JPH0254933A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable absorption of contaminated heavy metal from an element forming area by forming a gettering site at the main surface side of a semiconductor substrate. CONSTITUTION:Phosphorus ions are injected, as impurities, by 1X10<15>cm<-2> under acceleration voltage of 1.5MeV into a silicon substrate 11. A plurality of sheets of such substrates 11 are prepared, and each substrate 11 is subjected to heat treatment for 20min. under nitrogen environment having temperature of 800, 900, 1000, 1100 deg.C respectively. An oxygen deposition layer 13 is formed on the surface of the substrate through heat treatment. The oxygen deposition functions advantageously as a gettering site in the succeeding element forming process.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a semiconductor device that forms gettering sites for removing heavy metal contamination, etc. The present invention relates to a method of manufacturing a semiconductor device formed on the main surface side of a semiconductor device.

(Prior art) Heavy metal contamination introduced during the manufacturing process of conductor devices is
It forms a center for trapping and emitting free electrons (holes), causes leakage of pn junctions, and deteriorates the electrical characteristics of semiconductor devices. For example, in MO5 semiconductor devices, a 1° current caused by heavy metals causes a decrease in mutual conductance, etc., which is a major cause of a decrease in yield. On the other hand, the recent increase in the number of elements in semiconductor integrated circuits and the accompanying decrease in the element dimensions of semiconductor integrated circuits means that trace amounts of contamination affect element characteristics and the yield of integrated circuits.

Traditionally, methods for gettering such contamination include
A method is used in which heavy metal contamination is absorbed by mechanically damaging the back surface of a semiconductor substrate or introducing high-concentration impurities. However, since such back surface treatment is performed at the beginning of the manufacturing process, an extra step is required to prevent 2Ti staining from the front surface, and the effectiveness decreases by 1 mo after going through multiple heat treatment steps. There were drawbacks such as.

Further, in the manufacture of integrated circuits, there is a problem in that the thick field oxide film applies stress to the element isolation nfl region, causing impurities such as heavy metals to collect therein, making it easy to generate leakage current.

(Problems to be Solved by the Invention) As described above, in the conventional method of forming gettering sites on the back side of a semiconductor substrate, an extra step is required to prevent contamination from the surface, and the There is a problem in that the gettering ability deteriorates after undergoing multiple heat treatments to form gettering sites.

The present invention has been made in consideration of the above circumstances, and its purpose is to form a gettering site that does not require any extra steps and whose effectiveness does not decrease even after multiple thermal steps. An object of the present invention is to provide a method for manufacturing a semiconductor device that can contribute to improving the manufacturing yield of semiconductor devices.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to provide a pn of an element formed on a semiconductor substrate.
The purpose of this method is to perform ion implantation in a region deeper than the junction, then optimize the initial heat treatment conditions to form gettering sites on the main surface side of the substrate.

That is, the present invention is a method for manufacturing a semiconductor device having a gettering site, in which ions are implanted from the main surface of a semiconductor substrate into a region deeper than the pn junction of a semiconductor element formed on the substrate to remove the nuclei of crystal defects. In this method, a first heat treatment is performed at 900 to 1100° C. for 15 minutes or more to precipitate oxygen at the nuclei of the crystal defects. Here, if the heat treatment temperature is lower than 900° C., a defect layer to be trapped is not formed, and if the heat treatment temperature is higher than 1100° C., the solid solubility limit becomes high, so even if such defects exist, they are not trapped.

The present invention also provides a method for manufacturing a semiconductor device having gettering sites, in which a field oxide film for element isolation is formed on the main surface of a semiconductor substrate, and then ions are implanted into JJ and N through this oxide film to crystallize. Nucleation of the defects and subsequent initial heat treatment at 900-110°C
This method is performed at 0° C. for 15 minutes or more to form an inversion layer directly under the oxide film and to precipitate oxygen at the nuclei of the crystal defects.

(Function) According to the present invention, gettering sites are formed on the main surface side of the semiconductor substrate, so that the gettering sites can absorb heavy metal contamination in the element formation region, thereby improving the manufacturing yield of the elements. It is possible to measure it.

Furthermore, unlike the method of forming gettering sites on the back side of the substrate, there is no inconvenience such as the gettering effect being reduced by half during the heat treatment process.

(Example) First, before describing an example, the basic principle of the present invention will be explained.

