JPH0567063B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an apparatus that can easily determine the impurity concentration distribution in the depth direction of a semiconductor.

<Prior Art> Semiconductor devices obtain desired characteristics by diffusing impurities into a silicon wafer, and in order to control the diffusion, it is necessary to accurately measure the impurity concentration distribution in the depth direction. One of the conventional techniques for measuring the impurity concentration in the depth direction is a technique for measuring the resistivity of the surface of a semiconductor to be measured while etching the surface little by little. That is, resistivity ρ
There is a relationship between ρ = (Neμ) ^-1 N = net impurity concentration e = charge μ = mobility of many carriers, and by measuring the resistivity ρ, ,
The impurity concentration N can be determined.

The procedure for such impurity concentration measurement is shown in FIG. In FIG. 5, first, the initial surface resistance of the semiconductor to be measured is measured. Next, this semiconductor is mounted on a jig, and its surface is anodized very slightly.

FIG. 6 shows an example of a jig for anodizing.
In Fig. 6, 1 is a Teflon sample holder, 2 is an electrode, 3 is an electrolyte reservoir, 4 is an O-ring, 5 is a semiconductor to be measured, 6 is a Bakelite holder, 7 is a nylon screw, 8 is a cover, 9 ,10
is a terminal. Electrodes (not shown) installed in the electrolytic reservoir 3 between the terminal 9, the electrode 2, and the terminal 10 are electrically connected to each other. Semiconductor to be measured 5
is fixed to the Bakelite holder 6 with wax, and fixed to the sample holder 1 with a nylon screw 7 via an O-ring 4. Electrode 2
is pressed against the semiconductor to be measured 5 by a spring (not shown) to maintain electrical continuity.
Note that the electrolytic solution reservoir 3 is filled with electrolytic solution. When a voltage is applied between the terminals 9 and 10 in this state, the surface of the semiconductor to be measured 5 is anodized.

In FIG. 5, the thickness of the anodized oxide film is measured using an ellipsometer or the like. Thereafter, the oxide film thickness is removed by etching with hydrofluoric acid or the like, and the step height and surface resistance are measured. Check whether the measurement has been made to the specified depth, and if it has not been measured, repeat the process from anodic oxidation. Once the measurement is complete, calculate the impurity concentration from the surface resistance, combine it with the measured values of oxide film thickness and step,
Determine the impurity concentration in the depth direction.

Figure 7 shows the principle of surface resistance measurement. Surface resistance is usually determined by the four-point probe method. In Figure 7,
11 and 12 are probes, 13 is a variable voltage source, 14 is an ammeter, and 15 is a voltmeter. The variable voltage source 13 and the ammeter 14 are connected to the electrode 11, and the voltmeter 15 is connected to the electrode 12. The probes 11 and 12 are brought into contact with the semiconductor to be measured 5 with appropriate pressure. Probe 1
Assuming that the spacing between 1 and 12 is equal, the surface resistance ρs is determined as follows: ρs=4.532·V/I V=voltage indicated by the voltmeter 15=voltage indicated by the ammeter 14=current indicated by the ammeter 14.

<Problems to be solved by the invention> However, with this impurity concentration distribution measurement technology, measurement of one point in the depth direction requires five steps: anodization, oxide film thickness measurement, etching, step measurement, and surface resistance measurement. The semiconductor to be measured must be attached to and removed from the jig or measuring device each time. Furthermore, in order to obtain the distribution in the depth direction, such a process must be repeated 50 to 100 times. Therefore, the process became complicated and the measurement took a lot of time. Additionally, there were cases where the sample was accidentally broken during measurement or the surface became dirty, making measurement impossible.

<Object of the Invention> An object of the invention is to provide a semiconductor characteristic measuring device that has a simple structure and can easily measure the impurity concentration distribution of a semiconductor.

<Means for Solving the Problems> In order to solve the above-mentioned problems, the present invention provides a semiconductor characteristic measuring device that repeats etching and resistance measurement of the semiconductor surface to determine the impurity concentration distribution of the semiconductor. a holder having a holder, a chamber airtightly partitioned by a flexible support plate inside the holder at a predetermined distance from the edge of the opening of the holder, and a resistance measurement chamber provided protrudingly on the support plate. an electrode, a through hole formed in the holder and communicating with an opening formed between the support plate and the edge for injecting and discharging etching solution, and a pressure introduction hole communicating with the chamber. It is characterized by this.

