Phosphorus, dopant

Fig. 5.4. The distribution coefficients of arsenic and phosphorus dopants as a function of the rf power in the plasma at different gas phase concentrations (Winer and Street 1989).

A large body of research exists on the deposition and processing of structural polysilicon [8-10]. The key parameter for films made of structural polysilicon is residual stress and therefore the flatness of the films. The deposition of polysilicon from silane (SiH4) gas in a horizontal furnace has been extensively used. The addition of phosphorus as a dopant for the polysilicon has been used to control resistivity and stress. Including phosphorus dopant in the sacrificial oxide layer under the structural polysilicon layer and/or as ions implanted after deposition of the polysilicon is the most common methods used. 

For a given semiconductor at temperature T, Equation (9.51) shows that as the number of free electrons increases, the number of holes proportionately decreases, so that their product remains the same. Thus the amount of the phosphorus dopant that is introduced controls the amount of both the electrons and the holes in the semiconductor. We call the carriers of higher concentration the majority carriers, while those of lower concentration are the minority carriers. Since electrons are the majority carrier when we dope silicon with phosphorous, we call this material an n-type semiconductor. When the number densities of minority and majority carriers are controlled by the amount of dopant, we say we have an extrinsic semiconductor. In the limit of small dopant concentrations, [P i] << p, there is no effect of the substitutional impurity of the electronic defects in the semiconductor, and it behaves similarly to an intrinsic semiconductor. 

Introduction to phosphorus dopants in silicon (Si P) as a model system for electron paramagnetic resonance (EPR)... 

Phosphorus oxychloride 10025-87-3 Organic synthesis Plasticizers Gasoline additives Hydraulic fluids Insecticides Dopant for semiconductor grade silicon Flame retardants Tabun (GA) 1.05... 

Finally, we tried to activate dopant atoms using pulsed laser irradiation, which is effective in lowering the process temperature. The light source was a 308-nm XeCl excimer laser, which is a standard source for crystallizing a-Si films used in the LTPS process.19 A test sample of 76 nm thickness, prepared from the copolymerized solution (l-wt% phosphorus, 30-min UV irradiation, 500 °C 2hr annealing), was irradiated using a XeCl laser at various intensities to activate the dopant atoms. Figure 5.19 shows the relationship between the... 

Instead of depending on the thermally generated carriers just described (intrinsic conduction), it is also possible to deliberately incorporate various impurity atoms into the silicon lattice that ionize at relatively low temperatures and provide either free holes or electrons. In particular, Group 13 (IIIA) elements ( -type dopants) supply electrons and Group 15 (VA) elements (p-type dopants) supply holes. Over the normal doping range, one impurity atom supplies one hole or one electron. Of these elements, boron (p-type), and phosphorus, arsenic, and antimony ( -type) are most commonly used. When... 

Atoms of elements that are characterized by a valence greater than four, e g., phosphorus or arsenic (valence = 5), are one type of dopant. These high valence dopants contribute free electrons to the crystal and arc called donor dopants. If one donor atom is incorporated in the lattice, four of die five valence electrons of donor dopants are covalently bonded, but the fifth electron is very weakly bound and can be detached by only ca 0.03 eV of energy. Once it is detached, it is available as a free electron, i.e, a carrier of electric current. A silicon crystal with added donor dopants has excess electron carriers and is called n-type (negative) silicon. See Fig. 1(c). 

Instrumental Methods. Engineers in the IC industry prefer to use X-ray or FTIR spectroscopy to determine the quantities of phosphorus in thin films because of the speed of these methods. These spectroscopic methods are satisfactory for a relative indication of the dopant level in thin films or additives to metallization layers, but they do have serious drawbacks. X-ray spectroscopy is seriously affected by matrix effects and can easily be off by 15-20% of the actual concentration of dopant in thin films if the equipment is not properly calibrated against a material that has been analyzed by wet techniques. X-ray spectroscopy is further affected by the film thickness and the dopant profile throughout the film. 

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