JPH04127421A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain the molecular-beam epitaxial method, for Si, which can obtain a desired impurity concentration distribution by a method wherein a P molecular-beam generation amount from a P molecular-beam generation apparatus is controlled on the basis of a P molecular-beam amount detected by using a detection apparatus and a P-doping amount in an Si growth layer is matched to a prescribed value. CONSTITUTION:When a P-doped Si layer is grown by using a molecular-beam epitaxial (MBE) operation, a required P concentration is input to an impurity concentration control apparatus 17. Then, a corresponding ion current value is set, InP is heated and a P molecular beam is generated at a constant speed. While the MBE operation progresses, an ion current generated at a quadrupole mass spectrograph system 16 is always compared with a set value; a heating current at a Knudsen cell 15 is increased or decreased so as to compensate its excess or deficiency. As P in the InP is consumed, it is required to gradually raise a cell temperature in order to realize a prescribed ion current value. By this invention, however, it is controlled so as to match a P molecular beam amount, and the state of source InP is not affected.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a method for doping donor impurities in the epitaxial growth of Si, and when a compound containing a dopant element is used as a doping material, it is possible to The purpose of the epitaxial growth of Sl included in the present invention is to suppress the variation in the generation rate of dopant molecules caused by this, and to perform the epitaxial growth of Sl included in the present invention, a P molecular beam generator using a P compound as a raw material is used to perform the Si growth. When doping the layer with P as an impurity, a detection device for detecting the bimolecular dose is placed near the substrate on which the Si layer is grown, and the P is detected based on the bimolecular dose detected by the detection device.
The structure includes a process of adjusting the amount of P doped in the Si growth layer to a predetermined value by controlling the amount of P molecular beams generated from the molecular beam generator.

In the present invention, a compound such as InP is used as a source loaded in a Knudsen cell to facilitate the generation of bimolecular beams, and the amount of bimolecular beams generated is monitored by a quadrupole mass spectrometer. Through this control, fluctuations in the amount of bimolecular beams generated as the raw material decomposes progress can be coped with. It is also appropriate that the Si layer be grown by molecular beam epitaxy.

Since P has a high vapor pressure, it can be completely removed from the mass spectrometer or the inner walls of the processing chamber by baking.

[Industrial application field]

The present invention relates to a method of introducing impurities into a semiconductor growth layer, and typically relates to a method of doping P, which is an N-type impurity, in the formation of a Si layer by molecular beam epitaxy (MBE).

In recent years, technology for increasing the speed and integration of integrated circuit devices (ICs) formed on Si substrates has made significant progress, but quantum physical quantities such as the mobility of electrons and holes, which determine the characteristics of active elements, are , which is determined by the energy band structure of Si crystal, there is a limit to the improvement of IC characteristics if only Si is used.

One way to solve this problem and obtain higher performance devices is to use high-mobility semiconductor materials such as GaAs, but when forming devices mainly using Si, It has been proposed to form high-speed, high-performance devices using heterojunctions with other materials, and development is progressing. The partner material forming the heterojunction is a semiconductor material such as germanium (Ge) or a metal (Ni, Co, etc.)
silicide.

In producing a heterostructure device, MBE is the most suitable deposition growth method for forming device constituent layers, but the concentration distribution of impurities doped into the grown layer must be controlled with high precision. When adding impurities to the MBE growth layer, like the main component material, the impurity generates molecular beams that irradiate the substrate and incorporate into the growth layer, but the amount is several orders of magnitude lower than that of the main component material. Therefore, it is difficult to control the molecular beam generation rate.

[Problems to be solved by conventional technology and invention] Ordinary S
In the MBE of i, antimony (
Sb) is used. sb has a larger atomic radius than Si, which causes distortion in the crystal lattice, and also has a low solid solubility limit for Si, making it difficult to dope it at a high concentration.

Despite this, sb is used because phosphorus (P) and arsenic (A s ), which are widely used as n-type impurities, have the following drawbacks and are difficult to use as additive impurities in MBE. It is.

It is generally considered difficult to dope group V elements, which are n-type impurities, into the MBE grown layer;
This is due to the following reasons: a) the vapor pressure of the molecules is high; (b) the adhesion coefficient to the Si surface is small; and fc) surface segregation is likely to occur. Particularly in the case of P and As, the influence of the high vapor pressure of the molecules is large.

Molecular beams of added impurities in MBE are generated using a Knutsen cell, and the amount of generated molecular beams is controlled by adjusting the temperature of the cell. If we try to obtain a molecular beam generation rate corresponding to a predetermined doping amount using P or As molecules as an impurity source, the cell temperature will be controlled in a relatively low temperature range, but as in this cell, It is difficult to control objects with large heat capacity with high precision in a low temperature range.

Furthermore, when the vapor pressure of impurity molecules is high, the impurities attached to the wall surface of the vacuum chamber during MBE are re-evaporated and incorporated into the growth layer, making it easy for the amount of impurity doping to fluctuate.

