JPH0621360A - Epitaxial semiconductor substrate - Google Patents

Abstract

PURPOSE:To obtain an epitaxial semiconductor substrate which reduces fail rate of product characteristics by a construction wherein an epitaxial growth layer is formed immediately on a buried layer. CONSTITUTION:A silicon dioxide film is formed on a P-type substrate 30, and a prescribed burying region and a burying region 32 of a width 50mum are opened by patterning in an element forming region 31 and a region 33 to be a dicing line, respectively. Then, a coating diffusion agent containing antimony is applied by spin-coating, thereby a coating film of 250nm is formed and diffused only in the opened parts, so that an N<->buried layer 32 be formed, and the silicon dioxide layer and the coating film are wholly exfoliated by a fluoric acid. By introducing SiH, Cl, gas and PH gas, accordingly, an N-type epitaxial growth layer 34 is deposited by a cylinder-type epitaxial apparatus and thereby an epitaxial semiconductor substrate having a structure which reduces defectiveness of product characteristics and also can improve a throughput in an epitaxial growth process can be attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of an epitaxial semiconductor substrate, and more particularly to an epitaxial semiconductor substrate for BiCMOS which requires high speed and low power consumption.

[0002]

2. Description of the Related Art In recent years, various IC products such as logic and memory have been changed from the conventional CMOS structure to the CMOS
Bipolar CMOS with bipolar structure incorporated in the structure
Higher speed is achieved by adopting a (BiCMOS) structure.

FIG. 5 is a sectional view of a conventional semiconductor device having a CMOS structure. As is well known, the CMOS structure has a P channel MOSFET on the N substrate 1 and an N channel on the P well 2.
A channel MOSFET is provided. PMOSF
The ET and the NMOSFET are surrounded by the silicon oxide film 3 for element isolation, which surrounds the surface periphery of the element formation region. The gate electrode 4 faces the channel region on the substrate surface via the gate oxide film 5 and forms a so-called MOS structure. A P ⁺ layer 6 serving as a source / drain in the case of a PMOSFET and an N ⁺ layer 7 in the case of an NMOSFET are provided with the channel region sandwiched therebetween. The reference numeral 8 and 9 N is referred to as a channel stopper layer ^- a layer ^- layer and P.
The CMOS device has a characteristic that the power consumption is extremely low, but due to technological progress, high integration has become possible.

BiCMOS devices have been developed and are widely used in which the low power consumption and high integration of such CMOS devices and the high driving power and high speed of bipolar transistors coexist on the same chip.

FIG. 6 is a sectional view showing a schematic structure of a semiconductor device having a BiCMOS structure. NP in area 50
N bipolar transistor, N channel M in region 51
P-channel MOSFETs are formed in the OSFET and the region 52, respectively. Note that the same reference numerals as those in FIG. 5 represent the same or corresponding portions. A semiconductor device having this BiCMOS structure is usually an epitaxial semiconductor substrate in which a high concentration N ⁺ buried layer 11 and a P buried layer 12 are formed in a predetermined region on a P substrate 10 and then an N type epitaxial layer 13 is grown. Used to fabricate through conventional CMOS and bipolar processes. Note that FIG.
In the figure, reference numeral 14 represents a P ⁺ base layer, 15 a P ⁻ base layer, 16 an N ⁺ collector extraction layer, and 17 an N well.

FIG. 7 is a sectional view showing an example of an epitaxial semiconductor substrate used for a semiconductor device having a BiCMOS structure. The substrate is a P-type substrate 24 and an N ⁺ buried layer 2
1 and 23 and the P buried layer 22 are formed, and then the N type epitaxial growth layer 20 is deposited.

In the prior art, the thickness of the N type epitaxial layer 20 of the epitaxial semiconductor substrate as shown in FIG. 7 is determined by using a Fourier transform infrared spectrometer (FT-IR) to obtain a high concentration N ⁺ buried layer. It is obtained by measuring the film thickness above.

In the film thickness measurement by the FT-IR method, infrared rays are incident on the epitaxial layer to be measured, reflected by a high-concentration N ⁺ buried layer having a different optical property from the epitaxial layer, and reflected to the outside of the epitaxial layer. This is done by processing the data of the absorption spectrum of the reflected light returned to the. For this reason, measurement becomes impossible when the amount of reflected light becomes a very small amount below a predetermined value. For example, the film thickness of an epitaxial semiconductor substrate used in a device such as SRAM having a small number of bipolar regions, that is, a high concentration N ⁺ buried layer, cannot be measured.

