JP2011040469A - Method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of determining an etching finish time when a desired etching amount is obtained, based on an etching speed. <P>SOLUTION: Nitrogen compound layers 12-26 are formed on an SiC semiconductor substrate 10 (substrate). Then, the nitrogen compound layers 16-26 are etched. Here, the nitrogen compound layers 12-26 are arranged with an equal interval, and include a plurality of marker layers 16, 20, 24 containing nitrogen isotope 15N. The etching speed is found by detecting a peak of nitrogen isotope 15N content in an etching atmosphere, when etching the nitrogen compound layers 16-26. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device that etches a nitrogen compound layer containing nitrogen as a constituent atom, and more particularly to a method for manufacturing a semiconductor device that can obtain a desired etching amount without interrupting etching.

  In the etching of the sample, it was difficult to determine the etching end time, and the processing as designed could not be performed. Therefore, when etching the sample, the etching was interrupted halfway and the etching amount was measured. For this reason, there existed a problem that an etching process became complicated and became long.

  In contrast, there is a method in which a marker layer having a different isotope ratio of constituent atoms is provided at a predetermined depth of a sample, and etching is terminated when a peak of the isotope content corresponding to the marker layer is detected in an etching atmosphere. It has been proposed (for example, see Patent Document 1).

JP 2000-182968 A

  However, in the conventional method, the etching amount of the sample cannot be detected during the etching. Therefore, a desired etching amount other than the predetermined depth cannot be obtained.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a semiconductor device manufacturing method capable of obtaining a desired etching amount without interrupting etching.

  The present invention comprises a step of forming a nitrogen compound layer on a substrate and a step of etching the nitrogen compound layer, wherein the nitrogen compound layer is arranged at equal intervals and includes a plurality of marker layers containing nitrogen isotopes N15 When the nitrogen compound layer is etched, the etching rate is obtained by detecting the peak of the nitrogen isotope N15 content in the etching atmosphere, and a desired etching amount is obtained based on the etching rate. A method of manufacturing a semiconductor device, comprising: determining an etching end time.

  According to the present invention, a desired etching amount can be obtained without interrupting etching.

8 is a cross-sectional view for illustrating the method for manufacturing the semiconductor device according to the first embodiment. FIG. 8 is a cross-sectional view for illustrating the method for manufacturing the semiconductor device according to the first embodiment. FIG. 8 is a cross-sectional view for illustrating the method for manufacturing the semiconductor device according to the first embodiment. FIG. It is a figure which shows the mode of dry etching. FIG. 3 is a diagram of measuring the content of nitrogen isotope N15 in an etching atmosphere in the first embodiment. 8 is a cross-sectional view for illustrating the method for manufacturing the semiconductor device according to the first embodiment. FIG. FIG. 10 is a cross-sectional view for illustrating the method for manufacturing the semiconductor device according to the second embodiment. FIG. 6 is a diagram showing a measurement of the content of nitrogen isotope N15 in an etching atmosphere in the second embodiment. FIG. 10 is a cross-sectional view for illustrating the method for manufacturing the semiconductor device according to the third embodiment. FIG. 10 is a diagram showing the content of nitrogen isotope N15 in the etching atmosphere in the third embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same number is attached | subjected to the same component and description is abbreviate | omitted.

Embodiment 1 FIG.
First, as shown in FIG. 1, on a SiC semiconductor substrate 10 (substrate), a GaN buffer layer 12, a GaN active layer 14, GaN layers 16, 18, 20, 22, 24, and a GaN contact layer 26 (nitrogen compound layer). Are sequentially formed by epitaxial growth. Here, the GaN layers 16, 20, and 24 are marker layers that are arranged at equal intervals and include nitrogen isotope N15 in a part of nitrogen. Other GaN layers do not contain the nitrogen isotope N15.

  Next, as shown in FIG. 2, a photoresist 28 patterned by photolithography or the like is formed on the GaN contact layer 26. Then, as shown in FIG. 3, the GaN layers 16, 18, 20, 22, 24 and the GaN contact layer 26 are dry-etched using the photoresist 28 as a mask to form the groove 30.