Furthermore, the above-mentioned means is further provided with current measuring means for measuring the current during etching, and calculating means for calculating the amount of etching based on the output of the current measuring means.

<Function> Bring the holder into close contact with the measurement surface of the semiconductor to be measured,
An etching solution is introduced into the space surrounded by the semiconductor to be measured, a support plate, and a holder through the through hole to perform etching, and then the etching solution is discharged to measure the surface resistance of the semiconductor to be measured. Etching and surface resistance measurement can be performed using the same holder and without removing the semiconductor to be measured.

Further, the etching current during etching is measured, and the current is integrated by a calculating means to obtain the etching amount.

<Example> FIG. 1 shows an example of a semiconductor characteristic measuring device according to the present invention. In FIG. 1, 10 is an outer cylinder;
11 is a through hole formed in the outer cylinder 10, 12 is an inner cylinder,
13 is a pressure introduction port formed in the inner cylinder 12.
14 is a diaphragm, and this diaphragm 1
4 is provided with a protruding electrode 15 for resistance measurement. The diaphragm 14 is fixed to the outer cylinder 10 by the inner cylinder 12 without any gaps. 16 is a fixing plate for fixing the electrode 15, and the diaphragm 14 and the fixing plate 16 constitute a support plate.
17 is a terminal, which is connected to the electrode 15 by a conductor 18. Terminal 17 is fixed with filler 19. 20 is a terminal attached to the semiconductor to be measured 5. In addition, the outer cylinder 10, the inner cylinder 12, and the filler 19
The holder is closely fixed to the semiconductor to be measured 5.

Next, the operation of this embodiment will be explained based on the flowchart of FIG. The operation is performed in the following steps.

(1) Introduce compressed air from the pressure introduction port 13. The pressure in the hollow part of the holder increases, and the diaphragm 14 bends as shown in FIG. 3, causing the electrode 15 to come into contact with the semiconductor to be measured 5.

(2) Measure the surface resistance of the semiconductor to be measured 5.

(3) Open pressure inlet 13. The diaphragm 14 returns to its original position, and the electrode 15 separates from the semiconductor to be measured 5.

(4) Pour the etching liquid into the diaphragm 1 through the through hole 11.
4 and the semiconductor to be measured 5.

(5) Etching.

(6) Drain the etching solution.

(7) Compressed air is introduced from the pressure introduction port 13 and the electrode 15 is brought into contact with the semiconductor to be measured.

(8) Measure the surface resistance of the semiconductor to be measured 5.

(9) Measure the step and find the etching depth.

(10) When a predetermined depth is reached, the impurity concentration is determined from the surface resistance and the step difference, and the process ends. If you don't reach
Return to (4).

The surface resistance is measured using the electrode 15 using the four-probe method described in FIG. Further, etching is performed by chemical etching or electrolytic etching.

FIG. 4 shows a configuration for performing electrolytic etching. In FIG. 4, 21 is a variable voltage source, 22
23 is a current measuring means, and 23 is a calculation means. The variable voltage source 21 and the current measuring means 22 are connected in series,
It is connected to terminals 17 and 20 so that the terminal 17 side becomes the positive electrode. The output of the current measuring means 22 is output to the calculating means 23. In this configuration, when a current is passed between the semiconductor to be measured 5 of the electrode 15, the constituent atoms of the semiconductor to be measured 5 are ionized, dissolved into the etching solution, and etched. At this time, there is a relationship between the etching amount d and the current I(t) as follows: d=K/S∫ ^T ₀ I(t)dt K=proportionality constant S=etching area T=etching time. Therefore, if the calculation means 23 performs the calculation of the above equation, the etching amount can be calculated, and step measurement becomes unnecessary. Since the electrode 15 is commonly used for surface resistance measurement and electrolytic etching, it is switched by a switch (not shown).

In addition, in FIG. 4, 24 is a light source. n
In the type semiconductor, a barrier in the opposite direction is created at the boundary between the surface of the semiconductor to be measured 5 and the etching solution, so that almost no current flows, so that etching does not proceed. For this reason, light is irradiated onto the semiconductor surface to generate electrons and holes, causing current to flow. In this case, the support plate consisting of the diaphragm 14 and the fixed number 16 is made of a light-transmitting material, so that the surface of the semiconductor to be measured is sufficiently irradiated with light. The light may be guided from the pressure introduction port 13 using a fiber or the like.