Therefore, in the process of epitaxial growth of a substrate having a small amount of high-concentration N ⁺ buried layer, high-concentration N ^+
+ Epitaxially grow a test piece (wafer for film thickness measurement) with sufficient embedding at the same time as the semiconductor substrate used for the product, measure the film thickness of this test piece, and measure the film thickness of the epitaxial semiconductor substrate used for the product. Was used as a representative value. For this reason, the film thickness of the test piece and the film thickness of the substrate used for the product are different, and when it is actually commercialized, this film thickness deviates from the standard,
There were cases where product characteristics became defective. In addition, the test piece must be introduced at all times during the epitaxial growth, which increases the cost. In addition, in the normal epitaxial growth process, for example, 24 pieces are processed at the same time. There was a problem such as getting worse.

[0010]

As described above, in the epitaxial semiconductor substrate used for the semiconductor device having the BiCMOS structure, it is very important to control the thickness of the epitaxial layer. Therefore, the film thickness is measured for each lot of epitaxial growth, and the epitaxial growth condition of the next lot is determined based on the result.
Conventionally, the film thickness is measured using the FT-IR method, but there is a problem that the film thickness cannot be measured for an epitaxial semiconductor substrate having a small number of high-concentration buried layers.
For this reason, a test piece that is sufficiently filled with high concentration is prepared separately, and epitaxially grown at the same time as the product substrate, and the film thickness of this test piece is used as a representative value of the film thickness of the lot. However, this typical value has a small correlation with the actual film thickness of the product substrate, and often causes the occurrence of defective characteristics of the product. On the other hand, since the test piece is prepared separately from the product substrate, there is a problem that the throughput in the epitaxial growth process is reduced accordingly.

The present invention has been made in view of the above-mentioned problems of the prior art. It improves the control of the film thickness of the epitaxial semiconductor substrate used in the product, reduces the defective rate of the product characteristics, and increases the throughput in the epitaxial growth process. It is an object of the present invention to provide an epitaxial semiconductor substrate having a structure capable of improving

[0012]

According to the present invention, in an epitaxial semiconductor substrate in which an epitaxial growth layer is deposited on a semiconductor substrate, a high impurity concentration (about 10 ¹⁸ atoms / cm 3) is formed in a region outside the element formation region of the epitaxial semiconductor substrate. ³
The epitaxial semiconductor substrate has the buried layer described above) and the epitaxial growth layer is formed directly on the buried layer.

[0013]

The feature of the present invention is that, in the epitaxial semiconductor substrate in which the buried layer having a high impurity concentration of a size capable of measuring the film thickness of the epitaxial growth layer deposited on the semiconductor substrate does not exist in the element formation region, the buried layer is previously formed outside the element formation region. In the area (for example, the area that becomes the dicing line),
After forming a buried layer having a high impurity concentration of a size capable of measuring the film thickness, epitaxial growth is performed to manufacture an epitaxial semiconductor substrate.

Thus, in the prior art, a test piece for film thickness measurement was separately used, whereas in the present invention, the substrate used for the product is used and the film thickness deposited thereon is measured. The film thickness of the epitaxial semiconductor substrate can be easily and accurately controlled, and the throughput is improved because a separate test piece is not prepared for measuring the film thickness.

According to the trial results (described later), the width of the burying layer provided in a region other than the element forming region must be 25 μm or more in order to obtain good film thickness measurement accuracy.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of an epitaxial semiconductor substrate of the present invention, FIG. 2 is a partially enlarged view of a region serving as a dicing line of the substrate, FIG. 1A is a plan view, and FIG. It is the XY sectional view shown in a).

In FIGS. 1 and 2, the epitaxial semiconductor substrate is a P-type (100) substrate (resistivity: 150 mm).
6 Ωcm) 30 and an N ⁺ buried layer 32 formed in a region 33 to be a dicing line outside the element formation region 31, and about 2 μ deposited on the P-type substrate 30 including immediately above the layer 32.
N type epitaxial growth layer 3 with m film thickness and resistance of 0.5Ωcm 3
4 and.

The method of manufacturing this epitaxial semiconductor substrate is as follows. A silicon dioxide film having a thickness of 800 nm is formed on the P-type substrate 30, and a predetermined buried region (not shown) in the element forming region 31 and a buried region 32 having a width of 50 μm are patterned in the region 33 to be a dicing line. Make a hole. Then antimony was spin-coated a coating diffusing agent containing, to form a coating film of 250nm only opening portion, it is about 1 hour diffusion at 1190 ° C., N ⁺ buried layer 3
Form 2. Next, the silicon dioxide layer and the coating film are completely stripped with hydrofluoric acid. Next, Si H ₂ Cl ₂ gas and PH ₃ gas were introduced by a cylinder type epitaxial device, and about 2
An N-type epitaxial growth layer 34 having a thickness of μm is deposited to obtain the epitaxial semiconductor substrate shown in FIG.