The present inventors formed crystal defect nuclei in a region several μm from the substrate surface by high-energy ion implantation of several McV or more, and then performed heat treatment under various temperature conditions. As a result, in the samples heat-treated at 900 to 1 loo'c,
When measured using a transmission electron microscope, a dislocation loop was observed at the position Rp (ion penetration depth) determined by the ion implantation conditions. Furthermore, when measurements were performed using secondary ion mass spectrometry, an oxygen peak was observed aF+ at the same position as observed using the electron microscope, and it was confirmed that oxygen was precipitated at this position.

Furthermore, it has been observed that the above dislocation loops decrease at heat treatment temperatures below 900°C or higher than 1100'C, and when the heat treatment is conducted at 1200°C and 800'C, almost no such oxygen precipitation is observed. Ta. Note that the difference in heat treatment time has no effect, but if it is too short, 90%
Even at a temperature of 0 to 1100°C, oxygen precipitation is insufficient.

According to experiments conducted by the present inventors, it has been confirmed that a heat treatment time of 15 minutes or more is sufficient.

In the sample in which such precipitates were formed, no dislocations δP1 were observed in other regions. Therefore, by performing heat treatment at a temperature of 900 to 1100°C for 15 minutes or more after ion implantation as in the present invention, an oxygen precipitate layer can be formed on the main surface side of the substrate, and this precipitate layer can be used as a stable gettering layer. It can be used as a website.

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a sectional view showing the manufacturing process of a semiconductor device according to an embodiment of the present invention. First, as shown in FIG. 1(a), ions of phosphorus as an impurity 12 were implanted into a silicon substrate 11 at an acceleration voltage of 1.5 McV at I.times.10.sup.15 cm.sup.-2. Five such substrates were prepared.

Note that this ion implantation was performed at room temperature. Next, as shown in FIG. 1(b), these substrates 11 were heated in a non-oxidizing atmosphere at temperatures of 800°, 900°, and 900° respectively in a nitrogen atmosphere.
Heat treatment was performed at 1000.1100.1200° C. for 20 minutes. As a result of this heat treatment, an oxygen precipitate layer 13 was formed on the substrate surface side as shown in FIG. 1(C).

After the above heat treatment, the cross-sectional structure of the sample was examined using a transmission electron microscope. As shown in FIG. It was confirmed that oxygen was precipitated. Furthermore, when each substrate was examined by secondary ion mass spectrometry, it was found that <90 (1
, 100 (1,1100°C heat treated substrate has a depth
It was confirmed that an oxygen peak existed in the vicinity of 1.7 μm along with a phosphorus peak. However, in Figure 3, (a) is 8
00℃, (b) is 900℃, (c) is 1000℃
, (d) shows the case of heat treatment at 1100°C, and (e) shows the case of heat treatment at 1200°C. It was also confirmed that this oxygen precipitate effectively acts as a gettering site in the subsequent element forming process.

Note that the depth of 1.7 μm is sufficiently deeper than the element formation region when forming a normal element, and this gettering site does not cause any inconvenience to the element formation.

As described above, in the method of this embodiment, since ions are implanted over the entire surface at the initial stage of semiconductor element formation, gettering sites can be formed in two steps: ion implantation and heat treatment at a predetermined temperature. Further, since the formed gettering sites are oxygen precipitates, there are more gettering sites than in the conventional method of phosphorus gettering, and there are no problems such as outward diffusion.

Further, in the element formation step that follows this step, gettering ability is always added because oxygen precipitates during the process and new gettering sites are formed in the high temperature process of 900° C. or higher. Therefore, the substrate crystal defect-free treatment step can be carried out easily and reliably by greatly simplifying the process, and can contribute to improving the device manufacturing yield and the like.

Next, other embodiments of the present invention will be described.

FIG. 4 is a sectional view for explaining another embodiment method of the present invention, and this is an example in which the present invention is applied to element isolation between MOSFETs.

In this example, the field ion implantation is performed at high energy as in the previous example, and the same heat treatment as in the previous example is performed to form a part for gettering heavy metals etc. directly under the field. . As shown in FIG. 4(a), a field oxide film 42 is formed on a silicon substrate 41.
After forming, field ion implantation 43 was performed at high energy, followed by heat treatment similar to the previous example.

As a result, an inversion layer 44 is formed directly under the field oxide film 42.
It was possible to form an oxygen precipitated layer 45 in the region below it. In other words, field ion implantation and gettering layer formation can be performed simultaneously.

Here, the position of the oxygen precipitated layer 45 is located at the field oxide film 42.
If it is too close to , there is a risk of leakage in device isolation.