In such cases, impurities adhering to the walls of the vacuum chamber are usually released by baking in the pretreatment stage, but there is also the problem that impurities in the cell are also evaporated at the same time.

This inconvenience is caused by the high vapor pressure of P and As molecules, so if a P or As compound is used as an impurity source, its dissociation pressure will be lower than the vapor pressure of the molecule, and the above problem can be avoided. You can. However, when a compound is used as an impurity source, the relationship between the molecular beam generation rate and temperature changes as decomposition progresses, and the amount of impurity doped changes. Therefore, in order to use a compound of P or As as an impurity source, it is necessary to change and control the cell temperature in accordance with the progress of decomposition of the compound.

An object of the present invention is to provide a processing method for controlling the amount of molecular beam generation to a predetermined value when a compound is used as a doping source, thereby improving the Si MBE method to achieve a desired impurity concentration distribution. It is to provide.

[Means to solve the problem]

In order to achieve the above object, in the epitaxial growth of Si included in the present invention, when doping the Si growth layer with P as an impurity using a P molecular beam generator using a phosphorus (P) compound as a raw material, A detection device for detecting a bimolecular dose is placed near the substrate on which the Si layer is grown, and the P is determined based on the bimolecular dose detected by the detection device.
By controlling the amount of P molecular beams generated from the molecular beam generator, the amount of P doped in the Si growth layer is adjusted to a predetermined value.

Further, in a typical embodiment of the present invention, the Si epitaxial growth method is MBE, and the P compound is I
nP, the P molecular beam generator is a Knudsen cell, and the detection device disposed near the substrate is a quadrupole mass spectrometer, and according to the bimolecular dose measurement value by the quadrupole mass spectrometer. The rate of decomposition of the raw material compound in the Knudsen cell is thermally controlled.

[For production]

When InP is used as a P source and doped to the concentration normally used in Si (10" to 10"cm-"), the temperature range in which the Knudsen cell is maintained is 35
The temperature is 0 to 600°C, and within this range, temperature control is easy.

Furthermore, in this temperature range, the vapor pressure of In, another element constituting the source, is sufficiently low (the amount taken into the growth layer is negligible).

Furthermore, if the evaporation of P from InP continues, P may be depleted near the surface, but in reality, the remaining In becomes droplets and aggregates on the crystal surface, so the evaporation rate of P is significantly reduced. There's nothing to do.

However, fluctuations in the P evaporation rate due to changes in the surface condition exceed the range of changes in the impurity concentration distribution that is permissible when manufacturing semiconductor devices. It is necessary to compensate for the reduction in rate of development.

In the present invention, a detector (a quadrupole mass spectrometer in the example) capable of detecting a trace amount of bimolecular dose is placed near the substrate on which the Si layer is grown, and a Knudsen cell is used based on the P molecular dose value detected here. The temperature is adjusted so that the bimolecular dose corresponds to a desired impurity concentration distribution.

That is, when it is determined that the impurity concentration in the growth layer is lower than a predetermined value from the bimolecular dose detected by the analyzer,
The temperature of the Knudsen cell is raised to increase the rate of bimolecular beam generation, and conversely, when it is determined that the impurity concentration in the growth layer is higher than a predetermined value, the temperature of the cell is lowered.

Since the process of the present invention detects and responds to the amount of P molecular beam generation in real time, even if the situation of change in the generation rate of bimolecular beams is specific each time, P molecular beam generation is performed accordingly. amount will be compensated.

Note that although there is a slight delay in the temperature response of the Knudsen cell, the fluctuation in the amount of P molecular beam generation is monotonous and slow.
It is not difficult to achieve complete compensation through advance control.

Furthermore, in the process of the present invention, P molecules are generated as P instead of P4, so the P obtained when simple P is heated is
It is more effectively incorporated into the Si layer than in case 4, and a desired impurity concentration distribution can be obtained with a lower single molecule dose.

Although doping with As using an As compound as an impurity source can also be carried out in the same manner as in the present invention,
The vapor pressure of As molecules is lower than that of P molecules, and there is a drawback that As attached to the walls of the vacuum chamber cannot be removed by baking. Therefore, As attached to the wall surface
As increases, 10”-” to 10-” Torr As
Steam is generated and a large amount of As is doped into the Si layer.

The situation in which deposits can be effectively removed by baking only when the impurity element is P is the same for the head of a quadrupole mass spectrometer, and by selecting P as the impurity, it can be accurately removed every time. measurements are taken.

〔Example〕

FIG. 1 is a cross-sectional view schematically showing the structure of an MBE apparatus used for implementing the present invention. The MBE processing in the present invention will be described below with reference to the drawings.

A substrate holding device 11 is provided inside and above the vacuum chamber 10,
A Si substrate 12 is attached to the holding device. The substrate holding device 1 has the function of rotating the substrate within its plane and heating it to maintain it at a predetermined temperature.

An electron beam (EB) evaporator 13, which is a source of Si molecular beams, is installed at the bottom of the vacuum chamber IO, and above it, a film thickness meter 1 is installed close to the substrate to monitor the Si molecular beam dose.
4 is provided.

