JPS5994809A - Production of semiconductor element - Google Patents

Abstract

PURPOSE:To make it possible to produce semiconductor element with minimized minute defect which may appear in the epitaxial layer, by providing a method having the steps of allowing a growth of silicon single crystal layer on a substrate constituted by silicon single crystal in which the oxygen concentration is a specific value in terms of ppma and the carbon concentration is not smaller than 1ppma, and effecting a heat treatment on the silicon single crystal layer. CONSTITUTION:A heat treatment is conducted on a substrate having an oxygen (O) concentration of 25-50ppma and a carbon (C) concentration of 1ppma or higher, at a temperature range 600-800 deg.C within a nitrogen (N2) gas atmosphere. This heat treatment contributes to the minimization of minute defects which may exist in the epitaxial layer. In an example of the method, an epitaxial layer of silicon (Si) is formed on a substrate by a known method such as CVD method, and 700 deg.C-48hr heat treatment is effected on the substrate within a nitrogen (N2) gas atmosphere, following by an element forming step. According to this method, any defect caused in the epitaxial layer is absorbed by minute defect in the substrate, so that the number of defects in the epitaxial layer is diminished to ensure an improved property of the semiconductor element produced by this method.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a method for manufacturing a semiconductor device. In detail, silicon (Sl) formed on a silicon (Sl) crystal substrate
) A method for manufacturing a semiconductor device including a step of gettering and removing minute defects generated in an epitaxial layer by a subsequent step based on an intrinsic gettering method.

(2) Background of the technology Epitaxial scraps made of silicon (Si) crystals are mainly used for non-irregular and non-irradiated devices, but as devices become more highly integrated in recent years, stacking faults, dislocations, micro defects, etc. , those without crystal defects are required. This is because in highly integrated semiconductor devices, the dimensions of the operating area are extremely small, and the relative size of crystal defects cannot be ignored, making their effects difficult to ignore. .

However, in the above epitaxial layer, stacking faults,
Crystal defects such as dislocations and micro defects (shallow bits) are present. Of these, a particular problem is microscopic defects (shallow bits) that occur near the surface, with units of I
The number of defects per nR1t is about to7 ((1 m/α2)), and these will grow into large stacking faults in the subsequent de-glue process, causing poor device characteristics and a decrease in yield.

(3) Prior art and problems Therefore, in the prior art, in order to remove the above-mentioned micro defects, a geometrical irregularity is formed on the substrate surface, or a thin film of silicon nitride (st3n4) is deposited. The so-called extrinsic gettering method, which is a method of gettingtering the car metal layer etc. that causes micro defects from the outside by methods such as In many cases, the getter effect disappears during the process, so it is difficult to say that it is effective.

On the other hand, recently, oxygen atoms (0) in the surface layer of the substrate have been removed by high-temperature heat treatment on silicon (Sl) substrates that contain relatively large amounts of impurities such as oxygen atoms (0) and carbon atoms (C). After out-diffusion and removing oxygen precipitates (Sixty), etc., or crystal defects caused by them, are formed inside the substrate, and in the subsequent element formation process, in particular, micro defects and A method has been developed in which the active layer is made into a defect-free layer, that is, a dense dead zone, by getting the stacking faults into crystal defects formed internally in a previous process and eliminating them. This method is called intrinsic gettering (1G), which is a phenomenon in which minute defects generated inside the substrate adsorb harmful impurities and defects on the surface layer of the substrate.
This method uses this phenomenon and is called the Engineering G method.

Therefore, it would be industrially advantageous if the above-mentioned IG method could be applied to remove defects inside a silicon (Sl) epitaxial layer.

(4) Purpose of the Invention The purpose of the present invention is to meet this demand 1) by forming an element on scraps of Noricon (Sl) crystal formed by epitaxial growth on a silicon (Sl) crystal substrate. Another object of the present invention is to provide a method for manufacturing a semiconductor device, which includes a step of reducing as much as possible the bands of micro defects occurring in the epitaxial layer.

(5) Structure of the invention The present invention provides oxygen (o) (9 degrees is 25 to 50 (:[
)])ma), and the carbon (C) concentration is ICppma)
A silicon (Sl) crystal layer is grown on the substrate made of silicon (Sl) single crystal as described above, and then
o (°C: H2) In the method for manufacturing semiconductor devices, which is characterized by a step of performing a heat treatment at The amount of microdefects is determined by the initial carbon atoms (0
) It is known that it is also affected by concentration.

