Method for processing a substrate - Patent application

Abstract

The invention relates to a method for processing substrates, comprising the steps of processing a first substrate with at least one step carried out in an apparatus for carrying out thermal treatments, the first substrate being a substrate made of a semiconductor material or a piezoelectric material, decontaminating the apparatus for carrying out thermal treatments by thermal treatment of a decontaminated substrate, in particular a silicon substrate, and then processing a second substrate with at least one step carried out in an apparatus for carrying out thermal treatments, the first substrate being a substrate made of a semiconductor material or a piezoelectric material.

Description

[Technical field]

[0001] The present invention relates to a process for treating a substrate, and more particularly to a process for treating a semiconductor substrate and / or a piezoelectric substrate. [Background technology]

[0002] During heat treatment in processes using semiconductor and / or piezoelectric substrates, the diffusion of metallic elements, such as lithium, can result in contamination of the equipment performing the heat treatment, such as an oven. The level of contamination by this element can be determined, for example, by VPD-ICPMS (vapor phase decomposition and inductively coupled plasma mass spectrometry) as the number of atoms per square centimeter. The level of contamination can depend on the number of cycles performed with substrates containing metallic elements, the conditions of the process used and the type of substrate used. A significant increase in the level of contamination is observed, especially when the substrate breaks in the equipment. High levels of contamination in the equipment can reduce the subsequent production yield.

[0003] Contamination problems can also have a negative impact on manufacturers' production lines, since contamination in equipment with certain elements can prohibit carrying out various types of processes on one and the same equipment, greatly reducing manufacturing flexibility and forcing manufacturers to set up several separate manufacturing lines according to the processes and materials used. Summary of the Invention

[0004] The object of the present invention is therefore the introduction of a decontamination process that makes it possible to reduce the level of contamination by metallic elements in equipment carrying out heat treatments.

[0005] The object of the invention is achieved by a process for treating a substrate, comprising at least one step performed in an apparatus for carrying out a thermal treatment, a step of treating a first substrate, the first substrate being a substrate comprising a semiconductor material or a piezoelectric material, followed by a step of reducing the contamination level of the equipment by contaminating metal elements by carrying out a thermal treatment of a decontaminated substrate, in particular a silicon-based substrate, more particularly also a substrate made of monocrystalline or polycrystalline silicon, porous silicon or SiOCH, followed by a step of treating a second substrate, the second substrate being a substrate comprising a semiconductor material or a piezoelectric material, the second substrate being a substrate comprising a semiconductor material or a piezoelectric material, the second substrate being a substrate comprising a piezoelectric material, the second substrate being a substrate comprising a semiconductor material or a piezoelectric material, the second substrate being a substrate comprising a piezoelectric material, the second substrate being a substrate comprising a semiconductor material or a piezoelectric material, the second substrate being a substrate comprising a piezoelectric material, the second substrate being a substrate comprising a semiconductor material or a piezoelectric material, the second substrate being a substrate comprising a piezoelectric material, the second substrate being a substrate comprising a semiconductor material or a piezoelectric material, the second substrate being a substrate comprising a piezoelectric material, the second substrate being a substrate comprising a semiconductor material or a piezoelectric material, the second substrate being a substrate comprising a semiconductor material or a piezoelectric material, the second substrate being a substrate comprising a porous silicon or a semiconductor ...

[0006] According to one embodiment, the decontamination substrate used in the step of reducing the contamination level is a substrate dedicated to the decontamination step and is used only for this decontamination step. Thus, during the step of thermal treatment of the first and second substrates, the decontamination substrate is not present in the equipment performing the thermal treatment. Similarly, during the decontamination step, neither the first nor the second substrate is present in the equipment performing the thermal treatment.

[0007] According to an embodiment, the first and second substrates may be of different materials. According to an embodiment, the first substrate may be a piezoelectric substrate selected from lithium niobate (LiNbO3) and lithium tantalate (LiTaO3), and / or the second substrate may be a semiconductor substrate selected from silicon, silicon carbide (SiC), sapphire (Al2O3) or III-V semiconductor substrates, in particular gallium arsenide (GaAs). The use of a decontaminated substrate thus allows the same equipment to be used to carry out thermal treatments on two different types of substrates. Thus, different types of products, such as silicon-on-insulator (SOI) and piezoelectric-on-insulator (POI) type substrates, may be manufactured using the same equipment.

[0008] According to one embodiment, the contaminating metal element is lithium. The presence of lithium is prohibited in silicon-type processes, and even in processes using lithium niobate (LiNbO3) or lithium tantalate (LiTaO3) substrates alone or in combination with silicon-based substrates, too high a level of lithium can reduce production yields. The process according to the invention is effective in reducing the level of lithium in the equipment.