A Knudsen cell 15 is provided as a device for P doping, from which P molecules are emitted toward the Si substrate 12. A quadrupole mass spectrometer 16 for monitoring the single molecule dose is arranged near the Si substrate. Also,
Although not shown, the head of the mass spectrometer is equipped with a heater for baking and removing attached P.

The impurity concentration control device 17 uses 1 detected by the mass spectrometer 16.
adjusting the temperature of the Knudsen cell 15 according to the molecular dose;
Controls the rate of P molecular beam generation. As mentioned above, since the heat capacity of the cell is large, there is a slight delay time for the P molecular beam generation rate to change. Processing methods well known to those skilled in the art for predicting the line generation rate and controlling the heating power of the cell are provided as a control program for the device.

Here, a process for growing a P-doped Si layer by MBE using the apparatus shown in FIG. 1 will be described.

The growth of Si progresses by heating the Si loaded in the evaporator 13 to form a Si molecular beam, and irradiating the surface of the Si substrate with this molecular beam, as is normally done.

The thickness of the grown layer is constantly monitored by a film thickness meter 14, and the EB evaporator 13 is controlled based on this measured value.

At the same time, P is also supplied to the substrate surface in the following manner. First, place an InP wafer in the Knudsen cell 15 with a size of 10 mm
Load several pieces of 20 mm size with the creases adjusted. By heating this, InP is partially dissociated to generate 22 molecules and metal In.

In remains attached to the wafer surface, and P reaches the Si substrate surface in the form of molecular beams and is incorporated into the growing Si layer. At this time, the density of 22 molecules near the Si substrate is measured as an ion current by the quadrupole mass spectrometer 16.

There is a close correlation between the amount of P incorporated into the Si growth layer and the value measured by a mass spectrometer, and the relationship between the two is experimentally determined in advance and the control program of the impurity concentration control device 17 is performed. Incorporate it into.

When growing a P-doped Si layer by MBE, a required P concentration is input to the control device, a corresponding ion current value is set, InP is heated, and a bimolecular beam is generated at a constant rate. During MBE, the ion current generated in the analyzer 16 is constantly compared with the set value, and the heating current of the Knudsen cell is increased or decreased to compensate for excess or deficiency. P in InP
As the ion current is consumed, it is necessary to gradually increase the cell temperature in order to achieve a predetermined ion current value, but in the present invention, this is controlled according to the single molecule dose, so it is not affected by the state of the source InP. Never.

FIG. 2 shows the P concentration distribution in the Si layer when the Si substrate temperature is 600° C. and the MBE growth rate of the Si layer is 1 μm/hr. Among the two curves marked in the figure,
(a) shows the P concentration set to 1×10”cF3;
(b) is grown with the setting of l x 10110 l7'', and the initial value of the Knudsen cell temperature is 630, respectively.
℃, 500°C.

The minimum detection sensitivity of P2 by quadrupole mass spectrometer is 10”
Since it is less than Torr, the impurity concentration is 10”
It can be controlled down to 7cm3 or less.

In this embodiment, InP is used as a phosphorus compound as an impurity source, but other compounds such as GaP and AAP can also be used. In addition to MBE, other Si growth methods such as ion beam evaporation and sputter evaporation can be used, and the present invention can be carried out by combining these growth methods with controlling the amount of impurity doping using an ion current monitor. You can also do it.

〔Effect of the invention〕

As explained above, in the present invention, since the supply amount of P as an impurity is controlled according to the output of a mass spectrometer installed near the substrate, it is not affected by changes in the P source over time (the Si growth layer It is possible to realize a desired P concentration distribution in the inside.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing the structure of an apparatus used for carrying out the present invention, and FIG. 2 is a diagram showing the P concentration distribution in the Si growth layer in an example. In the figure, IO is a vacuum chamber; 2 is a substrate holding device, 2 is a Si substrate, 3 is an EB evaporator, 4 is a film thickness meter, 5 is a Knudsen cell, 16 is a quadrupole mass spectrometer, and I7 is an impurity concentration control device. The same figure schematically shows the structure of the device used for carrying out the present invention.

Claims (2)

[Claims] (1) A device (15
) is used to dope the Si growth layer with P as an impurity, a detection device (16) for detecting the P molecular dose is placed near the substrate (12) on which the Si layer is grown, and the detection device Based on the P molecular dose detected by
A method for manufacturing a semiconductor device, comprising the step of adjusting the amount of P doped in the Si growth layer to a predetermined value by controlling the amount of P molecular beams generated from a molecular beam generator. (2) In the epitaxial growth of the Si layer according to claim 1, the Si epitaxial growth method is performed by irradiating the substrate with a Si molecular beam, the P molecular beam generator is a Knudsen cell, and the The raw material compound is InP, and the detection device disposed near the substrate is a quadrupole mass spectrometer, which detects the amount of the raw material compound in the Knudsen cell according to the measured P molecular dose by the quadrupole mass spectrometer. 1. A method for manufacturing a semiconductor device, comprising a step of thermally controlling a decomposition rate.