RU2008661C1 - Method for surface treatment quality check of semiconductor plates - Google Patents

Abstract

FIELD: electrochemical methods of checking semiconductor materials. SUBSTANCE: plate under check is used as working electrode of electrochemical cell. The latter has, apart from working electrode, comparing electrode and auxiliary electrode. It also accommodates additional electrode made of material under check for deposition of impurities. EFFECT: facilitated procedure. 2 dwg

Description

 The invention relates to electrochemical methods for monitoring semiconductor materials and can be used to assess the quality of surface treatment of semiconductor wafers.

A known method of controlling the quality of the surface treatment of silicon wafers, which determine the potential φ _{nr of the} beginning of the anodic electrochemical reaction, the value of which is about the quality of surface treatment of the wafers. The value of φ _HP for a certain type of processing is associated with the electrochemical parameters of the elements formed on the plate.

 The main disadvantage of this method is that in the process of electrochemical processing on the electrode surface from a controlled material, impurities are deposited from the solution, which negatively affects the electrophysical parameters of semiconductor devices - elements of microelectronic devices.

 The purpose of the invention is to increase the accuracy of control.

To achieve the goal, an additional electrode from a controlled material is placed in the electrolyte, and during electrochemical processing, a potential difference is applied between the working (controlled) electrode and the additional electrode, the value of which is selected based on the condition φ _de > φ _re for anode electrochemical treatments and φ _de <φ _re for cathodic electrochemical treatments, and the ratio of the areas of the controlled electrode, the additional auxiliary electrode is selected based on the condition i _re-ve >> i _de-re .

By the potential value φ _{нр of the} beginning of the anodic electrochemical reaction, the properties of semiconductor wafers were controlled, since φ _нр is connected with the electrophysical parameters of the material.

 The essence of the method lies in the fact that the deposition of impurities from the solution occurs primarily on the surface of the additional electrode, since the potential on this electrode is greater than the anode and less for cathode electrochemical treatments compared to the potential on the working electrode. In this case, the potential is significantly shifted to the region of high anode voltages in comparison with the prototype, which indicates an increase in the accuracy of measurement of electrophysical parameters.

The invention is confirmed by the following example. The measurements were carried out using a device (Fig. 1), which contained an electrochemical cell 1, including a working electrode 2, a reference electrode 3, an electrolyte 4, an auxiliary electrode 5, and an additional electrode 6 made of a controlled material, on which the potential is greater for anode and less for cathode electrochemical treatments compared to the potential on the controlled electrode. The area of the additional electrode was selected based on the condition i _re-ve >> i _de-re .

The measurements were carried out when a linearly varying voltage was applied to the system from -2.5 to +4.0 V. The potential φ ' _{np of the} beginning of the anodic electrochemical reaction was determined by the voltage-current characteristic, the value of which controlled the properties of semiconductor wafers.

 Comparative results of measurements performed on silicon wafers after various types of processing are shown in the table.

 The above results show that the potential value of the anodic electrochemical reaction according to the proposed method is much higher than in the known solution, which makes it possible to increase the measurement accuracy, electrophysical parameters at the semiconductor-electrolyte interface.

In FIG. Figure 2 shows the current-voltage characteristic of the phase boundary of the studied electrode-solution, taken in a potentiostatic mode in the voltage range from -2.5 to 4.0 V (φ _n2 is the potential for the onset of hydrogen evolution), (φ _o2 is the potential for the onset of oxygen evolution) at sweep speeds of 20 mV / s. As can be seen from FIG. 2 (dashed line), with the introduction of an additional electrode, the potential of the onset of the anodic electrochemical reaction φ ' _нр significantly shifts to the region of high anodic voltages, the anode current decreases, and the curve changes in this region compared to the prototype, which indicates a decrease in adsorption complexes on the surface controlled electrode.

Thus, the proposed method for controlling the properties of a semiconductor material allows to increase the accuracy of the measurement of electrophysical parameters at the semiconductor-electrolyte interface, since the potential value φ ′ _{np of the} start of the anodic electrochemical reaction is much higher compared to the prototype. (56) Copyright certificate of the USSR N 1385940, cl. H 01 L 21/66, 1985.

Claims (1)

METHOD FOR CONTROLING QUALITY OF SURFACE TREATMENT OF SEMICONDUCTOR PLATES, including measuring the potential of the working electrode, which is a controlled plate placed in the electrolyte, relative to the reference electrode in the presence of an auxiliary electrode, and the medium for chemical processing of the semiconductor plate is used as the electrolyte, and the quality of processing is judged by the value measured potential, characterized in that, in order to increase the accuracy of control, an additional electrolyte is introduced an electrode made of a controlled material, and a voltage is applied between the working and additional electrodes, the value of which is selected based on the condition φ _da > φ _p.e for anode processes and φ _da <φ _p for cathode processes, and the ratio the areas of the working, additional and auxiliary electrodes are selected based on the condition
i

>> i _{-p.э} ,}
where φ _doe is the potential of the additional electrode;
φ _p.e is the potential of the working electrode;
i

- current between the working and auxiliary electrodes;
i _-p.э} - current between the additional and working electrodes.

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