioning of a replacement chamber on a conditioning stand according to an embodiment of the invention.

[0020] Fig. 2 shows the result of a comparison of lifetime measurements on semiconductor wafers with epitaxial layers. List of reference symbols used

[0021] 1 spare chamber

[0022] 2 lamp modules

[0023] 3 Rotation-lift unit 4 Gas supply

[0024] 5 Valve

[0025] 6 Pump

[0026] 7 Heating

[0027] 8 Measuring equipment

[0028] Detailed description of embodiments according to the invention

[0029] The replacement chamber 1 comprises an upper cover, a lower

[0030] Cover, a base ring, an upper and a lower clamping ring, a susceptor support shaft with support arms, a disk lifting shaft, and a susceptor. Other components include a lower lamp module 2 with lower reflectors and a rotation-lifting unit 3 for the shafts. Dry purge gas is passed through the replacement chamber 1 by means of a gas supply 4, with the amount of gas flow being adjusted by valves 5 at the gas inlet and the output of a pump 6 at the gas outlet. Furthermore, the flow plan calls for increasing the temperature inside the replacement chamber 1 by means of a heater 7 and determining the humidity of the purge gas after it leaves the replacement chamber 1 using a measuring device 8.

[0031] An epitaxial layer of silicon was deposited on substrate wafers made of single-crystal silicon. After a first number of semiconductor wafers with an epitaxial layer had been produced, in the case of a comparative example, the chamber in the deposition reactor was replaced with another chamber, and the other chamber in the deposition reactor was conditioned by purging with purge gas; in the case of an example, a replacement chamber was conditioned according to the present invention. A second number of semiconductor wafers with an epitaxial layer were then produced, the semiconductor wafers according to the comparative example in the other chamber, and the semiconductor wafers according to the example in the replacement chamber. Subsequently, lifetime measurements of minority charge carriers were carried out on the semiconductor wafers that had been produced after conditioning using m-PCD (microwave photoconductivity decay, au = arbitrary units).

[0032] Fig. 2 shows the measurement results for a number N of semiconductor wafers according to the comparative example (dashed curve) and according to the example (solid curve). The lifetime values ​​for the semiconductor wafers produced according to the invention were higher from the beginning and immediately showed an increasing trend.

[0033] The foregoing description of exemplary embodiments is intended to be exemplary. The disclosure provided herein will enable those skilled in the art to understand the present invention and the associated advantages, and will also encompass variations and modifications of the described structures and methods that are obvious to those skilled in the art. Therefore, all such variations and modifications, as well as equivalents, are intended to be covered by the scope of the claims.

Claims

Patent claims 1. A method for producing semiconductor wafers with an epitaxial layer in a chamber of a deposition reactor of a system, comprising repeatedly depositing an epitaxial layer onto a substrate wafer in the chamber of the deposition reactor, producing a first number of semiconductor wafers with an epitaxial layer, and during this process conditioning a replacement chamber of the deposition reactor outside the system by purging the replacement chamber with a purge gas; interrupting the repeated deposition of an epitaxial layer onto a substrate wafer; replacing the chamber with the replacement chamber; and resuming the repeated deposition of an epitaxial layer onto a substrate wafer in the replacement chamber of the deposition reactor, producing a second number of semiconductor wafers with an epitaxial layer.

2. Method according to claim 1, characterized in that the purge gas is passed through the replacement chamber, and the proportion of water in the purge gas upon entry into the replacement chamber is less than 50 ppm.

3. Method according to claim 1 or claim 2, characterized in that nitrogen, hydrogen, helium, argon or a mixture of at least two of the aforementioned gases is used as the purge gas.

4. Method according to one of claims 1 to 3, characterized in that during the conditioning of the replacement chamber the temperature inside the replacement chamber is increased compared to the temperature of the environment of the replacement chamber.

5. Method according to one of claims 1 to 4, characterized in that during the conditioning of the replacement chamber the pressure inside the replacement chamber is changed at least once in comparison to the pressure in the environment of the replacement chamber.

6. Method according to one of claims 1 to 5, characterized in that the moisture content of the purge gas is measured after it leaves the replacement chamber and the conditioning of the replacement chamber is continued as long as the moisture content has not yet reached or fallen below a predetermined threshold.

7. A method according to any one of claims 1 to 6, characterized in that the replacement chamber is sealed after conditioning and transported to the system in a closed state.

8. A method according to any one of claims 1 to 6, characterized in that the replacement chamber is transported to the system after conditioning and purge gas is passed through the replacement chamber.

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