Therefore, the inventors of the present invention believe that if suitable oxygen (0) and carbon (0) concentrations and heat treatment conditions exist in a silicon 7 (Bi) crystal substrate to achieve the above objectives, the engineered taxial layer I got the idea that the above IC method could also be applied to this, that is, the defects occurring in the epitaxial layer could be adsorbed to minute defects inside the substrate, and based on this idea, I conducted repeated experiments and determined the heat treatment conditions. nitrogen(
N2) 24-4 at 600-5oo(℃) in atmosphere
8 [hour] is the most appropriate case, and under that circumstance! Initial oxygen concentration is 25 (ppma
) As a result of investigating the relationship between the oxygen atom (0) reduction rate, that is, the defect generation rate, and the initial carbon atom (0) concentration by heat treatment for the above silicon (Sl) crystal substrate, a certain relationship was found as shown in the figure. I discovered that there is. That is, the figure shows the above heat treatment at 700 ('O) in a nitrogen (N2) atmosphere.
Initial carbon (C) # degrees (
ppma) (horizontal axis) and oxygen (0) reduction rate (%) (#¥
It shows the relationship with @). The above oxygen (0) concentration and initial carbon (C) 71 degrees were measured using an infrared spectrometer, and the oxygen (0) reduction rate is the oxygen (0) concentration after heat treatment relative to the oxygen (0) concentration before heat treatment. Oxygen (0)! It is expressed as a percentage. As is clear from the figure, in a silicon (Sl) substrate containing a given concentration of oxygen atoms (0), the initial carbon (C) concentration is 1 (
It was confirmed that a remarkable oxygen (0) reduction rate, that is, a remarkable defect generation rate, was obtained when the amount of oxygen (0) was greater than 100% (ppma). on the other hand,
The oxygen (0) concentration on the silicon (si) g plate is 25 (ppm)
a) or higher, but due to constraints such as epitaxial layer growth conditions and substrate warpage, the upper limit is 50 (
It has been confirmed that the oxygen (0) concentration of the silicon (Sl) substrate is 25 [ppma) or more and 50 (ppma) V or less.

Based on the above experimental facts, the inventor of the present invention found that when the oxygen (0) concentration of the substrate is 25 to 50 (ppma) and the carbon (0) lrJ rl is more than L (ppma), nitrogen (N2 ) It was confirmed that heat treatment in an atmosphere at 600 to 800 degrees Celsius for 24 to 48 hours was most effective in reducing defects in the epitaxial layer.

(6) Embodiment of the Invention A method for manufacturing a semiconductor device according to an embodiment of the present invention will be explained, and effects of the structure and characteristics of the present invention will be clarified.

As an example, we will discuss the case of using a p-type silicon (p-8i) wafer manufactured by the Czochralski method and having an oxygen (0) concentration of 30 (ppma) and a carbon (C) intensity of 1 (ppma). .

After forming an epitaxial layer of silicon (Sl) on the above substrate using a chemical vapor deposition method (CVN method) or the like, the substrate was heated at 70° C. for 48 hours in a nitrogen (N2) atmosphere. A heat treatment is performed, and then an element forming process is performed.

According to the above process, defects generated in the epitaxial layer are absorbed by minute defects inside the substrate, and conventionally 107 [defects/c]
silicon (S), which was recognized to exist in the
l) It was confirmed that the number of defects in the epitaxial layer was reduced to 103 to 104 [defects/ho2], which effectively contributed to improving the characteristics of the device.

(7) Effects and costs of the invention As is clear, according to the present invention, silicon (S
l) In a method for manufacturing a semiconductor device in which the device is formed in a layer made of silicon (Sl) crystal formed by epitaxial growth on a crystal substrate, a step of reducing as much as possible the amount of micro defects occurring in the epitaxial layer. It is possible to provide a method for manufacturing a semiconductor device including:

[Brief explanation of drawings]

The figure shows the initial oxygen (o) + a [25 (ppma:) or higher silicon (Sl) substrate when heat-treated at 700 ('O) for 48 [hours] in a nitrogen (N2) atmosphere ax at I7. (0) The reduction rate (%), that is, the defect occurrence rate, is expressed using the initial carbon (C) IAlf (ppma) as an independent variable.

Claims (1)

[Claims] A silicon crystal layer is grown on a substrate made of silicon crystal with an oxygen concentration of 25 to 50 (ppma) and a carbon concentration of 1 (ppma) or more.
1. A method for manufacturing a semiconductor device, comprising a step of heat treatment Mfi performed at a temperature of 0.0C (°C).