Next, regarding the epitaxial semiconductor substrate,
The substrate of the above-mentioned example and the substrate of the conventional example were compared.
As a sample of the conventional example, 12 wafers in which N ⁺ burying was performed only in a predetermined burying region in the element formation region and 2 test piece substrates in which an N ⁺ burying layer was formed on the entire surface were set as one lot. Lot made. For the samples of the examples, 12 sheets were treated as one lot, and 60 sheets were prepared in total for 5 lots. Wafers that are simultaneously mounted and processed in a cylinder-type epitaxial device are treated as one lot.

In the case of the conventional example, the film thickness of two test pieces of each lot was measured every time the epitaxial growth of one lot was completed, and the growth conditions of the next lot were determined.

In the case of the present invention, 12 used in products
The film thickness was measured in the buried layer on the dicing line of each wafer, and the growth conditions of the next lot were determined.

The epitaxial semiconductor substrate thus manufactured was put into a product process and a characteristic test was conducted. The result is shown in FIG. In the figure, the abscissa indicates each of the conventional example and the embodiment of the present invention, and the ordinate indicates the product yield. The product yield was 50% in the conventional example in which the film thickness was controlled by the test piece, whereas it was 80% when the film thickness was controlled by introducing the embedded layer in the region to be the dicing line as in this example. % And the yield improved.

FIG. 4 is a correlation diagram between film thickness distribution and product characteristics. The horizontal axis represents the film thickness, and the vertical axis represents the characteristic value of the product. In the figure, the mark ◯ shows the film thickness and the product characteristics of the film thickness when the respective substrates of the conventional example and the above-mentioned example are used. When the film thickness is bad and deviates from the standard value, the product characteristics are deteriorated, and the results shown in FIG. 3 are suggested.

Next, the widths of the buried layers formed in the regions to be the dicing lines are 15 μm, 25 μm and 50, respectively.
A plurality of epitaxial semiconductor substrates with a size of μm were manufactured in the same manner as in the above-mentioned embodiment, and the same position on each wafer was manufactured.
When the measurement was performed 10 times, the variations in the results were ± 2.5%, ± 0.8%, and ± 0.6%, respectively. That is, when the width of the buried layer exceeds the critical value near 25 μm, the variation sharply decreases, and when the width of the buried layer increases, the variation tends to be saturated. As a result, in order to obtain good film thickness accuracy, the width needs to be 25 μm or more.

In this embodiment, the buried region is formed in all the regions to be the dicing line, but the present invention is not limited to this. It suffices that the film thickness can be controlled, and it is sufficient that at least one region having a size of 25 μm × 25 μm or more is provided outside the element formation region.

[0026]

According to the present invention, a buried layer having a high impurity concentration and having a size capable of preliminarily measuring a film thickness is formed in a region outside an element forming region such as a region serving as a dicing line of an epitaxial semiconductor substrate to be manufactured. Since the epitaxial semiconductor substrate is manufactured by forming the film and forming the epitaxial semiconductor substrate, the problems of the prior art can be solved. According to the present invention, it is possible to provide an epitaxial semiconductor substrate having a structure capable of improving the film thickness management of the epitaxial semiconductor substrate used for the product, reducing the defective rate of the product characteristics, and improving the throughput in the epitaxial growth process. It was

[Brief description of drawings]

FIG. 1 is a plan view of an epitaxial semiconductor substrate of the present invention.

2 (a) is an enlarged plan view of a portion which becomes a dicing line of the substrate shown in FIG. 1, and FIG. 2 (b) is a sectional view.

FIG. 3 is a comparison diagram of yields of products using the conventional example and the epitaxial semiconductor substrate according to the example of the present invention.

FIG. 4 is a diagram showing a correlation between film thickness distribution and product characteristic values.

FIG. 5 is a cross-sectional view of a semiconductor device having a CMOS structure.

FIG. 6 is a sectional view of a semiconductor device having a BiCMOS structure.

FIG. 7 is a cross-sectional view showing an example of an epitaxial semiconductor substrate.

[Explanation of symbols]

30 Semiconductor Substrate (P-type Substrate) 31 Element Forming Area 32 High Impurity Concentration Embedding Layer (N ⁺ Embedding Layer) 33 Area Outside Element Forming Area (Dicing Line Area) 34 Epitaxial Growth Layer

Claims (1)

[Claims] 1. An epitaxial semiconductor substrate having an epitaxial growth layer deposited on a semiconductor substrate, which has a buried layer having a high impurity concentration in a region outside an element forming region of the epitaxial semiconductor substrate, and the epitaxial growth layer is formed directly on the buried layer. An epitaxial semiconductor substrate characterized in that