[0009] According to one embodiment, the process may include a step of determining the contamination level of at least one contaminating component in the equipment performing the thermal treatment before and / or after the decontamination step. Knowledge of the contamination level, for example by performing VPD-ICPMS measurements on the decontaminated substrate, makes it possible to adjust the parameters of the performance of the decontamination step, for example the duration, the temperature and / or the atmosphere applied, or to verify the result of the decontamination step.

[0010] According to one embodiment, a decontamination step can be performed if the contamination level exceeds a predefined contamination threshold. Thus, a decontamination step may be performed only if necessary.

[0011] According to one embodiment, the decontamination step can be carried out at a temperature of at least 500° C., in particular at least 800° C. The decontamination effect is more efficient starting from these temperatures.

[0012] According to one embodiment, the decontamination step can be carried out under an oxidizing atmosphere, in particular by introducing oxygen, the decontamination effect being more effective under an oxidizing atmosphere.

[0013] According to one embodiment, the decontamination step may be carried out for a predetermined period of time, in particular for at least 30 minutes, more particularly for at least 1 hour. These periods allow for a much more effective decontamination.

[0014] According to one embodiment, the decontamination step can be repeated at least once before continuing with the step of processing a second substrate, in particular a new decontamination substrate is used in each repetition. By repeating the step with a new decontamination substrate, the effectiveness of the decontamination can be increased.

[0015] According to one embodiment, the decontaminated substrate can be discarded after the thermal treatment, thus reducing the risk of re-contamination of the equipment.

[0016] The object of the present invention is also achieved by using a silicon substrate as the decontamination substrate in the above-mentioned process. All the advantages of the above-mentioned process can be obtained by using a silicon substrate.

[0017] The invention and its advantages will be explained in more detail subsequently by means of advantageous exemplary embodiments, particularly with the aid of the accompanying drawings in which reference numerals identify the features of the invention, in which: [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 diagrammatically illustrates a process for processing a substrate according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention will now be described in more detail using advantageous embodiments, in an exemplary manner and with reference to the drawings. It should be noted that the described embodiments are merely possible configurations, and that individual features as mentioned above can be provided independently of one another or can be omitted entirely during the implementation of the present invention.

[0020] FIG. 1 diagrammatically illustrates a process for treating a substrate according to one embodiment.

[0021] During step S1, a thermal treatment is performed in an apparatus for performing thermal treatments on a first substrate, the first substrate being a substrate comprising a semiconductor material or a piezoelectric material.

[0022] According to the process of the first embodiment, the first substrate is a piezoelectric substrate selected from lithium niobate (LiNbO3) and lithium tantalate (LiTaO3). The equipment can be, for example, an oven for heating one or more substrates, or a deposition reactor, for example a chemical vapor deposition (CVD) reactor.

[0023] The heat treatment may be an annealing treatment, a heat treatment required during layer deposition, a disruption treatment during the transfer process of a layer onto a support substrate for producing a POI substrate, such as the process known under the name SmartCut®, or any treatment requiring a temperature higher than ambient, i.e. about 20° C. to 25° C. Treatments at temperatures above 500° C. are particularly relevant.

[0024] It is known that contamination of thermal equipment with lithium atoms can occur following the phenomenon of diffusion during such thermal treatments. The level of contamination in the equipment depends on the number of cycles carried out with the first substrate, the conditions of the process used and the type of first substrate used. If the substrate is accidentally or intentionally broken in the equipment, for example during the crushing stage, a significant increase in contamination is observed.

[0025] According to the invention, a decontamination step S2 is subsequently carried out in order to reduce the contamination level of the equipment in which the thermal treatment is carried out. In order to reduce the presence of lithium in the equipment, a decontamination substrate is introduced into the equipment. In a first embodiment, a silicon substrate is used. This is a silicon wafer, with or without its native oxide. The silicon substrate is introduced at a temperature of about 350° C. and is then heated to at least 500° C., preferably at least 800° C. This temperature is maintained for at least 30 minutes, preferably at least 1 hour. This decontamination step is carried out under an oxidizing atmosphere, in particular by introducing oxygen into the equipment.

[0026] The decontaminated substrate is then discarded to prevent new contamination during reintroduction into the instrument.

[0027] VPD-ICPMS measurements were applied to new silicon substrates introduced into the instrument after step S2 and similarly heated to at least 500° C., preferably at least 800° C., for at least 30 minutes, preferably at least 1 hour, under an oxidizing atmosphere. These measurements showed a reduction in the surface density of lithium compared to the same measurements on the silicon substrates used during step S2. The VPD-ICPMS measurements work as follows: before the ICPMS analysis, the surface is wiped with 150 μl of HF / HNO3 solution, followed by dilution of this solution with 250 μl of HF / HNO3 solution, after which the native oxide layer is decomposed by etching, in particular by the use of HF in the gas phase.

[0028] After the decontamination step S2, the process continues with step S3, which is a process for treating a second substrate. The second substrate may be a substrate comprising a semiconductor material or a piezoelectric material. The second substrate may be of the same material as the first substrate or of a different material.