Further, in this embodiment, the electrode 15 is used in common as the resistance measuring electrode and the electrolytic etching electrode, but the electrolytic etching electrode may be provided separately. In this case, the electrode for electrolytic etching is
It is fixed at a position that does not come into contact with the semiconductor to be measured 5 and comes into contact with the etching solution.

In addition, the support plate is connected to the diaphragm 14 and the fixing plate 16.
Although the electrode 15 is moved by introducing compressed air from the pressure introduction port 13, the electrode 15 may be moved using an air cylinder, an electrode cylinder, or the like.

<Effects of the invention> As specifically explained above based on the examples,
According to the present invention, etching and surface resistance measurement can be performed using the same device. Therefore, the number of times the semiconductor to be measured is removed is reduced, and the impurity concentration can be measured quickly. Also,
Since there is less chance of contaminating or damaging the semiconductor to be measured, more accurate measurements can be made.

Further, by using electrolytic etching and determining the etching amount from the integrated value of electrolytic current, all measurements can be performed with the semiconductor to be measured attached to the apparatus. Therefore, the measurement can be performed more quickly and the semiconductor to be measured is not contaminated.

Furthermore, the structure of the apparatus can be simplified by using a diaphragm as a means for moving the electrodes, and by using the electrolytic etching electrode and the resistance measuring electrode in common. Furthermore, by using a light-transmitting material for the support plate so that light can be irradiated onto the surface of the semiconductor to be measured, even n-type semiconductors can be etched efficiently.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the semiconductor characteristic measuring device according to the present invention, FIG. 2 is a flowchart showing the procedure for measuring impurity concentration distribution, and FIG.
A configuration diagram showing the state during surface resistance measurement of the example shown in FIG.
FIG. 4 is a configuration block diagram for explaining the electrolytic etching of the embodiment shown in FIG. 1, and FIG. 5 is a flowchart for explaining conventional impurity concentration distribution measurement.
FIG. 6 is a block diagram showing an example of a conventional anodic oxidation jig, and FIG. 7 is a diagram showing the principle of surface resistance measurement using the four-probe method. 5...Semiconductor to be measured, 10...Outer cylinder, 11...
Through hole, 12... Inner cylinder, 13... Pressure introduction port, 14
... diaphragm, 15 ... electrode, 16 ... fixed plate, 17, 20 ... terminal, 21 ... variable voltage source,
22...Current measuring means, 23...Calculating means, 24
……light source.

Claims (1)

[Scope of Claims] 1. A semiconductor characteristic measuring device for repeatedly etching a semiconductor surface and measuring resistance to determine the impurity concentration distribution of the semiconductor, comprising: a holder having an opening; a chamber airtightly partitioned by a flexible support plate on the inner side separated by a distance; a resistance measurement electrode protruding on the support plate; and a resistance measurement electrode formed on the holder and formed on the support plate and the edge. 1. An apparatus for measuring characteristics of a semiconductor, comprising: a through hole communicating with an opening formed between the chambers and for injecting and discharging an etching solution; and a pressure introducing hole communicating with the chamber. 2. The semiconductor characteristic measuring device according to claim 1, wherein a diaphragm is used as the support plate. 3. The semiconductor characteristic measuring device according to claim 1, wherein a light-transmitting material is used as the support plate. 4. The semiconductor characteristic measuring device according to claim 1, wherein the resistance measuring electrode is used as an etching electrode. 5. In a semiconductor characteristic measuring device that repeatedly etches the surface of a semiconductor and measures resistance to determine the impurity concentration distribution of the semiconductor, the device comprises: a holder having an opening; A chamber airtightly partitioned by a flexible support plate, a resistance measuring electrode provided protrudingly on the support plate, and a resistance measuring electrode formed on the holder between the support plate and the edge. a through hole communicating with the opening for injecting and discharging the etching solution, a pressure introducing hole communicating with the chamber, a current measuring means for measuring the current flowing during the etching, and an etching amount determined by the output of the current measuring means. What is claimed is: 1. A semiconductor characteristic measuring device, comprising: calculation means for calculating. 6. The semiconductor characteristic measuring device according to claim 2, wherein a diaphragm is used as the support plate. 7. The semiconductor characteristic measuring device according to claim 2, wherein a light-transmitting material is used as the support plate. 8. The semiconductor characteristic measuring device according to claim 2, wherein the resistance measuring electrode is used as an etching electrode.