FIG. 4 is a diagram showing a state of dry etching. A semiconductor wafer 34 to be processed is placed in the vacuum chamber 32. This semiconductor wafer 34 is etched by Cl ₂ plasma 36. The nitrogen isotope N15 is released when the GaN layers 16, 20, 24 are etched. Therefore, the mass analyzer 38 connected to the vacuum chamber 32 detects the content of the nitrogen isotope N15 in the etching atmosphere.

  FIG. 5 is a diagram in which the content of nitrogen isotope N15 in the etching atmosphere is measured in the first embodiment. The horizontal axis is the etching time. The peaks 40, 42, and 44 of the nitrogen isotope N15 content correspond to the GaN layers 24, 20, and 16, respectively. The etching rate is obtained by detecting this peak. Then, an etching end time at which a desired etching amount is obtained is determined based on the etching rate.

  Next, as shown in FIG. 6, the photoresist 28 is removed. Then, a gate metal electrode 46 is formed on the GaN active layer 14 in the groove 30, and a source metal electrode 48 and a drain metal electrode 50 are formed on the GaN contact layer 26. The semiconductor device according to the present embodiment is manufactured through the above steps.

  As described above, in the present embodiment, when the nitrogen compound layer is etched, the peak of the content of nitrogen isotope N15 in the etching atmosphere is detected. Thereby, the etching rate can be accurately obtained without interrupting the etching. Based on this etching rate, it is possible to accurately determine the etching end time when a desired etching amount is obtained.

  Therefore, in this embodiment mode, a desired etching amount can be obtained without interrupting etching. Further, even if the nitrogen isotope N15 is used as a marker, the function of the semiconductor device is not affected.

Embodiment 2. FIG.
In the present embodiment, as shown in FIG. 7, GaN layers 52, 54, 56, 58, 60, 62, and 64 are sequentially formed instead of the GaN layers 16, 18, 20, 22, and 24 of the first embodiment. To do. Then, as in the first embodiment, the groove 30 is formed by dry etching using the photoresist 28 as a mask.

  Here, the GaN layers 52, 60, and 64 are marker layers that are arranged at equal intervals and include nitrogen isotope N15 in a part of nitrogen. Among these, the GaN layer 52 (first marker layer) is provided at a position corresponding to a desired etching amount which is the depth of the groove 30. A GaN layer 60 (second marker layer) is provided at a position one above the GaN layer 52. In the present embodiment, a GaN layer 56 (third marker layer) including a nitrogen isotope N15 in a part of nitrogen is provided between the GaN layer 52 and the GaN layer 60. Other GaN layers do not contain the nitrogen isotope N15.

  FIG. 8 is a diagram in which the content of nitrogen isotope N15 in the etching atmosphere is measured in the second embodiment. The horizontal axis is the etching time. The peaks 66, 68, 70, and 72 of the nitrogen isotope N15 content correspond to the GaN layers 64, 60, 56, and 52, respectively. Similar to the first embodiment, the etching rate is obtained by detecting this peak. Then, an etching end time at which a desired etching amount is obtained is determined based on the etching rate. Thereby, the same effect as in the first embodiment can be obtained.

  Further, in the present embodiment, when etching the nitrogen compound layer, a peak 70 having a period different from that of the peaks 66, 68, 72 is detected. When the peak 72 next to the peak 70 is detected, the etching is finished. Thereby, for example, even when the GaN layer 64 which is the uppermost marker layer disappears during other processing, the etching end time can be accurately determined.

Embodiment 3 FIG.
In the present embodiment, as shown in FIG. 9, GaN layers 74, 76, 78, 80, and 82 are sequentially formed instead of the GaN layers 16, 18, 20, 22, and 24 of the first embodiment. Then, as in the first embodiment, the groove 30 is formed by dry etching using the photoresist 28 as a mask.