Furthermore, the impurity concentration of the inversion layer 44 needs to be higher than a certain level for element isolation. Therefore, the ion implantation conditions are such that the dose is set so that the dopant concentration directly under the field oxide film is sufficient for device isolation, and the implantation energy is set so that the implanted dopant's projected range (Rp) is the center of the oxygen formation. The depth may be selected so that the precipitates are sufficiently deep to the extent that they do not cause leakage to device isolation.

The conditions were selected in this way and ions were implanted through the field oxide film, followed by the same treatment as in the previous example. As a result, there is almost no re-diffusion of dopants even after the heat treatment process, and at the same time, the elements are isolated under the field oxide film, and at the same time, gettering sites are created to eliminate the effects of impurities that conventionally occur due to stress. We were able to form it in a sufficiently deep area to the extent that it did not. S at this time
The IMS analysis results (results measured by secondary ion mass spectrometry) are shown in FIG. In this way, it has become possible to further form gettering sites with approximately the same number of steps as conventional element isolation ion implantation.

After the step shown in FIG. 4(a), a gate electrode 47 is formed through the gate oxide film 46 as shown in FIG. 4(b), and then using the gate electrode 47 as a mask, source/drain regions 48a, By performing ion implantation to form 48b, two elements separated by the field oxide film 42 are formed.
Two MOSFETs will be completed. Note that the ion implantation for forming the gettering site can also be performed after the element is formed.

Thus, according to the method of this embodiment, an oxygen precipitated layer can be formed on the substrate surface side, especially directly under the field oxide film,
This oxygen precipitated layer can be used as a gettering site. Therefore, as in the previous embodiment, it is possible to improve the device manufacturing yield. Furthermore, since the formation of the oxygen precipitated layer can be performed simultaneously with the field ion implantation, it is also possible to simplify the manufacturing process.

Note that the present invention is not limited to the embodiments described above. For example, the heat treatment conditions are not limited to 900 to 1100°C, and may be any temperature at which a precipitated layer of oxygen is formed on the surface of the substrate. In experiments conducted by the inventors, 900
It has been found that an oxygen precipitate layer is reliably formed within the range of ~1100°C.

Further, the heat treatment time is not limited to 20 minutes, but can be changed as appropriate depending on conditions such as the amount of ion implantation and the depth of implantation. - Numerically speaking, a processing time of about 15 minutes or more is sufficient. Further, the impurity to be ion-implanted is not limited to phosphorus, and any impurity that acts as a gettering site may be selected as appropriate. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, ion implantation is performed in a region deeper than the pn junction of an element formed on a semiconductor substrate, and by optimizing the subsequent initial heat treatment conditions, , it is possible to form a gettering site whose effect does not decrease even after a large number of thermal processes, and it is possible to contribute to improving the manufacturing yield of semiconductor devices.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the manufacturing process of a semiconductor device according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing the cross-sectional structure of a sample after the above process, and FIG. 4 is a cross-sectional view of a process for explaining another embodiment of the present invention, and FIG. 5 is a second diagram of a sample subjected to a heat treatment process following FIG. 4. FIG. 3 is a characteristic diagram showing analysis results by secondary ion mass spectrometry. 11.41... Silicon substrate, 1.2.43... Phosphorus (implanted impurity), 13.45... Oxygen precipitation layer, 42.
...Field oxide film, 44...Inversion layer, 46...
Gate oxide film, 47...gate electrode, 48a, 48b
...Source/drain region.

Claims (3)

[Claims] (1) A step of implanting ions from the main surface of the semiconductor substrate into a region deeper than the pn junction of the semiconductor element formed on the substrate to form crystal defect nuclei, followed by a first heat treatment for 900 days. A method for manufacturing a semiconductor device, comprising the step of precipitating oxygen at the nuclei of the crystal defects by performing the process at a temperature of 1100°C to 1100°C. (2) a step of forming a field oxide film for element isolation on the main surface of a semiconductor substrate; then a step of implanting ions into the substrate through the oxide film to form crystal defect nuclei; First heat treatment to 900-11
A method for manufacturing a semiconductor device, comprising: forming an inversion layer directly under the oxide film and precipitating oxygen at the nuclei of the crystal defects, the method being performed at 00°C. (3) The conditions for the ion implantation are that the dopant concentration under the oxide film is necessary and sufficient for device isolation, and the projected range (Rp) of the implanted dopant is set to a depth that does not cause leakage current to device isolation. 3. The method of manufacturing a semiconductor device according to claim 2.