[0029] If the same materials are used, the processing of the second substrate can be the same as the first substrate.

[0030] If another material is used, it may be, by way of example, a semiconductor substrate selected from silicon, silicon carbide (SiC), sapphire (Al2O3) or a III-V semiconductor substrate, in particular gallium arsenide (GaAs).

[0031] The treatment of the second substrate comprises at least one step, which is also carried out in equipment that carries out thermal treatments. Given that the equipment has been previously decontaminated, typically for lithium, the quality of the treatment of the second substrate is not or is less affected by contaminants. This makes it possible to obtain an increase in yield compared to a process without a decontamination step. With respect to the first substrate, the thermal treatment can be an annealing treatment, a thermal treatment required during layer deposition, a spallation treatment during the transfer process of a layer onto a support substrate for producing an SOI substrate, such as the process known for example under the name SmartCut®, or any other treatment requiring a temperature higher than ambient, i.e. of about 20 ° C to 25 ° C. Treatments at temperatures above 500 ° C are particularly relevant.

[0032] The decontaminated substrate used in the stage S2 of reducing the contamination level is a substrate dedicated to the decontamination stage and is used only for this decontamination stage. Thus, during the stages S1 and S2 of the thermal treatment of the first and second substrates, the decontaminated substrate is not present in the equipment performing the thermal treatment. Similarly, during the decontamination stage S2, neither the first nor the second substrate is present in the equipment performing the thermal treatment.

[0033] According to an alternative embodiment of the process according to the invention, before continuing with step S3, the decontamination step S2 is repeated at least once, using a new decontamination substrate in each repetition. Thus, the level of decontamination of the equipment can be further improved, since in each repetition of step S2 contaminating elements are captured on the decontamination substrate. This makes it possible to reduce the contamination level below the detection limit of the VPD-ICPMS measurement device. According to another alternative, the contamination measured by VPD-ICPMS is reduced below a predefined contamination threshold, for example 1×10 13 at / cm 2If so, process S2 is repeated. Instead of using VPD-ICPMS, it is also possible to measure the contamination by secondary ion mass spectrometry (also called "SIMS"). The process according to the invention makes it possible to reduce the contamination of thermal processing equipment, such as an oven, in an effective and simple manner to carry out using silicon substrates. Depending on the level of decontamination desired, the process can be repeated before continuing to use the equipment in a subsequent manufacturing process.

Claims

1. A method for processing a first substrate, the method comprising at least one step carried out in a thermal processing apparatus, the first substrate being a substrate comprising a semiconductor material or a piezoelectric material, and thereafter carrying out a thermal treatment of a decontaminated substrate, in particular a silicon-based substrate, more particularly a substrate made of monocrystalline or polycrystalline silicon, porous silicon or SiOCH, thereby reducing the contamination level of said equipment carrying out the thermal treatment by contaminating metal elements, and then processing a second substrate, the second substrate being a substrate comprising a semiconductor material or a piezoelectric material, the second substrate comprising at least one step performed in the thermal processing apparatus; A process for treating a substrate comprising:

2. The process for treating a substrate according to claim 1 , wherein the first substrate and the second substrate are of different materials.

3. The first substrate is made of lithium niobate (LiNbO ３ ) and lithium tantalate (LiTaO ３ ), and / or the second substrate is a piezoelectric substrate selected from silicon, silicon carbide (SiC), sapphire (Al ２ O ３ 3. The process for treating a substrate according to claim 2, which is a semiconductor substrate selected from the group consisting of gallium arsenide (GaAs) or III-V semiconductor substrates, in particular gallium arsenide (GaAs).

4. The process for treating a substrate according to any one of claims 1 to 3, wherein said contaminating metal element is lithium.

5. 5. The process for processing a substrate according to any one of claims 1 to 4, comprising a step of determining the contamination level of at least one contaminating component in the equipment performing the thermal treatment before and / or after the decontamination step.

6. The process for processing a substrate according to claim 5 , wherein the decontamination step is performed if the contamination level exceeds a predetermined contamination threshold.

7. Process for treating a substrate according to any one of the preceding claims, wherein the decontamination step is carried out at a temperature of at least 500°C, in particular at least 800°C.

8. Process for treating a substrate according to any one of claims 1 to 7, wherein the decontamination step is carried out under an oxidizing atmosphere, in particular by introducing oxygen.

9. Process for treating a substrate according to any one of the preceding claims, wherein the decontamination step is carried out for a predetermined period of time, in particular for at least 30 minutes, more particularly for at least 1 hour.

10. 10. The process for processing a substrate according to any one of claims 1 to 9, wherein the decontamination step is repeated at least once before continuing with the step of processing the second substrate, in particular a new decontaminated substrate is used in each repetition.

11. The process for treating a substrate according to any one of claims 1 to 10, wherein the decontaminated substrate is discarded after the thermal treatment.

12. Use of a silicon substrate as a decontamination substrate in the process according to any one of claims 1 to 11.

Images