  Here, the GaN layers 74, 78, and 82 are marker layers that are arranged at equal intervals and include nitrogen isotope N15 in a part of nitrogen. Among these, the GaN layer 74 (first marker layer) is provided at a position corresponding to a desired etching amount that is the depth of the groove 30. A GaN layer 78 (second marker layer) is provided at a position one above the GaN layer 74.

  In the present embodiment, a GaN layer 76 (third marker layer) including a nitrogen isotope N15 in a part of nitrogen is provided between the GaN layer 74 and the GaN layer 78. The content of the nitrogen isotope N15 in the GaN layer 76 is half of the content of the nitrogen isotope N15 in the GaN layers 74, 78, and 82. Other GaN layers do not contain the nitrogen isotope N15.

  FIG. 10 shows the content of nitrogen isotope N15 in the etching atmosphere measured in the third embodiment. The horizontal axis is the etching time. Peaks 84, 86, 88, and 90 of the nitrogen isotope N15 content correspond to the GaN layers 82, 78, 76, and 74, respectively. Similar to the first embodiment, the etching rate is obtained by detecting this peak. Then, an etching end time at which a desired etching amount is obtained is determined based on the etching rate. Thereby, the same effect as in the first embodiment can be obtained.

  Furthermore, in this embodiment, when the nitrogen compound layer is etched, a peak 88 having a period and a peak intensity different from those of the peaks 84, 86, and 90 is detected. When the peak 90 next to the peak 88 is detected, the etching is finished. Thereby, for example, even when the GaN layer 82 which is the uppermost marker layer disappears during other processing, the etching end timing can be accurately determined. Furthermore, since the peak 88 is different in peak intensity from the peaks 84, 86, and 90, it is easier to discriminate than the peak 70 of the second embodiment.

  In the above embodiment, the FET in which the GaN layer is formed on the SiC substrate has been described. Not limited to this, a sapphire substrate, a GaN substrate, or the like may be used. An AlGaN layer may be used instead of the GaN layer. Further, an insulating film layer such as SiN may be used as the nitrogen compound layer instead of a semiconductor layer such as GaN. Furthermore, the present invention can be applied not only to FETs but also to semiconductor lasers using GaN.

10 SiC semiconductor substrate (substrate)
12 GaN buffer layer (nitrogen compound layer)
14 GaN active layer (nitrogen compound layer)
16, 20, 24, 64, 82 GaN layer (nitrogen compound layer, marker layer)
18, 22, 54, 58, 62, 80 GaN layer (nitrogen compound layer)
26 GaN contact layer (nitrogen compound layer)
52,74 GaN layer (nitrogen compound layer, first marker layer)
60,78 GaN layer (nitrogen compound layer, second marker layer)
56,76 GaN layer (nitrogen compound layer, third marker layer)

Claims (3)

Forming a nitrogen compound layer on the substrate;
Etching the nitrogen compound layer,
The nitrogen compound layer has a plurality of marker layers arranged at equal intervals and including a nitrogen isotope N15,
When etching the nitrogen compound layer, an etching rate is obtained by detecting the peak of the content of nitrogen isotope N15 in the etching atmosphere, and an etching end time at which a desired etching amount is obtained based on the etching rate is determined. A method for manufacturing a semiconductor device, comprising: discriminating. The plurality of marker layers include a first marker layer at a position corresponding to the desired etching amount, and a second marker layer positioned on one of the first marker layers,
The nitrogen compound layer further includes a third marker layer including a nitrogen isotope N15 between the first marker layer and the second marker layer,
2. The etching of the nitrogen compound layer is detected when a peak of the content of nitrogen isotope N15 corresponding to the third marker layer is detected and the next peak is detected. The manufacturing method of the semiconductor device as described in any one of.   3. The method of manufacturing a semiconductor device according to claim 2, wherein a content of the nitrogen isotope N <b> 15 in the third marker layer is different from a content of the nitrogen isotopes N <b> 15 in the plurality of marker layers.

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